Respirology Flashcards
(100 cards)
A-a gradient
150 - PCO2/0.8 - PaO2
Normal = Age/4 + 4
Differential Diagnosis normal A-a gradient
Hypoventiliation - Drug intoxication - OHS/OSA - Neuromuscular dysfunction - Diaphragm injury (phrenic nerve / myopathy) - Brain bleed/stroke/tumor/meningitis High altitude
Differential Diagnosis wide A-a gradient
1) VQ Mismatch (improves w/ 100% FiO2) - COPD, PE
2) Shunt (does not improve completely with O2) - intracardiac (PFO/ASD/VSD), intrapulmonary (AVM), physiologic (severe PNA)
3) Diffusion Abnormality - ie. ILD
Diagnosis of asthma
- History of variable resp symptoms that vary over time & intensity
- PFT: variable expiratory airflow obstruction
a) Airflow obstruction: FEV1/FVC < LLN
b) Variability, any of:
- FEV1 >12% and 200 cc improvement post bronchodil OR after 4 wks anti-inflm tx OR between visits
- Diurnal peak flow variability of >10%
- Positive methacholine challenge test = Decrease FEV1 by 20% with <4mg/ml methacholine
- Positive exercise challenge test = Decrease in FEV1 by >=10% and 200 cc from baseline with exercise
Asthma Control Criteria
Control implies all criteria present:
Daytime symptoms <2 days/week
Nighttime symptoms <1 per week and mild
Reliever (SABA or bud/fom) <2 doses per week
Physical activity NORMAL
NO absence from work/school
Exaggerations infrequent and mild (no steroids/ED/admission, any one = severe)
Peak flow >= 90% personal best
<10-15% peak expiratory flow diurnal variation
Sputum eos <2-3%
Definition Uncontrolled Asthma
- Poor symptom control defined by lack of any one of asthma control criteria
- Frequent exacerbations (>=2 /year) req steroids
- One exacerbation in past year requiring hospitalization/ICU/MV
- Sustained airflow limitation of FEV<80% personal best
Definition severe asthma
- Asthma requiring use of HIGH dose ICS + 2nd controller for previous year
- Requiring oral steroid for >50% of the year for control
Work-up for severe asthma
Total IgE Peripheral and sputum eosinophil count FeNO where available Skin testing for aspergillus \+/- CT chest to evaluate for alternate pathology
Treatment algorithm asthma
Poorly controlled = daily ICS + prn SABA
Well controlled + risk of severe exacerbation = daily ICS or prn bud/form
Well controlled with NO risk of severe exacerbation = prn bud/form or prn SABA
- Low dose ICS-formoterol PRN (ie. symbicort)
- Low dose ICS-formoterol OD + PRN +/- add LTRA (esp if exercise/NSAID induced or allergic rhinitis)
- Medium dose ICS-formoterol OD + PRN +/- add LTRA
- High dose ICS-formoterol OD + PRN +/- add LTRA
- Refer for phenotypic ax +/- tiotropium, biologics, Macrolides (dec exacerbations), low dose steroids, bronchial thermoplasty
*sx control x2 mo + low risk of exacerbation = consider stepping down
Indications for anti-IgE (Omalozumab)
Serum IgE 30-700 and sensitive to 1+ perennial allergen, severe despite high dose ICS and one other controller
Indications for anti-IL5 (mepolizumab) or IL4/13 (dupilumab)
Serum eosinophils >300 and recurent exacerbation despite high dose ICS and one other controller
- Dupilumab also for those w nasal polyposis or mod/severe atopic dermatitis
Treatment asthma exacerbation
Ventolin + Atrovent PO or IV solumedrol/pregnisone \+/- MgSO4 Treat reversible triggers D/C home if PEF >70% personal best after 1 hr monitoring
Budesonide doses
Low = 200-400 Med = 400-800 High= >800
Fluticasone doses
Low = 100-250 Med = 250-500 High = >500
RADS vs occupational asthma
RADS = develops after single high dose exposure to vapour, gas or fumes
Occupational asthma = asthma that gets worse at work due to presence of some allergen
Spirometry - flattened inspiratory and expiratory curve
Fixed upper airway obstruction - eg goitre
- Glottic stenosis (prolonged intubation)
- Subglottic stenosis - GPA, sarcoid, polychondritis
Spirometry - flattened inspiratory curve, normal expiratory curve
Variable extra-thoracic obstruction - ie. vocal cord paralysis
Spirometry - flattened expiratory curve, normal inspiratory curve
Variable intra-thoracic obstruction - ie. tracheomalacia
Spirometry- scooped expiratory curve, normal inspiratory curve
Obstructive lung disease (asthma, COPD, CF)
Spirometry - small (but normal shaped) inspiratory and expiratory curves
Restrictive lung disease
If curves more rounded - think neuromuscular cause
Restrictive PFTs with 10% VC decline supine
Diaphragmatic dysfunction (eg post-op/CABG, mech vent, NMD eg ALS/MG) --> test MIP/MEP (decreased MIP = most sensitive for B/L diaphragm involvement; most specific - FVC)
RV/TLC > ULN
Gas trapping
TLC > ULN
TLC < ULN
TLC > ULN: Hyperinflation
TLC < ULN: Restriction
Isolated reduced DLCO with otherwise normal PFTs
Anemia (eg GIB) Pulmonary HTN Early ILD/emphysema (don't yet have restriction) PE Sarcoid