Water vapour still occupies the same pressure too—this means that there is less oxygen pressure available in the lungs and blood. Compare these two equations comparing the amount of oxygen in blood at altitude:
The hypoxia leads to an increase in minute ventilation (hence both low CO2, and subsequently bicarbonate), Hb increases through haemoconcentration and erythrogenesis. Alkalosis shifts the haemoglobin dissociation constant to the left, 2,3-BPG increases to counter this. Cardiac output increases through an increase in heart rate.The bodys response to high altitude includes the following:
↑ Erythropoietin → ↑ hematocrit and haemoglobin
↑ 2,3-BPG (allows ↑ release of O2 and a right shift on the Hb-O2 disassociation curve)
↑ kidney excretion of bicarbonate (use of acetazolamide can augment for treatment)
Chronic hypoxic pulmonary vasoconstriction (can cause right ventricular hypertrophy)People with high-altitude sickness generally have reduced hyperventilator response, impaired gas exchange, fluid retention or increased sympathetic drive. There is thought to be an increase in cerebral venous volume because of an increase in cerebral blood flow and hypocapnic cerebral vasoconstriction causing oedema. Diagnosis
Altitude sickness is typically self-diagnosed since symptoms are consistent: nausea, vomiting, headache, and can generally be deduced from a rapid change in altitude or oxygen levels. However, some symptoms may be confused with dehydration. Some severe cases may require professional diagnosis which can be assisted with multiple different methods such as using an MRI or CT scan to check for abnormal buildup of fluids in the lung or brain. Prevention
Ascending slowly is the best way to avoid altitude sickness. Avoiding strenuous activity such as skiing, hiking, etc.
Vanishing bile duct syndrome is a loose collection of diseases which leads to the injury to hepatic bile ducts and eventual ductopenia. Signs and symptoms
The presentation is dependent upon the underlying cause. The course can be rapid or chronic. Fatigue
Anorexia
Abdominal pain
Weight loss
Pruritus
Hyperlipidemia
Malabsorption
Fat-soluble vitamin deficiencies
Elevated alkaline phosphatase
Elevated gamma-glutamyltransferase
Elevated conjugated bilirubin

Cause
Congenital
In fetal and neonatal life the ductal plates are remodeled. The malformations can be atretic or fibrocystic. Atretic causes
Intrahepatic bile duct atresia (Alagille syndrome) (ALGS2 MIM:610205 and ALGS1 MIM:118450)
Extrahepatic bile duct atresia

Fibrocystic causes
Autosomal recessive polycystic kidney disease
Congential hepatic fibrosis
Carolis disease
Von Meyenburg complex

Chromosomal associations
Trisomy 17, 18 and 21

Genetic associations
Cystic fibrosis
Alpha 1 antitrypsin deficiency
Trihydroxycoprostanic acidemia
Bylers disease

Immunologic associations
Bile duct injury and loss can result from autoimmune destruction. T cells recognize biliary epithelial cell antigens causing injury and eventual atresia. Other causes
Primary biliary cirrhosis
Primary sclerosing cholangitis
Hodgkins lymphoma
Chronic graft-versus-host disease
Drugs(chlorpromazine)/Toxins
Ischemia

Diagnosis
Treatment
Treatment is dependent upon the underlying cause. Treatment is supportive as it is not possible to induce regrowth of lost ducts. Medical therapies
Ursodeoxycholic acid
Immunosuppression
General consensus is that more studies are needed before this can be considered
Organ transplant

References
External links
Uptodate:Hepatic ductopenia and vanishing bile duct syndrome