Supplemental O2 Delivery Modalities Steven Zhao May 2016

Objectives Recognize the primary types of oxygen delivery systems used in the hospital Understand the uses and limitations of each system

When do we use supplemental O2? O2, like any other medical therapy, has indications, contraindications, benefits, and risks Need to consider the dose, duration, and route of administration! Start with general overview – why do we use supplemental O2? Emphasize that it should only be ordered when needed for hypoxia. If you walk in the room and patient satting 100% on 2L, try to remove the oxygen! Examples of common mistakes with O2 – giving O2 to people w/ no objective hypoxemia; continuing O2 at higher doses than needed (not downtitrating) Examples of potential adverse effects of O2 – hyperoxygenating COPD pts, drying out mucosa/epistaxis, extra tubing to increase hospital confusion/delirium, etc

How to choose what kind of O2? Simple: nasal canula face mask Intermediate: venturi mask non-rebreather Advanced: high-flow nasal canula bipap O2 Wide range of O2 delivery devices that deliver different amounts of FiO2, and have various other pros/cons Grouped them into simple (unknown exact FiO2), intermediate (known exact FiO2), and advanced (known FiO2 and also has PEEP!)

Simple nasal canula Pros: Simple, readily available Relatively well tolerated Cons: Unknown FiO2 25-45% due to entrainment Can dry out mucus membranes (can add humidifier) Can be very uncomfortable, esp. at high flow rates No good if mouth-breathing most basic of all the modalities. Easy to use, but does not deliver a set FiO2 due to entrainment of room air along with the delivered oxygen.

Simple face mask Pros: Has larger reservoir for higher FiO2 More tolerable at high flow rates compared to NC Cons: Still no precise FiO2 delivery…around 40-60% Cannot drop below 5Lpm and maintain CO2 clearance Interferes with eating, talking, coughing Somewhat dependent on fit to face Simple face mask is really not that much better than NC. Can deliver slightly more FiO2 but still not exact amount. Practically, we rarely use this because if someone can’t tolerate NC they get bumped up to more advanced systems…

Venturi mask (entrainment mask) Pros: Can set precise FiO2 by changing adapter Cons: Similar to face mask, obstructs talking, eating, etc Also dependent on mask fitting This is the first setup that provides a defined/set FiO2 due to the physics of the valves (more entrainment). However it shares many of the same limitations as simple face mask so it doesn’t provide a lot of added benefit

Non-rebreather Pros: (close to) 100% FiO2! Great for RRTs etc Cons: Same problems as other mask devices In theory has 100% FiO2 but there is still some CO2 that is rebreathed Intended for temporary use only! One of the more commonly used devices. Great when you need to bring up sats as fast as possible w/o resorting to intubation etc. The large reservoir in theory prevents inhalation of exhaled/room air so it’s close to 100% FiO2. IMPORTANT: make sure to emphasize that placing someone on NRB is not intended to be long term solution. If someone is hypoxic to the point of requiring NRB they either need more definitive O2 management (NPPV vs intubation etc) or rapid correction of underlying cause of hypoxia (eg diuresis). Should NOT be leaving patients on NRB for more than a few hours without addressing the above

High-flow nasal canula Pros: Comfortable – humidified, warmed air similar to physiologic conditions in naso/oropharynx Can deliver precise, set FiO2 Extremely high flow rates provides low amounts of PEEP Leaves mouth free for talking/eating/coughing Cons: Not immediately available, sometimes limited supply HFNC is the new hot (pun intended) thing in noninvasive oxygen devices. It is a dramatic improvement compared to the previously discussed systems because it is more comfortable, precise, and physiologic. It also represents one of the easiest ways to provide some PEEP for alveolar recruitment. Top-left figure – explain that the canula has a more snug fit in the nares than simple NC, which is more comfortable and helps with PEEP. Top-right figure – note the 3 numbers: can set flow rate (20LPM in this case), FIO2 (40%), and temperature (typically at 37C). Bottom figure – HFNC exists as a bridge between simple O2 and more advanced therapies

High-flow nasal canula (cont’d) Since HFNC is such a new topic, here’s some evidence to support its use compared to simple canula NEJM article – small paper but possible mortality benefit to HFNC compared to face mask and bipap for acute hypoxic resp failure JAMA article – low-risk patients randomized to post-extubation standard oxygen vs HFNC; HFNC decreased rates of reintubation and respiratory failure

Bilevel noninvasive positive pressure ventilation (BiPAP) Pros: Can deliver set FiO2 and PEEP Provides ventilatory support Cons: Can be very uncomfortable Relative contraindication for AMS – risk for aspiration Mask fit very important Will gloss over bipap as NPPV is a whole separate talk by itself. Will also ignore cpap as it is not really used acutely inpatient Big picture for bipap is that it is like having a vent set on pressure support mode, but without the ETT. You set the inspiratory pressure (IPAP), expiratory pressure (EPAP), and FiO2. titrate the FiO2 and EPAP to achieve goal oxygenation, titrate the (IPAP-EPAP) to achieve goal ventilation This is obviously more advanced oxygen delivery but can be useful acutely for someone who is decompensating either as a bridge to or to try to avoid intubation entirely. Also very helpful for someone with significant work of breathing who you’re worried might tire out (though in these circumstances you should be seriously thinking about intubation entirely)

Clinical case 50M presents with dyspnea, productive thick brown sputum x 3d. He is undoctored with a 60 pack-year smoking history. Initial exam shows HR 100 RR 25 BP 120/80 SaO2 85% on RA with diffuse expiratory wheezing. Initial BMP notable for bicarb 35; CXR shows hyperinflation of lungs bilaterally with flattened diaphragms. You make the diagnosis of COPD exacerbation and start appropriate pharmacologic treatments. What supplemental O2, if any, should you place the patient on? Take home point: nasal canula is a great first line choice for supplemental oxygen in most patients. Remember to titrate to goal sat 88-92% if there is evidence of chronic CO2 retention (demonstrated here by baseline metabolic alkalosis).

Clinical case The same patient as above has now been admitted for 4 days and seems to be improving symptomatically. When you walk in to see him today he has 4L NC going with a bedside pulse-ox reading of 98%. What changes, if any, should you be making to his oxygen? Take home point: daily reassessments of oxygen requirements is key to prevent overtreatment and potential for side effects/harms. Try turning off the oxygen flow before you talk to/examine the patient so you can see their saturations on RA

Clinical case The next day, a rapid response is called on that same patient. The nurse reports that the patient had been refusing his nebulizers and steroids earlier. Now, he seems to be having a lot of trouble breathing. When you see him, he is in acute respiratory distress with a RR in the 30s, SaO2 on 10L simple face mask is 85%. Patient is using accessory muscles and has paradoxical abdominal breathing. What initial oxygenation delivery would you ask for? Take home point: In someone with clear evidence of respiratory failure, alternative oxygen systems are merely temporizing measures and intubation needs to be considered. A NRB would be a good choice to acutely improve oxygenation; bipap would also be helpful for this patient’s obstructive disease, but it is not always immediately available.

Clinical case An airway is called and the patient is intubated by anesthesia at bedside, and subsequently transferred to the ICU. Over the next few days, his vent requirements decrease and he just barely passes a SBT. Your attending wants you to extubate the patient. What oxygen delivery system should you have handy post-extubation? Take home point: extubation to bipap is often used in high-risk patients to bridge them over to unsupported breathing. Should also consider HFNC in all low-risk patients post extubation

Summary Modality What you set What you get Notes Simple NC 1-6LPM 25-45% FiO2 Easy, typical first line Simple FM 6-10LPM 40-50% FiO2 Not typically used Venti-mask 4-15LPM, different valves 25-50% FiO2 NRB 10-15LPM ~100% FiO2 Short term rescue therapy HFNC Any FiO2; flow rates up to 60LPM Any FiO2, ? PEEP Excellent longer-term choice, consider in all extubated patients BiPAP Any FiO2, IPAP, EPAP Pressure support ventilation without intubation Last line before intubation Bolded the 4 most commonly used modalities – don’t really use FM or ventimask very much Key points – NC provides variable FiO2, good for basic use but limited. NRB is 100% FiO2 for rapid correction of hypoxia but not good long-term treatment. HFNC is growing in scope, can deliver high FiO2 very comfortably for long periods and provides some PEEP. BiPAP is really close to mechanical ventilation, provides both oxygenation and ventilation support