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Biomedical subjects

R W Light

Publications and source records attributed to R W Light.

At least 163 records · Page 9Linked to original sources
PubMed1989

Nebulizer vs spacer for bronchodilator delivery in patients hospitalized for acute exacerbations of COPD.

This double-blind crossover study compared the efficacy of two methods of delivery (MDI-spacer and nebulizer) of inhaled albuterol to patients hospitalized for an acute exacerbation of COPD. Within 24 h of admission, 20 subjects (mean age, 69 years) with severe airflow obstruction (mean FEV, 0.69 L) were subjected to a treatment with an MDI-spacer (0.36 mg of albuterol or placebo) followed by treatment with a nebulizer (2.5 mg of albuterol or placebo). Active drug was given by only one device (randomly assigned in a double-blind manner), and the entire sequence was repeated in 4 h, with active drug given in the alternate device. Spirometric data and the Borg dyspnea score were obtained before and 1 h after each sequence of treatments. Treatment resulted in significant improvements in the FEV1, FVC, and Borg score. The percent improvement in the FEV1 was slightly larger after treatment with the nebulizer (16.7 percent vs 13.4 percent). Improvements in the Borg score were slightly larger after treatment with the MDI-spacer (-1.08 vs -0.73). However, these differences were not statistically significant. This study suggests that the MDI-spacer system is an effective method of sympathomimetic delivery in this setting, provided patients are able to master the technique.

Administration, Inhalation↗
PubMed1988

Antibodies to mycobacterial peptidoglycolipid and to crude protein antigens in sera from different categories of human subjects.

Sera from patients with disease caused by the Mycobacterium avium complex (M. avium and M. intracellulare), M. kansasii, or M. tuberculosis and from subjects who did not have a mycobacterial disease were tested by enzyme-linked immunosorbent assay against peptidoglycolipid antigens representing each of the 15 most common serovars of the M. avium complex and against crude protein antigen extracts of M. avium and M. tuberculosis. The highly specific peptidoglycolipid antigens yielded positive reactions in 83% of M. avium complex patients, 57% of active-tuberculosis patients, and 14% of subjects without mycobacterial disease. Reactions to more than 1 of the 15 peptidoglycolipid antigens were found only in patients with infections caused by mycobacteria, suggesting that a mycobacterial pulmonary lesion is readily colonized by mycobacteria other than the one that initiated the lesion. The two crude mycobacterial protein antigens were highly cross-reactive, with little if any capacity to discriminate between infections caused by any of the mycobacteria studied. Moreover, they did not appear to be more sensitive than the peptidoglycolipids. The data suggest that it is unlikely that a practical and reliable serological test can be developed that will distinguish between transient subclinical infection and significant disease caused by common environmental mycobacteria, such as members of the M. avium complex. Success in developing such a test for nonenvironmental mycobacteria, such as M. tuberculosis, appears more likely.

Antibodies, Bacterial↗
PubMed1988

Indomethacin and perception of dyspnea in chronic airflow obstruction.

A recent study showed that indomethacin reduces the perception of dyspnea during submaximal exercise in normal subjects (1). The purpose of this study was to determine whether indomethacin alters the perception of dyspnea in patients with chronic airflow obstruction during exercise. In a randomized double-blind crossover fashion, 11 subjects (FEV1 = 0.97 +/- 0.58 L) performed an incremental (15 W/min) cycle ergometer exercise test to exhaustion on 2 study days. Testing was performed 3 to 4 h after placebo or 50 mg of indomethacin. Perception of dyspnea was measured using the modified Borg scale. Minute ventilation, workload, and Borg scale measurements at exhaustion and during moderate exercise were determined. The data demonstrated no statistically significant differences between values obtained for minute ventilation, workload, or Borg scale measurements on placebo and indomethacin study days. Contrary to the previous findings in normal subjects, indomethacin failed to significantly alter perceived dyspnea during exercise in patients with chronic airflow limitation. This suggests that prostanoids do not play a major role in the perception of dyspnea in these patients during exercise.

Double-Blind Method↗
PubMed1988

Work of breathing and airway occlusion pressure during assist-mode mechanical ventilation.

We determined the effect of varying ventilator tidal volume (VT) and inspiratory flow (V) on the inspiratory muscle work (WI) during assist-mode mechanical ventilation (AMV) in four healthy subjects. In another four subjects, under constant chemoreceptor input, we determined the responses of neuromuscular output as assessed by the mouth occlusion pressure (P0.1) to alteration in WI. During AMV, the inspiratory external work of breathing is partitioned between WI and ventilator work. With a constant ventilator trigger sensitivity, we calculated WI (joules/L of volume) as the difference between the area subtended by the airway pressure-inspiratory volume curves and the ordinate of the assisted breaths subtracted from that of the controlled breaths at ventilator V of 40, 60 and 80 L/min and ventilator VT of 100, 125 and 150 percent spontaneous breathing VT. At all ventilator settings, WI was less than inspiratory muscle work of spontaneous breathing (SB) and was a function of both ventilator VT and V (p less than 0.05), but ventilator V has more effect on WI. Under isocapnia and hyperoxia, we measured P0.1 and WI during AMV at ventilator VT of 125 percent of spontaneous breathing VT and ventilator V of 60, 80 and 100 L/min. End-expiratory lung volume remained constant. P0.1 during AMV was similar to that of the SB. Although WI decreased with increasing ventilator V, P0.1 did not decrease significantly. We conclude that during AMV, both ventilator V and to a less extent ventilator VT determine W. In healthy subjects changes in WI do not affect P0.1.

Airway Resistance↗
PubMed1988

Etiology of carbon dioxide retention at rest and during exercise in chronic airflow obstruction.

The purpose of this project was to better define factors that influence the resting PaCO2 and the change in the PaCO2 from rest to exercise in patients with moderate to severe chronic airflow obstruction. Pulmonary function testing, symptom-limited exercise tests using arterial catheter lines, and resting ventilatory and mouth occlusion pressure responses to hypercapnia and hypoxia were obtained in 19 patients (mean FEV1 = 1.07 +/- .50 L). The resting PaCO2 was closely related to the resting hypercapnic response. The highest correlation coefficient was between the PaCO2 and the ventilation at PCO2 = 60 obtained from the resting hypercapnic response (r = -0.74, p less than 0.001). A higher PaCO2 also tended to occur in patients with a lower FEV1 and a lower PaO2. The resting PaCO2 was not correlated significantly with the VT or the VD/VT. The change in the PaCO2 from rest to exercise was not significantly related to any measure of resting hypercapnic or hypoxic response, but rather was most dependent on the ventilatory response to exercise (delta VE/delta VCO2). Patients with a lower FEV1 or smaller decreases in the PaO2 with exercise tended to have larger increases in PaCO2 with exercise. The delta VE/delta VCO2 was higher in those with a high FEV1, a low resting PaCO2, and a low resting SaO2.

Carbon Dioxide↗
PubMed1987

Massive pulmonary embolism complicating streptokinase treatment for deep vein thrombosis.

A fatal massive pulmonary embolus developed in a patient treated with streptokinase for acute deep vein thrombosis. This fatal complication occurred despite a careful selection of the patient and the presence of a lytic state. Embolization of a fragmented thrombus or/and attenuation of the lytic state leading to fresh embolization is/are the possible mechanism(s). Although rare, massive pulmonary embolus must be considered to be a major risk of thrombolytic therapy for deep venous thrombosis.

Humans↗
PubMed1987

Airway occlusion pressure. An important indicator for successful weaning in patients with chronic obstructive pulmonary disease.

The objective of this study was to determine whether airway occlusion pressure (P0.1) is a useful predictor for successful weaning during discontinuation of assisted ventilation (AV) in patients with chronic obstructive pulmonary disease (COPD). We studied 12 patients with COPD receiving AV with maximal inspiratory pressure (MIP) less than or equal to -20 cm H2O and FVC greater than or equal to 10 ml/kg. The P0.1, VT, frequency, mean inspiratory flow rate (VT/TI), inspiratory time to total breath cycle duration (TI/Ttot), and arterial blood gases were determined just prior to weaning, within 5 min after discontinuing AV (Time 0), and at 30, 60, 90, 120, 180, and 240 min. Five of the 12 patients failed to wean, defined as requiring AV within 24 h after discontinuing AV. At Time 0, all patients who subsequently failed to wean had a P0.1 of greater than 6 cm H2O, and those who were successfully weaned had a P0.1 of less than 6 cm H2O (p less than 0.001), although the arterial blood gas determinations were comparable in both groups. Throughout the study period, P0.1 in the patients who failed to wean was persistently higher than in the successfully weaned patients. Despite the high P0.1, VT and VT/TI decreased significantly at the termination of the study compared with those at Time 0 in 3 of the patients who failed to wean. Tachypnea was not useful in predicting failure to wean. The TI/Ttot in the patients who failed to wean was persistently lower than in the successfully weaned patients. We conclude that P0.1 is an important indicator for successful weaning.

Aged↗
PubMed1986

The relationship between pleural pressures and changes in pulmonary function after therapeutic thoracentesis.

The purpose of this study was to determine whether changes in pulmonary function after therapeutic thoracentesis are related to the pleural pressure or to changes in pleural pressure during thoracentesis. Spirometry was obtained before and 24 h after thoracentesis in 26 patients. Pleural pressures were measured with a U-shaped manometer initially and after each 400-ml aliquot of pleural fluid was removed. Thoracentesis was continued until the patient developed severe symptoms (chest pain or coughing), the pleural pressure dropped below -20 cm H2O, or no more fluid could be obtained. The mean vital capacity improved 410 +/- 390 ml in this group of patients who had 1,740 +/- 900 ml fluid removed. The improvement in the VC most closely correlated with the pleural pressure after 800 ml fluid had been withdrawn (r = 0.57, p less than 0.005). The ratio of the improvement in the VC to the amount of fluid removed most closely correlated with the pressure change after 800 ml fluid had been removed (r = -0.43, p less than 0.05). From this study we conclude that the improvement in the FVC after therapeutic thoracentesis is small relative to the amount of fluid withdrawn. Patients with higher pleural pressures after the removal of 800 ml pleural fluid and patients with smaller decreases in the pleural pressure after removal of 800 ml pleural fluid have greater improvements in their pulmonary functions after thoracentesis.

Drainage↗
PubMed1986

Cardiopulmonary responses to exercise in chronic airflow obstruction. Effects of inhaled atropine sulfate.

The purpose of this study was to evaluate the effects of inhaled atropine sulfate on the exercise capacity and cardiopulmonary responses to exercise in patients with chronic airflow obstruction (CAO). Eighteen patients underwent duplicate incremental (15 watts/min) maximal cycle ergometer exercise tests 60 minutes after either inhaled atropine (0.075 mg/kg) or placebo, in double blind randomized fashion on consecutive days. Bronchodilator medications were withheld before each study. Spirograms were obtained before and 60 minutes after each aerosol treatment. Atropine increased the FEV1 by 25 percent, from 1.37 +/- 0.49 to 1.71 +/- 0.52 L (p less than 0.001), as compared to placebo. Although the ventilation at exhaustion (VEmax) increased significantly (from 52.3 +/- 11.5 to 55.9 +/- 10.0 L/min, P less than 0.05) after atropine, the increase in the mean maximum work load (95 +/- 28 vs 101 +/- 19 watts) did not achieve significance. The drug resulted in a significant decrease in oxygen consumption at all equivalent workloads greater than "0" watts (unloaded cycling), presumably because the improvement in airway mechanics decreased the oxygen cost of ventilation. Atropine-induced increases in FEV1 did not result in a significant group mean increase in maximum exercise capacity, but the drug did result in a lower oxygen cost of performing work in patients with CAO.

Aged↗
PubMed1986

Optimal dose of fenoterol by metered-dose inhaler in asthmatic adults.

Three doses of fenoterol were administered by metered-dose inhaler to 20 adult subjects with asthma in order to determine the optimal dose for routine administration. Inhaled doses of 100 micrograms, 200 micrograms, and 400 micrograms of fenoterol with isoproterenol and placebo controls were administered in a randomized double-blind crossover regimen. We found that 200 micrograms of fenoterol by metered-dose inhaler produced a longer duration of action, greater peak response, and greater overall time-weighted responses in the forced expiratory volume in one second, in the mean forced expiratory flow during the middle half of the forced vital capacity, and in airway resistance than did the other drug regimens. The 400 micrograms dose of fenoterol produced no increase in response over that seen after the 200 micrograms dose. Side effects were minimal and no greater than with isoproterenol.

Administration, Intranasal↗
PubMed1986

Doxepin treatment of depressed patients with chronic obstructive pulmonary disease.

During each of two six-week treatment periods, 12 depressed outpatients with chronic obstructive pulmonary disease received increasing doses of doxepin hydrochloride or a placebo as tolerated. The mean maximal doses of doxepin hydrochloride and placebo were 105 and 128 mg, respectively. Three of the 12 patients dropped out because of doxepin's side effects. The depression and anxiety scores at the end of the treatment periods were virtually identical and not significantly different from baseline scores. Changes in the 12-minute walking distance were more closely correlated with changes in the depression and anxiety scores than with changes in the forced expiratory volume in 1 s or forced vital capacity. Thus, doxepin is ineffective in treating depressed patients with chronic obstructive pulmonary disease; improvements in the 12-minute walking distance were closely correlated with improvements in the depression or anxiety scores.

Aged↗
PubMed1985

Effect of desipramine on control of ventilation and depression scores in patients with severe chronic obstructive pulmonary disease.

Decreased ventilatory responses to carbon dioxide (CO2) correlate with elevated scores on tests for depression in normal subjects and with episodes of endogenous depression in psychiatric patients. Patients with severe chronic obstructive pulmonary disease (COPD) frequently develop resting hypercapnia due to impaired ventilatory mechanics or drive, and may also have elevated scores on tests for depression. Tricyclic antidepressant drugs can improve ventilatory mechanics and possibly drive. We hypothesized that antidepressant drugs might enhance ventilatory drive and improve arterial blood gases in patients with severe COPD and that these improvements might correlate with improvement in depression scores. Therefore, we studied the effects of desipramine versus placebo on spirometry, resting arterial blood gases, hypercapnic ventilatory and mouth occlusion pressure responses, and scores on the Beck and Zung self-rated depression scales. In our patients the resting arterial CO2 (PaCO2) was found to depend almost equally on ventilatory mechanics and drive. In addition, patients with higher depression scores tended to have a lower PaCO2 when the severity of airways obstruction was taken into consideration. In a 16-week, double-blind, crossover comparison of desipramine with placebo, both treatments led to significant improvement in depression scores. Desipramine had no effects on resting PaCO2, spirometry, or ventilatory control.

Aged↗
PubMed1985

Exercise performance following a carbohydrate load in chronic airflow obstruction.

We evaluated the effects of a large (920 cal) liquid carbohydrate (CHO) load on the maximum exercise capacity of 18 patients with chronic airflow obstruction [forced expiratory volume at at 1 s (FEV1) = 1.27 +/- 0.48 liters; FEV1/forced vital capacity = 0.41 +/- 0.11]. Patients underwent duplicate incremental cycle ergometer exercise tests to a symptom-limited maximum following CHO and a liquid placebo in single-blind fashion. Expired gas measurements were obtained during each power output. In 12 patients arterial blood gases were measured, and in six patients venous blood was obtained for measurement of glucose, electrolytes, and osmolality. With CHO, the maximum power output decreased from 86 +/- 30 to 76 +/- 31 W (P less than 0.001), whereas the ventilation at exhaustion was nearly identical (47.6 +/- 13.2 and 46.8 +/- 12.5 l/min). Arterial partial pressure of CO2 (PaCO2) at exhaustion decreased (P less than 0.025), arterial partial pressure of O2 (PaO2) increased (P less than 0.01), and the ventilatory equivalent for CO2 (VE/VCO2) increased (P less than 0.005) with CHO. At equivalent power outputs, CHO resulted in significant increases in VE (P less than 0.001) and VCO2 (P less than 0.001); PaCO2 was unchanged, whereas PaO2 increased (P less than 0.01). CHO increased the serum glucose at rest and during exercise. No changes in serum osmolality or electrolytes occurred during exercise following CHO. After CHO loading, the majority of patients appeared to reach their limiting level of ventilation at a lower power output. In contrast, there was no significant difference in the mean maximum power output with CHO in six normal control subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1985

Reproducibility of VO2max in patients with chronic air-flow obstruction.

The purpose of this study was to determine the variability in maximal oxygen consumption (VO2 max) determined from repeated exercise tests in patients with chronic air-flow obstruction (CAO). Three incremental maximal cycle ergometer tests were performed in each of 11 CAO patients who were familiar with such testing. Two tests (Test 1, Test 2) were carried out on the same day, separated by a 60-min rest period, and 1 (Test 3) was performed on a consecutive day. Group mean values for VO2 max were: 1.313 +/- 0.259, 1.311 +/- 0.281, 1.306 +/- 0.288 L/min, for Tests 1 to 3, respectively. These nearly identical values did not differ significantly. There was no systematic "fatigue" or "learning" effect from test to test. Other mean measurements obtained at maximal exercise were likewise not significantly different among the 3 tests. For tests performed on the same day, the mean of the absolute values of the individual patient VO2 max differences (delta VO2 max) was 53 +/- 30 ml. The delta VO2 max was less than 6% in 10 of the 11 patients and less than 10% in the remaining patient. For tests performed on consecutive days, delta VO2 max was 93 +/- 81 ml; delta VO2 max was less than 6% in 6 patients and less than 10% in 9 patients. From this study we concluded that repeated maximal exercise testing is highly reproducible for groups of CAO patients, although some individual patient variability is seen. Individual patient differences in delta VO2 max are less when the 2 tests are performed on the same day than when duplicate testing is performed on consecutive days.

Aged↗
PubMed1985

Effects of a large carbohydrate load on walking performance in chronic air-flow obstruction.

The purpose of this study was to determine whether a single large liquid carbohydrate (CHO) load (920 calories) affects walking performance in patients with chronic air-flow obstruction (CAO). Walking performance was measured using the 12-min walking test. Fifteen patients with stable CAO (FEV1, 1.30 +/- 0.41 L; FVC, 3.26 +/- 0.46 L) underwent 12-min walking tests 40 min after ingestion of either CHO or placebo on consecutive days in randomized double-blind fashion. Three practice walks were performed on a preliminary day in order to eliminate learning effects. Resting measurements of ventilation (VE) and carbon dioxide output (VCO2) were obtained prior to each walking test. Carbohydrate significantly increased both VCO2 (from 0.288 +/- 0.060 to 0.372 +/- 0.057 L/min, p less than 0.001) and VE (from 15.2 +/- 3.5 to 18.5 +/- 3.1 L/min, p less than 0.001) at rest. The total 12-minute walking distance decreased from 894 +/- 199 to 847 +/- 191 m following CHO (p less than 0.005). This distance decreased in 14 of the 15 study patients. The decrease in walking distance ranged from 1.5 to 168 m (0.2 to 15.2%). From this study we conclude that a large liquid carbohydrate load adversely affects walking performance in patients with CAO. This potential impairment of functional capacity should be considered when caloric intake is increased in attempts to improve nutritional status in this patient population.

Aged↗
PubMed1985

Prevalence of depression and anxiety in patients with COPD. Relationship to functional capacity.

The objective of this study was twofold: (1) to document the prevalence of depression and anxiety in patients with moderate or severe chronic obstructive pulmonary disease; and (2) to determine whether the presence of depression or anxiety adversely affected the functional capabilities of the patient as reflected by the distance he could walk in 12 minutes. Forty-five patients with an FEV1 less than 1,250 ml underwent pulmonary function testing including spirometry, single breath diffusing capacity, and arterial blood gas determinations. The degree of depression was assessed by the Beck depression inventory, while the degree of anxiety was assessed by the State-Trait anxiety inventory. Forty-two percent of the patients had significant depression, while only 2 percent of the patients had significant anxiety. There was a highly significant correlation between the depression scores and the anxiety scores (r = 0.81, p less than 0.001). There was no significant correlation between the level of depression or anxiety and the distance that the patient could walk in 12 minutes. From this study, we conclude that the prevalence of depression in patients with moderate or severe COPD approaches 50 percent while the incidence of anxiety is much lower (2 percent).

Aged↗
PubMed1985

Comparison of the effects of labetalol and hydrochlorothiazide on the ventilatory function of hypertensive patients with asthma and propranolol sensitivity.

Previous studies have shown that labetalol, a new alpha- and beta-adrenergic antagonist, is relatively safe for the treatment of hypertension in patients with chronic obstructive pulmonary disease (COPD). This multicenter study was designed to evaluate its effects in hypertensive patients with asthma and propranolol sensitivity. Hypertension was successfully controlled in 18 of 21 patients who received labetalol in increasing doses, up to 1,200 mg/day. The decrease in mean FEV1 (1.5 percent) two hours after the highest dose of labetalol was not statistically significant, although there was a gradual decline in mean baseline FEV1 during the four-week treatment period. Antihypertensive agents other than adrenergic antagonists should be considered for the management of hypertension in patients with asthma, especially those with marked reversibility of airflow. If treatment with beta-adrenergic antagonists is indicated, labetalol is recommended over other currently available agents.

Adolescent↗