Cardio - 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 are the 3 parts of the respiratory system that could be affected?
→ nervous system
→ respiratory muscle
→ pulmonary
What are the 3 ways of classifying respiratory failure?
→ acute
→ chronic
→ acute on chronic
What are the different types of acute respiratory failure?
→ pulmonary : infection, aspiration, primary graft dysfunction ( Lung Tx)
→ extra-pulmonary : trauma, pancreatitis, sepsis
→ neuro-muscular : myasthenia / GBS
What are some examples of chronic respiratory failure?
→ pulmonary / airways : COPD, lung fibrosis, CF, lobectomy
→ musculoskeletal : muscular dystrophy
What is acute on chronic respiratory failure?
→ infective exacerbation (e..g COPD, CF)
→ myasthenic crises
→ post-operative
What is ARDS?
Acute Respiratory Distress Syndrome
What factors are considered in order to classify ARDS?
→ timing : within 1 week of a known clinical insult or new or worsening symptoms
→ chest imaging : bilateral opacities - not fully explained by effusions, lobar / lung collapse, or nodules
→ respiratory failure not fully explained by cardiac failure or fluid overload
→ oxygenation levels determine severity
How is respiratory failure physiologically classified?
→ Type 1 or Hypoxemic
→ Type 2 or Hypercapnic
What is Type 1 respiratory failure?
→ Hypoxemic
→ failure of oxygen exchange
→ increased shunt fraction (QS / QT) due to alveolar flooding
→ hypoxemia refractory to supplemental oxygen
What oxygen levels are classified as Type 1 RF?
PaO2 < 60
What are the causes of Type 1 RF?
→ collapse → aspiration → pulmonary odema → fibrosis → pulmonary embolism → pulmonary hypertension
What is Type 2 RF?
→ hypercapnic
→ failure to exchange or remove CO2
→ decreased alveolar minus ventilation
→ dead space ventilation
What CO2 levels classify as Type 2 RF?
PaCO2 > 45
What are the causes of Type 2 RF?
→ nervous system → neuromuscular → muscle failure → airway obstruction → chest wall deformity
What is Type 3 RF?
→ peri-operative respiratory failure
→ Increased atelectasis (lung collapse) due to low functional residual capacity
→ (FRC) with abnormal abdominal wall mechanics
→ Hypoxaemia or hypercapnoea
How can Type 3 RF be prevented?
anesthetic or operative technique, posture,
incentive spirometry, analgesia, attempts to lower intra- abdominal pressure
What is Type 4 RF?
→ 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
→ Ventilatory effects on right and left heart
→ Reduced afterload (good for LV) Increased pre-load (bad for RV)
What are the risk factors for chronic RF?
→ COPD → pollution → recurrent pneumonia → CF → pulmonary fibrosis → neuro-muscular diseases
What are the risk factors for acute RF?
→ infection (viral, bacterial) → aspiration → trauma → pancreatitis → transfusion
What are some pulmonary causes of ARDS?
→ aspiration → trauma → burns (inhalation) → surgery → drug toxicity → INFECTION
What are some extra-pulmonary causes of ARDS?
→ Trauma → Pancreatitis → Burns (extra-thoracic) → Transfusion → Surgery → BM transplant → Drug Toxicity → INFECTION
What are the 4 major steps that drive ARDS?
→ infection or damage to the lung
→ immune response form macrophage already existing in the lung occurs - release IL-6, IL-8 + TNF-alpha
→ inflammation occurs due to signalling pathway, causing oedema
→ leucocyte migration into alveolar causes oedema to worsen
What has been the in vivo evidence for the mechanism of action for ARDS?
→ TNF signalling implicated → leucocyte activation + migration → DAMP release → cytokine release of IL-6, IL-1B, IFN-y → cell death (becrosis in lung biopsies, apoptotic mediators, FAS, FAS-1, BCI-2)
What are the pharmacological therapies currently being used?
→ steroids → salbutamol → surfactant → N-Acetylcysteine → Neutrophil esterase inhibitor → GM-CSF → statins
What pharmacological therapies are being trialled?
→ mesenchymal stem cells → keratinocyte growth factor → microvesicles → high dose Vitamin C, thiamine, steroids (for sepsis) → ECCO2R
What are the 3 principles of therapeutic interventions?
→ treat underlying disease
→ respiratory support
→ multiple organ support
How do you treat the underlying disease?
→ inhaled therapies (bronchodilators, vasodilators)
→ steroids
→ antibiotics
→ anti-virals
→ drugs (pyridostigmine, plasma exchange, IViG, rituximab)
How do you provide respiratory support for RF?
→ physiotherapy → oxygen → nebulisers → high flow oxygen → non-invasive ventilation → mechanical ventilation → extra-corporeal support
How do you provide multiple organ support?
cardiovascular 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 (leads to inadequate oxygenation, poor perfusion + hypercapnia)
→ infection (can lead to sepsis)
→ inflammation (can lead to severe inflammatory response)
→ systemic effects
What are some ARDS specific interventions?
respiratory support
→ intubation
→ ventilation
What are the different aspects of ventilation?
→ volume controlled
→ pressure controlled
→ assisted breathing modes
→ advanced ventilatory modes
What is the difference between compliance in a normal lung vs. an ARDS lung?
REDUCED in the injured lung compared to the normal
smth about UIP
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smth about LIP
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What are the pitfalls of ventilation?
→ minute ventilation (PaC02 control, can cause a build-up)
→ alveolar recruitment (can affect positive end expiratory pressure)
→ V/Q mismatch = ventilation without gas exchange
→ ventilator induced lung injury due to high driving pressure
What kind of imaging can guide + help ventilation therapy?
→ CT
→ ultrasound
Why can a lung USS be preferable over a CT scan?
radiation dangers
What scoring system can guide ventilation therapy?
Murray score
What is the Murray score?
an average of: → PaO2 / FI02 (on 100% oxygen) → CXR (chest x-ray) → PEEP (positive end expiratory pressure) → Compliance (ml/cmH2O) 0-4 points given to each
How does the Murray score classify severity?
→ 0 = normal
→ 1-2.5 = mild
→ 2.5 = severe
→ >3 = ECMO
What is the national ARDS approach?
→ telephone or online referral to 1 of 5 national centres → consultant case review → transfer of imaging → advice → retrieval → transfer → ongoing management
What is the inclusion criteria for treatment in ARDS?
→ severe RF without a cardiac cause
→ positive pressure ventilation is not viable
What is the exclusion criteria for treatment in ARDS?
→ contraindication to continuation of active treatment
→ significant co-morbidity (which could lead to dependency on ECMO support)
→ significant life-limiting co-morbidity
→ reversible disease process
→ unlikely to lead to prolonged disability
Why is aetiology important in treating ARDS with ECMO?
→ people affected by FLU tend to recover quickly when on ECMO
→ people affected by SARS need to be observed on ECMO + data needs to be observed carefully
How does ECMO work?
→ large cannula inserted through groin to femoral vein to take blood from IVC out to a pump
→ pump pushes blood through artificial membrane where gas exchange takes place
→ blood pumped back in through jugular axis into RA (right atrium)
What are the issues with ECMO?
→ time to access → geographical inequity of referral system → consideration for referral → cost + expense → obtaining access to internal jugular, subclavian or femoral → circuitry → haemodynamics → clotting / bleeding
