Ease of intubation using oral Microcuff RAE (Ring–Adair–Elwyn) tube with and without premounted Frova intubating introducer in children undergoing cleft lip and palate surgeries – A randomised controlled study

Abstract

Background and Aims:

Ring–Adair–Elwyn (RAE) tracheal tube is morphologically different from the routine endotracheal tubes. Unlike conventional endotracheal tubes, the passage of the RAE tube through the laryngopharynx and vocal cords might be challenging. We hypothesised that an oral RAE endotracheal tube railroaded over the Frova intubating introducer would reduce intubation time.

Methods:

Eighty children with cleft lip and palate anomalies without additional difficult airway predictors were enroled. They were randomly assigned to two groups: Group Frova (n = 40), which received preloaded oral RAE tracheal tubes with a Frova intubating introducer, and Group Non-Frova (n = 40), which received oral RAE tracheal tubes without the Frova introducer. The primary outcome was the tracheal intubation time. Secondary outcomes were the first-attempt intubation success rate, the need for external laryngeal manoeuvres (ELMs), ease of intubation and airway complications.

Results:

The mean age (months) was 21 [standard deviation (SD): 14.2] in Group Frova and 20.7 (SD: 13.5) in Group Non-Frova. The mean intubation time (sec) was not different between Group Frova and Group Non-Frova [39.15 (SD: 15.39) (95% confidence interval {CI}: 31.3, 47.0) vs. 35.76 (SD: 15.29) (95% CI: 27.9, 43.6); mean difference = 3.39 (95% CI: −3.6, 10.41); P = 0.338]. Furthermore, the first-attempt success rate was comparable between groups (34 vs. 29, P = 0.308). There was no difference in the requirement of ELMs (13 vs. 17, P = 0.261), and the ease of intubation was also comparable.

Conclusion:

Frova introducer-guided endotracheal intubation with an oral RAE tube does not decrease intubation time in children undergoing cleft lip and palate surgery.

INTRODUCTION

Airway management is always challenging in cleft lip and cleft palate repair surgery.[1,2,3] The structural design of the oral Ring–Adair–Elwyn (RAE) tube facilitates the surgical procedure by providing optimum space without the risk of tracheal tube compression. Microcuff oral RAE tubes have also been found to have significantly reduced exchange rates in cleft repair cases.[4,5] However, the morphology of the RAE tube may not be ideal for negotiation through the laryngopharynx and the vocal cord.

Frova intubating introducer (Cook Medical, Bloomington, IN, USA; 35 cm long, 8 Fr, 1.6 mm internal diameter) has a blunt curved tip. An endotracheal tube railroaded over the Frova significantly improves the ease of tracheal intubation in patients with unanticipated or anticipated difficult airway.[6] The Difficult Airway Society 2015 and All India Difficult Airway Association 2016 guidelines[7] recommend early use of introducer devices in case of difficult tracheal intubation. The preformed bend in oral RAE tubes makes their shape unique and substantially different from the conventional tube. This preformed shape may affect the ease of tracheal intubation and lead to multiple unsuccessful intubation attempts as well as airway manipulations.

The primary objective of this study was to compare the tracheal intubation time between the Frova introducer-guided oral RAE tracheal tube and the oral RAE tracheal tube without the Frova introducer in children undergoing elective surgery for cleft lip and cleft palate under general anaesthesia. The secondary objectives included comparing the first-attempt intubation success rate, the need for external laryngeal manoeuvres (ELMs), the ease of intubation (as assessed by a predefined scoring system) and the incidence of airway injury. We hypothesised that tracheal intubation using a Frova introducer-guided oral RAE tracheal tube would reduce intubation time and improve the success rate of first-attempt intubation, compared to an oral RAE tracheal tube used without the introducer.

METHODS

After obtaining approval from the Institutional Ethics Committee Board (vide approval number JIP/IEC/2018/478, dated 15 March 2019), the trial was registered with the Clinical Trials Registry-India (vide registration number CTRI/2019/05/019289, accessible at www.ctri.nic.in). Patients were enroled from May 2019 to April 2021. The study adhered to the Declaration of Helsinki (2013) and Good Clinical Practice guidelines. Written informed consent was obtained from the parents or legal guardians of all participants for study participation and the use of patient data for research and educational purposes.

Children aged 6 months to 4 years, belonging to the American Society of Anesthesiologists (ASA) physical status I and II and scheduled to undergo elective cleft lip and palate repair were included. Children with limited mouth opening, anticipated difficult airway such as those with micrognathia or retrognathia, significant facial asymmetry or midline abnormalities, restricted neck movement and a history of difficult intubation or recent respiratory tract infection were excluded. Randomisation was done using a computer-generated random number table created with Statistical Package for the Social Sciences (SPSS) statistics software version 24.0 [International Business Machines Corporation (IBM Corp), Armonk, NY, USA], employing varying block sizes to ensure balanced allocation. The group allocation was done using a sequentially numbered, opaque, sealed envelope by an anaesthesiologist not involved in the study. The patients were randomly assigned in a 1:1 ratio to undergo intubation with an oral Microcuff RAE tracheal tube (Kimberly–Clark Corporation, Health Care Atlanta, GA, USA at the time, later transitioned to Avanos Medical Alpharetta, GA, USA) preloaded over the Frova introducer (Group Frova) or with the oral Microcuff RAE tracheal tube alone (Group Non-Frova). The anaesthesiologists involved in airway management had at least 2 years of experience in providing anaesthesia for managing cleft lip repair procedures. The outcome assessor was blinded to the group allocation.

The preanaesthetic evaluation was done a day before surgery. Standard fasting guidelines for the paediatric population were followed. On the day of surgery, the enroled children received oral premedication (midazolam syrup 0.5 mg/kg) in the preoperative room. In the operating room, standard ASA monitors [electrocardiogram, non-invasive blood pressure and pulse oximetry (SpO₂)] were attached and baseline vitals were recorded. Anaesthesia induction was achieved with gradually increasing concentrations of sevoflurane in 100% oxygen. Intravenous (IV) fentanyl 1–2 μg/kg and atracurium 0.5 mg/kg were administered after securing the IV cannula.

In Group Frova, a manually straightened Microcuff oral RAE tube was used. The tube was loaded over a lubricated, 8-Fr Frova intubating introducer along with its stiffening cannula [Figure 1a]. The tip of the Frova introducer was extended 0.5–1 cm beyond the tip of the RAE tube [Figure 1b]. To achieve optimal laryngoscopy, gentle head extension was done using a shoulder roll or towel, and the laryngeal view was graded using the Cormack–Lehane (CL) classification with a Macintosh blade. The Frova introducer, with its angled tip, was gently advanced through the glottis, after which the RAE tube was advanced over it. Once the RAE tube’s tip crossed the glottic opening, the assistant withdrew the introducer while the anaesthesiologist advanced the tube to its designated position marked on the tube.

Figure 1.

(a) Oral Microcuff RAE tracheal tube railroaded over Frova introducer with stiffening cannula. (b) Tip of Frova introducer beyond the oral RAE tube. RAE = Ring–Adair–Elwyn

In Group Non-Frova, which involved standard oral RAE tube intubation, an oral RAE tube was used without a Frova introducer. The RAE tube, preshaped with its inherent curvature, was introduced into the airway after achieving a proper view using a Macintosh blade. The laryngeal view was graded using the CL classification during direct laryngoscopy. The RAE tube was advanced directly into the trachea without use of any introducers.

After successful intubation in both groups, the RAE tube was secured at the centre of the chin. Correct placement was confirmed by the presence of at least three consecutive square wave capnography waveforms and bilateral air entry on chest auscultation. A significant air leak was assessed by listening to an audible leak and auscultation over the trachea while delivering positive pressure ventilation at a peak inspiratory pressure of 20 cmH₂O. If an audible leak was detected with inadequate tidal volume delivery, the cuff was incrementally inflated. Volume-controlled ventilation (tidal volume of 8 ml/kg) was initiated at a rate of 18–24 breaths per minute. Anaesthesia was maintained with isoflurane (0.8%–1.2%) or sevoflurane (1.5%–2%) in an oxygen–air mixture, and other aspects of anaesthetic management were left to the discretion of the attending anaesthesiologist.

The primary outcome was the tracheal intubation time, defined as the interval from the introduction of the laryngoscope blade into the patient’s mouth to the appearance of at least three consecutive square wave capnography waveforms. Secondary outcomes included the number of attempts at redirection of the endotracheal tube, haemodynamic responses during intubation, the incidence of failed intubations, the need for ELMs, episodes of desaturation (defined as SpO₂ <95%) and the ease of intubation, which was assessed using an ordinal scale (1- easy, 2- difficult). The tracheal intubation process was timed by an independent observer who was not a part of the study.

Any attempt taken to redirect the tube or the Frova towards the glottis was regarded as one redirection attempt. If there were no redirection attempts, it was considered as the first attempt at intubation. The occurrence of airway injury or desaturation (SpO₂ <95%) was regarded as a failure, and the consultant anaesthesiologist decided the rescue procedure. In both groups, a Macintosh laryngoscope was used as the primary device for aiding intubation. In cases where a poor glottic view, such as CL grade 3 or more, was encountered, the C-MAC video laryngoscope was used as a rescue device. These cases were excluded from further analysis [Figure 2].

Figure 2.

CONSORT flow diagram. CL = Cormack–Lehane, CONSORT = Consolidated Standards of Reporting Trials, RAE = Ring–Adair–Elwyn, n = number of patients

The statistical analysis was conducted using SPSS software, version 24.0 (IBM Corp., Armonk, NY, USA). The distribution of categorical and ordinal variables, including gender, ASA classification, CL grading, first-attempt success rate, failed intubation rate, episodes of desaturation, airway injury and requirement of ELM, were expressed as frequency and percentage. Chi-squared test was used for gender, ASA classification, CL grading, first-attempt success rate, episodes of desaturation and requirement of ELM. Fisher’s exact test was applied to analyse failed intubation rate and airway injury. Continuous variables, including age (in months), weight (kg), height (cm) and total tracheal intubation time (sec), were expressed as mean [standard deviation (SD)] [95% confidence interval (CI)], depending on the normality of data distribution. Normality was assessed using the Shapiro–Wilk test. Weight, height, age and intubation time followed a normal distribution and were analysed using the independent Student’s t-test. Haemodynamic parameters, including heart rate (HR) and systolic blood pressure at various time points, were compared between the groups using a two-way repeated-measures analysis of variance test to account for within-subject and between-group variations. All statistical analyses were performed at a 5% level of significance, and the results were interpreted accordingly.

RESULTS

Eighty children were recruited for the study. Four were withdrawn (one in Group Frova and three in Group Non-Frova) as they could not be intubated according to the study protocol, and data analysis was carried out for 76 children [Figure 2]. The demographic characteristics, distribution of the types of surgery, and CL grade were comparable between the groups [Table 1].

Table 1.

Demographic characteristics of the recruited children

Parameter	Group Frova (n=39)	Group Non-Frova (n=37)
Age (months) [Mean (SD)]	20.97 (14.18)	20.68 (13.45)
Gender (male/female), n	23/16	17/20
Weight (kg) [Mean (SD)]	10.27 (3.03)	10.47 (3.22)
Height (cm) [Mean (SD)]	89.47 (15.05)	88.27 (16.12)
ASA class (I/II), n	36/3	37/0
Bilateral cleft palate	2	1
Bilateral cleft lip	9	9
Bilateral cleft palate with cleft lip	20	19
Unilateral cleft lip	8	8
CL grade I	19	20
CL grade II	17	12
CL grade III	2	5
CL grade IV	1	0

Data expressed as Mean (SD) or number of patients (n). ASA=American Society of Anesthesiologists, CL=Cormack–Lehane, SD=standard deviation

The mean intubation time was comparable between the groups [Group Frova 39.15 (SD: 15.39) (95% CI: 33.92, 44.38) sec vs. Group Non-Frova 35.76 (SD: 15.29) (95% CI: 30.72, 40.80) sec (P = 0.338)]. The first-attempt intubation success rate was not statistically significant between Group Frova [34/39 (87.1%)] and Group Non-Frova [29/37 (78.3%)] (P = 0.308). The need for ELM was also comparable between Group Frova [13/39 (33.3%)] and Group Non-Frova [17/37 (45.9%)] (P = 0.261) [Table 2]. Desaturation (SpO₂ <95%) was noted in two children in Group Non-Frova and one child in Group Frova (P = 0.525). However, these episodes were transient, resolved promptly and did not require rescue interventions. As none of the cases required a rescue technique or alternative intubation method, no ‘failed intubation’ was reported in either group. The perceived ease of intubation was similar between the groups (P = 0.492). HR and blood pressure were comparable [Tables 3 and 4].

Table 2.

Intubation condition and characteristics

Parameter	Group Frova (n=39)	Group Non-Frova (n=37)	Mean difference (95% CI)	P
Total intubation time (sec) [mean (SD)]	39.15 (15.39)	35.76 (15.29)	3.39 (−3.6, 10.41)	0.338
First-attempt success, n	34	29	1.1 (0.9, 1.4)	0.308
Failed intubation, n	0	0		-
Desaturation, n	1	2	2.1 (0.2, 22.2)	0.525
Airway injury, n	1	3		0.279
Requirement of ELM, n	13	17	1.4 (0.8, 2.4)	0.261

Data expressed as Mean (SD) (95% CI) or as number of patients (n). CI=confidence interval, ELM=external laryngeal manipulation, SD=standard deviation

Table 3.

Comparison of mean heart rate over time between the groups

Heart rate (bpm)	Group Frova (n=39)	Group Non-Frova (n=37)	Mean difference (95% CI)	P
Baseline	130 (15.5)	131.3 (17.1)	1.3 (−5.32, 7.9)	0.711
At intubation	119 (14.6)	126.1 (15.2)	6.34 (−0.27, 12.95)	0.331
1 min postintubation	138.8 (11.3)	141.9 (16.1)	3.1 (−3.52, 9.71)	0.230
2 min postintubation	137.6 (11.4)	140.8 (15.7)	3.2 (−3.42, 9.81)	0.131
3 min postintubation	134.8 (12.2)	138.4 (15.0)	3.66 (−2.95, 10.27)	0.186
4 min postintubation	131.8 (12.8)	135.2 (16.6)	3.4 (−3.22, 10.01)	0.142
5 min postintubation	129.8 (13.3)	132.8 (17.8)	2.96 (−3.65, 9.58)	0.197

Data expressed as Mean (SD) and (95% CI). CI=confidence interval, SD=standard deviation

Table 4.

Comparison of SBP over time between the groups

SBP (mmHg)	Group Frova (n=39)	Group Non-Frova (n=37)	Mean difference (95% CI)	P
Baseline	95.9 (15.4)	87.8 (17.1)	−8.17 (−14.45, 1.88)	0.032
At intubation	88.2 (11.5)	83.3 (13.40)	−4.83 (−11.11, 1.45)	0.132
1 min postintubation	101.8 (15.6)	105.1 (15.1)	3.26 (−3.02, 9.54)	0.311
2 min postintubation	98.5 (14.6)	100.8 (14.5)	2.35 (−3.93, 8.63)	0.468
3 min postintubation	95.4 (13.3)	95 (14.4)	−0.38 (−6.67, 5.90)	0.900
4 min postintubation	92.9 (10.6)	89.5 (13.8)	−3.44 (−9.72, 2.84)	0.289
5 min postintubation	90.6 (9.2)	87.1 (15.1)	−3.48 (−9.77, 2.8)	0.288

Data expressed as Mean (SD) and (95% CI). CI=confidence interval, SBP=systolic blood pressure, SD=standard deviation

DISCUSSION

The primary objective of this study was to compare the tracheal intubation time between the Frova introducer-guided oral RAE tracheal tube and the plain oral RAE tracheal tube in children posted for cleft lip and cleft palate surgery. The mean tracheal intubation time in Group Frova was comparable to that in Group Non-Frova.

A statistically non-significant higher intubation time in Group Frova compared to Group Non-Frova could be due to the additional step of the assistant removing the Frova introducer from the RAE tube after the tube tip passed through the vocal cords. In two children, the distal tip of the Frova hinged on the anterior commissure, making it difficult to thread the RAE tube into the vocal cords, which caused airway trauma. If an excessive curvature is used, it can be difficult to pass the tube through or below the glottis as it courses anteriorly. The intubation time estimated using the Frova introducer in this study was consistent with the findings in other studies using tracheal introducers.[8] However, the definition of intubation time varied across studies.

Studies have reported a high tracheal intubation success rate with the Frova introducer in various airway settings.[9,10] A single-centre trial showed higher success with Frova than with Bonfils fibrescope (93.3% vs. 83.3%).[11] However, its use with an RAE tube in surgical settings, including in cleft palate repairs, has not been studied earlier. The incidence of difficult airway during cleft palate surgery is estimated to be 4.7%–8.4%.[12] A cuffed oral RAE tube is preferred to prevent airway obstruction using a mouth gag, as it reduces the risks of endobronchial intubation and intraoral extubation compared to uncuffed tubes.[4,13,14] In our study, the Frova passed smoothly through the straightened RAE tube without resistance, and its preformed curvature remained unchanged, confirming its ease of use.

We observed a lower need for ELM in Group Frova, where more children had CL grade 2 views. Notably, the Frova introducer facilitated smooth glottic passage without requiring redirections. Although our study did not include children with micrognathia or retrognathia, its successful use in cleft lip and palate cases, along with Kim et al.’s[15] report demonstrating its effectiveness in facilitating smooth intubation in a Pierre Robin syndrome case under video laryngoscopy, suggests its potential role in managing difficult airways. In such anatomically challenging cases, the Frova introducer may aid endotracheal tube placement, simplifying intubation. However, further studies are needed to validate its effectiveness in this specific population. This study also compared the ease of intubation (as assessed by a predefined scoring system) and found no difference between the groups.

The Frova introducer is widely used in paediatric difficult airways with fewer complications.[16,17] Its higher success in CL grades IIa and IIb indicates its utility in cleft lip and palate surgeries, though it may increase intubation time. The stiffening cannula maintains the familiar RAE tube shape, ensuring ease of use. We leveraged Frova’s benefits without compromising the use of the oral RAE tube, achieving a high first-attempt success rate and avoiding repeated laryngoscopy, which can necessitate extra anaesthetic doses and cause airway trauma.

In this study, we withdrew four cases after allocation as these children had CL grades 3 and 4. We had to use video laryngoscopy for intubation as direct laryngoscopy with ELM was not successful in endotracheal intubation. Nonetheless, the Frova-mounted RAE tube was utilised in all these children.

The findings of this study have clinical relevance, particularly in paediatric patients with challenging airways. Group Frova showed a higher first-attempt success rate and reduced need for ELM (though statistically not significant), both of which can minimise complications like airway trauma and hypoxia. Although intubation time was slightly longer with Group Frova, this difference is clinically negligible compared to its potential benefits in facilitating smoother intubation. These results suggest that the Frova introducer may be particularly valuable in difficult airway scenarios, such as patients with craniofacial abnormalities, highlighting its utility in improving overall airway management in children.

Our study has certain limitations. It was a single-centre study with a small sample size. We excluded children with predictors of difficult airway. Therefore, our findings cannot be extrapolated to children with difficult airway or having predictors of difficult airway. Nevertheless, the Frova premounted RAE tracheal tube may offer better intubating conditions in children with CL grades 2 and 3. We need further studies in children with anticipated or unanticipated difficult airway with a larger sample size to validate the findings of this study in those populations.

CONCLUSION

Frova introducer-guided endotracheal intubation with an oral RAE tube did not decrease intubation time in children undergoing cleft lip and palate surgery. However, a marginally higher first-attempt intubation success rate with the Frova introducer appears encouraging.

Study data availability

De-identified data may be requested with reasonable justification from the authors (email to the corresponding author) and shall be shared after approval as per the authors’ institution policy.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Funding was received from the JIPMER Intramural Fund for this postgraduate dissertation.