6.9: Exercise capacity Flashcards
Why is it easier to ventilate the base of the lung rather than the apex
Tissue stretched at apex compared to base
Base more readily ventilates as it is more compliment
Ventilation at the apex of the lung
Pleural pressure is more negative
Greater transmural pressure gradient
Alveoli larger and less compliant
So less ventilation
Ventilation at the base of the lung
Pleural pressure is less negative
Smaller transmural pressure
Alveoli smaller and more compliant
More ventilation
Perfusion at the apex of the lung
Lower intravascular pressure (gravity effect)
Less recruitment
Greater resistance
Lower flow rate
Perfusion at the base of the lung
Higher intravascular pressure (gravity effect)
More recruitment
Less resistance
Higher flow rate
Excersise is
Purposeful, structured activity that involves gross muscular activity to improve physical condition
Physical activity is
Holistic term that includes all muscular activity of all intensities
Activities of daily living are
Basic independent self-care tasks done on daily basis that require coordination, strength and range of motion
4 factors affecting exercise capacity
Neurological (motor control)
Respiratory (ability for lungs to ventilate,gas exchange)
Cardiovascular (ability for heart to receive blood from lungs and pump to working muscles)
Muscular (local perfusion)
Outline why ventilation perfusion matching is important
Efficient gas exchange needs maximum coupling between ventilation and perfusion
Inadequacy of either gas or blood has significant impacts on removal of CO2 and blood oxygenation
3 ways to measure exercise capacity
Cardiopulmonary excersise test
Six-minute walk test
Incremental shuttle walk test
What is involved in the cardiopulmonary exercise test
Uses cycle ergo meter or treadmill
Intensity is incremental
Undertaken under close clinical supervision in controlled environment
ECG, ventilation, O2 and CO2 routinely measured
Outputs of cardiopulmonary exercise test
Lots of data
Peak VO2 - primary outcome
ECG changes monitored throughout
Advantages of cardiopulmonary exercise test
Quantifies performance in relation to metabolism
Precise and reproducible
Safety - continuous monitoring
Disadvantages of cardiopulmonary exercise test
Requires skilled technical support
Very expensive
Needs dedicated space
Process of six-minute walk test
Uses 20-30m flat course
Objective is to cover greatest distance as possible in 6min
Externally timed by assessor
Sub-maximal test
Outputs of six minute walk test
Total distance walked - primary outcome
Heart rate, pulse oximetry - secondary variables
Advantages of six minute walk test
Patient driven pace
Cheap
Validated in clinical populations
Disadvantages of six minute walk test
Requires unobstructed course
Pace nit reregulated
Incremental shuttle walk test involves
10m circuit
Externally paced by audio recording
Each minute has one extra length than previous minute
Outputs of incremental shuttle walk test
Total distance - primary outcome
Perceived exertion scales, heart rate, pulse oximetry - secondary variables
Advantages of incremental shuttle walk test
Cheap
Validated
External pacing helps achieve mex levels
Disadvantages of incremental shuttle walk
Requires an unobstructed course
For some incremental walking is difficult
Patient can be penalised for poor pace management
An exercise stress test to rule out ischemic heart disease is positive when
The ST segment of the ECG is depressed
