This discussion seems like it would benefit from a new perspective or approach.
This forum has some great discussions regarding using Arduinos for health monitoring and data collection. So, the topic itself is fine.
I believe the other members responding before me have the skills necessary to create an initial prototype quick and easy enough. So, what keeps them from doing this?
Medical device liability, forum purpose, and expected cost (time, supplies, money) benefit (compensation for time, supplies, expenses, lost opportunity elsewhere) analysis all demand members here leave this project within your responsibility. Take a look at the other medical projects on this forum and see how the projects with progress maintain the liability with the project originator.
The medical device liability and expected cost benefit analysis also keeps businesses from making this device available to you.
So, if you want to move forward with this project, you need to maintain the liable party status yourself and be the one to directly incur the cost burden. In other words, instead of “Someone do this for me.”, try “I am creating this device and have a specific issue preventing me from moving forward with my project.”
The first step for this project requires research into measuring the respiration rate. How are others doing this? Can their sensor device be used in this system? If this project requires a dedicated sensor device, what sensing method would be best for this project?
I did some internet searches on measuring respiration rate and quickly found that EKG devices are the usual method of measuring respiration rate by complex analysis of the heart beats. During a sleep study, a chest strap device was used for measuring respiration even though there were an unusually high number of EKG type leads in place. This means that you have the option of at least these two methods of measuring respiration.
One possible research path would look around a the available heart rate sensors and see if any of them make the individual heart beat information available to 3rd party monitoring devices. This would allow you to analyze the heart rate data and calculate the respiration rate yourself.