Intratracheal gas insuflation (ITG) and biphasic positive airway pressure (BIPAP): an integrated strategy in acute respiratory distress syndrome

Introduction

TGI can reverse undesired effects of Permissive Hypercarbia acting primarily to reverse and control high PaCO₂ and low pH values. During ventilation aided by TGI the gas flow, introduced by a catheter positioned 1 inch above carina dilutes the CO₂ in the proximal anatomic dead space. The continuous flow however, in conventional pressure control modes, can be additive to the inspired Vt value, leading to a fast progressive hyperinflation and high airway pressures with a prohibitive risk for volu/barotrauma. This unwanted effect may be neutralized by the use of BIPAP (Drager Evita I-II) as a pure Pressure Control Mode that compensates the additional flow required to the TGI technique.

Methods

5 ARDS (Lung Injury Score ≥2.5) patients on mechanical ventilatory support (MVS) with severe respiratory acidosis were enrolled. These patients had arterial pH levels ≤7.25 after all possible adjustments of the ventilatory parameters aiming to reverse the CO₂ values keeping low volumes and airway pressures. BIPAP was instituted and serial arterial blood gases were drawn at time 0, 30, 60, 90, 120 min, and 24 h after beginning BIPAP and TGI with a 7–9 l/min flow (same FIO₂ than the ventilator) through a 1 mm internal diameter catheter and conector (SIMS-PORTEX). The data was submitted to variance statistical analysis adjusted for repeated measures.

Results

A mean reduction of 8.6 mmHg (9.8%) of PaCO₂ after 30 min and 42.6 mmHg (46.8%) after 24 h was observed. The pH significantly increased after 60 min, after 90 min the mean pH value had risen 0.124 units. The PAO₂/FlO₂ ratio increased as well.

Conclusions

The combination of these two new and not very well known techniques, TGI and BIPAP, were useful in avoiding the adverse effects of high pressures and volumes to counteract the effects of high arterial CO₂ levels in patients with limited cardio-circulatory status and acute or chronic lung and cerebral diseases. In this small sample, considering the influence of time in the reduction of PACO₂ and in the increase of pH values, the best moment to verify the response of TGI is beyond 60 min.

Figure 1