Experimental tasks within the environment of an ICU simulated site Bc. Ondřej Čadek, Ing. Richard Grünes, Ph.D., Ing. Petr Kudrna, Ing. Roman Matějka, Ing. Martin Rožánek, Ph.D., Ing. Jan Suchomel (z českého originálu přeložila Progress Language Institute s.r.o.
Experimental tasks within the environment of an ICU simulated site Bc. Ondřej Čadek, Ing. Richard Grünes, Ph.D., Ing. Petr Kudrna, Ing. Roman Matějka, Ing. Martin Rožánek, Ph.D., Ing.
Reviewed by: Ing. Jakub Ráfl Česká technika - publishing house of the Czech Technical University in Prague (ČVUT) calls the authors’ attention to adhering to the copyright. The author is responsible for language and material correctness of the contents. The text has not been subject to language or text proofreading.
Acknowledgements: This publication was supported by the European social fund within the framework of realizing the project „Modernisation of teaching methods and improvement practical skills and habits of students in Biomedical technician branch“, CZ.1.07/2.2.00/15.0415. Period of the project’s realization 11/10/2010 - 28/02/2013.
Table of contents Introduction ............................................................................................................................................. 5 1. Principles and applications of tonometers ........................................................................................... 7 2. Principles and applications of electrocardiographs ........................................................................... 16 3. Principles and applications of defibrillators ................
Introduction Dear students, dear readers, you are now holding a coursebook dealing with the problem of laboratory practical trainings in the course Medical apparatus and devices at the Faculty of Biomedical Engineering of the Czech Technical University in Prague (FBMI ČVUT). However, the coursebook is suitable for other subjects as well, both at the FBMI ČVUT and at other faculties of ČVUT dealing with medical instrumentation or using it.
national budget. And this part has been issued thanks to this support, namely by means of the authors’ fees being paid from the above mentioned projects. To conclude with, please allow us to express our thanks to all those who participated in preparing the coursebook, and to express our belief that the educational text will contribute to better understanding of the issues taught and also to greater interest in the field which by all means is very interesting, far-reaching and also very quickly developing.
1. Principles and applications of tonometers Theoretical introduction Measuring the blood pressure in a non-invasive way is a common routine in diagnosing the patient’s health status. Knowing the current, as well as long-term values of the patient’s blood pressure may reveal even severe diseases. Timely diagnosis and treatment can also save the patient’s life.
Apparatus for blood pressure measurements The basic concept of blood pressure measurements has remained the same from historical apparatus to the new automatic systems.
spring changes its qualities over time, and so these instruments are less accurate on a longterm basis. This type of apparatus is depicted in Figure 1.2. Fig. 1.1: Standard mercury tonometer in a metal case with connected sleeve (cuff) and a balloon with air relief valve. Fig. 1.2: Aneroid pressure gauge, in which the mercury manometer was replaced by a spring watch manometer, again the sleeve (cuff) is connected.
The efforts to replace mercury but to keep a similar design lead to the introduction of so called pseudo-mercury tonometers. These are electronic tonometers, which do not have autonomous evaluation algorithms, but they only depict the value of the current pressure on a display or within a column of luminous diodes. This apparatus is depicted in Fig. 1.3. Fig. 1.
circulation within the artery above which the pressure sleeve (cuff) is placed. By gradual reduction of pressure in the sleeve (cuff), the circulation in this artery is restored and the values of blood pressure can be set by monitoring changes. Fig. 1.4: Digital automatic tonometers The palpation method is very simple and only allows for determining the value of the systolic pressure.
becomes fully transitory again, and the Korotkov murmurs fade away. At this moment, we read the current pressure value, and it is the diastolic pressure value. General legislation regarding tonometers Validation of tonometers abides by Law No. 505/1990 Coll., as amended by No. 119/2000 Coll. and subsequent modifications by Law No. 137/2002 Coll. According to the public notice (decree) No. 345/2002 Coll., tonometer is an assigned gauge subject to validation after every two years.
pulse measurement will be verified in three particular simulated situations via the NIBP simulator. Measurement tasks 1) Carry out measurement of pressure deviations in mercury tonometer for 5 values of pressure and record them in a chart; create the correction curve. 2) Carry out measurement of pressure deviations in pointer-type tonometer for 5 values of pressure and record them in a chart; create the correction curve.
For points 1), 2), and 3), the measurement procedure is the same. In mercury tonometer, do not forget to open the transport valve prior to the actual measurement, and to close this valve again after the measurement. After setting up the measurement apparatus, turn on the NIBP-1010 simulator and set up the pressure measurement node to “MANOMETER” and proceed in accordance with the user manual, Chapter “RUNNING AND TEST” on page 28 [1.7].
manual tonometers, and for digital tonometers, calculate percentual deviations of the measured values. For each group of tonometers (manual, digital), elaborate a protocol according to the teacher’s requirements.
2. Principles and applications of electrocardiographs To understand the principle of functioning of the actual electrocardiograph, it is necessary to understand the electrophysiological essence of the actual biosignal’s origin. The necessary introduction can be found in the chapters below.
Heart functions ‐ physiology A healthy heart works as a pump, which makes the blood circulate in the body. Blood is brought from the organs by veins, leading via the upper and the lower vena cava into the right atrium. By a contraction of the right atrium, the blood is ejected into the right ventricle. From the right ventricle, the blood is transported via the pulmonary arteries into the lungs, where it gets rid of carbon dioxide and arterializes.
precaution against the blood’s reflux from the ventricles to the atriums, but also as electrical insulation. In a healthy heart, the transmission of an electrical impulse via this insulation is only possible via the atrioventricular - AV node, which stimulates the ventricles with a delay against the SA node.
The action potential is accompanied by changes of tension on the membrane; see Fig. 2.4. These are caused by the flow of ions inside and outside of the cell, based on the changes in the membrane’s permeability for the specific ion. The action potential occurs when the membrane potential changes very quickly (in 1-3 ms) from approximately -90 mV to +20 or +25 mV. In this stage, the cell is depolarized.
We distinguish between two essential types of action potentials: 1) Action potential with fast depolarization This is typical namely for the cells of the working myocardium, see Fig. 2.5. When reaching the threshold value of the stimulus, the fast Na+ channels open and these cations flow from the extracellular area quickly inside the cell. Fast speed of the flow is given by the concentration and electrical gradient and the high amount of the Na+ channels.
Fig. 2.5: Processes of action potentials in the individual parts of the heart [2.6]. Spreading of the action potential Action potential is spread via the conduction system and then via the muscles in a single direction only. One cell activates the other. The progress of the stimulus in the single direction is caused by a temporary inability of the cell to react to irritation. This period of time is called an absolute refractory period.
Vm (mV) Time (ms) Absolute refractory period Relative refractory period Fig. 2.6: Absolute and relative refractory periods [2.6]. Variability of anatomical and physiological parameters Each individual has certain characteristic parameters describing the current state of his organism, see Tab. 2.1. These values change in connection with stress (physical or psychic). Tab 2.1 shows typical values for non-sportsmen and for trained endurance sportsmen [2.2].
Tab. 2.1: Typical values for sportsmen and non-sportsmen [2.2]. Non-sportsmen at rest Heart weight (g) Blood volume (l) Heart rate (min-1) Stroke volume (ml) up Sportsman at rest up 300 500 5.6 5.9 80 180 40 180 70 100 40 190 Fig. 2.7: Description of the ECG curve. Standard 12‐lead ECG system Clinically the most commonly used system for imaging the heart biopotentials uses a system of ten electrodes placed on the limbs and on the chest of the examined person.
The 12-lead system consists of: • Bipolar limb leads according to Einthoven (leads I, II, III) • Unipolar augmented leads - Goldberg’s leads (aVL, aVR, aVF) • Unipolar chest leads - Wilson’s leads (V1 - V6) Bipolar leads - leads according to Einthoven The electrodes are placed on the wrists of the upper limbs (R-red color, L-yellow color) and on the lower part of the left lower limb (F-green). A neutral electrode (N-black) is connected to the lower part of the right limb.
UaVR= ΦR – (ΦL+ ΦF)/2 UaVL= ΦL – (ΦR+ ΦF)/2 UaVF= ΦF – (ΦR+ ΦL)/2 Fig. 2.9: Unipolar leads’ geometry according to Goldberg. Wilson’s chest leads The limb leads mentioned so far represent the heart’s electrical activity in the frontal plane; yet the unipolar chest leads according to Wilson provide information about the heart’s electrical activity in a horizontal plane.
Other possible modifications of the leads Besides the already described 12 conventional leads, some other leads may be used in certain situations and for certain specific purposes [2.6]: Esophageal leads - The esophageal electrode is capable of sensing relatively high atrium potentials thanks to its presence in the vicinity of the left atrium, thus accurately determining the electrical activity of the atriums and its relation to the activity of the ventricles.
example, diodes connected in anti-parallel, Zener diodes connected in anti-series, or eventually voltage limiters consisting of two silicon transistors. Low-voltage discharge tubes are sometimes used. To prevent the overcurrent (current overload) of the voltage limiter, there is usually a serial resistor, and a spark gap for large discharges.
Filters Filtration is an inseparable part of signal processing. A filter is generally a circuit designed in such a way as to transmit signals of a certain frequency bands, while suppressing other frequencies. These circuits may be realized via passive components, such as resistors, coils and capacitors, or via active components, such as amplifiers. Fig. 2.12: Connection of the Driven Right Leg circuit. When processing the ECG signal, a frequency band of 0.05 Hz - 120 Hz is used.
barrier is specified by the size of the isolation voltage uiso, the isolation capacity C, and the isolation resistance R. From the point of view of the medical devices and instrumentation, it is very important that the values of the leaking currents past the isolation barrier remain as low as possible. Low values of the direct-current leaking currents are achieved via high isolation resistance. On the contrary, a very low value of the isolation capacity ensures low alternating leaking currents.
continuously. Fig. 2.13 shows a schematic diagram of the circuit, which is used to discover badly connected electrodes on the patient’s body. Fig. 2.13: Schematic diagram of the circuit checking quality of the electrodes’ connection [2.8]. To check the quality of the electrodes’ contact, a sinus signal of a 50 kHz frequency is brought between two electrodes connected to the patient from a mains source. There are two reasons for choosing this particular frequency.
• Set the simulator to a normal sinus rhythm with a physiological frequency Measure the ECG signal’s amplitude, calculate the amplitude’s size prior to the gain, and compare it with the physiological parameters cited in literature. Input amplifiers’ gain A = 1000. • Measure the duration of the ECG curve’s individual segments and compare them with the physiological parameters depicted in Fig. 2.7. 2) Carry out the biosignal’s analysis within the frequency domain.
[2.2] Despopoulos, A., Silbernagl, S. Atlas fyziologie člověka, 6. vyd. Praha, Grada Publishing s. r. o., 2004. 448 s. ISBN 80-247-0630-X. (in Czech) [2.3] Rokyta, R., et.al. Fyziologie pro bakalářská studia v medicíně, přírodovědných a tělovýchovných oborech, 1. vyd. Praha, ISV, 2000. 359 s. (in Czech) [2.4] Trojan, S., et. al. Lékařská fyziologie, 4. vyd. Praha, Grada Publishing s. r. o., 2003. 772 s. ISBN 80-274-0512-5. (in Czech) [2.5] Valentová, K.
3. Principles and applications of defibrillators Theoretical introduction Defibrillation is used to eliminate fibrillations (cardiac arrhythmias, 340-600 pulses/min) of the cardiac muscles by means of artificially created electrical discharge (pulse) of a great energy. Application of defibrillation is most common in ventricular fibrillation, ventricular flutter or in sustained polymorphous ventricular tachycardia (longer than 30 s).
only, and to biphasic pulse (Fig. 3.2), when the direct current is lead past the heart muscle in one direction during the first stage of the pulse, and in the other direction in the second stage. Some defibrillators use triphasic or quadriphasic defibrillation pulses. Fig. 3.2: Demonstration of biphasic depolarizing pulses (from the left: trapezoidal BTE and damped with delay DBT).
The trapezoidal pulse is also marked as MTE or BTE (Monophasic/Biphasic Truncated Exponential pulse), Fig. 3.1 and Fig. 3.2. Damped shape of the defibrillation pulse (DSW - Damped Sine Wave) is acquired via the discharging of the capacitor past a coil, the so called choke, i.e. “choking” coil (from blocking). Adding the choking coil into the capacitor’s circuit creates a serial oscillating circuit with losses, Fig. 3.4.
Fig. 3.5: Equivalent electrical diagram of a final stage of a monophasic defibrillator with damp-shaped defibrillation pulse with delay. Position 1 - charging of the capacitors, position 2 - discharging of the capacitors past the delay line (defibrillation pulse DMT). Synchronized cardioversion Synchronized cardioversion, or simply a cardioversion, is basically a synchronized defibrillation, which uses lower energy values of the defibrillation pulse.
ECG signal with additional ECG electrodes. Also the time interval of the R-R waves in the ECG signal is evaluated. In the fix-rate mode (bradycardia, asystole, tachycardia), it is possible to set up fixed repetitive frequency of stimulation pulses on the stimulator (usually 30-180 stimuli/min), independently from the heart’s activity.
R-R interval of spontaneous activity (TCL - Tachycardia Cycle Length), typically at 85 % of TCL. The distance of the subsequent stimulation impulses of the dose (BCL - Burst Cycle Length) may be fixed (stimulation scheme Burst), and it is usually the same as the CI, or the distance of the individual stimulation impulses is variable (stimulation scheme Ramp), typically decreasing by 10 ms always with the next BCL. The ATP dose is repeated until the tachycardia is interrupted.
Measurement tasks Prior to the actual measurement, get familiar with the manipulation with and the components of the available defibrillators (such as CardioServ, GE Healthcare [3.8] and BeneHeart D3, Mindray [3.9]) and the defibrillator analyser (DA-2006, BC Biomedical [3.7]). During the measurements, consult all your procedures with the teacher. Work with the user manuals [3.8] and [3.9] available at the subject’s website.
Ad task 1) Switch on the analyzer using the switch on the back side, see Fig. 3.7. Set up the analyzer to the required range according to the energies you selected on the defibrillator, see Fig. 3.8. Set up the scope of energy by means of the “Range” button to “High Defibrillator Range” for discharge energy up to 1000 J, or to “Low Defibrillator Range” for discharge energy up to 50 J. Wait until the analyzer’s display shows “Status: Ready for Defib“, and now the analyzer is ready for the measurement. Fig.
Fig. 3.8: Defibrillator analyzer - overall view with legend [3.6]. Read and record the applied discharge’s energy on the analyzer’s display - “Energy”, the peak voltage value - “Peak V”, the peak current value - “Peak I”, and the length of the defibrillation pulse. Use the “Playback last pulse” button to switch to the chart of the defibrillation pulse’s duration and sketch its shape. Ad task 2) Use the “Range” button to switch the analyzer into the “High Defibrillator Range” mode.
discharge buttons into the analyzer. Read the time for charging the defibrillator on the analyzer’s display “Chg Time: xxx.x sec”. Compare the value with the data stated by the manufacturer in the user manual [3.8, 3.9]. Ad task 3) Connect the patient cable in the connector for the ECG input on the defibrillator, and its second end to the simulated electrodes in the upper part of the analyzer’s front side via press studs.
Ad task 5) Safety-technical check: on the basis of the operation manual [3.8, 3.9] for the defibrillator and the electro-revisional apparatus Meditest 50 [3.7], first determine the defibrillator’s electrical insulation class, and then perform the electrical safety measurement, which is bound to the assigned MD class. Elaborate a protocol on STC, which you can find on the subject’s web site. Fig. 3.9: Converter for pacing, demonstration of stimulator and oscilloscope connection.
the operation (user) manual. Determine the type of the applied part the apparatus works with, the (electrical) insulation class and the MD classification class. Check‐up questions regarding the given issue 1) Describe the differences between defibrillation and synchronized cardioversion. 2) When is antitachycardia stimulation used and how is this stimulation different from defibrillation? 3) Describe the differences between monophasic and biphasic defibrillation pulse.
4. Principles and applications of pulse oxymeters Theoretical introduction Pulse oxymetry is a non-invasive optical method used for long-term monitoring of arterial blood’s oxygen saturation. The method is based on measuring the intensity of radiation (light) transmitted through vascular tissue. This intensity can be calculated via the Lambert-Beer Law (4.
There are more factors influencing the decrease of the radiation (light) intensity in a tissue. The thickness of the tissue the radiation (light) has to get through has the greatest influence on the decrease of the radiation’s (light’s) intensity. Further decrease of intensity is caused by the radiation (light’s) absorption in venous and arterial blood which passes through the tissue.
bound to hemoglobin, we identify it as oxyhemoglobin (oxy-Hb) or deoxyhemoglobin (deoxy-Hb). The volume of oxygen transported in blood is thus directly dependent on the amount of hemoglobin in the arterial blood. Besides oxy-Hb and deoxy-Hb, hemoglobin also exists as carbaminohemoglobin (Hb-carbamate) with bound CO2 and methemoglobin (metHb), which is not capable of binding oxygen. The individual states of hemoglobin have different physical qualities due to different chemical bonds.
consists of the direct component DC (absorption of light via a tissue with fixed amount of venous and arterial blood), and of the alternating component AC (absorption of light via pulsating arterial blood). Due to the fact that the photosensor (photodiode) sensing light transmitted through both the LED does not have the same sensitivity for both the wavelengths, we observe the alternating component of the light for both the wavelengths via the direct component.
With (4.3) it is possible to calculate a theoretical conversion curve between the R ratio and oxygen saturation in arterial blood SaO2 (Fig. 4.4), which is used in calibrating pulse oxymeters. By performing comparative measurements of O2 saturation via the pulse oxymeter and blood gas analyzer, it is possible to create the so called empirical conversion curve. The conversion curve may be approximated by a linear equation, which may be used to calculate the O2 saturation.
Fig. 4.5: Schematic diagram of the edutool - a model of an analogous part of a pulse oxymeter with marked check points.
Measurement procedure Ad task 1) ATTENTION: Supply the SpO2 simulator form a 12V source with the positive pole on the cover and the negative pole on the pin, see the bottom of the apparatus!!! The SpO2 simulator has etalons available - “artificial fingers” with different nominal values of SpO2. Try to attach the available etalons one by one to the simulator and place the pulse oxymeter clips on them with a SpO2 scanner.
meaning: K1 - oscillator’s clock pulses, K2, K3 - managing impulses of the R/IR diodes, K4 - output signal of the input amplifier, K5, K6 - managing signals of the S/H circuits, Sample and Hold circuits, K7, K8 - sensed signal divided into two channels, K9, K10 - DC (direct) components of the R/IR signal (measure by means of a digital voltmeter/multimeter), K11, K12 - AC (alternating) components of the R/IR signal, K13, K14 - voltage value of the VppAC component of the R/IR signal (measure by means of a dig
suitable gain/amplification to display the curve within the full possible dynamic range. Connect the edutool to the oscilloscope by means of a coaxial cable with BNC connectors. Display the plethysmographic curve on the oscilloscope and watch how its shape is changing in held breath and under the influence of movement artefacts. Read the heart frequency from the plethysmographic curve, and draw the course of the plethysmographic curve.
Check‐up questions regarding the given issue 1) Why is pulse oxymetry called “pulse”? 2) What is the principle for sensing the plethysmographic curve? 3) What are the sample and hold circuits (abbreviated to S/H) used for in the electrical circuit of the pulse oxymeter’s analogous part? 4) What general properties are important for the pulse oxymetry probes? References to used and recommended information sources [4.1] Design of pulse oximeters / edited by J.G. Webster.
5. Principles and application of infusion pumps and linear infusion pumps Infusion technology plays an important role in correct treatment of patients in the AR and IC units. This infusion technology ensures both continual and dose supply of drugs, supporting medicines, nutrition, etc. Compared to conventional system of drug administration, i.e. by the staff, gravitational or intravenous administrations, etc.
the entire pump for new utilization, but the entire set is again replaced. In case of using the above mentioned pumps, the medium flows directly through the pump’s body in such a way that it gets in contact with this pump’s mechanical elements. It is possible to sterilize these surfaces (chemically, thermally, etc.), yet the act itself is rather complicated and requires the removal of the actual drawing head, etc.
systems are used in infusion pumps, as they are not so selective regarding the tubing materials used, and moreover, it is possible to use various sizes, etc. This system is depicted in Fig. 5.2. Fig. 5.2: Rotation peristaltic head with the supporting trail. Other differences in the construction can be found in the number of the individual stoppers that get into contact with the tubing.
Concerning infusion dispensing, only the version using two stoppers and a supporting trail is used. This arrangement, together with the principle of the function, can be seen in Fig. 5.4. Fig. 5.4: Drawing principle by means of a rotation peristaltic head. This arrangement is very simple regarding maintenance, insertion of new tubing/set, etc. The picture depicts a peristaltic head with an inserted set.
Linear systems of the medium drive The second version used for drawing the media using the peristaltic transfer of the liquid is represented by the so called linear peristaltic drives. These drives use a linear peristaltic wave, which drives the medium in the tubing. This linear system is depicted in Fig. 5.6. Fig. 5.6: Drawing principle via a linear peristaltic head.
Linear infusion pumps Linear infusion pumps are used for similar purpose as the infusion pumps - to administer drugs. As opposed to the infusion pumps, however, they are modified for precise dosing of small volumes, which are dispensed via a syringe placed in such a dispenser. The substance in the syringe is pushed out via the injection dispenser’s arm. Fig. 5.8: Linear dispenser with installed syringe.
measurement accuracy. Another requirement stems from the standard ČSN EN 60601-1, which deals with electrical safety, both from the point of view of the attending staff, and of the patient. It is namely an inspection of the device’s insulation state, in order to prevent possible injury by the electrical current. The contents of the above mentioned legislation will be described in greater detail in the text below. Law No. 123/2000 Coll. on medical devices and on changing some related laws.
ČSN EN 60601-1, Part 1, General requirements for essential safety and necessary functioning This is a basic standard from an entire set of technical standards ČSN EN 60601, which define general technical requirements for the realization and electrical safety of medical devices. Among other things, the standard specifies the requirements for the so called applied part. The applied part can be found in most medical devices; it is used for diagnostics or for treatment.
• SEV LITOVEL 2P • POLYMED ID 20/50 • GOSSEN METRAWATT SECULIFE-IF + ACCESSORIES • ILLKO REVEX 2051 + ACCESSORIES • LUER syringe - 20 ml, 50 ml • 500ml beaker • Infusion set Procedure of the PSTC elaboration: 1) Carry out a detailed inspection of the apparatus for mechanical damage. 2) Check the integrity of the supply cable. 3) Check the functioning of the signalizing and controlling elements.
2) Check the integrity of the supply cable While checking, focus namely of the cable terminations, in place where the cable enters the termination. This is the place where the external insulation layer often crackles. Verify that the insulation is compact throughout the cable’s length and that the cable shows no signs of breaking or notching. Any occurrence of bulging on the cable is also unallowable, as it demonstrates damage of the conductors inside.
(for SEV LITOVEL 2P and POLYMED ID 20/50) To measure the apparatus’ insulation resistance, proceed in accordance with the user manual of REVEX 2051. Detailed measurement procedure can be found in chapter 4.3.1 on page 22 (for SEV LITOVEL 2P) and 4.3.2 on page 23 (for POLYMED ID 20/50). During the measurement, follow the instructions of the trainer and always proceed only in accordance with the manual of REVEX 2051. Record the result into the PSTC protocol and compare with the recommended maximum value.
To check the bubble detector, turn the infusion bottle in such a way as to allow for a small amount of air (a bubble) to be sucked into the infusion pump’s infusion set. Then wait whether the alarm sets off when the bubble passes through the infusion pump. Set up the infusion pumps and linear infusion pumps according to the measured parameters in the particular PSTC protocol. The actual controlling and set up for the individual parameters can be found in the respective operation manuals for each apparatus.
6. Using the patient simulator and breathing simulators in the area of ventilation technology Theoretical introduction Artificial lung ventilation is used as a technology substituting spontaneous breathing in case of the patient’s respiration failure. It is a rather old method, currently rather widespread and very frequently used.
application of the artificial lung ventilation, together with other risks, such as a greater infection risk, oxygen toxicity in its increased faction in inspired gas, etc. Such lung distress is identified as the “lung distress caused by artificial lung ventilation”. The modern trend thus prefers the so called protective ventilation modes, the main goal of which is to reduce the adverse effects of artificial lung ventilation on the patient.
of the controlling panel [6.3]. The Hamilton ventilator supports the following ventilation modes: • (S)CMV – (Synchronized) Controlled Mechanical Ventilation • SIMV – Synchronized Intermittent Mandatory Ventilation • Spont – Spontaneous Support • MMV – Minimum Minute Ventilation • PCV – Pressure Controlled Ventilation (S)CMV ventilation mode (Synchronized) Controlled Mechanical Ventilation is the basic mode of artificial lung ventilation. It fully substitutes the patient’s breathing.
Spontaneous breathing ventilation mode (SPONT) This mode is designed for patients with spontaneous breathing activity and is used for its support and greater effectiveness. VEOLAR offers the following support options: supply of air enriched with oxygen, continuous positive airway pressure (CPAP) and inspiratory assistance during inspirium (pressure support).
Throughout the MMV, the ventilator always assesses the last 8 breaths and converts their volume to the expected minute volume. This automatic regulatory process is functional within the limit of 3 kPa over CPAP and within 5 kPa absolutely. In case of alarm, the inspiratory pressure support remains constant until the cause of the alarm is cleared up and removed. In the MMV mode, the ventilator always reacts to the set-up of the inspiratory assistance (Pinsp).
Spontaneous breathing may take place in the mode of continuous positive-pressure breathing or inspiratory assistance up to the positive pressure value of 50 cm of H2O (depending on the pressure limit).
Measurement procedure ad 1) Calculate the minute ventilation according to the relation (6.1): (6.1) V M = Vt ⋅ f , and the alveolar ventilation according to the relation (6.2): (6.2) V A = (Vt − VD ) ⋅ f , where VM is minute ventilation, Vt is tidal volume, f is breathing frequency, VA is alveolar ventilation and VD is anatomical dead space (approx. 160 ml for an adult person). Record the calculated values in Tab. 6.1. Tab. 6.
Fig. 6.2: Controlling panel of the ventilator. The individual parameters of artificial lung ventilation are set up on the controlling panel: • Ventilation frequency (fCMV) - frequency of guided breathing. The frequency may be set up as the number of breaths per minute. • Tidal volume (VT) - to be set up by means of the VT button. It is the volume of air in one inspiration. In some modes, e.g. the pressure-guided ventilation, this parameter cannot be set up.
Fig. 6.3: Setting up the I:E ratio. Example: Breathing frequency fCMV is 15 breaths per minute. That corresponds to the duration of the entire breathing cycle of 4 seconds. If the expiration button is set to 75 %, then the inspiration will last 25 % of the entire breathing cycle. The I:E ratio in this case is 1:3. That means inspirium lasts for 1 second and expirium lasts for three seconds.
Fig. 6.4: Setting up the inspiration delay time. • Characteristics of flow during inspirium - the user may select among seven defined flow characteristics in the time of inspirium: progressive, constant, degressive, sinusoidal, 50% degressive, 50% progressive and modified sinusoidal. Their names are derived from the shape of the flow curve during inspirium.
Fig. 6.5: Alarm control panel The Yes and No buttons are used for confirming the ventilator’s messages and actions. The Info button allows for displaying the previous parameters and other information. The up and down arrow buttons allow for increasing and decreasing the parameter that is being set up. The last button suppresses the sound alarm for 2 minutes. The potentiometers allow for setting up maximum allowed breathing frequency and maximum allowed pressure in the airways.
Fig. 6.6: Patient monitor. The displayed parameters are immediate measured or calculated values. A column scale is used to display the measured pressures in the airways within the range of -30 and 130 cmH2O. Two LED diodes, “trigger” and “pause”, inform the staff about each activation of the patient’s trigger, or eventually in case there is an inspiratory pause “plateau“. The time the LED diodes are lightened corresponds to the actual duration of the plateau.
PEEP - positive end expiratory pressure or continuous positive pressure in the airways. Information on frequency: ftotal - total breathing frequency, i.e. the number of spontaneous and guided breaths during eight cycles, re-calculated to 1 minute; evaluation takes place after each breath. fspont - number of spontaneous breaths during the previous eight cycles, re-calculated to 1 minute; evaluation takes place after each breath.
Rinsp - inspiratory resistance; this resistance represents the dynamic resistance of the circuit, the endotracheal tube and the airways; this parameter is not evaluated in case of selected sinusoidal and degressive flows and in spontaneous ventilation.
What does the abbreviation PEEP stand for and what is its significance during ventilation: What does the symbol Ppeak mean and what is its significance during ventilation: Name the essential mechanical lung parameters and state their units: Describe the difference between volume-guided and pressure-guided ventilation: 81
References to used and recommended information sources [6.1] Wesbter, J.G. ed. Encyclopedia of Medical Devices and Instrumentation. Wiley. [online]. c1999-2009, poslední aktualizace 17. 8. 2008 [cit. 2009-05-12]. Dostupné z WWW: http://mrw.interscience.wiley.com/emrw/9780471732877/home/ [6.2] Hamilton Medical: Veolar – Operator’s Manual. Hamilton Medical AG, Rhaezuens, 1993. [6.3] Roubík, K., Rožánek, M., Grünes, R. Praktika z biomedicínské a klinické techniky 4.
7. Principles and application of electrosurgical apparatus Theoretical introduction Electrosurgery means application of radiofrequency (RF/VF) current within the scope of approx. 300 kHz to 5 MHz in order to achieve the required result of a surgical intervention. Typically, this concerns coagulation (conversion of a colloid system into a gross dispersive system) or surgical sections, when the tissue is affected or impaired. Further on, it might be desiccation of the tissue or destruction of the tissue.
The contents and the aim of the measurements High-frequency electrosurgery provides means for fine and accurate surgical interventions on vascular tissues. Using this method prevents undesirable extensive damage to the surrounding tissue. To achieve the best possible results, it is necessary to work with the unit’s performance set-up as gently as possible.
for the individual measurements, the actual set-up of the analyzer and its connection to the oscilloscope [7.6]. Fig. 7.1: Front panel of the electrosurgical apparatus CLINIC 170 W [7.5].
Fig. 7.2: Rear panel of the electrosurgical apparatus CLINIC 170 W [7.5]. Legend: 1 - pneumatic trigger connector - connecting the foot switch 2 - power cord plug 3 - power switch 4 - manufacturer’s label Output power measurement in dependence on the size of the load resistance for monopolar and bipolar modes and for all the four functions Connect the neutral electrode into the main panel of the electrosurgical unit.
After that, connect the electrosurgical apparatus in the electrical power network and switch it on via the rocker-type switch on the rear side of the apparatus (see Fig. 7.2).
Activate the apparatus via the foot switch. Gradually read all the output performance values on the tester’s display and record them in the respective table. Then switch the apparatus into the mixed section, coagulation and mixed coagulation functions and repeat the measurement. Repeat the same procedure for all the remaining modes and functions. Proceed likewise for the bipolar mode measurements, only following the instructions in the operation manual [7.
function, namely with leakage currents and functional currents flowing from the highfrequency apparatus via undesirable paths through the patient or the attending staff. When using an electrosurgical apparatus, direct connection of the patient with the apparatus cannot be avoided. As the ESU is powered by the 230 V/50 Hz electrical distribution network, there is a danger in the form of leakage currents on the network frequency (and their higher harmonic components).
• Digital apparatus for checking the medical electric apparatus MEDITEST 50 (ILLKO, s.r.o., Czech Rep.) • Oscilloscope and interconnecting BNC cable Measured results Record all the measured results in the tables below and compare them with the data stated by the manufacturer in the Operation manual. Add all the required information and have the protocol checked and signed by the trainer. To realize the safety-technical check, follow the instruction of the manufacturer in the operation manual [7.
Tab. 7.3: Dependence of the working current size on the setting of the output performance and the load resistance size at section in monopolar mode. Output power [-] Current size 50 Ω 100 Ω 200 Ω 500 Ω 750 Ω 1 2 3 4 5 6 7 Tab. 7.4: Dependence of the working current size on the setting of the output performance and the load resistance size at section in bipolar mode.
Tab. 7.5: Dependence of the working current size on the setting of the output performance and the load resistance size at coagulation in monopolar mode. Output power [-] Current size 50 Ω 100 Ω 200 Ω 500 Ω 750 Ω 1 2 3 4 5 6 7 Tab. 7.6: Dependence of the working current size on the setting of the output performance and the load resistance size at coagulation in bipolar mode.
Tab. 7.7: Dependence of the leakage current size on the setting of the ESU output performance in monopolar mode. Output power [-] Cut Mixed cut Coagulation Microcoagulation 1 2 3 4 5 6 7 Tab. 7.8: Dependence of the leakage current size on the setting of the ESU output performance in bipolar mode.
Conclusion Briefly comment on each point of the measurement. Evaluate the measured results and compare them with the data stated by the manufacturer in the operation manual [7.5]. Determine the type of the applied part the apparatus works with, the (electrical) insulation class and the MD classification class. Check‐up questions regarding the given issue 1) Explain the principle of the electrosurgical apparatus functioning. Describe the basic electrosurgery effects on live tissues.
4) Describe the functional principle of the electrosurgical apparatus’ analyzer RF 303. 5) Describe the significance of measuring the so called leakage currents. Safety‐technical check Based on the operation manual to the electrosurgical apparatus [7.5] and the electrical safety tester Meditest 50 [7.7], first determine the insulation class ESU and subsequently carry out the electrical safety measurement related to the determined MD class.
8. Principles and applications of the vital functions monitors Theoretical introduction Monitors of the patient’s vital functions play an important role not only during the surgical operation, but also during the post-operation recovery. Their essential aim is to unite several partial systems into one complex whole. By these systems, we mean the ECG, which can have one, five or up to twelve leads, depending on the complexity and the determination means of the actual monitor.
Just like any medical device, also the patient monitors and their utilization are subject to valid legislation. STC (safety-technical check), which ensues from the Law No. 123/2000 Coll., particularly from Chapter 27 thereof, is one of the most frequent activities of a biomedical technician in the healthcare facility. STCs stem from the necessity to check and verify the parameters of the medical instrumentation throughout their clinical operation.
that the safety and health of the users or third persons are threatened or the usability period determined by the manufacturer or the importer has expired. According to Chapter 24, the healthcare providers are obliged to adopt such measures in the medical devices with measurement functions, as to guarantee sufficient accuracy and reliability of the measurement. The provider must therefore guarantee to meet the requirements ensuing from the Law on metrology No. 505/1990 Coll., as amended.
ČSN EN 62353 Electrical medical devices Repetitive tests and post-repair tests of the electrical medical devices. The standard defines the essential requirements for carrying out periodically repeated checks and tests following repairs of the medical devices. It deals with the issue of electrical safety of the apparatus and functional tests of medical devices. It is a parallel to the standard ČSN 331600 for checking electrical appliances.
• Accessories for measuring the applied part’s current ILLKO RM 2050 • Simulator FLUKE medSim 300B Measurement procedure 1) Carry out a detailed inspection of the apparatus for mechanical damage. Check the apparatus very carefully to detect cracks; check namely the plastic moving mechanisms, which may show mechanical damage more frequently.
To measure the apparatus’ insulation resistance, proceed in accordance with the user manual of REVEX 2051. Detailed measurement procedure can be found in chapter 4.3.1 on page 22. During the measurement, follow the instructions of the trainer and always proceed only in accordance with the manual of REVEX 2051. Record the result into the PSTC protocol and compare with the recommended maximum value. Confirm whether the machine passed.
connection according to the user manual for medSim 300B. Turn the monitor on and set up the ECG measurement on at least two leads (e.g. II and V1), the pulse rate reading and the breathing frequency measurement. Always set up the monitor in accordance with the user manual.
9. The influence of user-adjustable parameters on the action of the patient simulator system METI ECS The interactive, whole-body patient simulator METI, model Emergency Care Simulator (ECS) is designed for training practical skills and handling emergency situations. Namely the training of healthcare personnel is presumed.
parameters change in one system, then all other parameters in a mutual bond change adequately, see the mutual interconnection in Fig. 9.2. Cardiovascular Respiratory Operator’s input Operator’s input Pharmacological Operator’s input Fig. 9.2: Mutual interconnection of the whole-body patient simulator’s parts Respiratory system The respiratory system model can be divided into two parts. The upper respiratory tract includes the nasal cavity, the nasopharynx, the pharynx and a part of larynx.
• Oropharyngeal oedema - the oedema size can be set up to various levels (medium severe to severe) and orotracheal intubation can thus be prevented. Thanks to the replaceable skin on the neck, it is possible in this case to carry out tracheotomy, which means a surgical intervention when a permanent opening is made on the neck, which ensures breathing, or coniotomy, i.e.
• Right atrial pressure • Pressure in the pulmonary artery • Cardiac output by means of thermodilution The system dynamically models the arterial blood gases values according to current alveolar concentrations of carbon dioxide and oxygen. It is possible to simulate both metabolic acidosis and alkalosis. Pharmacological system The whole-body patient simulator contains a pre-programmed pharmacokinetic and pharmacodynamic model for more than 60 different types of drugs.
Basic parameters of the model Some initial patient configurations and scenarios have already been pre-programmed to the ECS: Man, 33 years old, healthy, no previous health complications Woman, 29 years old, in the 40th week of pregnancy, no complications Woman, 70 years old, former smoker with mild hypertension Man, 61 years old, alcoholic and smoker with ischemic heart disease and chronic obstructive pulmonary disease (COPD), Man, 20 years old, healthy but hyperthermic, hypermetabolic an
CVP Central venous pressure mmHg Left Vol. The volume of the left lung ml Right Vol. The volume of the right lung ml Spont. VT Spontaneous tidal volume ml PACO2 Alveolar partial pressure of CO2 mmHg PAO2 Alveolar partial pressure of O2 mmHg Spont. RR Spontaneous respiratory rate breath/min Alv. N2O Alveolar partial pressure of N2O mmHg Alv. Iso. Alveolar partial pressure of Isoflurane mmHg Alv.Sevo. Alveolar partial pressure of Sevoflurane mmHg Alv. Halo.
4) Simulate disconnecting the cable by taking one of the Einthoven leads off of the mannequin simulator and observe the influence on the ECG signal. 5) Change selected parameters on the simulator according to the trainer’s instructions and observe the influence of the change on the simulator’s physiological parameters. 6) Simulate ventricular fibrillation and use the defibrillator under the trainer’s supervision and according to his instructions.
PACO2 = PAO2 = PaCO2 = PaO2 = pH = PvCO2 = PvO2 = ad 5b) Record the basic physiological parameters of the ECS simulator after an action carried out by the trainer: Action: HR (heart rate) = ABP (arterial blood pressure) = SpO2 = CO (cardiac output) = PACO2 = PAO2 = PaCO2 = PaO2 = pH = PvCO2 = PvO2 = ad 7) Record the basic physiological parameters of the ECS simulator approx.
• Intubation set • Ambu vac • Lung ventilator Veolar (Hamilton Medical, USA) Conclusion Summarize your findings and comment on the individual measurement tasks.
