WEEK 10 Flashcards
What is FVC?
The forced vital capacity
Forced = exhale as hard & long as possible
Vital = total volume minus the residual volume
Capacity = sum of more than one volume
This is where the graph plateaus i.e. the total amount of air exhaled
What is FEV-1?
The forced expiratory volume in 1 minute
What is the FEV-1/FVC ratio a measure of? What are the normal values?
Of airflow obstruction
> 0.7 is normal
With OBSTRUCTIVE pulmonary disease what change is made to the following (i) FVC (ii) FEV-1 (iii) FRC (iv) RV (v) TLC?
(i) normal or slightly decreased
(ii) decreased
(iii) increased
(iv) increased
(v) increased
With RESTRICTIVE pulmonary disease what change is made to the following (i) FVC (ii) FEV-1 (iii) FRC (iv) RV (v) TLC?
(i) decreases
(ii) normal or slightly decreased
(iii) decreased
(iv) decreased
(v) decreased
What does hypoxia tend to result from?
V/Q mismatching
What are 4 common obstructive lung diseases?
asthma
COPD
bronchiectasis
cystic fibrosis
List the 11 differences between asthma & COPD.
ASTHMA:
- non smoking related, allergic, tends to be younger pts, intermittent, not progressive, eosinophil filtration, diurnal variation, good corticosteroid and bronchodilator response, preserved FVC and TLC, normal gas exchange
COPD:
- smokers, non-allergic, over 50s, chronic, progressive decline, neutrophils, no diurnal variation, poor corticosteroid and bronchodilator response, reduced FVC and TLC, impaired gas exchange
How is asthma diagnosed? What are the symptoms associated with asthma?
It is diagnosed clinically
Symptoms: wheeze, breathlessness, chest tightness, cough
- especially likely if diurnal variation in symptoms and history of atopy
- also if their symptoms arise in response to allergen, exercise or cold air
What are the 3 pathophysiological components of asthma?
Airway narrowing/obstruction (which is reversible) Airway hyper-responsiveness Airway inflammation (from eosinophils)
What 3 non pharmacological treatment interventions has SIGN declared as effective?
- Achieve and maintain a normal BMI if overweight
- Breathing exercise programmes
- Stop smoking (pt and household members)
What is COPD? What is it characterised by?
Common, preventable and treatable disease that is characterised by persistent airflow limitation that is usually progressive and associated with an enhanced chronic inflammatory response in the airway and lung to noxious particles/gases
What is the epidemiology of COPD?
Tobacco smoking
Indoor/outdoor pollution from biomass fuels
Alpha 1 antitrypsin deficiency ( think if early onset COP i.e. early 40s)
What is the pathophysiology of COPD?
- Inflammation and fibrosis of the bronchial
- Hypertrophy of submucosal glands and hypersecretion of mucous
- Loss of elastic, parenchymal lung fibres (emphysema)
What is the clinical presentation of COPD? (HINT: there’s 7 points)
- Insidious (gradual) onset
- Usually 50s or 60s
- Chronic cough
- Sputum production (worse in morn)
- Increasing (over time) shortness of breath
- Diminishing exercise tolerance
- History of exposure to risk factors
What are the clinical observations of a (i) pink puffer (ii) blue bloater?
(i) pink, pursed lips (alveoli tend to collapse), barrel chest due to air trapping, use of accessory muscles and decreased breath sounds
(i) blue = cyanosed
bloater = signs of RHF
When do you give domiciliary oxygen therapy?
Patients with a pO2 < 7.3-8 kPa
Must have stopped smoking
Must be breathed for >15 hours/day to improve mortality
What is the various grades on the MRC breathlessness scale?
- Not troubled by strenuous exercise
- Short of breath when hurrying on the level or walking up a slight hill
- Walks slower than most ppl on level, stops after a mile or so, or stops after 15 mins walking at own pace
- Stops for breath after walking 100yrds or after a few minutes on level ground
- Too breathless to leave the house, or breathless when undressing
Define (i) case series (ii) cross-sectional survey (iii) case control study (iv) cohort study (v) RCT.
- CASE SERIES - tracks subjects with a known exposure i.e. pts who have received a similar treatment, or examines their medical records for exposures and outcomes
- CROSS SECTIONAL SURVEY - analyses data collected from a population, or a representative subset, at a specific point in time
- CASE CONTROL STUDY - compares patients who have a disease or outcome of interest (cases) with patients who do not have the disease or outcome (controls), and looks back retrospectively to compare how frequently the exposure to a risk factor is present in each group
- COHORT STUDY - one or more samples followed prospectively and evaluations with respect to a disease/outcome are conducted to determine which initial exposure characteristics (risk factors) are associated with it.
- RCT - splits participants into treatment and control group, the only expected difference between the groups in a RCT is the outcome variable being studied.
What are the advantages and disadvantages of a cross sectional survey?
ADV: - cheap and simple - ethically safe - useful for planning purposes DISADV: - cause and effect? - volunteer bias - unequal distribution of cofounders
What are the advantages and disadvantages of a cross sectional survey?
ADV: - cheap and simple - ethically safe - useful for planning purposes DISADV: - cause and effect difficult to obtain - volunteer bias - unequal distribution of confounders
What are the advantages and disadvantages of a case control study?
ADV:
- Simultaneously look at multiple risk factors
- Good for studying rare conditions or diseases
- Useful as initial studies to establish an association
DISADV:
- Retrospective study which relies on patient recall to determine exposure (recall bias) or patient records
- confounders
- selection of control group is difficult
What are the advantages and disadvantages of a cohort study?
ADV:
- ethically safe
- subjects can be macthed
- can show cause precedes the effect
- easier and cheaper than a RCT
DISADV:
- high drop out rate (follow up must be as complete as possible)
- exposure may be linked to hidden confounder
- blinding is difficult
- outcome of interest may take a long time to occur
What are the advantages and disadvantages of a RCT?
ADV:
- unbiased distribution of confounders
- Clearly identified populations
- randomisation helps statistical analysis
- more likely to be ‘blinded’
DISADV:
- expensive (time and money)
- volunteer bias (pop may not be representative)
- ethical issues if treatment group are seen to respond badly or better than expected