Welcome to the July 2015 REBELCast, where Swami, Matt, and I are going to talk oxygen. It is important to remember that oxygen is a drug, and just like any drug we prescribe to patients it has potential side effects. Although there is a paucity of clinical trial data to support routine use of supplemental oxygen, most health care providers still put oxygen on patients for possible physiological benefits. So with that introduction today we are going to specifically tackle:
- Topic #1: The AVOID Trial – Supplemental O2 vs Room Air for STEMI
- Topic #2: The FLORALI Trial – High Flow Nasal Cannula (HFNC) for Acute Hypoxemic Respiratory Failure
July 2015 REBELCast Podcast
Topic #1: The Avoid Trial – Supplemental 02 vs Room Air for STEMI
- Question #1: Does the administration of supplemental oxygen benefit patients who are normoxic with ST-Elevation Myocardial Infarction (STEMI)?
- Article #1: Stub D et al. Air Versus Oxygen in ST-Segment Elevation Myocardial Infarction. Circulation May 2015 [epub ahead of print]
- Background #1: The first report for supplemental oxygen for angina was in 1900, and since then, oxygen therapy has been a commonly used treatment of patients with ST-Elevation Myocardial Infarction (STEMI). The reason for this is the belief that supplemental oxygen will increase oxygen delivery to ischemic myocardium and help reduce myocardial injury. This belief is based off lab studies and older clinical trials, but there have been other studies that suggest potential adverse physiologic effects of supplemental oxygen (i.e reduced coronary blood flow, increased coronary vascular resistance, and production of reactive oxygen species) causing vasoconstriction and reperfusion injury. Ultimately, there are no studies evaluating the effects of supplemental oxygen therapy involving STEMI patients who are undergoing percutaneous coronary intervention. Taking all this information together there is a lot of uncertainty over the utility of routine supplemental oxygen therapy in acute myocardial infarction with no clear recommendations in normoxic patients in the most recent American Heart Association (AHA) STEMI guidelines. Despite this most patients with acute STEMI still have supplemental oxygen administered.
- What They Did #1:
- Compare supplemental oxygen therapy (face mask at 8 L/min) vs NO oxygen therapy in normoxic patients with STEMI (if O2 sat fell <94% received 4L/min nasal cannula or facemask 8L/min)
- Multicenter, Prospective, Open Label, Randomized Trial
- Conducted by Ambulance Victoria and 9 Metropolitan Hospitals in Melbourne, Australia
- Individuals involved with the delivery of oxygen therapy pre-hospital and in-hospital were not blinded to treatment, but 6 month follow up coordinator and investigators undertaking data analysis were masked to treatment assignment
- Bottom Line #1: This study does not demonstrate any significant benefit of routine use of supplemental oxygen therapy for reducing myocardial infarct size, improving patient hemodynamics, or alleviating symptoms, but we still need some studies with clinical endpoints before changing practice.
Topic #2: The FLORALI Trial – High Flow Nasal Cannula (HFNC) for Acute Hypoxemic Respiratory Failure
- Question #2: In patients with acute hypoxemic respiratory failure does oxygen through high-flow nasal cannula (HFNC) prevent intubation when compared to standard oxygen delivered through a facemask or non-invasive positive-pressure ventilation?
- Article #2: Frat JP et al. High-Flow Oxygen through Nasal Cannula in Acute Hypoxemic Respiratory Failure. NEJM 2015; 372 (23): 2185 – 96. (25981908)
- Background #2: It is a well-known fact that Non-Invasive Positive Pressure Ventilation (NIPPV) reduces the need for intubation and mortality in patients with acute exacerbations of chronic obstructive pulmonary disease (COPD) or cardiogenic pulmonary edema. The reason for this is a decrease in work of breathing and improvement of gas exchange. On the other hand in patients with acute hypoxemic respiratory failure the use of NIPPV with respect to intubation and mortality are conflicting. Thus far the literature does not conclusively support the use of NIPPV in patients with non-hypercapnic acute hypoxemic respiratory failure. Oxygen through HFNC can produce low levels of positive pressure ventilation due to the high flow rates, which may also decrease physiological dead space. To date, the effect of oxygen through HFNC on mortality and intubation rates of patients admitted to the intensive care unit (ICU) with acute hypoxemic respiratory failure has never been studied until now.
- What They Did #2:
- Prospective, Multicenter, Open-Label, Randomized, Controlled Trial from 23 ICUs in France and Belgium of patients without hypercapnia who had acute hypoxemic respiratory failure
- Patients randomized to HFNC (50LPM & FiO2 of 1.0 at initiation), standard oxygen therapy through a facemask (≥10 LPM), or NIPPV (Pressure-support level to obtain TV of 7 – 10 mL/kg of predicted body weight, Initial PEEP 2 – 10 cmH2O)
- Bottom Line #2: HFNC is non-inferior to NIPPV, in patients with hypoxemic respiratory failure, but further studies are needed to determine whether these initial findings of benefit are practice changing.
For More Details of the above Studies Checkout the July 2015 REBELCast Show Notes
For more on what others thought on these topics checkout:
The AVOID Trial
- Ryan Radecki at EMLit of Note: Oxygen – Friend or Foe?
- Thomas D at ScanCrit: Avoid the Oxygen Reflex
The FLORALI Trial
- Rory Spiegel at EMNerd: The Problem of Thor Bridge
- Steve Mathieu at The Bottom Line: FLORALI – High-Flow Oxygen Through Nasal Cannula in Acute Hypoxemic Respiratory Failure
- Feras Khan at UMEM Educational Pearls: High Flow Nasal Cannula (HFNC) for Hypoxemia
Post Peer Reviewed By: Anand Swaminathan (Twitter: @EMSwami)