A Clinical Study on Predicting the Depth of Double-Lumen Tube Insertion Based on Height and Sitting Height

This study employed a two-stage design: First, 82 patients undergoing DLT intubation was used to establish predictive formulas for predicting insertion depth based on sitting height (SH), body height (BH), and CT measurements.

and its deviation from the standard depth was quantitatively compared. Subsequently, a randomized controlled trial was conducted, in which 330 patients were randomly allocated into three groups to evaluate the predictive performance of the three methods.

This is a Two-Stage Design study planned to evaluate the predictive performance of the three methods in predicting insertion depth based on sitting height (SH), body height (BH), and CT measurements. A formula for predicting insertion depth based on sitting height (depth = 0.32 × sitting height) was identified to assist in the initial positioning of double-lumen catheters. Subsequently,the validation cohort of 336 participants were randomly divided into group A (SH), group B (BH), and group C(CT). The primary aim of this research was to evaluate the relationship between sitting height (SH), body height (BH), cricoid-carina distance (Ds-c), and the insertion depth of double-lumen endobronchial tubes (DLET) in the observed group, as well as to assess the accuracy of depth prediction models based on BH and Ds-c suitable for this demographic. Secondary outcome was to evaluate the accuracy of the three prediction formulas in the validation cohort.

Inclusion and Exclusion Criteria A total of 418 patients, aged 19 to 83 years, who underwent double-lumen tracheal intubation at Tongji Hospital between October and November 2024, were enrolled. Patients with anticipated or known difficult airways, severe spinal scoliosis, kyphosis, or significant tracheal deviation due to tumors or masses visible on chest radiographs were excluded from the study.This study was conducted in accordance with the Declaration of Helsinki and obtained approval from the Ethics Committee of Tongji Hospital, affiliated with Tongji Medical College (TJ-IRB202411040). Furthermore, it has been registered on clinicaltrials.gov (NCT06709053). Prior to participation, all patients provided written informed consent.

Measurement of Ds-c on CT Previous literature has established that various anatomical measurements on CT can predict intubation depth, including the distance from the vocal cords to the carina (Dv-c), cricoid to carina (Dc-c), and thoracic inlet to carina (Ds-c). While the model predicting Dv-c depth demonstrated the highest accuracy at 90%, this method's applicability was limited in our control group for two main reasons. Firstly, verifying the accuracy of Dv-c required CT scans that included the vocal cords, which were not part of the standard lung CT protocol at our center, resulting in most patients lacking vocal cord imaging. Secondly, marking the catheter at the glottis level before intubation was necessary for observational purposes, without interfering with the anesthesia induction process. Previous findings indicated that the prediction accuracy of Ds-c was superior to that of Dc-c; therefore, Ds-c was selected as the primary measurement in this study.

Optimal Position for a DLET The optimal positioning of the DLET was defined as having the bronchial cuff situated in the main bronchus, with the cuff edge positioned within 0.5 cm below the carina or at the carina level, ensuring that the opposite main bronchus was unobstructed. Additionally, the catheter tip was required not to obstruct the lobar bronchus opening, and the side hole should be positioned above the carina, directly facing the main bronchus opening on the contralateral side. Surgeons confirmed satisfactory lung collapse on the operative side.

Generation of Prospective Observational Cohort Data In the derivation cohort, we documented SH, BH, and Ds-c for all participants prior to surgery. Following the induction of general anesthesia, patients were positioned for surgery, and one-lung ventilation commenced. The investigator recorded the catheter type and depth after the surgeon approved lung collapse on the operated side, and the anesthesiologist confirmed the catheter's optimal position using FOB. Regression analysis was employed to derive the prediction formulas based on height and CT measurements.

Implementation of Intubation in the Validation Cohort In the validation cohort, patients meeting the inclusion criteria were randomly assigned to Group A (sitting height), Group B (body height), and Group C (CT-based measurement). SH, BH, and Ds-c were recorded by the researcher following the preoperative visit, and the predicted depth was calculated according to the corresponding formula for each group. After anesthesia induction, patients were positioned laterally, ensuring alignment of the head and neck with the spine. An additional observer, blinded to group assignments, utilized FOB through the side hole of the bronchial tube to assess the bronchial cuff's location. The target was to achieve the 'predicted depth.' Data were considered accurate if the depth fell within the 'optimal position' range. If the 'predicted depth' was not attained but a safe critical point was reached, adjustments to the catheter position were halted, and the data were recorded as inaccurate. Depths were classified as shallow if below the 'optimal position' and deep if exceeding it.

Statistical Analysis Data analyses and statistical tests were performed using R version 4.1.1. For normally distributed continuous data, means and standard errors (SE) were calculated and compared using Student's t-test. Non-parametric data were presented as medians (interquartile ranges) and compared using the Mann-Whitney U test as appropriate. Normality of distributions was assessed using skewness and kurtosis tests. Correlations were evaluated with the Spearman correlation coefficient. For multiple comparisons, one-way analysis of variance (ANOVA) was employed, followed by Tukey's post hoc test. Subsequent post hoc tests were conducted only if the ANOVA indicated statistical significance (P \< 0.05) and no significant variance inhomogeneity was detected. Differences between groups were assessed using the chi-square (χ2) test. Significance levels were denoted as follows: ns, P \> 0.05; \*, P \< 0.05; \*\*, P \< 0.01; \*\*\*, P \< 0.001; \*\*\*\*, P \< 0.0001

Eligibility Criteria:
Inclusion Criteria:

1. Voluntary participation in research;
2. Age ≥18 years and ≤80 years;
3. Patients receiving general anesthesia and DLT tracheal intubation.

Exclusion Criteria:

1. Patients with scoliosis or deformity;
2. Patients who are unable to stand upright or sit;
3. Patients with maxillary malformations or misaligned incisors;
4. The researchers judged that it was not suitable to participate in this study.