Hypercapnea

What is Hypercapnea?

Hypercapnia is a medical condition where the level of carbon dioxide (CO2) in your blood goes above 45 mm Hg. Carbon dioxide is a waste product created by the cells in your body when they process fats, sugars, and proteins. There are various systems within our body that help to regulate the amount of CO2. One of these is the pH buffering system which works with hydrogen carbonate (HCO3) and CO2. Because of the relationship between these elements, hypercapnia can result in problems with the balance of acid and base in your body.

What Causes Hypercapnea?

Hypercapnia occurs when there’s too much carbon dioxide (CO2) in the blood. This can happen because of two main reasons. One reason could be increased CO2 production within the body from things like fever, an overactive thyroid, increased breakdown of body tissues in severe infections or steroid use, overeating, metabolic acidosis (an excess of acid-forming chemicals in the body), and exercise. The other reason is a failure of the respiratory system to remove CO2 effectively. Basically, the lungs are not able to ventilate or ‘breathe out’ the CO2 the body has produced as efficiently as they should. This can happen due to issues with the brain’s messaging system (like a decreased urge to breathe), physical issues with the body, problems with the muscles involved in breathing, or parts of the lung not being useful for gas exchange. Also, inhaling air that has unusually high levels of CO2 can lead to hypercapnia.

Hypercapnia can either develop quickly (acute), over a longer period (chronic), or as a combination of both. We can mainly tell these apart by checking the pH and CO2 levels in the blood through a blood gas test, which measures different elements in your blood.

If the hypercapnia is acute, the CO2 levels in the blood would be higher than the normal reference range of 45 mm Hg and the bicarbonate (HCO3) level, a chemical that helps stabilize the blood’s pH, would be normal at about 30 mm Hg. However, the blood pH would be less than 7.35, indicating an acidic blood condition.

For chronic hypercapnia, the body might have had more time to react to the high CO2 levels. Just like in acute hypercapnia, the CO2 levels would be greater than 45 mm Hg, but the bicarbonate (HCO3) levels would also have gone up as the kidneys try to stabilize the blood pH. Consequently, the blood pH might be in the lower end of the normal range, indicating a slightly acidic effect.

In mixed-type hypercapnia (acute-on-chronic), you’d see high levels of CO2 and bicarbonate, but the blood pH would be less than 7.35, indicating the blood is more acidic than normal.

Risk Factors and Frequency for Hypercapnea

Hypercapnia is more of a condition caused by various diseases, rather than a standalone disease. Therefore, its occurrence rate directly relates to the specific diseases that cause it.

Signs and Symptoms of Hypercapnea

Hypercapnia, or too much carbon dioxide in your blood, can manifest in a variety of ways. Symptoms often vary based on the individual’s case. Some people may experience:

• Flushed skin
• Lethargy
• Difficulty focusing
• Mild headaches
• Disorientation
• Dizziness
• Shortness of breath
• Difficulty breathing during physical activity
• Nausea
• Vomiting
• Fatigue

In more severe cases, individuals may also experience confusion, paranoia, depression, abnormal muscle twitches, palpitations, irregular breathing, seizures, anxiety, or sudden fainting. People with existing conditions like asthma or chronic obstructive pulmonary disease (COPD) may be familiar with these symptoms as signs of a flare up.

In a physical exam, doctors might observe a range of signs suggesting an underlying condition. These can encompass:

• Fever
• Obesity
• Rapid heart rate
• Rapid breathing
• Difficulty breathing
• Altered mental state
• Wheezing when breathing out
• Crackling sounds when breathing in
• Decreased breath sounds
• Echoey sounds when the chest is tapped
• An enlarged chest
• Heart murmurs
• Signs of low oxygen
• Enlargement of the liver or spleen
• Neurological deficits
• Confusion
• Drowsiness
• Weakness in the muscles
• Swelling in the extremities
• Tremor of the hand when the wrist is extended (asterixis)
• Swelling of the optic disc (papilledema)
• Swollen superficial veins
• Obesity

Testing for Hypercapnea

When your doctor suspects that you may have a condition known as hypercapnia, they’ll run a series of tests. Hypercapnia is a condition where too much carbon dioxide builds up in your blood, and it can be caused by a range of conditions, so several tests are necessary to figure out what’s going on.

The tests that doctors usually order in these situations include:

– A complete blood count: This test is used to check if you have anemia or not. Anemia is a condition where your body lacks enough health red blood cells, which means that not enough oxygen is carried to your body’s tissues.
– A complete metabolic panel: This test checks levels of various substances in your blood, including sodium, potassium, and chloride. Changes in these levels can often be the source of your symptoms. This test also checks your bicarbonate (HCO3) levels, which helps your doctor determine if your body is trying to compensate for a condition called respiratory acidosis.
– Thyroid stimulating hormone test: This test is used to check if you have an overactive or underactive thyroid, conditions that can make your body produce too much or too little thyroid hormone respectively.
– An arterial or venous blood gas test: This is perhaps one of the most valuable tests as it allows your doctor to evaluate the acidity (pH status) of your blood, the amount of carbon dioxide (serum CO2), and bicarbonate in your blood. Bicarbonate plays a key role in maintaining the body’s pH balance. An anion gap can also be calculated to help determine if the cause of acidosis (which is when your body’s fluids contain too much acid) is related to your metabolism or your respiratory system.

Your doctor may also order a spirometry test, which measures how well your lungs are working. It helps to determine if you are presenting a lung disease that makes it difficult for you to breathe in (restrictive) or breathe out (obstructive). If you have symptoms such as breathing shortness, then it might suggest certain conditions like COPD or asthma.

You may also need to get a chest X-ray. Chest X-rays are essential in diagnosing many respiratory conditions because they allow the doctor to see the structures inside your chest. If further details are needed, a chest CT might be used. Both tests can reveal problems like pneumonia and pulmonary edema (which is when fluid fills up your lungs).

If your doctor suspects a heart disease, they might consider using an echocardiogram. This test uses sound waves (ultrasound) to make detailed images of your heart’s structure and function.

Other tests that your doctor may use include an ECG test, which measures the electrical activity of your heart, an EMG test, which measures the electrical activity of your muscles. Finally, you may undergo a sleep test called polysomnography if your doctor suspects you have a sleep disorder like sleep apnea, which is when your breathing repeatedly stops and starts while you sleep.

Treatment Options for Hypercapnea

Treating high levels of carbon dioxide in the blood (hypercapnia) should primarily focus on addressing the root cause. There are some direct methods that can help your body get rid of excess carbon dioxide by improving the air flow in your lungs, such as Bi-level Positive Airway Pressure (BiPAP), Continuous Positive Airway Pressure (CPAP), and mechanical ventilation via intubation.

BiPAP is often the preferred method for patients who are awake and able to protect their airway. This technique helps improve the exchange of air between the lungs and the atmosphere by providing varying levels of pressure in the airway. On the other hand, CPAP is used when there’s a need to keep the airways open, although it’s less effective in improving carbon dioxide exchange compared to BiPAP.

While those methods are less invasive, they can sometimes be uncomfortable and are often used as temporary therapies until the patient recovers or until a more invasive procedure can be performed. In cases where the patient is not able to protect their airway or isn’t fully awake and alert, mechanical ventilation (the process of using a machine to help you breathe) should be strongly considered. This method lets the doctors better control the breathing rate and depth, as well as the concentration of oxygen and pressure support.

It’s crucial to understand that BiPAP, CPAP, and mechanical ventilation aren’t cures by themselves. They are supportive measures that help stabilize the patient while the root cause of the problem is being addressed. No matter which method is used, it’s important to ensure that the level of oxygen in the blood is maintained at 90% or higher.

What else can Hypercapnea be?

Hypercapnia, which is a condition marked by excessive carbon dioxide in the bloodstream, can be caused by a variety of diseases and conditions including:

• Acute respiratory distress syndrome
• Asthma exacerbation
• Central or obstructive sleep apnea
• Chronic obstructive pulmonary disorder in a long-term or acute state
• Drug overdose
• Inhalation of external CO2
• Head or cervical cord injury
• Myasthenia gravis
• Myxedema
• Obesity-hypoventilation syndrome (also known as Pickwickian syndrome)
• Polyneuropathy
• Poliomyelitis
• Primary muscle disorders
• Porphyria
• Primary alveolar hypoventilation
• Pulmonary edema
• Tetanus

What to expect with Hypercapnea

The outcome of hypercapnia, a condition where there’s too much carbon dioxide (CO2) in your blood, can differ greatly based on the specific cause. Generally speaking, younger patients tend to have a better outlook than older patients.