Effect of nasal mask versus face mask ventilation on mean air leak in class 2 and class 3 obese adult patients undergoing elective surgery under general anaesthesia: a randomised controlled study

Participant Selection

After a thorough pre-anaesthetic evaluation and confirmation of eligibility based on inclusion and exclusion criteria, participants will be randomly allocated to one of two groups:

• Group A: Nasal mask ventilation
• Group B: Face mask ventilation

Randomization will be performed using a computer-generated list and concealed using sequentially numbered opaque sealed envelopes. Participants will receive detailed study information, and written informed consent will be obtained.

Preoperative Preparation

• Standard airway assessment including a focused airway examination (line of sight method) will be documented.
• Adjusted body weight (AjBW) will be calculated to guide tidal volume settings.
• Nil per oral (NPO) status will be maintained as per standard guidelines.
• Standard ASA monitoring will be attached upon arrival in the operating room.
• Gastric ultrasound will be performed pre-induction to assess baseline gastric residual volume.

Participants will be positioned using a ramped position (RAMP) to align the external auditory meatus with the sternal notch.

Preoxygenation with 100% oxygen at 10 L/min will be performed for 3 minutes.

Anaesthesia Induction

• Intravenous fentanyl (2 mcg/kg) and propofol (2–2.5 mg/kg) will be administered.
• An appropriately sized nasopharyngeal airway will be inserted post-induction.
• Once mask ventilation is confirmed, muscle relaxant will be administered for neuromuscular blockade.

Ventilation Settings

Ventilation will be performed in volume-controlled ventilation(VCV) mode with the following settings:

• Fresh gas flow: 10 L/min
• Tidal volume: 7 mL/kg of adjusted body weight
• Respiratory rate: 10 breaths/min
• Pressure limit: 40 cmH2O

Data Collection

After 3 minutes of ventilation, the following parameters will be recorded for 10 consecutive breaths, and the mean of the last 5 breaths will be analyzed:

• Set tidal volume (mL)
• Expired tidal volume (VtE) (mL)
• Air leak volume (set tidal volume – expired tidal volume) (mL)
• Peak inspiratory pressure (PIP) (cmH2O)
• Plateau pressure (PPLAT) (cmH2O)
• Oxygen saturation (SpO2) (%)
• End-tidal carbon dioxide (EtCO2) (mmHg)

Post-ventilation gastric ultrasound will be performed to assess residual volume. The difference between pre- and post-bag-mask ventilation gastric residual volumes will be recorded.

Criteria for Inadequate Ventilation

Ventilation will be considered inadequate if any of the following occur:

• No visible chest rise
• EtCO2 < 20 mmHg with low amplitude on capnography for three consecutive breaths

In cases of inadequate ventilation, airway adjuncts will be employed, and the patient will be excluded from the analysis.

Outcomes and Comparisons

The following parameters will be compared between Group A and Group B:

• Set tidal volume (mL)
• Expired tidal volume (mL)
• Air leak (mL)
• Leak fraction
• Peak inspiratory pressure (cmH2O)
• End-tidal carbon dioxide (mmHg)
• Oxygen saturation (%)
• Plateau pressure (cmH2O)
• Difference in gastric residual volume before and after bag-mask ventilation (mL)