Pulmonary Function Tests Flashcards
What is the last set of organs to full develop?
- lungs
When describing the developing of the lungs, what does antenatal refer to?
- pre embryonic - embryonic - foetal - everything prior to birth
Babies are at an increased risk of death if they are born prematurely, before 28 weeks of gestation. What is one of the main factors contributing to this?
- lack of surfactant - lungs can collapse
What is respiratory distress syndrome?
- babies born prematurely (28 weeks) - lungs unable to inflate and deflate unaided
What is the growth phase in lung development?
- birth to young adulthood - grow until 23 generations are present
What is the plateau phase in lung development?
- from mid 20s to late 30s
What is the decline phase in lung development?
- lung function, compliance, elasticity all begin to decline
What are a few factors that can influence antenatal development of the lungs?
1 - maternal smoking 2 - poor maternal nutrition 3 - placenta insufficiency
What is placenta insufficiency?
- low nutrients supplied by placenta to foetus
How can babies born prematurely affect lung development?
- ⬇️ surfactant
What factors can influence the babies lung development postnatally (after birth)?
- maternal smoking - infections - allergens
What are pulmonary function tests?
- tests designed to assess how well the lungs work
When are pulmonary function tests used?
- to diagnose a respiratory disease - in patients presenting with respiratory symptoms
What are some common respiratory symptoms that would initiate a pulmonary function test?
- cough - wheeze - shortness of breathe
Are pulmonary function tests used in smokers to diagnose disease?
- generally no - can be used to identify high risk groups though
In addition to diagnosing patients, can pulmonary function tests be used for prognosis?
- yes in chronic lung disease - asthma, COPD, pulmonary fibrosis - good for monitoring disease progression
Are pulmonary function tests useful when assessing a patients treatment?
- yes - provide objective measures of lung function
What do pulmonary function tests actually measure?
- airflow - lung volume - gas exchange - airway reactivity
What is airway reactivity?
- how airways react to allergens - asthma has a high airway reactivity
Roughly how much lung volume do we lose each each year in the decline phase of lung development?
- 30ml/year
What are some basic things that affect lung function, not disease factors?
- gender - age - weight - ethnicity - height
What are a patients lung function tests compared against?
- normative data collected over long periods
What are some things that patients must not do prior to a lung function test as they may affect the test results?
- take bronchodilator medication - exercise (30 mins prior) - smoke (24 hours prior) - alcohol (4 hours prior) - caffeine (24 hours prior)
What is the normal age patients can do lung function tests well?
- > 6 years old - < 6 years old are unable to do the tests
What is tidal volume?
- amount of air in and out of lungs at rest
What is inspiratory reserve volume?
- max air patient can inhale above tidal volume
What is expiratory reserve volume?
- max air patient can exhale below tidal volume
What is vital capacity?
- total air patient can breathe in and out maximally
- DOES NOT include residual volume
What is residual lung volume?
- air left in lungs after maximum exhalation
What is functional residual capacity?
- expiratory reserve volume (below tidal volume) + residual lung volume
What is total lung capacity?
- max air in and out of lungs including residual lung volume
What are dynamic lung volumes?
- those that are dependent on the rate at which they happen
- FORCED expiratory volume (FEV1)
- PEAK expiratory flow
Peak expiratory flow (PEF) is a common dynamic lung volume measured, what is it?
- maximum speed of expiration - measured in L/min
Forced expiratory volume 1 (FEV1) is a common dynamic lung volume measured, what is it?
- maximum air expelled in the first second
Forced vital capacity (FVC) is a common dynamic lung volume measured, what is it?
- total air exhaled
- following maximum inhalation
- FEV1 is measured from this
Relaxed vital capacity is a common dynamic lung volume measured, what is it?
- maximum air exhaled in a relaxed breathe - similar to a heavy sigh
What are some common conditions that are contradictions for completing dynamic lung volume tests?
- haemoptysis (coughing up blood)
- pneumothorax
- severe hypertension
- recent myocardial infarction
- tachyarrhythmia
- pulmonary embolism
- aortic aneurysm
- essentially anything involving high pressure
Why is a peak flow meter useful in a clinical setting?
- cheap - easy to use - portable
Peak expiratory flow measures the maximum speed of expiration, but what is it measuring in the airways that contributes to the rate of air?
- resistance in airways
Why can peak expiratory flow be reduced?
- increased resistance in airways - generally due to narrowing
What conditions would we expect to a reduction in peak expiratory flow?
- COPD - asthma - bronchiectasis
Why are routine measurements of peak expiratory flow not routinely conducted in patients with COPD?
- COPD is generally irreversible - may be used for prognosis - BUT will not get better
Why is peak expiratory flow measurement useful in self managed asthma?
- can see if patient is using inhales - can see if patient is responding to treatment
Why is peak expiratory flow used by occupational health in the workplace?
- good measure to identify risk of asthma
- asthma is most common respiratory occupational disease
- certain jobs ⬆️ risk of lung disease
How can neuromuscular disorders impair peak expiratory flow?
- unable to innervate muscles in chest properly
How does tracheal tumour or thyroid goitre (swelling of the thyroid gland) impair peak expiratory flow?
- ⬆️ resistance - block or narrow airways
What is diurnal peak flow monitoring?
- relates to the variation/fluctuation in peak expiratory flow rate
- measured over (24 hours)
- >20% variation in day = diurnal variation
How is diurnal peak flow monitoring monitored and why?
- patients given a peak flow meter and diary - measure throughout the day
What is the hormone that has been linked with diurnal peak expiratory flow?
- cortisol
Spirometry is the most common method for assessing lung function, what is it?
- pulmonary function tests - measures the amount and/or speed of air that can be inhaled and exhaled
What 3 measures are given during spirometry?
1 - forced vital capacity (FVC) 2 - forced expiratory volume in 1 second (FEV1) 3 - FEV1/FVC ratio
When using spirometry how many measures are taken, and which value is used?
- 3 attempts - maximum value used
Why is the shape of the graph in spirometry important?
- it will vary depending on lung disease - restrictive vs. obstructive
Above what values is classed as a normal forced expiratory volume?
- >80%
What is obstructive lung disease?
- inability to exhale
What is restrictive lung disease?
- inability to inhale
In obstructive lung disease, what happens to the forced expiratory volume 1 (FEV1), forced vital capacity (FVC) and FEV1/FVC ratio?
- ⬇️ FEV1 - difficult to exhale (can take up to 15 seconds) - ⬇️ FVC - but will eventually get air out - ⬇️ FEV1/FVC ratio
In restrictive lung disease, what happens to the forced expiratory volume 1 (FEV1), forced vital capacity (FVC) and FEV1/FVC ratio?
- ⬇️ FEV1 - ⬇️ FVC - ⬆️ FEV1/FVC ratio
In obstructive lung disease, does forced expiratory volume 1 (FEV1) or forced vital capacity (FVC) reduce more?
- FEV1 has larger ⬇️
- larger ⬇️ in FEV1 drives ⬇️ FEV1/FVC ratio
- FVC can actually increase due to trapped air
In restrictive lung disease, does forced expiratory volume 1 (FEV1) or forced vital capacity (FVC) reduce more?
- FVC has larger ⬇️ due to ⬇️ compliance - larger ⬇️ in FVC drive ⬆️ FEV1/FVC ratio
Is spirometry good for distinguishing between restrictive and obstructive lung disease?
- yes - BUT cannot confirm exact diagnose
What does GOLD stand for in COPD, and what are the 4 things the GOLD stage for COPD measures?
- Global initiative for Chronic Obstructive Lung Disease
1 - severity of current symptoms
2 - spirometry results
3 - COPD prognosis
4 - presence of comorbidities
In obstructive lung disease which airways are mostly affected?
- medium and large sized airways
In restrictive lung disease is the FEV1/FVC ratio always increased?
- no it can be normal as well
What are flow volume loops?
- inspiration and expiration plotted against volume and time on a graph
What are flow volume loops useful for?
- identify where an obstruction is - intra vs extrathoracic obstruction
What does extra-thoracic mean?
- outside of thoracic cavity - likely to be in thoracic wall or spinal problems
Why are flow volume loops not routinely used?
- hard to conduct - poor reproducibility - flow is dependent on high lung volumes
When are airways most dilated and airways resistance is at its lowest?
- at total lung capacity
During flow volume loop test, is inspiration or expiration more reproducible and energy dependent?
- inspiration = ⬆️ energy depended
- inspiration = ⬇️ reproducibility
- expiration is determined by elastic recoil, so good reproducability
What is static lung volume tests?
- test to measure total lung capacity - not dependent on flow rate
Are static lung volume tests able to make accurate diagnosis?
- yes
Why are static lung volume tests not used routinely?
- measured in a lab - not portable
How do static lung volume tests determine total lung capacity, including the residual lung volume?
- helium dilution method - whole body plethysmography
What is the helium dilution method?
- patient inhales known volume and concentration of helium - patient then exhales providing a final concentration and volume, including functional residual volume
Why is helium a good gas to use for determining static lung volumes?
- it is insoluble in blood and lung tissue - gas will not be absorbed and stays in the lungs
What is a plethysmograph?
- an airtight box - volumes and pressures in the box can be measured
How does plethysmography work?
- patients breathe normally in the airtight box - sensor in box measuring pressure change - sensor in mouth piece measuring pressure and air flow changes - changes in volume and pressure in the box can be used to determine functional residual volume
Is total lung capacity reduced in both restrictive and obstructive lung disease?
- both are affected, but in a different way
- restrictive = ⬇️ total lung capacity
- obstructive = ⬆️ total lung capacity
Why does obstructive lung disease cause an increase in total lung capacity?
- obstructive lung disease = inability to exhale - air is therefore trapped in the lungs
In restrictive lung disease, do intra and extra pulmonary pathologies reduce total lung capacity?
- yes - restrictive = inability to inhale
What is the transfer factor also commonly referred to as?
- diffusion capacity - DLCO or TLCO, used interchangeably
What is transfer factor used for?
- measured in a single breathe - ability of gas to diffuse between alveoli and capillaries
What is the A-a gradient?
- difference between alveolar (A) and arterial (a) concentration of oxygen
What can the transfer factor be used to estimate?
- A-a gradient
When using DLCO/TLCO, what is the transfer coefficient?
- transfer of a gas per unit of alveolar volume
How is the transfer coefficient calculated from the DLCO/TLCO?
- measures carbon monoxide in ventilated alveoli
- divided by the non ventilated alveoli
What must the transfer coefficient be corrected for?
- haemoglobin levels - anaemic patients would skew the results
What can reduce the TLCO/DLCO?
- ⬆️ ventilation/perfusion mismatch - ⬇️ blood flow (pulmonary embolism) - ⬇️ alveolar surface area (emphysema)
What can increase the TLCO/DLCO?
- ⬆️ pulmonary capillary blood flow - ⬆️ cardiac output (exercise) - polycythaemia (⬆️ red blood cells) - pulmonary haemorrhage
Do extra thoracic restrictive lung conditions affect TLCO/DLCO?
- no - lung tissue is not involved
Why do extra thoracic restrictive lung conditions not affect TLCO/DLCO?
- blood vessels vasoconstrict in unventilated section of the lungs
- blood flow is diverted from under ventilated part of lungs
In a patient who is a heavy smoker and has emphysema, would you expect to see a change in the TCLO/DLCO and transfer coefficient ?
- yes
- both would ⬇️
Why would a patient who is a heavy smoker with emphysema, be expected to have a low TCLO/DLCO and transfer coefficient ?
- emphysema = obstructive lung disease
- smoking is primary cause of obstructive lung disease (COPD)
- emphysema will ⬇️ surface area (SA) at alveoli
- ⬇️ SA = ⬇️ diffusion
- ⬇️ SA = ⬇️ ventilation
In a woman with suspected pulmonary fibrosis, which is a restrictive lung disease (inability to inhale) what would we expect to see in the forced vital capacity (FVC), forced expiratory volume 1 (FEV1) and the FEV1/FVC ratio?
- larger ⬇️ in FVC
- ⬇️ or normal FEV1
- ⬆️ FEV1/FVC ratio
When is the the DLCO/TLCO and transfer coefficient (KCO) especially useful when looking at a patient with restrictive lung disease?
- determine where restriction is intra or extra thoracic
- intra thoracic = ⬇️ TLCO/DLCO and KCO
- extra thoracic = normal TLCO/DLCO and KCO
What is the transfer coefficient (KCO) that is used in TLCO?
- KCO is the ratio between ventilated and non-ventilated lung tissue
- TLCO is then divided by VA which gives TLCO
