Hemodynamic and respiratory response to varying gradients between end-expiratory pressure and end-inspiratory pressure in patients breathing on continuous positive airway pressure.

: Nine patients on intermittent mandatory ventilation (IMV) and continuous positive airway pressure (CPAP) were allowed to breathe spontaneously at varying end expiratory pressure-end inspiratory pressure (EEP-EIP) gradients up to 10 cm H2O. There was no change in the mean cardiac output and oxygen delivery despite a lowered mean airway pressure (MAWP) when the gradient was increased. Three patients were uncomfortable at the higher gradients and another manifested evidence of fatigue of the muscles of respiration by raising her arterial PCO2 (PaCO2) and intrapulmonary shunt (Qs/Qt). In view of the difficulty experienced by some patients and lack of improvement in cardiac outputs (CO) during spontaneous inspiration when the EEP-EIP gradient is raised from zero to 5 and 10 cm H2O, it is recommended that the variation in airway pressure during spontaneous breaths while a patient is on CPAP be minimized.