Respiration and heart rate variation in normal infants during quiet sleep in the first year of life.

Forty-three all-night sleep recordings have been performed on 19 control infants of the ages 6 weeks, 6 months and 1 year. During eight hour periods 22 physiological parameters were sampled by a personal computer based monitoring system and stored on an optical disk. This paper reports on spectral analysis of breathing and heart rate patterns during the first and last episode of quiet sleep at three different age groups. The results demonstrate that the respiratory rate during quiet sleep decreases (6 weeks: 37.2 +/- 5.4; 6 months: 30.1 +/- 4.9; 1 year: 24.1 +/- 1.8; adults (mean age 25.1 +/- 2.8 years; n = 10): 14.8 +/- 1.8; values are means +/- one standard deviation in breaths/min) and the respiratory coefficient Pm/Ps (higher values of Pm/Ps indicate lower respiratory variability) increases with age (6 weeks: 2.3 +/- 0.7; 6 months: 3.2 +/- 1.1; 1 year: 3.4 +/- 1.0; adults: 4.5 +/- 1.0). The calculation of the heart rate in beats per minute (bpm) and heart rate variability (%) revealed the following results: 6 weeks: 127.4 +/- 11.5 bpm, 3.8 +/- 1.5%; 6 months: 119.4 +/- 17.3 bpm, 4.2 +/- 1.7%; 1 year: 110.3 +/- 21.5 bpm, 5.8 +/- 2.3%; adults: 59.2 +/- 8.5 bpm, 4.3 +/- 2.2%. A comparison of the cardiorespiratory data from the first and last quiet sleep period showed no significant differences within either age group.