Respiratory strand: Lecture 11 - Challenges to Normal Respiration Flashcards
How much oxygen do we need at rest?
1 MET
-4.8 mL/kg/min
-200 mL/min
Basal oxygen requirement increases several fold with exercise
What is the relationship between work done and oxygen consumption?
Increases lineally until levels off as you can’t physically burn any more oxygen as you can’t deliver any more oxygen to your lungs and tissues (heart and tissues maxed out).
At this point (VO2max) it becomes anaerobic respiration and you are generating an oxygen debt
How are changes in oxygen consumption carried out?
- changes are quick in onset
- psychological
- neural input to inspiratory centre
- proprioreceptors
- small changes in ABGs (arterial blood gases) e.g by becoming acidotic
- cardiovascular changes
- temperature regulation
How can we measure how fit an individual is?
VO2max - maximum oxygen use
Why is the partial pressure of oxygen lower at higher altitudes?
- atmospheric pressure decreases with distance above the earth’s surface
- even though the %oxygen doesn’t change at higher altitudes, the total pressure is less so the partial pressure of oxygen is less
How is the partial pressure of inspired O2 at alveolar level different to atmospheric and why?
Its less
As it travels down the trachea, bronchi etc it becomes mixed with water vapour at body temperature so its diluted
Then, when it reaches the alveoli, it becomes further diluted with CO2 thats leaving the alveoli
What is the numerical difference in pO2 in the atmosphere compared to alveoli?
Decreases from 21kPa to 13.3kPa respectively
What are the effects of hypoxia?
- confusion
- headache
- nausea
- intracranial pressure increase
- blurred vision
- pulmonary hypertension
- pulmonary/cerebral oedema
What is the saturated vapour pressure of water?
6.3kPa
How do we respond to high altitude?
- hyperventilation and respiratory alkalosis
- increased 2,3-DPG causes better unloading of oxygen
- polycythaemia (increasing number of RBCs and therefore haemoglobin) - slow to develop
- bicarbonate excretion from CSF and kidneys
- diuresis, hyponatraemia
- acetazolamide
What is cheyne stokes respiration?
Where the respiratory control gets very unordered
alternating shallow and deep breaths
Occurs in severe mountain sickness
What is free diving?
when he diver goes as deep as they can without oxygen
Why would a diver hyperventilate before diving?
to get co2 as low as possible relative to pO2
Why does death usually occur during the ascent back up from free diving?
Because of expansion of the chest
as oxygen is used up and the diver is hypoxic
For deep diving, what pressure is air supplied at?
Environmental pressure
