Expert calls for sparing oxygen use for dyspnea in the emergency department

PARIS – Oxygen therapy is used too often in patients with respiratory difficulties, says one expert, and should be given only 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 Dr. 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 Dr. 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 Dr. Negrello. The aim is to maintain normal oxygen levels, with SpO₂ between 92% and 96%.