Respiratory failure Flashcards
what is respiratory failure?
syndrome of inadequate gas exchange due to dysfunction of one or more components of respiratory system
what is ARDS?
acute respiratory distress syndrome
4 steps of ARDS classification?
by timing
chest imaging
origin of oedema
PF ratio (perfusion)
what are the classifications of respiratory failure?
acute
chronic
acute on chronic
what are the causes of acute respiratory failure?
pulmonary: infection, aspiration, primary graft dysfunction
extra-pulmonary: trauma, pancreatitis, sepsis
neuromuscular: myasthenia/GBS
what are the causes of chronic respiratory failure?
pulmonary: COPD, lung fibrosis, CF, lobectomy
musculoskeletal: muscular dystrophy
what are the causes of acute on chronic RF?
infective exacerbation e.g COPD
myasthenic crises
post operative
what are the physiological classifications of RF?
type 1 - hypoxemic
type 2 - hypercapnic
type 3 - perioperative
type 4 - shock
what is type 1 respiratory failure?
failure of oxygen exchange
PO2 <60
what are the causes of type 1 respiratory failure?
collapse aspiration pulmonary oedema fibrosis pulmonary embolism pulmonary hypertension
what is type 2 RF?
failure to exchange or remove carbon dioxide
what are the causes of type 2 RF?
nervous system neuromuscular muscle failure airway obstruction chest wall deformity
what is type 3 RF?
increased airway collapse due to low functional residual capacity with abnormal abdominal wall mechanics
hypoxemia or hypercapnoea
what is type 4 RF?
intubated and ventilated patients during shock (septic, cardiogenic, neurologic)
poor perfusion with positive pressure in thorax
what are the risk factors for chronic RF?
COPD pollution recurrent pneumonia cystic fibrosis pulmonary fibrosis neuromuscular diseases
what are the causes of acute RF?
infection aspiration trauma inflammatory response pancreatitis transfusion
what occurs during acute lung injury?
alveolar macrophages and type 2 cells activate
release of IL-6,8, TNF-a
protein rich oedema occurs
surfactant may degrade and make alveolus less efficient
migration of neutrophils into interstitium - proteases, inflamm mediators released
increases alveolar-capillary distance, less efficient gas exchange
what are the three umbrellas of therapeutic intervention for RF?
treat underlying cause
respiratory support
multiple organ support
how are the underlying causes of RF treated?
inhaled therapies - bronchodilators, pulmonary vasodilators
steroids
antibiotics/virals
drugs - pyridostigmine, plasma exchange, IVIG, rituximab
how is respiratory support provided in RF?
physiotherapy oxygen nebulisers high flow O2 non invasive ventilation intubation (mechanical vent) extra corporeal support (ECMO_
how is multiple organ support provided in people with RF?
CV support - fluids, vasopressors, inotropes, pulmonary vasodilators
renal support - haemofiltration, haemodialysis
immune therapies - plasma exchange, convalescent plasma
what are the consequences of ARDS?
poor gas exchange - inadequate oxygenation, poor perfusion, hypercapnoea
infection - sepsis
inflammation
systemic effects
what are the pitfalls to mechanical ventilation?
trapping of air not fully exhaled causing increased pressure
may lead to ventilator induced lung injury
therefore exhalation must be set to correct length
what are the parameters for the Murray scoring of acute lung injury/need for ECMO?
chest xray
lung compliance
oxygen saturations
PEEP
what scores mean what in the Murray scoring system?
normal - 0
1-2.5 - mild
2.5 - severe
3 - ECMO required
what are the inclusion criteria for ECMO?
severe respiratory failure of non cardiac cause
positive pressure ventilation not appropriate
reversible disease process
unlikely to lead to prolonged disability
what are the exclusion criteria for ECMO?
contraindication to continuation of active treatment
significant comorbidity so dependence on ECMO support
significant life limiting comorbidity
what is ECMO and its process?
Extracorporeal membrane oxygenation
catheter from femoral/jugular vein to IVC
withdrawal of blood, passed over artificial membrane to remove CO2 and oxygenate
