Effectiveness of Facial Mask NIV in Adults Under General Anesthesia: Two-Hand C-E vs V-E Techniques

Effectiveness of Facial Mask Non-Invasive Ventilation in Adults Under General Anesthesia: Two-Hand C-E vs V-E Techniques. A Double-Blind Randomized Trial

This study aims to compare two different ways doctors hold a face mask to help the participant breathe during general anesthesia. The investigators are evaluating which method, the "C-E" or the "V-E" technique, works best.

If the participant chooses to take part, on the day of surgery, after anesthesia has been administered and the participant is asleep, the doctor will use one of these two mask-holding techniques to assist breathing for a short period. The investigators will measure how effectively the participant is breathing, check carbon dioxide levels, and record the doctors' assessment of how easy and comfortable each technique was for them. This study will not alter any other aspect of the surgery or recovery.

Airway management is a routine part of an anesthesiologist's work when subjecting patients to different degrees of sedation, eventually reaching general anesthesia. It is also crucial in emergency care, where general practitioners, emergency physicians, and prehospital care technicians/technologists (APH) manage the airway, each with varying degrees of training and experience. In these scenarios, the doctor or APH provider will determine whether to maintain the airway using invasive or non-invasive methods to achieve proper ventilation. Factors such as patient characteristics, which may predict difficult mask ventilation combined with difficult laryngoscopy, include: Mallampati classification III or IV, obesity (BMI over 30 kg/m²), presence of teeth, history of obstructive sleep apnea, short thyromental distance, limited mandibular protrusion, cervical mass, limited neck extension, presence of a beard, male gender, or age over 46 years.

However, it has been observed that predictions about difficult mask ventilation or difficult intubation only correspond to actual difficult airway scenarios 25% of the time. Furthermore, difficult intubation and difficult mask ventilation were unanticipated in 93% and 94% of cases, respectively. Other factors that influence patient outcomes include the patient's current condition based on the context, such as elective surgery versus an emergency scenario. This can be the same patient at two different times, but the approach may vary depending on the physician's training and experience, whether it is an APH technician/technologist, a general practitioner, an emergency physician, or an anesthesiologist. These decisions are also influenced by the availability of equipment.

Mask ventilation is often considered intuitive, but it has been demonstrated to be difficult to learn and apply in both hospital and prehospital settings . In such scenarios, the face mask should always be available and serves as the initial approach before invasive airway management or rescue if intubation or a supraglottic device fails. Therefore, proper training in face mask ventilation skills, including the two-hand technique, is necessary to improve the seal, mandibular protrusion, and neck extension, targeting the determinants of difficult mask ventilation as defined by the ASA: "The inability to provide adequate ventilation (e.g., confirmed by detection of end-tidal carbon dioxide) due to any of the following: inadequate mask seal, excessive gas leak, or excessive resistance to gas entry or exit".

For two-handed mask ventilation, two techniques have been described: the C-E technique, in which the thumb and index fingers of each hand form a "C" around the mask while the third, fourth, and fifth fingers pull the jaw towards the mask in an "E" shape, and the V-E technique, in which the thumbs and thenar eminence of each hand press against the sides of the mask in a "V" shape while the rest of the fingers perform the "E" jaw traction .

Current evidence points to better performance of the V-E maneuver compared to the C-E maneuver. However, the performance of these maneuvers has not been uniformly evaluated with the use of adjuncts to face mask ventilation, such as the Guedel airway, or in patients under neuromuscular blockade.

Given the lack of scientific evidence, the results of our research would not only impact the work of anesthesiologists but also extend to emergency services and prehospital settings. This would lead to improved patient outcomes by enhancing knowledge of two-hand mask ventilation and raising the quality of care provided to patients

Inclusion Criteria:

• Adult patients over 18 years old
• Scheduled for elective surgery
• Require general anesthesia
• Consent to participate in the study

Exclusion Criteria:

• Presence of predictors of difficult ventilation: presence of a beard, --obstructive sleep apnea/hypopnea syndrome
• Anticipated difficult airway
• Classified as ASA IV or higher
• Oxygen saturation less than 92% upon admission
• Requirement for supplemental oxygen