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Biomedical subjects

D A Mahler

Publications and source records attributed to D A Mahler.

At least 55 records · Page 3Linked to original sources
PubMed1991

Ventilatory responses and entrainment of breathing during rowing.

The purpose of this investigation was to investigate the hypothesis that respiration was coupled with the mechanics of the rowing stroke. In the first part of the study, physiologic responses during incremental exercise on the variable-resistance rowing ergometer were compared in 16 untrained female subjects (U), 17 collegiate female rowers (C), and 21 elite oarswomen (E). Minute ventilation (VE) and frequency of respiration (fR) were examined on a log scale as their relationship with oxygen consumption (VO2) was exponential. The slopes for log VE/VO2 were similar for collegiate (0.65 +/- 0.02) and elite (0.59 +/- 0.01) rowers, but the slope was significantly higher for the untrained (0.87 +/- 0.01) subjects (P less than 0.001). Elite rowers utilized a higher tidal volume (VT) response per VO2 (0.68 +/- 0.04 vs 0.30 +/- 0.05; P = 0.01) and lower log fR response per VO2 (0.27 +/- 0.02 vs 0.50 +/- 0.03; P = 0.01) compared with collegiate rowers. The ratio of fR/strokes per minute (SPM) averaged 1.5 in E athletes but varied in the U and C groups. In the second part of the study, pattern and timing of respiration were recording using an inspiratory pneumotachygraph, analyzed, and compared with specific phases of the rowing stroke in ten untrained subjects and nine elite rowers. The ratio of inspiratory time (T1)/total respiratory time (TTOT) decreased during the drive phase and increased during the recovery phase in both untrained subjects and elite rowers.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Targeted inspiratory muscle training improves respiratory muscle function and reduces dyspnea in patients with chronic obstructive pulmonary disease.

STUDY OBJECTIVE: To examine the effects of targeted inspiratory muscle training on respiratory muscle function, clinical ratings of dyspnea, and perception of resistive loads in symptomatic patients with chronic obstructive pulmonary disease. DESIGN: Randomized, placebo-controlled trial with an 8-week treatment period. SETTING: Outpatient pulmonary clinic and pulmonary function laboratory. PARTICIPANTS: We studied 19 patients with moderate to severe chronic obstructive pulmonary disease, assigning 10 patients to an experimental group and 9 to a control group. INTERVENTIONS: Patients in both groups trained for 15 minutes twice each day using a device that provided breath-to-breath visual feedback of training intensity. Patients in the experimental group trained at six increasing levels of inspiratory resistance, whereas the patients in the control group trained at a constant, nominal level of resistance. MEASUREMENTS AND RESULTS: Although there was no statistically discernible difference in the effects of targeted muscle training on the mean difference in maximal inspiratory pressures between the two groups (9.83 cm H2O; 95% CI, -7.37 to 27.03), patients in the experimental group did show a significant increase in inspiratory muscle strength (15.03 cm H2O; P = 0.01). Experimental subjects also had decreased dyspnea after 8 weeks of training compared with control subjects (P = 0.003). Improvements in physiologic values and in dyspnea ratings were correlated. The perception of added resistive loads was not affected by inspiratory muscle training. CONCLUSIONS: Targeted inspiratory muscle training may enhance respiratory muscle function and reduce dyspnea in symptomatic patients with moderate to severe chronic obstructive pulmonary disease.

Aged↗
PubMed1989

Beta-endorphin activity and hypercapnic ventilatory responsiveness after marathon running.

To investigate the hypothesis that endurance exercise may lead to a decrease in ventilatory chemosensitivity as possibly mediated by an increase in endogenous beta-endorphins, we measured hypercapnic ventilatory responsiveness (HCVR) and circulating beta-endorphin immunoreactivity in six runners before and after a marathon (42.2 km) race and after administration of 10 mg iv naloxone. Similar testing was performed at identical time periods on the day before the marathon as control data. On each occasion, HCVR was measured twice 15 min apart, and the mean value was used for analysis. Six active (training distance 50-104 km/wk) and experienced (no. of marathons completed, 1-25) runners participated in the study. There were no significant changes in beta-endorphin activity or HCVR on the control day. All runners experienced a rise in beta-endorphin activity from premarathon (21.3 +/- 16.0 pg/ml) to immediate postmarathon (89.6 +/- 84.9 pg/ml) values (P less than 0.05). However, HCVR showed no significant change at any of the three testing periods on the marathon day. To investigate whether a time delay may have affected the lack of response to naloxone, additional testing was performed in five subjects, except that 10 mg iv naloxone was given within 10 min after completion of the marathon, and then HCVR was measured. Although there was a greater than fourfold increase in beta-endorphin immunoreactivity after the marathon, there was no significant change in HCVR after naloxone administration. We conclude that natural increases in endogenous beta-endorphin activity associated with marathon running do not modulate central chemosensitivity.

Adult↗
PubMed1989

Measurement of respiratory sensation in interstitial lung disease. Evaluation of clinical dyspnea ratings and magnitude scaling.

To evaluate measurements of respiratory sensation in ILD, we compared ratings of breathlessness from three clinical scales with the perceived magnitude of added elastic loads in 20 symptomatic ILD patients. Dyspnea ratings were obtained by two independent observers for each clinical method. Perceived magnitude of four elastic loads was selected from the Borg category scale; these estimates were summarized using the psychophysical power function equation. Ten age-matched healthy subjects also scaled the magnitude of added elastic loads. Dyspnea ratings from the three clinical scales were significantly interrelated. Mean exponents for mouth pressure developed during elastic loading were similar in the patient and control groups. Dyspnea ratings and exponents for elastic loads were not significantly correlated in ILD patients. Of the physiologic parameters examined, Dsb and gas exchange during exercise correlated significantly with clinical dyspnea ratings; none correlated with the exponent for added elastic loads. These data demonstrate that clinical dyspnea ratings provide valid measures of breathlessness in patients with ILD which are independent of the perception of respiratory loads.

Dyspnea↗
PubMed1989

The pulmonary function laboratory.

The pulmonary function laboratory is essential for evaluating patients with respiratory complaints and disorders. Lung function tests are widely used to detect evidence of disease, quantitate severity of dysfunction, elucidate pathophysiologic mechanisms, and assess response to therapy. For these reasons, standards for personnel, infection control and safety, equipment, and quality control are important considerations for the generation of physiologic data.

Humans↗
PubMed1988

Evaluation of clinical methods for rating dyspnea.

To evaluate available clinical methods (self ratings and questionnaire) for rating dyspnea, we (1) compared scores from the recently developed baseline dyspnea index (BDI) with the Medical Research Council (MRC) scale and the oxygen-cost diagram (OCD) in 153 patients with various respiratory diseases who sought medical care for shortness of breath; and (2) evaluated the relationships between dyspnea scores and standard measures of physiologic lung function in the same patients. The dyspnea scores were all significantly correlated (r = 0.48 to 0.70; p less than 0.001). Agreement between two observers or with repeated use was satisfactory with all three clinical rating methods. The BDI showed the highest correlations with physiologic measurements. Dyspnea scores were most highly related to spirometric values (r = 0.78; p less than 0.001) for patients with asthma, maximal respiratory pressures (r = 0.34 and 0.35; p less than 0.001) for patients with chronic obstructive pulmonary disease, and PImax (r = 0.51; p = 0.01) and FVC (r = 0.44; p = 0.03) for those with interstitial lung disease. These results show that: (1) the BDI, MRC scale, and OCD provide significantly related measures of dyspnea; (2) the clinical ratings of dyspnea correlate significantly with physiologic parameters of lung function; and (3) breathlessness may be related to the pathophysiology of the specific respiratory disease. The clinical rating of dyspnea may provide quantitative information complementary to measurements of lung function.

Aged↗
PubMed1988

Prediction of peak oxygen consumption in obstructive airway disease.

The hypothesis of this study was that non-exercise variables can be used to reliably predict peak oxygen consumption (VO2) in patients with obstructive airway disease (OAD). We also evaluated the impact of symptoms on exercise capacity. Selected predictor variables included age, lung function, respiratory muscle strength, gas exchange, and the Baseline Dyspnea Index (BDI). In 40 patients peak VO2 was 19.9 +/- 8.7 (mean +/- SD) ml.kg-1.min-1 during progressive, incremental exercise until limited by symptoms on a cycle ergometer. Multiple regression analysis yielded three significant predictors: forced expiratory volume in one second (FEV1), age, and BDI. Peak VO2 (ml.kg-1.min-1) = 5.5 (FEV1) - 0.3 (age) + 0.8 (BDI) + 19.3 (R2 = 0.79; SEE: 4.2 ml.kg-1.min-1). Comparisons between patients who stopped exercise because of breathlessness (N = 14) and those who stopped because of leg fatigue (N = 18) showed that lung function, inspiratory muscle strength, and peak VO2 were significantly reduced in the former group compared to the latter. Peak exercise ventilation (VE)/MVV ratio was similar in the breathless (95.3 +/- 23.8%) and leg fatigue (86.8 +/- 20.3) groups, but peak heart rate (HR)/pred. HRmax ratio was significantly higher in the leg fatigue group (86.8 +/- 12.6%) than in the breathless group (75.1 +/- 8.6%) (P = 0.006). We conclude that lung function, age, and the clinical rating of breathlessness reliably predict peak VO2 in patients with symptomatic OAD. Moreover, peak exercise performance in OAD appears to be affected by different physiological factors which may be distinguished by the major symptom limiting exercise.

Adult↗
PubMed1987

Comparison of clinical dyspnea ratings and psychophysical measurements of respiratory sensation in obstructive airway disease.

To investigate the hypothesis that clinical methods and psychophysical testing provide different information about breathlessness, we compared dyspnea ratings from a modified Medical Research Council (MRC) scale, the Oxygen-Cost Diagram (OCD), and the Baseline Dyspnea Index (BDI) with the perceived magnitude of added loads in 24 patients with obstructive airway disease (OAD) who experienced dyspnea on exertion. Age of the patients was 55.8 +/- 13.7 yr (mean +/- SD), FEV1 was 1.77 +/- 0.81 L, and FEV1/FVC ratio was 52.6 +/- 10.5%. Dyspnea ratings were obtained for each clinical method by 2 independent observers; estimates of the magnitude of 5 resistive loads (10 to 85 cm H2O/L/s) were obtained using the Borg category scale (0 to 10). For comparative purposes, 12 age-matched (48.9 +/- 13.5 yr) healthy subjects were also studied. Clinical ratings of dyspnea obtained in patients for MRC (range, 0 to 4), OCD (range, 23 to 98), and BDI (range, 0.5 to 12.0) were all highly interrelated (rs = 0.79, -0.83, and -0.71; p less than 0.001 for all comparisons). Exponents of the psychophysical power function for resistive breathing loads were similar for patients with OAD (0.57 +/- 0.27) and control subjects (0.63 +/- 0.18) (p = NS). Clinical dyspnea scores were significantly correlated with both FEV1 and FVC; however, neither dyspnea ratings nor lung function were significantly related to the exponent for added breathing loads in the patient group. These comparisons indicate that in patients with symptomatic OAD, clinical methods for rating dyspnea are interrelated and are correlated with lung function, but are independent of perception of resistive breathing loads.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

The role of theophylline in the treatment of dyspnea in COPD.

Dyspnea is influenced by both physiologic and psychologic factors. Breathlessness is common in patients with chronic obstructive pulmonary disease (COPD) and often is the reason that the individual patient seeks medical attention. In order to evaluate the different clinical studies involving the use of theophylline in COPD patients, it is important to consider the three distinct approaches for measuring dyspnea--psychophysical testing, clinical methods, and ratings during exercise. Four randomized, double-blind, placebo-theophylline trials from one to four weeks in duration have evaluated the impact of theophylline on lung function and breathlessness. In these studies, the overall improvement in forced expiratory volume in one second was quite consistent for theophylline compared with placebo therapy. When appropriate clinical methods for measuring dyspnea were used, theophylline showed a positive reduction in breathlessness. These reports suggest that theophylline provides modest objective and subjective improvement in patients with symptomatic chronic air flow obstruction.

Adult↗
PubMed1987

Dyspnea: diagnosis and management.

Multiple physiologic and psychologic factors contribute to the sensation of acute as well as chronic dyspnea. The causes of acute dyspnea frequently can be established by a brief history, physical examination, and chest radiograph. Appropriate therapy should be directed to reversing the specific etiology leading to the acute onset of breathlessness. Chronic dyspnea is probably the most common respiratory complaint of patients seeking medical care. Both aging and deconditioning may influence the development and severity of breathlessness in healthy and disease states. Pulmonary function testing, measurement of respiratory muscle strength, and cardiopulmonary exercise testing may be required to investigate the problem of chronic dyspnea. Once the diagnosis has been made, it is useful to measure or quantify breathlessness using clinical rating methods. This baseline assessment provides objective information for evaluating response to treatment. Initial therapy for improving chronic breathlessness should be directed at the specific cause of the problem. Additional strategies for reducing dyspnea include breathing techniques, exercise training, nutritional manipulations, psychologic interventions, respiratory muscle training, respiratory muscle rest, and sedative/hypnotic medications.

Acute Disease↗
PubMed1987

Cardiovascular responses to rowing.

The purpose of this investigation was to evaluate the cardiovascular responses to rowing. In the first part of the study, heart rate (HR) and cardiac output (Q) were measured at rest and at three steady-state exercise levels on the variable-resistance rowing ergometer in 10 female and 11 male subjects. Q was determined non-invasively by the equilibration method of CO2 re-breathing, and stroke volume (SV) was calculated. Subjects varied in rowing ability from healthy, inexperienced rowers to competitive athletes. The linear relationships between Q and oxygen consumption for the women (r = 0.57; P less than 0.001; slope = 5.2 +/- 1.1) (mean +/- SD) and the men (r = 0.58; P less than 0.001; slope = 6.1 +/- 1.4) were similar to published values for other types of upright exercises. For both mean and women, SV increased from rest to the first level of exercise, and then reached a plateau at or before the second exercise intensity. Between the second and third levels of exercise, SV decreased significantly in the female subjects (107 +/- 18 vs 94 +/- 16 ml; P less than 0.05), but not in the male subjects (128 +/- 1 1 vs 126 +/- 15 ml; P = not statistically significant). In the second part of the study, HR, Q, and SV were compared on the cycle and rowing ergometers on successive days in eight additional subjects. At similar levels of oxygen consumption and Q, HR was significantly higher, and SV was significantly lower during rowing exercise than with cycle exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Theophylline improves global cardiac function and reduces dyspnea in chronic obstructive lung disease.

Theophylline has been utilized widely as a bronchodilator, but only in recent years have its positive cardiovascular effects been recognized in patients with chronic obstructive pulmonary disease. After intravenous administration of aminophylline, pulmonary artery pressures and pulmonary vascular resistance are reduced, and both right and left ventricular ejection fraction are increased. Similar short- and long-term enhancement of biventricular performance is produced by orally administered long-acting theophylline. Possible mechanisms for this theophylline-induced improvement in right and left ventricular systolic pump performance include enhanced ventricular inotropy and reduced ventricular afterload. A recent study has established that orally administered theophylline also reduces dyspnea in patients with chronic obstructive pulmonary disease. Accordingly, in patients with chronic obstructive pulmonary disease theophylline may be useful for reducing pulmonary artery pressure and pulmonary vascular resistance, treating right or left heart failure, reducing dyspnea, and partially reversing airway obstruction.

Dyspnea↗
PubMed1986

Acute effects of passive smoking on lung function and airway reactivity in asthmatic subjects.

We studied the acute effects of one hour of passive cigarette smoking on the lung function and airway reactivity of nine young adult asthmatic volunteers. At the time of this study, the subjects were asymptomatic and had normal or nearly normal lung function. Passive smoking produced no change in expiratory flow rates. However, there was a small decrease in nonspecific bronchial reactivity, as assessed by methacholine inhalation challenge testing (p = 0.022). Pharmacologically active substances present in cigarette smoke, such as nicotine, may explain the observed change in airway reactivity. Although the finding of decreased airway reactivity might suggest that passive smoking produces a "protective" effect on the underlying asthma, the observed change in reactivity was slight and of uncertain clinical significance. We conclude that passive smoking presents no acute respiratory risk to young asymptomatic asthmatic patients.

Adult↗
PubMed1986

The aging lung.

Structural changes occur in the respiratory system with advancing age. Lung elasticity decreases, stiffness of the chest wall increases, and respiratory muscle strength declines. These alterations contribute to gradual, but progressive, reductions in forced vital capacity, expiratory flow rates, diffusing capacity, gas exchange, ventilatory drive, and respiratory sensation. Cigarette smoking accelerates the age-related decline in flow rates. Understanding the effects of aging on the lung is important in order to distinguish pathologic changes from changes that are part of the normal aging process.

Adult↗
PubMed1986

Chronic obstructive pulmonary disease.

Morbidity and mortality associated with chronic airway disease are expected to continue to rise over the coming years. Accordingly, increased attention will need to be directed toward the diagnosis and treatment of COPD in the elderly population. Cessation of cigarette smoking should be pursued in all patients regardless of age. The goals of bronchodilator therapy are to reduce respiratory symptoms and to improve functional capacity without causing adverse effects. In addition, supplemental oxygen, phlebotomy for polycythemia, general exercise training, and specific respiratory muscle training may further augment exercise tolerance. Complications of COPD, such as upper respiratory infections and right heart failure, should be recognized early and treated appropriately. Implementation of a pulmonary rehabilitation program, as discussed in the next article, should complement medical therapy in the treatment of elderly patients with COPD.

Adrenal Cortex Hormones↗
PubMed1986

Aging and exercise performance.

Diverse physiologic changes occur in the oxygen transport system during the aging process. Physical performance and VO2max decline with age, but the changes may be attenuated by exercise training. Increased ventilation is required during exercise in order to compensate for reduced efficiency of gas exchange. Cardiovascular alterations include prolonged duration of myocardial contraction, a slightly reduced left ventricular ejection fraction during exercise, decreased heart rate during both submaximal and maximal exercise, and attenuation of myocardial response to beta-adrenergic stimulation. Cardiac output during exercise can be maintained in the elderly owing to a greater dependence on ventricular filling. Appropriate exercise training leads to enhanced efficiency of the lungs, heart, and skeletal muscles. These physiologic benefits contribute to an increase in functional capacity and an enhanced sense of well-being. Exercise testing is recommended for individuals who have cardiorespiratory symptoms and for those at risk for the development of coronary artery disease. Reasonable goals for an aerobic training program are continuous activity for 30 minutes at a moderate intensity of exertion at least 3 days per week. The intensity of exercise should be based on a prescribed training heart rate. The exercise prescription should be individualized and should incorporate one or more activities for optimal enjoyment and compliance. Opportunities and facilities for indoor exercise are important during inclement weather. Regular physical exercise is important at any age!

Aged↗