Short apneas and their relationship to body movements and sighs in preterm infants

To test the hypothesis that there is an association among short apneas (3-10 s), body movements, and sighs, we studied 11 preterm infants (body weight 1,500 +/- 200 g, mean +/- SE; gestational age 30 +/- 1 weeks, postnatal age 28 +/- 5 days) using a flow-through system. A total of 1,166 apneas, 1,024 movements, and 473 sighs were recorded. Of the 1,166 apneas, 460 (39%) were associated with movements, 91 (8%) with sighs, and 226 (19%) with both movements and sighs. The rate of apneas associated with movements and sighs was significantly greater than expected if only a random association had occurred. These differences remained in quiet, rapid eye movement, and indeterminate sleep. The frequency of each of the three events was similar in a given sleep state. Of the 460 movements associated with apnea, 26% preceded, 23% followed, and 51% occurred during apnea. Similarly, of the 315 sighs associated with apnea, 44% preceded and 56% followed apnea. Apneas preceded by movements were longer than those without movements (5.6 +/- 0.2 vs. 4.9 +/- 0.1 s; p = 0.01). Oxygen saturation before apnea with movement (94 +/- 0.1%) was lower than before apnea alone (96 +/- 0.6%; p = 0.02) and also lower than before movement alone (96 +/- 0.1%; p = 0.001). These findings suggest: (1) there is a strong association among short apneas, movements, and sighs in these infants; (2) sighs appear not to be an isolated event and are likely to be part of a more general motor discharge, and (3) these events are accompanied by mild desaturations and bradycardias.(ABSTRACT TRUNCATED AT 250 WORDS)