Getting Started: The Approach to Respiratory Physiology

Learning Objectives

The act of breathing is essential to life, and the study of the physiology of the respiratory system is relevant for all medical specialties, from internal medicine to surgery to psychiatry. An understanding of gas exchange, the movement of oxygen into the blood to support aerobic metabolism in the mitochondria and removal of the metabolic byproduct, carbon dioxide, from the blood, is critical for all physicians providing clinical care. The multiple factors that can interfere with this process cut across specialties. The role of the respiratory system in maintaining equilibrium of the acid-base balance of the body is another essential topic for all practitioners. The unique blend of automatic and volitional control of breathing makes the understanding of human behavior a relevant issue as well. If you plan on entering the field of psychiatry someday, for example, you may be confronted with a patient with panic attacks, hyperventilation, and a series of symptoms that can best be understood within the context of respiratory physiology.

When you first heard you were about to study respiratory physiology, chances are that your first thought was: "I will be studying the lungs." Although the lungs are clearly an essential element of the processes we associate with breathing, they alone do not provide the whole story. Rather, one must step back and look at the system that is responsible for the movement of oxygen into the blood and carbon dioxide out. Without muscles to generate a negative pressure within the thorax to draw air into the lungs, for example, the lungs would be worthless. Without an area of the brain to monitor breathing and to send appropriately timed neurological impulses to the muscles and the peripheral nerves to carry those impulses, the muscles could not do their job. As you proceed from one chapter to another, we will periodically orient you to where we are in the respiratory system and show you how the different components interact.

At its core, physiology is a conceptual science. The study of physiology is critical to understanding the way that the body functions and the many mechanisms available to restore homeostasis when disease attacks. Our goal throughout this book is to emphasize conceptual understanding of the material. We want you to develop an appreciation of physiological principles at a depth sufficient to allow you to apply the concepts to new situations, thereby enabling you to make sense of a unique patient, the ultimate challenge in medicine. Our emphasis is on clinical physiology. Given the great range of information that physicians in training must learn, we emphasize principles that are most essential for you to care for patients and to have a strong foundation upon which to build as you move on to more advanced levels of study. Although we use clinical examples throughout the text to demonstrate the relevance of the material and the ways that the concepts are applied to patients, this is a physiology book, not a pathophysiology one. Thus, the book does not describe in detail specific disease states, diagnostic methods, or treatment options except as they may enhance your understanding of physiology. Given the emphasis on this clinical approach, we will not spend considerable time on some physiological points found in classic texts that are neither clinically relevant nor necessary to have a solid foundation in the field. We acknowledge that this is not a text aimed primarily at basic science physiologists. Rather, we strive to provide clinical physiologists with essential information needed for patient care today and the understanding to add to that knowledge in the future.

Much of what we know about physiology derives from careful observations of people and from animal models. From these observations, hypotheses have been constructed to help explain the findings. In some cases, hypotheses have been tested extensively and modified accordingly. In other situations, we are still working largely at the level of conjecture. Those who have a need for definitive answers in all circumstances may be frustrated at times in the study of physiology. The "proof" is not always available to us. Perhaps you may be intrigued by one of these areas of uncertainty and pursue further investigations to provide us all with greater insights into the workings of the human body.

This book is designed primarily for medical students who are embarking on the study of respiratory physiology for the first time, but the book also serves as an excellent review for advanced medical students, interns, and residents, especially for those whose initial instruction in respiratory physiology took a more traditional basic science approach to the subject. Nurses and respiratory therapists who care for patients with respiratory problems may also find this text useful. This book is not intended as a definitive or all-encompassing resource on respiratory physiology. Those pursuing advanced training in pulmonary and critical care medicine or anesthesiology may rely on this as a primer as they expand their knowledge into the subtleties of the field.