Inspiratory stridor R06.1

In 1972, Brandenburg described the 1st case of idiopathic stenosis with inspiratory stridor (Jering 2021).

Inspiratory stridor represents the manifestation of a sound occurring during inspiration that results from obstruction of the upper airway from the mouth and nose to the larynx (Herold 2022 / Kasper 2015).

Stridor is differentiated between inspiratory and expiratory stridor (Pfleger 2016).

Inspiratory stridor is divided into a:

• Mild form:

Stridor is found exclusively during exertion or excitement. There is no dyspnea.

• Moderate form:

In this case, the stridor already exists at rest. There is dyspnea, passive expiration, and intercostal or subcostal retractions.

• Severe form:

In the severe form, poor inspiratory air entry with marked dyspnea is found, stridor is now biphasic, expiration is active, and cyanosis and changes in consciousness may be emitted.

• Most severe form:

In this case, cyanosis and alterations of consciousness are found (Reuter 2022).

The loudness of the stridor also plays a role. The quieter an inspiratory stridor is, the more severe the respiratory obstruction can be (Reuter 2022).

In neonates, the most common cause of inspiratory stridor is laryngomalacia (Bedwell 2016).

In the idiopathic cause of inspiratory stridor, the incidence is 1: 400,000. Females are more frequently affected than males, and the age of manifestation is predominantly between 30 - 50 years (Jering 2021).

For example, inspiratory stridor - in addition to idiopathic stenosis - may be caused:

• supralaryngeal:
  • acute at:
    • pharyngeal or retrotonsillar abscesses
    • infantile rhinitis (Michalk 2018).
    • retraction of the tongue (Herold 2022)
  • chronic in:
    • Thyroglossal duct cyst
    • Choanal stenosis
    • Micrognathia
    • Macroglossia (Michalk 2018)
    • supraglottic:
  • acute in:
    • Foreign body ingestion
    • Epiglottitis
    • trauma (inhalation)
  • chronic in:
    • Laryngeal cyst
    • Laryngomalacia (benign congenital stridor [Rosenecker 2008])
    • tumor (Michalk 2018)
    • glottic / subglottic:
  • acute in:
    • Glottic edema
    • diphtheric croup (also called "true croup")
    • laryngitis subglottica
    • vocal cord dysfunction (Herold 2022)
    • Foreign body in the larynx or esophagus causing compression
    • Laryngospasm
    • pseudocroup (Herold 2022)
  • chronic in:
    • Tumor
    • Laryngeal papillomatosis
    • Arthritis of the laryngeal joints
    • Laryngeal sail
    • Vocal cord paresis
    • subglottic stenosis (congenital or acquired) (Michalk 2018)
    • relapsing polychondritis (Kasper 2015 / Freyschmidt 2013)
    • non-toxic multinodular goiter (Kasper 2015)
    • recurrent paresis
    • obstructive sleep apnea syndrome (Herold 2022)
    • multiple system atrophy =MSA (Cortelli 2019)

In glottic or supraglottic obstruction, an inspiratory sound is produced during breathing due to the tightness in the airway (Pfleger 2016).

• Extrathoracic stridor

This originates in the upper airway, upper trachea to subglottic region and manifests as inspiratory stridor.

• Biphasic stridor

Constriction in the middle trachea region manifests both inspiratory and expiratory and is referred to as biphasic stridor (Michalk 2018).

• Congenital anomalies:

Stridor in laryngomalacia usually develops in the first 1-2 months of life and is position-dependent. It usually does not affect the growth and development of the child. Only in a severe form of laryngomalacia, cyanosis, problems with feeding and insufficient weight gain may occur (Skirko 2022).

• Foreign body aspiration:

In this case, a sudden cough occurs initially, followed by dyspnea, whistling breathing, stridor, and the possible appearance of cyanosis (Eich 2015).

• Pseudocroup:

In pseudocroup, there is inspiratory stridor in mild and moderate stages. In severe cases, expiratory stridor is also found (Johnson 2014).

• Multisystem atrophy:

In this case, inspiratory stridor occurs at night, which has a high positive predictive value in terms of diagnosis (Cortelli 2019).

• Medical history

Since the causes of inspiratory stridor are manifold, the medical history is of particular importance. Pre-existing infections, development of stridor, existing underlying diseases, operations of the respiratory tract, etc. should be inquired about. In children, any foreign body aspiration that may be in question should be considered in particular (Schaps 2008).

• Physical examination

Physical examination should exclude swelling in the neck region or signs of hyperthyroidismor goiter(Schaps 2008).

In children, if epiglottitis is present, intubation or tracheostomy should already be prepared before the examination, as diagnostic measures can lead to complete obstruction in them (Classen 2013).

• Auscultation

Inspiratory stridor can be auscultated most over the neck (Kasper 2015).

• X-ray of the soft tissues of the neck

For laryngeal diagnostics, an a. p. soft tissue image is required and for epiglottis diagnostics, a lateral soft tissue image. However, the X-ray examination with high CT- load is rather of secondary importance (Michalk 2018).

• Laryngeal ultrasound

Laryngeal ultrasound (LUS) represents a non-invasive examination method and is primarily used in children for the diagnosis of stridor. With regard to general laryngeal disease, sensitivity is 87% and specificity is 100% (Friedman 2019).

• Airway Endoscopy:

Bronchoscopy is the main investigative modality with the highest diagnostic value.

Rigid bronchoscopy should be used to confirm respiration in cases of higher grade stenosis or manipulation of central airway stenoses (Brunkhorst 2021).

Flexible bronchoscopy can better assess vocal cord movement, laryngeal or tracheal stability (Schramm 2020).

• Esophagogram:

This can be used to localize narrowing in the esophageal area (Michalk 2018).

• Magnetic resonance imaging:

An MRI of the neck is primarily used to visualize the retropharynx, mediastinum, and great vessels (Michalk 2018).

• Spirometry

Spirometry and the flow volume curve can be used to differentiate fixed and dynamic extra- or intrathoracic airway stenoses (Brunkhorst 2021).

Therapy depends on the particular cause of the stridor.

• - Laryngomalacia:

The majority of patients can be treated conservatively. In about 10%, surgical therapy in the form of supraglottoplasty is required (Bedwell 2016).

The prognosis depends on the disease causing the stridor.

General information

Inspiratory stridor may be an acute life-threatening event requiring immediate intervention (Jering 2021), such as epiglottitis, or a harmless disorder (Michalk 2018), such as laryngomalacia (Probst 2008).

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