Hypoxia refers to the reduced partial pressure of oxygen at altitude. It thus represents an indirect effect of altered atmospheric pressure. The clinical manifestations at a given altitude are influenced primarily by duration of exposure, rate of ascent, and individual tolerance. However, the level of physical activity, the degree of health, physical conditioning, altitude acclimatization, and such factors as temperature, wind, and humidity may all modify the response in varying degrees.
The transfer of gases between lung, blood, and tissues depends upon differences in partial pressures. Alveolar air is saturated with water vapor, which exerts a constant pressure of 47 mm. of mercury. Carbon dioxide normally contributes about 40 mm. of mercury pressure to total alveolar pressure. Although total alveolar pressure is in equilibrium with atmospheric pressure, the space available for oxygen and other components of inspired air is approximately 87 mm. of mercury less than existing atmospheric pressure.
Mixing of inspired with residual air further reduces alveolar partial-pressure of oxygen from that in the atmosphere. The alveolar pressure constantly contributed by water vapor and C02 occupies an increasingly large proportion of alveolar pressure as atmospheric pressure declines. At sea level (alveolar Po2 = 103 mm. of mercury) hemoglobin is normally 95 to 98 per cent saturated. Not until altitudes of 10,000 feet (PB = 523 mm. of mercury and alveolar Po2 = 61 mm. of mercury) does hemoglobin saturation begin to fall below 90 per cent. Thereafter saturation declines rapidly with further increase in altitude and decline in alveolar partial pressure of oxygen.
Manifestations.
The first important physiologic effect of hypoxia occurs at about 5000 feet, when night vision begins to be impaired. Ventilatory and cardiovascular adjustments are minimal until about 10,000 feet, above which respiratory rate and depth and heart rate increase progressively to increase alveolar Po2 and cardiac output. Exertional dyspnea may appear, and in some people mental concentration becomes difficult. Vagal cardioinhibitory reflexes may lead to bradycardia and sometimes ectopic cardiac rhythms, and may precipitate syncope. Headache, slight giddiness, and restlessness are common.
Above 15,000 feet some persons experience lassitude and indifference whereas others exhibit increased activity, irritability, euphoria, and other disturbances of affect.
The impairment of judgment that begins at these altitudes jeopardizes the safety of fliers and mountain climbers. Cyanosis, loss of peripheral vision,’ dimming of vision, and variable degrees of muscular incoordination appear at altitudes of around 18,000 feet. Somewhere between this level and 25,000 feet, consciousness can nc* longer be retained for more than a few minutes. Rapid descent or administration of oxygen is essential to prevent death. If corrective action is taken soon enough, recovery is rapid and complete.
High-flying jet aircraft make it possible for many people of various ages and states of health to be exposed to the potential hazard of sudden hypoxia from rapid decompression. Should cabin pressure be abruptly lost at high altitudes, only a short period of consciousness would be possible with the breathing of ambient air.
At altitudes between 30,000 feet and 45,000 feet oxygen transfer across alveolar walls would be reversed, and the duration of consciousness would shorten progressively, from aboul 1 minute to 15 seconds, or the lung-to-brain circulation time of about 9 seconds plus around 6 seconds from oxygen already present in brain tissue. Rapid donning of oxygen masks and descent of the aircraft would shorten the period of severe hypoxia and minimize the possibility of serious injury.
Hypoxia is a condition of low oxygen levels in the body’s cells. As a result, cells throughout the body cannot function normally. Hypoxia needs to be watched out for, because if left untreated, this condition can cause tissue death and organ damage.
Normally, oxygen obtained from the breathing process will be transported by blood from the lungs to the heart. Next, the heart will pump oxygen-rich blood to all body cells through the blood vessels.
Hypoxia occurs when oxygen does not reach the cells in the body. This causes the oxygen levels in the body’s organs to decrease and is followed by the emergence of various complaints and symptoms.
Although they sound similar, hypoxia is not the same as hypoxemia. Hypoxemia is a condition when oxygen levels in the blood are low. Hypoxemia conditions can progress to hypoxia.
Causes of Hypoxia
Hypoxia can be caused by various conditions. The following are diseases and medical conditions that can cause hypoxia:
- Lung diseases , such as bronchitis, COPD, pulmonary hypertension , pulmonary edema, emphysema, pneumonia, pneumothorax, lung cancer, and COVID-19
- Heart disease , such as bradycardia, ventricular fibrillation, congestive heart failure, or coronary heart disease
- Blood disorders, such as anemia or methemoglobinemia
- Infection that causes sepsis
- Poisoning, such as cyanide poisoning or CO (carbon monoxide) poisoning
- Injuries that cause large amounts of bleeding
- Use of drugs, such as fentanyl or anesthetics
- Altitude sickness
- Lack of oxygen due to being trapped in a fire, being in a cold place, or drowning.
Types of Hypoxia
Based on the cause of the lack of oxygen in the body, hypoxia can be divided into several types, namely:
- Hypoxic hypoxia (hypoxemic hypoxia), which is caused by a lack of oxygen in the blood due to disorders of the respiratory tract.
- Histotoxic hypoxia, which occurs when the body’s cells cannot use available oxygen, one of which is due to cyanide poisoning
- Metabolic hypoxia, which occurs when the body’s cells need more oxygen than usual, one of the causes of which is sepsis.
- Stagnant hypoxia, caused by a lack of blood supply, for example due to shock due to bleeding
- Anemic hypoxia, which is caused by a lack of hemoglobin levels in red blood cells, one of which is the result of anemia
Apart from the causes and types above, there are several conditions that can put a person at greater risk of experiencing hypoxia, namely hypotension , asthma and ALS .
Hypoxia Symptoms
Each hypoxia sufferer can experience different symptoms. These symptoms can appear suddenly and get worse quickly (acute) or develop slowly (chronic).
The following are some common symptoms of hypoxia:
- Breathing becomes rapid
- Hard to breathe
- Headache
- Blurred vision
- The heartbeat becomes fast or slow
- Skin, nails and lips are bluish ( cyanosis ) or even dark red like cherries
- Weak
- Confused
- Loss of consciousness
- Excessive sweating
- Cough
- Difficulty speaking
When to see a doctor
Immediately consult a doctor if you experience the complaints mentioned above. Early examination and treatment is needed to prevent complications.
If you see someone feeling short of breath or having difficulty breathing, feeling weak, suddenly unable to talk, confused, or having seizures, immediately take them to the emergency room for medical treatment.
Diagnosis of Hypoxia
The doctor will ask about complaints experienced by the patient, as well as health conditions or illnesses that the patient has suffered from.
After that, the doctor will check for signs of hypoxia in the patient, for example by assessing the level of consciousness, looking at the color of the lips and tips of the nails, and checking blood pressure, respiratory rate, and heart rate.
While carrying out the examination, the doctor will carry out initial treatment to stabilize the patient’s condition.
To diagnose hypoxia and find out the cause, the doctor will perform the following supporting examinations:
- Oximetry test, to monitor oxygen levels in the blood with a device that is clipped to the finger ( pulse oximeter )
- Complete blood count , to check for signs of anemia or infection
- Pulmonary function test , to check whether the lungs are functioning normally
- Blood gas analysis , to evaluate metabolism and breathing, as well as possible poisoning
- Electrocardiogram (EKG), to look for signs of heart damage or irregular heartbeat
- X-ray or CT scan of the chest, to see abnormalities in the lungs, such as pneumothorax or lung infection
- CT scan or MRI of the head, to look for abnormalities in the brain, such as tumors, strokes, or bleeding.
- Echocardiography , to monitor the structure and condition of the heart so that damage or abnormalities in the heart or heart valves can be detected.
Hypoxia Treatment
Hypoxia treatment aims to restore the oxygen supply to the body’s cells so that the body’s organs can work properly and organ death does not occur. Hypoxia treatment is also aimed at treating the underlying cause.
Some treatment methods that can be used to overcome hypoxia are:
Oxygen
Oxygen administration aims to increase oxygen levels in the patient’s body. Additional oxygen therapy can be given through:
- Mask or nasal tube, the choice of which will be adjusted to the patient’s condition and the oxygen levels to be achieved.
- Hyperbaric therapy , for severe tissue hypoxia or patients with carbon monoxide poisoning.
- Breathing apparatus ( ventilator ), for severe hypoxia with difficulty breathing
Drugs
Doctors can also prescribe medications to treat the cause of hypoxia. Some medications that may be prescribed are:
- Inhaler or asthma medication, to treat asthma attacks
- Corticosteroid drugs , to relieve inflammation in the lungs
- Antibiotics , to treat bacterial infections
- Anti-seizure medication, to relieve seizures
Complications of Hypoxia
Decreased oxygen levels that are not immediately addressed can progress to shock , organ hypoxia, and lack of oxygen in the brain (cerebral hypoxia). As a result, organ failure and brain damage can occur.
In addition to causing decreased consciousness, brain damage can cause sufferers to experience permanent disability, even death.
Hypoxia Prevention
Hypoxia is difficult to prevent because it can occur unexpectedly. However, there are efforts you can make to reduce the risk of hypoxia, including:
- Use asthma medication regularly.
- Do breathing exercises.
- Avoid climbing to a certain height quickly, to prevent altitude sickness.
- Adopt a healthy lifestyle by exercising regularly, drinking enough water, and stopping smoking.
- Have regular check-ups with your doctor if you have a medical condition or illness that could increase your risk of hypoxia.
Apart from doing the things above, you need to see a doctor if you have had direct contact with someone suffering from COVID-19, especially if you experience symptoms of COVID-19 .
If you have COVID-19 and are self-isolating, you need to check your oxygen saturation regularly with a pulse oximeter . The goal is for early detection so that if it gets worse, you can immediately consult a doctor.
