The following is a summary of “Pendelluft in hypoxemic patients resuming spontaneous breathing: proportional modes versus pressure support ventilation,” published in the December 2023 issue of Critical Care by Arellano et al.
Pendelluft, a novel effort-dependent lung injury mechanism, might be prevented by neurally-adjusted ventilatory assist (NAVA) and proportional assist ventilation (PAV +), which improve synchrony compared to pressure support ventilation (PSV).
Researchers started a retrospective study to investigate whether NAVA and PAV+, compared to PSV, could reduce pendelluft, a potential lung injury mechanism, in patients recovering from acute respiratory distress syndrome (ARDS).
They underwent a crossover trial, receiving NAVA, PAV+, or PSV for 20 minutes with comparable assistance levels after more than 72 hours of controlled ventilation. The evaluation encompassed pendelluft (the percentage of lost volume from the non-dependent lung region displaced to the dependent region during inspiration), drive (quantified as the delta esophageal swing within the first 100 milliseconds [ΔP es 100 ms]), and inspiratory effort (expressed as the esophageal pressure–time product per minute [PTP min]). Analyzing the data involved repeated measures analysis with subsequent post-hoc tests and mixed-effects models.
The results showed 20 patients mechanically ventilated for a median of 9 days (interquartile range [5–14]), respiratory drive and inspiratory effort were marginally elevated with NAVA and PAV + in comparison to PSV, despite the matching of tidal volume (ΔP es 100 ms of –2.8 [−3.8–−1.9] cm H2O, −3.6 [−3.9–−2.4] cm H2O, and −2.1 [−2.5–−1.1] cm H2O, respectively; P<0.001 for both comparisons; PTPmin of 155 [118–209] cm H2O s/min, 197 [145–269] cm H2O s/min, and 134 [93–169] cm H2O s/min, respectively; P<0.001 for both comparisons). The magnitude of Pendelluft was higher in NAVA (12 ± 7%) and PAV + (13 ± 7%) compared to PSV (8 ± 6%), with a significant difference (P<0.001). Pendelluft magnitude demonstrated a strong association with respiratory drive (β = -2.771, P-value < 0.001) and inspiratory effort (β = 0.026, P<0.001), regardless of the ventilatory mode. After adjusting for PTPmin, a higher Pendelluft magnitude in proportional modes than PSV was observed (β = 2.606, P=0.010 for NAVA, and β = 3.360, P=0.004 for PAV +). Notably, this difference was evident only for PAV + when adjusted for respiratory drive (β = 2.643, P=0.009 for PAV +).
They concluded that NAVA/PAV+ didn’t stop pendelluft in recovering ARDS like PSV, implying effort, not mode, is critical.
Source: annalsofintensivecare.springeropen.com/articles/10.1186/s13613-023-01230-w
