Table 4.

First- and second-level group comparisons of CO₂ cerebrovascular responsiveness.

First-level analysis (reported at p = 0.001)
Group (mean ± SD)	Hyper response	Inverse response	Absolute voxel count	% hyper response	% inverse response
Controls	149,305 ± 11,399	1,285 ± 1,012	186,452 ± 5,179	80.1 ± 6.3	0.7 ± 0.6
Sports-related concussion patients	145,055 ± 25,767	1,119 ± 1,106	186,033 ± 5,168	77.9 ± 13.0	0.6 ± 0.6
t-Test	0.46	0.63	0.80	0.45	0.64
Second level analysis (reported at p = 0.005)
Group (mean ± SD)	Increased CVR response	Decreased CVR response	Abnormal voxel count	% CVR increase	% CVR decrease
Controls	2,964 ± 5,820	221 ± 248	3,185 ± 5,881	1.6 ± 3.1	0.12 ± 0.13
Sports-related concussion patients	13,413 ± 10,092	202 ± 286	13,615 ± 10,129	7.2 ± 5.4	0.11 ± 0.15
t-Test	0.001	0.82	0.002	0.001	0.82