The American review of respiratory disease
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We studied 47 excised human lungs in order to examine the relationship between the number of alveolar attachments surrounding bronchioles 2 mm or less in diameter and the presence of small airways disease and overall lung function. Expiratory pressure-volume curves, the FEV1, and the single-breath nitrogen washout were obtained from 11 lungs without emphysema and 36 lungs with various degrees of emphysema. The lungs were subsequently inflation-fixed at 20 cm H2O. ⋯ There was a negative correlation of the mean number of alveolar attachments and the small airways fibrosis score (r = -0.344, p less than 0.02). A correlation also existed between the number of alveolar attachments and the mean internal bronchiolar diameter (r = 0.561, p less than 0.001). We conclude that the alveolar attachments and elastic recoil are related to the size and function of the small airways.
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Am. Rev. Respir. Dis. · Oct 1985
Comparative StudyComparative effects of aminophylline on diaphragm and cardiac contractility.
The mechanisms by which aminophylline increases inspiratory muscle contractility are unclear. The present study compared the effects of aminophylline on cardiac as well as on diaphragm contractility and examined the interaction of aminophylline with verapamil, a calcium channel-blocking agent, on both types of muscle. Experiments were performed in mongrel dogs anesthetized with pentobarbitone. ⋯ Aminophylline increased both peak LV pressure and dPv/dt. The magnitude of the cardiac response was greater than the diaphragmatic response. Subsequent verapamil infusion completely reversed the effects of aminophylline on LV contractility but had only a small effect on diaphragm contractility.(ABSTRACT TRUNCATED AT 250 WORDS)
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Am. Rev. Respir. Dis. · Oct 1985
Intermittent positive-pressure hyperventilation with high inflation pressures produces pulmonary microvascular injury in rats.
The mechanisms by which intermittent positive-pressure ventilation with high inflation pressure (HIPPV) induces pulmonary edema remain uncertain. In this study we investigated the physiologic and anatomic changes related to HIPPV at 45 cmH2O peak inspiratory pressure in rats. Edema was quantified by the extravascular lung water obtained from postmortem weighing and by 22Na distribution space. ⋯ Additional anatomic damage appeared including epithelial lesions and hyaline membranes. Thus, HIPPV edema presents all the features of high permeability edema. These results may be of concern in the ventilatory management of patients with acute respiratory failure in order to avoid additional damages induced by local overinflation.
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Am. Rev. Respir. Dis. · Sep 1985
Distribution of pulmonary blood flow in relation to atelectasis in premature ventilated lambs.
To investigate the ability of the preterm, ventilated lung to redirect blood flow away from atelectatic regions, we studied lambs with respiratory distress syndrome and spontaneous atelectasis or atelectasis caused by bronchial obstruction with a balloon catheter. Pulmonary blood flow distributions were measured by quantifying 15-mu, microsphere-associated radioactivity within multiple pieces of lung. Lambs with well aerated or very atelectatic lungs had relatively uniform blood flow/gram lung in all pieces of lung. ⋯ In 5 lambs with well-aerated lungs, 18 +/- 3% of the lung by weight was made atelectatic by balloon occlusion of a major lower lobe bronchus. There was a 44 +/- 11% decrease in blood flow to the atelectatic lung segments. These studies document the ability of the lung of the premature, ventilated lamb to shunt pulmonary blood flow away from atelectatic lung volumes.
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Am. Rev. Respir. Dis. · Aug 1985
Acute cigarette smoke exposure increases alveolar permeability in rabbits.
We measured lung clearance of aerosolized technetium-labeled diethylenetriamine pentaacetic acid (99mTcDTPA) as an index of alveolar epithelial permeability in rabbits exposed to cigarette smoke. Eighteen rabbits were randomly assigned to 3 equal-size groups: control, all smoke exposure (ASE), and limited smoke exposure (LSE). Cigarette or sham smoke was delivered by syringe in a series of 5, 10, 20, and 30 tidal volume breaths with a 20-min counting period between each subset of breaths to determine 99mTcDTPA biologic half-life (T1/2). ⋯ We observed a significant difference at 20 and 30 breath exposures between the control and ASE group mean values (% baseline) for T1/2, arterial blood pressure, and peak airway pressure. A combination of light and electron microscopy showed focal alveolar edema and hemorrhage in the ASE and LSE groups but no alveolar-capillary membrane damage. In summary, acute cigarette smoke exposure increases alveolar permeability as measured by 99mTcDTPA clearance, but there was no detectable ultrastructural alteration of the alveolar-capillary membrane.