Respiratory failure Flashcards
What is type I resp failure?
- PaO2<60mmHg due to impairment of gas exchange
What is type II resp failure?
- PaCO2>50mmHg due to hypoventilation
What is the most important investigation into respiratory failure?
- arterial blood gas
What are some causes of hypoxemia?
- reduced inspired O2 (altitude, fire)
- VQ mismatch (pneumonia, PE)
- impaired diffusion (COPD, fibrosis)
- shunt
- hypoventilation
What are some causes of hypercapnoea?
- neuromuscular disease (e.g. MND, GB)
- chest wall abnormalities (kyphosis, flail chest)
- central depression (e.g. morphine OD)
- intrinsic lung disease (COPD)
- airway obstruction
What are some symptoms of respiratory failure?
- SOB
- drowsy
- confused
- headache
What are some signs of respiratory failure?
- tachypnoea and irregular breathing
- use of accessory muscles
- restlessness
- agitation
- low sats
- drowsiness
- signs of the cause
What investigations should be performed?
- ABGs
- CXR
- basic bloods
- CTPA (if PE suspected)
- VQ scan
- lung fx
- sleep study
- M/C/S sputum and blood if febrile
How should respiratory failure be managed?
- maintain adequate O2 delivery (care with CO2 retainers)
- reduce respiratory workload (CPAP or assisted non-invasive respiration, intubation)
- maximise ventilation
- maintain stable pH/electrolytes
- target the cause e.g. asthma, atelectasis
- bed rest, analgesia, humidification, physio
What are the indications for intubation?
- if PaO2 not sustained
- if type II failure develops
How is the A-a gradient calculated?
21% of 760mmHg (1atm)
= 150
150 inhaled and humidified and mixed with exhaled CO2 (PaCO2)
then the amount of PaO2 is subtracted to give the gradient
What is a normal A-a gradient?
5-20mmHg
What are some causes of elevated A-a gradient?
- diffusion problem with A-C membrane
- V/Q mismatch
What is acute respiratory distress syndrome?
- non-specific reaction of the lungs to a wide variety or direct pulmonary and indirect non-pulmonary insults
