Laryngology seminar
95-4-27
R3 陳甘斌
Cough
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The respiratory system basically has 4 protective mechanisms: cough, the gag
reflex, the mucociliary escalator and the phagocytic/lymphatic systems.
The two functions of cough : expel foreign material from the airway and remove
excessive secretions from the airway
The stimuli of cough may be categorized into 4 groups: chemical (e.g., cigarette
smoke), mechanical (e.g., vascular rings), thermal (e.g., cold dry air), and
inflammatory (e.g., increased mucus).
 Cough occurs in 4 phases:
1. The inspiratory phase. 2. The contractive phase 3. The compressive phase 4. The
expulsive phase
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The inspiratory phase: the posterior cricoarytenoid muscle, innervated by the
recurrent laryngeal nerves maximally abducts the vocal cords
The contractive and compressive phases: the true and false vocal cords close
tightly, with the false cords turned down, and the expiratory muscles (diaphragm,
abdominal, chest wall, and pelvic floor muscles) contract, resulting in a dramatic
increase in intrathoracic pressure.
The true vocal cords close first, followed by the false cords, then the
aryepiglottic folds. The later two actions are mediated by the thyroarytenoid
muscles.
The final phase of the cough cycle is expulsive, with rapid expiration (peak flow
of 25,000 cm/sec) and vibration of the vocal cords, supraglottic structures, and
posterior glottis.
Laryngospasm is a maladaptive exaggerated glottic closure reflex, mediated
solely by the SLN ( tactile stimulation of the endolarynx) . Stimulation of the
esophagus with acid or with sudden distension may cause laryngospasm.
Cough reflex:
 The reflex is not always present at birth; its presence in only 25% of children< 5
days old
 The reflex is mediated by four different types of cough receptors found between
the ciliated pseudostratified columnar epithelial cells from the pharynx to the
bronchi.
 Slow-adapting and rapidly-adapting receptors respond to tactile stimulation in
the carina and larger bronchi.
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C-fiber receptors respond to chemical and mechanical stimuli throughout the
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respiratory tract.
Pulmonary stretch receptors are found in the smooth muscle of the respiratory
tract and respond to mechanical stimulation.
In all, the highest concentration of receptors is found in the larynx and carina and
at other airway bifurcations. The carina is the single most sensitive site.
Upon stimulation of the cough receptors, the signal passes via cranial nerves IX
and X to the upper brainstem/pons.
Cortical input : cough can be initiated or suppressed in the awake patient.
Afferent information from receptors in the
larynx: by the superior laryngeal nerve to the cough center in the medulla.
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nose and paranasal sinuses: by the trigeminal nerve,
pharynx : by the glossopharyngeal nerve
external auditory canal ( Arnold’s nerve) and tympanic membrane (Jacobsen’s
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nerve)
pleura, and stomach : by the vagus nerve
the pericardium and diaphragm : by the phrenic nerve
Efferent information is carried from the cough center in the medulla by the
phrenic and spinal nerves to the diaphragm and intercostal muscles and by the
vagus nerve to the musculature of the larynx and tracheobronchial tree
Classification:
 Acute cough: lasting less than 3 weeks
 Subacute cough: lasting three to eight weeks
 Chronic cough: lasting more than eight weeks
 The common causes of cough:
. “I A m C oughing G reen a nd C opious S putum H abitually.” This represents I nfection,
A sthma, C ystic fibrosis, G astroesophageal reflux (and aspiration), A irway anomalies, C
iliary dysfunction, S inusitis, and H abit cough
Evaluation:
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The history should include age, character of cough, duration of symptoms, and
immunization status.
Holinger’s study : the etiology is often related to age.
The most common causes of chronic cough:
Children up to 18 months of age: aberrant innominate artery, cough-variant
asthma, and GER.
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Age 18 months to 6 years : sinusitis (50%), cough-variant asthma ( 27% )
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Age 6 to 16 years: cough-variant asthma (45%) , psychogenic cough (32%),
sinusitis (27%).
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Cystic fibrosis should be considered in a patient with malabsorption, failure to
thrive, rectal prolapse, and nasal polyps
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Persistent cough: most typically caused by reactive airway disease or bronchitis
Recurrent episodic cough: most commonly due to recurrent URI.
A barking cough suggests croup.
A frequent, repetitive, honking cough suggests a psychogenic cough. The only
type of chronic cough that is completely absent during sleep.
A paroxysmal cough with repeated coughs in quick succession followed by rapid
inspiration (“whoop”) suggests pertussis
A staccato cough suggests chlamydia pneumonia
Hemoptysis: unusual in children. Cause: bronchiectasis, CF, airway foreign body,
pulmonary hemosiderosis, and tuberculosis.
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In a child with symptoms of a URI and a persistent cough beyond 14 days,
Bordetella pertussis should be considered.
ACEI cough
‧Incidence: 0% ~ 39%, average 10%
‧Worse at night and in the supine position mimicking GER
‧Females > male, nonsmoker > smoker
‧Degradation of kinins, particularly bradykinin, in the airway is inhibited -> ACEI
allows kinins to accumulate, cough, rhinitis, angioedema, possible edema
‧Cromolyn sodium (tachykinin antagonist) can improve ACEI cough
‧PGE2, Substance P are possible tachykinins which involve ACEI cough
Examination:
Treatment:
Reference:
1. Schroeder. Knut MD. Effect of dextromethorphan, diphenhydramine, and placebo
on nocturnal cough and sleep quality for coughing children and their parents.
Journal of Pediatrics. 146(1):146-147, 2005 January.
2. Dykewicz. Mark S. Cough and angioedema from angiotensin-converting enzyme
inhibitors: new insights into mechanisms and management. Current Opinion in
Allergy & Clinical Immunology. 4(4):267-270, 2004 August.
3. Cantu. Carlos MD. Antonio MD. Luis MD. Fernando MD. Over-the-Counter
Cough and Cold Medication Use and Risk of Stroke. Stroke. 34(12):e234-e235,
2003 December.
4. Wubbel. Catherine MD. Chronic Cough in Children. Pediatric Case Reviews.
3(2):95-104, 2003 April.
5. Chang AB. Harrhy VA. Simpson J3. Masters IB4. Gibson PG. Cough, airway
inflammation, and mild asthma exacerbation. Archives of Disease in Childhood.
86(4):270-275, 2002 April.
6. Schroeder K. Fahey T. Should we advise parents to administer over the counter
cough medicines for acute cough? Systematic review of randomised controlled
trials . Archives of Disease in Childhood. 86(3):170-175, 2002 March.
7. Irwin RS. Madison JM. Primary Care: The Diagnosis and Treatment of Cough.
N Engl J Med 343: 1715-1721, 2000 Dec
8. Chang AB. Cough, cough receptors, and asthma in children. [Review] [133 refs]
Pediatric Pulmonology. 28(1):59-70, 1999 Jul.