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

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 (ΔPOCC) 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 (PTPPOCC) that combines ΔPOCC, Ti, and RR to estimate the esophageal pressure-time product (PTPESO). 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 PTPESO and calculated the non-invasive PTPPOCC (PTPPOCC-min = (0.75 × ΔPOCC × Ti / 2) × RR). Association was assessed using linear mixed-effects models. Diagnostic accuracy for detecting high (PTPESO >150 cmH₂O·s·min⁻¹) and low (PTPESO <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 PTPESO-min and PTPPOCC-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 PTPPOCC 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.