Table 5

Adjusted* partial Pearson correlations with OSAS severity measures within adolescents with OSAS

Variable	N	AHI (events/hour)†		% sleep time with SpO₂<90%†		SpO₂ nadir (%)		Peak ETCO₂ (mm Hg)		% sleep time with ETCO₂>50†
Variable	N	r	p Value	r	p Value	r	p Value	r	p Value	r	p Value
Tonsil volume, mm³	42	0.56	<0.001	0.67	<0.0001	−0.45	0.005	0.13	0.428	0.19	0.255
Adenoid volume, mm³	42	0.51	0.001	0.39	0.015	−0.30	0.070	0.05	0.766	−0.04	0.805
ATV, mm³	42	0.66	<0.0001	0.66	<0.0001	−0.46	0.003	0.11	0.497	0.09	0.579
NPAV, mm³	42	−0.08	0.616	0.11	0.527	0.01	0.965	−0.12	0.456	0.06	0.737
Nasopharyngeal cross-sectional area, mm²	42	−0.24	0.151	−0.20	0.220	0.03	0.866	−0.11	0.517	−0.03	0.860
Nasopharyngeal minimum area, mm²	42	−0.26	0.114	−0.16	0.340	−0.03	0.880	−0.13	0.423	−0.07	0.692
Slope of the pressure–flow response (activated), mL/s/cm H₂O	42	0.21	0.200	0.12	0.475	−0.05	0.769	−0.14	0.403	−0.24	0.142
Pcrit (activated), cm H₂O	42	0.36	0.027	0.34	0.037	−0.11	0.527	−0.06	0.733	−0.12	0.475
Slope of the pressure–flow response (hypotonic), mL/s/cm H₂O	42	0.05	0.743	0.05	0.752	0.10	0.566	−0.01	0.949	−0.21	0.200
Pcrit (hypotonic), cm H₂O	42	0.30	0.065	0.36	0.027	−0.02	0.923	0.16	0.335	0.02	0.888
EMGgg slope (activated), %/cm H₂O	32	0.16	0.422	0.28	0.151	−0.17	0.378	−0.04	0.833	0.13	0.523
EMGgg slope (hypotonic), %/cm H₂O	30	0.14	0.502	0.07	0.719	0.12	0.544	−0.34	0.088	−0.32	0.108
HCVR slope, L/min/mm Hg PETCO₂	31	0.12	0.561	−0.02	0.931	−0.04	0.840	0.07	0.717	−0.06	0.761
HCVR correlation coefficient	31	0.10	0.603	0.12	0.556	−0.05	0.795	−0.19	0.339	−0.25	0.202
CO₂ response during sleep, %ΔV_E	16	−0.42	0.172	−0.41	0.186	0.52	0.080	−0.07	0.834	−0.16	0.629

*Partial correlations controlling for age, gender, race and BMI Z-score.
†Measures natural log+1 transformed for normality; significant (p<0.05) correlations are shown in bold.
AHI, apnoea hypopnoea index; ATV, adenotonsillar volume; BMI, body mass index; EMGgg, genioglossal electromyogram; ETCO₂, end-tidal carbon dioxide; HCVR, hypercapnic ventilatory response; NPAV, nasopharyngeal airway volume; OSAS, obstructive sleep apnoea syndrome; Pcrit, critical closing pressure; SpO₂, arterial oxygen saturation; V_E, minute ventilation.