A device for recording flow and volume data in population surveys

A prospective study of the natural history of asthma. Remission and relapse rates

In this longitudinal study of a general population sample, remissions of asthma were common only during the second decade of life and were especially unusual in subjects ages 30 to 60 years on enrollment. Asthmatic subjects with severe symptoms, with reduced ventilatory function, or with a concomitant diagnosis of chronic bronchitis or emphysema on entry to the study were very unlikely to be in remission nine years later. Relapses of disease were common in subjects with a past history of asthma who were considered to be quiescent on enrollment to the study. Relapse rates tended to increase with age, at least up to the age of 70. Relapses were especially frequent among those "ex-asthmatics" who had persisting respiratory symptomatology on entry to the study.

Assessment of air vs helium-oxygen flow-volume curves as an epidemiologic screening test

Air and helium-oxygen maximum expiratory flow-volume curves were employed in an epidemiologic field study to assess the utility of density dependence as a screening test. Of 1,584 subjects tested, only 54.1 percent were able to perform the test with vital capacities for the two gases that agreed to within 5 percent. Subjects unable to perform the test properly tended to be older, with a greater prevalence of ventilatory function abnormalities and respiratory problems, than those who could perform the test. There was poor concordance between density dependence, or lack thereof, and standard ventilatory function measurements or evidence of respiratory disease. Under field survey conditions, the test of density dependence did not appear to be a useful screening tool.

Significance of intraindividual changes in maximum expiratory flow volume and peak expiratory flow measurements

To examine criteria to assess significant changes of measurements derived from the forced expiratory vital capacity (FVC), and to examine changes in the peak expiratory flow (PEF) maneuvers, ten subjects were tested on approximately 30 occasions. Since mini Wright peak flow meters are increasingly used for clinical and research purposes, peak flow intraindividual variability and relations to FVC peak flow were examined, each set of tests consisting of five FVC maneuvers and one peak flow. Measurements on a pneumotachograph included FVC, (FEV1), maximum mid-expiratory flow (MMF or FEF25-75%), and instantaneous maximum expiratory flow after 50 and 75 percent expiration of the FVC. PEF measurements were derived using the mini Wright peak flow meter and the pneumotachograph. The coefficients of variation for the FVC measurements were greatest for maximum expiratory flow measurements and least for the FVC and FEV1. Maximum values from each set of tests reduced the variability. From these values, criteria and estimates were derived to evaluate significant intraindividual change. The PEF measurements were evaluated also to determine intraindividual changes. The coefficients of variation were only 2 percent to 14 percent. The peak flows obtained were shown to correlate well with the PVC peak flow.

A pulmonary survey of grain handlers in the West of Scotland

A pulmonary survey was undertaken in a large granary in the West of Scotland. The lung functions and respiratory symptoms were compared in nineteen atopic and fifty-six non-atopic grain handlers with reference to their smoking habits and also to forty-eight control subjects with no previous exposure to grain dust. Cigarette smokers from the granary workers and the control group had more respiratory symptoms and significantly lower PF, FEV1, V25 and V50. The atopic grain handlers, on the other hand, had better ventilatory functions compared to non-atopic workers. This difference in the atopic group may be related to their lower cigarette consumption, shorter service in the granary or the process of self selection. The grain handlers with wheeze or breathlessness at work had significantly higher incidence of restrictive type MEFV curves and this could not be attributed to increased cigarette consumption, atopy or longer duration of employment and there was no correlation between severity of symptoms and occupational exposure. Although PF, FEV1, FVC, V25, V50 and V75 failed to show significant differences in granary workers and controls, the shape of MEFV curve may have significance as a sensitive indicator of the effect of grain dust as a preclinical stage.

A general purpose microprocessor for spirometry

A portable, inexpensive microprocessor is described for on-line spirographic analysis of FVC and its time derivatives and MVV, using a primary flow or volume signal. Resolution is +/- 0.02 L and maximal collection time 66 seconds. Algorithms according to the Snowbird Conference recommendations include back extrapolation, "end of test" determination and the selection criteria for satisfactory tests, and best FVC, FEV1 and other flow rates. Differentiation is digital and flow-volume outputs are available. Actual, predicted and percent predicted values for children or adults are displayed, or can be printed together with an interpretation and a flow-volume loop. Four hundred tests with a Stead-Wells spirometer, a pneumotachograph and a turbinometer using an explosive decompression FVC simulator showed standard deviations of +/- 0.04 L or L/sec or less, except for peak flow. Differences between microprocessor values and tracing analyses were less than 0.04 L. MVV with a reciprocating pump equalled exactly the MVV calculated from stroke volume and frequency (r = .999) from 8 to 325 L/min. Tests of 168 patients were comparable to the calibration devices.

Spirometric testing. Number of tests required and selection of data

To address the questions of whether three or five maneuvers for forced vital capacity (FVC) should be required for adequate spirometric testing and whether the largest or mean values for FVC and the forced expiratory volume in the first second (FEV1) should be used for analysis, we analyzed spirometric data obtained from approximately 3,000 people for each of three consecutive years. The following four algorithms for selection of data were tested: (1) the average of the best two of five measurements; (2) the average of the best two of the first three; (3) the best of five; and (4) the best of the first three. There were no significant differences between any two algorithms within a given year and no differences between any two years for any algorithm. We conclude that there is little to be gained by requiring more than three maneuvers for FVC or in using values other than the largest FEV1 and FVC.

Relation of protease inhibitor phenotypes to obstructive lung diseases in a community

To examine the relative risk for the development of obstructive lung disease in persons heterozygous for alpha1-antitrypsin deficiency, we determined protease inhibitor phenotypes in 2944 subjects in a general community population. Phenotype M was found in 89.5 per cent, MS in 7.1 per cent, and MZ in 3.0 per cent of the population. There were two persons of phenotype Z and six of phenotype SZ. The study also included respiratory questionnaires and spirometry. There were no statistically significant differences in the prevalence of respiratory symptoms and diagnoses or of ventilatory impairment among the three major phenotype groups (M, MS and MZ), nor were there differences in the rates of deterioration of function with age or smoking. Consequently, we do not consider population screening for heterozygous alpha1-antitrypsin deficiency to be worthwhile.

A community study of the relation of alpha1-antitrypsin levels to obstructive lung diseases

Since it is still uncertain whether moderate degrees of alpha1-antitrypsin deficiency predispose to the development of lung disease, data obtained from a stratified random sample of white households in Tucson, Arizona, consisting of 2586 subjects over five years of age, were analyzed. No relation was found between serum alpha1-antitrypsin levels, measured as trypsin inhibitory capacity, and ventilatory function, respiratory symptomatology, or frequency of diagnosed pulmonary diseases even among cigarette smokers. The data indicate that an intermediate level of alpha1-antitrypsin deficiency (i.e., inhibitory capacity between 20 and 62 per cent of the population's mean value) is not an important risk factor for the development of chronic obstructive lung diseases. The data militate strongly against the use of any quantitative determination of alpha1-antitrypsin as a test to identify subjects with moderate deficiency for the purpose of predicting later development of chronic respiratory disorders. The rate of severe deficiency is so low as to make population screening for such subjects impractical.