Respiratory failure (RESP) Flashcards
Define respiratory failure.
Acute or chronic inability of the respiratory system to maintain gas exchange causing hypoxia +/- hypercapnia - can lead to:
- failure to oxygenate the body
- failure to eliminate CO2
What is acute respiratory failure?
- characterised by an acute lack of oxygen transfer to the blood by the respiratory system or acute failure of the respiratory system to remove CO2 from the blood
- can be due to trauma, surgery or shock
What is chronic respiratory failure?
- long-term lack of oxygen delivery to the blood by the respiratory system
- causes progressively worsening respiratory acidosis with increased renal compensation and red cell count
List pulmonary causes of respiratory failure. (6)
- acute exacerbation of asthma
- PE
- ARDS
- pneumonia
- pulmonary trauma
- airway obstruction
List extrapulmonary causes of respiratory failure. (6)
- CNS depression (narcotic OD or brain trauma)
- respiratory muscle weakness (myasthenia gravis, MND)
- decreased chest wall compliance
- increased oxygen consumption or CO2 production (sepsis, cardiogenic shock)
- hypovolaemia
- shock
What are the types of respiratory failure? (4)
- type 1 respiratory failure: hypoxia only
- type 2 respiratory failure: hypoxia and hypercapnia
- type 3 respiratory failure: peri-operative
- type 4 respiratory failure: shock
Define type 1 respiratory failure.
Hypoxic (low oxygen PaO2<8kPa or <60mmHg) with normal CO2
Define type 2 respiratory failure.
Hypoxia AND hypercapnia (PaCO2>6kPa or >45mmHg)
List examples of type 2 respiratory failure. (2)
- respiratory muscle weakness due to neurological conditions
- COPD exacerbation
What are some causes of type 1 respiratory failure? (6)
- fluid filling - pulmonary oedema
- collapse of alveolar spaces - pneumothorax, pleural effusion
- redistribution of blood flow
- loss of blood flow - embolism, hypovolaemia, shock, anaemia
- loss of tissue - emphysema, trauma, fibrosis
- thickening/fluid buildup - pneumonia
What are some causes of type 2 respiratory failure? (4)
- poor ventilatory muscle function (GBS, drug OD)
- chest wall abnormalities (traumatic flail chest, kyphoscoliosis)
- obstruction of airways (asthma, COPD, PO)
- secretions (COPD, CF)
Describe type 3 respiratory failure. (5)
- peri-operative respiratory failure
- increased atelectasis due to low functional residual capacity
- abnormal abdominal wall mechanics
- results in hypoxemia and normal CO2/hypocapnia/hypercapnia
- prevented by anaesthetic or operative technique, positioning, analgesia
Describe type 4 respiratory failure. (3)
- patients that are intubated or ventilated during shock
- optimise ventilation to improve gas exchange
- unload respiratory muscles
What are the general clinical features of respiratory failure? (5)
- direct trauma to thorax/neck
- dyspnoea
- confusion
- tachypnoea
- inability to speak
What might you find on examination of respiratory failure? (5)
- accessory breathing muscle use
- stridor
- retraction of intercostal spaces
- cyanosis
- loss of airway/gag reflex
What are the clinical features of type 1 (hypoxemic) respiratory failure? (4)
- tachypnoea
- dyspnoea
- cyanosis
- pleuritic chest pain
What are the clinical features of type 2 (hypercapnic) respiratory failure? (5)
- hypoventilation
- headache
- anxiety
- papilloedema
- asterixis
What is a feature of the hypoxemia in type 1 respiratory failure?
Hypoxemia refractory to supplemental oxygen
What are some risk factors for respiratory failure? (7)
- cigarette smoking
- young/older age
- respiratory system illness - pulmonary infection, chronic lung disease, airway obstruction, alveolar/perfusion abnormalities, pneumothorax
- injury
- infection
- cardiac failure
- hypercoagulable states
What are the first-line investigations for respiratory failure? (2)
- pulse oximetry (<80%)
- ABG
What might ABG show in respiratory failure? (3)
- pH<7.38
- pO2<60mmHg (<8kPa)
- PaCO2>50mmHg (>6kPa)
What might pulmonary function tests show in respiratory failure? (5)
- PEFR <35-50% predicted
- FEV <35-50% predicted
- FVC <50-70% predicted
- FEV1 <50% predicted
- NIF above -25cm H2O
What are some differential diagnoses for respiratory failure? (4)
- hyperventilation secondary to metabolic acidosis - DKA, aspirin toxicity, Kussmaul breathing - ABG
- hyperventilation secondary to anxiety
- sleep apnoea
- obesity
What management approach do we take in respiratory failure?
ABCDE approach
What is the first step in management of respiratory failure?
Check for airway obstruction –> airway clearance (head tilt, chin lift, jaw thrust)
How do we manage respiratory failure with airway obstruction? (3+7)
- airway clearance (head tilt, chin lift, jaw thrust)
- supplementary oxygen
- treatment of underlying causes:
- infection –> Abx
- anaphylaxis –> adrenaline
- chronic lung disease –> bronchodilation/corticosteroids
- pneumothorax –> decompression/chest tube insertion
- hypovolaemia –> fluid resus
- PE –> thrombolysis/embolectomy
- malignancy –> chemotherapy
How do we manage respiratory failure with no obstruction AND stable? (2+4)
- supplemental oxygen
- non-invasive ventilation - if PaCO2 rising:
- CPAP or BiPAP - if oxygen delivered by nasal cannula/mask was unsuccessful
- BiPAP/CPAP favoured for respiratory failure secondary to acute congestive HF
- BiPAP very useful for management of hypercapnic respiratory failure
- CPAP more used in type 1 respiratory failure
How do we manage respiratory failure with no obstruction AND unconscious/unstable patient? (3)
- endotracheal intubation
- mechanical ventilation
- rapid sequence induction
How do we correct hypoxemia in respiratory failure via non-mechanical ventilation/oxygen support? (2)
- nasal cannula
- face mask
What are the two types of mechanical ventilation in respiratory failure?
- invasive (endotracheal intubation) - if patient unconscious and supplemental O2 not working
- non-invasive (CPAP or BiPAP) - patient with type 2 respiratory failure secondary to chest wall deformity, neuromuscular disease or OSA
Give an example of a group of patients we might offer CPAP/BiPAP to?
Acute exacerbation of COPD who are in respiratory acidosis (pH 7.25-7.35)
What state should patients be in for CPAP/BiPAP (non-invasive ventilation)?
Awake and conscious
What type of ventilation is used in type 1 respiratory failure?
CPAP - particularly useful in pulmonary oedema due to HF
What type of ventilation is used in type 2 respiratory failure?
BiPAP
What are some complications of respiratory failure? (7)
- pneumothorax
- endotracheal tube misplacement
- nosocomial infection
- nasal mucosa damage
- dental injury
- tracheal inflammation and stenosis
- skin necrosis
Describe the prognosis of respiratory failure.
Mortality is often related to patient’s overall health and potential development of systemic organ dysfunction that can occur with acute illness
