1 Design of a Vital Sign Protocol Format Using XML and ASN.1 Bayu Erfianto Graduation Committee prof. dr. ir. D. Konstantas dr. ir. I. Widya dr. ir. A. van Halteren A thesis submitted to the department of Computer Science of the University of Twente for the partial fulfillment of the requirements of the degree of Master of Science in Telematics Enschede, The Netherlands 2004
2 II Abstract Tele-monitoring of the condition of patients is an essential component of an electronichealthcare (e-health) system. In an electronic health record system, vital signs which reflect the condition of the patient have to be transferred over the heterogeneous communication network. One of the fundamental problems in dealing with communication in heterogeneous systems is to exchange data in such a way that the data received can be interpreted the same ways as the data before transmission. In the OSI model, the representation of data (including data structures and data types) to be exchanged is a function of the application layer . Meanwhile, the encoding of the data format into a specific bytes stream for transfer is addressed by the presentation layer. This separation of functions allows the application layer deal only with the data format, independent of the encoding type applied in Presentation Layer. The aim of this thesis is to investigate the tool-based design methods to construct a protocol data format for distributed applications that apply separation of data format specification at several abstraction levels, distinguishing between abstract syntax formats and distinguishing transfer syntax format which are meaningful for the applications and the underlying transport systems, respectively. The design methods address some features presented by XML-based data format, while to get more compact transfer syntax, the design methods makes use of ASN.1 encoding rules to produce binary-encoded data format. Many electronic health record systems use XML technology as data format in the application layer. One of the benefits of using an XML-based data format is independency from encoding issue applied in its underlying layer. However, considering to the transfer syntax, an XML-based data format consumes more data length. It is because of the encoding technique used by XML-based data format is based-on textual encoding. By applying encoding rules like in ASN.1 in the presentation layer, the electronic health record system may produce a more compact transfer syntax, due to the feature of ASN.1 encoding rules that can generate binaryencoded data format, which is more compact than textual encoding like used by XML. The design methods are then applied to construct a protocol data format specific for electronic health records, including vital signs data of both continuous-time and non continuous-time type.
3 Table of contents Table of contents III Abstract...II Table of contents... III List of Figures... V List of Tables...VII Chapter 1 Introduction Aim of the thesis Problem studied in this thesis Solution Approach Structure of the Thesis Chapter 2 Physiology of Vital Signs Electrocardiography Electromyography Respiratory Blood Pressure Oxygen Saturation Chapter 3 Vital Sign Format Standards Introduction CEN/TC-251 Standard Communication Protocol FDA DICOM DICOM Message Structure and Encoding DICOM Upper Layer PDU Structure...26 Chapter 4 Design Methods Design Principles Design Methods Message Framework Definition Abstract Syntax Format ASN XML XML Schema and ASN.1 Cooperation Mapping XML Schema to ASN Mapping ASN.1 to XML Schema...52 Chapter 5 Patient Medical Record Specification Design Requirements Patient Demographic Record Specification XML-based Patient Demographic Record ASN.1-based Patient Demographic Record ECG Record Specification Lead Record Specification XML and ASN.1-based ECG Record Specification Blood Pressure Record XML-based Blood Pressure Record Specification ASN.1-based Blood Pressure Record Specification...74 Chapter 6 Demonstrator Implementation Architecture of Demonstrator Interface Implementation Result and Analysis Analysis of Patient Demographic Record Analysis of Lead Record and ECG REcord...83
4 Table of contents IV Analysis of Blood Pressure Record Conclusion General Conclusion Future Work Appendix A: Generating ECG Data Appendix B: Trial Case Scenario Appendix C: Specification of Application Protocol Bibliography Index
5 V List of Figures Figure 1 The heart contraction of heart muscles...12 Figure 2 The Normal 12 Lead ECG Waveform ...13 Figure 3 ECG Lead Positions in the body...15 Figure 4 Normal Rhythm and Sinus Bradycardia ...15 Figure 5 S-EMG Electrode ...16 Figure 6 (a) EMG Signal detected by DE-21 electrode. (b) EMG signal digitized by sampling rate at 2 KHz or every 0.5 ms, taken from ...16 Figure 7 Human Respiratory System...17 Figure 8 Pressure Based (left) and Volume Based (right) Respiratory Waveform...18 Figure 9 Oxygen Saturation Measurement...19 Figure 10 SCP Message Layout...22 Figure 11 FDA Application GUI...24 Figure 12 DICOM Message Exchange...25 Figure 13 DICOM Message...25 Figure 14 DICOM Data Set...26 Figure 15 P-DATA-TF PDU...27 Figure 16 P-DATA Service...27 Figure 17 Hierarchical Tree of ECG Record ...28 Figure 18 XML Schema Diagram of ecgml Record...28 Figure 19 XML Schema Diagram of Record Type and Waveform Type...29 Figure 20 Abstract Syntax, Local Syntax, and Transfer Syntax...32 Figure 21 Design methods to constitute protocol data format by separating user point of view and transfer point of view at abstract syntax specification...35 Figure 22 Intuitive interpretation of Message Framework consisting Customer Information...36 Figure 23 Iconography of Message Object...37 Figure 24 Message Object Diagram of Customer Information...38 Figure 25 Abstract Syntax and Transfer Syntax Definition...39 Figure 26 Tag, Length, Value in used in ASN.1 Encoding Rule...40 Figure 27 Tag Encoding...41 Figure 28 Example of ASN.1 Tag Encoding...41 Figure 29 Example of in ASN.1Length Encoding...41 Figure 30 Two Examples of Contents Encoding...41 Figure 31 XML Schema Diagram of Customer...46 Figure 32 ASN.1 Compilation process using ASN1C...47 Figure 33 Generating the ASN.1 binary-encoded (BER) data format using ASN1C Java Version...48 Figure 34 Content of Customer.bert viewed by Objective System ASN.1 Viewer...48 Figure 35 XML Schema to ASN.1 Translator from French Telecom...51 Figure 36 asn2xsd command Tool...53 Figure 37 Message Object Diagram of Patient Demographic Record...57 Figure 38 XML Schema Diagram of Patient Demographic Record in...58 Figure 39 Message Object Diagram of ECG Record...63 Figure 40 Message Object Diagram of Lead Record...65 Figure 41 XML Schema Diagram of Lead Record...66 Figure 42 Multiplexing Lead data...69
6 List of Figures VI Figure 43 XML Schema Diagram of ECG Record...70 Figure 44 Message Object Diagram of Blood Pressure Record...72 Figure 45 Specification of Blood Pressure Record in XML Schema Diagram...73 Figure 46 Encoder and Decoder Architecture...78 Figure 47 Refined ASN.1 Encoder and Decoder Module...79 Figure 48 Encoder Architecture in UML package diagram...80 Figure 49 Encoder Architecture in UML package diagram...81 Figure 50 Encoder Interface...82 Figure 51 ECG Generator Interface...82 Figure 52 Decoder Interface...82 Figure 53 Binary encoded of Patient Demographic Record value (using BER). The size of this binary-encoded BER file is 206 Bytes. This binary-encoded file is viewed by ASN.1 Viewer from Objective System...83 Figure 54 Piece of binary-encoded BER file of Lead Record...85 Figure 55 Piece of binary-encoded BER file of ECG Record...86 Figure 56 Binary encoded of Patient Demographic Record value (using BER). The size of this binary-encoded BER file is 206 Bytes. This binary-encoded file is viewed by ASN.1 Viewer from Objective System...86 Figure 57 Plot of Synthetic ECG data generated from ECGSyn...92 Figure 58 Connection Establishment Phase...95 Figure 59 Send Data Phase...96 Figure 60 Disconnection Phase...96 Figure 61 The Location of Service Primitives in SAP...96 Figure 62 PDU Layout...98 Figure 63 PMR PDU Format...99
7 VII List of Tables Table 1 ECG Rhythm...15 Table 2 Categories for Blood Pressure Levels (in mmhg)...19 Table 3 P-DATA Field Description...27 Table 4 Description of ECGRecord...28 Table 5 Description of Waveform Record ...29 Table 6 Customer Record Description...38 Table 7 Patient Demographic Record Definition...57 Table 8 ECG Record Definition...63 Table 9 List of standardized ECG lead number descriptors based on CENT/TC Table 10 LeadData Record Definition...65 Table 12 Blood Pressure Record Definition...73 Table 11 Encoding Integer value using BER...84 Table 22 Lead Data...91 Table 13 Tele Trauma Definition...93 Table 14 Coronary Heart Disease Definition...93 Table 15 Respiratory Problem Case Definition...93 Table 16 Home Care and Remote Monitoring Case Definition...94 Table 17 High Risk Pregnancy Definition...94 Table 21 Service Description...97 Table 18 PDU ID...98 Table 20 Relationship among Trial Case and Vital Sign Priority...99
8 Chapter 1 Introduction 8 Chapter 1 Chapter 1 Introduction This thesis is about the design of a data format for an electronic health care (e-health) record. The additional task is to develop a demo to validate the data format. In this introductory chapter, aim of the thesis, problem studied in this thesis, solution approach, and the structure of the thesis will be presented. 1.1 Aim of the thesis The aim of this thesis is to investigate design methods to construct a protocol data format suitable for different composition of data for different health care specialties. The additional aim is to present demonstrator implementation to validate the data formats derived using the design methods. 1.2 Problem studied in this thesis Two main problems are studied in this thesis, though some other related problems also addressed. The first problem deals with the representation of physiological information for electronic health record purpose. The second problem deals with developing toolbased design methods to construct data format. The research questions presented in the following lines drive us to the problem studied in the thesis, as follows: How to present the physiological information of vital signs in an electronic health record? This question leads us to know what kind of parameters, components or elements required to construct an electronic health record. First of all we study the physiological information of a vital sign and come to investigate the available standards that are used for presenting the information of a vital sign. In an electronic health record system, the vital signs data that acquired from sensors are required to be presented in a data format before they are exchanged over a communication network. This data format makes the application program get an abstract understanding of vital signs data to be exchanged over a communication network. Hence, the receiver can do interpret as the same as the sender. The abstract understanding also separates between syntax used by data format in application level and the syntax for transmission.
9 Chapter 1 Introduction 9 There have been many efforts initiated by many academic institutions, governments, and manufacturers of medical instrument to propose the standard of data format for representation of vital signs or biomedical information, including biological signal, images or text. CEN/TC-251 (Comité Européen de Normalisation European, Committee for Standardization, Technical Committee 251) has proposed data format for electronic healthcare application [2, 8]. DICOM (Digital Imaging and Communication in Medicine) [29, 30, 31, and 32] has also defined its own standard which supports exchange between medical imaging system and health care information system. ecgml has also proposed data format for ECG Record application exchange by making use of XML technology as its data format . These efforts aimed at defining data format to carry the medical information over the heterogeneous communication network. By investigating the available vital sign format standards, this inspires us to construct the vital sign data format for our purpose. This will also allow us to study the advantages and disadvantages of those vital sign data format standards. The knowledge will be useful later if we want to build our own vital sign data format, which combines all the positive aspects of the investigated standards. What criteria are needed to develop the design methods to construct data format, and how to apply the developed design methods to construct electronic health record that meet our purpose? In the OSI model, the representation of data (including data structures and data types) to be exchanged is a function of the Application Layer . Meanwhile the encoding of the data format into a specific bytes stream for transfer is addressed by the Presentation Layer. This separation of function allows the Application Layer to deal only with the data format, independent of the encoding type applied in Presentation Layer. By considering the separation of functions among abstraction levels, and transfer syntax format, this thesis comes up the design methods to construct a common protocol data format. Furthermore, we will apply the design methods to construct protocol data format which meets our requirements. 1.3 Solution Approach To address the problems studied in this thesis and to achieve the objectives of this thesis, the activities to approach the solution have been taken as follows: Background study of physiology of vital sign The first task is to collect as many as information about the physiological of vital signs and investigate the required components to build vital sign format standard. However, there are only 5 vital signs that have been taken into account in this thesis i.e. ECG, EMG, Respiratory, Oxygen Saturation, and Blood Pressure. The description of this task is presented in Chapter 2. Investigate the available electronic health record and vital sign format standards The second task is then to investigate the available electronic health record and vital sign format standards. This investigation inspires us to adopt the format standards defined in CEN/TC 251, DICOM, and FDA. There is also ecgml,
10 Chapter 1 Introduction 10 which uses XML technology on top of application layer data format. The protocol data format used in ecgml complies with FDA standard. The description of this task is presented in Chapter 3 Investigate the requirements to develop design methods that is used to construct a data format This task will include design principles i.e. separating the data format specification, distinguishing abstract syntax format, and distinguishing transfer syntax. The design criteria and design choice has also been taken into account to construct of such data format. The description of this task is presented in Chapter 4 Applying the design methods to construct electronic health record data format This task reuses the developed design methods and integrates with the concept, nomenclature and other parameters where applicable from the available electronic health record and vital sign format standards to construct the protocol data format for electronic health records for our purpose. The description of this task is presented in Chapter 5 Develop a demonstrator to validate the design methods and developed data format The developed demonstrator is based-on graphical interface. The demonstrator consists of two parts: Encoder Application and Decoder Application. The architecture of demonstrator application is discussed in Chapter Structure of the Thesis This thesis is organized as follows: Chapter 1: Introduction Chapter 2: Physiology of Vital Sign describes the physiology of vital signs. It presents a brief overview of vital signs from the physiological point of view. Chapter 3: Vital Sign Format Standard discusses some standard used to construct vital signs data format. The presented standards are taken from DICOM, FDA, and CEN/TC It presents the ecgml as well, that is an application of encoding ECG data using XML. Chapter 4: Design Methods presents the design principles and design methods to develop a protocol data format Chapter 5: Patient Medical Record Specification presents the design methods applied to construct a protocol data format for patient medical record purpose. Chapter 6: Demonstrator Implementation presents a demonstrator application to validate the Patient Medical Record data format derived from the design methods. Chapter 7: Conclusion
11 Chapter 2 Physiology of Vital Signs 11 Chapter 2 Chapter 2 Physiology of Vital Signs Aim of this chapter is to present a brief overview of physiology of vital signs. However, this chapter will not discuss all type of vital signs. A brief introduction to electrocardiography is presented in Section 2.1. Section 2.2 gives a brief overview of electromyography. Section 2.3 will give brief overview of human respiratory system. Section 2.4 presents the blood pressure. This chapter will end up with Section 2.5, which gives a brief overview of Oxygen Saturation. 2.1 Electrocardiography Vital signs such as heartbeat, breathing rate, temperature, and blood pressure indicate human's general physical condition 1. The physician can observe, measure, and monitor these vital signs to assess human s health condition. One or more sensors can capture the physical information of a vital sign. Upon capturing the vital signs, the values can also be recorded into analog or digital medium. The electrocardiography is a technique of recording the bioelectrical signal generated by the heart activity. The activity of heart can be measured by placing a sensor on the body of a patient, recorded on a graphical paper and displayed as a graphical representation on a monitor. This graphical representation is called electrocardiogram. Thus, the acronym of ECG may stand for both electrocardiogram and electrocardiography. The following subsection will describe the basic physiology of human heart and its activity, summarized from [6, 7]. Basic Physiology of ECG The muscle of heart always makes contraction in a certain period to pump the blood to all part of human body. This contraction of heart is regulated in a center located in the right atrium 2 known as the sinus node 3 [see Figure 1]. Cells compose heart muscle. These cells have a special property: they spontaneously depolarize with various rates. 1 Definition of vital sign is taken from The Free Dictionary, available at 2 Chamber of the heart 3 An area of special heart tissue that generates the cardiac electric pulse controlled by autonomic nervous system (Mosby Medical Dictionary)
12 Chapter 2 Physiology of Vital Signs 12 The cells of the sinus node depolarize faster than the other heart cells, hence the heart rate is determined here. The electrical impulse generated in the sinus node spreads throughout the right atrium, causing them to contract. P wave represents the impulse from the sinus node to the AV node. When the impulse travels along the structure and reaches "bundle of His", this leads to the generation of the "PR Interval". When the impulse travels across the ventricle (from left to right atrium via left and right bundle branches), this will cause the ventricle to depolarize, it leads to the generation of QRS wave. The impulse resulted from ventricle contraction then propagates to the ventricular myocardium 4 via the "purkinje fibres". This will cause the ventricle to re-polarize. It leads to the generation of T wave. Right Atrium Left Atrium Right Ventricle Left Ventricle Figure 1 The heart contraction of heart muscles The ECG Wave Einthoven, the inventor of first ECG recording device, named the waves he observed on the ECG using five capital letters from the alphabet i.e. P, Q, R, S, and T . The wave on the horizontal axis represents a time domain and the Voltage in the vertical axis [see Figure 2]. On the electrocardiogram, the height and depth of a wave represent a measured voltage. An upward deflection of a wave is called positive deflection and a downward deflection is called negative deflection [6, 7]. The right side of picture on Figure 1 shows the correlation between heart contraction and the basic ECG waveform generated by ECG device . That waveform represents the intervals as well as standard in time (ms) and in voltage (mv). According to Figure 2, it can be summarized that the PQRST waves discuss earlier exist during one heartbeat period . The atrial depolarization wave, (P wave), is a small upward wave. The QRS Complex which represents ventricular depolarization , begins as a downward deflection, continues as a large, upright, triangular wave, and ends as a 4 The middle muscular layer of the heart wall (Webster Online Dictionary)
13 Chapter 2 Physiology of Vital Signs 13 downward wave to its base. The dome-shaped T wave indicates ventricular repolarization. Figure 2 The Normal 12 Lead ECG Waveform  The ECG waveform can also be annotated to give a remark in each PQRST wave. The averages values of ECG annotation point (from a normal ECG waveform) can be obtained as follows : Peak value of P wave 0.15 mv Peak value of Q wave -0.1 mv Peak value of S wave segment -0.3 mv Peak value of R 1.1 mv Peak value of T wave 0.2 mv Peak value of U wave 0.05 mv P to P Duration 800 ms P-wave duration 100 ms P to R duration 160 ms QRS Complex duration 70 ms Q to T duration 240 ms T wave duration 175 ms S-T Segment 140 ms The ECG data is represented in 2 dimensions of numerical data: time and voltage dimension. In this approach the sampling rate of ECG waveform is required. The following lines are the example of properties of an ECG waveform taken from : Digitization Sampling Rate = 100 samples/s; LSB = 5µV Sampling Interval = 8ms Absolute Error1 = 100µV in a single sample (outside P-QRS-T) Absolute Error2 = ±15µV in a single sample (within QRS) ECG Length = 10 seconds The ECG Leads The ECG signals can be measured by placing pairs of electrodes on the human body. However, the ECG waves from these signals have different shapes, depending on the
14 Chapter 2 Physiology of Vital Signs 14 position on where they are placed. In electrocardiography, those pairs of electrodes are called ECG lead. A standard has been established in electrocardiography that specifies 12 leads and the corresponding positions of the electrodes on the human body . The standard also provides way of obtaining the 12 standard ECG leads by combining the signals from different electrodes. The reason for recording and analyzing more than one single ECG lead is that different parts of the heart can be seen well from different positions by different leads. Hence, each ECG lead provides a different shape of the same heart activity. The 12 standard ECG leads are classified in limb leads, called I, II, III, AVR, AVL and AVF and chest leads called V1, V2, V3, V4, V5, V6 [6,7]. The limb leads provide views of the heart activity in the frontal plane and the chest leads provide views in the horizontal plane of the heart . Figure 3 depicts the position of ECG leads either limbs lead and chest lead in the body with corresponding electrode positions. The meaning of each lead in ECG 12 leads and the way of obtaining them are described in the following lines : I: is a lead obtained between a negative electrode placed on the right arm and a positive electrode placed on the left arm II: is a lead obtained between a negative electrode placed on the right arm and a positive electrode placed on the left foot III: is a lead obtained between a negative electrode placed on the left arm and a positive electrode placed on the left foot AVR: is a lead obtained between the average signal obtained from three negative electrodes (left arm, left leg and right foot) and the signal obtained from a positive electrode placed on the right arm AVL: is a lead obtained between the average signal obtained from three negative electrodes (right arm, left foot and right foot) and the signal obtained from a positive electrode placed on the left arm AVF: is a lead obtained between the average signal obtained from three negative electrodes (left arm, right arm and right foot) and the signal obtained from a positive electrode placed on the left foot V1: is a lead obtained between the reference negative electrode and a positive electrode placed on the chest in the V1 position V2: is a lead obtained between the reference negative electrode and a positive electrode placed on the chest in the V2 position V3: is a lead obtained between the reference negative electrode and a positive electrode placed on the chest in the V3 position V4: is a lead obtained between the reference negative electrode and a positive electrode placed on the chest in the V4 position V5: is a lead obtained between the reference negative electrode and a positive electrode placed on the chest in the V5 position V6: is a lead obtained between the reference negative electrode and a positive electrode placed on the chest in the V6 position V5: is a lead obtained between the reference negative electrode and a positive electrode placed on the chest in the V5 position V6: is a lead obtained between the reference negative electrode and a positive electrode placed on the chest in the V6 position
15 Chapter 2 Physiology of Vital Signs 15 Purposes of ECG Figure 3 ECG Lead Positions in the body Electrocardiography examination is used for detecting many heart problems. It may be used routinely for monitoring the patient's condition during and after surgery, as well as routine health care check. The physician can know the abnormality of heart function by evaluating and analyzing the heart rhythm depicted by electrocardiogram. By investigating the duration of various events within the ECG PQRS cycle, the physician can find out whether these ranges may be considered either as abnormal or not . ECG Wave Table 1 ECG Rhythm Normal range P wave less than 0.12s PR s QRS less than 0.10s The following lines give the example of abnormal rhythm of heart activity taken from . The general terms of abnormal ECG rhythm can be identified as follows: Bradycardia means that a heart rate is lower than normal. Tachycardia means that a heart rate that is higher than normal. Paroxysmal an arrhythmia (irregular heartbeat) that suddenly begins and ends. Sinus bradycardia occurs when the hearts rate is slower than 60 beats per minute. The sinus bradycardia rhythm is similar to normal sinus rhythm, except that the R-R interval is longer than normal. Each of P wave is followed by a QRS Complex. The PR interval is often slightly prolonged and occasionally, the P-waves might be abnormally wide. Figure 4 shows the normal cardiac and the cardiac, which gets sinus bradycardia. The ECG at the top shows normal sinus rhythm. The ECG at the bottom shows sinus bradycardia. R-R Figure 4 Normal Rhythm and Sinus Bradycardia 
16 Chapter 2 Physiology of Vital Signs Electromyography Electromyography (abbreviated as EMG) is a technique of recording the bio-electrical signal generated by the electrical activity of a muscle which involves the action of muscles and nerves and generates an electrical impulse known as EMG signal. In some medical conditions the electrical activity of the muscles or nerves behaves abnormally. Investigating and observing these electrical properties of the muscle or nerve can quickly help the physician to diagnose the muscle activities whether behaves normally or not. EMG is obtained by measuring the electrical impulse of a muscle. The measurement of EMG signal can be performed in two ways. The first way is intramuscular technique in which apply thin sensor inside the muscle. The second way is using the electrode attached on the body surface. The famous way is using the second one and result of this measurement well known as Surface EMG (S-EMG) . Figure 5 illustrates an S-EMG electrode placed on the muscle, taken from . Figure 5 S-EMG Electrode  The EMG measurement technique initially results the analog data. Thus, this S-EMG Device must digitize the analog S-EMG signal into digital (numerical) representation by implementing sampling technique. The sampling process depicted in Figure 6, generated by a sample Motor Unit Action Potential (MUAP) obtained with a DE-2.1 electrode . Figure 6 (a) EMG Signal detected by DE-21 electrode. (b) EMG signal digitized by sampling rate at 2 KHz or every 0.5 ms, taken from 
17 Chapter 2 Physiology of Vital Signs 17 The amplitude of the signal can vary from 0 to 10 mv (peak-to-peak) or 0 to 1.5 mv (rms). The usable energy of the signal is limited to the 0 to 500 Hz frequency range, with the dominant energy being in the Hz range . 2.3 Respiratory Respiration represents the rate of breathing in which a person inhales and exhales. Every 3 to 5 seconds, nerve impulses stimulate the breathing process, or ventilation, which moves oxygen into and out of the lungs. Hence, the respiration rate can be measured in terms of volume of oxygen per breathing period or in pressure in breathing period. Therefore, by observing this rate of breathing we can obtain a quick assessment of a person's health. Figure 7 Human Respiratory System The human respiratory system, as illustrated in Figure 11, consists of organs that supply oxygen to all part of the body . In addition to supplying the oxygen, the human respiratory system also plays a role in taking out the carbon dioxide from the human body. Respiration involves at least three distinguished events : Pulmonary ventilation; known as breathing process. The gas moves into and out of the lungs so that the alveoli of the lungs continuously get fresh oxygen. This relates to the two phases of breathing i.e. inspiration, when gas is flowing into the lungs, and expiration, when gas is leaving the lungs. External respiration; is the exchange oxygen and carbon dioxide in the eternal environment Internal respiration; exchanges O 2 and CO 2 between blood in the capillary vein and body cells. During the respiratory measurement, the measured volume of gas can be distinguished as follows : Tidal volume; the amount of gas moved during normal breathing. The amount of measurement is approximately 500cm 3. Inspiratory reserve volume; the amount of gas that can be taken vigorously over the tidal volume. The amount of measurement is approximately 3100cm 3. Expiratory reserve volume; the amount of gas that can be vigorously exhaled after a tidal expiration. The amount of measurement is approximately 1200cm3.
18 Chapter 2 Physiology of Vital Signs 18 Residual volume; RV is the amount of gas that remains in the lungs even after the most vigorous expiration. The amount of measurement is approximately 1200cm 3. The respiratory measurement can be represented in continues (time series) data as shown in Figure 8 or in non-time series data. If we use time-series data, there are two types of respiratory graphic format i.e. Pressure Mode ventilation 5 and Volume Mode ventilation. Volume Control and Pressure Control mode refer to the parameter that is set or being controlled by the ventilator . Inspiratory time is the parameter that controls cycling of the ventilator. The set volume or set pressure will be delivered within the set inspiratory time. Figure 8 Pressure Based (left) and Volume Based (right) Respiratory Waveform In Volume Control mode, the volume is constant and pressure will vary. On the contrary, in Pressure Control mode pressure is constant and volume will vary . The volume control mode and pressure control mode waveform are illustrated in the Figure Blood Pressure Blood is carried from the heart to all parts of body in vessels called arteries. Based on the definition taken from , blood pressure is the force of the blood pushing the walls of the arteries. Each time the heart beats, normally times a minute, it pumps out blood into the arteries. The blood pressure is at its highest beat when the heart pumping the blood into the body part. This is called systolic pressure. When the heart is at rest, between beats, the blood pressure falls down. This is known as diastolic pressure. Blood pressure is always given as these two numbers, the systolic and diastolic pressures such as 120/80 mmhg. The top number is the systolic and the bottom the diastolic. Table 2 gives the examples of classification of blood pressure level taken from . By means of that table the physician can see three cases of blood pressure level i.e. Normal condition, pre-hypertension and hypertension based on the value belongs to systolic 5 The process by which gases are moved in to and out of the lungs (Mosby Medical Dictionary)
19 Chapter 2 Physiology of Vital Signs 19 pressure and diastolic as well. Table 2 Categories for Blood Pressure Levels (in mmhg) Category Systolic (Top number) Diastolic (Bottom number) Normal Less than 120 Less than 80 Normal Less than 120 Less than 80 Pre-hypertension High Blood Pressure Stage Stage or higher 100 or higher 2.5 Oxygen Saturation Oxygen saturation is an indicator of percentage of hemoglobin saturated with the oxygen at the time of measurement. The instrument, well known as pulse oximetry, uses two sources of infra red light that are absorbed by hemoglobin and transmitted to a tissue to a photo detector . Figure 9 Oxygen Saturation Measurement The oxygen saturation values (SaO2) are obtained from the pulse oximetry. Normal oxygen saturation values are 97% to 99% in the healthy individual. An oxygen saturation value of 95% is clinically accepted in a patient with a normal hemoglobin level .
20 Chapter 2 Physiology of Vital Signs 20