Resp - Resp Failure Flashcards
What is respiratory failure
Syndrome of inadequate gas exchange due to dysfunction of one or more of the components for the respiratory system
What systems can cause respiratory failure
Nervous system
Respiratory musculature
Pulmonary
What in the nervous system can cause resp failure
CNS/Brainstem
Peripheral nervous system
NMJ
What in the muscles can cause resp failure
Diaphragm and thoracic muscles
Extra-thoracic muscles
What are the pulmonary causes of resp failure
Airway disease
Alveolar-capillary
Circulation
Where are respiratory problems more of a problem and in who
We see more chronic respiratory problems in northern America and Northern Europe - northern American males are worse off than females, and Russian women are worse off then males
What is the biggest rf for men
Smoking
What is the biggest rf for women
Household air pollution from solid fuels
What is ARDS
Acute respiratory distress syndrome
How do we define ARDS
Berlin definition
How can we class respiratory failure
Acute
Chronic
Acute on chronic
What are the causes of acute respiratory failure
Pulmonary causes e.g. infection, aspiration, primary graft dysfunction.
Extra-pulmonary causes e.g. trauma, pancreatitis, sepsis
Neuro-muscular e.g. myasthenia gravis, Guillain Barre syndrome
What are causes of chronic respiratory failure
COPD, lung fibrosis, CF, post lobectomy
MSK causes eg. muscular dystrophy
What are causes of acute on chronic resp failure
Infective exacerbation of chronic condition e.g. COPD/CF
Myasthenia crisis
Post op if you already have an underlying respiratory disease
What is type 1 resp failure
Hypoxemic: PaO2 <60 at sea level Failure of oxygen exchange Increased shunt fraction Due to alveolar flooding e.g. heart failure Refractory to supplemental oxygen
What can cause type 1 resp failure
Collapse of lobe Aspiration Pulmonary oedema Fibrosis Pulmonary embolism Pulmonary hypertension
What is type 2 resp failure
Hypercapnic PaCO2 > 45 Failure to remove CO2 Decreased alveolar minute ventilation Dead space ventilation
What can cause type 2 resp failure
Nervous system disease Neuromuscular disease Muscle failure Airway obstruction e.g. COPD Chest wall deformity e.g. trauma/ ageing
What is type 3 resp failure
Perioperative:
Atelectasis (lung collapse) of airway due to low FRC
Often ude to abdominal wall mechanisms
Can get hypoxemia and hypercapnia
How do we prevent type 3 resp failure
Anaesthetic or operative technique, posture, incentive spirometry, analgesia
What is type 4 resp failure
Shock causing poor perfusion of the lung - seen in septic, cariogenic and neurogenic shock - get vsasoplegia so pooling f the blood in the periphery
How do we manage type 4 resp failure
Intubation as consciousness falls due to shock - positive pressure ventilation
What are chronic rfs for resp failure
COPD Pollution Recurrent pneumonia CF Pulmonary fibrosis Neuromuscular diseases
What are acute rfs for resp failure
Infection Aspiration Trauma Pancreatitis Transfusion
What are the 2 main causes of ARDS
Pulmonary and extra-pulmonary
What are the pulmonary causes of ARDS
Largely infection Aspiration Trauma Burns Surgery Drug toxicity
What are the extra-pulmonary causes of ARDS
Infection trauma Pancreatitis Burns Transfusions Surgery BM transplant Drug toxicity
How does the lung response to injury leads to ARDS
Injury leads to damage of the lung interstitium.
This causes macrophage activation and the release of cytokines e.g. TNF-a and IL-8
We get alveolar fluid build up therefore protein rich oedema in the lungs
Therefore we get degradation and inactivation of surfactant meaning that the alveolus is less efficient at expanding
Inflammation of the alveolus leads to migration of leucocytes e.g. neutrophils which cause further damage
This widens the distance between the alveolus and the capillaries therefore less efficient gas exchange and respiratory failure
What in vivo evidence do we have for ARDS
TNF signalling Leucocyte activation and migration DAMP release Cytokine release e.g. IL-6/8 Cell death - necrotic tissue in ARDS
What tried pharmacological therapies can be used for ARDS
Steroids e.g. dexamethasone Salbutamol Surfactant N-ACh - reduces viscosity of secretions Neutrophil elastase inhibitors GM-CSF Statins
Why is evidence in ARDS for treatment very limited
ARDS is extremely severe and very heterogenous therefore hard to find overarching patterns for treatment
What are the 3 aspects of therapeutic intervention for ARDS
Treat underlying disease
Respiratory support
Multi-organ support
How do we treat underlying disease
Inhaled therapies e.g. bronchodilators Steroids ABx Antivirals Drugs e.g. rituximab
What can we give for respiratory support
Physiotherapy Oxygen (not in type 2) Nebuliser NIV Extra corporeal support
What can we give for multiorgsan support
CV support e.g. fluids. vasopressors
Renal support e.g. hemodialysis
Immune therapies e.g. plasma exchange
What are the sequelae of ARDS
Poor gas exchange leads to multi-organ dysfunction
Infection leads to sepsis
Inflammation leads to oedema
What do we base ventilation on
Pressure not volume - this is because pressure is more likely to cause damage to the lung
What is the peak pressure
Pressure that drives into the lung
What is the PEEP and why do we need it
Baseline pressure that keeps the airways open - this means less force is required at the start for recruitment therefore less likely to damage the airways - atelectasis is more likely if pressure falls below the PEEP
What is assisted breathing
We use a sensor and then when the patient is trying to inhale then we can give them some driving pressure
What is the difference between a normal PVL and a PVL in ARDS
There is marked reduction in compliance during ARDS therefore the PVL is much flatter - we are using a lot more pressure in order to generate a lower volume
When may air trapping occur
In people with type 2 hypercapnic failure - their airways are often constricted therefore cannot normally exhale fully. This means that they get air trapping and breath stacking
How do we mitigate air trapping
We give them longer periods to exhale in order to get as much air out as possible - make sure expiratory pressure is low enough fro them to be able to expire, but high enough to keep airways open
What is a lung recruitment CT
We use a driving pressure to distend the lung and see if its recruitable - we need to make sure pressure isn’t too high otherwise we may over distend the lung and trap gas in the chest to damage the lung and impart perfusion.
What are alternatives to CT lung recruitment
US at the bedside to examine the lung expansion and any fluid
What do we use to guide escalation of therapy
Murray scoring
What are the Murray score thresholds for escalating treatments
0 = normal
1-2.5 = mild
2.5 = severe
3 ECMO
How can we try and improve Murray score
Proning
When is ECMo indicated
Severe resp failure - Murray score is 3+
Positive pressure ventilation is not appropriate e.g. tracheal injury
Reversible disease process that is unlikely to lead to prolonged disability
When is ECMO contraindicated
Significant life-limiting co-morbidity - likely to remain on ECMO or life support
What happens in ECMO
Large cannula is passed through the femoral vein to the IVC, we then run blood through an external pump across an artificial membrane. Here, we flow gas to allow removal of CO2 and blood oxygenation. This can also be done in the jugular
