Usefulness of the forced expiratory volume in six seconds (FEV6) as an alternative for the forced vital capacity (FVC) in spirometry

Spirometry, and in particular the forced expiratory manoeuvre, is the most widely used lung function test, and is an invaluable tool in assessing respiratory disease. For the interpretation of spirometry, the commonly used diagnostic parameters are the forced vital capacity (FVC), the forced expiratory volume in one second (FEV1) and the FEV1/FVC ratio. However, spirometry is an effort-dependent test that requires full patient cooperation. Especially the effort to exhale completely, in order to obtain FVC, can be particularly demanding for some patients, resulting in the inability to perform acceptable and repeatable manoeuvres. Moreover, spirometry is increasingly used by primary care physicians, enhancing the need for easy-to-perform spirometric manoeuvres. This thesis focuses on the introduction of a shorter, fixed time duration of the forced expiratory manoeuvre, and evaluates the role of the forced expiratory volume in six seconds (FEV6) as an alternative for FVC. We investigated whether the same diagnosis can be made when using the FEV1/FEV6 ratio instead of the FEV1/FVC ratio for the detection of airway obstruction, and when using FEV6 instead of FVC for the detection of a spirometric restrictive pattern. In addition, new fixed cut-off points were determined for use with FEV1/FEV6 and FEV6. Finally, gender-specific algorithms were developed that define patient groups for which spirometry (FVC or FEV6) can reliably predict a reduced total lung capacity. These algorithms could help clinicians, particularly in primary care, to decide whether lung volume measurements are necessary for the detection of a restrictive ventilatory defect.