'Normal' lung function?
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You propose to use FEV1 as a percentage of the predicted value to assess whether a patient has or does not have airway obstruction. |
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This is not the correct answer. FEV1 (and the FVC) may be low because of an obstructive or a restrictive disorder. The latter condition precludes its exclusive use as an index of airway obstruction. Obstructive airway disease is associated with a reduction in the maximum flow that would be appropriate for lung size. FEV1 represents an average flow over 1 second. Therefore, to assess whether there is obstructive lung disease, one relies on FEV1%(F)VC, where the VC is used as a measure, albeit not ideal, of lung size. Even in the case of a restrictive ventilatory defect an FEV1 which is reduced out of proportion to the VC points to obstructive lung disease. |
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