Autoset Technology; Normal Airway; Flow Limitation; Snore - ResMed S9 Series Clinical Manual

AutoSet technology

The treatment pressure required by your patient may vary due to changes in sleep state, body position
and airway resistance. In AutoSet mode, the device provides only that amount of pressure required to
maintain upper airway patency.
The device analyzes the state of your patient's upper airway on a breath-by-breath basis and delivers
pressure within the allowed range according to the degree of obstruction. The AutoSet algorithm adjusts
treatment pressure as a function of three parameters: inspiratory flow limitation, snore, and apnea.

Normal airway

When your patient is breathing normally, the inspiratory flow measured by the device as a function of
time shows a typically rounded curve for each breath.
Inspiration
Time
Unrestricted inspiratory flow-time curve (rounded)
Open unrestricted airway

Flow limitation

As the upper airway begins to collapse, the shape of the inspiratory flow-time curve changes. The S9
recognises and treats traditional as well as less common flow-limited breath wave forms.
Time
Flattened inspiratory flow-time curve
Silent partial airway obstruction
(denoting partial obstruction)

Snore

Snoring is sound generated by vibrations of the walls of the upper airway. It is often preceded by flow
limitation or a partial obstruction of the airway.
Time
Noisy partial airway obstruction Snore superimposed on inspiratory flow-time curve
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