Part1.1 ECG LEAD arrangement

Intro:

As this one is my first blog regarding the design challenge, I would like to present my project idea and my motivation in brief at first.

I just love to play. Had a great time in my high school and university, playing football (soccer) and basketball. Sweet memories of these, comes along with sweet sweet sweet injuries as well [khikz].

I had a fracture in my left arm while playing basketball, had twisted right ankle for several times and now I have weak right toe due to ligament injury. WOW WOW WOW…. I have seen players getting a black out for a few seconds right in front of me due to rough tackles.

However, I know that electronics may not have many things to do to avoid these sorts of injuries, but being an electronics enthusiast I can try to use my little skills and experience in this area, which may open up a new door to others to develop something which may turn into a life saver some day. Who knows?

So, let’s get into the point -> I would like to develop a standalone device consists of separated modules to get the important health parameters of the player. It includes –

•                 Single lead ECG
•                 Temperature
•                 Certain muscle activities by EMG
•                 Concussions
•                 Plethysmograph and impedance measurement to get some other important parameters.

These modules will have wireless communication to a central hub placed on player's wrist band, which will combine all the parameters and send it to a smart phone using long range paired communication bridge.

So, my first blog regarding this design challenge starts from here –

Title:                                   Total Player Monitoring

By:                                       Md. Kamrul Hussain

Project Category:             Design Challenge

Project Name:                   Sudden Impact Wearables Design Challenge

Project duration:              Dec01, 2014 to March 27, 2015

Blog post: 01                                             Week: 01                                      Time period: Dec 01 -  03, 2014

Topic:                                    ECG LEAD arrangement and configuration [ LEAD I or LEAD II ]

Einthoven’s Triangle

LA = Left arm                    

RA = Right arm                 

LL = left leg

LEAD I = LA – RA

LEAD II = LL – RA

LEAD III = LL – LA

Conventional LEAD configuration

Conventional configuration that is followed in wearable health tech is LEAD I, as it can be implemented in a skin tight jersey or chest belt. Where the RLD [right leg drive] is introduced as the alternative ground or reference path to cancel out the common noise to improve the SNR [signal to noise ratio] by improving the CMRR [common mode rejection ratio] of the bio amp.

Below we can have a look on conventional LEAD arrangement for LEAD I configuration.

Cons

• The shirt has to be a tight enough and should not stretch much with body movement so that the stitched electrodes stay in

  

  place and don’t experience variation in electrode contact potential. In that case it may cause discomfort. Also some [basketball] jerseys are used to be loose.
• Electrodes placement may vary according to the body structure of the player, so it’s not much flexible.
• Need more care to wash.
• The chest belt may cause discomfort if fastened tightly. Otherwise contact potential difference may arise.
• In both case it can cause problem or unexpected data due to sudden force applied on the electrodes while controlling the ball using chest [specially in football].

                                                                                                                                                                                                 LEAD Arrangement 01                                   LEAD Arrangement 02

Proposed arrangement

Considering the cons for conventional method,I would like to switch into LEAD II instead of LEAD I following a little bit different arrangement. According to the Einthoven’s triangle RLD and LL electrodes can be shifted up to the waist.

In this image the new position of LL and RLD is shown.

The Right arm electrode will be connected using a strap, consisting a metal connector. A thin wire can be stitched or temporarily layered under the jersey to provide the connection in between the electrode and the processing unit.

The elastic liner of the shorts or trouser will held the LL and RLD electrodes firm enough onto the body surface. This will be an automatic replacement of chest belt and the players are already used to with it, so I believe that it would be a more comfortable solution.

The processing unit will be mounted around the elastic liner of the shorts using pouch with magnetic lock.

In this arrangement players won’t find any difficulties to control the ball using chest and also it gives more flexibility as there won’t be any modification needed for the jersey.

However, I have to check whether this arrangement will be comfortable and effective or not. The signals will be of reduced amplitude if the player has fat in his abdominal area. But in most cases we don’t have athletes and players with bulky figure

Circuit for basic Bio-amp

As the design kits are not available right now, I am using this basic bio-amp circuit for temporary experiments. I would like to check whether the proposed LEAD arrangement is capable of acquiring ECG LEAD II effectively or not.

If the basic Analog Front End using AD620 works with proposed arrangement, then AD8232 will replace it later on with same configuration. Otherwise, the conventional configuration will be used with arrangement 1 or 2.

The output of the proposed LEAD arrangement will be published next week in my 2^nd blog. It will be compared with the output of the conventional arrangements and configurations for feasibility check.