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ECE 3280 Principles and Practice of Biomedical Engineering Laboratory Electrocardiogram, dive reflex and Heart rate variability Section 30, Group 4 Felipe Zambrano (33%) Joshua Dean (33%) and KeithOldano (33%) Experiment Conducted September 30, 2011 Submitted October 14, 2011 Abstract The mammalian dive reflex occurs when a patient’s face comes in contact with cold water while holding their breath, which causes their heart rate to slow down through the process of bradycardia. While this is a process that occurs with all mammals, it can be difficult to accurately measure a patient’s heart rate while they undergo submersion. The experiment used an electrocardiogram (ECG) to record the patient’s heart rate while patient was under each of the following states: regular breathing while sitting down, standing up (diving position), hands in warm water, and hands in cold water; holding breath while standing, hands in warm water, and hands in cold water; immerse face in room temperature water, cold water, and colder water (ice water). Heart rate variability from each test was measured from uploading the raw ECG waveform into Matlab in which the derivative of the ECG signal was taken, processed through a zero array, compared to a threshold value, and finally had the RR intervals, which were
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determined through difference of the activation times, plotted against Beat number. From our analysis, we were able to determine a range of average heart rates for each of the tested conditions and plotted them in our appropriate chart with their percent error. Our range of values were from regular breathing sitting having a heart rate mean of 88.11 ± 2.27 BPM to immersed faced in colder water having 43.90 ± 2.59 BPM. Thus, our results indicate our subject having undergone bradycardia as part of the dive reflex. Additionally, our patient’s heart rate variability for the tested conditions provides an illustrative description of the dive reflex’s dependency on water temperature and immersed body part for others to use in future studies. Introduction The experiment is heavily focused on using the heart’s electrical system as a method for testing the mammalian dive reflex. The heart is able to pump blood to the body by the contraction of the heart’s walls, which are regulated be the heart’s electrical system. The system is made up of two types of cardiac muscle cells that do not contract: nodal cells, which are the cells located in the sinoatrial (SA) and atrioventricular(AV) nodes to establish the rate of cardiac contraction, and the conducting cells, which distribute the contractile stimulus to the contracting heart muscle cells. The AV bundle, the bundle branches, and the Purkinje fibers are conducting cells. The electrical system of the heart startswith the contraction stimulus being generated at the SA node and atrial activation begins at time =0. The stimulus spreads across the atrial surfaces and reaches the AV node with 50 msec having elapsed. At the AV node, there is a 100 msec
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This note was uploaded on 11/14/2011 for the course ECE 3820 taught by Professor Wang during the Fall '11 term at GWU.

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