Week 3 - CPET Flashcards
Give some advantages/disadvantages of field tests
Advantages
1. Can be used to measure progress
2. Can stratify patients - priority for operation/transplant.
3. Require minimal equipment
Disadvantages
1. Discrete data only, gives a set score e.g. distance walked, number of steps.
2. Patient may not reach their maximum unless they are very unwell/unfit.
Give some advantages and disadvantages of CPET compared to Field tests
Advantages
1. CPET allows the simultaneous study of the functional capabilities of different systems - respiratory, muscular and cardiovascular.
2. This can be at rest and maximal metabolic rate.
3. Can assess the causes of fatigue
4. Allows the reserve capacity of the body to be stressed, particularly in terms of its ability to deliver oxygen to peripheral muscles.
Disadvantages
1. It may not be suitable to push the patient to their maximum.
2. Requires specialist equipment.
Give uses of CPET
Differential diagnosis - why someone is breathless
Disability evaluation - can objectively evaluate how unwell someone is.
Intervention assessment - assess efficacy of therapeutic interventions.
Rehabilitation prescription - personalise exercise training/rehabilitation programmes.
Pre-operative risk - objectively risk assesses cardiopulmonary reserve during surgery.
When does anaerobic threshold usually occur?
Around 40% of predicted peak VO2.
It is the point where you transition from working aerobically to anaerobically.
Absolute vs relative contraindications to exercise/testing
Absolute - anything that is unstable e.g. angina, symptomatic heart failure. Recent changes in resting ECG. Acute systemic infection.
Relative - patient history, things that may or may not be controlled. Electrolyte abnormalities, disorders exacerbated by exercise, chronic infectious disease e.g. HIV, severe hypertension.
VO2 max in CPET details
In clinical populations and children peak value used instead as it is unlikely that they will reach their max.
Anaerobic threshold occurs between 40 and 60% of mac in athletic populations. - It aids exercise prescription.
It is possible to reach VO2 max with ventilatory reserve left.
By how much can minute ventilation increase during exercise?
25x
Increases in both respiratory rate and tidal volume.
Inability to increase VE due to lung disease may limit exercise capacity.
What are EqO2 and EqCO2?
They give a measure of instantaneous ventilatory and gas exchange efficiency: how many L does the patient have to breathe in to uptake 1L of oxygen or produce 1L of carbon dioxide.
What is a healthy person’s ventilatory demand?
20-25L in order to absorb 1L of oxygen.
25-30L to release 1L of carbon dioxide.
Elevated values indicate an inefficient gas exchange which can be caused by both an increased ventilatory dead space and/or an impaired gas diffusion.
What is a peak flow test?
Use?
A very simple measurement to determine how fast a patient can exhale.
Can be used to monitor diseases such as asthma (but not effective for diagnosis).
What is peak expiratory flow? (PEF)
The maximum rate of airflow that can be achieved for 10 milliseconds during a forced expiration.
A low PEF score indicates narrowing of the airways.
What is forced vital capacity?
The volume of air expelled by a forced maximal expiration from full inspiration.
Healthy patients this can be done in 4 seconds, in COPD it can take as long as 15 seconds.
FEV1/FVC ratio
The FEV1 expressed as a percentage of the FVC and provides a guide to the presence of airway limitation.
Healthy individuals expel 75% of total capacity in the first second.
What is FEV1?
The volume of air expelled in the first second.
What does spirometry measure?
What is its use?
The amount of air expelled from the lungs following maximal inspiration - FVC.
Diagnose respiratory impairment and differentiate between obstructive and restrictive impairments.
Quantify severity.
Monitor disease progression.
Correlates with mortality.
