(V.) Signal detection by PowerLab system - instruction (VII.) Examination of pulse by palpation Physiology I - practicals Dep. of Physiology, Fac. of Med., MU, 2015 © Michal Hendrych, Tibor Stračina Biosignal • Signal which is produced by living systems • According to physical properties: • Mechanical (e.g. pulse wave, arterial blood pressure) • Electrical (e.g. electrocardiography, electroencephalography) • Acoustic (e.g. heart sounds) • Chemical (e.g. partial pressure of CO2) • Optical (e.g. saturation of haemoglobin by pulse oximetry) Biosignal detection and recording Teaching system PowerLab • PowerLab is complete system for acquisition and assessment of biosignals • Fundamental part of the system is amplifier connected to various sensors • Examined person should be informed about the procedure and be prepared for examination Pulse (pulsus) • Mechanical manifestation of heart activity • Mechanical wave (pulse wave) arises after each contraction of LV and propagates along the arterial wall Palpation of pulse • Where: • A. radialis • A. carotis • A. femoralis • A. brachialis • A. poplitea How: • A. tibialis posterior • A. dorsalis pedis Examination of pulse • Frequency: number of pulses per one minute = pulse rate • Qualities: regularity, compressibility • According qualities, we can describe: • Pulsus regularis • Pulsus irregularis • Pulsus celer (Corrigan´s pulse: P. celer, altus, frequens) • Pulsus tardus • Pulsus durus – hardly compressible pulse – hypertension • Pulsus mollis – easily compressible pulse – hypotension • Pulsus magnus – high amplitude of pulse • Pulsus parvus – small amplitude of pulse • Pulsus filiformis – threadlike pulse – circulatory failure Heart rate • Physiological values: 60 – 100 beats per minute (BPM) • Tachycardia: increased heart rate • Bradycardia: decreased heart rate Modulation of HR by autonomic nervous system (ANS) • ANS modulates heart automaticity by modulation of SA node activity • Parasympathetic system – vagus nerve – „nervi retardantes“ • Via M2 receptors • Negative chronotropic effect • Decreased tonus of vagus nerve = increased HR • Sympathetic system – sympathetic cardiac nerves – „nervi accelerantes“ • via β1 receptors • Positive chronotropic effect • Increased sympathetic activity = increased HR Baroreflex • Mechanism for rapid control of arterial pressure • Mean arterial pressure (MAP) is detected by baroreceptors in aortic arch and carotic sinus • stretch-receptors (mechanoreceptors) • Afferent fibres: vagus nerve (n. X.) • Centre: rostral part of nucleus solitarius in medulla oblongata • Efferent fibres: parasympathetic fibres of vagus nerve (+ SS) • Mechanism: ↓MAP - ↓afferentation from baroreceptors – processing - ↓vagus tonus (+ ↑sympathetic tonus) - ↑HR - ↑MAP Respiratory arrhythmia • Changes of heart rate in accordance with breathing • During inspiration – ↓ intrathoracic pressure → ↑venous return (due to ↑ pressure gradient) → ↑systolic volume → ↑MAP → baroreflex → ↓HR → ↑ (balance of) MAP • During expiration, all changes are reversed (↑HR) • Time shift of the effect: Discrepancy between expected and measured changes of heart rate may be caused by reaction time of baroreflex, which is approx. 2 sec. In case of resting breathing, both of inspiration and expiration take approx. 2 sec, as well. Therefore, measured changes of HR may seem to be inverse (phase shifted). Zdroje obrázků • Slide 6 - https://www.pinterest.com/pin/144537469264742090/ [cited 31.8.2015] • Slide 6 - http://www.angiologist.com/general-medicine/pulse-palpation-andpulse-location/ [cited 31.8.2015] • Slide 12 - http://corposcindosis.wikia.com/wiki/File:Baroreflex.jpg [cited 31.8.2015] • Slide 14 - http://www.cardiachealth.org/postural-orthostatic-tachycardiasyndrome-pots [cited 31.8.2015]