Lecture 5 - potassium and CO2 infusion

Question 1

Discuss the Paterson (1989a) study?

Answer 1

Had 6 normals bike ergo up to 100Wew (inc Ve to 40L/min) and maximal sprint.
Showed changes in arterial K+ closely mirrored changes in Ve during exercise and recovery
-At 100w arterial K+ increased from 4-5mM, during sprint it increased to 7mM - these rises are very small though! Predicts the sensor must be highly sensitive.

Question 2

Paterson (1992) used 2 sedated monkeys at a constant PetCO2 to see the effects of K+ infusion on breathing. What did he find?

Answer 2

Showed an increase in plasma K+ from 6-8mM caused only a 1.4xfold increase in Ve.

Key issue that we don’t know a monkeys VO2 max, and the use of anaesthetic causes an underestimated response where breathing is depressed. Only 2.

Question 3

What did Warner and Mitchell (1990) find?

Answer 3

Had 7 unaesthetised goats treadmill, increased VO2 by 6x and Ve by 6x

K+ IV jugular infusion at rest provided to mimic exercise rises, this did not stimulate ventilation.

Question 4

Discuss Paterson (1989b)??

Answer 4

Had 4 hyperkalaemic renal patients that were given dextrose and insulin to lower their K+(a)

Showed that 30 mins post infusion K+a decreased from 7-5mM but no changes in ventilation (should stop in theory!)

Question 5

Discuss the Phillipson (1981) paper looking at whether CO2 infusion indicates Vo2 CR exist?

Answer 5

Had 4 sheep run on a treadmill or gave them an artificial lung.
CO2 was infused into the peripheral venous blood
Measurements were taken every 10 mins (ideally we measure through entire time course)
They found the same linear increase (X12fold) in Ve (2.5-30L/min) regardless of whether CO2 increase was from treadmill or CO2 infusion

Changes in VE were isoxic and isocapnic in 3/4 sheep.
They infused at the heart, missing potentially the key chemoreceptors, was it certain PaCO2 did not rise?

Question 6

Discuss Dolan et al (1981) ??

Answer 6

Had 7 dialysis patients, replaced a bicarbonate buffer with acetate(lowers CO2).

CO2 unloading reduced VCO2 by x0.8 fold and reduced ventilation from 7-6l/min

Again we don’t know about PaCO2, it would be better for a breath by breath analysis.