The nitrogen clearance of the lungs

Regional distribution of pulmonary ventilation and perfusion in elderly subjects

Using radioactive xenon, we measured the regional distribution of pulmonary ventilation and blood flow in six normal men, whose ages ranged between 65 and 75 yr. The measurements were made in the standing position. The static volume-pressure relation of the lungs was also measured in five of the subjects. The results indicate that by comparison with normal young men: (a) Blood flow to the upper lung zones was increased, although it still remained predominant in the lower zones. (b) Ventilation distribution during a vital capacity inspiration was similar to that seen in young subjects. (c) In five of the six elderly subjects, however, the distribution of ventilation in the resting tidal volume range was not preferential to the lower zones as it was in young men. This was probably caused by airway closure in the lower lung zones. The elderly subjects thus exhibit during normal tidal volume breathing a ventilation distribution pattern similar to that observed in young subjects when breathing at low lung volumes, i.e., near residual volume. This difference is probably due to the combined effect of the loss in elastic recoil of the lungs observed in the elderly subjects and of a decreased resistance to collapse of the aged airways. These findings suggest that in the elderly subjects there is a significant regional ventilation-perfusion impairment during quiet breathing, which may explain in part the reported increase in alveolar-arterial oxygen difference with advancing age.

The effect of thoracic irradiation for cancer of the breast on ventilation, perfusion and pulmonary permeability. A one-year follow-up

Regional and overall lung function was studied in 14 women during a one-year follow-up after postmastectomy irradiation for cancer of the breast. The dose was 40 Gy in the chest wall and 20-40 Gy in the apex of the lung. Immediately after irradiation there was a slight increase in pulmonary clearance of 99TCm-DTPA compared to baseline values. This increase, however, was not restricted to the field of irradiation. Three months after irradiation there were regional defects in the ventilation and perfusion scintigrams in 11 of the patients. At the same time there was a greater decrease in total lung capacity, vital capacity and diffusion capacity for CO than in ventilation and perfusion. One year after irradiation the lung function impairment had only insignificantly regressed. It is concluded that local lung irradiation may cause persistent regional and generalized lung function impairment. The early increase in pulmonary clearance of 99Tcm-DTPA could not be used as a predictor of subsequent lung function impairment.

Multiple breath nitrogen dead space

Ventilatory efficiency for eliminating CO2 is expressed by the physiological dead space, VD phys = (1-PE CO2/Pa CO2) x VT, where PE is the mixed exhaled and Pa the arterial CO2-tension and VT the tidal volume. We used data from the multiple breath N2-wash-out with oxygen for calculating a functional dead space for nitrogen. VDF N2 = (1-FEN2/FidN2) x VT.FEN2 is the mixed exhaled N2-fraction and FidN2 the calculated mean alveolar N2-fraction during a wash-out with the same number of breaths to reach 2% N2 in end tidal air, but having completely even distribution. FidN2 is shown to be 0.20 +/- 0.01 for wash-outs using 20-150 breaths. The method was applied to wash-outs from 21 healthy volunteers, 18 patients with chronic obstructive lung disease and two subjects with acute bronchospasm. VDF was well related to VD phys CO2 (r = 0.78) but higher than the latter. In subjects with lung disease VDF was inversely related to the degree of obstruction expressed by forced expiratory volume in one second per cent of vital capacity (r = 0.85). The subjects with bronchospasm had very high VD/VTF in relation to their FEV%. If airway dead space predicted from height and sex is subtracted from VDF, the resulting alveolar dead space will be a good expression for uneven gas distribution in the lungs. We also deduced a direct mathematical relation between lung clearance index and VD/VTF. The documented good reproducibility of LCI is thus also valid for VD/VTF, while the latter better expresses ventilatory efficiency.

High-dose local steroid treatment in bronchopulmonary aspergillosis. A pilot study

Two patients with allergic bronchopulmonary aspergillosis (ABPA) have been treated with a high dose (1600 micrograms daily) of inhaled corticosteroid for 18 months. A beneficial effect with regard to asthmatic symptoms was observed in both patients. During the first 14 months of the observation period no significant changes were observed in lung function parameters. Bronchial histamine challenge showed decreased hyperreactivity. IgE decreased in both patients, while specific IgE and IgG remained the same. After 14 months of treatment one of the patients developed severe, acute exacerbation of the ABPA and was treated with high-dose prednisolone and local steroid. The patient is now fully recovered and has continued on local steroid therapy. The other patient had no episodes of exacerbation and remains stable on this treatment.

Railroad workers with pleural plaques: I. Spirometric and nitrogen washout investigation on smoking and nonsmoking asbestos-exposed workers

Eighty-seven workers exposed to asbestos in a railroad car repair shop, with characteristic asbestos-induced pleural plaques, underwent extensive lung-function examination. Vital capacity (VC) showed the greatest reduction among the static lung volumes, with an asymmetrical distribution of one-fourth of the subjects below 80% of the predicted value. Logistic regression demonstrated VC to be sufficient for optimal discrimination of asbestos-exposed subjects from a group of matched controls. No further discriminatory power was gained by additional spirometric measures, lung mechanics, blood gas analysis, or diffusing capacity. Smoking had an influence on dynamic but not on static lung volumes. In conclusion, reduced static lung volumes among smoking asbestos-exposed workers with pleural plaques should, in the absence of other lung diseases, be mainly attributed to the asbestos exposure.

Assessment of the relative safety of the beta-blockers ICI 141,292 and atenolol in patients with bronchial asthma

ICI 141,292 is a beta-blocker with beta 1-selective partial agonist activity. To study its cardioselectivity in humans, comparable beta-blocking doses of 200 mg ICI 141,292 and 100 mg atenolol were given to 12 patients with stable bronchial asthma. Both drugs significantly reduced the midexpiratory flow rate at 50% of vital capacity, whereas no significant reduction in FEV1 or peak expiratory flow rate were observed. It is concluded that the cardioselectivity of ICI 141,292 did not differ significantly from that of atenolol. Since they both had a measurable effect on respiratory mechanics, they should probably not be prescribed in bronchial asthma, or only with the greatest possible caution.

Salbutamol inhalation in chronic asthma bronchiale: dose aerosol vs jet nebulizer

The effect of inhalation of 5 mg of salbutamol by a jet nebulizer and 0.3 mg from a metered aerosol was compared in 20 patients with chronic asthma. Half the patients, randomly selected, received one treatment method on day one and the other on day two. A battery of lung function tests suitable for detecting large and small airways obstruction showed only insignificantly more pronounced bronchodilatation after the use of the jet nebulizer. Neither was a better dilation of small airways with this method obvious. It is concluded that the higher dose by jet-nebulizer is only clinically motivated when the patients cannot perform the deep inhalations and breathholding necessary for efficient use of the dose aerosol.