Comparison of published reports on physiological effects of exposure to ozone (O3) suggests that Canadians are more reactive than southern Californians. Responses of subjects and experimental methods were compared in a cooperative investigation of this apparent difference in reactivity. Four Canadians and four Californians were exposed to 0.37 ppm O3 in purified air at 21 degrees C and 50% relative humidity for 2 hours with intermittent light exercise. Exposures to purified air alone served as controls. Responses of subjects were similar to those observed previously: Canadians on the average showed greater clinical and physiological reactivity to exposure than did Californians, who were no more than minimally reactive. Canadians also showed larger increases in erythrocyte fragility following exposure. No methodological differences sufficient to explain different results of previous studies were found. Although other possible explanations have not been ruled out entirely, adaptation of southern Californians to chronic ambient O3 exposure is a rational hypothesis to explain these results.

Acetylcholinesterase↗

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Revisiting "respiratory function in emphysema in relation to prognosis".

BACKGROUND: The 1956 paper by DV Bates, JMS Knott and RV Christie, "Respiratory function in emphysema in relation to prognosis" Quart J Med 1956;97:137-157 is largely reprinted with a commentary by the first author, Dr David Bates. Although the pathology of emphysema was well recognized at the time, the clinical diagnosis and assessment of its severity were known to be imprecise; physiological measurements assessing and following the clinical course had not been established. The study aimed to follow systematically a group of patients, selected by clinical criteria using standardized clinical and physiological techniques, over four years and correlate physiological and clinical changes in relation to prognosis and eventually to postmortem findings. Fifty-nine patients were recruited to an emphysema clinic at St Bartholomew's Hospital, London, England. Inclusion criteria were dyspnea without other causes and no cor pulmonale present. Patients' symptoms were assessed by a standardized questionnaire, and measurements were taken of lung volumes, maximal ventilatory volume, carbon monoxide diffusing capacity at rest, exercise and oxygen saturation by oximetry. During the four years of the study, 17 patients died (actuarial expected - four) and 13 presented with signs of pulmonary heart failure. All postmortem examinations (n=9) showed advanced emphysema. A seasonal variation in dyspnea was established (the period included the infamous 1952 London smog). Four patients improved, and the remainder were unchanged or deteriorated. Close relationships were shown between dyspnea and function results, particularly for the diffusing capacity of lungs for carbon monoxide (DLCO). A comparison among a group of patients with chronic bronchitis without dyspnea showed that the DLCO discriminated between them. A loss of the normal increase in DLCO during exercise was shown in emphysema. IMPORTANCE: The study showed the value of standardized clinical and physiological techniques in following chronic obstructive pulmonary disease patients, and of separating the effects of airflow obstruction from impaired gas exchange function. Impaired gas exchange was shown to be important in influencing prognosis.

History, 20th Century↗

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