Chemoreceptors are responsible for signaling vasoconstriction, vasodilation, bronchoconstriction, and bronchodilation. Causes
The main physiologic causes of hypocapnia are related to hyperventilation. Hypocapnia is sometimes induced in the treatment of medical emergencies such as intracranial hypertension and hyperkalemia. Self-induced hypocapnia through hyperventilation is the basis for the dangerous schoolyard fainting game. Deliberate hyperventilation has been used by underwater breath-hold divers for the purpose of extending dive time as it effectively reduces respiratory drive due to low CO2 levels. This allows one to break their standard limit of breath holding, at an increased risk of shallow water blackout (which is a significant cause of drownings). This risk is caused to due to air hunger being reduced (due to low blood carbon dioxide levels) but oxygen levels not being increased. In fact hypocapnia reduces the oxygen levels available to the brain due to the elevated affinity of oxygen to hemoglobin (Bohr effect) hence highly increasing the chances of blackout. Diagnosis
Neonatal infants
Monitoring the level of carbon dioxide in neonatal infants to ensure that the level is not too high (hypercarbia) or too low is important for improving outcomes for neonates in intensive care. Carbon dioxide can be monitored by taking a blood sample (arterial blood gas), through the breath (exhalation), and it can be measured continuously through the skin by using a minimally invasive transcutaneous device. The most effective and safest approach for measuring carbon dioxide in newborn infants is not clear.
Epidemiology
Trench fever is a vector borne disease in which humans are primarily the main hosts. The vector through which the disease is typically transmitted is referred to as the human body louse "Pediculus humanus humanus", which is better known as lice. The British Expeditionary Force Pyrexia of Unknown Origin Enquiry Sub-Committee concluded that the specific means by which the vector infected the host was louse waste entering the body through abraded skin. Although the disease is typically found in humans, the gram negative bacterium which induce the disease have been seen in mammals such as dogs, cats, and macaques in small numbers.Being that the vector of the disease is human body louse, it can be determined that the main risk factors for infection are mostly in relation to contracting body louse. Specifically, some risk factors include: body louse infestation, overcrowded and unhygienic conditions, body hygiene, war, famine, malnutrition, alcoholism, homelessness, and intravenous drug abuse.The identified risk factors directly correlate with the subpopulations of identified infected persons throughout the duration of the known disease. Historically, trench fever was found in young male soldiers of World War I, whereas in the 21st century the disease mostly has a prevalence in middle aged homeless men. This can be seen when looking at a 21st-century outbreak of the disease in Denver, Colorado, where researcher David McCormick and his colleagues came across the gram negative bacterium in 15% of the 241 homeless persons who were tested.