Am. J. Respir. Crit. Care Med.,
Volume 160, Number 1, July 1999, 137-143
Increased Intrapulmonary Oxygen Consumption in
Mechanically Ventilated Patients with Pneumonia
MARIO
HENSEL
and
WOLFGANG J.
KOX
Department of Anaesthesiology and Intensive Care, University Hospital Charité, Humboldt University Berlin, Berlin, Germany
Pulmonary oxygen consumption (
O2pulm) is believed to be increased in patients with lung infection.
In the present study, O2pulm was estimated from the difference between total oxygen consumption
measured with indirect calorimetry ( O2cal) and oxygen consumption assessed with the reverse Fick
method ( O2Fick). Seventy-five patients requiring mechanical ventilation were included, and were
divided for analysis into two groups according to the existence (n = 41) or absence (n = 34) of pneumonia. O2pulm was correlated with various parameters of impaired lung function. To assess the
metabolic function of the lung, the differences in lactate and glucose concentrations at different arterial-mixed venous concentrations were determined and transpulmonary lactate flux as well as glucose flux was calculated. As compared with O2pulm in patients without pneumonia (19.4 ± 1.2 ml/
min/m2), O2pulm was significantly increased in patients with pneumonia (50.7 ± 1.7 ml/min/m2 (p < 0.001). For intrapatient measurements of O2pulm, a sufficient reproducibility was achieved. O2pulm
increased with the lung injury score, number of afflicted lobes, venous admixture, the transpulmonary lactate flux, and the transpulmonary glucose flux, respectively. We speculate that the increased
O2pulm of infected lungs is due to different mechanisms, including increased oxidative metabolism by
essentially extrapulmonary structures such as neutrophils and macrophages, as well as by changes in
the metabolic function of lung tissue itself.
