A Randomized Controlled SaCo-VLM Trial

Background and Rationale

Supraglottic airway devices (SADs), including laryngeal mask airways (LMAs), are widely used for airway management during general anaesthesia. Conventional placement is usually confirmed through indirect assessments, including capnography, bilateral chest movement, absence of audible air leakage, and acceptable oropharyngeal leak pressure (OLP). Although these assessments indicate adequate ventilation and airway seal, they do not directly demonstrate anatomical alignment between the airway device and the glottic opening.

Previous fibreoptic and video-assisted studies have demonstrated that some supraglottic airway devices may be anatomically malpositioned despite meeting conventional placement criteria. Malposition may involve partial obstruction of the airway opening by surrounding structures or misalignment of the device with the glottis. Such abnormalities may remain undetected when ventilation is initially adequate.

Changes in head and neck position during surgery may further influence airway device alignment and performance. Neck rotation, extension, and flexion can alter the relationship between the supraglottic airway device and surrounding anatomical structures, potentially affecting airway seal pressure and ventilation.

The SaCo Video Laryngeal Mask Airway (SaCoVLM) incorporates a built-in camera that enables real-time visualisation of the glottis during and after insertion. This allows the anaesthetist to adjust the device's depth, rotation, or position based on direct visual feedback.

Although previous studies have investigated SaCoVLM placement and visual optimisation, limited evidence is available regarding whether video-adjusted insertion provides more stable anatomical positioning than conventional blind insertion when subsequent head and neck movements occur.

This study is designed to address this knowledge gap by comparing two insertion techniques using the same video-enabled airway device, thereby minimising confounding caused by differences in device design.

Study Design and Methodology

This is a prospective, single-centre, two-arm, parallel-group randomised controlled trial conducted at Universiti Malaya Medical Centre, Kuala Lumpur, Malaysia.

Participants will be randomly allocated in a 1:1 ratio to either video-adjusted insertion or conventional blinded insertion of the SaCoVLM. Randomisation will use a computer-generated sequence with permuted blocks of six. Group allocation will be concealed using sequentially numbered, opaque, sealed envelopes prepared by an independent research team member.

The same SaCoVLM device will be used in both groups. The only intended difference between groups is whether the anaesthetist can use the built-in video display to optimise device positioning during insertion.

In the video-adjusted group, the anaesthetist will view the built-in camera display during insertion and perform gentle positional adjustments to achieve an optimal glottic view.

In the conventional blinded group, the video display will be physically covered from the inserting anaesthetist. Placement will be performed using conventional insertion techniques and confirmed using standard clinical assessments without visual guidance.

All insertions will be performed by anaesthetists with more than five years of anaesthesia experience. Standardised general anaesthesia and intraoperative monitoring will be applied to both groups.

The inserting anaesthetist cannot be blinded because of the nature of the intervention. However, participants, postoperative assessment staff, and the independent assessor responsible for grading recorded glottic views will be blinded to group allocation.

Standardised Head and Neck Positioning

Following successful device insertion and confirmation using conventional placement criteria, each participant will undergo airway assessment in four standardised head and neck positions:

• T0: Neutral supine position (reference).
• T1: 45-degree lateral neck rotation.
• T2: 45-degree neck extension.
• T3: 30-degree neck flexion.

The angles will be standardised using a goniometer.

At each position, the glottic view will be recorded using the SaCoVLM camera, and OLP will be measured to assess the effectiveness of the airway seal.

In the conventional blinded group, the video display will remain concealed from the inserting anaesthetist, while images will be recorded for subsequent independent assessment.

Glottic exposure will be assessed using the four-grade SaCoVLM classification system. Grades 1 and 2 represent distorted or partially obscured views of the glottic opening, while grades 3 and 4 represent satisfactory glottic visualisation.

After completion of the positioning assessments, the participant will be returned to the neutral supine position for maintenance of general anaesthesia.

Clinical Assessments and Safety Monitoring

The study will also examine procedural efficiency, airway seal performance, physiological responses to insertion, and postoperative airway-related symptoms.

Insertion efficiency will be assessed through insertion time, number of attempts, and time required to confirm satisfactory device placement.

Heart rate and mean arterial pressure will be documented around the time of insertion. Participants will undergo postoperative assessment approximately one hour after surgery for airway-related symptoms, including coughing, sore throat, hoarseness, difficulty swallowing, and evidence of minor airway trauma.

All participants will receive standard intraoperative monitoring, including electrocardiography, non-invasive blood pressure measurement, pulse oximetry, capnography, and anaesthetic agent monitoring.

Device cuff pressure will be maintained at or below 60 cmH2O. Any clinically significant airway obstruction, inadequate ventilation, oxygen desaturation, or other airway complication will be managed promptly according to established clinical practice, including conversion to endotracheal intubation when indicated.

An independent Data and Safety Monitoring Board will oversee an interim assessment for safety and futility after approximately 50% of participants have been recruited.

Statistical Analysis

The primary analysis will follow the intention-to-treat principle, with a per-protocol sensitivity analysis.

Because glottic visualisation and OLP are repeatedly assessed within individual participants across different head and neck positions, mixed-effects statistical models will be used to account for correlations between repeated measurements.

The incidence of distorted glottic views will be analysed using a generalised linear mixed-effects model with a binomial distribution and logit link function. Study group, head and neck position, and their interaction will be included as fixed effects, with random intercepts for participants and inserting operators.

The interaction between study group and head and neck position will determine whether changes in glottic visualisation associated with repositioning differ between video-adjusted and conventional insertion techniques.

OLP will be analysed using a linear mixed-effects model with a similar structure.

Other continuous and categorical outcomes will be compared using appropriate parametric or non-parametric statistical tests. Secondary analyses will be considered exploratory.

All analyses will use two-sided statistical testing with a significance threshold of p < 0.05.

Clinical Significance

This study aims to determine whether real-time video-guided adjustment of a supraglottic airway device provides an anatomical positioning advantage over conventional blind insertion, particularly when the head and neck are subsequently repositioned.

If video-adjusted insertion reduces the occurrence of distorted glottic views, the findings may support the incorporation of direct visual assessment into routine supraglottic airway placement, especially during procedures involving head and neck movement.

Alternatively, if both insertion techniques demonstrate comparable performance, the findings may provide evidence supporting the continued use of conventional insertion and confirmation techniques.

The results are expected to improve understanding of the relationship between anatomical device positioning, airway seal performance, and conventional clinical placement assessments. This may contribute to future research and recommendations concerning airway management during general anaesthesia.