Normobaric oxygen therapy involves breathing oxygen at concentrations higher than ambient air, but at normal atmospheric pressure. This medical treatment is distinct from other forms of oxygen delivery because it does not require increased atmospheric pressure.
Defining Normobaric Oxygen Therapy
Normobaric oxygen therapy refers to the medical practice of delivering oxygen at a concentration greater than the approximately 21% found in normal air, while maintaining standard atmospheric pressure, typically around 1.0 atmosphere absolute (ATA). This distinguishes it from hyperbaric oxygen therapy, which involves increased pressure in a specialized chamber. Patients typically inhale near-pure oxygen, often approaching 100% concentration, through devices like a nasal cannula or a face mask. It is often recognized as “home oxygen therapy” by some health systems, highlighting its accessibility and use outside of specialized chambers.
Mechanism of Action
Increasing the inspired oxygen concentration during normobaric oxygen therapy raises the partial pressure of oxygen in the alveoli. This elevated partial pressure drives more oxygen to dissolve directly into the blood plasma, in addition to what is bound to hemoglobin. While hemoglobin’s oxygen-binding capacity is limited, the increased dissolved oxygen in the plasma significantly enhances overall oxygen delivery to tissues throughout the body. This improved oxygen supply supports cellular metabolism.
By reducing tissue hypoxia, normobaric oxygen therapy can aid in various physiological responses, such as mitigating inflammation and supporting wound healing. The elevation of interstitial partial pressure of oxygen in arterial blood, particularly in brain tissue, contributes to its neuroprotective effects in conditions like acute ischemic stroke.
Conditions Treated
Normobaric oxygen therapy serves as a supportive treatment for several medical conditions where enhanced oxygen delivery is beneficial. It is frequently used for individuals who require more oxygen due to respiratory issues, such as chronic obstructive pulmonary disease (COPD) exacerbations, severe asthma, cystic fibrosis, and pulmonary hypertension. The therapy is also applied in acute situations like carbon monoxide toxicity, where it helps to displace carbon monoxide from hemoglobin, allowing oxygen to bind more effectively.
Normobaric oxygen therapy can also be a supportive measure in acute ischemic events, such as stroke or myocardial infarction, protecting oxygen-deprived tissues. In cases of acute ischemic stroke, normobaric hyperoxia has shown protective effects on the penumbra, the area of brain tissue surrounding an ischemic core that is at risk of infarction. It has also been explored as a potential treatment for chronic cerebral circulation insufficiency, increasing oxygen content in ischemic-hypoxic brain tissue. Furthermore, it is used to manage cluster headaches and can help maintain adequate oxygen levels during the administration of inhaled anesthetics.
Treatment Experience and Safety
During a normobaric oxygen therapy session, a patient typically receives oxygen through a nasal cannula or an oxygen mask. The oxygen is often delivered from an oxygen concentrator, which can be placed near the patient, even in a home setting. Sessions can vary in duration, ranging from short periods to several hours, depending on the specific medical condition. For example, some protocols might involve 45-minute sessions performed twice a day.
While normobaric oxygen therapy is generally considered safe, certain safety considerations are observed. Minor side effects can include nasal dryness or irritation, which may occur if humidification is not used. Although rare, more serious complications like oxygen toxicity are possible with prolonged high-concentration use, which can potentially lead to lung damage or, in predisposed individuals, respiratory failure. Contraindications or situations requiring caution include certain types of lung diseases, a collapsed lung, or having a cold or fever.