Patients alter power of breathing as the primary response to changes in pressure support ventilation

The patient-ventilator relationship is dynamic as the patient's health fluctuates and the ventilator settings are modified. Spontaneously breathing patients respond to mechanical ventilation by changing their patterns of breathing. This study measured the physiologic response when pressure support (PS) settings were modified during mechanical ventilation. Subjects were instrumented with a non-invasive pressure, flow, and carbon dioxide airway sensor to estimate tidal volume, respiratory rate, minute ventilation, and end-tidal CO2. Additionally, a catheter was used to measure esophageal pressure and estimate effort exerted during breathing. Respiratory function measurements were obtained while PS settings were adjusted 569 times between 5 and 25 cmH2O. Data was collected on 248 patients. The primary patient response to changes in PS was to adjusting effort (power of breathing) followed by adjusting tidal volume. Changes in respiratory rate were less definite while changes in minute ventilation and end-tidal CO2 appeared unrelated to the change in PS. The data indicates that patients maintain a set minute ventilation by adjusting their breathing rate, volume, and power. The data indicates that the subjects regulate their Ve and PetCO2 by adjusting power of breathing and breathing pattern. •Spontaneously breathing patients respond differently to changes in ventilator setting.•We observed 248 intubated patients while changing pressure support.•POB, the most informative variable, changes inversely with changes in pressure support.•The patients regulate their Ve and PetCO2 by adjusting POB and breathing pattern.