Working with Voice Disorders

Theory and Practice

Stephanie Martin

• Publisher: Routledge
• Year: 2020
• ISBN:
  9781000284249
• Edition: 3
• Topic: Medicina
• Subtopic: Audiología y patología del habla

Now in a fully revised and updated third edition, Working with Voice Disorders offers practical insight and direction into all aspects of voice disorders, from assessment and diagnosis to intervention and case management. Using evidence-based material, it provides clinicians with pragmatic, accessible support, facilitating and informing decision-making along the clinical journey, from referral to discharge.

Key features of this resource include:

• A wealth of new, up-to-date practical and theoretical information, covering topics such as the prevention, assessment, intervention and treatment of a wide spectrum of voice disorders.

• 
  
  

• A multi-dimensional structure, allowing the clinician to consider both specific aspects of patient management and aspects such as clinical effectiveness, clinical efficiencies and service management.

• 
  
  

• Photocopiable clinical resources, from an at-a-glance summary of voice disorders to treatment and assessment protocols, and practical exercises and advice sheets for patients.

• 
  
  

• Sample programmes for voice information groups and teacher workshops.

• 
  
  

• Checklists for patients on topics such as the environmental and acoustic challenges of the workplace.

• 
  
  

• Self-assessed personalised voice review sheets and weekly voice diaries encourage patients to monitor their voice quality and utilise strategies to prevent vocal misuse.

• 
  
  

Combining the successful format of mixing theory and practice, this edition offers a patient-centred approach to voice disorders in a fully accessible and easy-to-read format and addresses the challenges of service provision in a changing world. This is an essential resource for speech and language therapists of varying levels of experience, from student to specialist.

1

Anatomy overview

Introduction

The process of producing voice

The respiratory system

Principal muscles of inspiration

Accessory muscles of inspiration

Muscles of expiration

Muscles that aid active expiration

Innervation of the respiratory system

Role of respiration

Lung volumes

Lung capacities

The phonatory system

Structure of the larynx

The resonatory system

Innervation of the resonatory system

Posture and alignment

The ageing process

Summary

Introduction

This chapter is intended principally as a brief overview of the anatomy, physiology and neuroanatomy of ‘voice production’. For those readers who are looking for very detailed information there are many widely available excellent resources, both publications and online. The purpose of this chapter is, however, to offer an easily accessible overview for readers outlining the structures and functions central to the production of voice and noting how they change over time.

The process of producing voice

Voice production is dependent on three different, but interrelated, systems:

•the respiratory system – responsible for the manner and pattern of breathing;

•the phonatory system – responsible for how sound is produced at the level of the larynx;

•the resonatory system – responsible for the modification of the sound.

These separate but interconnecting systems have been adapted to work together in the process of voice production, although their primary biological purpose is, of course, to assist in life support.

While recognition is given to the interdependence of the three systems, for the purpose of this chapter each system will be differentiated, one from the other. It is, however, important to remember that vocal quality changes are part of a composite and nuanced picture. Vocal quality changes that are recognised as disordered or different are often the result of cumulative changes within each system. Each system has its own individual and separate identity, but a change in one system may precipitate change in another, so a principal ‘cause’ of the disorder may be difficult to establish. Mathieson (2001) suggests that when a physiological change occurs in the larynx, a pathological change may well have been the precipitating feature, or indeed pathological change may be the result of physiological change, a view with which the author strongly concurs.

The respiratory system

The main purpose of the respiratory system is to maintain life by carrying air into the lungs where the exchange of gases, oxygen and carbon dioxide takes place.

Oxygen enters the bloodstream and excess carbon dioxide moves out through the capillaries surrounding the alveoli within the lungs. The respiratory system can be said to begin at the nose and the mouth, and end with the alveoli in the lungs. Within this system two distinctive respiratory tracts are identified. The upper respiratory tract is composed of the nasal and oral cavities, the pharynx and the larynx. In addition to its role in respiration, the upper respiratory tract has multiple functions, such as the processes of chewing, swallowing, articulation, resonance and phonation. The lower respiratory tract refers to the trachea, the bronchi and lungs, which are housed within the bony thoracic skeleton or ribcage, and in contrast to the upper respiratory tract, functions exclusively for the process of breathing for life and for phonation.

The upper and lower respiratory tracts comprise the vocal tract and, as may be surmised by their close alignment, are functionally interdependent so that modifications to one will affect the function of the other.

The respiratory tract has two parallel entrances, the nose and the mouth, through which air enters. These entrances merge into a common tract, known as the pharynx. The pharynx is a cone-shaped tube approximately 13–14 cm long, composed of muscular and membranous layers, wider at the top where it is continuous with the nasal cavity and opening laterally into the mouth. At its lower and narrower end it leads into the laryngeal inlet anteriorly and the oesophagus posteriorly. The area within the pharynx immediately behind the nose (the nasopharynx) and the area behind the mouth (the oropharynx) are separated by a muscular valve, the soft palate, which, when raised, closes off one section from the other, thus effectively preventing food or liquid escaping from the nose when swallowing. Along with the most inferior part of the pharynx, which contracts at rest and prevents any reflux of the stomach contents into the pharynx or air entering the oesophagus, the soft palate forms part of the involuntary protective mechanism in the respiratory tract. By far the most vigorous protective mechanisms, which are involuntary and reflexive, exist within the larynx. Some mechanisms attempt to ‘repel’ by closing off the airway and some attempt to ‘expel’ by forcing substances out of the respiratory tract.

The respiratory tract, passing through the laryngeal inlet, continues into the trachea, which divides into two branches, and subsequently into the smaller bronchi that enter the lungs, and ultimately into the alveoli. Protective mechanisms exist along the respiratory tract to prevent inadvertent damage; for example, the lungs are encased by the bony thoracic skeleton, or ribcage, consisting of 12 pairs of ribs. Each set of ribs has different dimensions and degrees of flexibility of movement.

The first pair is the shortest (the paired ribs increase in length up to rib 7 and then decrease in length up to rib 12) and immobile, fused to the breastbone or sternum at the front and at the back to the spinal vertebrae. Pairs two to seven are similarly attached, but by synovial joints which permit a degree of rotation, while pairs eight to ten are attached to each other at the front by flexible cartilage. Pairs 11 and 12 (sometimes referred to as ‘floating ribs’) are fixed at the back to the spinal vertebrae but have no fixed attachment at the front to the sternum. The somewhat idiosyncratic arrangement of the ribs is important, in that the pleural or membranous connection between the lungs and thoracic cavity allows expansion and contraction of this area as a single unit and along three planes for inspiration and expiration. During inspiration the vertical dimension is increased by contraction of the diaphragm, the upward movement of the ribs increases the transverse diameter while a simultaneous forward and upward movement of the sternum increases the antero-posterior diameter. The orientation of the ribs controls their mobility and this flexible cavity, which also contains major organs such as the heart, the aorta and vena cava, the trachea and oesophagus, can then accommodate changes in the size of the pear-shaped lungs, which expand to contain greater amounts of air when needed to support speech or song. Modification of the respiratory cycle to quick intake and slow release of air, which is essential for this process, may be contrasted with the equal phases of inspiration and expiration common to quiet, at rest, breathing for life, which is predominately under medullary control and heavily influenced by the level of carbon dioxide present in a particular environment (Table 1.1).

Table 1.1 Cycle of respiration

Phase	Muscles involved
Inspiration	Abdominal muscles and internal intercostals relax. External intercostals contract to fully expand the rib cage. Diaphragm contracts and descends which enlarges the lung space
Expiration – Stage 1	Without muscular effort to keep rib cage expanded it ‘relaxes’ back to rest position, known as ‘elastic recoil’, which initiates airflow
Expiration – Stage 2	Contraction of the internal intercostals added to last of ‘elastic recoil’ adds to lung pressure
Expiration – Stage 3	Abdominal muscles used to provide the final possible amount of lung pressure

The muscles of respiration have clearly defined roles and most are concerned either with inspiration (Figure 1.1) or expiration (Figure 1.2), but some, like the latissimus dorsi (the largest muscle in the upper body) have a more overarching function within respiration and are concerned with both inspiration and expiration.

Figure 1.1Muscles of inspiration

Figure 1.2Muscles of expiration

In resting respiration, air is inspired at approximately a dozen times per minute, but this muscular activity goes largely unnoticed despite the fact that there is active muscular contraction to enlarge the thorax. The diaphragm and the external intercostals are most responsible for this activity. For the purposes of speech and song,...