Hyperoxia affects the regional pulmonary ventilation/perfusion ratio: an electrical impedance tomography study.
BACKGROUND
The way in which hyperoxia affects pulmonary ventilation and perfusion is not fully understood. We investigated how an increase in oxygen partial pressure in healthy young volunteers affects pulmonary ventilation and perfusion measured by thoracic electrical impedance tomography (EIT).


METHODS
Twelve semi-supine healthy male volunteers aged 21-36 years were studied while breathing room air and air-oxygen mixtures (FiO2) that resulted in predetermined transcutaneous oxygen partial pressures (tcPO2) of 20, 40 and 60 kPa. The magnitude of ventilation (ΔZv) and perfusion (ΔZQ)-related changes in cyclic impedance variations, were determined using an EIT prototype equipped with 32 electrodes around the thorax. Regional changes in ventral and dorsal right lung ventilation (V) and perfusion (Q) were estimated, and V/Q ratios calculated.


RESULTS
There were no significant changes in ΔZv with increasing tcPO2 levels. ΔZQ in the dorsal lung increased with increasing tcPO2 (P = 0.01), whereas no such change was seen in the ventral lung. There was a simultaneous decrease in V/Q ratio in the dorsal region during hyperoxia (P = 0.04). Two subjects did not reach a tcPO2 of 60 kPa despite breathing 100% oxygen.


CONCLUSIONS
These results indicate that breathing increased concentrations of oxygen induces pulmonary vasodilatation in the dorsal lung even at small increases in FiO2. Ventilation remains unchanged. Local mismatch of ventilation and perfusion occurs in young healthy men, and the change in ventilation/perfusion ratio can be determined non-invasively by EIT.
Department of Anesthesiology, Shaoxing People's Hospital of Zhejiang University, Shaoxing City, China; Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden.
Y
Y
Li
E
E
Tesselaar
J B
JB
Borges
S H
SH
Böhm
F
F
Sjöberg
B
B
Janerot-Sjöberg
D000328:Adult; D000388:Air; D017097:Electric Impedance; D006339:Heart Rate; D006801:Humans; D008168:Lung / Q000033:anatomy & histology / Q000502:physiology; D008297:Male; D010100:Oxygen / Q000008:administration & dosage / Q000097:blood*; D011652:Pulmonary Circulation; D012016:Reference Values; D014054:Tomography / Q000379:methods*; D014664:Vasodilation; D014692:Ventilation-Perfusion Ratio / Q000502:physiology*; D055815:Young Adult
D010100:Oxygen