Effect of lower body negative pressure release on hyperpnea induced by inhaled gas.
Transient breath-by-breath ventilation (VI) and end-tidal gases were measured on 6 men in response to: (1) the release of lower body negative pressure (LBR); (2) the one-min inhalation of a gas mixture (GAS) containing 5.4% CO2, 14% O2, balance N2; (3) the two combined (LBR + GAS) with LBR preceding GAS inspiration by 5 sec. With LBR a + 29% peak response in VI occurred after 20 sec whereas with GAS and LBR + GAS, VI tended to level off after 25 sec at + 100% and + 180%, respectively. Simultaneously, PETCO2 had risen 2, 5 and 8 mm Hg and PETO2 had fallen 7, 14 and 19 mm Hg, respectively. LBR accelerated and potentiated the VI response to GAS. Leg volume indicated that 50% of the pooled blood returned from the legs after 4 sec, presumably with high PCO2 and low PO2 contributing an endogenous respiratory stimulus to the exogenous one of GAS. VI with LBR + GAS was greater than the sum of each, suggesting an enhancement of the chemoreceptor response by returning pooled blood.
D000328:Adult; D000368:Aged; D002245:Carbon Dioxide / Q000502:physiology; D002628:Chemoreceptor Cells; D003664:Decompression; D006801:Humans; D008150:Lower Body Negative Pressure; D008297:Male; D010100:Oxygen / Q000502:physiology; D012119:Respiration
D002245:Carbon Dioxide; D010100:Oxygen