title: Hypercapnia and hypocapnia in neonates.
abstract: BACKGROUND
  The arterial partial pressure of carbon dioxide (PaCO2) represents the balance between CO2 production and consumption. Abnormal increase or decrease in PaCO2 can affect the body's internal environment and function. Permissive hypercapnia has aroused more attention as a novel ventilatory therapy. The aim of this study was to elucidate the effects of hypercapnia and hypocapnia on the functions of such neonatal organs as the lung and brain.
  
  
  METHODS
  The PubMed database was searched with the keywords "hypocapnia", "hypercapnia" and "newborn".
  
  
  RESULTS
  Hypocapnia is a risk factor for potential damage to the central nervous system, such as periventricular leukomalacia, intraventricular hemorrhage, cerebral palsy, cognition developmental disorder, and auditory deficit. Hyperventilation can lessen pulmonary artery hypertension to certain extent, but hypocapnia can aggravate ischemia/reperfusion-induced acute lung injury. Severe hypercapnia can induce intracranial hemorrhage, even consciousness alterations, cataphora, and hyperspasmia. Permissive hypercapnia can improve lung injury caused by diseases of the respiratory system, lessen mechanical ventilation-associated lung injury, reduce the incidence of bronchopulmonary dysplasia and protect against ventilation-induced brain injury. In addition, permissive hypercapnia plays a role in expanding cerebral vessels and increasing cerebral blood flow.
  
  
  CONCLUSIONS
  Severe hypercapnia and hypocapnia can cause neonatal brain injury and lung injury. Permissive hypercapnia can increase the survival of neonates with brain injury or respiratory system disease, and lessen the brain injury and lung injury caused by mechanical ventilation. However, the mechanism of permissive hypercapnia needs further exploration to confirm its safety and therapeutic utility.
authors.affiliation: Department of Neonatology, Guangzhou Children's Hospital, Guangzhou Medical College, Guangzhou 510120, China. zhouwei_pu002@126.com
authors.forename: Wei
authors.initials: W
authors.lastname: Zhou
authors.forename: Wen
authors.initials: W
authors.lastname: Liu
mesh_terms: D002490:Central Nervous System / Q000503:physiopathology; D002493:Central Nervous System Diseases / Q000453:epidemiology; D002543:Cerebral Hemorrhage / Q000453:epidemiology / Q000503:physiopathology; D004734:Energy Metabolism / Q000502:physiology; D006801:Humans; D006935:Hypercapnia / Q000503:physiopathology* / Q000628:therapy*; D016857:Hypocapnia / Q000453:epidemiology / Q000503:physiopathology* / Q000628:therapy*; D007231:Infant, Newborn; D012121:Respiration, Artificial / Q000379:methods*; D012137:Respiratory System / Q000503:physiopathology; D012140:Respiratory Tract Diseases / Q000453:epidemiology; D012307:Risk Factors