Chest
Volume 130, Issue 2, August 2006, Pages 350-361
Journal home page for Chest

Original Research: SLEEP MEDICINE
Bench Model To Simulate Upper Airway Obstruction for Analyzing Automatic Continuous Positive Airway Pressure Devices

https://doi.org/10.1378/chest.130.2.350Get rights and content

Background

Automatic positive airway pressure (APAP) devices are increasingly being used in patients with obstructive sleep apnea. Some APAP devices present an unstable behavior when subjected to some events or artifacts. The aims were to develop a bench model capable of reproducing real flow, snoring, and obstructive patterns and to compare the response of APAP devices based on flow and snoring with other devices using, in addition, the forced oscillation technique (FOT).

Methods

The bench model subjected APAP devices to apneas with and without obstruction, obstructive hypopneas with and without snoring, periods of flow limitation, and artifacts such as leaks and mouth expiration.

Results

Almost all the devices increased the pressure when subjected to apneas with obstruction, but at different rates. The time required by each device to reach 10 cm H2O ranged from 2.5 to 13 min. In the presence of apneas without obstruction, all the devices based on flow and snoring increased the pressure at the same rate as during apneas with obstruction. However, the devices using FOT did not modify the pressure. Four devices did not modify the pressure in the presence of obstructive hypopneas, and all but one device increased the pressure in the presence of snoring. Mask leaks had little effect on the response of the devices, but four devices increased the pressure during mouth expiration artifacts.

Conclusions

When, in addition to the flow and snoring signals, the measurement of the upper airway resistance is included, the accuracy of the event detection algorithms is improved.

Section snippets

Patient Simulator

We modified the patient simulator model previously described33 by including an obstructive valve servocontrolled by a motor (HS-325BB; Hitec RCD; Powey, CA). This new model was able to reproduce not only real flow and snoring signals obtained from patients' recordings, but also the corresponding resistance of the upper airway (Fig 1). A driving signal generated by the computer was fed into the analog servocontrol of the motor, which regulated the aperture of the valve. The obstructive valve was

RESULTS

Tables 1and 2summarize the results of the different tests. The responses of the devices when subjected to a continuous repetition of apneas with obstruction (test 1, panel B in Fig 2) are shown in Figure 4. All the devices increased the pressure in response to this event but with different strategies. Devices F1, O1, and O3 increased the pressure linearly up to the maximum pressure allowed but with different speeds. Devices F2, F3, F4, F5, and O2 increased the pressure stepwise with differences

DISCUSSION

In this study, we developed a bench model to mimic not only the flow and snoring patterns obtained from patients, but also the corresponding upper airway obstruction. With this model, the new generation of APAP devices can be tested in the bench by reproducing the phenomena that occur in obstructive events. We analyzed several APAP devices capable of detecting the upper airway patency with respect to other devices based only on the analysis of the flow shape and snoring. The responses of the

ACKNOWLEDGMENT

The authors thank Mr. M. A. Rodriguez for technical assistance.

REFERENCES (50)

  • A Bachour et al.

    Mouth breathing compromises adherence to nasal continuous positive airway pressure therapy

    Chest

    (2004)
  • I Ayappa et al.

    Cardiogenic oscillations on the airflow signal during continuous positive airway pressure as a marker of central apnea

    Chest

    (1999)
  • MK Reeves-Hoche et al.

    Nasal CPAP: an objective evaluation of patient compliance

    Am J Respir Crit Care Med

    (1994)
  • J Krieger et al.

    Simplified diagnostic procedure for obstructive sleep apnoea syndrome: lower subsequent compliance with CPAP

    Eur Respir J

    (1998)
  • N Mc Ardle et al.

    Long-term use of CPAP therapy for sleep apnea/hypopnea syndrome

    Am J Respir Crit Care Med

    (1999)
  • HM Engleman et al.

    Compliance with CPAP therapy in patients with the sleep apnoea/hypopnoea syndrome

    Thorax

    (1994)
  • WJ Randerath et al.

    Auto-adjusting CPAP based on impedance versus bilevel pressure in difficult-to-treat sleep apnea syndrome: a prospective randomized crossover study

    Med Sci Monit

    (2003)
  • CA Massie et al.

    Comparison between automatic and fixed positive airway pressure therapy in the home

    Am J Respir Crit Care Med

    (2003)
  • C Hukins

    Comparative study of autotitrating and fixed-pressure CPAP in the home: a randomized, single-blind crossover trial

    Sleep

    (2004)
  • NT Ayas et al.

    Auto-titrating versus standard continuous positive airway pressure for the treatment of obstructive sleep apnea: results of a meta-analysis

    Sleep

    (2004)
  • K Behbehani et al.

    A sleep laboratory evaluation of an automatic positive airway pressure system for treatment of obstructive sleep apnea

    Sleep

    (1998)
  • H Teschler et al.

    Two months auto-adjusting versus conventional nCPAP for obstructive sleep apnoea syndrome

    Eur Respir J

    (2000)
  • F Series et al.

    Importance of sleep stage- and body position-dependence of sleep apnoea in determining benefits to auto-CPAP therapy

    Eur Respir J

    (2001)
  • T Penzel et al.

    Effect of sleep position and sleep stage on the collapsibility of the upper airways in patients with sleep apnea

    Sleep

    (2001)
  • H Teschler et al.

    Automated continuous positive airway pressure titration for obstructive sleep apnea syndrome

    Am J Respir Crit Care Med

    (1996)
  • Cited by (0)

    Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (http://www.chestjournal.org/misc/reprints.shtml)

    Dr. Rigau was an employee of Measure, Check & Control GmbH & Co. KG at the time that this study was carried out and at present is employed by Sibel S.A. Josep M. Montserrat has no declared conflict of interest. Dr. Wöhrle received 38.500 Euros from Weinmann GmbH and 27.000 Euros from ResMed/MAP for lectures between 2002 and 2004. Dr. Wöhrle also received 25.000 Euros from Measure, Check & Control GmbH & Co. KG as a research grant. Ms. Plattner is an employee of Measure, Check & Control GmbH & Co. KG. Mr. Schwaibold is an employee of Measure, Check & Control GmbH & Co. KG. Dr. Navajas has no declared conflict of interest. Dr. Farré has no declared conflict of interest.

    This study was carried out in the Unitat de Biofísica i Bioenginyeria (Universat de Barcelona, Spain) within the framework of a research contract with Measure, Check & Control GmbH & Co. KG.

    This work was supported in part by Measure, Check & Control GmbH & Co. KG, by Fondo de Investigación Sanitaria (V-2003-RED C11 F-O), and by Ministerio de Ciencia y Tecnología (SAF2002–03616 and SAF2004–00684).

    View full text