Hypobarism (mod6) Flashcards
(27 cards)
Definition of Hypobarism
Barometric pressure (pressure the atmosphere exerts on the body) decreases as mass of the atmosphere decreases, resulting in:
- high altitude sickness
- High altitude cerebral edema (HACE)
- High altitude pulmonary edema (HAPE)
0 Decompression sickness (bends)
Why does High altitude sickness occur?
If you don’t decel the mountain right
What is decompression sickness?
Rapid release of nitrogen because the pressure around us is much higher
- Barometric pressure that is decreased, pressure atmosphere is exerting on the body
Is barometric pressure higher or lower outside of the body?
Barometric pressure is higher on the outside of the body normally
Therapeutic intervention for Hypobarism?
Hyperbaric chamber to address CO poisoning, wound healing (prevent amputation’s), and oxygen toxicity.
2 gas laws associated with Hypobarism?
Henrys law and Daltons law of partial pressures
What is henrys law and how does it relate to hypobarism?
The amount of gas dissolved in a liquid is directly proportional to the partial pressure of the gas above the solution (and the solubility coefficient of the gas)
Dalton’s Law of Partial pressures in relation to Hypobarism
The total pressure of a mixture of gases is the sum of the pressures that each gas would exert if it were present alone
- Explains changes in the atmospheric content of specific gases at different altitudes
- As we ascent the barometric pressure is going to decrease, 33% of what you get at sea level and you get hypoxia
- When you ascent the whole problem is hypoxia
- Partial pressure decreases amount of O2
Pathophysiology at high altitudes
Decreased barometric pressure(as we ascend) –> Decreased partial pressure oxygen exerts –> affects pressure gradient across a/c membrane –> Hypoxemia ->Hypoxia–> if the ascent is gradual–>compensatory mechanisms
- If your’re not a climber and you’re not use to it it can put you into mountain illness
Acute versus Acclimatization reaction
- Acute reaction you’re in an airplane and cabin depressurizes and there’s no O2 available resulting in hypoxia
- Acclimatization is a gradual process (think about the different base camps at Everest)
What does Severity of Hypobarism depend on?
Not typically seen below 10,000 feet. Severity depends on:
- Altitude ascended to
- Rate of ascent (how fast, history of inflammatory disease can put you at risk)
- individual susceptibility
How can acute mountain illness be avoided
Allow acclimatization of the body, ascend at a good rate that body adjusts to
Pathophysiology acute mountain illness
Increased MV (hypoxic ventilatory response), including increased RR and Vt
- Respiratory alkalosis –>Triggers kidneys to offload HCO3 (kidneys cause us to pee more)
- Hemoglobin changes; offloading of plasma for greater concentration of hgb
- EPO stimulates RBC production
- Cardiac changes (increased CO and HR)
How long do the kidneys offload HCO3 when caused by acute mountain illness?
2-3 days; its why we are supposed to go slow
Hemoglobin changes caused by altitude sickness?
Kidneys pee off more in order to allow for greater hgb (offload plasma)
- Hematocrit increase and you build up more hemoglobin, building more trucks to take O2 to tissue
- We will not get from atmosphere and body compensates with the hemoglobin
- Climber takes 5-7 days to acclimatize
Cardiac changes caused by altitude sickness
Increased CO and HR
- oxygen dissociation curve will initially shift left than back right to where it was initially because of alkosis
- left shift to help with loss of O2, helps hemoglobin hold onto O2
How is the Oxyhemoglobin dissociation curve affected by altitude sickness?
Shifts left due to respiratory alkosis, it tries to compensate for loss of O2 and H+
Remember
- left shift = increased affinity for O2
- Right shift = decreased affinity for O2
Symptoms of Acute mountain illness (altitude sickness)
Begin within 4-12 hours; quick onset: often resolves without descent
- Headache
- nausea/vomitting
- loss of appetite
- decreased u/o
- insomnia
Pathophysiology, progression of acute mountain sickness?
Edema on part of the brain causing nausea/vomitting
- insomnia due to changes in resp alkalosis
- can advance to HACE
- low end of spectrum
symptoms of High altitude cerebral edema (HACE)
After 1-3 days, quick onset
- Altered mental status, extreme fatigue, inability to walk
- Acute myocardial infarction (AMI) that could lead to coma or brain herniation
Pathophysiology, progression of High altitude cerebral edema (HACE)?
Progression may be due to oxidative stress, systemic responses increasing CBF increasing ICP –> coma/brain herination
- Pressure of vessels in the brain increases causing leaking
Does High altitude pulmonary edema always occur with altitude illness?
Independent of acute altitude illness
Symptoms of High altitude pulmonary edema (HAPE)
slow onset, 1-5 days. Symptoms similar to pulmonary edema:
- Exertional dyspnea
- Cough and chest tigtness
- Crackles
- Orthopnea
Pathophysiology, progression of High altitude pulmonary edema (HAPE)
Pulmonary vasoconstriction–>increased hydrostatic pressure–>increased capillary permeability–>non-uniform, non-cardiogenic pulmonary edema
- vessels leak into the lungs
- only happening to certain areas in the arteries
- patchy non cardiogenic pulmonary edema
