{'fraction_non_alphanumeric': 0.03363832077502691, 'fraction_numerical': 0.0263724434876211, 'mean_word_length': 5.509632224168126, 'pattern_counts': {'":': 0, '<': 1, '<?xml version=': 0, '>': 1, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Establishment of Thoracic Surgical Difficulty Assessment Scale based on Delphi method.

OBJECTIVES
The difficulty of surgery, which is related to surgical safety, has only been mentioned as a subjective perception for a long time. There are few studies to quantitatively and systematically evaluate the difficulty of thoracic surgery. This study aims to establish a quantitative evaluation index system for thoracic surgical difficulty, and to evaluate its reliability and validity.


METHODS
During the 2 national thoracic surgery academic conferences, the factors that may affect the difficulty of thoracic surgery were evaluated by the thoracic surgeons via semi open questionnaires, and then the evaluation item pool of thoracic surgery difficulty was established. The importance of each indicator in the evaluation item pool was graded by 2 rounds of Delphi method. The average score, full score rate and coefficient of variation of each index were calculated, and the composite index method was used to decide whether to delete the indicator.Finally, the difficulty evaluation scale of thoracic surgery was constructed. The surgical data of patients with thoracic tumors were collected. The scale was used to evaluate the difficulty of thoracic surgery for lung, esophageal, and mediastinal tumors. The reliability and validity of the scale were evaluated by the commonly used difficulty evaluation indexes: Operation time, intraoperative estimated blood loss, Visual Analog Scale (VAS), side injury rate, and blood transfusion rate as standards.


RESULTS
A total of 230 questionnaires were distributed in the 2 rounds of survey, and 149 valid questionnaires were collected after eliminating duplicate questionnaires. Through 2 rounds of Delphi consultation with 20 experts, the difficulty evaluation indexes were scored and screened, and the difficulty evaluation scale of thoracic surgery was established. It included 5 main indexes (surgical decision-making, operation space, separation interface, reconstruction method, and surgical materials) and 16 secondary indexes [American Society of Anesthesiologists (ASA) classification, surgical trauma, operator experience, space size, space depth, space source, space adjacent, interface content, anatomical gap, visual field, interface size, reconstruction complexity, reconstruction scope, autologous materials, artificial biomaterials and instruments]. After weighting, the total score of Thoracic Surgery Difficulty Evaluation Scale was from 1 to 3. A Score at 1 standed for simplicity, and score at 3 standed for difficulty. Further data were collected for 127 cases of thoracic tumor surgery. The difficulty scores of surgery for lung, esophageal, and mediastinal tumor were 1.69±0.26, 1.86±0.18, and 1.56±0.31, respectively, and the Cronbach's α coefficients of the scale in 3 tumor surgeries were 0.993, 0.974, and 0.989, repectively, and the Spearman Brown coefficients were 0.996, 0.984, and 0.996, respectively. The Spearman correlation coefficients of operation difficulty score with operation time, estimated blood loss, and VAS were 0.360 and 0.634, 0.632 and 0.578, 0.696 and 0.875, respectively (all P<0.05). The incidence of postoperative complications in the difficult operation group (difficulty score >1.85) was higher than that in the non-difficult operation group (P=0.02).


CONCLUSIONS
The quantitative Thoracic Surgical Difficulty Assessment Scale has been successfully established, which shows good reliability and validity in thoracic tumor surgery. The Thoracic Surgical Difficulty Assessment Scale has broad application prospects in reducing the difficulty of the surgery, controlling surgical complications, and training surgeons.