令和２年度⼀般財団法⼈救急振興財団調査研究事業助成

窒息に対するバイスタンダー応急⼿当の質向上のための⼝頭指導に関する研究
⽇本医科⼤学付属病院

五⼗嵐 豊

共同研究者（敬称略）

鈴⽊ 健介

⽇本体育⼤学 保健医療学部

⼩川 理郎

⽇本体育⼤学 保健医療学部

本村 友⼀

⽇本医科⼤学千葉北総病院 救命救急センター

北⼩屋 裕

京都橘⼤学 健康科学部 救急救命学科

濱⼝ 拓郎

会津中央病院 救命救急センター

前島 璃⼦

⽇本医科⼤学武蔵⼩杉病院 救命救急センター

⾦ 成浩

⼤阪府泉州救命救急センター

吉野 雄⼤

会津中央病院 救命救急センター

乗井 達守

ニューメキシコ⼤学 救急部

横堀 將司

⽇本医科⼤学⼤学院 医学研究科 救急医学分野

横⽥ 裕⾏

⽇本体育⼤学⼤学院 保健医療学研究科

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概要①

窒息における死亡者は年間8000⼈以上であり、不慮の外因死の原因として第⼆位であり、公衆衛⽣上の重要な課題である。我々の先⾏研究によれば、後遺症を残さないためには5分以内に異物除去を⾏う必要がある。現在、救急隊到着までの平均時間は約8分であり、バイスタンダーによる応急⼿当が患者の予後を左右すると⾔っても過⾔ではない。⼀⽅で応急⼿当は57%しか実施されておらず、通信指令員から⾏われる⼝頭指導が重要である。
我々は、スマートフォン動画伝送システムを⽤いた⼝頭指導の可能性を探求するため、模擬通報訓練を⾏いビデオ通話と⾳声通話を⽐較し、応急⼿当の質を評価した。
⼤学１年⽣を対象に、乳児の窒息に対する救急通報のシミュレーションを⾏った。ランダムにビデオ通話を使⽤する群と⾳声通話のみの群に分けた。まず、窒息に対する応急⼿当を⼝頭指導下に⾏い、その後⼼肺停⽌となり⼼肺蘇⽣の⼝頭指導を⾏った。ビデオ通話の開始までに時間を要するため、両群ともに最初に⾳声のみによる⼝頭指導を⾏い、ビデオ通話群はその後にビデオ通話を⾏った。応急⼿当の評価は、ガイドラインの推奨事項に基づき３段階で⾏った(excellent, acceptable, poor)。
合計32例を対象とし、ビデオ通話群(n = 16)、⾳声通話群(n = 16)であった。窒息に対する応
急⼿当を⼝頭指導した後、poorの割合は両群とも有意差を認めなかった(56 % vs 50%, P =0.72)が、ビデオ通話による⼝頭指導を⾏い、poorの割合はビデオ通話群が有意に低くなった(13% vs 50%, P = 0.03)。CPRに対する⼝頭指導では、両群のpoorの割合に有意差は認めなかった。(75% vs 50%, P = 0.14)。⼝頭指導開始から正しい応急⼿当ができるまでの時間は、窒息に対する応急⼿当(99 (70-147) vs 70 (53-101); P＝0.10）もCPR(33 (28-49) vs 30 (28-34); Ｐ=0.24)も有意差を認めなかった。
乳児の窒息の応急⼿当のシミュレーションを⾏い、ビデオ通話によってpoorの割合は⾳声通話より有意に低くなった。ビデオ通話によって窒息の応急⼿当の質の改善することが⽰唆され
た。

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⽅法
研究デザイン
保健医療学部の⼤学１年⽣を対象に1歳未満の乳児に対する窒息の応急⼿当をシミュレーショ
ンを⾏った。成⼈に対して推奨される背部叩打法と腹部突き上げ法は、⽐較的簡単なので、より複雑な乳児に対する背部叩打法をシミュレーションした。学⽣は乳児に対する窒息の応急⼿
当をまだ学習しておらず、事前に本シミュレーションのことも知らせなかった。学⽣を２⼈１組とし、ランダムにビデオ通話群と通常の⾳声通話群に割り付けた。学⽣２⼈のうち、⼀⼈が応急⼿当を⾏い、もう⼀⼈が救急通報を⾏った。
合計４名の救急救命⼠の資格をもつ⼤学教員がdispatcherとして参加した。年齢は44から60歳（中央値45.5）であった。救急隊員として活動年数は20から41年（中央値23.5）であった。通
信司令員としての経験はないが、事前にprotocolに従って訓練を⾏った。
乳児はマネキン(Baby Anne, Laredal,Stavanger, Norway)を⽤いて、⾝体所⾒などは、ファシリテーターから情報を適宜付与した。
参加者には研究に対して⾮協⼒権を保証し同意を得た。本研究は、⽇本体育⼤学倫理委員会
による承認を得た(020-H079)。

⼝頭指導プロトコル
ビデオ通話は開始まで時間がかかるため、両群ともに最初は⾳声による⼝頭指導を⾏い、ビ
デオ通話群は⾳声による⼝頭指導の後にビデオ通話による⼝頭指導を⾏うこととした。
事前に総務省消防庁のprotocolと⼼肺蘇⽣ガイドラインにしたがって、本シミュレーションのprotocolを下記のごとく作成した(Supplementary table 1, 33081526)。祭りでボランティアをしている学⽣のもとに、⽣後11か⽉男の乳児を両親が連れてくる。乳児は⼩さなボールを⼝に⼊れた後、反応はあるが声が出せずに苦しそうにしている。両親は動揺しており、救急要請と応急⼿当を依頼される。救助者は⾳声通話で、乳児に対する背部叩打を通信司令員の指⽰を受けながら⾏う。その後、ビデオ通話群は、通信司令員が携帯電話にURLを送り、救助者がそのURLに接続してビデオ通話を開始する。ビデオ通話が開始した後は、通報者が携帯電話で応急⼿当の様⼦を撮影し、通信司令員がフィードバックを⾏う。いずれの群も開始から4分で患児の反応がなくなる。救助者は通信司令員の指⽰を受けながら⼼肺蘇⽣を⾏う。

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評価⽅法およびデータ収集
乳児の窒息の応急⼿当は、ガイドラインに基づいて以下の３つのポイントを推奨している。
①うつぶせ、②⼿のひらで乳児の顎を⽀える、③体より頭が下。この推奨を基にして３段階の評価を⾏った。excellent, ３つのポイントを満たし⼝頭指導のとおり。acceptable, ３つのポイントを満たすが⼝頭指導通りではない。poor, ３つのポイントを満たさない。（図１）
また、乳児の⼼肺蘇⽣に対して、以下の３つのポイントが推奨されている(33081526)。①両
乳頭部を結ぶ線の少し⾜側。②1分間に100~120回のテンポ。③指２本で⾏う。この推奨を基にして３段階の評価を⾏った。⼈⼯呼吸はCOVID-19感染を防⽌するため⾏わなかった。
excellent, ３つのポイントを満たし⼝頭指導どおり。acceptable, ３つのポイントを満たすが⼝頭指導通りではない。poor, ３つのポイントを満たさない。（図２）
また指導を開始してから、正しい応急⼿当が⾏われるまでの時間を計測した。すべてのトラ
イアルは固定したビデオカメラと、救助者の頭部にGoPro(GoPro, Inc., San Mateo, California,
USA)を装着し録画した。ビデオカメラの映像で応急⼿当が死⾓になる場合、応急⼿当が実施できているかどうかGoProの動画で判断した。2⼈(YI and YY)が評価して、評価が異なった場合には別の⼀⼈(TN)が最終的に判断した。

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図１ 乳幼児の窒息に対する応急処置の評価
A）⼝頭での指⽰に従い、以下の3点が満たされていれば「優 (excellent)」とした。①乳児の顔を下にして、②⼿のひらで乳児のあごを⽀え、③乳児の頭を体よりも低くする。
B）⼝頭での指⽰が守られていないが、3つのポイントを満たしている場合を「可 (acceptable)」とした。
C）3つのポイントのうち、少なくとも1つが満たされていない場合は「不良 (poor)」とした。

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図２ 乳幼児に対する⼼肺蘇⽣法の評価
A）⼝頭での指⽰に従い、以下の3点が満たされていれば「優 (excellent)」と評価した。乳⾸を結んだ線上から乳児の⾜元に向かってやや指を置く、②圧迫速度は1分間に100〜120回、③2本の指で押す。
B）3つのポイントを満たしていても、⼝頭での指⽰通りにならない場合は「可 (acceptable)」とした。
C）3つのポイントのうち少なくとも1つが満たされていない場合は「不良 (poor)」とした。

通信⽅法
通報者は、iPhone 11 (Apple Inc., Cupertino, California, USA)で4Gの通信回線を⽤いて通話を⾏った。すべての救助者に⼝頭指導が聞こえるよう、デフォルトでhands-free audioとなるよう設定した。⾳声通話とビデオ通話の効果を⽐較するため、⾳声通話を⾏う際もhands-freeaudioとし同じ条件とした。
ビデオ通話群では、通信司令員はノートパソコンでソフトウェア (Ryobi Systems Co., Ltd.,
Okayama, Japan)を⽤いた。通信には最⼤下り速度は187.5MbpsのWiFiを⽤いた。ビデオ通話

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中、通信指令員はコンピュータ上に携帯電話から送られてくる映像が表⽰される。その映像を⾒ながら、通信指令員は通報者に、カメラの位置や応急⼿当の⽅法を指⽰することができる。

統計解析
連続変数は中央値とinterquartile rangeで表した。2群の⽐較は、Mann-Whitney検定を⽤いた。カテゴリ変数は、χ2乗検定またはFisher検定のうち適切な⽅を⽤いた。P < 0.05を統計学的な有意差があると定義をした。統計解析には、StatFlex version 6.0(Artech Co., Ltd, Osaka,
Japan)を⽤いた。

結果
参加者
70名の学⽣に対して、合計35例のトライアルを⾏った。アンケートから乳児に対する応急⼿当を学習済みで⼝頭指導なしに実施できた2例と通信障害により⾳声通話が中断した1例は除外とし、全32例を対象とした(Figure 3)。
ビデオ通話群(n = 16)、⾳声通話群(n = 16)であった。年齢、性別、⽇常的にスマホを使っている⼈、119番通報したことのある⼈は、両群で差を認めなかった（表１）。

ビデオ通話の成功率
ビデオ通話群のうち、13例(81%)はビデオ通話に成功したが、3例(19%)は利⽤できなかった。2例は接続したが携帯電話を置いたままにしていたため、⾳声のみによる指導が⾏われた。
1例は通報者がURLをタップせず、⾳声のみによる指導が⾏われた。ビデオ通話に成功した中(n= 13)で、URLを送信してから接続までにかかる時間は35 (24-59)秒であった。

窒息に対する応急⼿当
⾳声通話による⼝頭指導後、poorの割合は両群とも有意差を認めなかった(56 % vs 50%, P =0.72)（図4-A）。しかし、⼝頭指導ではpoorであった9例のうち、8例がビデオ通話に成功し78

例がacceptableまたはexcellentへ改善したため、poorの割合はビデオ通話群が有意に低くなった(13% vs 50%, P = 0.03)（図4-B）。⾳声通話のみの群は、⼝頭指導を継続してもpoorの割合は変わらなかった。

⼼肺蘇⽣
両群ともpoorはなかった。CPRビデオ通話群の⽅がexcellentの割合が⾼かったが、有意差は認めなかった。(75% vs 50%, P = 0.14)（図4-C）。

応急⼿当開始までの時間
⼝頭指導開始から正しい応急⼿当ができるまでの時間は、⾳声通話群の⽅がやや短かったが有意差は認めなかった（99 (70-147) vs 70 (53-101) Ｐ＝0.10）。⼝頭指導開始から正しい
CPRができるまでの時間は、⾳声通話群の⽅がやや短かったが有意差は認めなかった。(33(28-49) vs 30 (28-34), Ｐ＝0.24)（図５）

図３ シミュレーションのフローチャート9

表１ 参加者の背景
ビデオ通話群(n = 32)

⾳声通話群(n = 32)p値

年齢19 (19-19)

19 (18-19)

0.57

性別（男性）

27 (84%)24 (75%)0.35

スマートフォン使⽤者

32 (100%)

32 (100%)

1.00

窒息の応急⼿当を学習済み

1 (3%)

5 (16%)

0.10

CPRを学習済み

20 (63%)17 (53%)0.45

救急通報の経験あり

6 (19%)

4 (12%)0.73

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図４ ⼝頭指⽰による応急処置の評価(A) 窒息時の応急処置の評価（両群とも⾳声通話による初期⼝頭指⽰後(B) 窒息に対する応急処置の評価（ビデオまたは⾳声通話による⼝頭指⽰の後(C) ⼼肺蘇⽣の評価

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図５ ⼝頭指導開始から応急処置が正しく⾏われるまでの時間(A) 窒息の応急処置 (B) ⼼肺蘇⽣法

12考察
乳児の窒息の応急⼿当のシミュレーションを⾏い、ビデオ通話によって応急⼿当が改善し、正しく実施できていない割合は、ビデオ通話群が有意に低くなった。⼼肺停⽌以外の応急⼿当に、ビデオ通話による⼝頭指導の有効性を⽰した研究はほとんどない。
dispatcherからのビデオ通話によるフィードバックによって、窒息に対する正しい応急⼿当ができていない割合が⾳声通話より有意に低くなった。また、ビデオ通話によって、救護者が気付かなくても、dispatcherが重要な⾝体所⾒や容態変化に気づく可能性がある。simulated
cardiac arrestを対象にした研究で、ビデオ通話は⾳声通話に⽐べて多くの呼吸停⽌を認識できた。
simulated CPAに対するCPRに関してたくさんの研究がされてきており、気道確保や換気量などbystanderの rescue breathing、胸⾻圧迫の深さとテンポ、位置、胸⾻圧迫と⼈⼯呼吸の⽐は、ビデオ通話群の⽅がよりoptimalであったと報告されている。しかし胸⾻圧迫開始までの時間とhands-oﬀの時間は、ビデオ通話の⽅が⻑かった。システマティックレビュー・メタ解析では、胸⾻圧迫の深さや⼿の位置がより適切でありCPRの質を改善することが⽰されている。
⼀⽅で、CPRは両群ともpoorと評価されず、⾳声通話でも正しく応急⼿当が実施できた。先⾏研究の結果と異なるのは、乳児のCPRは成⼈に⽐べてポイントが少ないため、評価項⽬が少なく満たしやすかったからと考えられる。また、保健医療学部の学⽣なので、乳児のCPRに関しては学習済みの学⽣も多かった。⾳声通話でも⼤部分が実施できる応急⼿当は、ビデオ通話の有効性は乏しいかもしれない。逆に⼿技の開始までに時間がかかり、かえって悪い影響となる可能性もある。CPRを対象にした研究では、ビデオ通話はCPR開始まで平均31.5秒の遅れがあった。CPRはなるべく早期に開始して中断しないことが有効であるが、異物除去は⼀回ごとに正しい応急⼿当を⾏う⽅がより重要かもしれない。
最初の⼝頭指導を⾏った後、poorが53%を占めた。乳児の窒息に対する応急⼿当が普及しておらず、⼝頭指導だけでは複雑な⼿技であることを反映している。ビデオ通話による⼝頭指導によって多くの症例で修正されたが、救助者が⼝頭指導の意味を正しく理解できなかったり、
dispatcherがうまく表現できないと、改善しない可能性がある。双⽅向通信によって、救助者に画像や動画を⾒せることによってさらに改善する余地がある。

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また3例(19%)でビデオ通話が正しく⾏われなかった。全員が普段からスマホを使⽤する若年者であったことから、スマホに慣れない救護者の場合、さらに⾼率に接続に失敗する可能性がある。
本研究は研究の限界が存在する。⼀つ⽬は、randomized control trialだが、open labelである。⼆つ⽬は、シミュレーションであるため、リアルワールドでのビデオ通話の有効性は不明である。⼼肺蘇⽣の場合、シミュレーションでは有効であったが、リアルワールドでは⽣存退院や神経学的転帰良好などの有効性が⽰せなかった。３つ⽬は、成⼈に対するビデオ通話の有効性は不明である。成⼈は、腹部突き上げ法と背部叩打法が推奨されているが、腹部突き上げ法については本研究で評価していない。窒息の応急⼿当に関するエビデンスはわかっていないこと(knowledge gap)が多くさらなる研究が必要である。

結語
乳児の窒息の応急⼿当のシミュレーションを⾏い、ビデオ通話によって正しい背部叩打法が実施できていない割合は⾳声通話より有意に低くなった。ビデオ通話の⽅が、⼝頭指導の開始から正しくできるまでに時間を要したが有意差は認めなかった。乳児の窒息の応急⼿当には、
ビデオ通話による⼝頭指導が有⽤であることが⽰唆された。

参考⽂献
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accessed 24 Dec 2020.
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2014;85(1):34-41. doi: 10.1016/j.resuscitation.2013.06.004 [published Online First:
2013/06/25]
7. Bohm K, Vaillancourt C, Charette ML, et al. In patients with out-of-hospital cardiac arrest,
does the provision of dispatch cardiopulmonary resuscitation instructions as opposed to
no instructions improve outcome: a systematic review of the literature. Resuscitation
2011;82(12):1490-5. doi: 10.1016/j.resuscitation.2011.09.004 [published Online First:
2011/09/20]
8. Tanaka Y, Taniguchi J, Wato Y, et al. The continuous quality improvement project for
telephone-assisted instruction of cardiopulmonary resuscitation increased the incidence of
bystander CPR and improved the outcomes of out-of-hospital cardiac arrests. Resuscitation
2012;83(10):1235-41. doi: 10.1016/j.resuscitation.2012.02.013 [published Online First:
2012/03/01]
9. Lin YY, Chiang WC, Hsieh MJ, et al. Quality of audio-assisted versus video-assisted
dispatcher-instructed bystander cardiopulmonary resuscitation: A systematic review andmeta-analysis. Resuscitation 2018;123:77-85. doi: 10.1016/j.resuscitation.2017.12.010[published Online First: 2017/12/16]
10. Topjian AA, Raymond TT, Atkins D, et al. Part 4: Pediatric Basic and Advanced Life
Support: 2020 American Heart Association Guidelines for Cardiopulmonary Resuscitationand Emergency Cardiovascular Care. Circulation 2020;142(16_suppl_2):S469-S523. doi:
10.1161/CIR.0000000000000901 [published Online First: 2020/10/22]

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11. Olasveengen TM, Mancini ME, Perkins GD, et al. Adult Basic Life Support: International
Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science
With Treatment Recommendations. Resuscitation 2020;156:A35-A79. doi:
10.1016/j.resuscitation.2020.09.010 [published Online First: 2020/10/26]
12. Fire and Disaster Management Agency of the Ministry of Internal Aﬀairs andCommunications. Textbook for an emergency dispatcher 2014 [Available from:https://www.fdma.go.jp/singi_kento/kento/items/kento125_15_text.pdf.
13. American Academy of Pediatrics Committee on Pediatric Emergency Medicine. First aid
for the choking child. Pediatrics 1993;92(3):477-9. [published Online First: 1993/09/01]
14. Maconochie IK, Aickin R, Hazinski MF, et al. Pediatric Life Support: 2020 International
Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science
With Treatment Recommendations. Circulation 2020;142(16_suppl_1):S140-S84. doi:
10.1161/CIR.0000000000000894 [published Online First: 2020/10/22]
15. Motomura T, Hattori Y, Hirabayashi A, et al. The usefulness of emergency call systemfrom civilians using smart phone video transmission system. JJSEM 2016;19:466-73.
16. Bolle SR, Scholl J, Gilbert M. Can video mobile phones improve CPR quality when used
for dispatcher assistance during simulated cardiac arrest? Acta Anaesthesiol Scand
2009;53(1):116-20. doi: 10.1111/j.1399-6576.2008.01779.x [published Online First:
2008/11/27]
17. Yang CW, Wang HC, Chiang WC, et al. Impact of adding video communication todispatch instructions on the quality of rescue breathing in simulated cardiac arrests--arandomized controlled study. Resuscitation 2008;78(3):327-32. doi:
10.1016/j.resuscitation.2008.03.232 [published Online First: 2008/06/28]
18. Yang CW, Wang HC, Chiang WC, et al. Interactive video instruction improves the qualityof dispatcher-assisted chest compression-only cardiopulmonary resuscitation in simulated
cardiac arrests. Crit Care Med 2009;37(2):490-5. doi: 10.1097/CCM.0b013e31819573a5[published Online First: 2008/12/31]

16

19. Lee JS, Jeon WC, Ahn JH, et al. The eﬀect of a cellular-phone video demonstration to
improve the quality of dispatcher-assisted chest compression-only cardiopulmonary
resuscitation as compared with audio coaching. Resuscitation 2011;82(1):64-8. doi:
10.1016/j.resuscitation.2010.09.467 [published Online First: 2010/11/03]
20. Choa M, Park I, Chung HS, et al. The eﬀectiveness of cardiopulmonary resuscitation
instruction: animation versus dispatcher through a cellular phone. Resuscitation
2008;77(1):87-94. doi: 10.1016/j.resuscitation.2007.10.023 [published Online First:
2008/01/01]
21. Hunt EA, Heine M, Shilkofski NS, et al. Exploration of the impact of a voice activateddecision support system (VADSS) with video on resuscitation performance by lay rescuers
during simulated cardiopulmonary arrest. Emerg Med J 2015;32(3):189-94. doi:
10.1136/emermed-2013-202867 [published Online First: 2013/11/19]
22. Hasselqvist-Ax I, Riva G, Herlitz J, et al. Early cardiopulmonary resuscitation in
out-of-hospital cardiac arrest. N Engl J Med 2015;372(24):2307-15. doi:
10.1056/NEJMoa1405796 [published Online First: 2015/06/11]
23. Lee SY, Song KJ, Shin SD, et al. Comparison of the eﬀects of audio-instructed andvideo-instructed dispatcher-assisted cardiopulmonary resuscitation on resuscitation
outcomes after out-of-hospital cardiac arrest. Resuscitation 2020;147:12-20. doi:
10.1016/j.resuscitation.2019.12.004 [published Online First: 2019/12/18]
24. Panchal AR, Bartos JA, Cabanas JG, et al. Part 3: Adult Basic and Advanced Life Support:
2020 American Heart Association Guidelines for Cardiopulmonary Resuscitation andEmergency Cardiovascular Care. Circulation 2020;142(16_suppl_2):S366-S468. doi:
10.1161/CIR.0000000000000916 [published Online First: 2020/10/22]
25. Norii T, Igarashi Y, Sung-Ho K, et al. Protocol for a nationwide prospective, observational
cohort study of foreign-body airway obstruction in Japan: the MOCHI registry. BMJ Open
2020;10(7):e039689. doi: 10.1136/bmjopen-2020-039689 [published Online First:
2020/07/22]
本研究は、両備システムズより機器の貸与および技術協⼒を得た。

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概要②

背景︓気道異物による窒息(FBAO)は、⽇本における事故死の第⼀位の原因となっている。いく
つかの研究で、院外⼼停⽌患者において病院前気管挿管は、⾼い死亡率と関連していることが⽰されている。しかし，低酸素⾎症は⼼停⽌を引き起こすため，FBAO患者では直ちに呼吸を再開させることが重要である。ここでは，FBAOによる院外⼼停⽌患者において，病院前気管挿管が⽣存率と関連しているかどうかを検討することを⽬的とした。2014年から2019年にかけて，
FBAOによる院外⼼停⽌患者を対象に多施設観察的窒息調査（MOCHI）を実施した．
⽅法︓患者を病院前（病院前で気管挿管。上気道デバイスは除く。）群と病院内（病院内で気管挿管）群に分類した．主要転帰は病院⽣存率であり，副次的転帰は退院時の良好な神経学的転帰と⾃⼰⼼拍再開であった。院内挿管前群と院内挿管群の間で、傾向スコアマッチング分析を⾏った。
結果︓登録された155⼈の患者のうち、58⼈と97⼈がそれぞれ病院前群と病院群に分類された。患者背景は両群間で同等であった。マッチングなし（病院前対病院内、35％対14％、P =0.005）および傾向スコアマッチング（病院前対病院内、34％対16％、P = 0.049）の解析では、両群間に有意差が認められた。
結論︓病院前での気管挿管は，FBAOによる院外⼼停⽌患者の⽣存率の上昇と有意に関連していた．病院での挿管とバイスタンダーによる⼼肺蘇⽣は，病院での⽣存率を向上させる独⽴変数
であった．

18

概要③

⽬的︓気道異物による窒息は、世界的に⼤きな公衆衛⽣上の問題である。no air-ﬂowおよび
low air-ﬂow時間の減少は、神経学的転帰の改善と強く相関している。気道閉塞時間と神経学的転帰との関係を評価した研究はないため、本研究ではその関係を検討した。
⽅法︓⽇本で実施されたこの多施設共同後⽅視観察研究では，4年間にわたって異物による気道閉塞の患者を対象とした。データは電⼦カルテから抽出した。⼤脳機能は，cerebral
performance category（CPC）スコアを⽤いて測定した。主要アウトカムは退院時にCPC 4または5と定義された好ましくないアウトカムであった。
結果 MOCHI登録患者386例のうち，119例が本研究に登録された。17例では5分以下，15例では6〜10分，40例では11〜20分，47例では21分以上で異物が除去された。好ましくない転帰の割合は，≦5分のグループが他のグループに⽐べて有意に低かった（≦5分，6％ vs 6-10分，47％，P＝0.01︔ vs 11-20分，68％，P＜0.001︔ vs 21分以上，70％，P＜0.001）。多変量解析
では、気道閉塞時間が6分以上（オッズ⽐[OR]32.6、95％信頼区間[CI]4.0〜264）、年齢が75歳以上（OR2.5、95％CI1.00〜6.37）が独⽴した予後不良因⼦であることが⽰された。
結論︓気道閉塞時間が⻑くなると、予後不良の割合と死亡率が増加した。異物による気道閉塞の患者に対しては，5分以内に異物を除去することが重要である。

19

会議等

第１回 2020年6⽉23⽇（⽕）18:00 web会議
第２回 2020年9⽉4⽇（⾦）14:00 web会議
第３回 2020年9⽉18（⾦）15:00 web会議
第４回 2020年9⽉23⽇（⽔）19:00 web会議
第５回 2020年11⽉5⽇（⽊）17:00 会議 ⽇本体育⼤学 横浜・健志台キャンパス
第６回 2020年11⽉23⽇（⽉）13:00 実証研究 ⽇本体育⼤学 横浜・健志台キャンパス

この研究は⼀般財団法⼈救急振興財団の「救急に関する調査研究事業助成」を受けて⾏ったも
のである。

20

（別添）発表予定の論文原稿

1. Do Video Calls Improve Dispatcher-assisted First Aid for Choking
Infant?: A randomized Controlled Trial/Simulation Study

2. Association between Prehospital Intubation and Survival of Cardiac
Arrest Patients with Foreign Body Airway Obstruction: A Multicenter
Observational Study and Propensity Score-matching Analysis

3. Association between Time of Airway Obstruction by Foreign Bodies
and Neurological Outcome: MOCHI1

Do Video Calls Improve Dispatcher-assisted First Aid for Choking Infants? :2

a Randomized Controlled Trial/Simulation Study

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Yutaka Igarashi1 Kensuke Suzuki2 Tatsuya Norii3 Tomokazu Motomura1,4
Yudai Yoshino1,5 Yutaka Kitagoya6 Shoji Yokobori1 Satoo Ogawa2
Hiroyuki Yokota2

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1) Department of Emergency and Critical Care Medicine, Nippon Medical School
1-1-5 Sendagi, Bunkyo-ku, Tokyo, 113-8603, Japan
2) Department of Emergency Medical Science, Nippon Sport Science University
1221-1 Kamoshida-cho, Aoba-ku, Yokohama, Kanagawa, 227-0033, Japan
3) Department of Emergency Medicine, University of New Mexico
700 Camino de Salud, Albuquerque, NM 87131, United States
4) Shock and Trauma Center, Nippon Medical School Chiba Hokusoh Hospital
1715 Kamagari, Inzai, Chiba 270-1694
5) Department of Emergency and Critical Care Medicine, Aidu Chuo Hospital
1-1 Tsurugamachi, Aizuwakamatsu, Fukushima, 965-8611, Japan
6) Department of Paramedic Science, Kyoto Tachibana University, Kyoto, Japan
34 Oyakeyamada, Yamashina-ku, Kyoto, 607-8175, Japan

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Corresponding author
Yutaka Igarashi
1-1-5 Sendagi, Bunkyo-ku, Tokyo, 113-8603, Japan
Tel +81-3-3822-2131
Fax +81-3-3821-5102
Email igarashiy@nms.ac.jp

Keywords: Airway Obstruction; First Aid; Pediatric Emergency Medicine; Emergency
Ambulance System; Prehospital Care
Word count: 2,516 words

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39

Abstract

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Background: As choking quickly leads to cardiopulmonary arrest, it is crucial that a

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bystander removes the foreign body, effectively. Although oral instructions through video

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calls by dispatchers improve the quality of chest compression, little is known if video calls

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improve the quality of first aid for choking. The aim of the study was to determine whether

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video calls with dispatchers improve the quality of first aid for choking infants.

45
46

Methods: Thirty-two first-year college students were randomly assigned in pairs of two to47

communicate either through video or audio calls and participated in simulated emergency

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calls for choking infants. Both groups began with oral instruction through voice calls, until49

the transition was made to video calls in the video group. The primary outcome was quality

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of first aid performance that was categorize as excellent, acceptable, or poor based on the51

guidelines.

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Results: There were 16 simulations in both the video- and voice-call groups. Following initial

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oral instructions, the proportion of rescuers receiving a score of “poor” did not differ

55

significantly between the groups (video, 56% vs. voice, 50%; P=0.72); however, the scores of56

seven rescuers improved after transitioning to video calls. Ultimately, the proportion

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receiving a score of “poor” was significantly lower in the video-call than in the voice-call58

group (13% vs. 50%, P=0.03).

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Conclusion: In this simulation of first aid for choking infants, the rate at which incorrect first61

aid was performed was statistically significantly lower following dispatcher instructions2

62

using video calls than using voice calls.

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What is already known on this subject

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Foreign-body airway obstruction is an important global public health issue. Oral instructions

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provided via video calls have been revealed to improve the quality of CPR by correcting the68

depth of chest compressions and the position of the hands. However, little is known if video

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calls improve the quality of first aid for foreign body airway obstruction.

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71

What this study adds

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In this simulation of first aid for choking infants, the rate at which incorrect first aid was73

performed was statistically significantly lower following dispatcher instructions using video

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calls than using voice calls. Our study suggests that oral instructions using video calls are

75

effective to improve the quality of first aid for choking infants.

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Introduction

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Foreign-body airway obstruction is an important global public health issue. In the United

81

States, it was the third leading cause of preventable injury-related death in 2018, killing82

approximately 5,100 people1. In Japan it caused about 8,400 deaths in 2019, making it the83

second leading cause of accidental death2. It occurs most often in children and the elderly3.

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Choking is an airway emergency, and as cardiac arrest can occur if the foreign body is not

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quickly removed, having a bystander administer first aid is extremely important. When a86

bystander removed a foreign object before emergency services arrived, the reported rate of87

favorable neurological prognoses was higher than when the object was removed by88

emergency services4. However, if the bystander is unable to perform appropriate first aid, it is89

important for the dispatcher to provide oral instructions. It has been demonstrated that90

dispatcher-assisted cardiopulmonary resuscitation (CPR) improves survival rates and91

neurological outcomes5-8. Further, oral instructions provided via video calls have been92

revealed to improve the quality of CPR by correcting the depth of chest compressions and the93

position of the hands9. However, little is known if video calls improve the quality of first aid

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for foreign body airway obstruction.

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In this study, we aimed to determine whether video calls with dispatchers improve the quality

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of first aid for choking infants compared to voice-only calls.

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Methods

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Study design and population

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We simulated first aid for choking infants, younger than 1 year, administered by first-year

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college students enrolled in a health sciences department. The back-blow and abdominal-102

thrust methods are recommended for adults and are relatively simple to perform. Therefore,4

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we chose the back-blow method for choking infants, which is more complicated. Students

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were not informed of the simulation in advance. We excluded students who had received

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training in first aid for choking infant and did not need oral instructions, and simulations in106

which the voice call was interrupted due to network failure. Students were placed in pairs and107

randomly assigned to the video-call or voice-call groups. One student administered the first108

aid while the other made the emergency call.

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Four faculty members, all certified emergency responders, acted as dispatchers. The

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dispatchers were 44 to 60 years old (median, 45.5) and had 20 to 41 years (median, 23.5) of

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experience as emergency responders. Although they had no experience as dispatchers, they112

were trained in the protocol in advance.

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A mannequin (Baby Anne, Laerdal, Stavanger, Norway) was used to represent the infant and114

a facilitator provided information on e.g., physical findings, as needed.

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Participants provided consent after being informed that they had the right not to participate in116

the study. This study was approved by an ethics committee (Nippon Sport Science University,

117020-H079).

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Patient and public involvement120

No patient involved.

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Dispatch protocol

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As video calls typically take a longer time to connect than voice calls, it was decided that124

both groups would initially receive oral instructions via a voice call, and that the video-call

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group would transition to oral instructions via a video call once the connection was made.

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This is consistent with the dispatch protocol with video calls that is currently trialed in Tokyo.

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The following protocol for the simulation was created in advance based on the protocol of the128

Japanese Fire and Disaster Management Agency and the CPR guidelines of the American

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Heart Association (AHA) and European Resuscitation Council (ERC) (Supplementary Table

1301)10-12. Parents bring an 11-month-old boy to a student volunteering at a festival. The boy has

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put a small ball in his mouth. He is responsive but unable to make any noise and appears to132

be struggling. The parents are upset and ask for first aid and for emergency services to be133

called. On a voice call, a dispatcher instructs the rescuer on how to perform the back blow on

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the infant. In the video-call group, the dispatcher sends a URL to the student's mobile phone,135

and the student connects to this URL to start the video call. After the video call starts, the136caller films the first aid with the mobile phone and the dispatcher provides feedback. In both

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groups, the child stops responding 4 minutes after the start of the simulation. The student then138

performs CPR under the direction of the dispatcher.

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Quality measurements and data collection

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Based on AHA, ERC and American Academy of Pediatrics guidelines, the there are three142

main recommendations for first aid on choking infants10 12 13. ① The infant should be

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positioned face down. ② The infant’s chin should be supported with the rescuer’s palm. ③

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The infant’s head should be placed lower than their body. Based on these recommendations,145

an evaluation was performed. A score of "excellent" was assigned when the oral instructions

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were followed and all three points were met. A score of "acceptable" was assigned when all

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three points were met, but not according to the oral instructions. For example, the infant is

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placed on the knee (incorrect), instead of on the forearm (correct) (Figure 1-B). A score of

149"poor" was assigned when at least one of the three points were not met (Figure 1). For

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example, the infant’s head is higher than their body (Figure 1-C).

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The following three points are recommended for infant CPR, according to AHA and ERC

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guidelines10 14. ① The rescuer’s fingers should be placed slightly toward the infant’s feet153

from the line connecting their nipples. ② The tempo should be 100-120 presses per minute.

154③ Compressions should be performed with two fingers. Artificial respiration was not

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performed, to prevent the spread of COVID-19. Based on these recommendations, an156

evaluation was performed as for the first aid recommendations above (Figure 2). In the figure

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2-B, a score of “acceptable” was assigned because the two-thumb–encircling hands technique158

is used, which is different from the oral instructions. In the figure 2-C, a score of “poor” was159

assigned because chest compressions are performed with the palm instead of with two fingers.

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In addition, we measured the time from the start of the instructions to the time when first aid

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was performed correctly. The simulations were recorded with a fixed video camera and a

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GoPro camera (GoPro, Inc., San Mateo, California, USA) attached to the rescuer's head. If

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the first aid occurred in a blind spot of the fixed video camera, the GoPro video was used to164

determine whether it was being performed properly.

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Communications technology

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The caller used an iPhone 11 (Apple Inc., Cupertino, California, USA) over a 4G network.

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The default call mode was set to hands-free audio so that the rescuer could also hear the oral

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instructions. This was done for both groups, to enable the direct comparison of the effects of170

voice and video calls.

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In the video-call group, the dispatcher used a laptop computer with video communications

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software (Ryobi Systems Co., Ltd., Okayama, Japan). A WiFi connection with a maximum

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download speed of 187.5 Mbps was used for the transmissions. During the video call, the174

dispatcher viewed the video sent from the mobile phone on the computer. While watching the

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video, the dispatcher could give instructions to the caller on the first-aid method and the176

position of the phone camera if needed.

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Statistical analysis

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Continuous variables were expressed as medians and interquartile ranges. The Mann-

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Whitney U test (two-tailed) was used for two-group comparisons. We compared two groups

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with an intention-to-treat analysis with chi-square test or Fisher's exact test (two-tailed) for182

comparing categorical variables, depending on which was more suitable. P<0.05 was

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considered a statistically significant difference. StatFlex version 6.0 (Artech Co., Ltd., Osaka,

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Japan) was used for the statistical analysis.

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Results:

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In total, 35 simulations were conducted with 70 students. Of these, 32 simulations were188

included in the analysis, after excluding 2 in which a student had already received training in

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first aid for infants and did not need oral instructions, and 1 in which the voice call was

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interrupted due to a network failure (Figure 3).

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There were 16 simulations in both the video- and voice-call groups. There were no192

differences between the groups in terms of age, sex, daily smartphone use, or experience

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calling emergency services (Table 1).

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Video-call success rate

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In the video-call group, the call succeeded in 13 (81%) simulations, but could not be used in197

3 (19%). In two simulations, the video call was connected, but the participant did not pick up

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the mobile phone; in one simulation, the caller did not tap on the URL. In these three199

simulations, instructions were only provided orally. Among the successful video calls (n=13),
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200

an average of 35 s (24-59) elapsed from sending the URL to the successful connection of the201

video call.

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First aid for choking

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After the initial oral instructions were provided by the dispatcher using a voice call, the205

proportion of participants receiving a score of “poor” was not significantly different between

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the groups (video call, 56 vs. voice call, 50%; P=0.72) (Figure 4-A). However, of the nine207

participants in the video-call group who received a score of “poor” following the initial oral

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instructions, eight successfully transitioned to a video call, of which seven received an

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improved score. Thus, after following all instructions, the proportion of participants receiving

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a score of “poor” was significantly lower in the video-call group than in the voice-call group211(13% vs. 50%, P=0.03). In the voice-call group, the proportion of participants receiving a212

score of “poor” did not change even with continued oral instructions (Figure 4-B).

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Cardiopulmonary resuscitation

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No participant received a score of “poor” in either group for CPR. The proportion who

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received a score of “excellent” was higher in the video-call group than in the voice-call

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group; however, this difference was not significant (75% vs. 50%, P=0.14) (Figure 4-C).

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Time until start of first aid

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The time from the start of oral instructions to when first aid was performed correctly was

221slightly shorter in the voice-call group than in the video-call group, although this difference222

was not significant (video call, 99 s (70-147) vs. voice call, 70 s (53-101): P=0.10). The time223

from the start of oral instructions to correct CPR was also slightly shorter in the voice-call

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group than in the video-call group, and this difference was not significant (video call, 33 s

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(28-49) vs. voice call, 30 s (28-34); P=0.24) (Figure 5).

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Discussion

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In simulations of first aid for choking infants, video calling improved the quality of the first229

aid; the proportion of participants that could not perform it correctly was statistically230

significantly lower in the video-call group. Very few previous studies have described the231

effectiveness of oral instructions using video calls for first aid other than for cardiopulmonary232

resuscitation15, and to our knowledge, this is the first study that showed efficacy of video

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calls with dispatchers on the quality of first aid for choking infants.

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Feedback from a dispatcher using a video call led to a statistically significantly lower

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proportion of participants who could not perform first aid for choking correctly compared to237

those in the voice-call group. Further, video calls may allow the dispatcher to notice

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important physical findings and changes in the person who is choking, even if the rescuer is239

not aware of them. In research on simulated cardiac arrest, more cases of respiratory arrest

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were recognized in video calls than in voice calls15 16.

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Much research has been conducted on CPR for simulated cardiopulmonary arrest. Video calls

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have been reported as more optimal than voice calls for assistance in airway management and243

minute ventilation in rescue breathing from bystanders17, as well as in chest compression

244

depth18, chest compression rate18-20, position19 20, and ratio of chest compressions to artificial

245

respirations21. However, the time until the start of chest compressions18 21 and the hands-off

246

time18 19 were longer with video calls. A systematic review and meta-analysis revealed that247

chest compression depth and hand position were better and CPR quality improved using

248

video calls compared to those using voice calls9.
10

249

That said, CPR was not evaluated as “poor” for participants in either group, and first aid was

250

correctly implemented even using voice calls. Unlike for adults, infant CPR is relatively

251

simple to perform, and thus it was easier for participants to fulfill the evaluation criteria in252

our study than if the simulation was of adult CPR. Further, as participants were students in a253

health sciences department, many had already been trained in infant CPR. The efficacy of254video calls may lower for first aid of adults, as it assistance can mostly be provided over a255

voice call. In fact, the effect of a video call may be negative as it delays initiation of the256

procedure. In a previous study of CPR, video calls delayed the start of the procedure by a257

mean of 31.5 s9. With CPR, starting as quickly as possible and continuing uninterrupted

258

improves its efficacy22; however, with first aid, it may be more important to perform foreign259

body removal maneuvers correctly.

260

After the initial oral instructions, the proportion of participants assigned a score of “poor”

261

was 53%. Knowledge of first aid for choking infants is not widespread, and this result reflects262

the fact that a complex procedure was attempted with oral instructions only. Most cases

263

improved when the voice call was switched to a video call; however, such improvements may

264

be impossible if the rescuer does not understand the oral instructions or the dispatcher does265

not communicate effectively. There is room for further improvement through interactive

266

communication in which images or videos are provided to the rescuer.

267

In three cases (19%), the video call did not work as intended, effectively remaining a voice268

call. The participants were all young adults who regularly used smartphones. If the rescuers

269

were individuals who were not accustomed to smartphones, the rate of video-call failure

270

might have been even higher.

271
272

Limitations:

11

273

This study had a number of limitations. First, while it was a randomized control trial, it was274

an open-label trial and both participants and reviewers were not blinded with regards to the275

group assignment, however, blinding was impractical due to the nature of the study. Second,276

because these were simulations, the real-world effectiveness of video-call assistance for first277

aid of choking infants is unknown. While CPR was performed efficaciously in the278

simulations, we could not demonstrate other real-world effects such as survival to discharge279

and neurological outcomes23. Third, since we used infant simulation cases, we cannot

280

comment on the efficacy and effectiveness of video-call assistance for first aid in choking

281

adults. Abdominal thrusts and back blows are recommended in adults, but we did not282

evaluate the former in this study. Therefore, more research is needed to close the knowledge283

gap in first aid for choking11 24 25.

284
285

Conclusion

286

In simulations of first aid for choking infants, the proportion of participants who were unable287

to perform back blows correctly with dispatcher assistance using video calls was statistically288

significantly lower than for those receiving such assistance using voice calls. Although the289time from the start of oral instructions to performing the procedure correctly was longer using

290

video calls than voice calls, the difference was not statistically significant. This suggests that291

oral instructions using video calls are effective to improve the quality of first aid for choking

292

infants.

293
294
295
296
297
298
299
300
301
302

References
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15. Motomura T, Hattori Y, Hirabayashi A, et al. The usefulness of emergency call system fromcivilians using smart phone video transmission system. JJSEM 2016;19:466-73.
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dispatcher assistance during simulated cardiac arrest? Acta Anaesthesiol Scand
2009;53(1):116-20. doi: 10.1111/j.1399-6576.2008.01779.x [published Online First:
2008/11/27]
17. Yang CW, Wang HC, Chiang WC, et al. Impact of adding video communication to dispatch
instructions on the quality of rescue breathing in simulated cardiac arrests--a randomized
controlled study. Resuscitation 2008;78(3):327-32. doi: 10.1016/j.resuscitation.2008.03.232[published Online First: 2008/06/28]
18. Yang CW, Wang HC, Chiang WC, et al. Interactive video instruction improves the quality of
dispatcher-assisted chest compression-only cardiopulmonary resuscitation in simulated
cardiac arrests. Crit Care Med 2009;37(2):490-5. doi: 10.1097/CCM.0b013e31819573a5[published Online First: 2008/12/31]
19. Lee JS, Jeon WC, Ahn JH, et al. The effect of a cellular-phone video demonstration to improve
the quality of dispatcher-assisted chest compression-only cardiopulmonary resuscitation as

13

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10.1016/j.resuscitation.2010.09.467 [published Online First: 2010/11/03]
20. Choa M, Park I, Chung HS, et al. The effectiveness of cardiopulmonary resuscitation instruction:
animation versus dispatcher through a cellular phone. Resuscitation 2008;77(1):87-94. doi:
10.1016/j.resuscitation.2007.10.023 [published Online First: 2008/01/01]
21. Hunt EA, Heine M, Shilkofski NS, et al. Exploration of the impact of a voice activated decision
support system (VADSS) with video on resuscitation performance by lay rescuers during
simulated cardiopulmonary arrest. Emerg Med J 2015;32(3):189-94. doi: 10.1136/emermed2013-202867 [published Online First: 2013/11/19]
22. Hasselqvist-Ax I, Riva G, Herlitz J, et al. Early cardiopulmonary resuscitation in out-of-hospital
cardiac arrest. N Engl J Med 2015;372(24):2307-15. doi: 10.1056/NEJMoa1405796[published Online First: 2015/06/11]
23. Lee SY, Song KJ, Shin SD, et al. Comparison of the effects of audio-instructed and videoinstructed dispatcher-assisted cardiopulmonary resuscitation on resuscitation outcomes after
out-of-hospital cardiac arrest. Resuscitation 2020;147:12-20. doi:
10.1016/j.resuscitation.2019.12.004 [published Online First: 2019/12/18]
24. Panchal AR, Bartos JA, Cabanas JG, et al. Part 3: Adult Basic and Advanced Life Support: 2020
American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency
Cardiovascular Care. Circulation 2020;142(16_suppl_2):S366-S468. doi:
10.1161/CIR.0000000000000916 [published Online First: 2020/10/22]
25. Norii T, Igarashi Y, Sung-Ho K, et al. Protocol for a nationwide prospective, observational cohort
study of foreign-body airway obstruction in Japan: the MOCHI registry. BMJ Open
2020;10(7):e039689. doi: 10.1136/bmjopen-2020-039689 [published Online First:
2020/07/22]

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Figure Legends
Figure 1. Evaluating first aid performance on choking infants(A) A score of “excellent” was assigned when the oral instructions were followed, and thefollowing three points were met: ① position the infant face down; ② support the
infant’s chin with your palm; and ③ place the infant’s head lower than their body.
(B) A score of “acceptable” was assigned when the oral instructions were not followed,
but the three points were met.
(C) A score of “poor” was assigned when at least one of the three points were not met.
Figure 2. Evaluating cardiopulmonary resuscitation for infants(A) A score of “excellent was assigned when the oral instructions were followed, and thefollowing three points were met: ① fingers placed slightly toward the infant’s feetfrom the line connecting their nipples; ② compression rates of 100–120 presses per
minute; and ③ press with two fingers.
(B) A score of “acceptable" was assigned when all three points were met but notaccording to the oral instructions.
(C) A score of “poor” was assigned when the at least one of the three points were not met.
Figure 3. Simulation flow chart
Figure 4. Evaluation of first aid following oral instructions(A) Evaluation of first aid for choking (after initial oral instructions via voice calls in bothgroups)(B) Evaluation of first aid for choking (after oral instructions via video or voice call)(C) Evaluation of cardiopulmonary resuscitation
Figure 5. Time from the start of oral instructions to performing first aid correctly(A) First aid for choking(B) Cardiopulmonary resuscitation
Acknowledgements
This study was conducted with funding from the Foundation for Ambulance Service
Development (not applicable).
We would like to express our thanks to Mr. Shinichi Shikano, Mr. Mitsunaga Hoshi, Mr.
Masanori Mitsuhashi, and Mr. Satoshi Harada for acting as dispatchers in the simulations.
We also received assistance from the Faculty of Medical Science at Nippon Sport Science
University.
Ryobi Systems Co., Ltd. provided technical support.
Conflicts of interest: none15

Table 1. Comparison of caller characteristics
Video-call group(n=32)

Voice-call group(n=32)

p value

Age, y; mean (interquartile 19 (19-19)
range)

19 (18-19)

0.57

Sex, male; n (%)

27 (84%)24 (75%)0.35

Daily smartphone use; n (%)

32 (100%)

32 (100%)

1.00

5 (16%)

0.10

20 (63%)17 (53%)

0.45

Experience calling emergency 6 (19%)
services; n (%)

4 (13%)

0.73

Trained in firstchoking*; n (%)

aid

Trained in CPR; n (%)

for 1 (3%)*Not for infants. CPR, cardiopulmonary resuscitationSupplementary Table 1
Time(min:s)

Dispatcher

Caller (example)

0:00

Simulation starts
I need an ambulance.
This is 119, fire department. Is it a fire? Is it
an emergency?
Please tell me the address for the ambulance.

It is 1221-1, Kamoshida.

What is happening?

A little boy appears to be choking.

About how old?

11 months.

Is he conscious? Is he responsive to your He's responsive.
voice?
Is he breathing comfortably? Is he breathing He seems to be struggling.
normally?
Is he shivering or sweating? Is he pale?

He doesn't look good.

Start of first I'm going to instruct you on how to administer Ok.
aidfirst aid. Is that ok?
The ambulance is coming. Please stay calm.
Please perform what I say.
It seems like the child cannot speak, so put
him on your left arm, supporting his jaw withyour palm. Strike the middle of his back withyour other palm.
Video call group only: I'm texting you a URL
to click on so that you can send me video.
Continue until the object that is stuck comesout. Let me know if he loses consciousness.
4:00

He's lost consciousness.
Do you know CPR?

I don't.

I will tell you how to do it, so please keep Ok.
helping until the ambulance arrives.
Hold the child face up in your arm and press Ok.
his chest with 2 fingers.
Keep massaging the heart like this until the Ok.
paramedics arrive.
Keep at it, they'll be there soon.
7:00

Simulation ends

1

Association between prehospital intubation and survival of cardiac arrest

2

patients with foreign body airway obstruction: a multicenter3

observational study and propensity score-matching analysis

4

5

Yutaka Igarashia*, Tatsuya Noriib,c, Kim Sung-Hod, Shimpei Nagatae, Takashi

6

Tagamia,f, Yudai Yoshinoa,g, Takuro Hamaguchia,h, Riko Maejimaa,i, Shoji

7

Yokoboria and Hiroyuki Yokotaa

8

aDepartment of Emergency and Critical Care Medicine, Nippon Medical School, Tokyo,

9

Japan; bDepartment of Emergency Medicine, University of New Mexico, Albuquerque,

10

US; cTrauma and Acute Critical Care Center, Osaka University Hospital, Osaka, Japan,

11

dDepartment of Critical Care Medicine, Osaka Habikino Medical Center, Osaka, Japan;

12

eDepartment of Emergency Medicine, Osaka Police Hospital, Osaka, Japan;

13

fDepartment of Emergency and Critical Care Medicine, Nippon Medical School Musashi

14

Kosugi Hospital, Kawasaki, Japan; gDepartment of Emergency Medicine, Aizu Chuo

15

Hospital, Aizu Wakamatsu, Japan; hDepartment of Emergency Medicine, Iwaki City

16

Medical Center, Iwaki, Japan; iDepartment of Emergency Medicine, Japanese Red Cross

17

Ashikaga Hospital, Ashikaga, Japan

18
1

19

Corresponding author

20
21

Yutaka Igarashi

22

Telephone: +81-3-3822-2131

23

Fax: +81-3-3821-5102

24

Email address: igarashiy@nms.ac.jp

25

Postal address: 1-1-5 Sendagi, Bunkyo-ku, Tokyo, 113-8603, Japan

26

2

27

Abstract

28

Background: Foreign body airway obstruction (FBAO) is the leading cause of accidental

29

death in Japan. Several studies have shown that endotracheal intubation is associated30with a higher mortality rate among patients with out-of-hospital cardiac arrest (OHCA).

31

However, it is important to immediately reinitiate breathing in patients with FBAO

32

because hypoxemia causes cardiac arrest. Here, we aimed to determine whether

33

prehospital intubation is related to survival in patients with OHCA caused by FBAO. We

34

conducted a multicenter observational choking investigation (MOCHI) in patients with

35

OHCA caused by FBAO during 2014-2019. Patients were classified into the prehospital

36(intubated with an endotracheal tube but not supraglottic devices in a prehospital

37

setting) and hospital (intubated in the hospital) groups. The primary outcome was38

hospital survival and secondary outcomes were favorable neurological outcomes at39discharge and return of spontaneous circulation (ROSC). We performed propensity

40

score-matching analysis between the prehospital and hospital intubation groups.

41

Results: Of the 155 patients enrolled, 58 and 97 patients were classified into the42

prehospital and hospital groups, respectively. The baseline characteristics were43

comparable between the two groups. There was a significant difference between groups

44

in the unmatched (prehospital vs. hospital intubation, 35% vs. 14%; P = 0.005) and45

propensity score-matched (prehospital vs. hospital intubation, 34% vs. 16%, P = 0.049)

46

analyses.

47

Conclusion: Prehospital intubation was significantly associated with a higher survival rate

48

among patients with OHCA caused by FBAO. Prehospital intubation and bystander49

cardiopulmonary resuscitation were independent variables for improving hospital

50

survival.

51
3

52

Keywords: airway obstruction; cardiopulmonary arrest; emergency medical services;53

intubation; resuscitation.

4

54

Background55
56

Foreign body airway obstruction (FBAO) is a common medical emergency and major

57

public health concern worldwide(1, 2). More than 9,000 people die annually from FBAO,

58

which is the leading cause of accidental death in Japan(3).

59Patients with FBAO usually experience cardiac arrest within minutes due to hypoxia.

60

Basic life support guidelines recommend that cardiopulmonary resuscitation (CPR) be

61

performed according to the circulation-airway-breathing (C-A-B) sequence for patients62with cardiac arrest; however, they recommend five rescue breath followed by chest

63

compressions for patients with cardiac arrest due to drowning(4). Like drowning, the64

airway-breathing-circulation (A-B-C) sequence is more rational for patients with FBAO.

65

Therefore, it is reasonable to presume that prehospital or early airway management66

improves the outcomes of patients with cardiac arrest caused by FBAO. While67

emergency medical service (EMS) personnel commonly perform advanced airway

68

management in patients with out-of-hospital cardiac arrest (OHCA), a number of recent

69

studies have shown that prehospital airway management, especially endotracheal

70

intubation, is associated with higher mortality in patients with OHCA(5-10). However,71

prehospital intubation could improve patient outcome in patients with OHCA caused by

72

FBAO because it can dislodge foreign bodies and establish more sufficient ventilation

73

during CPR, compared with bag-valve-mask ventilation alone. Therefore, we aimed to74

assess whether prehospital intubation is associated with better outcomes compared to75

hospital intubation among patients with cardiac arrest due to FBAO. No studies have76

examined whether prehospital airway management is associated with favorable

77

outcomes for cardiac arrest patients with FBAO.

78
5

79
80

Results

81
82

Among all 386 FBAO patients during the study period, a total of 155 patients with FBAO

83

met the inclusion criteria (Figure 1). Among these patients, 58 were intubated before

84

hospital arrival and 97 patients were intubated after hospital arrival. Baseline85

characteristics were not significantly different between the two groups except for eating

86

function, location of accident, bread as a foreign body and MOCHI classification (Table

871). In the propensity score-matched analysis, 44 matched pairs were compared, and no88

significant differences were observed in baseline characteristics (Table 2). Five patients89

were intubated by emergency physicians from a physician-staffed ambulance on the90

scene.

91

There was a significant difference in hospital survival between the two groups in the92

unmatched (prehospital vs. hospital, 35% vs. 14%; P = 0.005) and the propensity score-93

matched (prehospital vs. hospital, 34% vs. 16%; P = 0.049) analyses. However, there were94

no significant differences in favorable neurological outcomes between the two groups in95

the unmatched (prehospital vs. hospital, 2% vs. 4%, P = 0.258) and propensity score-

96

matched (prehospital vs. hospital, 0% vs. 7%; P = 0.078) analyses or in the rate of ROSC

97

in the unmatched (prehospital vs. hospital, 81% vs. 73%; P = 0.431) and propensity score-98

matched (prehospital vs. hospital, 77% vs. 75%, P = 0.803) analyses (Table 3).

99

In multiple logistic regression analyses, prehospital intubation (odds ratio [OR], 3.66;

10095% confidence interval [CI], 1.59.8.44) and bystander CPR (OR, 2.67; 95% CI, 1.12–6.35)

101

were independent variables affecting survival (Table 4).

102

6

103

Discussion

104
105

We found that prehospital intubation in patients with OHCA caused by FBAO was106

associated with better survival at hospital discharge after adjusting for potential

107

confounders. Moreover, prehospital intubation and bystander CPR were independent108

predictors of better survival.

109

In contrast, prehospital intubation was not associated with favorable neurological110

outcomes. Previous studies have shown that only 2–4% of patients who experience111

cardiac arrest caused by FBAO have favorable neurological outcomes(11, 12). The rate of112

favorable neurological outcomes were lower. Patients who had a disability before

113

choking did not have favorable neurological outcomes, even though they recovered

114

completely. Although cerebral performance categories (CPCs) were common to evaluate

115

patient outcome in patients with OHCA, we have to consider other outcome evaluation

116

such as fully recovered before choking or avoiding dead and persistent vegetative state.

117

Removal of foreign bodies before the occurrence of cardiac arrest may be important for118

preventing neurological sequelae and death. Moreover, there was no significant

119

difference in the rate of ROSC between groups because both prehospital and hospital

120

groups were ventilated sufficiently.

121

In the multiple logistic regression analyses, prehospital intubation and bystander CPR

122

were independent predictors for better survival. Many studies have shown that123

bystander CPR improves the outcomes of patients with OHCA(13-16). Bystander CPR

124

performed before EMS arrival was associated with a 30-day increase in survival rate (OR,125

2.15; 95% CI, 1.88.2.45)(14). Consistent with this, the present study showed that126

bystander CPR was an independent factor for improving the survival rate. Because

127

prehospital intubation was the other independent predictor, prehospital intubation
7

128

could therefore improve outcomes for patients with cardiac arrest caused by FBAO.

129

In this study, the proportion of patients who underwent prehospital intubation was 37%.

130

In Japan, the proportion of patients with cardiac arrest who underwent prehospital

131

intubation range was 6-22%(7, 17, 18). This proportion was similar to that reported in132

the Republic of Korea and United Kingdom; however, it was much lower than that133

reported in the United States and Finland(19-21). Many factors affected whether

134

prehospital intubation was performed, such as the length of transfer, direction, and135

supervision of medical control.

136

This study had several limitations. First, some important variables were not collected.

137

For example, the time to ROSC was not evaluated, despite it being a significant

138

prognostic factor in OHCA patients(22). Although the time of FBAO was often recorded,139

the time of cardiac arrest was rarely noted. A high rate of ROSC suggested that effective

140

CPR was performed in both groups. Similarly, data on treatment after hospital admission

141

were not collected in this study despite the potential for therapeutic hypothermia to142

affect the outcomes(23). Further prospective studies are needed to collect the143

abovementioned data and to use the protocol for the treatment of post cardiac arrest

144

syndrome. Second, the hospital intubation group may have included patients whom EMT

145

personnel tried to intubate but failed, although another large cohort study had

146

encountered a similar problem(7). In Japan, the proportion of prehospital intubation147

success was around 90% in small studies(24). Thus, a low proportion of intubation failure

148

by EMS personnel had little effect on this study. Third, treatment by physicians from149

physician-staffed ambulances may also have affected patient outcomes. As there were150

only five patients who underwent prehospital intubation by physicians, the effect was151

therefore limited in this study.

152
8

153
154

Conclusions

155

This study revealed that prehospital intubation in patients with OHCA caused by FBAO

156

was associated with a higher survival rate at hospital discharge. Prehospital intubation157

and bystander CPR were independent variables for better survival. However, prehospital158

intubation was not associated with favorable neurological outcomes or the occurrence

159

of ROSC.

160
161
162

Methods

163
164

We conducted a multicenter retrospective observational study in the emergency

165

department of eight hospitals in Japan. This study formed a part of the multicenter

166

observational selection investigation (MOCHI)(25). This study was approved by the167

ethics committees of all participating institutions (29-02-901).

168
169

Participants

170

Patients with out-of-hospital cardiac arrest caused by FBAO who were transferred to the171emergency department and underwent endotracheal intubation were included in this172

study. The exclusion criteria were aspiration of gastric contents, sputum, and173

hemoptysis; drowning; giant thyroid tumors; unwitnessed cardiac arrest; and loss of174

consciousness before FBAO. Patients in whom supraglottic devices were used were also

175

excluded because it is not known whether endotracheal intubation and supraglottic

176

airways have potential benefits for improving patient outcomes.

177

We enrolled patients from eight hospitals in Japan from January 1, 2014 to January 31,91782019. The eight hospitals included two university hospitals in Tokyo (a population of 13.5

179

million and area of 2,191 km2) and Osaka (a population of 8.8 million and area of 1,905

180km2) defined as urban areas, three teaching hospitals in urban areas, and three teaching

181

hospitals in rural areas (outside Tokyo and Osaka). Three hospitals used physician-staffed182

ambulances to transport physicians to the emergency scene.

183
184

Prehospital setting

185

Prehospital intubation was performed by EMS personnel or physicians in a physician-186

staffed ambulance. In Japan, EMS personnel can perform intubation on patients with187

cardiac arrest by following online directions from physicians(26). EMS personnel can also

188

perform the following procedures on patients with cardiac arrest caused by FBAO:

189

removing foreign body using Magill forceps and suction, securing the airway using

190

supraglottic devices such as an esophageal obturator airway and laryngeal mask, and191

administering epinephrine. The choice of either endotracheal intubation or a bag-valve

192

mask was at the discretion of the EMS personnel under online direction from physicians.

193

Although all fire departments have established their own protocols, there are currently

194

no standard protocols for patients with FBAO in Japan.

195
196

Data collection

197

We collected the following data from the patients’ medical records: age, sex, eating

198

function, location of accident, witness to choking, first aid by layperson, foreign body199

removal with first aid, foreign body, bystander CPR, and initial rhythm.

200

We classified the location of the FBAO into three types based on the anatomical and201

physiological characteristics: type 1, upper airway obstruction by a large foreign body202

that cannot pass through the vocal cords or a large amount of residue that completely
10

203

obstructs the airway; type 2, trachea and/or bilateral main bronchus obstruction by a204

foreign body or a large amount of residue; and type 3, unilateral bronchus and/or distal

205

bronchus obstruction by a foreign body, residue, or liquid(25). More than two raters

206

evaluated the cases in a blinded manner and classified them into three types in

207

accordance with the MOCHI algorithm (supplementary figure 1) (27).

208

The primary outcome was survival at hospital discharge. Secondary outcomes were209

neurological function at hospital discharge and return of spontaneous circulation (ROSC).

210

Neurological function was evaluated using CPCs(28). A favorable outcome was defined211

as CPC 1 (full recovery) or 2 (moderate disability), and an unfavorable outcome was212

defined as CPC 3 (severe disability), 4 (persistent vegetative state), or 5 (death).

213
214

Statistical analysis

215

Categorical variables are reported as the number and percentage of individuals and were216

analyzed using the chi-squared test or Fisher’s exact test. Continuous variables are217

reported as the median and interquartile range and were analyzed using a Mann-

218

Whitney U test. We performed propensity score-matching analysis between the219

prehospital and hospital intubation groups based on the estimated propensity score(29).

220

The propensity score was estimated using a logistic regression model for prehospital221

intubation as a function of the following patient characteristics and other factors: age,

222

sex, witness to cardiac arrest, bystander CPR, and MOCHI classification(13-16), accident

223

location, eating function, witness to choking, first aid by layperson, foreign body removal,

224

and initial rhythm. We performed a one-to-one matched analysis using nearest-neighbor

225

matching based on the estimated patient propensity scores. A match occurred when a226patient in the prehospital intubation group had an estimated score within 0.2 standard

227

deviations of a patient in the hospital intubation group.
11

228

Multivariate analysis was also performed as sensitivity analysis. Prehospital intubation,229

rice cake (mochi) as a foreign body, bystander CPR and age were chosen for multivariate

230

logistic regression analysis. Bystander CPR and age are known predictors of survival for231

patients with OHCA(13-16). P-values <0.05 were considered statistically significant. We

232

used SPSS software version 25 for statistical analyses (IBM Company, Chicago, IL, USA).

233

12

234

List of abbreviations

235

A-B-C: airway-breathing-circulation

236

C-A-B: circulation-airway-breathing237

CI: confidence interval

238

CPCs: cerebral performance categories

239

CPR: cardiopulmonary resuscitation

240

EMS: emergency medical service

241

FBAO: Foreign body airway obstruction

242

MOCHI: multicenter observational choking investigation

243

OHCA: out-of-hospital cardiac arrest244

OR: odds ratio

245

ROSC: return of spontaneous circulation

246
247

Declarations

248

Ethics approval and consent to participate: This study was approved by the ethics

249

committees of all participating institutions (29-02-901).

250

Consent for publication: Not applicable

251

Availability of data and materials: The datasets generated and/or analysed during the252

current study are not publicly available due to more unpublished articles but are

253

available from the corresponding author on reasonable request.

254

Competing interests: None

255

Funding: Foundation for Ambulance Service Development

256

Authors' contributions: Yutaka Igarashi, project administration, original manuscript;

257

Tatsuya Norii, project administration, review; Kim Sung-Ho, investigation; Shimpei

258

Nagata, investigation; Takashi Tagami, supervision; Yudai Yoshino, investigation;
13

259

Takuro Hamaguchi, investigation; Riko Maejima, investigation; Shoji Yokobori,260

supervision; Hiroyuki Yokota, supervision.

261

Acknowledgements: This study was supported by Foundation for Ambulance Service

262

Development. We would like to thank the directors and doctors of each participating

263

institution: Dr. Tatsuho Kobayashi (Aizu Chuo Hospital); Dr. Atsushi Koyama (Iwaki City

264

Medical Center); Dr. Naoto Yoshida (Ashikaga Red Cross Hospital); Prof. Takeshi Shimazu

265

and Dr. Shunichiro Nakao (Osaka University Graduate School of Medicine); Dr. Tetsuya

266

Hirota and Dr. Park Changhwi (Tane General Hospital); Dr. Yasuaki Mizushima (Osaka

267

Police Hospital); and Dr. Yozo Kashiwa (Osaka Habikino Medical Center).

14

268

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Hiltunen P, Jantti H, Silfvast T, Kuisma M, Kurola J, group FPs. Airway management inKang K, Kim T, Ro YS, Kim YJ, Song KJ, Shin SD. Prehospital endotracheal intubation

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Kawano Y, Shimokawa M, Kawaguchi M, Furuya H. Retrospective analysis of cases

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nationwide prospective, observational cohort study of foreign-body airway obstruction in Japan:349

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355

18

356

Figure legends

357

Figure 1. Inclusion criteria

358
359

Supplementary figure legends

360

Supplementary figure 1. MOCHI algorithm

361

FB, foreign body; MOCHI, Multi-center Observational Choking Investigation.

19

362

Disclosure363

Approval of the research protocol: 29-02-901

364

Informed consent: waived

365

Registry and the Registration No. of the study/trial: none

366

Conflicts of Interest: none

367

Funding: Foundation for Ambulance Service Development

20

Table 1
Demographics of patients with OHCA caused by FBAO

Characteristic

Prehospital intubation

Hospital intubation(N = 58)(N = 97)

Age, year, mean (interquartile rage)

83 (76–86)

82 (74.8–88)

0.62

Sex (female), n (%)

26 (45%)47 (48%)0.66

Eating function

P-value

0.45

Independent, n (%)

35 (60%)62 (74%)

Requiring assistance, n (%)

20 (34%)27 (28%)Location of accident

0.007

Home, n (%)

24 (41%)65 (67%)

Healthcare facility, n (%)

25 (43%)25 (26%)

Public, n (%)

9 (16%)

7 (7%)

Witness to choking, n (%)

47 (81%)78 (80%)0.92

First aid by layperson, n (%)

22 (38%)32 (33%)0.53

Foreign body removal with first aid, n (%)

2 (3%)

6 (6%)

0.46

Rice, n (%)

5 (9%)

16 (16%)

0.17

Mochi (rice cake), n (%)

3 (5%)

11 (11%)

0.19

Bread, n (%)

15 (26%)10 (10%)0.01

Meat, n (%)

7 (12%)

9 (9%)

0.58

Foreign body

MOCHI classification*

0.01

Type 1, n (%)

44 (76%)55 (57%)

Type 2, n (%)

7 (12%)

8 (8%)

Type 3, n (%)

3 (5%)

7 (7%)

Unknown, n (%)

4 (7%)

27 (28%)Bystander CPR, n (%)

29 (50%)43 (44%)

Initial rhythm

0.49
0.35

Asystole, n (%)

23 (40%)48 (49%)

PEA, n (%)

21 (36%)26 (27%)Vf, n (%)

1 (2%)

0 (0%)

Unknown, n (%)

5 (9%)

10 (10%)Table 2
Demographics of patients with OHCA caused by FBAO after propensity score matching

Characteristic

Age, year, mean (interquartile rage)
Sex (female), n (%)

Prehospital intubation

Hospital intubation(N = 44)(N = 44)83.5 (75.5-86)

83 (77.5-88)

0.48

24 (55%)21 (48%)0.52

Eating function

P-value

0.71

Independent, n (%)

28 (64%)26 (59%)Requiring assistance, n (%)

14 (32%)17 (39%)Location of accident

0.97

Home, n (%)

23 (52%)22 (50%)

Healthcare facility, n (%)

17 (39%)18 (41%)

Public, n (%)

4 (9%)

4 (9%)

Witness to choking, n (%)

38 (86%)36 (82%)

0.56

First aid by layperson, n (%)

17 (%)

16 (%)

0.83

Foreign body removal with first aid, n (%)

2 (%)

2 (%)

1.00

Rice, n (%)

5 (%)

7 (%)

0.53

Mochi (rice cake), n (%)

3 (%)

5 (%)

0.46

Bread, n (%)

11 (%)

5 (%)

0.10

Meat, n (%)

6 (%)

2 (%)

0.14

Type 1, n (%)

34 (77%)31 (70%)0.47

Type 2, n (%)

4 (9%)

6 (14%)

0.50

Type 3, n (%)

3 (7%)

3 (7%)

1.00

Unknown, n (%)

3 (7%)

4 (9%)

0.69

Bystander CPR, n (%)

21 (48%)21 (48%)1.00

Asystole, n (%)

18 (%)

16 (%)

0.66

PEA, n (%)

13 (%)

15 (%)

0.65

Vf, n (%)

0 (%)

0 (%)

1.00

Unknown, n (%)

5 (%)

5 (%)

1.00

Foreign body

MOCHI classification*

Initial rhythmTable 3.
Outcomes of patients who underwent prehospital endotracheal intubation and endotracheal intubation in the hospital
Unmatched
Prehospital intubation

Hospital intubation(N = 58)(N = 97)

20 (35%)14 (14%)

Favorable neurological outcome

1 (2%)ROSC

47 (81%)

Propensity score-matched
P-value

Prehospital intubation

Hospital intubation

P-value(N = 44)(N = 44)0.005

15 (34%)7 (16%)

0.049

4 (4%)

0.258

0 (0%)

3 (7%)

0.078

71 (73%)0.431

34 (77%)33 (75%)0.803

Primary outcome
Hospital survival
Secondary outcomes

CPC, cerebral performance category; ROSC, return of spontaneous circulation.

Association between Time of Airway Obstruction by Foreign Bodies and
Neurological Outcomes: MOCHI
Yutaka Igarashi1
Tatsuya Norii2,3
Kim Sung-Ho4
Shimpei Nagata5
Yudai Yoshino1,6
Takuro Hamaguchi1,6
Riko Maejima1,7
Shunichiro Nakao3
Takashi Tagami1,4
Shoji Yokobori1
1) Department of Emergency and Critical Care Medicine, Nippon Medical School
1-1-5 Sendagi, Bunkyo, Tokyo, 113-8603, Japan
2) Department of Emergency Medicine, University of New Mexico
700 Camino de Salud, Albuquerque, NM 87131, United States3) Department of Traumatology and Acute Critical Medicine, Osaka University
Graduate School of Medicine
4) Senshu Trauma and Critical Care Center
2-23 Rinku Ourai Kita, Izumisano, Osaka, 598-8577, Japan
5) Department of Clinical Epidemiology and Health Economics, The University ofTokyo
7-3-1 Hongo, Bunkyo, Tokyo, 113-8654, Japan
6) Department of Emergency and Critical Care Medicine, Aidu Chuo Hospital
1-1 Tsurugamachi, Aizuwakamatsu, Fukushima, 965-8611, Japan
7) Department of Emergency and Critical Care Medicine, Nippon Medical School
Musashi Kosugi Hospital1-396 Kosugicho, Nakahara, Kawasaki, Kanagawa, 2118533, Japan

Corresponding author
Yutaka Igarashi, MD, PhD
Department of Emergency and Critical Care Medicine, Nippon Medical School
1-1-5 Sendagi, Bunkyo, Tokyo, 113-8603, Japan
Tel: +81-3-3822-2131
Fax: +81-3-3821-5102
Email: igarashiy@nms.ac.jp

1

Running headTime of Airway Obstruction and Outcomes
Word counts
Abstract: 249 words
Main document: 1,706 words2

Abstract

Aim: Foreign body airway obstruction is a major public health concern worldwide.
Decreases in no- and low-flow time are strongly correlated with better neurologicaloutcomes. As no study has assessed the relationship between airway occlusion time andneurological outcomes, this study examined the relationship.
Methods: This multi-center retrospective observational study conducted in Japan
included patients with foreign body airway obstruction over a period of 4 years. Data
were extracted from electronic health records. Cerebral function was measured based onby the cerebral performance category (CPC) score. The primary outcome wasunfavorable outcomes, which were defined as CPC 4 or 5 at discharge.
Results: Among 386 patients in the MOCHI registry, 119 were enrolled in this study. In
17 patients, foreign bodies were removed in ≤5 min; 15 patients in 6–10 min; 40
patients in 11–20 min; and 47 patients in ≥21 min. The proportion of unfavorable
outcomes in the ≤5 min group was significantly lower than that in the other groups (≤5min, 6% vs 6–10 min, 47%, P=0.01; vs 11–20 min, 68%, P<0.001; vs ≥21 min, 70%,
P<0.001). Multivariate analysis showed that airway occlusion time ≥6 min (odds ratio[OR] 32.6; 95% confidence interval [CI] 4.0–264) and age ≥75 years (OR 2.5; 95% CI
1.00 - 6.37) were independent poor prognostic factors.
Conclusion: The proportion of unfavorable outcomes and mortality increased withincreasing airway obstruction time. It is important to remove foreign bodies within 5
min for patients with foreign body airway obstruction.

3

Keywords
Foreign body airway obstruction; Resuscitation; Airway management; Cardiac Arrest

4Introduction

Foreign body airway obstruction (FBAO) was the third cause of accidental deaths in the
US and killed approximately 4,000 people annually. 1FBAO was also the second causeof accidental death in Japan and killed more than 8,000 people annually.2 FBAO is amajor public health concern worldwide.
Both FBAO and out-of-hospital cardiac arrest (OHCA) correlate with first aid
bystanders and outcomes,3, 4 and first aid has been strongly recommended in guidelines
for basic life support.5, 6 In the case of OHCA, two time components have been defined:
no-flow time, i.e., the time from collapse to the start of bystander first aid, and low-flow
time, i.e., the time from the start of cardiopulmonary resuscitation (CPR) to the return ofspontaneous circulation. Adnet et al. found that decreases of no-flow time and low-flowtime values improved 30-day survival in patients with cardiac arrest.7 However, no
study has clarified the relationship between airway occlusion time and neurologicaloutcomes. Thus, this study aimed to reveal the relationship between airway occlusion
time and neurological outcomes to plan more effective initial treatments for patientswith FBAO.

5

Methods

Study design
This study was a retrospective observational study, the Multi-center Observational
CHoking Investigation (MOCHI) in Japan. In total, eight hospitals, two university
hospitals, and six general hospitals, comparable to level 1 or 2 trauma centers in theUSA, participated in this study. Ethics committee approval was obtained at all sites,
including the representative site (Nippon Medical School Hospital, 29-02-901).

Patient enrolment
We included adult patients with life-threatening mechanical airway obstruction causedby foreign bodies in the airway from 1 January 2015 to 28 February 2019. We excluded
patients with aspiration of sputum or gastric contents, loss of consciousness before
FBAO, a neck tumor that caused suffocation, or unwitnessed cardiac arrest or those whodrowned.
Additionally, patients with FBAO above the glottis (i.e., MOCHI classification type 1)
were included to accurately diagnose FBAO and target a more homogenous group.8
MOCHI classification type 1 is defined as upper airway obstruction by a large foreign
body that cannot pass through the vocal cords or a large amount of residue thatcompletely obstructs the airway.

Data collection
Data were extracted from electronic health records. Duration of airway obstruction was
calculated from the time of the accident to the time of removing foreign bodies. We
6

divided the duration of airway obstruction into four groups: ≤5 min, 6–10 min, 11–20
min, and ≥21 min referring to studies of drowning time and outcome.9 We collected thefollowing data regarding all patients: age, sex, comorbidity, activities of daily living,
living situation, eating function, accident location, witness removal attempt, witness
removal success, foreign bodies as a cause of choking, opening airway maneuver, andpeople performing first aid. We also collected the following data regarding patients who
had OHCA: presence of witness of cardiac arrest, bystander CPR, initial rhythm in thefield, intubation in the field, and return of spontaneous circulation.

Outcomes
Cerebral function is measured based on the cerebral performance category (CPC)score.10 The primary outcome was defined as unfavorable outcomes, which were
defined as a CPC score of either 4 (coma) or 5 (death) at discharge from the hospitals.
The secondary outcome was defined as hospital death and occurrence of cardiac arrest.

Statistical analysis
Continuous variables are presented as means and interquartile ranges and analyzed
using the Mann-Whitney U test. Categorical variables were analyzed using the chisquared test or Fisher’s exact test as appropriate. The group with duration of airway
obstruction ≤5 min was considered the reference, and other groups were compared withthe ≤5 min group. In the multivariate analysis, we selected unfavorable neurologicaloutcome as a dependent variable and the following as explanatory variables: age (≥75
years), sex (male), partially or fully dependent, home as a location, duration of airway

7

obstruction (≥6 min). P values <0.05 were considered statistically significant. We used
StatFlex version 6.0 (Artech Co., Ltd., Osaka, Japan) for statistical analysis.

Results

Among 386 patients in the MOCHI registry, 119 patients were enrolled in this study. In
17 patients, foreign bodies were removed in ≤5 min; 15 patients in 6–10 min; 40
patients in 11–20 min; and 47 patients in ≥21 min (Figure 1).

No significant differences were observed in patient characteristics between the ≤5 mingroup and the other groups (Table 1). Furthermore, there were no significant differencesin the food causing the FBAO between the ≤5 min group and the other groups. Among
patients in a nursing home, there were significantly more bystander removal attempts inthe ≤5 min group than in the 11–20 min (P=0.01) and ≥21 min (P=0.04) groups. There
was no significant difference in the opening maneuver among groups except for Magill
forceps.

The proportion of unfavorable outcomes in the ≤5 min group was significantly lower
than that in the other groups (≤5 min, 6% vs 6–10 min, 47%, P=0.01; vs 11–20 min,
68%, P<0.001; vs ≥21 min, 70%, P<0.001) (Figure 2). Furthermore, the mortality ratein the ≤5 min group was significantly higher than that in the other groups (≤5 min, 6%
vs 6–10 min, 20%, P=0.32; vs 11–20 min, 56%, P<0.001; vs ≥21 min, 64%, P<0.001).
8

The proportion of mortality in the 6–10 min group was also higher than that in the 11–
20 min and ≥21 min groups (6–10 min, 20% vs 11–20 min, 56%, P=0.03; vs ≥21 min,
64%, P=0.008).

The number of patients with OHCA was 69 (58%), and the number of OHCA in the ≤5
min group was significantly lower than that in the other groups (≤5 min, 6% vs 6–10
min, 53%, P=0.005; vs 11–20 min, 70%, P<0.001; vs ≥21 min, 68%, P<0.001). Among
patients with OHCA, the initial rhythm was asystole in 36 patients (52%), withpulseless electrical activity in 26 patients (38%), and 61 (88%) had return ofspontaneous circulation, one (1%) had CPC 2, and two (3%) had CPC 3 (Table 2).

Multivariate analysis showed that airway occlusion time ≥6 min (odds ratio [OR] 32.6;
95% confidence interval [CI] 4.0–264; P=0.001) and age >75 years (OR 2.5; 95% CI
1.00–6.37; P=0.049) were independent poor prognostic factors (Table 3).

Discussion

The proportion of unfavorable outcomes and survival was significantly lower in thegroup with an airway obstruction time of ≤5 min than in the other groups.

If the airway obstruction time is ≤5 min, the possibility of sequelae is very low. Only
one patient (6%) in our study had cardiac arrest and died, and no patients had a9vegetative state. Thus, 5 min can be a target time for foreign body removal in a choking
patient. Among patients with foreign bodies removed in ≤5 min, 47% of patients had
severe disability (CPC 3) because only 42% of patients had independent activities ofdaily living, and full recovery did not result in good recovery (CPC 1) or moderate
disability (CPC 2).

In drowning, which also causes hypoxia, submersion time of ≤5 min is related to a 10%
rate of death or severe neurologic impairments. The rate of death or severe neurologic
impairments with a submersion time of 6–10 min is 56%, with 11–25 min is 88%, andwith >25 min is almost 100%11-14. Thus, FBAO is similar to drowning in that theoutcomes differ greatly after 5 min.

There was no difference in food items in each group. Choking with rice cake (mochi) is
common in Japan,15 and it is thought to easily cause obstruction because of its
consistency;16 however, we did not find rice cakes difficult to remove, as reported inprevious studies.17

In nursing homes, there were significantly more patients in the ≤5 min group than in the
11–20 min and longer groups. We surmise that nurses and caregivers were present andsuction equipment was available, which may have led to earlier removal of foreign
bodies.

In Japan, the average time from emergency call to arrival at the scene is 8.7 min18.
Therefore, it is unlikely that emergency medical technicians can remove a foreign body10

within 5 min. The neurological prognosis of patients with a foreign body removed by a
bystander is better than that of patients with a foreign body removed by EMS (bystander
vs. EMS, 74% versus 32%; P=0.008).4 In this study, only 42% of patients had removal
attempts performed by bystanders. Thus, further promotion of first aid is recommended
among families living with elderly people and nursing homes.

When rescuers are unable to administer first aid, oral instruction by dispatchers isimportant. In the past, verbal guidance of first aid for cardiopulmonary arrest patients
has improved survival rates and neurological outcomes.19-22 Furthermore, with thewidespread use of smartphones, the use of video calls for verbal instruction has
improved the quality of CPR with more appropriate depth of chest compressions andhand positioning.23 The effect of verbal instruction by dispatchers on first aid for
choking is unknown and needs to be studied further.

This is the first study to reveal the relationship between airway obstruction time andprognosis in patients with FBAO.
This study had some limitations. First, it was a retrospective study, and the number ofcases was small because many of them did not have the time recorded. In addition, thetime was recorded by personal interview, which may have led to errors. A larger
prospective study is needed, and the planned Japanese MOCHI study will prospectively
collect data on patients with FBAO to improve knowledge and understanding of theepidemiology and treatment.24 Second, Some patients had good outcomes even if it took
a long time to remove the foreign body. Depending on whether the airway obstruction11was complete (no air flow) or partial (low air flow), the outcomes may differ even withthe same obstruction time. In addition, there is a possibility that no air flow and low air
flow may change owing to the movement of foreign bodies. However, there is noobjective method for continuous evaluation because it is only possible to subjectively
evaluate air entry via bag-valve-mask ventilation.

Conclusions

The proportion of unfavorable outcomes and mortality increased with increasing airway
obstruction time. In patients with FBAO, it is important to remove foreign bodies within
5 min. Airway obstruction for ≥6 min and age ≥75 years were poor prognostic factors.

12

Acknowledgements

The authors thank the following study hospitals and research personnel for theirassistance with this project: Dr. Tatsuho Kobayashi (Aidu Chuo Hospital), Dr. Naoto
Yoshida (Ashikaga Red Cross Hospital), Dr. Atsushi Koyama (Iwaki City Medical
Center), Dr. Yasuaki Mizushima (Osaka Police Hospital), Dr. Tetsuya Hirota, and Dr.
Park Changhwi (Tane General Hospital), Dr. Yozo Kashiwa (Osaka Habikino Medical
Center), Prof. Takeshi Shimazu (Osaka University Graduate School of Medicine) and all
personnel at participating hospitals who contributed the data.

Disclosure

Approval of the research protocol: Ethics committee approval was obtained at all sites,
including the representative site (Nippon Medical School Hospital, 29-02-901).

Informed Consent: Informed consent was waived because of the retrospective nature of
the study and the analysis used anonymous clinical data. Opt-outs were posted, andpatients who did not wish to cooperate in the study were guaranteed the right to noncooperation.

Registry and the Registration No. of the study/trial:N/A

Animal Studies: N/A
13

Conflict of Interest: Nothing to declare.

Funding: This study was conducted with funding from the Japanese Association for
Acute Medicine and the Foundation for Ambulance Service Development.

14

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17Figure legends

Fig. 1
Patient chart flow

Fig. 2
Relationship between airway occlusion time and neurological outcome
CPC 1, Good cerebral performance. Conscious. Alert, able to work and lead a normal
life; CPC 2, Moderate cerebral disability. Conscious. Sufficient cerebral function forpart time work in sheltered environment; CPC 3, Severe cerebral disability. Conscious.
Dependent on others; CPC 4, Coma, vegetative state. Not conscious; CPC 5, Death.
Certified brain dead or dead by traditional criteria10. CPC: cerebral performance
categories.

18

386 Patients were assessed for eligibility(All patients registered in MOCHI registry)
267 Were excluded
234 Did not record the time completely
33 Were not classified into MOCHI type 1
119 Were enrolled

17 Had foreign bodies
removed ≤5 min

15 Had foreign bodies
removed in 6–10 min

40 Had foreign bodies
removed in 11–20 min

47 Had foreign bodies
removed ≥21 min

Table 1
Patient demographics≤5 (n=17)n (%)

6-10 (n=15)

11-20 (n=40)≥21 (n=47)

n (%)

P valuen (%)

P valuen (%)

P valueAge

81 (73-85) 77 (72-87)

0.86

81 (75-86)

0.85

81 (75-88)

0.76

Sex (male)

9 (53%)

8 (53%)

0.98

19 (48%)0.71

23 (49%)0.78

Comorbidity
Cerebral infarction
Dementia
Schizophrenia
Depression
Parkinson’s disease
Aspiration
Diabetes
Hypertension
Coronary artery disease

3 (18%)
5 (29%)
0 (0%)
1 (6%)
2 (12%)
1 (6%)
2 (12%)
6 (35%)
0 (0%)

5 (33%)
5 (33%)
2 (13%)
2 (13%)
1 (7%)
1 (7%)
4 (27%)
4 (27%)
0 (0%)

0.42
1.00
0.21
0.59
1.00
1.00
0.38
0.71
1.00

6 (15%)
14 (35%)2 (5%)
4 (10%)
2 (5%)
0 (0%)
8 (20%)
14 (35%)4 (10%)

1.00
0.68
0.57
1.00
0.57
0.30
0.71
0.98
0.31

12 (26%)
14 (30%)2 (4%)
4 (9%)
0 (0%)
1 (2%)
5 (11%)
18 (38%)5 (11%)

0.74
0.98
0.60
1.00
0.07
1.00
1.00
0.83
0.31

Activity of daily living
Independent
Needs some assistanceBedridden

7 (42%)
5 (29%)
4 (24%)

4 (27%)
7 (47%)
0 (0%)

0.39
0.31
0.10

20 (50%)13 (33%)
3 (8%)

0.54
0.82
0.18

15 (32%)20 (43%)5 (11%)

0.49
0.34
0.23

Eating function
Independent
Requiring assistance

11 (65%)6 (35%)

13 (87%)
2 (13%)

0.23
0.21

31 (78%)7 (18%)

0.34
0.15

34 (72%)9 (19%)

0.55
0.16

Accident location
Home
Group home
Nursing home
Restaurant

6 (35%)
0 (0%)
7 (41%)
1 (6%)

8 (53%)
2 (13%)
2 (13%)
0 (0%)

0.30
0.21
0.12
1.00

21 (53%)6 (15%)
4 (10%)
4 (10%)

0.23
0.16
0.01
1.00

26 (55%)6 (13%)
7 (15%)
5 (11%)

0.16
0.18
0.04
0.68

Obstructed objects
Rice
Rice cake (mochi)
Bread
Meat

0 (0%)
2 (12%)
3 (18%)
3 (18%)

1 (7%)
6 (40%)
3 (20%)
3 (20%)

0.47
0.11
1.00
1.00

4 (10%)
8 (20%)
7 (18%)
5 (13%)

0.31
0.71
1.00
0.68

11 (23%)7 (15%)
4 (9%)
10 (21%)

0.05
1.00
0.37
1.00

Bystander removal attempt

15 (88%)4 (27%)<0.001

12 (30%)<0.00119 (40%)<0.001

Timing of successful airway opening
Before EMS arrival
On the scene/before arriving hospitalIn the hospital

15 (88%)1 (6%)
1 (6%)

3 (20%)
7 (47%)
1 (7%)<0.0010.01
1.00

1 (3%)
28 (70%)6 (15%)<0.001<0.0010.43

1 (2%)
16 (34%)28 (60%)<0.0010.03
0.0001

Opening maneuver
Abdominal thrust
Backblow
Chest thrust/compression
Removal with hands
Magill forceps
SuctionVacuum cleaner

0 (0%)
7 (41%)
1 (6%)
4 (24%)
0 (0%)
5 (30%)
0 (0%)

1 (7%)
2 (13%)
1 (7%)
0 (0%)
6 (40%)
3 (20%)
1 (7%)

0.47
0.21
1.00
0.10
0.006
0.69
0.47

2 (5%)
7 (18%)
5 (13%)
4 (10%)
10 (25%)
11 (28%)0 (0%)

0.57
0.09
0.66
0.22
0.05
1.00
1.00

3 (6%)
6 (13%)
13 (28%)7 (15%)
13 (28%)21 (45%)
1 (2%)

0.56
0.18
0.09
0.46
0.03
0.27
1.00

Out-of-hospital cardiac arrest

1 (6%)

8 (53%)

0.005

28 (70%)<0.00132 (68%)<0.001

EMS, emergency medical services

Table 2
Demographics and neurological outcomes of the patients who suffered cardiac arrest
caused by FBAO
≤5
(n=1)

6-10
(n=8)

11-20
(n=28)≥21(n=32)

Witness of cardiac arrest

0 (0%)

7 (88%)

25 (89%)27 (84%)

Bystander CPR

0 (0%)

3 (38%)

15 (54%)17 (53%)

Initial rhythm
Asystole
PEA
Vf/pulseless VT
Unknown

0 (0%)
0 (0%)
0 (0%)
1 (100%)3 (38%)
4 (50%)
0 (0%)
0 (0%)

11 (39%)14 (50%)0 (0%)
3 (11%)

22 (69%)8 (25%)
0 (0%)
2 (6%)

Airway management
Bag-valve-mask
Extraglottic airway device
Endotracheal intubation

1 (100%)0 (0%)
0 (0%)

2 (25%)
3 (38%)
3 (38%)

5 (18%)
11 (39%)13 (46%)

14 (44%)15 (47%)7 (22%)

Return of spontaneous resuscitation

1 (100%)7 (88%)

25 (89%)28 (88%)

Neurological outcomes
CPC 1
CPC 2
CPC 3
CPC 4
CPC 5

0 (0%)
0 (0%)
0 (0%)
0 (0%)
1 (100%)0 (0%)
1 (13%)
0 (0%)
4 (50%)
3 (38%)

0 (0%)
0 (0%)
2 (7%)
5 (18%)
21 (75%)0 (0%)
0 (0%)
0 (0%)
3 (9%)
29 (91%)

CPC, Cerebral performance categories; CPR, cardiopulmonary resuscitation; PEA,
pulseless electrical activity; Vf, ventricular fibrillation; VT, ventricular tachycardia.

Table 3
Association of patient characteristics with unfavorable neurological outcomes
Variables

Odds ratio (95% confidence interval)≥6 min32.6 (4.0 - 264)

Age ≥75

2.53 (1.00 - 6.37)

Home

1.56 (0.65 - 3.72)

ADL dependent 1.60 (0.70 - 3.70)
Sex (male)

0.54 (0.23 - 1.28)

ADL, activity of daily living.