Hypercapnia

Hypercapnia is a medical emergency that can give rise to life-threatening complications. Read and know more about this condition, including its causes, symptoms, diagnosis and treatment.

Hypercapnia Definition

Hypercapnia is a condition characterized by the presence of high amounts of carbon dioxide (CO2) in the bloodstream. It is also referred to as Hypercapnea. Generally, carbon dioxide can be found in the blood of every healthy person. It is only when the concentration of Co2 becomes abnormally high that the condition is viewed as a medical emergency and referred to as Hypercapnia.

The name of this disorder comes from the merger of two Greek terms “hyper” meaning “above” and “kapnos” standing for “smoke”.

Permissive Hypercapnia

It is the name given to Hypercapnia that is seen in patients of respiratory insufficiency. Oxygenation becomes so difficult in such individuals that even the most preferred method of mechanical ventilation fails to exchange adequate amounts of carbon dioxide. Carbon dioxide, which is a gaseous product of the respiratory process, is usually released through the lungs.

Types of Hypercapnia

The condition is broadly classified into two types:

Picture 1 – Hypercapnia (Excess CO2 in blood)

Chronic Hypercapnia

It is a type of Hypercapnia that is frequently seen in people suffering from severe hypoxic lung disease. It is related with a rise in pulmonary arterial pressure that is higher than in Hypoxia. It is said to enhance the death rate during peri-operative stage. The condition may be frequently found to accompany a number of respiratory disorders that affect exchange of gases in the lungs. This makes diffusion impossible. The carbon dioxide is not able to diffuse from the venous blood present in the alveoli. The airways may also be unable to provide all alveoli with proper ventilation.

Acute Hypercapnia

In this condition, respiratory failure can occur at anytime between a few minutes to a few hours. The pH value is lower than 7.3. This is unlike chronic cases where breathing failure takes several days or more to develop. Typically, the pH value only has a slight increase in chronic cases as the body is allowed time for renal compensation and a rise in bicarbonate concentration.

Hypercapnia Symptoms

In the early stages, the signs and symptoms of this disorder include:

• Full pulse
• Flushed skin
• Dyspnoea
• Tachypnea
• Extrasystoles
• Hand flaps
• Muscular twitches
• Lowered neural activity

Affected individuals may also suffer from a possible rise in blood pressure. People with mild forms of the condition may suffer from fatigue, mental confusion and headaches. The disorder may accelerate increased arterial blood pressure and enhanced heart rate. It can also increase the tendency to have arrhythmias (unusual rate of contractions in the cardiac muscles). In individual with severe forms of the ailment, the symptoms can worsen. Patients may suffer from problems like:

• Panic
• Convulsions
• Hyperventilation
• Unconsciousness
• Disorientation

In worst cases, patients may also die. Death occurs due to total deficiency of oxygen in blood. The oxygen in blood is entirely displaced by carbon dioxide which results in complete organ failure. Even if death does not occur, this acute medical condition may lead to permanent damage of the internal organs.

In a person with Hypercapnia, the central nervous system (CNS) can become depressed. This can give rise to problems like

• Blurred vision
• Confusion
• Dizziness
• Fatigue

It may also result in increased intercranial pressure, or build-up of pressure inside the skull. Patients may also suffer from breathing difficulties. Other symptoms, associated with the underlying cause, may also be detected.

Hypercapnea and Carbon Dioxide Levels

Normally, 40 mm Hg of carbon dioxide (CO2) is present in blood. Hypercapnia begins to occur when there is over 45 mm Hg of CO2 in blood. In mild to moderate levels of exposure, the amount of carbon dioxide varies between 45 and 65-70 mm Hg. In such cases, patients show a complete recovery after a point of time. In severe cases of exposure, the level of CO2 in blood is 75 mm Hg or more. This permanently damages the central nervous system (CNS). Unless treated properly in time, it may even lead to death.

Hypercapnia Causes

Exposure to surroundings containing massive amounts of carbon dioxide is the primary cause of this condition. It may also occur due to breathing of exhaled carbon dioxide again, as happens in closed rooms due to proper lack of ventilation. It can also happen due to:

• Lung disease
• Hypoventilation
• Reduced consciousness

The condition may also arise due to administering a patient of sleep apnea with supplemental oxygen. In this case, the disease may also arise along with Respiratory Acidosis.

The disease may also occur due to rise in bicarbonate levels in blood due to use of medicines. Use of diuretics, abuse of laxatives or prolonged use of steroids may contribute to increase of bicarbonate levels in the bloodstream.

A condition known as Chronic Obstructive Pulmonary Disease (COPD) is also one of the major causes of this disorder. It lowers oxygen efficiency and enhances the level of carbon dioxide in blood. Scuba divers, who practice skip breathing, have to hold their breath to save oxygen in their air tank. They often suffer from Hypercapnia.

Hypercapnia Diagnosis

The diagnosis of the disorder depends on end tidal capnography, arterial blood gas levels, arterial pH and physiological manifestations. It involves detecting clinical symptoms like:

• Rapid, shallow respiration related with hypoventilation
• Slow rate of respiration
• Obtundation
• CNS depression
• Hypertension
• Tachycardia
• Arrhythmias

The presence of other medical symptoms of this condition may depend on the type of underlying causative agents like respiratory fatigue, drugs, toxins, neuromuscular disorders and CNS disease.

Hypercapnia Differential Diagnosis

The differential diagnosis of this disease involves distinguishing it from other conditions like Hypoventilation, increased CO2 production, increased dead space ventilation or enhanced inhalation of CO2.

Hypercapnia Treatment

The treatment of this disease is based on its severity. Cure begins with addressing the underlying problem. If this proves to be ineffective, further treatment may involve:

• Intubation and mechanical ventilation
• Non-invasive positive pressure ventilation (BiPAP, CPAP)

Picture 2 – Severe Hypercapnia

As already said, an absence of proper treatment in time may lead to permanent damage to the heart or brain dye to the presence of an excessive amount of carbon dioxide (CO2) in the blood. Based on the severity of CO2 poisoning, patients are administered oxygen through any of the following options:

• Oxygen mask
• Ventilator
• Hyperbaric chamber

Hyperbaric chamber is a big chamber where the pressure of oxygen is kept twice above normal level. This forces the oxygen of the chamber into the body and leads to a faster removal of CO2 from the bloodstream. This option is used to cure carbon monoxide poisoning or respiratory disorders.

The best way to cure this condition involves removing the patient from an environment filled with carbon dioxide and supply him/her with fresh oxygen.

If the level of CO2 in blood is anywhere from mild to moderate (45 to 65-70 mm Hg), patients can be expected to have a full recovery within a short time. If the patient has a high exposure and the CO2 level in blood is more than 75 mm Hg, the central nervous system may suffer from permanent damage.

Hypercapnia Prevention

It is best to avoid carbon dioxide poisoning to prevent Hypercapnia. Air in areas, such as shafts and underground tunnels, are known to have high levels of Carbon dioxide. Naturally, such areas should be avoided. Environments like bunched up blankets or airtight tents should also be avoided as they can lead to re-breathing.

Some effective ways to prevent increase in carbon dioxide levels in the bloodstream include:

• Ensuring adequate ventilation in enclosed areas
• Refraining from skip breathing
• Using steroids properly
• Proper use of laxatives

Patients using medicines, such as prescription steroids or diuretics, or those suffering from ailments like COPD should undergo regular blood-testing to avoid Hypercapnia.

Hypercapnia Prognosis

The outcome of this disorder is ultimately based on the severity of the underlying agent. In most cases, however, the prognosis is a guarded one. The prognosis also depends on the general medical health of the suffering individual. Animals that suffer from the condition, and need mechanical ventilation, usually show a poor prognosis. The outcome can be good when the underlying condition is reversible, as in cervical intervertebral disk disease or cases of drug overdose.

Hypercapnia Complications

Some of the main complications that patients with this condition develop involve:

Cardiac arrhythmia

It is a condition characterized by irregularity or disturbance in heartbeat. This occurs due to an abnormal rate of contractions of the muscles in the heart.

Pulmonary edema

It is a condition marked by effusion of fluid into the interstitial spaces and the alveoli of the lungs.

Respiratory acidosis

One of the main complications of this disease, it is marked by a reduction in the pH scale of the blood due to an alteration in its chemical composition.

Respiratory acidosis can result in a number of reactions which may include acceleration of the CO2 level in the blood. Doctors should closely monitor the health of Hypercapnia patients so that they can administer proper treatment if symptoms of acidosis are found to develop.

Hypercapnia and COPD

As already said, Chronic Obstructive Pulmonary Disease (COPD) is one of the main causes of this disorder. It leads to a rise in the level of carbon dioxide due to deceased oxygen efficiency. Patients suffering from COPD experience difficulties in pushing air into their lungs. They also have problems in moving air out of the lungs. This makes it hard for the lungs to expel carbon dioxide and take in oxygen, which is an important part of the respiratory process. COPD may lead to problems like Hypercapnia (high level of CO2) as well as low oxygen level in blood (Hypoxemia).

In a healthy individual, respiration consists of inhaling oxygen and exhaling carbon dioxide. The exchange of these two respiratory gases occurs in small, grape-like air sacs (alveoli) located deep inside the lungs. In people suffering from COPD, the alveoli are destroyed which destroys this process of gaseous exchange. This allows the oxygen with less surface area to get into the bloodstream from the lungs. It also leaves little surface area for carbon dioxide to get into the lungs from the blood to be exhaled. This leads to a condition known as Hypoxemia, characterized by low oxygen content in blood. It may also lead to Hypercapnia.

Hypercapnia can be a potentially life-threatening condition. It may result in respiratory failure and death. Due to this COPD patients as well as their care providers should be aware of the problems resulting from Hypercapnia. They should get in touch with the primary caregivers of the patient as soon as they notice any change in condition.

Hypoxia and Hypercapnia

Hypercapnia is often confused with Hypoxia, which is a condition marked by lack of adequate oxygen supply to the body tissues. Hypercapnia, on the other hand, is characterized by the presence of an unusually high amount of CO2 in the circulating blood. This high CO2 concentration in blood mainly occurs as a result of exposure to high amounts of carbon dioxide as well as Hypoventilation.

Hypercarbia vs Hypercapnia

Hypercapnia is often referred to as Hypercarbia. Although used as a substitute for the former, Hypercarbia is somewhat different. Firstly, it is an older medical term that was used many decades ago to denote Carbon Dioxide Poisoning. The term is still in use in various parts of the world. However, Hypercarbia actually refers to presence of carbon dioxide at a higher than normal level in blood (typically higher than 45mmHg). Hypercapnia, on the other hand, refers to an excess amount of carbon dioxide (CO2) in blood that may range from >45 to >75mmHg.

As aforesaid, Hypercapnia is an emergency condition that requires prompt medical treatment. Hence, you should seek medical attention on an immediate basis if you detect the symptoms of this disorder in any friend or a member of your family. Timely medical care will help chances of an early recovery and prevent any future complications.

References:

http://www.normalbreathing.com/hypercapnia-hypercarbia.php

http://www.medscape.com/viewarticle/410886_2

http://www.healthblurbs.com/hypercapnia-causes-high-carbon-dioxide-levels-in-blood-symptoms/

http://www.instah.com/respiratory-disorders/hypercapnic-respiratory-failure/