Asthma Flashcards
How do you diagnose asthma?
1) Spirometry:
- FEV1/FVC <LLN or <75%, should be considered supportive of an asthma diagnosis and should prompt reversibility test
- Normal spiro does not rule out asthma
2) PEF:
- Should not be used as the primary test
- May be considered if no other lung function test is available
- Should be monitored over a two-week period - variation of >20% supportive of asthma. <20% variability does not rule out asthma
- useful to diagnosis occupational asthma
-
3) FeNO
- Cut-of: >40ppb
- <40 does not exclude asthma
- FeNO is lowered in smokers, impaired airway calibre, on ICS, on anti-IL4/IL13
- FeNO can be high in allergic rhinitis or chronic eosinophilic bronchitis
4) Bronchial challenge testing
- Asthma = Provocation concentration causing 20% fall in FEV1of methacholine (PC20-M) or histamine (PC20-H) <8mg/ml in steroid naïve & <16mg/ml in pts on regular ICS
- Indirect challenges (using mannitol or exercise) can be considered in pts which remain negative with direct constricting agents. PD mannitol <625mg suggestive of asthma
- Indirect challenges better correlated with the extent of airway inflammation
For pts already on maintenance ICS therapy:
- Do reversibility testing or bronchial challenge testing
- ICS gradually tapered and if Sx do not worsen or no significant decline in spiro/ PEF → bronchial challenge test
Reference: ERS 2022 Dx of asthma in adults
How do you manage asthma in general?
(Assess - Adjust - Review)
1) assess asthma control
- ACT score
- identify risk factors for poor control
- monitor spiro: before Rx, 3-6m post Rx, then annually
2) manage comorbidities
- look for:
allergic rhinitis
chronic rhinosinusitis
GORD
obesity
OSA
anxiety
depression
3) initiate treatment
Ax technique
provide written asthma plan
ask pt re goals & preference of Rx
- confirm Dx
- Mx comorbidities
- Ax Sx - ACT
- Asthma Action
Summary:
1) Assess
- Correct Dx
- Comorbidities (7)
- Sx (ACT)
- Asthma Action Plan
- Educate re technique & need for compliance
- Pt’s understanding/ goals
2) Adjust:
- based on ACT 3-6m post Rx
- ACT
- Ax technique/ compliance
3) Review:
- Spiro at baseline, 3-6m & annually
- ACT score
Phenotypes of asthma (5)
1) Allergic asthma - sputum is usu eosinophilic, assoc with other atopy (eczema, AR, drug/food allergy), childhood
2) Non-allergic asthma - sputum can be paucigranulocytic, neutrophilic or eosinophilic. not assoc with allergy
3) Adult-onset (late-onset) asthma - esp woman, usu non-allergic, needs high dose of ICS or relatively refractory to steroid. TRO occupational asthma
4) Asthma with persistent airflow limitation - in long standing asthma (persistent & incompletely reversible sec airway remodelling)
5) Asthma with obesity - min eosinophilic airway inflammation)
What is asthma?
What is the diagnostic criteria of asthma?
Resource: GINA 2023
Problem with bronchial challenge test: false positive in COPD, allergic rhinitis, CF & bronchopulmonary dysplasia
= A heterogenous disease,
- characterised by chronic airway inflammation,
- defined by the Hx of respiratory Sx e.g. wheeze, SOB, chest tightness & cough,
- that vary over time and in intensity,
- with variable expiratory airflow limitation.
3 diagnostic criteria of asthma:
1) Hx of typical variable resp Sx:
- wheeze/ SOB/ chest tightness/ cough
- variable over time & intensity
- worse at night or waking
- triggered by exercise, laughter, allergens, cold air
- worse with viral infections
2) Confirmed variable exp airflow limitation
- Options:
a) Spiro with reversibility test: Increase in FEV1 >12% and >200ml
b) Excessive variability in twice-daily PEF over 2 weeks: >10%
c) Increase lung function after 4 weeks of Rx: Increase FEV1 >12% and >200ml
d) Positive exercise challenge test: Decrease FEV1 >10% and >200ml
e) Positive bronchial challenge test: Decrease FEV1 ≥20% (with methacholine) or ≥15% (with hyperventilation, hypertonic saline or mannitol)
f) Excessive variation in lung function between visits: Decrease FEV1 >12% and >200ml
3) AND 2 documented exp airflow limitation
Conditions that increases and decreases FeNO
Conditions that increases FENO:
a) Type 2 airway inflammation asthma
b) Eosinophilic bronchitis
c) Atopy
d) Allergic rhinitis
e) Eczema
Conditions that decreases FENO:
a) Smokers
b) During bronchoconstriction
c) Early phase of allergic response
d) Neutrophilic asthma
Conditions that may increase or decrease FENO:
a) Viral resp infection
When is FeNO required in asthma setting?
- FENO is indicated in spiro which is above normal, instead of bronchodilator challenge
- FENO is to be done before spirometry
DDx of asthma
CCC-II-B-H-M
Age 12-39:
Chronic upper airway cough syndrome
Inducible laryngeal obstruction
Bronchiectasis
Cystic fibrosis
Congenital heart disease
AATD
Inhaled foreign body
Age 40+:
Inducible laryngeal obstruction
Hyperventilation, dysfunctional breathing
COPD
Bronchiectasis
Cardiac failure
Medication-related cough
Parenchymal lung disease
PE
CAO
All ages:
TB
Pertussis
Comorbidities that affect asthma control
a) AR
b) Rhinosinusitis
c) GORD
d) Obesity
e) OSA
f) Depression
g) Anxiety
Drugs that can affect asthma control
1) Cytochrome P450 inhibitors
- e.g. ketoconazolem ritonavir, itraconazole, erythromycin, clarithromycin
- effect:
a) increase systemic ICS SE (e.g adrenal insuff)
b) increase CVD adverse effects with LABA Salmeterol and Vilanterol
2) Paxlovid (nirmatrelvir + ritonavir)
- used in prevention to severe covid-19 infection
- effects:
a) Interacts with salmeterol & vilanterol –> need to swap to different LABA as these LABAs increases cardiac toxicity in combination with Paxlovid.
- Duration of swap is upon starting Paxlovid until 5d after stopping Paxlovid
Factors that contribute to difficult asthma control
a) poor technique
b) poor compliance
c) over-use of SABA
d) comorbidities: GORD, obesity, rhinosinusitis, OSA, allergic rhinitis
e) persistent environmental exposures: triggers at home/ work, smoking, allergen exposure, meds (NSAIDs, beta-blocker)
f) psychosocial factors: anxiety, depression, social difficulties
Controller options in Step 3 of asthma Mx
a) Sublingual allergen immunotherapy (SLIT): in AR & sensitised to house dust mites & FEV1 >70%
b) Add LAMA
c) Add LTRA (e.g. montelukast)
d) Add Theophylline MR
Controller options in Step 5 of asthma Mx
a) Add on Azithromycin
- Consider after high-dose of ICS/LABA
- Dose: 500mg 3x/week
- Things to do before initiating it: check sputum for NTM, ECG for prolonged QTc, risk of microbial resistance
- Duration of Rx is 6m at least (studies have not shown significant improvement in 3m)
b) Add on biologic
c) Add on bronchial thermoplasty: long term effects on lung function is not known
d) Add on OCS (last resort)
Asthma treatment according to the steps
Steps:
1: Sx <2/month
2: Sx <4-5d/week
3: Sx most days, OR waking up at night >1d/week
4: Daily Sx, OR waking up at night >1day/week, AND low lung function
Rx:
Preferred pathway:
Step 1-2: PRN ICS-formoterol
Step 3: Low dose ICS-formoterol
Step 4: Medium dose ICS-formoterol
Step 5: Add on LAMA +/- biologic. Consider high dose ICS-formoterol
Reliever: PRN ICS-formoterol (lower risk of exac compared to SABA as PRN)
** Alternative pathway**:
Step 1: ICS whenever SABA is taken
Step 2: Low dose ICS
Step 3: Low dose ICS-LABA
Step 4: Medium/ high dose ICS-LABA
Step 5: Add on LAMA.
Consider biologic
Other controller options:
Step 2: Low dose ICS whenever SABA taken, OR daily LTRA, OR HDLM SLIT
Step 3: Medium dose ICS, OR add LTRA, or add HDM SLIT
Step 4: Add LAMA OR LTRA OR HDM SLIT or switch to high dose ICS
Step 5: Add azithromycin (adults only) or LTRA.
Last resort: add low dose OCS
ICS doses according to strength, and triple therapy inhalers
Budesonide (DPI or MDI)
Low: 200mcg
Mod: >400mcg
High: >800mcg
Beclomethasone (extrafine)
Low: 100mcg
Mod: >200
High: >400
Beclomethasone (std particle)
Low: 200mcg
Mod: >500
High: >1000
When should we consider stepping down asthma treatment?
a) When asthma Sx have been very well controlled and lung function has been stable for ≥3m, with close supervision
b) Choose appropriate time: not travelling/ pregnant/ resp infection
c) Engage the pt with the process, provide clear instructions and pt has sufficient med to resume previous dose if needed.
d) Step down ICS by 25-50% at 3m interval
Vaccination advice in asthma
a) Annual fluvax in mod-severe asthma
b) Insufficient data for pneumococcal or pertussis vax
c) Covid-19 vax
Covid-19 vax & fluvax can be given on same day
Non-pharmacological intervention in asthma
i. Avoid meds that make asthma worse: e.g NSAIDs, ophthalmic or oral B-blocker – not absolute contraindication but need to monitor closely
ii. Healthy diet: high fruits & vege for general wellbeing
iii. Avoid indoor/ outdoor allergens/ weather condition: e.g. smoking, vaping, mold, pollen, pets, very cold weather/ haze
iv. Weight reduction: weight reduction + 2x/w aerobic & strength exercises more effective
v. Emotional stress Mx: mental health Ax, breathing exercise
vi. Address social risk
vii. Food avoidance: only recommended when it is confirmed by supervised oral challenge
viii. Asthma education
ix. Ensure correct technique
x. Vaccination – influenza & Covid-19
Which biologic agents to use in asthma?
Anti-IgE:
a) eos ≥260/microL
b) FeNO ≥20ppn
c) Allergen-driven
d) Childhood-onset
Anti-IL5/ Anti-IL5R:
a) Eos ++ (≥150 /microL or ≥300/microL)
b) more exac in previous year
c) Adult-onset
d) Nasal polyposis
Anti-IL4R:
a) Eos ++ (≥150 and ≤1500/microL)
b) High FeNO ≥25ppb
c) taking OCS
Anti-TSLP:
a) Eos ++
b) High FeNO
How to initiate and continue on biologics?
i. Choose the most appropriate biologic
ii. Trial of at least 4m and reassess response
iii. If good response, re-evaluate every 3-6m
- Consider reducing OCS (check for adrenal insuff. If unwell, need to get OCS for 6m post cessation of OCS), then stop other add ons. Continue mod dose ICS-LABA
- Consider stopping biologic after 12m if Sx well controlled on mod dose ICS-LABA & no further exposure to allergic trigger. Some pts may relapse.
iv. If unclear response, extend trial to 6 to 12m
v. If no good response, consider switching to different biologic.
vi. If still no good response, stop biologic. Do Mx as per non-Type2
– continue to optimise inhaler technique, adherence, non-pharmacological strategies, social/emo needs, communication with GP
Response review by looking at:
i. Asthma Sx, exac & lung function
ii. Other Type 2 comorbids – nasal polyposis, atopic dermatitis
iii. Meds: treatment side effects, affordability
iv. Pt satisfaction
What is the definition of asthma-COPD overlap?
Pts who have persistent airflow limitation together with clinical features that are consistent with both asthma and COPD
What are the triple therapy inhalers available?
Sites of where specific biologics work
How to manage asthma exac in primary care setting
Mx of exac of asthma in primary care:
A) Determine severity
Mild-mod features:
- Talk in phrases
- Prefers sitting (to lying)
- Not agitated
- RR increased
- No accessory muscle use
- HR 100-120
- SpO2 90-95%
- PEF >50% predicted
Severe features:
- Talks in words
- Sits hunched forward
- Agitated
- RR >30
- Accessory muscle use
- HR >120
- SpO2 <90%
- PEF ≤50% predicted
Life-threatening features:
- Drowsy
- Confused
- Silent chest
B) Treatment:
1) ABC
2) SABA 4-10p, every 20mins for 1h, then every 1-4h PRN
3) Pred 40-50mg (1mg/kg)
4) O2 – aim SpO2 93-95%
5) Ax for d/c in mild-mod, or transfer to hosp in life-threatening
- D/c if:
i) Sx improved not needing SABA, ii) PEF >60-80%,
iii) SpO2 >94%,
iv) resources at home adequate
6) If d/c: Cont reliever, start or step up controller, pred for 5-7d, f/up 2-7d. Abx only if with infection evidence
7) F/up:
- check whether exac resolving,
- reduce reliever,
- cont controller higher dose for 1-2w or 3m (depend on exact),
- check risk factors inc technique & adherence.
- Refer if >1-2 exac/year.
- Ax whether action plan needs to be modified
Doses for meds use in asthma exacerbation
Dosing of meds:
a) Salbutamol neb:
- Salbutamol 0.5% inhalation solution
- Dose: 2.5-5mg, repeat every 20mins for 1 hour
b) Salbutamol infusion:
- Salbutamol 5mg/5ml
- Dose:
Loading dose 0.25mg over 10mins
Dilute 0.5mls (0.5mg) of salbutamol in 20mls N/saline
Use syringe pump. Rate: 60mls/hr (20mls over 20mins)
Infusion dose: 5-20mcg/min
Dilute 3mls (3mg) of salbutamol in 50mls N/saline or D5%
1ml /hr = 1mcg/min
Run 5-20mls/hr
c) Ipratropium bromide
- Ipratropium bromide 0.025% inhalation solution (250mcg/ml)
- Dose: 0.5mg, repeat every 4-6h
d) MgSo4
- Dose: 2g over 20mins
e) Hydrocortisone
- Dose: 200mg stat, and 100mg TDS
f) Pred
- Dose: 1mg/kg (max 50mg) OD 5-7d
g) Adrenaline
- Use in angioedema/ allergy
- Adrenaline 1:1000 (1mg/ml)
- Dose:
IM: 0.5mg every 20mins (max 3 doses)
S/cut: (same as IM)
IV: 0.1mcg/kg/min
h) Aminophylline
- Not recommended due to adverse & cardiac effects
- Dose: iv 6mg/kg over 30mins, then IVI 0.5mg/kg/h. Check serum level with aim 8-12 mcg/ml
i) Ketamine
- Dose: 0.1-0.5mg/h
j) Propofol
- Dose: 5-50mcg/kg/min
Biologics dosing & SE
