Doxofylline and respiratory mechanics. Short-term effects in mechanically ventilated patients with airflow obstruction and respiratory failure.

To assess the short-term effects of a methylxanthine (doxofylline) on respiratory mechanics in mechanically ventilated patients with airway obstruction and respiratory failure, nine consecutive patients were examined within three days from the onset of mechanical ventilation. Flow, changes in pulmonary volume, and Paw were measured using a ventilator (Servo 900C). End-expiratory and end-inspiratory airway occlusion was performed to measure PEEPi, Cstrs, Rrsmax, and Rrsmin. Measurements were performed before and at 5, 15, and 30 minutes after an intravenous loading dose of doxofylline (5 to 6 mg/kg). We found that doxofylline determined, on the average, a marked decrease in respiratory resistance (Rrsmax and Rrsmin, -27.2 percent and -36.5 percent, respectively) without significant changes in Cstrs and Pmax. The PEEPi, reflecting pulmonary dynamic hyperinflation, was also significantly decreased by doxofylline (-41 percent, on the average). The Pmax was not reliable for evaluation of a single patient, since changes in the elastic pressure can offset changes in the resistive one. No patient experienced significant side effects due to doxofylline. We conclude that (1) the effects of therapy can be assessed noninvasively at bedside in critically ill patients; (2) doxofylline is a rapid and efficient bronchodilator in mechanically ventilated patients with ARF and airflow obstruction; and (3) the decrease in the respiratory resistance and PEEPi, associated with an improved mechanical efficiency of the respiratory muscles at a lower pulmonary volume, can provide better conditions for the patient-ventilator interaction and for weaning.