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Biomedical subjects

J T Sharp

Publications and source records attributed to J T Sharp.

At least 37 records · Page 2Linked to original sources
PubMed1986

Assessment of radiologic progression in rheumatoid arthritis. A randomized, controlled trial.

Radiologic assessment of progressive joint destruction in rheumatoid arthritis is generally considered to be the ultimate standard for evaluation of treatment. We compared alternative radiologic techniques by performing a randomized, controlled trial in which hand films of rheumatoid arthritis patients were read by several skilled observes. The number of joints evaluated (34 versus 18) was found to make relatively little difference, but the number of readers and their experience level was critical. Films should be read in pairs. Joint space narrowing and erosion scores were shown to contribute independent information. Use of recommended techniques can reduce the number of patients required and, thus, can reduce the cost of a clinical trial by more than half and can substantially increase the sensitivity and efficiency of a trial. Therefore, critical selection of the method of assessing study endpoint is of great importance.

Arthritis, Rheumatoid↗
PubMed1986

Theophylline in chronic obstructive pulmonary disease.

Although prolonged use of maintenance theophylline therapy in chronic obstructive lung disease remains controversial, evidence from well-designed studies indicates that it produces patient improvement as gauged by both objective and subjective measurements. An important reason to use sustained-release theophylline is to prevent episodes of bronchospasm by providing a smooth around-the-clock bronchodilator effect and thus reducing the need for periodic aerosolized beta agonists. Theophylline also increases diaphragmatic contractility and endurance, although there is disagreement concerning the practical clinical significance of this effect. The drug improves cardiovascular function by increasing myocardial contractility and by reducing pulmonary and systemic vascular resistances. The increased central respiratory drive produced by theophylline may be important in reducing the ventilatory depressant effects of oxygen therapy. The drug also acts to inhibit mediator release and improves several aspects of mucociliary function, although, again, the clinical significance of these actions has not been established.

Adrenergic beta-Agonists↗
PubMed1986

Reduction of aspirin-induced gastroduodenal mucosal damage with ranitidine.

A randomized, double-blind, placebo-controlled study was conducted to determine if concomitant administration of ranitidine, an H2-receptor antagonist, could reduce the gastroduodenal mucosal damage associated with short-term (3 day) aspirin therapy. Nineteen subjects received ranitidine 150 mg b.i.d. plus aspirin 650 mg q.i.d., and 21 received placebo b.i.d. plus aspirin 650 mg q.i.d. for 3 days. Gastric injury and duodenal injury were assessed separately on the basis of pre- and posttreatment endoscopic examinations. The ranitidine/aspirin group had significantly less mucosal damage in the stomach (p less than or equal to 0.01) and duodenum (p less than 0.05) than the placebo/aspirin group. There was no significant difference in mean serum salicylate levels between treatment groups after 3 days of aspirin consumption, indicating that the protective effect was achieved without compromising salicylate absorption.

Adolescent↗
PubMed1986

The rib cage in normal and emphysematous subjects: a roentgenographic approach.

The configuration and motion of the bony rib cage were studied from lateral chest roentgenograms in 10 young normal subjects (YN), 12 elderly normal subjects, and 12 hyperinflated emphysematous patients [chronic obstructive pulmonary disease subjects (COPD), mean total lung capacity (TLC) 133% of predicted]. The acute angles formed by the fourth through seventh ribs with an axial reference plane were measured at residual volume, functional residual capacity, and TLC in both supine and standing positions and correlated with corresponding lung volumes. both rib angles (RA) and changes in RA with lung volume were greatest with the fourth rib and decreased progressively going down (caudad) the chest. At TLC the RA of upper ribs was significantly less in EN and significantly greater in COPD than in YN. RA's were greater supine than standing. When RA information was used together with autopsy data on the angles formed by intercostal muscles with adjacent ribs, intercostal muscle lengths in hyperinflation could be calculated. Computed intercostal muscle length data suggested that hyperinflation should not be associated with degrees of intercostal muscle shortening or overstretching, that would interfere seriously with tension generation.

Adult↗
PubMed1986

Diaphragmatic responses to body position changes in obese patients with obstructive sleep apnea.

Patients with severe obesity and obstructive sleep apnea (OSA) have been shown to have abnormalities in respiratory muscle function and respiratory control. The present study was done to evaluate diaphragmatic function and the diaphragm fiber-length-compensating reflex in morbidly obese patients with OSA (1). Twelve normal subjects and 13 morbidly obese patients with OSA were studied in recumbent and upright positions. In the normal subjects, the diaphragm fiber-length-compensating reflex operated normally causing the diaphragm's inspiratory EMG to increase when the diaphragm's fibers shortened with assumption of the upright position. However, 8 of the 13 obese patients with OSA showed a decrease rather than an increase in the inspiratory diaphragmatic EMG on assuming the upright posture. Further data indicate greater diaphragmatic efficiency in the upright than in the supine position in a majority of the obese patients, a reversal of the normal response. Two possible explanations of these observations are: an abnormality of central respiratory control in obese patients with OSA and overstretching of the diaphragm in the recumbent obese patient. The observation of reduced maximal transdiaphragmatic pressures in the recumbent position in some of the obese patients with OSA supports the second explanation. Diaphragmatic overstretching may be an important mechanism in the development of hypoventilation in the morbidly obese.

Adult↗
PubMed1985

Reproducibility of multiple-observer scoring of radiologic abnormalities in the hands and wrists of patients with rheumatoid arthritis.

Forty-one coded radiographic films from 16 patients with rheumatoid arthritis were read by 13 observers, using 4 different methods for scoring abnormalities. Although absolute scores differed widely among individual observers, correlation coefficients were greater than 0.850 for approximately 2 of 3 comparisons. When films were ranked, using the median rank of all readers, 72% of individual ranks were within 10% of the median ranks. Among serial films on individual patients, 92% of comparisons between early and late films were interpreted as demonstrating progression of abnormalities when mean standardized scores showed an increase in scores of 15 units or greater. Films with lesser changes were interpreted inconsistently. This study shows good general agreement among readers in scoring radiologic abnormalities of hands and wrists, when applied to a film set showing a broad spectrum of severity, and defines the sensitivity of radiologic detection of disease progression.

Adult↗
PubMed1985

How many joints in the hands and wrists should be included in a score of radiologic abnormalities used to assess rheumatoid arthritis?

Numerous methods for reading abnormalities of rheumatoid arthritis in hand and wrist radiographs have been proposed over the past several decades. There are many differences among these methods, one of the more striking of which is the variation in the number of joints that are scored. In this study, we tested the number of joints that need to be read in order to represent abnormalities accurately and reproducibly, using the scores of multiple observers. Thirteen rheumatologists and radiologists each read a set of 41 hand and wrist films from patients with rheumatoid arthritis. Ten of 13 readers scored 27 joints in each hand and wrist; the other 3 readers scored fewer areas. Fourteen combinations of joints were selected based on the frequency of involvement and the technical adequacy of routine films in assessing a given area. After testing these 14 different combinations, 1 scheme, which included 17 areas read for erosions and 18 areas read for joint space narrowing, was tested further. The correlation coefficients for 10 intraobserver scores derived from this modified scheme compared with the original scores were between 0.981 and 0.997. Seventy-one of 78 interobserver comparisons were better using the new scheme than using the original scheme. These data indicate that the simplified scheme, using a combination of 17 joints to score erosions and 18 to score joint space narrowing, more accurately reflects the extent of abnormalities perceived by a panel of experts than does the original scheme. This abbreviated number of joints shortens the amount of time required to read a set of films and simplifies the scoring of films, since a number of areas that are difficult to read are eliminated from radiographic assessment.

Arthritis, Rheumatoid↗
PubMed1985

Effect of muscle length on electromyogram in a canine diaphragm strip preparation.

The relationship between diaphragm electromyogram (EMG), isometric force, and length was studied in the canine diaphragm strip with intact blood supply and innervation under three conditions: supramaximal tetanic (100 Hz) phrenic nerve stimulation (STPS; n = 12), supramaximal phrenic stimulation at 25 Hz (n = 15), and submaximal phrenic stimulation at 25 Hz (n = 5). In the same preparation, the EMG-length relationship was also examined with direct muscle stimulation when the neuromuscular junction was blocked. EMG from three different sites and via two types of electrodes (direct or sewn-in and surface) were recorded during isometric contraction at different lengths. Direct EMGs were recorded from two bipolar electrodes sutured into the strip, one near its central end and the other near its costal end. A third EMG electrode configuration summed potentials from the whole strip by recording potentials between central and costal sites. Surface EMGs were recorded by a bipolar spring clip electrode that made contact with upper and lower surfaces of the muscle strip with light pressure. In all conditions of stimulation with different types of electrodes, all EMGs decreased significantly (P less than 0.05) when muscle length was changed from 50 to 120% of resting length (L0). Minimal and maximal force outputs were observed at 50 and 120% of L0, respectively, in all experiments. The results of this study indicated that the muscle length is a significant variable that affects the EMG recording and that the diaphragmatic EMG may not be an accurate reflection of phrenic nerve activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Effect of metabolic acidosis upon sleep apnea.

The effects of metabolic acidosis upon the pattern of apnea during sleep were assessed in ten sleep apnea patients. Four had pure obstructive apnea, two pure central apnea, and four had mixed apnea. Acidosis was induced with acetazolamide. Acid-base shifts had little effect in pure obstructive and pure central apnea, but had a significant effect in mixed apnea. In two of the mixed apneic patients, metabolic acidosis converted predominantly central apnea into nearly pure obstructive apnea, prolonging apneic periods and worsening hypoxemia. A suggested explanation for this is the greater stimulating effect of acidosis upon the lower bellows muscles than upon the muscles which act to maintain patency of the upper airways. The observation that some patients with mixed sleep apnea appear to have central apnea while relatively alkalotic and obstructive apnea while acidotic emphasizes the need for more careful and detailed characterization of apneic disorders with respect to their responses to body states and therapeutic agents.

Acetazolamide↗
PubMed1985

Therapeutic considerations in respiratory muscle function.

Inspiratory muscle function is impaired in many patients with severe COPD. This functional impairment often leads to hypercapnic respiratory failure via inspiratory muscle fatigue. Factors responsible for this functional impairment are: (1) an excessive mechanical load (high resistance and low compliance) for the inspiratory muscles to overcome; (2) the low, flat configuration of the diaphragm owing to lung hyperinflation; (3) reduced inspiratory muscle blood flow relative to the increased respiratory work requirement; and (4) tachypnea which increases the duty cycle (TI/Ttot) for inspiratory muscles, increases hyperinflation, wastes ventilation, and otherwise causes deterioration of gas exchange. Therapy is directed toward improving inspiratory muscle function and has three strategic goals: (1) to reduce the load imposed on the inspiratory muscles and reduce their mechanical disadvantage; (2) to improve the contractile characteristics of the inspiratory muscles; and (3) if goals 1 and 2 cannot be attained otherwise, to rest the inspiratory muscles using mechanical ventilation. Inspiratory muscle training offers promise as a means of preventing hypercapnic respiratory failure. Available data suggest that some COPD patients benefit from it. To be determined are which patients will benefit from it and which will not, as well as which training regimens are most effective.

Airway Resistance↗
PubMed1984

The effect of maintenance theophylline therapy on lung work in severe chronic obstructive pulmonary disease while standing and walking.

There is controversy whether routine use of theophylline is warranted in chronic obstructive pulmonary disease (COPD). Effects on spirometry are minimal, and subjective relief is difficult to document. Therefore, we undertook to study the pulmonary effects of theophyline using a functional approach, namely, its effects on the lung mechanics of a standing or walking patient. In a double blind, placebo controlled crossover study, 400 mg of slow-release theophylline (TheoDur) were given twice a day in 13 trials to 10 patients with severe COPD. Lung mechanics were calculated on a breath-by-breath basis by a pulmonary mechanics computer from esophageal pressures and flow. Expired volumes were simultaneously collected. Spirometry was then performed. On the placebo limb, the spirometric response to 0.5 mg terbutaline given subcutaneously was compared with the theophylline response. At a mean serum theophylline level of 12.3 micrograms/ml, theophylline produced in the entire group a mean reduction in the work of breathing done on the lung (WL) of 16% (p less than 0.002) while walking, but a significant effect while standing was not detected. During both walking and standing, the mean reduction in lung resistance (RL) was 15 to 16% (p less than 0.002). Minute volume (VE) was increased at borderline significance, with a mean reduction while walking of 19% in the ratio of WL to VE (p less than 0.002). In the individual patient, changes in WL were influenced more by changes in VE than by changes in RL; in fact, changes in WL correlated best with changes in the product of (VE)2 and RL. Theophylline produced a mean increase of 15% in forced expiratory volume in one second (FEV1) and 16% in forced vital capacity (FVC).(ABSTRACT TRUNCATED AT 250 WORDS)

Forced Expiratory Volume↗
PubMed1984

Development of gross motor skills in the normal child.

This article describes the various functional achievements attained by the normal child in his progress toward upright walking. The average ages at which such motor accomplishments occur are considered along with their normal time of appearance.

Age Factors↗
PubMed1983

Speech production with flaccid paralysis of the rib cage, diaphragm, and abdomen.

Anteroposterior diameter changes of the rib cage and abdomen were measured during breathing maneuvers and utterance activities in an adult subject with flaccid paralysis of the rib cage, diaphragm, and abdomen. Data were charted to solve for lung volume, volumes of the rib cage and abdomen, chest wall configuration, and inferred neck muscle actions. Free breathing was accomplished through an alternate waxing and waning of neck muscle drive or through step-wise glossopharyngeal pumping. Connected speech was performed in breath groups begun by neck gestures that "cocked" the breathing apparatus and stored recoil energy in it for use during ensuing expirations. Some breath groups were also extended through intermittent glossopharyngeal pumping. Connected speech was characterized by frugal control of the air supply through compensatory adjustments in the larynx and upper airway. Compensations involved in the breathing maneuvers and utterance activities are described, and consideration is given to two understandings--the human potential for functional restoration and the clinical evaluation and management of individuals with neuromuscular impairment.

Abdomen↗