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.