Chest
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With the aim of testing a method that allows increasing concentrations of oxygen to be administered to patients with severe hypoxemia and hypercapnia while avoiding the risk of increasing respiratory acidosis, we studied 17 male patients with advanced chronic obstructive pulmonary disease (COPD) and severe hypercapnic respiratory failure. During 6 h and on one day only, all patients were given intermittent negative pressure ventilation (INPV) together with oxygenation starting at a concentration of 24 percent and increasing to 30 percent. ⋯ One hour after INPV ended, the mean values of PaO2, PaCO2, oxygen saturation, and pH were also significantly better than prestudy values. We conclude that INPV and oxygen therapy with increasing oxygen flow could constitute an alternative option to intubation and mechanical ventilation in cases of severe hypercapnic respiratory failure due to advanced COPD.
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Chronic pulmonary hypertension in humans is characterized by shortening of the pulmonary artery acceleration time as measured by Doppler echocardiography, such that the higher the pulmonary artery pressure, the shorter the pulmonary acceleration time. Increases in heart rate are also known to produce decreases in the pulmonary artery acceleration time. ⋯ The results in this acute animal model reveal that increases in heart rate produced significant decreases in Doppler pulmonary artery acceleration time at mean pressures below 25 mm Hg. However, with mean pulmonary artery pressures greater than 25 mm Hg, both heart rate and increases in pulmonary artery pressure had no significant effect on acceleration time.
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Bedside estimation of the height at which the internal jugular veins collapse, referenced to a standard hemodynamic location, theoretically reflects central venous pressure. This method has never been demonstrated as accurate when compared to invasive CVP measurements because of the great clinical skills and time required to visually identify the internal jugular venous waveform. Since the principles of the bedside method are sound, we utilized them in conjunction with the neck inductive plethysmograph, a device which has the capability of recording internal jugular venous and carotid arterial waveforms. ⋯ Here, CVPni was recorded as the value at least exceeding the value measured. In two other patients, obstruction of an internal jugular vein gave spuriously low values of CVPni. Our study indicates that this new neck inductive plethysmographic method is accurate compared to invasive catheter measurements of CVP and should serve as a safe, noninvasive alternative in situations where such measurements are required.
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The velocity pattern of the blood flow in the pulmonary artery was investigated in an animal model of acute pulmonary hypertension. Nine anesthetized, open-chest dogs were embolized with polystyrene microspheres, and the velocity pattern of the blood flow in the pulmonary artery was studied with use of an invasive pulsed Doppler technique. Phasic intraluminal velocity was recorded with use of a miniature piezoelectric crystal activated by 20-MHz Doppler pulses and mounted on the tip of a needle probe introduced into the pulmonary artery. ⋯ A significant shortening in the time to peak velocity (acceleration time) was found (p less than 0.005). Second-order regression analyses demonstrated an inverse correlation between the ratio of positive velocity time to negative velocity time and the mean pulmonary artery pressure in all animals (r = 0.71). These findings should be compared with the velocity patterns of the blood flow in the pulmonary artery obtained under pulmonary hypertensive conditions due to various causes to facilitate interpretation and understanding of clinical investigations.