DAC and BDR Response- An Uncharacterized Group

SESSION TITLE: Asthma - Bronchiectasis Posters SESSION TYPE: Original Investigation Poster PRESENTED ON: Wednesday, October 28, 2015 at 01:30 PM - 02:30 PM PURPOSE: Dynamic Airways Collapse (DAC) occurs during the expiratory cycle when increased intra-pleural pressure (IPP) exceeds the recoil pressure of the airways and occurs either due to loss of intrinsic airways elastic recoil or changes in the airway caliber. DAC recognized from the expiratory maximal flow-volume curve is attributed to emphysema and or Bronchiolitis Obliterans, assuming a loss of elastic recoil etiology. However many cases demonstrate a bronchodilator response (BDR). Within the BDR group, DAC may be attributed to reversible conditions affecting airway caliber rather than loss of intrinsic elastic recoil. We intend to characterize and describe this group of DAC patients with BDR. METHODS: The data are obtained from retrospective chart review of pulmonary function tests (PFT's) performed in our department according to ATS standards over the last few years. IRB waiver of consent was obtained. Patients were included if: their PFTs demonstrated DAC according to Dr Jayamanne's criteria (CHEST 1980): an abrupt decrease in flow from peak to an inflection point less than 50% of this figure, the inflection point occurs within the first 25% of the FVC and the remaining FVC is delivered at an unvarying low flow of <0.2L/sec. If a BDR is present, defined as an increase in FEV1 of 200ml and 12%. We separated DAC patients with and without BDR and conducted simple statistical comparisons of continuous variables. Low PFT values were defined by the 95% confidence limit. RESULTS: Of 82 consecutive patients with DAC; 57 (70%) did not demonstrate a BDR. These patients had a significantly lower DLCO compared to the DAC group with BDR. DLCO was decreased in 73% of the patients without BDR and only 4% of patients with BDR. Patients with DAC and BDR had better FEV1 and FVC compared to the non BDR DAC group. CONCLUSIONS: Most patients with DAC manifest with no BDR, low DLCO and high TLC. However, the DAC group with BDR defies expectations with a demonstrated reversibility and normal DLCO. The underlying etiology in the DAC without BDR group is related to loss of elastic recoil of the lung tissue, while the etiology is reduced airway caliber (edema, inflammation, bronchospasm) in the DAC with BDR group. CLINICAL IMPLICATIONS: Dynamic airways collapse occurs in asthmatics and is reversible. DISCLOSURE: The following authors have nothing to disclose: Ryu Tofts, Navitha Ramesh, Albert Miller No Product/Research Disclosure Information