Please select the eligibility criteria that correspond to the clinical trial below.
Title: Evaluation of Oxygenation by 100% Oxygen Via High Flow Nasal Cannula During Apnea in Adult Elective Surgical ENT Patients
Brief Summary: Oxygenation with high-flow nasal cannula with 100% oxygen has only been evaluated in a limited number of studies. Although data are convincing it is of importance to evaluate this new concept in our department before implementing it into clinical practice.

The general purpose of this project is to evaluate a new ventilation strategy during ENT-surgery based on oxygenation with high-flow nasal cannula with 100% oxygen with focus on gas exchange.


Options:
A: Inclusion Criteria:

* Able to provide informed consent.
* Undergoing general anaesthesia .
* Between the ages of 18 and 80 years.
* Body mass index (BMI) greater than 40 Kgm-2.

Exclusion Criteria:

* Unable to give informed consent.
* Significant cardiac history which is defined as current angina, myocardial infarction \<12 months before the date of the procedure.
* Significant peripheral vascular disease defined as claudication on minimal exertion or Ankle-Brachial index of \<0.7, a stroke or a transient ischaemic attack \<12 months before the procedure.
* Presence of significant heart-valve disease or congestive heart failure.
* Significant lower respiratory disease including brittle asthma; chronic obstructive pulmonary disease (GOLD stages 3 or 4).
* Strong predictors of both difficult intubation and difficult facemask ventilation on anaesthetic airway assessment.
* Patient with American Society of Anesthesiologists (ASA) grade of 4 for any reason.
B: Inclusion Criteria:

1. Adult, \>18 years old
2. ENT-surgery where apnea is of benefit for the surgeon (eg. intraoral or laryngeal surgery) and the anesthesia time is \<40 mins.
3. Capable of understanding the study information and sign the written consent.

Exclusion Criteria:

1. ASA\>2
2. NYHA \>2
3. BMI \>30
4. Pregnancy
5. Manifest cardiac failure or coronary disease
6. Neuromuscular disease
C: Inclusion Criteria:

1. Adult patients (18 years and above) requiring endotracheal intubation in the emergency department.
2. Intubation performed by the emergency medicine physician who are post graduate trainee year IV and above. The year IV and above cut off is taken because at this time the trainees have done more than 20 endotracheal intubations. The operators are assessed through direct supervision and confirmation through filing of their procedural log books

Exclusion Criteria:

1. Supervisor or operator feels specific intra-procedural oxygenation technique will be required.
2. Patients presenting with cardiac arrest
3. Pregnant patients (as the patients are at risk of aspiration and high oxygen delivery can have bad outcomes on the fetus)
4. Patients with 'Do not resuscitate' order.
5. Morbidly obese on assessment as such patient may need pre intubation preparation of the head side and more controlled settings.
6. Patient who are shifted from another hospital post intubation
7. Patients with interstitial lung disease or lung tumor
8. Neck trauma (expanding neck hematoma)
9. Neck and Oral cavity cancers, or patients with cancers of the neck and oral cavity who have undergone surgery, post radiation of the neck and oral cavity cancers.
10. Pulse oximetry \<90% in ambient air.
11. Body mass index \> 35kg/m2
D: Inclusion Criteria:

1. Age ≥ 18 years
2. Mechanical ventilation \> 24 hours
3. Signed Informed Consent
4. Successful spontaneous breathing trial
5. PaO2/FiO2 ratio ≤ 300 (or SpO2/FiO2 ratio ≤ 300 if SpO2 is lower than 98%) within 30 min after extubation while breathing through a Venturi mask with a delivered FiO2 of 31%

Exclusion Criteria:

1. Pregnancy
2. Presence of tracheostomy
3. Need for immediate post-extubation Non-Invasive Ventilation (\>3 consecutive failures of the spontaneous breathing trial and/or a PaCO2 \> 45 mmHg before the spontaneous breathing trial, with a respiratory rate ≥ 25/min)

Answer: B