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
