Effects of Varying Levels of Inspiratory Assistance with Pressure Support Ventilation and Neurally Adjusted Ventilatory Assist on Driving Pressure in Patients Recovering from Hypoxemic Respiratory Failure

BACKGROUND: Driving pressure can be readily measured during assisted modes of ventilation such as pressure support ventilation (PSV) and neurally adjusted ventilatory assist (NAVA). The present prospective randomized crossover study aimed to assess the changes in driving pressure in response to variations in the level of assistance delivered by PSV vs NAVA.METHODS: 16 intubated adult patients, recovering from hypoxemic acute respiratory failure (ARF) and undergoing assisted ventilation, were randomly subjected to six 30-min-lasting trials. At baseline, PSV (PSV100) was set with the same regulation present at patient enrollment. The corresponding level of NAVA (NAVA100) was set to match the same inspiratory peak of airway pressure obtained in PSV100. Therefore, the level of assistance was reduced and increased by 50% in both ventilatory modes (PSV50, NAVA50; PSV150, NAVA150). At the end of each trial, driving pressure obtained in response to four short (2-3s) end-expiratory and end-inspiratory occlusions was analyzed.RESULTS: Driving pressure at PSV50 (6.6 [6.1-7.8] cmH2O) was lower than that recorded at PSV100 (7.9 [7.2-9.1] cmH2O, P=0.005) and PSV150 (9.9 [9.1-13.2] cmH2O, P<0.0001). In NAVA, driving pressure at NAVA50 was reduced compared to NAVA150 (7.7 [5.1-8.1] cmH2O vs 8.3 [6.4-11.4] cmH2O, P=0.013), whereas there were no changes between baseline and NAVA150 (8.5 [6.3-9.8] cmH2O vs 8.3 [6.4-11.4] cmH2O, P=0.331, respectively). Driving pressure at PSV150 was higher than that observed in NAVA150 (P=0.011).CONCLUSIONS: NAVA delivers better lung-protective ventilation compared to PSV in hypoxemic ARF patients.TRIAL REGISTRATION NUMBER AND DATE OF REGISTRATION: The present trial was prospectively registered at www.clinicatrials.gov (NCT03719365) on 24 October 2018.