AirSPACE™ device for real-time positioning during laryngoscopy

Accepted Manuscript AirSPACE™ device for real-time positioning during laryngoscopy Tyrone Burnett, Jr., Omar L. Mancillas, Chunyan Cai, Semhar Ghebremichael, Sam D. Gumbert, Naveen Vanga, Carin A. Hagberg PII:

S2210-8440(17)30116-8

DOI:

10.1016/j.tacc.2017.06.004

Reference:

TACC 354

To appear in:

Trends in Anaesthesia and Critical Care

Received Date: 24 March 2017 Revised Date:

20 May 2017

Accepted Date: 27 June 2017

Please cite this article as: Burnett Jr. T, Mancillas OL, Cai C, Ghebremichael S, Gumbert SD, Vanga N, Hagberg CA, AirSPACE™ device for real-time positioning during laryngoscopy, Trends in Anaesthesia and Critical Care (2017), doi: 10.1016/j.tacc.2017.06.004. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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AirSPACE™ Device for Real-Time Positioning During Laryngoscopy

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Tyrone Burnett Jr. (BS)†a, Omar L. Mancillas (MD)†a, Chunyan Cai (PhD)†b, Semhar Ghebremichael (MD)†a,

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Sam D. Gumbert (MD)†a, Naveen Vanga (MD)†a, Carin A. Hagberg (MD)*a

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†a

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Houston (UTHealth) McGovern Medical School, 6431 Fannin St., MSB 5.020, Houston, Texas, 77030, U.S.A.,

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E-mail: [email protected]

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Research Assistant II, Department of Anesthesiology, The University of Texas Health Science Center at

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†a

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Houston (UTHealth) McGovern Medical School, 6431 Fannin St., MSB 5.020, Houston, Texas, 77030, U.S.A.,

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E-mail: [email protected]

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Research Assistant I, Department of Anesthesiology, The University of Texas Health Science Center at

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†b

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Houston (UTHealth) McGovern Medical School, 6410 Fannin St., UPB 1100.08, Houston, Texas, 77030,

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U.S.A., E-mail: [email protected]

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Assistant Professor, Department of Internal Medicine, The University of Texas Health Science Center at

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†a

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Houston (UTHealth) McGovern Medical School, 6431 Fannin St., MSB 5.020, Houston, Texas, 77030, U.S.A.,

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E-mail: [email protected]

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Assistant Professor, Department of Anesthesiology, The University of Texas Health Science Center at

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†a

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Houston (UTHealth) McGovern Medical School, 6431 Fannin St., MSB 5.020, Houston, Texas, 77030, U.S.A.,

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E-mail: [email protected]

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Associate Professor, Department of Anesthesiology, The University of Texas Health Science Center at

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†a

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Houston (UTHealth) McGovern Medical School, 6431 Fannin St., MSB 5.020, Houston, Texas, 77030, U.S.A.,

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E-mail: [email protected]

Assistant Professor, Department of Anesthesiology, The University of Texas Health Science Center at

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Center at Houston (UTHealth) McGovern Medical School, 6431 Fannin St., MSB 5.020, Houston, Texas,

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77030, U.S.A., E-mail: [email protected]

Corresponding Author: Carin A. Hagberg, MD

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Office Phone: 713-792-5888 E-mail: [email protected]

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Present Address:

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The University of Texas MD Anderson Cancer Center

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Division of Anesthesiology, Critical Care & Pain Medicine

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1400 Holcombe Blvd., Unit 409

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Houston, TX 77030

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Running (Short) Title: AirSPACE™ Technology in a Clinical Setting

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Joseph C. Gabel Professor and Chair, Department of Anesthesiology, The University of Texas Health Science

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ACCEPTED MANUSCRIPT 3 ABSTRACT

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Background: Patient positioning is critical in establishing an optimal laryngeal view during various airway

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management techniques, including direct laryngoscopy. The “sniffing” position, in which all 3 axes are aligned,

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has been the traditional method for direct laryngoscopy. [1, 2] The AirSPACE™ is a new positioning device that

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was developed to facilitate patient positioning during laryngoscopy via mechanical head and neck manipulation,

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potentially improving the visualization of laryngeal structures.

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Aim: The purpose of this study was to evaluate the performance of the AirSPACE™ device, as measured by the

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percentage of the Modified Cormack-Lehane (C-L) classification system, Grade’s III or IV specifically, for

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glottic visualization during the first attempt of laryngoscopy and intubation.

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Methods: Following IRB approval, 30 adult (≥18 y/o) patients with ASA status classifications I-III, requiring

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tracheal intubation and general anesthesia participated in this study. In order to assess the performance of the

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device, various measurements were obtained, including the initial C-L airway grade view during the first

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attempt, the C-L grade view after repositioning (if necessary), the time required for patient repositioning, the

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time required to obtain an optimal view of the glottis and CO2 detection, the time required to fully set up the

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AirSPACE™ device onto the designated OR table, the number of attempts required for a successful intubation,

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the minimum oxygen saturation (SpO2) while the airway was being secured, the method of laryngoscopy

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performed, subjective assessment evaluations from utilizing the AirSPACE™, and safety reporting of any

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adverse events.

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Results: Of the 30 patients enrolled in the study, only 3 (10.0%, 95% confidence interval: 2.1%-26.5%) were

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recorded with a C-L Grade III or IV, with an average repositioning time of 29.3 ± 8.4s. The frequency of initial

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C-L grade views was: I, 50.0%; IIa, 16.7%; IIb, 23.3%; III, 6.7%; and IV, 3.3%. For the 3 patients who required

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repositioning, 2 demonstrated improvement in the glottic view after repositioning, while one demonstrated no

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improvement. The time required to obtain an optimal view of the glottis and that for CO2 detection was 19.7 ±

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13.8s and 42.6 ± 22.0s, respectively. The average time required to set up the AirSPACE™ device was 4.29 ±

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1.81 minutes. The average minimum oxygenation during intubation was 99.7 ± 0.6%. Direct laryngoscopy

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(90%) was the preferred method when performing laryngoscopy and intubation, when compared to indirect

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ACCEPTED MANUSCRIPT 4 (10%) during the study period. Nearly half of the laryngoscopists assessed the difficulty of laryngoscopy and

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difficulty of ETT delivery as 1 (Very Easy), 43.3% and 46.7%, respectively, whereas 68.8% assessed

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AirSPACE™ device ease of use as 1 (Very Easy).

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Conclusion: This study, demonstrated that the AirSPACE™ device is an effective positioning mechanism that

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provided the laryngoscopist with a highly favorable glottic view initially. Yet, further research is warranted in

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evaluating the AirSPACE™’s effectiveness in improving glottic visualization of less favorable and more

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difficult airways on a much larger spectrum.

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Keywords: Airway management; airway equipment; laryngoscopy; tracheal intubation; patient positioning;

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positioning device

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1. INTRODUCTION Laryngoscopy and tracheal intubation are performed on a regular basis when establishing an airway for

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patients that undergo surgery. [1] Optimal visualization of laryngeal structures is essential in establishing a

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patent airway for these patients; a greater glottic opening is inversely correlated with the number of intubation

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attempts and the need for rescue intubation devices. [2] Fewer attempts at tracheal intubation result in less

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trauma and fewer complications. [3] A poor view of the laryngeal structures increases the likelihood of a

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difficult intubation. [4]

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Patient positioning is critical in establishing optimal laryngeal view during laryngoscopy. An optimal

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laryngeal view can be facilitated with proper head and neck positioning, including slight elevation of the head,

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neck flexion relative to the chest, and extreme atlanto-occipital extension. [2] The “sniffing” position, used

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traditionally for direct laryngoscopy, is achieved by neck flexion and head extension at the atlanto-occipital

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joint. [2] However, a study by Adnet et al. reported that the sniffing position offers no advantage over simple

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head extension, except in patients who are considered to be obese or have limited head extension. [3]

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In current clinical practice, the patient is typically placed in the sniffing position prior to laryngoscopy and

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intubation by layering blankets and pillows underneath the patient’s back, shoulders, neck, and/or head, as

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needed. However, these techniques can produce inconsistent positioning, may require additional resources and

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additional time, and may be inconvenient for intra-operative changes during patient positioning and upon

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removal of the positioning device(s) altogether. In morbidly obese patients, the “ramped” or head-elevated

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laryngoscopy position (HELP), with the patient’s external auditory meatus horizontally aligned with the sternal

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notch, is superior to the standard sniffing position. [2,3,5] Previous literature has reported the HELP position

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being achieved by layering blankets or using pre-designed foam elevation pillows. [5,6] If traditional

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positioning devices are used, they are customarily removed before the completion of the surgical procedure, and

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therefore are not present during extubation. Current literature demonstrates variation in the standard practice of

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head and neck positioning. [1-6] And as a result, a new positing device was invented with the intent to provide a

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more consistent, faster, and possibly significant intraoperative manageability during laryngoscopy and

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intubation.

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The AirSPACE™ (Air Sniffing Position And Chin Elevation — Revolutionary Medical Devices, Inc., Tucson,

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AZ, USA) is a positioning device which facilitates patient positioning by mechanically adjusting the patient’s

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head into the sniffing position, thereby potentially improving the visualization of laryngeal structures during

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laryngoscopy (Figure 1a). The purpose of this study was to evaluate the performance of the AirSPACE™ device

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in optimizing and improving the view of the larynx during laryngoscopy, as measured by the percentage of the

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Modified Cormack-Lehane (C-L) classification system (Grade’s III or IV) [7] during the first attempt of

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laryngoscopy and intubation. Secondary objectives consisted of the average initial C-L grade view and/or

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improvement in C-L Grade’s III or IV after device-assisted repositioning, the time required to place the patient

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in optimal reverse Trendelenburg positioning, in conjunction with, successful placement of the endotracheal

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tube (ETT) when using the AirSPACE™ device, the time required to obtain an optimal view and CO2 detection,

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the time required to fully set up the AirSPACE™ device onto the designated OR table, the number of attempts

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required for a successful intubation, the minimum oxygen saturation (SpO2) while the airway was being

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secured, the method of laryngoscopy performed, subjective assessments pertaining to the difficulty of

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laryngoscopy and intubation with the AirSPACE™, in addition to, the AirSPACE™’s ease-of-use. Also,

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AirSPACE™ safety and tolerability were secondary objectives that consisted of technical performance indicated

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by the incidence and nature of adverse events (AEs), serious adverse events (SAEs), unanticipated adverse

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device effects (UADEs) and their duration, resolution and required treatment; if any.

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2. METHODS Following protocol approval by the Institutional Review Board (IRB) of the University of Texas Health

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Science Center at Houston McGovern Medical School and the Research Committee of the Department of

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Anesthesiology, 30 adult patients scheduled for elective surgery at Memorial Hermann Hospital – Texas

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Medical Center were recruited to participate in this single site, non-randomized, open-label, single-group

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volunteer study. Key research personnel, including the principal investigator, co-investigators, and/or study

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coordinators obtained informed written consent.

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2.1 Statistical Methods

Thirty human subjects were enrolled into this study. Assuming the percentage for C-L grade views III-IV is

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20% [8], with this sample size, we expected to estimate this percentage with a precision level of 0.15 at 95%

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confidence level. Descriptive statistics, the mean ± standard deviation (SD) for continuous variables and

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frequency (percentage) for categorical variables, were used to summarize patient demographic, baseline clinical

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characteristics, vital signs, and clinical performance variables. The percentage of repositioning needed during

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laryngoscopy and intubation, as well as its 95% confidence interval, were calculated. All analyses were

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performed using SAS 9.4 software (Cary, NC).

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2.2 Patient Selection

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The study group was comprised of individuals scheduled to undergo surgery that met the following inclusion

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criteria: (1) age of 18 years old or older and (2) American Society of Anesthesiology (ASA) physical status I-

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III. Exclusion criteria included the following: (1) < 18 years of age, (2) ASA physical status IV or V, (3)

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presence of an underlying neuromuscular disease, (4) use of medications known to interfere with neuromuscular

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transmission, (5) history of cervical spine injury or cervical pathology, (6) presence of renal or hepatic disease,

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(7) presence of only one upper extremity, and (8) presence of open sores at the location(s) required for electrode

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application.

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ACCEPTED MANUSCRIPT 8 Cases involving surgical procedures, such as craniotomies and other invasive neurosurgical procedures that

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require access to the patient’s head, including prone positioning; facial repairs and reconstructions; invasive

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upper extremity involvement; and invasive airway management procedures were also excluded due to the

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necessary access and manipulation of a patient’s head, and/or sterilization of a cephalic surgical field. The types

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of surgical procedures that were included in this study were categorized into 3 specialties: urology, obstetrics

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and gynecology (OBGYN), and general surgery (Supplementary Table 1).

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Morphometric characteristics such as neck circumference, inter-incisor gap, thyromental distance, and

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sternomental distance were measured and recorded for all patients. The quality of each patient’s airway was

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evaluated using the ASA Task Force’s physical examination recommendations according to the most recent

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ASA Practice Guidelines for Management of the Difficult Airway. [9]

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2.3 Study Procedure

Each patient received general anesthesia and endotracheal intubation. In the operating room (OR), standard

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monitoring devices were applied, including a pulse oximeter, 3-lead electrocardiogram, and a non-invasive

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blood pressure cuff. Measures of blood pressure (BP), heart rate (HR), respiratory rate (RR), oxygen saturation

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(SpO2), and end-tidal carbon dioxide (EtCO2) were observed and recorded as a baseline (before the patient’s

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surgical preparation and draping), and periodically throughout the perioperative period. Vital signs were

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recorded immediately before oxygen administration, before induction of anesthesia, before ETT insertion,

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during laryngoscopy, after ETT insertion, and postoperatively during the patient’s recovery in the post-

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anesthesia care unit (PACU) as a precautionary measure during the study period. Study laryngoscopists

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included resident, fellow, and attending anesthesiologists, anesthesiologist assistants, and medical students.

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Study personnel set up the AirSPACE™ device before each patient was brought into the OR. The initial step to

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install the AirSPACE™ device was the removal of the existing headpiece of the operating table and storage.

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Mounting hasps (clamps) were placed onto the rails of the operating table; the AirSPACE™ device was placed

ACCEPTED MANUSCRIPT 9 and arranged into the allotted holes of the mounting hasps, then securely tightened for stability (Figure 1b).

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Once the device was secured, its electrical power cord was plugged into a standard 120 V outlet. Finally, the

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disposable AirSPACE™ headrest and protection cover were attached to the headrest pins of the device and

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arranged over the operating table (Figure 2). The time needed to set up the AirSPACE™ device was recorded in

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each case.

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AirSPACE™ disposables include the single-use impermeable protective cover, for both the AirSPACE™

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device and surgical table (if necessary), a disposable foam head donut (headrest), and a 15° head wedge as an

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accessory (Figure 3). The integrated head wedge and donut are designed to provide comfort, proper head

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positioning, and stability of the patient’s head during the administration of anesthetics, and even surgery. Both

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pieces, the head wedge and donut, are removable; thus allowing the surgeon and/or anesthesiologist to move the

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patient along the surgical table and reposition when desired.

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Prior to induction, the patient’s head was aligned and stabilized onto the headrest of the AirSPACE™ device.

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General anesthesia was induced by bolus administration of propofol (1.5 to 2 mg/kg) and fentanyl (1 mcg/kg)

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and maintained with an inhalation agent. Rocuronium (0.6 mg/kg) was administered to induce muscle

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relaxation. The lungs were mechanically ventilated to maintain an EtCO2 near 35 mmHg. Ventilation was

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maintained via anesthesia full facemask with 100% oxygen administration until the patient was completely

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relaxed (train of four on twitch monitor was 0).

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Each patient was placed in a neutral supine position prior to laryngoscopy and intubation. The laryngoscopist

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performed either direct or indirect laryngoscopy. Patient repositioning with the AirSPACE™ device was

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dependent on the initial C-L airway grade view obtained by the laryngoscopist. If the initial C-L airway grade

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view observed was either III or IV, the patient was repositioned in an attempt to improve the glottic view via

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neck flexion and head extension. Neck flexion was achieved by pressing the “head up/extension” or “head

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down/flexion” button on the AirSPACE™ remote. The AirSPACE™ device uses a four-button pendant to control

ACCEPTED MANUSCRIPT 10 two linear actuators — one to raise and lower the head up and down (Figure 4a), and the other to increase or

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decrease the angle of the head forward and backward (Figure 4b). Finally, a head-tilt, chin-lift, which is

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manually controlled by using all four buttons on the remote, allows the patient’s head to slide into the desired

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position along the slide rail of the head slide (Figure 4c). At the top of the head lift is the 15° head wedge and

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headrest, which consists of a donut pad to provide head and neck comfort, along with proper spinal alignment

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during anesthesia and surgery. The head slide and slide rail are designed to account for the difference between

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the patient’s linkage (pivot points) and the AirSPACE™’s linkage (pivot points). With the operating table in

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reverse Trendelenburg position, the device integrates 3 clinically recommended positions for airway

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management: (1) sniffing position, (2) HELP, and/or (3) active head and neck positioning. The time needed to

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perform laryngoscopy, the time needed to obtain an improved C-L airway grade view (via repositioning with

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the AirSPACE™), and the time needed until the first CO2 waveform was observed, were all recorded.

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No more than 3 intubation attempts were allowed for each patient. The number of intubation attempts and

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the minimum oxygen saturation during the entire airway procedure were recorded; oxygenation and ventilation

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were both maintained until the airway was secured. If more than three attempts were needed, the intubation

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procedure was deemed a device failure. After each successful intubation, the laryngoscopist was requested to

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assess the following: difficulty of laryngoscopy, difficulty of ETT delivery, adequacy of laryngeal view during

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passage of ETT, and AirSPACE™ ease-of-use. These subjective assessments were recorded via numerical rating

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scale that corresponded to a described degree of difficulty. By this scale, 1 = Very Easy and 5 = Not Possible,

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thereby representing the level of difficulty perceived by the laryngoscopist when they successfully secured the

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airway. [9] The AirSPACE™ device ease-of-use was represented by a classified rating scale, ranging from a

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Grade 0 = Very Easy to Grade 4 = Failed (Supplementary Table 2). If a successful intubation attempt was not

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achieved by the third attempt, the patient's airway was secured using an alternative method/device for tracheal

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intubation.

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3. RESULTS

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3.1 Repositioning with the AirSPACE™ The summary statistics of demographics, baseline morphometric characteristics, and anesthetist levels are

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reported in Table 1. Of the 30 patients enrolled in this study, only 3 (10.0%, 95% confidence interval: 2.1%-

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26.5%) were recorded with having an initial C-L grade of III or IV, with an average repositioning time of 29.3 ±

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8.4s. Therefore, 27 patients (90%) were classified with having an initial C-L grade view of I, IIa, or IIb. For the

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3 patients that had an initial C-L grade view of III or IV and were repositioned per protocol, 2 (66.7%) had an

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improvement in the glottic view after repositioning with the AirSPACE™ device, and only one (33.3%) showed

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no improvement. The distribution of initial C-L grade views for all 30 patients was: Grade I, 15; Grade IIa, 5;

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Grade IIb, 7, Grade III, 2; and Grade IV, 1 (Figure 5).

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Although only 3 patients needed repositioning per protocol, 7 patients were repositioned due to the

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laryngoscopist’s concern and interest of the AirSPACE™’s capabilities, even though a favorable glottic view

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was obtained initially. For these 7 patients that were repositioned, due to the laryngoscopist’s curiosity, 6

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(85.7%) had an improvement in the glottic view, while one (14.3%) showed no improvement. The average

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repositioning time for these 7 patients was 20.1 ± 12.0s. Of the 10 patients that were repositioned overall, 8 had

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an improvement in the C-L grade view (80%) and 2 demonstrated no improvement (20%). The average

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repositioning time for all 10 patients was 22.8 ± 11.4s. Ultimately, no patient demonstrated a decrease in the

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glottic view when repositioning was desired (Table 2).

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3.3 Intubation Attempt(s) Required

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Twenty-four of the 30 patients (80.0%) were intubated during the first attempt by the laryngoscopist. More

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than one intubation attempt was required for 6 patients (20%), with only one of the 6 patients requiring > 2

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attempts.

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3.4 Oxygen Saturation During Laryngoscopy and Intubation

ACCEPTED MANUSCRIPT 12 The average minimum SpO2 during intubation was 99.7 ± 0.6% for all 30 patients. The lowest recorded

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SpO2 during the airway procedure was 98% (three patients), and the highest was 100% (25 patients). Only two

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patients were recorded as having an oxygen saturation of 99%; further details pertaining to oxygen saturation

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during the entire airway procedure for all 30 patients are presented in Table 3.

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3.5 Laryngoscopy and Intubation with the AirSPACE™

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During the study period, 90% of the patients were intubated via direct laryngoscopy and 10% via indirect.

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The times required to obtain an optimal view and for CO2 detection for all 30 patients were 19.7 ± 13.8s and

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42.6 ± 22.0s, respectively. Twenty-nine of the 30 patients were successfully intubated with the AirSPACE™

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device (Table 4).

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3.6 Subjective Assessment for Level of Difficulty

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The laryngoscopists were requested to evaluate, via a numerical rating scale, the level of difficulty during the

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entire airway procedure using the AirSPACE™ device. Nearly half of the laryngoscopists assessed the difficulty

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of laryngoscopy and difficulty of ETT delivery as 1 (Very Easy), 43.3% and 46.7%, respectively; whereas

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68.8% assessed the AirSPACE™’s ease-of-use as Grade 1 (Somewhat Easy). Further details regarding

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laryngoscopist’s assessments are reported in Table 5.

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3.7 Safety Reporting

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There were no AEs, SAEs, or UADEs associated with the use of the AirSPACE™ device during the study period.

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4. DISCUSSION This study demonstrated that the AirSPACE™ device provides sufficient, initial, patient positioning, paired

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with a desirable glottic view, for 27 of the 30 patients (90%). It is an effective positioning mechanism that

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provided the laryngoscopist with a noticeable improvement in the glottic view via instantaneous airway

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manipulation (head repositioning) during laryngoscopy for 2 of the 3 patients that received an initial C-L grade

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view of III or IV. Although we reported the results of 7 patients that were repositioned, not based on protocol

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procedures, the end result of improving and optimizing such favorable C-L grade views, such as a IIa or IIb,

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adds value towards the purpose and intent of the AirSPACE™ device.

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Difficult laryngoscopy usually results from poor glottic visualization, and is, therefore, linked to the likelihood

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of a difficult intubation. [10] Correct positioning of the patient appears to be the main determining factor for

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obtaining good glottic visualization under direct laryngoscopy, including the use of the sniffing position. [11]

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Twelve of the 30 patients (40%) in this study had a body mass index (BMI) > 30 kg/m2, while the remaining 18

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patients (60%) had a BMI < 30 kg/m2. Of the 12 patients with a BMI > 30 kg/m2, only one patient (8.3%) was

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repositioned because of an initial C-L grade view of III that ultimately improved to a Grade I, therefore

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allowing a successful intubation on the first attempt. The other 11 patients (91.7%) had such a favorable initial

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C-L grade view that repositioning was unnecessary, and these patients were all successfully intubated during the

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first attempt. The AirSPACE™ device, along with reverse Trendelenburg orientation, is designed to help

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patients at risk for difficulties in mask ventilation, direct laryngoscopy, and tracheal intubation. [12]

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The methods of laryngoscopy used in this study are typical of the institution’s practice and were completely

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based on the anesthesiologist’s discretion and care plan. Thus, there is no preference for which laryngoscope or

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which method of laryngoscopy that should be paired with the use of the AirSPACE™ device while the airway is

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secured. The decision was made not to standardize the type of laryngoscope in order to illustrate the

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AirSPACE™’s capabilities with both direct and indirect methods.

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ACCEPTED MANUSCRIPT 14 During our postoperative observations and assessments in the post-anesthesia care unit, no patient reported

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head or neck discomfort (or any related issues), even though the surgical procedures ranged in duration from 2-

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5 hours. This suggests that the AirSPACE™ device is able to effectively support a patient’s head for extensive

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surgical procedures, even during lateral positioning.

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4.1 Limitations

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This study has several limitations. First, there was no standardization during repositioning of either the

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operating table or the AirSPACE™ device. The angle at which the operating table was set during repositioning

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into reverse Trendelenburg orientation was not measured, nor was the height and the angle of manipulation of

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the AirSPACE™ device itself. Furthermore, the number of study personnel required to install the AirSPACE™

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device onto the operating table was observed, but not recorded. Nonetheless, the AirSPACE™ device can be

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installed onto an OR table within 2 - 4 minutes by two people, and within 3 - 5 minutes by one person (this

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estimation is based on the data collected as part of Section 2.2 Study Procedure). Although there are no reports

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of the time required for patient positioning with other elevating apparatuses such as blankets, ramps, and

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pillows, further research is warranted to identify differences between the AirSPACE™ and standard elevating

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devices in average C-L view grade (along with improvement in view grade if necessary) in obese patients, first

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attempt intubation success rate, time required for patient repositioning, and assess economic considerations. The

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various skill levels of the laryngoscopists that were included in the study were not standardized as well, due to

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AirSPACE™’s simplistic and novel capabilities. For that reason, we can surmise using the AirSPACE™ as a

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teaching tool for students (medical, AA, CRNA) and/or less skilled anesthesia practitioners during

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laryngoscopy and tracheal intubation. As the experience level of the laryngoscopist varied, the overall 80%

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success rate for glottic view improvement and initial intubation with the AirSPACE™ could be attributed to the

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skill level of the laryngoscopist and/or operator error due to limited familiarity and capability with the device.

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Since there were only 3 patients with a C-L grade view of III or IV, our data is limited in performing a subgroup

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analysis in order to identify which predictors of a difficult intubation were associated between the 2 groups. In

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addition to, the requirement for more than one intubation attempt.

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5. CONCLUSION Appropriate patient positioning increases the likelihood of a successful laryngoscopy and tracheal

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intubation.[13] Although the sniffing position is commonly performed to improve laryngeal view during direct

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laryngoscopy, patients in this study were initially placed in a neutral, supine position during laryngoscopy until

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further movement was deemed necessary. The AirSPACE™ provided easy, ‘real-time’, mechanical airway

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manipulation during laryngoscopy whenever repositioning was necessitated, and therefore increased the

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likelihood of a successful tracheal intubation on the first attempt.

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Initial patient positioning with the AirSPACE™ device was sufficiently accurate in 27 of the 30 patients

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(90.0%). Overall, the AirSPACE™ device provided adequate positioning and improved the glottic view for 2 of

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the 3 patients (66.7%) that had an initial C-L grade view of III or IV. This study, demonstrated that the

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AirSPACE™ device is an effective positioning mechanism that provided the laryngoscopist with a highly

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favorable glottic view initially; yet, further research is warranted in evaluating the AirSPACE™’s effectiveness

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in improving glottic visualization of less favorable and more difficult airways on a much larger spectrum.

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Acknowledgement: Dr. Cai's research was supported by a National Institutes of Health Clinical and

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Translational Science Award grant (UL1 TR000371), awarded to the University of Texas Health Science Center

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at Houston in 2012 by the National Center for Clinical and Translational Sciences.

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Disclosures (Conflict of Interest): Dr. Hagberg has financial relationships with Ambu, Cadence

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Pharmaceuticals, Karl Storz Endoscopy, and MedCom Flow in the form of funded research, and is an unpaid

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consultant for Ambu, Covidien, and SonarMed.

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Funding Source: This work was supported by Revolutionary Medical Devices, Inc., in conjunction with

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Covidien-Medtronic.

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ACCEPTED MANUSCRIPT 17 REFERENCES

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[1] Sainsbury JE, Telgarsky B, Parotto M, Niazi A, Wong DT, Cooper RM. The effect of verbal and video

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feedback on learning direct laryngoscopy among novice laryngoscopists: a randomized pilot study.

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Canadian Journal of Anesthesia. 2016. 1-8.

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[2] Levitan RM, Mechem CC, Ochroch EA, Shofer FS, Hollander JE. Head-elevated laryngoscopy position:

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improving laryngeal exposure during laryngoscopy by increasing head elevation. Annals of Emergency

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Medicine. 2003. 41(3):322-30.

[3] Adnet F, Baillard C, Borron SW, Denantes C, Lefebvre L, Galinski M, Martinez C, Cupa M, Lapostolle F.

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Randomized study comparing the “sniffing position” with simple head extension for laryngoscopic view in

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elective surgery patients. The Journal of the American Society of Anesthesiologists. 2001. 95(4):836-41.

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[4] Mort TC. Emergency tracheal intubation: complications associated with repeated laryngoscopic attempts.

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Anesth Analg. 2004. 99(2):607-13.

[5] Benumof JL. Difficult laryngoscopy: obtaining the best view. Canadian Journal of Anesthesia. 1994. 41(5):361-5.

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[6] Rich JM. Use of an elevation pillow to produce the head-elevated laryngoscopy position for airway management in morbidly obese and large-framed patients. Anesth Analg. 2004. 98(1):264-5. [7] Shiga T, Wajima ZI, Inoue T, Sakamoto A. Predicting difficult intubation in apparently normal patients: a

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meta-analysis of bedside screening test performance. The Journal of the American Society of

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Anesthesiologists. 2005. 103(2):429-37.

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[8] Krage R, Van Rijn C, Van Groeningen D, Loer SA, Schwarte LA, Schober P. Cormack–Lehane classification revisited. British journal of anaesthesia. 2010 Jun 16:aeq136.

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[9] Apfelbaum JL, Hagberg CA, Caplan RA, Blitt CD, Connis RT, Nickinovich DG, et al. Practice Guidelines

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for Management of the Difficult Airway: An Updated Report by the American Society of Anesthesiologists

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Task Force on Management of the Difficult Airway. The Journal of the American Society of

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Anesthesiologists. 2013. 118(2):251-70.

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[10] Vijayakumar V, Rao S, Shetty N. A comparison of Macintosh and Airtraq laryngoscopes for endotracheal intubation in adult patients with cervical spine immobilization using manual in line axial

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stabilization: a prospective randomized study. Journal of Neurosurgical Anesthesiology. 2016. 28(4):296-

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302.

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[11] Prakash S, Kumar A, Bhandari S, Mullick P, Singh R, Gogia AR. Difficult laryngoscopy and intubation in

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the Indian population: An assessment of anatomical and clinical risk factors. Indian Journal of Anesthesia.

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2013. 57(6):569-75.

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[12] Reddy RM, Adke M, Patil P, Kosheleva I, Ridley S. Comparison of glottic views and intubation times in

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the supine and 25 degree back-up positions. BMC Anesthesiology. 2016. 16(1):113. [13] Cattano D, Melnikov V, Khalil Y, Sridhar S, Hagberg CA. An evaluation of the rapid airway management

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positioner in obese patients undergoing gastric bypass or laparoscopic gastric banding surgery. Obesity

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surgery. 2010. 20(10):1436-41.

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[14] Frerk C, Mitchell VS, McNarry AF, Mendonca C, Bhagrath R, Patel A, et al. Difficult Airway Society

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2015 guidelines for management of unanticipated difficult intubation in adults. British Journal of

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Anesthesia. 2015. 115(6):827-48.

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ACCEPTED MANUSCRIPT Table 1. Summary statistics of demographics, baseline morphometric characteristics, and anesthetist levels.

Total (n=30) 51.4±17.2 29.9±5.7

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18 (60.0) 12 (40.0) 19 (63.3) 11 (36.7) 4.6±0.9 5.6±1.6 13.5±2.2

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Demographics Age, years, mean±SD BMI, kg/m2, mean±SD BMI >30 kg/m2, n (%) No Yes Sex, n (%) Female Male Inter-incisor gap distance, cm, mean±SD Thyromental distance, cm, mean±SD Sternomental distance, cm, mean±SD Mallampati classification, n (%) 1 2 3 Anesthetist level, n (%) AA Attending CA-1 CA-2 CA-3 Fellow Medical student

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14 (46.7) 14 (46.7) 2 (6.7)

14 (46.7) 2 (6.7) 6 (20.0) 2 (6.7) 2 (6.7) 2 (6.7) 2 (6.7)

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resident-year.

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BMI, body mass index; SD, standard deviation; AA, anesthesiologist assistant; CA-1, 2, 3, clinical anesthesia

ACCEPTED MANUSCRIPT Table 2. Recorded C-L airway grade views during laryngoscopy when repositioned with the AirSPACE™.

C-L Grade View Before/After Repositioning with AirSPACE™ (n)

Direct

8

IIa/IIa (1) IIb/I (3) IIb/IIa (2) III/IIa (1) IV/IV (1)

Indirect

2

IIa/I (1) III/I (1)

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No. of Patients

Laryngoscopy Method

ACCEPTED MANUSCRIPT Table 3. Recorded vitals for all 30 patients during induction and laryngoscopy with the AirSPACE™.

Vital Signs

Total (n=30)

Preoxygenation HR, n

74.4±12.4

Preoxygenation Systolic BP, n mean±SD

137.2±16.1

Preoxygenation Diastolic BP, n

80.5±14.9

Preoxygenation RR, n mean±SD

Preinduction Systolic BP, n mean±SD

Preinduction Diastolic BP, n

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Preinduction RR, n mean±SD

Preinduction SpO2, n

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mean±SD

Preinduction EtCO2, n

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mean±SD

Pre-ETT Insertion HR, n mean±SD

Pre-ETT Insertion Systolic BP, n mean±SD

Pre-ETT Insertion Diastolic BP, n mean±SD Pre-ETT Insertion RR, n mean±SD Pre-ETT Insertion SpO2, n mean±SD

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98.7±1.8

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mean±SD

2

8.5±7.8

Preoxygenation SpO2, n Preinduction HR, n

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mean±SD

mean±SD

21

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mean±SD

26

30

71.1±12.6 29

136.3±14.2 29

80.0±14.4 23 8.9±3.9 30 99.6±1.2 26 29.8±8.6 30 77.0±12.3 30 132.7±18.6 30 77.8±13.1 30 11.7±5.7 30 100.0±0.2

ACCEPTED MANUSCRIPT Vital Signs

Total (n=30)

Pre-ETT Insertion EtCO2, n mean±SD

29 26.4±8.4

Post-ETT Delivery HR, n mean±SD

30 84.3±13.1

mean±SD

122.1±25.3

Post-ETT Delivery Diastolic BP, n mean±SD

11.6±2.3

Post-ETT Delivery SpO2, n

96.7±16.4

Post-ETT Delivery EtCO2, n

PACU Systolic BP, n

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PACU Diastolic BP, n mean±SD

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38.4±5.8 30

71.1±12.7 30

126.2±14.2 30 71.1±10.4 30 17.7±6.8

PACU SpO2, n

30

mean±SD

98.1±4.2

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PACU RR, n

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mean±SD

mean±SD

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mean±SD

PACU HR, n

28

77.1±15.8

Post-ETT Delivery RR, n

mean±SD

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Post-ETT Delivery Systolic BP, n

SD, standard deviation; BP, blood pressure; ETT, endotracheal tube; PACU, post-anesthesia care unit.

ACCEPTED MANUSCRIPT Table 4. Time required for laryngoscopy and intubation with the AirSPACE™.

No. of Patients

Action

Mean Duration ± SD, seconds

Direct

27 26 26

Time for optimal view Time for first CO2 waveform Total intubation time

17.9 ± 12.6 41.0 ± 22.5 58.8 ± 30.1

Indirect

3 3 3

Time for optimal view Time for first CO2 waveform Total intubation time

36.2 ± 16.1 56.6 ± 10.9 92.8 ± 9.3

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ACCEPTED MANUSCRIPT Table 5. Numerical rating scale scores and subjective assessments after utilizing the AirSPACE™.

14 (46.7) 13 (43.3) 2 (6.7) 0 (0) 1 (3.3)

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13 (43.3) 11 (36.7) 5 (16.7) 0 (0) 1 (3.3)

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Difficulty of Laryngoscopy (n=30) 1=Very Easy 2=Easy 3=Slight Resistance 4=Difficult 5=Not Possible Difficulty of Intubation (n=30) 1=Very Easy 2=Easy 3=Slight Resistance 4=Difficult 5=Not Possible AirSPACE™ Device Ease of Use (n=30) 0=Very Easy 1=Somewhat Easy 2=Somewhat Difficult 3=Very Difficult 4=Failed Laryngeal View during Passage of ETT (n=30) Complete Partial Obstructed

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Frequency, n (%)

Type of Airway Procedure

22 (73.3) 7 (23.3) 1 (3.4)

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ETT, endotracheal tube.

5 (16.7) 21 (70.0) 3 (10.0) 0 (0) 1 (3.3)

ACCEPTED MANUSCRIPT

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Figure 1. The AirSPACE™.

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(a) The AirSPACE™.

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(b) The AirSPACE™ installed and attached onto a surgical table.

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Figure 2. Fully assembled AirSPACE™ along with disposable surgical table cover and patient headrest.

ACCEPTED MANUSCRIPT Figure 3. AirSPACE™ disposables – (1) foam head donut (headrest), (2) 15° head wedge, and (3) impermeable

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protective cover (for both the AirSPACE™ device and surgical table).

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Figure 4. Mechanical movement and operation of the AirSPACE™ device.

The AirSPACE™ device, in a raised position, via fourbutton pendant remote that controls two actuators; one actuator raises and lowers the head lift (shown).

The AirSPACE™ device being angled via four-button pendant remote that controls two actuators; one actuator increases or decreases the angle of the headrest/headlift (shown).

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(a)

(b)

(c)

The head slide (black platform with lever and headrest pins) and slide rail of the AirSPACE™ device in the unlocked position; providing easy and smooth flexion and extension of the patient's head during laryngoscopy.

ACCEPTED MANUSCRIPT Figure 5. Initial C-L airway grade views when comparing laryngoscopy (direct versus indirect).

Initial C-L Airway Grade Views with Direct or Indirect Laryngoscopy 16 Direct 14

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10 8 6

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4 2 I (50%)

IIa (16.67%)

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0 IIb (23.33%)

III (6.67%)

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Initial C-L Airway View Grade

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Number of Patients

Indirect

12

IV (3.33%)

ACCEPTED MANUSCRIPT Highlights Patient positioning is critical in establishing a patent airway

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Proper head and neck positioning can optimize one’s laryngeal view

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The “sniffing” position has been the traditional method for direct laryngoscopy

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The AirSPACE™ device facilitates patient positioning via mechanical capabilities

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The AirSPACE™ device provides ‘real-time’ airway manipulation during laryngoscopy

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•