Thorax
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The standard plethysmographic method of measuring total lung capacity (TLC) has been reported to result in spuriously high estimates in patients with severe airway obstruction. The helium-dilution method is known to underestimate TLC in the same patients. To determine the magnitude of these possible errors we measured TLC by four methods in 20 patients with varying degrees of chronic obstructive lung disease and in 11 normal subjects. ⋯ If TLCes is taken as the closest estimate of true TLC, TLCm consistently overestimates and TLCHe underestimates TLC. There was no relationship between the degree of airway obstruction and (TLCm - TLCes) but there was between (TLCes - TLCHe) and severity of airway obstruction. We conclude that using mouth pressure in the plethysmographic measurement of TLC in patients with chronic obstructive lung disease results in consistent but slight overestimation of TLC.
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To assess the diagnostic value of measuring free plasma deoxyribonucleic acid (DNA) in patients suspected of having pulmonary embolism, we prospectively assayed the plasma of 40 consecutive patients who underwent pulmonary angiography for the presence of free plasma DNA. Fifteen of them had angiographic evidence of pulmonary embolism. Of these 15 only two (13%) had a positive result in the test for free double-stranded plasma DNA. We concluded that measuring free double-stranded plasma DNA is of no value in the diagnosis of pulmonary embolism.
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The accuracy of radiography of excised air-inflated lungs in assessing pulmonary emphysema at necropsy was evaluated in a series of 107 adults who had died in hospital by reading the radiographs and examining the pathological specimens independently. The radiographic and pathological assessments of the severity of emphysema correlated significantly (r = 0.87, p less than 0.0001). Mild emphysema was recognised radiographically in 88.7% and moderate in 94.9% of the lungs. ⋯ Radiographical diagnosis of centrilobular and paracicatricial emphysema was verified pathologically in all lungs showing mild emphysema, but that of panlobular emphysema in only 66.7%. Radiography of excised air-inflated lungs is a rapid, convenient, and reliable method of recognising and assessing the severity of appreciable degrees of centrilobular and paracicatricial emphysema, but less reliable in recognising panlobular emphysema. After the procedure the specimen remains available for almost any other technique.
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We induced chronic pulmonary hypertension in one group of rats by exposing them to chronic hypobaric hypoxia (380 mm Hg for three weeks) and in another group by administering a single subcutaneous dose of monocrotaline (60 mg/kg body weight). Both groups of rats showed increase of the right ventricular mean systolic blood pressure and right ventricular hypertrophy. We measured the surface area of histological sections of the left or right lungs and counted all small blood vessels with an external diameter of less than 50 microns and with a definite elastic coat lying distal to respiratory bronchioles. ⋯ The mean total number of small pulmonary blood vessels in nine rats with monocrotaline-induced pulmonary hypertension was 396.8 +/- 61.7 compared with 384 +/- 55.4 in three control rats. The number of small pulmonary blood vessels per mm2 lung tissue was 3.3 +/- 0.6 in the rats treated with monocrotaline compared with 3.6 +/- 0.6 in the control group. We conclude that the number of small pulmonary blood vessels is not reduced in rats with pulmonary hypertension induced by chronic hypoxia or monocrotaline.