Background: Postoperative monitoring of Deep Inferior Epigastric Perforator (DIEP) flaps is essential to detect early signs of vascular compromise. Current standard methods rely heavily on clinical judgment and frequent bedside assessments, which are labor-intensive and less objective. Near-Infrared Spectroscopy (NIRS) offers a promising alternative for continuous, non-invasive flap monitoring, but existing systems are wired and bulky, limiting patient mobility. To address this, a wireless, wearable NIRS patch (SPECTRA) was developed.

Objective: The aim was to translate clinical requirements into technical solutions for a wearable
NIRS device for DIEP flap monitoring, with a focus on functionality, clinical usability, and patient experience.

Methods: An iterative development process was followed. In the exploratory phase, design and material variations were tested under different movement conditions using kurtosis as a metric for signal robustness. Tensile testing was conducted to assess the elasticity of adhesive materials. Focus groups with clinical staff were held to evaluate clinical usability, user needs, and design preferences. Functional performance was evaluated by comparing the SPECTRA measurements with a gold standard system during arm occlusion, and by assessing signal quality during motion activities. This study also provided insights into patient experience. Hereafter, a preliminary pilot study examined the influence of Fitzpatrick skin type on signal quality.

Results: In terms of functionality, the SPECTRA device successfully detected occlusion-related
changes with strong correlation to the gold standard, and demonstrated signal recovery after motion. However, some motion artifacts remained a challenge, and patterned adhesives did not significantly reduce them. Regarding clinical usability, focus group discussions highlighted the importance of clear alarm thresholds, intuitive display formats, and seam integration with existing hospital systems. For patient experience, participants generally described the device as comfortable, lightweight, and unobtrusive. Preliminary analysis suggested that participants with darker skin tones (Fitzpatrick V–VI) may experience reduced signal quality.

Conclusion: This thesis demonstrates that wearable NIRS technology can capture meaningful
physiological changes during DIEP flap monitoring and recover signal quality after motion. Future research should focus on improving motion robustness, ensuring equitable performance across skin tones, and optimizing patient comfort for extended wear. By advancing functionality, clinical usability, and patient experience in parallel, this work lays the foundation for a next-generation NIRS device, one that is wireless, inclusive, and clinically integrated.