ISSN:
1432-2013
Keywords:
Ventilatory Response to $$P_{{\text{CO}}_{\text{2}} } $$
;
Respiration in Hypothermia
;
Threshold $$P_{{\text{CO}}_{\text{2}} } $$
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary Alveolar $$P_{{\text{CO}}_{\text{2}} } $$ -ventilatory response curves at different constant levels of alveolar $$P_{{\text{O}}_{\text{2}} } $$ were reconstructed from the alveolar $$P_{{\text{O}}_{\text{2}} } $$ -ventilatory response curves previously obtained during normothermia and hypothermia (about 10°C below normal body temperature) in anesthetized dogs. The $$P_{{\text{CO}}_{\text{2}} } $$ -ventilatory response was shifted parallel to a lower $$P_{{\text{CO}}_{\text{2}} } $$ as $$P_{{\text{O}}_{\text{2}} } $$ decreased in normothermia. During hypothermia the slope of the $$P_{{\text{CO}}_{\text{2}} } $$ -ventilatory response curve decreased markedly in the entire range of $$P_{{\text{CO}}_{\text{2}} } $$ levels. However, ventilatory minute volume during hypothermia increased as $$P_{{\text{O}}_{\text{2}} } $$ decreased, which is similar to the flat portion of the $$P_{{\text{CO}}_{\text{2}} } $$ -ventilatory response curve during hypoxia in human subjects. The slope of the $$P_{{\text{CO}}_{\text{2}} } $$ -ventilatory response curve in non-hypoxic condition was also decreased markedly during hypothermia. The threshold value of $$P_{{\text{CO}}_{\text{2}} } $$ (threshold $$P_{{\text{CO}}_{\text{2}} } $$ ) was obtained as the $$P_{{\text{CO}}_{\text{2}} } $$ at the point where the response curve of steep slope (normothermia) intersected the response curve of smaller slope (hypothermia). This threshold $$P_{{\text{CO}}_{\text{2}} } $$ , called “central threshold $$P_{{\text{CO}}_{\text{2}} } $$ ” in the present paper, decreased as $$P_{{\text{O}}_{\text{2}} } $$ decreased. Furthermore the so-called “apneic threshold $$P_{{\text{CO}}_{\text{2}} } $$ ” was obtained as the $$P_{{\text{CO}}_{\text{2}} } $$ where the steep slope of the response curve intersected the $$P_{{\text{CO}}_{\text{2}} } $$ axis. It is concluded that, in the absence of the function of the central chemoreceptors, ventilation is not much affected by the change in $$P_{{\text{CO}}_{\text{2}} } $$ and is maintained mainly by the drive of the peripheral chemoreceptors, and that, with normal function of the central chemoreceptors, ventilation increases proportionately as $$P_{{\text{CO}}_{\text{2}} } $$ increases only above a central threshold $$P_{{\text{CO}}_{\text{2}} } $$ .
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00587373
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