7 - Spirometry for Obstructive Lung Disease Flashcards
What are the components of pulmonary function testing?
Spirometry (pre and post bronchodilator)
Lung volumes - nitrogen wash out and plethysmogrophy
Diffusion capacity
What are contraindications to pulmonary function testing?
- Recent abdominal, thoracic, or eye surgery
- Hemodynamic instability
- Symptoms of acute severe illness
- Chest pain, nausea, vimiting, high fever, dyspnea
- Recent hemoptysis
- Pneumothorax
- Recent history of abdominal, thoracic, or cerebral aneurysm
What are patient instructions prior to testing?
- Should NOT drink alcohol for four hours prior to test
- Should not smoke at least one hour before test
- Do not eat a large meal two hours prior to test
- No vigorous exercise 30 min before
- Should wait at least one month post MI
What equiptment is used in a pulmonary function test?
- Spirometer
- Respirometer
- Pneumotachometer
- Body plethysmograph - body box
- Diffusion system
- Gas analysis
What information is used to be obtain prediction values for pulmonary function test?
- Height
- Weight
- Age
- Gender
- Race/ethnicity
We compare pts values to the values of what we think they should have. You need to see the numbers in the context of what you would expect them to be for their height, weight, age, gender, race/ethnicity.
Smoking would affect their actual valies but not their predictive values.
What are important aspects of performing a pulmonary function test?
- Coaching is important
- Test is effort dependent
- Expiration after MAXIMUM inspiration
- Start as rapidly as possible
- Continue with maximal effort until there’s no more air to be expelled
What are two criteria for spirograms?
Acceptability: free from artifacts such as cough and early termination; good start, satisfactory exhalation
Repeatability: after three acceptable spirograms (are the two largest F VCs within 0.2 L of each other? are the two largest FEV1s within 0.2 L of each other?)
Where are inspiration and expiration on the flow volume loop?
How does forced vital capacity change in obstructive and restrictive diseases? What does slow vital capacity (SVC) help with?
It’s decreased in both obstructive and restrictive diseases.
Slow vital capacity helps avoid air trapping.
What is the function of forced vital capacity (FVC)? What disease states impact it?
Test very sensitive and therefore disease that alter lung mechanisms will affect FVC (forceful exhale).
Impacted by obstructive diseases:
- COPD - lung tissue is lost and elasticity decreased
- Chronic bronchitis - mucosal thickening and thick secretions
- Asthma - bronchoconstriction, mucosal inflammation, edema
Airways narrow and flow resistance increases
What is FEV1? What is it a good indicator of?
Forced expiratory volume - maximal volume exhaled during the first second of expiration.
Best indicator of obstructive lung disease.
Best expressed as a percentage of the FVC
- Should be able to exhale 70% of the vital capacity in the first second
- Decreased in obstructive disorders because airways are narrowed and there’s increased resistance so air can’t move out as fast
What are the expiratory phase patterns seen in obstructive disease and restrictive disease compared to a normal pattern?
Obstructive - higher residual volume, less forceful expiratory phase, and scooped out exhalation. Can’t get the air out fast enough.
Restrictive, less volume but the shape is similar to normal.
Describe the pattern of lung volumes specific to normal people, those with severe empnhysema, and those with pulmonary fibrosis (restrictive)?
Young normal: 100% total lung capacity
Emphysema: increased total lung capacity from overexpansion from residual volume increase. Inspiratory capacity hasn’t changed much.
Fibrosis: total lung capacity is decreased
What are the three types of flow loop patterns for large central airways? Describe each and examples of what can cause them?
- Fixed obstruction - impacts both inhalation and exhalation the same. Exp: tracheal stenosis, goiter.
- Variable extrathroacic - outside of the thoracic cavity; inhalation problem. Exp: vocal cord dysfunction.
- Variable intrathoracic - inside the chest cavity; exhalation problem. Exp: mainstem bronchis tumor or tracheomalacia.
What are the “three” outcomes from spirometry? What happens to the FEV1/FVC ratio in each?
Normal: normal FEV1/FVC ratio; normal FVC
Obstruction: reduced FEV1/FVC ratio
- less than lower limit of normal (95% confidence interval)
- GOLD guidelines define as <70%
Restriction: normal FEV1/FVC ratio; reduced FVC (less than 80% of preducted OR < lower limit of normal)
What can cause obstructive ventilatory pattern?
Large conducting airways: tumors, foreign bodies
Peripheral airways: asthma and chronic bronchitis
Pulmonary parenchymal disease: emphysematous changes from cigarette smoking
If FEV1/FVC ratio is low, what should you do next?
The degree of obstruction.
You do this by looking at the percentage of FEV1 (functional expiratory volume). The smaller the percentage of expiratory volume you exhale, the more obstructed you are.
How else can you assess restrictive ventrilatory defects other than using TLC?
What are you thinking if the FEV1/FVC is less than the lower limit of normal? What if it’s above the lower limit of normal?
Below: obstruction
Above: ask if FVC is greater than the lower limit of normal.
If yes: normal
If no: suggestive of restrictoin
