Raffaele Pilla, Michael Matott, Carol S. Landon, Jay B. Dean. Molecular Pharmacology and Physiology, University of South. Florida, Tampa, FL. HBO2 stimulates ...
Poiklocapnic hyperoxic hyperventilation (pHH) precedes onset of CNS oxygen toxicity (CNS-OT): evidence for the hypothesis that hyperbaric hyperoxia (HBO2) stimulates medullary CO2chemoreceptors and respiration prior to seizure Raffaele Pilla, Michael Matott, Carol S. Landon, Jay B. Dean. Molecular Pharmacology and Physiology, University of South Florida, Tampa, FL HBO2 stimulates CO2-chemoreceptors, ventilation, and can cause CNS-OT (seizures). We hypothesize that a predictable pattern of pHH precedes seizure. 118 male rats were implanted with radiotransmitters to assess diaphragmatic EMG and EEG. After ≥7 days, a rat was placed in a sealed chamber inside a hyperbaric chamber. The rat chamber (100% O2) and hyperbaric chamber (air) were pressurized to 4 or 5 ATA. Each rat underwent 3 dives, 1 dive/week (n = 9 rats/group). Breathing 5ATA O2 induced seizure in 29.2 + 4.4min, preceded by an increased tidal volume (VT) and respiratory frequency (fRESP) ~5 and ~8min prior to seizure. Similar results were noted at 4ATA O2: seizures occurred after 96.1 + 10.2min preceded by increased VT and fRESP ~8min prior to seizure. We conclude that ventilation is a reliable predictor of an impending HBO2 seizure while breathing poikilocapnic hyperoxia at rest. In addition, the ventilatory response to normobaric hypercapnia (5% CO2 in air) was positively correlated with that of pHH at 4ATA (r2= 0.84) and 5ATA (r2= 0.65), suggesting that HBO2 was stimulating central CO2-chemoreceptor neurons, as we previously reported in rat brain slice studies (ONR).
