Participants
This study was approved by the Medical Ethics Committee of Henan Provincial People's Hospital. Written informed consent and information release approvals were obtained from all patients prior to their participation in the study. The clinical trial registration code was ISRCTN10722758. The study protocol complied with the 1975 Declaration of Helsinki.
This study was performed at the Henan Provincial People's Hospital. After gaining approval, 200 subjects were enrolled in this study from June 2019 to September 2019. The inclusion criteria are as follows: aged 18 to 65 years, elective single-port thoracoscopic lobectomy, and willingness to participate. The exclusion criteria are as follows: a history of chest wounds or infections, subcutaneous emphysema, and changed surgical schedule.
Study Protocol
Overview To guarantee the blinding principle of this study, 4 researchers were included in the study. One was the primary anesthesiologist (PR), who was one of the attending faculty members of the department, was responsible for patient care throughout the study and was able to view all of the patients’ vital signs and terminate the study protocol if the patient showed any signs of instability (no such events were reported). The second was a young thoracic surgeon (working experience less than 1 year) who performed the ultrasound examination (UR). The third was a highly experienced thoracic surgeon (working experience more than 20 years) who was in charge of locating the intercostal space through traditional manipulation methods (MR). The fourth was the final investigator (IR) who was in charge of verifying the intercostal space under direct vision through thoracoscopy.
After written consent was obtained, anesthesia was inducted for all patients. All subjects were monitored by electrocardiography, pulse oximetry, invasive blood pressure recordings and bispectral index values. For fluid supplementation, 1-3 ml/kg/h crystalloid was administered. Midazolam 0.05 mg/kg, sufentanil 0.5 μg/kg, etomidate 0.2 mg/kg and cisatracurium 0.2 mg/kg were intravenously administered for induction, followed by mechanical ventilation under double-lumen bronchial intubation; then, the patients were placed in a lateral position for surgery.
In this study, single-port thoracoscopic lobectomy was performed. The incision port was determined by a fixed thoracic team, which was independent of this study. There was no specific requirement for how this team should determine the intercostal space required. The location of the incision was evaluated by the UR and MR. All operations were performed by the fixed thoracic surgeon team. After induction, all patients were placed in a lateral position. The location of the incision port was then evaluated by the UR, MR and IR.
The positioning route was basically the same between the MR and the UR. The main difference between the two routes was the instrument adopted; one route was based on the hand, and the other was based on ultrasound. Briefly, the UR entered the operating room and determined which intercostal space he or she wanted to judge by ultrasound. The UR left the operating room when he or she determined a location. Then, the MR entered the operating room and determined which intercostal space he or she wanted to judge by hand. After completing his evaluation, the MR left the operating room, and the operation was started by the thoracic team. The IR entered the operating room and determined which intercostal space the incision port was actually in under direct vision with a thoracoscope. Conclusions made by the IR were recognized as the gold standard.
Positioning by the UR Previous studies suggest that a minimum of 25 to 50 examinations is needed for point-of-care ultrasound training for other topics in both the emergency department and the intensive care unit. A training curriculum of point-of-care ultrasound for the young thoracic surgeon was provided before the study started, which required a minimum of 50 examinations to complete training[9]. After the incision approach was determined, the thoracic team left the operating room. The UR went into the operating room and started his evaluation. The UR performed his examination using the Philips IU-22 machine with a 12-MHz linear probe (shown in Figure 1B). First, the probe was placed at the clavicle. Scanning was performed from the midline of the clavicle in a short-axis plane. The clavicle and subclavian arteries were first displayed on the screen. The color model could be useful for confirming the subclavian artery. The first rib, adjacent to the subclavian artery, could be easily found (shown in Figure 1C). The recognition of the first rib was important. The intercostal space below the first rib is the first intercostal space. Then, the probe was positioned downward until the probe approached the location of the surgical incision. Finally, the UR made his judgement on which intercostal space the surgical incision would be made in. Then, the UR left the operating room. The time required by the UR was recorded.
Positioning by the MR After the UR left the operating room, the MR went into the operating room and started his evaluation. The manipulation method, which is based on anatomic markers, was performed as follows (shown in Figure 1A). The forward protrusion, where the manubrium and the mesosternum meet, was recognized as the sternal angle. The sternal angle, attached by the second rib, could be felt by hand. The intercostal space below the second rib is the second intercostal space. After the location of the second intercostal space was confirmed, the MR continued feeling the intercostal space downward until he or she approached the location of the surgical incision. Finally, the MR made his judgement on which intercostal space the surgical incision approach would be made in. Then, the MR left the operating room. The time required by the MR was recorded.
Positioning by the IR After the UR and the MR completed their evaluations, the fixed thoracic team went into the operating room and started the operation. The standard method to confirm the location of the intercostal space was defined as counting and recognizing the ribs under direct vision after the thoracic cavity was opened. The final investigator went into the operating room and started his evaluation. After the thoracoscopic lens was placed into the thoracic cavity, the final investigator counted the ribs with the help of the thoracoscope (shown in Figure 1D). After the first rib and the subclavian artery was confirmed, the final results of where the incision was made could be easily finally verified. The conclusion made by the final investigator was recognized as the gold standard.
Data Acquisition Gender, age, body mass index, and height, and time required by the UR and MR were recorded. The results provided by the IR were regarded as the gold standard. The results provided by the UR and UR were scored as "Yes" or "No".
Statistical analysis According to the results of the preliminary experiment, the detection rates for the correct intercostal space with manipulation and ultrasound were 96.6% and 89.7%, respectively. The difference between the two methods was 6.9%, and the inconsistency rate was 10.3%. Assuming an α of 0.05 and a power value of 0.80, the McNemar method was used to test the differences in detecting the location of the intercostal space, and the minimum sample size was estimated to be 177 patients. Considering the data loss factor, a total of 200 patients were included in this study.
The diagnostic performance was evaluated with sensitivity, specificity, positive and negative predictive value, and accuracy. All proportions were tested using a chi-square test. The confidence intervals (CIs) of the above mentioned parameters were calculated with the Pearson method. The inter-relationships between ultrasound and the gold standard and between manipulation and the gold standard were analyzed with Spearman correlation coefficients. The data were presented as means and standard deviations or medians and quartiles. SPSS 22.0 software was used for the analysis, and the statistical data were analyzed with the chi-square test; p<0.05 was considered statistically significant.