CPAP & BiPAP Flashcards
(24 cards)
What does CPAP stand for?
Continuous Positive Airway Pressure
What are the indication for CPAP?
- Hypoxia, Type I RF
- Pneumonia/acute infection (prior to escalation to ventilator)
- Pulmonary oedema
- Obstructive sleep apnoea
What does CPAP help to increase?
FRC
What does CPAP supply?
Supplies constantfixed positive pressure throughout inspiration and expiration.
(Therefore, it is not a form of ventilation, but splints the airways open.)
What is CPAP delivered with?
Oxygen
CPAP
, it can allow a higher degree of inspired oxygen than other oxygen masks.
What does BiPAP stand for?
Bi-level Positive Airway Pressure
What is BiPAP also known as?
Non-invasive ventilation (NIV)
What is the key feature of BiPAP?
Its ability to deliver air at two different pressures:
- A higher-pressure during inhalation (IPAP)
- A lower pressure during exhalation (EPA)
What does BiPAP allow for?
- More complex settings (such as setting different pressures, volume support and tidal volumes)
- The machine then automatically selects the lowest IPAP to achieve the target tidal volume
What does BiPAP help to reduce?
Risk of barotrauma
What is BiPAP a good option for?
Good option prior to getting the patient on a ventilator
What are the indications of BiPAP?
- Type II RF
- Chronic COPD
- COPD exacerbations
- Weaning from ventilator
What are the precautions for CPAP & BiPAP?
- Recent facial or oesophageal Sx
- Nausea
- Vomiting
- Bullous emphysema
What are the contraindications for CPAP & BiPAP?
- Haemoptysis
- Inability to protect airway
- Facial trauma
- Burns
- Active untreated TB
- CVS/haemodynamic instability
- Undrained pneumothorax
- Transesophageal fistula
Why can CPAP & BiPAP cause an inability to protect the airway?
Absent cough reflex, which can result in aspiration, blockages in airway, etc.
Describe the physiology of CPAP.
- Increases pressure within the airway and holds open collapsed alveoli
- Pushing more oxygen across the alveolar membrane
- Forcing interstitial fluid back into the pulmonary vasculature
- It increases intrathoracic pressure which decreases venous return to the heart and reduces the preload (pressure in the ventricles at the end of diastole)
- This lowers the pressure that the heart must pump against (afterload), both of which improve left ventricular function
- Gas exchange is therefore maintained or improved
Airways at risk from excess fluid are stented open
Reduces increased WOB
What are the two pressure levels of BiPAP?
- Inspiratory Positive Airway Pressure (IPAP)
- Expiratory Positive Airway Pressure (EPAP)
(differences between IPAP and EPAP = pressure support)
What does IPAP’s mechanism of action in BiPAP?
- Improves pulmonary mechanical movement
- Supports inspiratory effort and reduces work of breathing; unloading respiratory muscles
- Improves Tidal Volume
- Improves CO2 removal
What does EPAP’s mechanism of action in BiPAP?
- It splints open the airway which improves alveolar gaseous exchange and limits further collapse
- Prevents rebreathing of CO2 and aids oxygenation
- Increases FRC & counteracts intrinsic PEEP
Summarise CPAP.
- Continuous pressure
- Same pressure during exhalation and inhalation
- Commonly used at home (less complicated)
- Needs little monitoring
- Cheaper
Summarise BiPAP.
- Continuous pressure
- Different pressures during exhalation and inhalation
- Not commonly used at home (complex)
- Needs monitoring of delivered pressures
- Expensive
What happens to Function Residual Capacity (FRC) when on CPAP?
Increases FRC
How does CPAP increase Function Residual Capacity (FRC)?
- By increasing the surface area of the alveoli
- This increase in alveoli surface area improves and allows for greater gas exchange (oxygenation & ventilation)
- This improves oxygenation
