Variability of the computerized single-breath nitrogen washout test in healthy adults. Results from a field survey in a French rural area

In 20 healthy subjects and 18 patients with bronchial obstruction, closing volume (CV) on single-breath nitrogen washout curves and inflection point (IP) on transpulmonary pressure-volume curves were recorded simultaneously during slow expiratory vital capacity maneuvers. IP and CV did not occur at identical lung volumes, IP being systematically larger than CV for small CV values. This discrepancy could not be attributed to an esophageal or mediastinal artifact. It is suggested that, though CV and IP both express “airway closure,” their sensitivity to closure may differ: CV underestimates closure because of a dead space effect; the latter may vary individually. On the other hand, IP may not reflect the true beginning of closure, particularly when it occurs at higher lung volumes.

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Volume Correction For Diffusion Capacity: Use Of Total Lung Capacity By Either Nitrogen Washout Or Body Plethymography Instead Of Alveolar Volume By Single Breath Methane Dilution

10.1164/ajrccm-conference.2010.181.1_meetingabstracts.a2115 ◽

2010 ◽

Author(s):

Anthony O. Uvieghara ◽

Jesus Lanza ◽

Viswanath P. Vasudevan ◽

Farhand Arjomand

Keyword(s):

Total Lung Capacity ◽

Alveolar Volume ◽

Diffusion Capacity ◽

Volume Correction ◽

Lung Capacity ◽

Nitrogen Washout ◽

Single Breath ◽

Breath Methane

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Mode shift of an inhaled aerosol bolus is correlated with flow sequencing in the human lung

Journal of Applied Physiology ◽

10.1152/japplphysiol.00655.2001 ◽

2002 ◽

Vol 92 (3) ◽

pp. 1232-1238 ◽

Cited By ~ 5

Author(s):

Christopher N. Mills ◽

Chantal Darquenne ◽

G. Kim Prisk

Keyword(s):

Vital Capacity ◽

Normal Subjects ◽

Phase Iii ◽

Mode Shift ◽

Nitrogen Washout ◽

Single Breath ◽

Posture Change ◽

Supine Posture ◽

Residual Capacity ◽

Phase Iii Slope

We studied the effects on aerosol bolus inhalations of small changes in convective inhomogeneity induced by posture change from upright to supine in nine normal subjects. Vital capacity single-breath nitrogen washout tests were used to determine ventilatory inhomogeneity change between postures. Relative to upright, supine phase III slope was increased 33 ± 11% (mean ± SE, P < 0.05) and phase IV height increased 25 ± 11% ( P < 0.05), consistent with an increase in convective inhomogeneity likely due to increases in flow sequencing. Subjects also performed 0.5-μm-particle bolus inhalations to penetration volumes (Vp) between 150 and 1,200 ml during a standardized inhalation from residual volume to 1 liter above upright functional residual capacity. Mode shift (MS) in supine posture was more mouthward than upright at all Vp, changing by 11.6 ml at Vp = 150 ml ( P < 0.05) and 38.4 ml at Vp = 1,200 ml ( P < 0.05). MS and phase III slope changes correlated positively at deeper Vp. Deposition did not change at any Vp, suggesting that deposition did not cause the MS change. We propose that the MS change results from increased sequencing in supine vs. upright posture.

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