Theory and Practice of Blood Flow Measurement

John P. Woodcock

• Publisher: Butterworth-Heinemann
• Year: 2013
• ISBN:
  9781483182735
• Topic: Sciences biologiques
• Subtopic: Anatomie humaine et physiologie

Theory and Practice of Blood Flow Measurement presents the methods for determining the metrics of blood flow in the major vessels. This book is organized into two sections encompassing 16 chapters that discuss the theories behind the different techniques of flow measurement and the performance of flowmeters and their practical application to determining blood flow volume in the tissues and organs. Considerable chapters are devoted to various methods of blood measurement, including dilution, transport, and thermal techniques, as well as the effect of catheter sampling on the shape of indicator dilution curves. Other chapters are concerned with the possible errors in the application of indicator dilution techniques and the types of dilution indicator, and measurement of indicator concentration. A chapter is devoted to the advantages and disadvantages of thermistor flowmeter. The last chapter focuses on the design of a thermal dilution catheter. The book can provide useful information to physicists, bioengineers, surgeons, students, and researchers.

SECTION ONE

MEASUREMENT OF BLOOD FLOW IN MAJOR VESSELS

Introduction to Measurement of blood flow in major vessels

This section is a review of techniques that have been used to study blood flow in the major blood vessels, and includes indicator dilution and thermal techniques, electromagnetic and ultrasonic flowmeters, pressure sensing flowmeters, Ludwig stromuhrs and bubble flowmeters, nuclear magnetic resonance, magnetorheography and a radio-frequency (r.f.) coil system. The theory on which the instruments are based is discussed, together with details of the calibration procedure and potential hazards. Section II is a discussion of blood flow measurement in the organs and tissues of the body—including the brain, liver, kidney, limbs and limb segments, muscle, skin, adipose tissue and bone. In the final chapter, the optimum characteristics of the ideal flowmeter are discussed, and the attributes of each of the types described are compared with the ideal instrument. In this way it is hoped to be able to suggest the optimum flow measuring technique to use in any specific case.

In arranging the subject content in this way it is inevitable that techniques described in Section I can also be used in Section II to study organ and tissue blood flow. In the chapter on thermal flowmeters which, for convenience, is in Section I, the techniques of calorimetry, conductivity and thermography are all used to measure organ or tissue blood flows and should by rights be included in Section II. However, it was felt that it is better to discuss flowmeters which depend on either the production or detection of heat under the one heading of thermal flowmeters and, as most of the thermal flowmeters in routine use are used to measure flow in a major vessel, it was decided to group these in Section I. The situation becomes clearer when the tables of blood flow measurements in the normal resting state are studied, because these show the techniques used to make the measurements.

CHAPTER 1

Circulation of the blood

Publisher Summary

This chapter discusses the circulation of blood. From the earliest times, it has been understood that blood plays an important part in the proper functioning of the body by providing heat and life. As long as the heart is uninjured, life and health can be restored to the body. Many serious diseases gain access to the body when it suffers from nourishment and lack of warmth. It is at this stage when it is realized that the circulation of blood is of the greatest importance for the maintenance of life. The basic understanding of the circulation is that the animal machine is governed by three main regulating systems: (1) respiration, which consumes oxygen and carbon dioxide and supplies the caloric; (2) transpiration, which increases or diminishes depending on whether it is necessary to eliminate more or less of the caloric; and (3) digestion, which returns to the blood what it loses by respiration and transpiration.

Empedocles of Agrigenti, as early as the sixth century B.C., contributed the idea of the inter-relation between the pneuma or source of health in the body, and the blood, which he considered to be the carrier of innate heat, issuing from the heart and returning back to it in a series of tides and pulsations (Sarton, 1952). Also in the sixth century B.C. Alcmaeon of Croton distinguished two types of blood vessel. In the Hippocratic Corpus (fifth century B.C.), the trachea and bronchi were designated arteries because it was understood that they transported the pneuma to the heart. Some blood vessels arising from the heart cavity were found at death to contain air and to be more or less empty of blood; these were also designated arteries. It is in this Hippocratic Corpus that the first suggestion that blood circulates is found. It is said that the arteries also carried blood, and connected with the veins, the blood being distributed to all the body giving warmth and life. The movement of blood is compared with the course of rivers returning to their sources after a passage through numerous channels (Wiberg, 1937).

Herophylos (fourth century B.C.) considered that pulmonary function was a four-stage process: first the absorption of fresh air, second the distribution of air in the body, third the collection of air returning from the body and, fourth, the evacuation of vitiated air to the exterior. Erasistratos (fourth century B.C.) considered that there were two separate systems for transporting air and blood. First, the blood, the source of matter, nourished all the body. Second, the pneuma, which consisted of the vital spirit and the animal spirit, was the source of energy animating matter. In the two transport system, blood was manufactured in the liver and moved through the veins to all the organs. A small fraction reached the right ventricle but was diverted because of the tricuspid valve into the lungs for nourishment. Meanwhile air was inspired into the lungs and flowed through the vein-like artery (pulmonary artery) to the left ventricle. In the left ventricle it became vital spirit and distributed to the body through the aorta and arteries. That part of the vital spirit which reached the brain was converted to animal spirit and transported by means of hollow nerves to the entire body. Erasistratos was the first person to recognize the undirectional flow of blood to the lungs and of air to the left ventricle from the lungs. Erasistratos also mentioned that the veins and arteries communicated through fine vessels.

Galen (A.D. 130–201) further refined the ideas on the movement of blood by introducing the concept of undirectional movement of blood and air through the lungs. Up until Galen’s time the venous, arterial and nervous systems were considered to be completely separate: the function of each was to distribute the natural, vital and animal spirits throughout the body. Galen recognized that blood was carried in both arteries and veins, otherwise the blood would ebb and flow. Fleming (1955) stresses that Galen did not advocate the ebb and flow...