Getting the Most Out of Nocturnal Pulse Oximetry

Abstract

Due to its noninvasive nature and the convenient patient interface consisting of a small sensor clipped or taped onto the skin, pulse oximetry is widely used in pulmonary medicine, critical care, and anesthesia. In sleep medicine, pulse oximetry is an essential tool for tracking the rapid fluctuations in arterial oxygen saturation that are characteristic for the unstable ventilation in patients with sleep apnea. Pulse oximetry has provided early insights into sleep-related breathing disturbances,1Block AJ Boysen PG Wynne JW et al.Sleep apnea, hypopnea and oxygen desaturation in normal subjects.N Engl J Med. 1979; 300: 513-517Crossref PubMed Scopus (470) Google Scholar and has opened the way for subsequent systematic investigations of sleep apnea. Today, the technique is an integral component of polysomnography and, by itself, is commonly used as a simple tool in the evaluation of sleep apnea. The clinical relevance of indexes derived from pulse oximetry alone or combined with other techniques that detect nocturnal breathing disturbances is emphasized by their correlation with impaired cognitive performance, cardiovascular diseases, and other consequences of sleep apnea.2Cheshire K Engleman H Deary I et al.Factors impairing daytime performance in patients with sleep apnea/hypopnea syndrome.Arch Intern Med. 1992; 152: 538-541Crossref PubMed Scopus (305) Google Scholar3Peppard PE Young T Palta M et al.Prospective study of the association between sleep-disordered breathing and hypertension.N Engl J Med. 2000; 342: 1378-1384Crossref PubMed Scopus (3915) Google Scholar Over the last few years, the development of pulse oximetry has progressed in three major domains: first, the size and weight of the hardware have been reduced so that most devices are now portable, and some are even available in miniaturized form; second, paper chart recordings have been replaced by digital signal acquisition; third, novel mathematical and statistical techniques are being applied to computer-assisted analysis of pulse oximetry recordings. This is particularly useful and efficient for processing overnight recordings extending over several hours. While conventional analysis of nocturnal pulse oximetry has consisted of visual inspection of tracings for identification of desaturation events, baseline and minimal values, and patterns of fluctuations in oxygen saturation,4Cooper BG Veale D Griffiths CJ et al.Value of nocturnal oxygen saturation as a screening test for sleep apnoea.Thorax. 1991; 46: 586-588Crossref PubMed Scopus (72) Google Scholar5Sériès F Marc I Cormier Y et al.Utility of nocturnal home oximetry for case finding in patients with suspected obstructive sleep apnea hypopnea syndrome.Ann Intern Med. 1993; 119: 449-453Crossref PubMed Scopus (189) Google Scholar6Epstein LJ Dorlac GR Cost-effectiveness analysis of nocturnal oximetry as a method of screening for sleep apnea-hypopnea syndrome.Chest. 1998; 113: 97-103Abstract Full Text Full Text PDF PubMed Scopus (87) Google Scholar this kind of subjective interpretation is being replaced by computerized scoring to automatically and objectively derive the variables previously obtained by tedious manual scoring. Additionally, computer analysis provides the opportunity to process pulse oximetry data by powerful statistical and mathematical methods. Several indexes derived by these techniques are listed in the Table 1, along with references to studies that have evaluated the diagnostic performance of nocturnal pulse oximetry with computer-assisted analysis for identification of patients with sleep apnea. The sensitivity of pulse oximetry ranged from 88 to 98%, and the specificity from 40 to 88% if an apnea/hypopnea index of 10/h or 15/h measured during polysomnography was defined as the upper limit of normal.5Sériès F Marc I Cormier Y et al.Utility of nocturnal home oximetry for case finding in patients with suspected obstructive sleep apnea hypopnea syndrome.Ann Intern Med. 1993; 119: 449-453Crossref PubMed Scopus (189) Google Scholar7Lévy P Pépin JL Deschaux-Blanc C et al.Accuracy of oximetry for detection of respiratory disturbances in sleep apnea syndrome.Chest. 1996; 109: 395-399Abstract Full Text Full Text PDF PubMed Scopus (166) Google Scholar8Olson LG Ambrogetti A Gyulay SG Prediction of sleep-disordered breathing by unattended overnight oximetry.J Sleep Res. 1999; 8: 51-55Crossref PubMed Scopus (64) Google Scholar9Vásques J Tsai WH Flemons WW et al.Automated analysis of digital oximetry in the diagnosis of obstructive sleep apnea.Thorax. 2002; 55: 302-307Google Scholar10Taha BH Dempsey JA Weber SM Automated detection and classification of sleep-disordered breathing from conventional polysomnography data.Sleep. 1997; 20: 991-1001Crossref PubMed Scopus (59) Google Scholar11Rauscher H Popp W Zwick H Computerized detection of respiratory events during sleep from rapid increases in oxyhemoglobin saturation.Lung. 1991; 169: 335-342Crossref PubMed Scopus (31) Google Scholar12Gyulay S Olson LG Hensley MJ et al.A comparison of clinical assessment and home oximetry in the diagnosis of obstructive sleep apnea.Am Rev Respir Dis. 1993; 147: 50-53Crossref PubMed Scopus (178) Google Scholar13Chesson AL Anderson WM Walls RC et al.Assessment of hypoxemia in patients with sleep disorders using saturation impairment time.Am Rev Respir Dis. 1993; 148: 1592-1598Crossref PubMed Google Scholar14Pépin JL Lévy P Lapaulle B et al.Does oximetry contribute to the detection of apneic events? Mathematical processing of the Sao2signal.Chest. 1991; 99: 1151-1157Abstract Full Text Full Text PDF PubMed Scopus (42) Google Scholar15Zamarrón C Gude F Barcala J et al.Utility of oxygen saturation and heart rate spectral analysis obtained from pulse oximetric recordings in the diagnosis of sleep apnea syndrome.Chest. 2003; 123: 1567-1576Abstract Full Text Full Text PDF PubMed Scopus (80) Google ScholarTable 1Indices Derived From Computer-Assisted Nocturnal Pulse Oximetry*IndexDescriptionSourceDesaturation or resaturation index (D2%, D3%, D4%)Number of dips or of rapid increases in oxygen saturation by a certain amount per hourVásques et al,9Vásques J Tsai WH Flemons WW et al.Automated analysis of digital oximetry in the diagnosis of obstructive sleep apnea.Thorax. 2002; 55: 302-307Google Scholar Taha et al,10Taha BH Dempsey JA Weber SM Automated detection and classification of sleep-disordered breathing from conventional polysomnography data.Sleep. 1997; 20: 991-1001Crossref PubMed Scopus (59) Google Scholar Rauscher et al11Rauscher H Popp W Zwick H Computerized detection of respiratory events during sleep from rapid increases in oxyhemoglobin saturation.Lung. 1991; 169: 335-342Crossref PubMed Scopus (31) Google ScholarCumulative time with low oxygen saturation (CT90, CT80, etc)Cumulative time spent below a certain threshold of oxygen saturationGyulay et al12Gyulay S Olson LG Hensley MJ et al.A comparison of clinical assessment and home oximetry in the diagnosis of obstructive sleep apnea.Am Rev Respir Dis. 1993; 147: 50-53Crossref PubMed Scopus (178) Google ScholarSaturation impairment timeIndex that integrates severity and duration of oxygen desaturationChesson et al13Chesson AL Anderson WM Walls RC et al.Assessment of hypoxemia in patients with sleep disorders using saturation impairment time.Am Rev Respir Dis. 1993; 148: 1592-1598Crossref PubMed Google ScholarDelta indexVariability of oxygen saturation quantified by the mean of the absolute differences in successive oxygen saturation values sampled at 12-s intervalsLévy et al,7Lévy P Pépin JL Deschaux-Blanc C et al.Accuracy of oximetry for detection of respiratory disturbances in sleep apnea syndrome.Chest. 1996; 109: 395-399Abstract Full Text Full Text PDF PubMed Scopus (166) Google Scholar Pépin et al14Pépin JL Lévy P Lapaulle B et al.Does oximetry contribute to the detection of apneic events? Mathematical processing of the Sao2signal.Chest. 1991; 99: 1151-1157Abstract Full Text Full Text PDF PubMed Scopus (42) Google ScholarPeak in the oxygen saturation and pulse rate periodogramSpectral analysis of oxygen saturation and pulse rate is applied to evaluate the presence or absence of a peak in the periodogram within a period range of 30 to 70 s as a sign of periodic apnea/hypopneaZamarrón et al15Zamarrón C Gude F Barcala J et al.Utility of oxygen saturation and heart rate spectral analysis obtained from pulse oximetric recordings in the diagnosis of sleep apnea syndrome.Chest. 2003; 123: 1567-1576Abstract Full Text Full Text PDF PubMed Scopus (80) Google Scholar Open table in a new tab The introduction of various novel approaches to quantify pulse oximetric information requires an evaluation of the relative utility of derived indexes in the diagnosis of sleep-disordered breathing. In the current issue of CHEST (see page 1694), Magalang and coworkers report a systematic comparison of several indexes derived from computer-assisted nocturnal pulse oximetry. Three large cohorts of patients with suspected sleep apnea were examined at two different institutions. The investigation confirms that the Delta index (Table 1), and desaturation indexes that reflect the variability of oxygen saturation, have a similarly high diagnostic accuracy for detection of patients with the obstructive sleep apnea syndrome. Moreover, the authors demonstrate that combining several pulse oximetry-derived variables to an aggregated model enhances the diagnostic yield over that of individual indexes. The study represents an important contribution to the validation of computerized analysis and interpretation of nocturnal pulse oximetry. Nevertheless, the efforts to get the most out of this fascinating noninvasive technique should continue. With further technical developments, and the advancement in our understanding of sleep apnea, new questions arise. For example, it is not clear to what extent the dynamic response characteristics,16Farré R Montserrat JM Ballester E et al.Importance of pulse oximeter averaging time when measuring oxygen desaturation in sleep apnea.Sleep. 1998; 21: 386-390Crossref PubMed Scopus (57) Google Scholar artifact detection and rejection algorithms,17Brouillette RT Lavergne J Leimanis A et al.Differences in pulse oximetry technology can affect detection of sleep-disordered breathing in children.Anesth Analg. 2002; 94: S47-S53PubMed Google Scholar and other technical specifications that differ among various brands of pulse oximeters affect their performance in sleep apnea diagnosis. Finally, the principal discussion over the reference standard against which novel techniques in sleep apnea diagnostic should be evaluated is also relevant for pulse oximetry. It seems that future evaluations of pulse oximetry would be more meaningful if performed in regard to major clinical outcomes of sleep apnea rather than in comparisons with polysomnography, a technique that has its own limitations, and depends itself on pulse oximetry for the detection of breathing disturbances. eyJraWQiOiI4ZjUxYWNhY2IzYjhiNjNlNzFlYmIzYWFmYTU5NmZmYyIsImFsZyI6IlJTMjU2In0.eyJzdWIiOiJiY2ZhODFhMmE1MDkwODE4ODdmZjI2ZDRkMzZlOGVmOCIsImtpZCI6IjhmNTFhY2FjYjNiOGI2M2U3MWViYjNhYWZhNTk2ZmZjIiwiZXhwIjoxNjcyMDg4ODk2fQ.DWME09xqFD4DfJ9dRcK3K-Dg8-yub6eDPOIcUvZMadbTinOiJWI0Ts1GUfsJYv5xPOe_XwZHGCegrBWvXRtkBLd9zM28VMRg7aVLIZqatAu2DUqFgTmj-7fDLfTieyN72-SfqmG42U8B9EwSHyw_Gv2f6vUyp8I7O9JkaxO14ZfhRag469sELbMTUDF3ug9mKCOulk8WYNJme43DzoSaISDkIDf1MN9mDfj__ghoY9N8NL277TLiXau3ohBBZDFabYH7oW-7rDBoHK7Ugoua_AriS5O_qLcbvLl2Ey5bFEE6gGRixuYdXejoVZj1EDc6vaW55l1aYRGph8gxRLZH4w Download .mp4 (3.94 MB) Help with .mp4 files Supplementary appendix eyJraWQiOiI4ZjUxYWNhY2IzYjhiNjNlNzFlYmIzYWFmYTU5NmZmYyIsImFsZyI6IlJTMjU2In0.eyJzdWIiOiJlOTRhNGU4YWQ2MTUyMjQyODA0MGFjZGQzMGRlNzhmNCIsImtpZCI6IjhmNTFhY2FjYjNiOGI2M2U3MWViYjNhYWZhNTk2ZmZjIiwiZXhwIjoxNjcyMDg4ODk2fQ.AB6fsVz2JaHOsQxSUKVYY4BCVnyrkWetwYg2_CT-QiNayiNZUe6BYlXf_meCkjMIfCVjuEmj6UqWHJ74BZdSmTczOEWKwR_HeLSZDGhjtjIqq7LX2tSKpH_3jb5psp8F2kYxqT4gL7CT6NgdguCAaIZCHWwH0EGhBXxB_KfOoIeyKLp6vcKiXH0UrpQ6H0ni9T61tnVgB5sqbI9pOQna9E9Y27MxcedorApbBOcRbzidxe4S90gfbMOfCyU81k-HHS15Mu-gGIV4fWMpThMsLfn5q2N_kPPW---URcGzWxSYCMBfxIS42H9wmsbgP0opDrEl3CQ8iPq6Sl79LzW7Xw Download .mp4 (2.98 MB) Help with .mp4 files Supplementary appendix Download .zip (10.67 MB) Help with zip files Supplementary appendix