The following is the summary of “Adaptive Support Ventilation and Lung-Protective Ventilation in ARDS” published in the December 2022 issue of Respiratory Care by Kassis, et al.
Tidal volume (VT) and breathing frequency (f) is modified in ASV, a partially closed-loop ventilation mode, to reduce the amount of mechanical work and driving pressure. While ASV is often utilized, its role in ARDS has not been thoroughly investigated. The study compared an adaptable pressure ventilation (APV) mode with a volume target of 6 mL/kg (the standard of care at Beth Israel Deaconess Medical Center) to an ASV mode in which the volume target is automatically adjusted. Patients were initially ventilated using either the standard of care (APV) or ASV, but after 1-2 hours, they switched to the other mode while keeping their minute ventilation constant. The primary metric was changed in VT from baseline after adjustment for ideal body weight (IBW). Post-crossover and longitudinal measurements of secondary outcomes included driving pressure, mechanics, gas exchange, mechanical power, and other metrics.
20 people with ARDS accepted to participate; 17 were randomly assigned and completed the trial (median PaO2/FIO2146.6 [128.3-204.8] mm Hg). All of the study participants were non-verbal and rarely breathed on their own. When accounting for IBW, the VT produced by ASV mode was somewhat higher than that of the control group (6.3% [5.9-7.0%] mL/kg IBW vs. 6.04% [6.0-6.1] mL/kg IBW, P=.035). Patients breathing in ASV mode breathed less frequently (25 [22-26] breaths/min vs. 27 [22-30] breaths/min, P=.01). Smaller delivered VT/IBW (R2 = 0.4936, P=.002) was associated with worse respiratory-system compliance in ASV.
Both conventional ventilation and ASV had similar 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). There were no modes of ventilation-related adverse effects in either the ASV or conventional groups. As a standard of care that is in line with lung-protective ventilation methods for primarily passive people with ARDS, ASV aims for the same circumstances. Subjects with stiffer lungs received less VT and mechanical power from ASV because VT was based on respiratory mechanics.