The reason for using an AUTO CPAP

The amount of pressure required for effective CPAP therapy varies according to sleep stage, sleep position, and other factors. Insufficient pressure results in ineffective therapy while too much pressure can lead to discomfort, non-compliance, and pressure-related side effects.

Preemptive Response

AutoSet devices act preemptively by increasing pressure in response to inspiratory flow limitation, which typically precedes snore and obstruction. This early intervention prevents snoring and obstructive apneas, thereby reducing respiratory arousals.

Sudden Apnea Response

Apneas may occur suddenly, without being preceded by flow limitation or snore. These sudden apneas are generally associated with sleep onset, change in body position, or REM onset. Following a sudden apnea, AutoSet devices will increase pressure relative to the severity of the event. If no further events occur, AutoSet devices reduce the pressure back to a minimum level.

The AutoSet Algorithm over all

The efficacy of the AutoSet algorithm is due to its ability to increase pressure in response to the severity of the three parameters (flow limitation, snore, and apnea):

• The greater the flow limitation, the more pressure delivered
• The louder the snoring, the more pressure delivered
• The longer the apnea, the greater the increase in pressure

By responding to these three separate parameters, AutoSet devices effectively normalize sleep while delivering a mean pressure typically 37% lower than fixed pressure therapy.¹

Upper Airway Status and Flow Curves

The most effective way to assess flow limitation is through analyzing the shape of the inspiratory flow-time curve, as shown in the diagrams below. A rounded inspiratory flow contour is the monitoring event that best predicts upper airway patency and a transition to deeper sleep stages without arousals. Studies recommend that this inspiratory flow contour characteristic be routinely used to achieve an optimal pressure level and is preferable to responding to apneas and hypopneas directly.

The rounded inspiratory flow curve in the left diagram indicates a normal breath. If the upper airway begins to narrow, causing flow limitation and upper airway resistance, the shape of the curve will flatten as shown in the right diagram.

ResMed Autoset CPAP

The AutoSet algorithm responds to three key respiratory parameters:

• Inspiratory flow limitation
• Snore
• Apnea
• Maintain pressure by compensating for mask leak.
• Provides effective therapy at the lowest mean pressure, typically 37% lower than fixed pressure therapy
• Adapts to patients’ changing pressure needs on a short- and long-term basis
• Responds to flow limitation, snore, apneas, and mask leak
• Provides greater breathing comfort through smooth, quiet pressure delivery
• Provides visual display for quality of mask fit; optional alert tone in presence of significant leaks
• The ResMed AutoSet adjusts the pressure according to the extent of flattening, in order to maintain airflow and restore the curve to normal.

·         The ResMed  Autoset’s measurement and response to flow limitation snore, and apnea is unique within the field of sleep-disordered breathing therapy.

Respironics Autoset CPAP

The remstar Auto CPAP looks at the shape of the curve of a patients airflow signal. It is all based on four parameters Roundness, Flatness, Peak and shape. Based on these parameters of breathing the remstar Auto CPAP can seek out instances of flow limitation. The Remstar Auto CPAP also performs a secondary Analysis based on peak flow. It does this to determine the occurrence of breathing problems like Apnea and hyponeas. It detects snoring based on a frequency analysis of the pressure signal. When it detects one of these events the Remstar Auto CPAP begins to increase the pressure level until the patient resumes normal breathing. Once the breathing returns to normal the Remstar Auto CPAP then returns to lowering the pressure to deliver optimal therapy.

Puritan Bennet Autoset CPAP

• 420E has the ability to detect Cardiogenic Oscillations - ONLY ONE in the market.

• The 420E will not only detect Central/Mixed Apneas but it will also let us know how long and how often these apneas

• Ability to setup four different intervals of pressures.  Titration can be prolonged to increase compliance. This feature can also be used during fixed CPAP pressures to assess patients’ physiologic response to different pr

• Algorithm response at Flow Limited breaths (30% flow reduction) vs. Hypopnea breaths (50% flow reduction). 

• Understand that Flow Limitation is a precursor to OSA. 

• This response level makes the 420E the most sensitive Auto CPAP in the market. 

• The 420E increase pressures at smaller intervals (0.2 cmH2O) therefore reducing/eliminating the incidence of micro

• Automatic Altitude compensation allows for the unit to deliver accurate pressures no matter where the patient is. 

• Compliance is increased because altitude changes can and will cause greater OSA incidence unless properly treated

What the 420 E considers an Apnea event No breath detection for greater than 10 seconds + 5/8 of the average of the last 3 previous breaths.

The 420 e will then increase pressure by 1 cm H2o after apnea detection. If there is no response after 15 seconds it will increase again 1 cm H20 it will increase for a third time after another 15 seconds by 1cm H2o. There will no more then 3 cmH2o pressure increases on the same apnea. No action taken if the apnea is detected over the preset upper maximum pressure set by the physician. Returns to preset back up pressure after 2 minutes without breathing.

What the 420 E considers a central apnea is apnea with an open airway due to the presence of Cardiac oscillations as seen in the flow wave during the last 5 seconds.

The pressure will not be increased if an apnea with an open airway is detected (central Apnea)

Runs of flow limited cycle’s starts after two flow breaths or 10 intermediate breaths. It ends after 2 normal breaths.

A run determination leads to immediately to a pressure increase. Pressure increase values are 0.3cm H2o if a hypopnea occurs during the run and 0.1cm H2o if a hypopnea does not occur.

Hyponea 50% reduction of the flow signal amplitude compared with the average amplitude of the last 8 breaths for at least 10 seconds.

Pressure will not be increased if only a hypopnea is detected. If the hypopnea occurs during a run of inspiratory flow limitations there will be an enlargement of the pressure increase due to the run.

Snoring is the acoustic vibration (30-280 Hz) lasting more than 7% of the average time of the three previous breaths.

There will be an increase of 1 cmH2o pressure after the detection of snoring. There will be three other pressure increases each two cycles if the run is not ended. After this increase of pressure a 1 minute period begins during which no increase of pressure due to snoring will be allowed. The pressure can not exceed the maximum upper pressure limit set by the physician.

If there is a leak it shows up as the mean flow being greater than the theoretical max flow computed according to the pressure. When this happens all commands are blocked.  If the measured leak is over the maximum theoretical value the pressure level delivered by the device will remain the same even if events are detected.

If no event is detected there will be a decrease in pressure of 0.5 cm H2o after five minutes. If still no events dected another decrease of 0.5 cm H2o every minute there after. It can not go lower then the minimum pressure prescribed by the physician