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Division of Emergency Medical Services, Public Health - Seattle & King County, Seattle, WA, United StatesDepartment of Medicine, Division of Cardiology, University of Washington, Seattle, WA, United States
Division of Emergency Medical Services, Public Health - Seattle & King County, Seattle, WA, United StatesDepartment of Medicine, Division of General Medicine, University of Washington, Seattle, WA, United States
Department of Emergency Medicine, University of Washington, Seattle, WA, United StatesDepartment of Medicine, Division of Pulmonary, Critical Care, and Sleep Medicine, University of Washington, Seattle, WA, United States
Respiratory mechanics, such as tidal volume (VT) and inspiratory pressures, may affect outcome in hospitalized patients with respiratory failure. Little is known about respiratory mechanics in the prehospital setting.
Methods
In this prospective, pilot investigation of patients receiving prehospital advanced airway placement, paramedics applied a device to measure respiratory mechanics. We evaluated tidal volume (VT) per predicted body weight (VTPBW) to determine the proportion of breaths within the lung-protective range of 4–10 mL/kg per PBW overall, according to ventilation bag volume (large versus small) and cardiac arrest status (active CPR, post-ROSC, non-arrest).
Results
Over 16-months, 7371 post-intubation breaths were measured in 54 patients, 32 patients with cardiac arrest and 22 with other conditions. Paramedics ventilated 19 patients with a small bag and 35 patients with a large bag. Overall, mean VT was 435 mL (95% CI 403, 467); VTPBW was 7.0 mL/kg (95% CI 6.4, 7.6) with 75% within the lung-protective range. Mean VTPBW and peak pressure differed according to arrest status (absolute difference −0.36 mL/kg and 32 cmH2O for active CPR compared to post-ROSC), though not according to bag size.
Conclusions
We observed that measuring respiratory mechanics in the prehospital setting was feasible. Tidal volumes were generally delivered within a safe range. Respiratory mechanics varied most significantly with active CPR with lower VTPBW and higher peak pressures, though did not seem to be affected by bag size. Future work might examine the relationship between respiratory mechanics and outcomes, which may identify opportunities to improve clinical outcomes.
EMS providers are equipped with the skills and tools which can enable them to restore ventilation and oxygenation in critically ill patients. Airway management typically begins with oxygen supplementation and manual delivery of breaths by bag-valve mask (BVM) ventilation, often followed by placement of an advanced airway, most commonly endotracheal intubation.
In hospitalized patients, mechanical ventilation with high volumes and elevated inspiratory pressures are known to precipitate and exacerbate lung injury, contributing to significant morbidity and mortality.
Studies have shown delivery of lower tidal volumes and distending pressures can reduce mortality, especially in patients with the acute respiratory distress syndrome (ARDS).
Guidelines for patients with ARDS recommend limiting tidal volumes to 4–8 mL/kg of predicted body weight (PBW) and limiting inspiratory pressure to a plateau pressure < 30 cmH20.
An official American Thoracic Society/European Society of intensive care medicine/society of critical care medicine clinical practice guideline: Mechanical ventilation in adult patients with acute respiratory distress syndrome.
Association between use of lung-protective ventilation with lower tidal volumes and clinical outcomes among patients without acute respiratory distress syndrome: a meta-analysis.
Effect of a Low vs Intermediate Tidal Volume Strategy on Ventilator-Free Days in Intensive Care Unit Patients Without ARDS: A Randomized Clinical Trial.
suggesting that protective lung strategies may be important in the prehospital setting.
There is limited evidence to guide optimal prehospital ventilation. Knowledge about manual ventilation has been derived largely from animal, cadaver, and simulation studies, or examined through indirect measurement of respiratory parameters, such as end-tidal carbon dioxide and thoracic impedance.
We aimed to address this gap by measuring real-time respiratory mechanics during manual ventilation provided by EMS personnel following endotracheal intubation.
Design & methods
Study design, setting, and population
This investigation was a prospective, observational study of a convenience sample of adults who received advanced airway management by a single EMS agency between August 2018 and January 2020. The agency serves a population of over 250,000 residents who reside in urban, suburban, and rural areas. The primary 9-1-1 medical response is two-tiered. The first tier is provided by firefighter emergency medical technicians trained and equipped with BVM for ventilation support.
The second tier is comprised of paramedics who are dispatched in cases of more severe illness. Paramedics are trained in advanced airway techniques including rapid sequence intubation with neuromuscular blocking agents and supraglottic airway use.
Endotracheal intubation is the primary strategy for advanced airway management. OHCA patients are treated according to local protocols that are consistent with the American Heart Association and International Liaison Committee on Resuscitation guidelines.
Executive Summary: 2020 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations.
Adult Advanced Life Support: 2020 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science with Treatment Recommendations.
Following endotracheal intubation, cardiopulmonary resuscitation is provided with continuous chest compressions with breaths interposed without any pause in chest compressions. The investigation was designed and reported in a manner consistent with STROBE guidelines.
The study was reviewed and approved by the University of Washington Investigational Review Board and the Public Health Seattle & King County Research Administrative Review Committee.
Ventilation measurement and study procedures
The device under study (Capnostat® Philips Healthcare Corporation, Bothell, WA) was placed between the endotracheal tube and the ventilation bag and passively recorded ventilation parameters in a blinded fashion that did not disclose values to care providers. The Philips Capnostat® technology is used to measure mechanical ventilation in the hospital setting and has been clinically validated. The device measures inspiratory tidal volume (mL), inspiratory and expiratory airway pressure (cmH2O), inspiratory flow rate (LPM), and end tidal carbon dioxide (mm Hg) for each breath (Fig. 1). The ventilation measuring device was applied by paramedics as early as possible during the course of care, including during resuscitation from OHCA with ongoing chest compressions and following return of spontaneous circulation. Recordings for each patient continued until termination of resuscitation efforts or arrival at the hospital. Breaths were studied strictly after intubation in order to avoid measurements confounded by poor facemask seal during BVM. The EMS agency transitioned from using large ventilation bags (Adult CPR-2 CPR-2 Bag® Mercury Medical, Clearwater, FL; volume 1685 mL, tidal volume 700–1050 mL) to small ventilation bags (Small Adult CPR-2 CPR-2 Bag® Mercury Medical, Clearwater, FL; volume 1000 mL, tidal volume 450–725 mL) during the study period.
The current investigation used electronic EMS patient records to assess patient characteristics, incident circumstances, and EMS care. For OHCA patients, data were organized according to the Utstein template.
Cardiac arrest and cardiopulmonary resuscitation outcome reports: Update of the Utstein resuscitation registry templates for out-of-hospital cardiac arrest: A statement for healthcare professionals from a task force of the international liaison committee.
The EMS patient record was supplemented with information from a separate advanced airway registry, the real-time defibrillator recordings, and hospital records. The airway registry captures detailed information about the circumstances, care, and outcome specific to advanced airway management.
The airway ventilation data were linked to the EMS patient report, the airway registry, and the defibrillator recording, along with available hospital records. Height was extracted from hospital data; if a patient died before hospital arrival or height was missing from the hospital record, height was imputed as the average height of American men (175.3 cm) and women (161.3 cm) over age 20 from 2015-2018.
National Center for Health Statistics Vital and Health Statistics. Anthropometric Reference Data for Children and Adults: United States, 2015-2018. 2021;3. Accessed September 17, 2021. https://www.cdc.gov/nchs/products/index.htm.
Waveforms of the respiratory mechanics were processed using Matlab software to obtain the tidal volume (mL), peak pressure (cmH2O), end-tidal carbon dioxide (mm Hg), and maximum inspiratory flow (L/min) for each breath (Fig. 1). Minute ventilation (L/min) was computed from the tidal volume and the respiratory rate, which was calculated as the total number of breaths delivered minute by minute. In order to calculate a standardized inspiratory tidal volume adjusted for predicted body weight (VTPBW), the predicted bodyweight (PBW) was computed from sex and height with the Devine formulas.
An official American Thoracic Society/European Society of intensive care medicine/society of critical care medicine clinical practice guideline: Mechanical ventilation in adult patients with acute respiratory distress syndrome.
An official American Thoracic Society/European Society of intensive care medicine/society of critical care medicine clinical practice guideline: Mechanical ventilation in adult patients with acute respiratory distress syndrome.
Effect of a Low vs Intermediate Tidal Volume Strategy on Ventilator-Free Days in Intensive Care Unit Patients Without ARDS: A Randomized Clinical Trial.
An official American Thoracic Society/European Society of intensive care medicine/society of critical care medicine clinical practice guideline: Mechanical ventilation in adult patients with acute respiratory distress syndrome.
although plateau pressure and maximum pressure differ, pressures greater than 35 cmH2O may present some risk of barotrauma.
Because ventilation may be affected by bag size and chest compressions, each breath was characterized by the bag volume (large vs small) and arrest status. Arrest status was classified into three groups: (1) arrest with active chest compressions (OHCA with CPR); (2) arrest post return of spontaneous circulation (ROSC) (OHCA post ROSC); and (3) non-arrest. A patient who achieved ROSC could contribute ventilations to both the OHCA with CPR and OHCA post ROSC groups.
Statistical analysis
We used descriptive statistics to summarize demographic, clinical, and airway data of the overall cohort and the different subgroups. In the primary analysis, we used generalized linear mixed-effects models with patient as a random effect to estimate mean ventilation measures. The secondary analysis evaluated how bag size and arrest status were related to two key variables: VTPBW and peak pressure. Adjusted absolute differences for VTPBW and peak pressure were estimated by linear mixed-effects models with patient as a random effect and bag size and arrest status as fixed effects. Similarly, adjusted odds ratios for the delivery of a lung-protective breath and the delivery of a breath with elevated peak pressure were estimated by logistic mixed-effects models. Statistical tests were chi-squared for categorical and F-test for continuous variables. We implemented a Bonferroni correction for 12 comparisons at a level of significance of 0.05 and considered a p-value < 0.004 as significant.
R version 4.0.3 with package lme4 were used for statistical analysis.
A total of 7371 post-intubation breaths from 54 patients were analyzed. The median age of patients was 67 [IQR 51,77] years, 43% were female (Table 1). Nearly 60% of patients (32 of 54) were treated for OHCA (Fig. 2). Of the patients without OHCA (22 of 54), the clinical assessment was respiratory failure in 9 (41%), altered mental status with concern about airway protection in 4 (18%), stroke in 2 (9%), overdose in 3 (14%), trauma in 2 (9%), and other medical etiologies in 2 (9%). Overall, 19 patients (36%) were ventilated with the smaller bags, and 35 (64%) were ventilated with the larger bags (Table 1). Height was missing for 15 (28%) patients.
Table 1Patient characteristics and ventilation parameters, stratified by bag size and cardiac arrest status.
Overall
Bag Size
Arrest Status
Bag Size 1000 mL
Bag Size 1500 mL
OHCA post ROSC
OHCA with CPR
Non-arrest
Patients, N
(N = 54)
(N = 19)
(N = 35)
(N = 19)*
(N = 17)*
(N = 22)
Age (years)
67 (51, 77)
69 (59, 81)
63 (41, 76)
69 (58, 76)
70 (59, 84)
59 (37, 76)
Female, %(n)
43% (23)
63% (12)
31% (11)
42% (8)
24% (4)
59% (13)
Height (cm)
170 (158, 178)
163 (157,169)
173(156, 182)
171(153, 180)
179(165, 190)
169(159, 176)
Indication for airway management
OHCA, %(n)
59% (32)
63% (12)
57% (20)
100% (19)
100% (17)
Respiratory, %(n)
17% (9)
16% (3)
17% (6)
41% (9)
Altered mental status, %(n)
7% (4)
0% (0)
11% (4)
18% (4)
Stroke, %(n)
4% (2)
5% (1)
3% (1)
9% (2)
Overdose, %(n)
6% (3)
11% (2)
3% (1)
14% (3)
Trauma, %(n)
4% (2)
0% (0)
6% (2)
9% (2)
Other Medical, %(n)
4% (2)
5% (1)
3% (1)
9% (2)
Initial vital signs
SpO2 %
90 (75, 97)
96 (70, 97)
89 (78, 96)
92 (81, 97)
Heart Rate
0 (0, 109)
0 (0, 92)
0 (0, 120)
112 (92, 123)
Systolic Blood Pressure
0 (0, 132)
0 (0, 130)
0 (0, 138)
141 (118, 183)
Respiratory Rate
0 (0, 22)
0 (0, 16)
6 (0, 22)
23 (13, 30)
EMS Care provided
ALL RSI mentioned, %(n)
52% (28)
53% (10)
51% (18)
32% (6)
6% (1)
100% (22)
Emesis noted, %(n)
41% (22)
37% (7)
43% (15)
53% (9)
53% (9)
23% (5)
Initial EtCO2, %(n)
29 (17, 43)
37 (16,45)
27(17, 43)
32 (24,38)
25**
28 (17, 40)
Post intubation breaths measured per case
107 (68, 170)
116 (63, 163)
106 (80, 189)
153 (71, 223)
73 (41, 105)
105 (88, 155)
ABG
pH
7.24 (7.05, 7.33)
7.25 (7.20, 7.33)
7.23 (7.03, 7.32)
7.14 (7.03, 7.23)
7.05 (6.81, 7.11)
7.30 (7.23, 7.34)
pCO2
53 (41, 62)
42 (36, 59)
56 (46, 64)
53 (41, 73)
85 (64, 115)
50 (41, 60)
pO2
134 (71, 258)
135 (81, 353)
117 (63, 246)
107 (65, 395)
87 (49,194)
147 (73, 246)
HCO3
22 (18, 24)
22 (18, 24)
22 (17, 24)
18 (15, 23)
20 (18, 23)
24 (22, 25)
Base excess
−5.3 (−11.4, −0.9)
−6.5 (−8.9, −1.6)
−5.2 (−13.0, −0.4)
−10.0 (−14.7, −6.3)
−10.0 (−17.4, −6.6)
−3.0 (−5.1, 0.5)
Disposition
Overall Survival, %(n)
46% (25)
58% (11)
40% (14)
32% (6)
6% (1)
86% (19)
Duration of hospital stay, days
5 (3, 9)
4 (3, 10)
5 (2, 8)
4 (1, 6)
2 (1, 11)
5 (3, 11)
Duration of ventilation, days
2 (1, 4)
2 (1, 3)
3 (1, 5)
3 (2, 5)
3 (2, 5)
2 (1, 3)
Unless otherwise specified, values are medians (interquartile range).
*4 patients have measurements with ongoing CPR and after ROSC and are counted in both columns.
Fig. 2Flow diagram of patients and breaths. * In each of the Small Bag and Large Bag groups, there were two patients in both OHCA with CPR” and “OHCA post ROSC” groups. Abbreviations: OHCA = out-of-hospital cardiac arrest.
Overall, there was a median 107 breaths per case (IQR 68, 170). Mean VTPBW was 7.0 mL/kg PBW (95% CI 6.4, 7.6). 75% (95% CI 68%, 83%) of all breaths were within the 4–10 mL/kg PBW range. Mean peak pressure was 39 cmH2O (95% CI 34,44) with 52% >35 cmH2O. The mean VT was 435 mL (95% CI 403,467), and the mean respiratory rate was 10 breaths per minute (bpm) (95% CI 9, 11), producing a mean minute ventilation of 4.1 L/min (95% CI 3.8, 4.5) (Table 2).
Table 2Overall respiratory mechanics of all breaths measures (n = 7371), as estimated by generalized linear mixed-effect model estimates, adjusting for patient clustering.
Overall n = 7371
Mean
95% CI
VT PBW (mL/kg)
7.0
6.4, 7.6
VT (mL)
440
400, 470
Respiratory rate (bpm)
10
9, 11
Peak pressure (cm H2O)
39
34, 44
EtCO2 (mmHg)
48
43, 52
Flow max inspiratory (L/min)
46
43, 19
Minute Ventilation (L/min)
4.1
3.8, 4.5
Proportion
95% CI
Lung-protective VT PBW
89%
81, 94%
Peak pressure > 35 cmH2O
47%
22, 73%
Values are estimated means (95% CI) using generalized linear mixed-effect models with patient as random effect.
Abbreviations: EtCO2 = end tidal carbon dioxide (mmHg), VT = tidal volume (mL), VTPBW = tidal volume standardized by predicted body weight.
Fig. 3 presents the distribution of VTPBW according to individual patient, bag size, and arrest status. Of the total 7371 breaths, 4681 (64%) were measured in 35 patients using a large bag and 2690 (36%) in 19 patients using a small bag. There were no significant absolute differences in VTPBW, peak pressure, or proportion of breaths within the therapeutic lung-protective range between bag sizes (Table 3). Thirteen patients had breaths measured during CPR, 15 patients had breaths measured following ROSC. There were 2908 (39%) breaths in the non-arrest group, 1404 (19%) breaths in the OHCA with CPR group, and 3059 (42%) breaths in the OHCA post ROSC group. In comparison to the OHCA post ROSC group, VTPBW was smaller (absolute difference −0.36 mL/kg (95% CI −0.58, −0.13)), and peak pressure was greater (absolute difference 32 cmH2O (95% CI 31, 33)) in the OHCA with CPR group (Table 3). The odds of delivering a breath with elevated peak pressure was significantly higher in the OHCA with CPR group than OHCA post ROSC group (odds ratio 20, 95% CI 11, 35). Meanwhile, there was no difference in VTPBW, peak pressure, or lung-protective breath proportion between the non-arrest and OHCA post ROSC groups (Table 3).
Fig. 3Each breath measured in VT/PBW (mL/kg), stratified by each individual case (A), bag size (B), and arrest status (C). Each dot represents a breath measured. The lung-protective range of 4 to 10 mL/kg PBW is marked with the dotted horizontal lines. Horizontal bar marks median value. Abbreviations: VT = tidal volume (mL), PBW = predicted body weight (kg), OHCA = out-of-hospital cardiac arrest, ROSC = return of spontaneous circulation, CPR = cardiopulmonary resuscitation compressions.
Table 3Comparisons by bag size and among arrest status.
Bag Size
Arrest Status
Large Bag vs. Small Bag
OHCA with CPR vs. OHCA post ROSC
Non-arrest vs. OHCA post ROSC
Adjusted Absolute Difference (95% CI)
p-value
Adjusted Absolute Difference (95% CI)
p-value
Adjusted Absolute Difference (95% CI)
p-value
VTPBW (mL/kg)
0.06 (−1.18, 1.31)
0.46
−0.36 (−0.58, −0.13)
0.001*
−0.18 (−1.39, 1.03)
0.39
Peak pressure (cmH2O)
−2.5 (−10, 5.3)
0.27
32 (31, 33)
<0.001*
−1.49 (−9.09, 6.11)
0.35
Odds Ratio (95% CI)
p-value
Odds Ratio (95% CI)
p-value
Odds Ratio (95% CI)
p-value
Lung-protective VT PBW
0.56 (0.15, 2.03)
0.38
1.46 (0.96, 2.22)
0.08
5.9 (1.6, 22)
0.01
Peak pressure > 35 cmH2O
0.48 (0.07, 3.40)
0.46
20 (11, 35)
<0.001*
0.14 (0.02, 0.95)
0.05
*p < 0.004, significant after Bonferroni correction for 12 comparisons at p-value 0.05.
Values are adjusted absolute differences (95% CI) for continuous variables and odds ratios for binary variables, using generalized linear mixed-effect models with patient as random effect, and adjusting for bag size and arrest status.
Abbreviations: OHCA = out-of-hospital cardiac arrest, CPR = cardiopulmonary resuscitation with chest compressions, ROSC = return of spontaneous circulation, VTPBW = tidal volume standardized by predicted body weight.
Respiratory mechanics in the prehospital setting are challenging to measure. Hence, there is a lack of measured respiratory parameters using manual ventilations—information that is necessary if we are to evaluate ventilation characteristics and improve clinical outcomes. In this observational study of patients treated with advanced airway in the prehospital setting, we demonstrated the feasibility of measuring respiratory mechanics. It was possible to obtain novel data which characterized manual ventilation in both OHCA and non-arrest patients, which is fundamental if we are to evaluate ventilation characteristics with the goal of improving clinical outcomes. While pulse oximetry, end-tidal CO2, and transthoracic impedance metrics can provide some insight, they do not measure other respiratory dynamic parameters such as tidal volume or airway pressures that have been associated with clinical outcomes. We demonstrated feasibility of such measurement in dynamic circumstances.
There is currently modest evidence regarding ventilation in the prehospital emergency circumstance. Clinical guidelines for OHCA resuscitation recommend a respiratory rate of 10–12 per minute and just enough tidal volume “to achieve chest rise over 1–2 seconds” as operational guidance. In prior human studies involving cardiac arrest resuscitation, research has largely focused on ventilation rates with some evidence indicating harm with rapid ventilation rates that exceed guidelines.
The current results indicate that the ventilation rate was on average about 8 breaths/min during CPR and about 10 breaths/min post ROSC. The results suggest that excessive ventilation rates were not a common problem during CPR, post ROSC, or for other conditions, a finding that is reassuring given prior reports.
Adult Advanced Life Support: 2020 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science with Treatment Recommendations.
The current study provides novel information about tidal volume and inspiratory pressure in the prehospital setting. In-hospital studies of mechanical ventilation suggest that standardized tidal volumes between 4 to 10 mL/kg PBW accompanied by lower airway pressures can reduce lung injury and clinical sequelae.
An official American Thoracic Society/European Society of intensive care medicine/society of critical care medicine clinical practice guideline: Mechanical ventilation in adult patients with acute respiratory distress syndrome.
Using this basic framework, we observed that most – though not all – ventilations were within lung-protective volume. Whether this variability during the relatively brief but early period (i.e. < 1 hour) of ventilation has immediate or downstream clinical consequence is uncertain. The variability however does suggest there is likely a range that occurs in clinical practice that may influence physiology and potentially outcome. Whether reducing variability or targeting a respiratory parameter (tidal volume or airway pressure) in the prehospital circumstance can improve outcome is not known, but these findings indicate this could be a strategy for further investigation.
We observed that patients with ongoing CPR had elevated peak pressure and lower tidal volume compared with OHCA patients without ongoing CPR. Whether these different respiratory mechanics are clinically important is not certain, and may reflect the effects of concomitant chest compressions, increased airway resistance, or decreased respiratory system compliance. During CPR, physiology is markedly altered, and lung-protective needs may differ so that the distinct respiratory profiles may be appropriate. In contrast, we did not observe different ventilation parameters according to the bag size after adjustment for patient clustering and arrest status, suggesting that this change in equipment alone may not produce measurable physiologic differences, or that paramedics were able to titrate ventilations to provide mostly appropriate rates, volumes, and pressures regardless of bag size.
Limitations
While the dataset included a large number of breaths, the modest number of study patients requires statistical approaches that account for clustering by patient and potentially limit power to make comparisons to include associations between respiratory mechanics and outcomes. We used a Bonferroni correction to address multiple comparison as a conservative interpretation of the results; other methodological approaches can be used to consider significance in such circumstances. The use of a random effect for patient is assuming the same within patient correlation for all observations, and that this within-patient correlation is identical in all groups, relationships which may not necessarily be true. Patient heights were missing for those who died in field or died prior to measurement, introducing some selection bias for more ill patients having an imputed average height and likely a less accurate VTPBW. This study occurred in a single high-performing EMS agency, which may have implications for generalizability. The investigation did not have case-specific information about the provider’s education or experience, which could influence ventilation performance. The choice of bag size was not randomized, but rather occurred as part of agency-wide implementation of the smaller bag and results may be confounded by other characteristics not included in the multivariable model. The ventilation measuring device was only applied in instances where there was time and space so as not to impede patient care; this might have introduced selection bias where patients who were less ill had the device applied. Given logistics of the ventilation measuring device application in the current study, measurement typically occurred after endotracheal intubation. Thus, the results are relevant for advanced airways; respiratory mechanics likely differ prior to intubation. For example, ventilations are often delivered by a bag mask in a different strategy that interrupts compressions to deliver ventilations. The device measures peak pressure and is unable to measure plateau pressure, so we were unable to measure pulmonary compliance. Finally, we had limited data about underlying pulmonary disease.
Conclusions
In prehospital patients receiving an advanced airway, respiratory mechanics can be measured in real-time. Tidal volumes were generally delivered in a lung-protective range of 4–10 mL/kg, though variation exists in particular with chest compressions. During chest compressions, VTPBW was observed to be lower, while peak airway pressures were observed to be higher, when compared to the post ROSC group. Bag size did not appear to affect respiratory mechanics. These results suggest an opportunity for future work to advance care if we can measure and understand the relationship between respiratory mechanics and clinical care, and in turn affect ventilation strategies to improve clinical outcomes.
Author contribution statement
BY, MS, TR, NJ, DJ made contributions and design of the study. JB, MG, JS, SG, JB were instrumental in acquiring the data. JB, BY, and HK completed data analysis. BY, TR, NJ, HK, PK, DJ, MG, and MS helped interpret the data results. BY, JB, TR, HK, and NS drafted the manuscript, and all provided critical input in revision. All authors have given final approval of the manuscript submitted and agree to be accountable for the work. The authors have no additional writing assistance to disclose.
Conflicts of Interest Statement
DJ and MG are employees of Philips Healthcare, which donated the Capnostat monitors for the study. The other authors have no conflicts of interest to report.
Acknowledgments
The authors would like to acknowledge the dedication of the Bellevue Fire Department paramedics and the provision of ventilation measuring devices from Philips, Eindhoven.
Appendix A. Supplementary data
The following are the Supplementary data to this article:
An official American Thoracic Society/European Society of intensive care medicine/society of critical care medicine clinical practice guideline: Mechanical ventilation in adult patients with acute respiratory distress syndrome.
Association between use of lung-protective ventilation with lower tidal volumes and clinical outcomes among patients without acute respiratory distress syndrome: a meta-analysis.
Effect of a Low vs Intermediate Tidal Volume Strategy on Ventilator-Free Days in Intensive Care Unit Patients Without ARDS: A Randomized Clinical Trial.
Executive Summary: 2020 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations.
Adult Advanced Life Support: 2020 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science with Treatment Recommendations.
Cardiac arrest and cardiopulmonary resuscitation outcome reports: Update of the Utstein resuscitation registry templates for out-of-hospital cardiac arrest: A statement for healthcare professionals from a task force of the international liaison committee.
National Center for Health Statistics Vital and Health Statistics. Anthropometric Reference Data for Children and Adults: United States, 2015-2018. 2021;3. Accessed September 17, 2021. https://www.cdc.gov/nchs/products/index.htm.
Effect of a Low vs Intermediate Tidal Volume Strategy on Ventilator-Free Days in Intensive Care Unit Patients Without ARDS: A Randomized Clinical Trial.
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