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Hypercapnia is a condition characterized by elevated levels of carbon dioxide in the blood. This primarily occurs when the lungs are incapable of expelling the carbon dioxide from the body.


In the early stages, the signs and symptoms of hypercapnia include onset of dyspnea, full pulse, extrasystoles, tachypnea, flushed skin, development of muscle twitches and hand flaps [6].

Affected individuals have an elevated blood pressure and there is a significant decrease in the neural activity. Patients also complain of lethargy, confusion and headache. In addition to these, other symptoms include increase in arterial blood pressure along with increased cardiac output, which eventually predisposes the individual to develop arrhythmias [7].

In severe cases, when PaCO2 increases beyond 75mm Hg, then individuals also experience convulsions, disorientation, hyperventilation and panic. In extreme cases, development of such symptoms can gradually lead to unconsciousness and finally death.

  • The severity of pneumonia was assessed by CURB-65 and PSI scores. An arterial blood gas analysis was obtained within 24 hours of admission.[ncbi.nlm.nih.gov]
  • We previously reported that hypercapnia alters expression of host defense genes, inhibits phagocytosis, and increases the mortality of Pseudomonas pneumonia in mice.[ncbi.nlm.nih.gov]
  • There are a number of causes including asthma, pulmonary embolism, pneumonia, pulmonary fibrosis, adult respiratory distress syndrome and pneumothorax.[nursingtimes.net]
  • […] in evolving untreated pneumonia [ 12 ; 13 ].[journals.plos.org]
  • Among patients with hypercapnia, 127 of 177 (71.75%) died, and the main causes of death were respiratory failure (84/127, 66.14%), pneumonia (15/127, 11.81%) and lung cancer (7/127, 5.51%).[bmjopen.bmj.com]
  • After admission to the intensive care unit, despite treatment with maximal conventional bronchodilatative therapy, the clinical picture deteriorated with evident signs of respiratory muscle fatigue.[ncbi.nlm.nih.gov]
  • Call your doctor as soon as possible if you experience any change in your symptoms or general health, especially if you notice profound fatigue, a decrease in concentration or confusion, muscle twitches, or palpitations.[copd.about.com]
  • 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.[primehealthchannel.com]
  • Prolonged hypoxemia Hypoxemia which may result in respiratory fatigue. Respiratory depressant drugs. Pathophysiology Carbon dioxide (CO2) metabolism: Produced by cellular metabolism.[vetstream.com]
  • Treatment with nocturnal O2 during a 2-yr period was associated with stable cardiovascular function but severe morning headaches and lethargy, presumably related to nightly bouts of hypercapnia and acidosis during sleep.[ncbi.nlm.nih.gov]
  • "Headache in Divers" . Headache: The Journal of Head and Face Pain . 41 (3): 235–247. doi : 10.1046/j.1526-4610.2001.111006235.x . PMID 11264683 .[en.wikipedia.org]
  • The International Classification of Headache Disorders 3rd edition On behalf of the Classification Committee of The International Headache Society I am proud to present the third edition of the International Classification of Headache Disorders (ICHD-[ihs-classification.org]
  • According to other sources, symptoms of mild hypercapnia might include headache, confusion and lethargy.[en.wikipedia.org]
  • Call your doctor as soon as possible if you experience any change in your symptoms or general health, especially if you notice profound fatigue, a decrease in concentration or confusion, muscle twitches, or palpitations.[copd.about.com]
Altered Mental Status
  • The rationale of such practice is based on the assumption that hypercapnia, although associated with altered mental status, is well tolerated.[ncbi.nlm.nih.gov]
  • mental status after supplemental oxygen as a result of acute on chronic respiratory acidosis and elevated Pa CO 2 Please rate topic.[step1.medbullets.com]
  • Despite higher pressure-support levels, hypercapnic patients had lower expiratory tidal volume and lower minute ventilation under NIV and had more frequently acidosis and altered mental status.[annalsofintensivecare.springeropen.com]
  • These include Altered mental status (agitation, somnolence) Peripheral or central cyanosis or decreased oxygen saturation on pulse oximetry Manifestations of a "stress response" including tachycardia, hypertension, and diaphoresis Evidence of increased[mcgill.ca]
  • Treatment with nocturnal O2 during a 2-yr period was associated with stable cardiovascular function but severe morning headaches and lethargy, presumably related to nightly bouts of hypercapnia and acidosis during sleep.[ncbi.nlm.nih.gov]
  • According to other sources, symptoms of mild hypercapnia might include headache, confusion and lethargy.[en.wikipedia.org]
  • Symptoms and signs may include: Paranoia, depression, and confusion, which may progress to coma Muscle twitches Seizures Palpitations Panic or a feeling of impending doom Dilation or widening of superficial veins in the skin Papilledema , swelling of[copd.about.com]


Measurement of arterial blood gases in patients with hypercapnia is indicated in the preliminary levels. This would give insight about the levels of carbon dioxide accumulated in the blood. In order to diagnose the underlying etiology, it is necessary to conduct various tests such as pulmonary function tests. This would help in confirming the presence of chronic obstructive pulmonary disease. In addition, chest radiographs also form an important part of the diagnostic procedure [8].

In instances, when hypercapnic respiratory failure is suspected, the levels of thyroid hormone should be detected in order to determine hypothyroidism. Studies have shown that hypothyroidism is a major reversible factor that causes respiratory failure.

Hypercapnia also has deleterious effect on the cardiovascular system; therefore, electrocardiography should be performed to rule out the presence of cardiovascular disease as the underlying cause. This test would also help in detection of arrhythmias.

  • Our main findings are as follows: (1) hypercapnia accelerated adipogenesis in visceral and subcutaneous preadipocytes, whereas hypocapnia inhibited adipogenesis; (2) hypercapnia did not affect adipocyte hypertrophy; (3) hypercapnia-accelerated adipogenesis[ncbi.nlm.nih.gov]
  • Because of the relationship between hypoxia and hypercapnia, we investigated the effect of hypercapnia on the HIF pathway.[ncbi.nlm.nih.gov]
  • The cerebral metabolic rate of oxygen (CMRO2) is reduced during apnea that yields profound hypoxia and hypercapnia.[ncbi.nlm.nih.gov]
  • Hypercapnia also reduced forskolin-stimulated CFTR-dependent anion secretion in primary human airway epithelia.[ncbi.nlm.nih.gov]
  • Since hypercapnia maintained rSO2 without changes in oxygenation index and hemodynamic parameters, mild hypercapnia should be maintained during shoulder arthroscopy in sitting position under general anesthesia.[ncbi.nlm.nih.gov]


The primary line of treatment for hypercapnic patients is careful administration of oxygen in order to prevent the condition from deteriorating. However, too much or too little oxygen can have its own share of ill effects, and therefore the amount of oxygen to be given should be carefully decided.

Once the condition of the patient has been stabilized, and hemodynamic status have been brought under control then efforts should be channelized for correcting the underlying condition. In severe cases, if signs of respiratory failure are evident, then concerned patients need to be stabilized through ventilator support. Affected individuals would also be required non-invasive positive pressure ventilation [9].


Treating underlying conditions can successfully restore lung functioning. Long-term oxygen therapy is indicated in patients with chronic obstructive pulmonary disease and which has a poor prognosis. Clinical trials have suggested that, the development of hypercapnia has been observed to be an adaptive mechanism in certain group of individuals, which helps in reduction of energy for the ventilator work. Such a type of adaptive mechanism can be an important marker indicating favorable prognosis in individuals with hypercapnia.


Hypercapnia is often a common accompaniment of chronic obstructive pulmonary disease. Other causes include exposure to toxins, overdose of certain drugs, hypoventilation and lung disease. Individuals with diminished consciousness can also develop hypercapnia. Environments having high concentration of carbon dioxide, practically observed in conditions of volcanic eruptions, can also lead to increased inhalation of the gas, eventually leading to the condition of hypercapnia. Hypercapnia is often observed in hospitalized patients who are being treated for chronic obstructive pulmonary disease, because such patients are treated through the method of hypoxic drive which employs administration of oxygen to such patients. Such a type of method can many a times turn life threatening [2].


Individuals suffering from obesity hypoventilation syndrome, eventually also develop hypercapnia as a secondary complication. In a study conducted on 219 patients with obstructive sleep apnea syndrome, it was revealed that 17% of patients also develop hypercapnia. In addition, the study also showed that, hypercapnia also developed in 13% patients with obesity hypoventilation syndrome. The relationship between these conditions majorly occurs due to restrictive ventilator defect [3].

Sex distribution
Age distribution


Hypercapnia is defined as carbon dioxide levels more than 45mmHg. Increase in concentration of carbon dioxide can also have a profound effect on the levels of carbonic acid which may drop dramatically. Such series of events give rise to condition of respiratory acidosis [4].

Respiratory acidosis can also occur in conditions of chronic obstructive pulmonary disease, obesity hypoventilation syndrome, chest wall disorders, obstructive sleep apnea and central nervous system depression. Factors that significantly affect the ventilation also have an effect on the exhalation of carbon dioxide from the blood and give rise to respiratory acidosis [5].


Several predisposing factors can be taken care of to prevent the onset of hypercapnia. Effective management of hypothyroidism can significantly reduce the onset of hypercapnia. In addition, controlling and proper correction of chronic obstructive pulmonary disease can also help prevent development of hypercapnia [10].


Hypercapnia, defined as abnormally elevated carbon dioxide levels in the blood, often triggers a spontaneous effect that increases the need for oxygen and hence induces increase in breathing. This in turn induces arousal during sleep. In cases, when such a type of reflex does not occur, then it can turn fatal and is one of the major reasons for sudden infant death syndrome. Hypercapnia is known to cause rapid onset of intracellular acidosis, if it not timely controlled [1].

Patient Information

  • Definition: Hypercapnia is defined as concentration of carbon dioxide above 45mmHg. The condition is also referred to as hypercarbia. Ineffective management of hypercapnia can favor development of respiratory failure.
  • Cause: Several factors impair the lungs to exhale the carbon dioxide from the body, causing a rise in its levels. These factors include lung disease, hypoventilation and state of reduced or altered consciousness. Hypercapnia can also occur in conditions of sleep apnea when the patients are administered oxygen.
  • Symptoms: Symptoms of hypercapnia include tachypnea, extrasystoles, decreased neural activity, and elevated blood pressure. In addition, other signs include full pulse, hand flaps, flushed skin and muscle twitches. In severe instances, individuals suffer from convulsions, disorientation, hyperventilation and panic.
  • Diagnosis: The arterial blood gases are measured in the preliminary levels. This is then followed by various tests to evaluate the underlying etiology. Pulmonary function tests are done to diagnose chronic obstructive pulmonary disease. In addition, electrocardiography is also indicated to assess cardiac functioning.
  • Treatment: Treatment is geared towards stabilizing the condition of the patient in order to prevent respiratory failure. This is done by careful administration of oxygen. In the preliminary levels, non-invasive positive pressure ventilation is provided. Thereafter, methods are channelized to correct the underlying condition of the patient. Ventilation may be required in severe cases.



  1. Weinberger SE, Schwartzstein RM, Weiss JW. Hypercapnia. N Engl J Med 1989; 321:1223.
  2. Rudolf M, Banks RA, Semple SJ. Hypercapnia during oxygen therapy in acute exacerbations of chronic respiratory failure. Hypothesis revisited. Lancet 1977; 2:483.
  3. Fleetham JA, Arnup ME, Anthonisen NR. Familial aspects of ventilatory control in patients with chronic obstructive pulmonary disease.Am Rev Respir Dis 1984; 129:3.
  4. Ehrsam RE, Heigenhauser GJ, Jones NL. Effect of respiratory acidosis on metabolism in exercise. J Appl Physiol. Jul 1982;53(1):63-9
  5. Cham GW, Tan WP, Earnest A, Soh CH. Clinical predictors of acute respiratory acidosis during exacerbation of asthma and chronic obstructive pulmonary disease. Eur J Emerg Med. Sep 2002;9(3):225-32. 
  6. Durrington HJ, Flubacher M, Ramsay CF, et al. Initial oxygen management in patients with an exacerbation of chronic obstructive pulmonary disease. QJM 2005; 98:499.
  7. PRICE HL.Effects of carbon dioxide on the cardiovascular system. Anesthesiology 1960; 21:652.
  8. Celli BR, MacNee W, ATS/ERS Task Force. Standards for the diagnosis and treatment of patients with COPD: a summary of the ATS/ERS position paper. EurRespir J 2004; 23:932.
  9. Plant PK, Owen JL, Elliott MW. Early use of non-invasive ventilation for acute exacerbations of chronic obstructive pulmonary disease on general respiratory wards: a multicentrerandomised controlled trial.Lancet. Jun 3 2000;355(9219):1931-5.
  10. Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease: Updated 2007 http://www.goldcopd.org

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Last updated: 2017-08-09 17:41