Table 3.

Cardiorespiratory and neural responses to hyperoxic end-expiratory apnea

	Normoxic Baseline	Hyperoxic Baseline	Hyperoxic Apnea	P Value
Heart rate, beats/min	64 ± 2	63 ± 2	67 ± 5	0.53
Systolic blood pressure, mmHg	145 ± 4	146 ± 4	157 ± 6*†	<0.01
Diastolic blood pressure, mmHg	78 ± 2	79 ± 3	89 ± 3*†	<0.01
Mean blood pressure, mmHg	100 ± 3	101 ± 3	113 ± 4*†	<0.01
Oxygen saturation (% $\text{S}{\text{p}}_{{\text{O}}_2}$)	99 ± 0	100 ± 0		0.07
$\text{P}{\text{a}}_{\text{O}}{}_{{}_2}$, mmHg	110 ± 5	444 ± 19*		<0.01
$\text{P}{\text{a}}_{\text{C}\text{O}}{}_{{}_2}$, mmHg)	38 ± 1	36 ± 2*		0.03
Respiratory rate, breaths/min	11 ± 1	12 ± 1		0.17
Tidal volume, L/breath	0.75 ± 0.18	0.80 ± 0.15		0.47
Minute ventilation, mL/min	7.6 ± 1.3	8.8 ± 1.3*		0.048
Burst frequency, bursts/min	24 ± 4	21 ± 2	28 ± 5	0.14
Burst incidence, bursts/100 heartbeats	38 ± 6	33 ± 3	47 ± 8	0.12
Mean burst area, AU/min	1.3 ± 0.3	1.1 ± 0.2	1.2 ± 0.3	0.93
AP frequency, APs/min	155 ± 35	155 ± 30	253 ± 71	0.12
AP incidence, APs/burst	6 ± 1	8 ± 2	8 ± 1	0.18
AP incidence, APs/100 heartbeats	249 ± 61	258 ± 55	502 ± 188	0.28
Mean cluster incidence, clusters/burst	3.7 ± 0.5	3.6 ± 0.3	4.2 ± 0.6	0.57
Max cluster incidence, clusters/burst	6.4 ± 0.7	6.6 ± 0.6	7.0 ± 1.3	0.78
Max cluster number	13.2 ± 1.7	11.9 ± 0.9	11.2 ± 2.2	0.31
Data duration, s	107 ± 9	103 ± 9	32 ± 11*	0.01

Data are reported as means ± SE for n = 9 subjects. AP, action potential; AU, arbitrary units; $\text{S}{\text{p}}_{{\text{O}}_2}$, arterial O₂ saturation from pulse oximetry. Data were analyzed with a 1-way repeated-measures ANOVA. Normality was assessed with the Shapiro–Wilk test. If not normally distributed, a Friedman repeated-measures ANOVA on ranks was conducted. Pairwise comparisons were done with the Holm–Sidak method. Bold type signifies statistical significance.

^*P < 0.05 vs. normoxia;

^†P < 0.05 vs. hyperoxia.