Ch. 8 Physiology of Mastication and Deglutition

Mastication and Swallowing Overview

• Mastication is the act of chewing, which mechanically breaks down food into smaller, more manageable pieces to facilitate easier swallowing and digestion. This process involves the coordinated action of teeth, jaws, and muscles.

• Decomposition refers to the act of swallowing, a complex physiological process that involves the movement of a bolus from the mouth, through the pharynx, and into the esophagus.

• Relevant concepts from Chapter 6 include specific muscles involved in mastication such as the masseter, temporalis, and pterygoid muscles.

• Children may exhibit munching patterns instead of a rotary chew during early development, which can impact their swallowing and eating skills.

• Rehabilitation post-stroke or oral surgery may involve targeted mastication practice, which can help improve motor control and swallowing reflexes.

• Bolus: Prepared food, whether liquid or solid, that is swallowed as a single mass; its proper formation is crucial for safe and effective swallowing.

Swallowing Evaluation

• Types of Tests:

  • Subjective tests (initial evaluation) are often conducted by healthcare professionals to assess the patient's ability to swallow based on patient reports and clinical observations.

  • Objective tests include advanced techniques such as Fiber Optic Endoscopic Evaluation of Swallowing (FEES) and Modified Barium Swallow (MBS), which provide visual and functional assessment of swallowing dynamics.

  • An oral motor exam is part of the evaluation process to assess the muscle strength and coordination involved in oral preparation and transit phases.

• Test Procedures:

  • Presenting various food textures (thick, smooth, solid) during the evaluation helps to identify safe swallowing strategies tailored to the patient's needs.

  • Adjusting approaches based on patient condition (such as the presence of intubation or cognitive deficits) is vital to ensure accurate assessment and safety.

  • Monitoring for signs of aspiration or swallowing difficulties is crucial to prevent complications, such as pneumonia.

FEES and MBS Tests

• FEES: Fiber-Optic Endoscopic Evaluation (Structures)

  • Involves passing a nasal scope to visually evaluate swallowing dynamics and structure integrity, assessing any potential abnormalities.

  • It visualizes anatomical structures and vocal cords, helping to identify functional deficits during swallowing.

  • The FEES procedure allows viewing before (anatomical assessment), during (noting the white-out period indicative of swallowing), and after the swallowing events, crucial for comprehensive evaluation.

• MBSS: Modified Barium Swallow Study (entire swallow)

  • This involves taking x-ray recordings of the swallowing process from oral to esophageal phases, which is vital for detecting swallowing disorders.

  • It examines bolus movement and muscle function, including assessing aspiration risks and the safety of various food consistencies.

Stages of Mastication and Swallowing

• Oral Phase:

  • Prepares bolus for swallowing, which is instrumental in the safe transition of food from the mouth to the throat.

  • This phase is divided into the Oral Preparatory Stage (involving chewing and mixing food with saliva) and the Oral Transport Stage (involving pushing the bolus back into the pharynx).

• Pharyngeal Stage:

  • Triggered by the bolus reaching the posterior tongue area; this stage becomes involuntary once initiated, highlighting the transition to reflexive swallowing.

  • Important actions during this stage include laryngeal elevation (to protect the airway), airway protection mechanisms (closure of the epiglottis), and relaxation of the upper esophageal sphincter to allow food passage.

• Esophageal Phase:

  • This is the involuntary passage of food to the stomach using peristalsis, which is a series of wave-like muscle contractions that move food through the esophagus.

Muscles Involved in Swallowing

• Various muscle groups are intricately involved in the mastication process:

  • Facial muscles (such as orbicularis oris for lip closure), mandibular muscles (including masseter and temporalis for jaw movement), lingual muscles (for bolus manipulation), and soft palate muscles (to prevent nasal regurgitation) assist in forming and moving the bolus efficiently.

  • Cranial nerves (like V, VII, IX, and X) play essential roles in muscle innervation for motor and sensory functions, providing feedback crucial for coordinated swallowing.

Alterations with Aging

• Presbyphagia: This term describes changes in swallowing function due to aging, impacting safety and efficiency in older adults.

• Effects include reduced muscle strength, decreased coordination, and altered sensory trigger locations for swallowing, often leading to increased dysphagia.

• Commonly, older adults may exhibit delayed swallow triggers or changes in texture preference, necessitating tailored dietary recommendations to ensure safety.

Reflexes in Swallowing

• Reflexes such as the cough reflex and gag reflex are vital in protecting the airway during swallowing.

• Others include the chewing reflex (to initiate chewing), sucking reflex (important in infants), and the apnea reflex (temporary breath-holding during swallowing to prevent aspiration).

Dysphagia Overview

• Defined as difficulty swallowing, dysphagia can occur at any swallow stage, resulting in varying symptoms such as coughing, a sensation of food sticking in the throat, and difficulty managing different textures.

• There is a significant risk of aspiration pneumonia due to dysphagia, as food can inadvertently enter the airway, leading to serious respiratory complications.

Compensatory Strategies for Dysphagia

• Dietary modifications, such as offering pureed foods and thickened liquids, are essential strategies to enhance swallowing safety.

• Swallowing techniques (like chin tuck and effortful swallow) can be taught to enhance both safety and efficiency of swallowing.

• Rehabilitation approaches must consider the social implications of dysphagia, informing patients about NPO (nothing per oral) orders and changes in diet to mitigate issues related to social participation at mealtimes.

IDDSI (International Dysphagia Diet Standardisation Initiative) provides a framework for texture-modified diets, enabling consistent terminology and practices across different healthcare settings.

• Developed to standardize food and liquid consistency for safer swallowing, this framework is crucial for clinical practice.

• It categorizes textures into a spectrum for ease of understanding: regular, easy-to-chew, soft bite-size, minced and moist, and pureed, aiding healthcare professionals in creating safe dietary plans for dysphagia patients.

• Maintaining nutritional intake is paramount for dysphagia patients to ensure overall health and well-being.

Patient Experience Considerations

• Importance of maintaining social engagement while managing dietary restrictions is crucial for the emotional and psychological well-being of patients with dysphagia.

• Balancing patient preferences with safety in swallowing techniques is essential to provide a supportive and individualized approach.

• Discussing strategies for social dining experiences is vital to minimize discomfort or isolation due to dietary restrictions, ensuring that patients feel included and valued during mealtimes.