PP31 DETECTION OF NOCTURNAL HYPOVENTILATION VIA TRANSCUTANEOUS CARBON DIOXIDE MONITORING IN CHILDREN INVESTIGATED FOR SLEEP-DISORDERED BREATHING: A CROSS-SECTIONAL STUDY

Nur-Liyana Ahmad Danial1, Kah Peng Eg1,2, Shih Ying H’ng2, Siti Hajar Tubirin2, Jessie Anne de Bruyne2, Anna Marie Nathan1,2

1Universiti Malaya, Kuala Lumpur.
2Universiti Malaya Medical Centre, Kuala Lumpur

Introduction
Patients with sleep-disordered breathing (SDB) are at risk of nocturnal hypoventilation (NH). However, there is no consensus in NH definition for children.

Objectives
To evaluate the prevalence of NH in patients investigated for SDB using transcutaneous carbon dioxide (TcCO2) capnography, to determine the clinical factors associated with NH, and to assess the correlation of TcCO2 pressure (PtcCO2) levels with oxygenation indices and apnoea-hypopnoea index (AHI).

Methodology
Patients who underwent a diagnostic TcCO2 capnography either with polysomnography (PSG) or overnight pulse oximetry (OPO) over an 18-month period were recruited. Prevalence of NH was determined based on four definitions: PtcCO2>50mmHg >25% total sleep time (TST), PtcCO2>50mmHg >2%TST, peak value PtcCO2>50 mmHg, or PtcCO2>10mmHg above baseline awake value. The clinical factors associated with NH and correlation between PtcCO2 with oxygenation indices and AHI were determined.

Results
Sixty patients were included and 38% had severe SDB (AHI>10). The prevalences of NH were 45.0%, 63.3%, 70.0%, and 73.3% respectively. NH prevalence was higher in severe SDB across all definitions. Patients with previously diagnosed obstructive sleep apnoea (OSA) (Adj. OR:3.62, p-value=0.050) and congenital heart disease (CHD) (Adj. OR:8.46, p-value=0.020) were more likely to have NH. Maximum PtcCO2 showed moderate correlation with AHI and oxygen desaturation index, while weak negative correlation was seen between maximum PtcCO2 and oxygenation indices.

Conclusions
NH is prevalent in children investigated for SDB. Patients with OSA and CHD are at higher risk. No strong correlation between PtcCO2 levels with AHI and oxygenation indices highlights the importance of TcCO2 monitoring in a sleep study.