Sighs and Their Relationship to Apnea in the Newborn Infant

Abstract

To test the hypothesis that sighs are mechanistically important in triggering apnea, we studied 10 preterm infants, group 1: body weight 1.8 ± 0.1 kg, gestational age 33 ± 1 weeks, postnatal age 21 ± 4 days, and 10 term infants, group 2: body weight 3.9 ± 0.15 kg, gestational age 40 ± 0.4 weeks, postnatal age 1.4 ± 0.2 days. Instantaneous ventilatory changes associated with a sigh were studied in another 10 preterm infants, group 3: body weight 1.6 ± 0.11 kg, gestational age 32 ± 0.4 weeks, postnatal age 25 ± 4 days. Ventilation was measured using a nosepiece and a flow-through system. Sleep states were recorded. Sighs were more frequent in preterm than in term infants (0.4 ± 0.04 vs. 0.18 ± 0.03 sighs/min; p = 0.03) and in rapid eye movement than in quiet sleep (0.5 ± 0.05 vs. 0.3 ± 0.05 sighs/min; p = 0.05). Of 722 apneas, 235 (33%) were associated with a sigh; of these, 113 (48%) preceded and 122 (52%) followed a sigh. Sighs induced with airway occlusion (groups 1 and 2) were more frequent after occlusion on 21 than on 35% O₂, particularly when O₂ saturation was low and negative airway pressure high. Instantaneous ventilation measured over 10 breaths preceding a sigh did not show any trend indicating the possible appearance of a sigh. Tidal volume increased from 7.5 ± 0.7 before the sigh to 18.9 ± 0.7 ml/kg (p < 0.01) during a sigh, with a significant increase in inspiratory drive. Ventilation increased from 0.327 ± 0.041 to 0.660 ± 0.073 1/min/kg. These findings suggest that: (1) sighs appear to have a minimal, if any, causal relationship with apnea; (2) hypoxia (21 % O₂ + occlusion) seems to be an important determinant for triggering sighs, and (3) there are no changes in instantaneous ventilation preceding a sigh which indicate an imminent sigh.

Different Patterns of Sighs in Neonates and Young Infants

“…As already reported [3], sighs are more frequent in REM sleep than in NREM sleep. Preterm infants show a higher rate of sighs than term infants (group I -preterm: 0.51 sighs/min; group III -term: 0.36 sighs/min), confirming the findings of Alvarez et al [4]. The frequency of sighs decreases with increasing gestational age.…”

“…Generally, the total number of central apneas 15 s and the total number of sighs decrease with increasing gestational age. Alvarez et al [4] reported that of the sigh-associated apneas he found in his study, 48% preceded a sigh. In our investigations, we did not try to prove the existence of apneas preceding any kind of sigh because we interpret postapnea sighs as an inspiratory overreaction to the preceding central apnea or respiratory pause.…”

“…Sighs are often associated with arousals and followed by apnea especially in newborn and in preterm infants. Results of some studies varied from 65% of the apneas preceded by sighs [3] to only 17% of the apneas [4]. With the intention of verifying these data we found that sighs show three dif- (see table 2).…”

“…In recent years a relationship between sighs and apneas in neonates was suggested [4]. As polygraphic recordings show different patterns of sighs we designed this study to examine their prevalence and the relationship to gestational age, breathing frequency, central apneas and NREM and REM sleep.…”

The Influence Of Sighing Respirations On Infant Lung Function Measured Using Multiple Breath Washout Gas Mixing Techniques

“…Infants sigh frequently during sleep (Alvarez et al 1993) so adoption of this guideline renders a relatively large proportion of MBW testing cycles unreportable. There are currently few data to formally evaluate the recommendation to exclude testing cycles containing sighs.…”