Yonago Acta medica 2003;46:133–144

Evaluation of Exhaled Nitric Oxide in Thoracic Surgery
Patients under One Lung Ventilation Using a Newly Designed Online Exhaled Nitric Oxide Measuring System
Yukari Minami, Renyu Liu*, Yuichi Ishibe, Naoto Okazaki, Tae Funakoshi and
Keiichiro Ueda
Department of Surgery, Division of Anesthesiology and Critical Care Medicine, Tottori University Faculty of Medicine, and *Department of Anesthesia, University of Pennsylvania Medical
Center, Philadelphia, PA 19104 United States
Measurement of exhaled nitric oxide (NO) has been gaining much interest lately. However,an ideal measuring system is not yet available in the clinical setting. The aims of the present
study were to construct an exhaled NO measuring system and to investigate the effects of
one lung ventilation (OLV) on exhaled NO output in patients who underwent thoracic
surgery. At first, the NO measuring system was constructed with an NO analyzer, a
respiratory flowmeter and a data processing computer system in which the algorithm wasindwelled for correcting the distorted NO output wave form. Then, accuracy of this system
was tested by using a simulator. This simulator was reworked in order to simulate NO
production from the lung under both spontaneous respiration and mechanical ventilation.
The data of peak NO concentration (pNO) and NO output (VNO) obtained with the NO
monitoring system were significantly correlated with “alveolar” NO concentration (aNO)and exhaled NO volume from the simulator. Then, exhaled NO was measured in 12 thoracic
surgery patients who underwent OLV using this system. pNO and VNO were significantly
decreased by about half during OLV, and returned to baseline 25 min after releasing
OLV. These data suggest that the newly designed online exhaled NO measuring systemaccurately detected aNO and exhaled NO volume in a breath-by-breath manner, and OLV
for about 3 h did not influence the NO output from the lung after releasing OLV in thoracic
surgery patients.
Key words: exhaled nitric oxide; one lung ventilation; online measurement; simulator; thoracic
surgery

The presence of endogenous nitric oxide (NO) in
the exhaled air of animals (Gustafsson et al., 1991)
and humans (Borland et al., 1993) has been reported. The exhaled NO level from the lungs has been

affected by various pathophysiological conditions
including inflammation (Belvisi et al., 1995; Hill etal., 1995), other respiratory diseases (Hill et al., 1995;
Kharitonov et al., 1996), septic shock (Stewart et al.,Abbreviations: aNO, alveolar nitric oxide concentration; BLV, bilateral lung ventilation; ETCO2, partial pressure ofend tidal carbon dioxide; mNO, mean nitric oxide concentration; NO, nitric oxide; OLV, one lung ventilation; PaO2/
FIO2, ratio of arterial partial pressure for oxygen to fractional inspired oxygen concentration; pNO, peak nitric oxide
concentration; ppb, parts per billion; Q, respiratory flow rate; RR, respiratory rate; TV, tidal volume; τ, time constant;TVex, expiratory tidal volume; VNO, exhaled nitric oxide output

133

Y. Minami et al.

1995) and ischemia-reperfusion injury (Blebea etal., 1996).
A guideline was published to provide recommendations for a standardized procedure for exhaled NO measurement (American Thoracic Society,1999), because differing methods may cause somemisunderstanding of absolute exhaled NO concentration (Robbins et al., 1996; Byrnes et al., 1997).
According to the recommendations of online NO
measurement, NO output represents the amount of
exhaled NO per unit time, and is calculated from theproduct of NO concentration and expiratory flow
rate. A high quality of accuracy in a NO analyzer
and flow sensor is required. However, the output
wave form of the recently available fast response
NO analyzer is still distorted because of unsatisfactory response time and delay time due to transit
time through the sample tubing in a particular application. Therefore, it is necessary to correct the output wave form to obtain accurate real-time NO output. The 1st aim of the present study was to construct an online real-time exhaled NO measuringsystem in a breath-by-breath manner and to evaluate the accuracy and usefulness of this system.
One lung ventilation (OLV) is a special technique employed during thoracic surgery to separate
both lungs and secure a large surgical field. In general, a controlled ventilation setting during OLV
maintains tidal volume (TV) and respiratory rate(RR) values similar to those used in bilateral lungventilation (BLV). These ventilating conditions
create a risk of lung injury for the ventilating lungbecause of a relatively high TV and consequent
high airway pressure. Recently, OLV with TV andzero end-expiratory pressure values similar to thoseused in BLV have been reported to deteriorate pulmonary mechanics, to induce pulmonary hypertension and also to increase the release of thromboxane B2 in an isolated rabbit lung model (Gamaet al., 2003). Furthermore, the effects of OLV on exhaled NO have not been investigated. We hypothesized that lung injury might be caused by OLV andexhaled NO output might change after releasing
OLV. The 2nd aim of the present study was to measure exhaled NO and to investigate the effects of
OLV on NO production from the lungs of patients
who underwent thoracic surgery.

Subjects and Methods

Construction and evaluation of a real-time exhaled NO measuring system
System setup
The measuring system consisted of an NO gas
analyzer, a respiratory flowmeter, a capnometer anda data-collecting computer system (Fig. 1). The

Respiratory flowmeter
Capnometer
Flow sensor

A/D convertor

Anesthesia
machineSimulator

Gas sampling (CO2)

ComputerNO analyzer

Gas sampling (NO)Fig. 1. Setup of the online exhaled nitric (NO) measuring system. The system consists of a simulator, an anesthesia
machine, an NO analyzer, a capnometer and a respiratory flowmeter. Output of these data are digitized and recordedin the computer for secondary processing.

134

Exhaled NO under OLV using new system

NO/N2 gas
670 ppb

O2

MFC

N2

MFC

CO2

MFC

Onlineexhaled NO
measuringsystemBellows

Left lung
Vane
pump

Anesthesia
machineAirwayGas monitor
NO analyzer

Bellows
Right lungconcentration of NO was measured with an NO
analyzer (NOA 280, software version 2.05, Sievers
Instruments, Boulder, CO), based on the chemiluminescence method with a sampling volume of 200
mL/min. The CO2 concentration and respiratory
flow rate (Q) were simultaneously monitored by amulti-parameter airway gas monitor (Capnomac
Ultima, Datex-Engstrom Division, Instrumentation
Corporation, Helsinki, Finland). The original NO,
CO2 and Q data were digitized by the MacLab system,
which consists of a MacLab hardware unit (MacLab/
400, AD Instruments, Castle Hill, Australia) and asoftware application program (Chart, version 3.5, AD
Instruments), and processed as described below.

Fig. 2. Relationship of thesimulator, anesthesia machineand online exhaled NO measuring system. To simulate
nitric oxide (NO) production
from the bellows of the simulator, the standard NO gas isinfused into the alveolar component gas in the bellows,which is regulated by a mass
flow controller (MFC). Exhaled NO parameters and alveolar NO concentration aremeasured using an online exhaled NO measuring system
and an NO analyzer in breathby-breath manner, respectively. See the text for details.

original NO wave was corrected using the 2-exponential correction based on the report by Arieli and Van
Liew (1981).
Calculation of exhaled NO output
This system can display real-time waves
breath-by-breath, and record the processed data forpeak NO concentration (pNO), mean NO concentration (mNO) and exhaled NO output (VNO) in tidal
ventilation. The VNO is calculated by numericalintegration of the product of the NO concentrationand flow rate as defined in the guideline (American
Thoracic Society, 1999).
Evaluation of the online NO measuring systemusing the simulator
The human patient simulator (METI, Inc.,
University of Florida, Sarasota, FL) was connectedto the semiclosed anesthesia machine (Ohmeda,
Modulus II, BOC Health Care, Madison, WI)
through the end of the tracheal tube. The sensors of
the online NO measuring system were interposed
between the end of the tracheal tube and the respiratory circuit of the anesthesia machine as shown in
Fig. 2. The simulator reproduces the airway pressure flow characteristics of the natural lung undernormal and pathophysiological conditions. Uptake
and delivery of the following “alveolar” gases in-Correction of the original NO wave
Accurate drawing of NO concentration waves
and gas flow rate is critical for ensuring reproducible measurements, but several factors distort theoutput waves from the analyzer. Major factors are
sampling tube volume connected to the analyzer
and delay in the response chamber of the chemiluminescence reaction. Using this system, 10 consecutive response curves were obtained by switching the sample gas from NO free air to standard NO
gas (NO 670 parts per billion in N2, Taiyo Toyo
Sanso, Osaka, Japan), and delay time and 2 time
constants (τ 1 and τ 2) were obtained. Then, the135

Y. Minami et al.

side the bellows are physically created by gas
substitution, that is, O2, CO2 and N2. We connected
the NO infusion line to the bellows. Using the gas
substitution technique, a constant flow of “alveolar” gas is sent from the bellows by a vane pump. A
portion of this gas is sampled by a gas analyzer,
which determines the partial pressures of O2 andCO2. “Alveolar” NO concentration (aNO) was determined by online NO gas analyzer (NOA 280), which
was set parallel to the gas analyzer (Fig. 2). Inspiratory and expiratory gas compositions could thus bemeasured with a standard monitor (Capnomac
Ultima), and expired NO gas concentration wasmeasured with the NO gas analyzer. We selected“standard man awake” and “standard man relaxed”
scenarios preconfigured by the manufacturer formeasurements during spontaneous breathing andcontrolled ventilation, respectively.
Respiratory parameters such as TV (mL), RR(breath/min) and partial pressure of end tidal carbon
dioxide (ETCO2, kPa) were adjusted according toour study protocol. These respiratory parameters
were regulated by setting the simulator during
spontaneous breathing and setting the respirator on
the anesthesia machine during controlled ventilation. The standard NO gas was infused into the lungcomponent gases of the bellows of the simulator tosimulate NO production from the lung, by changing
the infused NO gas flow rate of 45 or 90 or 180 mL/min, which is equivalent to NO production of approximately 30.2 or 60.3 or 120.6 nL/min, respectively. After aNO in the bellows reached a constantvalue, aNO and all exhaled NO parameters (pNO,mNO and VNO) were measured.

was changed 4 times and parameters were measured. These series of measurements were repeatedunder both spontaneous breathing (n = 20) andcontrolled ventilation (n = 19).

Application of the online real-time NO measuring system to thoracic surgery patientsAs this is a prospective and observational study
without intervention other than specific monitoringprocedures, the Ethical Committee of Tottori University Faculty of Medicine approved this study
without obtaining informed consent from the patients. Exhaled NO was measured in 12 patients
undergoing thoracic surgery during which OLV
was required. To provide a control, exhaled NO
was also measured in 5 non-thoracic surgery patients, who did not require OLV during surgery.
The patients were premedicated with 25 to 50
mg hydraladine and 0.5 mg atropine intramuscularly. After induction with 2.0 mg/kg propofol, 5 µg/
kg fentanyl and 0.05 mg/kg pancuronium, anesthesia was maintained with propofol and fentanyl. No
inhalational volatile anesthetics were used because
exhaled NO is underestimated in the presence ofpotent inhalational volatile anesthetics (Liu et al.,2000). Thoracic epidural anesthesia was also applied in some patients of both groups. The trachea
of each patient was intubated with a double lumen
endobronchial tube. Surgery was performed with
OLV by collapsing the non-dependent lung in thelateral decubitus position. The lungs of patientswere ventilated with a TV of 10 to 12 mL/kg at a
rate of 10 breaths/min during BLV. Respiratory
minute volume was kept constant during NO measurement by adjusting both TV and RR to keep
ETCO2 at about 3.5 to 4.5 kPa. During OLV, respiratory minute volume was adjusted to maintainthe same level of ETCO2 as that during BLV. Arterial partial oxygen pressure was measured with astandard blood gas analyzer, and the ratio of arterial
partial pressure for oxygen to fractional inspired oxygen concentration (PaO2/FIO2) was calculated. Lung
compliance was measured with multi-parameter
airway gas monitor (Capnomac Ultima).

Study protocol
Exhaled NO parameters of pNO, mNO, VNO
and aNO were measured by changing ETCO2 4.2 ±0.1 kPa (hyperventilation) or 5.4 ± 0.1 kPa (normoventilation) or 6.4 ± 0.2 kPa (hypoventilation),while keeping a constant infused NO flow rate (180mL/min). Subsequently, the same parameters were
measured by changing the infused NO flow rate to
90 or 45 mL/min while keeping ETCO2 5.4 ± 0.1
kPa (normoventilation). While keeping the same
ETCO2 conditions, the combination of TV and RR
136

Exhaled NO under OLV using new system

Abacus Concepts, Berkeley, CA) was used for thestatistic analysis and P < 0.05 was considered to bestatistically significant.

Data collection
The original data were recorded just before
OLV; 5, 20 and 60 min after beginning of OLV; justbefore reestablishment of BLV; and 5 and 25 minafter reestablishment of BLV. The data for patients
who underwent non-thoracic surgery were recorded
before, during and after surgery.

Results

Drawing of the real-time NO wave and evaluation of the measuring system

Data analysis and statistics
pNO, mNO and VNO were calculated from a
consecutive analysis of NO waves for 40 s and compared to aNO using a single linear regression test.
Using the same statistical analysis, VNO was compared to the calculated exhaled NO volume, which
was defined as aNO × expiratory TV (TVex) × RR.
The parametric data of patient characteristics, respiratory parameters and blood gas data were presented as mean ± SD. Respiratory parameters andblood gas data were analyzed with analysis ofvariance with repeated measures and subsequent
post hoc test. As exhaled NO parameters were notdistributed uniformly with the Bartlett test, they
were analyzed by the nonparametric analysis ofFriedman’s χ 2-test, and when statistical significance was observed, a subsequent Wilcoxon’s t-test
with Bonferroni’s correction was performed. Commercially available software (Statview, version 4.5

Delay time of the 10 consecutive measurements
was 2.1675 ± 0.0736 s. Mean time constants were0.1208 ± 0.0089 s and 0.5656 ± 0.0075 s in τ1 andτ2, respectively. Consequently, the distorted output
curve for NO was corrected by the following formula for C:
C = C0 + (τ1 + τ2) × dC0/dt + τ1 τ2 × d2C0/dt2= C0 + 0.6863 dC0/dt + 0.0683 d2C0/dt2
where C0 is the original NO concentration, C iscorrected NO concentration and t is time.
The representative corrected NO is showncombined with waves of original NO, CO2 and Q in
Fig. 3. Respiratory parameters of the simulator are
summarized in Table 1. aNO decreased according
to the increase in resiratory minute volume.

(ppb, L/min, %, ppb)
30

20

10

0

–10

–20

–30
20

40 (s)

30

Original NO (ppb)
Flow (L/min)

CO2 (%)
Corrected NO (ppb)

Fig. 3. Representative traces of original nitric oxide (NO), corrected NO, carbon dioxide (CO2) and gas flow after
time phase adjustment. Time phase adjustment and NO wave correction are described in the text for details. ppb,
parts per billion.

137

Y. Minami et al.

Table 1. Characteristics of the simulator
Infused NO Respiratory condition
180 mL/min

Spontaneous breathing
ETCO2 RR
TVex
aNO

Controlled ventilation
ETCO2
RR
TVex
aNO

Hyper-ventilation

4.4
4.3
4.1
4.3

6.4
10.6
15.0
20.3

735
857
600
409

21.4
15.5
15.7
17.9

4.1
4.3
4.4
4.1

6.0
9.7
15.3
20.1

1006
1333
692
635

17.8
12.8
14.5
12.9

Normo-ventilation

5.5
5.5
5.5
5.3

6.7
11.3
16.6
20.5

516
439
388
334

24.2
21.0
19.3
19.7

5.5
5.3
5.5
5.5

6.0
10.4
16.1
21.1

571
526
411
308

24.1
20.3
19.6
21.0

Hypo-ventilation

6.4
6.5
6.7
6.4

5.2
10.0
13.4
19.5

354
297
319
261

29.3
26.8
23.0
22.7

6.3
6.3
6.1
–

6.0
10.1
15.1
–

368
206
134
–

27.5
31.2
34.8
–

90 mL/min

Normo-ventilation

5.5
5.5
5.5
5.3

7.0
12.2
17.1
20.4

544
460
404
351

13.4
11.9
11.0
10.9

5.3
5.3
5.5
5.2

6.0
10.1
15.3
20.3

669
526
439
376

12.0
11.4
10.7
9.9

45 mL/min

Normo-ventilation

5.3
5.5
5.5
5.3

6.4
12.1
17.1
20.4

529
451
415
362

8.7
7.9
7.0
7.3

5.5
5.3
5.3
5.5

6.0
10.1
14.7
20.1

451
517
506
341

8.2
7.0
6.1
6.4

aNO, alveolar nitric oxide concentration (ppb); ETCO2, partial pressure of end tidal carbon dioxide (kPa); infusedNO, infused flow rate standard nitric oxide gas (670 ppb) into the bellows of the simulator; RR, respiratory rate (rateper minute); TVex, expiratory tidal volume (mL); –, not performed.

A: Spontaneous breathing
(ppb)
40

B: Controlled ventilation
(ppb)
40

pNO

pNO

30

30

20

20

mNO

mNO
10

10

n = 20
0
0

10

20

30

n = 1940 (ppb)

0
0

10

20

30

40 (ppb)aNO

aNO

mNO = 0.649 × aNO–1.243; r 2 = 0.958
pNO = 1.067 × aNO–1.116; r 2 = 0.993

mNO = 0.668 × aNO–0.900; r 2 = 0.977
pNO = 1.061 × aNO–0.742; r 2 = 0.993

Both pNO and mNO significantly correlatedwith aNO during spontaneous breathing (n = 20,
Fig. 4A) and controlled ventilation (n = 19, Fig.

Fig. 4. Peak nitric oxide concentration (pNO) and mean
nitric oxide concentration(mNO) in a tidal breath significantly correlated with alveolar nitric oxide concentration (aNO) during spontaneous breathing (A) and duringcontrolled ventilation (B).

4B). In particular, pNO coincided with aNO undera wide range of respiratory patterns. When thestandard NO gas was infused into the bellows of the138

Exhaled NO under OLV using new system

A: Spontaneous breathing

B: Controlled ventilation

150

150

VNO

(nL/min)200

VNO(nL/min)
200

100

50

100

50

n = 20
0

0

50

100

150

n = 19200 (nL/min)

0

0

50

100

150

200 (nL/min)

Exhaled NO

Exhaled NO
VNO = 1.054 × exhaled NO–10.258; r 2 = 0.990

VNO = 0.950 × exhaled NO + 0.688; r 2 = 0.981

Fig. 5. Exhaled nitric oxide output (VNO) significantly correlated with exhaled NO volume during
spontaneous breathing (A)and during controlled ventilation (B). Exhaled NO
volume was defined as the
products of alveolar nitricoxide concentration (aNO),
expiratory tidal volume(TVex) and respiration rate
(RR).

changed during OLV. These variables returned tobaseline after releasing OLV (BLV-5 and 25) (Fig.
6).

stimulator at rates of 45, 90 and 180 mL/min, aNO
yielded 40.4 ± 9.9 nL/L (n = 8), 66.4 ± 11.3 nL/L (n= 8) and 111.9 ± 33.7 nL/L (n = 23), respectively.
VNO correlated significantly with the actually
exhaled NO volume (aNO × TVex × RR) from thesimulator regardless of changes in respiratory
patterns during both spontaneous breathing (Fig.
5A) and controlled ventilation (Fig. 5B).

15

(mL/kg)

TV

10

*

*

*

*

*

*

*

*

5
0
20

RR

Measurement on thoracic surgery patients
The characteristics of the patients are shown in
Table 2. The mean duration of OLV was about 3 h.
In non-thoracic surgery, TV/kg, RR and ETCO2
were maintained constantly during surgery. In
thoracic surgery, TV/kg and RR significantly

(rpm)

10

0

ETCO2

6

(kPa)

4
2

Table 2. Characteristics of the patients

Number of patientsAge (year)
Height (cm)Weight (kg)Surgery time (h:m)
OLV time (h:m)

Thoracic
surgery

Non-thoracic
surgery

12
57.9 ± 20.6
156.5 ± 9.9
50.9 ± 7.3
4:09 ± 2:17
3:13 ± 1:26

5
54.2 ± 15.8
161.5 ± 11.3
65.1 ± 19.3
2:44 ± 2:09
–

OL
V5
OL
V20
OL
V60
Be
for
eB
LV
BL
V5
BL
V25

Be

for
e

OL
V

0

Fig. 6. Changes in tidal volume per body weight (TV/kg), respiratory rate (RR) and end tidal CO2 (ETCO2) inthoracic surgery. Data were collected before OLV, justbefore one lung ventilation (OLV); OLV-5, 5 min after
beginning of OLV; OLV-20, 20 min after beginning of
OLV; OLV-60, 60 min after beginning of OLV; before
BLV, just before reestablishment of bilateral lung ventilation (BLV); BLV-5, 5 min after reestablishment of
BLV; BLV-25, 25 min after reestablishment of BLV.
Values are mean ± SD. *P < 0.05, different from before
OLV. ETCO2 was in physiological ranges resulting in
reduced TV and increased RR during OLV.

Values expressed as mean ± SD.
h:m, hour:minute; OLV, one lung ventilation; –, not performed.

139

Y. Minami et al.

Table 3. Changes in PAW, CL and PaO2/FIO2

OLV but still sustained a low level compared tobaseline. PaO2/FIO2 decreased during OLV but
returned to baseline after reestablishment of BLV(Table 3).
In thoracic surgery, pNO (P = 0.0084), mNO(P = 0.027) and VNO (P = 0.0056) significantly decreased during OLV. These variables returned tobaseline after releasing OLV (BLV-5 and 25) (Fig.
7). In non-thoracic surgery, there were no changes
in pNO, mNO and VNO during surgery (Fig. 8).

Before OLV During OLV After OLV
PAW (kPa)
1.7 ± 0.2
2.3 ± 0.3* 2.0 ± 0.3†
CL (mL/kPa) 495 ±158
250 ± 93* 402 ± 112*†
PaO2/FIO2
65.3 ± 8.9 20.0±11.1* 57.8 ±13.6†
Values expressed as mean ± SD.
CL, lung compliance; OLV, one lung ventilation;
PaO2/FIO2, ratio of arterial partial pressure for oxygento fractional inspired oxygen concentration; PAW,
peak airway pressure.
* P < 0.05 versus before OLV; †P < 0.05 versus during
OLV.

Discussion
In thoracic surgery, peak airway pressure significantly increased during OLV but returned after
reestablishment of BLV. Lung compliance significantly decreased during OLV and increased after
(ppb)

40

*

20

*

10

pNO

*

0

0
(ppb)

15

mNO

mNO

VNO

50

En
d

le
dd
Mi

25

5

V-

V-

BL

LV

(nL/min)

0

BL

60

5
0

Be

for

eB

20

V-

OL

5

V-

V-

LV

OL

OL

eO

10

100

VNO

for

(ppb)

ing

Fig. 7. Changes in peak*5
nitric oxide concentra* * *tion (pNO), mean nitricoxide concentration
0(mNO) and exhaled ni(nL/min)100
tric oxide output (VNO)
in thoracic surgery. Data50*
were collected before* * *OLV, just before one
lung ventilation (OLV);0
OLV-5, 5 min after beginning of OLV; OLV20, 20 min after beginning of OLV; OLV-60,
60 min after beginningof OLV; before BLV, just before reestablishment of bilateral lung ventilation (BLV); BLV-5, 5 min after reestablishment of BLV; and BLV-25, 25 min after reestablishment of BLV. In this box and whisker plot, the central line represents the median, boxes represent the 25thand 75th percentiles, and whiskers represent the 10th
and 90th percentiles. *P < 0.05, different from before
OLV. All exhaled parameters decreased during OLV
and returned to before-OLV values up till 25 min after
the reestablishment of BLV.
Be

20

gin
n

10

(ppb)

Be

pNO

30

We redesigned the online real-time system to measure exhaled NO. The NO wave was corrected bymeasuring actual delay time and 2 time constants.

Fig. 8. Changes in peak nitric oxide concentration(pNO), mean nitric oxide concentration (mNO) and exhaled nitric oxide output (VNO) in non-thoracic surgery.
Data were collected at the beginning, beginning of operation; middle, middle of operation; and end, end of theoperation. In this box and whisker plot, the central line
represents the median, boxes represent the 25th and 75th
percentiles, and whiskers represent the 10th and 90th
percentiles. No exhaled nitric oxide parameters changed
significantly throughout the study.

140

Exhaled NO under OLV using new system

the lung by keeping a constant infused volume ofNO (180 mL/min) in the bellows, we changed theETCO2 from 4.0 to 6.5 kPa. aNO decreased according to the increase in respiratory minute volume andvice versa. Exhaled NO parameters of pNO andmNO strongly correlated with the changes in aNO.
In particular, pNO readings represented the aNOlevel. Changes in combination of TV and RR under
the same respiratory minute volume did not influence the readings of pNO and mNO. VNO represented actually exhaled NO volume from the simulator even when changing the infused NO volume.
These data suggest that pNO measured with this system reflect aNO whenever a wide range of changes
occur in TV and RR. Furthermore, VNO exactly reflected the exhaled NO volume regardless of changes
in respiratory patterns and infused NO volume.
We are able to take this system to the bedsideas all analyzers and standard gas are mounted on atrolley combined with a MacLab system and laptop
personal computer. Taken together with these
considerations we believe this system could be auseful tool for real-time exhaled NO measurements,
not only in the laboratory but also in critical caresuch as during anesthesia, postoperative intensive
care and respiratory care in medicine.
Using this system, we have shown that OLV
for about 3 h did not affect NO output from thelungs after releasing OLV. To our knowledge,
effect of OLV on exhaled NO output have not been
investigated previously.
The data on exhaled NO parameters of pNO
and VNO before OLV were at the same level as
previously reported by investigators (Törnberg etal., 2003). Therefore, it was thought that this system had enough accuracy for clinical application.
These parameters rapidly decreased by 40 to 70%
during OLV. According to the results of this study
in the 1st half, pNO and VNO represent alveolar
NO concentration and actually exhaled NO volume
from the lung, respectively, if there was no production or consumption during passage through thelower airway tract. Theoretically, pNO representsaNO, whereas VNO represent the actual exhaled
NO volume, but not NO production from the lung,This system was able to detect “alveolar” NO andexhaled NO volume accurately in a breath-bybreath manner, regardless of changes in respiratory
minute volume and respiratory patterns during bothspontaneous breathing and controlled ventilation.
Fast response analyzers are widely used tomeasure gas concentration during the breathingcycle. The amount of gas entering or leaving thelungs is calculated by a numerical integration of the
product of analyzer’s output concentration and flow
rate. A typical example is CO2 output measurement
using capnogram and pneumotachogram, both ofwhich have sufficient performance to respond to
rapid changes of CO2 concentration and Q. Exhaled NO can likewise be analyzed by a fast response NO analyzer. A fast response chemiluminescence analyzer such as a Sievers NOA for exhaled
NO measurement has a high performance fast response time, but its output wave is still distorted,
resulting in misleading of readings when employed
to detect peak concentration or the area under acurve. Large errors may be produced in real-time
online exhaled NO measurements, if used without
correcting the output curve. Although the output of
the analyzer for step-change inputs is a sigmoid
rather than an exponential function, a simpler empirical approach was applied with a 1-exponential
correction of the output. However, we could obtainsatisfactory results of reliable and reproducible
measurements of NO using a 2-exponential correction to restore distortion of the curve. Exact correction of delayed time due to sampling tubes is also
critical, especially in phase adjustment between NO
concentration and flow rate. In general, the respiratory flow pattern, which is detected by the inline
flow sensor, is applied as a standard technique fortime phase adjustment because various sensing
techniques are highly sensitive to flow changes.
Therefore, we required flow patterns measured withpneumotachograms.
We infused NO into the bellows of the simulator. The NO concentration of constantly flowing
gas sent from the bellows was defined as aNO, andaNO × TVex × RR were defined as exhaled NO volume. Simulating the constant NO production from141

Y. Minami et al.

because a large amount of alveolar NO rapidly diffuses into the pulmonary circulation, combining
with hemoglobin in the capillary blood flow. Therefore, pulmonary blood flow is considered to be an
important regulating factor of aNO and exhaled NO
volume. These pulmonary circulation effects havebeen shown very effectively in a laboratory study
by Fernández and colleagues (2003), who reported
a clear increase of exhaled NO by balloon occlusionof the pulmonary artery. Increases in exhaled NO
after atrial septal defect closure are also a clinicalfinding, indicating the role of the pulmonary bloodflow effect on exhaled NO level (Humpl et al., 2002).
As the ventilation area was almost halved during
OLV, it is likely that aNO might be halved if minuteventilation was maintained at the same level as before OLV, when NO production from the lung was
kept constant. In practice, however, a relative increase in respiratory minute volume to the dependent lung during OLV may further facilitate thisreduction of pNO. VNO decreased about by halfduring OLV. This is not surprising because theventilation area decreased by half during OLV. The
present study was performed in the lateral decubitus
position, under which pulmonary blood flow in thedependent lung increases by about 10% (Wulff and
Aulin, 1972; Rehder et al., 1973). The hypoxic pulmonary vasoconstriction of the collapsed lung promotes the pulmonary blood flow shift to the dependent lung, yielding the blood flow to the dependentlung of 70 to 80% of the cardiac output during OLV(Fiser et al., 1982; Rogers and Benumof, 1985).
Therefore, a relative increase in pulmonary bloodflow to the dependent lung might contribute to a reduction of exhaled NO.
After releasing OLV, all parameters of exhaled NO returned to levels before OLV. This finding has 2 clinical implications. The collapsed nondependent lung might not be injured during thecollapse and re-expansion process, and be almost
completely re-expanded after releasing OLV. Furthermore, the ventilated dependent lung might beprotected against barotrauma or volutrauma during
OLV. Sustained oxygenation and relative high lungcompliance after releasing OLV suggest normallung function even after OLV for 3 h, although thecollapsed non-dependent lung did not yet completely expanded after 25 min after reestablishmentof BLV. Our findings agree with the report by Oka
and colleagues (1998) that OLV for about 3 h did
not affect resistance and reactance in respiratory
system after re-expansion. Acute re-expansion of
the collapsed lung for a prolonged period leads tothe development of pulmonary edema, and hightidal and high pressure ventilation induces
respirator-induced lung injury (Dreyfuss et al.,
1995; Broccard et al., 1999). Prolonged OLV or inappropriate ventilation patterns during OLV might
reduce NO production, resulting in lung injury andaffect lung function. The lung’s protective ventilation strategies (Amato et al., 1998), low TV andpositive end-expiratory pressure, are suggested toreduce lung injury due to volutrauma and barotrauma. Our ventilation pattern, relatively low TV
and increased RR, and short OLV time might contribute to prevent lung injury during OLV.
In the previous study we showed that NO output decreased after cardiopulmonary bypass accompanied by low lung compliance and returned by
16 h after cardiopulmonary bypass (Ishibe et al.,2000), but we could not follow up postoperatively
in this study. After the end of thoracic surgery ourpatients were extubated from their tracheas in ashort time. This measuring system restricts use
under the spontaneous airway without tracheal intubation. Exhaled NO measurements are convenientand less invasive, and basal exhaled NO output reflects bronchiolar and alveolar epithelial activity,
but the lower sensitivity of exhaled NO measurements is pointed out for detection capillary endothelial injury (Sartori et al., 1999). Kövesi and colleagues (2003) emphasized a stimulation test withintravenous nitroglycerin to reveal endothelial dysfunction after cardiopulmonary bypass. Further
studies are required to elucidate the effect of OLV
on lung function and NO output from the lung.
We redesigned the online real-time exhaled
NO measuring system. This exhaled NO measuringsystem accurately reflected the alveolar NO concentration and exhaled NO volume from the simu-

142

Exhaled NO under OLV using new system

8 Byrnes CA, Dinarevic S, Busst CA, Shinebourne EA,Bush A. Effect of measurement conditions on measured levels of peak exhaled nitric oxide. Thorax
1997;159:697–701.
9 Dreyfuss D, Soler P, Saumon G. Mechanical ventilation-induced pulmonary edema. Interaction withprevious lung alterations. Am J Respir Crit Care
Med 1995;151:1568–1575.
10 Fernández-Mondéjar E, Hambraeus-Jonzon K,
Ronéus A, Hedenstierna G. Nitric oxide increases
dramatically in air exhaled from lung regions withoccluded vessels. Acta Anaesthesiol Scand 2003;
47:312–318.
11 Fiser WP, Friday CD, Read RC. Changes in arterial
oxygenation and pulmonary shunt during thoracotomy with endobronchial anesthesia. J Thorac Cardiovasc Surg 1982;83:523–531.
12 Gama de Abreu M, Heintz M, Heller A, Széchényi
R, Albrecht DM, Koch T. One-lung ventilation withhigh tidal volumes and zero positive end-expiratory
pressure is injurious in the isolated rabbit lungmodel. Anesth Analg 2003;96:220–228.
13 Gustafsson LE, Leone AM, Persson MG, Wiklund
NP, Moncada S. Endogenous nitric oxide is present
in the exhaled air of rabbits, guinea pigs and humans.
Biochem Biophys Res Commun 1991;181:852–857.
14 Hill GE, Ruggeroli A, Pohorecki R, Alonso A,
Robbins RA. Cigarette smoking reduces endogenous airway nitric oxide production during cardiopulmonary bypass in humans. Anesth Analg 1995;
81:170–172.
15 Hill GE, Snider S, Galbraith TA, Forst S, Robbins
RA. Glucocorticoid reduction of bronchial epithelial inflammation during cardiopulmonary bypass.
Am J Respir Crit Care Med 1995;152:1791–1795.
16 Humpl T, Campbell R, Stephens D, Van Arsdell G,
Benson LN, Holtby HM, et al. Levels of exhaled nitricoxide before and after surgical and transcatheter
device closure of atrial septal defects in children. J
Thorac Cardiovasc Surg 2002;124:806–810.
17 Ishibe Y, Liu R, Hirosawa J, Kawamura K, Yamasaki
K, Saito N. Exhaled nitric oxide level decreases
after cardiopulmonary bypass in adult patients. Crit
Care Med 2000;28:3823–3827.
18 Kharitonov SA, Chung KF, Evans D, O'Connor BJ,
Barnes PJ. Increased exhaled nitric oxide in asthma
is mainly derived from the lower respiratory tract.
Am J Respir Crit Care Med 1996;153:1773–1780.
19 Kövesi T, Royston D, Yacoub M, Marczin N. Basaland nitroglycerin-induced exhaled nitric oxide before and after cardiac surgery with cardiopulmonary
bypass. Br J Anaesth 2003;90:608–616.
20 Liu R, Ishibe Y, Okazaki N, Kimura K. Chemi-

lator. Using this system, we have shown that 3 hlung collapse and re-expansion did not influence
NO output from the lung after releasing OLV in
thoracic surgery patients.
Acknowledgments: The authors thank Professor Eiji
Shimizu, Division of Internal Medicine and Molecular
Therapeutics, Department of Multidisciplinary Internal
Medicine, Professor Kazuo Yamada, Division of Medical
Biochemistry, Department of Pathophysiological andTherapeutic Science, and Professor Shigeo Hino, Divisionof Virology, Department of Microbiology and Pathology,
School of Medicine, Tottori University Faculty of Medicine, for their reviewing the manuscript.
Supported in part by Grant-in-aid No. 11671497 for
Scientific Research from the Ministry of Education, Science, Sports and Culture of Japan.

References
1 Amato MB, Barbas CS, Medeiros DM, Magaldi RB,
Schettino GP, Lorenzi-Filho G, et al. Effect of aprotective-ventilation strategy on mortality in theacute respiratory distress syndrome. N Engl J Med
1998;338:347–354.
2 American Thoracic Society. Recommendations forstandardized procedures for the on-line and off-line
measurement of exhaled lower respiratory nitricoxide and nasal nitric oxide in adults and children1999. Am J Respir Crit Care Med 1999;160:2104–
2117.
3 Arieli R, Van Liew HD. Correction for the responsetime and delay of mass spectrometers. J Appl Physiol 1981;51:1417–1422.
4 Belvisi M, Barnes PJ, Larkin S, Yacoub M, Tadjkarimi
S, Williams TJ, et al. Nitric oxide synthase activity
is elevated in inflammatory lung disease in humans.
Eur J Pharmacol 1995;283:255–258.
5 Blebea J, Bacik B, Strothman G, Myatt L. Decreased nitric oxide production following extremity
ischemia and reperfusion. Am J Surg 1996;172:
158–161.
6 Borland C, Cox Y, Higenbottam T. Measurement of
exhaled nitric oxide in man. Thorax 1993;48:1160–
1162.
7 Broccard AF, Hotchkiss JR, Suzuki S, Olson D,
Marini JJ. Effects of mean airway pressure and tidal
excursion on lung injury induced by mechanical ventilation in an isolated perfused rabbit lung model.
Crit Care Med 1999;27:1533–1541.

143

Y. Minami et al.

luminescence underestimates nitric oxide concentration in the presence of potent inhalation anaesthetics. Br J Anaesth 2000;84:596–599.
21 Oka T, Ozawa Y, Sato J. Lung collapse during one
lung ventilation does not change low frequency
respiratory mechanics. Masui 1998;47:1427–1432(in Japanese).
22 Rehder K, Wenthe FM, Sessler AD. Function ofeach lung during mechanical ventilation with ZEEP
and with PEEP in man anesthetized with thiopentalmeperidine. Anesthesiology 1973;39:597–606.
23 Robbins RA, Floreani AA, Von Essen SG, Sisson
JH, Hill GE, Rubinstein I, et al. Measurement of exhaled nitric oxide by three different techniques. Am
J Respir Crit Care Med 1996;153:1631–1635.
24 Rogers SN, Benumof JL. Halothane and isoflurane
do not decrease PaO2 during one-lung ventilation in
intravenously anesthetized patients. Anesth Analg
1985;64:946–954.
25 Sartori C, Lepori M, Busch T, Duplain H,
Hildebrandt W, Bärtsch P, et al. Exhaled nitric oxide

does not provide a marker of vascular endothelial
function in healthy humans. Am J Respir Crit Care
Med 1999; 160:879–882.
26 Stewart TE, Valenza F, Ribeiro SP, Wener AD,
Volgyesi G, Mullen JB, et al. Increased nitric oxide
in exhaled gas as an early marker of lung inflammation in a model of sepsis. Am J Respir Crit Care Med
1995;151:713–718.
27 Törnberg DC, Bjorne H, Lundberg JO, Weitzberg E.
Multiple single breath measurements of nitric oxidein the intubated patient. Am J Respir Crit Care Med
2003;168:1210–1215.
28 Wulff KE, Aulin I. The regional lung function in thelateral decubitus position during anesthesia andoperation. Acta Anaesthesiol Scand 1972;16:195–
205.

Received September 29, 2003; accepted November 6, 2003
Corresponding author: Yukari Minami

144