Respiratory function testing - CW? (RM Mod) Flashcards
Name a few of the indications for pulmonary function test
Primary - Give a measure of change over time.
Symptoms of breathlessness, wheeze, cough
Assessment of smokers and those exposed to pollutants
Differentiating respiratory from cardiac causes
Disease progression
Response to treatment
How is the initial flows of a forced expiratory manoeuvre different to the later flows?
The initial flow is effort dependent and generated by muscle force, the later flow is effort independent and dictated by elastic recoil and airway resistance.
If FEV1/FVC is reduced below the lower limit of normal there is likely what type of limitation? How do you determine the severity?
reduced FEV1/FVC is related to obstructive disease. To determine the severity you look at the FEV1 and assess it against the predicted values. The percentage of predicted FEV1 for the measured value indicates the severity.
FEV1/FVC may be normal but there may still be symptoms of respiratory distress. What other respiratory limitation might be occurring and what measure is important to diagnosing?
If FVC is lower than the LLN, restrictive disease may be occurring. This is confirmed by assessing the total lung capacity (TLC)
How is bronchial provocation testing used to assess severity of disease?
A provocative agent is given to intentionally reduce FEV1. The lower the dose given to reduce the FEV1 by 15% the more severe the disease.
Body plethysmography is used to derive paramters that spirometry can’t. What type of values are measured and what parameters are derived?
Plethysmography is used to assess total lung capacity (TLC) and residual volume (RV). To derive these measurements, firstly the functional residual capacity, inspiratory/expiratory capacity and vital capacity are measured. TLC and RV are derived.
In emphysema, what changes in flow and capacity would you expect?
FEV1 is reduced. FEV1/FVC is reduced. Peak expiratory flow is reduced. FEF75-25 is reduced. Residual volume increases leading to an increase in TLC.
What is being assessed in a gas transfer test? Describe the anatomical and physiological components being assessed.
Gas transfer assesses the lung’s ability to take up oxygen. It tests:
- The membrane function – can it transfer the gas?
- The alveolar surface area in total
- The integrity of the capillary vascular bed
- Haemoglobin concentration and reactivity
Name some pathologies where gas transfer is diminished.
Emphysema Cystic fibrosis Parenchymal lung diseases (interstitial lung disease, sarcoidosis, asbestosis) Anemia Pulmonary oedema Pulmonary thromboembolism
When might gas transfer increase?
Polycythemia
Exercise
Left to right intracardiac shunt
Asthma and obesity (unknown mechanisms)
What is the purpose of predicted values for pulmonary assessment?
Provides a mean, and upper and lower limit of normal for that patient based on their demographics (height, weight, race, age, gender). Thus allows you to determine whether they are within the normal range or how far outside it.
What is spirometry? What does it measure?
The most basic test for respiratory diseases. Measures airflow and vital lung capacity as well as various other volumes.
Can detect and quantify the extent of airway obstruction or lung restriction, as well as any response to bronchodilators.
Volumes and flows are reported as Body Temperature and Pressure Saturated (BTPS)
Define FEV1
Volume expired in the first second of a forced maximal expiration initiated after a maximal inspiration.
Define FVC
Maximum volume of air which can be expired with maximal force (after a maximal inspiration) during a forced manoeuvre.
Define FEV1/FVC (Forced Expiratory Ratio)
FEV1 expressed as a percentage of FVC. Ratio determines whether its obstruction or restriction.
