Lesson 3

Heart Rate and Oxygen Pulse as a Function of Work Rate

Heart Rate (HR) and VO2/HR (O2 pulse or stroke volume x arteriovenous O2 difference) versus time and work rate . HR is high and VO2/HR is low for a given work rate in patients with certain cardiovascular defects. With chronotropic incompetence or beta blockade without systolic or diastolic dysfuntion, the O2 pulse could be normal or high.

Heart Rate and Carbon Dioxide Output as a Function of Oxygen Uptake

HR versus VO2, and VCO2 versus VO2. In normal subjects, HR increases linearly with VO2 to their predicted maximums. In patients with heart failure, without chronotropic incompetence, the increase is steep. The relationship may lose its linearity, with HR increasing progressively more rapidly than VO2 in patients with myocardial ischeamia.

Ventilatory Equivalents for Oxygen and Carbon Dioxide

Ventilatory equivalent for O2 and CO2 (VE/VO2 and VE/VCO2) verus time and work rate.VE/VO2 decreases to a nadir at the AT. VE/VCO2 decreases to a nadir in the period between the AT and the ventilatory compensation point. Both values are high in diseases with uneven ventilation-perfusion relationships (increased Vd/Vt).

+ lesson 1 and 2

Panel 2VO2VCO2Panel 5panel 6

Question 1:  Is exercise limited by impaired O2 flow?

Example of Disorders:
1. Due to ischaemic, myopathic, valvular, congenital heart disease? (panel 2,3,5)
2. Due to Pulmonary vascular disease? (panel 2,3,5,6)
3. Due to Pheripheral arterial disease? (panel 3,5)
4. Due to anaemia, hypoxemia, or elevated COHb? (panel 2,3,5)

Markers for Abnormality:

1. ECG; AT; VO2/HR; VE/VCO2
2. VO2/WR; AT; VO2/HR; VE/VCO2
3. BP; VO2/WR; VCO2/WR
4. VO2/HR

 

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