Table 2.

Physiological Variables During the Hyperventilation (HV) Test

	Steady-state changes with hyperventilation
			p Value
	Baseline values (mean ± standard error)	HV values (mean ± standard error)	HV test (baseline versus HV values)	Exam time	Interaction (HV test × time)	HV test for exams 1–5 versus 6–10a	HV test for exams 6–10 versus 11–15a	HV test for exams 1–5 versus 11–15a
Intracranial pressure (mm Hg)	19.3 ± 0.5	13.2 ± 0.4	<0.0001	.0520	<0.0001	<0.0001	.7649	.0002
Mean arterial pressure (mm Hg)	91.9 ± 0.6	89.1 ± 0.6	<0.0001	<0.0001	.0051	.0002	.1988	.1902
Jugular venous o2 saturation (%)	72.8 ± 0.6	68.5 ± 0.7	<0.0001	.1471	.1965
Brain tissue Po2 (mm Hg)	34.2 ± 3.1	31.5 ± 3.3	.0003	.6881	.0188	.0143	.2010	.0074
End-tidal co2 (mm Hg)	35.7 ± 0.3	29.6 ± 0.3	<0.0001	<0.0001	.0725
Inspired o2 fraction	.44 ± .29	.44 ± .25
Arterial Po2 (mm Hg)	152 ± 3	143 ± 3	.0001	<0.0001	.6108
Arterial Pco2 (mm Hg)	37.1 ± 0.3	30.7 ± 0.3	<0.0001	.0274	.0268	.0198	.6859	.2949
Flow velocity (cm/sec): Left	75.5 ± 1.4	61.7 ± 1.2	<0.0001	<0.0001	<0.0001	<0.0001	.0242	<0.0001
Flow velocity (cm/sec): Right	73.4 ± 1.4	59.6 ± 1.2	<0.0001	<0.0001	<0.0001	<0.0001	.9491	<0.0001
Autoregulatory index: Left	2.7 ± 0.1	3.9 ± 0.1	<0.0001	<0.0001	.7721
Autoregulatory index: Right	2.5 ± 0.1	4.0 ± 0.1	<0.0001	<0.0001	.0842

^aFor Pbto₂, the comparisons are between exams 1–4, exams 5–8, and exams 9–12.