Which spirometry test findings are characteristic of significant loss of lung elastic recoil?

Updated: May 14, 2020
  • Author: Kevin McCarthy, RPFT; Chief Editor: Nader Kamangar, MD, FACP, FCCP, FCCM  more...
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Answer

Answer

In patients that have significant loss of lung elastic recoil (pulmonary emphysema, COPD), spirometry may show negative effort dependence of forced expiratory flow. The effort that has the highest peak expiratory effort may produce a lower FEV1 because of the dynamic compression of the airways that results from the loss of elastic recoil support of airways that is characteristic of emphysema. In this circumstance, reporting the highest FEV1 coming from an effort with submaximal expiratory effort can lead to confusing results, particularly if a setting of assessing spirometric response to bronchodilators. Although not yet a spirometry acceptability standard, it appears that when reporting the FEV1 considering only efforts that have a time to peak flow (TPEF) less than or equal to 0.12 seconds helps eliminate this effect. This parameter can be displayed on most laboratory-based spirometry testing systems. 

Inspection of the volume-time tracing aids in identification of early termination of expiration by evaluating the presence of an expiratory plateau. In the absence of an expiratory plateau, a 15-second expiratory time ensures the quality of the FVC. Inspection of the start of the volume-time tracing can help identify a hesitant start, which can result in a falsely low FEV1. Repeatability of the FVC and the FEV1 helps ensure that the results truly represent the patient's lung function. Attention should be focused on the repeatability of two key parameters: FVC and FEV1. It should be noted that while repeatability of the FVC and FEV1 strengthens the confidence that the forced exhalations started from full inflation, it is possible to demonstrate repeatability of these parameters even when forced exhalations start from a lung volume below full inflation. Demonstration that the difference between the largest FIVC and the FVC is no more than the larger of 0.100 L or 5% of the largest FIVC is a key acceptability criterion.


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