SPTH 365 Dysphagia and Related Disorders: Diagnosis

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SPTH 365 Dysphagia and Related Disorders
Diagnosis

• Lecture Eight
• Pulmonary Structure, Function and Implications
  for Swallowing

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Outline

• Anatomy of respiratory tract
• Pulmonary defense mechanisms
• Pulmonary disease

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Introduction(Curtis and Langmore, 1998)

• Respiratory and gastrointestinal passages share
  the oropharynx and hypopharynx as a result of
  common origin in the embryonic foregut
• With each swallow food/ fluid passes anteriorly
  to posteriorly over the larynx
• With each breath air passes in the opposite
  direction

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Respiratory Tract Anatomy

• Upper respiratory tract
• Nasal cavity
• Oropharynx
• Larynx
• Lower respiratory tract
• Trachea
• Bronchi
• Lungs

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Lower Respiratory Tract

• Trachea
• U- shaped cartilaginous rings
• Posterior aspect is open and approximates the
  oesophagus
• Extends from larynx to upper thoracic cavity at
  the bifurcation
• Inferior end divides into two mainstream or
  primary branches at the carina
• Tracheal rings are separated from each other by
  fibroelastic membrane, allowing for expansion
  during inspiration and flexibility during
  swallowing
• Lined with ciliated epithelial columnar cells and
  mucous producing goblet cells

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Lower Respiratory Tract

• Bronchi
• Left and right mainstream bronchi
• Left mainstream bronchi distributes more
  laterally to two pulmonary lobes
• Right mainstream bronchi distributes more
  later-inferiorly to three pulmonary lobes
• Right more common pathway for aspirated material,
  only if patient upright at time of aspiration

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• Bronchi further divide into secondary (lobar)
  and tertiary (segmental) groups
• Divide further into bronchioles, ending at
  terminal bronchioles and then alveolar sacs
• Gas exchange occurs at terminal bronchi and
  alveoli

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Lower Respiratory Tract

• Lungs
• Pair of separate cone-shaped organs
• Light, spongy and elastic
• Each lung housed in airtight sac (visceral
  pleura)
• Parietal pleura lines the inner chest wall
• The pleural cavity is filled with fluid
• Connected to the chest wall via pleural linkage
  that helps to resist collapse of the lungs and
  assists in inspiration
• Right and left lung.difference in lobes

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Anatomy of the Lungs
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Muscles of Respiration

• Diaphragm
• Major muscle of inspiration
• Unpaired
• Inserts into lower portion of rib cage via
  central tendon
• Central tendon is pulled forward and down during
  inspiration and thus increases the vertical
  dimension of the thorax
• During expiration returns to rest by elastic
  recoil
• Separates thoracic and abdominal cavities

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Point of attachment of central tendon
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Muscles of Respiration

• Thoracic
• Internal Intercostals
• Contributes to rib elevation during inspiration
• In conjunction with abdominals depresses ribs for
  expiration
• External Intercostals
• Elevates ribs during inspiration, leads to an
  increase in thoracic dimension in
  anterior-posteriorly and transverse.
• Pectoralis major and pectoralis minor
• Accessory muscles of inspiration
• Pulls sternum and ribs upwards, leads to anterior
  posterior increase in thoracic dimension

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Muscles of Respiration

• Abdominal
• All contribute during forced expiration
• Rectus Abdominis
• Sternum downwards and depresses ribs during
  expiration, results in decreased thoracic
  dimension
• External and Internal Obliques
• Pulls ribs downwards and depresses visceral
  contents
• Transverse Abdominis
• Contracts abdomen, compresses visceral contents

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Muscles of Respiration

• Neck Musculature
• Sternocleidmastoid
• Raises sternum and clavicle during inspiration
• Scalene
• Raises upper ribs during inspiration

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Muscles of Respiration

• Distressed breathing recruits muscles of neck and
  shoulder girdle
• All respiratory muscles are striated therefore
  susceptible to myopathies, myotonias and
  degenerative neurological disease (e.g ALS),
  diseases of neorumuscular junction
  (e.g myasthenia gravis) and inflammatory
  neuropathies (e.g Guillain-Barre)

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Motor Innervation of the Respiratory Mechanism
(Dikeman and Kazandjian, 1995)

• Diaphragm Phrenic Nerves (paired C1 C5)
• External intercostals Intercostal spinal nerves
• Anterior rami T2 T11
• Internal intercostals Internal spinal nerves
• Anterior rami T2 T11
• Pectoralis Major Lateral and medial pectoral
  nerves
• (C5 C8 and T11)
• Pectoralis Minor Medial pectoral nerve (C8 T1)

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Motor Innervation of the Respiratory Mechanism
(Dikeman and Kazandjian, 1995)

• Sternocleidomastoid Spinal Accessory
• Scalene Spinal Nerves C2-C8
• Rectus Abdominus
• External Obliques All thoracic spinal nerves
• Internal Obliques
• Transversus Abdominus

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Neurophysiology of Breathing

• Controlled by the Respiratory Control Centre in
  the reticular formation of the brainstem
• The centre is responsible for maintaining CO2 and
  O2 balance
• Eubanks and Bone (1990) the regulation of
  breathing is made possible by the constant
  analysis of the chemical state of the blood
• Chemoreceptors respond to the change in CO2 and
  O2 balance

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• Stretch receptors
• In the smooth muscle of the airway
• Respond to expansion and deflation of the lungs
  and bronchi
• Control centre sends impulse to spinal cord and
  to the phrenic nerve, cranial and spinal nerves
  which innervate the intercostal muscles

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Ventilation

• During inspiration the dimension of the thoracic
  cavity expands due to
• Contraction of the diaphragm
• Expansion of the rib cage
• As the dimension of the thoracic cavity enlarges
  the pressure within it decreases
• When alveolar pressure is less than ambient
  pressure, air flows into the alveoli
• Air flow continues until the alveolar and ambient
  pressures are equalised

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Ventilation

• Expiration during quiet breathing is passive
• Gravity moves thorax downwards
• Torque springs ribs back into resting position
• Elastic recoil compressed abdominal viscera
  recoil and push diaphragm upwards
• As the lungs and alveoli recoil , the air within
  the alveoli sacs is compressed
• The pressure differential is reversed,
  atmospheric pressure is now less than alveolar,
  so air leaves the lungs until the pressures are
  equalised again
• Diseases that cause airway collapse may change
  the expiratory process from passive to active

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Airway Protection

• Protection by a number of mechanisms
• Superior and anterior laryngeal excursion results
  in epiglottic deflection
• Thyrohyoid approximation collapses quadrangular
  membrane to cork the supraglottic airway
• Arytenoids moving anteriorly over the airway
• Epiglottis moving posteriorly over the airway
• True and false vocal fold closure
• Co-ordination of respiration and deglutition
• Respiration is inhibited in normals during
  swallowing, known as swallow apnoea

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• Glottic closure reflex during swallow
• Carried by efferent fibres of recurrent laryngeal
  nerve
• Complete VF closure
• Prevention of simultaneous signals for
  diaphragmatic descent and VF closure makes it
  almost impossible to breathe and swallow at the
  same time
• Threshold for inhibiting respiration is below
  that of evoking a swallow, thus giving further
  protection

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Co-ordination of respiration and swallowing

• Both thought to be controlled by brainstem nuclei
  in the medulla. Interneurons connecting the two
  areas but also with cortical influences
• Ascending vagus carries afferent impulse to
  medullary respiratory centre, synapse with
  recurrent laryngeal nerve, activates
  cricoarytenoid muscles (abduct vocal folds). The
  abduction of the vocal folds occurs several
  milliseconds prior to diaphragmatic descent

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Pattern of co-ordination(Dikeman and Kazandjian,
1995)

• Inspiration
• Expiration
• Initiation of pharyngeal swallow
• Onset of swallow apnea
• Passage of the bolus
• Continuation of expiration

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• Coelho (1987)
• Evaluated swallowing respiration coordination in
  normals
• Approx 80 swallows interrupt mid-expiratory
  phase
• Always resume during expiration
• Preiksaitis et al (1992)
• Same pattern occurs bolus/ non bolus swallow

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• Neurologically impaired population
• Incoordination between respiration and swallowing
  in CVA
• Selley (1989) pattern variable 43 inhale post
  swallow
• Langmore and Murray (unpublished data)
  mid-inspiratory cycle

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Nishino, T. Hiraga, K. (1991).

• Looked at co-ordination of swallowing and
  respiration in patients recovering from general
  anaesthesia
• Hypothesized that the co-ordination would depend
  on behavioural control and therefore be lost
  during unconscious state
• Swallowing occurred in both insipiratory and
  expiratory phases with no pattern
• Transient interruption of airflow during
  swallowing occurred whether the swallow occurred
  during inspiration or expiration, suggesting
  mechanical airway closure and CNS involvement in
  the inhibition of respiration during swallowing

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Hiss, S. G., Treole, K., Stuart, A. (2001).

• Effects of Age, Gender, Bolus Volume and Trial on
  Swallowing Apnea Duration and Swallowing/
  Respiratory Phase Relationships
• 60 normal adults
• 10 female and 10 male across 3 age ranges 
• Nasal airflow used to measure swallow apnea
  duration (SAD)
• Saliva bolus, 10, 15, 20, 25 ml x3 trials each
   

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Hiss, S. G., Treole, K., Stuart, A. (2001).

• SAD stable over trials.
• SAD
• Increased with Age
• Longer for females
• Increased with increase in bolus size

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Huckabee and Kelly (2002)

• Coordination of respiration and swallowing during
  wake and sleep with younger and older subjects
• Statistically significant differences were
  identified between sleep and bolus swallows in
  regard to phase of respiratory cycle where
  swallowing occurred (plt.001).
• Although swallowing apnea SA occurred for both
  conditions most frequently in the middle of the
  expiratory phase, there was greater variability
  and significantly more occurrences of SA
  occurring during the expiratory-inspiratory cusp
  during sleep conditions.

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Huckabee and Kelly (2002)

• There was a statistically significant difference
  between age groups (youngers and elders) with
  elders demonstrated slightly more predominant
  apnoea on inspiratory/expiratory cusp than
  youngers (Chi Square p.04).
• SA duration within expiratory phase is
  consistently shorter than apnoea duration during
  other phases.
• SA duration was sig. different based on age
  (f18.926, plt.001) with youngers have shorter
  apnoea duration.

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Defense Mechanisms of the Lower Respiratory Tract

• Surfactant a liquid produced by specialised
  epithelial cells within the alveoli.
• Surfactant provides lubrication for alveoli
  expansion and maintains surface tension within
  the alveoli to prevent collapse.
• Alteration of the concentration of the surfactant
  prevents the maintenance of surface tension and
  thus causing the alveoli to collapse
• Liquids in the lungs can alter the concentration
  of surfactant

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Defense Mechanisms of the Lower Respiratory Tract

• Solids block small airways and interrupt with gas
  exchange
• Alveoli collapse occurs as a result of occlusion
  of gas exchange areas
• Inflammation which is induced by aspirated
  material leads to increased distance between
  inspired air and the alveoli capillaries, thus
  reducing the efficiency of gas exchange

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Defense Mechanisms of the Lower Respiratory Tract

• This alveoli collapse is known as atelectasis
• Development of atelectasis is accelerated by high
  O2 concentration of inspired air which occurs
  during ventilation and general anaesthesia

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Mechanisms for Airway Clearance

• Cough and mucociliary action first line of
  defense
• Once material is below the terminal bronchi,
  cellular mechanisms are needed for clearance
• Size of aspirated material determines where
  material impinges
• Particles tend to gather at branch points
• Vulnerable gas exchange areas protected by
  repeated branching

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• Cough
• Triggered by stimulation of sensory receptors in
  the oropharynx, nasopharynx, larynx and proximal
  segments of lower respiratory tract
• Triggered via glossopharyngeal nerve in the
  oropharynx and superior laryngeal nerve for the
  rest of the pharynx and larynx
• Creates high forces that sweep the trachea

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Physiology of Cough

• Deep inspiration
• Increased pressure thoracic and abdominal
  cavities
• Glottis opens suddenly (sub glottic pressure
  continues to increase)
• Lumens of posterior tracheal wall and major
  conducting airways collapse forming a narrow
  crescent
• Expiratory airflow rapidly accelerates

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• Cough sequence can be repeated multiple times
  without taking a new breath.reduces lungs to
  residual volume
• Diaphragm and abdominal muscles contribute to
  effectiveness of cough

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Cough in old geezers

• Feinberg et al (1990)
• Reflexive cough on penetration of bolus into
  larynx is decreased in elderly
• Pontoppidan and Beecher (1990)
• Elderly decreased sensation to inhaled ammonia
• Cough can cause trauma to the lungs or thoracic
  structures. May dangerously increase intra
  cranial or introcular pressure in patients with
  intracranial tumours, cerebral trauma or glaucoma
  (Curtis and Langmore, 1998)

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• Mucociliary Action
• Beating of cilia moves mucous and foreign
  particles embedded in it towards the major
  airways and trachea
• Referred to as Mucociliary Escalator (Wanner,
  1986)
• Cilia extend to terminal branches and into the
  larynx, where material is swallowed or
  expectorated
• Effective for liquids and small particles

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• Cilia defects may be congenital or acquired
• Immotile cilia syndrome
• Acquired due to anaesthesia, severe alcohol
  intoxication etc
• Smoking reduces the beat frequency of the cilia
• Cystic fibrosis makes the mucosa difficult to
  shift
• Chronic bronchitis leads to excessive secretions
  and patchy destruction of cilia

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• Lymphatic Clearance
• Clears liquids
• Lymphatics prevent oedema by returning fluid to
  lymph nodes
• Also carry foreign materials to lymph nodes
• Lung lymphatics begin at level of respiratory
  bronchioles, join to form vessels of increasing
  size, adjacent to bronchioles and arterioles

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• Lymphatic clearance
• Liquid portion of lymph returned to blood vessels
  via thoracic duct into subclavian vein
• 400 700 ml/ day cleared in normals
• Can remove macromolecules such as blood proteins
  but not food particles
• Decreased clearance leads to fluid in pleural
  space which impairs gas exchange and increases
  infection risk
• Disease reduces effectiveness (iecongestive
  heart failure)

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Cellular Immune Defenses of Lower Respiratory
Tract

• Alveolar Macrophages Debris gobbler!
• Alveoli protected by macrophages which are
  phagocytic
• 1 2 / alveolus
• Originate in bone marrow but maintain numbers by
  in situ proliferation
• Phagocyte, then carry substance to lymph node
• All of these mechanisms serve to move out the
  aspiratebut dont deal with infection.
• Immune response initiated by presentation of
  lymphocytes

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Cellular Immune Defenses of Lower Respiratory
Tract

• Lymphocytes
• Found within four distinct anatomical
  compartments
• Four types of lymphocytes

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Lymphocyte Class and Function

• B Cells T Cells
• Recognise antigens
• Produces antibody for opsonisation of bacteria to
  aid phagocytosis
• Deficiency of antibody increases incidence of
  respiratory infection

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Lymphocyte Class and Function

• NK Cells
• Targets tumours, dividing cells, pathogens
• No specific lung disease associated with NK Cell
  dysfunction
• Neutrophils
• Circulating white blood cells
• Defend against bacteria and fungi
• When numbers or function decrease there is an
  increased risk of pneumonia
• Recruited to lungs within hours of infection
• Releases products to kill pathogens but this can
  be harmful to the lung itself

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Clinical Complications of Aspiration

• Acute Airway Occlusion
• Acute obstruction is an emergency
• Small solids pass larynx and lodge in bronchi
• Remove bronchscopically
• Non removal can lead to pneumonia, granulomas,
  inflammation
• Removal itself causes inflammation
• Liquid aspiration equal or greater than tracheal
  volume will lead to asphyxia

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Clinical Complications of Aspiration

• Toxic Aspiration Syndromes
• The volume and pH of the aspirate determines
  degree of injury
• Acid injures the lung immediately
• Chemical burn of the lung (reflux, vomit)
• Range of treatment options but the use of
  antibiotics remains controversial

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Clinical Complications of Aspiration

• Bacterial infections associated with aspiration
• Aspiration pnuemonitis refers to spectrum of
  anaerobic bacterial infections of lungs and
  pleural space due to aspiration of anaerobic
  organisms
• When focal pneumonitis is not handled by cellular
  defense, then an abcess may develop

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• Anaerobic pulmonary infections
• Present without pain
• Low grade fever, night sweats, weight loss,
  fatigue, malaiseoften misdiagnosed
• Intermittent loss of consciousness predisposes

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• Oral secretion and pneumonia
• Most acquired by aspiration of oral secretions,
  few by inhalation (TB), few blood borne (plague)
• Likelihood of pneumonia is a result of the size
  and virulence of the bacterium
• Integrity of the patients mechanical and immune
  defenses is important
• Debate whether there is increased likelihood of
  pneumonia if aspirate is food

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• Granulomatous and Fibrotic Response to Chronic
  Aspiration
• Inconclusive evidence whether longstanding and
  repeated aspiration of small amounts of food
  leads to interstitial pulmonary fibrosis

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Langmore et al (1998)

• Looked at identifying factors that predicted the
  development of pneumonia
• Followed 189 elderly subjects from outpatient
  clinics, inpatient and nursing homes
• Subjects had clinical swallowing exam, VFSS, FEES
  and a lot of other exams and interview
• Followed up annually for 4 years

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Langmore et al (1998)

• Best predictors
• Dependence in feeding
• Dependence in oral care
• Number of decayed teeth
• Tube feeding
• More than one medical diagnosis
• Number of medications
• Smoking
• Dysphagia was concluded as an important risk but
  insufficient on its own to cause pneumonia

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