Pairing Rapid Prototyping with Wireframes and UI Design

Project Overview

This case study details the user experience (UX) design process for the Nevro Patient Therapy App (PTA) and Pathfinder applications. Developed in collaboration between Karten Design and Nevro with Velentium as the development partner, these applications aimed to provide patients with enhanced control and insights into their HFX implant therapy. The project focused on creating intuitive interfaces for managing stimulation, tracking progress, and receiving personalized recommendations.

Project Duration: Feb 2018 – October 2018

Design Roadmap

Our design process was iterative and collaborative, comprising of an initial 3-month design sprint followed by six bi-weekly sprints. We had weekly reviews for continuous feedback from Nevro and Velentium. Key phases included:

1. Information Architecture & User Flows: Mapping core navigation pathways for onboarding, daily therapy adjustments, and pain logging.
2. Wireframing & Visual Design: Building low-fidelity structural layouts in tandem with a visual designer who established the production UI language.
3. Interactive Prototyping: Creating prototypes to test physical device pairing routines and custom slider mechanics.
4. Spec Documentation & Content Inventory: Tagging wireframe elements with a permanent alphanumeric ID system linked to a master copy directory.

Product Strategy: Consolidating Two Apps Into One

Patients using the Nevro HFX implant for chronic pain needed a reliable mobile app to adjust therapy programs and log daily outcomes. Initially, the client requested two separate apps:

• Nevro PTA (Patient Therapy App): A manual remote-control app for daily stimulation adjustments and basic pain tracking.
• Nevro Pathfinder: An automated recommendation tool that suggested new program settings based on logged survey data.

Having two standalone apps for the same medical hardware presented clear usability issues: patients would have to switch between apps to manage a single device, creating confusion and doubling engineering maintenance. I recommended merging both toolsets into a single, unified application structure, simplifying the experience for patients and reducing long-term code complexity.

Core UX Priorities

• Clarity: Simplifying complex medical device controls into clear, recognizable interface patterns.
• Patient Engagement: Making daily pain journaling feel quick and rewarding without overwhelming the user.
• Accessibility (FDA Requirement): Structuring the DOM hierarchy to fully support screen readers and dynamic text sizing.

Onboarding & Hardware Pairing

The initial setup flow was critical for a smooth patient onboarding experience. Key steps included:

• EULA Acceptance – Ensuring required medical disclaimers were read and accepted.
• Compatibility Check – Verifying the phone’s operating system and Bluetooth version supported the implant hardware.
• Bluetooth Discovery & Pairing – Guiding the user through searching for and pairing with their implanted device.
• Profile Setup – Personalizing therapy goals and selecting target pain areas.
• Push Notifications – Setting up gentle reminders for daily pain surveys.
• App Security – Adding PIN and biometric protection to prevent accidental adjustments.

Onboarding User Flows

Use the arrows below to browse through the onboarding wireflows.

Testing the Onboarding Flow

Below is an early prototype walkthrough demonstrating how we tested the Bluetooth setup and hardware pairing flows with users.

Final UI: Bluetooth Pairing States

Following prototype feedback, our visual designer created step-by-step animations and UI states to guide patients clearly through hardware pairing.

Designing Around Physical System Latency

When a patient adjusts stimulation levels in the app, there is a physical delay while the phone sends the Bluetooth signal to the implanted device and receives confirmation back. To prevent patients from tapping repeatedly or worrying that the app froze, we designed explicit loading transitions that clearly show signal progress during these delay windows.

Stimulation Controls & Feedback States

Data Visualization & Pain Progress Tracking

To give patients useful feedback on how their treatment was progressing, we designed clear data summary screens showing pain scores over time.

Below are three early prototype variations we tested to evaluate different graph layouts and scrolling behaviors:

Timing Prompts Around Treatment Cycles

Implanted spinal stimulators require roughly 48 hours for a patient’s body to adjust to a new setting. Prompting a patient for a pain survey right after a setting change yields inaccurate data. To address this, the UI suppresses survey prompts during the 48-hour adjustment window, then displays a clear survey banner on the home screen when it’s time to log feedback.

Survey Flows & Screen States

Home Screen Survey Prompts

Survey Wireflow Map

Survey Cards & Exit Confirmations

Hardware State Alerts

Device alerts—such as low battery or lost Bluetooth connection—are displayed cleanly in the app header and via OS push notifications.

Leveraging Content Strategy to Mitigate Risk

In medical software, interface text and safety disclaimers go through continuous legal and clinical review. Updating text strings directly inside design files during early sprints created unnecessary bottlenecks for our stakeholders at Nevro and our development partners.

To mitigate this risk, I implemented a content inventory system that comprised of a spreadsheet and annotation IDs. Every single piece of text, instructional copy, default field value, list of menu options, header, error, and alert in the wireframes was tagged with an annotation marker, whose corresponding row in the spreadsheet contained copy and any conditional logic rules if applicable. Medical and legal leads could update wording directly in the spreadsheet without requiring designer edits to the wireframes and UI design files on a weekly basis.

This approach also makes it much easier to implement multi-lingual and localization features, which are required for compliance with FDA regulations.