Biomedical Engineering - Module I

Introduction to Biomedical Engineering

• Definition: The application of engineering principles and design concepts to medicine and biology.
• Purpose: Provides support to clinical and biomedical applications in healthcare for diagnosis, monitoring, and therapy.

Overview of Biomedical Instrumentation System

Major Components

1. Energy Source: Energizes the system.
   • Examples: Electric, light, infrared, mechanical, ultrasound.
2. Measurand: The physical quantity or condition being measured.
   • Examples: Internal (e.g., blood pressure), surface (e.g., ECG), emanating (e.g., infrared radiation), derived from tissue samples (e.g., blood).
3. Sensor/Transducer: Converts a physical measurand into an electric output.
4. Signal Conditioning: Amplifies, filters, and processes the signal from the sensor.
5. Output Display: Displays measurement results in a perceivable form: numerical, graphical, etc.

Auxiliary Components

• Calibration Signal: To ensure accurate measurement.
• Control and Feedback Signal: Adjusts sensor and directs output.

Measurement Types

1. Vivo: Measurements made on or within the human body (e.g., blood pH measurement).
2. Vitro: Measurements performed outside the body (e.g., blood sample pH measurement).

Anatomy and Physiology

Key Terms

• Anatomy: The study of body structures.
  • Types: Gross anatomy (macroscopic), microscopic anatomy (cytology, histology).
• Physiology: The study of how body parts function.
  • Classification: Cell physiology, pathophysiology, circulatory physiology, respiratory physiology.

Major Body Systems

1. Cardiovascular System
   • Description: Complex system for blood circulation and waste removal.
2. Respiratory System
   • Components: Nasal cavity, trachea, lungs, bronchi, bronchioles, alveoli, capillaries.
   • Function: Supplies oxygen, removes carbon dioxide.
3. Nervous System
   • Components: Brain, spinal cord, neurons.
   • Functions: Sends, receives, and interprets information.
   • Subdivisions: Central (CNS) and Peripheral Nervous System (PNS).
     • CNS: Processes information, includes brain and spinal cord.
     • PNS: Connects CNS to organs and limbs, includes somatic and autonomic systems.
     • Autonomic: Regulates involuntary functions (sympathetic & parasympathetic).

Bioelectric Potentials

Sources of Bioelectric Potentials

• Definition: Signals generated by the body's systems during functions.
• Examples: Nerve conduction, heartbeat, muscle activity.

Resting and Action Potentials

• Resting Potential: When a cell is at rest, it is polarized with a potential of $-60 ext{mV}$ to $-100 ext{mV}$.
• Action Potential: When a cell is excited, it becomes depolarized, achieving a potential of approximately $+20 ext{mV}$.
• Propagation of Action Potentials: The rate at which action potentials move down nerve fibers/via conductive cells.
  • Ranges from $20-140 ext{m/s}$ in nerves, $0.2-0.4 ext{m/s}$ in heart muscle.

Types of Bioelectric Signals

1. Electrocardiogram (ECG): Measures the electrical activity of the heart.
2. Electroencephalogram (EEG): Records electrical activity of the brain.
3. Electromyogram (EMG): Measures muscle electrical activity.
4. Electroretinogram (ERG): Measures electrical activity from the retina.
5. Electro-oculogram (EOG): Measures changes in eye position.
6. Electrogastrogram (EGG): Records gastric myoelectrical activity.

Electrode Theory

• Function: To measure bioelectric potentials using transducers and electrodes.
• Types of Electrodes:
  1. Microelectrodes: Measure potentials near or within a single cell.
  2. Surface Electrodes: Measure signals like ECG and EEG.
  3. Needle Electrodes: Penetrate skin to record signals.
• Nernst Equation: Describes the relationship between ionic concentration and electrode potential.

Bio-Potential Amplifiers

• Purpose: Amplifies low-level bio-potentials for processing.
• Types:
  1. Differential Amplifiers: Commonly used with limitations.
  2. Instrumentation Amplifiers: Overcome limitations of differential amplifiers.
  3. Carrier Amplifiers: Modulates signals using amplitude modulation.
  4. Chopper Amplifiers: Avoid drift by converting signals.
  5. Isolation Amplifiers: Provide electrical isolation between circuits.

Conclusion

• Biomedical engineering integrates engineering with healthcare to improve medical devices and systems for better diagnosis and treatments, leveraging concepts of bioelectric potentials, anatomy, and physiological systems in its design.