Activity 3.4: Evidence-based practice and research (page 73)
Janet has experienced postural hypotension which has caused her fainting episode. On standing, blood pressure (BP) will fall as gravity pulls blood downwards. This drop is usually quickly detected by the baroreceptors and the heart rate is increased, and blood vessels undergo vasoconstriction to maintain BP. This baroreceptor response tends to become less efficient (blunted) with age. Janet takes a combined beta blocker and diuretic pill to treat her hypotension and this could significantly increase the risk of postural hypotension.
The beta blocker component slows Janet’s heart rate reducing her cardiac output while the diuretic will increase urine production, lowering Janet’s blood volume. Janet will require further assessment to determine if there are any other underlying causes for her postural hypotension. Based on this episode, Janet should be advised to rise slowly to allow her BP to normalise and she may have to be switched to a different type of antihypertensive medication.
Activity 3.5: Multiple-choice questions (pages 77–9)
1) c, 2) a, 3) b, 4) c, 5) d, 6) b, 7) d, 8) d, 9) a, 10) c
Further reading
Boore J et al. (2016) Chapter 12: The cardiovascular and lymphatic systems, in Essentials of Anatomy and Physiology for Nursing Practice. London: SAGE Publications Ltd.
A textbook to develop your knowledge of human anatomy and physiology that is aimed specifically at nurses.
Tortora G and Derrickson B (2017) Tortora’s Principles of Anatomy and Physiology (15th edition). New York: John Wiley & Sons.
In-depth coverage of human anatomy and physiology.
Useful websites
www.nhs.uk/conditions/arrhythmia
A simple overview of arrhythmias.
www.cvphysiology.com/Heart%20Disease/HD002
A summary explaining in simple terms the phases of the cardiac cycle.
www.nhs.uk/conditions/high-blood-pressure-hypertension
An overview of hypertension and its causes.
www.nice.org.uk/guidance/ng136
Overview of current criteria for diagnosing and managing hypertension.
Chapter 4 The respiratory system
Nikki Williams
Chapter aims
After reading this chapter, you will be able to:
describe the key functions of the respiratory system;
identify the major anatomical structures of the respiratory system;
highlight the regions of the conducting and respiratory zones;
describe the processes of ventilation and gaseous exchange;
explain how oxygen and carbon dioxide are transported in the blood;
describe the mechanisms of respiratory control and the role played by the respiratory system in acid base balance.
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.
Figure 4.1 Overview of the respiratory tract
The respiratory tract is divided into upper (Figure 4.2) and lower regions.
The upper respiratory tract
The nose and nasal cavity
The nose functions as the primary inlet for air during inspiration. The upper, rigid section of the external nose is formed by the nasal bones and the frontal process of the maxilla (upper jaw bone);