Single-breath DLCO Research Articles

Standardization of spirometry and single breath DLCO tests

Standardization of spirometry and single breath DLCO tests

Asbestos-related pleural plaques and lung function.

The present study examines the association between asbestos-related pleural plaques and lung function in a group of workers with occupational exposure to asbestos. Exposure, smoking, and respiratory histories, chest radiographs, flow-volume loops, and single breath DLCOs were obtained on 383 railroad workers. A score based on the ILO-1980 classification system was used to quantify the extent of plaquelike thickening. In order to eliminate potential confounders, we excluded from final analysis subjects with diffuse pleural thickening (n = 10) or small irregular opacities classified as profusion 0/1 or greater (n = 6) on chest radiograph. Definite pleural plaques were observed in 22.6%. The single breath DLCO was similar in the groups with and without plaques (p = 0.0550). Decrement in FVC and the occurrence of pulmonary restriction were associated with the presence of definite plaques (p = 0.0306 and 0.0431, respectively) and with quantitative pleural score (p = 0.0135 and 0.0126), controlling for duration of asbestos exposure and smoking. A test for trend revealed an association between level of diagnostic certainty (none, suspect, definite) for pleural plaques and these measures of lung function (p less than 0.02). Our findings reveal an association between asbestos-related pleural plaques and decrement in lung function as measured by FVC and criteria for pulmonary restriction.

Characteristics of adjustment of lung diffusing capacity to work.

The response of lung diffusing capacity for CO (DLCO) to the onset of exercise or a change in work load was studied in four healthy males. Single-breath DLCO was measured during the transients 1) from rest to 40% of maximum O2 uptake (VO2 max); 2) from rest to 80% VO2 max; and 3) from steady-state exercise at 40 to 80% VO2 max. Protocols 1 and 2 consisted of 8.5 min of exercise while 3 consisted of 10.5 min of exercise at 40% VO2 max followed by 8.5 min at 80% VO2 max. DLCO was measured at 10, 20, 30, 60, 90, 240, and 510 s after onset of change in load. Half times of the responses (1, 39: 2, 43; 3, 56 s) were not statistically different. The percentage of the total response completed at each time interval indicated that 3 was significantly (P less than 0.05) slower than 1 and 2 at 10 and 20 s. The rapid response of DLCO at the onset of exercise may reflect a neural component in pulmonary vascular control during exercise.

Disappearance curves and single-breath DLCO from consecutive samples during slow expiration.

The disappearance of CO in three expirates consecutively sampled after various breath holding periods was measured in seven normal subjects. The CO disappearance curves in the three expired portions were nearly linear and parallel each other, but the curves for later sampled expirates were lower, and even those for earlier sampled expirates passed under unity at time zero when extrapolated on a logarithmic graph of relative expired alveolar CO concentration against breath holding time. The slope of each disappearance curve shows "the true diffusing capacity at breath holding lung volume", eliminating an effect of rapid CO absorption at a lower lung volume during expiration. This effect is considered the cause of the downward shift of the decay curve, and the shift is magnified in slow expiration. In addition, the three parallel lines indicate a homogeneous distribution of DL/VA within the lungs. Subsequently, DLCO in conventional calculations had greater values in shorter breath holding time and later sampling.

119 PULMONARY FUNCTION AND EXERCISE RESPONSES IN CHILDREN WITH MITRAL VALVE PROLAPSE (MVP)

A recent report (Zuwallack et al. Chest 76:17, 1979) on 20 adults with MVP showed increased residual volume in 63%, decreased steady state diffusion capacity (DLCO) in 50%, and increased alveolar-arterial O2 gradients in 42%. We evaluated 18 children (mean age 13.52 ± 3.3 SD years) with MVP and no history of lung disease. Lung volumes, forced expiratory flow rates, airway resistance, single breath DLCO, single breath oxygen closing volume and an incremental cycle ergometer exercise test with work loads increasing by 0.3 watts/kg every 3′ were performed. During the last 1′ of each load, heart rate (HR), end-tidal and mixed-expired PO2 and PCO2, minute ventilation, oxygen saturation and blood pressure (BP) were measured. EKG was continuously monitored. Pulmonary function results were normal before and after exercise. Peak work loads, HR, ventilation, oxygen consumption and BP response were all normal; no CO2 retention or O2 desaturation was noted. Four subjects had unifocal premature ventricular contractions at rest, which were abolished with exercise in three. We conclude that children with MVP have normal pulmonary functions and normal cardiorespiratory response to exercise and, therefore, should not be discouraged from exercise based solely on the MVP. The reason for the differences in lung function between children and adults remains unclear.