Mice with blunted hypoxic ventilatory response are susceptible to respiratory disturbance during hypoxia.
Hypoxia causes a life-threatening situation, and the ventilatory response to hypoxia plays an important role in preventing death. We have hypothesized that persons with a blunted hypoxic ventilatory response may have a weak defense response to hypoxic episodes and be susceptible to fatal respiratory disturbances. However, precise correlations between the hypoxic ventilatory response and respiratory disturbances are not well understood. In the present study we examined the hypoxic and hypercapnic ventilatory responses in nine inbred mouse strains (A/J, AKR/N, BALB/c, C3H/He, C57BL/6, DBA/2, NZW, SWR/J, and 129Sv). Breathing frequency, tidal volume and minute ventilation of unanesthetized and unrestrained mice were assessed by whole body plethysmography. Age-matched mice were exposed for 3 min to 10% O(2) in N(2) gas or 10% CO(2) in hyperoxic gas to determine the acute ventilatory response to chemical stimuli. Basal respiratory variables and hypoxic ventilatory responses differed among the strains, but the hypercapnic ventilatory response did not differ. The hypoxic ventilatory response was the highest in AKR/N mice and the lowest in SWR/J mice. These findings suggest that genetic factors may have influenced the hypoxic ventilatory response but not the hypercapnic ventilatory response. To examine the effects of severe hypoxic stress on the respiratory cycle, we exposed the strain with the highest or lowest hypoxic ventilatory response to 6% O(2) in N(2) until the onset of apnea. The "appearance time of apnea", which is defined as the time from the hypoxic loading to the onset of apnea, was shorter in the SWR/J strain than in the AKR/N strain. We suggest that a lower hypoxic ventilatory response may be a risk factor for apnea under hypoxia.
Adachi
Tetsuya
T
Department of Cardiovascular and Respiratory Medicine, Tohoku University School of Medicine, Kawauchi 41, Sendai 980-8576, Japan.
Ogawa
Hiromasa
H
Okabe
Shinichi
S
Kitamuro
Tomomi
T
Kikuchi
Yoshihiro
Y
Shibahara
Shigeki
S
Shirato
Kunio
K
Hida
Wataru
W
D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D001049:Apnea / Q000209:etiology / Q000503:physiopathology; D004195:Disease Models, Animal; D006935:Hypercapnia / Q000503:physiopathology*; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D051379:Mice; D008806:Mice, Inbred AKR; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D008815:Mice, Inbred Strains / Q000502:physiology*; D010993:Plethysmography, Whole Body; D012123:Pulmonary Ventilation / Q000502:physiology*; D012129:Respiratory Function Tests; D013045:Species Specificity