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Biomedical subjects

M I Lewis

Publications and source records attributed to M I Lewis.

At least 55 records · Page 3Linked to original sources
PubMed1986

Aminophylline and fatigue of the sternomastoid muscle.

We examined the influence of intravenously infused aminophylline on the contractility of the sternomastoid muscle in 8 subjects. The muscle was stimulated directly using bipolar surface electrodes at 1, 10, 20, and 50 pulses per second (pps), and the force response was recorded. The ratio of force produced at 20 pps and 50 pps (20/50 ratio) was calculated. The effect of aminophylline on the 20/50 ratio was assessed at 2 dosages producing different blood serum levels (10.7 mg/L and 15.3 mg/L). At the lower dosage of aminophylline the potential prophylactic and curative influence of aminophylline was tested using 3 different experimental paradigms performed on separate days: (1) Baseline force frequency responses were determined before and 15 and 35 min after a headlifting maneuver; headlifting resulted in a decrease in the 20/50 ratio (low frequency fatigue). (2) The same sequence as in (1), with the addition of a continuous infusion of aminophylline started after the baseline force frequency responses. (3) The same sequence as in (1) except that the aminophylline infusion was begun only after the headlifting maneuver. After the fatiguing maneuvers, there were comparable and significant falls in the 20/50 ratio on all experimental days. The infusion of aminophylline did not significantly affect the baseline 20/50 ratio. In addition, aminophylline did not prevent the fatigue-related decrease in the 20/50 ratio or enhance its recovery. Experimental paradigms 1 and 2 were repeated at the higher aminophylline levels. Again, aminophylline did not prevent or reverse sternomastoid fatigue. We conclude that aminophylline in therapeutic dosages does not prevent or reverse low frequency fatigue of the sternomastoid muscle.

Adult↗
PubMed1986

Resistive breathing training in patients with chronic obstructive pulmonary disease.

In order to investigate the effect of resistive breathing training on ventilatory muscular endurance, we examined the maximal sustained ventilatory capacity in ten patients with chronic obstructive pulmonary disease (COPD) before and after a six-week program of resistive breathing training. In addition, we investigated the effect of altered breathing strategy on resistive breathing performance. The patients performed two 15-minute sessions of resistive breathing daily for six weeks using an inspiratory resistive device (Pflex). Before and after the training, we found no significant change in spirometric data, pulmonary volumes, maximal inspiratory pressure, and maximal expiratory pressure. Of the ten patients, seven failed to show an improvement in their performance of resistive breathing. Furthermore, the maximal sustained ventilatory capacity was unchanged after the resistive breathing training. After the completion of the training program, seven of the patients participated in an additional experiment in which they were instructed to take long slow inspirations while breathing through the resistive device. With this change in breathing pattern, five of the seven were able to improve their performance of resistive breathing. Analysis of the breathing strategy showed that a reduction in the peak mouth pressure, breathing frequency, and external resistive work with a longer inspiratory time was beneficial. We conclude that neither resistive breathing performance nor ventilatory muscular endurance, as measured by sustained hyperpnea, is improved by resistive breathing training performed according to the current instructions with the resistive device, and alterations in breathing strategy have a profound effect on the performance of resistive breathing. The lack of details of breathing strategy in previous studies of resistive breathing makes it difficult to determine if previously demonstrated improvements were due to a real enhancement of ventilatory muscular performance or merely secondary to a different strategy.

Aged↗
PubMed1984

Experience at an adolescent and adult cystic fibrosis clinic. An analysis and overview.

Cystic fibrosis (CF) is the most common serious genetic condition in the White population groups. Thirty-three White patients (mean age 20 years, range 14-32 years) seen at an adult CF clinic at the Johannesburg Hospital between January 1980 and January 1983 are reviewed. All had elevated sweat chloride levels. There was a family history of CF in 45,5% of the cases. Most were of normal height but significantly underweight. Chronic obstructive pulmonary disease was present in 94% of the patients. Pulmonary infections played a major role in both symptomatic exacerbations and progressive lung disease. Most frequently, mucoid Pseudomonas aeruginosa and/or Staphylococcus aureus were cultured from the sputum. The management of infective exacerbations is discussed. Other respiratory complications included cor pulmonale, haemoptysis, recurrent pneumothorax and sinusitis. Chest radiographs and pulmonary function tests are also analysed. Gastro-intestinal complications included pancreatic exocrine insufficiency (94%), intestinal obstruction, cholelithiasis, and liver disease. Insulin-dependent diabetes occurred in 9%. Five pregnancies were recorded in 4 patients. By January 1983 there had been 7 deaths (mean age 19,4 years). Most of the patients are highly motivated, with few psychological problems, and appear to be well-functioning and integrated members of society.

Adolescent↗
PubMed1984

Finger skin temperature and manual dexterity - some inter-group differences.

The relationship between finger skin temperature (FST) and performance was demonstrated with four manual dexterity tasks all of which were performed by black and white, male and female subjects. At air temperatures below 24 degrees C the white subjects tended to have warmer FSTs than the black subjects; white subjects were also able to equal the performance of the black subjects at air temperatures as much as 6 degrees C below that required by the black subjects.

Journal Article↗