Monitoring of breathing effort through pressure time product measurement using airway occlusion pressure (PTPPOCC study).

Abstract

Background: Monitoring respiratory effort is crucial to prevent ventilator-induced lung injury and diaphragmatic dysfunction, but esophageal manometry (the gold standard) is invasive an can be cumbersome. The airway occlusion pressure (ΔP_OCC) correlates with inspiratory effort but does not account for inspiratory time (Ti) or respiratory rate (RR). We aimed to validate a novel non-invasive index (PTP_POCC) that combines ΔP_OCC, Ti, and RR to estimate the esophageal pressure-time product (PTP_ESO).

Methods: We conducted a prospective, multicenter, physiological, crossover study. Three levels of inspiratory pressure (5, 10, and 15 cm H₂O) were randomly applied in patients with invasive mechanical ventilation in pressure support mode. We simultaneously measured PTP_ESO and calculated the non-invasive PTP_POCC (PTP_POCC-min = (0.75 × ΔP_OCC × Ti / 2) × RR). Association was assessed using linear mixed-effects models. Diagnostic accuracy for detecting high (PTP_ESO >150 cmH₂O·s·min⁻¹) and low (PTP_ESO <50 cmH₂O·s·min⁻¹) inspiratory effort was evaluated using ROC curves.

Results: A total of 49 patients were analyzed. A significant positive association was found between PTP_ESO-min and PTP_POCC-min (regression coefficient: 0.98; 95% CI: 0.86-1.1 p-value < 0.001). The mixed-effects model demonstrated good overall predictive performance (conditional R² = 0.80), although substantial inter-individual variability was observed (marginal R² = 0.40). The AUC for detecting high or low inspiratory effort was 0.91 (95% CI: 0.87-0.94), and 0.91 (95% CI: 0.88-0.94) respectively. Agreement analysis revealed proportional bias with wide limits of agreement.

Conclusions: The PTP_POCC index showed good performance for identifying extremes of respiratory effort in mechanically ventilated patients. Despite limited individual agreement, its strong association and high specificity may make it a useful tool for confirming very low or excessively high inspiratory effort and for identifying patients at risk of over or under assistance.

Trial registration: The study was registered on ClinicalTrials.gov under the identifier NCT06040138 ( https://clinicaltrials.gov/study/NCT06040138 ), first submitted date 2023-09-05.