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Biomedical subjects

S F Davies

Publications and source records attributed to S F Davies.

At least 19 recordsLinked to original sources
PubMed1991

Aerosol pentamidine prophylaxis following Pneumocystis carinii pneumonia in AIDS patients: results of a blinded dose-comparison study using an ultrasonic nebulizer.

PURPOSE: To compare the efficacy and safety of three different doses of prophylactic aerosol pentamidine in patients with one prior episode of Pneumocystis carinii pneumonia (PCP) and the acquired immunodeficiency syndrome. PATIENTS AND METHODS: The design of the study was a double-blind, randomized, dose-comparison clinical trial conducted at 13 medical centers within the United States. In stage I of the trial, patients were randomized to receive either 5 mg, 60 mg, or 120 mg of aerosol pentamidine delivered biweekly with the Fisoneb (Fisons, Inc., Rochester, New York) ultrasonic nebulizer. After 24 weeks of therapy, patients entered stage II of the trial, where the 5-mg group was re-randomized to either the 60-mg or 120-mg group. RESULTS: One hundred seventy-five patients entered stage I of the trial and received prophylaxis for a mean of 123.6 days. Seven assigned to the 5-mg biweekly dosing schedule had a confirmed recurrence of PCP, compared with none in the 60-mg group (p = 0.007) and three in the 120-mg group (p = 0.304). During stage II of the trial, eight patients in the 60-mg group and one additional patient in the 120-mg group had recurrent PCP. After 52 weeks of observation, the likelihood of being PCP-free was 88.0% in the 60-mg group and 93% in the 120-mg group (p = 0.712). Minor adverse events related to aerosol pentamidine administration included cough, taste perversion, chest pain, bronchospasm, and dyspnea. These side effects were more common in the 60-mg and 120-mg treatment groups and resulted in withdrawal from the study by one patient. Serious events were more common after 24 weeks of therapy and included asymptomatic hypoglycemia (five), pancreatitis (two), pneumothorax (one), and extrapulmonary pneumocystosis (one). CONCLUSIONS: These results demonstrate that biweekly administration of 60 mg or 120 mg of aerosol pentamidine significantly decreases PCP recurrence when compared with a 5-mg regimen or findings in historic controls and is generally well tolerated. There is no significant difference in effect or safety between these two dosing regimens in patients followed for at least 52 weeks of therapy.

Adult↗
PubMed1990

Evidence of subclinical blastomycosis in forestry workers in northern Minnesota and northern Wisconsin.

PURPOSE: To investigate the incidence of remote subclinical blastomycosis in a high-risk population of forestry workers. PATIENTS AND METHODS: The study consisted of 39 male forestry workers from northern Minnesota and northern Wisconsin, areas endemic for blastomycosis but not for histoplasmosis. All subjects were histoplasmin skin test-negative, and none had ever been diagnosed with blastomycosis or pneumonia. An antigen-specific lymphocyte stimulation assay was performed to determine the presence of blastomycosis. RESULTS: Peripheral blood lymphocytes from 12 of 39 subjects demonstrated specific antigen-induced proliferation when stimulated with a purified alkali- and water-soluble antigen derived from the cell wall of Blastomyces dermatitidis. CONCLUSION: The finding that 30% of these men had evidence of previous blastomycosis suggests that subclinical cases do occur sporadically, and are probably more common than diagnosed symptomatic cases. This is similar to histoplasmosis, in which the majority of infections are subclinical. However, the reservoir of persons with previous undiagnosed blastomycosis is probably small compared to the huge number of persons (perhaps 30 million) with prior histoplasmosis.

Adult↗
PubMed1990

Influence of acid-base status on plasma catecholamines during exercise in normal humans.

The influence of acid-base status on plasma catecholamines during exercise was investigated in six healthy volunteers. Incremental exercise to 175 W was performed on a bicycle ergometer under four conditions: 1) control, 2) during forced hyperventilation (HV), 3) after pretreatment with acetazolamide (AZE), and 4) while breathing 4% CO2. Resting plasma norepinephrine (PNE) and epinephrine (PE) were not different among the four protocols despite higher resting pH during HV and lower resting pH after AZE [control, 7.4 +/- 0.02; HV, 7.48 +/- 0.03 (P less than 0.005); AZE, 7.36 +/- 0.01 (P less than 0.005) (P values indicate significant differences from the control protocol)]. Resting pH was not different from control during the 4% CO2 study (7.4 +/- 0.01). At the 175-W exercise load, there were significant differences in both pH and PNE. During the control test, pH was 7.38 +/- 0.02, PNE was 951 +/- 164 pg/ml, and PE was 264 +/- 132 pg/ml. During HV, pH was 7.46 +/- 0.5 (P less than 0.001), PNE was 976 +/- 67 pg/ml, and PE was 210 +/- 27 pg/ml. After AZE, pH was 7.31 +/- 0.2 (P less than 0.001), PNE was 1,866 +/- 561 pg/ml (P less than 0.005), and PE was 382 +/- 264 pg/ml. While subjects breathed 4% CO2, pH was 7.29 +/- 0.02 (P less than 0.001), PNE was 1.842 +/- 617 pg/ml (P less than 0.01), and PE was 467 +/- 275 pg/ml.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetazolamide↗
PubMed1990

Histoplasmosis: update 1989.

Histoplasmosis is a relatively mature disease that was first described 85 years ago. Histoplasmosis was long thought to be a rare and uniformly fatal illness. However, widespread use of skin testing in the 1940s proved that it was a common infection, especially in the central United States, and almost invariably benign. Primary histoplasmosis often presents as a self-limited, nonspecific respiratory infection, and thus, it was realized that a huge iceberg of subclinical and mildly symptomatic cases had been missed for years, since only the highly symptomatic and progressive infections had been diagnosed. Once the disease was recognized as a common one, many new clinical forms of the illness were recognized, including diffuse infiltrates due to heavy exposure, chronic cavitary disease resembling tuberculosis, and complications of primary infection, including mediastinal granuloma and the superior vena caval syndrome. Despite the mature state of histoplasmosis, it is still a disease capable of producing surprises. In this article, the history of histoplasmosis is reviewed, as well as current major concepts about the epidemiology, pathogenesis, clinical features, diagnosis, and treatment of this infection. Newer developments are then highlighted using the same outline.

Chronic Disease↗
PubMed1989

Blastomycosis.

Blastomycosis is the least understood of the major endemic mycoses in North America. The fungus exists in the soil in its mycelial form, and when the proper growth conditions exist growth and spore formation will occur. When microfici containing the growing mycelium of blastomyces are disturbed, an infecting aerosol is formed. The spores are inhaled and eventually settle in the alveoli where multiplication by binary fission occurs. Following development of cell-mediated immunity the infection is localized in the lung. During the pre-immune phase of the infection spread to extrapulmonary sites may occur. Most common sites of involvement include the skin, bones, prostate and central nervous system. Pulmonary disease may resolve spontaneously or progress. Treatment is required for progressive pulmonary illness and all episodes of extrapulmonary disease. For life-threatening blastomycosis or blastomycosis of the central nervous system amphotericin B is the treatment of choice, while ketoconazole is an excellent alternative for patients who are not critically ill or have no central nervous system involvement.

Amphotericin B↗
PubMed1989

Nocturnal rocking bed therapy: improvement in sleep fragmentation in patients with respiratory muscle weakness.

Three patients with respiratory muscle weakness developed sleep fragmentation due to nonobstructive apnea and hypopnea. In two patients in whom inspiratory muscle electromyogram was recorded, the apneas and hypopneas were terminated only by arousal and excessive recruitment of accessory muscles. Nocturnal rocking bed ventilatory support resulted in immediate improvement in sleep fragmentation and inhibited arousal-associated phasic accessory muscle activation, resulting in improvement in daytime hypercapnia and subjective sleepiness. Sleep fragmentation may occur more commonly than generally appreciated in neuromuscular disease patients who are independent of daytime ventilatory support. The use of nocturnal rocking bed is an effective noninvasive method of reversing sleep fragmentation and daytime sequelae when obstructive apnea is absent.

Adult↗
PubMed1989

Comparative effects of transdermal clonidine and oral atenolol on acute exercise performance and response to aerobic conditioning in subjects with hypertension.

We compared the effects of transdermal clonidine and oral atenolol on acute exercise performance and on conditioning response to an 8-week program of regular aerobic exercise in young, otherwise healthy subjects with mild hypertension. The study was a double-blind, randomized, parallel-group study with placebo control. Twenty-seven subjects (11 receiving transdermal clonidine, 8 receiving oral atenolol, and 8 receiving placebo) completed the study. Atenolol controlled blood pressure in all 8 subjects, vs 6 of 11 in the transdermal clonidine group and 0 of 8 in the placebo group. Both active drugs lowered systolic blood pressure during exercise. With clonidine treatment, the antihypertensive effect during exercise was smaller and was observed only at low and moderate workloads. Acute exercise performance (subjects receiving drug but still unconditioned) was assessed by endurance time at a constant workload equal to the highest workload completed on a previous 2-minute incremental exercise test. Endurance time was reduced 35% by atenolol but not by transdermal clonidine or placebo. Neither active drug interfered with the progress of the conditioning program, as measured by gradual lengthening of exercise time. However, as assessed by change in oxygen uptake standardized to a heart rate of 170 beats per minute, the improvement in conditioning was twice as great in subjects receiving transdermal clonidine and placebo (+20%, +18%) as it was in those receiving atenolol (+8%). Subjects receiving placebo and transdermal clonidine lost weight; subjects receiving oral atenolol gained weight. The changes in weight were small.

Administration, Cutaneous↗
PubMed1989

The effect of phenylpropanolamine on blood pressure during upright bicycle exercise in normal subjects.

We studied the effect of a single oral dose (37.5 mg immediate release) of phenylpropanolamine (PPA) in six normal subjects during upright incremental bicycle exercise to symptom tolerance. The study was double blind and placebo controlled with a crossover design. The patients rested supine for 90 minutes after dosing, sat quietly on the bicycle for five minutes, and then began exercise. After PPA systolic blood pressure was increased during supine rest (135 +/- 14 mmHg vs 120 +/- 10 mmHg for placebo; P less than 0.01) and while sitting on the bicycle prior to exercise (131 +/- 8 mmHg vs 121 +/- 8 mmHg for placebo; P less than 0.05). However, PPA did not alter the expected increase in systolic blood pressure with progressive exercise. Systolic blood pressure at maximum exercise (254 +/- 43 watts) was 185 +/- 14 mmHg for PPA vs 182 +/- 13 mmHg for placebo (difference not significant). This suggests that the physiological factors controlling blood pressure during exercise (increased cardiac output, vasodilation of vessels in exercising muscles and vasoconstriction of non-exercising vascular beds) are not altered significantly by a dose of PPA sufficient to increase resting systolic blood pressure, at least in normal subjects.

Adult↗
PubMed1988

Diagnosis of pulmonary fungal infections.

The diagnosis of pulmonary fungal infections is reviewed. An overview of the major endemic and opportunistic fungal infections is followed by a brief discussion of the available diagnostic tools. These include: (1) direct microscopic examination of secretions or body fluids; (2) histopathologic examination of tissue biopsies; (3) cultures of secretions, body fluids, or ground-up tissue; and (4) immunological tests ("fungal serologies"). In the final section, a current diagnostic approach is given that identifies the diagnostic tests more likely to be helpful for each infection.

Aspergillosis↗
PubMed1988

Granulomatous diseases of the lung that mimic respiratory infections.

Granulomatous diseases of the lung may have clinical, roentgenographic, and pathological features that closely mimic respiratory tract infections. The protean manifestations of sarcoidosis allow confusion with a wide variety of infectious diseases. Acute hypersensitivity pneumonitis closely mimics an infectious illness; even subacute or chronic presentations may be mistaken for infections. Less commonly, the manifestations of intravenous talc granulomatous disease may also mimic infection.

Alveolitis, Extrinsic Allergic↗
PubMed1987

Extreme dyspnea from unilateral pulmonary venous obstruction. Demonstration of a vagal mechanism and relief by right vagotomy.

A 43-yr-old woman developed severe exertional dyspnea after an unsuccessful attempt to correct a total right anomalous pulmonary venous connection. A clotted anastomosis resulted in unilateral pulmonary venous obstruction. Investigation excluded airway disease, left ventricular failure, and severe pulmonary hypertension as the cause of dyspnea. Exercise studies demonstrated a markedly abnormal ventilatory pattern consistent with excess vagal stimuli to the respiratory center. Temporary and then permanent vagal interruption markedly altered the respiratory pattern and improved her functional status from New York Heart Association Class III to Class I, confirming that vagal afferents were the cause of the dyspnea.

Adult↗
PubMed1987

An overview of pulmonary fungal infections.

An overview of important pulmonary mycoses is presented. Four endemic mycoses occur in restricted geographic areas: histoplasmosis, blastomycosis, coccidioidomycosis, and paracoccidioidomycosis. Three opportunistic mycoses have causative agents that are ubiquitous in nature but cause infection only in compromised hosts: aspergillosis, mucormycosis, and candidiasis. Cryptococcosis is acquired by inhalation but usually presents as a chronic meningitis. Pulmonary sporotrichosis is rare; the usual subcutaneous form of the disease is acquired by inoculation. The clinical features of these infections are discussed, with special emphasis on recent advances in diagnosis and treatment.

Antifungal Agents↗
PubMed1987

Role of serodiagnostic tests and skin tests in the diagnosis of fungal disease.

Serodiagnostic tests have a significant role in the diagnosis of a number of fungal infections. The bases for these tests are reviewed and their sensitivity, specificity, and applications are discussed. Skin test antigens are also reviewed. Their diagnostic role is currently limited, but they have some utility as epidemiological tools.

Antibodies, Fungal↗
PubMed1986

Effect of respiratory alkalosis during exercise on blood lactate.

A biofeedback model of hyperventilation during exercise was used to assess the independent effects of pH, arterial CO2 partial pressure (PaCO2), and minute ventilation on blood lactate during exercise. Eight normal subjects were studied with progressive upright bicycle exercise (2-min intervals, 25-W increments) under three experimental conditions in random order. Arterialized venous blood was drawn at each work load for measurement of blood lactate, pH, and PaCO2. Results were compared with those from reproducible control tests. Experimental conditions were 1) biofeedback hyperventilation (to increase pH by 0.08-0.10 at each work load); 2) hyperventilation following acetazolamide (which returned pH to control values despite ventilation and PaCO2 identical to condition 1); and 3) metabolic acidosis induced by acetazolamide (with spontaneous ventilation). The results showed an increase in blood lactate during hyperventilation. Blood lactate was similar to control with hyperventilation after acetazolamide, suggesting that the change was due to pH and not to PaCO2 or total ventilation. Exercise during metabolic acidosis (acetazolamide alone) was associated with blood lactate lower than control values. Respiratory alkalosis during exercise increases blood lactate. This is due to the increase in pH and not to the increase in ventilation or the decrease in PaCO2.

Acetazolamide↗