Six methods to determine expiratory time constants in mechanically ventilated patients: a prospective observational physiology study.

BACKGROUND: Expiratory time constant (τ) objectively assesses the speed of exhalation and can guide adjustments of the respiratory rate and the I:E ratio with the goal of achieving complete exhalation. Multiple methods of obtaining τ are available, but they have not been compared. The purpose of this study was to compare six different methods to obtain τ and to test if the exponentially decaying flow corresponds to the measured time constants. METHODS: In this prospective study, pressure, flow, and volume waveforms of 30 postoperative patients undergoing volume (VCV) and pressure-controlled ventilation (PCV) were obtained using a data acquisition device and analyzed. τ was measured as the first 63% of the exhaled tidal volume (VT) and compared to the calculated τ as the product of expiratory resistance (RE) and respiratory system compliance (CRS), or τ derived from passive flow/volume waveforms using previously published equations as proposed by Aerts, Brunner, Guttmann, and Lourens. We tested if the duration of exponentially decaying flow during exhalation corresponded to the duration of the predicted second and third τ, based on multiples of the first measured τ. RESULTS: Mean (95% CI) measured τ was 0.59 (0.57-0.62) s and 0.60 (0.58-0.63) s for PCV and VCV (p = 0.45), respectively. Aerts method showed the shortest values of all methods for both modes: 0.57 (0.54-0.59) s for PCV and 0.58 (0.55-0.61) s for VCV. Calculated (CRS * RE) and Brunner's τ were identical with mean τ of 0.64 (0.61-0.67) s for PCV and 0.66 (0.63-069) s for VCV. Mean Guttmann's τ was 0.64 (0.61-0.68) in PCV and 0.65 (0.62-0.69) in VCV. Comparison of each τ method between PCV and VCV was not significant. Predicted time to exhale 95% of the VT (i.e., 3*τ) was 1.77 (1.70-1.84) s for PCV and 1.80 (1.73-1.88) s for VCV, which was significantly longer than measured values: 1.27 (1.22-1.32) for PCV and 1.30 (1.25-1.35) s for VCV (p < 0.0001). The first, the second and the third measured τ were progressively shorter: 0.6, 0.4 and 0.3 s, in both ventilation modes (p < 0.0001). CONCLUSION: All six methods to determine τ show similar values and are feasible in postoperative mechanically ventilated patients in both PCV and VCV modes.

Development and evaluation of a mechanical ventilator-sharing system.

Background: During the COVID-19 pandemic surge in the hospitalization of critically ill patients and the global demand for mechanical ventilators, alternative strategies for device sharing were explored. We developed and assessed the performance of a system for shared ventilation that uses clinically available components to individualize tidal volumes under a variety of clinically relevant conditions. The feasibility of remote monitoring of ventilators was also assessed. Methods: By using existing resources and off-the-shelf components, a ventilator-sharing system (VSS) that ventilates 2 patients simultaneously with a single device, and a ventilator monitoring system (VMS) that remotely monitors pulmonary mechanics were developed. The feasibility and effectiveness of VSS and VMS were evaluated in benchtop testing using 2 test lungs on a single ventilator, and then performance was assessed in translational swine models of normal and impaired lung function. Results: In benchtop testing, VSS and VMS delivered the set individualized parameters with minimal % errors in test lungs under pressure- and volume-regulated ventilation modes, suggesting the highest precision and accuracy. In animal studies, the VSS and VMS successfully delivered the individualized mechanical ventilation parameters within clinically acceptable limits. Further, we found no statistically significant difference between the target and measured values. Conclusion: The VSS adequately ventilated 2 test lungs or animals with variable lung conditions. The VMS accurately displayed mechanical ventilation settings, parameters, and alarms. Both of these systems could be rapidly assembled for scaling up to ventilate several critically ill patients in a pandemic or mass casualty disaster situations by leveraging off-the-shelf and custom 3D printed components.

Recapitulation of human pathophysiology and identification of forensic biomarkers in a translational model of chlorine inhalation injury.

Chlorine gas (Cl2) has been repeatedly used as a chemical weapon, first in World War I and most recently in Syria. Life-threatening Cl2 exposures frequently occur in domestic and occupational environments, and in transportation accidents. Modeling the human etiology of Cl2-induced acute lung injury (ALI), forensic biomarkers, and targeted countermeasures development have been hampered by inadequate large animal models. The objective of this study was to develop a translational model of Cl2-induced ALI in swine to understand toxico-pathophysiology and evaluate whether it is suitable for screening potential medical countermeasures and to identify biomarkers useful for forensic analysis. Specific pathogen-free Yorkshire swine (30-40 kg) of either sex were exposed to Cl2 (≤240 ppm for 1 h) or filtered air under anesthesia and controlled mechanical ventilation. Exposure to Cl2 resulted in severe hypoxia and hypoxemia, increased airway resistance and peak inspiratory pressure, and decreased dynamic lung compliance. Cl2 exposure resulted in increased total leucocyte and neutrophil counts in bronchoalveolar lavage fluid, vascular leakage, and pulmonary edema compared with the air-exposed group. The model recapitulated all three key histopathological features of human ALI, such as neutrophilic alveolitis, deposition of hyaline membranes, and formation of microthrombi. Free and lipid-bound 2-chlorofatty acids and chlorotyrosine-modified proteins (3-chloro-l-tyrosine and 3,5-dichloro-l-tyrosine) were detected in plasma and lung tissue after Cl2 exposure. In this study, we developed a translational swine model that recapitulates key features of human Cl2 inhalation injury and is suitable for testing medical countermeasures, and validated chlorinated fatty acids and protein adducts as biomarkers of Cl2 inhalation.NEW & NOTEWORTHY We established a swine model of chlorine gas-induced acute lung injury that exhibits several features of human acute lung injury and is suitable for screening potential medical countermeasures. We validated chlorinated fatty acids and protein adducts in plasma and lung samples as forensic biomarkers of chlorine inhalation.

Determining respiratory rate using measured expiratory time constant: A prospective observational study.

PURPOSE: Potential negative implications associated with high respiratory rate (RR) are intrinsic positive end-expiratory pressure (PEEPi) generation, cardiovascular depression and possibly ventilator induced lung injury. Despite these negative consequences, optimal RR remains largely unknown. We hypothesized that without consideration of dynamics of lung emptying (i.e., the expiratory time constant [RCEXP]) clinician settings of RR may exceed the frequency needed for optimal lung emptying. MATERIALS AND METHODS: This prospective multicenter observational study measured RCEXP in 56 intensive care patients receiving pressure-controlled ventilation. We compared set RR to the one predicted with RCEXP (RRP). Also, the subgroup of patients with prolonged RCEXP was analyzed. RESULTS: Overall, the absolute mean difference between the set RR and RRP was 2.8 bpm (95% CI: 2.3-3.2). Twenty-nine (52%) patients had prolonged RCEXP (>0.8 s), mean difference between set RR and RRP of 3.1 bpm (95% CI: 2.3-3.8; p < 0.0001) and significantly higher PEEPi compared to those with RCEXP ≤ 0.8 s: 4.4 (95% CI: 3.6-5.2) versus 1.5 (95% CI: 0.9-2.0) cmH2O respectively, p < 0.0001. CONCLUSIONS: Use of RRP based on measured RCEXP revealed that the clinician-set RR exceeded that predicted by RCEXP in the majority of patients. Measuring RCEXP appears to be a useful variable for adjusting the RR during mandatory mechanical ventilation.

Time constant to determine PEEP levels in mechanically ventilated COVID-19 ARDS: a feasibility study.

BACKGROUND: We hypothesized that the measured expiratory time constant (TauE) could be a bedside parameter for the evaluation of positive end-expiratory pressure (PEEP) settings in mechanically ventilated COVID-19 patients during pressure-controlled ventilation (PCV). METHODS: A prospective study was conducted including consecutively admitted adults (n = 16) with COVID-19-related ARDS requiring mechanical ventilation. A PEEP titration using PCV with a fixed driving pressure of 14 cmH2O was performed and TauE recorded at each PEEP level (0 to 18 cmH2O) in prone (n = 29) or supine (n = 24) positions. The PEEP setting with the highest TauE (TauEMAX) was considered to represent the best tradeoff between recruitment and overdistention. RESULTS: Two groups of patterns were observed in the TauE plots: recruitable (R) (75%) and nonrecruitable (NR) (25%). In the R group, the optimal PEEP and PEEP ranges were 8 ± 3 cmH2O and 6-10 cmH2O for the prone position and 9 ± 3 cmH2O and 7-12 cmH2O for the supine position. In the NR group, the optimal PEEP and PEEP ranges were 4 ± 4 cmH2O and 1-8 cmH2O for the prone position and 5 ± 3 cmH2O and 1-7 cmH2O for the supine position, respectively. The R group showed significantly higher optimal PEEP (p < 0.004) and PEEP ranges (p < 0.001) than the NR group. Forty-five percent of measurements resulted in the most optimal PEEP being significantly different between the positions (p < 0.01). Moderate positive correlation has been found between TauE vs CRS at all PEEP levels (r2 = 0.43, p < 0.001). CONCLUSIONS: TauE may be a novel method to assess PEEP levels. There was wide variation in patient responses to PEEP, which indicates the need for personalized evaluation.

Development of a Pleural Pressure Catheter via Continuous Fiberoptic Esophageal Pressure Measurements.

There is growing research showing the importance of measuring esophageal pressure as a surrogate for pleural pressure for patients on mechanical ventilators. The most common measurement method uses a balloon catheter, whose accuracy can vary based on patient anatomy, balloon position, balloon inflation, and the presence of other tubes in the esophagus. The authors present the development and initial testing results of a new combination catheter, utilizing fiberoptic pressure sensing to provide more accurate esophageal pressure measurements and allowing for the incorporation of a feeding tube and temperature sensor.

Use of a Portable Electronic Interface Improves Clinical Handoffs and Adherence to Lung Protective Ventilation.

Background: Mechanical ventilation (MV) is used to support patients with respiratory impairment. Evidence supports the use of lung-protective ventilation (LPV) during MV to improve outcomes. However, studies have demonstrated poor adherence to LPV guidelines. We hypothesized that an electronic platform adapted to a hand-held tablet receiving real-time ventilatory parameters could increase clinician awareness of key LPV parameters. Furthermore, we speculated that an electronic shift-change tool could improve the quality of clinician handoffs. Methods: Using a specially designed Wi-Fi dongle to transmit data from three ventilators and a respiratory monitor, we implemented a system that displays data from all ventilators under the care of a Respiratory Care Practitioner (RCP) on an electronic tablet. In addition, the tablet created a handoff checklist to improve shift-change communication. In a simulated ICU environment, we monitored the performance of eight RCPs at baseline and while using the system. Results: Using the system, the time above guideline Pplat decreased by 74% from control, and the time outside the VT range decreased by 60% from control, p = 0.007 and 0.015, respectively. The handoff scores improved quality significantly from 2.8 to 1.6 on a scale of 1 to 5 (1 being best), p = 0.03. Conclusion: In a simulated environment, an electronic RT tool can significantly improve shift-change communication and increase the RCP's level of LPV adherence.

Programmed multi-level ventilation in COVID-19-related acute respiratory distress syndrome: a multi-center retrospective observational study.

OBJECTIVE: We evaluated pressure-controlled ventilation (PCV) with multiple programmed levels of positive end expiratory pressure (programmed multi-level ventilation; PMLV) in patients with coronavirus disease 2019 (COVID-19)-related acute respiratory distress syndrome (ARDS). METHODS: We conducted a multicenter, retrospective study from November 2020 to February 2021. PMLV was used with PCV in all patients with intensive care admission until improvement in oxygenation (fraction of inspired oxygen [FiO2] ≤0.50 and oxygen saturation [SpO2] >92%). The observed outcomes were improvement of hypoxemia, length of mechanical ventilation, partial pressure of carbon dioxide (PaCO2) stability, and adverse events. RESULTS: Of 188 mechanically ventilated patients with COVID-19-related ARDS, we analyzed 60 patients treated with PMLV. Hypoxemia improved in 55 (92%) patients, as measured by the change in partial pressure of oxygen/FiO2 and SpO2/FiO2 ratios on day 3 versus day 1, and in 32 (66%) ventilated patients on day 7 versus day 3. The median (interquartile range) length of mechanical ventilation for survivors and non-survivors was 8.4 (4.7-14.9) and 6.7 (3.6-10.3) days, respectively. CONCLUSIONS: PMLV appears to be a safe and effective ventilation strategy for improving hypoxemia in patients with COVID-19-related ARDS. Further studies are needed comparing the PMLV mode with the conventional ARDS ventilatory approach.

COVID-19-related acute respiratory distress syndrome treated with veno-venous extracorporeal membrane oxygenation and programmed multi-level ventilation: a case report.

We report a patient with severe coronavirus disease 2019 (COVID-19) acute respiratory distress syndrome (ARDS) treated with veno-venous extracorporeal membrane oxygenation (VV ECMO) and programmed multi-level ventilation (PMLV). VV ECMO as a treatment modality for severe ARDS has been described multiple times as a rescue therapy for refractory hypoxemia. It is well known that conventional ventilation can cause ventilator-induced lung injury. Protective ventilation during VV ECMO seems to be beneficial, translating to using low tidal volumes, prone positioning with general concept of open lung approach. However, mechanical ventilation is still required as ECMO per se is usually not sufficient to maintain adequate gas exchange due to hyperdynamic state of the patient and limitation of blood flow via VV ECMO. This report describes ventilation strategy using PMLV during "resting" period of the lung. In short, PMLV is a strategy for ventilating non-homogenous lungs that incorporates expiratory time constants and multiple levels of positive end-expiratory pressure. Using this approach, most affected acute lung injury/ARDS areas can be recruited, while preventing overdistension in healthy areas. To our knowledge, case report using such ventilation strategy for lung resting period has not been previously published.

Montelukast in hospitalized patients diagnosed with COVID-19.

OBJECTIVE: Several therapeutic agents have been assessed for the treatment of COVID-19, but few approaches have been proven efficacious. Because leukotriene receptor antagonists, such as montelukast have been shown to reduce both cytokine release and lung inflammation in preclinical models of viral influenza and acute respiratory distress syndrome, we hypothesized that therapy with montelukast could be used to treat COVID-19. The objective of this study was to determine if montelukast treatment would reduce the rate of clinical deterioration as measured by the COVID-19 Ordinal Scale. METHODS: We performed a retrospective analysis of COVID-19 confirmed hospitalized patients treated with or without montelukast. We used "clinical deterioration" as the primary endpoint, a binary outcome defined as any increase in the Ordinal Scale value from Day 1 to Day 3 of the hospital stay, as these data were uniformly available for all admitted patients before hospital discharge. Rates of clinical deterioration between the montelukast and non-montelukast groups were compared using the Fisher's exact test. Univariate logistic regression was also used to assess the association between montelukast use and clinical deterioration. A total of 92 patients were analyzed, 30 who received montelukast at the discretion of the treating physician and 62 patients who did not receive montelukast. RESULTS: Patients receiving montelukast experienced significantly fewer events of clinical deterioration compared with patients not receiving montelukast (10% vs 32%, p = 0.022). Our findings suggest that montelukast associates with a reduction in clinical deterioration for COVID-19 confirmed patients as measured on the COVID-19 Ordinal Scale. CONCLUSIONS: Hospitalized COVID-19 patients treated with montelukast had fewer events of clinical deterioration, indicating that this treatment may have clinical activity. While this retrospective study highlights a potential pathway for COVID-19 treatment, this hypothesis requires further study by prospective studies.

Impact of a Formal Research Committee on Respiratory Therapists' Publications.

BACKGROUND: Presenting research at national and international meetings is an important aspect of the practice of respiratory care. Our department regularly presented abstracts but few projects were written up as manuscripts. We also noted that we did not have a centralized strategy to evaluate individual projects and provide mentorship. To address these challenges, we formed a Research Committee that meets monthly. We hypothesized that the formation of this committee would be associated with an increase in published manuscripts. METHODS: We evaluated all original research abstracts authored or co-authored by Duke respiratory therapists presented at the AARC Open Forum between 2009 and 2019. Abstracts were grouped into two time periods; 1) 2009-2013 (before the formation of the research committee) and 2) 2014-2019 (after the formation of the research committee). Abstracts were evaluated based on authors, type of study, patient population, and whether the abstract resulted in a manuscript. Primary outcome was the percentage of abstracts published as manuscripts. RESULTS: A total of 56 abstracts were presented by 23 different lead authors, with 16 (29%) published as manuscripts. After formation of the committee, fewer abstracts per year were presented, but these abstracts were more likely to be published as manuscripts (53% vs 18%, P = .02). For abstracts published as manuscripts, there was a significant difference in the type of study before and after committee formation (P = .042), but there were no differences in lead author credentials, senior author credentials, author gender, or patient population. CONCLUSIONS: The formation of a research committee was associated with an increase in the percentage of abstracts published as manuscripts.

Effect of cyclo-oxygenase inhibitor use during checkpoint blockade immunotherapy in patients with metastatic melanoma and non-small cell lung cancer.

BACKGROUND: Immune checkpoint inhibitors (ICIs) improve survival outcomes in metastatic melanoma and non-small cell lung cancer (NSCLC). Preclinical evidence suggests that overexpression of cyclo-oxygenase-2 (COX2) in tumors facilitates immune evasion through prostaglandin E2 production and that COX inhibition synergizes with ICIs to promote antitumor T-cell activation. This study investigates whether concurrent COX inhibitor (COXi) use during ICI treatment compared with ICI alone is associated with improved time-to-progression (TTP), objective response rate (ORR) and overall survival (OS) in patients with metastatic melanoma and NSCLC. METHODS: We retrospectively reviewed 90 metastatic melanoma and 37 metastatic NSCLC patients, treated with ICI between 2011 and 2019. Differences in TTP and OS by ICI+COXi versus ICI alone were compared using Kaplan-Meier and Cox regression. Interaction between ICI+COXi versus ICI alone and pretreatment neutrophil-lymphocyte ratio (NLR) was examined. Independent radiology review per Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 was performed. RESULTS: For patients with melanoma, median TTP was significantly prolonged in ICI+COXi versus ICI alone (245 vs 100.5 days, p=0.002). On multivariate analysis, ICI+COXi associated with increased TTP (HR 0.36, 95% CI 0.2 to 0.66, p=0.001), adjusted for age, pretreatment NLR, and gender. For NSCLC patients, ICI+COXi also associated with increased TTP compared with ICI alone on multivariate analysis (HR 0.45; 95% CI 0.21 to 0.97; p=0.042) adjusted for age. ORR at 6 months was significantly higher in patients who received ICI+COXi compared with ICI alone in both melanoma (58.6% vs 19.2%, p=0.0005) and NSCLC (73.7% vs 33.3%, p=0.036) cohorts. In the melanoma cohort, high pretreatment NLR (>5) associated with decreased TTP (HR 3.21, 95% CI 1.64 to 6.3; p=0.0007); however, ICI+COXi significantly associated with increased TTP in high NLR (>5) patients (HR 0.08, 95% CI 0.03 to 0.25), but not in low NLR (≤5) patients (HR 0.65, 95% CI 0.32 to 1.32). Similar outcomes were found in an adjusted melanoma cohort after RECIST review. CONCLUSIONS: Our study suggests that COXi use concurrently with ICI significantly associated with longer TTP and improved ORR at 6 months in patients with metastatic melanoma and NSCLC compared with ICI alone. Furthermore, COXi use appears to reverse the negative prognostic effect of a high NLR by prolonging TTP in patients with melanoma.

Patients alter power of breathing as the primary response to changes in pressure support ventilation.

INTRODUCTION: The patient-ventilator relationship is dynamic as the patient's health fluctuates and the ventilator settings are modified. Spontaneously breathing patients respond to mechanical ventilation by changing their patterns of breathing. This study measured the physiologic response when pressure support (PS) settings were modified during mechanical ventilation. METHODS: Subjects were instrumented with a non-invasive pressure, flow, and carbon dioxide airway sensor to estimate tidal volume, respiratory rate, minute ventilation, and end-tidal CO2. Additionally, a catheter was used to measure esophageal pressure and estimate effort exerted during breathing. Respiratory function measurements were obtained while PS settings were adjusted 569 times between 5 and 25 cmH2O. RESULTS: Data was collected on 248 patients. The primary patient response to changes in PS was to adjusting effort (power of breathing) followed by adjusting tidal volume. Changes in respiratory rate were less definite while changes in minute ventilation and end-tidal CO2 appeared unrelated to the change in PS. CONCLUSION: The data indicates that patients maintain a set minute ventilation by adjusting their breathing rate, volume, and power. The data indicates that the subjects regulate their Ve and PetCO2 by adjusting power of breathing and breathing pattern.

Respiratory Therapist Endotracheal Intubation Practices.

BACKGROUND: Endotracheal intubation is a common procedure performed by respiratory therapists (RTs). The purpose of this study was to describe current RT intubation practices in North Carolina through the use of a survey instrument. METHODS: A survey was developed by the authors using REDCap. The survey was sent via email to all licensed RTs in North Carolina. Information collected included respondent demographics, intubation practices (including training and skill maintenance), and attitudes about RT intubation practices. RESULTS: Of the 411 respondents, 68% intubated at their facility, representing 81 unique institutions. RTs who performed intubation were more likely to be from community hospitals and less likely to be from level 1 trauma centers. Respondents reported intubating adult (91%), pediatric (61%), and neonatal (65%) patients. The most common areas in which RTs reported performing intubation were the adult ICU (80%), emergency department (76%), outside the operating room for emergencies (76%), neonatal ICU (43%), the delivery room (45%), and pediatric ICU (25%). The median (interquartile range) number of supervised intubations required to be considered competent was 5 (3-5). The most common numbers of intubations required to be considered competent were 5 (32%), 3 (26%), 10 (16%), 2 (4%), and 0 (3%). The perceived number of intubations to achieve competence was 6 (range 5-10) and did not differ based on years of experience. Most respondents believed their RT intubation program was safe (93%) and effective (91%), and that RTs were well-trained (81%), that their intubation skills were objectively evaluated (66%), and that RTs receive sufficient feedback on performance (68%). CONCLUSIONS: RTs in North Carolina frequently performed intubation and had high confidence in their programs. Further studies are needed to establish standardized training for endotracheal intubation, document success rates for intubations, and evaluate the use of video laryngoscopy by RTs.

Evaluating Endotracheal Tube Depth in Infants Weighing Less Than 1 Kilogram.

BACKGROUND: Endotracheal tube (ETT) depth in premature infants is of critical importance because potentially life-threatening adverse events can occur if the tube is malpositioned. Analysis of current data indicates that the accuracy of current resuscitation guidelines for infants <1 kg is poor. We hypothesized that a weight-based formula that is used clinically in our institution would accurately predict appropriate ETT placement in infants weighing < 1 kg. METHODS: The medical records, from July 2013 to November 2016, of all infants < 1 kg who were intubated were retrospectively reviewed and included. The 2 formulas utilized were the Duke formulas 5.5 cm + 1 cm/kg for infants 500-999 g or 5.0 + 1 cm/kg for infants <500 g. The appropriate ETT position was defined as the tip of the ETT below the thoracic inlet and above the carina, at approximately thoracic vertebrae 2 or 3 on an initial chest radiograph. The formula was defined as being accurate if the documented ETT depth was within 0.2 cm of the predicted depth. Post hoc analysis of current resuscitation guidelines (6 cm plus the weight of the infant in kg) was performed after the Duke formula performed worse than expected. RESULTS: A total of 131 subjects (mean ± gestational age, 26 ± 1.8 wk; mean ± weight, 729 ± 140 g) were included. The documented depth was accurately predicted by the Duke formula for 47% of the subjects, with 69% of the ETTs appropriately positioned as seen on a chest radiograph. Sensitivity was 46.6%, specificity was 53.6%, positive predictive value was 68.8% and negative predictive value was 31.4% for the Duke formula. Post hoc analysis current resuscitation guidelines found that the documented depth was accurately predicted for 23% infants, with 70% of these appropriately positioned ETTs. CONCLUSIONS: Our weight-based, institutional formula had a low sensitivity for predicting proper ETT depth. Weight-based formulas may have clinical utility; however, analysis of current data did not support use in infants < 1 kg. Rapid radiologic assessment of ETT placement is required for this patient population.

Nonsurgical Treatment of Ankle Arthritis.

Nonsurgical treatment of ankle arthritis can be a short-term fix or a long-term solution. An understanding of the biomechanics of the ankle is helpful in the successful use of orthotics and bracing. Pharmacologic and/or biologic treatments can be used exclusively or in concert with mechanical interventions to decrease pain, improve function, and potentially extend the life span of an arthritic ankle.

Clinical Management Strategies for Airway Pressure Release Ventilation: A Survey of Clinical Practice.

BACKGROUND: Airway pressure release ventilation (APRV) is a commonly used mode of ventilation designed to increase mean airway pressure and thus oxygenation. Different strategies for clinical management have been described in the literature but are largely based on physiologic concepts, animal data, and small clinical trials. The purpose of this study was to determine how APRV is currently managed by surveying practicing respiratory therapists with experience using APRV. METHODS: A 15-item survey was developed by the authors and posted on the AARConnect online media platform in January 2016 after being declared exempt by our institution's institutional review board. Survey questions were derived from a literature review of recommended APRV settings. Responses were limited to one per institution. RESULTS: The survey was completed by 60 respondents who used APRV. Of the 4 key initial APRV settings (P high, P low, T high, and T low), there was good agreement among survey responders and published guidelines for setting initial T high (4-6 s) and initial P low (0 cm H2O). There was some disagreement regarding initial P high, with 48% of responders matching P high to conventional ventilation plateau pressures but another 31% using conventional ventilation mean airway pressure plus 2-5 cm H2O. The most disagreement was with the T low setting, with only 47% of survey responders agreeing with published guidelines about using the expiratory flow signal to set T low. There was good agreement among survey responders and published guidelines for what changes to make when gas exchange was outside of the targeted range. A substantial number of respondents accepted P high and APRV release volumes that may exceed lung-protective limits. CONCLUSIONS: There is only limited consensus among practitioners for initial APRV settings, probably reflecting the paucity of good clinical outcome data and confusion surrounding the physiology of this mode.