Ease and Safety of Securing Airway by Railroading ProSeal Laryngeal Mask Airway over Bougie versus Traditional Digital Insertion Technique.

Background: ProSeal insertion is usually more time-consuming with lower first-attempt success. Aim of the Study: We aimed to compare the incidence of successful placement of ProSeal laryngeal mask airway (PLMA) in the first attempt by railroading it over soft gum-elastic bougie introduced into esophagus versus traditional digital insertion technique. Time taken and ease of securing airway, associated hemodynamic responses, and trauma were also assessed. Settings and Design: This was a prospective randomized study conducted in a tertiary care institute. Subjects and
Methods: Forty patients were recruited into two groups. Following induction in Group P, PLMA was introduced using digital technique, whereas in Group B, a soft gum-elastic bougie was introduced into esophagus and then PLMA was railroaded over the bougie. Correct placement was confirmed with end-tidal carbon dioxide waveform. Statistical Tests Used: Fisher's exact test and independent samples t-test were used for statistical analysis.
Results: Successful first-attempt insertion was significantly higher in Group B compared to Group P (100% vs. 70%). Percentage of easy insertion was also significantly higher in Group B (95% vs. 65%). Time taken to insert ProSeal was significantly shorter in Group B (30.8 ± 7.8 vs. 59.5 ± 44.6 s). No patient in Group B had blood-stained secretion versus 70% in Group P. Mean arterial pressures at and after ProSeal insertion were significantly higher in Group P. However, heart rate remained comparable in both the groups.
Conclusion: Bougie-guided ProSeal insertions had significantly higher first-attempt insertion success rates and were significantly faster and less traumatic with blunted blood pressure response compared to traditional digital insertion technique. Copyright:

INTRODUCTION

Supraglottic airway devices (SADs) were introduced into clinical practice to provide a patent airway for ventilation under anesthesia or during resuscitation. The disadvantages of the first-generation devices were mostly rectified in the subsequent generations, but ease of insertion had come down for some newer SADs, especially ProSeal laryngeal mask airway (PLMA). A gastric drainage channel is incorporated lateral to main airway tube in PLMA to aid gastric drainage. A gastric tube can be introduced through this channel to stomach to aspirate contents and can be used to detect the malposition of PLMA.[1] ProSeal is usually inserted blindly after induction of anesthesia and is more time-consuming compared to intubation.[2] Moreover, the frequency of successful PLMA placement in the first attempt is generally lower.[3] Compared to the two conventional PLMA insertion techniques, it has been suggested that bougie preloaded PLMA placement could be easier, quicker, and relatively atraumatic with a higher rate of correct placement as compared to conventional insertion techniques.[4]

Our primary objective was to compare the incidence of successful placement of PLMA in the first attempt by railroading it over soft gum-elastic bougie introduced into esophagus versus traditional digital insertion technique. The secondary objectives included assessment of ease of securing airway, time taken for it, and the hemodynamic responses during the procedure. Evidence of trauma was also assessed by the presence of blood-stained secretions or blood on the device on removal at the end of the surgery. Proper placement of PLMA following bougie-guided technique was also assessed using a flexible bronchoscope.

SUBJECTS AND METHODS

The present study was designed as a prospective, randomized trial. Institutional Ethical Committee clearance (IEC-AIMS-2019-ANES-123 dated July 25, 2019) and written informed consent for participation in the study and the use of the data for research and educational purposes were obtained from patients prior to recruitment. The study was registered in the Clinical Trials Registry of India (CTRI/2019/08/020727). Forty surgical patients aged 18–60 years, with American Society of Anesthesiologists physical status (ASA PS) 1–3 and Mallampati score 1–2, were included in the study. Patients undergoing surgeries on breast and upper limb requiring general anesthesia using ProSeal were included. Those with obesity, hiatus hernia, pregnancy, full stomach, diabetics, and restricted mouth opening and patients for emergency surgeries were excluded. The procedures followed the guidelines laid down in the Declaration of Helsinki.

As literature search did not yield any similar published data, we initiated the study as a pilot study in twenty patients with ten in each group. Taking successful insertion of ProSeal at the first attempt as a primary objective, it was found that a group of patients in whom bougie was used for insertion of ProSeal had higher success rate compared to insertion without bougie (100% vs. 60%). From this result, with 95% confidence interval and 90% power, minimum sample size was calculated as 19 per group and hence we recruited forty patients into the study.

Randomization was done with computer-generated random number sequence, and patients were recruited equally to either Group B or Group P. Allocation to groups was not disclosed to investigators as sequentially numbered opaque-sealed envelopes were used for the same. Preoperatively, 6-h fasting for solid foods and 2 h for clear fluids were ensured for all patients. The anesthesia protocol was same for all the study subjects.

In the operation theater, a large-bore intravenous access was obtained and patients were started on Ringer's lactate at the dose of 10 mL.kg−1 body weight. Before induction of general anesthesia, pulse oximeter, noninvasive blood pressure monitor, and electrocardiogram were attached. All patients received glycopyrrolate 0.2 mg, midazolam 2 mg, and fentanyl 2 μg.kg−1 body weight intravenously. Propofol was used for induction at 1.5–2 mg.kg−1 body weight till patient stopped responding to verbal commands. Following induction, when it was possible to open the mouth easily with a relaxed lower jaw, insertion of the airway device was attempted.

In Group P, PLMA was introduced using digital technique. After application of a lignocaine jelly on the posterior and lateral sides of deflated ProSeal, it was held like a pen and introduced into oral cavity. The PLMA was then advanced along the palatal curve using the index finger into the hypopharynx until there was a definite resistance. In Group B, a soft gum-elastic bougie, approximately 30 cm from upper incisors, was introduced into esophagus following a gentle laryngoscopy [Figure 1a]. The bougie was prevented from slipping back by firmly holding it while removing the laryngoscope. The proximal end of the bougie was then introduced into distal opening of the ProSeal drain tube [Figure 1b] which was taken out through the proximal opening. With one hand, the proximal end of the bougie was held and then ProSeal was railroaded over the bougie [Figure 1c].

Figure 1

(a) Gum-elastic bougie introduced into esophagus. (b) ProSeal being loaded onto the bougie. (c) ProSeal being railroaded over bougie

Correct placement was confirmed with chest expansion during positive pressure ventilation and appearance of end-tidal carbon dioxide waveform and by auscultation. If there was difficulty in opening, the mouth as jaw was not relaxed, or if there was any patient movement during device insertion, the depth of anesthesia was increased with an additional bolus of propofol 0.5 mg.kg−1 intravenously.

The time taken for successful device insertion was calculated from the introduction of ProSeal into oral cavity in Group P and introduction of laryngoscope in Group B to appearance of square wave form in capnograph in the monitor. This was recorded by an anesthesia technician using a stopwatch who was not actively taking part in the anesthesia procedure. In the absence of these confirmatory signs, ProSeal was taken out to be reintroduced. Maximum three attempts were allowed for proper placement. We intubated patients in whom we could not place ProSeal satisfactorily. Such patients were excluded from the study.

Placement of ProSeal over laryngeal inlet was assessed using a flexible bronchoscope, and the fiber-optic view was graded and scored as described in Table 1.[5] Ease of securing airway by both techniques, number of attempts taken for correct placement, time taken for it, and the hemodynamic responses during the procedure were assessed. Ease of insertion was evaluated by the anesthetist who performed the procedure and was graded as easy/moderate difficulty/hard/impossible. Trauma during securing airway as evidenced by the presence of blood-stained secretions or blood on ProSeal while removing was also looked for. The heart rate (HR) and mean arterial pressure (MAP) were recorded before induction, after induction, immediately after securing airway, and 1, 3, and 5 min later also. We did not use any relaxant intraoperatively, and the patients were kept breathing spontaneously. At the end of the surgery, PLMA was removed when patients were still deep after placing a nasopharyngeal airway.

Table 1

Fiber-optic assessment of anatomical position of the ProSeal against the glottic opening

Grade	Anterior-posterior rima glottidis (APrima) distance
Grade I	75%-100%
Grade II	50%-75%
Grade III	25%-50%
Grade IV	0%-25%
Grade V	No vocal cords, only epiglottis visible
Grade VI	No epiglottis or epiglottis visible

Statistical analysis

The categorical variables of both the groups were analyzed using Fisher's exact test. Comparison of hemodynamic and demographic variables was performed with independent samples t-test. SPSS version 20.0 for Windows (IBM Corporation, Armonk, NY, USA) was used for statistical analysis.

RESULTS

The data of 40 patients were analysed [Figure 2]. Age, weight, gender, and ASA PS of patients in both the groups were comparable in both the groups [Table 2]. Successful first-attempt insertion was significantly higher in Group B compared to Group P (100% vs. 70%, P = 0.02) [Table 3]. Percentage of easy insertion was also significantly higher in Group B (95% vs. 65%, P = 0.044) [Table 3]. Time taken to insert ProSeal was significantly shorter in Group B compared to Group P (30.8 ± 7.8 vs. 59.5 ± 44.6 s, P = 0.01) [Table 3]. Incidence of desaturation to <95% was comparable in both the groups [Table 3]. Ninety percent of patients in Group B had functional observational battery assessment score of Grade 1–2, while it was 35% in Group P. This difference was statistically significant (P = 0.001). No patient in Group B had blood-stained secretions on device. However, significantly higher number of patients (30%) had blood-stained secretions in Group P (P = 0.02) [Table 3]. No patient in both the groups required intubation due to failed device insertion.

Figure 2

Consort flow diagram

Table 2

Comparison of demographics and American Society of Anesthesiologists physical status

Variables	Group B	Group P	P
Age (years), mean±SD	41.6±9.7	43.9±12.3	0.524
Weight (kg), mean±SD	65.8±7.3	65.1±7.7	0.786
Male, n (%)	14 (70)	12 (60)	0.740
Female, n (%)	6 (30)	8 (40)

SD = Standard deviation

Table 3

Comparison of ease and number of attempts at insertion, FOB grade, presence of blood staining, and incidence of saturation <95%

Variables	Group B, n (%)	Group P, n (%)	P
Easy insertion	19 (95.0)	13 (65.0)	0.044
Moderate to hard insertion	1 (5.0)	7 (35.0)
Attempts
1	20 (100)	14 (70)	0.020
2 or more	-	6 (30)
Saturation <95%
Yes	20 (100)	18 (90)	0.487
No	-	2 (10)
FOB grade
1-2	18 (90)	7 (35)	0.001
3-6	2 (10)	13 (65)
Bloodstain
No	20 (100)	14 (70)	0.020
Yes	-	6 (30)
Time to secure airway in second, mean±SD	30.8 (7.8)	59.5 (44.6)	0.010

SD = Standard deviation, FOB = Fiberoptic bronchoscopic

MAP at baseline and after induction were comparable in both groups. However, MAP at intubation and 1 min, 3 min, and 5 min after intubation were significantly higher in Group P compared to Group B (P < 0.05). HR and saturation levels at all time points were comparable in both the groups [Table 4].

Table 4

Comparison of heart rate and mean arterial pressures

Variables	Mean±SD		P
	Group B	Group P
HR baseline	87.3±16.0	93.6±15.0	0.206
HR after induction	89.2±12.1	85.5±13.0	0.350
HR intubation	87.7±15.7	86.6±10.5	0.805
HR 1 min	83.3±14.5	85.5±11.3	0.605
HR 3 min	81.1±15.8	88.9±12.4	0.088
HR 5 min	81.8±13.2	88.2±13.5	0.134
MAP baseline	86.6±10.5	87.7±15.7	0.805
MAP after induction	82.1±15.8	82.5±13.7	0.932
MAP intubation	76.4±9.7	82.3±12.2	0.099
MAP 1 min	71.8±8.8	80.0±11.9	0.017
MAP 3 min	70.6±6.9	78.0±10.1	0.010
MAP 5 min	74.6±8.6	82.0±10.7	0.022

MAP = Mean arterial pressure, SD = Standard deviation, HR = Heart rate

DISCUSSION

We observed that bougie-guided ProSeal insertions were faster, and less traumatic, with higher first-attempt insertion rates as compared to traditional digital insertion technique. Bougie-guided insertions were also associated with blunted blood pressure response as well. Both techniques resulted in comparable HR responses. Fiber-optic bronchoscopic assessment of proper placement revealed that significantly more number of patients in Group B had favorable view indicating proper placement of ProSeal over laryngeal inlet.

The three common malpositions described with the use of ProSeal are (a) PLMA not inserted deep enough with the distal tip remaining in the medial pharynx, (b) tip of PLMA facing glottis which obstructs the airway with air leak through drainage tube, and (c) folding of the tip of the PLMA cuff posteriorly which obstructs the drainage tube.[67] The third malposition usually does not affect the seal or ventilation, but chances of gastric insufflation, regurgitation, and aspiration increase markedly. If PLMA drainage tube is preloaded with a lubricated gastric tube with its end at the distal tip of PLMA, the tip of the cuff getting folded posteriorly can be prevented. With this technique, the gastric tube can be successfully passed into the esophagus easily.[8]

Howath et al. had demonstrated that gum-elastic bougie-guided insertion was also equally effective.[9] In this technique, a lubricated gum-elastic bougie was passed through the ProSeal LMA drainage tube with the straight end of the bougie protruding 30 cm beyond the tip of ProSeal, which was inserted into the esophagus under direct laryngoscopic vision. Then, the laryngoscope was removed and ProSeal was inserted further down over the gum-elastic bougie. This technique was found to have a high success rate with low incidence of trauma. Other two studies had also shown that bougie-guided insertion of ProSeal LMA had higher success rate with less trauma as compared to the use of insertion tool or digital technique.[1011] Although the use of introducer tool had made ProSeal insertions easier, it was shown that correct placement at the first attempt was higher with the bougie-guided technique (100%) than digital (88%) or with the use of introducer tool (84%, P < 0.001).[12] The use of metal introducer could be associated with a higher risk of soft-tissue trauma as well.

Most of the previous studies have used either bougie preloaded ProSeal or bougie was introduced intro esophagus following laryngoscopy. In our study, we did not prime the ProSeal with gum-elastic bougie. We did a gentle laryngoscopy to just lift the tongue away from the posterior pharynx, and the bougie was introduced blindly into the esophagus. Then, after removing the laryngoscope, PLMA was railroaded. By reducing time of scopy and force required to lift the structures to visualize esophagus, we intended to reduce the hemodynamic stress response to laryngoscopy. Although this procedure was slightly time-consuming over the use of a primed PLMA, we did not find any significant difference in time taken to secure airway. Although there was a chance of bougie entering the trachea instead of esophagus, we did not encounter any such case as it would have resulted in gas leak through the gastric drain tube on positive pressure ventilation.

In our study, no muscle relaxant was used for insertion of the device as the plan of anesthesia in these cases was general anesthesia with spontaneous ventilation. We did not observe any patient movement during laryngoscopy probably because we avoided a proper laryngoscopy as it was only used to lift the tongue and/or the patients were deep with dose of propofol given. However, few cases in Group P, who required multiple attempts at insertion of ProSeal, needed additional propofol bolus due to patient movement during the repeated attempts.

In pediatric patients with simulated difficult laryngoscopy, PLMA insertion with combined introducer tool and stylet technique had higher success rate than digital or introducer tool technique alone. In this study, the combined technique involved attaching introducer tool to the PLMA along with a flexible stylet inserted through the drain tube of the ProSeal.[13] Rusch Flexi-Slip stylet may be considered as an alternative in patients encountered with difficulty in proper placement of PLMA.[14]

The major limitation of our study was that even though all device insertions were performed by a single anesthetist with more than 5-year experience, which eliminated subjective variations due to varying levels of expertise, the first-time success rate with digital technique was found to be lower compared to previous studies possibly due to varying patient factors, which could explain the higher incidence of trauma and lower fiber-optic view score seen with digital technique. Another limitation of the study was that only the patients were blinded. The depth of anesthesia at which ProSeal insertion was attempted was assessed only by clinical means like an unresponsive patient with a relaxed jaw. The use of advanced techniques like bispectral index monitoring would have ensured uniform depth of anesthesia in all subjects. Fiber-optic assessment of LMA positioning, as with ProSeal placement, could have been more informative.

CONCLUSION

Bougie-guided ProSeal insertions had significantly higher first-attempt insertion success rate and were significantly faster and less traumatic with blunted blood pressure response compared to traditional digital insertion technique.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.