This chapter covers the core concepts in respiratory physiology for the FRCA exam. We explore the basic principles of respiratory physiology and ventilation, and go into detail on ventilation-perfusion matching, lung compliance, shunt, dead-space and the alveolar gas equation.

A primary brain injury occurs at the time of initial mechanical trauma. An additional secondary brain injury begins immediately after impact. Inflammatory and neurotoxic processes result in raised intracranial pressure, decreased cerebral perfusion and ischaemia. This secondary injury is worsened by further physiological insults such as hypotension and hypoxia.

Assessment of the patient begins with an ABCD approach and should take place alongside resuscitation. Airway management is the priority, and this must be safely secured when indicated. Cervical spine injury is often associated with a head injury. The neck should be immobilised. Hypoventilation causes hypoxia and hypercapnia. Controlled ventilation to achieve a PaCO2 of 4.5 - 5 kPa and a PaO2 of > 13 kPa is recommended to control intracranial pressure. Hypotension reduces cerebral perfusion; a mean arterial pressure of > 90 mmHg should be targeted. Neurological assessment is undertaken using the Glasgow Coma Scale (GCS). A GCS less than 8 is considered a serious head injury and is often an indication for tracheal intubation. Other indications are described. Transfer to a neurosurgical unit is often required. Safe transfer guidelines must be followed.

An anaesthetist may control the airway through the application of several methods and the use of specific equipment. Primarily, the patient’s position must be optimised to allow for an open airway. An appropriate face mask should be fitted around the patient’s mouth ensuring there are no leaks. In the case of an obstructed upper airway the use of oral or nasal devices, such as a Guedel or nasopharyngeal airway, can allow the obstruction to be bypassed and aid effective oxygenation. Supraglottic airway devices (SADs), such as the laryngeal mask or i-gel, are frequently used to provide oxygenation and ventilation in spontaneously breathing patients and form part of the difficult airway algorithm. A variety of devices and generations are now available which have additional benefits of allowing gastric content suction and the passage of flexible scopes to visualise the airway and aid intubation. The tracheal tube is discussed with all its features and benefits of allowing for a definite and secure airway.

A difficult or failed intubation may occur in the elective or emergency setting, and it is therefore important that every anaesthetist has a plan and knows the failed intubation algorithm. The Difficult Airway Society (DAS) in the UK have published guidelines on the management of failed tracheal intubation which are discussed in this chapter, also described as the ‘Can’t intubate, can’t ventilate’ algorithm. The algorithm follows a stepwise approach starting with Plan A the goal to achieve tracheal intubation and how this may be optimised. Plan B describes the use of supraglottic airway devices to allow for oxygenation when intubation has not succeeded. Plan C advises the clinician to return to facemask ventilation in the case of failed oxygenation and consider waking up the patient if circumstances allow. Plan D describes emergency front-of-neck asses using a scalpel cricothyroidotomy approach.

Neuromuscular disorders cause respiratory failure when they significantly impair the respiratory muscle pump. This is a complex system involving the diaphragm, intercostal, neck, shoulder girdle, abdominal wall and possibly paraspinal muscles. The dilator muscles of the palate, pharynx and larynx maintain a patent airway and air conduit. The diaphragm is the main muscle of inspiration, but is aided by the parasternal intercostals, and additionally by the accessory respiratory muscles in forceful inspiration, diaphragmatic weakness or compromised diaphragmatic function as is the case in lung emphysema. Exhalation is passive, but forceful expiration and cough require the abdominal wall and a portion of the intercostals. This chapter focuses on the physiology of the muscles involved in respiration, and the recognition of developing neuromuscular respiratory failure, its clinical evaluation and assessment, and basic principles of management.

Managing the mechanical ventilator in critical illness is far from formulaic. Criteria of intubation are rarely contemplated when a patient is struggling to maintain a patent airway. Once the airway is secured, adjustments in ventilator settings and modes are continuously made, and there is a fair amount of trial and error. Weaning from the ventilator is not standardized (and probably never will be), and protocols (if there are any) are based on consultant preferences and mostly experience. The consensus statement of the European Society of Intensive Care Medicine on mechanical ventilation (MV) in acute brain injury has clearly shown that evidence for certain approaches was either insufficient or lacking and that a substantial amount of research is needed to demonstrate the feasibility, safety, and efficacy of different management approaches in this category of patients.

This chapter reviews considerations in each intervention during the patient’s clinical trajectory of ventilation in the neurosciences ICU. The reader will find that early intubation and mechanical ventilation are initiated because patients cannot protect their airways or have insufficient respiratory drive to maintain oxygenation and normocarbia.

Respiratory regulation comprises respiratory rhythmogenesis, formation of the respiratory motor pattern, control of blood oxygen and carbon dioxide, increase of minute ventilation during physical activity, adaptation of respiration to the sleep-wake cycle, coordination of breathing with swallowing, cough, sneezing, choking and voluntary activity such as speech or singing. Other factors such as growth and maturation, emotion, pregnancy, injury, disease, body temperature, pain and aging lead to changes in respiration. The presence of a respiratory rhythm generator in the brainstem is now known to be a common feature of all vertebrates. Knowledge about respiratory regulation is mainly derived from animal models, but respiratory regulation in humans is subject to an increasing number of physiological, electrophysiological, neuroradiographic, histopathological and genetic studies. This chapter provides an overview of respiratory regulation, focused on neuroanatomical, neurophysiological and clinical apsects.

The key question in mechanical ventilation is whether invasive or non-invasive is the option being applied to the individual patient. In order to answer this question, it is necessary to recognize the pathophysiology and understand which physiological system has failed and needs to be supported. In this chapter we outline the optimal treatment options for respiratory insufficiency type 1 and 2. The reader will be made familiar with the basic principles of non-invasive and invasive ventilation. The aim is to arbitrate an overview as well as basic flowchart for the treatments depending on which of the aforementioned respiratory insufficiencies are to be treated. The chapter also comprises a quick guide to the initial ventilator settings.

Comprehensive knowledge of the anatomy and physiology of the respiratory system is crucial in respiratory medicine. A profound understanding of physiology allows the practitioner to deduce pathological processes and initiate therapeutic steps based on rational decisions. The choice of a suitable ventilation mode or setting typically stems from an understanding of the pathophysiological processes. Understanding the respiratory chain at the cellular level, ventilation and perfusion, as well as the delicate interplay of macroscopic and microscopic mechanisms, supports the development of precise and individualized ventilation strategies. Knowledge of mucociliary clearance and the various lung volumes is also crucial to ensure optimal management of tracheobronchial secretions, oxygen supply and CO2 elimination.

This chapter covers respiratory physiology, including lung volumes and mechanics, ventilation and perfusion, compliance, diffusion, oxygen transport, carbon dioxide transport, effects of hypercarbia and hypoxemia, arterial blood gas interpretation, work of breathing, control of ventilation, non-respiratory functions of the lung, and the effects of perioperative smoking. The material is presented in a concise review format, with an emphasis on key words and concepts.

General anesthesia is a complex drug-induced state of consciousness, amnesia, analgesia and immobility. General anesthesia causes changes to physiological, cardiovascular, and respiratory status. This chapter discusses the techniques for induction of general anesthesia, airway assessment/management, and the ASA difficult airway algorithm.

This chapter summarizes basic concepts of respiratory physiology, including lung volumes and capacities, lung mechanics, gas exchange, ventilation and perfusion, and effects of perioperative smoking.

Anaesthesia for ENT surgery in children is varied, interesting and challenging. It ranges from grommet insertion and adenotonsillectomy, some of the most commonly conducted procedures in children, to the rare and evolving fields of airway reconstruction and EXIT procedures. Excellent teamwork and situational awareness are crucial to be safe and effective. This is particularly important in airway surgery given the small size of the paediatric airway, which is shared and often crowded with instruments, the sensitive physiology of small children and their frequent and complex comorbidities. Multidisciplinary team meetings and shared decision-making is increasingly important for these complex procedures and also on occasion for commonly conducted ENT procedures where there is a paucity of data around central issues such as postoperative admission criteria in children with obstructed sleep apnoea (OSA) and analgesia after tonsillectomy. Ultimately agreed local guidance should be followed as further investigations continue. An area of particular interest is the development of more effective modes of oxygenation such as high-flow oxygen delivery.

Healthcare-associated infections and more specifically surgical site infections, represent one of the biggest challenges facing practitioners in the perioperative environment. This chapter addresses the key points related to the causes of infection, and how they can be prevented. Infections are caused by pathogenic organisms, consequently, it is important to understand how they enter the body. The chain of infection model describes a series of links that outlines how infections can spread and provides a foundation to understand how they can be prevented. It is essential that perioperative practitioners understand how to break the chain of infection as well as the consequences of not doing so.

This chapter explains the key aspects of operating department design that facilitate a highly skilled multidisciplinary team to provide essential care to a vulnerable group of patients. It is important that the surgical facilities are designed to support the smooth flow of patients from admission to discharge. Surgical activities are broad ranging from scheduled or unscheduled, complex, to routine day surgery. Theatre services are central within the hospital system and rely on interdependant relationships with other hospital departments. This presents organisational, planning, and design challenges, as healthcare providers seek to improve services and utilise existing infrastructure to offer facilities that meet demand in a fast-paced and progressive field. Patients are entitled to receive high-quality healthcare, which is provided safely and effectively, and theatre teams should expect to deliver those high standards of care in an appropriate workspace. Theatre design is an essential component of the perioperative pathway, allowing surgical interventions to be carried out safely and efficiently to enable the best possible patient outcomes.

This chapter explains the fundamental principles of respiratory physiology for the perioperative practitioner. First, it describes the relevant respiratory anatomy, its function, and how it applies to the anaesthetic context. Second, it describes the different lung volumes and their relevance and application during artificial ventilation. Finally, it explains the physiology of perfusion and its application to ventilation and how they can be affected by different patient positions during anaesthesia and surgery.

Anaesthetic breathing systems are used to deliver oxygen and anaesthetic gases to patients and remove carbon dioxide. A breathing system is most commonly attached to an anaesthetic machine, which is designed to deliver the fresh gas flow to the patient via a facemask, a supraglottic device or an endotracheal tube. The breathing system used can affect the composition of the gas and volatile anaesthetic mixture inhaled by the patient, and so it is important to understand the different breathing systems used in anaesthesia. This chapter describes the key components of the different breathing systems and explores the benefits and disadvantages of the circuits in the Mapleson classification.