RESUMEN
Orthostatic hypotension (OH) is prevalent in older adults and can cause falls and hospitalization. Diagnostic intermittent blood pressure (BP) measurements are only a proxy for cerebral perfusion and do not reflect daily-life BP fluctuations. Near-infrared spectroscopy (NIRS)-measured cerebral oxygenation potentially overcomes these drawbacks. This study aimed to determine feasibility, face validity, and reliability of NIRS in the home environment. Ten participants with OH (2 female, mean age 77, SD 3.7) and 11 without OH (5 female, mean age 78, SD 6.7) wore a NIRS sensor at home on two different days for 10-11 h per day. Preceded by a laboratory-situated test, cerebral oxygenation was measured during three standardized supine-stand tests per day and during unsupervised daily life activities. Data availability, quality, and user experience were assessed (feasibility), as well as differences in posture-related oxygenation responses between participants with and without OH and between symptomatic (dizziness, light-headedness, blurred vision) and asymptomatic postural changes (face validity). Reliability was assessed through repetitive supine-stand tests. Up to 80% of the standardized home-based supine-stand tests could be analyzed. Oxygenation recovery values were lower for participants with OH (p = 0 .03-0.15); in those with OH, oxygenation showed a deeper maximum drop for symptomatic than asymptomatic postural changes (p = 0.04). Intra-class correlation coefficients varied from 0.07 to 0.40, with no consistent differences over measurements. This proof-of-concept study shows feasibility and face validity of at-home oxygenation monitoring using NIRS, confirming its potential value for diagnosis and monitoring in OH and OH-related symptoms. Further data are needed for conclusions about reliability.
RESUMEN
BACKGROUND: Obstructive sleep apnea (OSA) is a highly prevalent condition; however, the majority of patients remain undiagnosed. There is a potential to expand the diagnostic capacity of sleep laboratories. The study objective was to validate a portable respiratory monitoring device (Alice PDX) against polysomnography (PSG) in the laboratory and to assess its reliability at home. METHODS: A total of 85 patients with suspected OSA (80% male, mean age 49.1±13.5 years, body mass index 29.7±6.9 kg/m2, Epworth Sleepiness Scale 10.0±5.1) were randomized to 3 diagnostic nights: 1 night simultaneous in-laboratory PSG and PDX recording; 1 night self-applied PDX at home, and 1 night in-laboratory PSG. Study data were manually scored according to American Academy of Sleep Medicine criteria. RESULTS: The Alice PDX was in diagnostic agreement with simultaneously recorded reference PSG in 96.4% of studies. In 2.4% of studies the in-laboratory PDX underestimated and in 1.2% of studies it overestimated the apnea hypopnea index (AHI). The difference between the AHI from the reference PSG and the home study was similar to the difference between the PSGs (2.79 vs 0.79, p=0.08). CONCLUSION: In a population with a high suspicion of OSA, the Alice PDX showed a high level of diagnostic agreement with a simultaneous PSG and performed valid home diagnostic studies for OSA. If manually scored, the portable device can be used by sleep specialists for diagnosing moderate-to-severe obstructive sleep apnea in cases with a high pretest probability for the disease over a wide range of disease severity. The technology can be deployed reliably outside of the sleep laboratory setting.