MD2101 Lecture 5 Diagnostic Devices for Respiratory System PDF

Lecture 5. Diagnostic Devices for Respiratory System Introduction to Biomedical Engineering Technology Boreom Lee [email protected] , X 3272 Department of BioMedical Science and Engineering Gwangju Institute of Sciences and Technology Copyright. Most figures/tables/texts in this lectu...

Lecture 5. Diagnostic Devices for Respiratory System Introduction to Biomedical Engineering Technology Boreom Lee [email protected] , X 3272 Department of BioMedical Science and Engineering Gwangju Institute of Sciences and Technology Copyright. Most figures/tables/texts in this lecture are from the textbook “Introduction to Biomedical Engineering Technology by Laurence Street 2016” and this material is only for those who take this class and cannot be distributed to anyone without the permission from the lecturer.  Pulmonary Function Analyzers Respiratory cycle – Normal resting breathing Inhalation: relatively constant volume of air inhaled, with a consistent pattern of flow Exhalation: removes the same volume, with somewhat different, but still consistent, flow patterns – Forced respiration Forced inhalation Forced exhalation  some air remaining in the lungs that cannot be expelled (with mixing, not always the same air with each breath) 2 Pulmonary Function Analyzers 3  Pulmonary Function Analyzers Parameters of respiratory(or pulmonary) system – ERV (expiratory reserve volume): maximum amount of air that can be exhaled starting from the low point of the normal breathing cycle – FEV1 (forced expiratory volume in 1s): the volume of air exhaled in the first second of an forced vital capacity (FVC) test – FEV1/FVC: the ratio of these two values (%) – FRC (functional residual capacity): the amount of air left in the lungs at the end of normal resting breath – FVC: maximum amount of air that can be exhaled in a single breath (with full effort) 4  Pulmonary Function Analyzers Parameters of respiratory(or pulmonary) system – IC (inspiratory capacity): maximum volume of air that can be taken into the lungs in a full inhalation Starting from the low point of the breathing cycle IC = tidal volume (VT) + inspiratory reserve volume (IRV) – IRV: maximum amount of air that can be inhaled from the end-inspiratory position Starting from the high point of the breathing cycle – MV (minute ventilation): the total volume of air exhaled from the lungs per minute (also called total volume) – MVV (maximum voluntary ventilation): The greatest volume of air that can be breathed per minute by voluntary effect Maximum breathing capacity 5  Pulmonary Function Analyzers Parameters of respiratory(or pulmonary) system – RV (residual volume): the amount of air remaining in the lungs at the end of a maximal exhalation – TLC (total lung capacity): the amount of air contained in the lung at the end of a maximal inhalation – VC (vital capacity): the volume of air that can be expelled from the lungs after a maximal inhalation VC = IC + ERV – VT: the volume of gas inhaled and exhaled during one breathing cycle 6  Pulmonary Function Analyzers Simple device: simply measure volumes Complex computerized systems – Measure every aspect of respiration – Charts and tables – Analysis, comparison with previous tests – Archiving – Full information about each patient including medications 7 Pulmonary Function Analyzers 8 Pulmonary Function Analyzers 9 Pulmonary Function Analyzers 10  Incentive Spirometer The simplest devices for evaluating respiratory function Tubes containing a ball meter or vane Patient breathes though the tube  a deflection in the measuring component that is proportional to breathing effort Often used to help patients keep up breathing exercises after surgery or recovery from some respiratory disease 11  Graphing Spirometer Simple spirometers – A breathing tube for the patient – A bellows or piston mechanism that can move when air from the patient’s breathing enters or leaves the system – Indicated by a pointer and calibrated strip, or by a pen moving against a chart recorder or drum recorder – Spirometer graph: volume against time, pressure against time, or pressure against volume More complex spirometers – Flow transducers that can provide direct rather than calculated flow rates Digital read-outs, built-in printers, or memory for storing past results 12  Pulmonary Function Analyzer Complete pulmonary function analyzers – Utilize flow transducers similar to those in spirometers The data is handled differently – Computer system analyzes the data values for most or all of the parameters described above Values, flow/volume charts: displayed on a video screen or printed Extensive analysis and documentation for all relevant information 13 Pulmonary Function Analyzer 14  Pulmonary Function Analyzer Exercise equipment: provide physical stress O2 and CO2 levels – may be measured within the patient breathing circuit Pulse oximetry – may be integrated 15  Respiration Monitors Respiration: one of the basic vital signs Automatic monitoring – Detection of variations in impedance of the chest directly – Placing a band with a sensor around the chest – Having an air-flow sensor near the patient’s nose or mouth – Magnetic field to the chest  variations in intensity of the field on the opposite side of the chest – indicative of the lung volume 16  Respiration Monitors Impedance pneumography – A constant electrical current – passed through the patient’s chest – Changes in voltages btw the contact points (e.g., the ECG electrodes)  impedance inferred Increased impedance: an increased volume of air in the lungs Analyzed for respiration tracing, along with ECG tracing Numeric value of breaths per minute 17 Respiration Monitors 18  Capnography Monitors CO2 level – Critical in determining the state of a patient’s health and in planning a course of treatment – High CO2 level: strong indicator of hypoxia  if left untreated, can lead to brain damage or death – Blood CO2 measurement – Amount of CO2 in exhaled breaths: additional information 19  Capnography Monitors Capnograph – A sensor with an infrared emitter and receiver CO2 absorbs certain frequencies of infrared light differently than does room air Passing a sample of exhaled air from the patient through this sensor: analyzing the variations in absorbance  accurate values of CO2 levels Requires regular user calibration - by placing the sensor on a closed cell that containing a known concentration of CO2 Has to warm up to a certain temperature (∵measurements vary with temperature) Need have the infrared signal modulated (turned on and off rapidly) to perform analysis: by motor driving a rotating shutter 20  Capnography Monitors Capnograph – Newer sensors Spectroscopy or nanotubes coated with special chemicals for CO2 measurements Faster sampling with shorter (or eliminated) warm-up times and smaller sample volumes Alleviate the need for user calibration – Most patient beneficial for capnography – on a ventilator, either during anesthesia or in an intensive care situation 21  Capnography Monitors Capnograph – Mainstream sampling A sensor mounted directly in the breathing circuit More reliable results Sensor & attachment apparatus: more bulky than that of sidestream sampling systems – Sidestream sampling – draw off a sample from the circuit to an external sensor 22  Oxygen Analyzers Effects of O2 levels – High level Adult – Can tolerate high O2 concentration for breathing – O2 conc. close to 100%  pulmonary edema, reduced gas exchange in the lungs, and oxidation of some substances within the body Too high level in neonates – Blood vessel formation significantly altered, especially in the retina and lens  vision impairment or blindness – Monitored to keep O2 level < 40% – Too low level Inadequate oxygenation in patients with impaired pulmonary or circulatory function, or when in anesthesia – Maintaining delivered O2 levels at specific value  important! 23  Oxygen Analyzers Oxygen analyzer – Chemical reaction btw certain chemicals (e.g., KOH) and O2  electrical potential produced – “Electrogalvanic fuel cell” O2 in contact with the chemical in a cell with electrodes  potential developed – proportional to the O2 conc. O2 is consumed as the material in the cell oxidizes – The supply of “fuel” in the cell is limited  the chemical reaction – will eventually cease Cells kept in very well-sealed containers until in use Replaced when depleted 24 Oxygen Analyzers 25  Oxygen Analyzers Calibration – The exact potential produced within the cell – vary somewhat over time (∵the reactant in the cell is used up) – The system must be calibrated whenever a cell is replaced, and regularly while in use Indication necessary for calibration – Two known O2 concentrations (room air vs 100% O2) Room air (20.95% O2) – Almost no significant variation except at high elevations – Thus used as a convenient calibration point Exposing the cell  taking voltage readings Used to adjust the compensation required to produce linear results 26  Bronchoscopy Systems Similar in many ways to other endoscopic systems – To see within the upper part of a patient’s respiratory system – Look for Damage, restriction, or abnormal tissues Components – Tubes (actual bronchoscope) Inserted via the mouth or nose, past the larynx And through the epiglottis to the trachea and the left/right bronchi – Light source, camera, one or more video monitors – Video recorder and/or printer – A mechanism for flushing and suctioning – Various associated apparatus 27 Bronchoscopy Systems 28  Bronchoscopy Systems Bronchoscope (or “scope”) – Optical channels Deliver light to the end of the scope Send an image from the end of the scope back to the viewer – One or more hollow sections Admit instruments Used for irrigation, suction and insufflation – Flexible scopes Made thinner  reach further into bronchial passages Fiber-optics 29  Bronchoscopy Systems Bronchoscope (or “scope”) – Rigid scopes Allow certain instruments or lasers – introduced through mouth Biopsies, dilations, or burning of small growths Usually used only with general anesthesia; only introduced though the mouth Lenses used within the tube to transmit illumination and images – Cracked/damaged lenses (rigid), broken optical fibers (flexible)  reduced illumination and image quality 30  Bronchoscopy Systems Bronchoscope (or “scope”) – Camera sensor Most scopes until recently: at the proximal end – to pick up the visual images transmitted by the fiber-optic channels Some new scopes with advances in miniaturization: imaging chips mounted on the distal end – eliminate some transmission problems (∵wires made smaller and more flexible than optical components) 31 Bronchoscopy Systems 32