Table 2.

Summary of linear mixed effects regression models and Pearson correlations on forearm and forehead

Location	Relationship	$m$ (95 CI)	$b$ (95 CI)	IQR of (data/fit − 1)	$R$
Forearm	${⟨\mathrm{BFI}⟩}_{2.1}=mP+b$	$-2.9(-3.9,-2.0)\times {10}^{-11}({\mathrm{cm}}^2/\mathrm{s})/\mathrm{mmHg}$	$6.9(5.6,8.2)\times {10}^{-9}{\mathrm{cm}}^2/\mathrm{s}$	0.62	$-0.57$*
	${⟨\mathrm{BFI}⟩}_{3.1}=mP+b$	$-2.6(-3.4,-1.8)\times {10}^{-11}({\mathrm{cm}}^2/\mathrm{s})/\mathrm{mmHg}$	$5.8(4.6,6.8)\times {10}^{-9}{\mathrm{cm}}^2/\mathrm{s}$	0.61	$-0.60$*
	$\mathrm{PI}=mP+b$	$1.8(1.4,2.2)\times {10}^{-3}1/\mathrm{mmHg}$	0.08 (0.01, 0.15)	0.64	0.66*
	${\mathrm{rBFI}}_{2.1}=m\mathrm{\Delta }P+b$	$-4.1(-4.8,-3.4)\times {10}^{-3}1/\mathrm{mmHg}$	0.83 (0.72, 0.94)	1.08	$-0.74$*
	${\mathrm{rBFI}}_{3.1}=m\mathrm{\Delta }P+b$	$-4.0(-4.7,-3.4)\times {10}^{-3}1/\mathrm{mmHg}$	0.78 (0.67, 0.89)	0.77	$-0.75$*
	$\mathrm{rPI}=m\mathrm{\Delta }P+b$	$0.03(0.02,0.04)1/\mathrm{mmHg}$	$1.55(0.36,2.73)$	0.46	0.56*
Forehead	${⟨\mathrm{BFI}⟩}_{2.1}=mP+b$	$-6.7(-7.6,-5.7)\times {10}^{-11}({\mathrm{cm}}^2/\mathrm{s})/\mathrm{mmHg}$	$1.6(1.2,1.9)\times {10}^{-8}{\mathrm{cm}}^2/\mathrm{s}$	0.99	$-0.55$*
	${⟨\mathrm{BFI}⟩}_{3.1}=mP+b$	$-4.7(-5.7,-3.7)\times {10}^{-11}({\mathrm{cm}}^2/\mathrm{s})/\mathrm{mmHg}$	$1.6(1.3,2.0)\times {10}^{-8}{\mathrm{cm}}^2/\mathrm{s}$	0.66	$-0.37$*
	$\mathrm{PI}=mP+b$	$-9.2(-43,24)\times {10}^{-5}1/\mathrm{mmHg}$	0.21 (0.16,0.27)	0.58	$-0.11$
	${\mathrm{rBFI}}_{2.1}=m\mathrm{\Delta }P+b$	$-4.8(-5.4,-4.3)\times {10}^{-3}1/\mathrm{mmHg}$	0.97 (0.88,1.05)	0.79	$-0.88$*
	${\mathrm{rBFI}}_{3.1}=m\mathrm{\Delta }P+b$	$-3.2(-4.0,-2.4)\times {10}^{-3}1/\mathrm{mmHg}$	1.04 (0.93, 1.14)	0.26	$-0.71$*
	$\mathrm{rPI}=m\mathrm{\Delta }P+b$	$6(-239,252)\times {10}^{-5}1/\mathrm{mmHg}$	1.31 (1.06,1.57)	0.59	0.01

Note: $⟨\mathrm{BFI}⟩$, mean blood flow index; PI, blood flow pulsatility index;$\mathrm{rBFI}\equiv ⟨\mathrm{BFI}⟩/{⟨\mathrm{BFI}⟩}_o$; $\mathrm{rPI}\equiv \mathrm{PI}/{\mathrm{PI}}_o$; $P$, probe pressure; subscript “o” indicates initial baseline probe pressure; subscripts “2.1” and “3.1” refer to data acquired at 2.1- and 3.1-cm source-detector separations (PI only computed at 2.1 cm); IQR is interquartile range of the fractional difference (measured data)/(estimate from best-fit line) − 1; $R$ is Pearson’s correlation. *$p<0.001$; $p>0.05$ for other two comparisons.