Pressure in a CPAP machine is measured in centimeters of water pressure (cm H2O).
A Continuous Positive Airway Pressure (CPAP) machine is a common treatment device used primarily for conditions like sleep apnea. Its fundamental function is to deliver a consistent stream of pressurized air through a mask to the user's airway. This pressure helps keep the airway open, preventing collapse during sleep.
The reference confirms that CPAP is a method of delivering PEEP (Positive End-Expiratory Pressure) and crucially, it maintains a set pressure throughout the entire breathing cycle, including both inhalation and exhalation. This constant pressure is precisely controlled and reported using a specific unit: centimeters of water pressure (cm H2O) [1].
Understanding cm H2O
- What it means: cm H2O is a standard unit of pressure often used in medical and respiratory applications. It represents the pressure required to support a column of water one centimeter high.
- Why it's used: While other units like millimeters of mercury (mmHg) or Pascals (Pa) exist, cm H2O is widely adopted for respiratory pressure measurements because the pressures involved are relatively low, making this unit convenient and easy to work with.
Key Aspects of CPAP Pressure Measurement
- Constant Pressure: Unlike some other ventilation modes, CPAP provides a single, consistent pressure level that the machine aims to maintain continuously [1].
- Prescription: The specific pressure setting (e.g., 8 cm H2O, 10 cm H2O) is typically prescribed by a healthcare professional based on a sleep study or titration study.
- Monitoring: Modern CPAP machines often have built-in sensors to monitor and display the delivered pressure, ensuring it matches the prescribed setting.
Table: Common Pressure Units
| Unit | Abbreviation | Context |
|---|---|---|
| Centimeters of Water | cm H2O | Respiratory (CPAP, BiPAP) |
| Millimeters of Mercury | mmHg | Blood Pressure |
| Pascals (or Kilopascals) | Pa (kPa) | General Pressure, Physics |
Understanding the unit of measurement, cm H2O, is key to interpreting CPAP prescriptions and monitoring machine performance.
\
