Profile of alveolar gases during periodic and regular breathing in preterm infants.
To determine the changes in alveolar PCO2 (PACO2) and PO2 (PAO2) during periodic and regular breathing epochs in the same infants, we studied 11 preterm infants during quiet sleep (birth weight 1,630 +/- 94 g; gestational age 31 +/- 1 weeks; postnatal age 32 +/- 3 days). A total of 94 breathing/apneic cycles were analyzed and compared with regular periods. During periodic and regular breathing epochs, there were negative correlations of PAO2 on PACO2. Short (< or = 5 s) and long (> 5 s) apneas for individual infants occurred along the regression line for that infant. There was not a single overall critical PACO2 below which apnea occurred, but for individual infants the PACO2 and the PAO2 of the breath preceding apnea varied within a limited range. Apneas occurred in clusters of PACO2 and PAO2 along the average regression line of PAO2 on PACO2. Analysis of the data showed that apnea occurred at the lowest PACO2 and highest PAO2 levels if allowance was made for circulation time. During apnea, 'the best fit' for the increase in PACO2 and the decrease in PAO2 was linear, rather than logarithmic. The findings suggest the following. (1) There is not a single overall critical level of PACO2 for apnea to occur, but in a given infant this level varies within a limited range. This indicates that these infants are likely breathing near the apnea threshold. (2) Short and long apneas appear to occur randomly along the regression of PAO2 on PACO2 for a particular infant. (3) The changes in alveolar gases are linear during apnea.(ABSTRACT TRUNCATED AT 250 WORDS)
Pereira
M R
MR
Department of Pediatrics, University of Manitoba, Winnipeg, Canada.
Reis
F C
FC
Landriault
L
L
Cates
D B
DB
Rigatto
H
H
D001049:Apnea / Q000378:metabolism*; D002245:Carbon Dioxide / Q000032:analysis; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D008297:Male; D010100:Oxygen / Q000032:analysis; D011650:Pulmonary Alveoli / Q000378:metabolism*; D011659:Pulmonary Gas Exchange; D012119:Respiration
D002245:Carbon Dioxide; D010100:Oxygen