Premium
Repetitive hypoxia rapidly depresses cardio‐respiratory responses during active sleep but not quiet sleep in the newborn lamb
Author(s) -
Johnston Renea V.,
Grant Daniel A.,
Wilkinson Malcolm H.,
Walker Adrian M.
Publication year - 1999
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1999.0571m.x
Subject(s) - hypoxia (environmental) , arousal , heart rate , blood pressure , anesthesia , medicine , respiratory system , psychology , oxygen , chemistry , neuroscience , organic chemistry
1 Arousal from sleep is an important protective response to hypoxia that becomes rapidly depressed in active sleep (AS) when hypoxia is repeated. This study questioned whether there might also be selective depression of cardio‐respiratory responses to hypoxia during AS. 2 Nine newborn lambs (7‐22 days of age) were studied over three successive nights. The first and third nights were baseline studies (inspired oxygen fraction, F i,O2 = 0.21). During the second night, during every epoch of sleep, lambs were exposed to 60 s episodes of isocapnic hypoxia ( F i,O2 = 0.10). 3 During quiet sleep (QS), the probability of arousal in hypoxia exceeded the probability of spontaneous arousal ( P < 0.001 ) throughout repeated exposures to hypoxia. Similarly, there were persisting increases in ventilation (135 ± 25 %), blood pressure (3 ± 1 %) and heart rate (3 ± 1 %). 4 By contrast, rapid depression of all responses occurred during repetitive hypoxia in AS. Thus, the probability of arousal in hypoxia exceeded the probability of spontaneous arousal during the first 10 hypoxia exposures ( P < 0.001 ) but not thereafter. Similarly, during the first 10 exposures to hypoxia, the changes in ventilation (88 ± 15 %) and blood pressure (5 ± 1 %) were greater than subsequent responses ( P < 0.05 ). 5 We conclude that, when repeated, hypoxia rapidly becomes ineffective in stimulating protective arousal, ventilatory and blood pressure responses in AS, but not in QS. Selective depression of responses during AS may render the newborn particularly vulnerable to hypoxia in this state.