Transcript Heart Rate
BIOL 204 – Week 5 Lab Electrocardiography Heart Sound & Blood Pressure Objective 1: ECG An electrocardiogram is a graphical recording of the hearts electrical changes during a cardiac cycle (heart beat) - Electrical changes initiated and propagated through the myocardium by specialized cells of the heart’s intrinsic conduction system Structures of the Intrinsic Conduction System Voltage changes seen The voltage changes are recorded by leads which can be placed in different locations on the body We will use limb leads, placed on the appendages to record ECGs in this lab Lead 1: RA -, LA + most sensitive to electrical activity spreading horizontally across the heart Lead 2 RA -, LL + most sensitive to electrical activity spreading vertically vertically (from the base to apex) the Lead 3 LA - . LL + also records electrical activity spreading from the base to the apex, but from a different orientation When an ECG tracing is recorded using these lead combinations, a series of wave forms are generated which respond to the spread of electricity through the heart after it originates at the SA node Y (vertical) axis measure voltage: - typically, 10 squares = 1 mV X axis measures time: - At a chart speed of 25 mm/sec: each small block = 0.04 sec and each large block (5 small blocks) = 5 X 0.04 sec. = 0.20 sec. Objective 1: ECG A typical ECG tracing In this exercise you will evaluate a baseline ECG then identify and discuss changes in the ECG at rest and after period of exercise. 10 squares = 1 mV Each small block = 0.04 sec To determine the heart rate from an ECG tracing: count the number of small squares from one R wave to the next R wave and divide that number into 1500 Heart Rate (bpm) = 1500/#small squares P wave duration QRS complex duration T wave duration P-R (P-Q) interval duration Q-T interval duration Heart rate Normal values P wave duration 0.08 – 0.1 sec QRS complex duration 0.06 – 0.1 sec T wave duration 0.16 – 0.24 sec P-R (P-Q) interval duration 0.12 – 0.20 sec Q-T interval duration 0.38 sec Heart rate 75 bpm Objective 2: Heart Sounds In this lab activity you will record the ECG and heart sounds from a subject and, with the aid of an electronic stethoscope, hear those characteristic sounds of the heartbeat, typically described as a "lub-dub." Equipment Required PC Computer IWX/214 data acquisition unit USB cable IWX/214 power supply C-AAMI-504 ECG cable and electrode lead wires ES-100 electronic stethoscope Alcohol swabs; Disposable ECG electrodes R - Lub time T - Dub time Objective 3: Arterial Blood Pressure http://www.youtube.com/watch?v=UYcSrcLVJHI Evaluating Circulation Pulse is a pressure wave alternate expansion & recoil of elastic artery after each systole of the left ventricle pulse rate is normally between 70-80 beats/min • tachycardia is rate over 100 beats/min/bradycardia under 60 Measuring blood pressure with sphygmomanometer – Korotkoff sounds are heard while taking pressure – systolic blood pressure from ventricular contraction – diastolic blood pressure during ventricular relaxation • provides information about systemic vascular resistance – pulse pressure is difference between systolic & diastolic – normal ratio is 3:2:1 -- systolic/diastolic/pulse pressure Pulse Points Measuring Blood Pressure http://www.youtube.com/watch?v=UYcSrcLVJHI http://www.youtube.com/watch?v=tB8nISCEcs8 – Tips http://www.youtube.com/watch?v=8e6qtnHa8ps – Inflating the blood pressure cuff http://www.youtube.com/watch?v=PrRWkMoFNRc&feature=PlayList&p=BAA168C2B0F4 8FED&index=0&playnext=1 –interpreting the values To determine the heart rate from an ECG tracing: count the number of small squares from one R wave to the next R wave and divide that number into 1500 Heart Rate (bpm) = 1500/#small squares 10 squares = 1 mV Each small block = 0.04 sec P wave duration QRS complex duration T wave duration P-R (P-Q) interval duration Q-T interval duration Heart rate