Accuracy of the double indicator method for measurement of extravascular lung water depends on the type of acute lung injury.
OBJECTIVE
The double indicator method is sensitive to alterations in the distribution of pulmonary blood flow. This distribution is influenced by the type of lung injury. The aim of this study was to compare measurements of lung water by the double indicator method with measurements obtained by gravimetry in a direct lung injury model induced by tracheal instillation of hydrochloric acid and in an indirect lung injury model induced by the intravenous injection of oleic acid.


METHODS
Prospective, randomized laboratory study.


METHODS
Animal research laboratory.


METHODS
Forty-two female pigs (28+/-3 kg).


METHODS
Pigs were anesthetized and ventilated and were allocated into three groups: control (n = 6), hydrochloric acid (4 mL/kg intratracheally, n = 24), or oleic acid (0.1 mL/kg intravenously, n = 12).


RESULTS
Hydrochloric acid instillation or oleic acid injection resulted in a similar hypoxemia and induced a two- to three-fold increase in extravascular lung water (EVLW) by gravimetry (EVLWG) at 3 hrs compared with controls. In the oleic acid group, there was a significant correlation between EVLWG and EVLW by double indicator method (EVLWDI; r =.88, p <.0001). The bias for EVLWDI - EVLWG measurements was -5.2 mL/kg (95% confidence interval, -5.7 to -4.7 mL/kg) with 95% limits of agreement of -7 to -3.4 mL/kg. In the hydrochloric acid group, there was no significant correlation between EVLWDI and EVLWG values, and the double indicator method failed to detect pulmonary edema in 65% of the animals (EVLWDI <8 mL/kg). The bias was -7.9 mL/kg (95% confidence interval, -9.3 to -6.5 mL/kg) with 95% limits of agreement of -14.4 to -1.4 mL/kg.


CONCLUSIONS
The double indicator method is useful for evaluation of pulmonary edema in indirect lung injury, as induced by oleic acid, but produces misleading values in direct lung injury, as produced by hydrochloric instillation.
Roch
Antoine
A
Service de Réanimation Polyvalente, Hôpitaux Sud, Marseille, France.
Michelet
Pierre
P
Lambert
Dominique
D
Delliaux
Stéphane
S
Saby
Christophe
C
Perrin
Gilles
G
Ghez
Olivier
O
Bregeon
Fabienne
F
Thomas
Pascal
P
Carpentier
Jean-Pierre
JP
Papazian
Laurent
L
Auffray
Jean-Pierre
JP
D000704:Analysis of Variance; D000818:Animals; D004195:Disease Models, Animal; D015633:Extravascular Lung Water / Q000378:metabolism*; D005260:Female; D006439:Hemodynamics; D006851:Hydrochloric Acid / Q000008:administration & dosage; D007201:Indicator Dilution Techniques; D019301:Oleic Acid / Q000008:administration & dosage; D011379:Prognosis; D011446:Prospective Studies; D011654:Pulmonary Edema / Q000175:diagnosis* / Q000209:etiology / Q000473:pathology; D011897:Random Allocation; D012128:Respiratory Distress Syndrome / Q000175:diagnosis* / Q000209:etiology / Q000473:pathology; D015656:Respiratory Mechanics; D013552:Swine
D019301:Oleic Acid; D006851:Hydrochloric Acid