Thomas W. Chick

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.

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)

The effect of nitroglycerin on gas exchange, hemodynamics, and oxygen transport in patients with chronic obstructive pulmonary disease

The present study was designed to investigate pharmacological vasodilation in patients with chronic obstructive pulmonary disease (COPD). This may have long-term therapeutic implications. Sublingual nitroglycerin (GTN) was administered to 16 patients with COPD and no evidence of organic heart disease (except one patient) in an attempt to determine severity of the decrease in arterial oxygenation. Gas exchange and hemodynamic studies were performed before and after GTN. Alveolar-arterial O2 tension gradient increased 5 mm Hg, arterial Po2 decreased 2 mm Hg, and cardiac output decreased from 4.36 to 3.85 liters/min. There was a decrease in pulmonary artery pressures, but pulmonary vascular resistance did not change. Total O2 transport (the product of cardiac output and arterial O2 content) decreased, due mainly to a decrease in cardiac output. From these studies we conclude that GTN significantly decreases O2 transport in patients with COPD and normal left ventricular function; this decrease is due mainly to a reduction in cardiac output. Impairment of gas exchange is slight. Based on these considerations pharmacological vasodilation with nitroglycerine in COPD is probably not warranted.

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.

Treatment of decompensated chronic obstructive pulmonary disease in the emergency department--correlation between clinical features and prognosis.

STUDY OBJECTIVE Patients with decompensated chronic obstructive pulmonary disease (COPD) are at high risk of relapse after treatment in an emergency department. The purpose of this study was to determine if the risk of relapse correlates with the clinical features of the disease. PATIENTS Three hundred fifty-two patients with documented COPD who were treated for dyspnea in the ED of the Albuquerque Veterans Administration Medical Center over a three-year period. METHODS We reviewed the clinical features and pulmonary function tests of the patients, who were considered to have COPD if the baseline prebronchodilator one-second forced expiratory volume (FEV1) was less than 80% predicted, and less than 80% of the forced vital capacity and inhaled bronchodilators failed to increase the FEV1 to levels of more than 80% predicted. Visits for pneumonia, pneumothorax, pleural effusion, or pulmonary emboli were excluded. A relapse was defined as an unscheduled revisit to the ED within 14 days of initial treatment. Data were entered into a microcomputer data base and analyzed by a commercial statistical package. RESULTS Of 877 visits in which the patient was treated and released from the ED, 281 (32.0%) resulted in relapse and were considered unsuccessful Compared with successful visits, unsuccessful visits were characterized by a shorter duration of dyspnea (P = .002), a lower entry FEV1 (P = .027), a lower discharge FEV1 (P = .040), a greater number of treatments with nebulized bronchodilators (P = .009), more frequent use of parenteral adrenergic drugs (P = .006), and less frequent use of oral prednisone on discharge (P = .016). Patients with one or more relapse visits during the study period (relapsers) differed from nonrelapsers in several respects. Relapsers had a greater bronchodilator response on baseline FEV1 than nonrelapsers (P = .047). Nevertheless, relapsers required more bronchodilator treatments in the ED (P less than .001); were treated more frequently with parenteral adrenergic drugs (P less than .001), IV glucocorticoids (P less than .001), and oral prednisone (P less than .001); and recovered less of their baseline FEV1 (P less than .014). CONCLUSION Bronchodilator response on baseline pulmonary function testing appears to identify patients with COPD who have a poor prognosis after emergency treatment. Their poor response to intensive bronchodilator treatment suggests that loss of bronchodilator response may be involved in the pathogenesis of respiratory decompensation.

Oronasal distribution of ventilation at different ages

The route of breathing, oral or nasal, is a determinant of the doses of inhaled pollutants delivered to target sites in the upper and lower respiratory tracts. We measured partitioning of ventilation, using a divided oronasal mask during a submaximal exercise test, in 37 male and female subjects who ranged in age from 7 to 72 y. The following four patterns of breathing were evident during exercise: (1) nasal only (13.5%), nasal shifting to oronasal (40.5%), oronasal only (40.5%), and oral only (5.4%). Children (i.e., 7-16 y of age) displayed more variability than adults with respect to their patterns of ventilation with exercise. Young adults (i.e., 17-30 y of age) who initially breathed nasally with exercise switched to oral ventilation at a lower percentage of the previously measured maximum ventilation (10.8%) than older subjects (31.8%). The partitioning of ventilation between the nasal and oral routes follows complex patterns that cannot be predicted readily by the age, gender, or nasal airway resistance of the subject.

The Effect of Nitroglycerin in Gas Exchange on Chronic Obstructive Pulmonary Disease1, 2

Nitroglycerin was administered to a group of 11 patients with chronic obstructive pulmonary disease in a dose of 0.4 mg sublingually. Arterial blood gases and blood pressure and pulse were measured at 5-min intervals for 30 min after nitroglycerin. There was a slight decrease in arterial O2 tension for the duration of the study; the maximal change was from a mean pre-nitroglycerin value of 53.5 mm Hg to 50.3 mm Hg at 20 min. In addition, there was a slight reduction in arterial CO2 tension and bicarbonate for 25 min. It is postulated that decreased O2 transport (due to increased hypoxemia and probably decreased cardiac output) plus hypocapnia were a sufficient stimulus to raise blood lactate. It is recommended that in patients receiving nitroglycerin who have obstructive airway disease, attention be directed toward the effect on arterial blood gases.

Evaluation of the Relationship between Heart Rate and Ventilation for Epidemiologic Studies

Estimation of pulmonary exposure and dose in air pollution epidemiology has been impaired by the lack of methods for directly measuring ventilation in ambulatory subjects. Heart-rate monitoring offers an approach to estimate ventilation by using ventilation-on-heart-rate (VE-HR) regressions established during exercise testing to estimate ventilation in the field. Conventional methods and protocols for testing were used to evaluate the relationship between VE and HR during three tasks: (1) exercising on a cycle ergometer, (2) lifting, and (3) vacuuming. The relationship between VE and HR was curvilinear and was best fit with linear regression models, using a natural log transformation of VE. Considerable interindividual variability in slopes and intercepts was observed across all types of exercise tests. The variability about the fitted regression lines for individual subjects was minimal; for example, individual R2 values for the maximum exercise test on 15 men ranged from 0.90 to 0.99 (mean = 0.97). The regression slopes established during upper-body exercise were greater by approximately 30%, relative to those derived in lower-body exercise (paired t test, p < .001). However, VE-HR regression slopes derived from tests in which progressively increasing workloads were used were comparable to those obtained during variable and nonprogressive protocols. These findings indicate that predictive accuracy is maximized by deriving VE-HR regressions for individual subjects and for both lower- and upper-body activities.

Rate‐Adaptive Cardiac Pacing in Children Using a Minute Ventilation Biosensor

YABEK, S.M., ET AL.: Rate‐Adaptive Cardiac Pacing in Children Using a Minute Ventilation Biosensor.Chronotropic integrity is required for a normal cardiac output response to exercise. We evaluated a rate‐adaptive ventricular demand pacemaker (Telectronics, META‐MV) which uses minute ventilation as the sensed physiological variable for adjusting pacing rate, in seven young patients with a mean age of 11.4 years. All patients had clinically significant bradycardia related to complete heart block (n = 4) or sinus node dysfunction (n = 3). For the entire group, paced heart rates increased from 70 ± 10 beats/min to 151 ± 19 beats/min with exercise testing. The onset of rate adaptation took < 30 seconds. Changes in paced rate were linearly related to workload, VO2 (5.9 to 20.7 mL/min/kg) and minute ventilation (8–65 L/min). The decline in pacing rate after exercise was related directly to the gradual decrease in minute ventilation and VO2. Our data show that minute ventilation closely and accurately reflects the metabolic demands of varying workloads in children and can be used to achieve physiological, rate‐adaptive pacing.

Sources of variability in posterior rhinomanometry

Sources of variability in nasal airway resistance measured by posterior rhinomanometry were studied in 5 subjects tested on 5 different days and 56 subjects tested on 2 different days. On each day, a questionnaire on upper airway health and nasal symptoms was completed. The mean individual difference in nasal airway resistance between the 2 test days in the group of 56 subjects was 5.3% (SD 52.7%). Between-subject variability accounted for 74.9% and 72.5% of the total variability in the group of 5 and the group of 56 subjects, respectively. For the 5 subjects, by accounting for a change in upper airway symptoms or upper respiratory tract infection that occurred over the 5 test days, there was a significant decrease in the between-subject variability. The difference in sources of variation due to a change in upper airway symptoms was not seen in the group of 56 subjects. We conclude that the largest source of variability in nasal airway resistance is due to between-subject differences.