Respiratory Flashcards
Natural Hx asthma
30-70% children with episodic asthma will have less severe of absent Sx by late adolescence
Severity in childhood determines severity in later life
Most sensitive and specific symptom of asthma
Wheeze
% of children with asthma who have allergies
66%
80% have positive SPT to dust mites
Classification of wheeze in children 1-4 years
Infrequent preschool (viral) wheeze Frequent preschool (viral) wheeze Multi-trigger wheeze
Diagnosing asthma in children (Aus asthma handbook)
- Symptoms and signs suggestive of asthma
(If not or suggestive of another diagnosis needds further Ix)
2a. Perform spirometry if child able => if FEV1 >12% of baseline 10-15 mins after bronchodilator Dx as asthma
(If not for further Ix eg. bronchial provocation test, cardiopulmonary exercise test => if these suggest asthma can still Dx asthma)
2b. If child not able to perform spirometry trial of treatment => if clear response to treatment Dx as asthma
(If not Dx as wheezing disorder, asthma not confirmed)
True/False- normal spirometry in the absence of symptoms does not exclude asthma
True
Spirometry pattern: low flow, normal volume
Fixed central/upper airway obstruction
Spirometry pattern: normal inhalation, scooped out exhalation with decreased flow
Obstructive picture
Spirometry pattern: Flow roughly normal, volume reduced
Restrictive picture
Spirometry pattern: Normal flow and normal exhalation morphology but decreased volume
Incomplete exhalation
Spirometry pattern: Normal exhalation, reduced flow in inhalation
Variable upper airway obstruction
What is on the axes in the spirometry loop
X: volume
Y: flow
What defines a bronchodilator response on spirometry
Salbutamol 4 puffs
Repeat spirometry 15 mins post
FEV1 increase >= 12% from baseline + 200mL (if FVC <1.5L, >100mL)
Direct airway challenge test
Inhalation of increasing concentrations of histamine or methacholine
In asthma: will result in fall of FEV1 >20% => if normal asthma is excluded
Good sensitivity, poor specificity- positive test does not confirm asthma
Indirect airway challenge test
Exercise challenge- in exercise-induced bronchospasm will result in FEV1 decrease 10-15%
Negative response is useful in excluding asthma in children with exercise-related breathlessness
Serial peak expiratory flow monitoring
PEF varies throughout the day
Serial measurement shows poor concordance with disease activity- low specificity and sensitivity for asthma
Fractional exhaled nitric oxide
Positive FeNO suggests eosinophillic inflammation and provides supportive, but not conclusive, evidence of asthma
Will also be raised in oesionphillic bronchitis, allergic rhinitis, eczema
Will be low in: smokers, during the early phase of an allergic response, neutrophillic asthma
Stepwise Mx asthma in children
- SABA PRN
- Low dose ICS / montelukast / cromone
- High dose ICS / low dose ICS + montelukast / ICS/LABA combination*
- Referral
*>= 12 years
Review each step in 2-4 weeks if montelukast/cromone, 4 weeks if ICS
Ensure adherence and technique before stepping up
Step up if poor control
Step down if good control for 3 months
Definition of good asthma control
Daytime sx <= 2x per week and rapidly relieved by SABA
No limitation of activities
No nighttime Sx
Need for relieved <= 2 x per week (does not include prophylactic before exercise)
Definition of partial asthma control
Daytime sx >2x per week and rapidly relieved by SABA
Any limitation of activities
Any nighttime Sx
Need for relieved >2 x per week (does not include prophylactic before exercise)
Definition of poor asthma control
Daytime Sx >2x per week and not quickly and completely controlled by reliever
Any 3x partial control Sc within a week
Inhaled corticosteroids for asthma- low and high doses (microg)
Beclometasone diproprionate (Qvar) - 100-200; 200-400 Beclomethasone dipropionate ultrafine - 100; 200 Budesonide (Pulmicort) - 200-400; 400-800 Ciclesonide (Alvesco) - 80-160; 160-320 Fluticasone propionate (Flixotide) - 100-200; 200-500
Initial preventor choice by age group
<12 months: specialist referral
1-2 years: sodium cromoglycate PO for multi-trigger wheeze
2- 5 years with frequent intermittent asthma, mild persistent asthma, frequent viral wheeze or multi-trigger wheeze: montelukast PO
2-5 years with mod-severe persistent asthma or mod-severe multi-trigger wheeze: low dose ICS
>6 years frequent intermittent: montelukast or cromone
>6 years and mild persistent: monktelukast or cromone
>6 years and mod-severe: low dose ICS
Patterns of asthma in 1-5 year olds
Infrequent intermittent - flare up less than every 6 weeks, Sx free in between
Frequent intermittent- flare up more often than every 6 weeks, Sx free in between
Mild persistent asthma- daytime Sx more than 1x per week but not daily, nighttime Sx >2x per month but not weekly
Mod persistent asthma- Daily daytime Sx, weekly nighttime Sx, restriction in activity or sleep
Severe persistent asthma- continual daytime Sx, frequent nighttime Sx, frequent restriction of activities or sleep
Patterns of asthma in 6 years and older
Infrequent intermittent - flare up less than every 6 weeks, Sx free in between
Frequent intermittent- flare up more often than every 6 weeks, Sx free in between
Mild persistent asthma- FEV1 >80% predicted + at least one of: daytime Sx more than 1x per week but not daily, nighttime Sx >2x per month but not weekly
Mod persistent asthma- Any of: FEV1 <80% predicted, dDaily daytime Sx, weekly nighttime Sx, restriction in activity or sleep
Severe persistent asthma- Any of: FEV <60% predicted, continual daytime Sx, frequent nighttime Sx, frequent restriction of activities or sleep, frequent flare ups
Inhaled devices recommended by age group
<2 years: small volume spacer and mask
2-4 years: small volume spacer, may transition to no mask
5-7 years: large volume spacer and no mask
8-15 years: large volume spacer and mask, dry powder device, breath-activated device
Low dose ICS acheives _% of maximum efficacy
80-90%
Effect of ICS on height
Small and temporary decreased height velocity- within first 2 years of treatment
Difference ~0.7% adult height
(Note that severe uncontrolled asthma will also reduce height)
Why is LABA monotherapy unsafe
Internalisation of the B2 receptors can result in paradoxical bronchospasm and no response to SABAs
Sensitisation risk is reduced when using with LABA
MOA cromones
MAST cell stabiliser
MOA montelukast
Leukotriene receptor antagonist
MOA omalizumab
Anti-IgE- given as a subcute injection every 2-5 weeks
MOA mepolizumab
Anti-IL5
Use of steroids in acute episodes asthma for children <5 years
Should only be used for those in hospital, on O2, with multi-trigger wheeze phenotype
Effect of sleep on respiratory physiology
Decreased muscle tone => airway resistance doubles, tidal volume halves
Therefore any impairment of ventilation will be worse in sleep (except laryngomalacia)
Stages of sleep
N1- transition to light sleep, easily roused
N2- light sleep (k complexes and spindles)
N3- deep sleep or slow wave sleep, still, very hard to rouse, regular breathing
REM- dream sleep, decreased tone, partial paralysis, vivid dreams, irregular breathing, increased upper airway resistance, decreased tidal volume
REM sleep
Longer in the second half of the night - more obstruction and hypoxia in the second half of the night
Babies sleep patterns
50:50 REM and quiet sleep
Identifying sleep stages on sleep study
N2: - Chin EMG medium movement - EEG: quiet, k complexes, spindles N3: - Chin EMG small - EEG: big slow waves REM: - Chin EMG smallest - Quiet EEG, eye movements, no Ks or spindles
ADHD and sleep
Decreased sleeping
Increased movement in sleep
Parasomnias
Partial awakening from N3 sleep
Usually 6-90 mins in to sleep- end of first cycle of deep sleep
Consider and underlying cause of arousal eg. OSA/periodic limb movement disorder
Treatment of night terrors
Clonazepam if frequent
Treatment f periodic limb movement disorder
Can be from partial iron deficiency in the basal ganglia- treat with iron to keep ferritin >50
Narcolepsy
Lack of neurotransmitter orexin (AKA hypocretin)- usually autoimmune disorder that attacks cells that secrete orexin
HLA for DR2
Ix: hypocretin-1 levels in CSF, multiple sleep latency test (REM sleep during the day)
Assoc with cataplexy 70%- drop attack with extreme emotion
Mx:
- Sodium oxybate, TCAs or SSRI for cataplexy
- Modafinil
- Methylphenidate or dexamphetamine
- Scheduled naps
Lung volumes
- Tidal vol
- TLC
- Vital capacity
- Residual vol
- Insp capacity
- Exp reserve vol
- FRC
Tidal vol: normal insp to normal exp (6-7mL/kg)
Total lung capacity
Vital capacity: forced insp to forced exp
Residual vol: air left after forced exp
Insp capacity: normal exp to full insp
Exp reserve vol: normal exp to forced exp
Functional residual capacity: exp reserve vol + residual vol
Change in lung volumes with restrictive disease
Smaller TV, FRC, insp capacity
Change in lung volumes with obstructive disease
Larger RV, exp reserve vol
Normal FVC, reduced FEV1, reduced FEV1/FVC
Obstructive
Obstructive spirometry pattern
Normal FVC, reduced FEV1, reduced FEV1/FVC
Low FVC, low FEV1, normal FEV1/FVC
Restrictive or failure to inhale or exhale completely
Spirometry: Restrictive
Low FVC, low/normal/increased FEV1, normal/increased FEV1/FVC
Spirometry: Failure to inhale or exhale completely
Low FVC, low FEV1, normal FEV1/FVC
Low FVC, normal or increased FEV1, normal or increased FEV1/FVC
Restrictive or inadequate effort
Low FVC, low FEV1, low FEV1/FVC
Mixed, severe obstruction, or obstruction with inadequate effort
Reference values for spirometry
FVC <80% predicted FEV1 <80% predicted FEV1/FVC <76-78% (actual value) TLC <80% predicted FEF25-75% <66% predicted
FEF25-75%
Most sensitive for airway obstruction
Effort independent
Relationship between chest wall compliance and FRC
Unusually low (restrictive) or high (obstructive) FRC causes decreased lung compliance FRC is primarily determined by chest wall compliance (FRC is the point at which outward recoil of the chest wall is equal to the inward recoil of the lungs)
How does restrictive lung disease cause hypoxaemia
Restrictive lung disease = reduced FRC
FRC is the volume available for gas exchange at all times - if reduced then have reduced volume available for gas exchange in expiration = hypoxia in expiration