Accuracy of thermistors and thermocouples as flow-measuring devices for detecting hypopnoeas

The aim of this work was to assess the accuracy of thermistors/thermocouples as devices for detecting hypopnoeas in sleep studies. Conventional thermistor/thermocouples were studied with a respiratory model allowing the simulation of inspiratory (22 degrees C) and expiratory (37 degrees C) flows. The thermistor signal (V'th) was compared with a pneumotachograph (V'th): 1) for sinusoidal and square-wave airflows (+/-0.05 to +/-0.8 L.s(-1), 10-20 breaths.min(-1) (bpm)); 2) when changing the distance from the thermistor to the nose (0-20 mm); and 3) when doubling the section of the nostrils. The thermistor was strongly nonlinear and flow reductions (hypopnoeas) were underestimated: a 50% reduction in V' (+/-0.5 L.s(-1), 15 bpm, sinusoidal) resulted in only an 18% reduction in V'th. V'th depended considerably on the airflow pattern: for V'=+/-0.5 L.s(-1), V'th increased by 100% from sinusoidal (20 bpm) to square-wave (10 bpm). For V'=+/-0.5 L.s(-1), 15 bpm, sinusoidal flow, V'th increased by 79% when the distance thermistor-nose varied from 20-0 mm, and V'th decreased by 37% when doubling the nose section. We concluded that thermistor/thermocouples are inaccurate flow-measuring devices when used at the airflow conditions typical of sleep studies. Their use for quantifying hypopnoeas may lead to considerable underdetection of these respiratory events.

This article has been cited by other articles:

				B. V. Vaughn and P. Giallanza Technical Review of Polysomnography Chest, December 1, 2008; 134(6): 1310 - 1319. [Abstract] [Full Text] [PDF]

				H. Nakano, T. Tanigawa, Y. Ohnishi, H. Uemori, K. Senzaki, T. Furukawa, and S. Nishima Validation of a single-channel airflow monitor for screening of sleep-disordered breathing Eur. Respir. J., October 1, 2008; 32(4): 1060 - 1067. [Abstract] [Full Text] [PDF]

				H. Muzumdar and R. Arens Diagnostic Issues in Pediatric Obstructive Sleep Apnea Proceedings of the ATS, February 15, 2008; 5(2): 263 - 273. [Abstract] [Full Text] [PDF]

				I. Koutsourelakis, G. Georgoulopoulos, E. Perraki, E. Vagiakis, C. Roussos, and S. G. Zakynthinos Randomised trial of nasal surgery for fixed nasal obstruction in obstructive sleep apnoea Eur. Respir. J., January 1, 2008; 31(1): 110 - 117. [Abstract] [Full Text] [PDF]

				H. Nakano, T. Tanigawa, T. Furukawa, and S. Nishima Automatic detection of sleep-disordered breathing from a single-channel airflow record Eur. Respir. J., April 1, 2007; 29(4): 728 - 736. [Abstract] [Full Text] [PDF]

				I. Koutsourelakis, E. Vagiakis, C. Roussos, and S. Zakynthinos Obstructive sleep apnoea and oral breathing in patients free of nasal obstruction Eur. Respir. J., December 1, 2006; 28(6): 1222 - 1228. [Abstract] [Full Text] [PDF]

				R. B. Berry, G. L. Koch, S. Trautz, and M. H. Wagner Comparison of Respiratory Event Detection by a Polyvinylidene Fluoride Film Airflow Sensor and a Pneumotachograph in Sleep Apnea Patients Chest, September 1, 2005; 128(3): 1331 - 1338. [Abstract] [Full Text] [PDF]

				C. Sahlin, E. Svanborg, H. Stenlund, and K. A. Franklin Cheyne-Stokes respiration and supine dependency Eur. Respir. J., May 1, 2005; 25(5): 829 - 833. [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]

				A. Bachour and P. Maasilta Mouth Breathing Compromises Adherence to Nasal Continuous Positive Airway Pressure Therapy Chest, October 1, 2004; 126(4): 1248 - 1254. [Abstract] [Full Text] [PDF]

				M.R. Madronio, E. Di Somma, R. Stavrinou, J.P. Kirkness, E. Goldfinch, J.R. Wheatley, and T.C. Amis Older individuals have increased oro-nasal breathing during sleep Eur. Respir. J., July 1, 2004; 24(1): 71 - 77. [Abstract] [Full Text] [PDF]

				J R Stradling and R J O Davies Sleep {middle dot} 1: Obstructive sleep apnoea/hypopnoea syndrome: definitions, epidemiology, and natural history Thorax, January 1, 2004; 59(1): 73 - 78. [Abstract] [Full Text] [PDF]

				P. Bottini, M.L. Dottorini, M. Cristina Cordoni, G. Casucci, and C. Tantucci Sleep-disordered breathing in nonobese diabetic subjects with autonomic neuropathy Eur. Respir. J., October 1, 2003; 22(4): 654 - 660. [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. 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]

				C. CRACOWSKI, J.-L. PEPIN, B. WUYAM, and P. LEVY Characterization of Obstructive Nonapneic Respiratory Events in Moderate Sleep Apnea Syndrome Am. J. Respir. Crit. Care Med., September 15, 2001; 164(6): 944 - 948. [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]

				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]

				D. E. WEESE-MAYER, M. J. CORWIN, M. R. PEUCKER, J. M. DI FIORE, D. R. HUFFORD, L. R. TINSLEY, M. R. NEUMAN, R. J. MARTIN, L. J. BROOKS, S. L. DAVIDSON WARD, et al. Comparison of Apnea Identified by Respiratory Inductance Plethysmography with That Detected by End-tidal CO2 or Thermistor Am. J. Respir. Crit. Care Med., August 1, 2000; 162(2): 471 - 480. [Abstract] [Full Text] [PDF]

				J. ARGOD, J.-L. PÉPIN, R. P. SMITH, and P. LÉVY Comparison of Esophageal Pressure with Pulse Transit Time as a Measure of Respiratory Effort for Scoring Obstructive Nonapneic Respiratory Events Am. J. Respir. Crit. Care Med., July 1, 2000; 162(1): 87 - 93. [Abstract] [Full Text]

				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]