Journal of Applied Physiology, Vol 63, Issue 1 229-237, Copyright © 1987 by American Physiological Society
Interactive effects of CO2 and upper airway negative pressure on breathing pattern
E. van Lunteren
The interactive effects of upper airway negative pressure and hypercapnia
on the pattern of breathing were assessed in pentobarbital-anesthetized
cats. At any given level of pressure in the upper airway, hypercapnia
increased respiratory rate, reduced inspiratory time, and augmented tidal
volume, inspiratory airflow, and the peak and rate of rise of diaphragm
electrical activity. Conversely, at any given level of CO2, upper airway
negative pressure decreased respiratory rate, prolonged inspiratory time,
and depressed inspiratory airflow and diaphragm electromyogram (EMG) rate
of rise. Application of negative pressure to the upper airway shifted the
relationship between tidal volume and inspiratory time upward and
rightward. The relationship between inspiratory and expiratory times,
however, was linearly correlated over a wide range of chemical drives and
levels of upper airway pressure. These results suggest that in the
anesthetized cat upper airway negative pressure afferent inputs 1) interact
in an additive fashion with hypercapnia to alter the pattern of breathing,
2) interact multiplicatively with CO2 to influence mean inspiratory airflow
and diaphragm EMG rate of rise, 3) depress the generation of central
inspiratory activity, 4) increase the time-dependent volume threshold for
inspiratory termination, and 5) affect the ratio between inspiratory and
expiratory times in a similar manner as alterations in PCO2.
