Lecture 8: Cardio Pulmonary Exercise Testing Interpretation Flashcards
What is the physiological explanation of the anaerobic (ventilator) threshold as described by Wasserman?
The AT is the time point in incremental exercise, which indicates a shift in the type of metabolism within the cells (muscle cells). From this point on, a solely aerobic metabolism won’t suffice to meet the demand of exercise therefore meaning the contribution of anaerobic glycolysis increases to meet this energy demand. As a result of this, the ratio of CO2:O2 begins to increase.
Describe the V-slope method of assessing the anaerobic threshold from CPET results?
The V-slope method allows you to plot CO2 against VO2 on a graph. A line is displayed representing ‘1’, this line or slope represents the relationship between VO2 and VCO2 being completely proportional therefore any increase in one means the same in the other. The point at which this line becomes >1 represents the AT, from here a line of best fit must be drawn through the increase, this represents the increase of CO2 compared with O2. V-slope method allows AT to be expressed as PkVo2, anything below 40% is Abnormal.
Describe the normal ϪVo2/ϪWR trajectory, define abnormalities observed during CPET?
The normal trajectory of VO2 and WR is linear, therefore an increase in one is proportional to an increase of WR. A normal range would ideally be >10 however the lowest value we accept as normal is 8.4ml.min.w.
individuals suffering with CV disorders display a reduced trajectory especially above the AT, the reason being is because of an increase in the contribution of anaerobic metabolism and subsequently an inadequate O2 supply.
What does abnormal O2 pulse progression during CPET tell us about the possible cause of dyspnoea?
Abnormal O2 pulse progression during a CPET indicates that the VO2 being consumed relative to HR is decreased, therefore VO2 consumption no longer increases with exercise. this indicates a decrease in stroke volume (Vs) and can potentially be associated with a cardiac problem, such as systolic heart failure. Therefore meaning the heart is unable to pump sufficient amounts of oxygenated blood to accommodate for metabolic demands.
What is the main utility of assessing the PETCO2 values during a CPET?**
PETCO2 is the gradient between the CO2 exhaled and the CO2 within the blood. PETCO2 is shown to be a useful index for pulmonary bloody flow.
