Usefulness of Transbronchial Cryobiopsy in Interstitial Lung Disease

Abstract

ReviewInterstitial lung disease (ILD) is a term that describes a group of more than 200 lung disorders that show varying degrees of infl ammation and fi brosis of the pulmonary interstitium. The etiology and pathophysiology of many of these disorders still remains poorly understood and is the topic of ongoing research and debate. The diagnostic approach to ILD can be complex and often requires a multidisciplinary team approach with involvement of a pulmonologist, radiologist and pathologist.A lung biopsy is often needed to determine the particular subcategory of interstitial lung disease. Unfortunately, conventional transbronchial biopsy with forceps has a very poor diagnostic yield in ILD. A large review of 801 patients showed a diagnostic yield of less than 30% [1]. Surgical lung biopsy is considered the "gold standard" but has a high mortality with several studies showing a mortality of 1.7% to 4.2% in elective cases and 16% to 17.5% in urgent cases [2][3][4][5][6]. In the last several years, the introduction of bronchoscopic transbronchial cryobiopsy has been an exciting development in this regard. This particular diagnostic intervention has the potential to provide diagnosis in ILD with a safety profi le closer to conventional transbronchial biopsy and a diagnostic yield approaching surgical lung biopsy.The cryobiopsy apparatus consists of a cryo-generator that contains Nitric Oxide or Nitrous Oxide gas. Cryo-generators with Carbon Dioxide as the cyogen are also available and are less costly than Nitric Oxide or Nitrous Oxide based systems.A fl exible cryoprobe ranging in diameter from 1.9 to 2.6 mm is connected to the generator. A foot paddle allows the operator to release the gas from the generator to exit at the tip of the probe. Utilizing Joule-Thompson effect of fl uids, the rapid expansion of gas exiting at the tip of the probe causes a rapid drop in temperature and freezes the tissue surrounding the tip of the probe. Freezing times from 3-6 seconds are generally considered adequate. Care is taken to keep the probe 5-10 mm away from the pleural lining on the fl uoroscopic view to avoid advertent freezing of the visceral pleura which could cause a pneumothorax. The probe and scope are then pulled back gently removing the frozen tissue attached at the tip of the cryoprobe. An endobronchial blocker has been used by some operators to control bleeding but its use is not universal or standardized [7]. As opposed to conventional transbronchial biopsy with forceps, cryobiopsy provides a larger specimen with the area of sample ranging from 11.11 mm2 to 64.2 mm2 as compared to 0.58 mm2 to 20.88 mm2 for conventional transbronchial biopsy sample size [8][9][10][11][12]. Moreover, there is avoidance of crush artifact leading to better preservation of tissue architecture.The larger sample size and preservation of tissue architecture translates into a better diagnostic yield as well. A systematic review and meta-analysis of 11 studies (731 patients), showed a diagnostic yield from 74 to 98% when transbronchial cryob...