Questions · High-Flow Nasal Oxygen for Preoxygenation
9 questions, 0 approved. Approve them one at a time — a quiz shows nothing you have not.
Recall — derived from a kept point
A colleague states that high-flow nasal oxygen "ventilates" an apnoeic patient. In one or two sentences, say what high-flow nasal oxygen does and does not do to arterial CO2 during apnoea, and what that means for how you monitor the patient.
Answer: It does not clear carbon dioxide. Arterial CO2 accumulates across a wide range of flow rates, so treat high-flow nasal oxygen as apnoeic oxygenation and monitor CO2 rather than assuming the patient is being ventilated.
Call it apnoeic oxygenation, not ventilation - the oxygen buys you time while the CO2 keeps climbing.
Source claim: High-flow nasal oxygen does not clear carbon dioxide: arterial CO2 accumulates across a wide range of flow rates, so treat it as apnoeic oxygenation and monitor CO2 rather than assuming ventilation.
High-Flow Nasal Oxygenation, Not Ventilation: Time to Stop Holding Our Breath, British journal of anaesthesia 2026
recall · CA-1 · phrased by llm
A systematic review and meta-analysis compared high-flow nasal cannula with standard preoxygenation in obese patients having elective surgery. Name the two outcomes that favoured high-flow nasal cannula, name the outcome that did not improve, and state in one sentence what that pattern means for how you use the technique.
Answer: Safe apnoea time was longer and patients found it more comfortable, but the odds of desaturating below 92% were not reduced. In this pooled analysis high-flow nasal cannula buys time rather than removing the risk of desaturation.
The extra apnoeic time is real, but in this meta-analysis it did not translate into fewer desaturations below 92% - plan as though the patient can still desaturate.
Source claim: In obese patients high-flow nasal cannula lengthened safe apnoea time and was more comfortable, but did not reduce the odds of desaturating below 92% — it buys time rather than removing the risk.
High-Flow Nasal Cannula for Apneic Oxygenation in Obese Patients for Elective Surgery: A Systematic Review and Meta-Analysis, Anesthesia and analgesia 2023
recall · CA-2 · phrased by llm
A randomised trial compared high-flow nasal cannula with non-invasive ventilation for preoxygenating obese patients. Describe how the two techniques compared on end-tidal oxygen, on desaturation below 95%, and on patient comfort, and say which technique the oxygenation endpoints favoured.
Answer: High-flow nasal cannula gave a lower end-tidal oxygen and more desaturation below 95% than non-invasive ventilation (30% versus 12%), although patients found high-flow far more comfortable. The oxygenation endpoints favoured non-invasive ventilation in this trial.
Comfort and oxygenation can point in opposite directions - in this trial the more comfortable technique was the one that desaturated more often.
Source claim: Compared with non-invasive ventilation, preoxygenating obese patients with high-flow nasal cannula gave a lower end-tidal oxygen and more desaturation below 95% (30% versus 12%), although patients found it far more comfortable.
High-Flow Nasal Cannulae Versus Non-Invasive Ventilation for Preoxygenation of Obese Patients: The PREOPTIPOP Randomized Trial, EClinicalMedicine 2019
recall · CA-2 · phrased by llm
A meta-analysis reports that high-flow nasal oxygen achieved a higher PaO2 and about 131 seconds more safe apnoea time than facemask preoxygenation. A resident concludes that high-flow nasal oxygen therefore prevents desaturation during intubation. State whether the cited result supports that conclusion, and explain what the data did and did not show.
Answer: It does not support it. The pooled data showed a higher PaO2 and about 131 seconds more safe apnoea time, but no reduction in desaturation during intubation - the oxygenation and time endpoints improved while the desaturation endpoint did not.
A better surrogate - PaO2, seconds of apnoea - is not the same as fewer desaturations, and here the two came apart.
Source claim: High-flow nasal oxygen achieved a higher PaO2 and about 131 seconds more safe apnoea time than facemask, without reducing desaturation during intubation.
A Comparison of High-Flow Nasal Cannula and Standard Facemask as Pre-Oxygenation Technique for General Anesthesia: A PRISMA-compliant Systemic Review and Meta-Analysis, Medicine 2022
recall · CA-3 · phrased by llm
Median apnoea time in morbidly obese patients reached 18 minutes with either high-flow nasal or low-flow facemask oxygen, but desaturation below ___% was less likely with high flow (hazard ratio 0.27).
Answer: 92
Median apnoea time in morbidly obese patients reached 18 minutes with either high-flow nasal or low-flow facemask oxygen, but desaturation below 92% was less likely with high flow (hazard ratio 0.27).
Apnoeic Oxygenation in Morbid Obesity: A Randomised Controlled Trial Comparing Facemask and High-Flow Nasal Oxygen Delivery · PMID 35027169
recall · CA-1 · phrased by derived
The point with one number taken out. No model wrote any of this: the stem is the sentence you reviewed, minus a digit, and the paper it came from is named beneath it.
Open prompts
Walk me through your setup for this before we start.
open · CA-1 · phrased by derived
What are you watching on the monitor that would tell you this is going wrong?
open · CA-1 · phrased by derived
What is your first move if it does?
open · CA-1 · phrased by derived
What would you want ready in the room before induction?
open · CA-1 · phrased by derived
Questions only — nothing here asserts anything, which is why a model is allowed to phrase them. Where no model was reachable these are the level defaults.