Adaptive Support Ventilation and Lung-Protective Ventilation in ARDS.

BACKGROUND: Adaptive support ventilation (ASV) is a partially closed-loop ventilation mode that adjusts tidal volume (VT ) and breathing frequency (f) to minimize mechanical work and driving pressure. ASV is routinely used but has not been widely studied in ARDS.

METHODS: The study was a crossover study with randomization to intervention comparing a pressure-regulated, volume-targeted ventilation mode (adaptive pressure ventilation [APV], standard of care at Beth Israel Deaconess Medical Center) set to VT 6 mL/kg in comparison with ASV mode where VT adjustment is automated. Subjects received standard of care (APV) or ASV and then crossed over to the alternate mode, maintaining consistent minute ventilation with 1-2 h in each mode. The primary outcome was VT corrected for ideal body weight (IBW) before and after crossover. Secondary outcomes included driving pressure, mechanics, gas exchange, mechanical power, and other parameters measured after crossover and longitudinally.

RESULTS: Twenty subjects with ARDS were consented, with 17 randomized and completing the study (median PaO2 /FIO2 146.6 [128.3-204.8] mm Hg) and were mostly passive without spontaneous breathing. ASV mode produced marginally larger VT corrected for IBW (6.3 [5.9-7.0] mL/kg IBW vs 6.04 [6.0-6.1] mL/kg IBW, P = .035). Frequency was lower with patients in ASV mode (25 [22-26] breaths/min vs 27 [22-30)] breaths/min, P = .01). In ASV, lower respiratory-system compliance correlated with smaller delivered VT /IBW (R2 = 0.4936, P = .002). Plateau (24.7 [22.6-27.6] cm H2 O vs 25.3 [23.5-26.8] cm H2 O, P = .14) and driving pressures (12.8 [9.0-15.8] cm H2 O vs 11.7 [10.7-15.1] cm H2 O, P = .29) were comparable between conventional ventilation and ASV. No adverse events were noted in either ASV or conventional group related to mode of ventilation.

CONCLUSIONS: ASV targeted similar settings as standard of care consistent with lung-protective ventilation strategies in mostly passive subjects with ARDS. ASV delivered VT based upon respiratory mechanics, with lower VT and mechanical power in subjects with stiffer lungs.