Everything you need to know about hypercapnia

Hypercapnia refers to a change in the concentration of blood gases which can have more or less serious consequences on our health. What are the symptoms, causes and consequences? We take stock.

Definition: what is hypercapnia?

Our blood constantly carries a certain amount of oxygen (O2) and carbon dioxide (CO2). We talk about hypercapnia when the carbon dioxide concentration exceeds 45 millimeters of mercury (mmHg).

This symptom results from a failure of the respiratory system which no longer manages to purify the carbon dioxide in the blood. It is almost systematically associated with hypoxia.

Chronic or acute hypercapnia: what differences?

  • Chronic hypercapnia – As its name suggests, it manifests itself permanently by a blood CO2 level above 45 mmHg and a normal blood pH (because the kidneys recover the bicarbonates in the urine, which allows it to be maintained).
  • And acute hypercapniawhich is a life-threatening emergency – It is characterized by a blood CO2 level above 45 mmHg, but also by an abnormally low blood pH which indicates acidification of the blood (acidosis).

What is hypocapnia?

Hypocapnia, as its name may suggest, designates an abnormally low level of carbon dioxide in the blood. It is often due to pulmonary hyperventilation: the speed of breathing increases, which results in an excessive rejection of carbon dioxide (CO2) present in the body.

What is the “normal” level of CO2 in the blood?

The “normal” concentration of carbon dioxide in the blood is between 38 and 45 mm of mercury.

When do we speak of hypercapnia? What are the signs?

Hypercapnia is evidence of poor adaptation of ventilation to the body’s needs. She doesn’t understand no specific clinical picture. The symptoms are those of the pathology that caused it. Most of the time :

  • a asthenia (fatigue) ;
  • of the headaches ;
  • a mental confusion ;
  • a disorientation ;
  • of the hand tremors (lapping tremor);
  • a excessive sweatingWhere hypersalivation ;
  • a high blood pressure ;
  • a drowsiness ;
  • etc

As a reminder, hypercapnia is also often accompanied by hypoxialinked to an insufficient quantity of oxygen to supply the organs and muscles.

Hypercapnia can be revealed through blood gas analysis (or blood gas). This analysis can be performed from a blood sample in the radial artery (at the wrist). It allows to measure:

  • the partial pressure of oxygen (PaO2);
  • partial pressure of carbon dioxide (PaCO2);
  • blood pH (blood acidity);
  • oxygen saturation (SaO2);
  • and bicarbonate ions (HCO3) which regulate blood pH.

COPD, obesity, scoliosis… What are the causes of hypercapnia?

This symptom can be caused by many pathologies, including respiratory diseases, neurological diseases and muscular diseases. Among the most common causes:

  • theobstructive pulmonary disease (COPD);
  • them scoliosis Where kyphosis which lead to a deformation of the rib cage;
  • the obesity-hypoventilation syndrome (SOH);
  • them neuromuscular diseases that prevent the respiratory muscles from working properly (such as Charcot’s disease);
  • them central nervous system disordersincluding cerebrovascular accident (CVA);
  • them central nervous system tumors ;
  • the taking certain medications (barbiturates or codeine, for example);
  • some rare genetic diseases ;
  • etc

What can be the consequences of hypercapnia?

As a symptom, hypercapnia has no real consequences. The pathologies which are at the origin of it can however have certain consequences, in particular hypoxia, which can be at the origin ofa shortness of breathofgreat fatigue, headaches, even drowsiness.

Hypercapnia can also be associated with vasoconstrictionitself the cause of arterial hypertension (HTA), and at a flapping tremorcharacterized by sharp and brief muscle twitches.

Acute hypercapnia attacks can also generate more disturbing symptoms, such as involuntary muscle contractions, palpitations, paranoia, or panic attacks, etc.

The management of chronic hypercapnia is based on treatment of his case (lung disease, obesity, neuromuscular disease, drug poisoning, etc.). The main objective remains to improve the ventilation of the patient to remove excess CO2. Treatment can include different techniques depending on the situation and the judgment of the doctors:

  • non-invasive ventilation – This technique consists in supporting the ventilatory capacities of the patients: they are equipped with a mask connected to a ventilator device which delivers them a light pressure of air and a little oxygen. The patient thus breathes on his own.
  • or intubation (an invasive process) – This technique involves inserting an endotracheal tube into the patient’s mouth, which descends into the airways. In fact, patients are not able to breathe on their own.

Doctors will also take care of the underlying causes of the pathologies in question (bronchodilators for COPD or antibiotics for an infection, for example). Hypoxia requires oxygen therapy sessions.

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