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 (V_T) 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 V_T 6 mL/kg in comparison with ASV mode where V_T 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 V_T 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 P_aO2/F_IO2 146.6 [128.3–204.8] mm Hg) and were mostly passive without spontaneous breathing. ASV mode produced marginally larger V_T 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 V_T/IBW (R² = 0.4936, P = .002). Plateau (24.7 [22.6–27.6] cm H₂O vs 25.3 [23.5–26.8] cm H₂O, P = .14) and driving pressures (12.8 [9.0–15.8] cm H₂O vs 11.7 [10.7–15.1] cm H₂O, 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 V_T based upon respiratory mechanics, with lower V_T and mechanical power in subjects with stiffer lungs.