CPAP and BiPAP machines are medical devices that help people breathe more effectively during sleep or illness. They are most often used to treat obstructive sleep apnea, a condition in which the throat repeatedly narrows or closes during sleep. By sending gently pressurized air through a mask, the machine helps keep the airway open so oxygen can continue moving into the lungs.
This can reduce snoring, improve sleep quality, and lower stress on the heart and brain.
Key Facts
- CPAP means continuous positive airway pressure, which delivers one steady pressure during both inhaling and exhaling.
- BiPAP means bilevel positive airway pressure, which delivers a higher pressure for inhaling and a lower pressure for exhaling.
- Pressure in CPAP and BiPAP therapy is commonly measured in cm H2O.
- Typical CPAP pressures are often in the range of about 4 to 20 cm H2O, depending on the patient and prescription.
- Airflow path: machine outlet to tubing to mask to nose or mouth to upper airway to lungs.
- Pressure relationship: P = F/A, so the same force spread over a larger mask area creates less pressure on the face.
Vocabulary
- CPAP
- CPAP is a breathing support device that provides one continuous level of positive air pressure to keep the airway open.
- BiPAP
- BiPAP is a breathing support device that provides two pressure levels, usually higher for inhaling and lower for exhaling.
- Obstructive sleep apnea
- Obstructive sleep apnea is a sleep disorder in which relaxed throat tissues repeatedly block airflow during sleep.
- Positive airway pressure
- Positive airway pressure is air pressure above normal atmospheric pressure that helps hold breathing passages open.
- Mask seal
- A mask seal is the contact area between the mask cushion and the face that helps prevent air leaks.
Common Mistakes to Avoid
- Thinking CPAP adds oxygen by itself is wrong because most CPAP machines use room air unless a separate oxygen source is prescribed.
- Confusing CPAP and BiPAP is wrong because CPAP uses one pressure level while BiPAP uses different pressures for inhaling and exhaling.
- Overtightening the mask is wrong because it can cause skin irritation and may deform the cushion, making leaks worse instead of better.
- Ignoring air leaks is wrong because leaks can reduce delivered pressure, dry the airway, and make the therapy less effective.
Practice Questions
- 1 A CPAP machine is set to 10 cm H2O. If a patient uses it for 7.5 hours each night for 14 nights, how many total hours of therapy are recorded?
- 2 A BiPAP machine is set to IPAP = 16 cm H2O and EPAP = 6 cm H2O. What is the pressure difference between inhaling and exhaling?
- 3 Explain why a steady stream of pressurized air can reduce airway collapse in obstructive sleep apnea, even though the machine is not breathing for the patient.