Biomedical subjects
M D Morgan
Publications and source records attributed to M D Morgan.
NSNA in the 1960's.
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The practical implementation of multidisciplinary pulmonary rehabilitation.
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P300 event-related potentials in stutterers and nonstutterers.
This study investigated possible differences between adult stutterers and nonstutterers in the P300 event-related potential. Responses to tonal stimuli were recorded from electrodes placed over the left (C3) and righ (C4) hemispheres. The two groups exhibited different patterns of interhemispheric activity. Although all 8 participants in the fluent group exhibited P300s that were higher in amplitude over the right hemisphere, 5 of the 8 disfluent participants had higher amplitude activity over the left hemisphere. These results provide evidence that stutterers and nonstutterers may exhibit differences between hemispheres in the processing of some types of nonlinguistic (tonal) stimuli.
The effect of a time delay on the measurement of capillary blood gases.
Patients using domiciliary nasal ventilation, or long-term oxygen, require regular assessment which could be carried out in the home. Blood gas analysis may be regarded as an essential part of the assessment. The present study investigated the effect of a 1-h time delay on the measurement of capillary blood gases. Four samples of arterialized earlobe blood were collected from 15 outpatients. One sample was analysed immediately, the other three were stored on crushed ice and analysed at intervals of 30, 45, and 60 min post-collection. In order to examine any range effect, a wide range of PaO2 values were examined. The delay, at all levels, resulted in minor changes in the measurement of PaO2, which would be unlikely to alter clinical management. The technique might be used for the reliable assessment of patients in the home.
Rehabilitation for people with chronic lung disease.
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Comparison of peak oxygen consumption during cycle and treadmill exercise in severe chronic obstructive pulmonary disease.
BACKGROUND: In normal subjects treadmill exercise usually produces the greatest maximal oxygen consumption (VO2max). This may not be true for patients with severe chronic obstructive pulmonary disease (COPD) in whom bicycle exercise, which offers support for the shoulder girdle, may produce a higher oxygen consumption than treadmill exercise. The aim of this study was to determine which mode of exercise produced the greatest oxygen consumption in patients with severe COPD. METHODS: Eight patients with severe COPD (forced expiratory volume in one second (FEV1) more than three standardised residuals below predicted) exercised to a symptom limited maximum on a bicycle and on a treadmill on separate days. The workload on the bicycle wa increased by 10 watts each minute, and the treadmill gradient was increased by 2.5% alternate minutes whilst the speed remained constant. Measurements of oxygen consumption (VO2), ventilation (VE), heart rate, and oxygen saturation were made, and capillary blood gases were measured before and immediately after exercise. Lactate concentration was measured before and four minutes after exercise. RESULTS: There were no differences at peak exercise between the two forms of exercise for VO2 (median 11.7 and 12.2 ml/min/kg for bicycle and treadmill, respectively), for VE (median 26.6 and 25.0 l/min, respectively), and for heart rate (median 119 and 115 beats/min, respectively). The median lactate levels after bicycle exercise were higher than those after the treadmill (2.42 v 0.94 mmol/l). CONCLUSIONS: Although only a small number of patients was studied and individual variability was large, there was no clear difference between the two forms of exercise. Regular bicycle exercise was unfamiliar to this group of patients and generated the greatest lactate response. The results do not support the hypothesis that bicycle exercise will produce a better performance in patients with severe COPD, but the two modes of exercise cannot be used interchangeably.
Comparison of oxygen uptake during a conventional treadmill test and the shuttle walking test in chronic airflow limitation.
The purpose of this study was to investigate the relationship between performance on the shuttle walking test and maximal oxygen uptake (VO2max) during a conventional treadmill test in patients with chronic airflow limitation. Two different techniques were used to measure oxygen consumption, i.e. conventional Douglas bag techniques (treadmill test) and a portable oxygen consumption meter (shuttle test). Initially, 19 patients performed a shuttle walking test (after one practice walk) and a maximal treadmill walking test, in a randomized, balanced design. Subsequently, 10 patients, (after one practice) completed an unencumbered shuttle walking test and one supporting the portable oxygen consumption meter, in random order. The results of the first experiment revealed a strong relationship between performance during the shuttle walking test and VO2max during the treadmill walking test (r = 0.88). The results of the second experiment consistently demonstrated an incremental increase in oxygen consumption and ventilation in response to the increasing intensity of the shuttle walking test. Again, a strong relationship between VO2max and performance on the shuttle test was demonstrated (r = 0.81). We concluded that the shuttle walking test is a valid field exercise test of functional capacity. Performance on the test relates strongly to VO2max, the traditional indicator of cardiorespiratory capacity.
False reassurance of pulse oximetry. Misunderstanding leads to dangerous practice.
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Endurance exercise capacity in adults with cystic fibrosis.
We have compared the maximal and endurance exercise capacities in 22 (15 male) adult cystic fibrosis (CF) patients with a resting oxygen saturation (SaO2) > or = 90%, with age and sex matched controls (CON). The maximum oxygen uptake (VO2max) and heart-rate were lower for the CF group whereas the maximum ventilation reached a higher percentage of predicted. Furthermore, for the CF group there was a relationship between the % predicted VO2max and measures of lung function, confirming a ventilatory limit to maximum exercise in patients with more severe disease and a near normal maximum exercise capacity in those with mild disease. Endurance capacity, defined as the duration of exercise at 80% of each individuals VO2max, was however similar for the two groups [CF: 22.21 (15.82) vs. CON: 24.94 (13.05) min]; despite the CF group exercising under less efficient ventilatory conditions. Endurance capacity was not related to the measurements of lung function. Of the seven CF patients desaturating at maximal exercise (SaO2 < 90%), five desaturated at a work load of 80% VO2max, whereas only one desaturated at 50% VO2max. This study confirms that with increasing severity of disease, maximal exercise capacity may be limited in adult CF patients, whereas endurance capacity (at the same relative work load) is unimpaired. Furthermore, CF patients who desaturate during a progressive maximal exercise test are likely to desaturate during constant work load exercise if the intensity is high but unlikely to do so if the intensity is low. The information from these exercise tests would be of value for prescribing individual training programmes and for evaluating the effects.
Measurement of inspiratory muscle performance with incremental threshold loading: a comparison of two techniques.
BACKGROUND: Incremental threshold loading (ITL) is a test of inspiratory muscle performance which is usually performed by breathing through a weighted inspiratory plunger, the load on the inspiratory muscles being increased by externally adding weights to the intake valve. This is not a true threshold device and may be inaccurate. This method was compared with a true threshold device consisting of a solenoid valve which only opens to supply air at a predetermined negative mouth pressure. METHODS: Six naive, normal subjects (three men and three women) aged 22-24 years underwent three tests using each system. The inspiratory loads were increased every minute by equivalent amounts, -10 cm H2O with the solenoid valve and by 50 g with the weighted plunger, until the subjects could not inspire or sustain inspiration for a full minute. Six experienced subjects (four men and two women) aged 23-41 years were subsequently randomised to perform ITL with the solenoid valve, twice with the breathing pattern fixed and twice free. RESULTS: The solenoid valve generated a more accurate mouth pressure response and was less variable at higher loads than the weighted plunger. The work performed (expressed as the pressure-time product) was less with the solenoid valve but was more reproducible. ITL with the solenoid valve was not influenced by controlling the breathing pattern of the subjects. CONCLUSIONS: The solenoid valve has several features that make it superior to the weighted plunger as a device for ITL. It generates a more accurate mouth pressure response which is less variable at higher loads. Increases in load are smoother and quicker to introduce. ITL with the solenoid valve is not influenced by varying breathing patterns and does not require any external regulation.
Respiratory medicine: fighting for survival.
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Detection and quantification of pulmonary emphysema by computed tomography: a window of opportunity.
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Development of a shuttle walking test of disability in patients with chronic airways obstruction.
BACKGROUND: The aim was to develop a standardised and externally paced field walking test, incorporating an incremental and progressive structure, to assess functional capacity in patients with chronic airways obstruction. METHODS: The usefulness of two different shuttle walking test protocols was examined in two separate groups of patients. The initial 10 level protocol (group A, n = 10) and a subsequent, modified, 12 level protocol (group B, n = 10) differed in the number of increments and in the speeds of walking. Patients performed three shuttle walking tests one week apart. Then the performance of patients (group C, n = 15) in the six minute walking test was compared with that in the second (modified) shuttle walking test protocol. Heart rate was recorded during all the exercise tests with a short range telemetry device. RESULTS: The 12 level modified protocol provided a measure of functional capacity in patients with a wide range of disability and was reproducible after just one practice walk; the mean difference between trial 2 v 3 was -2.0 (95% CI -21.9 to 17.9) m. There was a significant relation between the distance walked in the six minute walking test and the shuttle walking test (rho = 0.68) but the six minute walking test appeared to overestimate the extent of disability in some patients. The shuttle test provoked a graded cardiovascular response not evident in the six minute test. Moreover, the maximal heart rates attained were significantly higher for the shuttle walking test than for the six minute test. CONCLUSIONS: The shuttle walking test constitutes a standardised incremental field walking test that provokes a symptom limited maximal performance. It provides an objective measurement of disability and allows direct comparison of patients' performance.
Effect of methacholine induced bronchoconstriction on the spectral characteristics of breath sounds in asthma.
BACKGROUND: Analysis of breath sounds by digital techniques offers an attractive non-invasive method of monitoring changes in airway calibre. Asthmatic breath sounds have been analysed and related to changes in forced expiratory volume in one second (FEV1). METHODS: Bronchoconstriction was induced with methacholine in six asthmatic subjects on two occasions and changes in FEV1 and breath sound spectra were measured. RESULTS: Audible wheeze appeared after a mean (SE) fall in FEV1 of 35% (6.3%) but the level was not reproducible within patients. The mean and median frequency of the spectra of breath sounds correlated with the percentage of predicted FEV1 (r = -0.5 and -0.6 respectively; p < 0.001). Inclusion of the quartile frequencies in a stepwise multiple regression reduced the residual variance by a further 9%. CONCLUSION: Detecting changes in airway calibre by this method of sound analysis so far produces qualitative data only and will not yield quantitative data in individual patients.
Experience of using the CRQ (Chronic Respiratory Questionnaire).
We have examined the role of the Chronic Respiratory Questionnaire in practice. The questionnaire covers aspects of disability in patients with chronic lung disease in terms of dyspnoea, fatigue, emotional function and mastery. It therefore provides a measure of physical disability and quality of life in patients with lung disease. The questionnaire was validated in older patients with chronic obstructive lung disease and is particularly responsive to changes within an individual. Its major disadvantages include the lack of sensitivity in patients with minor symptoms or possibly those in a younger age group and that it is also not possible to make comparisons between populations with the CRQ. It is, however, particularly good at demonstrating changes in disability in older patients with chronic airways disease.
Minitracheotomy: a simple alternative to tracheostomy in obstructive sleep apnoea.
A patient with obstructive sleep apnoea sufficiently severe to cause papilloedema was managed temporarily with a minitracheotomy. This allowed arterial oxygen saturation to return to normal while he lost weight, before surgery for his enlarged tonsills.
Origin and behaviour of emphysematous bullae.
Giant emphysematous bullae are believed to produce symptoms of pulmonary compression and collapse by containing gas under pressure that has been generated through valvular feeding airways. To examine this hypothesis, we have measured oxygen and carbon dioxide tensions (PO2, PCO2) in four patients and pressure within the bullae in three patients immediately before surgery. During spontaneous tidal respiration PO2 in the bulla was higher than arterial PO2 but did not rise as fast during the breathing of oxygen. The intra-bulla pressure during inspiration was negative (-5.5 to -19 cm H2O) and similar to pleural pressure in phase and degree. During intermittent positive pressure ventilation in two patients airway pressures were transmitted to the bulla with the development of a positive end expiratory pressure within the bulla. Histological examination of the walls of the bullae in the four patients and adjacent lung tissue in an additional patient failed to identify any valvular mechanism. The available information suggests that bullae develop after retraction and collapse of surrounding lung away from a region of weakness.