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Biomedical subjects

R W Light

Publications and source records attributed to R W Light.

At least 109 records · Page 6Linked to original sources
PubMed1995

The effects of pentoxifylline on oxygenation, diffusion of carbon monoxide, and exercise tolerance in patients with COPD.

Pentoxifylline has been reported previously in an unblinded study to improve oxygen saturation, treadmill walk time, and resting diffusion of carbon monoxide (Dco) in patients with COPD. We recruited 12 patients with moderate to severe COPD whose exercise capacity was limited by ventilation or who developed hypoxemia with exercise. Patients were randomized to receive pentoxifylline or placebo, each for a 12-week period in a prospective, double-blind, crossover design study, to assess the effects of pentoxifylline on oxygenation, resting Dco, and exercise tolerance using arterial blood gas analysis. Eleven patients with a mean FEV1 of 0.94 L and a mean Dco of 9.85 mL/min/mm Hg completed the study. One patient withdrew from the study after developing pneumonia. There were no significant differences in resting oxygenation, resting Dco, or spirometry after 12 weeks of pentoxifylline relative to placebo. The 12-min walk test and dyspnea index for activities of daily living were also not significantly different while taking pentoxifylline. Finally, at maximal exercise, there were no differences in workload attained, exercise duration, oxygen consumption, carbon dioxide production, minute ventilation, oxygen saturation, PO2, alveolar-arterial oxygen pressure difference, or Borg score while taking pentoxifylline relative to placebo. We conclude that pentoxifylline does not improve oxygenation, resting Dco, exercise tolerance, or dyspnea in patients with moderate to severe COPD.

Carbon Monoxide↗
PubMed1995

Theophylline-ranitidine interaction in elderly COPD patients.

Most controlled studies in humans indicate that ranitidine does not alter theophylline metabolism, even at high doses. However, there have been several case reports published recently which demonstrate the development of theophylline toxicity mostly in older patients receiving stable oral doses of this drug when ranitidine was administered simultaneously. We studied eleven elderly (mean age, 69.0 +/- 6.2 years) patients with chronic obstructive pulmonary disease (COPD). During one week the patients took slow-release theophylline, 200 mg every 12 h, followed by one week intake of the same dose of theophylline plus ranitidine tablets, 150 mg every 12 h. At the end of each period, blood samples were obtained 0, 1, 2, 3, 4, 5, 6, 7, 8 and 12 h after the morning dose for the determination of serum theophylline levels. The peak theophylline concentration (Tmax) was achieved after 4.1 +/- 0.9 h while the patients were taking theophylline, and after 2.9 +/- 1.4 h with the combined regimen. This difference was statistically significant (P < 0.01). In only 3/11 subjects did Tmax remain unchanged during both phases of the study. The mean theophylline clearance rates while the patients were receiving theophylline alone (39.58 +/- 19.89 ml/min) and when they were receiving both medications (34.42 +/- 10.55 ml/min) were similar. The mean serum levels while the patients were receiving theophylline alone were slightly higher but not statistically different. These results suggest that the reported increases in serum theophylline levels in older patients receiving theophylline and ranitidine cannot be ascribed to slower theophylline metabolism in the geriatric patients with COPD who is also given ranitidine.

Age Factors↗
PubMed1995

Diseases of the pleura.

In this review, three aspects of pleural disease are discussed. Although it was thought for many years that the origin of pleural fluid was the capillaries in the parietal or visceral pleura, recent evidence suggests that in many cases the origin of pleural fluid is the interstitial space of the lung. The interstitial space of the lung appears to be the source of the pleural fluid in patients who have congestive heart failure, parapneumonic effusions, pulmonary embolism, and lung transplants. The Hantavirus pulmonary syndrome is characterized by rapidly progressive, noncardiogenic pulmonary edema in relatively young, previously healthy individuals. The mortality rate with this syndrome is approximately 60%, and at autopsy most patients have large pleural effusions. Patients after lung transplantation frequently have profuse drainage from their chest tubes because most of the fluid that enters the lung must exit through the pleural space. The incidence of pleural effusion is very high in patients who have a complication of their lung transplantation, but the pleural fluid findings in patients after lung transplantation have not been well studied. Similarly, virtually all patients who undergo liver transplantation have a right-sided pleural effusion. The effusion usually reaches its maximum size around the third postoperative day. If the effusion increases in size after this time, serious complications should be suspected. The approach to pleural diseases has been altered with the advent of videothoracoscopy. Videothoracoscopy should be considered in patients who have undiagnosed pleural effusions and are not improving; in patients who have had recurrent pneumothorax, or a spontaneous pneumothorax with a persistent airleak or unexpanded lung; or in patients who have a traumatic hemothorax with clotted blood.

Endoscopy↗
PubMed1994

Reanalysis of the 12-minute walk in patients with chronic obstructive pulmonary disease.

The purpose of this study was to determine the correlation between different intervals in the 12-min walk test, to determine which of the intervals best correlated with maximal oxygen intake (VO2max) and maximal CO2 expelled (VCO2max) and to determine the degree of correlation between changes in the VO2max and changes in the walk test and spirometry. Nine elderly (age, 67 +/- 4 years) patients with moderate COPD (FEV1, 1.32 +/- 0.28 L) who were ventilatory limited were seen 6 times over a 14-week period. At each visit they performed spirometry, a 12-min walk, and a symptom-limited maximal exercise test. During the 12-min walk the distances traversed in each 2-min interval were recorded. A Borg score was obtained at the end of each 2 min. The distances that the patients walked in each 2-min interval were very similar, but the mean Borg score became higher the longer the patient walked. The Borg score after 2 min was 1.64 +/- 1.15, while the Borg score after 12 min was 5.70 +/- 3.59. The correlation coefficients between the distance walked at various intervals and the oxygen consumption (VO2)/kg (approximately 0.65) and the VCO2/kg (approximately 0.52) were very similar. However, changes in the VO2/kg were more closely correlated with changes in the 12-min walk (r = 0.72), than with changes in the 6-min walk (r = 0.64), the 4-min walk (r = 0.59), or the 2-min walk (r = 0.53). This latter observation suggests that the 12-min walk may be preferable to tests in which the patient walks 4 or 6 min for documenting changes in the exercise capabilities.

Aged↗
PubMed1994

Significance of iatrogenic pneumothoraces.

The purpose of this study was to review the cases of iatrogenic pneumothorax that occurred between October 1983 and December 1988 at the Veterans Administration Medical Center, Long Beach, Calif, to determine the treatment and complications. During this time period, 106 patients were identified with iatrogenic pneumothorax, and the charts of 98 were available for review. There were 90 cases of spontaneous pneumothorax at this institution during the same time period. The most common cause of iatrogenic pneumothorax was transthoracic needle aspiration (35), followed by thoracentesis (30), subclavian venipuncture (23), and positive pressure ventilation (7). In 11 cases, the cause was due to miscellaneous triggers. The majority of the patients (65 of 98) were treated with chest tubes. The chest tubes were in place 4.7 +/- 3.9 days. Nine of the patients required a second chest tube. Aspiration of the pneumothorax only was attempted in five patients, and all patients subsequently received a chest tube. Two patients died from iatrogenic pneumothorax. One patient receiving positive pressure ventilation developed an unrecognized tension pneumothorax. The other patient developed a pneumothorax after thoracentesis and was treated with a chest tube, which led to a staphylococcal empyema and death. From this study, we conclude that the incidence of iatrogenic pneumothorax exceeds that of spontaneous pneumothorax and that there is substantial morbidity and some mortality from iatrogenic pneumothorax.

Aged↗
PubMed1994

Relationship between pleural effusion and pericardial involvement after myocardial revascularization.

The explanation for the high incidence of pleural effusion after cardiac surgery is unclear. There is a high incidence of left pleural effusion with inflammatory pericardial disease. We hypothesized that after coronary artery bypass grafting (CABG) there would be a higher incidence of pleural effusions in patients with pericardial involvement. We prospectively studied 47 patients undergoing elective CABG; 17 had only saphenous vein grafts (SVG group) and 30 received at least one internal mammary artery graft (IMA group) in addition to SVG. Patients had a chest radiograph, chest ultrasound, and an echocardiogram on the 7th, 14th, and 30th postoperative days. Seven days after the surgery, 42 to 47 patients (89.4 percent) had a pleural effusion and 36 (76.6 76.6 percent) pericardial involvement. No relationship was found between the presence of a pleural effusion and a pericardial effusion (p > 0.05). On the 14th postoperative day, 36 patients (76.6 percent) had a pleural effusion while 33 patients (70.2 percent) had a pericardial effusion. There was a significant relationship between the presence of a pleural effusion and a pericardial effusion (p < 0.05). On the 30th postoperative day, 27 patients (57.4 percent) had a pleural effusion and 25 (53.2 percent) had a pericardial effusion. Again, there was a significant relationship between a pleural effusion and a pericardial effusion (p < 0.05). Finally, there was no relationship between the ejection fraction and the presence of pleural effusion at any time (p > 0.05). From this study, we conclude that there is a high prevalence of both pleural and pericardial effusion postoperatively in patients undergoing CABG. Both types of effusions tend to be asymptomatic, gradually disappear, and are more common in the IMA group. Patients who have a persistent pericardial effusion are more likely to have a persistent pleural effusion.

Coronary Artery Bypass↗
PubMed1994

Subclinical surface alterations of human pleura. A scanning electron microscopic study.

Pleuritis or pleural effusion frequently develops in patients with pneumonia or heart failure. Most of these pleural changes regress without intrapleural intervention. The detailed mechanisms of the regression of the pleural changes in humans are not well documented. We studied the parietal pleura of nine patients with lung cancer and two patients with coronary artery disease by scanning electron microscopy (SEM). All patients had neither radiographic nor gross evidence of pleural disease but all had mixed surface alterations by SEM. Focal denudation of mesothelial cells was common. Deeper injuries exposed thick and thin interweaving collagen bundles. Patchy depositions of amorphous or crystallized fibrin covered normal and damaged pleural surfaces, frequently admixed with macrophages, red blood cells, and tissue debris. Reactive mesothelial cells appeared to proliferate over the fibrin. Our findings suggest that subclinical pleural alterations occur often in patients with pulmonary or cardiac diseases and that an intact pleural surface in those patients is restored mainly by the proliferation of reactive mesothelial cells.

Coronary Disease↗
PubMed1994

Comparison of the effectiveness of tetracycline and minocycline as pleural sclerosing agents in rabbits.

Parenteral tetracycline, one of the most commonly used agents for producing pleurodesis, is no longer available because of stricter regulations governing the manufacturing process. The objective of this project was to determine whether minocycline, a tetracycline derivative, is an effective sclerosant in an experimental model in rabbits. We also studied the relationship of the dose and the volume injected to the degree of pleurodesis. The following medications were instilled intrapleurally in anesthetized male rabbits: tetracycline, 35 mg/kg; or minocycline, 4, 7, 10, or 20 mg/kg, diluted to a total volume of 1 or 2 ml of bacteriostatic saline solution; or minocycline, 40 mg/kg, diluted to a total volume of 2 ml of the solution. Twenty-eight days after the instillation, the animals were killed. The pleural spaces were assessed grossly for evidence of pleurodesis and microscopically for evidence of fibrosis and inflammation. The degree of pleurodesis grossly and microscopically after the injection of 7, 10, 20, or 40 mg/kg of minocycline was comparable to that after the injection of 35 mg/kg of tetracycline, while the dose of 4 mg/kg was less effective. In the animals who received the higher doses of minocycline intrapleurally (ie > or = 20 mg/kg), there was an excess mortality both early (chi 2 = 3.61, 0.05 < p < 0.10) and late (chi 2 = 11.0, p < 0.005) which appeared to be related to the development of hemothorax. The intrapleural injection of the tetracycline derivatives was significantly (p < 0.05) more effective when the total volume of the solution was 2 ml rather than 1 ml. The present study demonstrates that minocycline is an effective agent for producing pleurodesis in the rabbit. Minocycline given intrapleurally at doses of 7 mg/kg or above is comparable to tetracycline, 35 mg/kg. Higher doses of minocycline (> or = 20 mg/kg) produce a high mortality that seems to be related to hemothorax. Since, in humans, a large experience confirms only 20 mg/kg of tetracycline is needed to produce adequate pleurodesis safely, we recommend a dose of 4 mg/kg of minocycline for the production of pleurodesis.

Animals↗
PubMed1994

Intrapleural talc for the prevention of recurrent pneumothorax.

The ipsilateral recurrence rate after the first spontaneous pneumothorax treated with tube thoracostomy is reported to be between 23 percent and 52 percent. The incidence of recurrence after the first recurrence is substantially higher. Chemical pleurodesis has been attempted to decrease the recurrence rate. Tetracycline has been widely utilized, but parenteral tetracycline is no longer available. Therefore, alternative sclerosing agents have been used. Talc has been demonstrated to be effective in preventing recurrences and it has minimal long-term effects. This prospective study was designed to determine the efficacy of talc pleurodesis in patients with recurrent spontaneous pneumothorax. Eighteen patients admitted between May 1985 and March 1993 to the Department of Thoracic Surgery underwent thoracoscopy and were treated by tube thoracostomy with chemical pleurodesis. All the patients had had at least two pneumothoraces and six had had at least six pneumothoraces. Sterile asbestos-free talc, 2g, was aerosolized throughout the pleural surface. One or two chest tubes were inserted, left clamped for 2 h, and unclamped after this time. The tubes were removed when no air had escaped for 24 h. Only one (5.6 percent) patient had recurrence of the pneumothorax, and a second insufflation of talc resulted in no new recurrence after a follow-up of 10 months. The remaining 94.4 percent did not have recurrence of pneumothorax within an observation period of 38.5 +/- 28.1 months. The follow-up was more than 2 years for 66.7 percent with no recurrence and was more than 5 years for 33.3 percent. We conclude from these observations that the insufflation of 2 g of talc into the pleural space is a safe effective treatment for control of recurrent spontaneous pneumothorax.

Adult↗
PubMed1994

Distribution of pleural injectate. Effect of volume of injectate and animal rotation.

It is controversial whether rotation is necessary for patients undergoing pleurodesis. In addition, the optimal volume of the injectate remains to be determined. The purpose of this study was to determine the importance of rotation and the volume of the agent on the intrapleural dispersion of agents injected into the pleural space of rabbits. Technetium 99m pertechnetate (99mTc) in 0.5, 1.0, or 2.0 ml of saline solution was injected into ten lightly anesthetized rabbits, half of whom were rotated for 1 min after the injection. Static images were obtained in the anterior projection 1 and 5 min after the injection. After the second scan, the limits of the lung were defined by obtaining a perfusion scan immediately after the intravenous injection of macroaggregates of 99mTc-labeled serum albumin. The degree of dispersion was significantly greater in the nonrotated groups both at 1 min (F = 8.11, p = 0.0085) and at 5 min (F = 5.89, p = 0.0274). In addition, the homogeneity of the distribution of the injectate was not improved with rotation. From this study, we conclude that rotation of the animal for 1 min after the intrapleural injection does not improve the distribution of the injectate throughout the pleural space. Furthermore, a volume of 0.5 ml is sufficient for all pleural surfaces to be exposed.

Animals↗
PubMed1994

Intrapleural talc for the prevention of recurrence in benign or undiagnosed pleural effusions.

Chemical pleurodesis has become the preferred treatment for definitive management of malignant pleural effusions. The treatment of patients with recurrent benign or undiagnosed pleural effusions, however, remains a difficult clinical problem. Tetracycline has been widely used as a sclerosing agent, but parenteral tetracycline is no longer available. Therefore, alternative sclerosing agents are needed. Talc was used for the first time in 1935, and subsequently there have been several reports documenting its effectiveness in the treatment of malignant pleural effusion and pneumothorax. The objective of this study is to present our experience with a low dose of aerosolized talc for controlling nonmalignant pleural effusions. Between May 1985 and October 1992, twenty-two patients underwent talc pleurodesis at the time of thoracoscopy for control of a nonmalignant effusion. The cause of the effusion was cirrhosis in six patients, systemic lupus erythematosus in two, chylothorax in five, and no diagnosis in nine patients. Follow-up has ranged from 18 days to 5 years. Only two patients (9 percent), one with cirrhosis and another with an undiagnosed pleural effusion, had a recurrence of the effusions. We conclude that the intrapleural administration of 2 g of aerosolized talc is an effective treatment for recurrent benign (including chylothorax) or undiagnosed pleural effusions.

Adolescent↗
PubMed1994

Arrhythmogenic effects of combined orally administered theophylline and albuterol in patients with chronic obstructive pulmonary disease.

1. Studies in asthmatic subjects have reported conflicting results about the arrhythmogenic effects of beta agonist and theophylline. The purpose of the present study was to evaluate the effects of the combination of these drugs in patients with chronic obstructive pulmonary disease (COPD). 2. Twelve COPD patients (FEV1 = 1.2 +/- 0.3 L; PaO2 = 65.7 +/- 9.0 mmHg) were evaluated by 24-h Holter monitoring on three different days. The first evaluation was done after the patient had been without any treatment for at least 24 h, the second after sustained-release theophylline for one week and the third after oral beta agonist (albuterol) and theophylline for one week. 3. Mean serum level of theophylline was 1.9, 15.6 and 11.7 micrograms/ml, and mean heart rate was 78.3, 82.0 and 84.5 beats/min for the first, second and third period, respectively. Four patients showed more than 10 premature atrial contractions/h in the baseline Holter, and this rate did not increase after either treatment. Three patients had more than 10 premature ventricular contractions/h (PVC) at baseline, with no increase while receiving theophylline or the combination of theophylline and albuterol. However, one patient did have worsening of the arrhythmia while taking both drugs. There were 5 single PVCs/h at baseline and 150 single and 9 coupled PVCs/h plus 1 episode of non-sustained ventricular tachycardia during combined therapy. 4. We conclude that the combination of theophylline and a beta agonist (albuterol) may increase the premature ventricular contraction rate and the complexity of ectopic activity in COPD patients.

Administration, Oral↗
PubMed1993

Effect of hypercapnia on the arousal response to airway occlusion during sleep in normal subjects.

The effect of an acute increase in PCO2 on the arousal response to occlusion of a mask covering the nose with the mouth sealed during non-rapid-eye-movement sleep was studied in six normal males aged 28.3 +/- 8.3 (SD) yr. Baseline occlusions, while subjects breathed a room air-O2 mixture adjusted to produce an arterial O2 saturation of 98%, were alternated with hypercapnic occlusions in which a small amount of 100% CO2 was added to increase the preocclusion end-tidal PCO2 by 3.5 +/- 0.59 Torr above the baseline value. The maximum deflections in supraglottic airway pressure (Pmax) were measured on the initial occluded breath (PmaxI) and the final breath preceding arousal (PmaxF). In the hypercapnic occlusions, the time to arousal was shorter (23.7 +/- 13.9 vs. 35.2 +/- 15.9 s, P < 0.03) and PmaxI and rate of change in Pmax were higher. However, the PmaxF in the baseline (20.2 +/- 4.1 cmH2O) and hypercapnic occlusions (20.4 +/- 4.4 cmH2O) did not differ. We conclude that an increase in PCO2 before airway occlusion shortens the time to arousal by increasing the initial occluded inspiratory effort (suction pressure) and the rate of increase in effort but does not change the arousal threshold.

Adolescent↗
PubMed1993

Effects of buspirone on anxiety levels and exercise tolerance in patients with chronic airflow obstruction and mild anxiety.

The objective of this study was to determine if buspirone would alleviate anxiety and improve exercise tolerance of anxious patients with chronic airflow obstruction (CAO). Eleven male patients with mild to moderate anxiety and CAO completed this study comparing buspirone, 10 to 20 mg given three times a day, with placebo. Patients were evaluated with State Trait Anxiety Inventory, spirometry, 12-min walk, incremental exercise on a cycle ergometer to symptom limitation and measurement of dyspnea with a modified Borg scale at exercise levels and the end of each 2 min on 12-min walk. There were no significant differences in anxiety scores, work load, maximum oxygen consumption per minute, maximum expired volume per minute, PETCO2, PETO2, 12-min walking distance or dyspnea scores after 6 weeks of buspirone or placebo therapy. We conclude that administration of buspirone has no significant effect on anxiety levels, exercise capabilities or PETO2 or PETCO2 in patients with CAO and mild anxiety.

Aged↗
PubMed1993

Does the hypoxic ventilatory response predict the oxygen-induced falls in ventilation in COPD?

The purpose of this study was to determine whether supplemental oxygen-induced decreases in ventilation (VE) and mouth occlusion pressure (P0.1) in patients with COPD are related to the ventilatory or P0.1 responses to hypoxia (delta VE/delta SaO2, delta P0.1/delta SaO2). We measured these responses in 14 patients with a (mean +/- SD) FEV1 of 0.95 +/- .41 L. The VE and P0.1 were also measured while the patients sequentially breathed either room air or supplemental oxygen (1-2 L/min) for 10 min in a randomized single blind fashion. The mean (+/- SEM) SaO2 increased from 90.8 +/- 0.99 percent to 95.2 +/- 0.46 percent and the VE decreased during oxygen breathing from 12.3 +/- 0.46 to 11.6 +/- 0.47 L/min (p < 0.03). However, the individual changes in VE were not significantly related to the corresponding changes in SaO2 (CHG SaO2), (delta VE/delta SaO2), or (delta VE/SaO2) (CHG SaO2). Similarly, the P0.1 decreased from 2.50 +/- 0.27 to 2.26 +/- 0.20 cm H2O (p < 0.05), but the individual changes in P0.1 were not significantly related to (CHG SaO2), (delta P0.1/delta SaO2), or (delta PO.1/delta SaO2) (CHG SaO2).

Aged↗
PubMed1993

Effects of nebulized morphine sulfate on the exercise tolerance of the ventilatory limited COPD patient.

We have shown previously that the administration of morphine (0.8 mg/kg) to patients with COPD increases the VO2max by 19.3 percent. A recent study demonstrated that the administration of low-dose nebulized morphine (approximately 2 mg) increased the endurance time of patients with severe lung disease by 1 min (35 percent) with few systemic side effects. This double-blind crossover study evaluated the effects of various doses of nebulized morphine (0, 1, 4, and 10 mg) on the exercise tolerance and the psychologic status of COPD patients. In the present study, eight COPD patients (FEV1 = 0.90 +/- 0.26 L, workload max = 76 +/- 29 W, VO2max = 950 +/- 264 ml, VEmax = 34 +/- 7 L), who were ventilatory limited were tested on four separate days. On each testing day, the patients underwent incremental exercise testing and psychologic testing before and 45 min after receiving the nebulized solution. The mean changes (+/- SD) in the exercise test results after each of the four different regimens were as follows: [table: see text] Although there tended to be larger increases in the workload, VO2max, and VEmax after the largest dose of morphine, none of the changes was statistically significant. Likewise, there were no significant differences in spirometry, resting metabolic measurements, or psychologic test scores after the four different regimens. We conclude that aerosolized morphine in the doses used in this study has no significant beneficial effect on the exercise tolerance of patients with COPD.

Aerosols↗