This randomized controlled study was conducted in Cairo University Hospital after institutional board review approval (N-107-2018) from September 2018 till February 2019. The study was registered before recruitment of the first participant at clinicaltrials.gov registry system on 21 August 2018 (NCT03640442). Written informed consents was obtained from all participants before enrollment. Randomization was achieved using computer-generated sequence. Concealment was achieved using opaque closed envelopes by research assistant who had no further involvement in the study.
The study included: obese female patients (body mass index above 30 kg/m2) aged above 18 years scheduled for any operation under general anesthesia with endotracheal intubation. Patients with facial or neck scars, edentulous patients, patients with unstable cervical spine, patients with limited neck extension and patients with airway masses were excluded.
On arrival to the operating room, airway assessment for the patients was performed (Mallampati score, thyromental distance, mouth opening, and neck extension). Patients received the routine preoperative medications (metoclopramide 10 mg intravenous and ranitidine 50 mg intravenous). Routine monitors was applied (electrocardiogram, non-invasive blood pressure monitor, and pulse oximetry was applied before induction of anesthesia. End-tidal capnography was applied after endotracheal intubation). Before induction of anesthesia, patients were randomized to be initially settled into either ramped group (n=30) or modified ramped group (n=30).
Details of each position
Ramped position: This position was achieved by elevation of the shoulders and the head elevation till achieving alignment of sternal notch and external auditory meatus (as shown in figure 2).
Modified ramped position: This position was achieved using a special pillow (shown in figure 3). The shoulders were elevated, and the head was extended to the most possible range to bring the breasts away from the laryngoscopy.
Anesthesia was induced using propofol (2 mg/kg), atracurium (0.5 mg/kg), and fentanyl (2 mcg/kg). Ventilation was maintained using face mask for 3-4 minutes, then, the endotracheal tube was inserted using proper sized Macintosh blade. If laryngeal visualization was not sufficient in the modified-ramped position group, the head was manually elevated to achieve the ramped position. The position of endotracheal tube was confirmed using capnography. The special pillow was removed after confirming successful intubation.
Incidence of difficult laryngoscopy defined as “failure to insert the laryngoscope in the oral cavity due to large breast with the need to reposition the patient to insert the laryngoscope”. The term “reposition” means: the need to make further elevation of the patient shoulders by the assistant in order to extend the patient neck and to move the breasts away from the handle of the laryngoscope.
Time till complete visualization of the vocal cords: defined as the time from starting to handle the laryngoscope till visualization of the vocal cords.
Time of endotracheal intubation: time from starting to handle the laryngoscope till confirmation of the endotracheal tube position by capnography.
Cormack-Lehane  grade of vocal cord view (with and without cricoid pressure).
Incidence of relatively difficult mask ventilation: defined as the need of high force and/or oral airway insertion for maintenance of adequate mask ventilation.
Number of trials for endotracheal tube insertion.
Incidence of hypoxemia (defined as oxygen saturation less than 90%) during the period starting from induction of anesthesia till insertion of the endotracheal tube
Oxygen saturation every 30 seconds starting from induction of anesthesia till confirmation of the position of endotracheal tube
End-tidal CO2 reading just after insertion of the endotracheal tube.
Incidence of airway trauma (teeth, lips, and tongue trauma)
Our primary outcome was the incidence of difficult laryngoscopy. According to a pilot study, we found that the incidence of difficult laryngoscopy in obese females is 80%. We used G power software (184.108.40.206) to calculate a sample size that detects an absolute risk reduction of 40% in the incidence of difficult laryngoscopy. A total number of 54 patients was calculated to have a study power of 80% and alpha error of 0.05. the number was increased to 60 patients to compensate for dropouts.
SPSS 15 package was used for data analysis. Categorical data were analyzed using Chi square test. Continuous data were analyzed using unpaired t test or Mann Whitney-U test as appropriate. Repeated measures were analyzed using analysis of variance (ANOVA) test for repeated measures. P value of 0.05 or lower is statistically significant.