Basic Biomedical Engineering interview questions

150 questions with answers (BME-001 to BME-150). Try each one aloud before reading the answer.

Anatomy & Physiology for Engineers

BME-001 · What is homeostasis?

The body's ability to keep internal variables such as temperature, pH, glucose and blood pressure within narrow limits using negative-feedback loops of sensors, a controller (often the brain or endocrine glands) and effectors.

BME-002 · What is the resting membrane potential of a typical neuron?

About −70 mV, inside negative relative to outside. It is set mainly by K⁺ leak channels and maintained by the Na⁺/K⁺-ATPase pump, which moves 3 Na⁺ out and 2 K⁺ in per ATP.

BME-003 · What is an action potential?

A rapid, all-or-none reversal of membrane potential. Voltage-gated Na⁺ channels open and depolarize the cell to about +30 mV, then K⁺ efflux repolarizes it. It propagates along nerve and muscle fibres without decrement.

BME-004 · What is the order of the heart's conduction system?

SA node → atrial muscle → AV node → bundle of His → left and right bundle branches → Purkinje fibres → ventricular muscle.

BME-005 · What is cardiac output?

The volume of blood the heart pumps per minute: CO = heart rate × stroke volume. At rest, 70 beats/min × 70 mL ≈ 5 L/min.

BME-006 · What is normal adult blood pressure?

About 120/80 mmHg. The first figure is systolic pressure, during ventricular contraction; the second is diastolic pressure, during relaxation.

BME-007 · What are the main components of blood?

Plasma (about 55% of volume; water, proteins, electrolytes) and formed elements (about 45%): red blood cells, white blood cells and platelets. An adult has about 5 L of blood.

BME-008 · What is tidal volume?

The volume of air moved in or out in one normal breath, about 500 mL in an adult at rest.

BME-009 · What is the function of the nephron?

It is the kidney's functional unit. It filters plasma in the glomerulus, then reabsorbs and secretes solutes along the tubule to form urine, regulating fluid volume, electrolytes and pH.

BME-010 · What is the difference between systemic and pulmonary circulation?

Pulmonary circulation carries blood from the right ventricle to the lungs and back to the left atrium for gas exchange. Systemic circulation carries oxygenated blood from the left ventricle to the body and back to the right atrium.

BME-011 · What are the four basic tissue types?

Epithelial (covering and lining), connective (support, including bone and blood), muscle (contraction) and nervous (signalling).

BME-012 · What is the normal pH of arterial blood?

7.35–7.45. Below this is acidaemia and above it is alkalaemia. Bicarbonate buffering, the lungs and the kidneys keep it in range.

BME-013 · What are the three types of muscle?

Skeletal (striated, voluntary), cardiac (striated, involuntary, joined by intercalated discs) and smooth (non-striated, involuntary, found in vessels and organs).

Biomedical Instrumentation

BME-014 · What is biomedical instrumentation?

The design and use of devices that measure, monitor or record physiological variables such as biopotentials, pressure, flow, temperature and blood gases, for diagnosis, monitoring and research.

BME-015 · What are the basic blocks of a medical instrumentation system?

Measurand → sensor/transducer → signal conditioning (amplification, filtering, isolation) → digitization and processing → output (display, storage, alarms). Calibration, power and feedback support these blocks.

BME-016 · What is a transducer?

A device that converts one form of energy into another, usually a physical or chemical quantity into an electrical signal, for example a strain gauge converting pressure into a resistance change.

BME-017 · What does a biopotential electrode do?

It is the interface that converts ionic current in the body into electron current in the lead wire through electrochemical reactions at the electrode–electrolyte junction.

BME-018 · Why are Ag/AgCl electrodes widely used?

They are nearly non-polarizable, with a low and stable half-cell potential. This gives low noise, low DC offset drift and reduced motion artifact compared with polarizable metal electrodes.

BME-019 · What is an instrumentation amplifier?

A differential amplifier with very high input impedance, high CMRR and gain set by a single resistor. It amplifies the small difference between two electrodes while rejecting the common-mode voltage.

BME-020 · What is CMRR?

Common-mode rejection ratio: the ratio of differential gain to common-mode gain, CMRR = Ad/Ac, usually expressed as 20 log₁₀(Ad/Ac) dB. Biopotential amplifiers need high values, typically above 100 dB.

BME-021 · What is a sphygmomanometer?

A cuff-based instrument for measuring blood pressure non-invasively. The cuff occludes the brachial artery and pressure is read as it deflates, either from Korotkoff sounds (auscultatory) or from cuff oscillations (oscillometric).

BME-022 · What is the difference between invasive and non-invasive blood pressure measurement?

Invasive measurement uses an arterial catheter connected to a pressure transducer and gives a continuous beat-to-beat waveform. Non-invasive measurement uses a cuff and gives intermittent readings with lower risk.

BME-023 · What is a thermistor and why is it used for body temperature?

A semiconductor resistor whose resistance changes strongly with temperature; NTC types decrease in resistance as temperature rises. Its high sensitivity and small size suit clinical probes.

BME-024 · What is a strain gauge?

A resistive sensor whose resistance changes with mechanical strain. Gauge factor GF = (ΔR/R)/ε, about 2 for metal foil gauges. It is used in pressure transducers and force sensors.

BME-025 · What is plethysmography?

Measurement of volume changes in a body part or organ, often due to blood flow. Methods include impedance, photoplethysmography (PPG, optical) and air or water displacement.

BME-026 · What is a spirometer?

An instrument that measures inhaled and exhaled air volume and flow over time. It gives values such as FVC, FEV₁ and the FEV₁/FVC ratio, used to diagnose obstructive and restrictive lung disease.

Biosignal Processing (ECG, EEG, EMG)

BME-027 · What is an ECG?

An electrocardiogram records the heart's electrical activity from body-surface electrodes. The P wave is atrial depolarization, the QRS complex is ventricular depolarization and the T wave is ventricular repolarization.

BME-028 · What does an EEG measure?

The brain's electrical activity, mainly summed postsynaptic potentials of cortical pyramidal neurons, recorded from scalp electrodes. Amplitudes are about 10–100 µV.

BME-029 · What is an EMG?

An electromyogram records the electrical activity of skeletal muscle, the summed motor unit action potentials, using surface or needle electrodes. It is used for neuromuscular diagnosis, biomechanics and prosthesis control.

BME-030 · What is a biosignal?

Any time-varying signal from a living system that carries physiological information. It can be electrical (ECG, EEG, EMG), mechanical (blood pressure, heart sounds), optical (PPG) or chemical (blood gases).

BME-031 · What are the typical amplitude and bandwidth of the ECG?

About 0.5–4 mV, with around 1 mV for the R wave. The diagnostic bandwidth is about 0.05–150 Hz; monitoring bandwidth is narrower, about 0.5–40 Hz.

BME-032 · What are the EEG frequency bands?

Delta 0.5–4 Hz (deep sleep), theta 4–8 Hz (drowsiness), alpha 8–13 Hz (relaxed, eyes closed), beta 13–30 Hz (active thinking) and gamma above 30 Hz.

BME-033 · What is the Nyquist sampling theorem?

To reconstruct a band-limited signal without aliasing, the sampling frequency must exceed twice its highest frequency component: fs > 2fmax. Diagnostic ECGs are typically sampled at 500–1000 Hz.

BME-034 · What is baseline wander?

A low-frequency drift of the ECG baseline, usually below 0.5 Hz. It is caused by respiration, body movement and changes in electrode–skin impedance, and is removed by high-pass filtering or baseline estimation.

BME-035 · What makes up a standard 12-lead ECG?

Three bipolar limb leads (I, II, III), three augmented unipolar limb leads (aVR, aVL, aVF) and six precordial chest leads (V1–V6). Only 10 electrodes are needed.

BME-036 · What is Einthoven's triangle?

An equilateral triangle formed by the right arm, left arm and left leg, with the heart at its centre. The limb leads follow Einthoven's law: Lead II = Lead I + Lead III.

BME-037 · What does the QRS complex represent?

Depolarization of the ventricles. Normal duration is under 0.12 s. Atrial repolarization happens at the same time and is hidden within it.

BME-038 · What is heart rate variability?

The beat-to-beat variation in RR intervals. It reflects autonomic nervous system balance; reduced HRV is linked to stress, heart failure and higher cardiac risk.

BME-039 · What is an evoked potential?

The brain's or nerves' electrical response to a specific stimulus (visual, auditory or somatosensory). It is time-locked to the stimulus and extracted from background EEG by averaging many trials.

Medical Imaging

BME-040 · What are the main medical imaging modalities?

X-ray radiography, computed tomography (CT), magnetic resonance imaging (MRI), ultrasound, and the nuclear medicine methods PET and SPECT. Optical methods such as endoscopy and OCT are also used.

BME-041 · Which imaging modalities use ionizing radiation?

X-ray radiography, fluoroscopy, mammography and CT use X-rays. PET and SPECT use gamma rays from radiotracers. MRI and ultrasound do not use ionizing radiation.

BME-042 · How is a projection X-ray image formed?

X-rays pass through the body and tissues attenuate them differently according to density and atomic number. Bone attenuates strongly and air very little, so the transmitted intensity forms a shadow image on a detector.

BME-043 · What is computed tomography?

An imaging method that acquires X-ray projections from many angles around the patient and computationally reconstructs cross-sectional slices of attenuation coefficients, removing the overlap seen in plain radiographs.

BME-044 · What is the Hounsfield unit?

The CT number scale: HU = 1000 × (μ − μwater)/(μwater − μair). Water is 0 HU, air is −1000 HU, fat is about −100 HU and dense bone is around +1000 HU or more.

BME-045 · What is MRI?

Magnetic resonance imaging places the patient in a strong static field, excites hydrogen nuclei with RF pulses, and uses magnetic field gradients to spatially encode the signals the nuclei emit as they relax.

BME-046 · What frequency range does diagnostic ultrasound use?

Typically 2–15 MHz. Lower frequencies penetrate deeper (abdomen, heart); higher frequencies give better resolution for superficial structures such as the thyroid, breast and vessels.

BME-047 · What is an ultrasound transducer?

A probe containing piezoelectric elements, commonly PZT, that convert electrical pulses into acoustic waves and returning echoes back into electrical signals.

BME-048 · What is nuclear medicine imaging?

Imaging the distribution of an administered radioactive tracer to show physiological function. Examples are PET with ¹⁸F-FDG and SPECT with ⁹⁹ᵐTc agents.

BME-049 · What is a contrast agent?

A substance that increases the visibility of structures. Examples are iodine or barium for X-ray and CT, gadolinium chelates for MRI, and gas microbubbles for ultrasound.

BME-050 · What is fluoroscopy?

Real-time X-ray imaging using continuous or pulsed exposure and a flat-panel detector or image intensifier. It is used to guide catheters, perform barium studies and position orthopaedic implants.

BME-051 · What is spatial resolution in imaging?

The smallest separation at which two objects can still be seen as distinct, often expressed in mm or line pairs per mm and characterized by the modulation transfer function (MTF).

BME-052 · What is mammography?

Low-energy X-ray imaging of the breast, typically at about 25–35 kVp, often with molybdenum or rhodium targets. It maximizes soft-tissue contrast for detecting masses and microcalcifications.

Biomaterials

BME-053 · What is a biomaterial?

A material designed to interact with biological systems to evaluate, treat, augment or replace a tissue, organ or function. Examples are implants, sutures, catheters and scaffolds.

BME-054 · What is biocompatibility?

The ability of a material to perform its intended function with an appropriate host response in a specific application, without unacceptable toxicity, inflammation, thrombosis or rejection.

BME-055 · What are the main classes of biomaterials?

Metals (Ti alloys, stainless steel, CoCr), ceramics (alumina, zirconia, hydroxyapatite), polymers (UHMWPE, PMMA, silicone, PLGA), composites, and natural materials (collagen, chitosan, alginate).

BME-056 · What is the difference between bioinert, bioactive and bioresorbable materials?

Bioinert materials (alumina, zirconia) cause minimal interaction. Bioactive materials (hydroxyapatite, bioactive glass) bond chemically to tissue. Bioresorbable materials (PLA, PGA, tricalcium phosphate) degrade and are replaced by tissue.

BME-057 · What is hydroxyapatite?

A calcium phosphate, Ca₁₀(PO₄)₆(OH)₂, with a Ca/P ratio of 1.67. It resembles bone mineral and is used as a bioactive coating on implants and as bone graft substitute.

BME-058 · Which metals are commonly used for implants?

316L stainless steel (fracture fixation), commercially pure titanium and Ti-6Al-4V (stems, dental implants), cobalt-chromium-molybdenum alloys (bearing surfaces), and nitinol (stents, guidewires).

BME-059 · What is osseointegration?

A direct structural and functional connection between living bone and the surface of a load-bearing implant without an intervening fibrous layer. It was first described for titanium by Brånemark.

BME-060 · What is UHMWPE and where is it used?

Ultra-high-molecular-weight polyethylene, a tough polymer with low friction and good wear resistance. It is the standard bearing material for acetabular liners in hips and tibial inserts in knees.

BME-061 · What is PMMA bone cement?

Polymethyl methacrylate that polymerizes in situ from a powder and liquid monomer. It acts as a grout that fixes joint-replacement components to bone. Its setting reaction is exothermic.

BME-062 · What is a hydrogel?

A water-swollen, cross-linked polymer network, often more than 90% water, such as PEG, alginate or polyHEMA. Hydrogels are used in contact lenses, wound dressings, drug delivery and cell encapsulation.

BME-063 · What is nitinol?

A near-equiatomic nickel-titanium alloy with shape memory and superelasticity, both from a reversible austenite–martensite transformation. It is used in self-expanding stents, guidewires and orthodontic wires.

BME-064 · What is passivation of implant metals?

A thin, stable oxide film forms on the surface, such as TiO₂ on titanium or Cr₂O₃ on stainless steel and CoCr. It strongly reduces corrosion in body fluids that are rich in chloride.

BME-065 · What is the foreign body response?

The host reaction to an implanted material: protein adsorption, acute inflammation, macrophage adhesion, fusion into foreign-body giant cells and, finally, fibrous encapsulation of the implant.

Biomechanics

BME-066 · What is biomechanics?

The application of mechanics to biological systems. It covers the motion, forces and deformation of tissues, joints, fluids and whole bodies, including gait, bone mechanics and blood flow.

BME-067 · What are stress and strain?

Stress is force per unit area, σ = F/A, measured in Pa. Strain is relative deformation, ε = ΔL/L₀, and is dimensionless.

BME-068 · What is Young's modulus?

The slope of the linear elastic region of the stress–strain curve, E = σ/ε. Cortical bone is about 17–20 GPa, Ti-6Al-4V about 110 GPa and cartilage only a few MPa.

BME-069 · What is viscoelasticity?

Material behaviour that combines elastic (spring-like) and viscous (dashpot-like) responses, so the stress depends on strain rate and history. Most soft tissues and bone are viscoelastic.

BME-070 · What is Wolff's law?

Bone adapts its mass and architecture to the loads placed on it. Increased loading causes deposition and reduced loading causes resorption, which is why bone is lost in disuse and around stiff implants.

BME-071 · What is the gait cycle?

The period from heel strike of one foot to the next heel strike of the same foot. In normal walking it has a stance phase of about 60% and a swing phase of about 40%.

BME-072 · What are the three classes of levers in the body?

First class: the fulcrum lies between effort and load (head nodding on the atlas). Second class: the load lies between (rising on the toes). Third class: the effort lies between (elbow flexion by the biceps), which is the most common type.

BME-073 · What is a ground reaction force?

The force the ground exerts on the body during contact, equal and opposite to the force the body applies. During walking, the vertical peaks are about 1.1–1.2 times body weight. It is measured with force plates.

BME-074 · What is the difference between cortical and cancellous bone?

Cortical (compact) bone is dense, with porosity of about 5–10%, and forms the shafts of long bones. Cancellous (trabecular) bone is porous, with porosity of about 50–90%, and fills the ends of long bones and vertebrae. It is much less stiff but metabolically more active.

BME-075 · What are creep and stress relaxation?

Creep is increasing strain under constant stress. Stress relaxation is decreasing stress under constant strain. Both are signatures of viscoelastic materials such as ligaments and intervertebral discs.

BME-076 · What is the difference between kinematics and kinetics?

Kinematics describes motion (position, velocity, acceleration, joint angles) without considering forces. Kinetics studies the forces and moments that cause the motion.

BME-077 · What does anisotropy mean for bone?

Bone's mechanical properties depend on loading direction. Cortical bone is stiffer and stronger along the long axis of the osteons than transverse to it.

BME-078 · What is hemodynamics?

The study of blood flow and the forces involved: pressure, flow rate, resistance, vessel compliance and wall shear stress throughout the circulation.

Therapeutic & Life-Support Devices

BME-079 · What is a defibrillator?

A device that delivers a high-energy electric shock through the chest to depolarize a critical mass of myocardium at once. This terminates ventricular fibrillation or pulseless VT so the SA node can resume control.

BME-080 · What is an AED?

An automated external defibrillator. It analyses the ECG through adhesive pads, decides whether the rhythm is shockable, and guides a lay rescuer with voice prompts to deliver a shock.

BME-081 · What is an implantable cardioverter-defibrillator (ICD)?

An implanted device that continuously monitors the heart rhythm. It treats ventricular tachyarrhythmias with anti-tachycardia pacing or internal shocks, and usually also provides bradycardia pacing.

BME-082 · What is a mechanical ventilator?

A machine that moves gas into and out of the lungs for patients who cannot breathe adequately. It controls tidal volume or pressure, respiratory rate, inspired oxygen fraction (FiO₂) and PEEP.

BME-083 · What is PEEP?

Positive end-expiratory pressure: airway pressure held above atmospheric at the end of expiration. It keeps alveoli open, improves oxygenation and reduces atelectasis.

BME-084 · What is a heart-lung machine?

A cardiopulmonary bypass system used during open-heart surgery. A pump replaces the heart's function and an oxygenator replaces the lungs', with heat exchangers and filters, so the heart can be stopped.

BME-085 · What is ECMO?

Extracorporeal membrane oxygenation: prolonged support in which blood is drained, oxygenated and cleared of CO₂ in a membrane oxygenator, then returned. It is used for severe respiratory or cardiac failure.

BME-086 · What is an infusion pump?

A device that delivers fluids or drugs into a patient at a controlled rate and volume. Types include volumetric (peristaltic), syringe, ambulatory and PCA (patient-controlled analgesia) pumps.

BME-087 · What is an electrosurgical unit?

A generator that passes high-frequency current, typically hundreds of kHz to a few MHz, through tissue to cut or coagulate by resistive heating. It can be used in monopolar or bipolar mode.

BME-088 · What is a cochlear implant?

A neuroprosthesis for severe sensorineural hearing loss. An external processor converts sound into electrical stimulation patterns that an electrode array in the cochlea delivers directly to the auditory nerve.

BME-089 · What is a ventricular assist device?

A mechanical pump, usually implanted, that supports a failing ventricle. LVADs are the most common. They are used as a bridge to transplant or as destination therapy.

BME-090 · What is TENS?

Transcutaneous electrical nerve stimulation: low-intensity electrical pulses delivered through skin electrodes for pain relief, thought to work through gate-control and endorphin mechanisms.

Tissue Engineering

BME-091 · What is tissue engineering?

An interdisciplinary field that combines cells, scaffolds and bioactive signals to create biological substitutes that restore, maintain or improve tissue function.

BME-092 · What is the tissue engineering triad?

Cells (the source of new tissue), scaffolds (the 3D structural template) and signals (growth factors and mechanical or electrical cues). A bioreactor is often added as a fourth element.

BME-093 · What is a scaffold?

A porous 3D structure, natural or synthetic, that supports cell attachment, proliferation and matrix deposition. Ideally it degrades as new tissue forms.

BME-094 · What are stem cells?

Unspecialized cells capable of self-renewal and differentiation into specialized cell types. Examples are embryonic stem cells, adult stem cells such as mesenchymal stem cells, and induced pluripotent stem cells.

BME-095 · What are induced pluripotent stem cells (iPSCs)?

Adult somatic cells reprogrammed to a pluripotent state by expressing transcription factors (Oct4, Sox2, Klf4, c-Myc), first shown by Yamanaka in 2006. They allow patient-specific cells without using embryos.

BME-096 · What is a bioreactor in tissue engineering?

A controlled culture system that provides nutrient and oxygen transport, waste removal and mechanical stimuli to growing tissue. Examples are spinner flasks, rotating-wall vessels and perfusion systems.

BME-097 · What is the extracellular matrix?

The non-cellular network of proteins (collagen, elastin, fibronectin, laminin) and proteoglycans around cells. It provides structure and biochemical and mechanical cues that control cell behaviour.

BME-098 · What do autologous, allogeneic and xenogeneic mean?

Autologous: from the same patient. Allogeneic: from another individual of the same species. Xenogeneic: from a different species, such as porcine heart valves.

BME-099 · What is decellularization?

Removing cells from a tissue or organ with detergents, enzymes or physical methods, while keeping the ECM structure. The resulting scaffold can be recellularized and has reduced immunogenicity.

BME-100 · What is 3D bioprinting?

Layer-by-layer deposition of bioinks (cell-laden hydrogels) and biomaterials by extrusion, inkjet or light-based methods to build tissue constructs with defined architecture.

BME-101 · What is electrospinning?

A process that uses a high voltage, typically kV, to draw a polymer solution into nano- to micro-scale fibres collected as a non-woven mat. The mats mimic the fibrous architecture of ECM.

BME-102 · What is an organ-on-a-chip?

A microfluidic device lined with living cells that reproduces key functions and mechanical environments of an organ, such as lung or gut. It is used for drug testing and disease modelling.

Biosensors

BME-103 · What is a biosensor?

An analytical device that combines a biological recognition element with a transducer to convert a biochemical event into a measurable signal. A common example is the enzyme-based glucose sensor.

BME-104 · What types of bioreceptors are used in biosensors?

Enzymes, antibodies (immunosensors), nucleic acids (DNA probes), aptamers, whole cells, receptors and synthetic receptors such as molecularly imprinted polymers.

BME-105 · What transducer types are used in biosensors?

Electrochemical (amperometric, potentiometric, impedimetric, conductometric), optical (absorbance, fluorescence, SPR), piezoelectric (QCM), thermal (calorimetric) and field-effect transistor based.

BME-106 · What is an amperometric biosensor?

A sensor that holds the working electrode at a fixed potential and measures the current from oxidation or reduction of an electroactive species. The current is proportional to analyte concentration.

BME-107 · What is a potentiometric sensor?

A sensor that measures the potential difference between an indicator electrode and a reference electrode at near-zero current. The potential varies logarithmically with ion activity, following the Nernst equation; a pH electrode is an example.

BME-108 · What is the Clark oxygen electrode?

An amperometric sensor in which a Pt cathode behind an O₂-permeable membrane reduces oxygen at about −0.6 V relative to Ag/AgCl. The current is proportional to pO₂. It is the basis of blood-gas pO₂ measurement and early glucose sensors.

BME-109 · Which enzyme is used in most glucose sensors?

Glucose oxidase (GOx), which is highly specific and stable. Glucose dehydrogenase with cofactors such as FAD or PQQ is also widely used in test strips.

BME-110 · What is a continuous glucose monitor?

A wearable system with a subcutaneous enzyme-electrode sensor that measures glucose in interstitial fluid every few minutes. It sends readings, trends and alarms to a receiver or phone.

BME-111 · What is the limit of detection?

The lowest analyte concentration that can be reliably distinguished from a blank. It is commonly calculated as LOD = 3σ_blank / calibration slope.

BME-112 · What is selectivity in a biosensor?

The ability to respond only to the target analyte in the presence of interferents. It comes mainly from the specificity of the bioreceptor and from permselective membranes.

BME-113 · What is a lateral flow assay?

A paper-based strip test in which the sample flows by capillary action past labelled antibodies, often gold nanoparticles, to test and control lines that show a visible result. Pregnancy tests and rapid antigen tests use this format.

BME-114 · What is bioreceptor immobilization?

Attaching the biological element to the transducer surface by adsorption, covalent bonding, entrapment in a gel or polymer, cross-linking (for example with glutaraldehyde) or affinity binding. It keeps the element active and stable.

Regulatory Standards & Quality

BME-115 · What is a medical device?

An instrument, apparatus, software, implant or similar article intended for diagnosis, prevention, monitoring, treatment or alleviation of disease or injury. Unlike drugs, it does not achieve its principal intended action by pharmacological, immunological or metabolic means.

BME-116 · What is ISO 13485?

The international standard for quality management systems for medical device organizations. It covers design, production, supplier control, documentation, CAPA and regulatory requirements throughout the device lifecycle.

BME-117 · What is IEC 60601-1?

The international standard for basic safety and essential performance of medical electrical equipment. It covers electrical, mechanical, thermal and radiation hazards, and is supported by collateral (-1-x) and particular (-2-x) standards.

BME-118 · What is ISO 14971?

The international standard for applying risk management to medical devices. It covers identifying hazards, estimating and evaluating risks, controlling them, and monitoring residual risk throughout the lifecycle.

BME-119 · What are the FDA device classes?

Class I is low risk (general controls, for example bandages). Class II is moderate risk (special controls, usually 510(k), for example infusion pumps). Class III is high risk (PMA required, for example implantable pacemakers).

BME-120 · What is a 510(k)?

An FDA premarket notification that shows a device is substantially equivalent to a legally marketed predicate device. A successful submission results in FDA clearance.

BME-121 · What is the EU MDR?

The EU Medical Device Regulation (EU) 2017/745, which replaced the Medical Device Directives. It classifies devices as I, IIa, IIb and III, and tightens requirements for clinical evidence, post-market surveillance and traceability.

BME-122 · What is CE marking?

A mark by which the manufacturer declares that a device conforms to the applicable EU regulations, allowing it to be sold in the EU/EEA. It requires Notified Body involvement for most classes above Class I.

BME-123 · What is a Notified Body?

An independent organization designated by an EU member state to assess the conformity of medical devices, including QMS audits and technical documentation review, before CE marking.

BME-124 · What are design controls?

A set of quality-system practices for device development: design planning, inputs, outputs, reviews, verification, validation, transfer, changes and a design history file. Both FDA requirements and ISO 13485 mandate them.

BME-125 · What is the difference between verification and validation?

Verification asks "did we build the device right?": design outputs meet design inputs. Validation asks "did we build the right device?": the device meets user needs and intended use under actual or simulated use conditions.

BME-126 · What is ISO 10993?

The series of standards for the biological evaluation of medical devices. It covers the evaluation framework within risk management and specific tests such as cytotoxicity, sensitization, irritation, systemic toxicity, genotoxicity and implantation.

Clinical Engineering & Electrical Safety

BME-127 · What is clinical engineering?

The branch of biomedical engineering that manages healthcare technology in hospitals: procurement, installation, maintenance, safety testing, training, incident investigation and technology planning.

BME-128 · What is the difference between macroshock and microshock?

Macroshock is current entering and leaving through the skin, where only a fraction reaches the heart, so milliampere levels are needed for harm. Microshock is current applied directly to the heart, through catheters or pacing wires, where microampere levels can cause VF.

BME-129 · What is leakage current?

Unintended current that flows from live parts of equipment to earth, to the enclosure or through the patient. It is mainly caused by capacitive coupling and insulation imperfections.

BME-130 · What is the difference between Class I and Class II electrical equipment?

Class I relies on basic insulation plus a protective earth connection to accessible metal parts. Class II relies on double or reinforced insulation and has no protective earth. Internally powered equipment is a third category.

BME-131 · What are type B, BF and CF applied parts?

B (body) parts may be earthed and are not for direct cardiac use. BF (body floating) parts are isolated from earth. CF (cardiac floating) parts are highly isolated, with the lowest leakage limits, for direct cardiac contact.

BME-132 · What is preventive maintenance?

Scheduled inspection, calibration, part replacement and performance and safety testing of medical equipment to reduce failures and keep it accurate.

BME-133 · What is a CMMS?

A computerized maintenance management system: software that tracks equipment inventory, work orders, PM schedules, service history, recalls and costs for a clinical engineering department.

BME-134 · What is an applied part?

The part of medical electrical equipment that, in normal use, must come into physical contact with the patient to perform its function, such as ECG electrodes, SpO₂ probes or an ultrasound probe.

BME-135 · What 50/60 Hz current levels cause perception, let-go loss and ventricular fibrillation?

For hand-to-hand or hand-to-foot contact lasting about 1 s, perception is about 1 mA, the let-go threshold is about 10–20 mA and VF can occur from roughly 75–100 mA upward. Microshock VF can occur near 100 µA.

BME-136 · What is equipotential bonding?

Connecting all exposed conductive parts and equipment in a patient area to a common earthing point. This minimizes potential differences that could drive current through a patient, which is critical where microshock is possible.

BME-137 · What is an isolated power system in a hospital?

An ungrounded supply derived from an isolation transformer and fitted with a line isolation monitor. A single fault to ground does not cause a dangerous current or trip the supply, so critical equipment keeps running.

BME-138 · What is IEC 62353?

The standard for recurrent (in-service) and after-repair testing of medical electrical equipment. It covers visual inspection, protective earth resistance, insulation resistance and leakage tests, and is suited to hospital use.

Healthcare Informatics & AI

BME-139 · What is an EHR?

An electronic health record: a longitudinal digital record of a patient's health information (history, medications, labs, imaging, notes) that can be shared across care settings.

BME-140 · What is HL7?

Health Level Seven, a standards organization and family of messaging standards for exchanging clinical and administrative data between health information systems. HL7 v2 is widely used for ADT, orders and results.

BME-141 · What is FHIR?

Fast Healthcare Interoperability Resources, an HL7 standard that represents health data as modular resources (Patient, Observation, Medication) exchanged through RESTful APIs in JSON or XML.

BME-142 · What is DICOM?

Digital Imaging and Communications in Medicine: the standard file format and network protocol for medical images and their metadata. It ensures interoperability between scanners, PACS and workstations.

BME-143 · What is PACS?

A picture archiving and communication system that stores, retrieves, distributes and displays medical images digitally, replacing film.

BME-144 · What is HIPAA?

The U.S. Health Insurance Portability and Accountability Act. Its Privacy and Security Rules set requirements for protecting individually identifiable health information held by covered entities and their business associates.

BME-145 · What is PHI?

Protected health information: individually identifiable health information (such as name, dates, record numbers and diagnoses linked to a person) that is created or held by a covered entity under HIPAA.

BME-146 · What is Software as a Medical Device (SaMD)?

Software intended for one or more medical purposes that performs them without being part of a hardware medical device. An example is an app that analyses images to detect disease.

BME-147 · What is telemedicine?

Delivering clinical care remotely using telecommunications, such as video consultations, remote patient monitoring and tele-radiology.

BME-148 · What are sensitivity and specificity?

Sensitivity = TP/(TP + FN), the proportion of diseased patients correctly identified. Specificity = TN/(TN + FP), the proportion of healthy patients correctly identified.

BME-149 · What is a clinical decision support system?

Software that gives clinicians patient-specific assessments or recommendations, such as drug interaction alerts, risk scores and diagnostic suggestions, to support decisions at the point of care.

BME-150 · What are ICD-10 and SNOMED CT?

ICD-10 is the WHO classification of diseases used for coding diagnoses, statistics and billing. SNOMED CT is a comprehensive clinical terminology for detailed, computer-processable clinical documentation.

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