The European respiratory journal : official journal of the European Society for Clinical Respiratory Physiology
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Inhaled carbon dioxide decreases ventilation/perfusion ratio (V'/Q') heterogeneity in dogs. The aim of this study was to test whether inhaled CO2 improves the V'/Q' by inhibition of nitric oxide production and whether inhibition of endogenous NO production in the lung alters gas exchange and V'/Q' matching. Eleven healthy dogs were anaesthetized and mechanically ventilated. ⋯ Inspired carbon dioxide improves ventilation perfusion ratio matching and is associated with a more homogeneous distribution of pulmonary blood flow. Although inspired carbon dioxide causes a reduction in exhaled nitric oxide, the differences in pulmonary perfusion distributions found between carbon dioxide and N(omega)-nitro-L-arginine methyl ester suggest that the carbon dioxide effect is not mediated by a reduction in nitric oxide production. The improved ventilation perfusion ratio matching with inhibition of nitric oxide synthase suggests the intriguing possibility requiring further study that endogenous production of nitric oxide in the lung does not subserve ventilation perfusion ratio regulation.
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The study was designed to identify markers of oxidative injury, related to the nitric oxide derived cascade, in bronchoalveolar lavage (BAL) fluid from intensive care patients suspected of ventilator-associated pneumonia (VAP) and/or acute respiratory distress syndrome (ARDS). Thirty-eight patients developing VAP and/or ARDS (VAP/ARDS group) were compared to 20 ventilated patients without VAP/ARDS (control group). Myeloperoxidase (MPO) and elastase, taken as markers of neutrophil activation were measured by enzymatic techniques, and nitrated proteins (NTPs) by an immunological method. ⋯ NTP concentration correlated with MPO and elastase activity and neutrophil number (r=0.93, 0.91 and 0.87, respectively), but not to protein concentration and arterial oxygen tension/inspiratory oxygen fraction. The cytotoxicity of BAL correlated with NTP concentration (r=0.92) and MPO activity (r=0.89). It was concluded that the concentrations of nitrated proteins in bronchoalveolar lavage fluid correlated with the oxidant activity of neutrophils and that, bronchoalveolar lavage fluid cytotoxicity was correlated with the nitrated protein concentration and may be mediated by oxidants.
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Expiratory flow limitation promotes dynamic hyperinflation during exercise in chronic obstructive pulmonary disease (COPD) patients with a consequent reduction in inspiratory capacity (IC), limiting their exercise tolerance. Therefore, the exercise capacity of patients with tidal expiratory flow limitation (FL) at rest should depend on the magnitude of IC. The presented study was designed to evaluate the role of FL on the relationship between resting IC, other respiratory function variables and exercise performance in COPD patients. ⋯ Subgroup analysis showed that IC was the sole predictor in FL patients, and FEV1/FVC in non-FL patients. Detection of flow limitation provides useful information on the factors that influence exercise capacity in chronic obstructive pulmonary disease patients. Accordingly, in patients with flow limitation, inspiratory capacity appears as the best predictor of exercise tolerance, reflecting the presence of dynamic hyperinflation.