Too Much Oxygen?
This month, JEMS readers respond to an article published in the May issue, “Apneic Oxygenation: Why & how to give a non-breathing patient oxygen.” Prior to authoring the article, Joshua Sappenfield, MD, was once a skeptic of the technique, and the article presents the findings of his own investigation into its effectiveness. Response from readers has been mixed. Some have embraced apneic oxygenation, while others remain skeptical. Sappenfield responds to readers’ concerns.
We started using this technique approximately six months ago and have had great success. It’s not always needed … but it’s hard to predict when it will be needed (e.g., difficult intubation) so it’s great to use every time and only need it a small portion of the time.
EtCO2 guides ventilation; SpO2 guides oxygenation.
We use this technique in our rapid sequence intubation protocol, and anecdotal evidence suggests that the time to desaturation less than 93% has been greatly increased. In fact, I have not experienced a single desaturation less than 95% since adoption of apneic oxygneation via nasal cannula. It’s a great tool for rapid sequence intubation.
I wonder if this would have any benefit to cardiac arrests? If it was able to aid oxygenation, resulting in reduced ventilation then it may be some help.
Is there any research done in this area?
Aren't studies showing that we actually over oxygenate our patients, specifically during cardiac arrest?
Author Joshua Sappenfield, MD, responds: Concern has been expressed that critically ill patients may have received damage from high concentrations of inspired oxygen. One recent study has defined the breadth of the issue as well as highlighted the lack of definitive evidence of the optimal concentration for oxygen delivery.(1) The high levels of oxygen may cause reabsorption atelectasis, increase oxidative stress and worsen reperfusion injury. One of the researchers’ conclusions is that “high fractional inspired concentrations of oxygen cause pulmonary damage, possibly more so in patients with injured lungs, but this damage is difficult to identify clinically and knowledge of safety thresholds for oxygen administration are unclear.”(1)
In another systematic review, the authors found three times as many patients died in the group that received oxygen after a myocardial infarction. However, the number of deaths wasn’t statistically significant and the authors stated that this may be a chance finding.(2) A prospective randomized control trial is currently underway to further elucidate whether oxygen therapy really is detrimental after a myocardial infarction.(3)
Apneic oxygenation is different because it’s used for a short period of time before a definitive airway can be established. This is a scenario where patients may be at high risk of becoming hypoxic. This short time period limits the amount of harm that can come from high concentrations of oxygen. It is recommended that a provider use a high concentration of oxygen to pre-oxygenate if they’re performing a rapid sequence induction.(4) Additional indications include patients who have decreased functional residual capacity, are at risk for regurgitation, have higher oxygen consumption, or may be difficult to mask or intubate.(4) Reasons to pre-oxygenate every patient include the high rate of observed oxygen desaturation in healthy patients and the difficulty in predicting when complications may occur.(4) The use of high concentrations of oxygen with apneic oxygenation prevents harm to the patient by extending the time it takes for the patient to become hypoxic and require ventilation. After an advanced airway is in place, the fraction of inspired oxygen should be titrated down based on pulse oximetry and arterial blood gas samples.
1. Martin DS, Grocott MP. Oxygen therapy in critical illness: precise control of arterial oxygenation and permissive hypoxemia. Crit Care Med. 2013;41(2):423–432.
2. Cabello JB, Burls A, Emparanza JI, et al. Oxygen therapy for acute myocardial infarction. Cochrane Database Syst Rev. 2010;(6):CD007160.
3. Stub D, Smith K, Bernard S, et al. A randomized controlled trial of oxygen therapy in acute myocardial infarction. Air vs. oxygen in myocardial infarction study (AVOID Study). Am Heart J. 2012;163(3):339–345.
4. Tanoubi I. Oxygenation before anesthesia (pre-oxygenation) in adults. Anesthesiology Rounds. 2006;5(3):1–6.