Am. J. Respir. Crit. Care Med.,
Volume 162, Number 2, August 2000, 363-368
Reverse-Thrust Ventilation in Hypercapnic Patients
with Acute Respiratory Distress Syndrome
Acute Physiological Effects
NICOLA
ROSSI,
GUIDO
MUSCH,
FABIO
SANGALLI,
MURIEL
VERWEIJ,
NICOLO
PATRONITI,
ROBERTO
FUMAGALLI,
and
ANTONIO
PESENTI
Department of Anesthesia and Intensive Care, Ospedale San Gerardo Nuovo dei Tintori, University of Milan, Monza, Milan, Italy
Techniques of tracheal gas insufflation (TGI) have been shown to
enhance CO2 clearance efficiency in mechanically ventilated patients with acute respiratory distress syndrome (ARDS). Clinical studies have explored the effects of such techniques only at moderate intratracheal gas flow rates, with TGI superimposed to mechanical ventilation in a continuous fashion, or synchronized to
the expiratory phase of the duty cycle. We examined the effects of
intratracheal pulmonary ventilation (ITPV), delivering the entire
tidal volume (VT) in the proximity of the tracheal carina, with all
the gas flow supplied continuously through a reverse-thrust catheter (RTC). A potential limitation in the application of TGI is dynamic hyperinflation. Therefore, in a subgroup of patients, we also
evaluated the effects of ITPV on end-expiratory lung volume
(EELV) by respiratory inductive plethysmography (RIP). Eleven patients with ARDS under volume-cycled mechanical ventilation
were subsequently switched to ITPV at the same baseline respiratory rate, I:E ratio, and VT. At the same minute volume, PaCO2 decreased from 70 ± 12.3 to 59 ± 9.5 mm Hg, with a percent reduction of 15 ± 4% (range from 10 to 20%). The CO2 decrease was
greater in patients with higher baseline PaCO2 levels (
PaCO2 = 0.29 × PaCO2
9.48, r = 0.95). During transition from mechanical
ventilation to ITPV, tracheal positive end-expiratory pressure
(PEEPtr) decreased with a correspondent decrease in EELV. Both
were restored by increasing the PEEP at the ventilator by 3.6 ± 2.0 cm H2O. These data suggest that in patients with ARDS ITPV effectively reduces dead space ventilation and the employment of the
RTC may limit or avoid dynamic hyperinflation.