BiomedicalInstrumentation

Transcription

1 University of Zagreb Faculty of Electrical Engineering and Computing BiomedicalInstrumentation Measurementofrespiration prof.dr.sc. Ratko Magjarević October 2013

2 Respiratorysystem Consistsofthelungs, airways and the chest wall Function of respiratory systemisgas exchange(o 2 andco 2 ) betweenthe blood and the atmosphere Gas exchange is passive due to diffusion

3 Gas exchange Parcijalni tlak plinova u različitim dijelovima respiratornog i cirkulacionog sustava (mmhg) Lokacija po2 (mmhg) pco2 (mmhg) ph2o (mmhg) pn2 (mmhg) Udahnuti zrak 158,0, 0,3 5,7 596,0 Alveolarni zrak 100,0 40,0 47,0 573,0 Izdahnuti zrak 116,0 32,0 47,0 565,0

4 Respiratorymeasurementsinstrumentation Imaging x-ray, CT, MRI Lung volume change estimation or detection Fluoroscopes Electrical, mechanical or pneumatic devices placed around torso Nasal temperature sensors Transthoratic electrical impedance meters Force plates for movement detection associated with breathing

5 Characteristic respiratoryvalues The following five static lung volumes can be measured: VT (tidal volume), IRV (inspiratory reserve volume), ERV (expiratory reserve volume), IC (inspiratorycapacity) and VC (vital capacity).

6 Breathingwaveform

7 Spirometers Most digital spirometers display the following graphs: A volume-time curve, showing volume (liters) along the Y-axis and time (seconds) along the X-axis A flow-volume loop, which graphically depicts the rate of airflow on the Y-axis and the total volume inspired or expired on the X-axis

8 The shape of the flowvolume loop can indicate the location of airflow limitation, such as the large upper airways or smaller distal airways

9 Spirometers PneumotachometerThis type of spirometeris also referred to as a differential pressure transducer (DPT) and measures the flow of air by detecting pressure differences across the two sides of a fine wire-mesh within a flow head. One advantage of this spirometeris that the subject under investigation can breathe in fresh air during the experiment. However, a DPT does not providean output reading of absolute pressure within the system. Whole body plethysmographthe whole body plethysmographprovides a more accurate measurement for the components of lung volumes comparedto conventional spirometers. In this technique, the subject is enclosed in a small airtight chamber when the measurement is taken. This method obtains the absolute volume of air within the subject s lungs.

10 Respiratoryrate measurement Spirometryis a non-invasive method of lung function testing, which measures the amount (volume) and/or speed (flow) of air that can be inhaled and exhaled. Most lung function tests involve fairly simple breathing tasks and are usually not uncomfortable. Breathing requirements for some test measurements may be normal and quiet. Other tests require forced inhalation or exhalation after a deep breath. Spirometry can be used for assessing lung conditions such as asthma, emphysema, pulmonary fibrosis and cystic fibrosis. methodes

11 Respiratoryrate measurement methods Pneumotachometerisa device that measures the flow of respiratory gases. The pressure gradient is directly related to flow, thus allowing a computer to derive a flow curve measured in liters per minute. Lung function can be determined by measuring airflow and the corresponding changes in lung volume.

12 Measurement and visualization in real time mode both quiet (spirometry), and forced (pneumotachometry) breathing, measurements of maximal breathing capacity; Simultaneous review of several curves of forced expiration and self-acting (or hand-held) choice of best test; Construction of spirometry graphs (volume-time) and pneumotachometries(flowvolume, volume-time) in real time,

13 Forced expiratory flow (FEF)

14 Forced expiratory flow (FEF) Forced expiratory flow (FEF) is the flow (or speed) of air coming out of the lung during the middle portion of a forced expiration. Forcedvitalcapacity(FVC) is the volume of air that can forcibly be blown out after full inspiration, measured in liters. FVC is the most basic maneuver in spirometry tests. Forced expiratory volume in 1 second (FEV1)represents the proportion of a person's vital capacitythat they are able to expire in the first second of expiration Forcedexpiratory flow25 75% (FEF25 75%) a mean of the flow during an interval

15 Forced expiratory flow (FEF) Measurement Approximate value Male Female Forced vital capacity(fvc) 4.8 L 3.7 L Tidal volume(vt) 500 ml 390 ml Total lung capacity (TLC) 6.0 L 4.7 L Average values for forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1) and forced expiratory flow 25 75% (FEF25 75%), according to a study in the United States 2007 of 3,600 subjects aged 4 80 years.y-axis is expressed in litresfor FVC and FEV1, and in litres/second for FEF25 75%.

16 A plethysmographis an instrument for measuring changes in volume within an organ (e.g.lungs) or whole body Pulmonary plethysmographsare commonly used to measure the functional residual capacity (FRC) of the lungs the volume in the lungs when the muscles of respiration are relaxed and total lung capacity.

17 Water-sealedspirometar

18 Peakexpiratoryflow The peak expiratory flow(pef), or peak expiratory flow rate (PEFR) is a person's maximum speed of expiration, as measured with a peak flow meter, a small, hand-held device used to monitor a person's ability to breathe out air. It measures the airflow through the bronchi and thus the degree of obstruction in the airways.

19 Impedance pneumography Impedance pneumographyis a commonly-used technique to monitor a person s respiration rate, or breathing rate. It is implemented by either using two electrodes (Figure 6.4a) or four electrodes (Figure 6.4b). The objective of this technique is to measure changes in the electrical impedance of the person s thoraxcaused by respiration or breathing.

20 Piezoelectricsensors Mountedon a beltthepiezoelectric device that responds linearly to changes in length It measures changes in thoracic or abdominal circumference during respiration. These measurements can indicate inhalation, expiration and breathing strength and can be used to derive breathing rate.

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22 Literature A. Šantić, Biomedicinska elektronika, poglavlje 7.5 Mjerenje karakterističnih veličina respiracije Weber, J., MedicalInstrumentation, Chapter 9, Measurement of the Respiratory System