Optimize Initial Freezing Time of Transbronchial Cryobiopsy for the Diagnosis of Interstitial Lung Disease: A Prospective Randomized Parallel Group Study.

BACKGROUND Transbronchial cryobiopsy (TBCB) is increasingly being identified as a potential alternative for the diagnosis of interstitial lung disease (ILD). The specimen size of TBCB is positively related to the freezing time. However, the proper initial freezing time for the clinical application of TBCB in ILD remains unknown. METHODS A prospective randomized parallel group study was employed to investigate ILD patients with unclear diagnosis, who were admitted to the First Affiliated Hospital of Guangzhou Medical University from May 2019 to October 2020 and required TBCB. All patients were randomly divided into 4 groups according to the different freezing times of TBCB: 3 s, 4 s, 5 s, and 6 s groups. All operations were performed under intravenous anesthesia with endotracheal intubation, 60-65 bar pressure of freezing gas source, and 1.9-mm cryoprobe. Compare differences among groups in specimen size, complications, pathological diagnosis efficiency, and multidisciplinary discussion (MDD) diagnostic efficiency. RESULTS A total of 100 patients were recruited and randomly assigned into 4 groups (n = 25 each group). The specimen sizes of TBCB in ILD were positively correlated with the freezing time (r = 0.639, p < 0.05). None of the patients experienced Grade 3 severe bleeding. Pneumothorax occurred in 1 patient in the 4 s, 5 s, and 6 s groups, respectively. The diagnostic yield of MDD in the 3 s, 4 s, 5 s, and 6 s groups were 64%, 88%, 88%, and 96%, respectively (p < 0.05), but showing no significant differences among 4 s, 5 s, and 6 s groups. CONCLUSIONS The specimen size and diagnostic efficiency of TBCB in ILD increased with a longer freezing time. When the freezing gas pressure is 60-65 bar, we recommended 4 s as the initial freezing time of TBCB, and this time is associated with high diagnostic efficiency and low incidence of complications.