Respiratory Flashcards
Changes in airway diameter with inspiration/expiration
Upper airways narrow with inspiration, dilate with expiration
Lower airways dilate with inspiration, compressed by expiration
This is why stridor is heard in inspiration, and wheeze is heard in expiration
which spirometry measure is most sensitive in kids with small airway disease
FEF 25-75
most sensitive marker of obstruction
(but is also very variable)
what is the maximal allowable variation in flow volume loops on repeat testing
5%
what measure best approximates height if this cannot be done (ie underlying disease)
arm span approximates standing height
Simple spirometry rules
Low FEV1/FVC= obstruction present
Normal FVC= rules out restriction
Normal FEF 25-75= rules out obstruction
Positive bronchodilator response = increase by 12% in FEV1 and increase by 200ml from baseline
what parameter is used as a marker of lung function in obstructive disease
FEV1
Most useful long term measure of disease progression in obstructive lung disease
Used for monitoring of lung function in CF, corrolates well with severity of obstructive lung disease
What parameter is used to monitor lung function in restrictive disease
FVC
max air blown out after full inspiration
- this is normal or reduced in obstructive disease due to gas trapping and hyperinflation
- always reduced in restrictive disease; degree of reduction linked with degree of impairment
but should do sleep study first
eg DMD
FVC <60%= REM sleep disordered breathing
FVC <40%= NREM + REM sleep disordered breathing
FVC <20%= daytime respiratory failure
What are the hallmarks of restrictive disease
Characterised by reduced lung volumes or reduced lung compliance
Reduced total lung capacity (TLC) and FVC <80%
Reduced FEV1 (<80% of the predicted normal)
Reduced FVC (<80% of the predicted normal)
FEV1/FVC ratio normal or increased (>0.7)
Reduced FRC (due to reduced compliance)
Hallmarks of obstructive lung disease
Reduced FEV1 (<80% of the predicted normal)
Reduced FVC (but to a lesser extent than FEV1)
FEV1/FVC ratio reduced (<0.7)
Reduced FEF max and FEF 25-75 (this is earliest change in small airway obstruction)
Increased TLC, VC, FRC and RV due to incomplete expiration/gas trapping
Reduced peak expiratory flow, inspiration relatively preserved
When would you see an increased FRC?
FRC = functional residual capacity
Volume left in lungs after tidal expiration
Caused by intrathroacic obstruction ie incomplete exhalation
Causes restrictive lung disase
Intrinsic lung disease = interstitial fibrosis
Chest wall pathology = eg. Scoliosis, abnormal chest wall
Neuromuscular disease = eg. DMD
CF (mixed)
Obesity
Causes obstructive lung disease
o Asthma
o CF
o Bronchiolitis obliterans
Emphysema
Narrowest part of paediatric airway
subglottis: from underside of true vocal cords to inferior margin of cricoid cartilage
Upper airway obstruction (extrathoracic) - flow volume loop
Upper airway narrows in inspiration therefore Inspiratory curve reduced
Expiratory curve normal
eg. supraglottic leisons
laryngeal paralysis, unilateral vocal cord paralysis, laryngomalacia, croup/epiglottitis , laryngeal web
Variable intrathoracic upper airway obstruction - flow volume loop
o During inspiration the intrathoracic obstruction expands due to negative pleural pressure normal curve
o During expiration pleural pressure positive relative to airway pressure flattened curve
Flow volume loop = normal inspiratory curve, flattened/truncated expiratory curve
eg tracheomalacia, bronchomalacia, vascular rings and webs, FB in bronchus
what would you seen if there was fixed central or upper airway obstruction
Flow volume loop flattened in both inspiration and expiration (both limited equally)
As there cant be any increase in volume during expiration due to the fixed nature
**subglottis is the narrowest part of the trachea, so mild narrowing leads to huge increase in resistance.
Subglottic stenosis second most common cause of stridor (after laryngomalacia). Stridor is biphasis or primarily inspiratory. May have first symptoms with URTI as oedema and secretions narrow an already compramised airway. recurrent croup is common
eg tracheal stenosis, subglottic stenosis, bilateral VC paralysis, subglottic haemangioma, laryngea web, vascular ring
Diffusion capacity (DLCO)
The DLCO measures the ability of the lungs to transfer gas from inhaled air to the red blood cells in pulmonary capillaries.
Causes of false positive sweat test results
Adrenal insufficiency
Neohrogenic DI
Hypothyroidism
Hypoparathyroidism
Malnutrition
Metabolic syndromes -eg GSD
Atopic dermatits
Familial cholestasis syndrome
Pancreatitis
G6pd
Causes false negative sweat test
Oedema
Inadequate stimulation/collection
Minerallocorticoid use
Pathogenesis of bronchiolitis obliterates
Bronchiolitis obliterans (BO) is a rare, chronic lung disease of bronchioles and smaller airways.
It most commonly occurs in children after lung infection e.g. adenovirus, mycoplsma, measles, influenza, pertussis. Other causes include connective tissue disease, toxin fume inhalation, post lung or BM transplant. With adenovirus, it is types 7 and 21 which are the most concerning.
After the initial insult, inflammation leads to obliteration of the airway lumen causing air trapping or atelectasis. Bronchiolitis obliterans organising pneumonia (BOOP) is a fibrosing lung disease that includes histological features of BO with extension into alveoli with proliferation of fibroblasts
Clinical, there is initially cough, fever, cyanosis, and respiratory distress . Progression leads to increasing cough, SOB, wheezing, and sputum production.
CXR is relatively normal or demonstrates hyperlucency and patchy infiltrates. PFTs have variable findings, but typically an obstructive picture. VQ scan has a typical moth-eaten matched defects. CT shows patchy areas of hyperlucency and bronchiectasis
An open lung biopsy is required for definitive diagnosis. There is no definitive therapy, but corticosteroids may be beneficial. Immunomodulators are used in post-transplant patients.
Some patients rapidly deteriorate and die within weeks, and most non-transplant patients survive with chronic disability. 60-80% BOOP patientss survive but relapse can occur
DLCO results in pulmunary vascular disease
In pulmonary hypertension, the DLCO is reduced. The VA is typically normal, and the KCO (DLCO/VA) is reduced due to impairment at the alveolar-capillary interface.
DLCO results in interstitial lung disease
DLCO is decreased by diffuse alveolar capillary damage. The VA is low due to the loss of aerated alveoli. The KCO (DLCO/VA) is often reduced to a lesser extent than the DLCO
DLCO results in pneumonoectomy
If no lung disease in the remaining lung:
VA is decreased due to discrete loss of alveolar units. Blood flow is diverted to the remaining lung and the KCO (DLCO/VA) is usually increased. As a result, the DLCO is slightly decreased.
DLCO results in bronchiectasis/bronchiolitis obliterans
DLCO low
Improved when corrected for reduced alveolar volume (KCO reduced to a lesser extent than DLCO)
DLCO increased in..
Pulmunary haemorrhage
L–>R cardiac shunts
Mild left heart failure (increase capillary blood volume)
Obesity
Asthma
High altitute
Polycythemia
EVALI
E cigarette or vaping associated lung injury
causes:
lipoid penumonia
eosinophilic pneumonia
hypersensitivity pneumonitis
diffuse alveolar haemorrhage
ARDS
granulomatous pneumonitis
organising pneumonia
spontaneous pneumothorax
MOA Ivacaftor in CF
Potentiatior
Used for Class 3 mutations (at least 1 allele) eg G551b
Holds defective CFTR open so chloride can flow through / potentiates the channel opening probability of CFTR at cell surface
**remember this mutation is a gating mutation, so CFTR gets to cell membrane but doesnt allow Cl thorugh
For kids > 12 months
MOA Lumacaftor in CF
**used in combination with ivacaftor= orkambi **
Corrector
Used if patient is homozygous for dF508 allele
Facilitates the processing and trafficking of CFTR to increase CFTR at cell surface ie
Helps CFTR protein form correct shape, move to cell surface and stay there longer
Age 6-11
MOA Trikafta in CF
Elexacaftor/tezacaftor/ivacaftor + ivacaftor
Must have at least 1 dF508 allele
Elexacaftor helps protein form into correct shape to allow traffic to cell surface
Tezacaftor also improves processing and trafficking of CFTR proteins
Age >12 yrs
ABPA treatment
Prednisolone 6-12 weeks
Antifungals (itraconozone, voriconazone) for 4 weeks after stopping steroids
Anti IgE (omalizumab)
CF related diabetes
occurs in 2nd decade of life
affects 20% adults
due to impaired secretion of insulin secondary to destruction of islet cells (obstructive damage to pancreas due to thick secretions)
often presents as a decline in lung function and weight loss
OGTT best screening test, fasting hyperglycemia and elevated Hba1c comes much later
Microvascular complications less common than other types of diabetes but they do occur; macrovascular complications are rare
Rx: insulin
meconium ileus
10-20% of newborns with CF
Presents as GI obstruction - distension, emesesis, failure to pass mec in first 48 hours
Can present as mec peritonitis from intrauterine bowel rupture
rx; contrast enema + laparotomy
Distal intestinal obstruction syndrome
5-10% , usually >15 years
accumulation of fecal material in terminal portion of ileum and caecum –> bowel obstruction
presents as cramping abdo pain, distension and constipation
Risks of fat soluable vitamin deficiencies in CF
Vit A- night blindness
Vit E- neurological dysfunction (ataxia, weakness, hyporeflexia), haemolytic anemia
Vit K- bleeding
Vit D- reduced bone density
Exocrine pancreatic insufficiency in CF
> 85% affected
present in 2/3 from birth
symptoms: steattorhooea, poor weight gain, vitamin deficiency, oedema, hypoproteinemia, electrolyte loss, anemia
also leads to oxolate renal stones
Liver problems in CF
Liver involvement common
Focal biliary cirrhosis in up to 70%
Obstruction to bile flow leads to increased toxic bile acids and hepatocyte injury
Presentation
Asymptomatic deranged LFTs
Neonatal cholestasis
Hepatic steatosis and steatohepatis
Focal biliary cirrhosis
Cholelirhiasis and cholecystutis
Microgallbladder
Fertility in CF
Delayed puberty on average 2 years
90 % of males have azoospermia due to failure of development of wolfian duct structures
Female fertility impaired due to malnutrition and thick cervical mucous but pregnancy well tolorated in those with good lung function
MOA pulmozyme
Colonisation if bacteria in airways —> accumulation of neutrophils
Death of neutrophils —> increased DNA in mucous leading to even further thickening
Pulmozyme is a recombinant DNAase that cleaves extracellular DNA released from dead neutrophils in sputum thus reducing viscosity
Improves pulmonary function and decreases exacerbations
Antibiotics for exacerbation of CF pseudomonas positive
Mild- oral ciprofloxacin
Severe- iv tobramycin + piptaz or ceftazadime
Symdeko in CF
Tezacaftor + ivacaftor
Approved for >12 years with homozygous delF508 or at least 1 residual function mutation
Tezacafor is a corrector, helps the defective protein form correct shape, traffic to cell surface and stay there longer
Fewer side effects than lumacaftor+ ivacaftor
If f508 positive, Trinkafta is the gold standard
Azithro in CF
Anti inflammatory action
3 times weekly from time of aquisition of pseudomonas
Don’t give if infected with no tuberculous mycobacteria
Pulmunary sequestration
is a congenital pulmonary malformation, comprised of a mass of non-functioning primitive tissue that does not communicate with the tracheobronchial tree.
Bacterial tracheotis presentation
Bacterial tracheitis is an uncommon infectious cause of acute upper airway obstruction. It is more prevalent than acute epiglottitis in children who have been vaccinated with Haemophilus influenza B. Bacterial tracheitis can be suspected in patients who present with croup-like symptoms (barking cough, stridor and fever) and preceding viral infection, but have a more toxic presentation and do not respond to standard croup therapy, because they have developed a secondary bacterial infection (e.g., Staphylococcus aureus, Moraxella catarrhalis or Haemophilus influenza). Acute airway obstruction can develop secondary to subglottic oedema and sloughing of the epithelial lining or accumulation of mucopurulent membrane within the trachea.
Bacterial tracheitis is differentiated from epiglottitis, because in the case of epiglottitis there would be a rapid prodrome, DROOLING, ABSENT COUGH, muffled voice, tripod positioning, and the chest X-ray would show pathology at the epiglottis.
Rx: nebulised adrenaline, oxygen, IV ceftriaxone
Discuss VQ mismatch in asthma
Worsening of hypoxaemia with administration of B2-agonists with air - hypoxia is not going to improve if V/Q mismatch is present.
Pattern of ventilation-perfusion is bimodal in acute severe asthma, ranging from normally perfused areas to areas of hypoxic pulmonary vasoconstriction.
Blood flow to the underventilated lung is decreased, thus maximising oxygenation by matching pulmonary perfusion to alveolar ventilation.
Administration of B2-agonists causes pulmonary vasodilation, thus increasing perfusion to underventilated lung units à worsening of VQ mismatch and increasing hypoxaemia
Salbutamol also increases cardiac output
Therefore, salbutamol should always be delivered with O2 in acute severe asthma, and O2 should be continued after the cessation of drug delivery
Discuss ABPA
. The diagnostic criteria for ABPA is:
Predisposing conditions (one must be present):
Cystic fibrosis
Asthma
Acute or subacute clinical deterioration (cough, wheeze, exercise intolerance, exercise-induced asthma, decline in pulmonary function, increased sputum) not attributable to another etiology.
PLUS
Obligatory criteria (both must be present):
Aspergillis skin test positivity or detectable IgE levels against Aspergillus fumigatus
Elevated total serum IgE concentration (typically>1000IU/mL, but if the patient meets all other criteria an IgE value <1000IU/mL may be acceptable)
Other criteria (at least two must be present):
Precipitating serum antibodies to Aspergillus fumigatus
Radiographic pulmonary opacities consistent with ABPA
Total eosinophil count >500cells/microL in glucocortoid-naïve patients
Chest CT is not essential to make the diagnosis because the chest X-ray has signs consistent with ABPA (parenchymal opacities and atelectasis due to mucoid impaction).
Sputum microscopy and culture will not give additional information to make the diagnosis.
Compliance calculation
Compliance = change in volume / change in pressure
Mantaux test interpretation
An induration of 5mm or more is considered positive in:
A recent contact with a person with tuberculosis disease
HIV infected people
People with fibrotic changes on chest X-ray consistent with prior tuberculosis
Patients with organ transplants
People who are immunosuppressed for other reasons
An induration of 10mm or more is considered positive in:
Recent immigrants (<5 years) from high prevalence countries
Children <4 years old
Infants, children and adolescents who are exposed to adults in high risk categories
People with clinical conditions that place them at high risk
An induration of 15mm or more is considered positive in:
Any person, including people with no known risk factors for tuberculosis