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Biomedical subjects

D J Chinn

Publications and source records attributed to D J Chinn.

8 recordsLinked to original sources
PubMed1992

Standardization of single-breath transfer factor (TLCO); derivation of breathholding time.

Breathholding time is usually defined using the procedure of Ogilvie et al. or of Jones and Meade; these procedures depend on knowing when inspiration begins and, for the latter, when it ends. Some alternative procedures do not require this information. With a view to standardizing the measurement, transfer factor of the lungs for carbon monoxide (TLCO) was measured in 18 adults with labile airflow obstruction, who were assessed before and after inhalation of salbutamol. The inflection points defining the start and end of inspiration were defined visually (method 1), and by extrapolation of the linear part of the inspiratory limb of the single-breath trace (method 2). The spirograms met recognized standards of quality and were rated by experienced observers. Compared with method 1 the TLCO and related indices by method 2 were lower using the procedure of Jones and Meade and higher using the procedure of Ogilvie et al. in each case by, on average, 1.0%. The within- and between-day variabilities were independent of the method used. Thus, the extrapolation and visual methods yielded interchangeable results when applied by experienced operators. However, extrapolation may be easier for inexperienced operators.

Albuterol↗
PubMed1991

Is respiratory function diminished?

An association between diminished respiratory function and an environmental agent should reflect the magnitude of the exposure and not be due to technical error, bias, confounding factors, or chance. Bias is difficult to avoid; the best course is to make comparisons within a population of exposed individuals, not between them and a control group; the population should be defined and a high response rate achieved. The principal confounding factors are age, smoking, and other environmental exposures; their effects should be fully estimated for the population in question as otherwise they will be wrongly attributed to the environmental agent. Finally, the results should be scrutinized and, if possible, a second independent study should be planned.

Cross-Sectional Studies↗
PubMed1990

Longitudinal respiratory survey of shipyard workers: effects of trade and atopic status.

A respiratory sample survey of 609 shipyard workers was conducted in 1979: the men were reassessed an average of 7.2 years later. The 53 deaths between the surveys were related to age, level of lung function and smoking but not to trade as a welder or caulker/burner. Of the survivors, 488 (88%) were seen, including 425 men who had retired or been made redundant. Redundancy was related to age, smoking, and respiratory symptoms; the average reduction in duration of employment per symptom was 0.44 years. Changes in respiratory symptoms included onset of chronic bronchitis and wheeze on most days (numbers respectively 77 and 109) and increased breathlessness on exertion (n = 89); significant related factors included smoking, previous metal fume fever or pneumonia, and, for breathlessness, trade as a welder or caulker/burner. Electrocardiographic evidence for myocardial ischaemia was also associated with increased breathlessness. The annual declines in FEV1 and other spirometric indices were related to age, to being a smoker at the time of the initial survey, and to trade as a welder or caulker/burner compared with trades that did not involve welding or burning. There was significant interaction between these effects. In a subsample of 124 redundant workers there was also significant interaction between the effects of fumes and atopy (skin test positive to common antigens) or a raised serum IgE concentration. It was concluded that welding fumes interacted with smoking and an atopic constitution to cause respiratory impairment. The results related mainly to exposures in the past and were not necessarily relevant for present day conditions in the industry.

Age Factors↗
PubMed1986

Accuracy of gas analysis in lung function laboratories.

Fifty lung function laboratories in England and Wales analysed test gas mixtures of carbon monoxide and helium. Most of them also analysed mixtures of oxygen and carbon dioxide in nitrogen. The percentage accuracy of the results was within 1% of the expected value in only 14% of determinations of carbon monoxide concentration, 28% for carbon dioxide, 37% for helium, and 48% for oxygen. The accuracy of ratios of two concentrations of helium and carbon monoxide was better than that of the individual gas samples. Overall the variation in results between laboratories was wide, the coefficient of variation ranging from about 3% for analysis of helium to 9% for carbon dioxide. This variation affected the values calculated for carbon monoxide transfer factor, where 20% were in error by more than 5%, and for the calculated value of the respiratory exchange ratio, where the interlaboratory coefficient of variation was about 10%. Errors in analysis were due to unsatisfactory calibration of analysers; five oxygen analysers had large zero errors; five carbon monoxide analysers and one helium analyser had notably curvilinear calibration curves. Insufficient information was obtained to ascertain the nature of the errors in analysis of carbon dioxide. Given the improvements in instrumentation, these results are evidence for deterioration in analytical standards in lung function laboratories from the standards of 20 years ago.

Carbon Dioxide↗
PubMedDate not supplied

Within- and between- subject variability of indices from the closing volume and flow volume traces.

The within-subject variability of consecutive measurements of indices derived from the closing volume (CV) trace and from the maximal expiratory flow volume (MEFV) curve was studied in 24 subjects. The variability of the closing volume and of the maximal expiratory flow rates at 50 percent (Vmax. 50) and 75 percent (Vmax. 75) of the expired vital capacity was about three to eight times greater than that of the FEV1, FVC or FEV1 percent. The lung volume measured from total lung capacity to the onset of airway closure (OAC) was about five times more reproducible than the CV. The coefficients of variation for the CV (as a percentage of the vital capacity), the Vmax. 75, and the OAC, both in litres and as a percentage of the vital capacity, were significantly correlated with age. No difference in the mean coefficients of variation for the CV, OAC, Vmax. 50 or Vmax. 75 were found with respect to sex, smoking habit or previous experience with the test routines. The between-subject variability of the FEV1, FVC, FEV1 percent, transfer factor, diffusion coefficient, Vmax. 50, Vmax. 75, CV and OAC was evaluated from a study of 75 asymptomatic lifetime non-smokers. The variability of the Vmax. 50, Vmax. 75 and CV was about two to eight times greater than that of the other tests used, irrespective of sex. The OAC (percent VC) was three to four times less variable than the CV. The variability of the Vmax. 50 and Vmax. 75 was reduced by, on average, 7 percent when these flow rates were expressed per litre of FVC.

Adult↗