Reliability of extravascular lung thermal volume measurements by thermal conductivity technique in sheep.
We tested the accuracy, sensitivity, and reproducibility of a new lung water computer, based on the thermal conductivity technique, in 22 anesthetized closed-chest ventilated sheep with different treatments: 1) controls (n = 8), 2) 0.05 ml/kg of oleic acid + 100 ml/kg of lactated Ringer solution (n = 6), and 3) airway instillation of saline [3.1 +/- 1.3 (SD) g/kg, n = 8]. After 4 h, we determined the extravascular lung water gravimetrically. We found a significant overall correlation between the final extravascular lung thermal volume and the gravimetric extravascular lung mass (P < 0.001). Although the average ratio of extravascular lung thermal volume to extravascular lung mass was 0.97 +/- 0.25 ml/g for all groups, the computer overestimated extravascular lung mass in controls by 10% (17 g) and underestimated it in sheep with oleic acid by 15% (95 g) and in sheep with airway instillation by 8% (37 g). The computer also underestimated the small quantities of saline placed via the airway in the alveolar space by 75% (61 g). Reproducibility of three consecutive measurements was 4.3% (SE). We conclude that the thermal conductivity technique has an ability to detect the baseline extravascular lung mass but has a poor ability to detect an accurate increment of the extravascular lung water under poor tissue perfusion in anesthetized ventilated sheep.
Kambara
K
K
Cardiovascular Research Institute, University of California, San Francisco 94143-0130.
Jerome
E H
EH
Serikov
V B
VB
Arakawa
M
M
Staub
N C
NC
D000818:Animals; D001834:Body Water / Q000502:physiology; D004553:Electric Conductivity; D006041:Goats; D066298:In Vitro Techniques; D008176:Lung Volume Measurements / Q000379:methods*; D009929:Organ Size / Q000502:physiology; D010477:Perfusion; D011652:Pulmonary Circulation; D012756:Sheep; D013814:Thermal Conductivity