Myth Buster: A high FiO2 is protective

So you have a patient come into the emergency room in severe respiratory distress, possibly heart failure, but the SpO2 is normal. In the past it was acceptable to place these patients on a nonrebreather to prevent the patients condition from deteriorating, thus allowing you time to react. This, however, may no longer be acceptable.

I think doctors have gotten much better at not panicking in this regard, as even patients with heart failure, while the used to always get a nonrebreather, that seems to no longer be the case. As with chest pain and any other condition, no oxygen is given unless the SpO2 drops below 94%.

The reasoning for the change was described in an October, 2013, article in Respiratory Care, by Thomas Blakeman.  He said:

According to Downs, the only true indication for prophylactic hyperoxyxgenation is prior to tracheal intubation. Downs furher states that, hypothetically, a patient on FiO2 of 100% and having a PaO2 of 650 m Hg, could drop to 90 mm Hg due to lung function deterioration over a period of 15-20 minutes, but the SpO2 would not drop below 98%. This drop would not be enough to indicate a problem. But over the next 5 minutes the SpO2 wold drop to 92%, alerting the caregiver to investigate. In this scenario the elapsed time until a problem is detected would be 20-25 minutes. If that same patient was on an FiO2 of 30% with a PaO2 of 90 mm Hg and an SpO2 of 99% and experienced the same problem, the SpO2 would decrease to 94% within 10 minutes, alerting caregivers to a problem much earlier. Additionally, if a patient is already receiving FiO2 of 100%, there is no room to increase once a problem is detected."

So, over-oxygenating, a common occurrence in hospitals, may mask an underlying problem, delaying treatment.

References:

1. Blakeman, Thomas C., "Evidence for Oxygen in the Hospitalized Patient: Is more Really the Enemy of Good," Respiratory Care, October, 2013, volume 58, number 10, pages 1679-1693

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Myth Buster: Routine use of oxygen is safe

There is now ample evidence that oxygen is a drug with side effects.  No longer should health care providers administer oxygen under the philosophy "it may not help, but it won't hurt."

Oxygen used to be considered useful, or at least harmless, for any of the following situations, despite lack of evidence it does any good:

• Emergency departments
• Post-anasthesia care units
• Conscious sedation
• Chest pain
• Shortness of breath
• Critical Care Units

ACLS used to recommend 2-4lpm by nasal cannula for chest pain. The idea here is that if a low flow of oxygen to the heart is causing the chest pain, the oxygen "might" help.  

However, there was never any science to show this.  Plus, it makes no sense, because if you are getting an SpO2 reading of 98%, then you know the heart has an ample amount of oxygen.  If it's not getting enough oxygen it's because of a blockage in the coronary arteries, not the supply of oxygen to the heart. 

ACLS currently recommends oxygen only if the SpO2 is less than 94%.  This makes much more sense to me.  

Plus, most hospital-wide oxygenation protocols call for an SpO2 of 90-94%, and even 88% is often acceptable.  This makes sense particularly if you look at the deoxyhemoglobin curve.  

One of the main reasons why it's important not to oxygenate until the SpO2 decreases is that the use of supplemental may mask that an underlying problem may be occurring.  

A patient may have decreased ventilations, but this will not be recognized because the SpO2 is already artificially maintained with supplemental oxygen.  When such a patient is not on oxygen, a dip in SpO2 would be noticed at a routine check, and oxygen could be administered at this time, with appropriate measures being taken to recognize and resolve the underlying cause. 

The new policies make sense, especially when you consider that oxygen is a drug with side effects and an expense. To oxygenate based on a myth that it will help but won't hurt is not good medicine. 

References:

1. Blakeman, Thomas C., "Evidence for Oxygen in the Hospitalized Patient: Is more Really the Enemy of Good," Respiratory Care, October, 2013, volume 58, number 10, pages 1679-1693

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