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Biomedical subjects

A Harver

Publications and source records attributed to A Harver.

28 records · Page 2Linked to original sources
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

Constancy of individual exponents for category production of inspired lung volume.

Individual exponents for production of inspired lung volume were compared both within experimental sessions (after a delay of 5 to 10 min.) and between sessions (after a delay of 1 yr.). Reliable correlations were observed between pairs of individual exponents regardless of the time elapsed between repetitions of the task. Constancy of exponents may reflect a propensity for subjects to respond in characteristic ways to psychophysical scaling tasks.

Adult↗
PubMed1984

Pulmonary changes induced by frontal EMG training.

Earlier research suggested that the effects of facial muscle tension changes on other responses are not widespread but limited to a rather narrow set of pulmonary events. Further evidence in support of the specificity of the facial muscle-pulmonary relationship was provided in the present study by monitoring changes in several responses as a function of muscle tension training. Feedback training for increases and decreases in muscle tension at both facial and limb muscle sites was given to adult males. The effects of these manipulations on PEFR, RR, and HR were examined. Increases in facial muscle tension resulted in PEFR decreases whereas increases in limb muscle tension did not. Decreases in facial muscle tension were not observed as a function of training and no PEFR changes resulted from these conditions. Neither RR nor HR were related to the facial EMG changes observed during feedback training. These observations demonstrated the specificity inherent in the relationship between facial muscle tension and PEFR, and lent support to the hypothesis that these two responses are linked reflexively.

Adolescent↗
PubMed1984

An intraindividual comparison of standard and mini-Wright scores.

The relationship between peak expiratory flow rate scores recorded with the standard Wright meter and those recorded with the mini-Wright meter was determined by correlating these scores on an intraindividual basis. These correlations were compared with correlations between pairs of standard scores. The latter were computed so as to provide an estimate of peak expiratory flow rate variability unrelated to recording apparatus. The results showed that pairs of standard Wright scores were more highly related to one another than were pairs of standard and mini-Wright scores. From these observations it was concluded that standard and mini-Wright scores are not equivalent and therefore may not confidently be interchanged.

Adolescent↗