RELATIONSHIP BETWEEN PULMONARY OXYGEN-CONSUMPTION, LUNG INFLAMMATION,AND CALCULATED VENOUS ADMIXTURE IN PATIENTS WITH ACUTE LUNG INJURY

Objective. To determine in patients with acute lung injury whether inc reased pulmonary oxygen consumption (VO2pulm), computed as the differe nce between oxygen consumption measured by indirect calorimetry (VO2me as) and calculated by the reverse Fick method (VO2Fick), would. (1) co rrelate with the degree of lung inflammation assessed by bronchoalveol ar lavage (BAL); (2) lead to an overestimation of calculated venous ad mixture (Q(va)/Q(t)). Design: Prospective study. Setting. University h ospital, medical intensive care unit. Intervention: None. Measurements and results: In nine mechanically ventilated patients with acute lung injury (Apache II 12 +/- 5, lung injury score 2 +/- 0.6, mean +/- SD) , whole-body VO2 (VO2wb) was determined simultaneously by indirect cal orimetry and the reverse Fick technique, after which BAL was immediate ly performed. VO2meas was significantly higher than VO2Fick (128 +/- 2 4 and 102 +/- 18 ml/min per m(2), respectively, p < 0.001). Median VO2 pulm was 25.3 mi/min per m(2) (range 1.98-51.5), thus representing 19 +/- 11% of VO2wb. Total BAL cellularity was increased in all patients (median 47, range 24-200 x 10(4)/ml), as was the total polymorphonucle ar (PMN) count (median 78 range 5-93 x 10(4)/ml). Macrophage counts we re in the normal range. There were raised BAL levels of interleukin-6 (IL-6) (median 945, range 23-1800 ng/ml) and elastase (median 391, ran ge 5-949 ng/ml). Median protein levels were 270 mu g/ml (range 50-505) . There was no correlation between VO2pulm and BAL cellularity, PMNs, elastase, IL-6, or protein. Q(va)/Q(t) was 31.7 +/- 8%. Q(va)/Q(t), co rrected for the presence of VO2pulm, (Q(va)/Q(tcorr)), was 30.3 +/- 8% (p < 0.01 vs Q(va)/Q(t)), a 4.2% overestimation due to VO2pulm There was no correlation between Q(va)/Q(t), or Q(va)/Q(tcorr) and VO2pulm C onclusions. In mechanically ventilated patients with acute lung injury , VO2pulm was increased and led to a 19 % underestimation of VO2wb det ermined by the reverse Fick method, as well as to a 4.2% overestimatio n of calculated Q(va)/Q(t). Lung inflammatory activity was increased, as assessed by BAL cellularity, IL-6 and elastase levels. However, the re was no correlation between VO2pulm and the intensity of pulmonary i nflammation.