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Biomedical subjects

D S McCarthy

Publications and source records attributed to D S McCarthy.

At least 37 records · Page 2Linked to original sources
PubMed1992

Laboratory evaluation of alignment and kinematics in a unicompartmental knee arthroplasty inserted with intramedullary instrumentation.

The purposes of this study were to evaluate the reliability of intramedullary (IM) instrumentation for unicompartmental total knee replacement and to assess the stability characteristics of the knee after implantation of a relatively unconstrained articular surface. Five adult, human cadaver lower extremities including hip, knee, and ankle were used to evaluate IM alignment. Five adult, fresh-frozen knee specimens were used to evaluate knee kinematics. Long anterioposterior roentgenograms were used to evaluate valgus angle and position of the center of the knee relative to the mechanical axis of the lower extremity. IM instrumentation returned the knee to normal alignment in all cases. The greatest valgus angle change was 3 degrees, and the position of the center of the knee relative to the mechanical axis was not significantly altered. Knee kinematics after unicompartmental knee replacement followed the predicted pattern of normal stability in extension and had slightly less varus-valgus laxity at 30 degrees (p less than 0.01), 45 degrees (p less than 0.01), and 60 degrees (p less than 0.05), and less anteroposterior displacement at 45 degrees (p less than 0.01) and 60 degrees (p less than 0.05). This study offers encouraging evidence that unicompartmental knee replacement with unconstrained components can restore normal knee kinematics, and that alignment can be restored with a high degree of accuracy with an intramedullary alignment system.

Adult↗
PubMed1984

Hypomagnesemia and respiratory muscle power.

Although hypomagnesemia is common and causes weakness in humans, it is not known what effect its correction has on respiratory muscle power. We designed an experiment to test the hypothesis that correction of hypomagnesemia will improve respiratory muscle power. We measured muscle power and lung volumes in 16 control subjects and 17 patients (11 alcoholics, 6 nonalcoholics) on 3 consecutive days. After baseline measurements on Day 1, patients were randomized and the study was double blinded. Patients were given magnesium intravenously or dextrose as placebo. Measurements were repeated on Day 2, and the patients were then given magnesium if they had previously been given placebo, and vice versa. Measurements were done again on Day 3. There was no significant difference in lung volumes in patients or control subjects over the 3 days. There were no changes in respiratory muscle power in control subjects, but there was an improvement in all parameters of muscle power measured after magnesium therapy in patients. Hypomagnesemia should be excluded as a cause of muscle weakness because its replacement may improve muscle power.

Adult↗
PubMed1983

Postural relief of dyspnoea in severe chronic airflow limitation: relationship to respiratory muscle strength.

Maximal static inspiratory and expiratory pressures (Pimax and Pemax) were measured in six different positions in 40 patients with advanced chronic airflow limitation and in 140 normal subjects to determine whether posture influences respiratory muscle strength. Patients with chronic airflow limitation were studied on days 1 and 5 of an acute exacerbation. There was no postural effect on maximal static pressures in the normal subjects. We divided our patients with chronic airflow limitation into "moderate" and "severe" groups on the basis of a Pimax in the standing position greater or less than 35 cm H2O. The seated leaning-forward position was the preferred posture in 22 of the 23 "severe" patients and 13 of the 17 "moderate" patients. Pimax was greater in the seated leaning-forward position than in the other positions studied (p less than 0.001) on days 1 and 5 in the "severe" patients and (p less than 0.05) on day 5 in the "moderate" patients. Posture had no influence on Pemax in patients with chronic airflow limitation. There was a significant improvement in both Pimax (p less than 0.01 for the "severe" group and p less than 0.05 for the "moderate" group) and Pemax (p less than 0.01 for both groups) between days 1 and 5. The seated leaning-forward position was the optimum posture for the patients to generate maximum inspiratory pressures and to obtain greatest subjective relief of dyspnoea.

Adult↗
PubMed1980

Lung elastic recoil and reduced airflow in clinically stable asthma.

Lung volumes, maximum expiratory flow rates, and static volume-ressure curves were measured in 16 patients with clinically stable asthma. It was found that flow rates were reduced in such patients because of the combined effects of reduced elastic recoil (transpulmonary pressure) and intrinsic diseases of the airways. In nine patients treated with an aerosol of isoprenaline, flow rates improved as a result of reduction in airways resistance as the static recoil pressure of the lungs fell further in those patients. The possibility is suggested that muscle tone in peripheral airways or alveolar ducts contributed to the elastic recoil measurements.

Adult↗
PubMed1980

Chronic obstructive pulmonary disease following idiopathic pulmonary fibrosis.

The rapid development of irreversible airflow obstruction in two nonsmoking women who recovered from acute idiopathic pulmonary fibrosis is discussed. Pulmonary fibrosis was diagnosed clinically and by lung biopsy. Recovery both clinically and radiologically was complete. Several pulmonary function studies in both patients showed a typical restrictive pattern (reduced lung volumes and carbon dioxide diffusing capacity, normal FEV1/FVC ratio). Within one year both patients exhibited an obstructive pattern of dysfunction (hyperinflation, gas trapping, reduced airflow measurements). These patients illustrated irreversible airway obstruction following recovery from the restrictive stage of pulmonary fibrosis.

Airway Resistance↗
PubMed1980

Xenon-133 ventilation and perfusion studies in bronchiectasis.

Thirty-nine Xenon-133 ventilation and perfusion studies in 36 patients with bronchiectasis were analyzed retrospectively. These patients showed a marked reduction in ventilation with a less severe reduction in pulmonary arterial perfusion, resulting in areas of low ventilation-perfusion ratios. In those patients with bronchographic confirmation, xenon studies had greater sensitivity (0.89) than the chest radiographs (0.71). Where both the radiograph and the scan are normal, bronchiectasis is virtually excluded; therefore bronchography is not indicated.

Adolescent↗
PubMed1978

133Xe uptake by fatty livers.

Of 19 studies on 15 patients with morbid obesity and fatty infiltration of the liver, 16 had increased uptake and retention of 133Xe in the liver following 5-minute rebreathing of 133Xe and oxygen. This observation shows a high correlation with the histologically proven presence of fat in the hepatocytes, and offers a simple, accurate and precise indication of the excess fat in the liver.

Adult↗
PubMed1976

Measurement of 'closing volume' initiated from functional residual capacity.

Comparison of the nitrogen method closing volume (CV) test, with oxygen inspiration initiated at residual volume (RV method) and functional residual capacity (FRC method), was made in 91 seated normal subjects. For RV and FRC methods, respectively CV%VC (mean+/-SD) was 14.4% (+/-6.2) and 17.5%(+/-7.5) (P=0.005); slope of Phase III of CV trace was 0.99% N2/1 (+/-0.76) and 1.66% N2/1(+/-1.07) (P=0.005); size of cardiogenic oscillations was 1.05% N2(+/-0.42) and 1.21% N2(+/-0.40) (P=0.001). These data confirm earlier predictions, based on a calculated increased lung top to bottom N2 gradient in the FRC method. Support for this mechanism was obtained in 5 additional normal subjects in whom the increased CV%VC, slope of Phase III and size of cardiogenic oscillations with the FRC method were eliminated when the top-to-bottom N2 gradient was reduced by breathing a reduced FIN2. Measurements made using the classical RV method cannot be directly compared to those using the FRC method.

Adult↗
PubMed1976

Lung involvement in angioimmunoblastic lymphadenopathy (ail).

Two patients with angioimmunoblastic lymphadenopathy (AIL) in whom the disease process involved the lungs are reported. One patient died in respiratory failure. Details of the radiologic appearance, abnormalities of lung function and lung histology are presented together with response to steroid therapy in one patient. Life-threatening involvement of the lung parenchyma can be a mode of presentation of the disease and can contribute to the morbidity and mortality of the disorder.

Aged↗
PubMed1976

The effect of acute, intensive cigarette smoking on maximal expiratory flows and the single-breath nitrogen washout trace.

The effect of acute, intensive cigarette smoking on forced vital capacity and the single-breath expired N2 trace was studied in 82 smokers. There were significant decreases in the "effort-dependent" tests, such as peak flow and 1-sec forced expiratory volume, but no change in the more "effort-independent" tests, such as maximal mid-expiratory flow and maximal expiratory flow at 25 per cent of the vital capacity. Closing volume was unchanged in absolute terms and as a percentage of vital capacity. Closing capacity was unchanged in absolute terms and as a percentage of total lung capacity, but there was a significant increase in the slope of Phase III of the N2 washout curve after the acute smoking session. The tests of function that changed significantly after acute, intensive smoking were the ones that improved in 52 subjects who modified their smoking habits. The data suggest that acute, intensive cigarette smoking may be associated with an increase in resistance to air flow in the larger airways or a reduction in effort, and with increased nonuniformity of intraregional distribution of ventilation.

Adult↗
PubMed1976

Computer analysis of the single-breath nitrogen washout curve.

A computerized system has been developed to analyze the parameters that can be derived from the nitrogen washout curve. Analog signals for air flow, volume, and nitrogen concentration are entered either on-line or off-line into a 24,000 mini-computer. The program calculates vital capacity, total lung capacity, and residual volume, as well as the slope of phase III, closing volume in liters, total lung capacity, residual volume, closing capacity, closing volume/vital capacity ratio, and closing capacity/total lung capacity ratio. Validation tests showed excellent correlation between hand- and computer-calculated values of closing volume(r=0.864), vital capacity (r=0.997), total lung capacity (r=0.991), and slope of phase III (R=0.926). We concluded that the computerized system for analysis of the expired nitrogen washout curve is as reliable as hand calculations and is immeasurably faster.

Diagnosis, Computer-Assisted↗
PubMed1976

Effect of modification of the smoking habit on lung function.

The effect of smoking cessation or modification on lung function was determined during a 48-week period. In a large number of the cigarette smokers, a disturbance of lung function was not revealed by conventional tests, such as the 1-sec forced expiratory volume; however, an abnormality was often demonstrable in tests that may reflect alterations in small airways, such as closing volume and Phase III of the single-breath expired N2 curve. There was no relation between the degree of abnormality of lung function and the presence of respiratory symptoms, but there appeared to be a relationship to lifetime smoking history, the heaviest smokers having the poorest function. Cessation, or more than 25 per cent decrease in the number of cigarettes smoked, was attened by improvement in the slope of Phase III of the N2 washout curve, closing volume, and closing capacity, as well as forced vital capacity, 1-sec forced expiratory volume, and peak flow. Resumption of smoking after cessation was attended by a deterioration in the slope of Phase III and closing capacity. The data suggest that the functional abnormalities in smokers are related to smoking and are at least partially reversible by cessation or significant modification of the smoking habit.

Adolescent↗
PubMed1975

Intraindividual variability in maximal expiratory flow-volume and closing volume in asymptomatic subjects.

The variability of the parameters derived from analysis of the forced vital capacity and the expired nitrogen trace after a vital capacity inhalation of oxygen (closing volume) within a day, from day to day, and from week to week, has been determined. Effort-dependent tests as vital capacity and peak expiratory flow showed the least variability. The greatest variability was seen in effort-independent tests of function such as the maximal expiratory flow rate at 25 per cent (75 per cent of expired vital capacity) and 50 per cent of vital capacity, as well as closing volume. The degree of variability in the tests used was uninfluenced by the periodicity of the tests or the age or smoking habits of the subjects tested. It is suggested that variability of tests of respiratory function should be taken into account in their interpretation.

Adolescent↗