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Biomedical subjects

M J Walshaw

Publications and source records attributed to M J Walshaw.

14 recordsLinked to original sources
PubMed1992

A mask to modify inspired air temperature and humidity and its effect on exercise induced asthma.

BACKGROUND: Heat and moisture loss from the respiratory tract during exercise are important triggers of exercise induced asthma. METHODS: A new heat and moisture exchange mask has been developed which both recovers exhaled heat and water and has a sufficiently low resistance for use during exercise. The effect of the mask on inspired air temperature was studied in four normal subjects. Eight asthmatic subjects performed identical exercise protocols on three separate days, breathing room air through a conventional mouthpiece, a dummy mask, and the new heat and moisture exchange mask. Seven different asthmatic subjects exercised while breathing cold air at -13 degrees C through a dummy or active mask. RESULTS: All subjects found the new mask comfortable to wear. The mean inspired temperature when the mask was used rose to 32.5 (1.4) degrees C when normal subjects breathed room air at 24 degrees C and to 19.1 (2.7) degrees C when they inhaled subfreezing air at -13 degrees C. The heat and moisture exchange mask significantly reduced the median fall in forced expiratory volume in one second (FEV1) after exercise to 13% (range 0-49%) when asthmatic subjects breathed room air compared with 33% (10-65%) with the dummy mask and 28% (21-70%) with the mouthpiece. The fall in FEV1 when the asthmatic subjects breathed cold air was 10% (0-26%) with the heat and moisture exchange mask compared with 22% (13-51%) with the dummy mask. CONCLUSION: Use of a heat and moisture exchange mask can raise the inspired temperature and humidity and ameliorate the severity of exercise induced asthma. The mask may be of practical value in non-contact sport or for people working in subzero temperatures.

Adolescent↗
PubMed1991

Bronchial reactivity in patients undergoing long-term haemodialysis for chronic renal failure.

Trapping of neutrophils within the lung occurs in patients undergoing haemodialysis and is also a possible mechanism in the pathogenesis of bronchial hyper-responsiveness. Falls in peak expiratory flow rate occur in most dialysis patients, and some develop overt asthmatic symptoms. To see whether these changes in airway function are secondary to increases in bronchial reactivity during haemodialysis, we therefore performed histamine challenge testing in 6 non-asthmatic patients before and after haemodialysis. No change in reactivity was observed, suggesting that haemodialysis does not commonly result in bronchial hyper-reactivity in non-asthmatic individuals.

Adult↗
PubMed1990

Nocturnal oxygen desaturation in patients using long-term oxygen therapy for chronic airflow limitation.

Nocturnal oxygen desaturation in patients receiving long-term oxygen therapy is described despite adequate daytime oxygenation (PaO2 greater than 8 kPa). Domiciliary oximetry overnight was performed on ten patients receiving long-term oxygen treatment for chronic airflow limitation: six patients were well saturated throughout the night with a fall in SaO2 to below 90% for only 1% of the monitoring time; four showed significant desaturation with a fall in SaO2 to below 90% for periods of 15-47% of the monitoring time.

Aged↗
PubMed1990

Factors influencing the compliance of patients using oxygen concentrators for long-term home oxygen therapy.

A previous study in the Liverpool district on patients receiving long term oxygen treatment using a domiciliary oxygen concentrator showed that only 55% were both using oxygen therapy correctly and had stopped smoking. To try and identify which factors influence patient behaviour, all 55 patients in this district receiving long-term oxygen therapy for hypoxaemic chronic airflow limitation were studied. We found that those with more symptoms were more likely to comply with this therapy. The prescription of a concentrator on the advice of a hospital physician did not improve on the compliance rates attained in those patients assessed by the general practitioner alone.

Adult↗
PubMed1990

Expiratory lung crackles in patients with fibrosing alveolitis.

Inspiratory lung crackles are a diagnostic feature of interstitial pulmonary fibrosis, but expiratory crackles are not well documented. In a phonopneumographic study of 13 patients with fibrosing alveolitis, expiratory crackles were audible with the stethoscope in 12. Phonopneumographic analysis of these 12 patients showed the crackles to be fine with the initial wave deflection of the expiratory and inspiratory crackles in opposite directions. They were few in number, occurred predominantly in mid- and late expiration, and were not affected by varying the volume history or by breath holding maneuvers. These observations support the theory that some crackles are produced by vibration of the walls of peripheral airways. In addition, this group of patients showed a significant correlation between the number of expiratory crackles and the reduction in predicted transfer factor, suggesting that expiratory crackles may be a clinical indicator of the severity of disease in fibrosing alveolitis.

Aged↗
PubMed1989

Cardiac arrhythmias during acute exacerbations of chronic airflow limitation: effect of fall in plasma potassium concentration induced by nebulised beta 2-agonist therapy.

The effect on cardiac rhythm of the fall in plasma potassium concentration induced by nebulised beta2-agonist therapy was studied in 20 patients admitted to hospital with an acute exacerbation of their reversible chronic airflow limitation. Arrhythmias considered serious or potentially life-threatening were recorded in 13 patients (65%). However, there was no significant increase in these arrhythmias in the hour following administration of nebulised beta2-agonist despite a significant fall in plasma potassium concentration during this period.

Acute Disease↗
PubMed1988

Prescription of oxygen concentrators for long term oxygen treatment: reassessment in one district.

When oxygen concentrators became available on form FP10 in 1985 the Department of Health and Social Security issued clear guidelines for their prescription for long term treatment. Reassessment of those patients prescribed a concentrator in one district showed that 29 out of 61 patients did not fulfil these criteria. Furthermore, in only 28 cases was the daily use of the machine appropriate, though this did not reflect poor patient cooperation but was a result of inadequate prescribing instructions. In addition, 12 out of 54 patients continued to smoke. Overall, in only 18 of the 61 cases was both the prescription appropriate and the concentrator properly used. These results suggest a need for better cooperation between general practitioner and hospital in the initial assessment of patients for long term oxygen treatment and better education of both doctor and patient in the use of oxygen concentrators.

Adult↗
PubMed1987

The effect of seasonal and domestic factors on the distribution of Euroglyphus maynei in the homes of Dermatophagoides pteronyssinus allergic patients.

A survey of the house dust mite population was carried out in the homes of fifty asthmatic Liverpool individuals with strongly positive skin tests to Dermatophagoides pteronyssinus. As expected, D. pteronyssinus was the commonest species found. However, Euroglyphus maynei made up 37% of the total adult mite count and was the predominant species in 48% of beds examined. There was a good correlation between increasing numbers of E. maynei and decreasing social class, but only a weak one with percentage relative humidity. Ionic sodium levels in bed dust were found to correlate with decreasing social class and increasing E. maynei levels. In nineteen beds, mites were sampled at 4-monthly intervals for 1 year--this showed a relative decrease in the proportion of E. maynei compared with other mites in the autumn, when relative humidity was high. A further twenty beds underwent intensive house dust eradication (including the use of plastic covers) for 1 year--these beds showed a progressive fall in the proportion of E. maynei recovered, suggesting that this mite is more vulnerable to anti-house dust mite measures. Euroglyphus maynei is a common house dust mite and further work needs to be done to assess its antigenic nature and clinical significance.

Animals↗
PubMed1986

Allergen avoidance in house dust mite sensitive adult asthma.

Fifty adult asthmatic patients with strongly positive skinprick tests to the house dust mite were admitted into a prospective randomised controlled trial of house dust mite avoidance in the community. Twenty-two of the experimental group completed one year of dust avoidance and 19 of these tolerated the use of plastic mattress and pillow covers. Twenty of the control group (who did not alter their housecleaning habits) also completed one year of study. A fall in mite and dust levels was noted in the homes of the experimental but not the control group. Fifteen of the experimental group who completed the study were strongly RAST positive (score 3 or more) to the house dust mite. These patients had a significant improvement in FEV1/FVC, PEFR, PC20, use of treatment, and symptom score at one year, whilst the seven experimental patients who were not strongly RAST positive (score 2 or less) did not, suggesting that the change noted in the former patients was not merely due to a placebo effect. Fifteen of the control group who completed the study were also strongly RAST positive for the house dust mite and these patients showed no change in any of the parameters. This study demonstrates that adult asthmatic patients can successfully carry out house dust eradication procedures in the community over a long period of time, and that those patients who are allergic to the house dust mite appear to have both subjective and objective improvement in their asthma.

Adult↗