Pumping devices are the 'heart' of any hydraulic/ pneumatic systems to keep them functioning.  Similarly, human hydraulic system functions only on account of a superior pumping device - the heart - that serves without any letup.

Sometimes, on account of stress, hyper-tension (high blood pressure), drinking excessive alcohol or caffeinated beverages, heart infections or electrolyte imbalance, heart beats faster than normal, resulting in reduced pumping efficiency and hence lower oxygen levels.  This results in shortness of breath, dizziness, lightheadedness, fainting, sudden weakness among side-effects.  This condition is called Tachyarrhythmia ( the heard beats faster at anywhere between 100 to 400 beats ).  This could lead to a heart failure by cardiac arrest, if not diagnosed and treated.

An electro-mechanical device called the Defibrillator has come in as a boon to patients with such irregular heartbeats.  This device provides electric shocks to the heart to restore normal rhythm.  The device consists of a micro-processor controlled battery actuated electric-impulse generating unit that is encapsulated in a canister.  The device can be implanted into the muscle under the collarbone with lead wire(s) getting attached to the heart at required location.

In addition to monitoring the heart beat and administering shock pulses, if required, the heart condition and events are stored as electronic data in the device, for analysis of patient condition by qualified physicians.

When designing such medical devices for critical functions, many a design challenge needs to be overcome.  Some of them include size, shape, implant constraints, lead-wire(s) management, data acquisition, battery selection and placement, infection prevention by design among others.  External defibrillators are also used in hospitals and health-care centres.  Companies such as Zoll Medical have devised Defibrillators, interestingly, using SolidWorks.

When such medical devices are designed, it is important to understand the requirements in terms of Fit, Form and Function and evaluate alternatives before refininng design parameters.  Innovations in such designs becomes a reality when combined with lateral thinking.  For example, instead of conventional two-wire leads required for any battery operated device, a manufacturer has designed a Defibrillator using a Titanium canister that serves as one terminal while the other terminal is attached to the heart.  This obviates the requirements for two lead wires and its associated complexities in the context of implant inside a human body !! ( Image: Courtesy Zoll Medical USA )

Click Here to Watch Video (11.7 MB) How to address the Assembly Tolerance requirement?  Which Part tolerances contribute to the required Assembly Tolerance?  These are questions asked by, almost, every design engineer when he or she develops drawings of design for fit, form and function.

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