Lung
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In 10 anesthetized adult rabbits, we studied the effect of spontaneous breathing and positive pressure ventilation on pleural pressure on the costal lung surface (Ppl) and in the zone of apposition of the rib cage to the diaphragm (Papp). Ppl and Papp were measured by rib capsules installed in the 5th or 6th rib and 11th or 12th rib, respectively. Esophageal (Pes) and gastric (Pga) pressures were measured with air-filled balloons. ⋯ Changes in transdiaphragmatic pressure in the zone of apposition (delta Pga-delta Papp) were near zero (-0.4 +/- 0.3 cm H2O), much smaller in magnitude than those (delta Pga-delta Ppl) associated with the lung (3.0 +/- 1.5 cm H2O). These results are consistent with the concept that during breathing, abdominal pressure is transmitted to the zone of apposition of the rib cage to the abdomen. During spontaneous breathing at rest, the pleural space in the zone of apposition is mechanically independent of the pleural space associated with the lung.
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To investigate the influence of nasal continuous positive airway pressure (CPAP) on apnea-related desaturation, we compared the sleep apnea-related desaturations obtained during a polysomnographic study before and during nasal CPAP in 15 sleep apnea patients. An individual desaturation curve was determined with a regression analysis by plotting the lowest SaO2 value reached during each apnea against its duration; these data were collected throughout the night. At baseline, we only considered the apneas with a preapneic SaO2 value greater than 90% and a minimal SaO2 value above or equal to 60%. ⋯ The preapneic SaO2 value was 94.8 +/- 0.3% at baseline and 95.5 +/- 0.2% during CPAP (p = 0.5). The desaturation area decreased from 267 +/- 48% SaO2/sec at baseline to 152 +/- 41% SaO2/sec during CPAP (p less than 0.001). We conclude that CPAP improves the apnea-related desaturation independently of the shortening of apneas and of any difference in the preapneic SaO2 value.
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We have determined the effect of hydrostatic edema on total and segmental vascular resistances in the rat lung. Lungs of 12 adult rats, body weight 515 +/- 42 g, were isolated and perfused with blood. To investigate the role of vasoactivity on edema effects, we studied two groups of lungs; group I (n = 6) were untreated and group II (n = 6) were treated with papaverine hydrochloride to paralyze the vasculature. ⋯ The increase in total and segmental vascular resistances was not significantly different in the two groups of lungs. We conclude that in isolated rat lungs only severe edema results in an increase in total vascular resistance, mainly due to an increase in arterial and microvascular resistances, with a smaller increase in venous resistance. This appears to be a mechanical effect of edema on the vasculature and not a result of active vasomotion.
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Randomized Controlled Trial Multicenter Study Clinical Trial
Prevention by ambroxol of bronchopulmonary complications after upper abdominal surgery: double-blind Italian multicenter clinical study versus placebo.
A double-blind multicenter study was carried out to evaluate the effectiveness of ambroxol, a drug able to promote surfactant synthesis, in the prevention of postoperative bronchopulmonary complications. A total of 252 patients with chronic obstructive lung disease (COLD) undergoing upper abdominal surgery were randomly allocated to receive either 1 g/day of ambroxol intravenously for 6 consecutive days in the perioperative period or placebo. Pulmonary complications were evaluated by clinical studies, radiographic, and blood gas analysis. ⋯ In addition, analysis of variance showed that the PaO2 values of the ambroxol-treated group after surgery decreased less than those of the placebo-treated group (p less than 0.05) from the preoperative values. The treatment was well tolerated, although nausea was significantly more frequent in the ambroxol-treated group. We think that ambroxol should be considered as an alternative and new pharmacologic approach for the prevention of postoperative pulmonary complications.
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Review Comparative Study
Pulse oximetry versus arterial blood gas specimens in long-term oxygen therapy.
Portable pulse oximeters are now widely available for the assessment of arterial oxygenation, and the U. S. Medicare program considers saturation readings to be acceptable substitutes for arterial PO2 in selecting patients for long-term oxygen therapy (LTOT). ⋯ Pulse oximetry cannot detect hypercapnia or acidosis. For these and other reasons, pulse oximetry should not be used in initial selection of patients for LTOT, as a substitute for arterial blood gas analysis in the evaluation of patients with undiagnosed respiratory disease, during formal cardiopulmonary exercise testing, or in the presence of an acute exacerbation. Pulse oximetry is an important addition to the clinician's armamentarium, however, for titrating the oxygen dose in stable patients, in assessing patients for desaturation during exercise, for sleep studies, and for in-home monitoring.