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D J Chinn

Publications and source records attributed to D J Chinn.

35 records · Page 2Linked to original sources
PubMed1994

Transit time indices derived from forced expiratory spirograms: repeatability and criteria for curve selection and truncation.

Transit time analysis applied to spirograms truncated with respect to volume, not time, could be informative in population surveys. The present paper asks the questions: How does averaging several forced expirations affect the within subject variability at different levels of truncation? If only one spirogram is analysed, how should it be chosen? Are the results likely to be influenced by prior bronchodilation? The subjects were 46 men, selected by stratified random sampling from a shipyard population. Spirograms were obtained in quintuplicate, on two occasions, an average of nine days apart. Using the three "best" spirograms, transit time indices were calculated from average moments and from single curves selected in eight different ways; the analyses were performed on complete expirations, and after truncation by volume at levels between 75-99% of forced vital capacity (FVC), and by time (at 6 s). Indices from averaged moments were found to be more reproducible and yielded higher intra-class correlations than indices from single curves. Of the latter, the curve selected as having the largest forced vital capacity also yielded acceptable results. Prior inhalation of a bronchodilator aerosol did not reduce the variability. The averaging procedure is recommended for respiratory surveys of working men. For this application, the optimal level of truncation appeared to be by volume at 90% FVC, but on theoretical grounds truncation at 75 and 99% of FVC could also be informative.

Adult↗
PubMed1994

Experience of a standardised method for assessing respiratory disability.

A standardised method of scoring respiratory disability based on measurement and/or estimation of maximal oxygen uptake has recently been developed by the European Society for Clinical Respiratory Physiology. In the present study, we wanted to determine how the results obtained using this objective method compared with those by the more traditional empirical method used in a Medical Boarding Centre (MBC) for Respiratory Diseases. The subjects were 62 men who were claiming industrial injuries benefit on account of prior exposure to a respiratory hazard. The MBC ratings and the disability scores were correlated and, in the case of men with moderate or severe disability, numerically equivalent. The results provided independent confirmation that the MBC ratings were influenced by the forced expiratory volume, radiological category of pneumoconiosis and grade of breathlessness. In subjects in whom the measured and estimated maximal oxygen uptakes were inconsistent, the information obtained during the exercise test could identify which of several factors contributed to the exercise limitation. Since the new method might be expected to reduce the difficulties experienced in assessing respiratory disability, its use is recommended.

Adult↗
PubMed1993

Pre-employment lung function at age 16 years as a guide to lung function in adult life.

BACKGROUND: A study was conducted to find out if pre-employment lung function at age 16 improved the estimation of that between ages 25 to 27 compared with the use of reference values based on smoking history, stature, body mass index, and other concurrent anthropometric variables. METHODS: Apprentices attending a shipyard training school were assessed on six occasions from entry during their 17th year to age 25 to 27; results for 114 such men were analysed. The measurements were of stature, body mass, fat free mass and body fat, thoracic dimensions, forced expiratory volume and indices of forced expiratory flow, total lung capacity, and its subdivisions, transfer factor and KCO. RESULTS: At best about half the variance in the final lung function could be accounted for with the concurrent reference variables. For each lung function index the proportion of explained variance was substantially increased by also including in the prediction equation the pre-employment lung function expressed in standard deviation units. CONCLUSION: Estimation of the longitudinal decline in lung function during adult life should be based on initial and final measurements of which the first should ideally be at age 25 but those at age 16 can be used instead: such measurements have long term value and should be preserved.

Adolescent↗
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↗
PubMed1988

Measurement technique influences the response of transfer factor (TICO) to salbutamol in patients with airflow limitation.

Single-breath transfer factor obtained using a multibreath estimate of alveolar volume (TI) was measured before and after salbutamol in twenty patients with reversible airflow limitation. The effective breathholding time was calculated by four methods due respectively to Ogilvie and colleagues as modified by the American Thoracic Society (ATS), ATS Epidemiological Standardization Project (ESP), Jones and Meade in which allowance was made for the time of sample collection and a simplified method in which the allowance for sampling was in terms of volume, not time. Two patients could perform the test procedure only after salbutamol. Amongst the remainder the transfer factor calculated using a single-breath estimate of alveolar volume (TI') was on average 12% less than TI. Carbon monoxide transfer coefficient (KCO), TI and TI' were highest by the ESP method and lowest by the Ogilvie method. Inhalation of salbutamol (200 gamma) did not affect TI' by any method or TI and KCO by the Jones and Meade method but results by the other methods were reduced; in the case of the modified Ogilvie method the reduction was 3.9%. This error was due to overestimation of effective breathholding time by neglecting the reduction of 39% which occurred in the time of sample collection. The time of inspiration was unchanged whilst the time of deadspace washout was reduced by 16%. After bronchodilatation the absence of a change in TI' was due to the overestimation of effective breathholding time being offset by an increase in the proportion of alveolar volume measured by the single-breath procedure.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
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

Modelling the lung function of Caucasians during adolescence as a basis for reference values.

BACKGROUND: In childhood the relationship between lung size and stature changes during the adolescent growth spurt. This is not allowed for in models of lung function based on stature alone. For spirometric indices inclusion of an age x stature interaction (A x St) can overcome the difficulty. AIM: The study tested the hypothesis that this simple, interactive model might also be effective for total lung capacity and its subdivisions and the single breath transfer factor for carbon monoxide. SUBJECTS AND METHODS: Data were available for 695 asymptomatic non-smokers (Caucasians) aged 7-20 years (440 boys, 255 girls). Each lung function index was described using the above model and the fit was compared with that from a linear, power or polynomial model based on stature alone. RESULTS: After allowing for stature, the A x St interaction term was significant for almost all indices. The improved fit was most apparent for the lung function of older adolescent boys. Reference values using the model are reported. CONCLUSIONS: A simple model based on stature and an interaction between stature and age can account for the changing relationship between body habitus during the growth spurt and lung size and transfer factor in a single equation encompassing children and adolescents. Its use is recommended for deriving reference values when the explanatory variables are limited to stature and age.

Adolescent↗
PubMedDate not supplied

Transit time analysis of spirograms: which blow is best?

Moment analysis applied to the forced expiratory spirogram describes the distribution of fractions of the forced vital capacity with respect to time (t). The first three moments (based on t1, t2 and t3) are used to derive respectively the mean transit time (MTT), its standard deviation, also related indices and an index of skewness. The moments are all obtained from the same spirogram (out of 3 or 5), but the criteria for selection have not been defined. We have looked to see which curve yields the most reproducible indices. 46 naive male volunteers performed five forced expirations on two occasions nine days apart. The spirograms were truncated with respect to volume at 99% of forced vital capacity, the time of which was taken as forced expiratory time (FET), and separately at 6 s when FET exceeded this. The absolute values and reproducibility between days of the first three moments were not significantly different for the first three compared with all five blows. Transit time indices were extracted from the first three blows in nine different ways; they included deriving a mean curve from the averaged moments, taking the curve with the shortest MTT, that with the largest FVC, etc. Reproducibility was best when the indices were calculated from the averaged moments; that for the curve with the shortest MTT was nearly as good. The curve with the shortest FET, largest peak expiratory flow, largest FEV1/FVC ratio or largest area under the flow-volume curve were for most indices equally reproducible, but the absolute results were not always interchangeable.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
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↗