Adaptive mechanical ventilation with automated minimization of mechanical power-a pilot randomized cross-over study.
BACKGROUND
Adaptive mechanical ventilation automatically adjusts respiratory rate (RR) and tidal volume (VT) to deliver the clinically desired minute ventilation, selecting RR and VT based on Otis' equation on least work of breathing. However, the resulting VT may be relatively high, especially in patients with more compliant lungs. Therefore, a new mode of adaptive ventilation (adaptive ventilation mode 2, AVM2) was developed which automatically minimizes inspiratory power with the aim of ensuring lung-protective combinations of VT and RR. The aim of this study was to investigate whether AVM2 reduces VT, mechanical power, and driving pressure (ΔPstat) and provides similar gas exchange when compared to adaptive mechanical ventilation based on Otis' equation.


METHODS
A prospective randomized cross-over study was performed in 20 critically ill patients on controlled mechanical ventilation, including 10 patients with acute respiratory distress syndrome (ARDS). Each patient underwent 1 h of mechanical ventilation with AVM2 and 1 h of adaptive mechanical ventilation according to Otis' equation (adaptive ventilation mode, AVM). At the end of each phase, we collected data on VT, mechanical power, ΔP, PaO2/FiO2 ratio, PaCO2, pH, and hemodynamics.


RESULTS
Comparing adaptive mechanical ventilation with AVM2 to the approach based on Otis' equation (AVM), we found a significant reduction in VT both in the whole study population (7.2 ± 0.9 vs. 8.2 ± 0.6 ml/kg, p <  0.0001) and in the subgroup of patients with ARDS (6.6 ± 0.8 ml/kg with AVM2 vs. 7.9 ± 0.5 ml/kg with AVM, p <  0.0001). Similar reductions were observed for ΔPstat (whole study population: 11.5 ± 1.6 cmH2O with AVM2 vs. 12.6 ± 2.5 cmH2O with AVM, p <  0.0001; patients with ARDS: 11.8 ± 1.7 cmH2O with AVM2 and 13.3 ± 2.7 cmH2O with AVM, p = 0.0044) and total mechanical power (16.8 ± 3.9 J/min with AVM2 vs. 18.6 ± 4.6 J/min with AVM, p = 0.0024; ARDS: 15.6 ± 3.2 J/min with AVM2 vs. 17.5 ± 4.1 J/min with AVM, p = 0.0023). There was a small decrease in PaO2/FiO2 (270 ± 98 vs. 291 ± 102 mmHg with AVM, p = 0.03; ARDS: 194 ± 55 vs. 218 ± 61 with AVM, p = 0.008) and no differences in PaCO2, pH, and hemodynamics.


CONCLUSIONS
Adaptive mechanical ventilation with automated minimization of inspiratory power may lead to more lung-protective ventilator settings when compared with adaptive mechanical ventilation according to Otis' equation.


TRIAL REGISTRATION
The study was registered at the German Clinical Trials Register ( DRKS00013540 ) on December 1, 2017, before including the first patient.
['Becher|Tobias|T|0000-0003-2026-7629', 'Adelmeier|Anna|A|', 'Frerichs|Inéz|I|', 'Weiler|Norbert|N|', 'Schädler|Dirk|D|']
D000368:Aged D018592:Cross-Over Studies D005260:Female D005858:Germany D006439:Hemodynamics D006801:Humans D008170:Lung Compliance D008297:Male D008875:Middle Aged D010865:Pilot Projects D057285:Precision Medicine D011446:Prospective Studies D012121:Respiration, Artificial D015656:Respiratory Mechanics D013990:Tidal Volume
Adaptive mechanical ventilation Mechanical power Lung-protective ventilation Acute respiratory failure Personalized medicine Ventilator-induced lung injury