Issue link: http://www.e-digitaleditions.com/i/730359
18 OCTOBER2016 Inhalation be true. However, in an age when smoking has been banned in many public places, other causes of COPD, such as pollution, have become more apparent. Another difference between asthma and COPD patients is the reversibility of FEV 1 . Generally, patients with asthma may be more likely to exhibit reversibility of FEV 1 (i.e., improvement) than those with COPD. However, due to the inherent characteristics of the diseases or sub- optimal treatment, one may not be able to use inhalation medication or disease definitions to determine whether a patient's FEV 1 is reversible. A term that has become more popular in recent years is the "asthma COPD overlap syndrome" or ACOS. While the definition of this phenomenon is unclear, it at least hints at the need for better descriptions of the obstructive dis- eases. The concept of lung health and the subsequent use of FRI may facilitate this discussion. Earlier we mentioned the limitations of FEV 1 in providing information regarding regional or subtle changes in lung structure and function. Nonetheless, a novel technology such as FRI will initially still have to be compared to the gold standard endpoint, which is in this case FEV 1 . Flu- idda's studies typically look at strong FEV 1 responders with a signal above the measurement error and correlate the observed regional FRI changes (e.g., lobar hyperinfla- tion, lobar airway volumes and resistances) with the FEV 1 changes. This approach reveals the mechanisms behind the FEV 1 response, which can subsequently be used to assess the potential presence of these mechanisms in a patient group with more modest FEV 1 , thereby facilitat- ing more efficient phenotyping. These principals were applied in a recent study 3, 4 that demonstrated a subset of COPD patients showed im- provements in FEV 1 by more than 150 ml when treated with roflumilast, a systemic phosphodiesterase-4 (PDE4) inhibitor, in addition to a triple combination inhalation treatment (ICS/LABA/LAMA). Based on the observed changes in FRI parameters, it appeared that the systemic drug reached areas in the lung that are chronically under- treated by the triple inhalation therapy. The drug subse- quently reduced the regional (lobar) hyperinflation and caused a redistribution of airflow, altering the deposition patterns of the concomitant inhalation medication, lead- ing to the significant improvement in FEV 1 and exercise tolerance observed. In other words, the lung health of this subset of patients was improved by providing a combina- tion of systemic and inhalation therapies. Figure 1 Healthy FEV 1 =108%p Expiration Inspiration Asthma FEV 1 =108%p COPD FEV 1 =28%p Figure 1. Airway volumes at inspiration (total lung capacity, TLC) and expiration (functional residual capacity, FRC) for a healthy subject (FEV 1 = 108% predicted), a "mild asthmatic patient" (FEV 1 = 108% predicted) and a COPD patient (FEV 1 = 28% predicted). Although the FEV 1 is identical for the healthy and asthmatic patients, their airway dynamics, and consequently their lung health, are very different. The change in airway volume in the healthy subject (grey geometries on the left) is limited between inspiration and expiration. The asthmatic patient (pink geometries in the middle), however, already shows a large degree of airway closure on expiration (airways disappear in the image), a pattern that can also be observed in severe COPD patients (red geometries on the right). In this example, FEV 1 would classify a patient as mildly asthmatic yet the patient's central and distal airway dynamics seem to be more akin to those of a COPD patient.