R Condos, RG Norman, I Krishnasamy, N Peduzzi, RM Goldring and DM Rapoport
Department of Medicine, New York University Medical Center, New York 10016.

Many patients with obstructive sleep apnea syndrome (OSAS), despite therapy with nasal continuous positive airway pressure (CPAP), have persisting daytime somnolence that may be due to a persistently elevated upper-airway resistance associated with electroencephalographic (EEG) arousals. We tested the hypothesis that elevated upper-airway resistance can be inferred from the contour of the inspiratory flow tracing obtained from a conventional CPAP circuit. This may provide a noninvasive method for determining optimal CPAP. Data were collected during a CPAP titration of an upper-airway model and in eight patients with OSAS. Estimated inspiratory resistance was calculated from esophageal pressure, CPAP mask pressure, and inspiratory flow. At high CPAP, resistance was low and inspiratory flow contour was found to be rounded. At low CPAP, resistance was high and flow contour developed a plateau suggesting flow limitation. We also noted that the CPAP pressure at which high resistance developed, and at which flow limitation appeared, showed hysteresis. We conclude that when respiration is stable, the contour of inspiratory flow tracing from a CPAP system can be used to infer the presence of elevated upper- airway resistance and flow limitation. Optimizing flow contour may be an alternative to eliminating apneas in evaluation of the optimal therapeutic level of CPAP in OSAS.

This article has been cited by other articles:

				A. C. Halbower, S. L. Ishman, and B. M. McGinley Childhood Obstructive Sleep-Disordered Breathing: A Clinical Update and Discussion of Technological Innovations and Challenges Chest, December 1, 2007; 132(6): 2030 - 2041. [Abstract] [Full Text] [PDF]

				D. Pevernagie, J. F. Masa, J. C. Meurice, R. Farre, O. Marrone, and D. Rodenstein Treatment of obstructive sleep-disordered breathing with positive airway pressure systems Eur. Respir. Rev., December 1, 2007; 16(106): 125 - 131. [Abstract] [Full Text] [PDF]

				M. Younes, M. Ostrowski, R. Atkar, J. Laprairie, A. Siemens, and P. Hanly Mechanisms of breathing instability in patients with obstructive sleep apnea J Appl Physiol, December 1, 2007; 103(6): 1929 - 1941. [Abstract] [Full Text] [PDF]

				R. K. Kakkar and R. B. Berry Positive Airway Pressure Treatment for Obstructive Sleep Apnea Chest, September 1, 2007; 132(3): 1057 - 1072. [Abstract] [Full Text] [PDF]

				S. P. Patil, H. Schneider, A. R. Schwartz, and P. L. Smith Adult Obstructive Sleep Apnea: Pathophysiology and Diagnosis Chest, July 1, 2007; 132(1): 325 - 337. [Abstract] [Full Text] [PDF]

				R. F. Fregosi, S. F. Quan, W. L. Morgan, J. L. Goodwin, R. Cabrera, I. Shareif, K. W. Fridel, and R. R. Bootzin Pharyngeal critical pressure in children with mild sleep-disordered breathing J Appl Physiol, September 1, 2006; 101(3): 734 - 739. [Abstract] [Full Text] [PDF]

				F. Lofaso, G. Desmarais, K. Leroux, V. Zalc, R. Fodil, D. Isabey, and B. Louis Bench evaluation of flow limitation detection by automated continuous positive airway pressure devices. Chest, August 1, 2006; 130(2): 343 - 349. [Abstract] [Full Text] [PDF]

				A. S. Jordan, A. Wellman, J. K. Edwards, K. Schory, L. Dover, M. MacDonald, S. R. Patel, R. B. Fogel, A. Malhotra, and D. P. White Respiratory control stability and upper airway collapsibility in men and women with obstructive sleep apnea J Appl Physiol, November 1, 2005; 99(5): 2020 - 2027. [Abstract] [Full Text] [PDF]

				R. C. Heinzer, M. L. Stanchina, A. Malhotra, R. B. Fogel, S. R. Patel, A. S. Jordan, K. Schory, and D. P. White Lung Volume and Continuous Positive Airway Pressure Requirements in Obstructive Sleep Apnea Am. J. Respir. Crit. Care Med., July 1, 2005; 172(1): 114 - 117. [Abstract] [Full Text] [PDF]

				T. Inazawa, T. Ayuse, S. Kurata, I. Okayasu, E. Sakamoto, K. Oi, H. Schneider, and A.R. Schwartz Effect of Mandibular Position on Upper Airway Collapsibility and Resistance J. Dent. Res., June 1, 2005; 84(6): 554 - 558. [Abstract] [Full Text] [PDF]

				R. Farre, J.M. Montserrat, and D. Navajas Noninvasive monitoring of respiratory mechanics during sleep Eur. Respir. J., December 1, 2004; 24(6): 1052 - 1060. [Abstract] [Full Text] [PDF]

				K. F. Mansour, J. A. Rowley, and M. S. Badr Noninvasive determination of upper airway resistance and flow limitation J Appl Physiol, November 1, 2004; 97(5): 1840 - 1848. [Abstract] [Full Text] [PDF]

				T. Ayuse, T. Inazawa, S. Kurata, I. Okayasu, E. Sakamoto, K. Oi, H. Schneider, and A.R. Schwartz Mouth-opening Increases Upper-airway Collapsibility without Changing Resistance during Midazolam Sedation J. Dent. Res., September 1, 2004; 83(9): 718 - 722. [Abstract] [Full Text] [PDF]

				A. Noseda, C. Kempenaers, M. Kerkhofs, S. Braun, P. Linkowski, and E. Jann Constant vs Auto-Continuous Positive Airway Pressure in Patients With Sleep Apnea Hypopnea Syndrome and a High Variability in Pressure Requirement Chest, July 1, 2004; 126(1): 31 - 37. [Abstract] [Full Text] [PDF]

				C. L. Marcus, L. B. Fernandes Do Prado, J. Lutz, E. S. Katz, C. A. Black, P. Galster, and K. A. Carson Developmental changes in upper airway dynamics J Appl Physiol, July 1, 2004; 97(1): 98 - 108. [Abstract] [Full Text] [PDF]

				J.F. Masa, J. Corral, M.J. Martin, J.A. Riesco, A. Sojo, M. Hernandez, and N.J. Douglas Assessment of thoracoabdominal bands to detect respiratory effort-related arousal Eur. Respir. J., October 1, 2003; 22(4): 661 - 667. [Abstract] [Full Text] [PDF]

				S. T. Kuna Can Continuous Positive Airway Pressure Be Self-Titrated? Am. J. Respir. Crit. Care Med., March 1, 2003; 167(5): 674 - 675. [Full Text] [PDF]

				H. Trang, V. Leske, and C. Gaultier Use of Nasal Cannula for Detecting Sleep Apneas and Hypopneas in Infants and Children Am. J. Respir. Crit. Care Med., August 15, 2002; 166(4): 464 - 468. [Abstract] [Full Text] [PDF]

				ATS/ERS Statement on Respiratory Muscle Testing Am. J. Respir. Crit. Care Med., August 15, 2002; 166(4): 518 - 624. [Full Text] [PDF]

				S. J. Heitman, R. S. Atkar, E. A. Hajduk, R. A. Wanner, and W. W. Flemons Validation of Nasal Pressure for the Identification of Apneas/Hypopneas during Sleep Am. J. Respir. Crit. Care Med., August 1, 2002; 166(3): 386 - 391. [Abstract] [Full Text] [PDF]

				A. R. Gold, C. L. Marcus, F. Dipalo, and M. S. Gold Upper Airway Collapsibility During Sleep in Upper Airway Resistance Syndrome* Chest, May 1, 2002; 121(5): 1531 - 1540. [Abstract] [Full Text] [PDF]

				B. FAUROUX, J. PIGEOT, M. I. POLKEY, G. ROGER, M. BOULE, A. CLEMENT, and F. LOFASO Chronic Stridor Caused by Laryngomalacia in Children . Work of Breathing and Effects of Noninvasive Ventilatory Assistance Am. J. Respir. Crit. Care Med., November 15, 2001; 164(10): 1874 - 1878. [Abstract] [Full Text] [PDF]

				K. I. Berger, I. Ayappa, B. Chatr-amontri, A. Marfatia, I. B. Sorkin, D. M. Rapoport, and R. M. Goldring Obesity Hypoventilation Syndrome as a Spectrum of Respiratory Disturbances During Sleep Chest, October 1, 2001; 120(4): 1231 - 1238. [Abstract] [Full Text] [PDF]

				F. Series and I. Marc Importance of sleep stage- and body position-dependence of sleep apnoea in determining benefits to auto-CPAP therapy Eur. Respir. J., July 1, 2001; 18(1): 170 - 175. [Abstract] [Full Text] [PDF]

				R. Farre, J. Rigau, J.M. Montserrat, E. Ballester, and D. Navajas Evaluation of a simplified oscillation technique for assessing airway obstruction in sleep apnoea Eur. Respir. J., March 1, 2001; 17(3): 456 - 461. [Abstract] [Full Text] [PDF]

				R. Thurnheer, P. K. Wraith, and N. J. Douglas Influence of age and gender on upper airway resistance in NREM and REM sleep J Appl Physiol, March 1, 2001; 90(3): 981 - 988. [Abstract] [Full Text] [PDF]

				W. J. RANDERATH, O. SCHRAEDER, W. GALETKE, F. FELDMEYER, and K.-H. RUHLE Autoadjusting CPAP Therapy Based on Impedance Efficacy, Compliance and Acceptance Am. J. Respir. Crit. Care Med., March 1, 2001; 163(3): 652 - 657. [Abstract] [Full Text] [PDF]

				L. Hernandez, E. Ballester, R. Farre, J. R. Badia, R. Lobelo, D. Navajas, and J. M. Montserrat Performance of Nasal Prongs in Sleep Studies : Spectrum of Flow-Related Events Chest, February 1, 2001; 119(2): 442 - 450. [Abstract] [Full Text] [PDF]

				P. Kowallik, I. Jacobi, A. Jirmann, M. Meesmann, M. Schmidt, and H. Wirtz Breath-to-Breath Variability Correlates With Apnea-Hypopnea Index in Obstructive Sleep Apnea Chest, February 1, 2001; 119(2): 451 - 459. [Abstract] [Full Text] [PDF]

				R. FARRÉ, J. RIGAU, J. M. MONTSERRAT, E. BALLESTER, and D. NAVAJAS Relevance of Linearizing Nasal Prongs for Assessing Hypopneas and Flow Limitation During Sleep Am. J. Respir. Crit. Care Med., February 1, 2001; 163(2): 494 - 497. [Abstract] [Full Text]

				T. Aittokallio, T. Saaresranta, P. Polo-Kantola, O. Nevalainen, and O. Polo Analysis of Inspiratory Flow Shapes in Patients With Partial Upper-Airway Obstruction During Sleep Chest, January 1, 2001; 119(1): 37 - 44. [Abstract] [Full Text] [PDF]

				A. Boudewyns, N. Punjabi, P. H. Van de Heyning, W. A. De Backer, C. P. O'Donnell, H. Schneider, P. L. Smith, and A. R. Schwartz Abbreviated Method for Assessing Upper Airway Function in Obstructive Sleep Apnea Chest, October 1, 2000; 118(4): 1031 - 1041. [Abstract] [Full Text] [PDF]

				K. REES, R. N. KINGSHOTT, P. K. WRAITH, and N. J. DOUGLAS Frequency and Significance of Increased Upper Airway Resistance during Sleep Am. J. Respir. Crit. Care Med., October 1, 2000; 162(4): 1210 - 1214. [Abstract] [Full Text] [PDF]

				M P Bureau and F Sériès Comparison of two in-laboratory titration methods to determine effective pressure levels in patients with obstructive sleep apnoea Thorax, September 1, 2000; 55(9): 741 - 745. [Abstract] [Full Text]

				M. D. Epstein, S. A. Chicoine, and R. C. Hanumara Detection of Upper Airway Resistance Syndrome Using a Nasal Cannula/Pressure Transducer Chest, April 1, 2000; 117(4): 1073 - 1077. [Abstract] [Full Text] [PDF]

				Y. Kawauchi, T. Oshima, S. Suzuki, Y. Saitoh, and H. Toyooka Advancement of the mandible facilitates nasal breathing in human subjects sedated with midazolam Can J Anesth, March 1, 2000; 47(3): 215 - 219. [Abstract] [Full Text] [PDF]

				E. C. Fletcher, J. Stich, and K. L. Yang Unattended Home Diagnosis and Treatment of Obstructive Sleep Apnea Without Polysomnography Arch Fam Med, February 1, 2000; 9(2): 168 - 174. [Abstract] [Full Text] [PDF]

				A. Oksenberg, D. S. Silverberg, E. Arons, and H. Radwan The Sleep Supine Position Has a Major Effect on Optimal Nasal Continuous Positive Airway Pressure : Relationship With Rapid Eye Movements and Non-Rapid Eye Movements Sleep, Body Mass Index, Respiratory Disturbance Index, and Age Chest, October 1, 1999; 116(4): 1000 - 1006. [Abstract] [Full Text] [PDF]

				C. L. Marcus, J. Lutz, A. Hamer, P. L. Smith, and A. Schwartz Developmental changes in response to subatmospheric pressure loading of the upper airway J Appl Physiol, August 1, 1999; 87(2): 626 - 633. [Abstract] [Full Text] [PDF]

				R. P Smith, J. Argod, J.-L. Pépin, and P. A Lévy Pulse transit time: an appraisal of potential clinical applications Thorax, May 1, 1999; 54(5): 452 - 457. [Full Text]

				E. Bijaoui, S. A. Tuck, J. E. Remmers, and J. H. T. Bates Estimating respiratory mechanics in the presence of flow limitation J Appl Physiol, January 1, 1999; 86(1): 418 - 426. [Abstract] [Full Text] [PDF]

				J. ARGOD, J.-L. PEPIN, and P. LEVY Differentiating Obstructive and Central Sleep Respiratory Events through Pulse Transit Time Am. J. Respir. Crit. Care Med., December 1, 1998; 158(6): 1778 - 1783. [Abstract] [Full Text] [PDF]

				F. Series and I. Marc Effects of inspiratory and expiratory positive pressure difference on airflow dynamics during sleep J Appl Physiol, November 1, 1998; 85(5): 1855 - 1862. [Abstract] [Full Text] [PDF]

				S. A. CLARK, C. R. WILSON, M. SATOH, D. PEGELOW, and J. A. DEMPSEY Assessment of Inspiratory Flow Limitation Invasively and Noninvasively during Sleep Am. J. Respir. Crit. Care Med., September 1, 1998; 158(3): 713 - 722. [Abstract] [Full Text] [PDF]

				J H Ficker, G H Wiest, G Lehnert, B Wiest, and E G Hahn Evaluation of an auto-CPAP device for treatment of obstructive sleep apnoea Thorax, August 1, 1998; 53(8): 643 - 648. [Abstract] [Full Text]

				C. L. Marcus, J. Lutz, J. L. Carroll, and O. Bamford Arousal and ventilatory responses during sleep in children with obstructive sleep apnea J Appl Physiol, June 1, 1998; 84(6): 1926 - 1936. [Abstract] [Full Text] [PDF]

				R. FARRE, R. PESLIN, J. M. MONTSERRAT, M. ROTGER, and D. NAVAJAS Flow-dependent Positive Airway Pressure to Maintain Airway Patency in Sleep Apnea-Hypopnea Syndrome Am. J. Respir. Crit. Care Med., June 1, 1998; 157(6): 1855 - 1863. [Abstract] [Full Text] [PDF]

				J.-J. HOSSELET, R. G. NORMAN, I. AYAPPA, and D. M. RAPOPORT Detection of Flow Limitation with a Nasal Cannula/ Pressure Transducer System Am. J. Respir. Crit. Care Med., May 1, 1997; 157(5): 1461 - 1467. [Abstract] [Full Text]

				D. NAVAJAS, R. FARRÉ, M. ROTGER, R. BADIA, M. P. de-MORALES, and J. M. MONTSERRAT Assessment of Airflow Obstruction during CPAP by Means of Forced Oscillation in Patients with Sleep Apnea Am. J. Respir. Crit. Care Med., May 1, 1997; 157(5): 1526 - 1530. [Abstract] [Full Text]