Avoid Oxygen Desats
Recently we discussed the use of noninvasive ventilation in kids presenting with respiratory distress. Despite enjoying procedures, I do fell good about myself when I have been able to avoid intubating a child.
Unfortunately, that is not always possible and what makes me fell absolutely ill is the sound the monitor makes as the patient’s oxygen saturation drop … accentuated then by the sound of bradycardia… usually, someone needs to check my pulse at that time. I really want to be able to avoid oxygen desats completely!!
So, what can I do to help maximize the rate of uncomplicated success of our pediatric Rapid Sequence Intubation and minimize the chance I will need to change my pants?
Anatomy and Physiology Basics
- Kid’s airways are small in caliber and in length.
- This leads less dead space and low Functional Residual Capacity (FRC).
- This means less of a reservoir for us to fill up with oxygen during preoxygenation.
It gets bigger as they get bigger
- The alveolar surface area increases from 2.8 meters squared at birth to 75 meters squared as an adult.
- Essentially they have less alveoli to back up the diseased / injured alveoli.
They are flexible
- Flexibility is generally an excellent trait to have, but the child’s airway can be too flexible (ie, compressible).
- Be vigilant and ensure that the team is maintaining appropriate positioning.
- Aligning the external auditory canal with the sternal notch is just as vital in kids as in adults.
- Be leery of anyone placing their hands on the patient’s neck.
- Traditional “cricoid” pressure or “BURP” will not only have limited benefit, it can completely compress the flexible airway.
Their engines run hotter than adult’s
- Generally, adults consume oxygen at a rate of ~2-4 ml/kg/min.
- Kids consume oxygen at a rate of ~6-8 ml/kg/min.
So, if they consume it faster and they have less area for you to fill up with 100% FiO2 (lower FRC), than they will have oxygen desats more rapidly. This effect can be exaggerated when dealing with a very sick infant as their metabolic demands may be even higher and their pulmonary reserve even less.
Strategies to help Avoid Oxygen Desats
- Good positioning
- As always, sometimes the most basic step is the most important!
- Take time to personally ensure that the positioning is optimal… don’t rely on others for such an important factor.
- Align external auditory canal with sternal notch.
- Reverse trendelenberg position can also increase time to oxygen desats.
- Nasal +/- oral airways
- Have these ready… but with good positioning you don’t often need them.
- A good jaw thrust (another “basic” maneuver that can be a huge difference maker) can often help displace the tongue.
- No cricoid pressure
- Can’t emphasize this too much. Stop people from crushing the kid’s trachea!
- BUT… do consider using “external laryngeal manipulation”
- You use the “helper’s” hands to move the larynx into view.
- Very helpful for anterior airways (like kids have).
- Fill up the FRC tank with 100% FiO2.
- Don’t cut corners here either.
- Some patients may even require some positive pressure to help get their oxygen sats up (High Flow Nasal Cannula may come in handy).
- Continuous nasal canula oxygenation during apneic period
- Many people refer to this as “high flow nasal cannula.”
- “High flow nasal cannula” actually uses a different instrument other than your traditional nasal cannula.
- It can be used to help prolong safe apneic times and avoid oxygen desats.
- It is also possible to use the traditional nasal cannula with the flow turned up during the intubation.
- What is the right flow rate?
- That is not fully known in kids (particularly since this would vary with age / size.
- Generally somewhere between 5L and 15L.
As always, make your first attempt your best attempt!
Weingart SD, Levitan RM. Preoxygenation and prevention of desaturations during emergency airway management. Ann Emerg Med. EPub Nov 3 2011.
Gausche-Hill M. Presentation at ACEP Advanced Pediatric Assembly 2013: High Flow Nasal Cannula During RSI: Does it Prevent Desaturations?