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 systems can respiratory failure act on?
- nervous system
- CNS/Brainstem
- peripheral nervous system
- neuro-muscular junction
- respiratory muscle
- diaphragm and thoracic muscle
- extra-thoracic muscles
- pulmonary
- airway disease
- alveolar- capillary circulation
what are the risk factors for respiratory failure?
males: smoking biggest risk factor
women: household air pollution from solid fuels
how is ARDS classified?
4 criteria used to classify ARDS
what is the trend with Acute respiratory distress syndrome over time?
increased severity with age
increased mortality
what is the classification of ARDS physiologically?
- type I or hypoxemic
- type II or hypercapnic
- type III
- type IV
what occurs in type 1 respiratory failure?
- PaO2<60 at sea level
- Failure of oxygen exchange
- Increase shunt fraction
- Frequently Due to alveolar flooding
- Hypoxemia refractory to supplemental oxygen
what happens in type II respiratory failure?
- PaCO2>45
- Failure to exchange or remove CO2
- Decreased alveolar minute ventilation
- Dead space ventilation
what happens in type III respiratory failure?
- Perioperative respiratory failure
- Increased atelectasis due to low functional residual capacity (FRC) with abnormal abdominal wall mechanics
- Hypoxaemia or hypercapnoea
- Prevention: anesthetic or operative technique, posture, incentive spirometry, analgesia, attempts to lower intra- abdominal pressure
what happens in type IV respiratory failure?
- Shock
- Type IV describes patients who are intubated and ventilated during shock (Septic/cardiogenic/neurologic)
- Optimise ventilation improve gas exchange and to unload the respiratory muscles, lowering their oxygen consumption
what are the ventilatory effects of respiratory failure?
reduced afterload (good for LV)
increased pre-load (bad for RV)
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 respiratory failure?
infection (viral and bacterial)
aspiration
trauma
pancreatitis
transfusion
how do pulmonary causes cause ARF?
- aspiration
- trauma
- burns: inhilation
- surgery
- drug toxicicity
- infection
affect alveolus and airways to alveolus
how do extra-pulmonary causes cause ARDS?
- trauma
- pancreatitis
- burns
- transfusion
- surgery
- BM transplant
- drug toxicity
- infection
systemic disease causing cytokine release and activation of neutrophils/macrophages in vascular supply
what is the mechanism of acute lung injury?
- inflammation:
- Release further cytokines
- IL6, IL8
- TNF-alpha and IL8
- Causes alveolar fluid build-up/ protein rich oedema in lung`
- Cause degradation or inactivation of surfactant so alveolus less efficient as expanding
- Release further cytokines
- Immune response
- Tracheal migration of leukocytes ( neutrophils) into interstitium causing damage before getting to site of response due to chemokines
- Secrete proteases and inflammatory mediators -> fluid build up + damage
- Increased distance between alveolus and capillary due to leukocytes and odema
- Greater distance for gas exchange -> less efficient
what is the leukocyte response and inflammatory response in acute lung injury govered by?
infection
systemic (bacteraemia)
directly in airways or higher up in airways
what overall concepts is acute lung injury response governed by?
infection
inflammation
immune response
the interplay between these 3
what is the in vivo evidence of the infection, inflammation, and immune response in respiratory failure?
- TNF signalling implicated in vivo and in vitro
- Reduced injury in TNFR-1
- Leucocyte activation and migration
- Macrophage activation: alveolar
- Neutrophil lung migration
- DAMP release
- HMGB-1 and rage
- Cytokine release
- IL-6, 8
- IL-1B
- IFN-gamma
- Cell death
- Necrosis in lung biopsies
- Apoptotic mediators
- FAS, FAS-Ligand, BCI-1
what are the 3 aspects to be treated in ARDS?
treat underlying disease
respiratory support
multiple organ support
what are the therapeutic interventions to treat underlying disease?
- inhaled therapies
- bronchodilators
- pulmonary vasodilators
- steroids
- antibiotics
- anti-virals
- drugs
- pyridostigmine
- plasma exchange
- IViG
- rituximab
what are the therapeutic interventions for respiratory support?
physiotherapy
oxygen
nebulizers
high flow oxygen
non-invasive ventilation
mechanical ventilation
extra-corporeal support
what are the therapeutic interventions for multiple organ support
- cardiovascular support
- fluids
- vasopressors
- inotropes
- pulmonary vasodilators
- renal support
- haemofiltration
- hemodynamics
- immune therapies
- plasma exchange
- convalescent plasma
what are the consequences of ARDS?
- Poor gas exchange
- Inadequate oxygenation
- Poor perfusion
- Hypercapnoea
- Infection
- Sepsis
- Inflammation
- Inflammatory response
- Systemic effects
what are the ARDS specific intervention?
- Respiratory support
- Intubation and ventilation
- ARDS necessitates mechanical intervention
- Types of ventilation
- Volume controlled
- Pressure controlled
- Assisted breathing modes
- Advanced ventilatory modes
- Procedures to support ventilation -> pronation
what is the normal pressure-volume loop and how is it affected by ARDS?
what are the pitfalls of ventilation in asthma and COPD?
- In asthma and COPD there can be air trapping (not full air exhalation)
- This can cause an increased pressure
- Causing ventilator induce lung injury
- Harder to manage CO2 and minute ventilation and causes V/Q mismatch as ventilation without gas exchange vice- versa
how can you determine the ventilation levels?
imaging and guiding therapy
- Lung recruitment: CT
- Determine pressure to put ventilation at as shows alveolar recruitment at different pressure levels
- Lung ultrasound
- Evaluate how well expanded someone’s lung is and any fluid that is present
what is used the guide the escalation of therapy?
- Uses Murray score
- Measures PF ratio
- Chest X-Ray
- PEEP
- Lung compliance
- Score >3 -> ECMO or pH <7.2
what are the ECMO inclusion criteria?
- Severe respiratory failure
- Non cardiac cause (Murray lung injury score 3.0 or above)
- Positive pressure ventilation is not appropriate
- E.g significant tracheal injury
what are the ECMO exclusion criteria?
- Contraindication to continuation of active treatment
- Significant co-morbidity -> dependent to ECMO support
- Significant life limiting to co morbidity
overall what does ECMO treatment require?
- Reversible disease process
- Unlikely to lead to prolonged disability
how does ECMO work?
- Pass canula in IVC below right atrium
- Canula can be placed through internal jugular, subclavian, femoral
- Withdraw blood into pump and through artificial membrane
- This causes removal CO2 and oxygenation
- Blood passes back into RA
what are the issues with ECMO?
- Time to access
- Referral system- geographical inequity
- Consideration of referral
- Technical
- Obtaining access
- Haemodynamics
- Clotting/bleeding
- Costs
what are the benefits of ECMO?
- Increased survival
- Improve oxygen delivery
- Improve CO2 removal
- Rest ling and prevent ventilator-associated lung injury
- Resolve respiratory acidosis
- Reduce multiple organ dysfunction arising from hypoxaemia and hypercarbia
