Master the Early Signs & Symptoms of Hypoxia

The body’s response to decreased oxygenation in the bloodstream releases catecholamines like epinephrine and norepinephrine. These catecholamines activate a sympathomimetic response (“fight or flight” response) and can produce feelings of apprehension, restlessness, and irritability.

Central and peripheral chemoreceptors, found in the brain and peripheral nervous system, respectively, detect hypoxemia and stimulate a respiratory response by increasing the lung’s ventilatory rate and depth.

An increased demand of oxygen for cellular aerobic respiration and a decreasing available supply of oxygen in the bloodstream produces the feeling of dyspnea with further exertion. To correct this imbalance, the demand for oxygen must decrease or the availability of oxygen must increase.

The heart’s response to decreasing available oxygen in the bloodstream leads to tachycardia. An increasing heart rate with a preserved or increased stroke volume increases cardiac output (heart rate x stroke volume = cardiac output) of oxygenated blood to the body’s tissues.

Tachycardia increases blood pressure (hypertension) and is a compensatory (corrective) sign of early hypoxia. However, if metabolic demand increases and/or oxygen supply drops despite such compensatory signs, the body cannot sustain nor survive these conditions.

The heart is very sensitive when detecting low oxygen levels. When available oxygen decreases without a compensatory response to correct the problem, the cardiac muscle (myocardium) can sustain cellular damage and death. Cellular death of the myocardium disrupts both the electrical signal through the heart and the heart muscle’s ability to contract, resulting in the development of dysrhythmia or arrhythmia.

In response to early-hypoxia, hypertension, loss of total body water through diaphoresis (e.g. dehydration), and increasing cellular demand for oxygen can lead to problems in the kidneys. These problems arise from decreasing serum (bloodstream) availability through the kidneys and decreased perfusion to the kidney’s cells (nephrons), marking dysfunction to concentrate and produce urine.

A feeling of extreme tiredness occurs as both a compensatory response to decreased metabolic demand, improving the availability of oxygen in the bloodstream, and as a result of decreased oxygen to parts of the brain (e.g. decreased cortical activation). This fatigue may occur as an early or late symptom.