ACUTE Flashcards
In broad terms, how should respiratory failure be managed?
- A –> E assessment
- O2
- Determine the cause: investigate
Treat according to cause
How should oxygen therapy be escalated in a hypoxic patient?
- High-flow O2 (15L) via non-rebreathing mask (70% FiO2)
- NIV (CPAP or BiPAP)
- Intubation & mechanical ventilation
What investigations should be done to determine the cause of respiratory failure?
• Bloods: FBC, U&E, blood cultures, coagulation screen, CRP
• ABG
• CXR
ECG
What type of NIV should be used in type I respiratory failure? Why?
CPAP.
There is inadequate oxygenation. Alveoli need to be kept open/fluid pushed out of the lung.
What type of NIV should be used in type II respiratory failure? Why?
BiPAP.
There is inadequate ventilation. Alveoli need to be stretched open during inspiration and kept open during expiration.
What is the definition of respiratory failure?
PaO2 < 8
What is V/Q mismatch?
Ventilation perfusion mismatch or V/Q defects are defects in the total lung ventilation/perfusion ratio.
One or more areas of the lung receive oxygen but no blood flow, or they receive blood flow but no oxygen.
Name three causes of V/Q mismatch.
• Alveolar collapse
• Fluid build-up
- Bronchoconstriction
What are the two types of respiratory failure?
Type I - low O2, normal or low CO2
Type II - low O2, high CO2
Describe the pathophysiology of type I RF.
Inadequate oxygenation (hypoperfusion) due to:
1. Alveolar collapse e.g. pneumonia 2. Fluid in the alveoli e.g. heart failure
Ventilation is preserved - CO2 is normal or low –> V/Q mismatch.
Describe the pathophysiology of type II RF.
Inadequate ventilation (hypoperfusion AND hypoventilation) due to:
1. Obstruction: COPD, asthma, muscular dystrophy
CO2 is high. No V/Q mismatch.
When might pulse oximetry be misleading?
CO poisoning Poor peripheral perfusion/shock Hypothermia Nail varnish Excessive movement
Name some causes of acute dyspnoea.
Respiratory: • Asthma/COPD • Pneumonia • Pleural effusion • Pneumothorax Cardiac: • Pulmonary oedema • MI • PE (see PE/DVT) • Arrhythmias Trauma: • Aspiration/FB • Flail chest • Haemothorax • Drowning Other: • Hypovolaemia or fever • Hyperventilation syndrome Respiratory compensation for metabolic acidosis e.g. DKA
How might a patient present with pulmonary oedema?
• Tachypnoea • Tachycardia • Frothy pink sputum • ^JVP • Basal crackles or wheeze Signs of reduced CO: sweaty, cool and pale
Name some features of pulmonary oedema on a CXR.
• Cardiomegaly • Kerley A, B or C lines • Fluid in interlobar fissures • Pleural effusions Bat wing hilar shadows
What can cause non-cardiogenic pulmonary oedema?
ARDS (sepsis, trauma, pancreatitis), IV fluid overload, drowning, altitude, smoke inhalation
What is the treatment for pulmonary oedema?
PODMAN
- Position
- Oxygen
- Diuretics
- Morphine
- Anti-emetic
- Nitrates
What is primary and secondary hyperventilation? How should they be managed?
Primary = psychogenic:
- Patient may be agitated or distress
- Exclude serious secondary causes and reassure
Secondary = due to compensation:
- Identify cause: metabolic acidosis, poisoning, pain, hypovolaemia
- Treat the cause
What will the ABG show in a patient who is hyperventilating?
^O2.
CO2 is low as it’s ‘blown off’.
pH >7.45
Respiratory alkalosis.
How does hyperventilation lead to perioral and peripheral paraesthesia?
Hypocalcaemia.
H+ and Ca+ bind to albumin. In alkalosis, H+ dissociate from albumin and Ca+ are taken up.
What is the definition of shock?
Acute circulatory failure with inadequate tissue perfusion and cellular hypoxia.
What are the first signs of shock (compensated)?
^HR
Pallor Anxiety Sweating Tachypnoea >CRT Narrow pulse pressure
What are the late signs of shock?
Hypotension
Bradycardia
Arrest
What are the four types of shock?
- Hypovolaemic
- Cardiogenic
- Distributive
- Obstructive
How can you classify the pathological processes of shock? (think like a plumber)
There is a problem with:
- Fluid - hypovolaemia
- Pump - obstructive, cardiogenic
- Pipes - distributive
What is the general approach to treating shock?
- A–>E (+call for help)
- O2
- Treat underlying cause