UPDATED 2017/08/23

Single-breath nitrogen washout test

Image result for single nitrogen breath test

Slope III (N2%) >1.0-2.5% = uneven alveolar ventilation.
@ Predicted value (male) = 0.0130 x Age + 0.5555
@ Predicted value (female) = 0.0126 x Age + 0.6419

Closing volume (CV)/vital capacity (VC) >15-25% = increased closure of airways.
@ Predicted value (male) = 0.3077 x Age + 0.5698
@ Predicted value (female) = 0.2989 x Age - 0.6206

Age = Sex =

Predict Value: SlopeIII(N2%)= CV/VC(%)=

THIS SINGLE NITROGEN WASHOUT STUDY SHOWS UNEVEN ALVEOLAR VENTILATION.
THIS SINGLE NITROGEN WASHOUT STUDY DOSE NOT FULFILL THE CRITERIA OF UNEVEN ALVEOLAR VENTILATION.

THIS CLOSING VOLUME TEST SHOWS INCREASED AIRWAY CLOSURE.
THIS CLOSING VOLUME TEST DOSE NOT FULFILL THE CRITERIA OF INCREASED AIRWAY CLOSURE.

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**請病人吐氣吐到RV，然後緩慢吸入100%氧氣直到TLC，然後再請病人緩慢吐氣至RV。以吐出的氣體體積為橫軸，吐出氣體的氮氣濃度為縱軸作一曲線，可以依曲線不同的斜率分成四個phases。在Phase 1吐出的氣體為純氧，曲線斜率幾乎為0，代表呼吸道絕對死腔(absolute dead space)的部分。到了phase 2時曲線斜率陡峭上升，這一段代表支氣管的部分(bronchial/transitional phase)，為不同氣體交換單位逐一吐出。到了phase 3，也就是肺泡期(alveolar phase)，曲線的斜率變平緩，這一段代表在不同肺體積之下的不均勻通氣(ventilation inhomogenicity, VI)，不均勻通氣其中約30-40%由重力分佈所貢獻，其他部分則由周邊呼吸道所貢獻。到了phase 4時曲線斜率再度上升，在這個階段再肺基底部受重力影響的小呼吸道完全閉合，此時吐出的氣體主要來自上肺葉，由於上肺葉比下肺葉通氣差，所含氣體氮氣濃度較高，導致區線斜率上升。整段phase 4的吐出氣體體積稱為closing volume (CV)。

single breath nitrogen washout test
(Respir Med 2009;78(3): 339-355)

N2 750-1250(%) >1.5% = uneven alveolar ventilation.

Slope III (N2%) >1.0-2.5% = uneven alveolar ventilation.
@ Predicted value (male) = 0.0130 x Age + 0.5555
@ Predicted value (female) = 0.0126 x Age + 0.6419

Closing volume (CV)/vital capacity (VC) >15-25% = increased closure of airways.
@ Predicted value (male) = 0.3077 x Age + 0.5698
@ Predicted value (female) = 0.2989 x Age - 0.6206