A29-16 Standardization of the Six-minute Walk Test Using a Ring-type Pulse Oximeter: Clinical Evaluation of a World-first Reflectance Device (Patent Pending)

Rationale

Systemic sclerosis-associated interstitial lung disease (SSc-ILD) requires precise monitoring of exertional desaturation for mortality prediction. The six-minute walk test (6MWT) is the gold standard for functional assessment, yet accurate SpO₂ monitoring in SSc patients presents significant technical challenges. Raynaud’s phenomenon and severe digital vasospasm frequently cause signal loss or “spurious hypoxemia” in conventional transmission-mode fingertip sensors targeting the nail bed. Literature indicates measurement failure in up to 37.7% of SSc patients, leading to inaccurate disease severity classification or inappropriate oxygen titration. Reliable, motion-tolerant monitoring is urgently needed to ensure clinical safety and data integrity for patients with severely impaired peripheral perfusion and microvascular dysfunction.

Methods

We evaluated a medical-grade ring-type pulse oximeter (patent pending) utilizing reflectance photoplethysmography (PPG) from the proximal phalanx, a site significantly less susceptible to vasospasm than distal digits. The device features a proprietary 6MWT mode specifically engineered to synchronize SpO₂, heart rate, and movement intensity using high-frequency sampling and advanced noise-reduction algorithms. Under IRB approval (R7-37,47), we compared its performance with conventional sensors in SSc-ILD patients during standardized 6MWT protocols. Accuracy was further validated using arterial blood gas (ABG) analysis as the reference standard in cases where conventional sensors failed to provide physiologically plausible data.

Results

The ring-type device successfully provided stable and continuous SpO₂ readings in 100% of instances where conventional sensors exhibited signal loss. In a representative case of severe vasospasm, the ring recorded a stable SpO₂, while the fingertip sensor failed to generate any pulse signal. During 6MWT, conventional sensors frequently displayed alarming false-low values (averaging ∼60%) despite clinical stability and absence of symptoms. Conversely, the ring maintained reliable physiological tracking (85-97%) throughout exercise, preventing unnecessary and potentially biased test interruptions. The integrated smartphone system immediately generated standardized clinical reports, significantly enhancing clinician efficiency and reducing interobserver variability in data interpretation.

Conclusions

This study demonstrates the first successful standardization of the 6MWT using a ring-type oximeter. This patent-pending technology overcomes technical barriers in physiological monitoring for patients with digital circulatory failure. Beyond exercise testing, its waterproof and motion-resilient design supports continuous monitoring during high-risk daily activities, such as bathing, where chronic respiratory patients are vulnerable to sudden hypoxemia. This innovation facilitates accurate functional assessment and remote monitoring in real-world settings. Our findings define a new potential standard of care for SSc-ILD and other chronic respiratory conditions requiring robust, objective functional data to optimize patient management, therapeutic decision-making, and long-term clinical safety.

This abstract is funded by: This study was supported by the provision of ring-type pulse oximeter devices from Shinsei Corporation for research purposes. No other external funding was received.