Efficacy and Safety of Three Inflation Methods of the Laryngeal Mask Airway Ambu Auraonce: a Randomized Controlled Study

doi:10.21203/rs.3.rs-2463230/v1

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Efficacy and Safety of Three Inflation Methods of the Laryngeal Mask Airway Ambu Auraonce: a Randomized Controlled Study

https://doi.org/10.21203/rs.3.rs-2463230/v1

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published 03 Aug, 2023

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BACKGROUND: Laryngeal mask airway (LMA) is commonly used for airway management. A cuff hyperinflation was associated with complications, poor ventilation and increased risk of gastric insufflation. This study was designed to determine the best cuff inflation method of AuraOnceÔ LMA during bronchoscopy and EBUS (Endobronquial Ultrasound Bronchoscopy) procedure.

We designed a Randomized controlled, doble-blind, clinical trial to compare the efficacy and safety of three cuff inflation methods of AuraOnceÔ LMA.

METHODS: 210 consenting patients scheduled for EBUS procedure under general anesthesia, using AuraOnce^â LMA were randomized into three groups depending on cuff insufflation: residual volume (RV), half of the maximum volume (MV), unchanged volume (NV). Parameters regarding intracuff pressure (IP), airway leak pressure (OLP), leakage volume (LV) were assessed, as well as postoperative complications (PC).

RESULTS: 201 (95.7%) patients completed the study. Mean IP differed between groups (MV: 59.4±32.4 cm H2O; RV: 75.1±21.1 cm H2O; NV: 83.1±25.5 cmH20; P<0.01). The incidence of IP > 60 cmH2O was lower in the MV group compared to the other two (MV: 20/65(30.8%); RV:47/69 (68.1%); NV 48/67 (71.6%); p<0.01). The insertion success rate was 89,6% (180/201) at first attempt, with no difference between groups (p=0.38). No difference between groups was found either for OLP (p=0.53), LV (p=0.26) and PC (p=0,16).

CONCLUSION: When a cuff manometer is not available, a partial inflation of AuraOnceÔ LMA cuff using MV method allows to control intracuff pressure, with no significant changes of OLP and LV compared to RV and NV insufflation method.

Registration Clinical Trial: NCT04769791

Cuff inflating volume

intracuff pressure

manometer

laryngeal mask

Oropharyngeal leak pressure

postoperative complications

Since laryngeal mask airway (LMA) Classic™ (cLMA) first presentation by Archie Brain in 1983 [1], supraglottic airway devices (SGA) have become an established tool for airway management. In the past 10 years, the use and number of SGAs has been constantly growing.

So far, there is no consensus regarding the ideal inflation volume of the LMA cuff before its insertion. In most published studies, the anesthesiologists use their preferred technique. Common practice is to inflate the LMA cuff without measuring intra-cuff pressure with a manometer [2].

The cLMA was designed to be inserted with the cuff completely deflated, but several studies showed that a higher rate of successful placement could be obtained if the cuff was partially inflated [1, 3, 4]. Matta et al [4] found a 97.7% successful rate with a partially inflated cuff, versus 92% with a fully deflated cuff. Brimacombe and Berry [5] reported the opposite. An inflation of the cuff at resting volume before insertion maintained a tolerable cuff pressure after insertion [6]. Min-Soo Kim et al [7], in a randomized control study, showed similar results comparing resting volume with half the maximum volume, considering a successful insertion of cLMA both in children and adults.

It is unclear whether insertion techniques affect the incidence of pharyngo-laryngeal adverse events. Complications were described, such as sore throat, nerve and laryngeal injury [8–12], or exceptional severe cranial nerve injuries arising from pressure neuropraxia [13]. More than 20 case reports of recurrent laryngeal, hypoglossal, and lingual nerve injuries were also reported [14]. The use of LMA was associated with the Tapia syndrome, an ipsilateral palsy of the recurrent laryngeal and the hypoglossal nerves [15].

Some of these case reports identified overinflation of the LMA cuff as a likely predisposing factor [16–18]. One study showed no difference in pharyngo-laryngeal complications between high and low intra-cuff pressures [19].

The seal between the LMA and the peri-glottic tissue is determined by the laryngeal mask´s cuff pressure [20]: Both insufficient and excessive cuff pressure can lead to air leakage, resulting in an ineffective ventilation.

Approximately half of the recommended maximum volume produced a cuff pressure above the recommended pressure of 60 cmH₂O in pediatric patients [21–22]. However, only 2 adult [23–24] and 3 pediatric studies [21, 22, 25] were performed so far, assessing cuff inflating volumes and pressures of LMAs.

In our daily practice, no evidence permits to recommend a way of preparing the LMA (partially inflated cuff or standardized inflation method before insertion), that would guarantee a high insertion success rate, and maintain the cuff pressure in a clinically acceptable range, without cuff pressure measurement.

This randomized controlled study was designed to compare the efficiency and safety of 3 inflation methods of Ambu AuraOnce™ LMA cuff in adult patients.

In this prospective randomized controlled clinical trial, 210 consecutive consenting patients scheduled for bronchoscopy and fiberbronchoscopic Endobronchial Ultrasound (EBUS) under general anesthesia with LMA were included. This study adhered to the applicable CONSORT guidelines. This study was approved by the Ethics Committee of La Paz University Hospital, Madrid, Spain ([Jesús Frías Iniesta; COD HULP:4888; Approved on 10/07/2017]) and written informed consent was obtained from all subjects participating in the trial prior to enrollment. The trial was registered in the U.S Clinical Trial Register. (NCT04769791.Principal investigator: Teresa Prim, Date of registration: 12/02/2021) NCT04769791

The primary outcome was to compare three different cuff inflating methods of AuraOnce™ LMA (Ambu®, Ballerup, Denmark), to control the intracuff pressure during fibrobronchoscopy procedures.

The secondary outcomes were to compare the conditions of insertion (time of insertion, insertion attempts, failed insertion), the safety and efficiency of sealing, measuring the oropharyngeal leak pressure (OLP), the positioning of LMA using a fiberoptic laryngeal view score, and postoperative pharyngolaryngeal complications during recovery period and 24 hours after the procedure.

Inclusion criteria were an age > 18 years, body mass index (BMI) < 40 kg.m^-2, ASA physical status I-III and patients fasted for 6 hours before procedure. Patients with any pathology of the neck, upper respiratory or alimentary tract lesions, risk of aspiration, BMI > 40 kg.m^-2 or predictors of difficult airway were excluded.

Patients were randomly allocated to one of the three groups according to a computer-generated randomization list (https://www.graphpad.com/quickcalcs/randMenu/).

One researcher participated in the preparation of LMAs before each procedure without disclosing this information to anyone, according to the assignment list to ensure the double-blinding of the study. This investigator was not involved with anesthesia or data collection.

The size of laryngeal mask was chosen in accordance with body weight following manufacturer recommendations (size 3: 30–50 kg, size 4: 50–70 kg and size 5: >70 kg).

The three preparation methods for cuff inflation were using:

unchanged volume (NV group): LMA was unpacked and used without inflating or deflating the cuff,
half of the maximum inflation volume (MV group): the cuff was completely deflated and inflated with half the maximum inflation volume (10 mL for size 3, 15 mL for size 4, and 20 mL for size 5), in accordance with the manufacturer’s guidelines,
or resting volume (RV group): created by opening the pilot balloon valve to equalize with atmospheric pressure during ten minutes.

After standard monitoring, general anesthesia was induced with Propofol 2.5 mg.kg^− 1 and fentanyl 1 mcg.kg^− 1 intravenously and maintained with Target Controlled Infusion (TCI) of propofol (Schnider pharmacokinetic model, 2–3 microg/mL) and remifentanil (Minto pharmacokinetic model, 0.5 ng/mL), using the Injectomat® TIVA Agilia infusion system (Fresenius-kabi). TCI was titrated according to Bispectral index (BIS® monitor, two channel, Covidien Medical, Boulder, CO).

Face mask ventilation with 100% oxygen was used after patients’ loss of eyelash reflex. A water-based lubricant was applied on the back plate of LMA before insertion, and the randomized laryngeal mask was inserted with standard maneuver, by the same experienced anesthesiologist (> 1 year use experience). The initial position of LMA was assessed by visualization of bilateral chest movement and the square pressure wave pattern on mechanical ventilation.

If effective ventilation could not be achieved, a gentle adjustment of insertion was performed (depth change, chin lift, jaw thrust, and/or extension/flexion of head position). After several attempts of adjustments, if LMA had to be removed and re-inserted to acquire ideal position, this second attempt of LMA insertion was registered. If an adequate position of LMA could not be achieved after this second attempt, the airway was controlled with another device or with tracheal intubation and the patient was excluded from the trial.

The patients´ lungs were ventilated with a [Maquet Flow-i C20] anesthesia ventilator with a Tidal volume of 8 ml/kg, a respiratory rate of 12–14 per min, an inspiratory: expiratory (I: E) ratio of 1:2 and a positive end expiratory pressure (PEEP) of 5 cmH20.

After the well-positioned LMA was secured, the cuff was connected with a closed-system manometer, composed of a three-way stopcock, a 5 ml syringe and a manometer (reusable Ambu^® cuff pressure gauge), and intracuff pressure (IPi) was measured. If this pressure exceeded 60 cmH₂0, the cuff was deflated 1 mL by 1 mL with the syringe until intracuff pressure reached 60 cmH₂0. The volume withdrawn from the cuff (Vs) and the final intracuff pressure were recorded (IPf).

The oropharyngeal leak pressure (OLP) was measured by closing the adjustable airway pressure relief valve (APL) of the breathing circuit to 40 cmH₂0 at a fixed gas flow rate of 4 L/ min and reading the airway pressure on the manometer when equilibrium of airway pressure was established, or we heard air leakage²³.

Before measuring OLP, various ventilatory parameters were measured under mechanical ventilation:

the inspiratory peak airway pressure (IPAP) below 40 cmH₂0,

the leakage volume (LV) (difference between inspiratory and expiratory tidal volume) in three consecutive respiratory cycles, which was considered significant if higher than 30mL,

the plateau and mean pressures, and compliance at the corresponding cuff inflating volume.

The fiberoptic view of the larynx was assessed according to an established scoring system, from 1 cm above the mask aperture bars [26]:

1: vocal cords not visualized,

2: vocal cords and anterior epiglottis visible,

3: vocal cords plus posterior epiglottis visible,

4: only vocal cords visible.

According to this score, 1 was considered the worst and 4, the best visual condition.

Intraoperative respiratory complications such as desaturation (pulse oximetry < 90%), hiccups or stridor were noted. Any adverse event (aspiration/regurgitation, bronchospasm, airway obstruction, coughing, gagging or vomiting) and corresponding interventions were recorded.

After the procedure, all patients were transferred to the recovery unit and observed for at least two hours. When modified Aldrete score reached 10 points, patients were discharged to the ward [27].

Adverse effects until 24h after procedure were recorded with a telephone interview. We registered the following complications: sore throat, dysphonia (spelling difficulty or pain on speaking), dysphagia, hoarseness, nausea, and vomiting.

Their intensity was assessed by using a 0 to 10 visual analogical scale (EVA).

The sample size was calculated based on the primary end point. In a previous study, Kim et all [7] measured an intracuff pressure of LMA Classic with half of the recommended volume of 54.5 ± 16.1 cmH₂0. Assuming a type I (α) error of 0.05 and a type II (β) error of 0,1 (power of 0.9), with a bilateral test, 55 patients in each group would be needed to detect an intracuff pressure difference of 10 cmH₂O between the 3 groups.

Considering dropouts, 70 patients were included in each group, for a total of 210 patients.

All data were recorded using a standardized data collection sheet and analyzed using the statistical software SAS v.9.4 (SAS Institute Inc. 2013. Base SAS® 9.4 SAS/STAT Cary, NC).

Results were presented as mean ± SD, range or 95% confidence interval [CI], number (percentage), or numbers according to the characteristics of each variable. Normality was tested for continuous data using Kolmogoroff-Smirnov test.

Comparisons of continuous variables were performed using 2-tailed Student “t” test or Mann-Whitney U test if normality couldn’t be confirmed. Chi-square or Fisher´s exact test was used for categorical data. In addition, Mann-Whitney U test was used to compare ordinal data.

Comparisons of continuous variables for the 3 groups were performed using an Analysis of Variance (ANOVA) together with a Bonferroni post-hoc test, or a Kruskal-Wallis H test when appropriate to compare groups pair by pair.

Statistical significance was set for p < 0.05.

A total of 201/210 (95.7%) patients completed the study (Fig. 1 CONSORT flow diagram). Patients’ characteristics were comparable in the three groups (Table 1).

Patients in MV group presented statistically lower mean intracuff pressure than those in RV or NV groups (MV: 59.43 ± 32.44 cm H₂O; RV: 75.07 ± 21.08 cm H₂O; NV: 83.134 ± 25.5 cmH₂0; P < 0.01), with a mean difference of Intracuff pressure of 15.64 ± 4.6 cmH20 (p = 0.02) between MV and RV groups, and 23.7 ± 4.6 cmH2O (P < 0.01) between MV and NV groups (Fig. 2).

Intracuff pressure exceeded 60 cmH₂O in 57.2% of patients, with a lower incidence if MV was used to inflate LMA cuff (MV: 20/65(30.8%); RV:47/69 (68.1%); NV 48/67 (71.6%); p < 0.01).

Insertion parameters and fiber-optic view of vocal cord are summarized in Table 2. The overall insertion success rate was 95.7% (201/210). Failed insertion of LMA was followed by orotracheal intubation in two patients [RV (1) NV (1)]. Five (2.5%) patients required, a change of LMA. The first-attempt placement in180/201 (89,6%) didn’t show significant differences between groups (MV: 93.8%, RV: 84.1%; NV: 91%; p = 0.37).

Overall fiberoptic view scores ≥ 3 were observed in 189/201 (94%) patients, with no significant difference between groups (p = 0,46). The requirement for adjustment maneuver after the insertion of the LMA was associated with worse fiber-optic view (Adjustment: [81% SCORE 3–4]; No adjustment: [97,1% SCORE 3–4]; p = 0,016).

No significant difference was found for OLP and LV despite the significant differences in intracuff pressure (Table 3).

The pressure-volume study for each size and group demonstrates the maximum pressure limits (60 cmH2O) being exceeded well below the recommended maximum inflation volume. The main of final cuff volume to achieve an intracuff pressure of 60 cmH2O was 12.74 \(\pm\) 2.27 mL for size 4 LMA and 17.43 \(\pm\) 4.78 mL for size 5 LMA. A significant difference was observed between groups in final cuff volumes to achieve an intracuff pressure ≤ 60 cmH20 (RV: 12.8 ± 2.0 mL; MV: 16.4 ± 3.3 mL; NV: 17.5 ± 3.3 mL; p < 0,01).

Seven patients, all of them in MV Group, presented complications associated with hypoxia during anesthesia maintenance. The postoperative pharyngo-laryngeal complications did not differ among groups (Table 4). Patients with dysphagia at 2h (p = 0,002) and complications after 24h (p = 0,04) had been submitted to a significantly longer procedure.

This study showed that inflating the cuff of AuraOnce™ LMA with half of the maximum volume permitted an optimum control of intracuff pressure, compared to the other two methods that far exceeded the established limits of pressure. However, the 3 methods were comparable regarding easy of insertion, sealing efficacy and complications.

The optimum volume of air to inflate the cuff before LMA insertion has not been established so far, despite the publication of various studies introducing partial cuff inflation methods [1, 4, 28, 29]. This optimum volume should consider that hyperinflation and infrainflation of LMA cuff are associated with a higher incidence of poor sealing [30].

Our results of overall intracuff pressure of 59.4\(\pm\)32.4 cmH₂0 in MV group are similar to those described by Kim et al. [7], in which LMA Classic cuff was prepared with half the maximum volume (intra-cuff pressure of 54.5 ± 16.1 cmH₂0).

In the original manufacturer’s instructions, the LMA should be inserted with the cuff fully deflated, and inflated once it is correctly positioned. However, using this method, the success rate remains at approximately 92% [4]. In this study, even though there was no control group in which the LMA was inserted with the cuff completely deflated, we confirmed that an easy insertion of the LMA was obtained with the cuff partially inflated, with a success rate superior to 95%.

When inserting the LMA partially inflated, cases of airway obstruction due to epiglottis backwards movement were described [5]. In our study, the performance of a fiberoptic inspection allowed to check a correct placement in all patients with optimum fiber-optic view scores (3 or 4) in 94% patients.

Our success rate differs from that of Brimacome and Berry [5], who compared four insertion techniques and found an insertion of the LMA with the cuff partially inflated to be less successful than with the cuff fully deflated. The volumes they used in the semi-inflated and fully inflated groups were higher than ours: for size 3 and 4 LMAs in semi-inflates groups, they used the same volumes as we used for size 4 and 5 LMAs respectively in our study. This possible over-inflation in their study can explain the difference of results. Also, they used a size 3 LMA for women and a size 4 LMA for men, but didn’t respect the manufacturer’s recommendations which depend on body weight, like we did.

The mean OLP we observed was higher in respect to other studies of first-generation LMAs, revealing a better sealing of the airway. Hell et al. [31], using LMA-Auraonce inflated with an intracuff pressure of 60 cmH2O found a mean OLP of 23.7 \(\pm\)5.94 cmH2O, slightly lower than ours. Our data are also consonant with the results of a meta-analysis which included studies where OLP was measured when using Auraonce LMAs [32]. Our results showed apparently better results of OLP (26.3 \(\pm\) 7,4 cmH₂O) than those obtained with other first generation LMAS (LMA-Soft seal [33] (26 cmH₂O\(\pm 6.8\)), LMA-Class [34] (23.7 \(\pm\)7\(\text{c}\text{m}\text{H}2\text{O}\)) or LMA-Unique [35] (22.1 \(\pm 6 \text{c}\text{m}\text{H}2\text{O}\))), even though this possible advantage should be confirmed in randomized controlled trials.

The incidence of pharyngo-laryngeal complications (approximately 55%) observed was greater than that commonly reported following LMA use (5 to 34%) [36], although we adjusted the IP < 60 cmH₂0. The main reason for this difference is probably that we included sore throat as a complication in our study. Even though pain scores were low (3 to 4 /10 scores EVA) and all had a rapid recovery, they increased the total incidence of complications. In fact, when analyzing the incidence of sore throat only, our study showed similar incidence to that reported in the studies of Brimacombe et al. [37] and Seet et al [8]. Another factor that may have contributed to a higher incidence of sore throat in our study may be related to that EBUS procedures can be responsible for an irritation of the airway in the postoperative period due to an intubation of pharynx, larynx and trachea for a long duration. The statistical association between the duration of the procedure and the onset of a dysphagia at 2h (p = 0.02) on one side, and the persistence of complications at 24h (p = 0.04) on the other hand support this hypothesis. Finally, the injuries caused by the fiberbronchoscope on the airway could be masking the real incidence of adverse effects.

The mean of final cuff volume of size 4 (12.7 ±2.3 mL) and 5 (17.4 ± 4.8 mL) to obtain an optimum intracuff pressure and sealing of Auraonce LMAs are not significantly different from the half of the maximum recommended volume (15mL for size 4 and 20mL for size 5) by the manufacturer and corresponds to the inflated volume we used in patients in the MV group. These results are in agreement with previous studies of pressure and volume correlation [21–22, 24].

Our study presents some limitations. Firstly, we assessed the 3 methods using only the Ambu AuraOnce™ first generation LMA, so, it may be difficult to apply the results to other LMAs with another inflating cuff. Further studies should be conducted using these methods with other types of SGA. Secondly, we probably overestimated postoperative pharyngo-laryngeal complications, due to the characteristics of the procedure in which the airway was manipulated for a certain time. To better assess this outcome, further studies in other scenarios should be performed.

In conclusion, in various clinical situations when a cuff manometer is not available, the partially inflated cuff method, using AuraOnce™ LMA with half the maximum recommended inflation volume seems a reasonable recommendation to obtain an adequate range of intracuff pressure, low incidence of leaks and high rate of successful insertion.

Authors’ contributions:

TP: has given substantial contributions to study design, patient recruitment and data collection. Also writing up of the first draft of the paper and data analysis.

NB and FG: have given substantial contributions to study conception and design, data collection and manuscript writing.

EG: has given substantial contributions to manuscript writing and revising it critically.

JD: has given substantial contributions to statistical analysis and manuscript writing.

All authors read and approved the final version of the manuscript.

Conflict of interest:

We also state that the manuscript has been read and approved by all authors and there is no conflict of interest and ethical clearance from hospital ethics committee of Hospital La Paz, Madrid has been taken.

Financial disclosure:

No financial support was obtained from the manufacturers for the presented study. This research was carried out without funding.

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Efficacy and Safety of Three Inflation Methods of the Laryngeal Mask Airway Ambu Auraonce: a Randomized Controlled Study

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