Efficacy of tracheal gas insufflation in acute respiratory distress syndrome with permissive hypercapnia.

Abstract

This study was conducted to assess the CO2-elimination efficiency of tracheal gas insufflation (TGI) in 20 patients with acute respiratory distress syndrome and to compare its efficacy during volume-controlled (VCV) and pressure-controlled ventilation (PCV). TGI was initially applied as an adjunct to VCV, with continuous flows (Vcath) of 4 and 6 L/min delivered through a catheter positioned 2 cm above the carina. Total effective tidal volume (VTeff) was held constant. The percent reductions in PaCO2 (% delta PaCO2) were 13.3 +/- 2.1 and 16.7 +/- 2.7% at Vcath 4 and 6 L/min, respectively, which correlated well with the percent reduction in the end-tidal PCO2 from baseline (% delta PETCO2) (r = 0.75, p < 0.001). An inverse relationship (r = -0.65, p < 0.001 and r = -0.59, p < 0.01 at Vcath 4 and 6 L/min, respectively) was found between the % delta PaCO2 and the baseline ratio of artery to PETCO2 difference to PaCO2, which was determined as the fraction of alveolar dead space (VDalv) relative to total alveolar ventilation. Twelve patients were subsequently switched to PCV combined with Vcath 6 L/min, which provided a % delta PaCO2 of 16.1 +/- 3.0% (p = NS versus 17.1 +/- 2.6% during VCV). These data suggest that in patients with ARDS the change in PETCO2 may be helpful in predicting the decrement in PaCO2 during TGI, and the existence of a high VDalv tends to limit its effectiveness. Further, the efficacy of TGI with VCV is equivalent to that with PCV.

Reverse-Thrust Ventilation in Hypercapnic Patients with Acute Respiratory Distress Syndrome

“…Our results are similar to those reported with continuous TGI at moderate catheter flow rates (4-6 L/min) in patients with acute respiratory failure (13,15,27). More recently, Belghith and colleagues obtained an average Pa CO 2 reduction of approximately 20% at a catheter flow rate of 4 L/min in a group of severely hypercapnic patients with ARDS (19).…”

Acute effects of combined high-frequency oscillation and tracheal gas insufflation in severe acute respiratory distress syndrome*

“…4A) implies a PEEP effect (10). Similar TGI flows have been previously used successfully during CMV (17)(18)(19).…”

Untitled

“…Since increasing the fraction of unperfused alveoli decreases the efficacy of TGI (as measured by percentage change in VD and PaCO 2 relative to baseline conditions), the ratio (PaCO 2 -PETCO 2 )/PaCO 2 may provide useful clinical information. Indeed, in both animal [8] and human studies [17,26] this ratio was closely correlated ( r ≃ 0.70) with observed percentage reduction in PaCO 2 from baseline during TGI. The exact role of capnography to monitor the efficacy of TGI remains to be established, but available data suggest that it may be used to optimize Vc and ventilator settings.…”

“…In most human studies, a small-caliber catheter was introduced through an angled side-arm adapter attached to the endotracheal tube (ETT) and positioned just above the main carina [4,15,16,17]. Catheter placement was usually performed with bronchoscopic guidance or estimated from a recent chest roentgenogram.…”