1B exercise capacity Flashcards
Define exercise
Purposeful, structured activity that involves gross muscular activity to improve physical condition (e.g. jogging, stretching)
Define physical activity
A holistic term that includes all (purposeful and incidental) muscular activity of all intensities (e.g. walking, stairs)
Define activities of daily living
Basic independent self-care tasks done on a daily basis that require coordination, strength and range of motion
What (in the lungs) is needed for efficient gas exchange?
- Maximum coupling between ventilation and perfusion
- Inadequacy of either V or Q will have significant impact on removal of CO2 and blood oxygenation
How does the capillaries react to non-ventilated alveoli due to pathology?
- Pulmonary circulation has specialised cells to detect local O2 conc
- If there’s an ischaemic environment with low O2, the capillaries will vasoconstrict
- This increases resistance and decreases blood flow so blood preferentially goes to other more ventilated areas in lungs
What does the cardiopulmonary exercise test involve?
- Uses a cycle ergometer or treadmill
- Intensity is incremental
- Undertaken under close clinical supervision in a controlled environment
- ECG, ventilation, O2 and CO2 routinely measured
What are the outputs of cardiopulmonary exercise test?
- Lots of data
- Peak VO2 usually the primary outcome (volume of oxygen consumed)
- ECG changes monitored throughout
What are the advantages to a cardiopulmonary exercise test?
- Quantifies performance in relation to metabolism
- Precise and reproducible
- Continuous monitoring for safety
What are the disadvantages of a cardiopulmonary exercise test?
- Requires skilled technical support (calibration)
- Very expensive (initial and ongoing costs)
- Needs dedicated space
What is the six minute walk test?
- Uses a 20-30m flat course (e.g. corridor)
- Objective is to cover greatest distance as possible in 6 minutes
- Externally timed by assessor
- Sub-maximal test
What are the outputs of a six-minute walk test?
- Primary outcome is total distance walked in 6 mins
- Secondary variables may be ‘perceived exertion’ scales, heart rate and pulse oximetry
What are the advantages of the six minute walk test?
- Patient-driven pace- speeding up, slowing down and rest OK
- Cheap to deploy
- Validated in many clinical populations
What are the disadvantages of the six minute walk?
- Requires a significant unobstructed course, it often undertaken in a public hospital corridor
- The pace is not reregulated
What does the incremental shuttle walk test involve?
- Uses a 10m circuit
- Externally paced by an audio recording (like a bleep test)
- Each minute has one extra length than the previous minute e.g. minute 1 = 3 lengths of 20s, minute 2 = 4 lengths of 15s)
What are the outputs of the incremental shuttle walk test?
- Primary outcome is total distance walked before volitional end
- Secondary variables may be ‘perceived exertion’ scales, heart rate and pulse oximetry
Describe this chart
- Pink lines indicate the ventilatory (anaerobic) threshold
- Top right chart- there is a gradient change at the anaerobic threshold where volume of CO2 produced is at a much higher rate than O2 being consumed
- Middle chart- shows VE (ventilation- amount of gas moving in and out of lungs). Starts to increase a lot at anaerobic threshold because of higher rate of VCO2 from then so ventilation needs to be higher to maintain acid-base homeostasis
- Top left chart- red line is VO2 which shows it plateaus- this means we have recorded max VO2- tricky to reach with older patients since they might not be able to ride the bike well in the cardiopulmonary test due to weak legs/uncomfortableness in sitting on saddle
- Bottom middle chart- RER is respiratory exchange ratio- VCO2 divided by VO2- this increases exponentially showing unsustainable rates of exercise as VCO2 increases a lot due to reliance on anaerobic energy production
