Helium dilution technique

Abstract: Total lung capacity (TLC), functional residual capacity, residual volume, and corresponding 95% confidence intervals were measured in 245 healthy nonsmoking person (122 women, 123 men) using a single-breath helium technique. Prediction equations for lung volumes were generated by multiple linear regression. The resultant equations are similar to previously published equations using multiple-breath gas equilibration techniques. Measured 95% confidence intervals can be closely approximated by using two times the standard error of the estimate for each equation, but cannot be approximated by using +/- 20% of the predicted value. Radiographic TLC was not significantly different from the helium dilution TLC.

Abstract: Study objective To determine the effect of obesity on pulmonary function Design Case-control study, using nonobese, age- and height-matched [corrected] nonsmokers Setting Metabolic and obesity clinics of two major teaching hospitals Patients One hundred and three obese, lifelong nonsmokers without cardiopulmonary disease Controls One hundred and ninety healthy, nonobese nonsmokers recruited from among hospital personnel Measurements and main results Complete pulmonary function measurements in all patients and controls These measurements included maximum expiratory flow-volume curve, lung volumes and airway resistance using body plethysmograph, single-breath diffusing capacity for carbon monoxide, and total lung capacity using the helium dilution technique Obese persons were found to have lower functional residual capacity, expiratory reserve volume, and total lung capacity by helium dilution than nonobese controls In addition, residual volume and diffusing capacity were higher in the obese group Finally, we found that obese men, but not women, had reduced maximum expiratory flow rates at 50% and 75% of exhaled vital capacity Conclusion Obesity may contribute independently of smoking habits to chronic airflow limitation in men

Abstract: Pulmonary function tests were performed on a total of 125 healthy infants younger than 25 postconception (pc) months of age. Maximal expiratory flow at functional residual capacity (VmaxFRC) was measured from partial expiratory flow-volume curves, and functional residual capacity (FRC) was measured by the helium dilution technique. There was a highly significant (p < 0.01) linear regression for both maxFRC and FRC with increasing body length. The highest size-corrected flows (maxFRC/FRC) were obtained in the healthy premature (2.7 FRC/s, n = 6) and full-term (2.5 FRC/s, n = 5) infants, and there was a relatively constant value between 13 and 25 pc months of age (1.2 FRC/s), which was simillar to those reported in older children and adults. In an age-matched group of infants 10 to 16 pc months of age, females had both higher absolute flows (126 versus 102 ml/s, p < 0.03) and size-corrected flows (1.4 versus 1.0 FRC/s, p < 0.001) than did males. These physiologic data support the concepts that (1) neonates ...