Volume of trapped gas in lungs of healthy humans.

The volume of trapped gas (Vtg) that could be mobilized by maximal breaths at the end of a nitrogen washout to 2% N2 was measured in 70 healthy women and 62 healthy men while seated. The average Vtg was found to be 102 +/- 21 (SD) ml in men and 73 +/- 18 ml in women. The Vtg was positively related to total lung capacity (TLC) (r = 0.67; P less than 0.001). An average percent Vtg/TLC of 1.4 +/- 0.31 (DS) % was applicable to both sexes. Vtg/TLC (%) was positively related to age (4 = 0.45; P less than 0.001). The error of a single determination was 8 ml, i.e., the reproducibility was very high. The existence of lung compartments that are unventilated or extremely underventilated may explain part of the physiological alveolararterial O2 difference. An increase in Vt has been found to be a very sensitive sign of subclinical bronchospasm.

Improvement after training of children with exercise-induced asthma.

Fifty children with exercise-induced asthma (EIA) volunteered to take part in a study of the influence of training on EIA. 1) Ten children did not change physical activity. 2) Twelve children trained after premedication with salbutamol inhalations. 3) Thirteen children trained after premedication with disodium chromoglicate (DSCG) and used that drug for treatment. 4) Fifteen children trained in their own regimen, commonly after premedication with salbutamol. Their training programme (groups 2-3) consisted of high load exercise periods of two minutes interrupted by intervals of rest for two minutes during 30 minutes followed by interval swimming for another 30 minutes, twice a week for 3-4 months. Before the training period the degree of EIA was tested with a battery of lung function tests before and after running for 6 minutes on a treadmill at heart rate 170. EIA after training was measured applying the same procedure. Cardiocirculatory performance was evaluated before and after training with work on a cycle ergometer and expressed as W/kg body weight at heart rate 170. The children in groups 2, 3 and 4 improved their physical working capacity by 11% (p less than 0.01), 21% and 11%, respectively, but no improvement was found in group 1. Significant improvements in EIA after the training periods were found in all training groups, but basal asthma improved most in group 3, probably due to the basal treatment with DSCG.

Lung function studies in children with allergic rhinitis.

Thirty carefully selected children with seasonal allergic rhinitis but without history or signs of lung involvement were examined clinically and by lung function tests during the pollen season as well as in the pollen-free season. During the pollen-free season the children had - if anything - slightly better lung function than a healthy control material. During the pollen season the only change was a slight increase in FRC and a decrease in lung clearance index, directly proportional to the change in FRC. Sixteen of the children performed an exercise test in the pollen-free season. A small increase in the volume of trapped gas (VTG) was noted, indicating a subclinical spasm in small airways. Salbutamol inhalation after exercise reduced VTG below base-line values, indicating disappearance of subclinical bronchospasm. Hay fever children thus have a tendency towards bronchospasm after, exercise in the pollen-free season, which, however, is of no clinical importance, as their VTG also after the exercise was less (better) than the predicted normal.

Lung function in cystic fibrosis: acute effect of salbutamol.

Pulmonary function tests including spirometry, N2 washout and volume of trapped gas (VTG) were obtained in 12 children with cystic fibrosis (CF), 6-18 years of age, before and after inhalation of 0.2 mg salbutamol. 11 children had pathologically increased VTG while the lung clearance index (LCI) was abnormal in 9, V'max 25/TLC (maximal flow at 25% of vital capacity/total lung capacity) in 8, residual volume in 6, but FEV1 in only 2 children. VTG/TLC% increased with age while V'max 25/TLC and FEV1 did not change. Neither was clinical score related to age in our subjects. No improvement in lung function occurred after salbutamol inhalation. VTG proved most sensitive for showing abnormality in children with CF.

The volume of trapped gas: a new and sensitive test for the detection of exercise-induced bronchospasm in children.

The volume of trapped gas (VTG) was measured at the end of a nitrogen multiple breath wash out procedure in 16 asthmatic and 10 healthy children before and after exercise. When compared to conventional spirometric variables VTG was the most sensitive test for detection of exercise-induced asthma (EIA). The VTG was significantly higher before exercise in the asthmatic children and increased significantly after exercise, while it did not change in the healthy controls. The significance of changes caused by EIA increased if VTG/TLC % or VTG/VC % wer used. Salbutamol inhalation normalized the VTG in all the asthmatic children.