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Respiratory Disturbance Index (RDI) for Predicting Obstructive Sleep Apnea (OSA)

Purpose: To evaluate a patient for the risk of obstructive sleep apnea using the scores of Friedman et al.

Description

Friedman et al developed a respiratory disturbance index (RDI) to help identify patients with obstructive sleep apnea (OSA). A simpler OSA score based on the same parameters was also useful in identifying affected patients. The authors are from Rush-Presbyterian-Saint Luke's Medical Center in Chicago.


 

Parameters:

(1) grade of body mass index (BMI)

(2) Mallampati score (from 1 to 4, as described in 31.05.01)

(3) tonsillar size grade (from 0 to 4, as described in 09.13.04)

 

body mass index =

= (body weight in kilograms) / ((body height in meters)^2)

 

BMI

Grade

< 20 kg per square meter

0

20 - 25

I

25.01 - 30

II

30.01 - 40

III

> 40

IV

 

RDI (from page 1902) =

= (apneic events per hour) + (hyponeic events per hour)

 

RDI =

= (4.675 * (grade of body mass index)) + (7.816 * (Mallampati score)) + (3.988 * (grade of tonsillar size)) - 7.544

 

RDI

Interpretation

< 20

OSA unlikely

>= 20

OSA present

>= 45

severe OSA

based on discussion on page 1904

 

The authors then described an "OSA score" based on the sum the parameter grades:

 

OSA score =

= (BMI grade) + (Mallampati score) + (tonsillar size grade)

OSA Score

Findings

Interpretation

>= 8

at least one component grade 4

positive for OSA

>= 8

2 or 3 components grade 3

positive for OSA

<= 4

none of the components grade 4

negative for OSA

based on discussion page 1904

 


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Specialty

Objective

ICD-10