Changes in respiratory mechanics during respiratory physiotherapy in mechanically ventilated patients

OBJECTIVE: To evaluate the changes in ventilatory mechanics and hemodynamics that occur in patients dependent on mechanical ventilation who are subjected to a standard respiratory therapy protocol. METHODS: This experimental and prospective study was performed in two intensive care units, in which patients dependent on mechanical ventilation for more than 48 hours were consecutively enrolled and subjected to an established respiratory physiotherapy protocol. Ventilatory variables (dynamic lung compliance, respiratory system resistance, tidal volume, peak inspiratory pressure, respiratory rate, and oxygen saturation) and hemodynamic variables (heart rate) were measured one hour before (T(-1)), immediately after (T(0)) and one hour after (T(+1)) applying the respiratory physiotherapy protocol. RESULTS: During the period of data collection, 104 patients were included in the study. Regarding the ventilatory variables, an increase in dynamic lung compliance (T(-1) = 52.3 ± 16.1mL/cmH(2)O versus T(0) = 65.1 ± 19.1mL/cmH(2)O; p < 0.001), tidal volume (T(-1) = 550 ± 134mL versus T(0) = 698 ± 155mL; p < 0.001), and peripheral oxygen saturation (T(-1) = 96.5 ± 2.29% versus T(0) = 98.2 ± 1.62%; p < 0.001) were observed, in addition to a reduction of respiratory system resistance (T(-1) = 14.2 ± 4.63cmH(2)O/L/s versus T(0) = 11.0 ± 3.43cmH2O/L/s; p < 0.001), after applying the respiratory physiotherapy protocol. All changes were present in the assessment performed one hour (T(+1)) after the application of the respiratory physiotherapy protocol. Regarding the hemodynamic variables, an immediate increase in the heart rate after application of the protocol was observed, but that increase was not maintained (T(-1) = 88.9 ± 18.7 bpm versus T(0) = 93.7 ± 19.2bpm versus T(+1) = 88.5 ± 17.1bpm; p < 0.001). CONCLUSION: Respiratory therapy leads to immediate changes in the lung mechanics and hemodynamics of mechanical ventilation-dependent patients, and ventilatory changes are likely to remain for at least one hour.