Pulse transit time for scoring subcortical arousal in infants with obstructive sleep apnea

An altered autonomic control and response to respiratory events during sleep have been reported in infants with obstructive sleep apnea but appropriate methods are not established. We assessed the feasibility of pulse transit time (PTT) in detecting subcortical arousals in eight infants (median age 7 days) suffering from the Pierre Robin sequence and obstructive sleep apnea.

Sleep studies including recordings of PTT performed before and after successful orthodontic treatment for their OSA were analyzed. PTT arousals (i.e., fall in PTT by > or =15 ms lasting for > or =3 s) were visually scored using specific analysis software. Apnea-related PTT arousals and spontaneous PTT arousals were distinguished and predicting factors for the occurrence of uninterpretable PTT signal and PTT arousals were analyzed.

Six-hundred and seven apneas were analyzed. Uninterpretable PTT signal appeared in 394 (65%) apneas and were due to a disturbed pulse waveform in 63%. Predictors for the occurrence of uninterpretable PTT signal were type of apnea (odds ratio, 95% confidence interval for obstructive apnea = 0.5, 0.4-0.9) and duration of apnea (odds ratio, 95% confidence interval per second duration = 1.4, 1.3-1.5). Of 213 apneas with interpretable PTT signal, 43 (7% of all apneas) were followed by a PTT arousal. Predictor for their occurrence was treatment status (odds ratio, 95% confidence interval for pre-treatment status = 3.4, 1.3-8.8). Spontaneous PTT arousals during control periods appeared more frequently pre-treatment compared to post-treatment (41% vs. 16%; p-value = 0.001). There were only weak correlations between changes in PTT, heart rate, and arterial oxygen saturation (correlation coefficient <0.3).

The feasibility of PTT in scoring apnea-related subcortical arousals in infants may be questionable. However, scoring spontaneous PTT arousals may be an approach for assessing sleep disruption in infants with obstructive sleep apnea.