ASV® and lung-protective ventilation in ARDS patients

News

Date of first publication: 12.09.2022

A recent study from the US found that settings targeted by ASV were consistent with lung-protective ventilation strategies in ARDS patients.

ASV® and lung-protective ventilation in ARDS patients

The researchers performed a randomized crossover trial in 17 mostly passive, moderate-to-severe ARDS patients to compare the automated settings in Adaptive Support Ventilation (ASV) mode with the hospital’s standard-of-care mode, adaptive pressure ventilation (APV) (Baedorf Kassis EN, Bastos AB, Schaefer MS, et al. Adaptive Support Ventilation and Lung-Protective Ventilation in ARDS [published online ahead of print, 2022 Aug 16]. Respir Care. 2022;respcare.10159. doi:10.4187/respcare.101591). In ASV mode, the breathing frequency and tidal volume are automatically adjusted to maintain a set minute ventilation, while tidal volume (VT) was set to 6 ml/Kg IBW in APV mode according to the hospital’s standard of care. Patients were ventilated for 1–2 hours in each mode, maintaining a consistent minute ventilation.

The primary outcome was tidal volume (VT) corrected for ideal body weight. Overall, automated adjustment of VT in ASV resulted in just slightly higher VT (6.29 [5.87–6.99] mL/kg IBW vs 6.04 [6.01–6.06] mL/kg IBW, P = .035). The authors noted that while statistically significant, this difference was too small in absolute terms to be considered clinically relevant. Of greater importance was the fact that VT remained at all times under 8 mL/kg and thus within the generally accepted lung-protective range. In addition, VT in ASV was found to be lower in a subset of patients with low compliance and a short RCexp, indicating individual titration according to the patient’s respiratory mechanics.

In terms of secondary outcomes, frequency in ASV was marginally lower, while plateau pressures, driving pressures, and mechanical power were similar in both modes. However, mechanical power was found to be lower in ASV mode in the patients with lower compliance, and particularly in those where VT was also reduced.

The results show that the settings in ASV were consistent with lung-protective strategies. In addition, ASV adjusted VT according to the patient’s respiratory mechanics, with lower VT and mechanical power being delivered in subjects with stiffer lungs.

Footnotes

References

1. Baedorf Kassis EN, Bastos AB, Schaefer MS, et al. Adaptive Support Ventilation and Lung-Protective Ventilation in ARDS [published online ahead of print, 2022 Aug 16]. Respir Care. 2022;respcare.10159. doi:10.4187/respcare.10159

Adaptive Support Ventilation and Lung-Protective Ventilation in ARDS.

Baedorf Kassis EN, Bastos AB, Schaefer MS, et al. Adaptive Support Ventilation and Lung-Protective Ventilation in ARDS [published online ahead of print, 2022 Aug 16]. Respir Care. 2022;respcare.10159. doi:10.4187/respcare.10159

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 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 VT based upon respiratory mechanics, with lower VT and mechanical power in subjects with stiffer lungs.