Restricted oxygen flow to the body's tissue that leads to<unk>  can be caused by a variety of situations or other underlying conditions. # High altitude (above 3048 metres/10,000 feet) # Hypoventilation – failure of respiratory pump due to any cause (fatigue, barbiturate poisoning, pneumothorax, etc.) #Ventilation perfusion mismatch #Obstructed airway #Drowning # Abnormal pulmonary function # Chronic obstructive pulmonary diseases (COPD) # Neuromuscular diseases or interstitial lung disease #Constrained blood flow to a tissue (such as atherosclerosis or vasoconstriction) #Blockage in blood flow like a sickle cell crisis #Low or no blood flow caused by bleeding or heart attack #Malformed vascular system such as an anomalous coronary artery #Limited oxygen transportation due to anemia While respiring in the open air at high altitudes, the human body experiences altitude sickness and hypoxemia due to a low partial pressure of oxygen, decreasing the carriage of oxygen by hemoglobin. * Above 3000 metres (10,000 feet) - enough<unk>  stimulation to cause increased ventilation * Above 3700 metres (12,000 feet) - first irritability appears * Above 5500 metres (18,000 feet) - severe symptoms * Above 6100 metres (20,000 feet) - consciousness lost While breathing pure oxygen, through oxygen cylinder or other means, the maximum height a human can reach while their body is in atmospheric pressure is 13,700 metres (45,000 feet)
Generalized hypoxia
Cardiovascular drift
Cyclospasm
Bradypnea
Exercise intolerance
Apnea
Respiratory arrest
Orthostatic hypotension