measuring lung function Flashcards
1
Q
what is spirometry? 3
A
- can be done slowly of forced
- most often done as forced expiration
- FVC of tiffeneau manoeuvre: deep breath, don’t hold your breath, put lips around outside of the tube and blow out for as long and hard as you can
2
Q
how do we interpret spirometry? 4
A
- FE1/FVC: ratio of FEV1 and FVC values
- for all other results, compare to actual predicted values
- predicted values may vary by gender, height and age
- abnormal result: any result <80% of the predicted value or any results less than the lower limit of normal
3
Q
how much of FVC should be exhaled in the first second?
A
- 70%
- if FEV1.FVC is <0.7 then an obstruction is present
4
Q
what do expiratory flow- volume loops show? 3
A
- early airflow obstruction
- mid expiratory flow rates are usually more affected
- PEFR (peak expiratory flow rate) may be normal
- where an obstruction is located in the tracheobronchial tree
5
Q
when is peak flow used normally? 2
A
- for people with asthma
- it can show extrathoracic obstructions including tracheal, stenosis
6
Q
explain a peak flow rate? 7
A
- easy to perform
- easy to maintain device
- diagnosis of asthma
- monitoring day-day variation
- picking up exacerbations
- assessing response to treatment
- mandatory for patients on nebulised Rx
7
Q
how can we measure lung function?
A
- helium dilution
- plethysmography
8
Q
name some causes for lung restriction? 5
A
- alveolar filling process (pneumonia)
- lung tissue disease: fibrotic lung disease
- pleural disease: pneumothorax, large pleural effusion, fibrosis of pleural tissue
- chest wall disease
- weakness due to nerve or muscle disease
9
Q
where does gas exchange take place? 5
A
- takes place at the alveoli
- depends on adequate ventilation of alveoli
- influenced by alveolar surface area and thickness of alveolar membrane
- delivers oxygen to where is combines with Hb
- gets rid of carbon dioxide to exhaled air
10
Q
how do we measure gas transfer? 6
A
- CO diffuses like O2
- CO binds to Hb and is carried away
- inhale known volume of gas with low concentration of CO and helium
- hold breath for the known time
- measure CO and He in expired air
- He dilution give alveolar volume