RESPIRATORY FAILURE Flashcards
What is respiratory failure?
Syndrome of inadequate gas exchange due to dysfunction of one or more components of the respiratory system
What is the epidemiology of chronic respiratory disease?
3rd leading cause of death however mortality, prevalence and DALY rates is dropping due to treatments becoming more effective
What is acute respiratory failure called?
Acute respiratory distress syndrome (ARDS)
How can respiratory failure/disease be classified?
Acute
Chronic
Acute on chronic
What does acute respiratory failure/disease entail?
Pulmonary: infection, acid aspiration, primary graft dysfunction
Extra-pulmonary: trauma, pancreatitis, sepsis
Neuro-muscular: myasthenia/GBS
What does chronic respiratory failure/disease entail?
Pulmonary: COPD, lung fibrosis, CF, lobectomy
Musculoskeletal: muscular dystrophy
What does acute on chronic respiratory failure/disease entail?
Infective exacerbation of COPD, CF
Myasthenic crises
Post operative (underlying respiratory disease and then undergo surgery)
How is respiratory failure physiologically classified
Type I (hypoxemic) Type II (hypercapnic) Type III (perioperative respiratory failure) Type IV (shock)
What does type I respiratory failure entail?
Hypoxemic (PaO2 < 60) - failure of O2 exchange:
- Increased shunt fraction
- Due to alveolar flooding
- Supplemental oxygen doesn’t help much
What does type II respiratory failure entail?
Hypercapnic (PaCO2 > 45) - failure to remove CO2:
- decreased alveolar minute ventilation
- dead space ventilation
What does type III respiratory failure entail?
Perioperative:
- Increased atelectasis due to low function residual
capacity with abnormal abdominal wall mechanics
which limits the amount the chest can open up
- Hypoxaemia or hypercapnoea
How can type III respiratory failure be prevented?
Anesthetic or operative technique
Posture
Incentive spirometry
Analgesia (not tensing abdomen so intra-abdominal pressure lowers)
What does type IV respiratory failure entail?
Patients who are intubated and ventilated during shock:
- Septic, cardiogenic or neurologic causing poor
perfusion to lungs
How should type IV respiratory failure be managed?
Optimise ventilation to improve gas exchange and unload the respiratory muscles, lowering oxygen consumption
What are the effects of +ve pressure ventilation on the heart?
Reduced afterload (good for left ventricle) Increased pre-load (bad for right ventricle)
What are some causes of type I respiratory failure?
Lung collapse Aspiration Pulmonary oedema Fibrosis Pulmonary embolism Pulmonary hypertension
What are some causes of type II respiratory failure?
Problems with nervous system, neuromuscular, muscle failure (muscles weak so can’t drive adequate tidal volumes/respiratory rates)
Airway obstruction e.g. COPD
Chest wall deformity e.g. trauma, ageing
What are the chronic risk factors for respiratory failure?
COPD Pollution Recurrent pneumonia Cystic fibrosis Pulmonary fibrosis Neuro-muscular diseases
What are the acute risk factors for ARDS?
Infection (viral/bacterial maybe both at some time)
Aspiration (when conscience level drops gastric contents into lungs)
Trauma
Pancreatitis
Transfusion
What are the pulmonary causes of ARDS?
Aspiration Trauma Burns: inhalation Surgery Drug toxicity
What are the extra-pulmonary causes of ARDS?
Trauma Pancreatitis Burns Transfusion Surgery BM transplant Drug toxicity
What drives the inflammatory response in acute lung injury?
TNalpha, IL8, IL6 cause fluid build up (oedema) causing alveolar to be less efficient at expanding
Migrating neutrophils cause damage and oedema outside which increases the distance between alveoli and capillary
What are some drugs which can be used for intervention of acute respiratory failure/ARDS?
Steroids Salbutamol Surfactant (promising in children) N-Acetylcysteine (increases viscosity of secretions so easier to clear) Neutrophil esterase inhibitor GM-CSF Statins
What are some therapies currently being trialled to help with acute respiratory failure/ARDS?
Mesenchymal stem cells Keratinocyte growth factor Microvesicles High dose vitamin C, thiamine, steroids ECCO2R (removal of CO2)
What are the 2 endotypes of ARDS?
Hyper inflammatory ARDS
Hypo inflammatory ARDS
What are some therapeutic interventions for respiratory failure?
Treating underlying disease:
- Bronchodilators, pulmonary vasodilators
- Steroids
- Antibiotics
- Anti-virals
- Pyridostigmine, plasma exchange, rituximab
Respiratory support:
- Physiotherapy
- Oxygen (don’t give type II as can exacerbate it)
- Nebulisers
- High flow oxygen
- Non-invasive ventilation
- Mechanical ventilation
- Extra-corporeal support if ^ fails (membrane lung oxygenates and gets rid of CO2)
Multiple organ support:
- Cardiovascular support e.g. fluids, vasopressors
- Renal support e.g. haemofiltration, haemodialysis
- Immune therapies e.g. plasma exchange, convalescent
plasma
What are some ways respiratory support can be done for patients?
Non-invasive ventilation
Intubation
ECMO cannulation (extra-corporeal support)
Proning
What are the effects and complications of ARDS?
Poor gas exchange –> low oxygenation, poor perfusion, hypercapnoea causing failure to highly metabolic organs
Infection –> sepsis
Inflammation
Systemic affects
What changes can be seen in a pressure volume loop of a patient with ARDS?
Reduced compliance
Reduced upper inflection point (UIP) and lower inflection point (LIP)
What happens if pressure is increased above the upper inflection point (UIP)?
Additional alveolar recruitment requires disproportionate increases in airway pressure which can cause lung damage and inflammation
What is lower inflection point (LIP)
Minimum baseline pressure needed for optimal alveolar recruitment
Below this the lungs will collapse
Why shouldn’t you put too much pressure on inhaled air and increase exhalation time for patients with tight airway diseases on the ventilator?
Patients with tight airway diseases don’t completely exhale meaning some air is trapped which can build up increasing pressure and volume preventing effective ventilation of patient
What types of imaging can be done for patients with respiratory failure?
Lung CT, lung ultrasound
How is severity of respiratory failure graded and scored?
Murray score taking average of all 4 parameters:
- PaO2/FIO2
- CXR
- PEEP
- Compliance
What are the score boundaries on the Murray score?
0 = normal
1-2.5 = mild
> 2.5 = severe
> 3 = ECMO
When is ECMO considered for patients?
When treatments fail and still have high Murray score
Describe the procedure of ECMO
Large cannula passed up through femoral vein and IVC. Blood withdrawn via tubing to pump which pushes the blood across artificial membrane.
At the membrane gases flowed over the top allowing removal of CO2 and O2 perfusion. Blood then returned
Very invasive
