Table 2.

Respiratory changes to hypercapnia (5% CO₂ in air) across brain-state alternations

	REM-like		Transition		nREM-like
	AIR	5% CO2	AIR	5% CO2	AIR	5% CO2
Respiratory period (s)	0.38 ± 0.01	0.41 ± 0.02	0.38 ± 0.01	0.40 ± 0.02	0.43 ± 0.01	0.43 ± 0.02
		+5.0 ± 2.6% (0.06)		+4.8 ± 2.7% (0.06)		+1.0 ± 1.8% (0.28)
Tidal volume (ml)	1.77 ± 0.12	1.96 ± 0.12*	1.77 ± 0.11	1.95 ± 0.12*	1.78 ± 0.12	1.98 ± 0.12*
		+0.9 ± 2.4% (3.2 × 10−3)		+10.3 ± 3.6% (0.015)		+11.7 ± 3.7% (8.7 × 10−3)
Minute ventilation (ml/min × 100 g)	97.3 ± 3.5	105.7 ± 7.6	97.0 ± 4.8	105.0 ± 7.9	89.7 ± 4.2	99.5 ± 8.0*
		+8.1 ± 4.8% (0.07)		+7.6 ± 5.9% (0.11)		+10.2 ± 4.9% (0.047)
Sigh rate (s/h)	46.5 ± 9.8	60.1 ± 14.9*	52.7 ± 7.0	66.9 ± 14.7	16.5 ± 5.6	25.9 ± 8.7
		+35.6 ± 14.6% (0.03)		+19.8 ± 17.4% (0.09)		+45.9 ± 37.3% (0.12)
Peak ∫DIAEMG (a.u.)	0.98 ± 0.16	1.22 ± 0.22*	0.96 ± 0.16	1.19 ± 0.21*	1.00 ± 0.16	1.22 ± 0.20*
		+23.4 ± 9.5% (0.03)		+23.9 ± 10.4% (0.04)		+21.7 ± 7.7% (0.02)
Peak ∫GGEMG (a.u.)	0.79 ± 0.1	1.38 ± 0.38*	0.74 ± 0.8	1.28 ± 0.24*	1.00 ± 0.17	1.78 ± 0.32*
		+64.4 ± 18.0% (0.009)		+65.2 ± 18.2% (9 × 10−3)		+84.1 ± 21.7% (5 × 10−3)
Peak ∫ABDEMG (a.u.)	1.28 ± 0.24	2.77 ± 1.12	1.02 ± 0.03	2.37 ± 0.40*	1.00 ± 0.02	2.01 ± 0.38*
		+96.5 ± 43.2% (0.09)		+132 ± 36% (0.02)		+103 ± 41% (0.04)

Peak EMG activity is calculated based on baseline level of activity during nREM-like state in air breathing. Averaged respiratory period, tidal volume, minute ventilation, sigh rate, and integrated peak EMG activity for DIA, GG, and ABD muscles for REM-like, transition, and nREM-like states during control and hypercapnia. Values in italics indicated the percentage of change compared with control (AIR) measurements for each state, and values in parentheses indicates statistical changes significance (p value) within state (with asterisks indicating statistical significance of the relative changes).