Abstract
Background: The optimal level of positive end-expiratory pressure (PEEP) during mechanical ventilation for COVID-19 pneumonia remains debated and should ideally be guided by responses in both lung volume and perfusion. Capnodynamic monitoring allows both end-expiratory lung volume ([Formula: see text]) and effective pulmonary blood flow (EPBF) to be determined at the bedside with ongoing ventilation.
Methods: Patients with COVID-19-related moderate to severe respiratory failure underwent capnodynamic monitoring of [Formula: see text] and EPBF during a step increase in PEEP by 50% above the baseline (PEEP low to PEEP high ). The primary outcome was a > 20 mm Hg increase in arterial oxygen tension to inspired fraction of oxygen (P/F) ratio to define responders versus non-responders. Secondary outcomes included changes in physiological dead space and correlations with independently determined recruited lung volume and the recruitment-to-inflation ratio at an instantaneous, single breath decrease in PEEP. Mixed factor ANOVA for group mean differences and correlations by Pearson’s correlation coefficient are reported including their 95% confidence intervals.
Results: Of 27 patients studied, 15 responders increased the P/F ratio by 55 [24-86] mm Hg compared to 12 non-responders (p < 0.01) as PEEP low (11 ± 2.7 cm H 2 O) was increased to PEEP high (18 ± 3.0 cm H 2 O). The [Formula: see text] was 461 [82-839] ml less in responders at PEEP low (p = 0.02) but not statistically different between groups at PEEP high . Responders increased both [Formula: see text] and EPBF at PEEP high (r = 0.56 [0.18-0.83], p = 0.03). In contrast, non-responders demonstrated a negative correlation (r = – 0.65 [- 0.12 to – 0.89], p = 0.02) with increased lung volume associated with decreased pulmonary perfusion. Decreased (- 0.06 [- 0.02 to – 0.09] %, p < 0.01) dead space was observed in responders. The change in [Formula: see text] correlated with both the recruited lung volume (r = 0.85 [0.69-0.93], p < 0.01) and the recruitment-to-inflation ratio (r = 0.87 [0.74-0.94], p < 0.01).
Conclusions: In mechanically ventilated patients with moderate to severe COVID-19 respiratory failure, improved oxygenation in response to increased PEEP was associated with increased end-expiratory lung volume and pulmonary perfusion. The change in end-expiratory lung volume was positively correlated with the lung volume recruited and the recruitment-to-inflation ratio. This study demonstrates the feasibility of capnodynamic monitoring to assess physiological responses to PEEP at the bedside to facilitate an individualised setting of PEEP.
Trial registration: NCT05082168 (18th October 2021).
Keywords: COVID-19; Lung perfusion; Lung volume; Mechanical ventilation; Monitoring; Positive end-expiratory pressure.
【저자키워드】 COVID-19, mechanical ventilation, monitoring, positive end-expiratory pressure., Lung perfusion, Lung volume, 【초록키워드】 Respiratory failure, severe COVID-19, Pneumonia, feasibility, severe respiratory failure, Ventilation, lung, oxygen, outcome, non-responders, response, breath, Patient, Responder, correlation, group, moderate, physiological, Oxygenation, PEEP, End-Expiratory Pressure, Positive end-expiratory pressure, Volume, Confidence intervals, Primary outcome, P/F ratio, mean difference, responders, fraction, negative correlation, ANOVA, Pearson, physiological response, dead, correlation coefficient, non-responder, effective, secondary, decrease, arterial oxygen tension, pulmonary blood flow, recruited, reported, facilitate, less, changes in, demonstrated, correlated, increase in, to define, statistically, Decreased, baseline, instantaneous, Mechanical, mechanically ventilated patient, P/F, positively correlated, was increased, 【제목키워드】 severe COVID-19, lung, moderate, blood flow, Positive end-expiratory pressure, Volume,