PSC1002/L20 Adaptations to Altitude Flashcards
What is the partial pressure of a given gas determined by? (2)
Concentration of the gas within the mixture
Total pressure of the mixture
Define Dalton’s Law.
Pressure exerted by a mixture of gases is equal to the sum of the partial pressures of each gas in the mixture
What is the effect of altitude on gas exchange? (2)
Less O2 diffused into muscles
Less O2 diffused into blood
What is the response of the body to a hypobaric environment? (3)
Increased rate and depth of ventilation
Chemoreceptors stimulated by low PO2
PO2 drives respiration due to hypoxia
What is the role of the kidneys in high altitudes?
Maintaining pH homeostasis
What are PaO2 and acid-base homeostasis in the context of chronic hypoxia? (2)
Hypoxic ventilatory response (HVR)
Renal excretion of bicarbonate (HCO3)
What may be the result of an inadequate renal response to respiratory alkalosis via hypocapnia? (2)
Increased blood pH
Blunted HVR
Decreased oxygen saturation
Decreased cerebral blood flow
Describe the hyperventilation cycle initiated by hypoxia. (5)
Hypoxia
Increased ventilation
Increased PO2
Decreased in PCO2 & increased pH
Decreased ventilation
How does renal compensation to metabolic alkalosis work? (2)
Decrease in HCO3 in proximal tubule (excreted)
Decrease in H+ secretion by a-intercalated cells (acid retention)
How does renal compensation improve ventilation? (4)
Reducing impact of respiratory induced alkalaemia
Decreased PCO2 detected by central chemoreceptors
Decreased respiration
Increased [H+] detected by peripheral chemoreceptors
Increased respiration
What factors can increase oxygen affinity/left shift? (3)
Decreased temperature
Decreased 2-3 DPG
Decreased [H+]
CO
What factors can decrease oxygen affinity/right shift? (3)
Increased temperature
Increased 2-3 DPG
Increased [H+]
Describe the effect of increased 2-3 DPG.
Hb releases O2 at a higher PO2 making more O2 available to tissues during hypoxia
Explain how short-term exposure to high altitude results in increased haematocrit. (3)
Increase in urination
Increase respiratory loss of H2O as Increased ventilation rate and dry air
Increased haematocrit
Explain how long-term exposure to high altitude results in increased haematocrit. (4)
Increased haemopoiesis
Decrease O2 tension in kidney
Kidney releases erythropoietin
Increased haematocrit
Describe how increased capillary numbers (angiogenesis) are beneficial to high altitude. (3)
Improved diffusion of oxygen by shortening diffusion distance
Increases SA for gas exchange both at alveoli and tissue
More mitochondria and cellular respiratory enzymes formed
What does the incidence and severity of acute mountain sickness depend on? (3)
Rate of ascent
Altitude attained
Length of time at altitude
Degree of physical exertion
Individual’s physiological susceptibility
What are the major symptoms of acute mountain sickness? (3)
Headache
Fatigue
Dizziness
Anorexia
Cyanosis
What can acute mountain sickness progress into? (2)
HAPE - high altitude pulmonary edema
HACE - high altitude cerebral edema
What occurs during HAPE? (5)
Alveolar hypoxia
Hypoxic pulmonary vasoconstriction
Increased capillary pressure
Increased hydrostatic pressure & damage to capillary wall
Oedema
What are the symptoms of HACE? (3)
Severe headache
Confusion
Agitation/irritability
Nausea/emesis
Ataxia
Hallucinations
Seizures
Coma
How does HACE occur? (3)
Cerebral hypoxia
Vasogenic oedema/cytotoxic oedema
Impaired brain function
Define vasogenic oedema.
Movement of fluid into CNS across leaky blood brain barrier increases intracranial pressure
Define cytotoxic oedema. (2)
Retention of fluid by cells in CNS
Cells swell and increases intracranial pressure
What is the immediate response to HAPE and HACE? (2)
Descent
Place patient in Gamow bag
