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      Chapter 4 The respiratory system

      Nikki Williams

      Chapter aims

      After reading this chapter, you will be able to:

      Case study: Jake – asthma

      Jake is 13 years old and has had asthma for several years. His asthma is generally well controlled, but it is made worse if he suffers from a respiratory tract infection or is exposed to a substance to which he is allergic. One afternoon, Jake and his classmates were on a cross-country run when after a few minutes Jake complained of a tight chest and started to cough profusely. Unfortunately, Jake had left his salbutamol (bronchodilator) inhaler in his bag in the changing room. Jake’s close friend Isaac stayed with him and reassured him, while another friend ran to tell their PE teacher who found Jake’s school bag. Within a few minutes, the teacher was able to give Jake his inhaler. After four puffs of salbutamol, Jake was feeling well enough to walk slowly back to school.

      Introduction

      Chronic respiratory diseases, such as the asthma affecting Jake, are routinely encountered and managed by nurses. Since the respiratory tract is in constant contact with the external environment, it is vulnerable to infection from pathogens and physical damage from toxic irritants. A significant problem in the UK and throughout the world is smoking, which progressively damages the airway and lung tissue, increasing the risk of chronic obstructive pulmonary disease (COPD) and other lung diseases, including cancer. This chapter will focus on the primary role of the respiratory tract in facilitating gaseous exchange.

      We will begin by examining the structure and function of the upper and lower respiratory tract and the nature of the conduction and respiratory zones. Since nurses need a thorough understanding of the mechanics of breathing, we will explore the physical principles of inhalation and exhalation and identify the principal lung volumes and capacities. The process of gaseous exchange across the alveolar wall will be described together with the mechanisms of oxygen and carbon dioxide transport in the blood.

      We will conclude the chapter by examining how breathing is controlled and how the breathing rate may influence the pH of the blood, contributing to acid base balance. Throughout the chapter we will reinforce key points with exercises and case studies highlighting common pathologies routinely encountered by nurses in clinical practice.

      Functions of the respiratory system

      The respiratory tract has multiple diverse functions, summarised in Table 4.1.

Table 4.1

      Overview of the respiratory system

      The respiratory system facilitates gas exchange by bringing air from the environment into contact with blood flowing through the pulmonary circulation (Chapter 3). The major structures of the respiratory tract include the nose, pharynx, larynx, trachea, bronchi, bronchioles, alveolar ducts, alveoli and lungs and are highlighted in Figure 4.1.