Paediatric Respiratory 1 Flashcards
What is estimated tidal volume at rest?
6-7 mL/kg body weight
What happens to FEV1/FVC in restrictive and obstructive lung disease?
- Normal in restrictive, may be increased (normal 75-80%)
- Decreased if obstructive
Describe what happens to the flow-volume loop in restrictive and obstructive lung disease:
- Restrictive - flow less affected, narrow oblong. May be smaller overall
- Obstructive - volume less affected, concave expiratory loop
What diseases lead to decreased FRC?
- Alveolar interstitial diseases
- Thoracic deformities
- Restrictive lung diseases
examples: scoliosis, neuromuscular diseases
What diseases lead to increased FRC?
- Intrathoracic airway obstruction
- Obstructive lung diseases
- examples: bronchiolitis, asthma
Poiseuille’s law:
Resistance to laminar flow = ( 8 x length x viscosity ) / (pi x radius^4)
R=8lη÷Πr4
Describe the different types of sleep and what you might see on a PSG:
N1 - sleep transition
N2 - light sleep with spindles (look like fuzzy caterpillars) and K complexes (up then down waves)
N3 - slow wave and deep sleep, small EMG
REM - lots of eye movement, very small EMG
What medication(s) are used to treat periodic limb movement disorder?
- Often see less iron in basal ganglia
- Check ferritin, Fe supplement aim top 1/2 of normal range/above 50
- In adults use antiparkinsonian meds
What paO2 corresponds with sats of 50%, 70%, 80%, 90% and 97% on pulse oximetry?
50% = PaO2 27mHg 70% = PaO2 40mmHg 80% = PaO2 45mmHg 90% = PaO2 60mmHg 97% = PaO2 96mmHg
Which factors shift the oxygen dissociation curve to the right?
To the right = more free oxygen available e.g. for exercising muscles! Breaks Hb and O2 apart/decrease affinity.
- increased temperature
- increased PCO2
- decreased pH
- increased 2,3-diphosphoglycerate.
Which factors shift the oxygen dissociation curve to the left?
To the left = you want the Hb and O2 to stick together/increase affinity e.g. in lungs
- decreased temperature
- decreased PCO2
- increased pH
- decreased 2, 3 diphosophoglycerate
What should the PVR be in childhood (as % of systemic resistance)?
3 days after birth - 50%
2-3/12 after birth - 15%
Definition of pulmonary arterial hypertension:
- Mean PA pressure ≥25 mm Hg
WITH - Normal pulmonary capillary wedge pressure ≤15 mmHg (i.e. normal venous pressure)
- Increased PVR index ≥3 Wood units/m^2
What are the cells that react to lung inflammation and what chemicals do they produce?
- Alveolar macrophages
- Tumor necrosis factor-α and interleukin-1β
Where are the mutations causing cystic fibrosis and what are the most common ones?
- CFTR protein on Chromosome 7
- Commonest is deletion F508 (class 2, protein transport problems) In Australia/NZ - Gly551Asp/G551D (defective regulation of CFTR, class 3) - Gly542X (no CFTR, class 1)
How common is cystic fibrosis?
1/3500 live births in white populations
How common is meconium ileus in CF?
10-15%
Some genetics seem to make it more likely
What are the diagnostic criteria for CF?
Typical clinical features (respiratory, GI, GU) / sibling with CF / positive newborn screening test
plus
Lab evidence:
2X elevated sweat chloride (>60 mEq/L) obtained on separate days (NB: intermediate is 30-59, can still have CF) or 2 CF mutations or an abnormal nasal potential difference measurement
What is the screening test for CF in NZ?
Tier 1: Measurement of immunoreactive trypsin (IRT).
Tier 2: If the IRT level is in the highest 1%, this is followed by genetic analysis using a limited panel
of the most common CF genetic mutations in NZ.
What is Kartagener Triad?
- Situs inversus totalis (50% of patients with primary ciliary dyskinesia have it; 25% of patients with situs inversus have PCD)
- Chronic sinusitis
- Bronchiectasis
What is FVC 25-75% useful for?
- Indicator of mild airway obstruction
- Small airways disease
What genetic/syndromic anomalies are associated with choanal atresia?
- CHARGE syndrome
- Treacher-Collins
- Kallmann syndrome
- VA(C)TER(L) association
- Pfeiffer
What is ABPA associated with?
- Asthma or CF
How does monteleukast work?
- Block effects of cysLT1 receptor (leukotriene receptor antagonists)
Vocal cord dysfunction/paralysis on flow-volume loop…
Flattening of inspiratory curve
Tracheal stenosis on flow-volume loop…
Flattening of inspiration and expiration curve
What is omalizumab and what do you use it for?
- Humanized, monoclonal anti‐IgE antibody that binds specifically to circulating IgE molecules, thus interrupting the allergic cascade.
- > 12yo severe allergic asthma when all other avenues exhausted. Given by a subcut injection – may get site reactions.
- Well tolerated, but occasional anaphylaxis
How does carbon monoxide cause toxicity?
- Reversible binding of carbon monoxide to cytochrome A3.
- Binds to the usual OXYGEN site of Hb.
What is surfactant and which cells make it?
- Mixture of phospholipids + proteins
- Synthesized, packaged, secreted by alveolar type II pneumocytes (AEC2s) in distal air spaces
What does surfactant do?
- Decrease surface tension at end-expiration
- Prevent atelectasis and VQ mismatch
What is ivacaftor approved for?
- CF treatment - class 3 mutations
- Gly551Asp/G551D
What is surfactant mostly made of?
- Phosphatidycholine
When do you get false negatives on a sweat test?
- <75g sweat
- Malnutrition
- Mineralocorticoid use
- Adrenal insufficiency
- Fucosidosis
- G6PD deficiency
What are the wheezy viruses?
- Rhinovirus
- RSV
- Increased risk of wheeze persisting at age 6
What is Orkambi and what is it for?
- CF with homozygous F508del mutation
- ivacaftor and lumacaftor
- corrector - protein folds properly then stays open
What is Pulmozyme?
- Pulmozyme - recombinant human deoxyribonuclease I - enzyme which selectively cleaves DNA
- dornase alfa
- Inhaled, anti-neutrophil, reduces gas trapping, improves airway clearance & CT findings by making the mucous less viscous.
What factors increase 2, 3 DPG?
- Hormones: thyroxine, HGH, adrenaline, testosterone
- High altitude (paO2 lower, need more to get oxygen off Hb to tissues)
Flattened expiratory curve in flow-volume loop:
Intrathoracic upper airway obstruction e.g. tracheomalacia
Flattened inspiratory curve in flow-volume loop:
Extrathoracic upper airway obstruction e.g. vocal cord paralysis or dysfunction
Flattened rectangular shape to all of flow-volume loop:
Fixed upper airway obstruction e.g. neck lump, tracheal stenosis or goitre
What is compliance and how does it vary in younger vs older children?
- Lung compliance is the change in lung volume per unit change in pressure
- Neonates have LOW lung compliance i.e. need high pressures to ventilate
- but HIGH chest wall compliance
What is the response to bronchodilator in asthma?
FEV1 increases by 15%
Decreased FEV1:FVC is…
- More likely obstructive
- Should also have decreased FEV1
- Decreased FEF 25-75% if small airways affected
Poor technique clues on flow-volume loop…
- Abnormal dips in expiratory curve
- early starts of inspiratory curve
Why are changes in FRC important?
- FRC maintains PAO2/PACO2 at more constant levels during inspiration and expiration
- decreased FRC -> decreased PAO2 in expiration as decreased volume, therefore hypoxemia
- compensate with increased PEEP and increased I-time in ventilation
- increased FRC - lungs are less compliant
What are signs/factors suggesting poor prognosis for CF?
- Poor nutritional status
- Pseudomonas aeruginosa
- Burkholderia cepacia
- Diabetes
- Frequent exacerbations
- Female gender
What are the indications for lung transplant in CF?
- FEV1 <30% predicted
- Rapid decline in lung function
- Declining exercise tolerance
- Nutritional problems
- Life threatening complications
What are the features of diaphragmatic hernia?
- 1/2-3000
- Affects contralateral lung
- Long term nutritional problems
- 30-60% malrotation
- R side 12%/L side 88%
How does mepolizumab work?
Anti IL-5
What happens physiologically with sleep?
Decreased muscle tone -> 2X airway resistance, 1/2 VT
Sleep worsens all ventilatory issues (except laryngomalacia)
