What is the function of oxygen (O2) in the human body?

From the Guidelines

The primary function of oxygen in the human body is to facilitate cellular respiration, generating energy in the form of ATP, which is essential for various bodily functions, including muscle contraction, nerve signaling, and tissue repair. When we breathe in oxygen, it enters our bloodstream through the lungs and is transported by hemoglobin in red blood cells to all tissues and organs throughout the body 1. Inside cells, oxygen serves as the final electron acceptor in the electron transport chain within mitochondria, enabling the efficient breakdown of glucose and other nutrients to produce energy. This aerobic metabolism produces significantly more ATP than anaerobic processes, providing the energy needed for all bodily functions, including maintaining body temperature. Without adequate oxygen, cells would need to rely on less efficient anaerobic metabolism, which produces less energy and leads to the buildup of lactic acid, causing fatigue and potentially tissue damage.

Some key points to consider when evaluating the function of oxygen in the human body include:

• The importance of maintaining a target saturation range of 94-98% for acutely ill patients, except those at risk of hypercapnic respiratory failure, where a target saturation range of 88-92% should be used 1
• The potential risks of hyperoxia, including direct pulmonary toxicity, coronary vasoconstriction, and decreased cardiac output 1
• The role of oxygen therapy in increasing oxygen delivery to tissues, and the importance of correcting other physiological disturbances, such as low cardiac output and severe anaemia, to optimize oxygen delivery 1
• The complex mechanisms of carbon dioxide retention in patients with chronic obstructive pulmonary disease (COPD) and the importance of targeted lower concentration oxygen therapy to avoid oxygen-induced hypercapnia 1

Overall, the function of oxygen in the human body is critical for maintaining proper bodily functions, and its use should be carefully managed to avoid potential risks and optimize patient outcomes. The goal of oxygen therapy should be to maintain a target saturation range that balances the benefits of oxygenation with the risks of hyperoxia, while also addressing other physiological disturbances that may impact oxygen delivery.

From the Research

Function of Oxygen in the Human Body

• Oxygen is necessary for aerobic metabolism, and the human body cannot produce or store oxygen, requiring a continuous and adequate delivery of oxygen to body tissues via the circulation 2.
• Oxygen molecules must be constantly delivered to all cells throughout the human body and utilized effectively in the process of mitochondrial oxidative phosphorylation, which is necessary for generating energy through the formation of adenosine triphosphate 3.
• The human body has several oxygen-sensing mechanisms for preventing both hypoxia and hyperoxia, ensuring a proper balance between the oxygen supply and demand and preventing organs and cells from suffering hyperoxia-induced oxidative stress 3, 4.

Importance of Oxygen Homeostasis

• Lack of oxygen, commonly termed as hypoxia, is frequently encountered in different disease states and is detrimental to human life 4.
• The human body has evolved to maintain oxygen homeostasis by different molecular systems that are either activated in the case of oxygen under-supply, or to scavenge and to transform oxygen radicals when excess amounts are encountered 4.
• Mitochondrial respiration is responsible for more than 90% of oxygen consumption in humans, and cells utilize oxygen as the final electron acceptor in the aerobic metabolism of glucose to generate ATP 5.

Clinical Applications of Oxygen Therapy

• Oxygen therapy is one of the prime clinical interventions, as it is life-saving, readily available, easy to apply, and economically affordable 4.
• Long-term oxygen therapy (LTOT) can improve survival in those with severe daytime hypoxaemia, whereas those with less severe hypoxaemia may only have improved exercise capacity and dyspnoea 6.
• Noninvasive ventilation (NIV) may reduce mortality and need for intubation in individuals with COPD and acute hypercapnic respiratory failure, and may also improve survival and quality of life in individuals with stable, chronic hypercapnia 6.