The European respiratory journal : official journal of the European Society for Clinical Respiratory Physiology
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Reduced tolerance to high altitude may be associated with a low ventilatory and an increased pulmonary vascular response to hypoxia. We therefore, examined whether individuals susceptible to acute mountain sickness (AMS) or high altitude pulmonary oedema (HAPE) could be identified by noninvasive measurements of these parameters at low altitude. Ventilatory response to hypoxia (HVR) and hypercapnia (HCVR) at rest and during exercise, as well as hypoxic pulmonary vascular response (HPVR) at rest, were examined in 30 mountaineers whose susceptibility was known from previous identical exposures to high altitude. ⋯ Pulmonary artery pressure (Ppa) estimated by Doppler measurements of tricuspid valve pressure at an FI,O2 of 0.21 and 0.12 (10 min) did not lead to a further discrimination between subjects susceptible to HAPE and AMS with the exception of three subjects susceptible to HAPE who showed an exaggerated HPVR. It is concluded that a low ventilatory response to hypoxia is associated with an increased risk for high altitude pulmonary oedema, whilst susceptibility to acute mountain sickness may be associated with a high or low ventilatory response to hypoxia. A reliable discrimination between subjects susceptible to high altitude pulmonary oedema and acute mountain sickness with a low ventilatory response to hypoxia is not possible by Doppler echocardiographic estimations of hypoxic pulmonary vascular response.
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Dynamic hyperinflation and the development of intrinsic positive end-expiratory pressure (PEEPi) are commonly observed in patients with severe chronic obstructive pulmonary disease (COPD) in acute respiratory failure. Previous studies have shown that externally applied PEEP reduces PEEPi and its adverse effects in mechanically-ventilated COPD patients. The purpose of this study was to determine the effects of graded amounts of continuous positive airway pressure (CPAP) on the degree of inspiratory effort, pattern of breathing, gas exchange, and level of dyspnoea in a group of spontaneously breathing, nonintubated COPD patients in acute hypercapnic respiratory failure. ⋯ Arterial oxygen tension (Pa,O2) and arterial carbon dioxide tension (Pa,CO2) either improved or remained stable with CPAP. We conclude that the noninvasive application of CPAP to spontaneously breathing patients with severe COPD in acute respiratory failure decreases inspiratory effort and dyspnoea whilst improving breathing pattern. It is conceivable that the early institution of CPAP in this setting may obviate the need for intubation and conventional mechanical ventilation.