Wa. Tweed et al., TIDAL VOLUME, LUNG HYPERINFLATION AND ARTERIAL OXYGENATION DURING GENERAL-ANESTHESIA, Anaesthesia and intensive care, 21(6), 1993, pp. 806-810
Citations number
39
Categorie Soggetti
Anesthesiology,"Emergency Medicine & Critical Care
Impaired pulmonary oxygen (O2) exchange is common during general anaes
thesia but there is no clinical unanimity as to methods of prevention
or treatment. We studied 14 patients at risk for pulmonary dysfunction
because of increased age, obesity, cigarette smoking, or chronic lung
disease. Pulmonary O2 exchange was measured during four conditions of
ventilation: awake spontaneous, conventional tidal volume (CV(T), 7 m
l.kg-1) or high tidal volume (HV(T), 12 ml.kg-1) controlled ventilatio
n, and five min after manual hyperinflation (HI) of the lungs. The F(I
)O2 was controlled at 0.5, and F(ET)CO2 was kept constant by adding de
ad space during HV(T). Eight patients were ventilated with N2O/O2 and
six with air/O2. Arterial blood gases were used to calculate the (A-a)
DO2. In seven patients (A-a)DO2 worsened after induction of anaesthesi
a, while in seven there was no change or an improvement. Manual HI sig
nificantly reduced (A-a)DO2, but changing tidal volume (VT) had no eff
ect. Using a multivariate model to predict O2 exchange, obesity and ty
pe of surgery were significantly associated with worsening, while leve
l of V(T) and inspiratory gas (N2O or N2) were not significant predict
ors. Thus patient and surgical factors were more important determinant
s of pulmonary gas exchange during anaesthesia than were tidal volume
or inspiratory gas. Manual HI is a simple and effective manoeuvre to i
mprove gas exchange.