Early endotracheal intubation is not associated with the rate of return of spontaneous circulation following cardiac arrest at the emergency department:an exploratory analysis

Cardiac arrest poses a significant global public health challenge,manifesting in approximately 550,000 cases annually within the United States.[1]In-hospital cardiac arrest(IHCA)is commonly attributed to airways and respiratory issues.[2]Recommendations emphasize the expertise of responders in airway management.[3]Various options exist,such as chest compression-only cardiopulmonary resuscitation(CPR),bag-mask ventilation(BMV),and advanced airways.The BMV and advanced airways are not deemed equivalent or superior based on previous evidence.[4]Achieving consistency in choosing and timing the optimal airway approach during IHCA is crucial.The current American Heart Association guidelines suggest an advanced airway strategy when endotracheal intubation(ETI)success rates are high,but the optimal time for advanced airway management remains unclear.[5]Wong et al[6]revealed that survival improved by less than 5 min with advanced airway management.According to a subgroup analysis of IHCA patients in emergency departments(EDs),early intubation was associated with a 1.5-fold greater rate of return of spontaneous circulation(ROSC)than in other locations.[7]ED patients’constant monitoring and immediate management,with readily available intubation equipment,enhance early intubation and survival rates.[6]Nonetheless,IHCA patients intubated within the first 15 min had a lower ROSC rate.

Comment on: Effect of intubation in patients with functional epiphora after endoscopic dacryocystorhinostomy

Dear Editor,We read with interest the article by Han et al[1]in which they retrospectively assessed the effect of bicanalicular intubation for functional epiphora after a failed endoscopic dacryocystorhinostomy(DCR).They confirmed the post-DCR“functional obstruction”based on fluorescein dye disappearance(FDDT)and irrigation test[1].

Treatment of acute dacryocystitis by translacrimal canalicular drainage and D-silicone intubation

AIM:To demonstrate the outcomes of translacrimal canalicular drainage using a lacrimal probe and intranasal drainage by D-silicone intubation for acute dacryocystitis(AD).METHODS:This retrospective study included 23 patients with AD and had undergone abscess decompression with the use of lacrimal probe and intranasal drainage by D-silicone intubation between January 2019 and December 2022.Patients received abscess decompression and systemic antibiotic-corticosteroid from the time of diagnosis.D-silicone tube was inserted within 10d after diagnosis and removed 3-6mo after intubation.The procedure and outcomes of this method were evaluated.RESULTS:All patients showed improvement of signs and symptoms of AD within 72h.No intraoperative and postoperative complications were observed.No recurrence of lacrimal sac abscesses occurred after D-silicone tube removed.CONCLUSION:Lacrimal probe and D-silicone intubation appear to be a feasible,minimally invasive,safe,and effective method,which could be a reasonable choice in the treatment of AD.

Ultrasound-guided sphenopalatine ganglion block for effective analgesia during awake fiberoptic nasotracheal intubation: A case report

BACKGROUND Awake fiberoptic nasotracheal intubation(AFNI)is the preferred airway ma-nagement strategy for patients with difficult airways.However,this procedure can cause significant physical and psychological distress.This case report explores the application of a sphenopalatine ganglion(SPG)block as an alternative anal-gesic modality to mitigate the discomfort associated with AFNI.CASE SUMMARY A 63-year-old female with a history of right maxillary osteosarcoma underwent craniotomy for a suspected malignant brain lesion.The patient’s medical history included prior surgery,chemotherapy,and radiation therapy,resulting in signi-ficant jaw impairment and limited neck mobility.Considering the anticipated air-way challenges,AFNI was planned.A SPG block was performed under real-time ultrasound guidance,providing effective analgesia during nasotracheal intuba-tion.CONCLUSION The SPG block represents a promising analgesic approach in AFNI,offering po-tential benefits in alleviating pain involving the nasal and nasopharyngeal regions as well as improving patient cooperation.

Assessing the Impact of General Anesthesia and Bronchial Intubation in Conjunction with Thoracic Paravertebral Nerve Block on Cellular Immunity and Surgical Management in Tuberculous Pyothorax Patients

Objective:This study aims to investigate the impact of combining general anesthesia with bronchial intubation and thoracic paravertebral nerve block during surgery for patients with tuberculous pyothorax.Methods:Eighty patients diagnosed with tuberculous pyothorax,admitted to the hospital between January 2023 and September 2023,were randomly selected for this study.The patients were divided into control and study groups using a numerical table method.The control group underwent general anesthesia with bronchial intubation,while the study group received general anesthesia with bronchial intubation in conjunction with thoracic paravertebral nerve block.Subsequently,the patients were monitored to assess mean arterial pressure,heart rate variations,and adverse reactions to anesthesia.Results:The study group exhibited significantly lower mean arterial pressure and heart rate levels during the post-surgical incision,immediate end of surgery,and immediate extubation periods compared to the control group(P<0.05).Furthermore,the Ricker and Ramsay scores in the study group were significantly lower than those in the control group(P<0.05).Conclusion:The combined use of general anesthesia via bronchial intubation and thoracic paravertebral nerve block has been found to stabilize mean arterial pressure and heart rate while providing effective sedation for surgical treatment in patients with tuberculous septic thorax.

Cardiopulmonary prognosis of prophylactic endotracheal intubation in patients with upper gastrointestinal bleeding undergoing endoscopy

BACKGROUND:It is controversial whether prophylactic endotracheal intubation(PEI)protects the airway before endoscopy in critically ill patients with upper gastrointestinal bleeding(UGIB).The study aimed to explore the predictive value of PEI for cardiopulmonary outcomes and identify high-risk patients with UGIB undergoing endoscopy.METHODS:Patients undergoing endoscopy for UGIB were retrospectively enrolled in the eICU Collaborative Research Database(eICU-CRD).The composite cardiopulmonary outcomes included aspiration,pneumonia,pulmonary edema,shock or hypotension,cardiac arrest,myocardial infarction,and arrhythmia.The incidence of cardiopulmonary outcomes within 48 h after endoscopy was compared between the PEI and non-PEI groups.Logistic regression analyses and propensity score matching analyses were performed to estimate effects of PEI on cardiopulmonary outcomes.Moreover,restricted cubic spline plots were used to assess for any threshold effects in the association between baseline variables and risk of cardiopulmonary outcomes(yes/no)in the PEI group.RESULTS:A total of 946 patients were divided into the PEI group(108/946,11.4%)and the non-PEI group(838/946,88.6%).After propensity score matching,the PEI group(n=50)had a higher incidence of cardiopulmonary outcomes(58.0%vs.30.3%,P=0.001).PEI was a risk factor for cardiopulmonary outcomes after adjusting for confounders(odds ratio[OR]3.176,95%confidence interval[95%CI]1.567-6.438,P=0.001).The subgroup analysis indicated the similar results.A shock index>0.77 was a predictor for cardiopulmonary outcomes in patients undergoing PEI(P=0.015).The probability of cardiopulmonary outcomes in the PEI group depended on the Charlson Comorbidity Index(OR 1.465,95%CI 1.079-1.989,P=0.014)and shock index>0.77(compared with shock index≤0.77[OR 2.981,95%CI 1.186-7.492,P=0.020,AUC=0.764]).CONCLUSION:PEI may be associated with cardiopulmonary outcomes in elderly and critically ill patients with UGIB undergoing endoscopy.Furthermore,a shock index greater than 0.77 could be used as a predictor of a worse prognosis in patients undergoing PEI.

Percutaneous transhepatic cholangial drainage-guided methylene blue for fistulotomy using dual-knife for bile duct intubation: A case report

BACKGROUND Difficult bile duct intubation is a big challenge for endoscopists during endoscopic retrograde cholangiopancreatography(ERCP)procedure.We report a case of percutaneous transhepatic cholangial drainage(PTCD)-guided methylene blue for fistulotomy using dual-knife for bile duct intubation.CASE SUMMARY A 50-year-old male patient had developed obstructive jaundice,and ERCP procedure need to be performed to treat the obstructive jaundice.But intubation cannot be performed if the duodenal papilla cannot be identified because of previous surgery for a perforated descending duodenal diverticulum.We used PTCD-guided methylene blue to identify the intramural common bile duct before dual-knife fistulotomy,and bile duct intubation was successfully completed.CONCLUSION The method that combing methylene blue and dual-knife fistulotomy to achieve bile duct intubation during difficult ERCP is safe and effective.

General anesthesia with endotracheal intubation ensures the quick removal of magnetic foreign bodies:A case report

BACKGROUND The incidence of ingestion of magnetic foreign bodies in the gastrointestinal tract has been increasing year by year.Due to their strong magnetic attraction,if multiple gastrointestinal foreign bodies enter the small intestine,it can lead to serious complications such as intestinal perforation,necrosis,torsion,and bleeding.Severe cases require surgical intervention.CASE SUMMARY We report a 6-year-old child who accidentally swallowed multiple magnetic balls.Under timely and safe anesthesia,the magnetic balls were quickly removed through gastroscopy before entering the small intestine.CONCLUSION General anesthesia with endotracheal intubation can ensure full anesthesia under the condition of fasting for less than 6 h.In order to prevent magnetic foreign bodies from entering the small intestine,timely and effective measures must be taken to remove the foreign bodies.

The ED_(50)of Remazolam Toluenesulfonate Combined with a Subthreshold Dose of Esketamine for Inhibiting Cardiovascular Response to Tracheal Intubation in Elderly Patients

Objective:To explore the half-effective dose(ED_(50))of remazolam toluenesulfonate combined with subthreshold amounts of esketamine for inhibiting cardiovascular response to tracheal intubation in elderly patients.Method:We included 42 patients,aged 65-75,who required general anesthesia and single-lumen endotracheal intubation for elective surgery.The first patient was administered remazolam toluenesulfonate at a dose of 0.20 mg/kg.Once the patient lost consciousness,their alertness/sedation score(OAA/S score)was≤1,and their BIS score was≤60,and a subthreshold dose(0.3 mg/kg)of esketamine was given.The subsequent doses were adjusted using a sequential approach based on the cardiovascular response to tracheal intubation observed in the previous patient.The dose was modified in increments or decrements of 0.01 mg/kg.The ED_(50)and 95%CI of remazolam toluenesulfonate were calculated using the Dixon and Massey sequential distribution test method.Result:The inhibition of endotracheal intubation response was positively correlated with the dose of remazolam toluenesulfonate,and the depth of sedation could not be achieved when the amount was≤0.22 mg/kg.The ED_(50)of remazolam toluenesulfonate combined with a subthreshold dose of esketamine in inhibiting cardiovascular response to tracheal intubation in elderly patients was 0.30(0.28,0.33)mg/kg.There was no statistically significant difference in blood pressure between the induction of anesthesia and before the operation.Conclusion:When compounded with 0.3 mg/kg esketamine,the ED_(50)of Remazolam toluenesulfonate in inhibiting cardiovascular response to endotracheal intubation in elderly patients was 0.30 mg/kg(95%CI0.28-0.33 mg/kg).

Digital Intubation without Stylet: Myth or Reality? Case Report

Digital intubation was discovered as one of the first methods to face a difficult airway without direct laryngoscopy. From the very beginning, this technique has been surrounded by much controversy, mainly because it required to be performed by an expert. Nowadays, it remains a useful technique when treating patients with difficult airways, so it is of utmost importance all personnel involved with airway management must know and perfect this technique when scenarios where conventional laryngoscopy or rescue devices for difficult airway are not available or contraindicated. The present work’s main objective is to suggest digital intubation as a safe and effective technique for the management of patients with difficult airways when there are no other devices available. The authors present a successful case of digital intubation on a patient with a difficult airway, demonstrating this technique is useful when performed by expert practitioners and when there is no other equipment available.

Clinical Application of Modified Anyang Type 2 Esophageal Intubation Instrument──A New Esophageal Intubation Method

The preliminary experience in the clinical use of Anyang Type 2 esophageal intubation instrument, designed by ourselves, in 11 patients with severe esophageal obstruction due to advanced carcinoma of the esophageal was reported. The diagnosis of all 11 cases was confirmed by bariummeal roentgenography. After intubation, all the patients could take liquid or soft diet by mouth.There was no operative mortality and the patients survived 2 to 14 months (mean5.7 months). All of them could take food by mouth before death. The clinical application proved that the intubation has been a safe and suitable management.

Difficult Endotracheal Intubation -Scales and Causes

The aim of the study is to assess the possibility of intubation in each patient, the lyche to be difficult intubation, to fred all the causes of the difficult intubation, to fred and apply appropriate scales for difficult intubation, to estimate the frequency of difficult intubation. Endotmcheal intubation is the basic reanimation procedure performed both in hospital and out-of-hospital settings. It is carded out whenever chest movements and spontaneous respiration are compromised. Respiratory arrest may occur for a variety of reasons （such as cardac arrest, coma of any origin, poisining） or direct damage to the airways, e.g. in various traumas （damages to the face, oropharynx, larynx, trachea, chest）. The basic endotracheal intubation kit contains： laryngoscope, endotracheal tubes, connectors （tube and Ambu bag connectors）, complete Ambu kit （face mask and bag）, 20 mL syringe for cuff inflating, suction apparatus, stylete, and Magill forceps. In order to assess the successfulness of endotracheal intubation, it is necessary first to identify patients who need to be intubated. With the aim of identifying such patients, numerous screening tests and scales have been created to predict difficult intubation. The best known and most commonly used are the Mallampati and Wilson classifications as well as the LEMON airway assessment method. Nevertheless, difficult intubation accounts for 1% of cases. It usually occurs when manipulation of the laryngoscope blade is not possible in obese patients and patients with short neck, in congenital restricted mouth opening, limited neck movement as well as limited temporomandibular joint mobility; in cases of edema, fibrosis and lesions of the tongue, pharynx and larynx; when there are anatomical variations and congenital malformations of the oral cavity, pharynx, larynx, head, neck and chest.

Comparison of Cardiac Output and Hemodynamic Responses of Intubation among Different Videolaryngoscopies in Normotensive and Hypertensive Patients

Tracheal intubation with Macintosh laryngoscope（MAC） might result in severe cardiovascular complications. The results of conducted studies investigating the effects of videolaryngoscopies on hemodynamic response of tracheal intubation are conflicting. We know little about the effects of videolaryngoscopies on cardiac output changes during tracheal intubation. We compared cardiac output（COP） and hemodynamic responses in normal blood pressure（n=60） and hypertensive patients（n=60） among 3 intubation devices： the MAC, the UE videolaryngoscopy ？（UE）, and the UE video intubation stylet ？（VS）. Cardiac index（CI）, stroke volume index（SVI）, heart rate（HR）, systolic blood pressure（SBP） and diastolic blood pressure（DBP） were recorded using Lidco Rapid V2？ preinduction, preintubation, and every minute for the first 5 min after intubation. We assessed oropharyngeal and laryngeal structures injury as well. Intubation time was significantly shorter than MAC groups（P〈0.001） only in UE group of normotensive and hypertensive patients. In normotensive patients, there were no significant differences in any of COP variables or hemodynamic variables among the three devices. In hypertensive patients, SBP and DBP in the MAC group were significantly higher（P〈0.05 or 〈0.01） than the UE and VS groups at 1, 2 and 3 min after intubation, but there were no significant differences in CI, SVI and HR among the three devices. There was no significant difference in oropharyngeal and laryngeal structures injury among all groups. It was concluded that both the UE and VS attenuate only the hemodynamic response to intubation as compared with the MAC in hypertensive patients, but not in normotensive patients.

Evaluation of Risk Factors for Arytenoid Dislocation after Endotracheal Intubation: a Retrospective Case-control Study

Objective To investigate the risk factors for postoperative arytenoid dislocation. Methods From September 2003 to August 2013, the records of 16 patients with a history of postoperative arytenoid dislocation were reviewed. Patients matched in terms of date and type of procedures were chosen as the controls(n=16). Recorded data for all patients were demographics, smoking status, alcoholic status, preoperative physical status, airway evaluation, intubation procedures, preoperative laboratory test results, anesthetic consumption and intensive care unit stay. For arytenoid dislocation cases, we further analyzed the incidences of the left and right arytenoid dislocation, and the outcomes of surgical repair and conservative treatment. Categorical variables were presented as frequencies and percentages, and were compared using the chi-squared test. Continuous variables were expressed as means±SD and compared using the Student's unpaired t-test. To determine the predictors of arytenoid dislocation, a logistic regression model was used for multivariate analysis. Results Sixteen patients with postoperative arytenoid dislocation were enrolled, with a median age of 52 years. Most postoperative arytenoid dislocation patients(15/16, 93.75%) received surgical repair, except one patient who recovered after conservative treatment. None of the postoperative arytenoid dislocation patients were smokers. Red blood cell(P=0.044) and hemoglobin(P=0.031) levels were significantly lower among arytenoid dislocation cases compared with the controls. Conclusions Non-smoking and anemic patients may be susceptible to postoperative arytenoid dislocation. However, neither of them was independent risk factor for postoperative arytenoid dislocation.

A comparison between monocanalicular and pushed monocanalicular silicone intubation in the treatment of congenital nasolacrimal duct obstruction

AIM: To compare the success rate of monocanalicular versus pushed monocanalicular silicone intubation(PMCI)of the nasolacrimal duct for congenital nasolacrimal duct obstruction(CNLDO).METHODS: In a prospective randomized clinical trial 53 eyes of 49 patients with CNLDO underwent either monocanalicular silicone intubation(MCI)(n =28 eyes) or PMCI(n =25 eyes). All procedures were performed by 1oculoplastic surgeon. Treatment success was defined as the complete resolution of epiphora at 3mo after tube removal.RESULTS: The surgical outcome was assessed in 20 eyes with MCI and 20 eyes with PMCI. The mean age of treatment was 26.25 ±10.08mo(range, 13-49mo) for MCI and 26.85±12.25mo(range, 16-68mo) for PMCI. Treatment success was achieved in 18 of 20 eyes(90.0%) in the MCI group compared with 10 of 20 eyes(50%) in the PMCI group(P =0.01). In the PMCI group, the tube loss(30%)was greater than the MCI group(5%), however the differences between the 2 groups proved to be not significant(P =0.91).CONCLUSION: Our results indicate that MCI has higher success rate in CNLDO treatment compared with PMCI in this small series of patients.

One-stitch anastomosis through the skin with bicanalicular intubation:a modified approach for repair of bicanalicular laceration

AIM:To evaluate the efficacy and safety of one-stitch anastomosis through the skin with bicanalicular silicone tube intubation in repairing of bicanalicular laceration.METHODS:The clinical data of 15 consecutive patients with both superior and inferior canalicular laceration in one eye who underwent surgical repair using one-stitch anastomosis through the skin and bicanalicular stent were retrospective studied.All the operations were performed under surgical microscope,5-0 silk sutures were used and were with bicanalicular silicone tube(diameter was 8mm) intubation,for one lacerated canaliculi one-stitch anastomosis through the skin.The stents were left in place for 3 months postoperatively and then removed.The follow-up period was 3-36 months(average 14 months). RESULTS:In 15 patients,13 patients were cured entirely,1 patient was meliorated,1 patient with no effects.All patients had got good recovery of eyelid laceration with no traumatic deformity in eyelid and canthus.Complication was seen in one case,for not followed the doctor’s guidance to come back to hospital to had the suture removed on the 7thday after operation,when he came at the 15thday,the inferior canalicular wall and eyelid skin were corroded by the suture caused 2mm wound,and the inside silicone tube was exposed,a promptly repair with 10-0 nylon suture was done,the wound healed in a week.There were no early tube protrusions and punctal slits in the patients.CONCLUSION:One-stitch anastomosis through the skin with bicanalicular silicone tube intubation is a good method in repair of bicanalicular laceration in one eye,the cut ends can be anastomosed directly,and with excellent cosmetic results,it is acceptable for the patients.For there is no suture remained in the wound permanently,so there is no suture-related granuloma which may cause obstruction or stenosis of canaliculi.It is simple,economical,effective and safe.

Bicanalicular versus monocanalicular intubation after failed probing in congenital nasolacrimal duct obstruction

AIM：To investigate the clinical outcomes of different intubation techniques in the cases of failed primary probing.METHODS： This retrospective study was performed on338 patients with the diagnosis of congenital nasolacrimal duct obstruction with age 1-4y that had failed primary probing.Intubation was performed under light sedation in operating room and the stent was left 3mo in place.Clinical outcome was investigated 3mo after tube removal.RESULTS： Bicanalicular intubation method had higher complete and relative success rates compared to monocanalicular intubation（P =0.00）.In addition,Monoka intubation had better outcomes compared to Masterka technique（P =0.046）.No difference was found between genders but the higher the age,the better the outcomes with bicanalicular technique rather than monocanalicular.CONCLUSION： Overall success rate of bicanalicular intubation is superior to monocanalicular technique especially in older ages.Also,based upon our clinical outcomes,Masterka intubation is not recommended in cases of failed probing.

Transparent-cap-fitted colonoscopy shows higher performance with cecal intubation time in difficult cases

AIM:To investigate the efficacy of cap-fitted colonoscopy(CFC) with regard to cecal intubation time.METHODS:Two hundred and ninety-five patients undergoing screening colonoscopy at Gospel Hospital,Kosin University College of Medicine were enrolled in this randomized controlled trial between January and December 2010.Colonoscopies were conducted by a single endoscopist.Patient characteristics including age,sex,body mass index,history of abdominal surgery,quality of preparation,and the presence of diverticulosis were recorded.RESULTS:One hundred and fifty patients were allocated into a CFC group and 145 into a non-CFC(NCF) group.Cecal intubations were achieved in all patients.Cecal intubation time in the CFC group was significantly shorter than in the NCF group for specific conditions:age ≥ 60 years,prior abdominal surgery,and poor bowel preparation.The number of detected adenomas was higher in the CFC group than in the NCF group(P = 0.040).CONCLUSION:CFC facilitated shortening of the cecal intubation time in difficult cases,and was more sensitive for detecting adenomas than was NCF.

The incidence of oxygen desaturation during rapid sequence induction and intubation

BACKGROUND: Rapid sequence induction and intubation(RSII) is an emergency airway management technique for patients with a risk of pulmonary aspiration. It involves preoxygenation, administration of predetermined doses of induction and paralytic drugs, avoidance of mask ventilation, and laryngoscopy followed by tracheal intubation and keeping cricoid pressure applied till endotracheal tube cuff be inflated. Oxygen desaturation has been seen during RSII. We assessed the incidence of oxygen desaturation during RSII.METHODS: An institution-based observational study was conducted from March 3 to May 4, 2014 in our hospital. All patients who were operated upon under general anesthesia with RSII during the study period were included. A checklist was prepared for data collection.RESULTS: A total of 153 patients were included in this study with a response rate of 91.6%. Appropriate drugs for RSII, equipments for RSII, equipments for diffi cult intubation, suction machine with a catheter, a monitor and an oxygen backup such as ambu bag were not prepared for 41(26.8%), 50(32.7%), 51(33.3%), 38(24.8%) and 25(16.3%) patients respectively. Cricoid pressure was not applied at all for 17(11.1%) patients and 53(34.6%) patients were ventilated after induction of anesthesia but before intubation and endotracheal cuff inflation. A total of 55(35.9%) patients desaturated during RSII(SPO2<95%). The minimum, maximum and mean oxygen desaturations were 26%, 94% and 70.9% respectively. The oxygen desaturation was in the range of <50%, 50%–64%, 65%–74%, 75%–84%, 85%–89 % and 90%–94% for 6(3.9%), 7(4.6%), 5(3.3%), 10(6.5%), 13(8.5%) and 14(9.2%) patients respectively.CONCLUSION: The incidence of oxygen desaturation during RSII was high in our hospital. Preoperative patient optimization and training about the techniques of RSII should be emphasized.

Video versus direct laryngoscopy on successful firstpass endotracheal intubation in ICU patients

BACKGROUND: Airway management in intensive care unit(ICU) patients is challenging. The aim of this study was to compare the rate of successful first-pass intubation in the ICU by using the direct laryngoscopy(DL) and that by using the video laryngoscopy(VL).METHODS: A randomized, non-blinded trial comparing first-pass success rate of intubation between VL and DL was performed. Patients were recruited in the period from August 2014 to August 2016. All physicians working at ICU received hands-on training in the use of the video and direct laryngoscope. The primary outcome measure was the first-pass intubation success. RESULTS: A total of 163 ICU patients underwent intubation during the study period(81 patients in VL group and 82 in DL group). The rate of successful first-pass intubation was not significantly different between the VL and the DL group(67.9% vs. 69.5%, P=0.824). Moreover, the overall intubation success and total number of attempts to achieve intubation success did not differ between the two groups. In patients with successful first-pass intubation, the median duration of the intubation procedure did not differ between the two groups. The Cormack-Lehane grades and the percentage of glottic opening score were similar, and no significant differences were found between the two groups. There were no statistical differences between the VL and the DL group in intubation complications(all P>0.05). CONCLUSION: Among ICU patients requiring intubation, there was no significant difference in the rate of successful first-pass intubation between VL and DL.