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.

Tracheal gas insufflation reduces the tidal volume while PaCO2 is maintained constant.

OBJECTIVE: The aims of the present study were two-fold: first, to confirm the effect of tracheal gas insufflation (TGI) throughout the respiratory cycle on alveolar ventilation at various catheter flows and constant total inspired VT as an adjunct to conventional volume cycled mechanical ventilation in patients with acute lung injury; second, to test the efficacy of TGI in the reduction of toal VT, peak and mean airway pressure while maintaining PaCO2 in its baseline value. The hemodynamic effect and the consequences on oxygenation as result of the reduction of VT, were also estimated. DESIGN: Prospective study of patients with acute lung injury requiring mechanical ventilation. SETTING: 12 bedded, adult polyvalent intensive care unit in a teaching hospital. PATIENTS: 7 paralyzed and sedated patients with acute respiratory failure were studied. All patients were clinically and hemodynamically stable without fluctuation of the body temperature. All patients were orally intubated with cuffed endotracheal tubes, and mechanically ventilated with a standard circuit of known compliance. INTERVENTIONS: Continuous flows (4 and 6 l/min) were delivered through a catheter positioned 1 cm above carina while tidal volume or PaCO2 were maintained constant at their baseline value. RESULTS: In this study a modest level of TGI significantly enhanced CO2 elimination in patients with acute respiratory failure. Improved ventilatory efficiency resulted from the functional reduction of dead space during TGI allowing the same PaCO2 to be maintained at the same frequency with lower tidal volume and lower airway pressure requirement. Tidal volume, peak and mean airway pressure decreased linearly with catheter flow, without significant changes in oxygenation, while PaCO2 remained stable. CONCLUSION: The results of this study suggest that TGI may be an useful adjunct mode of mechanical ventilation that limits alveolar pressure and minute ventilation requirements.