Respiratory Flashcards
What are causes of false-positive and false-negative sweat tests?
- False-positive: adrenal insufficiency, nephrogenic diabetes insipidus, atopic dermatitis, familial cholestasis syndrome, Klinefelter’s, GSD, mucopolysaccharidosis, G6PD
- False-negative: oedema, malnutrition, mineralcorticosteroid use
Describe the factors that affect oxygenation and ventilation?
- Oxygenation is primarily affected by:
FiO2
Mean airway pressure
Lung volume
- Ventilation (CO2) is primarily affected by: Minute volume (MV = TV x RR)
A higher minute volume will remove more CO2 and thus decrease the arterial CO2 concentration.
At which stage of lung development is the earliest time when surfactant is produced?
Canalicular (week 16-24), type 1 and 2 pneumocytes formed
Discuss pulmonary alveolar proteinosis
- Progressive accumulation of surfactant (lipid and protein)
due to insufficient surfactant clearance. - Surfactant homeostasis is maintained by balanced
production by T2 alveolar cells and
clearance by uptake and catabolism in alveolar macrophages - Reduction in PU.1 expression results in impaired AM
function. GM-CSF signaling is also impaired in PAP. - It is believed that PAP results from accumulation of
surfactant that is produced in normal quantity but is
unable to be catabolised and cleared by macrophages. - SOB, cough, exercise intolerance
- Pulmonary infiltrates on CXR, pink sputum with lipid at bottom
- Tx: lung lavage, not temporary solution
Discuss surfactant production
- Surfactant is composed of lipids and proteins that are produced by alveolar type II pneumocytes
- Surfactant protein B deficiency is a
rare inherited disorder which is usually rapidly fatal
Discuss the differences between:
- Congenital lobar emphysema
- Bronchogenic cyst
- CPAM
- Pulmonary sequestration
- CLE: hyperinflation due to obstruction of developing airway, usually LUL, air-filled, herniates across mediastinum, compression of contralateral lung, usually symptomatic neonate. Usually symptomatic. Associated CHD. Resect only if symptomatic
- Bronchogenic cyst: usually mediastinal but can be anywhere, fluid-filled, sharply marginated. Risk infections. Remnant of primitive foregut
- CPAM: abnormality of branching morphogenesis of the
lung, cystic and adenomatous elements, connection with tracheobronchial tree, can arise anywhere along it, blood supply from pulmonary circulation. Often asymptomatic, usually lower lobes. Resection as malignancy risk - Sequestration: non-functioning mass of lung tissue, lacks communication with tracheobronchial tree, receives arterial blood supply from systemic circulation, usually lower lobes, dull to percuss with decreased BS, predispose to recurrent infections. Usually asymptomatic at birth. May have have continuous or systolic murmur over back. Surg resection or coil embolisation
Side effects of montelukast?
Headache, abdo pain, thirst, nightmares
Main infections in CF and treatments
- Staph (augmentin/clindamycin)
- Burkholderia (cotrimoxazole)
- Pseudomonas (ciprofloxacin)
Discuss the DLCO
- The diffusion capacity (DLCO) reflects the integrity of alveolar blood membrane.
- DLCO measures the diffusion of gas across alveoli which is in turn determined by the alveolar surface area and integrity of the alveoli and the pulmonary vascular network.
- DLCO is reduced in conditions where the diffusion surface area is reduced e.g. pulmonary fibrosis or emphysema
Findings in bronchodilator and histamine challenges?
- FEV1 inc >12% or >200ml in bronchodilator challenge = +ve
- FEV1 dec by >20% in histamine challenge = +ve
Methenamine silver nitrate is used to stain for?
- Fungi and Pneumocystis carinii. Pneumocystis is a genus of unicellular fungi.
- Also use toluidine blue stain
How do you calculate compliance?
Compliance = change in volume / change in pressure
What is the physiological dead space?
- The anatomical dead space + alveoli that aren’t involved.
- The volume of the lung that does not eliminate CO2
Obstructive lung function tests
- Asthma, Bronchiectasis, Emphysema, Cystic Fibrosis
- FEV1/FVC < 80%
- FVC normal or decr
- FEF 25-75 decreased
- TLC normal or increased
Restrictive lung funcion tests
- Interstitial Fibrosis, Scoliosis, Obesity, Lung Resection,
Neuromuscular diseases, Cystic Fibrosis - FEV1/FVC inc or normal, FVC decr, FEV1 decr
- TLC decr
- FEF 25-75 normal or decr
Fixed upper airway obstruction
- Tracheal stenosis, bilateral vocal cord paralysis, goitre
‐ Inspiration and expiration are limited equally - Flattened curve on insp and exp
Variable extrathoracic obstruction
‐ Limitation of inspiratory flow, flattened inspiratory loop
‐ e.g. Vocal cord paralysis, vocal cord dysfunction
‐ During expiration the vocal cords are passively blown aside
‐ During inspiration vocal cord moves passively with the inhalation and obstructs the glottis
Variable intrathoracic obstruction
‐ Flattening of expiratory limb
‐ e.g. Tracheomalacia
‐ During expiration there is loss of support resulting in resulting in a narrow trachea and reduced flow
‐ During forced inspiration the negative pleural pressure holds the floppy trachea open
Causes of decreased DLCO
- Too few alveolar/capillary units
- Thickened membranes or interstitial space
- also affected by Hb level, cardiac shunting, alveolar volume
- measure of severity of ILD
What is the KCO?
DLCO corrected for alveolar volume
Cause of low DLCO in obstructive disease?
Bronchiolitis obliterans, CF
DLCO in restrictive lung disease - low and normal causes?
- DLCO helps in differential diagnosis of restrictive lung disease
- Low DLCO with reduced lung volumes suggests ILD, sarcoid, pneumonitis, pulm fibrosis
- Normal DLCO associated with low volumes is consistent with extrapulmonary cause of restriction – pleural effusion, obesity, neuromuscular weakness, kyphoscoliosis
What can result in a high DLCO?
- Pulmonary hemorrhage (Extra blood in lungs to absorb CO)
- Asthma
Causes of low DLCO with normal pulmonary function tests
- Vasculitis - Wegners, MPA
- CHF
- Pulmonary emboli
- Pulmonary hypertension
- SLE
- Early ILD
What is the FeNO, and causes of low and high tests?
- Fractional exhaled nitric oxide
- Positive test suggests eosinophilic inflammation
- Positive >35ppb = asthma, eosinophilic bronchitis, allergic rhinitis, eczema
- Lower: smokers, neutrophilic asthma
Nasal nitric oxide - causes of low results
- Screening tool before ciliary brushing or biopsy taken
- Low NO = primary ciliary dyskinesia and cystic fibrosis
- Abnormal <250, true PCD <100
Positive exercise challenge
Fall of FEV1 >10% from baseline
