Various lung and heart conditions require supplemental oxygen to prevent chronic hypoxemia, or low blood oxygen levels. If you are breathing through your mouth while receiving supplemental oxygen through a nasal tube, you are not receiving the full benefits of your oxygen therapy.
Conditions Requiring Supplemental Oxygen
If you have chronic obstructive pulmonary disease, you might benefit from supplemental oxygen. Your doctor will estimate how much oxygen you need to be supplied with in order to maintain a healthy blood gas level. Patients with COPD often suffer from insufficient gas exchange because of damage to their airways.
Pathophysiology of COPD
When you develop obstruction of your airways, as is seen in cases of COPD, eventually your lungs will become hyper-inflated. Emphysema, a specific form of COPD, results from an imbalance between enzymes in the lungs. The result is destruction of the elastic tissue throughout the lungs, making the act of exhalation more difficult and energy consuming. Other forms of COPD involve chronic inflammation in the airways, leading to increased air-trapping because of narrowed airways. This change is associated with the deposition of connective tissue surrounding the airways, increasing resistance to flow. Regardless of the mechanism of disease, COPD results in hypoxemia, or low blood oxygen levels, which results in many complications.
Complications of COPD
Pulmonary hypertension is commonly observed in patients with COPD. Because of the inflammation and connective tissue buildup, the arteries of the pulmonary capillary networks become sclerotic, thus increasing the pressure in the respiratory vascular tree. This can lead to right-sided heart failure because of the increased resistance to pumping through the lungs.
Consequences of Mouth Breathing
Oxygen supplementation is generally prescribed in patients with a arterial blood oxygen concentration of less than 90 percent while breathing room air. In these patients, the lungs are so diseased that they cannot absorb sufficient oxygen from normal room air. The use of oxygen supplementation will increase the fraction of inhaled oxygen, thus increasing their arterial oxygen content. Mouth breathing while on oxygen defeats the purpose of the supplementation because rather than directly breathing in the correct concentration of oxygen to compensate for your COPD, you are breathing mostly room air, which is known to give you low oxygen blood gas levels.