John L. Hankinson

Acute bronchoconstriction induced by cotton dust: dose-related responses to endotoxin and other dust factors.

Fifty-four healthy humans, selected for their acute airway responsiveness to cotton dust, had spirometric tests immediately before and after 6 hours of exposure to card-generated cotton dust from seven different cottons (of several grades and growing regions). During exposures, we measured airborne concentrations of viable fungi and bacteria (total and gram negative), vertically elutriated gravimetric dust, and vertically elutriated endotoxin. Correlation between each of these five exposure indices and exposure-related acute changes in forced expiratory volume in 1 s showed a statistically significant relationship between all of the indices except concentration of viable fungi. Of the other four indices, endotoxin was the most highly correlated (r = -0.94; p less than 0.00001), and gravimetric dust was the least correlated (r = -0.34; p less than 0.05). These findings suggest that gram-negative endotoxin may play a major role in the acute pulmonary response to inhaled cotton dust.

Effects of Industrial Respirator Wear During Exercise in Subjects With Restrictive Lung Disease

Few studies have examined the response of individuals with restrictive lung disease (RLD) to respirator wear. Such information should be of theoretical and practical interest when the need to determine fitness to wear respirators is considered. Seventeen females performed progressive submaximal treadmill exercise. Twelve control subjects with total lung capacity (TLC) = 5.71 +/- .19L (mean +/- SEM) and DLCO = 25.8 +/- 1.0 mL/min/mmHg were compared to five RLD subjects with TLC = 3.70 +/- 0.22 and DLCO = 14.5 +/- 0.7. Mean age, height and weight were similar. Separate exercise trials were performed with no added resistance (NAR), and with 5 cm H2O/L/sec inspiratory and 1.5 cm H2O/L/sec expiratory resistance (R2) to stimulate widely used respiratory masks. Comparisons of exercise data were made at an oxygen consumption of 0.8 L/min. With NAR, RLD subjects had significantly higher minute ventilation (VE) (29.0 vs. 21.2 L/min for controls), higher respiratory rate (RR), and lower tidal volume (VT). Heart rate, end-tidal PCO2 (PETCO2), and mouth pressure swing (Poral) were not different from control values. With R2 compared to NAR, the controls had reduced RR and VE; and increased VT, PETCO2, and Poral. While changes with R2 for the RLD subjects were in the same directions as controls, only the increase in Poral was statistically significant. Analysis of the differences showed that none of the changes with R2 in RLD subjects was different from control changes except for the greater increase in Poral and the smaller increase in VT. The former was explained by the RLD subjects higher VE and flow rates, and the non-linear nature of R2 at higher flow rates.(ABSTRACT TRUNCATED AT 250 WORDS)

The Use of Inductive Plethysmography in the Study of the Ventilatory Effects of Respirator Wear

The authors recently developed an ambulatory system, in which a self-contained respiratory inductive plethysmograph (RIP) was used, to measure noninvasively the volume and time components of breathing. Since it does not use nasal or oral devices, such a system is particularly suitable for use in studying the effects of respiratory protective masks on respiratory parameters. In order to validate this portable system, 22 healthy subjects were exercised on a treadmill; RIP and pneumotachographic minute ventilation measurements were compared. A short, graded submaximal exercise protocol was run 3 times by each subject under each of the following conditions: no oral mouthpiece; oral mouthpiece with pneumotachograph; and wearing an industrial protective mask (half facepiece, twin cartridge). Chest and abdominal RIP signals, a time signal and either a pneumotachograph or heart-rate signal were recorded on a small cassette recorder worn at the belt. The data tapes were later edited and analyzed by computer. Data from 5 subjects were excluded because of equipment malfunction. The average error in RIP-measured ventilation compared to values simultaneously measured by a pneumotachograph in the 17 remaining subjects over all exercise levels was -3.16%. Marked variability (SD = 11.26%), however, was found in individuals at different exercise levels and especially between subjects. Use of a respirator was associated with a decreased respiratory frequency, an increased tidal volume and minute ventilation, and an unchanged heart rate. At present, the portable RIP system has substantial variability that limits its ability to measure ventilation accurately.

Computer determined closing volumes

Abstract The measurement of closing volume has been proposed as a simple and sensitive test of small airways disease. One factor which may limit the sensitivity of the closing volume technique is the between-reader variability. To eliminate the between-reader variability, a computer program was implemented to determine closing volume, under the assumption that the computer determinations would at least be consistent. The closing point is the point of departure of the nitrogen concentration from the computer-generated best-fit least squares line through the latter one-half of Phase III. The most critical part of this procedure is defining the latter one-half of Phase III. Computer-determined closing volumes (CVs) and closing volumes expressed as a percentage of the expired vital capacity (CV%VCes) on 320 tracings were compared with four independently determined hand values. The differences between the computer and hand-determined closing volumes and closing volumes expressed as a percentage of the expired vital capacity were small enough to consider the computer as another reader and were not clinically significant.

Miners with Clinically Important Declines in FEV1: Analysis of Data from the U.S. National Coal Study

Abstract Several previous studies, including the U.S. National Study of Coal Workers Pneumoconiosis (NSCWP), have demonstrated a loss of FEV1 over time that is related to occupational dust exposure in miners. However, much of the variation in loss of FEV1 in the mining cohorts studied remains unexplained. This study sought to identify individual miners with clinically important FEV1 declines and investigate risk factors for the declines. Subjects were chosen from NSCWP longitudinal cohorts. All miners with at least 6 years follow up (N = 5900) were grouped into strata based on age, height, smoking status, gender, and initial FEV1. Within these strata, pairs of miners were selected whose annual rate of FEV1 decline differed by more than 60 ml/y, and 344 pairs were entered into the analysis. Miners with high rates of decline were assigned to the study group; those with low rates of decline served as referents. On the initial questionnaire, study miners had more cough and phlegm than referents (p < 0.01). A...

Automated pulmonary function testing: Interpretation and standardization

Several different approaches can be used in automated interpretation of pulmonary function tests. All of these approaches either directly or indirectly benefit from standardization, primarily by facilitating comparison of data between laboratories and studies. For most pulmonary function tests, the most difficult portion to automate and standardize is the measurement technique. Yet, unless the problems of measurement technique are resolved, any interpretation of the pulmonary function test will be less than optimal.Both the American Thoracic Societys recommended spirometry standard and the National Heart, Blood and Lung Institutes recommended procedure for determining closing volume have problems in defining measurement technique. One suggested solution to the problems of standardizing measurement technique is the establishment of a set of standard waveforms which can be used to validate automated procedures. The establishment of a set of well defined patient waveforms, for many pulmonary function tests, may well be the most important part of a pulmonary function standard, particularly with regard to measurement technique. In addition, with the aid of such a data base, the task of automating a pulmonary function test is clearly facilitated.

Helium-oxygen spirometry in experimental cotton dust exposure

Acute lung function responses to cotton dust were examined in 50 healthy adult volunteers known to respond acutely to cotton dust inhalation. Pre- and post-exposure air and helium-oxygen spirometry and specific airways conductance were employed for this purpose. Exposures were carefully controlled in a room ventilated with air from a model cardroom, lasted 6 h each, and were separated by 48 h intervals. Cotton dust exposure produced significant decrements in specific airways conductance (P<0.02), and in vital capacity, maximum expiratory flows breathing air (P<0.004) and on 80% helium-20% oxygen (HeO2) gas mixture (P<0.004). Cigarette smokers tended to have greater spirometric responses to cotton dust than nonsmokers, but differences between the groups were significant only for peak flow rate (PFR) andmax25 breathing HeO2 (P<0.05). Density dependence, defined as the mean HeO2:air ratio formax50 andmax25, was unaffected by cotton dust exposure. Changes in density dependence were not observed over shifts or between control and cotton dust exposures (P>0.05). This was true for the group as a whole as well as for the various smoking subgroups. The occurrence of central (SGAW, PFR, FEV1) and peripheral (max50,max25) airways narrowing among our subjects may explain the absence of a density dependence response to the levels of cotton dust used. Since only MEFV curves were employed, however, our ability to detect changes in density dependence may have been limited by the potential effect of the vital capacity maneuver on airways tone.