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Adjustable Chair For Measuring Blood Pressure in Children

Spring 2020 MAE 156B Sponsored Project

University of California, San Diego

Figure 1: Team picture with final chair assembly built

Figure 2: The final CAD iteration of the adjustable blood pressure measurement chair. Features include an adjustable backrest and

armrest, an attachable footrest, and multiple safety features to ensure the well-being of both the doctors and the patients. Changes were made to CAD design while assembling physical final design. 

Motivation:

Blood pressure is checked in children starting at age 3 following a specific set of guidelines on positioning. However, this positioning is not always achievable for children, and there is data in the adult literature demonstrating that inappropriate positioning can significantly affect the acquired measurements. A cost-effective, easily-adjustable chair for children needs to be made that allows pediatricians to accurately measure blood pressure in children efficiently. Given the absence of data in the pediatric literature, a successful chair model could be piloted in clinics to study to what degree optimal positioning affects blood pressure measurements.

                                                                                      

Figure 3: Our sponsors' current forms of measurement: a children's chair for their smaller patients (left) with no adjustability and limited support;

an examination table for larger patients (right) with no adjustability and insufficient support. 

Background:

In the pediatric office, blood pressure is checked annually starting at 3 years of age following the current American Association of Pediatrics Clinical Practice Guideline for Screening and Management of High Blood Pressure in Children and Adolescents. This guideline recommends that blood pressures be measured with both feet flat and uncrossed, arm supported at heart level, and the back upright and supported against the seat. However, this positioning is not always achievable given the wide range in age, height, and weight. Additionally, there is data in the adult literature (but not in the pediatric literature) demonstrating that inappropriate positioning during blood pressure measurements can have a significant impact on the obtained measurements. Currently, there is not a cost-effective, easily-adjustable chair for children that is commercially available, and current options are not easily adjustable and/or lack important elements. 

Figure 4: Proper blood pressure measurement positioning: feet flat on the ground, back straight and

supported, arm supported at heart level ("How to Take a Blood Pressure in Children", 2020).

Objectives:

Primary Objective:  Design and build a working prototype that:

Secondary Objective: Design should be:

Response to COVID-19:

In the case that our team was unable to assemble and deliver a final product to our sponsors due to the COVID-19 pandemic, we had planned to order all necessary parts and deliver them with a detailed assembly guide to our sponsors, so they could assemble the chair by themselves. Thankfully, our project has been largely unaffected overall, and we were able to come together to assemble the parts together into a final product for our sponsors. Because we were unable to use the UC San Diego machine shop, we tried to utilize as many commercial, off-the-shelf components as possible in our design to minimize the machining necessary, and most of our fabricated parts were 3D printed, since it was available to us. Additionally, we were able to effectively work together remotely by holding consistent weekly team meetings and maintaining shared, updated CAD files online. 

Link to Executive Summary: click here

Final Design:

In depth summary of final design and performance: click here

The final design is built around a standard office chair base and features an adjustable armrest for arm height, adjustable backrest for seat depth, and adjustable pneumatic piston and stationary footrest for seat height. The armrest consists of a hinging desk and linear slider with constant force springs and locks using a friction break. The backrest is built using a 4-bar linkage, providing both vertical and horizontal adjustment, covered by two side panels for safety and locks using a dual sliding lock mechanism. The footrest is non-removable and allows the seat height to reach the desired minimum of 9 inches. The design of this chair also focused on minimizing the amount of fabrication necessary amidst the COVID-19 pandemic, with the exception of 3D printing, which was readily available to our group.

 

  

Figure 5: Final chair assembly

Performance:

The final chair design features three adjustable mechanisms that allow for the required adjustments of seat depth, seat height, and arm height. This allows the user to adjust the chair to the appropriate position for children from 3 to 10 years old. Because the mechanisms are easy to adjust, the total adjustment time is reduced to around 15 seconds. Additionally, the design also includes significant considerations involving safety and cost.

Adjustment overview video:

External Links:

Citations: