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- Introduction to Biomedical Instrumentation: Focuses on devices for data collection, diagnosis, and therapeutic/prosthetic functions within the respiratory and cardiovascular systems.
- Definition of Health Technology: The WHO definition includes all instruments, equipment, drugs, procedures, and organizational systems; the Italian Ministry of Health’s definition is more restricted to medical devices (excluding drugs).
- Health Technology Assessment (HTA): A crucial discipline for evaluating health technologies to guide appropriate acquisition and utilization decisions, evolving from past phases of indiscriminate buying and budget cuts.
- Respiratory System Physiology:
- Main function: Air transport (inspiration/expiration) and gas exchange (O2/CO2) in the alveoli.
- Evaluations are performed on long (days, months, years for screening, monitoring pathologies, follow-up) and short (critical situations, ICU for continuous or very frequent measurements) temporal scales.
- Key muscles: Diaphragm and external intercostals for spontaneous inspiration; internal intercostals and abdominals for forced expiration or in pathological states.
- Mechanics: Inspiration involves muscle contraction, chest expansion, and pressure changes; expiration is typically passive elastic recoil.
- Lung-Chest Wall Interaction: Lungs are elastic and tend to collapse, while the chest wall tends to expand. They adhere due to negative intrapleural pressure, forming a virtual “solder.” Loss of this negative pressure (e.g., pneumothorax) leads to lung collapse.
- Respiratory Pressures:
- Intrapleural Pressure (PPL): Always negative relative to atmospheric pressure.
- Alveolar Pressure (PALV): Sub-atmospheric during inspiration, supra-atmospheric during expiration.
- Transpulmonary Pressure (PTP = PALV - PPL): Must always be positive to prevent alveolar collapse.
- Air moves by convection due to pressure differences.
- Respiratory Volumes and Ventilation:
- Tidal Volume (VT): Air exchanged in one breath (typically 0.5 L).
- Anatomical Dead Space (VD_anatomical): Air in the conduction zone (no gas exchange), approx. 150 mL.
- Alveolar Dead Space (VD_alveolar): Air reaching alveoli but not participating in gas exchange.
- Physiological Dead Space: Sum of anatomical and alveolar dead space.
- Alveolar Ventilation (VA): (VT - VD) x Respiratory Frequency; represents air effectively participating in gas exchange and is a critical clinical parameter.
- Models for Measurement:
- Measurements can be direct (using specific devices) or indirect (requiring models to estimate values, like alveolar pressure).
- Weibel's Morphological Model: A simplified, symmetrical representation of the tracheobronchial tree, divided into a conduction zone (generations 0-17) and a respiratory zone (generations 18-23).
- Mass Balance Equation: A fundamental concept describing gas exchange dynamics, where the change in mass of a substance equals convective inflow minus diffusive outflow, explaining O2 and CO2 movement.