Effect of the prone position on patients with hydrostatic pulmonary edema compared with patients with acute respiratory distress syndrome and pulmonary fibrosis.

This study examined the effect of the prone position on mechanically ventilated patients with hydrostatic pulmonary edema (HPE). Eight patients with acute HPE and mechanically ventilated in the prone position (Group 1) were studied. Six patients with acute HPE and mechanically ventilated in the supine position (Group 2), 20 patients with ARDS (Group 3), and 5 patients with pulmonary fibrosis (PF) (Group 4) served as control patients. Patients with HPE, who after being mechanically ventilated for at least 6 h needed an FI(O(2)) >/= 0.6 to achieve an Sa(O(2)) of approximately 90%, and did not respond to recruitment maneuvers, were turned to the prone position. Parameters of oxygenation, lung mechanics, and hemodynamics were determined in both the supine and prone positions. All patients with HPE exhibited improvement of oxygenation when they were placed in the prone position. The Pa(O(2))/FI(O(2)) ratio increased from 72 +/- 16 in the supine position to 208 +/- 61 after 6 h in the prone position (p < 0.001); the rise in Pa(O(2)) was persistent, without detrimental effect on hemodynamics. Fifteen of 20 patients with ARDS (75%) improved oxygenation when in the prone position. The Pa(O(2))/FI(O(2)) ratio increased from 83 +/- 14 in the supine position to 189 +/- 34 after 6 h in the prone position (p < 0.001). In contrast, 5 of 20 patients with ARDS (25%) and none of the patients with PF responded favorably to prone positioning. Patients with HPE and early ARDS responded better to prone positioning than did patients with late ARDS and PF. Patients with HPE and ventilated in the supine position had a lower Pa(O(2))/FI(O(2)) ratio and the duration of mechanical ventilation was longer compared with that of patients in the prone position. Our results show that the prone position may be a useful maneuver in treating patients with severe hypoxemia due to pulmonary edema. The presence of pulmonary edema, as in early ARDS and HPE predicts a beneficial effect of the prone position on gas exchange. In contrast, the presence of fibrosis, as in late ARDS and pulmonary fibrosis, predisposes to nonresponsiveness to prone positioning.

Respiratory effects of tracheal gas insufflation in spontaneously breathing COPD patients.

OBJECTIVE: To evaluate the effect of tracheal gas insufflation (TGI) in spontaneously breathing, intubated patients with chronic obstructive pulmonary disease (COPD) undergoing weaning from the mechanical ventilation. DESIGN: A prospective study in humans. SETTING: Polyvalent intensive care unit (14-bed ICU) in a 700-bed general university hospital. PATIENTS: Twelve patients with chronic obstructive pulmonary disease (COPD) who required intubation and mechanical ventilation were studied. All patients met standard criteria for weaning from mechanical ventilation. Seven patients (group 1) had been transorally intubated during episodes of acute respiratory failure. Five patients, all men (group 2), had previously undergone tracheostomy and had a transtracheal tube in place. INTERVENTIONS: Intratracheal, humidified, O2-mixture insufflation (TGI) was given via a catheter placed in distal or proximal position. Gas delivered through the intratracheal catheter was blended to match the fractional of inspired gas through the endotracheal tube. Continuous flows of 3 and 6 l/min in randomized order were used in each catheter position. Prior to data collection at each stage, an equilibration period of at least 30 min was observed, and thereafter blood gases were analyzed every 5 min. A new steady state was assumed to have been established when values of both PaCO2 and V CO2 changed by less than 5% between adjacent measurements. The last values of blood gases were taken as representative. The new steady state was confirmed within 35-50 min. Baseline measurements with zero Vcath were made at the beginning and end of the experiment. RESULTS: This study shows that VT, MV, PaCO2, and VD/VT are reduced in a flow-dependent manner when gas is delivered through an oral-tracheal tube (group 1). The distal catheter position was more effective than the proximal one. In contrast, when gas was delivered through tracheostomy (group 2), TGI was ineffective in the proximal position and less effective than in group 1 in distal position. CONCLUSION: Under the experimental conditions, tracheal gas insufflation decreased dead space, increased alveolar ventilation and possibly reduced work of breathing. From the preliminary data reported here, we believe that TGI may help patients experiencing difficulty during weaning.