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 signs and symptoms of respiratory failure?
Shortness of breath - predominant feature Breathlessness Increased RR Cyanosis Wheezing Coughing Chornic Cough Reduced exercise tolerance Fatigue
Dysfunction is which parts of the respiratory system can lead to respiratory failure?
- Nervous system:
CNS/Brainstem - e.g. respiratory system that lies within the ventro-lateral medulla
Peripheral nervous system
Neuro-muscular junction - e.g. myasthenia gravis - Respiratory muscle:
Diaphragm and thoracic muscles
Extra-thoracic muscles
(often seen in muscular underlying diseases) - Pulmonary (most frequent):
Airway disease - e.g. asthma, COPD
Alveolar-capillary - e.g. damage due to fibrosis
Circulation
What is the epidemiology of respiratory failure?
Chronic respiratory diseases are the third biggest cause of mortality across the world (after cardiovascular disease, neoplastic disease)
Since 1990 til now, increase in respiratory diseases in Northern Europe and Northern America
In 1990 and now, there is a lack of chronic respiratory disease in Sub-Saharan Africe and South-East Asia
39.8% rise in chronic respiratory diseases since 1990
From 1990 to 2017, the prevalence, mortality, and DALY rates per 100k dropped by 14·3%, 42·6%, and 38·2% which suggests that treatment is getting more effective
Why is chronic respiratory disease the 3rd leading cause of death in the UK?
What are the risk factors?
Men - predisposed due to smoking
Women - predisposed due to air pollution from solid fuels
What is the epidemiology of acute respiratory failure (AKA acute respiratory distress syndrome - ARDS)
More difficult to assess as patients present very differently and it’s a heterogeneous disease
It could be down to pneumonia or an effective exacerbation, COPD worsening pulmonary hypertension, cystic fibrosis, infective exacerbation, lots of different ways people may present
Of ADRS -
Prevalence: 6-7 per 100,000 = 6-700 people/yr in UK
30 to 40% Mortality (ALIEN/Esteban)
35, 40 and 46% (Severity dependent. Bellani)
Severity and advance age –> increase mortality
What criteria is used to classify acute respiratory distress syndrome (ARDS)?
To classify, ARDS, the acute respiratory distress syndrome, we use a Berlin definition and for this, we look at:
Timing - within 1 week of a known clinical insult / new symptom / worsening repiratory symptom
Chest imaging - unexplained bilateral opacities not fully explained by effusions or lobar collapse
Origin of oedema - unexplained by cardiac failure or fluid overload
Oxygenation -
Mild (200mmHg < PO2/FiO2)
Moderate (100 mmHg < PO2/FiO2)
Severe (PO2/FiO2 < 100mmHg)
FiO2 (the fraction of inspired oxygen)
What increases mortality rates in those with ARDS?
Severity and advance age
What are the 3 classifications of acute respiratory failure?
- Acute
- Chronic
- Acute on Chronic
What are the causes of acute respiratory failure?
Pulmonary: infection, aspiration, primary graft dysfunction (result of a lung transplant)
Extra-pulmonary: trauma, pancreatitis, sepsis,
Neuro-muscular: myasthenia / GBS
What are the causes of chronic respiratory failure?
Pulmonary/Airways: COPD, lung fibrosis, cystic fibrosis (CF), post lobectomy
Musculoskeletal: muscular dystrophy
What are the causes of acute on chronic respiratory failure?
Infective exacerbation of chornic disease - worsening chronic condition e.g. COPD, CF
Myasthenic crises
Post operative - from underlying respiratory disease
What are the different respiratory failure classifications?
Physiological classifications:
Type I - failure of oxygen exchange
Type II - failure to exchange / remove CO2
Type III - perioperative respiratory failure (collapse of airways from low functional residual capacity)
Type IV - shock
What is the difference between Type I and Type II respiratory failure?
Type I (hypoxemic) = failure of oxygen exchange (low PO2) - may be due to collapsed lung, aspiration, pulomnary oedema fibrosis, pulmonary embolism, pulmonary hypertension, increased shunt fraction in heart failure, alveolar flooding
Type II (hypercapnic) = failure to exchange or remove carbon dioxide - may be due to dead space ventilation, decreased alveolar ventilation, nervous system disease, neuromuscular diseases, muscle failure, airway obstruction, chest wall deformity
What is Type III and Type IV respiratory failure?
Type III (preioperative respiratory failure) = collapse of the airways due to low functional residual capacity with abnormal abdominal wall mechanics - can lead to hypoxaemia or hypercapnoea
Type IV (shock) = patients who are intubated and ventilated during shock leads to poor perfusion of the lung (cardiogenic, septic or neurologic shock)
How can Type III respiratory failure be prevented?
Good anaesthetic or operative technique, good posture, incentive spirometry, analgesia, attempts to lower intra-abdominal pressure
How can Type IV respiratory failure be treated?
Optimise ventilation to improve gas exchange and to unload respiratory muscles, which lowers their O2 consumpction
What are the effects of ventilators on the left and right sides of the heart?
Ventilator gives positive pressure
Good for left ventricles (LV) = reduced afterload on the heart (as postive pressure from ventilator = increased pressure in the chest)
Bad for right ventricle (RV) = increased preload (increased positive pressure in thorac makes RV work harder)
What are the chornic 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, bacterial Aspiration - aspirate acidic gastric contents into lungs which induces a response Trauma Pancreatitis Transfusion
What are the 5 origins for shortness of breath in acute respiratory failure?
Explore the history of the shortness of the breath
- Lower respiratory tract infection - viral or bacterial
- Viral e.g. flu, covid, MERS
- Bacterial e.g. streptoccocal pneumonia, staph pneumonia, pseudomonas
These induce acute lung injury and potential respiratory failure - Aspiration - gastric contents
- Trauma
- Pulmonary vascular disease - pulmonary embolus, haemoptysis
- Extrapulmonary - pancreatitis, new medications
What are the causes of ARDS?
Pulmonary causes: Aspiration Trauma Burns Inhalation Surgery Drug toxicity Infection
Extra-pulomnary causes: Trauma Pancreatitis Burns Transfusion Surgery Bone marrow transplant Drug toxicity Infection
Mechanisms unknown
What are the different components that make up the lung unit?
Alveolus
Interstitium
Vascular supply - microvascular lung vessel
What occurs in acute lung injury?
Injury in lung leads to damage of interstitium which is the area surrounding the alveoli
And within the alveolus itself, you have resident alveolar macrophages and when they’re activated by an infection or inflammation, will release further cytokines like IL-6, IL-8 and TNF Alpha
There are also type II pneumocytes within the alveolus alongside the macrophages that differentiate down to Type I when activated by an infection
And in response to this inflammatory setup, you often get alveolar fluid build-up or protein-rich oedema forming within the lung
You can get a degradation of surfactant (alveolus becomes less efficient at expanding) which can cause alveolar collapse
And when you have inflammation of the alveolus you often get tracking or migration of leukocytes out of the blood vessels such as neutrophils squeezing through into the interstitium where they can cause damage before getting into alvelous there they secrete proteases and other inflammatory mediators, which can cause some damage and build up a fluid within all of these tissues
In the diseased version of the alveolus, there is a greater distance between alveolus and blood vessel due to oedema which makes gas exchange less efficient
