Abstract
BACKGROUND: Extubation readiness testing (ERT) is often performed in children with congenital heart disease prior to liberation from mechanical ventilation. The ideal ERT method in this population is unknown. We recently changed our ERT method from variable (10, 8, or 6 cm H2O, depending on endotracheal tube size) to fixed (5 cm H2O) pressure support (PS). Our study assessed the association between this change and time to first extubation and need for re-intubation.
METHODS: We studied 2 temporally distinct cohorts, one where ERT was conducted with variable PS and another using PS fixed at 5 cm H2O. Data were prospectively collected as part of a quality improvement project. The primary outcome was time to first extubation. Secondary outcomes were need for re-intubation and percentage of successful ERTs. We performed Poisson regression or logistic regression for the association between PS during ERT and time to first extubation or re-intubation, respectively.
RESULTS: We included 320 subjects, 186 in the variable PS group and 152 in fixed PS group. In unadjusted analysis, median time to first extubation was longer in the fixed PS group compared to the variable PS group (4.1 [2.0–7.1] d vs 3.1 [1.1–5.9] d, P = .02), and there was no difference in re-intubation rate (11% vs 8%, P = .34). Subjects in the fixed PS group were significantly more likely to be mechanically ventilated after cardiac arrest, have a Society of Thoracic Surgeons-European Association for Cardio-Thoracic Surgery (STAT) category of 4 or 5, be extubated on day shift, receive enteral feeds at extubation, have higher respiratory support at extubation, and higher dead-space-to-tidal-volume ratio. After controlling for these variables in multivariable regression, we found no association between the choice of PS and time to first extubation or re-intubation.
CONCLUSIONS: The use of a fixed PS of 5 cm H2O instead of variable PS during ERT was not associated with longer time to first extubation or extubation failure.
- extubation readiness testing
- spontaneous breathing trials
- children
- congenital heart disease
- respiratory therapy
- protocol
- pressure support
- mechanical ventilation
Introduction
Mechanical ventilation frequently is required in the treatment of children admitted to the pediatric cardiac ICU (PCICU), especially among those recovering from surgery to correct or palliate congenital heart disease (CHD). The respiratory support needs of these unique patients are influenced by numerous factors, including exposure to cardiopulmonary bypass and blood products, abrupt changes in physiology, malnutrition, passive- or shunt-dependent pulmonary blood flow, unbalanced pulmonary and systemic circulation, and the occurrence of postoperative complications. These factors can increase the complexity of postoperative respiratory care, prolong duration of mechanical ventilation, and can result in higher rates of extubation failure.1,2 Re-intubation rates as high as 32% have been reported in this setting but are most commonly between 7–17%.3-5
Timely identification of a patient’s ability to separate from invasive mechanical ventilation is important to prevent ventilator-associated morbidity. Daily extubation readiness testing (ERT) is used at many centers to identify children who meet criteria for liberation from invasive mechanical ventilation.6 ERT has been shown to decrease the duration of mechanical ventilation and the need for re-intubation and has a high sensitivity for identifying patients ready to be removed from invasive mechanical ventilation.3,6,7 However, most published studies on liberation from mechanical ventilation have excluded children with CHD. A single-center randomized controlled trial (RCT) in children with CHD found that daily ERT resulted in lower rates of extubation failure and shorter ICU length of stay (LOS) but no difference in duration of mechanical ventilation or mortality.3 A recent retrospective, single-center study found that ERT had a low sensitivity to predict extubation failure.7
In our dedicated PCICU, all patients are screened daily for ERT eligibility. As part of a multifaceted quality improvement project, we evaluated our clinical practice to identify barriers to the daily conduct of ERT in children with critical heart conditions recovering from cardiac surgery or associated procedures. During that process, we also modified our ERT protocol to better align with the knowledge that most children may receive excessive pressure support (PS) during ERT.6,8-10 Historically, our ERT protocol employed a variable PS (10, 8, or 6 cm H2O) depending on endotracheal tube (ETT) size; this was changed to conducting ERT with a fixed PS of 5 cm H2O, regardless of ETT size. The purpose of this study was to evaluate subject outcomes following changes to our ERT methodology from variable to fixed PS. We hypothesized that the change to conducting ERT with a fixed PS of 5 cm H2O would not be associated with a longer time to first extubation or higher rate of re-intubation compared with ERT using variable PS.
QUICK LOOK
Current Knowledge
Extubation readiness testing (ERT) is commonly performed in children with congenital heart disease (CHD). There is limited evidence about how to perform ERTs in children with CHD. ERTs may be performed using variable pressure support (PS), fixed PS, CPAP, or T-piece.
What This Paper Contributes to Our Knowledge
ERT method was not associated with time to first extubation or re-intubation. These results indicate that the specific method of ERT may not be as important as ensuring ERTs are done daily in eligible patients. Most ERT failures were due to tachypnea in the fixed PS group compared to low tidal volume in the variable PS group.
Methods
This study was deemed exempt by the Duke University Institutional Review Board as part of quality improvement effort, so written informed consent was waived for participation. Data were prospectively collected daily on all children receiving invasive mechanical ventilation in our PCICU. Subjects ventilated through a tracheostomy, those who died without an extubation attempt, or were transferred out of the PCICU prior to extubation were excluded. The respiratory therapist (RT) providing direct patient care filled out a data collection form kept at the bedside that included the current date, date and time mechanical ventilation was initiated, ventilator mode, peak inspiratory pressure, PEEP, mean airway pressure (
), dead-space-to-tidal-volume ratio (VD/VT), FIO2, ERT eligibility, and reason to forgo ERT (if applicable). In addition, the outcome of the ERT (passed or failed) was noted. In subjects that failed ERT, the reason for failure (eg, tachypnea, low VT) was noted. In subjects that passed the ERT, the type of support used at extubation or the reason the subject was not extubated was recorded. To determine VD/VT, the RT entered the PaCO2 at the time the arterial blood gas was sent, and then VD/VT was calculated automatically by the NM3 monitor (Philips Healthcare, Eindhoven, Netherlands). The NM3 monitor uses the mean expired CO2 to calculate VD/VT. Additional data on demographics, fluid balance, type of surgery, extubation shift (day or night), enteral feeding, need for preoperative intubation, and use of cardiopulmonary bypass in the operating room were extracted from the medical record by trained RTs. Data were then entered into a secure Research Electronic Data Capture (REDCap) database (REDCap, hosted at Duke University Medical Center, Durham, North Carolina).11
We studied 2 cohorts, one including subjects admitted to the PCICU between March 2019–January 2020 where daily ERT was performed with variable PS based on ETT size (variable PS group) and another for admissions between October 2020–August 2021 where a fixed PS of 5 cm H2O (fixed PS group) was used. All subjects were screened daily by night shift, around 4:00 am, for ERT eligibility. The ERT generally was performed between 5:00 am and 7:00 am so its outcome would be available before morning huddle and clinical rounds. If subjects passed ERT but were not extubated, ERT was repeated each day, provided they were eligible, until the subject was extubated. The procedure employed in our variable group prescribed that ERT would be performed at least daily in subjects who met eligibility criteria; these were (1) ventilation through an ETT, (2) closed sternotomy wound, (3) PEEP ≤ 7 cm H2O, (4) Δ pressure ≤ 20 cm H2O, (5) absence of hemodynamic instability, (6) absence of neuromuscular blockade or deep sedation, and (7) subject triggering breaths on the ventilator. The ERT was conducted using a PEEP of 5 cm H2O and variable PS depending on ETT size. A PS of 10 cm H2O was used in subjects intubated with 3.0 mm and 3.5 mm ETTs; a PS of 8 cm H2O was used in subjects intubated with 4.0 mm and 4.5 mm ETTs, and a PS of 6 cm H2O was used in subjects intubated with an ETT ≥ 5.0 mm.
In the first month of a washout period (February 2020–September 2020), we changed our ERT procedure to employ a PS of 5 cm H2O regardless of ETT size. This was done to align our protocol with data showing that higher levels of PS are not needed for smaller diameter ETTs at physiologic inspiratory flows (provided the ETT is appropriately sized) and may lead to excessive support during the spontaneous breathing trial.9,10 ERT eligibility criteria for the fixed PS group were similar as for the variable PS group. Additional ERTs could be performed at the discretion of the clinical team. The ERT was conducted for 60–120 min but was terminated in subjects that met failure criteria; these were development of significant respiratory distress, breathing frequency or heart rate higher than accepted age range, SpO2 below lesion-specific goal, hemodynamic instability, or VT < 5 mL/kg in the variable PS group or VT < 4 mL/kg in the fixed PS group. The minimal VT required to pass ERT was lowered to 4 mL/kg to allow ERT to be more consistent with the normal physiologic range of 4–8 mL/kg.
Postoperative subjects were classified according to the Society of Thoracic Surgeons-European Association for Cardio-Thoracic Surgery (STAT) category, which ranges from 1 (lowest complexity) to 5 (highest complexity). Subjects were then grouped a priori into those with a STAT category ≤ 3, 4, 5, and subjects receiving a ventricular assist device (VAD). In addition, non-indexed surgeries (eg, chest washouts, chest re-explorations) were combined with non-cardiac surgeries (eg, gastrostomy tube placement) for data analysis. The total number of ERTs and failed ERTs was categorized into ≤ 1 and ≥ 2. Ventilator settings and VD/VT were analyzed as continuous variables and subsequently categorized at a Δ pressure < or ≥ 12 cm H2O; PEEP < or ≥ 6 cm H2O; 
< or ≥ 9 cm H2O; FIO2 ≤ or > 0.40; and VD/VT < 0.30, 0.30–0.40, and > 0.40. Fluid balance was taken as the cumulative total for hospital stay as of 07:00 on the day of extubation. Reason(s) for failing ERT was recorded and classified as low VT, tachypnea, desaturation, apnea or poor effort or bradypnea, and hemodynamic instability. For subjects with multiple reasons for failing ERT, all reasons were reported separately.
Our primary outcome was time to first extubation. Secondary outcomes included the percentage of failed ERTs and need for re-intubation within 48 h. A power analysis for our primary outcome was performed to detect a 12-h difference in time to first extubation, assuming a mean 3.3 ± 1.5 d, determined we would need a minimum of 142 subjects in each group to detect a difference, with 0.80 power and 0.05 alpha. To account for potential attrition (eg, transfers, deaths), we planned to enroll a minimum of 150 subjects in the fixed PS group. Re-intubation was considered as the primary outcome; however, given our baseline re-intubation rate of 9.4%, it would have taken a sample size of 541 in each group to detect a decrease to 5% with 80% power, the lowest plausible re-intubation rate in this subject population. Illness severity was categorized into 3 groups: one composed of non-indexed cardiac surgery, non-surgical subjects, or post-procedure; a second group composed of subjects with STAT categorizations ≤ 3; and a third composed of subjects with STAT 4 and STAT 5 categorization and those following implantation of a VAD.
We used frequencies (with percentages) and medians (with 25th and 75th percentiles) to describe categorical and continuous study variables, respectively. We compared the distribution of clinical characteristics, ERT data, and clinical outcomes between ERT groups (fixed PS vs variable PS) using the chi-square test, Fisher exact test, or Wilcoxon rank-sum test, where appropriate.
To evaluate the adjusted association between ERT group (fixed PS vs variable PS) and clinical outcomes, we fitted 2 multivariable regression models: (1) Poisson regression for time to first extubation, reported as incidence rate ratio (IRR); and (2) logistic regression for re-intubation within 48 h, reported as odds ratio (OR). We adjusted both models for characteristics found to be statistically difference at a P < .10 between ERT groups. These variables included age, cardiac arrest as indication for mechanical ventilation, illness severity (STAT category), enteral feeds at extubation, timing of extubation, respiratory support at extubation, and time to first ERT. Statistical significance was set at a P < .05. Statistical analyses were performed using Stata SE 17.0 (StataCorp, College Station, Texas).
Results
We studied a total of 338 subjects, 186 in the variable PS group and 152 in the fixed PS group. Ten subjects were excluded from the variable PS group (6 died while mechanically ventilated; 2 received a tracheostomy, and 2 were transferred prior to extubation), and 8 subjects were excluded from the fixed PS group (4 died while mechanically ventilated; 2 received a tracheostomy, and 2 were transferred prior to extubation). Therefore, the final analysis included 320 subjects, with 176 in the variable PS group and 144 in the fixed PS group.
In unadjusted univariable analysis, subjects in the fixed PS group were more likely to be mechanically ventilated following cardiac arrest (5.6% vs 0.6%, P = .007), have a STAT category of 4 or 5 or be post-VAD placement (52.8% vs 38.6%, P = .02), be extubated on day shift (89.6% vs 78.4%, P = .007), be receiving enteral feeds before extubation (61.1% vs 35.8%, P < .001), and have different distribution of respiratory support following extubation (noninvasive ventilation [8.3% vs 4.0%], high-flow nasal cannula [83.3% vs 76.7%], P = .008) compared to the variable PS group (Table 1). There were no other statistically significant differences between the variable PS and fixed PS groups for clinical characteristics or need for re-intubation (Tables 1 and 2).
Clinical Characteristics
Outcomes, Extubation Readiness Testing Data, and Respiratory Parameters at Extubation
There were no statistically significant differences between the variable PS and fixed PS groups for the distribution of number of failed ≤ 1 ERT (86.9% vs 85.2%) and 2 or more times (13.1% vs 14.8%, P = .66), respectively, (Table 2). The rate of re-intubation within 48 h (8% vs 11.1%, P = .34) was also similar between the variable PS and fixed PS groups, respectively, (Table 2). In unadjusted univariable analysis, subjects in the fixed PS group had a longer time to first extubation (median 4.1 [interquartile range 2.0–7.1] vs 3.1 [1.1–5.9], P = .02), longer time to first ERT (median 2.5 [1–5] d vs 2 [1–4] d, P = .049), and higher VD/VT (0.38 [0.31–0.43] vs 0.32 [0.24–0], P = .002) compared to the variable PS group, respectively, (Table 2). There was no difference in median time to extubation after passing ERT (0 [0–1] d vs 0 [0–1] d, P = .82).
To adjust for observed differences between the 2 groups in the univariable analyses, we conducted a multivariable Poisson regression analysis for time to first extubation (primary outcome) and a multivariable logistic regression for re-intubation rate within 48 h (a secondary outcome). Poisson regression did not identify an association between ERT group (variable PS or fixed PS) and time to first extubation (IRR 0.95 [95% CI 0.85–1.05], P = .33). The multivariable logistic regression did not identify an association between ERT group (variable PS or fixed PS) and the rate of re-intubation at 48 h (OR 1.13 [95% CI 0.49–2.65], P = .77). Results are summarized in Table 3.
Results for Multivariable Analysis
ERT Eligibility Assessments
We studied a total of 2,025 daily ERT assessments, 1,009 in the variable PS group and 1,016 in the fixed PS group (Table 4). There were no statistically significant differences between variable and fixed PS groups for ERT eligibility (39% vs 40%, P = .84), extubation after passed ERT (57% vs 57%, P = .70), ventilator settings when ERT was performed, and ventilator settings when ineligible for ERT. Compared to the variable PS group, subjects in the fixed PS group had a higher VD/VT (0.34 ± 0.11 vs 0.39 ± 0.1, P < .001). This higher VD/VT in the fixed PS group was observed whether subjects were deemed eligible (0.33 ± 0.11 vs 0.39 ± 0.1, P < .001) or ineligible (0.35 ± 0.11 vs 0.39 ± 0.1, P < .001) to undergo ERT upon assessment (Table 4).
Individual Extubation Readiness Testing Assessments
The most common reasons ERT was not performed were use of neuromuscular blockade (17.5%), sedation (16.2%), provider request (12.5%), increase in ventilator support in the preceding hours (12.2%), and use of extracorporeal membrane oxygenation (10.8%). In univariable analysis, subjects in the fixed PS group were less likely to pass the ERT compared to those in the variable PS group (63.7% vs 70.7%, P = .03). In addition, a greater number of assessments in the fixed PS group was ineligible for ERT due to PEEP > 7 cm H2O (12.0% vs 7.9%, P = .033), provider request (16.0% vs 9.5%, P = .006), and use of high-frequency ventilation (1.6% vs 0.2%, P = .03) but were less likely to be ineligible for ERT due to sedation (10% vs 22%, P < .001) compared to the assessments in the variable PS group. Subjects in the fixed PS group were less likely to fail ERT due to low VT (31% vs 56%, P < .001) or apnea, poor effort, or bradypnea (8.0% vs 20.0%, P = .002) and more likely to fail ERT due to tachypnea (60% vs 19%, P < .001) or desaturation (22.0% vs 9.0%, P = .008). There were no differences for subjects failing due to both tachypnea and low VT (13% vs 11%, P = .12) or hemodynamic instability (0.7% vs 1.1%, P = .12).
Re-intubated Versus Successfully Extubated
A total of 30 (9.4%) subjects were re-intubated. Subjects receiving mechanical ventilation following cardiac arrest (10% vs 2%, P = .01) or who were intubated preoperatively (27% vs 9%, P = .008) were more likely to fail extubation and require re-intubation (Supplemental Table 1, see related supplementary materials at http://www.rcjournal.com). There were no statistically significant differences for age, weight, cyanotic heart disease, other indications for mechanical ventilation, STAT category, use of cardiopulmonary bypass in the operating room, fluid balance, type of respiratory support following extubation, enteral feeds, shift extubated, total number of ERT, respiratory parameters, or time to first extubation between subjects who were successfully extubated and those who were re-intubated within 48 h (Supplemental Table 1).
Discussion
We did not observe a difference in time to first extubation or need for re-intubation using a fixed PS during ERT compared to variable PS. While univariate analysis revealed an association between fixed PS and longer time to first extubation, this was confounded by higher illness severity in the fixed PS group. This difference in time to first extubation was not significant after controlling for severity of illness markers between the groups. There was also no association between variable or fixed PS in the need for re-intubation. Reasons for ERT failure differed between ERT methods, with those in the fixed PS group being more likely to fail due to tachypnea or desaturation and less likely due to low VT or apnea or poor respiratory effort.
Conceptually, ERT should be performed with an amount of support equivalent to that which the patient is expected to receive after extubation. Thus, based purely on physiology, the ideal method for identifying patients ready to extubation would be a T-piece trial or using 0/0 (PS/PEEP) while remaining on the ventilator. Importantly, the primary utility of ERTs is to identify patients ready to liberate from mechanical ventilation, not mimic postextubation physiology. To date, available data in adults have not shown an advantage to the T-piece method when compared to PS,12 although PS does result in a lower work of breathing.13 In children, ERTs are often performed using variable pressure based on the incorrect assumption that the ETT results in increased resistance, and higher pressure is needed to overcome resistance in smaller ETTs.7,14,15 This is based on a bench model that used supraphysiologic inspiratory flows,16 and more recent data in subjects found resistance from the airway to be similar as that of the ETT.10 Multiple studies have concluded that conducting spontaneous breathing trials using PS overestimates readiness for extubation; however, these studies were not outcome-based RCTs and excluded children with CHD.8,10
Subjects in the fixed PS group received higher support at extubation. This was most likely related to higher illness severity and longer duration of mechanical ventilation but could also have been related to more conservative management practices or other unmeasured factors. Postextubation respiratory support was not determined via protocol but rather by the clinical team, and we lack high-quality data on optimal noninvasive respiratory support after extubation for children with CHD. Somewhat paradoxically, subjects in the fixed PS group failed ERTs more commonly for tachypnea and not low VT, which may have been related to lowering the targeted VT from 5 to 4 mL/kg. Lowering the VT target is more consistent with physiologic VT, which ranges from 4–8 mL/kg in children. Future studies should evaluate VT and breathing frequency targets during ERT.
There are no RCTs comparing different ERT methods in pediatric subjects. The single RCT in children with CHD used a PS of 10 cm H2O in their intervention group compared to a gradual decrease in synchronized intermittent mandatory ventilation rate and inspiratory pressure to 15 cm H2O; once the breathing frequency was set to zero, PS was decreased by 2 cm H2O every 6 h until it reached 8 cm H2O.3 That study found no difference in time on mechanical ventilation; however, there was a significant increase in successful extubation in the ERT group, with the intervention arm being associated with a 2.5 times higher likelihood of successful extubation.3 Greater illness severity, time on cardiopulmonary bypass, and organ dysfunction scores were associated with re-intubation; and those requiring re-intubation had longer pediatric ICU (PICU) stay, longer time in the hospital, and higher mortality.3 The median duration of mechanical ventilation was < 24 h in both groups, and the subjects had significantly less complex surgeries compared to our subjects.3 These factors make it difficult to draw parallels with our results as both groups in our study received daily ERT assessment by RT protocol. Despite higher complexity and illness severity in our study, our re-intubation rate was lower (9% vs 17%). This may be related to the well-established ERT practice within our institution, difference in patient characteristics, or a yet unrecognized factor.
Daily screening for ERT eligibility is currently recommended despite limited data in children with CHD.3,6,14,17 The largest published pediatric RCT excluded children with CHD due to their complexity.14 An earlier trial evaluating protocol-based ventilator weaning also excluded subjects with single ventricle physiology.15 A secondary analysis of subjects intubated for lower respiratory tract infection in the RESTORE trial found ERTs to have a positive predictive value of 0.92 for extubation success.17 That study excluded postoperative and single ventricle subjects. One single-center RCT has been performed in children with CHD and found daily ERT was associated with higher extubation success and shorter ICU LOS but no difference in duration of mechanical ventilation.3 This trial is difficult to interpret because ERT eligibility was not based on pre-specified criteria; subjects were on minimal ventilator settings when randomized, and ERTs were performed using 10 cm H2O of PS, which was a minimal decrease in ventilator support.3 A retrospective, single-center study found that ERTs had a low sensitivity for extubation failure; however, 35% of subjects were extubated without an ERT, and the criteria for ERT eligibility were not protocolized.7
The decision to extubate in children with CHD is complex due to limited cardiopulmonary reserve, hemodynamic alterations from positive-pressure breathing, airway abnormalities, pulmonary edema, pulmonary hypertension, and upper-airway obstruction, in addition to standard reasons for extubation failure such as respiratory muscle weakness, impaired cough, and lung disease. Our overall re-intubation rate overall was 11%, which is identical to the 11% reported in a recent large multi-center database study of neonates.1 An important limitation of that study was the lack of granular data on extubation assessment strategies at the individual centers. Our re-intubation rate was lower than other single-center studies that reported re-intubation rates of 17% in single ventricle subjects,4 22% in those after the Norwood operation18 and 27% in infants post systemic-to-pulmonary shunt placement.17 None of the cited studies reported the method used to assess extubation readiness. A recent single-center study reported a re-intubation rate of 8%; however, the criteria for ERT eligibility were not protocolized, and only 65% of subjects received an ERT prior to extubation.7 Our cohort was similar to theirs; however, we performed ERTs in over 90% of subjects and included all subjects receiving mechanical ventilation, whereas their analysis was restricted to subjects ventilated for more than 48 h.7 Importantly, we also had a higher ERT failure rate (33% vs 18%), indicating we may have been more aggressive about identifying subjects with ventilator liberation potential. Studies of ERT failure rates in children with CHD are limited, with Faustino et al17 reporting a failure rate of 57% for the initial ERT in a cohort of children intubated for respiratory failure, whereas Ferguson et al8 reported an ERT failure rate of 17% and Foronda et al14 14%. None of these studies included children with CHD.
Our univariate analysis found an association between fixed and variable pressure support groups; however, there was no difference for reintubation for those extubated on night shift. This is similar to reports from 2 tertiary PICUs that also found no difference.18,19 A large study of 39,000 adult cardiac surgery subjects extubated overnight found no relationship between re-intubation and overnight extubation.20 Extubation overnight is also not associated with greater need for re-intubation in the neonatal ICU.21 These results indicate extubation decisions should not be influenced by shift.
Limitations
Our study has several limitations. First, due to our study design, the 2 groups were unbalanced, and we were unable to gather data on all potential confounding variables that may be associated with extubation. Second, our study was not designed to detect a difference in re-intubation and thus might have been underpowered for this specific outcome. Third, we did not record detailed data on vital signs and gas exchange during ERT; and despite our best efforts, the rationale for why subjects who passed ERT but were not extubated was not consistently recorded. We did not collect data on the specific distribution of lesions or operations performed, and using STAT category may not be the ideal method to stratify illness severity. Data on VD/VT were incomplete, and we were unable to include it in multivariable analysis. Lastly, we did not have data on the cardiac function, atrioventricular valve regurgitation, cuff leak test, daily fluid balance, sedation strategies, or inotropes at the time of extubation.
Conclusions
Conducting ERT with a fixed PS was not associated with longer time to first extubation or need for re-intubation compared to ERT conducted with variable PS.
Footnotes
- Correspondence: Andrew G Miller MSc RRT RRT-ACCS RRT-NPS FAARC. E-mail: Andrew.g.miller{at}duke.edu
See the Related Editorial on Page 440
Mr Miller is a section editor for Respiratory Care and discloses a relationship with Saxe Communications. Dr Rotta discloses relationships with Breas US, Vapotherm, Elsevier, and S2N Health. The remaining authors have disclosed no conflicts of interest.
Supplementary material related to this paper is available at http://www.rcjournal.com.
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