Purpose: The characterization of apneas during polysomnography (PSG) as obstructive or central is a key element of a sleep study. Pulse transit time (PTT) has demonstrated its potential as a noninvasive surrogate marker for inspiratory efforts. The aim of the study was to assess the ability of PTT to classify apneas as central or obstructive, as compared to respiratory inductance plethysmography (RIP) in children.
Methods: Overnight PSG with simultaneous PTT recording was performed on 11 consecutive children (mean age 8.9 years, range 1-18.2 years). The same observer scored the apneas using two blinded configurations: (1) the RIP scoring used the nasal pressure, thermistors, thoracic and abdominal movements, and pulse oximetry signals: (2) the PTT scoring used PTT in combination with all the other signals without the thoracic and abdominal movements.
Results: One hundred fourteen apneas out of a total of 520 respiratory events were analyzed. With RIP, 58 (51%) apneas were scored as obstructive and 56 (49%) as central. Using PTT, 77 (68%) of the apneas were scored as obstructive and 37 (32%) as central. When using PTT, 30 apneas scored as central by RIP were scored as obstructive. PTT was highly sensitive (81%) but poorly specific (46%) in scoring 58 apneas as obstructive. PTT was less sensitive (46%) but highly specific (81%) to score 56 apneas as central.
Conclusion: PTT may be used as an additional tool to RIP to improve the scoring of apneas as obstructive or central in children. The high percentage of artifact is a limitation of PTT.
Keywords: Apneas; Child; Polysomnography; Pulse transit time; Respiratory inductance plethysmography.