Common practice and concepts in anesthesia: time for reassessment: is the sniffing position a "gold standard" for laryngoscopy?

Airway ultrasound for patients anticipated to have a difficult airway: Perspective for personalized medicine

Airway ultrasound allows for precise airway evaluation, particularly for assessing the difficult airway and the potential for front of neck access. Many studies have shown that identification of the cricothyroid membrane by airway ultrasound is more accurate than digital palpation. However, no reports to date have provided clinical evidence that ultrasound identification of the cricothyroid membrane increases the success rate of cricothyroidotomy. This is a narrative review which describes patients with difficult airways for whom airway ultrasound may have been useful for clinical decision making. The role of airway ultrasound for the evaluation of difficult airways is summarized and an approach to the use of ultrasound for airway management is proposed. The goal of this review is to present practical applications of airway ultrasound for patients predicted to have a difficult airway and who undergo cricothyroidotomy.

Two head positions for orotracheal intubation with the trachway videolight intubating stylet with manual in-line stabilization: A randomized controlled trial

BACKGROUND

The Trachway Videolight Intubating Stylet is a video-assisted system with a rigid but malleable intubating stylet that facilitates endotracheal intubation. Minimizing cervical spine movement with manual in-line stabilization is essential for patients with cervical spine injuries such as multiple trauma. However, the intubation time of the Trachway Videolight Intubating Stylet and complications associated with intubation in patients with manual in-line stabilization in the neutral-head and head-lift positions remain unclear.

METHODS

Patients (20-80 years old) who were scheduled to undergo surgery that required general anesthesia with tracheal intubation were randomly allocated to either a neutral-head (n = 62) or a head-lift position (n = 62) group. Manual in-line stabilization was performed to limit cervical spine mobility. We aimed to evaluate orotracheal intubation time and success rate in these 2 positions with the Trachway Videolight Intubating Stylet.

RESULTS

Intubation was faster in the head-lift than in the neutral-head position (20 ± 10 and 25 ± 13 seconds, respectively, P = .000); intubation was equally successful in the 2 positions (96.8% vs 96.8%). Responses to intubation did not differ between positions (heart rate, P = .142; visual analog scale scores for throat soreness, P = .54). The only significant predictor of intubation time was the body mass index in the head-lift position group (P = .005).

CONCLUSIONS

Intubation using the Trachway Videolight Intubating Stylet with manual in-line stabilization is faster in the head-lift position, and therefore preferable. However, if the head-lift position is not suitable, the neutral-head position is a sensible alternative, with comparable intubation success rate, heart rate change, and postoperative throat soreness.

Comparison of vocal cord view between neutral and sniffing position during orotracheal intubation using fiberoptic bronchoscope: a prospective, randomized cross over study

Background

In intubation using fiberoptic bronchoscope (FOB), partial or complete obstruction of upper airway makes the FOB insertion difficult. Thus, maneuvers to relieve such obstructions are recommended. There have been no studies to determine whether the sniffing or neutral position is superior for this purpose. Therefore, this study was performed to examine the effects of these two positions including vocal cord view.

Methods

Fifty-four patients scheduled to receive general anesthesia by orotracheal intubation were eligible for inclusion in the study with informed consent. After confirmation of proper head positioning depending on the group, the view of the vocal cord was acquired in each position. Images were reviewed using the percentage of glottic opening (POGO) score.

Results

A total of 106 images of vocal cords from 53 patients were obtained. The mean of difference of POGO score was 11.09, higher for the neutral position and standard deviation was 23.73 (p = 0.002). Neutral position increased POGO score in 31 patients and decreased POGO score in 13 patients compare to sniffing position (p = 0.017). There were no significant differences between the two head positions with regard to intubation time or degree of convenience during intubation.

Conclusions

Neutral position improved the view of glottic opening than sniffing position during oral fiberoptic intubation. However, there was no difference in the difficulty of tube insertion between the two positions.

Trial registration

Clinical Trials.gov identifier: NCT02931019, registered on October 12, 2016.

Man behind the laryngoscopy is important

Tracheal intubation is the most fundamental and effective resuscitation skill in many emergency situations. It is also performed to facilitate various surgical procedures and mechanical ventilation in critically ill patients. Tracheal intubation is also one of the most commonly taught clinical skills.

Previsional space during direct laryngoscopy: Implication in the difficult laryngoscopy

The laryngoscope should displace oral soft tissues forward out of the operator's vision. Therefore, the space in front of the view may be critical for determining the laryngoscopic view. The aim was to investigate the difference in the previsional space during difficult versus easy laryngoscopy (EL).Under general anesthesia, digital photographs of the lateral view of the head and neck were taken in the horizontal sniffing position, after head extension, and during laryngoscopy with a defined force (50 N). Three points (thyroid notch (T), maxillary incisor (I), and mandibular mentum (M)) were marked on the photograph. The previsional space was defined as the TIM triangle. We compared these areas and other variables of the TIM triangle between male patients with difficult laryngoscopy (DL: Cormack-Lehane III-IV, n = 12) versus those of age- and body mass index-matched male patients with EL (Cormack-Lehane I-II, n = 12).When the head was extended, the areas TIM triangle in DL were significantly smaller than in EL. During laryngoscopy, all values of the TIM triangle in DL, including the TIM area (16.4 ± 3.7 vs 22.6 ± 2.8 cm, P < .01), were significantly smaller than the values in EL.The previsional space was smaller in patients with DL than in those with EL. The TIM triangle could suggest new way to explain the mechanism underlying DL.

A Randomized Study Comparing the Sniffing Position with Simple Head Extension for Glottis Visualization and Difficulty in Intubation during Direct Laryngoscopy

Background:

Proper positioning of the head and neck is important for an optimal laryngeal visualization. Traditionally, sniffing position (SP) is recommended to provide a superior glottic visualization, during direct laryngoscopy, enhancing the ease of intubation. Various studies in the last decade of this belief have challenged the need for sniffing position during intubation. We conducted a prospective study comparing the sniffing head position with simple head extension to study the laryngoscopic view and intubation difficulty during direct laryngoscopy.

Materials and Methods:

Five-hundred patients were included in this study and randomly distributed to SP or simple head extension. In the sniffing group, an incompressible head ring was placed under the head to raise its height by 7 cm from the neutral plane followed by maximal extension of the head. In the simple extension group, no headrest was placed under the head; however, maximal head extension was given at the time of laryngoscopy. Various factors as ability to mask ventilate, laryngoscopic visualization, intubation difficulty, and posture of the anesthesiologist during laryngoscopy and tracheal intubation were noted. In the incidence of difficult laryngoscopy (Cormack Grade III and IV), Intubation Difficulty Scale (IDS score) was compared between the two groups.

Results:

There was no significant difference between two groups in Cormack grades. The IDS score differed significantly between sniffing group and simple extension group (P = 0.000) with an increased difficulty during intubation in the simple head extension. Patients with simple head extension needed more lifting force, increased use of external laryngeal manipulation, and an increased use of alternate techniques during intubation when compared to SP.

Conclusion:

We conclude that compared to the simple head extension position, the SP should be used as a standard head position for intubation attempts under general anesthesia.

Angular change in the line of vision to the larynx: implications for determining the laryngoscopic view

BACKGROUND

We measured the angular change from the line of vision to the larynx around the upper incisors under defined laryngoscopic forces and investigated its association with the laryngoscopic view.

METHODS

Laryngoscopy was performed under general anesthesia with muscle paralysis in male patients with a difficult laryngoscopy (DLG, n = 11) and in male patients matched for age and body mass index with an easy laryngoscopy (ELG, n = 11). A Macintosh blade #3 was used for the procedure. The line of vision was marked on lateral photographs during laryngoscopy by simultaneously delineating two straight lines: a line from the upper incisors to the lowest surface of the laryngoscope blade and a line from the upper incisors to the thyroid notch. The angle difference, defined as the angle between those two lines, was measured at laryngoscopic forces of 10-50 N.

RESULTS

The angle difference was significantly greater in the DLG than in the ELG at 50 N [median, 18.0° (range, 16.5-21.0°) vs 12.0° (12.0-13.5°), respectively; P < 0.001] and at lower forces (10-40 N; P ≤ 0.001). A higher Cormack-Lehane grade was associated with a greater angle difference at 50 N (P < 0.001).

CONCLUSIONS

Compared with ELG, DLG is associated with a larger angle difference, i.e., a larger gap between the underside of the blade and the thyroid notch at all laryngoscopic forces (10-50 N). The concept of angle difference, based on the angular change in the line of vision around the upper incisors, may provide a new approach to understanding DLG. This study was registered with the Clinical Research Information Service, registration number KCT0000433.

Age and gender are important considerations in choosing the sniffing position for laryngoscopic view

AIMS

The sniffing position is considered to be the standard position for direct laryngoscopic viewing. This crossover study evaluated age and gender as variables in comparing the benefits of the sniffing position over simple head extension for laryngeal view during direct laryngoscopy.

METHODS

Laryngoscopy with a curved blade was performed on 200 anesthetized adults (100 males, 100 females) presenting for routine elective surgery. Glottic visualization was assessed by using the percentage of glottic opening (POGO) score in both simple extension and sniffing positions without the aid of the assistant or external laryngeal manipulation. Each gender group was divided into a younger group (< 50 years) and an older group (≥ 50 years). POGO scores were compared between both positions within each group.

RESULTS

Mean (SD) POGO scores increased significantly only in younger male patients from 43% (39%) in the head extension position to 76% (30%) in the sniffing position.

CONCLUSION

The sniffing position seems to be advantageous for getting a better laryngeal view during laryngoscopy for tracheal intubation in adult male patients less than 50 years old.

Optimal headrest height for the best laryngoscopic view: by anatomical measurements

BACKGROUND

We hypothesized that the oro-pharyngolaryngeal axes, occipito-atlanto-axial extension (OAA) angle and intubation distance would be influenced by the height of headrests.

METHODS

Twenty patients were enrolled. The Macintosh 3 blade was used for direct laryngoscopy without a headrest or with the headrest of 6 or 12 cm high in randomized order, whereas a lateral radiograph of the neck was taken when the best laryngoscopic view was obtained. The following measurements were made: (1) the axis of the mouth (MA), the pharyngeal axis (PA), the laryngeal axis (LA), and the line of vision (LV). The various angles between these axes were defined: α angle between MA and PA, β angle between PA and LA, and δ angle between LV and LA. (2) Intubation distance, (3) mentovertebral distance, and (4) OAA angle.

RESULTS

Compared with 12-cm and no headrest, the δ angle decreased significantly with 6-cm headrest (19.4°/29.2°/29.2° in 6-cm/12-cm/no headrest, respectively; P < .001), and the intubation distance increased significantly (46.2/37.3/38.7 mm in 6-cm/12-cm/no headrest, respectively; P < .001). Mentovertebral distance was smallest (107.0/106.7/98.5 mm; P < .05) at 12-cm headrest. Occipito-atlanto-axial extension angle was largest significantly (40.7°/35.2°/34.5°; P < .05) at 6-cm headrest.

CONCLUSION

We conclude that compared with no or 12-cm headrest, 6-cm headrest could facilitate more alignment of these axes, increase the OAA angle, and enlarge the intubation distance.

[French clinical guidelines for prevention of perianaesthetic dental injuries: long text]

INTRODUCTION

Dental injuries represent the most common claims against the anaesthesiologists. Dental lesions are frequent complications of orotracheal intubation and major causal factors are, firstly, preexisting poor dentition, and, secondly, difficult laryngoscopy and tracheal intubation. The aim of this work was to prioritize propositions for prevention in perianaesthetic dental injury and for care in case of dental trauma.

METHOD

A GRADE consensus procedure consisting of three rounds was conducted. A purposively selected heterogeneous panel (n=15) of experts, comprising 10 practitioners in anesthesiology, one practitioner who is jurist and anaesthesiologist, two practitioners in maxillofacial surgery, and two practitioners in dentist surgery. In cases where the data did not appear conclusive, recommendations were based on the consensus opinion of the board members. The guidelines represent the best current evidence based on literature search and professional opinion.

RESULTS

The entire panel completed all three rounds and 31 plus six propositions were written for adult and paediatric clinical practice in anaesthesiology, respectively. The experts highlight the interest of preoperative visit for minimizing dental injuries: the practitioner must identify risk factors for difficult intubation and ventilation, describe precisely patient's preoperative dental condition, including upper incisor most commonly involved teeth in dental trauma. Patients have to be informed by practitioner for risk dental injury and anaesthesiology staff must choose his anesthesia protocol before the induction of intubation narcosis, avoiding insufficient anaesthesia and lack of experience by the anaesthesiologist. The choice of accurate proceeding during laryngoscopy, tracheal intubation and extubation for example, can aid in the prevention of dental injury, reduce the number of claims and the cost of litigation process.

DISCUSSION

These guidelines delineate an approach for the prevention of perianaesthetic dental trauma and for the immediate or urgent care in case of perianaesthetic dental injury.

Laryngeal exposure during laryngoscopy is better in the 25 degrees back-up position than in the supine position

BACKGROUND

Good visualization of the glottis is important for tracheal intubation. This study evaluated whether the 25 degrees back-up position improves the quality of the laryngeal view during laryngoscopy.

METHODS

Laryngoscopy with a curved blade was performed on 40 anaesthetized patients. The patients were randomly assigned to two groups. Laryngeal views were captured with a rigid 0 degrees endoscope. Views were recorded for each patient in Group A (n = 20) during laryngoscopies performed with the patient lying first in the supine position and then in the 25 degrees back-up position. Laryngeal views for patients in Group B (n = 20) were first captured while the patient was in the 25 degrees back-up position and then while the patient was in the flat supine position. An anaesthetist blinded to the position graded the quality of the images using the percentage of glottic opening (POGO) score.

RESULTS

Comparing the two positions, mean (sd) POGO scores increased significantly from 42.2 (27.4)% in supine position to 66.8 (27.6)% in 25 degrees back-up position (P < 0.0001).

CONCLUSIONS

During laryngoscopy, the laryngeal view, as assessed by POGO scores, improves significantly in the 25 degrees back-up position when compared with the flat supine position.

The sniffing position provides greater occipitoatlanto-axial angulation than simple head extension: A radiological study

PURPOSE

While the anatomic sniffing position has traditionally been considered the standard head and neck position for laryngoscopy, recent evidence suggests that the sniffing position provides no significant advantage over simple head extension. To establish if the sniffing position provides an anatomic advantage, we compared the occipito-atlanto-axial extension angle, a key determinant for obtaining a good laryngeal view during laryngoscopy, in simple head extension and sniffing positions.

METHODS

Thirty volunteers with normal cervical spines were studied. Radiological examinations of the lateral cervical spine were taken and compared in each of the following three positions for each subject: neutral position (flat on the table with no pillow and without head extension or flexion); simple head extension (head maximally extended without a pillow); and the sniffing position (head extension with cervical flexion obtained by 7 cm occipital elevation).

RESULTS

Mean angles of the occipito-atlanto-axial extension in simple head extension and the sniffing position were 20.4 degrees+/-5.1 degrees and 24.2 degrees+/-5.6 degrees, respectively (P<0.01).

CONCLUSION

The anatomic sniffing position provides greater occipito-atlanto-axial extension compared to simple head extension. These findings should be taken into consideration when optimizing patient positioning for laryngoscopy.