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Biomedical subjects

M J Belman

Publications and source records attributed to M J Belman.

At least 19 recordsLinked to original sources
PubMed1992

Isolated reduction in single-breath diffusing capacity in the evaluation of exertional dyspnea.

UNLABELLED: STUDY SETTINGS AND INTERVENTIONS: Sixty individuals complaining of dyspnea on exertion, but with normal spirometry and lung volumes and normal chest roentgenograms were reviewed for this study. These individuals were selected from a large group of outpatients (552 individuals over a seven-year period) who were referred to our laboratory for exercise testing to determine the cause of their exertional dyspnea. They were grouped according to the single-breath diffusing capacity, with those less than 70 percent of predicted in the low DCO group (group 1) and those greater than 70 percent of predicted in the normal DCO group (group 2). Both study groups underwent an incremental exercise test. RESULTS: Twenty-three individuals had a DCO less than 70 percent of predicted. During exercise, seven of these (30 percent) had an abnormal PaO2 and five had an abnormal P(A-a)O2. Thirty-seven people had a normal DCO. Thirty-six of these (97 percent) had a normal PaO2 and P(A-a)O2 during exercise. Overall, eight individuals had an abnormal PaO2 or P(A-a)O2 during exercise; seven of these had an abnormally low DCO at rest. CONCLUSIONS: Based on this selected group of a subpopulation, we conclude that the DCO is an important determinant of the diagnostic approach to a patient with dyspnea who is otherwise normal. If all pulmonary functions, including DCO are normal, an exercise study will fail to reveal abnormal PaO2 or P(A-a)O2 in 97 percent of the cases. However, a low DCO has a poor predictive value with respect to abnormal gas exchange during exercise. Therefore, when investigating exertional dyspnea, based on this selected subpopulation, if the spirometry, lung volumes, and DCO are normal, one may forego additional invasive gas exchange evaluation. However, an abnormal DCO warrants further physiologic testing.

Blood Gas Analysis↗
PubMed1992

Noninvasive determinations of the anaerobic threshold. Reliability and validity in patients with COPD.

We compared the intraobserver and interobserver agreement of blood (BGT) and gas exchange (GET) methods for determination of the anaerobic threshold (AT) in patients with COPD. In addition, we determined the sensitivity and specificity of the gas exchange methods for determination of the AT. Two noninvasive methods, the V-slope (VS) and the ventilatory equivalents method (VEM) were compared with two blood sampling methods, the log standard HCO3 (SB) vs log VO2 (SBT) and base excess (BE) vs VO2 (BET). Twenty-nine patients with COPD (FEV1 < 60%) performed incremental exercise tests to exhaustion while breath-by-breath gas exchange measurements were made. Blood samples were drawn at the end of each minute for SB and BE. Two trained observers determined the VO2 at the threshold for each of the four indices on two separate occasions two weeks apart. Our results demonstrated the following: only modest interobserver and intraobserver agreement was noted by Spearman rank correlations; the VEM was as sensitive as the VS in COPD patients; and the presence of a true metabolic acidosis was not reliably predicted by GET methods. Moreover, although the blood methods accurately identified the presence of metabolic acidosis, there was disagreement on the actual point of the BGT. We conclude that gas exchange indices were not helpful for the determination of metabolic acidosis in patients with COPD.

Adult↗
PubMed1992

Factors limiting exercise performance in lung disease. Ventilatory insufficiency.

Because of the additive effects of impaired ventilatory muscle function on the one hand and the increased ventilatory load on the other, increasing attention is now directed at therapies to improve ventilatory muscle function. Three main approaches are being used: (1) reduction in load; (2) increase in intrinsic ventilatory muscle function; and (3) reduction in dyspnea perception. While promising results have been achieved, additional investigative work is required to resolve outstanding questions.

Dyspnea↗
PubMed1991

A target feedback device for ventilatory muscle training.

In a previous study, we successfully used a target feedback device, together with an external resistor, to train the ventilatory muscles of patients with chronic obstructive pulmonary disease. In this article, we describe the details of the design and function of the target feedback device. When used in conjunction with an external resistance, the target feedback device provides timing and pressure targets, together with feedback information, on whether these targets are achieved. The target feedback device consists of readily available electronic components and is relatively simple to construct. Adjustment of an external pressure knob permits setting of pressure targets. Adjustment of internal components is possible and allows control of breathing frequency, inspiratory time, and breathing waveform.

Breathing Exercises↗
PubMed1991

Variability of breathlessness measurement in patients with chronic obstructive pulmonary disease.

The purpose of our study was to evaluate the reproducibility of a Borg rating of dyspnea in patients with COPD. We examined nine patients with COPD who performed a SST on four separate days within a ten-day period. The patients walked on a treadmill for 6 min. At the end of each minute, patients matched a Borg rating to the intensity of their breathlessness. We measured the HR, VE, VO2, VT and f at the end of each minute. While the mean VO2, VE, HR, VT and f stabilized after one or two attempts, the Borg ratings decreased with successive tests. We conclude that the Borg scale for measuring breathlessness shows progressive decreases with repetition whereas VO2, VE, HR, VT and f stabilize after one or two practice attempts. This suggests that desensitization to dyspnea may play a role in the improvement of patients after exercise.

Aged↗
PubMed1991

Exercise training below and above the lactate threshold in the elderly.

In this study we report the effects of training at intensities below and above the lactate threshold on parameters of aerobic function in elderly subjects (age range 65-75 yr). The subjects were randomized into high-intensity (HI, N = 8; 75% of heart rate reserve = approximately 82% VO2max = approximately 121% of lactate threshold) and low-intensity (LI, N = 9; 35% of heart rate reserve = approximately 53% VO2max = approximately 72% of lactate threshold) training groups which trained 4 d.wk-1 for 30 min.session-1 for 8 wk. Before and after the training, subjects performed an incremental exercise test for determination of maximal aerobic power (VO2max) and lactate threshold (LT). In addition, the subjects performed a 6-min single-stage exercise test at greater than 75% of pre-training VO2max (SST-High) during which cardiorespiratory responses were evaluated each minute of the test. After training, the improvements in VO2max (7%) for LI and HI were not different from one another (delta VO2max for LI = 1.8 +/- 0.7 ml.kg-1.min-1; delta VO2max for HI = 1.8 +/- 1.0 ml.kg-1.min-1) but were significantly greater (P = 0.02) than the post-testing change observed in the control group (N = 8). Training improved the LT significantly (10-12%; P less than 0.01) and equally for both LI and HI (delta LT for for LI = 2.3 +/- 0.6 ml O2.kg-1.min-1; delta LT for HI = 1.8 +/- 0.8 ml O2.kg-1.min-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1990

Improvement in exercise performance after pulmonary arteriovenous malformation embolization.

Balloon or coil embolization has become established therapy for multiple PAVMs. We were able to evaluate a 32-year-old woman with multiple PAVMs characterized by significant orthodeoxia, intrapulmonary shunt, dyspnea and limited exercise tolerance before and after balloon and coil embolization. After embolization of three of her largest PAVMs, repeat evaluation revealed improvement in her symptoms, orthodeoxia and intrapulmonary shunt. She was able to exercise two additional work rates with a sustained improvement in oxygenation, a decrease in the P(A-a)O2 difference and higher maximum oxygen consumption. These studies provide objective evidence of persistent improvement in function and endurance at rest and during exercise after embolization.

Adult↗
PubMed1990

Efficacy of positive vs negative pressure ventilation in unloading the respiratory muscles.

We compared the efficacy of positive pressure ventilation (PPV) vs negative pressure ventilation (NPV) in providing ventilatory muscle rest for five normal subjects and six patients with chronic obstructive pulmonary disease (COPD). All participants underwent measurement of transdiaphragmatic pressure (Pdi), pressure time integral of the diaphragm (PTI), integrated diaphragmatic electromyogram (iEMG), minute ventilation (Ve), tidal volume (Vt), and end-tidal CO2 (etCO2) during 15 minutes of PPV and NPV. For each subject, ventilator adjustments were made to obtain Ve similar to levels measured during quiet breathing (QB). We found that the iEMG, Pdi, PTI, and average coefficient of variation of the tidal volume (CV-Vt) were consistently lower during PPV as compared with NPV (p = 0.01). The iEMG normalized for Ve and Vt was also significantly lower during PPV (p = 0.01). During PPV, subjects were mildly hyperventilated (lower etCO2 and higher Ve) compared with QB and NPV, but no significant correlation was noted between the change in etCO2 and the change in iEMG. The change in PTI was significantly correlated with the change in iEMG (p less than 0.01). We conclude that in the short term, PPV is more effective than NPV in reducing diaphragmatic activity. Positive pressure ventilation may be the preferred method of assisted ventilation in future studies of ventilatory muscle rest therapy.

Aged↗
PubMed1988

Ventilatory muscle training in the elderly.

To test the hypothesis that declining ventilatory function in the elderly impairs exercise capacity, we tested maximal exercise capacity and ventilatory function before and after a program of ventilatory muscle training in 25 elderly subjects (ages 65-75 yr). Ventilatory muscle training was performed by means of isocapnic hyperpnea for 30 min/day, 4 days/wk for 8 wk. Before and after the training, we measured maximal exercise capacity by means of an incremental exercise test (IET) and ventilatory muscle endurance by means of the maximum sustained ventilatory capacity (MSVC). Ratings of perceived exercise (RPE) for breathlessness and leg effort were evaluated each minute by means of a modified Borg scale during both the IET and a 12-min single-stage exercise test (SST) performed at approximately 70% of the maximal exercise capacity. The trained group showed a significant increase in the MSVC, from 71.9 +/- 26.4 to 86.9 +/- 20.9 l/min (P less than 0.01), whereas the control group showed no change (66.3 +/- 22.5 to 65.1 +/- 22.1 l/min). In addition, the maximal voluntary ventilation increased in the trained group, from 115 +/- 41 to 135 +/- 36 l/min (P less than 0.01). Neither the trained nor the control group showed an increase in maximum O2 uptake, maximum CO2 consumption, or maximum minute ventilation during the IET. Evaluation of the RPE during both the IET and SST showed that although there was a small decrease in RPE for breathing and leg discomfort, changes between the control and treated groups were similar.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1988

Targeted resistive ventilatory muscle training in chronic obstructive pulmonary disease.

To overcome the problem of altered breathing strategy during resistive ventilatory muscle training (VMT), we used a single-orifice inspiratory resistance together with a target feedback device (TFD) in patients with chronic obstructive pulmonary disease (COPD). In a preliminary study (study A), we showed that the resistance plus TFD was effective in controlling breathing strategy. We subsequently used the resistor plus TFD in a 5-wk study (study B) of VMT in 17 COPD patients who were randomized into high-intensity (HI) and low-intensity (LI) training groups. Compared with the LI group, the HI group showed significant increases in static maximal inspiratory pressure (21.3 vs. 5.0 cmH2O), maximal sustained ventilatory capacity (MSVC, 3.2 vs -0.1 l/min, sustained maximal mouth pressure (12.1 vs. 0.6 cmH2O), mean mouth pressure (6.9 vs. 3.9 cmH2O), peak inspiratory flow rate (12.3 vs. 4.0 l/min), and maximal sustained work rate (12.2 vs. 4.2 cmH2O.l-1.min-1). We conclude that targeted VMT with control of breathing strategy improves both ventilatory muscle strength and endurance.

Biofeedback, Psychology↗
PubMed1988

Respiratory muscle training.

The application of skeletal muscle training principles to the respiratory muscles is a relatively new field. Strength and endurance training of the respiratory muscles can be achieved in normal humans and in patients with neuromuscular and chronic obstructive pulmonary diseases. Careful monitoring is required throughout a training program to ensure that the respiratory muscles are, in fact, being trained. This is a promising area, although further research is necessary to determine the indications for respiratory muscle training. Furthermore, it is still necessary to determine the optimal mode of training.

Breathing Exercises↗
PubMed1988

Nutrition and the respiratory muscles.

Malnutrition may be an important complicating factor in acute and chronic lung disease. Animal studies have demonstrated significant atrophy of diaphragm muscle fibers following prolonged undernutrition resulting in a marked reduction in diaphragm muscle strength as well as alteration in other contractile and fatigue properties of the muscle. In severe chronic obstructive pulmonary disease (COPD), malnutrition is common and may, in conjunction with the influences of hyperinflation on diaphragm performance, predispose to respiratory muscle fatigue and failure. The course of progressive weight loss in patients with COPD is not known but may, in part, be related to a "hypermetabolic" state arising from an increased oxygen consumption of the respiratory muscles secondary to enhanced resistive loads and impaired mechanical efficiency of the respiratory muscles. Reports of the impact of nutritional repletion on respiratory muscle performance in critically ill patients, as well as in patients with COPD, are preliminary. Further studies are necessary to establish whether such measures impact meaningfully on both the morbidity and mortality of these patients.

Animals↗
PubMed1987

Nutritional supplementation in ambulatory patients with chronic obstructive pulmonary disease.

We examined the effect of nutritional supplementation for 8 wk on respiratory muscle function (RMF) in 21 malnourished patients with COPD. Patients were randomized to a fed group or to a control group. Patients in the fed group were provided with an enteral formula in addition to their usual diet. Daily calorie and protein intake and weekly anthropometric measures were made. Pulmonary function tests were measured on Weeks 1, 4, and 8. Respiratory muscle strength was measured by means of maximal inspiratory and expiratory pressures (MIP), (MEP), and respiratory muscle endurance was measured by the maximal sustained ventilatory capacity (MSVC). The mean weight of the fed group increased from 52.2 +/- 6.4 to 53.3 +/- 6.9 kg (NS). The mean daily caloric intake of the fed group was significantly increased during the study (p less than 0.02). The mean calorie intake during the study of the fed group was 174 +/- 17% of the estimated basal energy expenditure. During the study period, no change was observed in anthropometric measures, pulmonary function studies, or RMF. Because patients tend to decrease their own food intake while receiving enteral formulas, it is difficult to provide sufficient calories and protein needed to effect changes in nutritional status and RMF in an outpatient COPD population. In addition, we compared RMF in 12 poorly nourished male patients (87.6 +/- 6.1% of ideal body weight) and 13 well-nourished male patients with severe COPD. Both groups had comparable degrees of air-flow limitation and hyperinflation. No difference was noted between the groups in either MIP, MEP, or MSVC.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Effect of nutritional deprivation on diaphragm contractility and muscle fiber size.

The influence of nutritional deprivation on the contractile and fatigue properties of the diaphragm was studied in adult rats. Food access was restricted to one-third of normal daily intake until the body weight of nutritionally deprived (ND) animals was approximately 50% of controls (CTL). Isometric contractile properties were studied in an in vitro nerve muscle strip preparation. Both twitch (Pt) and tetanic (Po) tensions of diaphragms from the ND animals were markedly reduced compared with CTL; however, Pt/Po was higher for the ND group. The shape of the force-frequency curve (normalized to Po) was generally similar between the two groups, except at 5 and 10 pulses/s stimulation, where greater relative tensions were produced in diaphragms from the ND animals. Diaphragm fatigue was induced by repetitive stimulation at either 20 or 100 pulses/s. Endurance time (defined as the time required for tension to fall to 50% of initial) of diaphragms from ND animals was prolonged at both 20 and 100 pulses/s. Immediately after induction of fatigue, force-frequency curves for both ND and CTL diaphragms were shifted to the right. However, this rightward shift was attenuated in the ND group compared with CTL. Nutritional deprivation had no effect on the proportions of different fiber types within the diaphragm but did result in a significant decrease in the cross-sectional area of both fast-and slow-twitch fibers. This decrease in cross-sectional area was significantly greater for fast-twitch fibers. We conclude that these changes in diaphragm contractile and fatigue properties occur as a result of the influence of malnutrition on muscle fiber cross-sectional area.

Animals↗