|Year : 2019 | Volume
| Issue : 4 | Page : 157-163
Clinical evaluation of Ambu® Aura-i™ – A new intubating laryngeal mask airway as an independent ventilatory device and a conduit for tracheal intubation in pediatric patients
Triveni M Rangaswamy1, Avnish Bharadwaj2, Priyanka Jain3
1 Department of Anaesthesiology, Bangalore Medical College and Research Institute, Bengaluru, Karnataka, India
2 Department of Anaesthesiology, Mahatma Gandhi University of Medical Services and Technology, Jaipur, Rajasthan, India
3 Department of Anaesthesiology, Sawai Man Singh Medical College, Jaipur, Rajasthan, India
|Date of Submission||21-Feb-2019|
|Date of Decision||01-Aug-2019|
|Date of Acceptance||16-Oct-2019|
|Date of Web Publication||11-Dec-2019|
Dr. Triveni M Rangaswamy
#62, 1st Main Road, 2nd Cross, Central Excise Layout, R.K. Hegde Nagar, Bengaluru - 560 077, Karnataka
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background: Ambu® Aura-i™, a recently introduced second generation supraglottic airway device has been designed to function as an independent ventilatory device as well as a conduit for passage of conventional cuffed tracheal tubes through it. There is dearth of literature on experience of tracheal intubation through intubating laryngeal mask airway (ILMA) in paediatric age group. This study was conducted to study the ventilatory effectiveness and the intubating characteristics of Ambu® Aura-i™ in paediatric patients.
Aim: To study the effectiveness of Ambu ® Aura-i ™ as a supraglottic device for its ventilatory effectiveness and intubation characteristics in paediatric patients.
Objectives: To study the Ventilatory effectiveness of Ambu ® Aura-i ™ in terms of: 1) Time taken in insertion of Ambu ® Aura-i ™. 2) No of attempts made for successful insertion of Ambu ® Aura-i™. 3) Tidal volume attained on positive pressure ventilation. 4) Etco2, Spo2 and Leak pressure achieved. To study the Intubating characterstics of Ambu ® Aura-i ™ in terms of :- 1) Grade of alignment of the ventilating orifice achieved in relation to the larynx in the fibre optic view. 2) Time taken in intubation through Ambu ® Aura-i ™. 3) Number of attempts made in intubation. 4) Time taken for removal of the Ambu ® Aura-i ™ after intubation through it has been accomplished.
Method: Sixty three children undergoing elective surgery under general anaesthesia requiring intubation of trachea, weighing between 5-30 kg were stratified into 3 groups (n= 21) each. Ambu® Aura-i™ size 1.5 , 2.0 ,2.5 were used based on their body weight for airway management. Ventilatory effectiveness was studied in terms of success rate, number of attempts made at insertion, time taken in insertion, tidal volume delivered and leak pressure achieved. Intubating characterstics studied during fibreoptic guided tracheal intubation included grade of alignment of the ventilating orifice achieved in relation to the larynx in fibre optic view, time taken in fibreoptic guided tracheal intubation, success rate and number of attempts made at intubation. Time taken in removal of the device and complications observed were also recorded.
Results: Ambu® Aura-i™ insertion, fibreoptic guided tracheal intubation and device removal were successful in all the patients in first attempt. The mean time taken in successful device insertion was 10.83±2.04 sec. The mean tidal volume delivered was 7.88±1.33 ml/kg body weight and mean leak pressure achieved was 16.27±5.2 cm H2O. The fibreoptic guided intubation was possible in first attempt in 100% of the patients (n=63). The Fibre optic view was grade 1 in 82.55% patients (n=52 /63) and grade 2 in 17.46% (n=11/ 63) patients. The mean time taken in fibre optic guided intubation was 12.68 ±2.82 sec. The mean time taken in removal of the device over the tracheal tube was 12.27 sec. There was no significant incidence of trauma to soft tissues, sore throat, laryngospasm or hoarseness of voice.
Conclusion: On the basis of observations of this study, we conclude that Ambu ® Aura-i ™ is not only an effective ventilatoy device, but also an excellent conduit for fibre optic guided intubation using conventional uncuffed endotracheal tube in paediatric patients. Ambu ® Aura-i ™ , is also valuable for establishing rapid airway access in emergent difficult paediatric airway.
Keywords: Ambu® Aura-i™, fiberoptic-guided tracheal intubation, pediatrics
|How to cite this article:|
Rangaswamy TM, Bharadwaj A, Jain P. Clinical evaluation of Ambu® Aura-i™ – A new intubating laryngeal mask airway as an independent ventilatory device and a conduit for tracheal intubation in pediatric patients. Int J Crit Illn Inj Sci 2019;9:157-63
|How to cite this URL:|
Rangaswamy TM, Bharadwaj A, Jain P. Clinical evaluation of Ambu® Aura-i™ – A new intubating laryngeal mask airway as an independent ventilatory device and a conduit for tracheal intubation in pediatric patients. Int J Crit Illn Inj Sci [serial online] 2019 [cited 2020 Sep 25];9:157-63. Available from: http://www.ijciis.org/text.asp?2019/9/4/157/272765
| Introduction|| |
Airway management continues to remain one of the most challenging tasks for anesthesia and critical care providers. Intubation of the trachea has remained the gold standard for airway management during anesthesia.
Laryngeal mask airway (LMA) introduced in clinical practice by Dr. Archie Brain in 1983 has revolutionized the airway management. Although the classic LMA is a useful and versatile device for airway management, its major limitation is unsuitability for intubation through it. Brain et al., 1997, bioengineered a new laryngeal mask prototype, intubating LMA (ILMA) with superior ventilatory and intubation characteristics. The major drawback of the ILMA, however, is that it is not suitable for use in pediatric patients since it is available in sizes appropriate for above 30 kg patients only.
Ambu® Aura-i™ is a recently introduced second-generation supraglottic airway device available in various sizes including sizes suitable for pediatric patients. It has been designed with the airway tube molded with built-in anatomically correct curve according to the pediatric airway. The airway tube is flexible at the cuff and rigid at the connector for easy, atraumatic insertion and removal. The reinforced tip of the cuff does not bend during insertion, thus making the positioning accurate. The cuff is soft and 0.4 mm thin ensuring the best possible seal with least possible intracuff pressure. The smooth sides of the cuff make the insertion atraumatic. It is available in various sizes based on the body weight ranging from <5 kg to >30 kg and is meant for single use.
There is a limited literature on the clinical use of ILMA in pediatric patients, and this descriptive observational study was intended evaluate the ventilatory effectiveness as well as the intubating characteristics of this new device, Ambu® Aura-i™ in pediatric patients. The goal of the study was to assess the ventilatory effectiveness of Ambu® Aura-i™ in terms of time taken in insertion, success rate, number of attempts made, tidal volume, and leak pressure achieved and to study the intubating characteristics of Ambu® Aura-i™ in terms of grade of alignment of the ventilating orifice achieved in relation to the larynx in the fiberoptic view, time taken in intubating, and removal of the device over the tracheal tube while recording the complications if any.
| Methods|| |
Study design and population
This study was a hospital-based descriptive observational approved by the institutional review board and the ethical committee and has been performed over a period of 7 months from April 2014 to October 2014 in Jaipur, Sawai Man Singh Medical College and Hospital, and all included patients guardians were informed and signed written consent was obtained prior to the procedure. All data are maintained confidential. The sample size required to verify the expected average time taken for inserting the Ambu® Aura-i™ size 1–3, its variation at 95% confidence interval and 80% power was calculated as 63, based on a similar previous study by Jagannathan et al.,
The inclusion criteria were pediatric patients undergoing elective surgery under general anesthesia requiring intermittent positive pressure ventilation, weighing between 5 and 30 kg, and the American Society of Anesthesiologists Physical Status I and II. Patients with guardians willing to give informed written consent.
Exclusion criteria included parents' refusal for informed consent; any contraindication to ILMA insertion: abnormal airway anatomy, assessed by – passive mouth opening, micrognathia, thyromental distance, and submental compliance; intraoral growth; and patients with history of cardiopulmonary disease and severe gastrointestinal reflux.
Eligible patients were consecutively stratified into three groups (n = 21 each) and suitable sizes Ambu® Aura-i™ 1.5, 2.0, and 2.5 were used for patients of body weight 5–10 kg, 11–20 kg, and 21–30 kg, respectively, for airway management till all the devices were used. All patients received syrup midazolam 0.5 mg/kg, 30 min before induction of anesthesia to facilitate parental separation. On arrival in operation room, standard monitoring was setup and preoxygenation with 100% oxygen was done. The technique of anesthesia included intravenous injections of glycopyrrolate 0.04 mg/kg, fentanyl 2 μg/kg, and propofol 3 mg/kg from a previously secured vascular access. Intravenous lignocaine 0.5 mg/kg preceded induction of anesthesia by 90 s. Depth of anesthesia for Ambu® Aura-i™ insertion was assessed by degree of jaw relaxation and pattern of ventilation. Additional bolus of propofol was given if needed.
Based on the body weight of the patient, appropriate size Ambu® Aura-i™ was selected and prepared for use. The airway tube of Ambu® Aura-i™ was held like a flute, with three fingers placed on the flat part of the connector shell and the thumb on the vertical line on the connector shell, which was oriented anteriorly toward the patient's nose. The other hand was placed under the patient's head. The Ambu® Aura-i™ was inserted as per the technique recommended by the manufacturer. The cuff was inflated with air and intracuff pressure was then standardized to 60 cmH2O using pressure gauge with the device connected to breathing circuit. All Ambu® Aura-i™ insertions were done by single investigator (TMR). Injection atracurium 0.6 mg/kg was then administered for laryngeal relaxation and assisted ventilation with 100% oxygen was started with expiratory valve closed, and a fresh gas flow of 3 l/min until equilibrium was seen on the pressure gauge (valve adjusted and pressure not allowed to exceed 40 cmH2O) to obtain the leak pressure.
The study parameters were assessed as follows:
Time taken in insertion (seconds)
This was defined as the time from picking up the device to the chest rise was seen with a positive pressure breath and end-tidal carbon dioxide (EtCO2) was observed on monitor.
Assessment of successful placement
Successful placement was determined by the ability to achieve 7–8 ml/kg tidal volume, bilateral chest excursion, equal air entry, and square wave capnogram upon delivery of a positive pressure breath. The insertion of the device was considered Failure if it took more than three attempts or if any of the attempts required more than 150 s to accomplish the procedure. Any complication during insertion, namely apnea, hypotension, coughing, desaturation, or laryngospasm was noted. All the observations of device insertion were recorded by an independent observer (PJ).
Fiberoptic-guided tracheal intubation and assessment of glottis view
Another independent investigator who was an expert in fiberoptic bronchoscopy (AB) then performed the fiberoptic-guided tracheal intubation through the Ambu® Aura-i™, who also graded the glottis view. Pediatric flexible fiberoptic bronchoscope (Karl Storz) was lubricated and preloaded with the suitable size uncuffed endotracheal tube (ET) (size 4, 4.5 and 5 mm i.d for Ambu® Aura-i™ size 1.5, 2, and 2.5, respectively). The bronchoscope was inserted through the lumen of the Ambu® Aura-i™ to assess the glottis view. The grading of the glottis view was done to a score of 1–5 defined as follows: Grade 1 = only larynx seen; Grade 2 = larynx and posterior surface of epiglottis seen; Grade 3 = larynx and tip of anterior surface of epiglottis seen, <50% visual obstruction of epiglottis to larynx; Grade 4 = larynx and tip of anterior surface of epiglottis seen, >50% visual obstruction of epiglottis to larynx; And Grade 5 = epiglottis downfolded and larynx cannot be seen. Bronchoscope was maneuvered into the trachea to visualize the carina. Tracheal tube was pushed over the bronchoscope and intubation was done with the preloaded poly vinyl chloride (PVC) uncuffed tracheal tube (portex) helped by an assistant. The tracheal tube was secured with adhesive tape and positive pressure ventilation commenced.
Time taken in intubation was defined as the time from insertion of fiberoptic bronchoscope through the airway tube of Ambu® Aura-i™ to the observation of end-tidal CO2 on monitor. In case of multiple attempts, the number of attempts made for successful intubation was noted. Any difficulty encountered during intubation or any complication during this process was noted down. These observations were noted by investigator (PJ) who was unaware of the glottic view.
After successful tracheal intubation, the cuff of Ambu® Aura-i™ was deflated. The tracheal tube was disconnected from its connector, and the device was carefully removed over the tracheal tube using another ET of one size smaller for railroading. The endotracheal tube was secured using adhesive tape and connected to the breathing circuit after the confirmation of its correct placement. Further, anesthesia commenced with positive pressure ventilation using intermittent atracurium, sevoflurane in nitrous oxide and oxygen.
Time taken in removal of device
This was started with the disconnection of the breathing circuit, and ended when EtCO2 was observed and recorded.
Assessing intubation success
The intubation was recorded as a failure, and the trachea was intubated by direct laryngoscopy if correct placement of the device was not achieved after three attempts, fiberoptic intubation through the device was not successful after two attempts, or if tracheal tube was dislodged during device removal. Complications such as blood staining on the device, aspiration, bronchospasm, laryngospasm, oxygen desaturation (SpO2<90), and postextubation stridor were also recorded. These observations were recorded by an independent observer (PJ).
Data recording and statistical analysis
Outcome analysis data were recorded intraoperatively using a standardized data collection sheet and analyzed using Microsoft Excel Spreadsheet, coded appropriately, and later cleaned for any possible errors in an Statistical Package for the Social Studies (SPSS, Armonk city, New York, USA) for Windows Version 20.0. Statistical Analysis Software with JMP®, Analysis was carried out using Statistical Package for the Social Studies for Windows version 20.0.
| Results|| |
We could successfully insert Ambu® Aurai™ in 100% of the patients (63/63).
Ambu® Aurai™ could be inserted successfully in the first attempt in 62/63 cases. One patient required the second attempt; however, the time taken in insertion in the second attempt was not more compared to others. The insertion was easy in majority of the patients. The mean time taken for the insertion of Ambu® Aurai™, in group 1 was 11.24 seconds, in group 2 was 10.86 seconds, and group 3 was 10.38 seconds [Table 1].
|Table 1: Parameters of Ambu® Aura i-™ insertion Group comparisons done by ANOVA, Significant difference set to P<0.05|
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Ventilation through Ambu® Aurai™, as assessed clinically by bilateral chest expansion, breath sounds on auscultation was satisfactory in all the cases.
The mean value of the leak pressure obtained in our study was: Group 1 – 16.1 ± 5.2; Group 2 – 16.2 ± 3.2; and Group 3 – 16.5 ± 6.6 cm of water. These values were not statistically significant from each other [Table 1].
Tidal volume of 7–8 ml/ kg body weight and EtCO2 between 35 and 40 mmHg was achieved in all the cases [Table 1].
The placement of the Ambu® Aurai™ was assessed by grading the glottis view with the aid of fiberoptic bronchoscope. Fiberoptic Grade 1 was observed in 52/63 (82.55%) cases and Grade 2 was observed in 11/63 (17.46%) cases [Table 2].
The changes in the hemodynamic parameters such as heart rate and mean arterial pressure were not significant. The oxygen saturation during the process was maintained within good range.
The device was successfully removed in 63/63 cases (100%). The mean time taken in removal of Ambu® Aurai™ in group 1 was 13.86 seconds, in group 2 was11.42 seconds and in group 3 was11.81 seconds [Table 3].
There was no significant incidence of trauma to soft tissues, sore throat, laryngospasm, or hoarseness of voice. No incidence of accidental extubation during device removal was seen. No incidence of decrease in SpO2<90% was recorded any time during this study.
| Discussion|| |
Brain et al. studied the magnetic resonance imaging images of oropharyngeal anatomy in adults and bioengineered a new device ILMA, possessing superior ventilatory and intubation characteristics compared to LMA. It has been found to be appropriate airway device for obtaining quick and reliable ventilatory access as a rescue airway device in difficult airway and emergent scenario., It has design features suitably adapted to facilitate blind tracheal intubation with high success rate., ILMA has been later validated to facilitate fiberoptic guided intubation also. The ILMA, however, is available only in three sizes suitable for patients weighing 30 kg and above. It has a handle to steer and manipulate its insertion, which interferes with its convenient use.
Difficult airway is a problem in pediatric patients also, and therefore, an airway device with applications similar to ILMA was needed since blind tracheal intubation is not recommended in pediatric patients. Ambu® Aura-i™ a newly introduced second-generation supraglottic airway device appears to fill this void since it is available in all sizes and is suitable for ventilation and facilitating fiberoptic-guided intubation. There is paucity of literature on clinical use of Ambu® Aura-i™ in pediatric patients, and only isolated case reports of its successful use in difficult pediatric airway scenario are available.,,,,,, We, therefore, determined the suitability and effectiveness of Ambu® Aura-i™ as an independent ventilatory device as well as a conduit for fiberoptic-guided tracheal intubation in pediatric patients weighing 5–30 kg having normal airway [Table 4].
We observed that Ambu® Aura-i™ provides rapid and effective ventilation with high first attempt success rate. We could rapidly accomplish effective ventilation with Ambu® Aura-i™ insertion within 12 s. There were no significant differences between the groups on Ambu® Aura-i™ insertion time [Table 1].
Jagannathan et al., in their comparative study between Aura-i and Air-Q reported a slightly lesser mean insertion time for Ambu® Aura-i™, although they did not include children weighing 20–30 kg. Their mean insertion time was well within 11 s. The observed difference appears clinically inconsequential. Our results are compared with Jagannathan et al. results. The mean insertion observed in this study (<12 s) was comparable to the insertion time for Ambu® AuraOnce (8.0 s) and Ambu® Aura Gain (10 s) which are the first- and second-generation supraglottic airway devices, a study by Stogermuler et al. [Table 1].
We used grading criteria similar to Jagannathan et al. The grade of the glottis view in our study was Grade 1 or Grade 2 in 100% of patients, indicating good visibility of glottis and suitability for fiberoptic-guided tracheal intubation. Jagannathan et al., in their study, observed Grade 1 to Grade 4. In a study by Stogermuler et al., 2018, larynx plus anterior epiglottis view was seen in 100% of the pediatric patients in Ambu® AuraOnce and Ambi® Aura Gain. The grade of the glottis view greatly influences the time taken in intubation. Less than 50% visualization of glottis with or without partial obstruction due to downfolding/floppy epiglottis may require certain degree of manipulation in order to pass the fiberoptic scope into the glottis, as the glottis view is not completely in line with respect to the opening of the Ambu® Aura-i™. A study by Kleine-Brueggeney et al. suggests that success of blind intubation is unacceptably low and cannot be recommended for elective or rescue purposes. If intubation through a pediatric supraglottic airway device is desired, they suggest that fiberoptic guidance is used [Table 2].
The short intubation time for fiberoptic-guided intubation makes it suitable for use in pediatric patients in difficult intubation and emergent scenario. The removal of Ambu® Aura-i™ took 12.27 s. This was quite comparable to the time taken to remove Ambu® Aura-i™ and Air-Q in pediatric patients, namely 18 and 15.7 s, respectively, by Jagannathan et al. 2012, and here was no complication during removal [Table 3].
The airway leak pressure is used as indicator for airway seal. The mean leak pressure observed in this study across all groups (16.2 cmH2O) were similar to the results obtained for pediatric patients using Ambu® Aura i™ and Air-Q, namely 16.3 and 18.3 cmH2O, respectively, by Jagannathan et al. 2012. However, it was lower than the leak pressures reported for Ambu® AO and i Gel, which was 22.5 and 25.4 cmH2O, respectively, by Alzahem et al. The observed leak pressure was also comparable to the one obtained from Ambu® Aura-i™ by Darlong et<i>al. [Table 1].
Jagannathan et al., 2012, in their study graded the ease of insertion into four grades using a subjective scale – Grade 1 = no resistance, 2 = mild resistance, 3 = moderate resistance, and 4 = inability to place device. They reported the Grade 1 scale of insertion in all the cases. The speed, ease, and the first-time success rate of insertion are encouraging, considering the minimal clinical use of the Ambu Aura-i by us prior to the study.
It is obvious that the success rate of tracheal intubation through the ILMA depends on its appropriate placement in such a way that the tip of tracheal tube faces the glottis and enters the trachea through the vocal cord. In case the placement is not ideal, the airway could be negotiated with the flexible nature of the bronchoscope and facilitates intubation.
It was possible to successfully intubate all the patients. The intubation was successful in the first attempt in all the three groups. It was possible to intubate all the patients irrespective of the grade of the view. This shows Ambu® Aura-i™ assisted intubation is very successful in pediatric patients.
Our study is one of the few clinical studies conducted on the pediatric age group. There is still dearth of literature on experience of tracheal intubation through ILMA in this age group. This study was conducted to study the ventilatory effectiveness and the intubating characteristics of Ambu® Aura-i™ in pediatric patients, it suffers from several limitations. First, we included only pediatric patients, weighing <30 kg body weight for the reason that the fiberoptic-guided intubation, though an ILMA remains unexplored in this group of patients. Hence, the purpose was to conduct an obsevational study and gather experience in this area. Further, due to their known anatomical features, we consider neonates as special and different from older pediatric patients and therefore did not include them in our study. Second, our study lacks the strength of a randomized clinical study; however, we ensured sufficient power to the study, while calculating the sample size (80% power of analysis and 5% level of significance) and also selected robust endpoints for the study, i.e., time taken in insertion of device and time taken in intubation and other observations were recorded by independent investigator who did not perform the Ambu® Aura-i™ insertion or tracheal intubation through it. Further, the grading of laryngeal view on fiberoptic assessment was done by an expert independent investigator, and the person inserting the Ambu® Aura-i™ remained blind to the glottis grade.
Due to the specific design features, this device was convenient to insert. However, in the initial cases, the time taken in the insertion of the device was slightly more as compared to the latter cases. In spite of not having prior exposure to the use of Ambu® Aura-i™, the learning process was easy and the learning curve was fairly flat. The device was easy to insert and with practice the time taken in insertion was much lesser than initial cases. Hence, this device can be used very effectively in emergency scenario also, as the device has proved to be effective for ventilation as well as intubation through it and the learning process is easy [Figure 1].
| Conclusion|| |
On the basis of the observations of this study, we conclude that Ambu® Aura-i™ is not only an effective ventilatory device, but also an excellent conduit for fibre optic guided intubation using conventional uncuffed endotracheal tube in paediatric patients. Ambu® Aura-i™ may also be valuable for establishing rapid airway access in emergent difficult paediatric airway
The authors would like to thank Dr. Manisha Saxena, Dr. Mahipal Dhaka, Prashanth D'souza.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
Ethical conduct of research
This study was approved by the Institutional Review Board / Ethics Committee. The authors followed applicable EQUATOR Network (http://www.equator-network.org/) guidelines during the conduct of this research project.
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[Table 1], [Table 2], [Table 3], [Table 4]