Blundur (2015)

Blundur (“doze” in Icelandic) is a non-invasive sensor to quantify respiratory effort during sleep, developed together with the Kempenhaeghe sleep institute.  

Project Info:
Time: 4 Months

Kempenhaeghe Heeze

Dutch Design Week 2015


A sleep apnea is a chronic disorder where the body repeatedly stops breathing during the sleep. It’s estimated to affect 300.000 people in the Netherlands alone. The most important measure to distinguish complex types of apneas is by means of respiratory effort. The current reference method to quantify respiratory effort is by means of a catheter in the esophagus. This method is uncomfortable for patients and sometimes poorly tolerated. Alternative less invasive solutions like thoracic belts, do not meet the requirements with regards to signal quality and reliability.


Kempenhaeghe, the largest sleep institute in the Netherlands, was working on a non-invasive sensor to quantify respiratory effort from the outside of the trachea, using a pressure transducer.

“In theory this method has a lot of potential, in practice it’s seriously hampered by the device-patient interface.”

Sebastiaan Overeem, Doctor/Researcher Kempenhaeghe


In this project, a new patient-device interface was developed to create a stable and more comfortable sensor that could be used during a polysomnography study. The last part of the project was spend on developing a standalone data logging solution to allow for longer term monitoring in the home environment of the patient.

Watch the video:



To define the requirements for the final design, I discussed the goals for the project with the team of Kempenhaeghe and conducted a contextual inquiry to learn more about the context in which the sensor would be used. 


The main focus for Kempenhaeghe was to have a well-functioning prototype to start early with clinical validation. Therefore it was decided to keep electronics away from the body and to focus on a prototype that is easily reproducible without a lot of manufacturing effort. An important insight from the contextual inquiry is that sensors are applied hours before the actual sleep study. Therefore the sensor should be able to be easily and comfortably connected and disconnected from the data aquisition system.



Based on these requirements I started a process of testing and validation by collecting data about the sensor response.

Data First

I decided to start the process by creating an amplification, filtering and data collection circuit to quickly validate different iterations of the sensor system during the night. The circuit would amplify and filter the signal before saving the sensor signal to a SD card.

Tracheostoma Patches

I learned about the use of tracheostoma patches for laryngectomy patients. Laryngectomy patients breathe using an opening in their neck. The tracheostoma patches are used to hold filters and voice prostheses using an airtight seal.

Proof of Concept

I saw an opportunity to use the tracheostoma patches as proven method in the development for a patient-device interface. Using some scrap materials I created a quick proof of concept to validate with the data collection system. 

Sensor Response



The graph above shows how the sensor response changes for normal breathing on the left and obstructed breathing on the right. Obstructed breathing results in higher and wider peaks, since it takes more effort and more time in order to obtain enough oxygen. 

Sensor Design

The first test results were promising, using the tracheostoma patches I was able to get an airtight seal for longer periods of time. Based on these results I designed and 3D printed a custom connector, using this connector I was able to collect data during a full night of sleep. Based on testing with multiple people, several adjustments were made. The connection to the tubing was put on an angle to create a strain relief and a luer-lock was added to comfortably attach and detach the tubing.


An illustration of the proposed solution using tracheostoma patches.

Home Monitoring

After developing the sensor into a stable design that is easy to apply, the last part of the project was spent on developing a home-monitoring solution.  

“We’ll start with comparing the different sensor technologies in a clinical setting, but the intention of these kinds of technologies is that they potentially could be applied in the home situation.”

Sebastiaan Overeem, Doctor/Researcher Kempenhaeghe


Kempenhaeghe showed interest in home-monitoring, to gain longer-term sleep data of patient in a “natural environment.” For me it was an opportunity to continue exploring product design and prototyping. The goal was to find a balance between a medical and consumer product that would fit in the home of a patient. Because the physician needs to be able to quickly explain and hand-over the device for home-monitoring after consulting, the focus was on making the device plug and play. 


The prototype was created by stacking lasercutted parts together, filling and a lot of sanding to get a smooth surface. The top is created by layering magohany veneer and cutting/engraving it using a lasercutter.


The goal of the home-monitoring solution is to make it very easy to start a measurement. The device directly start collecting data when you plug it in. A small led on the back of the device will start pulsing to your breathing, to reassure that the sensor is properly applied to the skin. The LED is only visible when connecting the sensor and will not annoy users during the night.

Below some of the productphoto's shot at the end of the project:


With my designs and research data I went back to Kempenhaeghe to evaluate the project and discuss future opportunities. The team of Kempenhaeghe responded very positively.

“Since the solution is so simple and non-invasive, we are quickly able to start testing with patients. With consent of the patient, we are able to add the sensor to the polysomnography study quite easily.”

Sebastiaan Overeem, Doctor/Researcher Kempenhaeghe


“We didn’t dare to dream of such a solution! I have high expectations!”

Nele Vandenbussche, Doctor/Researcher Kempenhaeghe


After finishing the project, Kempenhaeghe started testing the sensor with multiple patients with positive results. They are currently working on the scientific validation of the sensor. To be continued!



Dutch Design Week

Blundur was part of Mind the Step 2015, an exhibition in one of the large venues of the Dutch Design Week, the Klokgebouw. See the picture below.


I hope you enjoyed this project.

How about looking at another one below?!