Search PubMed⌕ Search

Biomedical subjects

R W Light

Publications and source records attributed to R W Light.

At least 181 records · Page 10Linked to original sources
PubMed1985

The use of labetalol for the treatment of hypertension in patients with reversible airway obstruction.

Beta-adrenergic blocking agents are commonly used for the management of hypertension, cardiac arrhythmias, and angina pectoris; several of these agents are now available for clinical use (1-5). A significant side effect of these agents in patients experiencing reversible airway obstruction is that they block the effects of beta-adrenergic agonists and can precipitate or worsen bronchospasm (6-8). Labetalol, a new adrenergic antagonist with both alpha- and beta-adrenergic blocking effects, has been shown to have certain advantages for the management of hypertension and is widely used for this purpose in many countries (9). To evaluate its effects on airway resistance in patients with obstructive lung disease, the authors conducted two separate clinical studies. This article summarizes the results of these trials.

Airway Resistance↗
PubMed1985

Exudative pleural effusions secondary to gastrointestinal diseases.

Several different diseases of the gastrointestinal tract may have an associated exudative pleural effusion. In the acutely ill patient with a pleural effusion, the possibility of esophageal perforation should always be considered. It is important to establish this diagnosis as soon as possible since the mortality rate increases markedly if drainage of the mediastinum is delayed for even 12 or 24 hours. The best screening test for esophageal rupture is the level of amylase in the pleural fluid. All patients with undiagnosed exudative pleural effusions should have the amylase level in their pleural fluid measured to rule out a pancreatic etiology for their pleural effusion. In patients with acute pancreatitis, the clinical presentation may be dominated by chest symptoms. Such patients have small to moderately sized pleural effusions that resolve rapidly once appropriate therapy is instituted. If symptoms persist, the possibility of a pancreatic abscess or a pancreatic pseudocyst should be considered. Patients with pancreatic pseudocysts may develop a sinus tract between the pseudocyst and the pleural space. In this situation a large pleural effusion develops. Frequently there are no abdominal symptoms and the diagnosis will not be made unless a pleural fluid amylase is obtained. Patients with exudative pleural effusions that contain predominantly polymorphonuclear leukocytes should be suspected of having an intra-abdominal abscess, particularly when there is no associated parenchymal infiltrate. Subphrenic, intrahepatic, and splenic abscesses all have a high incidence of accompanying pleural effusion. Abdominal CT scanning is the method of choice to establish each of these diagnoses.

Abdomen↗
PubMed1985

Chylothorax and pseudochylothorax.

Both chylothorax and pseudochylothorax are characterized by milky or turbid pleural effusions. The importance of distinguishing these two conditions cannot be overemphasized because the prognosis and management are different.

Adult↗
PubMed1985

Parapneumonic effusions and empyema.

Nearly 50 per cent of patients with acute bacterial pneumonia have an accompanying pleural effusion (parapneumonic effusion). With appropriate antibiotic therapy, the pleural effusion will resolve along with the pneumonia in the majority of patients. However, in a small fraction, the pleural effusion will not resolve unless drainage of the pleural space is instituted. Such patients are said to have complicated parapneumonic effusions. It is important to identify patients with complicated parapneumonic effusions as early as possible, since tube drainage of the pleural space becomes increasingly difficult the longer its institution is delayed. The possibility of a complicated parapneumonic effusion should be considered in every patient with bacterial pneumonia. If both diaphragms cannot be distinctly identified throughout their length on the lateral chest radiograph, decubitus chest radiographs should be obtained. If the thickness of the fluid on the decubitus radiograph is greater than 10 mm, a diagnostic thoracentesis should be performed. Only pleural fluid analysis can identify patients with complicated parapneumonic effusions. Complicated parapneumonic effusions are characterized by low pleural fluid pH and glucose levels, a high pleural fluid LDH, and a positive Gram stain of the pleural fluid. Tube thoracostomy should be performed immediately in a patient with an acute bacterial pneumonia if the pleural fluid glucose is below 40 mg per 100 ml, the pleural fluid pH is below 7.00, or if the Gram stain of the pleural fluid is positive. Patients with pleural fluid pH above 7.20, pleural fluid LDH below 1000 IU per L, and pleural fluid glucose levels above 40 mg per 100 ml respond well to only the administration of appropriate antibiotics.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-Bacterial Agents↗
PubMed1985

Pleural effusion associated with pulmonary embolization.

Pulmonary embolization should be considered as a possible cause of any pleural effusion of unknown etiology. This disorder may be the one that is most commonly overlooked in the work-up of patients with pleural effusions. Although para-embolic effusions have classically been considered to be bloody exudates with a predominance of polymorphonuclear leukocytes, many such effusions have none of these characteristics. Up to 25 per cent may be transudates and the RBC count exceeds 100,000 per mm3 in fewer than 20 per cent of such effusions. The WBC may range from less than 100 to more than 50,000 cells per mm3. Characteristics of these effusions are so variable that no diagnostic patterns can be said to occur. Paraembolic effusions usually begin to resolve within a few days after institution of anticoagulant therapy, although those that are associated with parenchymal infiltrates may resolve more slowly. Unless complications occur (which are rare), pulmonary embolism with associated pleural effusion is treated no differently than is pulmonary embolism without effusion.

Anticoagulants↗
PubMed1984

Exercise performance with added dead space in chronic airflow obstruction.

Individuals with chronic airflow obstruction (CAO) are thought to have limited exercise tolerance primarily because of impaired ventilatory mechanics. We studied the effects of added external dead space (DS) on exercise capacity [maximum O2 consumption (VO2max)], maximum exercise ventilation (VEmax), and blood gases (arterial PO2, PCO2, pH) in 22 patients with CAO [forced expired volume at 1 s (FEV1) = 0.96 +/- 0.41 liter]. Maximum exercise testing (Emax) was performed by incremental cycle ergometry. Patients exercised at base line (BL) and with DS (0.25 liter if FEV1 less than 0.8, and 0.50 liter if FEV1 greater than 0.8 liter), in random-order single-blind fashion. DS resulted in a 12.2% increase in VEmax (P less than 0.001); tidal volume increased (P less than 0.025) while respiratory frequency was unchanged. The VO2max and maximum CO2 production decreased (P less than 0.001) with DS. Arterial PCO2 at rest and at exhaustion increased with DS (P less than 0.001). The pH and arterial PO2 showed small declines at rest and at Emax. Thus, at the lower maximum work load achieved with DS, the patients ventilated more and tolerated a higher arterial PCO2 and a lower arterial PO2 and pH before stopping from dyspnea as compared with the BL exercise run. In contrast, the VO2max of nine normal control subjects was unaffected by the addition of DS. Although VEmax can be increased in CAO patients with DS, this increase is not sufficient to prevent further CO2 retention or a decrease in exercise capacity. We conclude that exercise performance is limited primarily by impaired ventilatory mechanics in CAO.

Aged↗
PubMed1984

Hemodynamics of patients with severe chronic obstructive pulmonary disease during progressive upright exercise.

This study evaluated the relationship between the oxygen consumption (VO2) and cardiac output and heart rate during progressive exercise in the upright position in 26 patients with severe chronic obstructive pulmonary disease. Forced expiratory volume in one second (FEV1) was 0.82 +/- 0.21 L, and single-breath carbon monoxide diffusing capacity was 39 +/- 20% predicted. Cardiac outputs were measured by the direct Fick method. The patients as a group had a normal cardiac output for the level of VO2. The mean pulmonary artery pressure in our patients (22.5 +/- 10.1 mmHg) was increased at rest; during exercise, it increased abnormally to 45.5 +/- 18.9 mmHg. The heart rates were increased both at rest and during exercise, and the increase in heart rate for an increase in VO2 was higher than normal. The relative tachycardia observed was probably related to a combination of abnormal arterial blood gases, concomitant bronchodilator administration, deconditioning, and right ventricular dysfunction. The relative tachycardia did not appear to have an adverse effect on exercise tolerance because the ratio of maximal exercise ventilation to the FEV1 exceeded 35 in those patients with observed maximal heart rates above 90% of predicted. The results of this study suggest that improvements in the exercise tolerance of these patients is dependent upon improving their ventilatory capabilities or the efficacy of their ventilation.

Aged↗
PubMed1984

Effects of digoxin on exercise capacity and right ventricular function during exercise in chronic airflow obstruction.

We evaluated 12 patients with stable chronic airflow obstruction (CAO) and no clinical evidence of left ventricular disease to determine the effects of oral digoxin on exercise capacity (VO2 max) and on right ventricular pump function during exercise. In this randomized, double blind, placebo controlled, cross-over study, patients performed exercise tests and underwent measurement of ejection fractions after two weeks of therapy with oral digoxin (0.25 mg/day) and after two weeks of placebo. Incremental upright exercise testing to a symptom-limited maximum was performed on a cycle ergometer. Right and left ventricular ejection fractions (RVEF, LVEF) were obtained in the supine position at rest and at approximately 75 percent of the maximum workload by gated equilibrium radionuclide angiography. All patients had abnormal right ventricular function, manifested either by a low resting RVEF (less than 45 percent) or a subnormal response to exercise (less than 5 percent increase). The small increases in RVEF with digoxin (mean +/- SE) at rest (44 +/- 5 vs 41 +/- 4 percent) and during exercise (46 +/- 4 vs 44 +/- 3 percent) did not achieve statistical significance. With digoxin, small increases in exercise duration (10.0 +/- 1.5 vs 9.0 +/- 1.4 min), maximum workload achieved (48 +/- 6 vs 42 +/- 5 W), VO2 max (0.85 +/- 0.06 vs 0.81 +/- 0.06 L/min), and oxygen-pulse (O2-P) (6.6 +/- 0.5 vs 6.3 +/- 0.4 ml/beat) occurred. Only the increase in O2-P was significant (p less than 0.05). From this study we conclude that digoxin does not significantly improve exercise capacity in severe chronic airflow obstruction with impaired right ventricular function, nor does it improve RVEF either at rest or during supine submaximal exercise.

Digoxin↗
PubMed1984

Treatment of chronic obstructive pulmonary disease with corticosteroids. Comparison of daily vs alternate-day therapy.

We compared the efficacy of corticosteroid therapy initiated as an alternate-day regimen to that of a four-times-daily regimen in patients with stable chronic obstructive pulmonary disease. In this double-blind study, 44 patients with moderate to severe COPD (mean FEV1 740 +/- 310 ml) were hospitalized and randomly allocated to receive methylprednisolone, 8 mg qid, 64 mg qod, or placebo for a ten-day period. The mean FEV1 and FVC improved significantly to a comparable degree in both steroid-treated groups, but not in the placebo-treated group. Eight of the 29 steroid-treated patients (28 percent) had improved FEV1 of more than 25 percent compared with only one of the 15 placebo-treated patients. Those in the qod group also had notable improvement in SaO2. Although the correlation between the improvement after the administration of nebulized bronchodilators and that after corticosteroid therapy was significant, some patients had more than a 25 percent improvement in their FEV1 with corticosteroids, but less than a 10 percent improvement after nebulized bronchodilators. We conclude that a substantial proportion of all patients with stable COPD will have a greater than 25 percent improvement in their flow rates with corticosteroid administration. Since the response to a qod regimen is comparable to that of a qid regimen, and since the qod regimen is associated with fewer side effects, we recommend that a qod regimen be tried initially.

Adrenal Cortex Hormones↗
PubMed1984

Specificity of immunosuppression by human alveolar cells.

To study their effect on T- and B-lymphocyte functions, we obtained human alveolar cells, predominantly macrophages, by bronchoalveolar lavage. The cellular target of suppression by alveolar cells of lymphoproliferation was defined by cell separation techniques. THe results indicate a direct effect on T cells by alveolar cells via a soluble mediator released from alveolar cells. In contrast to the profound suppression of mitogen-induced T-cell proliferation, no significant suppression by equivalent numbers of alveolar cells was observed in assays of B-lymphocyte function or in the interactions of helper and suppressor T cells with B lymphocytes. These observations are consistent with an immunoregulatory role for alveolar cells, most likely alveolar macrophages: inhibiting cell-mediated immune responses and delayed hypersensitivity in the lung, while favoring antibody responses.

B-Lymphocytes↗
PubMed1983

Comparison of the effects of labetalol and hydrochlorothiazide on the ventilatory function of hypertensive patients with mild chronic obstructive pulmonary disease.

Labetalol is a new adrenergic antagonist with both alpha- and beta-blocking effects. The effects of labetalol and hydrochlorothiazide on the hypertension and ventilatory function of patients with both hypertension and mild reversible chronic pulmonary disease were compared. In this double-blind study, 20 patients were randomly allocated to receive increasing doses of labetalol (100 to 400 mg three times a day) or hydrochlorothiazide (25 to 50 mg three times a day) over a four-week treatment period. Patients returned at weekly intervals for spirometry baseline, two hours after receiving the medication for the following week, and five minutes after an exercise test. Each treatment reduced the blood pressure significantly and to a comparable degree. There was no significant decrease in ventilatory function two hours after administration of the drug at any visit for either drug. Ventilatory function did not deteriorate significantly following exercise with either drug. With labetalol there was a progressive statistically significant decline in baseline forced expiratory volume in one second from 1,860 +/- 190 ml to 1,685 +/- 190 ml during the four-week study period, although no patient became symptomatic from shortness of breath. We conclude that labetalol is an effective antihypertensive agent that does not adversely effect ventilatory function immediately, but that may lead to a decline in ventilatory function when administered long-term.

Aged↗
PubMed1983

Improved exercise tolerance of the polycythemic lung patient following phlebotomy.

The present study evaluated the effects of therapeutic phlebotomy on the exercise tolerance and the maximal carbon dioxide output of polycythemic patients with chronic obstructive pulmonary disease. Fifteen maximal exercise studies were performed before and after phlebotomy in patients with moderate to severe chronic obstructive pulmonary disease (mean forced expiratory volume in one second [FEV1]= 970 ml). After phlebotomy there were no significant differences in pulmonary function, blood gases, oxygen consumption, or carbon dioxide production at rest. However, after phlebotomy there was a significant increase in the exercise tolerance of the patients. The mean workload, the duration of exercise, the maximal oxygen consumption, the maximal carbon dioxide production, and the ventilation at maximal exercise all increased significantly. The improved exercise tolerance after phlebotomy appeared due to an increased cardiac output generated mainly through an increased stroke volume. We hypothesize that the increased stroke volume was due to a higher ejection fraction of the right ventricle secondary to a lower pulmonary artery pressure. This study provides further evidence that patients with chronic obstructive pulmonary disease who have polycythemia benefit by therapeutic interventions that maintain their hematocrits below 55 percent.

Aged↗
PubMed1983

Effects of verapamil on pulmonary haemodynamics during hypoxaemia, at rest, and during exercise in patients with chronic obstructive pulmonary disease.

The haemodynamic effects of intravenous verapamil at rest, during hypoxaemia, and during progressive exercise were evaluated in 10 patients with chronic obstructive lung disease. Verapamil produced significant decreases in the peak heart rate and systemic blood pressure during exercise but exercise capacity and pulmonary gas exchange at exhaustion were unaffected. There were no significant changes in pulmonary artery pressure or total pulmonary vascular resistance during exercise or during the breathing of either air or a hypoxic gas mixture at rest. No clinically useful benefit was found with verapamil in the dosage used in this group of patients and the value of calcium antagonists in the treatment of patients with chronic obstructive lung disease requires further clarification.

Aged↗
PubMed1983

Effect of ethanol and naloxone on control of ventilation and load perception.

The respiratory depressant effects of ethanol and their potential reversibility by naloxone were studied in 10 normal subjects. Ventilatory and mouth occlusion pressure (P0.1) responses to hypercapnia and hypoxia without and with an inspiratory resistive load (13 cmH2O X 1(-1) X S) were measured. The resistive load detected with 50% probability (delta R50) and the exponent (n) in Stevens' psychophysical law for magnitude estimation of resistive loads were studied using standard psychophysical techniques. Each of these studies was performed before ethanol ingestion, after ethanol ingestion (1.5 ml/kg, by mouth), and then again after naloxone (0.8 mg iv). Ethanol increased delta R50 (P less than 0.05) and decreased n (P less than 0.05). Naloxone caused no further change in these parameters. The load compensation (Lc), defined as the ratio of loaded to unloaded response slopes, was not significantly changed after ethanol and naloxone. No correlation was found between the Lc and delta R50 or n. The ventilatory and P0.1 responses to hypercapnia and hypoxia with and without inspiratory resistive loading decreased after ethanol (P less than 0.05, hypercapnia; NS, hypoxia). After naloxone the hypercapnic ventilatory responses increased (P less than 0.05). This suggests that the respiratory depressant effects of ethanol may be mediated via endorphins.

Adult↗
PubMed1983

Increased serum theophylline clearance with orally administered activated charcoal.

The purpose of this study was to determine whether the oral administration of activated charcoal would increase the clearance of theophylline. Seven normal subjects received aminophylline intravenously (8 mg/kg) on 2 separate days. On Day 1 at 2-h intervals starting immediately after the completion of the aminophylline infusion, subjects ingested 4 doses of a slurry of activated charcoal (30 g each). On Day 2 they received no charcoal. The order of the days the subjects received charcoal or no charcoal was randomized. Plasma theophylline levels were determined by an enzyme immunoassay (Syva) every 2 h after the completion of the intravenous infusion. The theophylline half-life was reduced with charcoal from 10.2 to 4.6 h (p less than 0.001), and clearance increased from 35.6 to 72.6 ml/kg/h (p less than 0.001). In a patient with an initial serum theophylline concentration of 31.0 micrograms/ml and signs of toxicity (arrhythmias and seizures), the administration of charcoal (4 doses of 30 g every 2 h) reduced the half-life from 34.4 to 5.7 h concomitant with rapid resolution of signs of toxicity. We conclude that orally administered activated charcoal significantly enhances the clearance of theophylline and offers a new therapeutic modality in the treatment of theophylline toxicity.

Administration, Oral↗
PubMed1983

Naloxone reverses ethanol-induced depression of hypercapnic drive.

Ethanol depresses the ventilatory responses to hypercapnia and hypoxia. We hypothesized that this ventilatory depression, like some other central nervous system effects of ethanol, might be mediated via endorphins. In a double-blind placebo-controlled study, we assessed the effect of the opiate antagonist naloxone on ventilatory responses during ethanol intoxication in 18 normal men. Standard rebreathing studies were done at baseline, after ethanol (1.5 ml/kg, p.o.), and after each of 2 intravenously administered injections. One of the injection sequences PP, NP, or PN (N = naloxone, 0.8 mg; P = placebo, 2 ml) was randomly assigned to each subject. The ventilatory responses were reduced after ethanol administration compared with those at baseline (p less than 0.05). In groups NP and PN, naloxone restored the hypercapnic response (p less than 0.05). Placebo injection did not significantly alter the response slopes. Hypoxic ventilatory responses showed the same trends but did not reach statistical significance. This study shows that naloxone reverses ethanol-induced depression of hypercapnic drive, suggesting that an opiate-mediated mechanism is responsible for this depression.

Adult↗
PubMed1983

Prevention of suctioning-related arterial oxygen desaturation. Comparison of off-ventilator and on-ventilator suctioning.

The purpose of this study was to determine the frequency and severity of arterial oxygen desaturation during and after endotracheal suctioning in a group of ventilator-dependent patients with acute respiratory failure (the majority of whom had underlying obstructive lung disease) and to evaluate the efficacy of several maneuvers designed to minimize desaturation. The adaptor method presented obviates both removal from and reconnection to the ventilator during suctioning, as well as the need to alter ventilator settings. It is concluded that on-ventilator adaptor suctioning is a simple and effective measure for minimizing suctioning-related arterial oxygen desaturation.

Arteries↗