Table 2.

Impedance-pH features in gastro-esophageal reflux disease patients and healthy volunteers

Impedance-pH features	GERD patients	HVs	P value
% pH < 4 upright	6.9 (5.5-12; 28)	1 (0.2-1.9; 5)	< 0.0001
% pH < 4 recumbent	3.5 (1.2-7; 18)	0 (0-0.1; 2.1)	< 0.0001
% pH < 4 total	5.5 (4.3-9; 22)	0.7 (0.2-1.4; 4.2)	< 0.0001
GER total	65 (54-108; 177)	32 (18-43; 54)	< 0.0001
GER acid	53 (34-72; 95)	17 (8-31; 45)	< 0.0001
GER nonacid	20 (15-37; 116)	18 (14-26; 45)	0.0615
Prox. extension	31 (20-48; 86)	9 (4-17; 30)	< 0.0001

GER: Gastroesophageal reflux; GERD: Gastroesophageal reflux disease; HV: Healthy volunteer.