Peter Warren

House dust mite allergen levels in two cities in Canada: effects of season, humidity, city and home characteristics

The homes of 120 patients with asthma, 57 in Vancouver and 63 in Winnipeg, were studied. The characteristics of the homes were assessed by a questionnaire. Dust samples were collected and the indoor relative humidity was measured four times during the year covering all four seasons in both cities. Mite allergen levels were determined using monoclonal antibodies against Der p I and Der f I by the ELISA method. The mean levels of both mite allergens in mattress and floor samples in the homes in Vancouver and in Winnipeg were relatively low for all seasons. Mite allergen levels were found to be associated with city, season and individual home differences. They were significantly higher in Vancouver than in Winnipeg. Der p I and Der f I in mattress samples in both cities and Der f I in floor samples in Vancouver, varied by season. The indoor relative humidity level in the homes in Vancouver were also significantly higher than those in Winnipeg. There was, however, no significant association between the levels of indoor relative humidity and the levels of mite allergens after adjusting for variations in city, season and individual home. Although individual home differences were highly associated with mite allergen levels, only a few home characteristics were found to be related to mite allergen levels such as the type and the age of the home, the type of heating, the use of feather pillows and the number of occupants in the homes. Whether low levels of mite allergens are partially responsible for the relatively low prevalence of childhood asthma in Canada remains to be investigated.

Hypersensitivity reactions to grain dust

Abstract Allergic and respiratory investigations were performed in 17 subjects with respiratory symptoms and occupational exposure to grain dust. Common symptoms included chronic cough and sputum production, grain fever, wheezing and dyspnea on exposure to grain dust. Results of pulmonary function tests demonstrated a pattern of obstructive airway disease. Immediate hypersensitivity to grain dust was common. Both immediate and late reactions were observed on inhalation challenge studies. There was a good correlation between the hypersensitivity reactions on skin testing and on bronchial provocation. Inhalation of crude grain dust extract may produce systemic symptoms of malaise, myalgia, headache, and leukocytosis even in normal subjects. There was no evidence of precipitin-mediated hypersensitivity.

Respiratory abnormalities in workers exposed to grain dust.

Survey of 68 grain elevator agents in Southern Manitoba disclosed that 75% had respiratory symptoms. Chronic cough and sputum, and dyspnea associated with exposure to grain dust were common. These symptoms were reported in more than half of the smokers and ex-smokers and in more than one quarter of the nonsmokers. Twenty-seven percent of the subjects also developed systemic symptoms of “grain fever” after exposure to grain dust. Lung function tests demonstrated abnormal spirometric results in 37%, while estimation of the “closing volume” demonstrated abnormality in 42.5% of the subjects, even after the values have been standardized for smoking habit. The high prevalence of respiratory symptoms and abnormal lung function among these subjects indicated that exposure to grain dust was an important etiologic factor in their development. Hypersensitivity to grain dust was found in eight subjects by prick skin testing and in six subjects by precipitin test. There was no significant correlation between the prese...

A case-control study of the role of cold symptoms and other historical triggering factors in asthma exacerbations

BACKGROUND Asthma exacerbations can be provoked by many triggers such as allergens, respiratory irritants and viral infections. The relative importance of these has not been prospectively documented in a case-control study. OBJECTIVE To assess the relative importance of colds and other nonclimatic historical triggers of asthma exacerbations. METHODS One hundred and nineteen adults and children with asthma in two Canadian cities participated in a one-year study of the role of exacerbating factors in asthma. Among these, 36 pairs (21 adult, 15 children) completed the case-control study. Patients were considered cases if they developed an acute asthma exacerbation and notified the centre within 24 h to allow the completion of a questionnaire and viral studies (cultures of nasopharyngeal swabs and serology). Control people with asthma were matched for sex, age and area of residence, had no exacerbation during the preceding four weeks and participated within 48 h of the case patients. RESULTS Case patients versus control patients had a mean age of 22 years versus 20 years, 50% versus 55% were male, and 92% versus 86% had at least one positive aeroallergen skin test. Cases were more likely to have taken regular inhaled steroids (63% versus 33%, P<0.002). Cases were more likely to report the following within the previous week: fever (P<0.001), sore throat (P<0.001), increase in nasal symptoms (P<0.01), increased dust exposure (P<0. 05), exposure to others with a cold (P<0.001) and, over the previous year, increased passive smoke exposure (P<0.05). Viral cultures and paired serology were negative. CONCLUSIONS Symptomatic colds were the most common trigger of asthma exacerbations in the winter and spring, while a transient increase in dust exposure was also identified as a significant trigger. The association with chronic, passive smoke exposure and the use of inhaled costicosteroid medications likely reflected less stable pre-study asthma in those with exacerbations.

Jack Bowman: Winnipeg's contributions to the treatment and prevention of Rhesus hemolytic disease of the newborn.

Jack Bowman (1925-2005) was a Canadian pediatrician who was on the staff of the Winnipeg Childrens Hospital. He was trained by Bruce Chown who had started the Rhesus (Rh) hemolytic disease of the Newborn program and in due course succeeded Chown as director of the program. Jack began as one of the three pediatricians (including his twin Bill) who performed exchange transfusions on the affected infants. In due course with his colleague in obstetrics, he was the first in North America to perform intrauterine transfusions for the babies at risk of stillbirth. He was a leader in the prevention of Rh disease by the administration of anti-Rh immunoglobulin to the Rh-negative mothers and established that this could be done safely and effectively during pregnancy. He introduced to North America the column fractionation method of preparing the immunoglobulin that produced a higher yield of a purer product that could be given intravenously. Jack Bowman successfully combined research with clinical practice throughout his career.

Window on the breast: 19th century English developments in pulmonary diagnosis

The transition from the 18th to the 19th century witnessed the revolution in medicine that established clinical diagnosis as we know it today. Physical examination, which is now regarded as an art, developed with a strong basis in science. The humoral notion of disease was replaced by the concept of diseased organs, and physicians now diagnosed the patient’s illness with the underlying condition in mind. Moreover the method of diagnosis switched from listening to a wholly subjective account of the patient’s symptoms to verification of the disorder by listening to the sounds of the body. Physicians used their knowledge of the physics of sound to technologically enhance their senses and added mechanics to provide even more objectivity to the diagnosis. The

Huffing and puffing

When my kids were little I loved reading them the story of the three little pigs. It was great fun to voice the big, bad wolf and his boastful words, especially in contrast with the squealing voices of the little pigs. The moral of the story is found in the security of the pig who built his house solidly on a firm, secure foundation. There is certainly a Biblical principle in that moral, but this week in my Bible reading, I found myself thinking more about what we learn from the wolf.