Hypoxemia: Definition, Causes, and Treatment
Definition of hypoxemia
Hypoxemia (also known as oxygen desaturation) is defined as an abnormally-low partial pressure of oxygen in the arterial blood. Oxygen cascade (or oxygen delivery from the outer air to body cells) is highly sensitive to various abnormalities that can appear anywhere in the air (e.g., reduced oxygen content), airways, lungs, or cardiovascular system. The examples and causes are explained below. Oximeters are commonly used these days in hospitals and by critical-care professionals to define blood oxygen levels and diagnose hypoxemia.
On an average, the normal oxygen levels in our blood stream are about 85 mm Hg. In people suffering from hypoxemia, this falls down to as low as 60 mmHg. During hypoxemia, the oxygen saturation in the body is less than 90 percent. This is the formal definition of hypoxemia. Normal pulse oximeter readings can range from 95 to 100 percent. If the same falls below 80 percent, the condition is referred to as severe hypoxemia.
Hypoxemia has a profound negative effect on quality of life (Nonoyama et al, 2007; Orth et al, 2008; Sans-Torres et al, 1999; Tanni et al, 2007). Even nocturnal hypoxemia (i.e., temporary hemoglobin desaturation during sleep) has negative effects on life quality (Young et al, 2011).
Causes of hypoxemia
1) The inspired air has reduced oxygen content (e.g., at high altitude or due to other causes).
2) Insufficient gas exchange is caused by alveolar hypoventilation (or breathing too little) with chest breathing. It can happen, for example, during sleep or during physical exercise for people with lung diseases.
3) Some parts of the lungs are obstructed, or damaged, or have insufficient ventilation (e.g., as for emphysema, COPD and other conditions).
4) Blood shunting causes the arterial and venous blood to mix and this causes reduced oxygenation of the arterial blood.
5) Impaired alveolar-capillary diffusion (e.g., due to thick mucus during exercise in people with cystic fibrosis).
In many cases, transition into a horizontal position, sleep (especially REM sleep), overeating, slouching (or poor posture) and physical exercise (e.g., in cystic fibrosis and COPD) can cause hypoxemia or greatly worsened hypoxemia. Nocturnal desaturation is common for many conditions, including cystic fibrosis (Coffey et al, 1991), heart disease (Tanigawa et al, 2006) and diabetes (Mahler et al, 2011).
The main cause of chronic hypoxemia
hypoxemia may occur suddenly, or due to an accident or unusual and
exotic situations, most cases of chronic hypoxemia relate to gradual
worsening of blood oxygenation due to chronic lung diseases, such as cystic
fibrosis, COPD (severe asthma, bronchitis, emphysema, and so on), lung
cancers, bronchiectasis and many others. In such cases, gradual
deterioration in blood oxygenation is accompanied by hypercapnia (too much CO2
in the arterial blood) and has a simple single cause: an abnormal
breathing pattern that is manifested in the following factors:
- thoracic (or chest, or shallow) breathing
- mouth breathing.
Ventilation rates (chronic diseases)
Hyperventilation, regardless of ventilation-perfusion ratio (or the presence of lung problems during the initial stages), leads to alveolar hypocapnia. This, in turn, causes a cascade of pathological effects that involve drying and overcooling of airways, constriction of airways, inability of the body to heal lung damage, over-production of thick mucus, suppression of the immune system, possible appearance of allergies, over-expression of hypoxia-inducible factor 1, oxidative stress, and many other effects (see the CO2-related links below). Alveolar hyperventilation leads to appearance of 2 other factors: chest breathing and mouth breathing.
Chest breathing immediately leads to reduced-blood oxygenation since lower portions of the lungs get about 6-7 times more blood, due to gravity, in comparison with the top parts of the lungs.
Mouth breathing causes reduction in alveolar CO2 due to reduced-dead volume, possible reduction in absorption of nasal NO (nitric oxide), as in cystic fibrosis, and frequent respiratory infections. Alveolar hypocapnia directly contributes to worsened ventilation-perfusion ratio.
For uneducated and archaic views on hypoxemia, you may check this Wikipedia article: click here.
Treatment for hypoxemia
Note. Severe cases of hypoxemia require the attention of emergency or critical care professionals. Their treatment for hypoxemia may include mechanical ventilation and supplemental oxygen therapy.
Successful treatment of chronic hypoxemia in patients with COPD, cystic fibrosis, emphysema, severe asthma, and other lung diseases has been demonstrated clinically by more than 600 Russian MDs.
Their treatment is based on breathing retraining using either the legendary Buteyko breathing technique or the Frolov breathing device therapy. Breathing exercises with the Amazing DIY Breathing Device often produce a large immediate increase in oximeter readings in comparison with any other breathing device or technique, if this reading was low at rest.
However, one also needs to address lifestyle-risk factors (supine sleep, mouth breathing, overeating, insufficient or incorrect physical exercise, nutritional deficiencies, and many others) in order to achieve permanent changes in automatic breathing patterns. These factors are analyzed in the Section Learn here.
Reference pages: Breathing norms and the DIY body oxygen test:
- Breathing norms: Parameters, graph, and description of the normal breathing pattern
- Body-oxygen test (CP test) : How to measure your own breathing and body oxygenation (two in one) using a simple DIY test
References: pages about CO2 effect:
- Vasodilation: CO2 expands arteries and arterioles facilitating perfusion (or blood supply) to all vital organs
- The Bohr effect: How and why oxygen is released by red blood cells in body tissues
- Nerve stabilization: Carbon dioxide has powerful calmative and sedative effects on brain neurons and nerve cells
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Tanigawa T, Yamagishi K, Sakurai S, Muraki I, Noda H, Shimamoto T, Iso H, Arterial oxygen desaturation during sleep and atrial fibrillation, Heart. 2006 Dec;92(12):1854-5.
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Young AC, Wilson JW, Kotsimbos TC, Naughton MT, The impact of nocturnal oxygen desaturation on quality of life in cystic fibrosis, J Cyst Fibros. 2011 Mar;10(2):100-6.
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