Ba. Gentz et al., CARBON-DIOXIDE DYNAMICS DURING APNEIC OXYGENATION - THE EFFECTS OF PRECEDING HYPOCAPNIA, Journal of clinical anesthesia, 10(3), 1998, pp. 189-194
Study Objective: To compare the rate of increase of arterial carbon di
oxide tension (PaCO2) during apneic oxygenation preceded by acute resp
iratory hypocapnia with that during apnea preceded by respiratory euca
pnia. Design: Randomized, prospective, single crossover study. Setting
: Operating room at a teaching hospital. Patients: 19 ASA physical sta
tus I, II, and III patients requiring general endotracheal anesthesia
and invasive monitoring for elective surgery. Interventions: Two venti
latory states preceding apneic oxygenation were studied in each patien
t. The first respiratory state was established using controlled mechan
ical ventilation in the stable, anesthetized patient, followed by a 5-
minute period of apneic oxygenation. Arterial and mixed central venous
blood gas samples were obtained simultaneously pier to and at 1-minut
e intervals during apnea, Ventilatory parameters were then changed to
establish the second respiratory state. During the subsequent period o
f apnea, the study: was repeated as above. Measurements and Main Resul
ts: Arterial and mixed central venous partial pressure of carbon dioxi
de (pCO(2)) levels were measured. A greater increase in PaCO2 was foun
d during the first minute of apneic oxygenation in the hypocapneic gro
up compared with the eucapneic group. The venoarterial gradient of pCO
(2) was also greater in the hypocapneic group prior to apnea. Conclusi
ons: Acute hypocapnia compared with eucapnia prior to apneic oxygenati
on is associated with a greater rise in PaCO2 in the anesthetized pati
ent. This finding may be due in part to widening of the venoarterial g
radient of pCO(2). (C) 1998 by Elsevier Science Inc.