Tut5: Respiratory Flashcards
What is Asthma?
Chronic inflammatory disorder of the airways
Results in widespread obstruction of the airways that is reversible either spontaneously or with treatment
What are the effects of Asthma?
- Bronchoconstriction
- Inflammation
- Airways hyper responsiveness
What is the key diagnostic criteria of Asthma?
History of (NZGG2002)
- Cough
- Wheeze
- shortness of breath
Evidence of REVERSIBLE airflow obstruction either
- spontaneously over time or
- in response to treatment
What is the difference between Asthma and COPD as seen by the Expiratory flow rate vs. volume curves?
Asthma is reversible airflow obstruction, this is seen by the dashed curve rising towards normal after treatment
In the COPD graph this dashed curve does not rise. This indicates no reversibility of airflow obstruction after treatment
What does spirometry measure?
The amount and rate of air a person breathes, in order to diagnose illness or determine progress in treatment
What is tidal volume?
The volume breathed in each breath
What is Expiratory Reserve Volume?
The maximal amount of air that can be exhaled from the lungs after a normal expiration
What is Residual Volume?
The volume of gas left in the respiratory system after exhaling maximally
What is Vital Capacity
A measure of the maximum volume of gas in the respiratory system that can be exchanged with each breath
What is total lung capacity
a measure of the volume of gas in the respiratory system at the end of a maximal inspiration
What is the difference between a volume and a capacity?
A capacity is the sum of at least two volumes
What is Forced Expired Volume in 1 second?
Provides a measure of the resistance of the airways to flow
What is the formula for Vital Capacity
VC = IRV+ERV+Vt
How does Peak expiratory flow rate help diagnose asthma?
Asthma attacks with acute wheezing + Reduced peak expiratory flow rate = highly specific for asthma
Single PEFR recordings have little diagnostic, but a variability of >15% is highly specific for asthma
What is the difference between peak expiratory flow and spirometry?
PEF = more simple measurement.
Can be performed by patient at home using hand held peak flow meter
Not a sensitive enough measure for detecting the small changes characteristic of COPD
Spirometry = provides an objective measure of lung function as it records the whole of the FVC manoeuvre
What are the values for diagnosis of asthma using PEFR?
If day to day PEFR range is >15% indicative of asthma
Disadvantages of this method:
- Mild airflow obstruction not detected in normal PEFR readings
- Validity dependent upon patient effort and coaching
- No calibration so may lead to variation
What are the values of PEFR for Bronchodilator response to therapy?
> 15% improvement with either:
40mg oral prednisone for 2 weeks OR
Inhaled corticosteroids at 400mcg beclomethasone or equivalent, 2x daily, for four weeks
How is bronchial hyper-responsiveness treated?
with methacholine, histamine or saline challenge when diagnosis is unclear or exercise
(15% fall in PEFR)
How is asthma diagnosed in spirometry?
If FEV1/FVC ratio <70%, indicative of asthma
What is FEV1/FVC ratio?
Measurement of forced expiratory volume in one second and forced vital capacity.