Background Airway closure during central apnoea is frequently observed in neonates and may play an important role in preserving oxygenation by maintaining lung volume. However, respiratory efforts against a closed airway have the potential to worsen oxygen (O2) desaturation and prolong the apnoea.
Objective To investigate the effect of patency of the airway on the length of central apnoeas and the degree of O2 desaturation.
Methods We studied 15 preterm infants with significant mixed apnoeas (birth weight 1.6 ± 0.1 kg; gestational age 30 ± 1 weeks; postnatal age 36 ± 1 days). For each infant, all mixed apnoeas observed during the study period (n = 68) were matched 1 : 2 with the longest central apnoeas.
Results Although mixed apnoeas were significantly longer than central apnoeas (11.7 ± 0.6 vs 8.9 ± 0.2 s; p<0.0001), their initial central component was significantly shorter than the length of central apnoeas (6.9 ± 0.4 vs 8.9 ± 0.2 s; p<0.0001). In mixed apnoeas, the onset of O2 desaturation occurred faster (7.3 ± 0.3 s), SpO2 decreased lower (84 ± 1%), and recovered slower (8.5 ± 0.6 s) compared with central apnoeas (8.0 ± 0.2 s, 89 ± 1%, 6.6 ± 0.3 s respectively; p<0.005). In mixed apnoeas, the speed of O2 desaturation was significantly slower before (0.1 ± 0.1%/s) compared with after the obstruction (0.7 ± 0.1%/s; p<0.0001).
Conclusions These findings suggest that the length of central apnoea is not affected by active closure of the airway, respiratory efforts against a closed airway prolong apnoea and worsen the degree and slope of desaturation.