Features of aspirin exacerbated respiratory disease
- Acquired condition, usual onset in 30s
- Characterised by mucosal swelling of sinuses and nasal membranes, formation of polyps and asthma
- Have symptoms after ingesting aspirin or NSAIDs
Symptoms:
- Upper airway symptoms - nasal congestion, rhinorrhoea, sneezing
- Lower respiratory symptoms - laryngospasm, cough, wheeze
- Most patients are triggered by alcohol, especially red wine and beer
Normal sinus CT essentially excludes AERD
Diagnostic: aspirin challenge test
Tx: ICS Leukotriene antagonist Nasal steroids Nasal polyps usually recur very soon after surgery
Covid 19
- Large enveloped single stranded RNA virus
- Viral spike protein: binds to ACE2 receptor, host co-receptor TMPRSS2
- Host cell tropism: resp cells but also conjunctiva, endothelial, kidney, gut, neural
Functional residual capacity
FRC is the volume of gas at which the tendency of the lungs to collapse and the tendency of the chest wall to expand are equal
For COPD, what is the treatment
SYMPTOMS
1st Line: LAMA (tiotropium)
2nd Line: LAMA (tiotropium)/LABA (salmeterol, formoterol) - must have persistent symptoms despite monotherapy
EXACERBATIONS
1st Line: ICS/LABA
2nd Line: ICS/LABA + LAMA
Medications for smoking cessation
Bupropion
- MOA: increase dopamine and norepinephrine via reuptake inhibition
- SE: stimulant, tachycardia, weight loss, neuropsych symptoms (insomnia), reduction of seizure threshold, risk of serotonin syndrome
- Preferred in those with mild untreated depression, avoid in those with bipolar
Varenicline
- Nicotinic Ach receptor partial agonist
- Stimulates dopamine activity - decreases nicotine cravings and withdrawal
- SE
Mood disturbances, eg: suicide, depression
Sleep disturbances
Seizures
- Avoid in unstable psychiatric symptoms or history of suicidal ideation
Nausea
What causes a right shift of the oxy-hb dissociation curve?
Right Shift (reduced affinity)
CADET
- CO2
- Acid (increased H+)
- Increased 2-3 DPG
- Exercise
- Increased temperature
Left Shift
- Decreased Temp
- Decreased 2-3 DPG
- Decreased H+
- CO
Which of the following findings has the best negative predictive value for a ruling out diagnosis of asthma in a patient with current symptoms of dyspnoea and cough
A. Negative mannitol bronchoprovocation
B. Lack of significant response of salbutamol on spirometry
C. Lac of significant response to salbutamol on PEFR
D. Low (<10bbp) fraction of exhaled nitric oxide
E. Negative metacholine bronchoprovocation
E. Negative metacholine bronchoprovocation
Diagnosis of asthma on spirometry
Spirometry
- Can be completed normal
- FEV1/FVC < 0.7
- Assess of reversibility = significant when >12% AND > 200mL increase in FEV1
Diagnosis of asthma - Methacholine test (direct test)
Metacholine challenge test is bronchoprovocation testing where the patient is asked to inhale methacholine to evaluate for symptoms of asthma
- > 20% fall in FEV1 at concentration < 8mg/ml
- SENSITIVIE BUT NOT SPECIFIC
- Good negative predictive value for excluding active asthma
- False positives seen in Allergic rhinitis CF Heart failure COPD Bronchitis
Diagnosis of Asthma
Indirect
Mannitol or hypertonic 4.5% saline (indirect test)
Exercise or eucapnic voluntary hyperpnea
Mannitol/Hypertonic Saline
- > 15% fall in FEV1
- Better positive predictive value for asthma than methacholine - MORE SPECIFIC BUT LESS SENSITIVE
Exercise
- >10-15% fall in FEV1
Allergic bronchopulmonary aspergillosis
Acute eosinophilic pneumonia
Allergic Bronchopulmonary Aspergillosis
- Aspergillus precipitins
- RAST or skin prick test positive to aspergillus
- Central bronchiectasis
- Very high total IgE >1000
Acute Eosinophilic Pneumonia
- Usually <1 week duration of fever, cough, dyspnoea
- Peripheral eosinophilia uncommon
- CXR diffuse rather than focal
- Diagnosis made from BAL > 25% eosinophils (bronchoalveolar lavage)
- Rapid response to steroids, rarely recurs
A boy with well controlled asthma presents with status asthmaticus. He is treated aggressively and becomes hypotensive + bradycardic. What is the likely culprit agent? A. Magnesium B. Aminophylline C. Ipratropium D. Salbutamol E. Hydrocortisone
A. Magnesium
Which of the following is the first branching of the bronchial tree that has gas exchanging capabilities? A. Terminal Bronchioles B. Respiratory bronchioles C. Alveoli D. Segmental bronchi E. Alveolar ducts
B. Respiratory bronchioles
Respiratory bronchioles –> alveoli –> alveolar ducts all involved in gas exchange
Structural changes in the lung with age
Change in tissue elastic properties
- Decrease in elastic fibres
- increase in type 3 collagen (lungs made up of collagen 1 and 3 normally)
- Changes in cross linking and fibre orientation
Change in surface properties
- Decrease in number of alveoli
- Increase in size of alveolar ducts
- Decrease in surface to volume ratio
FEV1/FVC ratio decreases with age
Residual volume = gas trapping increased with age
Compliance vs elastic recoil
Lung compliance: change in unit lung volume per unit change in the pressure gradient across the lung wall
Elastance = 1/compliance
Stiff lungs have LOW COMPLIANCE AND HIGH ELASTANCE
Young Person: elastic recoil is high which is driving the flow causing FEV1 to be higher and the ratio to be higher
Factors affecting lung compliance
- Lung volume
- Age: older = more compliant, more likely to expand and elastic recoil is less
- Pulmonary blood volume (venous congestion - stiffer lungs)
- Disease
Pulmonary Fibrosis = less compliant
Emphysema = more compliant
Pulmonary compliance, a measure of the lung expandability, is important in ideal respiratory system function. It refers to the ability of the lungs to stretch and expand. Lung compliance can be calculated by dividing volume by pressure.
- A decreased compliance might show restrictive lung diseases. Restrictive lung disease can result from mechanical issues with peripheral hypoventilation, including poor muscular effort or structural dysfunction. Conditions like muscular dystrophy, polio, myasthenia gravis, and Guillain-barre syndrome can cause poor muscular effort. Scoliosis or morbid obesity can also cause structural limitations
- Increased compliance can indicate a state of disease where there is degeneration of tissue that causes the lungs to have to work harder to expand, such as emphysema. With emphysema, the tissue damage means that it is easier to inhale, as there is less resistance, but it is harder to exhale
What is residual volume?
Volume of air still remaining in the lungs after the expiratory reserve volume (additional air that can be forcibly exhaled after the expiration of a normal tidal volume)
What is the total lung capacity
Maximum amount of air that can fill the lungs
TLC = TV + IRV + ERV + RV (vital capacity + residual volume)
Tidal Volume
Inspiratory Reserve Volume
Expiratory Reserve Volume
Residual Volume
What is the functional residual capacity
The amount of air remaining in the lungs after a normal expiration (FRC = RV + ERV)
Residual Volume + Expiratory Reserve Volume
Some of the air in the lungs does not participate in gas exchange. Such air is located in the anatomical dead space within bronchi and bronchioles - that is outside the alveoli.
What is the vital capacity?
The total amount of air that can be expired after fully inhaling (VC = TV + IRV + ERV = approximately 80% of TLC). Value varies according to age and body size
Total lung capacity - residual volume
Which of the following is NOT true at functional residual capacity?
A. It is about 75% TLC
B. The elastic recoil of the chest wall is outward
C. The elastic recoil of the lung is inward
D. The relaxation pressure of the lung and chest wall combined is at atmospheric pressure
E. There is no airflow
A. It is about 75% TLC
40% TLC
What happens in the lung obstructive disease?
Residual volume increases
Thus FRC increases
These occurs due to gas trapping
Eventually leads to increased TLC leading to hyperinflation
What is DLCO
Only test of INTEGRITY OF ALVEOLAR-CAPILLARY MEMBRANE
- Determined by alveolar-capillary membrane THICKNESS, SURFACE AREA, CAPILLARY HB VOLUME
- Does not correlate with gas eschange efficiency
Causes of reduced DLCO
LESS MEMBRANE
- Less Lung: lobectomy/pneumonectomy
- Destruction of lung: emphysema
- Destruction/alteration of membrane: pulmonary fibrosis
RELATED TO TEST MANOEUVRE
- Poor gas mixing: asthma/COPD
- Unable to breath up to TLC: chest wall deformity/respiratory wall weakness
LESS BLOOD IN CAPILLARIES
- Less capillaries: emphysema, pulmonary fibrosis
- Less blood: pulmonary vascular disease, pulmonary htn, heart failure
