PARIS — Oxygen therapy is used too often in patients with respiratory difficulties, says one expert, and should only be given when oxygen saturation levels (SpO2) drop below 93%, as per the current guidelines. Florian Negrello, MD, an emergency medicine specialist at University Hospital of Martinique in Fort-de-France, reiterated this message at the 2023 conference held by France's emergency medicine society (Urgences 2023). The recommendation is intended to prevent hyperoxia; increasing evidence indicates the harmful effects of such a state on the body.
"This is a real problem. Oxygen therapy is given all too readily despite studies now showing that excess oxygen is harmful, especially in patients with head trauma, ischemic stroke, or cardiac arrest," stated the session's moderator, Patrick Plaisance, MD, PhD, a doctor at Lariboisière Hospital in Paris.
No Proven Hypoxia
Described as difficulty breathing or shortness of breath, dyspnea is common in the emergency department, occurring in 5%-9% of patients. Close to 20% of intensive care unit admissions involve patients with dyspnea. "Since this is a very subjective symptom, it's possible it's being underdiagnosed," said Negrello.
Lower respiratory tract infection, acute heart failure, chronic obstructive pulmonary disease, and exacerbation of asthma are the four main diagnoses linked to dyspnea, but this symptom is also seen in several medical conditions (gastrointestinal, metabolic, neurologic, etc.), he noted.
Often seen as a harmless treatment option, oxygen therapy is commonly administered to patients with breathing difficulties even when no hypoxemia is documented. This is particularly the case for patients brought into hospital via ambulance who are treated with oxygen without even having had their blood oxygen levels, SpO2, and partial pressure of oxygen checked.
In the United States, one of the few studies published on the topic showed that one third of patients transported via ambulance are put on oxygen, with SpO2 being measured in just 5% of these cases. Finally, just 17% of patients receiving oxygen were experiencing hypoxia, defined as SpO2 < 94%.
Oxidative Stress
Recently, several research studies have revealed the potential dangers of unjustified use of oxygen, which can lead to hyperoxia and increased mortality in hospitalized patients.
A meta-analysis reported a linear relationship between severe hyperoxia, in-hospital mortality, and length of stay in intensive care. Another study revealed a greater mortality rate in patients with acute respiratory distress syndrome (ARDS) experiencing an episode of hyperoxia, regardless of the severity of ARDS.
Oxygen toxicity in intensive care is said to be linked to oxidative stress caused by increased growth of reactive oxygen species but also to the systemic inflammation caused by hyperoxia, explained Negrello. Excess oxygen may also cause lung lesions with necrosis, the severity of which is proportional to the fraction of inspired oxygen and the length of exposure.
According to the most up-to-date international recommendations published in 2018 on the use of oxygen therapy in treating acute conditions, oxygen should not be used when SpO2 ≥ 93%. When treatment has been started, it must be stopped when SpO2 reaches 96%. SpO2 cannot be maintained above 96%, according to experts.
These threshold values can be found in the COVID-19 treatment guidelines produced by the French-Language Society of Respiratory Medicine, with oxygen therapy being recommended when SpO2 < 92%, added Negrello. The aim is to maintain normal oxygen levels, with SpO2 between 92% and 96%.
Use Sparingly
For patients with COPD, the target levels are lower, due to the risk of hypercapnia (higher than normal carbon dioxide levels in the blood). Oxygen saturation levels should then be kept between 88% and 92%, "by using the minimum amount of oxygen necessary," per the guidelines.
"Oxygen should be used sparingly," concluded Negrello. "To treat our patients without harming them, we must be able to use it at the right time, meaning when a patient really has low blood oxygen, by focusing on normal saturation levels as the end goal."
SpO2 measurement is the first step to be taken to determine oxygen requirements, followed by, if necessary, blood gas analysis once the patient has been admitted, he explained.
Questioned at the end of his session on how long oxygen therapy can be given for, Negrello reiterated that the risk for death is correlated with the length of time spent in a state of hyperoxia but that it is difficult to establish a maximum timeframe to be adhered to strictly.
Given that excess oxygen is harmful to patients in intensive care, "it would be better, when in doubt, to focus on physiological levels" and simply stop treatment when target saturation levels are reached.
This article was translated from the Medscape French Edition.
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