Exercise capacity Flashcards
What occurs to pleural pressure, transmural pressure, alveoli and thus ventilation as you go down the lung?
Pleural pressure becomes less negative
Smaller transmural pressure
Alveoli are smaller and more compliant
More ventilation at lung base
How does perfusion vary down the lung and what causes this?
Higher intravascular pressure
(gravity effect)
More recruitment
Less resistance
Higher flow rate
Higher perfusion at base of lung
How does ventilation:perfusion change going up the lung at rest
How does ventilation:perfusion change going up the lung during exercise
What is the ultimate function of the increased perfusion of the lungs during exercise?
Filling up the layers of lung blood vessels to reduce the preference of the lung base for ventilation
What is involved in a CP exercise test?
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 can you measure in a CP exercise test?
Lots and lots of data
Peak VO2 usually the primary outcome
ECG changes monitored throughout
What are the advantages and disadvantages of a CP exercise test
Advantages
Quantifies performance in relation to metabolism
Precise and reproducible
Continuous monitoring for safety
Disadvantages
Requires skilled technical support (calibration and
Very expensive (initial & ongoing costs)
Needs dedicated space
What is involved in a 6min walk test?
Uses a 20-30 m flat course (e.g. corridor)
Objective is to cover greatest distance as possible in six minutes
Externally timed by assessor
Sub-maximal test
What are the outputs of the 6min walk test?
Primary outcome is total distance walked in six minutes
Secondary variables may be ‘perceived exertion’ scales, heart rate and pulse oximetry
What are the advantages and disadvantages of the 6min walk test
Advantages
Patient-driven pace – speeding up, slowing down & rest OK
Cheap to deploy
Validated in many clinical populations
Disadvantages
Requires a significant unobstructed course, it often undertaken in a public hospital corridor
The pace is not reregulated
What is involved in the incremental shuttle test
Uses a 10 m circuit
Externally paced by an audio recording (like 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 test
Primary outcome is total distance walked before volitional end
Secondary variables may be ‘perceived exertion’ scales, heart rate and pulse oximetry
What are the advantages and disadvantages of the incremental shuttle test
Advantages
Cheap to deploy
Validated in many clinical populations
The external pacing helps some to achieve maximum levels
Disadvantages
Requires an unobstructed course, it is often undertaken in a public hospital corridor
For some the incremental nature is difficult (min. speed 1.8km/hour)
Ceiling effect of 1020 m
Patient can be penalised for poor pace management
