INTRODUCTION: The success of predicting post-operative functional status based on FEV₁ has been variable and DLco is increasingly being considered as an alternative measure. We aimed to scrutinize the prediction of post-operative lung function status by application of up-to-date reference equations for both these parameters, and to understand why DLco should be preferred over FEV₁ to predict post-operative lung function.

METHODS: Thirty four patients (66+10(SD)years) with lung neoplasm were evaluated 2 months after lobectomy or segmentectomy, using standard lung function testing and multiple breath washout (MBW) to also assess ventilated lung (FRC_MBW).

RESULTS:  Volumetric lung reduction averaged -22+10(SD)% baseline. In those patients with abnormal baseline FEV₁ (n=19; 70+10(SD)%pred; z-score: -3.1+1.4(SD)), actual post-operative FEV₁ reduction was significantly less than predicted (-12.5% vs -21.6%; p=0.028) and similar to ventilated FRC_MBW reduction (-13.2%; p=0.8). For DLco, predicted and actual post-operative values were similar, irrespective of baseline DLco abnormality.

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DISCUSSION: Using up-to-date reference equations and methods we show how patients with abnormal baseline FEV₁ are much less adversely affected than predicted based on anatomical segment counting.  Anatomical segment-based post-operative DLco prediction is more appropriate to reflect actual post-operative lung physiology than FEV₁.