Nitrous Oxide for Identifying the Intersegmental Plane in Segmentectomy: A Randomized Controlled Trial
Phase: NA
Conditions: Pulmonary Nodule, Solitary, Pulmonary Nodule, Multiple, Lung Cancer
Sponsor: The First Affiliated Hospital with Nanjing Medical University

Study Protocol and Statistical Analysis Plan  
 
 
 
Nitrous Oxide for Identifying the Intersegmental Plane in Segmentectomy: A   
Randomized Controlled Trial 
 
Registration number: NCT04302350    
 
 October 25, 2020 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Study Protocol 
 
This study was registered at www.ClinicalTrials.gov (registration number: NCT04302350). 
The study protocol was approved by the Ethics Committee of The First Affiliated Hospital of 
Nanjing Medical University (Nanjing, Jiangsu province, China) and written consent was 
obtained from all participants. The study was conducted at The First Affiliated Hospital of 
Nanjing Medical University, Nanjing, China between January 15, 2020 and May 15, 2020. 
We contacted patients aged 20-70 y, with an American Society of Anesthesiologists (ASA) physical 
grade I or II, a body mass index (BMI) between 18 and 30 kg/m2, with early stage lung cancer（diameter 
of tumor consolidation ≤ 2cm, none evidence of lymph node or distant metastasis, c-stage ⅠA1 or ⅠA2）
（active limited resection）and patients at high risk due to poor general condition who cannot 
undergo lobectomy (c-stage IA1 to IA3) (passive limited resection). Exclusion criteria included a 
history of severe asthma or pneumothorax, pulmonary bullae on chest CT and patient refusal. High-
resolution lung nodule CTA (Iopromide) and three-dimensional computed tomography bronchography 
and angiography (3D-CTBA) were applied to confirm nodules location and associated vessels and bronchi, 
and the simulated surgical path and resection range were confirmed before surgery.  
Eligible subjects were randomly assigned to Group75, Group50 or Group0 at a 1:1:1 ratio. The order 
of allocation was generated by computer personnel that were not involved in trial through a computer 
program. Concealment was carried out using opaque envelopes, which were opened after the patients’ 
arrival in operating room. Patients, surgeons, anesthesiologists, assessors, and statisticians were blinded to 
treatment allocation.  
After admission, patients were routinely monitored for electrocardiogram, pulse oximetry, and invasive 
arterial blood pressure. When anesthesia induction was completed, intubation was carried out using an 
appropriate-size double-lumen endobronchial tube (DLT) under visual laryngoscope and the position of 

the DLT was confirmed with ﬁberoptic bronchoscopy and adjusted as needed. OLV of the dependent lung 
with FiO2=1.0 was begun in the lateral position, by inflation of the bronchial cuff of the DLT, clamping the 
DLT to the nonventilated lung proximally and opening the distal port of the DLT lumen to the atmosphere. 
Tidal volumes were 5 mL/kg ideal bodyweight (male: height -100, and female: height - 105) without 
positive end expiratory pressure (PEEP). In order to avoid possible confounding effects of inhalation of 
volatile anesthetics on oxygenation, all subjects received total intravenous anesthesia. 
According to preoperative 3D-CTBA evaluation of bronchial and vascular structure of pulmonary nodules 
and pulmonary segments, the target segmental bronchus, arteries and intra-segment veins were accurately 
identified and dissected by ligation or stapler cutting. After that, the anesthesiologist began to make 
preparations for the lung inflation. The portable nitrous oxide concentration detector (TD600-SH-B-N2O, 
tiandi shouhe, Beijing, China) was installed to detect N2O concentration (vol%), and then adjusted the 
anesthesia machine to the manual control mode. The flow of the selected gas mixture was set to 8L/min 
(Group75 set to N2O:O2=6:2, Group50 set to N2O:O2=4:4, Group0 set to O2=8), avoiding the interference 
of the total gas flow. When the N2O concentration detector reached the predetermined gas concentration, 
and then the collapsed lung was re-expanded completely with controlled airway pressure under 20 cmH2O 
(1cm H2O=0.098 kPa) by the anesthesiologist. This procedure took approximately 1 min, and then 
FiO2=1.0 was performed after the initiation of the OLV. 
 
 
 
 
 
 
 
 
 
 
 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
                         Fig. 1 Consort flow diagram 
 
Assessed for eligibility (n=81) 
Excluded (n=3) 
  Did not meeting inclusion criteria (n= 2) 
  Declined to participate (n= 1) 
Analysed(n=24) 
Excluded from analysis (n= 0) 
Lost to follow-up (n= 0) 
Allocated to Group75(n= 26) 
Lost to follow-up (n= 0) 
Allocated to Group0 (n=26) 
Analysed(n=18) 
Excluded from analysis (n=0) 
Allocated to Group50 (n= 26) 
Lost to follow-up (n= 0) 
Analysed(n=23) 
Excluded from analysis (n=0) 
Randomized (n= 78) 
Did not received allocated 
intervention (n= 2) 
The operation was changed to 
open thoracotomy(n=1) 
Grade2 (n= 1) 
 
 
Did not received allocated 
intervention (n= 3) 
Had intraoperative SPO2<90% (n= 
1) 
The operation was change to 
lobectomy (n= 1) 
 Grade2 (n= 1) 
 
Did not received allocated 
intervention (n= 8) 
 had intraoperative SPO2<90% 
(n= 2) 
 the operation was change to 
lobectomy (n= 2) 
 grade1 (n= 1) 
 grade2 (n= 3) 
Complete investigations and 
measurements (n= 24) 
Complete investigations and 
measurements (n= 23) 
Complete investigations and 
measurements (n= 18) 
Enrolment 
Allocation 
Follow-up 
Analysis 

Statistical Analysis Plan 
A power analysis indicated a sample size of 48 patients were needed based on the following 
assumptions: (i) α = 0.05 (two-sided significance level); (ii) 1-β = 0.9; (iii) the appearance time of visible 
ISP is 5-12 min in view of previous study [7]. Taking into consideration loss to follow-up and possible 
dropouts, 81 patients were ultimately enrolled.  
The data collected were entered into a Microsoft Access database and then analyzed with SPSS 
software (version 24; IBM SPSS, Chicago, IL, USA). Primary outcome analysis was performed by one-
way analysis of variance, and LSD-t test for pairwise comparison. Secondary outcome analyses included 
one-way analysis of variance for parametric variables (SPO2, PaO2 value, duration of surgery, total thoracic 
drainage, duration of drainage, postoperative hospital stay, lung function) and χ-square tests for 
nonparametric variables (incidence of postoperative complications, ASA grades). P value <0.05 (both sides) 
was considered statistically significant. Univariate and multivariate linear regression analysis were used to 
determine the predictors for the intersegmental plane. The β value and 95% confidence interval (95% 
CI) of each of the significant variables were calculated.