Journal of Applied Physiology, Vol 62, Issue 4 1453-1459, Copyright © 1987 by American Physiological Society
Effect of cardiogenic gas mixing on arterial O2 and CO2 tensions during breath holding
S. M. Kelly, A. P. Brancatisano and L. A. Engel
To examine the effect of cardiogenic gas mixing on gas exchange we measured
arterial tension of O2 (PaO2) and arterial tension of CO2 (PaCO2) during 3-
to 5-min breath holds (BH) before and after infusing 50 ml of saline into
the pericardial space (PCF) of seven anesthetized, paralyzed, mechanically
ventilated dogs. During BH the ventilator was disconnected and a bias flow
of 50% O2 at 4-5 l/min was delivered through the side ports of a small
catheter whose tip was positioned 1 cm cephalad of the carina. Paired runs,
alternately with and without PCF, were performed in triplicate in each dog.
Initial PaO2 was similar for control runs [81 +/- 3 mmHg (SE)] and PCF runs
(78 +/- 3 mmHg; P greater than 0.1). After 3-min BH, PaO2 in PCF runs (33
+/- 3 mmHg) was less than that in control runs (58 +/- 4 mmHg) (P less than
0.001). In contrast, the pattern of PaCO2 during BH did not differ with
PCF. After 3-min BH, PaCO2 was 49 +/- 3 mmHg with PCF and 49 +/- 2 mmHg in
the control runs (P greater than 0.7). In two dogs, repeated 50-ml
reductions in lung volume, produced by rib cage compression, did not alter
the time course of PaO2 during BH. Although cardiac output decreased
slightly with PCF, hemodynamic changes due to PCF were unlikely to account
for the observed fall in PaO2. Our results indicate a substantial effect of
cardiogenic gas mixing on O2 uptake when tracheal gas is O2 enriched during
breath holding.(ABSTRACT TRUNCATED AT 250 WORDS)
