Determinants of pulmonary perfusion measured by electrical impedance tomography.
Electrical impedance tomography (EIT) is a non-invasive imaging technique for detecting blood volume changes that can visualize pulmonary perfusion. The two studies reported here tested the hypothesis that the size of the pulmonary microvascular bed, rather than stroke volume (SV), determines the EIT signal. In the first study, the impedance changes relating to the maximal pulmonary pulsatile blood volume during systole (Delta Z(sys)) were measured in ten healthy subjects, ten patients diagnosed with chronic obstructive pulmonary disease, who were considered to have a reduced pulmonary vascular bed, and ten heart failure patients with an assumed low cardiac output but with a normal lung parenchyma. Mean Delta Z(sys) (SD) in these groups was 261 (34)x10(-5), 196 (39)x10(-5) ( P<0.001) and 233 (61)x10(-5) arbitrary units (AU) (P=NS), respectively. In the second study, including seven healthy volunteers, Delta Z(sys) was measured at rest and during exercise on a recumbent bicycle while SV was measured by means of magnetic resonance imaging. The Delta Z(sys) at rest was 352 (53)x10(-5 ) and 345 (112)x10(-5 )AU during exercise (P=NS), whereas SV increased from 83 (21) to 105 (34) ml (P<0.05). The EIT signal likely reflects the size of the pulmonary microvascular bed, since neither a low cardiac output nor a change in SV of the heart appear to influence EIT.
Smit
Henk J
HJ
Department of Pulmonary Medicine, VU Medical Center, PO Box 7057, 1007 MB Amsterdam, The Netherlands.
Vonk Noordegraaf
Anton
A
Marcus
J Tim
JT
Boonstra
Anco
A
de Vries
Peter M
PM
Postmus
Pieter E
PE
D000368:Aged; D002307:Cardiography, Impedance / Q000379:methods*; D017097:Electric Impedance; D005080:Exercise Test; D005260:Female; D006333:Heart Failure / Q000175:diagnosis* / Q000503:physiopathology*; D006801:Humans; D008168:Lung / Q000098:blood supply / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011652:Pulmonary Circulation; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis* / Q000503:physiopathology*; D015203:Reproducibility of Results; D012129:Respiratory Function Tests / Q000379:methods*; D012680:Sensitivity and Specificity; D014054:Tomography / Q000379:methods