Clinical tool
CPAP pressure calculator
Estimate your starting CPAP pressure with the Miljeteig and Hoffstein formula (1993), the best-known prediction formula, used as a starting point before titration.
Indicative result only. This formula gives a starting estimate: it does not replace titration or adjustment by your sleep doctor. Never change your CPAP pressure without medical advice.
Your measurements
Use the AHI from your initial diagnosis (before CPAP)
Body mass index
Measure halfway up the neck, just below the Adam's apple, with your head straight.
The apnea-hypopnea index measured during your sleep study, before any treatment. It is in the sleep center report.
Fill in the form and click Calculate to get your estimated pressure.
Estimated pressure
The Hoffstein formula explained
The formula
P = (0.16 × BMI)
+ (0.13 × neck circumference)
+ (0.04 × AHI)
− 5.12
Miljeteig H, Hoffstein V. Am Rev Respir Dis. 1993;147(6 Pt 1):1526-30.
What the validation found
In the validation study (Hoffstein and Mateika, 1994), the optimal pressure was within ±2 cmH₂O of the prediction in 24 of 26 patients.
It is a small study: of the 26 patients, two were more than 4 cmH₂O away from the prediction.
The authors propose it as a starting point, to shorten titration.
Why these 3 measurements?
In the original study, these three measurements explained 76% of the variation in the pressure needed.
- BMIObesity increases the load on the upper airway, and the pressure needed to keep it open.
- NeckIt reflects the fat around the pharynx, which presses directly on the throat.
- AHIIt measures how severe the apnea is: the more frequent the events, the higher the pressure tends to be.
Alternatives to the formula
- →Laboratory titration : The reference method: a full-night polysomnography, with adjustments in real time.
- →Auto-CPAP : The device adjusts the pressure continuously; after a few weeks, its 95th percentile can serve as the basis for a fixed setting.
- →Other equations : Other prediction formulas have been published; they are less widely used.
Sources: Miljeteig H, Hoffstein V. Am Rev Respir Dis. 1993;147(6 Pt 1):1526-30. Hoffstein V, Mateika S. Am J Respir Crit Care Med. 1994;150(2):486-8.
Other useful tools
Frequently asked questions
Was this page useful?
Thank you for the feedback.