INTRODUCTION

Delivering artificial ventilation to patients who are unconscious and not breathing through a face mask is a fundamental skill in airway management. However, this procedure can be challenging. Obstructions in the upper airway can occur at various points, such as the nostrils, soft palate, lips, base of the tongue, tonsillar pillars, epiglottis, velopharynx, or even the vocal cords. This difficulty increases in obese patients or those with thick, muscular necks. The main goal of mask ventilation for patients under general anesthesia is to keep the airway open and ensure proper oxygenation. When traditional mask ventilation proves difficult, various alternative techniques have been developed. One such method is the conventional thenar eminence technique. In the conventional thenar eminence technique, pressure is applied downward using the thenar eminences of both hands, while the fingers pull the jaw upward towards the mask ⁽¹⁾. This upward motion can cause the mouth to close, obstructing the airway at the oropharynx. The modified thenar eminence technique addresses this issue by combining an upward force at the chin with a forward and downward motion of the mandible, which helps open both the mouth and oropharynx.

So, in this crossover study we will compare two methods of mask ventilation and their efficacy in maintaining upper airway patency during mask ventilation assessed by expired tidal volume (VTE), peak airway pressure (P_MAX) and EtCO₂ in unanticipated difficult airway in unconscious apneic patients during induction of general anesthesia.

STUDY HYPOTHESIS

We hypothesize that the modified thenar eminence technique of mask ventilation can be superior to the conventional thenar eminence technique in terms of expired tidal volume (VT_E), peak airway pressure (P_max), EtCO₂ in unanticipated difficult airway in unconscious apneic patients during induction of general anesthesia.

AIMS AND OBJECTIVES

AIMS:

This prospective, randomized, double blinded crossover study will be undertaken to compare the modified thenar eminence technique of mask ventilation and conventional thenar eminence technique in unconscious apneic patients during induction of general anesthesia.

PRIMARY OBJECTIVE:

· To compare the expired tidal volume (VT_E) between the two techniques

SECONDARY OBJECTIVES

· To assess the Peak airway pressure (P_MAX)

· To assess EtCO₂ 

Sample size: The sample size is calculated using the Open epi software version 3 using the parameter “Expired tidal volume” from the reference study ^[1]. The sample size ratio is 1, assuming a power of 95% with 99% confidence interval and the difference in mean is 57, with standard deviations of 50 and 55, the sample size for each group is 31. Considering attrition rate of 10% dropout a total of 35 patients per group will be required, so a total of 70 patients will be in this study. 

Materials and Methodology

Following the Institutional Ethics Committee approval,

 registration in clinical trial and obtaining written & informed consent of patient’s relatives’ study will be done.

Conventional Thenar Eminence Technique

Patients are placed in a supine position with their head in a neutral or slightly extended "sniffing" position to align the laryngeal, pharyngeal, and oral axis. Following anaesthesia induction, an appropriately sized mask that covers the patient’s nose and mouth without extending over the chin is selected. The thenar eminence of both hands is placed on the inferior border of the mask, with the index, middle, and little fingers positioned along the sides of the mask and the thumb on the upper part. Downward pressure is applied using the thenar eminence and fingers to create a tight seal.

Modified Thenar Eminence Technique

For the modified thenar eminence technique, the patient’s head and neck are positioned similarly to the conventional technique. Following anaesthesia induction, the anaesthesiologist extends the patient’s head. The jaw thrust is applied using the four fingers of both hands, and the mouth is opened using both thumbs placed over the lower jaw. The assistant then places the mask over the face while maintaining the mouth in the open position. The anaesthesiologist applies pressure using the thenar eminence of both hands to achieve a tight seal.

Study Procedure

Eligible patients undergoing elective surgery under general anaesthesia will be selected after obtaining informed and written consent. In the operating theatre, standard ASA monitors, including pulse oximetry (SpO₂), electrocardiogram (ECG), end-tidal carbon dioxide (EtCO₂), and non-invasive blood pressure (NIBP) monitors, will be established. Premedication includes Inj. Glycopyrrolate (0.004 mg/kg IV), Inj. Ondansetron (0.15 mg/kg IV), and Inj. Fentanyl (2 µg/kg IV). A clear, transparent disposable plastic face mask of size 3 or 4 with a high-volume and low-pressure cuff is used. Patients will be preoxygenated for three minutes with 100% oxygen using closed circuit. General anaesthesia will be induced with 2-3 mg/kg of Inj. Propofol until the loss of eyelid reflexes, and muscle paralysis is achieved with vecuronium (80-100 µg/kg).

Randomization will be done by computer generated number. Allocation concealment will be done using opaque envelopes to randomize patients into two groups.

Group M: Patients receives mask ventilation using the modified thenar eminence technique first, followed by the conventional technique.

Group C: Patients receives the conventional thenar eminence technique first, followed by the modified thenar eminence technique.

The attending anaesthesiologist will provide mask ventilation for three minutes without additional positive end-expiratory pressure. The ventilator will be set to deliver 8 ml/kg tidal volume at a rate of 12 breaths per minute in volume control mode. The expired tidal volume (VT_E) will be stabilized during the first few breaths, after which study parameters will be recorded for five consecutive breaths. The attending anesthesiology resident will be blinded to the ventilator data but has access to the monitor displaying vitals and capnography. 

Data collection includes expired tidal volume (VT_E), peak airway pressure (P_MAX), and EtCO₂.Another anaesthesiology resident records the ventilator data and auscultates over the patient’s epigastrium to detect gastric insufflation. Any audible leak around the mask will be noted. If the patient could not be ventilated with either of the technique or if oxygen saturation (SpO2) drops below 88% or the patient becomes hemodynamically unstable, the protocol calls for immediate action. An appropriately sized Igel will be inserted to secure the airway. If Igel is inserted, the study will be aborted, and efforts will shift toward stabilizing the patient. This protocol ensures that patient safety is prioritized, with clear guidelines on when to intervene.

Once the study is successfully completed, an endotracheal tube (ETT) will be inserted for more secure airway management during the surgery. Maintenance of anesthesia with Inj. Vecuronium (10-15 µg/kg) (Intermittent dose), Oxygen + Sevoflurane. The surgery will be started and intraoperative monitoring of hemodynamic parameters like HR, BP (SBP, DBP, MAP), monitored throughout the procedure and documented. 

After completion of procedure, thorough oral and endotracheal suction will be done and Inj.  Glycopyrrolate 0.008mg/kg IV, Inj. Neostigmine 0.05 mg/kg IV, for reversal will be given, cuff deflated, endotracheal tube will be removed when the patient has fully established protective airway reflexes with adequate tidal volume, adequate muscle tone/power, hemodynamic stability and patient starts following verbal commands. Patient will be shifted to post anesthesia care unit for observation.  

STUDY END POINT

The study will end in 15 to 20 minutes once the patient is intubated and put on control mode of mechanical ventilation.