Effects of acute hyperbaric oxygenation on respiratory control in cats.
We studied ventilatory responsiveness to hypoxia and hypercapnia in anesthetized cats before and after exposure to 5 atmospheres absolute O2 for 90-135 min. The acute hyperbaric oxygenation (HBO) was terminated at the onset of slow labored breathing. Tracheal airflow, inspiratory (TI) and expiratory (TE) times, inspiratory tidal volume (VT), end-tidal PO2 and PCO2, and arterial blood pressure were recorded simultaneously before and after HBO. Steady-state ventilation (VI at three arterial PO2 (PaO2) levels of approximately 99, 67, and 47 Torr at a maintained arterial PCO2 (PaCO2, 28 Torr) was measured for the hypoxic response. Ventilation at three steady-state PaCO2 levels of approximately 27, 36, and 46 Torr during hyperoxia (PaO2 450 Torr) gave a hypercapnic response. Both chemical stimuli significantly stimulated VT, breathing frequency, and VI before and after HBO. VT, TI, and TE at a given stimulus were significantly greater after HBO without a significant change in VT/TI. The breathing pattern, however, was abnormal after HBO, often showing inspiratory apneusis. Bilateral vagotomy diminished apneusis and further prolonged TI and TE and increased VT. Thus a part of the respiratory effects of HBO is due to pulmonary mechanoreflex changes.
Torbati
D
D
Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia 19104-6085.
Mokashi
A
A
Lahiri
S
S
D000818:Animals; D002415:Cats; D005260:Female; D006931:Hyperbaric Oxygenation; D006935:Hypercapnia / Q000503:physiopathology*; D000860:Hypoxia / Q000503:physiopathology*; D010100:Oxygen / Q000633:toxicity*; D012119:Respiration / Q000187:drug effects / Q000502:physiology*
D010100:Oxygen