The European respiratory journal : official journal of the European Society for Clinical Respiratory Physiology
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This study was undertaken to assess the physiological effects of proportional assist ventilation (PAV), administered noninvasively through a nose mask, on ventilatory pattern, arterial blood gases, lung mechanics, and inspiratory muscle effort in stable, hypercapnic patients with chronic obstructive pulmonary disease. In 15 patients, PAV was set by adjusting volume assist (VA) and flow assist (FA) according to the "run-away" technique and the patient's comfort respectively. The level of support was fixed at 80% of the total possible assistance and averaged 13.9+/-4.1 cmH2O x L(-1) and 4.1+/-1.3 cmH2O x L(-1) x s for VA and FA, respectively. ⋯ These data show that nasal proportional assist ventilation can provide physiological benefits to the stable hypercapnic chronic obstructive pulmonary disease patients. In fact, proportional assist ventilation, which was well tolerated by all patients, unloaded the inspiratory muscles and improved arterial blood gases. Further studies can clarify whether these beneficial physiological effects of nasal proportional assist ventilation can bear profitable consequences in the overall clinical management of chronic obstructive pulmonary disease patients with chronic carbon dioxide retention.
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Noninvasive positive pressure ventilation delivered by nasal mask or facemask has been used widely in the last decade to manage chronic ventilatory failure in adults with neuromuscular and chest wall disease. However, it has been thought that paediatric patients would not be able to tolerate masks, and previous anecdotal reports on the paediatric application of mask ventilation have not assessed the effects on nocturnal and arterial blood gas control. Domiciliary mask ventilation has been used in 40 children with ventilatory insufficiency due to congenital neuromuscular and skeletal disease aged 9 months-16 yrs. ⋯ Diurnal mean+/-SD oxygen tension in arterial blood (Pa,O2) increased from 8.5+/-1.8-10.9+/-1.7 kPa (p<0.001) and mean carbon dioxide tension in arterial blood (Pa,CO2) fell from 7.0+/-1.6-5.9+/-0.8 kPa (p=0.01) following initiation of ventilatory support. Mean and minimum nocturnal Pa,O2 and peak transcutaneous carbon dioxide tension (Ptc,CO2) (n=21) improved significantly. Mask ventilation can be used successfully in young children and reverses ventilatory insufficiency due to congenital neuromuscular and skeletal disease.
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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.