The effect of the phase relationship between the arterial blood gas oscillations and central neural respiratory activity on phrenic motoneurone output in cats.
The aim of the present experiments in artificially ventilated, anesthetized cats was to investigate in which circumstances the timing of the arterial blood gas oscillations within the respiratory cycle can be of importance in determining phrenic motoneurone output. The phase relationship phi was defined as the relative position of the peak of the phrenic bursts within the current continuously measured PaO2 oscillations. It was judged breath by breath whether there was a relationship between phi and neural tidal volume, and neural inspiratory and expiratory duration. Within cats, PETCO2 was kept constant at about 1.5-2% above apneic threshold. It was found that phi indeed partly determined these ventilatory parameters provided the oscillations were large enough. This was evident in normoxia; in moderate hypoxia the influence of phi was demonstrable more easily, i.e. at smaller oscillation amplitudes. In both conditions the effect of phi on neural tidal volume was most pronounced. Neural tidal volume was maximal when peak inspiration coincided with the expiratory trough of the PaO2 oscillations. A 1:1 phase lock between phrenic activity and the ventilatory only occurred when the pump frequency was close to the cats own breathing frequency. Bilateral carotid sinus nerve section abolished the effects of phi.
D000818:Animals; D001158:Arteries; D002415:Cats; D005260:Female; D000860:Hypoxia / Q000503:physiopathology; D008297:Male; D009046:Motor Neurons / Q000502:physiology*; D010100:Oxygen / Q000097:blood*; D010507:Periodicity; D010791:Phrenic Nerve / Q000502:physiology*; D011659:Pulmonary Gas Exchange; D012119:Respiration; D012121:Respiration, Artificial; D013990:Tidal Volume; D014628:Vagotomy
D010100:Oxygen