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Biomedical subjects

T W Chick

Publications and source records attributed to T W Chick.

At least 37 records · Page 2Linked to original sources
PubMed1990

Recovery of gas exchange variables and heart rate after maximal exercise in COPD.

Studies of the limited exercise capacity in patients with COPD have not assessed the recovery phase, although the phenomenon of increased oxygen uptake after exercise has been thoroughly investigated in normal subjects. Therefore, we compared the recovery of gas exchange variables and HR after maximal cycle ergometry in 16 patients with varying severities of airflow obstruction and ten aged control subjects. Aerobic capacity was reduced in the patients with COPD, and the rates of recovery of VE, VO2, VCO2, excess VCO2, and HR were all significantly slower in the patients with COPD than in the controls. When expressed as the half-time for recovery, patients with COPD had values which were approximately twice that of control subjects for gas exchange and HR. The extent of recovery was similar in patients and controls. We conclude that in patients with COPD, postexercise relative hyperpnea and hypermetabolism are significantly prolonged. In addition, impaired elimination of increased body stores of carbon dioxide may contribute to impaired adjustment to acid-base disorders in these patients.

Aged↗
PubMed1990

Intravenous and oral corticosteroids for the prevention of relapse after treatment of decompensated COPD. Effect on patients with a history of multiple relapses.

To determine if a regimen of intravenous and oral corticosteroids reduces the relapse rate after treatment of decompensated COPD in the ED, 30 patients were studied. Forty-five visits in which intravenous and oral corticosteroids were given (T visits) were compared with an equal number of matched visits in which they were withheld (N visits). No differences were noted between T and N visits with respect to clinical findings, laboratory results and other forms of therapy. Treatment with corticosteroids reduced the relapse rate within 24 h of discharge. At 48 h, the cumulative relapse rate for T visits (8.9 percent) was significantly lower than for N visits (33.3 percent; p = 0.005). For patients with a history of multiple relapses, a regimen consisting of intravenous and oral corticosteroids reduces the risk of relapse after ED treatment of decompensated COPD.

Acute Disease↗
PubMed1990

Aminophylline in the outpatient management of decompensated chronic obstructive pulmonary disease.

The objective of this study was to determine if IV aminophylline reduces the risk of relapse after treatment of decompensated COPD in an ED. Forty-six visits in which IV aminophylline was given (T visits) were compared with an equal number of visits in which it was withheld (N visits) with respect to pretreatment serum theophylline level, number of treatments with nebulized bronchodilators and use of parenteral beta-adrenergic drugs, IV corticosteroids and prednisone. The difference in 48-h relapse rates for T and N visits was examined by McNemar's test. No differences were found between T and N visits with respect to vital signs, pretreatment FEV1, arterial blood gas values, hematocrit level or blood leukocyte count. The 48-h relapse rate for T visits (22.2 percent) was significantly higher than for N visits (6.7 percent; p = 0.035). Aminophylline does not appear to be beneficial for outpatients with decompensated COPD and may be harmful.

Aged↗
PubMed1990

Effects of acute hypoxia on cardiopulmonary responses to head-down tilt.

Six male subjects were exposed on two separate occasions to simulated microgravity with 28 degrees head-down tilt (HD) for 1 h with baseline followed by recovery at + 17 degrees head-up. Pulmonary ventilation, gas exchange, spirometry, and central and cerebral blood flow characteristics were compared while breathing ambient air (PIO2 = 122 mm Hg) and reduced FIO2 equivalent to 14,828 ft (PIO2 = 81 mm Hg). With hypoxia (HY), the increased tidal volume served to attenuate the drop in arterial saturation by reducing deadspace ventilation. Arterial and mixed venous PO2 values, estimated from peripheral venous samples and cardiac output (CO), were both maintained during HD in HY. Mixed venous PO2 was elevated by an increase in CO associated with a reduction in systemic resistance. Changes in spirometric indices during HD were not accentuated by HY, making the presence of interstitial edema unlikely. Cerebral flow and resistance showed minor reductions with HD. Tissue oxygenation and cardiopulmonary function were not notably effected by HD during HY, but a combination of these two stressors may predispose subjects to subsequent orthostatic intolerance during initial recovery.

Acute Disease↗
PubMed1990

Effects of glycerol-induced hyperhydration prior to exercise in the heat on sweating and core temperature.

Hypohydration reduces exercise performance and thermoregulatory capacity in the heat. Hyperhydration prior to exercise may decrease, delay, or eliminate the detrimental effects of hypohydration. The rapid clearance of excess fluid makes hyperhydration of subjects with common beverages difficult. Glycerol, a natural metabolite which is rapidly absorbed, has osmotic action, and is evenly distributed within the body fluid compartments, was tested as a possible hyperhydrating agent. In six subjects, the following fluid regimens at time 0 were randomly administered on three separate days: in trial 1, glycerol (1 g.kg-1 body weight) plus water (21.4 ml.kg-1 body weight); in trial 2, water (21.4 ml.kg-1); and in trial 3, water (3.3 ml.kg-1) was ingested at time 0. The subjects performed moderate exercise (equivalent to 60% VO2max in a comfortable environment) in a hot dry environment. The exercise started at 2.5 h after the fluids were ingested. The urine volume prior to exercise was decreased when glycerol was ingested, thus resulting in glycerol-induced hyperhydration. During the exercise following the glycerol-induced hyperhydration, there was elevated sweat rate and lower rectal temperature during the moderate exercise in the heat. There were no changes in hemoglobin, hematocrit, or serum electrolyte concentrations following glycerol intake. These data support the hypothesis that glycerol-induced hyperhydration reduces the thermal burden of moderate exercise in the heat.

Adult↗
PubMed1989

Use of emergency medical services by patients with decompensated obstructive lung disease.

Little information is available about the risk of relapse when patients with decompensated obstructive lung disease are treated in an emergency department for dyspnea. The purpose of our study was to determine if the risk of relapse was related to the severity and type of airway obstruction or to the time and duration of treatment. Over a period of 29 months, 496 patients with decompensated chronic obstructive pulmonary disease (COPD), asthma, or both were seen in the ED of the Albuquerque Veterans Administration Medical Center. Of 868 visits in which patients were treated and released, 244 (28.1%) were followed by a relapse within 14 days. Those who relapsed had a slightly higher one-second forced expiratory volume at baseline than those who did not (50.1 +/- 22.2% versus 45.5 +/- 20.6% predicted, P = .054). For 94 patients (group 1), asthma was the exclusive clinical diagnosis, and all available pulmonary function tests showed a bronchodilator response. For 268 patients (group 2), COPD was the exclusive diagnosis, and all tests showed no bronchodilator response. One hundred thirty-four patients (group 3) were either diagnosed as having both disorders or had varying bronchodilator response on sequential testing. The risk of relapse for group 3 patients (35.6%) was higher than for those in groups 2 (23.1%, P less than .001) or 1 (19.7%, P = .001). The frequency of relapse was higher for nighttime than daytime visits (36.1% versus 24.5%, P = .006) and for weekend than weekday visits (33.6% versus 26.6%, P = .049). Prognosis did not vary with the season or duration of treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Asthma↗
PubMed1988

Regionally variable pulmonary artery responses to C3a.

Products of the complement (C) cascade may have direct effects on pulmonary vascular tissue and contribute to pulmonary vasoconstriction in states of C activation. We studied the effects of C3a, a C-derived vasoactive peptide, on isolated rabbit hilar (HPA) and main pulmonary arteries (MPA). C3a elicited concentration-dependent constriction of HPA (10(7) M to 5 x 10(7) M) but minimal response in MPA at all concentrations tested. The difference between HPA and MPA responses was significant (P less than 0.05, paired t test). To evaluate HPA desensitization to C3a, the peptide was reapplied at 60 min in some tissues and at 120 min in others. All tissues consistently exhibited less constriction at 60 min than observed with previous exposures. Histamine contribution to the HPA response to C3a was determined by exposing the tissues for 30 min before C3a application to pyrilamine (1 x 10(-5) M), an histamine H1-receptor antagonist. Pyrilamine reduced the HPA response to C3a by 70-85%. We conclude that 1) isolated rabbit PA responses exhibit regional variability to C3a over a range of concentrations; 2) C3a desensitizes HPA for at least 60 min, but the tissue demonstrates variable recovery within 120 min; and 3) HPA responses to C3a are reduced by pyrilamine, an H1-receptor antagonist.

Animals↗
PubMed1988

Effects of pentoxifylline on pulmonary hemodynamics during acute hypoxia in anesthetized dogs.

The effects of pentoxifylline on pulmonary hemodynamics were studied in anesthetized dogs during acute alveolar hypoxia. In Series A, 7 dogs received pentoxifylline orally (18 mg/kg/day) for 11 wk and 7 untreated dogs served as control animals. During anesthesia and controlled ventilation, acute alveolar hypoxia was induced (10 to 13% inspired O2) and pulmonary and systemic hemodynamic and blood rheologic measurements were compared with normoxia. In control dogs, cardiac index did not change during hypoxia, but pulmonary vascular resistance index (PVRI) increased 79%, erythrocyte filterability decreased significantly (p less than 0.05), and relative viscosity of blood corrected for hematocrit did not change. In the pentoxifylline-treated dogs, cardiac index increased 28% and PVRI increased only 20%; in contrast to the control dogs, relative viscosity of blood was decreased by 18% and no significant changes in filterability were observed. The increase in PVRI in relation to the drop in arterial O2 saturation was significantly larger (p less than 0.05) in the control dogs. Pentoxifylline also increased P50 by 2.8 mm Hg (p less than 0.05). In Series B, hemodynamic measurements were made during variations in blood flow (induced by restricting venous return) in 3 treated (26 mg/kg/day for 3 wk) and 3 control dogs. In these experiments, pulmonary artery pressure was significantly lower at comparable flows during both normoxia and hypoxia. In both studies, the hemodynamic effects of the drug on the systemic circulation were less than on the pulmonary circulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1988

The effect of antihypertensive medications on exercise performance: a review.

This review describes the effects of antihypertensive drugs on the performance of aerobic exercise. All available antihypertensive drugs lower blood pressure both at rest and decrease the rate of increase during exercise. However, they differ in their effects on exercise performance. The ideal antihypertensive agent should not have significant depressant effects on the myocardium, should not promote arrhythmias, should preserve the distribution of blood flow to exercising muscle, and should not interfere with substrate utilization. Diuretics, one of the most commonly prescribed class of antihypertensives, have few deleterious effects on exercise performance but have adverse metabolic effects; beta blockers have many adverse effects on exercise performance. Agents which have the least potential for adverse effects on exercise performance and metabolic effects are the converting enzyme inhibitors, calcium channel blockers, and alpha blockers, and central alpha agonists. The literature concerning each of these drugs is reviewed and recommendations are made for prescribing for the hypertensive who wishes to engage in vigorous exercise.

Adrenergic beta-Antagonists↗
PubMed1987

The effect of exercise on secretory and natural immunity.

Secretory immunity. 1. Intense endurance exercise suppresses salivary immunoglobulins. The exercise-induced decrease is specific for the secretory antibodies IgA and IgM. 2. The suppression of secretory Ig is transitory, lasting at least one hour, and returning to pre-exercise levels by 24 hours after a single bout of severe exercise. These results suggest that anecdotal statements by athletes and their coaches of an increased susceptibility to upper respiratory infection after severe exercise could be related to changes in secretory immunity. Natural immunity. 1. Natural killer activity of PBL is suppressed one hour after intense endurance exercise. This effect is transitory, since activity returns to pre-exercise levels by 24 hours after a single bout of exercise. 2. The decrease in NK lytic activity is due to a decrease in the percentage of NK cells (Leu-11a+ cells). When NK cell activity is expressed on a per cell basis, it appears that activity is enhanced after exercise.

Adult↗
PubMed1986

Depression of papillary muscle contractility by plasma incubated with pneumococci.

Mechanisms of death in pneumococcal disease are poorly understood. We have previously shown that intravenous pneumococcal products in dogs caused a mean decrease in cardiac output of 58%. The present study used measurements of the force and rate of contraction of isolated rabbit papillary muscle to determine whether pneumococci (PNC) altered myocardial contractility. Nine papillary muscles were superfused with various solutions including Tyrode's, Tyrode's incubated with sonicated type 1 PNC, normal rabbit plasma, and rabbit plasma incubated with PNC. Compared to untreated Tyrode's solution, PNC-treated Tyrode's solution did not alter papillary muscle contractility. However, compared to untreated rabbit plasma, plasma incubated with PNC caused a mean decrease of 18% in the force of contraction and 16.7% in the maximum rate of force development in nine studies. We conclude that PNC do not directly affect papillary muscle contractility. However, the interaction of PNC and plasma does cause a decrease in rabbit papillary muscle contractility.

Animals↗
PubMed1986

The effect of nifedipine on cardiopulmonary responses during exercise in normal subjects.

We investigated the effects of a single dose of nifedipine (10 mg orally) on exercise performance during progressive incremental cycle ergometry in nine sedentary normal subjects in a double-blind, placebo-controlled crossover study. Maximum work load after nifedipine (213 +/- 42 watts; mean +/- SD) was less than after placebo (222 +/- 41 watts; p less than 0.05). Maximum oxygen consumption was unchanged. In addition, the drug decreased lactate threshold from 19.7 +/- 4.9 ml O2/min/kg to 15.5 +/- 5.5 ml O2/min/kg (p less than 0.02); gas exchange anaerobic threshold was unaffected. There were higher plasma lactate concentrations at low and intermediate exercise intensities after nifedipine compared with placebo (p less than 0.05). Systolic blood pressure was lower at high work loads (p less than 0.05) and heart rate was higher at low work loads (p less than 0.05) after nifedipine. We conclude that the short-term administration of nifedipine limits peak performance and increases plasma concentration of lactic acid in normal subjects. One or more of the following mechanisms may account for these observations: nifedipine decreases blood flow to skeletal muscle by diverting blood to nonexercising tissues; nifedipine increases catecholamine levels, thereby augmenting lactic acid production; and nifedipine decreases skeletal muscular contractility by selectively impairing fatigue-resistant fibers.

Adult↗
PubMed1986

A group comparative study of the safety and efficacy of nedocromil sodium (Tilade) in reversible airways disease: a preliminary report.

Nedocromil sodium in a dose of 4 mg b.i.d. or q.i.d. by inhalation was used to treat asthmatic patients in a double-blind, placebo-controlled, randomized, parallel study. 80 patients (39 active drug and 41 placebo) received q.i.d. dosage and 87 patients (45 active drug and 42 placebo) received b.i.d. dosage. The patients selected were not on oral or inhaled steroids but required oral sustained-release theophylline with or without an inhaled beta-agonist aerosol. There was a significant reduction in daytime asthma symptoms (p = 0.04) and asthma severity (p less than 0.01) 6 weeks after the onset of therapy in the nedocromil sodium q.i.d. treated group as compared with placebo. In the nedocromil sodium b.i.d. treated group, the following variables showed statistically significant improvements compared with placebo: daytime and night-time asthma (p = 0.002 in both instances), wheezing assessed by auscultation (p = 0.03) and overall asthma severity (p less than 0.01). All these variables showed improvements within 2 weeks of the onset of therapy and became statistically significant at 6 weeks. Side-effects were minor and occurred only in a small number of patients. It can be concluded from this study that nedocromil sodium is a safe and effective drug in the management of asthma.

Adrenal Cortex Hormones↗
PubMed1984

Pulmonary leukostasis in fatal human pneumococcal bacteremia without pneumonia.

An asplenic man developed fulminant pneumococcal bacteremia without pneumonia. He died of irreversible shock within 24 h. Autopsy revealed extensive pulmonary vascular leukostasis. This condition has been described in laboratory animals after intravascular challenge with endotoxin, gram-negative bacilli, and gram-positive organisms including pneumococci. This case illustrates that death in pneumococcal disease can occur in the absence of pneumonia and may be attributable to cardiovascular collapse. We present a proposed mechanism based on activation of complement and release of vasoactive mediators.

Adult↗
PubMed1984

Pneumococcal-induced pulmonary leukostasis and hemodynamic changes: role of complement and granulocytes.

In the present study we investigated the cardiopulmonary dysfunction caused by systemic pneumococcal (PNC) disease. We studied the hemodynamic and hematologic effects of intravascular challenge with nonviable PNC in normal, granulocyte-depleted, and genetically C3-deficient dogs. In normal dogs PNC administration caused a decrease in cardiac output (CO) of 58% (p less than 0.001), an increase in pulmonary vascular resistance (PVR) of 151% (p less than 0.02), and an increase in systemic vascular resistance (SVR) of 72% (p less than 0.02). The PNC challenge also caused significant decreases in both circulating granulocytes (-73%; p less than 0.02) and platelets (-58%; p less than 0.02). Histologic examination revealed granulocyte plugging within small pulmonary vessels. PNC challenge in granulocyte-depleted and C3-deficient dogs resulted in hemodynamic and hematologic changes that were not significantly different from those seen in normal PNC-challenged animals. Infusion of PNC-activated plasma resulted in hematologic changes that were not significantly different from those seen in PNC-challenged animals. Infusion of plasma treated with ethylenediamenetetraacetic acid (EDTA) prior to PNC incubation induced the same hematologic alterations but the hemodynamic response was less pronounced. To control for PNC constituents not removed by centrifugation and filtration, saline was incubated with PNC. After the PNC was removed, infusion of the saline induced no significant hemodynamic changes, although profound granulocytopenia occurred. We conclude that an intact complement system, but not normal numbers of circulating granulocytes, is essential to PNC-induced hemodynamic changes. PNC generates a plasma factor in vitro that does not require an intact complement system or cellular machinery to induce granulocytopenia without hemodynamic effect.

Animals↗
PubMed1980

Tachyphylaxis to inhaled isoproterenol and the effect of methylprednisolone in dogs.

Acute tachyphylaxis can be induced to inhaled isoproterenol (ISO) in anesthetized, closed-chested mongrel dogs. The responsiveness to ISO measured as the percent reduction in methacholine-induced bronchoconstriction was decreased significantly (p less than 0.01) after a 1-hr period of repeated ISO inhalations (ISO-loading). Intravenous administration of methylprednisolone (1 mg/kg) reversed the decrease in responsiveness to ISO.

Animals↗
PubMed1977

Subsensitivity of beta responses during therapy with a long-acting beta-2 preparation.

The question whether some tolerance or subsensitivity of various beta receptors develops during therapy with long-acting oral beta-2 agents has practical and theoretical importance. We applied a strong beta-2 stimulus (terbutaline, 5.0 mg orally) at weekly intervals for up to three weeks in 19 stable asthmatics and bronchitics while commencing 5.0 mg terbutaline three times daily. The evening dose was omitted before each morning challenge. Challenges were continued at one and two weeks off terbutaline in some patients to test return of beta function. Patients received no ephedrine for two weeks before the study but were allowed aminophylline or isoproterenol inhalations up to 18 and 4 hr before challenges, respectively. Pulmonary function, pulse, and blood pressure were monitored at 0, 60, 120, and 180 min, and metabolic parameters measured at 0 and 180 min. There was significant drug tolerance in the drop and minimum diastolic pressure reached, rise in lactate, cyclic AMP, and blood glucose, and drop in eosinophils. Peak FEV1 and V50 dropped slightly, but vital capacity and minimal airway resistance did not change significantly. During continuous therapy this slight bronchial subsensitivity is probably obscured by elevated baseline function. It might assume importance during periods of excessive inhaler use or abrupt drug withdrawal.

Asthma↗