Early application of airway pressure release ventilation may reduce the duration of mechanical ventilation in acute respiratory distress syndrome

Abstract

Purpose: Experimental animal models of acute respiratory distress syndrome (ARDS) have shown that the updated airway pressure release ventilation (APRV) methodologies may significantly improve oxygenation, maximize lung recruitment, and attenuate lung injury, without circulatory depression. This led us to hypothesize that early application of APRV in patients with ARDS would allow pulmonary function to recover faster and would reduce the duration of mechanical ventilation as compared with low tidal volume lung protective ventilation (LTV).

Methods: A total of 138 patients with ARDS who received mechanical ventilation for <48 h between May 2015 to October 2016 while in the critical care medicine unit (ICU) of the West China Hospital of Sichuan University were enrolled in the study. Patients were randomly assigned to receive APRV (n = 71) or LTV (n = 67). The settings for APRV were: high airway pressure (Phigh) set at the last plateau airway pressure (Pplat), not to exceed 30 cmH2O) and low airway pressure ( Plow) set at 5 cmH2O; the release phase (Tlow) setting adjusted to terminate the peak expiratory flow rate to ≥ 50%; release frequency of 10-14 cycles/min. The settings for LTV were: target tidal volume of 6 mL/kg of predicted body weight; Pplat not exceeding 30 cmH2O; positive end-expiratory pressure (PEEP) guided by the PEEP-FiO2 table according to the ARDSnet protocol. The primary outcome was the number of days without mechanical ventilation from enrollment to day 28. The secondary endpoints included oxygenation, Pplat, respiratory system compliance, and patient outcomes.

Results: Compared with the LTV group, patients in the APRV group had a higher median number of ventilator-free days {19 [interquartile range (IQR) 8-22] vs. 2 (IQR 0-15); P < 0.001}. This finding was independent of the coexisting differences in chronic disease. The APRV group had a shorter stay in the ICU (P = 0.003). The ICU mortality rate was 19.7% in the APRV group versus 34.3% in the LTV group (P = 0.053) and was associated with better oxygenation and respiratory system compliance, lower Pplat, and less sedation requirement during the first week following enrollment (P < 0.05, repeated-measures analysis of variance).

Conclusions: Compared with LTV, early application of APRV in patients with ARDS improved oxygenation and respiratory system compliance, decreased Pplat and reduced the duration of both mechanical ventilation and ICU stay.

Keywords: Acute respiratory distress syndrome; Airway pressure release ventilation; Low tidal volume; Spontaneous breathing.

Conflict of interest statement

Ethics approval and consent to participate

This study was approved by the ethics committee of West China Hospital of Sichuan University in accordance with the Helsinki Declaration. Written informed consent was obtained from the patients’ authorized surrogates. The clinical trial registration number was NCT02639364.

Conflicts of interest

All authors declare that they do not have any conflict of interest relevant to this study.

Figures

Fig. 1

Flow diagram of patient enrollment, showing randomization, completion of study treatment, reasons for discontinuation of study treatment and inclusions into per protocol population. APRV Airway pressure release ventilation, EMCO extracorporeal membrane oxygenation, LTV low tidal volume ventilation, PCV pressure-controlled ventilation

Fig. 2

Respiratory and hemodynamic parameters, and analgesia and sedation variables at baseline and on days 1, 2, 3, and 7 after enrollment. Data are presented as the mean (filled symbols) and standard errors (whiskers). P values were calculated by repeated-measures analysis of variance. a Plateau pressure, b mean airway pressure, c respiratory system compliance, d ratio of the partial pressure of arterial oxygen to the fraction of inspired oxygen (PaO2:FiO2), e heart rate, f mean arterial pressure, g average doses of norepinephrine, h Richmond Agitation Sedation Scale (RASS) scores, i average doses of fentanyl, j average doses of midazolam, k average doses of propofol. All parameters and variables were compared between the two groups at baseline and on days 1, 2, 3, and 7 after enrollment with the Student’s t test. Delta denotes that the two-sided P value was <0.05

Fig. 2

Respiratory and hemodynamic parameters, and analgesia and sedation variables at baseline and on days 1, 2, 3, and 7 after enrollment. Data are presented as the mean (filled symbols) and standard errors (whiskers). P values were calculated by repeated-measures analysis of variance. a Plateau pressure, b mean airway pressure, c respiratory system compliance, d ratio of the partial pressure of arterial oxygen to the fraction of inspired oxygen (PaO2:FiO2), e heart rate, f mean arterial pressure, g average doses of norepinephrine, h Richmond Agitation Sedation Scale (RASS) scores, i average doses of fentanyl, j average doses of midazolam, k average doses of propofol. All parameters and variables were compared between the two groups at baseline and on days 1, 2, 3, and 7 after enrollment with the Student’s t test. Delta denotes that the two-sided P value was <0.05

Fig. 3

Percentage of breathing without assistance from enrollment to day 28 in the APRV and LTV groups