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Accuracy of autotitrating CPAP to estimate the residual Apnea–Hypopnea Index in patients with obstructive sleep apnea on treatment with autotitrating CPAP

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Abstract

Objective

Autotitrating continuous positive airway pressure (auto-CPAP) devices now have a smart card (a pocket-sized card with embedded integrated circuits which records data from the CPAP machine such as CPAP usage, CPAP pressure, large leak, etc.) which can estimate the Apnea–Hypopnea Index (AHI) on therapy. The aim of this study was to determine the accuracy of auto-CPAP in estimating the residual AHI in patients with obstructive sleep apnea (OSA) who were treated with auto-CPAP without a CPAP titration study.

Patients and Methods

We studied 99 patients with OSA from April 2005 to May 2007 who underwent a repeat sleep study using auto-CPAP. The estimated AHI from auto-CPAP was compared with the AHI from an overnight polysomnogram (PSG) on auto-CPAP using Bland–Altman plot and likelihood ratio analyses. A PSG AHI cutoff of five events per hour was used to differentiate patients optimally treated with auto-CPAP from those with residual OSA on therapy.

Results

Bland and Altman analysis showed good agreement between auto-CPAP AHI and PSG AHI. There was no significant bias when smart card estimates of AHI at home were compared to smart card estimates obtained in the sleep laboratory. An auto-CPAP cutoff for the AHI of six events per hour was shown to be optimal for differentiating patients with and without residual OSA with a sensitivity of 0.92 (95% confidence interval (CI) 0.76 to 0.98) and specificity of 0.90 (95% CI 0.82 to 0.95) with a positive likelihood ratio (LR) of 9.6 (95% CI 5.1 to 21.5) and a negative likelihood ratio of 0.085 (95% CI 0.02 to 0.25). Auto-CPAP AHI of eight events per hour yielded the optimal sensitivity (0.94, 95% CI 0.73 to 0.99) and specificity (0.90, 95% CI 0.82 to 0.95) with a positive LR of 9.6 (95% CI 5.23 to 20.31) and a negative LR of 0.065 (95% CI 0.004 to 0.279) to identify patients with a PSG AHI of  ≥ 10 events per hour.

Conclusion

Auto-CPAP estimate of AHI may be used to estimate residual AHI in patients with OSA of varying severity treated with auto-CPAP.

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Acknowledgements

Work was performed at: Western New York Veteran Affairs Healthcare System, Buffalo, New York.

Himanshu Desai, M.D., has no financial or personal conflict of interest in presenting this manuscript.

Anil Patel, M.D., has no financial or personal conflict of interest in presenting this manuscript.

Pinal Patel, M.B.B.S., has no financial or personal conflict of interest in presenting this manuscript.

Brydon J. B. Grant, M.D., has no financial or personal conflict of interest in presenting this manuscript.

M Jeffrey Mador, M.D., has no financial or personal conflict of interest in presenting this manuscript.

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Correspondence to M. Jeffery Mador.

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Desai, H., Patel, A., Patel, P. et al. Accuracy of autotitrating CPAP to estimate the residual Apnea–Hypopnea Index in patients with obstructive sleep apnea on treatment with autotitrating CPAP. Sleep Breath 13, 383–390 (2009). https://doi.org/10.1007/s11325-009-0258-2

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  • DOI: https://doi.org/10.1007/s11325-009-0258-2

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