V/Q distribution and correlation to atelectasis in anesthetized paralyzed humans.
Regional ventilation and perfusion were studied in 10 anesthetized paralyzed supine patients by single-photon emission computerized tomography. Atelectasis was estimated from two transaxial computerized tomography scans. The ventilation-perfusion (V/Q) distribution was also evaluated by multiple inert gas elimination. While the patients were awake, inert gas V/Q ration was normal, and shunt did not exceed 1% in any patient. Computerized tomography showed no atelectasis. During anesthesia, shunt ranged from 0.4 to 12.2. Nine patients displayed atelectasis (0.6-7.2% of the intrathoracic area), and shunt correlated with the atelectasis (r = 0.91, P < 0.001). Shunt was located in dependent lung regions corresponding to the atelectatic area. There was considerable V/Q mismatch, with ventilation mainly of ventral lung regions and perfusion of dorsal regions. Little perfusion was seen in the most ventral parts (zone 1) of caudal (diaphragmatic) lung regions. In summary, shunt during anesthesia is due to atelectasis in dependent lung regions. The V/Q distributions differ from those shown earlier in awake subjects.
Department of Anesthesiology, Huddinge University Hospital, Sweden.
L
L
Tokics
G
G
Hedenstierna
L
L
Svensson
B
B
Brismar
T
T
Cederlund
H
H
Lundquist
A
A
Strandberg
D000328:Adult; D000368:Aged; D000768:Anesthesia, General; D001784:Blood Gas Analysis; D005260:Female; D006439:Hemodynamics / Q000187:drug effects / Q000502:physiology; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D010243:Paralysis / Q000139:chemically induced / Q000503:physiopathology*; D001261:Pulmonary Atelectasis / Q000000981:diagnostic imaging / Q000503:physiopathology*; D011652:Pulmonary Circulation / Q000187:drug effects / Q000502:physiology; D012121:Respiration, Artificial; D015899:Tomography, Emission-Computed, Single-Photon; D014057:Tomography, X-Ray Computed; D014692:Ventilation-Perfusion Ratio / Q000502:physiology*