Respiratory Flashcards
What shifts the oxygen dissociation curve to the left
Shifts to L → Lower oxygen delivery, caused by Low [H+] (alkali) Low pCO2 Low 2,3-DPG Low temperature
Another mnemonic is ‘CADET, face Right!’ for CO2, Acid, 2,3-DPG, Exercise and Temperature
lung function tests
obstructive: describe FEV1, FVC and FEV1% (FEV1/FVC) & causes
restrictive: ‘ ‘
OBSTRUCTIVE
FEV1 - significantly reduced
FVC - reduced or normal
FEV1% (FEV1/FVC) - reduced
CAUSES Asthma COPD Bronchiectasis Bronchiolitis obliterans
RESTRICTIVE
FEV1 - reduced
FVC - significantly reduced
FEV1% (FEV1/FVC) - normal or increased
CAUSES Pulmonary fibrosis Asbestosis Sarcoidosis ARDS Infant respiratory distress syndrome Kyphoscoliosis e.g. ank spondylitis Neuromuscular disorders Severe obesity
pneumothorax mx
Primary
- <2cm + pt not SOB: consider discharge (or aspirate) - If >2cm and/or SOB: aspirate w 16-18G cannula - If aspiration fails (>2cm or still SOB) then chest drain
Secondary
- >50y old and >2cm and/or SOB: chest drain
- If 1-2cm and not SOB: aspiration (if aspiration fails»_space; chest drain)
- <1cm: give oxygen and admit for 24h
Admit all for at least 24h
lung volumes
- tidal volume
- inspiratory reserve volume
- expiratory reserve volume
- residual volume
- functional residual capacity
- vital capacity
- total lung capacity
- physiological dead space
Tidal volume (TV)
• volume inspired or expired with each breath at rest
• 500ml in males, 350ml in females
Inspiratory reserve volume (IRV) = 2-3 L
• maximum volume of air that can be inspired at the end of a normal tidal inspiration
• inspiratory capacity = TV + IRV
Expiratory reserve volume (ERV) = 750ml
• maximum volume of air that can be expired at the end of a normal tidal expiration
Residual volume (RV) = 1.2L
• volume of air remaining after maximal expiration
• increases with age
• RV = FRC - ERV
Functional residual capacity (FRC)
• the volume in the lungs at the end-expiratory position
• FRC = ERV + RV
Vital capacity (VC) = 5L
• maximum volume of air that can be expired after a maximal inspiration
• 4,500ml in males, 3,500 mls in females
• decreases with age
• VC = inspiratory capacity + ERV
Total lung capacity (TLC) is the sum of the vital capacity + residual volume
Physiological dead space (VD)
• VD = tidal volume * (PaCO2 - PeCO2) / PaCO2
• where PeCO2 = expired air CO2
transudate - definition and causes (incl which is most common)
- HF (most common)
- Low albumin (liver disease, nephrotic syn, malabs)
- Hypothyroidism
- Meigs’ syndrome
<30g/L protein
exudate
- what is it
- causes incl most common
Exudate (>30 protein)
- Infection: pneumonia (most common exudate cause), TB, subphrenic abscess - CTD: RA, SLE - Cancer: lung cancer, mesothelioma, mets - Pancreatitis - PE - Dressler's syn - Yellow nail syndrome
different types of lung cancer
- adenocarcinoma
- squamous cell
- large cell
- small cell
- carcinoid
· Adenocarcinoma: most common type in non-smokers. But most people who develop it are smokers. Peripheral. Gynaecomastia. HPOA.
· Squamous cell: strongly ass w smoking. high calcium (PTH related protein secretion). Central tumour. Clubbing. Hypertrophic pulmonaey osteoarthropathy. Ectopic TSH > hyperthyroid. can cavitate
· Large cell: peripheral. Poor prognosis. Can secrete b-hcg
· Small cell: ectopic ADH > low Na, lambert-eaton syndrome (myasthetic like syndrome)
○ ectopic ACTH > cushing’s (htn, hyperglycaemia, low K, alkalosis, muscle weakness)
Lung carcinoid: ‘cherry red ball’ on bronchoscopy, good prognosis, smoking not a RF, don’t usually see carcinoid syndrome
lung fibrosis causes
- upper zones
- lower zones
upper zone fibrosis: CHARTS
• C - Coal worker’s pneumoconiosis/progressive massive fibrosis
• H - Histiocytosis/ hypersensitivity pneumonitis (extrinsic allergic alveolitis)
• A - Ankylosing spondylitis (rare)
• R - Radiation
• T - Tuberculosis
• S - Silicosis/sarcoidosis
Fibrosis predominately affecting the lower zones
• IPF
• most CTDs (except ankylosing spondylitis) e.g. SLE
• drug-induced: amiodarone, bleomycin, methotrexate
asbestosis
lung fibrosis causes
- upper zones
- lower zones
upper zone fibrosis: CHARTS
• C - Coal worker’s pneumoconiosis/progressive massive fibrosis
• H - Histiocytosis/ hypersensitivity pneumonitis (extrinsic allergic alveolitis)
• A - Ankylosing spondylitis (rare)
• R - Radiation
• T - Tuberculosis
• S - Silicosis/sarcoidosis
Fibrosis predominately affecting the lower zones
• IPF
• most CTDs (except ankylosing spondylitis) e.g. SLE
• drug-induced: amiodarone, bleomycin, methotrexate
asbestosis
long term asthma mx
- Newly diagnosed: SABA
- Not controlled on SABA or new diagnosis w syms 3x/wk or night time waking: SABA + ICS
- SABA + ICS + LTRA
- SABA + low dose ICS + LABA (continue LTRA dep on pts response to it)
- SABA +/- LTRA. Switch ICS/LABA to MART (incl low dose ICS)
- SABA +/- LTRA. Medium dose ICS MART
○ Or consider: fixed dose of moderate dose ICS and separate LABA - SABA +/- LTRA and one of
○ High dose ICS (not as a MART)
○ Trial of additional drug: long-acting muscarinic rec antag, theophylline
Seek advice from expert
dx of asthma
17 or older:
- Are syms better on days away from work/during holidays: if yes, refer to specialist (consider occupational asthma) - All should have spirometry w bronchodilator reversibility test & FeNO test
occupational: Serial measurements of peak expiratory flow are recommended at work and away from work.
features of mod/severe/life threatning/near fatal asthma
Moderate PEFR 50-75% best or predicted Speech normal RR < 25 / min Pulse < 110 bpm
SEVERE PEFR 33 - 50% best or predicted Can't complete sentences RR > 25/min Pulse > 110 bpm
LIFE THREATENING PEFR < 33% best or predicted Oxygen sats < 92% Silent chest, cyanosis or feeble respiratory effort Bradycardia, dysrhythmia or hypotension Exhaustion, confusion or coma Normal pCO2 (4.6=6)
Near-fatal: raised pCO2 and/or needing mechanical ventilation w raised inflation pressures
COPD mx
MANAGEMENT
1. SABA or SAMA
2. Still SOB or have exacerbations: Asthmatic fts or steroid responsive:
○ Yes: SAMA or SABA + LABA + ICS
○ No: SABA PRN. LABA and LAMA regularly
3. SABA PRN. LABA + LAMA + ICS
Asthmatic/steroid responsive
- Previous dx asthma or atopy - Raised eosinophils - Sig variation in FEV1 over time (at least 400ml) - Sig diurnal variation in peak exp flow (at least 20%)
resp alkalosis causes
anxiety leading to hyperventilation pulmonary embolism salicylate poisoning* CNS disorders: stroke, subarachnoid haemorrhage, encephalitis altitude pregnancy
*salicylate overdose leads to a mixed respiratory alkalosis and metabolic acidosis. Early stimulation of the respiratory centre leads to a respiratory alkalosis whilst later the direct acid effects of salicylates (combined with acute renal failure) may lead to an acidosis
raised TLCO
• asthma • pulmonary haemorrhage (Wegener's, Goodpasture's) • left-to-right cardiac shunts • polycythaemia • hyperkinetic states male gender, exercise
