Pediatric/Adolescent WatchPAT 400 Reliability Pilot Study

This is a prospective, single-center, blinded, within-subject diagnostic-accuracy pilot study. Each participant undergoes simultaneous overnight recording with both attended, technician-monitored polysomnography (PSG) - the clinically indicated standard-of-care test they are already scheduled for - and the WatchPAT 400 device, on the same single night. This within-subject design was chosen specifically to eliminate night-to-night physiological variability as a confounder in the agreement analysis, a limitation common to studies that compare sequential rather than simultaneous recordings.

Obstructive sleep apnea (OSA) affects an estimated 1-6% of children and is associated with meaningful health consequences if left undiagnosed and untreated, including behavioral and cognitive effects (attention, learning, hyperactivity), cardiovascular strain, and impaired growth. Because current diagnostic capacity is constrained by the resource intensity of PSG, many children with symptoms suggestive of OSA experience substantial delays before a formal diagnostic sleep study can be obtained, during which these consequences may accrue. A validated, less burdensome diagnostic alternative could meaningfully shorten that diagnostic gap.

OSA in children is conventionally diagnosed using attended, in-laboratory PSG, which requires a multi-sensor montage including EEG, EOG, chin/leg EMG, nasal airflow sensors, thoracoabdominal respiratory belts, and pulse oximetry. While PSG remains the diagnostic reference standard, it is resource-intensive, requires specialized pediatric sleep laboratory capacity that is not universally available, and can be poorly tolerated by some children due to the number and placement of sensors. Peripheral arterial tonometry (PAT)-based home sleep apnea testing has emerged as a substantially less burdensome alternative, using far fewer sensors, but has historically lacked adequate validation in pediatric populations. This study investigates whether the newest-generation PAT device can close that evidence gap.

The WatchPAT 400 derives its outputs from three primary physiological signals: a peripheral arterial tonometry (PAT) signal measured at the finger, which reflects sympathetic nervous system activity and vasomotor tone; pulse oximetry, which reflects peripheral oxygen saturation; and actigraphy, which distinguishes sleep from wake states and detects body position. An additional chest-worn sensor measures respiratory effort, snoring intensity, and body position. The device's proprietary algorithm combines these signals to automatically generate a PAT-derived apnea-hypopnea index (pAHI), respiratory disturbance index (pRDI), estimated sleep staging, oxygen desaturation metrics, hypoxic burden (a measure of the cumulative depth and duration of oxygen desaturation over the recording, distinct from simple event counts), and, in this newest device generation, a central apnea-hypopnea index (pAHIc) and automated flagging of candidate cardiac arrhythmia/premature-beat events. This algorithmic processing is a fixed, FDA-cleared feature of the commercial device and is not modified or developed by the study investigators; its output is independently reviewed by a blinded study physician rather than accepted as a final result.

The WatchPAT 400 builds on an earlier-generation device platform (WatchPAT 300, FDA 510(k) K180775) that has an existing, though limited, body of pediatric and adolescent validation literature reporting reasonable correlation with PSG-derived respiratory indices in patients generally 12 years of age and older. The WatchPAT 400 itself, however, was only FDA-cleared in September 2025 (510(k) K250460), and its newly added features - the central apnea index and hypoxic burden reporting in particular - have essentially no published pediatric validation data at the time this study was designed. This pilot is intended to generate some of the first such data.

Outcome interpretation in this study is blinded and bidirectional: one sleep physician scores the PSG without access to the WatchPAT recording or its automated report, while a second sleep physician independently scores the WatchPAT recording without access to the PSG results. This separation is intended to prevent either physician's interpretation from being influenced by the comparator, which is a common source of bias in prior device-validation literature.

Because most children referred for snoring do not, in fact, have clinically significant OSA, enrollment is enriched using a validated parent-reported symptom questionnaire (OSA-18) score threshold indicating at least moderate probability of pediatric OSA. This threshold was deliberately set to preserve a clinically meaningful spread of underlying OSA severity (rather than restricting to only the highest-probability referrals), so that the resulting cohort is expected to include participants with no OSA, mild OSA, moderate OSA, and severe OSA on PSG. This approach is intended to reduce the spectrum-bias risk common to diagnostic-accuracy pilot studies that enroll only clearly symptomatic, high-probability cases.

The study's statistical approach reflects its explicit framing as a Phase 1 pilot: the primary analysis (intraclass correlation coefficient with 95% confidence interval, and Bland-Altman limits of agreement between PSG-derived AHI and WatchPAT-derived pAHI) is powered to generate a preliminary but not definitive estimate of agreement, along with the population's actual OSA prevalence and device technical-failure rate. These pilot estimates are intended to inform the sample size of a subsequent, adequately powered Phase 2 confirmatory study (anticipated enrollment of approximately 100-150 participants), rather than to establish definitive diagnostic-accuracy claims on their own.

Secondary analyses include sensitivity, specificity, positive predictive value, and negative predictive value at standard AHI severity thresholds; Cohen's weighted kappa for inter-rater agreement on OSA severity category between the two blinded physicians; and an exploratory analysis of the device's central apnea index, which is analyzed within FDA labeling only for the subset of participants aged 17 and older, and as an explicitly investigational, off-label endpoint for younger participants.

Because the WatchPAT 400 automatically flags candidate cardiac arrhythmia/premature-beat events - a feature not present in the prior device generation, and one the manufacturer explicitly states is not intended as a cardiac diagnostic tool - any such flag generated during a study recording is reviewed by the principal investigator, who determines whether referral for further cardiac evaluation is clinically warranted, independent of and in addition to the participant's usual clinical care. The principal investigator also reviews accumulating safety and feasibility data at defined enrollment intervals throughout the study and has established criteria for suspending enrollment if safety or technical-performance concerns arise.

This is an investigator-initiated study, conducted without external industry sponsorship. Because WatchPAT 400 is used outside its FDA-cleared age indication for part of this study population, and its central apnea parameter is used outside labeling for participants younger than 17, this study is being conducted under a Non-Significant Risk (NSR) device determination per 21 CFR 812.2(b), with device results used for research comparison purposes only and not to guide any participant's clinical care. If this pilot demonstrates acceptable reliability, findings will directly inform the design of a larger confirmatory study and the longer-term goal of expanding validated, well-tolerated home sleep testing options for children, including populations who currently have particular difficulty completing conventional PSG.