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Year : 2020  |  Volume : 4  |  Issue : 2  |  Page : 35-38

Comparison of glottis views with fixed-height pillow versus adjustable-pillow height by pressure infusion bag for successful intubation

Department of Anesthesia, Gujarat Cancer and Research Institute, Ahmedabad, Gujarat, India

Date of Submission02-Jan-2020
Date of Acceptance12-Feb-2020
Date of Web Publication11-May-2020

Correspondence Address:
Dr, Kinna Shah
Model House, Shastri Park, Nehrunager Cross Roads, Ambawadi, Ahmedabad - 380 016, Gujarat
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Source of Support: None, Conflict of Interest: None

DOI: 10.15562/bjoa.v1i1.5

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Background: This study aimed to get optimal sniffing position for successful intubation rate and measuring intubation time. The classical rationale for the sniffing position is that the alignment of the mandibular axis, pharyngeal axis, and laryngeal axis is facilitated, permitting successful direct laryngoscopy. Patients and Methods: A total of 100 patients without any anticipated difficult airway were enrolled after informed consent is given. After induction of anesthesia, patients were randomly divided into two groups. In Group PB, a deflated pressure infusion bag was put under the nape of the neck and occiput. The anesthetist performed laryngoscopy with the left hand while inflating the bag with the right hand up to the best glottic view without external pressure is achieved. The height of the bag was measured. In Group PI, 10-cm fixed-height noncompressible pillow was placed behind the head up to the shoulder. The best glottic view of the entire glottis without external pressure was noticed. Grading of glottic opening grade, SPO2, intubation time, and intubation trials were also noted. Results: Failure to intubate was noted in one patient in Group PB and two in Group PI. Intubations successful in 45 (90%) patients in Group PB as compared to 38 (76%) patients in Group PI (P < 0.05). Laryngoscopic view in Group PB was superior to that with Group PI (P < 0.05), with mean pressure bag height of 4.86 cm. Conclusion: The use of pressure infusion bag for adjustable-pillow height provides more success in intubation condition by head elevated position than the fixed height of 10 cm.

Keywords: Intubation, position, pressure bag, sniffing

How to cite this article:
Shah K, Thakkar J, Vaidya D. Comparison of glottis views with fixed-height pillow versus adjustable-pillow height by pressure infusion bag for successful intubation. Bali J Anaesthesiol 2020;4:35-8

How to cite this URL:
Shah K, Thakkar J, Vaidya D. Comparison of glottis views with fixed-height pillow versus adjustable-pillow height by pressure infusion bag for successful intubation. Bali J Anaesthesiol [serial online] 2020 [cited 2023 Mar 22];4:35-8. Available from: https://www.bjoaonline.com/text.asp?2020/4/2/35/270764

  Introduction Top

Tracheal intubation remains one of the safest means of establishing commands on airway. A key step of successful intubation is proper position of patient. The sniffing position is the all-time favorite position by anesthesiologists for obtaining good glottic visualization during direct laryngoscopy.[1]

The classical rationale for the sniffing position is that the alignment of the mandibular axis, pharyngeal axis, and laryngeal axis is facilitated, permitting successful direct laryngoscopy. This alignment may be hypothetically obtained by flexing the neck on the chest and by elevating the head approximately 7–10 cm with a pad under the occiput. This head position resembles a person sniffing the morning air.

Different maneuvers or easily available things such as blankets or change in table position have been tried. Different positions by heightened pillows were used with variable success rate. Proper positioning should always be verified by observing the horizontal alignment of the external auditory meatus (EAM) and sternum.[2]

At our institute, no pillow or blanket is used in intubation. We intubate patients in supine with manual head extension and external cricoid pressure application as and when required. To our knowledge, no studies are available in the Indian setup with regard to the use of such kind of alternative option to fixed-sized pillow. The purpose of this prospective randomized study was to achieve a head-up position by pressure inflation bag application for successful endotracheal intubation by an easily available device in operation theater – a pressure infusion bag.

  Patients and Methods Top

Institutional review board approval and written informed consent were obtained for this study. In this single-blinded study, we enrolled 100 patients of American Society of Anesthesiologists (ASA) Class 1 and 2 aged between 20 and 65 years who underwent elective abdominal surgery and need oral intubation under general anesthesia. We excluded patients with a previous history of difficult intubation, those who had undergone previous head-and-neck surgery, those with loose upper incisors, and patients requiring rapid sequence induction.

Preanesthetic airway assessment was done in sitting position by an attending anesthesiologist, who was not involved in the study. We had included patients of Grade I and II modified Mallampati classification. Neck circumference at cricoid cartilage and thyromental distance(cm) was measured. The primary outcome measure was the incidence of dififcult laryngoscopy (Cormack Grade 3 or 4). The secondary outcome measures included additional maneuvers or alternative technique used by the performing anesthetist.

Lorazepam 1 mg on the previous night and diazepam 5 mg in the morning before surgery were prescribed as premedications. Standard ASA monitoring (electrocardiogram, pulse oximetry, capnography, and noninvasive blood pressure) was established. The evaluating anesthetists were not blinded to the head elevation aid. Operation table height was maintained at the patient's forehead to the xiphisternum of the intubating anesthesiologist.

Before induction of anesthesia, the patients were randomly allocated to either fixed-height pillow (Group PI) or pressure infusion bag (Group PB). Group PI included supine patients intubated with head in the “sniffing position” by placing an incompressible pillow under the head (height = 10 cm).

Induction of anesthesia was carried out with glycopyrrolate 0.2 mg and thiopentone sodium 5 mg/kg. Succinylcholine 2 mg/kg was administrated as a muscle relaxant to facilitate intubation. Patients' lungs were ventilated with 100% oxygen by a mask for 60 s. Mask ventilation was graded as easy, difficult, or impossible. The need for an oropharyngeal airway was also noted.

We used Macintosh blade no. 3 for female and no. 4 for male patients. All laryngoscopies were performed by same anesthesiologist of more than 10 years' experience. In Group PI, laryngoscopy was done by putting a 10-cm pillow. In Group PB, a deflated 1-L pressure infusion bag was put at the nape of the neck (between the occiput and atlantooccipital joint). A deflated bag was inflated by the operator's right hand while laryngoscopy was performed with the left hand. The inflation continued until EAM-to-sternal notch alignment was achieved; at this point, Cormack and Lehane (CL) grading of the glottis was noted. Intubation trials were noted. Height of the pressure bag was noted in Group PB.

After evaluation of laryngoscopy grade, external laryngeal manipulation (ELM) was permitted, if necessary, to facilitate the insertion of the tracheal tube. Oral intubation was done with a cuffed endotracheal tube size 7 for female and size 8 for male patients. If at any time during the study the patient's SpO2 falls below 94%, then 100% oxygenation was provided by mask ventilation. The rest of the anesthesia was continued as per standard protocol.

Measurement of intubation time was taken from the introduction of the laryngoscope blade till the inflation of the cuff in seconds. Three attempts with oxygenation in between were given before another intubation technique. Complications, such as fall of peripheral oxygen saturation and dysrhythmias during laryngoscopy, were also noted. Laryngoscopy was considered prolonged if its duration exceeded 30 s.

The anesthesiologist recorded the degree of discomfort (1 = no discomfort, 2 = mild discomfort, 3 = moderate discomfort, and 4 = severe discomfort) for mask ventilation and tracheal intubation for the two head elevation heights in each patient following the completion of anesthetic induction.

SPSS Inc. Released 2007. Data analysis was done by using SPSS version 16 (IBM). Chi-square test was applied for assessing statistical significance of modified Mallampati grade, glottis visualization grade. P < 0.05 was considered statistically significant. Comparison of CL grading across fixed height was carried out by Medcalc proportion calculator.

  Results Top

Group PB and Group PI were comparable in demographic profile with respect to age, sex, height, and weight, and regarding Mallampati airway grade distribution, interincisor gap, hyomental distance, thyromental distance, and sternomental distance. The blade size was standardized for consistency, and both the groups were comparable regarding Mallampati grade distribution. The incidence of difficult mask ventilation or esophageal intubation was nil in our study. Intubations under direct laryngoscopy were successful in 45 (90%) patients in Group PB as compared to 38 (76%) patients in Group PI (P < 0.05), as shown in [Table 1].
Table 1: Intubation success

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In this study, The higher intubation success rate was observed in Group PI (pressure infusion bag group). The intubation failure rate was none in Group PB. Intubation was not possible in two patients of Group PI. We intubated them without pillow. The increase in heart rate and mean blood pressure in response to laryngoscopy and intubation was lesser in Group PB as compared to Group PI. Airway manipulation was less required for intubation in Group PB (pressure bag), thus reducing the sympathetic response. We found a statistically significant difference in glottis visualization grade [Table 2].
Table 2: Laryngoscopic visualization grading based on Cormack and Lehane classification

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Comparison of CL grading across fixed height was done by Medcalc proportion calculator. In Group PB, five patients (10%) had a Grade 2 CL view before inflation, and this did not alter after inflation. Improvement by one grade was noted in five patients and two grades in seven patients with progressive pressure bag inflation. No deteriorations in view occurred in both groups. The average time for laryngoscopy was 9.0 ± 2.1 s in Group PB compared to 15 ± 4.34 s in Group PI. The laryngoscopic glottis visualization grading in Group PB was superior to that with Group PI (P < 0.05), with The mean pressure infusion bag height of 4.86 cm. It's my request to correct in abstract also as 4.86 cm.

None of the patients showed a SpO2 reading <95% during the intubation in both groups. Dunn's multiple comparison test of CL grade is shown in [Table 3]; it is clear that CL grading at 4.88-cm pillow height is significantly lower than CL grading without pillow and pillow heights of 7.0 cm.
Table 3: Cormack-Lehane grade

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Comparison of CL grading across progressively increasing height of the pillow was done by Friedman's analysis of variance followed by Dunn's test as post hoc test to compare between any two pillow heights. In Group PI, four patients required ELM for Cormack Grade 1 and 2 views. Two patients intubated in the pillow group required two attempts at intubation; one required ELM and one patient required malleable stylet. Successful intubation was possible after removal of the pillow in two patients of Group PI.

  Discussion Top

A historical and experimental review of the literature reveals that direct exposure of the larynx has developed primarily as an art, without sophisticated investigations based on anatomic principles. Glottic exposure alone is not completely representative of intubation difficulty. Sniffing position is recommended as a gold standard for direct laryngoscopy. For best glottis view, oropharyngolaryngeal axis should come in a straight line, which can be obtained in sniffing position. Alternative techniques include repositioning of the patient, change of blade or tube, addition of a stylet, change to nasotracheal intubation, or use of fiberoscopy or intubating laryngeal mask airway.

Al-Jadidi et al.[3] noted that the head needs to be raised between 4 and 10 cm to align EAM-SN. Class I CL view was observed in 13 (54.2%) patients on an uninflated pressure bag. In nine (37%) and two (8%) patients, respectively, the glottic view was Class II and III initially, but improved by one grade in six patients and two degrees in one patient with progressive pressure bag inflation. No laryngeal view deterioration was noted.

There should be maximal laryngeal view and the least discomfort of anesthesiologist during tracheal intubation for making arrangement for optimal pillow height intubation. It should not be too high that cannot insert laryngoscope blade or not too low that could not provide head extension. There is a wide variability in fat deposits at the upper back and at the nape of the neck in patients, which leads to a lower head position if no or one pillow is used during laryngoscopy. Hence, a need arises to have some external markers and use of inflatable pillows.

A clinical study to find the optimal pillow height for the best direct laryngoscopic view was performed without a pillow and using 3-, 6-, and 9-cm-thick pillows in fifty patients using an integrated video system. They recommended a 9-cm pillow to improve the laryngeal view.[4] Greenland et al.[5] did a pilot study in ten adult un-anesthetized volunteers. After serial sagittal magnetic resonance imaging scan plotting, they concluded that secondary markers such as EAM and suprasternal notch may assist in correctly positioning any patients in the sniffing position in obese and nonobese patients.

“Ramped” position was achieved by horizontal alignment between the EAM and the sternal notch, which is superior to the standard “sniff” position for direct laryngoscopy in morbidly obese patients.[6] Laryngoscopic views were improved with a 9-cm pillow. In five patients with a short neck (<15 cm), better laryngoscopic view was observed with a 3- or 6-cm pillow compared with the 9-cm pillow. Hence, neck length had a statistically significant correlation (ρ =0.326, P = 0.027) with the pillow height, providing the best laryngoscopic views.[7]

Many studies emphasize over sniffing position.[8],[9],[10],[11] Jeon et al.[12] in their radiological study showed that “sniffing position” provided greater occipito-atlanto-axial extension angle, which was largest statistically significantly (40.7°, P < 0.05) at 6-cm headrest, with a larger intubation distance (46.2 mm) with 6-cm headrest. A pillow of 8-cm height did not improve laryngeal view and alignment of airway axes, but increased anesthesiologist discomfort compared to a pillow of 4-cm height during tracheal intubation in adult patients.[13] Park et al.[7] preferred the use of a 9-cm pillow during direct laryngoscopy in the sniffing position.[7]

Elevation of the patient's head to 8–10 cm with pads under the occiput, with the shoulder remaining on the table, and extension of the head at the atlantooccipital joint may help in aligning the laryngeal, pharyngeal, and oral axes, such that the passage and line of vision from the lips to the glottic opening are nearly a straight line.[14] Adnet et al.[15] reported that the sniffing position offered no advantage over simple head extension for improvement of glottis visualization, except in obese and head extension-limited patients.

Our study was conducted to validate the benefit of sniffing position by the systemic use of easily available pressure infusion bag in the operating theater. This study shows that the “sniff” position produced by the mean height of 4.88-cm pressure bag provided the best laryngoscopic view, while 4.5-cm height was needed in other studies.[16] No study is available regarding the variable pillow height by pressure infusion bag for the best laryngoscopic view in the Indian population. Hence, we had used an inflatable pressure bag that allows adjustable head height. Unfortunately, the sniff position cannot be achieved in all patients using a pillow or a head ring of a fixed height, as the fat in the nape of neck interscapular area is variable in each individual, so getting the sniffing position correctly with fixed pillow height may not work in all patients. Nearly 90% of intubations were judged to be easy in Group PB compared to Group PI.

This study is limited for several reasons. The results of the present study are difficult to apply to patients who have difficult airways with limited mouth opening and further study is required in obese patients. The fixed height of 10-cm pillow was selected as it is commonly available in our hospital. We used curved blades, which causes minor changes when force is applied to the laryngoscopic handle. The main limitation of our study that we can”t make our intubator blind to object (pressure infusion bag or pillow) used at the head end for intubation process.

  Conclusion Top

Successful intubation conditions were found in 45 (90%) patients of Group PB by progressive inflation of a pressure bag, which was put between the occiput and the atlantooccipital joint. The laryngoscopic view with 4.86-cm pressure bag was better to that of view with the 10-cm pillow. Routine conventional head rings or pillow of fixed height should be abandoned in favor of inflatable headrests.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Prakash S, Rapsang AG, Mahajan S, Bhattacharjee S, Singh R, Gogia AR. Comparative evaluation of the sniffing position with simple head extension for laryngoscopic view and intubation difficulty in adults undergoing elective surgery. Anesthesiol Res Pract 2011;doi:10.1155/2011/297913.  Back to cited text no. 1
El-Orbany M, Woehlck H, Salem MR. Head and neck position for direct laryngoscopy. Anesth Analg 2011;113:103-9.  Back to cited text no. 2
Al-Jadidi AM, Khan RM, Sharma PK, Kaul N. Dynamic optimisation of the sniff position during laryngoscopy using a pressure infusion bag. Anaesthesia 2012;67:677-8.  Back to cited text no. 3
Levitan RM, Mechem CC, Ochroch EA, Shofer FS, Hollander JE. Head-elevated laryngoscopy position: Improving laryngeal exposure during laryngoscopy by increasing head elevation. Ann Emerg Med 2003;41:322-30.  Back to cited text no. 4
Greenland KB, Edwards MJ, Hutton NJ. External auditory meatus-sternal notch relationship in adults in the sniffing position: A magnetic resonance imaging study. Br J Anaesth 2010;104:268-9.  Back to cited text no. 5
Collins JS, Lemmens HJ, Brodsky JB, Brock-Utne JG, Levitan RM. Laryngoscopy and morbid obesity: A comparison of the “sniff” and “ramped” positions. Obes Surg 2004;14:1171-5.  Back to cited text no. 6
Park SH, Park HP, Jeon YT, Hwang JW, Kim JH, Bahk JH. A comparison of direct laryngoscopic views depending on pillow height. J Anesth 2010;24:526-30.  Back to cited text no. 7
Bhattarai B, Shrestha SK, Kandel S. Comparison of sniffing position and simple head extension for visualization of glottis during direct laryngoscopy. Kathmandu Univ Med J (KUMJ) 2011;9:58-63.  Back to cited text no. 8
Adnet F, Borron SW, Racine SX, Clemessy JL, Fournier JL, Plaisance P, et al. The intubation difficulty scale (IDS): Proposal and evaluation of a new score characterizing the complexity of endotracheal intubation. Anesthesiology 1997;87:1290-7.  Back to cited text no. 9
Pal R, Chauhan S, Ved BK, Lad SR. Evaluation of laryngoscopic view, intubation difficulty and sympathetic response during direct laryngoscopy in sniffing position and simple head extension: A prospective and randomized comparative study. Int J Res Med Sci. 2015;3:1895-901.  Back to cited text no. 10
Takenaka I, Aoyama K, Iwagaki T, Ishimura H, Kadoya T. The sniffing position provides greater occipito-atlanto-axial angulation than simple head extension: A radiological study. Can J Anaesth 2007;54:129-33.  Back to cited text no. 11
Jeon YT, Hwang JW, Kim K, Jung CK, Park HP, Park SH. Optimal headrest height for the best laryngoscopic view: By anatomical measurements. Am J Emerg Med 2012;30:1679-83.  Back to cited text no. 12
Hong HJ, Yun M, Kim SH, Hwang JW, Lee HC. A pillow of 8 cm height did not improve laryngeal view and alignment of airway axes but increased anesthesiologist discomfort compared to a pillow of 4 cm height during tracheal intubation in adult patients. Korean J Anesthesiol 2016;69:138-42.  Back to cited text no. 13
Lee HC, Yun MJ, Hwang JW, Na HS, Kim DH, Park JY. Higher operating tables provide better laryngeal views for tracheal intubation. Br J Anaesth 2014;112:749-55.  Back to cited text no. 14
Adnet F, Borron SW, Dumas JL, Lapostolle F, Cupa M, Lapandry C. Study of the “sniffing position” by magnetic resonance imaging. Anesthesiology 2001;94:83-6.  Back to cited text no. 15
Sinha S, Layek A, Bhattacharjee S, Hazra A. The effect of different pillow heights on direct laryngoscopic views: A prospective randomised controlled study. Egypt J Anaesth 2013;29:279-83.  Back to cited text no. 16


  [Table 1], [Table 2], [Table 3]


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