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Biomedical subjects

P D Scanlon

Publications and source records attributed to P D Scanlon.

At least 37 records · Page 2Linked to original sources
PubMed1995

Role of chest physicians in detection and treatment of occupational and environmental respiratory disease. A practice survey.

A survey of American College of Chest Physicians (ACCP) members was conducted to determine their degree of involvement in the diagnosis and prevention of occupational and environmental respiratory disease (OERD). Although the response rate was relatively low, the results are likely to be representative. Calculations based on the data estimate that in the prior year, chest physicians on the average saw 15 patients with OERD caused by work, 13 worsened by work, and 28 affected by the home environment. Asthma appears to be a more common occupational or environmental concern than pulmonary fibrosis. Chest physicians clearly perceived a need for more education in OERD. The survey also demonstrated that although many chest physicians perform routine industrial surveillance testing, it is often done without using standardized methods. Furthermore, chest physicians are actively involved with medical/legal aspects of OERD. Overall, the survey documents the role of chest physicians in the area of OERD and emphasizes significant educational needs.

Adult↗
PubMed1994

Bronchoconstriction occurring during exercise in asthmatic subjects.

To demonstrate physiologic changes associated with asthma symptoms that many patients with asthma develop during exercise, we used sustained constant-load and interval exercise protocols with subjects breathing dry room temperature air. In constant-load exercise, subjects pedaled a stationary bicycle at 50% of their maximal power capacity for 36 min. In interval protocols, subjects pedaled at 60% of maximal capacity for 6 min and then 40% of maximal for 6 min; the 12-min cycle was repeated three times for a total exercise time of 36 min. Maximal expiratory flow versus volume maneuvers (MEFV) were obtained before, at 6-min intervals during, and at 5-min intervals after exercise. Changes in peak expiratory flow (PEF), forced expiratory volume in 1 s (FEV1), and forced expiratory flow at 50% of pre-exercise vital capacity (FEF50) were compared with pre-exercise values. Within 15 min after a maximal 1-min incremental exercise protocol, mean flows decreased compared with pre-exercise (PEF, mean -22%, range -46 to 5%; FEV1, mean -21%, range -42 to -3%; FEF50, mean -41%, range -80 to 3%; all p < 0.05). There were no significant changes in MEFV flows until 18 min of constant-load exercise, when FEV1 and FEF50 fell (FEV1, mean -6%, range -15 to 2%; FEF50, mean -14%, range -32 to 6%; both p < 0.05), although changes in PEF were minimal and were not significantly different compared with pre-exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Comparison of four methods for calculating diffusing capacity by the single breath method.

In 283 patients referred for testing in an outpatient pulmonary function laboratory, we studied the single-breath diffusing capacity of the lungs for carbon monoxide (Dco) using the Ogilvie (Og), Jones-Meade (JM), Epidemiological Standardization Project (ESP), and three-phase iterative methods (3PIT, similar to the three equation method). The Dco maneuvers were performed using automated equipment and American Thoracic Society (ATS) recommended procedures. There were small but significant differences in mean Dco, the ESP method yielding the largest, followed in order by JM, 3PIT, and Og methods. The 3PIT and JM Dcos were in close agreement in all degrees and patterns of pulmonary function abnormality. The Og Dco method was 6 percent less than JM in patients with normal pulmonary function, although the difference was less in patients with expiratory flow limitation, restriction, or reduced Dco. There were no differences in the reproducibility of Dco measurements among the methods. Based on these results and a review of the literature, we conclude the following: (1) when measuring single-breath Dco using automated equipment that follows ATS recommended procedures for collecting a single expired gas sample of 500-ml volume, calculated Dco is largest using ESP method, following by JM, 3PIT, and Og methods; (2) in patients with reduced Dco associated with obstructive or restrictive abnormalities, the Og, 3PIT, and JM timing methods are nearly equivalent; and (3) reproducibility of Dco is the same by all methods.

Airway Obstruction↗
PubMed1993

Preoperative pulmonary function testing for patients with lung cancer.

Preoperative functional assessment of patients who are scheduled to undergo pulmonary resection for carcinoma of the lung can assist the clinician in determining perioperative risk. Physiologic alterations that occur after thoracotomy, including changes in lung volume, ventilatory pattern, gas exchange, and respiratory defense mechanisms, impose an increased risk of complications in patients with moderate to severe respiratory impairment. The use and shortcomings of preoperative spirometry and arterial blood gas analysis as predictors of perioperative complications are reviewed. Quantitative radionuclide scintigraphy, and in some cases exercise testing, can further determine the operative risk of patients with lung cancer. For patients with increased risk, implementation of prophylactic measures may decrease postoperative complications.

Blood Gas Analysis↗
PubMed1992

A study of aqueous humor formation in patients with cystic fibrosis.

The circadian pattern of aqueous formation and the effect of timolol on aqueous flow was studied in 12 patients with cystic fibrosis. Cystic fibrosis is a disease characterized by a defect in a chloride channel-associated regulatory protein found in epithelial cells. Improper regulation of these chloride channels, causes abnormal composition of exocrine secretions, including respiratory tract, gastrointestinal tract, exocrine pancreas, and sweat glands. Ocular findings previously reported include abnormal endothelial cell permeability, decreased tear secretion, and abnormal tear composition. In this study, aqueous humor flow was measured by fluorophotometry. No statistically significant difference was found when flow rates measured during the morning, during the afternoon, at night, and after topical timolol treatment were compared to normal values. The conclusion is that the beta adrenergically regulated chloride selective channels defective in patients in cystic fibrosis do not play a major role in the formation of aqueous humor or they are not regulated by the cystic fibrosis transmembrane conductance regulator (CFTR).

Administration, Topical↗
PubMed1990

Effect of inhaled methacholine on inspiratory flow.

One hundred consecutive outpatients with symptoms suggestive of asthma who came to the Pulmonary Function Laboratory for a methacholine challenge test were studied. In addition to the forced expiratory maneuvers, forced inspiratory maneuvers were performed before and after the maximal response to methacholine. In 24 patients, the methacholine challenge suggested that they had asthma (forced expiratory volume in 1 s [FEV1] decrease greater than or equal to 20 percent). Six of these 24 patients also had a decrease in maximal forced inspiratory flow (FIFmax) greater than or equal to 20 percent and nine had a decrease in forced inspiratory flow at 50 percent of vital capacity (FIF50) greater than or equal to 20 percent, suggesting that bronchoconstriction can cause decreased inspiratory as well as expiratory flows. In 76 patients, the methacholine challenges were "negative" (FEV1 decrease less than or equal to 20 percent), suggesting that they did not have asthma. Nevertheless, in 11 of these 76 patients the FIFmax decrease was greater than or equal to 20 percent, and in 14 patients the FIF50 decrease was greater than or equal to 20 percent, suggesting that intermittent central airway obstruction is responsible for these patients' symptoms.

Administration, Inhalation↗
PubMed1989

Respiratory mechanics in acute quadriplegia. Lung and chest wall compliance and dimensional changes during respiratory maneuvers.

We measured lung and chest wall compliance as well as rib cage and abdominal dimensions in the supine position in five acute C4-7 quadriplegics. Studies were performed serially from 1 to 12 months after injury. Results were compared with those of control groups of chronic (greater than 1 yr after injury) quadriplegics and normal volunteers. We found that lung compliance was lower in acute and chronic quadriplegics (0.129 +/- 0.023 and 0.176 +/- 0.043 L/mm Hg, respectively) than in normal subjects (0.278 +/- 0.086 L/mm Hg) and that these changes apparently occurred within 1 month of injury. Specific lung compliance appeared to be reduced to a lesser degree, suggesting that the changes in lung compliance were partly due to reduced lung volumes and partly to altered mechanical properties of the lung. During respiratory maneuvers, abdomen and rib cage dimensional changes demonstrated rib cage distortion. This distortion was less severe in chronic than in acute quadriplegics. The improvement in chest wall stability was likely due to increased strength of cervical accessory muscles of respiration and improved coupling of the various rib cage elements in chronic quadriplegics.

Acute Disease↗
PubMed1987

Bronchoconstrictor effects of leukotriene E4 in normal and asthmatic subjects.

The bronchoconstrictor activity of an aerosol of leukotriene E4(LTE4) was compared with that of histamine in 5 normal and in 6 asthmatic subjects to define the relative potency of LTE4 between the groups using 3 indices of airway response. The FEV1 and the flow rate measured at 30% of vital capacity from partial and maximal expiratory maneuvers (V30-P and V30-M) were measured. The geometric mean (GSEM) concentration of LTE4 required to reduce the V30-P by 30% was 0.30 (1.46) mM in the normal subjects, and 0.058 (1.63) in the asthmatic subjects; LTE4 was 39-fold more potent than histamine in the former and 14-fold in the latter group. Further, we observed that when normal and asthmatic subjects were compared at a degree of bronchoconstriction resulting in a 30% decrement in the V30-P after inhaling LTE4, there was a greater response in the asthmatic group than in the normal group of the accompanying change in the FEV1. The decrements in the FEV1 were not significantly different between the 2 groups after inhaling histamine. This study demonstrates that LTE4 is a potent bronchoconstrictor agonist in humans and suggests that airway responsiveness to this agonist differs substantially with the index of bronchoconstriction used for assessment of airway response.

Aerosols↗
PubMed1987

Chronic exposure to sulfur dioxide. Physiologic and histologic evaluation of dogs exposed to 50 or 15 ppm.

Seven adult mongrel dogs were exposed to SO2 gas at 2 different concentrations (15 and 50 ppm) on a daily basis for 5 to 11 months. Mucous hypersecretion and airway obstruction (a sustained increase in pulmonary resistance) developed in 4 dogs exposed to 50 ppm SO2. Histologic examination of the dogs' airways demonstrated epithelial thickening and an increase in size of the mucous glands. No inflammatory cell infiltration of the airways was noted and, in addition, responsiveness to inhaled histamine and methacholine did not change. The increase in lung resistance correlated with increase in mucous gland volume and airway wall thickening, but not with any change in airway responsiveness. Dogs exposed to 15 ppm SO2 showed minimal histologic and physiologic changes compared with control dogs. Previous work with a similar model of chronic bronchitis, using higher level SO2 exposure, has demonstrated an association of airway inflammation with decreased responsiveness to inhaled bronchoconstrictors. In the present study, with a lower exposure level to SO2 (50 versus 200 ppm), we found similar histologic findings associated with airway obstruction, but in the absence of airway inflammation, responsiveness to inhaled bronchoconstrictors was unchanged. This supports the theory that chronic airway inflammation may be associated with decreased responsiveness to inhaled bronchoconstrictors. This contrasts with the hyperresponsiveness induced by acute exposure to irritant gases noted by others.

Airway Resistance↗
PubMed1984

Morphologic correlation of physiologic changes caused by SO2-induced bronchitis in dogs. The role of inflammation.

Chronic bronchitis was induced in 6 mongrel dogs by exposure to SO2 gas for 6 to 18 months. All of the dogs developed cough and mucus hypersecretion. Chronic airway obstruction and decreased airway responsiveness to inhaled histamine developed in 5 of the dogs. Histologic changes in dogs evaluated after SO2 exposure included significant mucous gland hypertrophy and hyperplasia, epithelial thickening, and a decrease in the number of luminal cells containing undischarged secretory granules. Acute and chronic inflammation were found in the dogs with airway obstruction and decreased responsiveness to histamine, but such inflammation was absent in the one dog that failed to develop physiologic changes. After a period of recovery from SO2 exposure of 9 to 21 months, inflammation regressed dramatically and the other histologic changes returned toward normal. Physiologic changes regressed somewhat in those dogs that had had changes. These findings suggest that inflammation may be an important factor influencing the development of airway obstruction and altered airway responsiveness in the setting of chronic bronchitis.

Airway Resistance↗