Sleep Study Metrics
Every sleep study metrics calculator on CalcEngines — unit converters, derived indices and interpretive tools, each with its formula, a worked example and the reference intervals it is judged against.
8 calculators in this section
- Apnoea-Hypopnoea Index Calculator (AHI, RDI, REI)The AHI, the RDI and the REI from one set of event counts, and the divergence computed — a home study divides by recording time and reads systematically lower on the very same night.
- Arousal Index CalculatorArousals per hour of sleep, split into the respiratory-related and the rest — because the two sub-indices sum to the total, and which half dominates is the part a single arousal index cannot say.
- Central Apnoea Fraction and CSR InterpreterTwo separate criteria decide whether a study is centrally predominant — an index of 5 or more per hour AND more than half the events central — and a night can meet either one without the other.
- OSA Severity Grading InterpreterRead an index against the published severity strata — and see why the strata are not the diagnostic criteria, why the adult and paediatric stratifications are different, and what the strata are criticised for.
- Oxygen Desaturation Index Calculator (ODI)Compute the ODI at both the 3% and the 4% desaturation rule from one night's counts, and see the gap — the stricter rule can move the same recording across a threshold without anything about the patient changing.
- Sleep Efficiency and Latency CalculatorSleep efficiency from total sleep time and time in bed, with the wake after sleep onset the report may not print, recovered from the identity that time in bed is latency plus sleep plus wake.
- Sleep Stage Percentage CalculatorN1, N2, N3 and REM as shares of total sleep time, derived from the stage minutes alone — so the four percentages sum to exactly 100 and cannot disagree with a separately entered sleep time.
- Time Below 90% Saturation Calculator (T90)Convert the T90 percentage a report prints into minutes, and read it against the published MrOS cut-off — the measure the AASM promoted to recommended reporting in version 3 as it demoted the desaturation index.