Computerized single-breath nitrogen washout: Predicted values in a rural French community

Abstract

Comparative manual and computer measurements of the alveolar N2 slope and closing volumes have indicated systematic differences. When a computerized system is used in field surveys, predicted values are to be obtained under the same conditions. Therefore, we measured the alveolar nitrogen slope (phase III, HID, closing volume (CV), and closing capacity (CC) from single-breath N 2 washout maneuvers in 158 healthy subjects (68 females), ages 21 to 64 years, from a rural community living in a nonpolluted area of northeast France. PIII, the CV to vital capacity ratio (CV:VC, %), and the CC to the total lung capacity ratio (CC:TLC, %) were regressed against age, height, weight, and the body mass index (BMI, kg/m 2) and prediction equations with 95% confidence intervals were computed. PIII increased with age in both sexes and tended to decrease with height in males (r = -0.19, p = .08). The CV:VC and CC:TLC ratios depended on age and, in males, increased with the BMI. Despite accepting a 15% difference between the test VC and the spirometric VC, only 46.3% of asymptomatic nonsmokers produced a valid single-breath nitrogen washout (SBN2) test. This high failure rate limits the usefulness of the test for epidemiologic purposes when older populations "naive" to pulmonary function testing are studied under field-survey conditions.

Intrabreath Diffusing Capacity of the Lung in Healthy Individuals at Rest and During Exercise

“…The CH 4 slope also increased with age. This is consistent with the increased phase III slope during nitrogen washout in the elderly 32 and probably reflects the degenerative changes in the small airways as the individual ages, resulting in increased time constants. The CH 4 slope also was greater in women than in men, but the reason for this is unclear.…”

Closing volume: a reappraisal (1967–2007)

“…At an age of 70 years, the mean difference in CC between females and males amounts to 2.5% TLC. Using a computerised (automatic) analysis of phase IV, Teculescu et al (1996) found similar results in 158 healthy non-smokers in whom the rate of increase of CC/TLC with age was slightly higher in females than in males, though in this case not significantly. The regression equations of Teculescu et al (1996) Knudson et al (1977) obtained with the single-breath N 2 method were somewhat lower at all ages.…”

“…), and (2) performance of two expirations to RV, which may represent an unbearable burden for subjects who are old and/or sick. In fact Teculescu et al (1996) and Viegi et al (1988) reported that assessment of CC is not ''a useful test for epidemiological purposes'' because of a high task failure rate, especially in elderly subjects. An useful alternative is the assessment of the ''open capacity'' (OC), i.e.…”

“…), the discrepancies among the various studies cannot be explained. Furthermore, in these studies different methods were used to assess RV and the junction of Eur J Appl Physiol (2007) 99:567-583 573 phases III and IV: visual inspection (Buist and Ross 1973) or automatic analysis (Teculescu et al 1996).…”

The effects of obesity on lung volumes and oxygenation

“…If the FRC is lower than the CC, the A-a gradient should increase, as some lung units are closed during normal tidal breathing; if the A-a gradient increases sufficiently, the patient is hypoxemic. But measuring closing capacity is difficult and is rarely done, and the equations to predict closing capacity based on age and height have not been sufficiently standardized [13,14].…”