Hypoxemia: Definition, Causes, and Treatment
Definition of hypoxemia
Hypoxemia (also known as
low 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
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
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)
- mouth breathing.
Ventilation rates (chronic diseases)
| All references or
click below for abstracts
|| Medical textbooks
|| Results of 14 studies
||13 (+-2) L/min
|| Chalupa et al, 2004
|| Johnson et al, 1995
||14 (+-6) L/min
|| Bowler et al, 1998
||13 (+-4) L/min
|| Kassabian et al, 1982
|| McFadden, Lyons, 1968
||14 (+-2) L/min
|| Palange et al, 2001
||12 (+-2) L/min
|| Sinderby et al, 2001
|| Stulbarg et al, 2001
Fauroux et al, 2006
Browning et al, 1990
Ward et al, 1999
|CF and diabetes*
Ward et al, 1999
Dodd et al, 2006
McKone et al, 2005
||13 (+-2) L/min
|| Bell et al, 1996
|| Tepper et al, 1983
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
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. This website provides detailed instructions for Buteyko breathing exercises. However, after testing my students, I know that there are even better methods that work nearly twice more effectively. The names of these methods are provided below down here as your bonus content.
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.
Coffey MJ, FitzGerald MX, McNicholas WT, Comparison of oxygen desaturation
during sleep and exercise in patients with cystic fibrosis, Chest. 1991
Lebecque P, Lapierre JG, Lamarre A, Coates AL, Diffusion capacity and oxygen
desaturation effects on exercise in patients with cystic fibrosis, Chest.
Mahler DA, Gifford AH, Waterman LA, Ward J, Machala S, Baird JC, Mechanism
of Greater Oxygen Desaturation during Walking Compared with Cycling in COPD,
Chest. 2011 Jan 27.
Neumann C, Martinez D, Schmid H, Nocturnal oxygen desaturation in diabetic
patients with severe autonomic neuropathy,
Diabetes Res Clin Pract. 1995 May;28(2):97-102.
Nonoyama ML, Brooks D, Guyatt GH, Goldstein RS, Effect of oxygen on health
quality of life in patients with chronic obstructive pulmonary disease with
transient exertional hypoxemia, Am J Respir Crit Care Med. 2007 Aug
15;176(4):343-9. Epub 2007 Apr 19.
Orth M, Walther JW, Yalzin S, Bauer TT, de Zeeuw J, Kotterba S, Baberg
HT, Schultze-Werninghaus G, Rasche K, Duchna HW, Influence of nocturnal
oxygen therapy on quality of life in patients with COPD and isolated
sleep-related hypoxemia: a prospective, placebo-controlled cross-over trial
[German], Pneumologie. 2008 Jan;62(1):11-6.
Sans-Torres J, Domingo C, Rué M, Durán-Tauleria E, Marín A, An assessment of
the quality of life of patients with COPD and chronic hypoxemia by using the
Spanish version of the Chronic Respiratory Disease Questionnaire [Spanish],
Arch Bronconeumol. 1999 Oct;35(9):428-34.
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.
Tanni SE, Vale SA, Lopes PS, Guiotoko MM, Godoy I, Godoy I, Influence of the
oxygen delivery system on the quality of life of patients with chronic
hypoxemia, J Bras Pneumol. 2007 Apr;33(2):161-7.
Young AC, Wilson JW, Kotsimbos TC, Naughton MT, The impact of nocturnal
oxygen desaturation on quality of life in cystic fibrosis, J Cyst Fibros.
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