76: Altitude & Acid-Base Problems Flashcards
Remember that although the O2 partial pressure is the same at high altitude as at sea level (_____%), the overall barometric P lower, therefore O2 Pressure is _____ than at sea level.
Remember that although the O2 partial pressure is the same at high altitude as at sea level (21%), the overall barometric P lower, therefore O2 Pressure is lower than at sea level.
Give the equation of calculating the partial pressure of inspired air:
PO2 = 0.21 x (Variable – 47) = X mm Hg
Calculate the partial pressure of inspired air at sea level, where the total pressure is 760 mm Hg.
PO2 = 0.21 x (760 – 47) = 150 mm Hg
Calculate the partial pressure of inspired air at sea level, where the total pressure is 255 mm Hg.
PO2 = 0.21 x (255 – 47) = 44 mm Hg
Mild symptoms of hypoxemia at high altitude caused by inadequate response to hypoxemia resulting in reduced blood flow to the _____:
Drowsiness & Muscular Fatigue
Occasional Headache or Nausea
Sometimes euphoria
Gradual decline in cognition
Mild symptoms of hypoxemia at high altitude caused by inadequate response to hypoxemia resulting in reduced blood flow to the brain:
Drowsiness & Muscular Fatigue
Occasional Headache or Nausea
Sometimes euphoria
Gradual decline in cognition
Arterial hypoxemia stimulates peripheral chemoreceptors causing increased _____ drive:
_____ cardia = ↑ heart rate and contractility increases cardiac output, enhancing oxygen delivery.
Alveolar ventilation _____ = due to a maximum of about 1.7 times normal, raising alveolar PAO2, but PCO2 and H+ are both concurrently reduced because of increased ventilation.
This increase in ventilation can lead to respiratory _____osis.
Arterial hypoxemia stimulates peripheral chemoreceptors causing increased sympathetic drive:
Tachycardia = ↑ heart rate and contractility increases cardiac output, enhancing oxygen delivery.
Alveolar ventilation increases = due to a maximum of about 1.7 times normal, raising alveolar PAO2, but PCO2 and H+ are both concurrently reduced because of increased ventilation.
This increase in ventilation can lead to respiratory alkalosis.
Acclimatization to high altitude (chronic hypoxemia) :
After initial _____ in ventilatory rate due to hypoxia, ventilation continues to _____, driving up the alveolar partial pressure of _____.
Initial hyperventilation causes respiratory _____, which inhibits respiratory drive.
CO2 + H2O ↔ _____ ↔ H+ + HCO3-
_____ compensation restores normal pH, allowing ventilation to increase further. Kidney reabsorbes _____ bicarbonate so we lose more bicarbonate. So when kidney begins helping out, it allows us to _____ our ventilation even more.
Alveolar ventilation can increase 4-5 times after 2-5 days instead of the 70% increase initially.
Acclimatization to high altitude (chronic hypoxemia) :
After initial rise in ventilatory rate due to hypoxia, ventilation continues to increase, driving up the alveolar partial pressure of oxygen.
Initial hyperventilation causes respiratory alkalosis, which inhibits respiratory drive.
CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3-
Renal compensation restores normal pH, allowing ventilation to increase further. Kidney reabsorbes less bicarbonate so we lose more bicarbonate. So when kidney begins helping out, it allows us to increase our ventilation even more.
Alveolar ventilation can increase 4-5 times after 2-5 days instead of the 70% increase initially.
Renal compensations take hours to _____ to work for respiratory acidosis & alkalosis.
For _____ acidosis and alkalosis we have pulmonary compensations which work immediate.
Renal compensations take hours to days to work for respiratory acidosis & alkalosis.
For metabolic acidosis and alkalosis we have pulmonary compensations which work immediate.
Cardiovascular adaptation to chronic hypoxia include:
_____ cardiac output and vaso _____ (low blood PO2) increases blood flow to most organs.
_____ hematocrit (erythropoietin) = stimulates RBC production in the marrow.
Increased synthesis of 2,3-DPG _____ oxygen affinity to Hemoglobin in red blood cells, favoring unloading and delivery of oxygen to tissues.
Effect of DPG on the Oxygen dissociation curve is to shift the curve to the _____ favoring unloading and delivery of oxygen to tissues.
Pulmonary _____ tension (low PO2 constricts lung vascular smooth muscle) can lead to right heart hypertrophy and pulmonary edema.
Cardiovascular adaptation to chronic hypoxia include:
Increased cardiac output and vasodilation (low blood PO2) increases blood flow to most organs.
Increased hematocrit (erythropoietin) = stimulates RBC production in the marrow.
Increased synthesis of 2,3-DPG lowers oxygen affinity to Hemoglobin in red blood cells, favoring unloading and delivery of oxygen to tissues.
Effect of DPG on the Oxygen dissociation curve is to shift the curve to the right favoring unloading and delivery of oxygen to tissues.
Pulmonary hypertension (low PO2 constricts lung vascular smooth muscle) can lead to right heart hypertrophy and pulmonary edema.
Long-term adaptations to high altitude include:
Hypoxia-Inducible Factor 1 (HIF-1) Is a transcription factor that activates genes involved in erythro _____ and angio _____.
_____ HEMATOCRIT (HCT) FROM 40-45% TO > 55%. Renal hypoxia stimulates production and release of ERYTHROPOIETIN (EPO).
_____ PULMONARY DIFFUSING CAPACITY BY 2-3X Due to increased Blood Volume in pulmonary capillaries, and increased pulmonary capillary surface area with increased ventilation.
_____ TISSUE VASCULARITY triggered by growth factos released by hypoxic tissue.
_____ EXPRESSION OF OXIDATIVE ENZYMES IN MITOCHONDRIA enhances ability to extract O2.
Long-term adaptations to high altitude include:
Hypoxia-Inducible Factor 1 (HIF-1) Is a transcription factor that activates genes involved in erythropoiesis and angiogenesis.
Increased HEMATOCRIT (HCT) FROM 40-45% TO > 55%. Renal hypoxia stimulates production and release of ERYTHROPOIETIN (EPO).
Increased PULMONARY DIFFUSING CAPACITY BY 2-3X Due to increased Blood Volume in pulmonary capillaries, and increased pulmonary capillary surface area with increased ventilation.
INCREASED TISSUE VASCULARITY triggered by growth factos released by hypoxic tissue.
INCREASED EXPRESSION OF OXIDATIVE ENZYMES IN MITOCHONDRIA enhances ability to extract O2.
_____ mountain sickness:
Headache & Muscular Fatigue
Dizziness
Dyspnea
Sleep Disturbance
Peripheral Edema
Nausea & Vomiting
Caused by _____ edema due to cerebral vasodilation and by pulmonary edema due to hypoxic pulmonary vasoconstriction.
AMS CAN BE FATAL IF O2 IS NOT GIVEN OR IF INDIVIDUAL IS NOT TAKEN TO A LOWER ALTITUDE.
Acute mountain sickness:
Headache & Muscular Fatigue
Dizziness
Dyspnea
Sleep Disturbance
Peripheral Edema
Nausea & Vomiting
Caused by cerebral edema due to cerebral vasodilation and by pulmonary edema due to hypoxic pulmonary vasoconstriction.
AMS CAN BE FATAL IF O2 IS NOT GIVEN OR IF INDIVIDUAL IS NOT TAKEN TO A LOWER ALTITUDE.
_____ mountain sickness:
May occur after _____ residence at high altitude.
_____ response to hypoxemia with HCT > 60%, increasing blood viscosity and vascular resistance
_____ the risk of thrombosis
Combined with increased pulmonary vascular resistance, increased blood viscosity increases the afterload on the _____ heart, leading to congestive heart failure in the right heart (also right heart hypertrophy).
Chronic mountain sickness:
May occur after prolonged residence at high altitude.
Exaggerated response to hypoxemia with HCT > 60%, increasing blood viscosity and vascular resistance
Increases the risk of thrombosis
Combined with increased pulmonary vascular resistance, increased blood viscosity increases the afterload on the right heart, leading to congestive heart failure in the right heart (also right heart hypertrophy).
See yellow acid-base problems sheet.
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