Table 3.

Bivariate and multivariable analysis of time course of genioglossus activity during events

	Peak Genioglossus
Independent Variable	Individual Patient Ensemble Average	Multipatient Ensemble Average
	Median (IQR)	Estimate (95% CI)
ΔEMGgg per reduction in drive (standardized)	0.85 (0.43 to 0.96)	0.75 (0.63 to 0.86) P = 1 × 10−10
ΔEMGgg per reduction in pressure (standardized)	0.31 (−0.17 to 0.88)	0.50 (0.38 to 0.61) P = 5 × 10−8
Drive-vs.-pressure contribution*	2.90 (0.47 to ∞)	1.50 (1.16 to 1.99)
ΔEMGgg per reduction in drive (unstandardized)	9.4 (3.8 to 17.3)	14.4 (12.2 to 16.5) P = 1 × 10−10
ΔEMGgg per reduction in pressure (unstandardized)	2.8 (−2.1 to 24.8)	7.3 (5.6 to 8.9) P = 5 × 10−8

Definition of abbreviations: %_max = percentage maximum; CI = confidence interval; EMGgg = genioglossus activity; IQR = interquartile range; Pes = esophageal pressure; SD = standard deviation.

For individual patient analysis, values are determined from β coefficients from individual regression models fit to each patient and presented as median (IQR) across subjects. For multipatient analysis, values are determined from a single regression model fit to the ensemble-averaged data (Figure 2). Data were first standardized by 1 SD so the relative contributions of drive and pressure could be compared (1 SD in drive = 9.5%_eupnea, Pes = 12.4%_eupnea, peak genioglossus activity = 18.3%_baseline or 1.8%_max). Percentage baseline refers to the pre-event baseline peak genioglossus value. Unstandardized multivariate ensemble-average results describe the reduction in EMGgg in percentage baseline per 10%_eupnea reduction in drive or pressure; a 10%_eupnea change in pressure is equivalent to 0.9 cm H₂O average. Model fits were good (median [IQR] individual multivariate model R = 0.91 [0.88–0.98], multipatient multivariate model R = 0.97). EMGgg refers to breath-by-breath peak value of the moving time-averaged signal.

^*Drive-vs.-Pressure contribution reflects the ratio of the standardized drive and pressure β coefficients.