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Pumping the pulse: a bicycle pump to simulate the arterial pulse waveform

2018; American Physical Society; Volume: 42; Issue: 2 Linguagem: Inglês

10.1152/advan.00004.2018

1522-1229

Sajal Clarence Singh, Anand Bhaskar, Vinay Oommen,

Phonocardiography and Auscultation Techniques

IlluminationsPumping the pulse: a bicycle pump to simulate the arterial pulse waveformSajal Clarence Singh, Anand Bhaskar, and Vinay OommenSajal Clarence SinghDepartment of Physiology, Christian Medical College, Vellore, Tamil Nadu, India, Anand BhaskarDepartment of Physiology, Christian Medical College, Vellore, Tamil Nadu, India, and Vinay OommenDepartment of Physiology, Christian Medical College, Vellore, Tamil Nadu, IndiaPublished Online:04 Apr 2018https://doi.org/10.1152/advan.00004.2018MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat INTRODUCTIONThe teaching of the cardiovascular system often involves both didactic lectures and practical sessions. During lectures, concepts such as systolic, diastolic, and pulse pressures are often discussed using textbook figures. The examination of the pulse is commonly demonstrated in a practical setting by examining oneself or a volunteer. Changes in the pulse rate, such as an increase in rate, can be demonstrated in these sessions by making the subject exercise. Other changes in the pulse, such as bradycardia and low-volume and high-volume pulses are usually discussed theoretically.Didactic teaching of the cardiovascular system can be made more interesting with the help of simple experiments that can be demonstrated in the classroom setting. Many educators have used analogies and models to demonstrate concepts of cardiovascular function. This includes the water tower analogy (8); using bottles and valves (7); syringes, balloons, and tubing (6); using a group dynamic activity (2); a hand pump activity (5); using singing card beepers (1); pulse plethysmographs (3); and using water supply, pressure transducers, and flow sensors to model hemodynamics (4).This paper describes a live demonstration of the arterial pulse waveform using a bicycle pump and a pressure transducer, used in a classroom setting.Materials required.Bicycle pumpSilicone tubing (5-mm inner diameter)Pressure transducerData acquisition systemComputer/laptopConstruction of the model.The bicycle pump was connected to the pressure transducer by means of a soft silicone tubing (~2 m in length) and appropriate connectors (Fig. 1). The pressure transducer used was a commercially available intra-arterial blood pressure transducer (iPex pressure monitoring kit, BL Life Sciences). The pressure transducer was connected to the data acquisition system through a preamplifier. For the described experiments, a data acquisition system and software that were developed in house were used (CMCdaq, developed by the Departments of Bioengineering and Physiology, Christian Medical College, Vellore). These experiments can also be performed using other commercially available pressure transducers and data acquisition systems.Fig. 1.A: schematic of the experimental setup showing the bicycle pump connected to a pressure transducer through a silicone tube. The data were collected with the help of a data acquisition system. The silicone tube was pressed against the table to feel the expansion of the tube with each pumping cycle. B: equipment used for the demonstration.Download figureDownload PowerPointThe action of the pump was observed on the screen as pressure changed. In this setup, the bicycle pump represented the heart (left ventricle), and the silicone tubing represented a peripheral artery.Care was taken to ensure that the air pressure from the pump remained well within the permissible limits of the pressure transducer to avoid damage to the equipment.The rate and the depth of pumping were controlled manually. The bicycle pump was operated at 1 push/s (60 pushes/min), and the waveform was observed on the screen. Care was taken to ensure that the pump piston was not pulled all the way upwards, so that the pressure did not fall to zero, but rather was maintained within a fixed range. The waveform thus obtained resembled that of an arterial blood pressure recording with a systolic and diastolic pressure.Presentation of the model.This model was presented to a group of 37 allied health students during the lecture series in cardiovascular physiology. This group consisted of students studying to become physiotherapists, occupational therapists, medical laboratory technicians, and neuro-electrophysiology technicians. The students had been introduced to the concepts of arterial pulse and blood pressure.The model was set up (Fig. 1) in the front of the class, and the data acquired during the acquisition were projected live on a screen to be visible to the entire class. The entire demonstration took ~30 min. The pumping was performed by the lecturer. A postgraduate student assisted in this demonstration.The demonstration involved the following scenarios.A normal recording was taken of the pressure waveform generated (Fig. 2). The pumping was carried out at a rate and force to ensure that the waveform did not return to the baseline. This tracing was used to discuss the concepts of systolic pressure, diastolic pressure, and pulse pressure.The students were asked to press the silicone tube with their fingers against the hard surface of the table, in a manner similar to a person palpating the pulse. The pumping was continued, and the students were able to feel the expansion of the tube with each pump cycle. This simulated the palpation of the normal pulse. Interested students took turns coming forward and palpating the expansion of the tube.For the next demonstration, the pumping was first carried out at 1 cycle every second. One of the students volunteered to keep time. After the baseline recording was made, the rate and force of pumping were altered. This was used to demonstrate common variations in the pulse waveform, such as tachycardia, bradycardia, a low-volume pulse, and a high-volume pulse (Fig. 2). The students observed the changes in waveforms on the screen.Fig. 2.Recordings made with a bicycle pump demonstrating the concepts of systolic pressure, diastolic pressure, pulse pressure, and variations in pulse rate and pulse volume.Download figureDownload PowerPointFeedback.An anonymous written feedback was collected from the students at the end of the lecture series on cardiovascular physiology. One of the questions that was asked of the students dealt with how useful this illustration was in understanding concepts in cardiovascular physiology. This was an open-ended question. The student responses were analyzed and grouped into three categories, "useful," "not sure," and "not useful" (Fig. 3). The response was overwhelmingly positive. A total of 31 students responded to this question. There were 83.9% (26 students) who felt that this model was useful; 9.7% (3 students) were neutral/not sure in their response; and 6.5% (2 students) felt that this was not useful. The students who found this model useful commented that this model helped them remember, kept them awake, and was interesting.Fig. 3.Compilation of feedback obtained from students (n) regarding the usefulness of the bicycle pump model in understanding concepts in cardiovascular physiology.Download figureDownload PowerPointOther possible uses.With practice in controlling the rate and force of pumping, we were able to make recordings that simulated other variations in pulse waveforms, such as pulsus bisferiens and pulsus alternans (Fig. 4). This was fairly easy to record once the person pumping got familiar with the system. This was not demonstrated to the students, however, as these topics were not discussed in the lecture series. This could be a useful and interesting activity for student groups of other streams.Fig. 4.Pressure recordings made with a bicycle pump and a pressure transducer to simulate abnormal pulsations.Download figureDownload PowerPointLimitations.The pulse waveform that is generated using the bicycle pump, although useful to discuss aspects of the pulse, is not a perfect reproduction of the arterial pulse waveform. This is something that has to be made clear to the students. However, with practice and timing of pumping, the waveform can be made to be nearly similar to the arterial pulse waveform.The waveforms record pressure changes. However, the waveforms commonly recorded with a pulse plethysmograph record volume changes. This distinction must be kept in mind while using this technique.The pressure recordings are due to pressure changes of the air column present in the tube. While this serves to demonstrate the pulse, it does differ from the blood pressure waveform, which deals with pressure changes in a noncompressible fluid.The pressures exerted while using a bicycle pump are far higher than the arterial pressures. To avoid confusing students, the pressure waveform was recorded as a voltage output from the pressure transducer, and the actual pressure values were not displayed.Conclusion.We found that the bicycle pump could be used to demonstrate the concepts of systolic, diastolic, and pulse pressures, and the various changes in the arterial pulse. The demonstration helped students feel the pulse and visualize the arterial pulse waveform and its variations. In departments in which a data acquisition system and a pressure transducer are available, the demonstration is easy to set up for use in a theory lecture and also permits student participation. The students were positive in their feedback, as this model was both interesting and helped them clarify their concepts. This simple activity can be used to make a didactic lecture more lively.DISCLOSURESNo conflicts of interest, financial or otherwise, are declared by the authors.AUTHOR CONTRIBUTIONSS.C.S. and V.O. conceived and designed research; S.C.S. and V.O. performed experiments; S.C.S., A.B., and V.O. analyzed data; S.C.S., A.B., and V.O. interpreted results of experiments; S.C.S., A.B., and V.O. drafted manuscript; S.C.S., A.B., and V.O. edited and revised manuscript; S.C.S., A.B., and V.O. approved final version of manuscript; A.B. and V.O. prepared figures.ACKNOWLEDGMENTSPortions of this study were previously presented at the SIMEDUCON conference held at Christian Medical College, Vellore, on March 3, 2018.REFERENCES1. Belušič G, Zupančič G. Singing greeting card beeper as a finger pulse sensor. Adv Physiol Educ 34: 90–92, 2010. doi:10.1152/advan.00015.2010. Link | ISI | Google Scholar2. Carvalho H. A group dynamic activity for learning the cardiac cycle and action potential. Adv Physiol Educ 35: 312–313, 2011. doi:10.1152/advan.00128.2010. Link | ISI | Google Scholar3. Djelić M, Mazić S, Žikić D. A novel laboratory approach for the demonstration of hemodynamic principles: the arterial blood flow reflection. Adv Physiol Educ 37: 321–326, 2013. doi:10.1152/advan.00176.2012. Link | ISI | Google Scholar4. Pontiga F, Gaytán SP. An experimental approach to the fundamental principles of hemodynamics. Adv Physiol Educ 29: 165–171, 2005. doi:10.1152/advan.00009.2005. Link | ISI | Google Scholar5. Pressley TA, Limson M, Byse M, Matyas ML. The healthy heart race: a short-duration, hands-on activity in cardiovascular physiology for museums and science festivals. Adv Physiol Educ 35: 275–279, 2011. doi:10.1152/advan.00026.2011. Link | ISI | Google Scholar6. Rodenbaugh DW, Collins HL, Chen CY, DiCarlo SE. Construction of a model demonstrating cardiovascular principles. Am J Physiol 277: S67–S83, 1999. PubMed | ISI | Google Scholar7. Russ RD. A simple model to demonstrate the isovolumic contraction and rapid ejection phases of the cardiac cycle. Am J Physiol 275: S246, 1998. doi:10.1152/advances.1998.275.6.S246. Link | Google Scholar8. Swain DP. The water-tower analogy of the cardiovascular system. Adv Physiol Educ 24: 43–50, 2000. doi:10.1152/advances.2000.24.1.43. Link | ISI | Google ScholarAUTHOR NOTESAddress for reprint requests and other correspondence: V. Oommen, Dept. of Physiology, Christian Medical College, Bagayam Campus, Vellore, Tamil Nadu 632002, India (e-mail: [email protected]ac.in). Download PDF Previous Back to Top Next FiguresReferencesRelatedInformation Collections More from this issue > Volume 42Issue 2June 2018Pages 256-259 Copyright & PermissionsCopyright © 2018 the American Physiological Societyhttps://doi.org/10.1152/advan.00004.2018PubMed29616565History Received 3 January 2018 Accepted 16 February 2018 Published online 4 April 2018 Published in print 1 June 2018 Metrics