What Type of CPAP Should You Choose—Single or Bi-level?

Auto-adjusting Single-Level CPAP Machines
Home-use CPAP machines are generally divided into Single-level and BI-level types. A single-level machine provides just one continuous pressure, while a bi-level machine provides two pressures: an inspiratory positive airway pressure (IPAP) and an expiratory positive airway pressure (EPAP). During inhalation, the pressure is higher to help open the airway and allow enough air in; during exhalation, the pressure is lower to help release air more easily and reduce resistance.

When Is a Bi-level CPAP Machine Appropriate?

1. Patients requiring higher therapeutic pressure (severe OSA with pressure over 15 cmH₂O)

2. Patients with a higher need for comfort

3. Patients with obesity hypoventilation syndrome and carbon dioxide retention

4. Patients with cardiopulmonary diseases

Why Can Bi-level Auto CPAP Machines Treat Patients Requiring Higher Pressure? Why Are They More Comfortable?
Take the RESMED S10 series as an example:

• The AirSense 10 (single-level) has a maximum pressure of 20 cmH₂O

• The AirCurve 10 (bi-level) has a maximum pressure of 25 cmH₂O

Clearly, bi-level machines can deliver higher pressures, making them more effective for patients with severely blocked airways.

What Type of CPAP Should You Choose—Single or Bi-level?

To simplify, there are mainly three types of machines on the market:

1. Single-level CPAP – Available in semi-auto and fully auto modes

2. Auto-adjusting Bi-level CPAP

3. Bi-level ST CPAP

These three basically cover the whole CPAP market.

Most sleep apnea patients (moderate to severe AHI) only need a single-level machine. Bi-level auto CPAPs are more suited for people weighing 250–300 pounds or more. Both types are designed to treat sleep apnea by providing continuous positive airway pressure when breathing pauses or hypoventilation occur during sleep, helping open or widen the airway and reduce the number of apnea events.

Bi-level ST CPAP Machines
Bi-level ST (Spontaneous/Timed) machines are specifically intended for patients with chronic obstructive pulmonary disease (COPD) or neuromuscular disorders like ALS or Parkinson’s. Their main function is to help expel carbon dioxide, improve blood oxygen saturation, and reduce respiratory muscle fatigue. These machines are not suitable for treating sleep apnea.

Alright, that’s all for today. Thank you all!