Late Breaking Abstract - Abnormal breathing patterns limit exercise in mechanically ventilated patients: an observational study

<bold>Background:</bold> While early exercise is recommended in patients on mechanical ventilation, the understanding of exercise physiology in these patients is limited. In the general population, abnormal breathing patterns can reduce exercise tolerance. This study aimed to assess prevalence of abnormal breathing patterns during exercise in mechanically ventilated patients. Secondary, we investigated its relation to exercise tolerance. <bold>Method:</bold> A prospective, observational study was conducted. Mechanically ventilated patients performed incremental, maximal exercise, and were connected to a calorimeter. Three investigators categorised breathing patterns as normal or abnormal during exercise, based on 9-panel plots. An increase in tidal volume preceding an increase in respiratory frequency was defined as normal. External power and percentage of predicted maximal oxygen consumption (VO_2max) were compared between groups using Bayesian methods. <bold>Results:</bold> 27 patients were included. The breathing pattern of 16 patients (59.3%) was categorised as abnormal. Abnormal breathing patterns were associated with lower external power, Bayes factor (BF) 5.1, 95% credible interval (CI) -4.68 – -2.85, and with a lower percentage of predicted VO_2max achieved, BF 0.87, 95% CI -5.75 – 0.87. <fig><object-id>erj;64/suppl_68/OA5568/F1</object-id><object-id>F1</object-id><object-id>F1</object-id><graphic></graphic></fig> <bold>Conclusion:</bold> Abnormal breathing patterns during exercise are prevalent in mechanically ventilated patients, and are associated with lower exercise tolerance.