Ventilation inhomogeneity in 1-antitrypsin deficient emphysema

¹ Lung function Laboratory, Dept of Pulmonology, Leiden University Medical Centre, Leiden, The Netherlands

^* To whom correspondence should be addressed. E-mail: l.fregonese{at}lumc.nl.

	Abstract

The slope of phase III of the single-breath nitrogen wash-out test (sbN₂-test) measures ventilation inhomogeneity and, in smokers, is strongly associated with small airways pathology. To study ventilation inhomogeneity in emphysema related to type Z alpha-1-antitrypsin and to assess its relationship with indices of parenchymal damage and airways obstruction. Eighteen subjects, ex-smokers, with type Z alpha-1-antitrypsin and emphysema confirmed by CT scan were studied in a cross-sectional design. Post-bronchodilation flow-volume curves and gas transfer parameters were measured; sbN₂-test curves were obtained and the slope of phase III was determined. The mean value of the slope (4.6±1.3%N₂/liter) was higher than reference values +2 standard deviations; it was significantly correlated with TL_CO(R= -0.75; p=0.0001) and K_CO (R= -0.58; p=0.012), but not with airways obstruction. There was no correlation between phase III slope values and cumulative smoking. In patients with type Z AAT emphysema, the increased ventilation inhomogeneity reflects parenchymal abnormalities predominantly, demonstrating that measurement of airways obstruction is not sufficient to characterize the disease. Determination of sensitivity of sbN2-test slope in detecting disease progression may give complementary information to spirometry.