Your lungs work round the clock, carefully taking in oxygen and removing carbon dioxide (CO2) at precise rates. When there is an imbalance in the breathing process and the body fails to properly flush out CO2, it leads to a build-up of the gas in the bloodstream. This condition is known as hypercapnia.
“Simply put, hypercapnia is an excess of CO2 in the bloodstream,” says Dr Bhagyesh Shah, an intensivist at CIMS Hospital, Ahmedabad, Gujarat. “Around 35–45mmHg (millimetres of mercury, a unit of pressure) is considered the normal range. The CO2 which is being absorbed in your body and is then moved out through the breathing process should optimally remain in this range.”
Any value beyond 45mmHg is considered a case of hypercapnia or excess CO2.
What leads to hypercapnia?
“A CO2 build-up occurs when one is unable to take in enough oxygen while inhaling or eliminate CO2 completely while exhaling,” says Dr Sachin Kumar, a senior pulmonologist at Sakra World Hospital, Bengaluru. “The condition is known as hypercapnia or hypercarbia.”
He adds that hypercapnia is most commonly seen in people with underlying conditions that affect one’s respiratory system such as chronic obstructive pulmonary disorder (COPD), asthma and obstructive sleep apnea (OSA).
According to Dr Sachin, a CO2 build-up in the bloodstream can occur in two ways:
- it could either be a rapid onset over a few hours or
- it could be a chronic onset that can occur over a few weeks or even months.
Acute onset cases — such as an acute asthma or COPD attack — can cause a rapid carbon dioxide build-up. People who are obese and those who suffer from OSA are also prone to developing hypercapnia. Sometimes, neurological problems like weakness of the muscles (which are essential in the breathing process) can also lead to it.
What happens to the body during hypercapnia?
The symptoms of hypercapnia — ranging from mild to severe — often depend on the level of CO2 build-up in the body and the underlying causes, say doctors.
According to Dr Sachin, the initial signs in mild cases include:
- Breathing difficulties
- Flushing of the skin
- Light-headedness
- Headaches
- Lack of focus
- Feeling disoriented
- Fluctuations in blood pressure.
On the other hand, severe cases of hypercapnia can cause:
- Respiratory failure
- Coma
- Feelings of agitation and confusion
- Muscle twitches.
Dr Sachin says that in cases of chronic CO2 build-up — where the body has been dealing with a gradual increase of the gas over a period of time — one is able to carry on with their daily routine without any issues even though the CO2 levels may be alarmingly high.
“This is only because in chronic cases, the body gets used to a particular level of carbon dioxide over some time,” he says.
Dr Sachin recalls the case of a 58-year-old obese man. “He came in with two main symptoms: he would snore through the night and was exhibiting signs of daytime sleepiness,” says the doctor. “He would doze off while simply seated. He also reported breathlessness upon mild exertion.”
Though it looked like a case of sleep apnea at first, a closer examination revealed that the man had an abnormally high level of CO2 in his bloodstream — almost 78mm Hg (as against the normal limit of 45mm Hg). “His face looked flushed — a classic sign of CO2 build-up in the bloodstream,” Dr Sachin adds. “This is why we decided to check his CO2 levels through an arterial blood gas (ABG) test in which a blood sample was taken from his artery.”
Doctors found that the CO2 build-up had occurred due to obesity hypoventilation syndrome, a breathing disorder that results in low oxygen levels.
“The CO2 levels in this case were alarmingly high, but his body got used to a high level of CO2 over some time since it was a chronic case,” Dr Sachin says. “These people may show up to the outpatient department of the hospital without showing any obvious signs. In normal circumstances, the person would not be able to function as per usual with this level of CO2 in their blood.”
Treatment of Hypercapnia
Dr Shah says people with hypercapnia are provided supportive respiratory therapy while the underlying cause of the condition is treated. A continuous positive airway pressure (CPAP) machine or a bi-level positive airway pressure (BiPAP) machine, also referred to as a non-invasive ventilator, is often recommended to keep the airway open and the breathing rate high to flush out the excess CO2, he says.
“We advise them to continue being on device support at home — for two to three hours in the day and nighttime,” says Dr Shah. “We then gradually ask them to switch to using it only at night. Once they feel they are fine, they can keep switching it on and off depending on whether they face any breathing difficulties or not.”
He adds that a close follow-up is needed for at least the next six months since hypercapnia can recur. “People at high risk for hypercapnia may even have to use these machines for a lifetime,” says Dr Shah. “In some severe cases, a BiPAP machine may not work. In such cases, we may need to put the person on a mechanical ventilator, which is an invasive form of ventilation in which a tube has to be inserted into their trachea.”
Takeaways
- Excess build-up of carbon dioxide (CO2) in the body can lead to hypercapnia or hypercarbia.
- Hypercapnia can cause a range of symptoms ranging from mild (causing headaches and dizziness) to severe (causing respiratory failure and coma).
- Hypercapnia can be diagnosed with an arterial blood gas (ABG) test in which a blood sample is taken from one’s artery.
