Prospective Evaluation of Foreign Body Airway Obstruction Interventions Among Adults and Children: A Non-randomized Pilot Cohort Study
Conditions: Foreign Body Airway Obstruction
Sponsor: University of Calgary

Prospective Evaluation of Foreign Body Airway Obstruction 
Interventions Among Adults and Children:  A Non-randomized 
Pilot Cohort Study 
 
STUDY PROTOCOL AND STATISTICAL ANALYSIS PLAN 
 
October 16th, 2025 – Version 1 
October 27th, 2025 – Version 2 
o Updated sample size calculation, and analysis of e4ectiveness 
outcomes.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 
Objectives 
• Primary: 
o To determine the feasibility of prospectively identifying and recruiting 
patients with foreign body airway obstruction (FBAO) in Alberta, Canada. 
• Secondary:  
o To determine the eDectiveness and safety of basic life support (BLS) FBAO 
interventions among diDerent patient age categories experiencing out-of-
hospital FBAO  
Research Question – Feasibility Study (Primary Objective) 
1. What is the rate of eligible FBAO patients recruited per month through prospective 
identiﬁcation in Alberta, Canada, and what proportion of satisfactory data 
collection is obtained? 
Research Questions – Future EFectiveness and Safety Studies (Secondary 
Objective) 
1. Among conscious adults and children with an out-of-hospital FBAO, which initial 
BLS FBAO intervention (abdominal thrusts, back blows or chest compressions) is 
more eDective and safer? 
2. Among conscious adults and children with an out-of-FBAO who failed initial 
management, is continuing the same intervention more eDective than changing 
interventions? 
3. Among conscious adults and children with an out-of-hospital FBAO who failed 
initial management, which BLS FBAO intervention or combination of interventions is 
more eDective and safer? 
Methods 
Study Design 
We will conduct a study to assess the feasibility of identifying and recruiting a prospective 
cohort of patients who experience an out-of-hospital FBAO in Alberta, Canada. The results 
of this pilot study will inform a future appropriately powered prospective cohort study 
examining the eDectiveness and safety of FBAO interventions.  
We will follow two reporting guidelines to ensure inclusion of all relevant sections:  
• Consolidated Standards of Reporting Trials (CONSORT) extension to randomised 
pilot and feasibility trials [1] 
• STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) 
guideline [2] 

The Conjoint Health Research Ethics Board of the University of Calgary (REB25-0419) and 
Alberta Health Services approved the study. 
 
Setting 
The study will be conducted in Alberta, Canada, where a single, publicly funded health 
authority (Alberta Health Services) delivers healthcare services, including emergency 
medical services (EMS) delivered by paramedics, to a population of 4.4 million people. 
Three levels of EMS care exist: Emergency Medical Responder (EMR), Primary Care 
Paramedic (PCP), and Advanced Care Paramedic (ACP). ACPs can perform advanced FBAO 
interventions like Magill forceps removal and intubation, while all levels receive training on 
basic interventions. 
Study Population 
Eligible patients will be adults or children aged older than 2 years who experience an out-
of-hospital FBAO and are assessed by EMS or attend an emergency department for the 
incident. We deﬁne FBAO cases as individuals who present with a history of an object or 
substance not native to the airway introduced, followed by clinical signs of obstruction 
(e.g., stridor, cyanosis, hypoxemia, inability to move air) [3,4]. 
Only patients who are conscious when they receive the ﬁrst FBAO intervention will be 
included. We will exclude cases where the patient has abnormal airway anatomy such as a 
tracheostomy, or who are unconscious upon receipt of ﬁrst FBAO intervention. 
Patient Identiﬁcation  
FBAO cases will be prospectively identiﬁed through two strategies: 
1. A notiﬁcation will be sent to researchers using Alberta Health Services’ EMS 
electronic Patient Care Record (ePCR; Siren ePCR Version 4.6.26, Medusa Medical 
Technologies, Halifax, NS) when a case meets validated FBAO identiﬁcation criteria 
based on paramedic diagnosis, protocol use, or treatment applied [4]. 
• The ePCR is the sole paramedic prehospital charting system used in Alberta 
and therefore includes population-based data for the province, including 
demographics, vital signs, and standardized reporting of incident, patient, and 
treatment details. It also includes a free-text narrative synopsis, including 
information on the events preceding the FBAO, interventions performed by 
bystanders, patient assessments, and all interventions 
 
2. A notiﬁcation will be sent to researchers when a patient presents to an Alberta 
emergency department with an FBAO-related complaint (e.g., respiratory foreign 
body, respiratory arrest, stridor, dysphagia, cardiac arrest). 
 
An emergency medicine physician will review identiﬁed cases to determine whether they 
meet the FBAO deﬁnition, based on the paramedic and emergency medicine 

documentation, vital signs, and imaging. A second physician will review 10% of cases to 
ensure excellent interrater reliability (Cohen’s kappa > 0.8).  
Patient Recruitment and Consent 
Adult patients, or the primary parent(s)/caregiver(s) of pediatric patients, will be contacted 
by a healthcare provider not aDiliated with the research team once identiﬁed as an FBAO 
case to seek their interest in participating by telephone. If agreeable to participate, a 
research assistant will subsequently follow up with the patient (or parent/caregiver) to 
obtain informed consent and complete a short interview for data collection.  
In the case that a patient is unable to participate in an interview due to severe injury, death, 
or inability to be contacted, then a waiver of consent has been obtained to use the medical 
record for data collection. 
All eligible participants will be recruited consecutively. We will conduct the pilot over a 
period of 6 months from November 1st, 2025, to April 30th, 2026. If we proceed with a larger 
eDectiveness study (see Sample Size below), the research team will decide based on 
available resources at that time if we will immediately continue with recruitment and 
include the pilot study’s patients in the larger study’s cohort.  
Data Collection 
Research assistants will conduct virtual structured interviews. We will develop a 
standardized data collection tool and pilot it among ﬁve individuals without healthcare or 
research training to ensure easy comprehension. Research assistants will receive training 
on the data collection tool before contacting patients.  
In the situation where participants are unable to be interviewed, two research team 
members will extract data directly from the medical record independently and in duplicate. 
Disagreement between data extractors will be resolved by a third researcher. Data extractor 
agreement will be measured using Cohen’s kappa.  
Variables and Analysis by Research Objective 
Primary Objective: Feasibility Study 
Outcome: This study’s primary focus is on the feasibility of prospectively identifying and 
recruiting FBAO patients, with the following outcome measures: 
• Number of eligible patients recruited per month (Primary) 
• Proportion of eligible patients recruited (Secondary) 
• Proportion of recruited patients with > 90% of variables collected (Secondary) 
Exposure: Given the primary aim of the feasibility study is a descriptive analysis of the 
outcome variables, no exposure variable is deﬁned. 
Sample Size: Abdominal thrusts and back blows are the two primary FBAO interventions 
used on adults and children, so the sample size is based on data of these two techniques 

[3]. We estimate that 640 patients will need to be recruited to obtain 80% power using a 
statistical signiﬁcance of 0.05 and two-sided z-test of independent proportions to detect, 
with successful proportion of abdominal thrusts and back blows equal to 59.5% and 72.2% 
respectively, with a ratio of patients who received abdominal thrusts versus back blows 
equal to 3.5 [3].  
To complete an intervention eDectiveness study in 48 months, we would need to recruit a 
mean of 13.3 patients per month. The slowest acceptable recruitment rate would be if 
recruitment required one additional year to obtain our desired sample size (60 months 
total). This would require recruitment of 10.6 patients per month. Using the traDic light 
approach for a feasibility study’s sample size, we set the green criterion (progression, no 
concerns) to 13 patients or more per month and the red criterion (major problems, 
potentially not remediable concerns) to less than 10 patients per month. The amber zone 
will be set as 10-13 patients per month, which represents a recruitment rate range that may 
be compatible with a successful future study; however, we will ﬁrst aim to identify and 
address remediable recruitment challenges before deciding whether to proceed [10]. 
Analysis: We will conduct a descriptive analysis of the recruited cohort’s demographics, as 
well as the FBAO incident situational factors (categorical: frequency and proportions; 
continuous: medians and interquartile ranges). We will calculate the mean recruitment 
rate by dividing the number of recruited patients over the entire study period by the number 
of months recruitment was ongoing. We will track the number of patients who were eligible 
over the entire study period and determine our proportion of successful recruitment by 
dividing the count of recruited patients by the count of eligible patients. Finally, among our 
recruited patients, we will review the data collection forms and determine the number of 
patients who had 90% or more of variables obtained to ensure satisfactory data collection 
processes are in place. 
Secondary Objectives: EDectiveness and Safety  
Outcomes: The feasibility study will inform the development of several future studies 
investigating the secondary objectives focusing on FBAO intervention eDectiveness and 
safety. These objectives’ outcome variables will be: 
• FBAO relief: defined as successful if the responder(s) determines that the patient 
did not require further FBAO intervention due to improvement/resolution of their 
respiratory distress (Primary) 
• Survival to acute care discharge (e.g., Emergency Medical Services [EMS], 
emergency department, or hospital discharge). If transferred to a long-term care 
facility due to permanent neurological function decline, we will still consider this an 
acute care discharge (Secondary) 
• Survival to discharge with favourable neurological outcome (Secondary): defined as 
the patient being able to be discharged to their previous home environment, with 
the ability to perform the same activities of daily living as before the FBAO incident 
• Intervention-associated injuries (Secondary) 

Question One: Among conscious adults and children with an out-of-hospital FBAO, which 
initial BLS FBAO intervention is more eCective and safer? 
• Exposure: Initial FBAO intervention (abdominal thrusts, back blows, chest 
compressions) 
Question Two: Among conscious adults and children with an out-of-hospital FBAO who 
failed initial management, is continuing the same BLS intervention more eCective than 
changing interventions? 
• Population: Adults who experience an out-of-hospital FBAO and are attend by EMS 
or present to the emergency department in Alberta, Canada, and received at least 5 
initial interventions (e.g., 5 abdominal thrusts) 
o For this question, we will require the patient received at least 5 unsuccessful 
initial interventions to capture only patients who do not respond immediately 
to initial treatment and require further intervention.  
o After 5 initial interventions, resuscitation guidelines recommend either 
continuing the initial intervention (Heart and Stroke Canada, and American 
Heart Association [5]) or alternating to another technique (European 
Resuscitation Council, Canadian Red Cross, and Lifesaving Society Canada 
[6-9]). By excluding the patients that initially responded to 5 or less attempts, 
we are creating a more similar patient population when comparing 
alternating techniques (e.g., abdominal thrusts and back blows) versus those 
who continued the same technique (e.g., 20 abdominal thrusts) to help 
address resuscitation time bias. 
• Exposure: Receiving a single BLS FBAO intervention versus an intervention 
combination (abdominal thrusts [AT], back blows [BB], chest compressions [CC], AT 
and BB, AT and CC, BB and CC) after an initial 5 attempts 
Question Three: Among conscious adults and children with an out-of-hospital FBAO who 
failed initial management, which BLS FBAO intervention or combination of interventions is 
more eCective and safer? 
• Exposure: FBAO intervention combination (abdominal thrusts [AT], back blows [BB], 
chest compressions [CC], AT and BB, AT and CC, BB and CC) 
Analysis: As this pilot study will be underpowered to accurately estimate precision of the 
outcomes, we will limit reporting of these results to a descriptive analysis. We will include 
descriptive statistics of the patients’ demographics and FBAO incident situational factors 
for the total study population, as well as stratiﬁed by the exposure variable (categorical: 
frequency and proportions; continuous: medians and interquartile ranges). We will also 
report descriptively the outcome variables listed above.  
We will summarize missingness of all variables to determine appropriateness of imputation 
for future studies.  

We will perform similar analyses for several subgroups: adults (aged > 13 years), children 
(aged 3-12 years), patients residing in long-term care, patients with limited mobility, and 
patients who received ﬁrst intervention with bystanders versus paramedics.  
Covariates  
Variable Name 
Variable Type 
Possible Values 
Patient  
Age 
Continuous 
0 - 100 
Sex 
Categorical 
Male, Female, Other 
Estimated Patient Weight 
Numerical 
 
Estimated Patient Height 
Numerical 
 
History of Choking 
Categorical 
Yes, No, Unknown 
Medical Comorbidities 
Open response 
Free Text 
Speciﬁcally ask: Stroke, 
Dementia or Alzheimer’s, 
DiCiculty Swallowing or 
Chewing, Parkinson’s 
Disease 
List, select all that apply 
Any of the speciﬁc answers 
Pre-FBAO ADL 
Independence 
Categorical 
Independent, Dependent, 
Unknown 
If Dependent: Which ADLs 
require assistance? Which 
ADLs are completely 
dependent? 
List, select all that apply 
Ambulation/mobility, 
Eating/feeding, Personal 
hygiene/bathing, Dressing, 
Toileting  
If Limited Mobility: What is 
their mobility? 
Categorical 
Walk independent, Uses 
cane, Uses walker, Uses 
wheelchair, Limited to bed  
Long term care resident 
Categorical 
Yes, No, Unknown 
 
 
 
Situation 
Location 
Categorical 
Home, Long term care 
residence, Restaurant, 
School, Other public place, 
Unknown 
Foreign body 
Open response 
Free text 
Witnessed Status 
Categorical 
Witnessed, Unwitnessed, 
Unknown  
Witness Relation 
Categorical 
Family or friend (known 
person), bystander 
(unknown person), 
Unknown 
 
 
 
Bystander Response 

Dispatcher Instruction 
Categorical 
Given, Not Given, Unknown 
Bystander Response 
Categorical 
Yes, No, Unknown 
If Bystander Responded: 
Bystander Sex or Gender Categorical 
Male, Female, Other, 
Unknown 
Bystander (estimated) Age Continuous 
0 - 100 
Bystander (estimated) 
Weight 
Continuous 
 
Bystander (estimated) 
Height 
Continuous 
 
Bystander Training Categorical 
Healthcare training, First 
aid/CPR/BLS, None, 
Unknown 
Patient Status During 
Bystander Response 
Categorical 
Conscious/responsive + 
talking/crying/eDective 
cough; 
Conscious/responsive + 
ineDective cough/no 
sounds; altered; 
unresponsive/unconscious  
Initial Bystander 
Intervention 
Categorical 
Abdominal Thrusts, Back 
Blows, Chest Compression, 
Suction Devices, Other, 
Unknown 
Number of Initial 
Intervention Attempts 
Numeric 
0 - 100 
Initial Intervention Success Categorical 
Yes, No, Unknown 
How Was Success 
Determined 
Open response 
Free text 
Repeat for Each Bystander Intervention 
 
 
 
EMS and Emergency Department Response 
EMS Called 
Categorical 
Yes, No, Unknown 
If EMS Attended 
Patient Still Choking when 
EMS Arrives 
Categorical 
Yes, No, Unknown 
Patient Status During 
Paramedic Response 
Categorical 
Conscious/responsive + 
talking/crying/eDective 
cough; 
Conscious/responsive + 
ineDective cough/no 
sounds; altered; 
unresponsive/unconscious  

Initial Paramedic 
Intervention 
Categorical 
Abdominal Thrusts, Back 
Blows, Chest Compression, 
Suction Devices, Other, 
Unknown 
Number of Initial 
Intervention Attempts 
Numeric 
0 - 100 
Initial Intervention Success Categorical 
Yes, No, Unknown 
How Was Success 
Determined 
Open response 
Free text 
Repeat for Each Paramedic Intervention 
Intubated on scene 
Categorical 
Yes, No, Unknown 
Cardiac arrest on scene 
Categorical 
Yes, No, Unknown 
Transported to hospital 
Categorical 
Yes, No, Unknown 
Management in the 
Emergency Department 
Open Response 
Free text 
 
 
 
Other Outcomes 
 
 
Survived to acute care 
discharge 
Categorical 
Yes, No, Unknown 
Post-FBAO ADL 
Independence 
Categorical 
Independent, Dependent, 
Unknown 
If Dependent: Which ADLs 
are dependent? 
List, select all that apply 
Ambulation/mobility, 
Eating/feeding, Personal 
hygiene/bathing, Dressing, 
Toileting  
If Limited Mobility: What is 
their mobility? 
Categorical 
Walk independent, Uses 
cane, Uses walker, Uses 
wheelchair, Limited to bed  
Discharged Location 
Categorical 
Home, Long term care, 
other acute care facility, 
dead 
Intervention-associated 
injuries 
Open response 
Free text 
Hospital Length of Stay 
Numeric 
0 – 100 
Intensive Care Length of 
Stay 
Numeric 
0 – 100 
Intubated at any time 
Categorical 
Yes, No, Unknown 
ADL = Activities of daily living; EMS = Emergency medical services; FBAO = Foreign body 
airway obstruction 
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