Diphtheritic croup

Stages of laryngeal stenosis development

The disease proceeds with a sequential increase in airway obstruction symptoms. At the initial stage, moderately severe intoxication is noted. Then the patient's voice changes pitch, sounds become increasingly muffled until persistent aphonia (complete voicelessness) sets in. Concurrently, a rough, "barking" cough develops.

As the laryngeal lumen narrows, inspiratory dyspnea develops:

• Inhalation becomes noticeably prolonged.
• A specific wheeze appears, which sounds delicate in the early stages but later becomes audible from a considerable distance from the patient (distant wheeze).
• With further disease progression, not only inspiration but also expiration becomes difficult.

Paroxysms of intense suffocation occur. Initially, they are short, lasting only a few minutes. Resolution of the attack is accompanied by coughing, profuse sweating, and expectoration of viscous sputum along with casts of fibrinous membranes. If a tracheotomy is not performed in time, the duration of the attacks increases.

Appearance and hemodynamics at the peak of the attack

During an episode of suffocation, the patient assumes a forced upright position (orthopnea), resting their hands on the bed to fix the shoulder girdle and engage accessory muscles in the act of breathing.

Objective signs of stenosis:

• The mouth is wide open, the lower jaw is jutting forward.
• The nasal wings flare intensely during inspiration.
• There is a marked retraction of compliant chest areas (intercostal spaces, supraclavicular fossae).
• The face acquires a purplish hue, and acrocyanosis increases.

An important hemodynamic symptom of severe croup is pulsus paradoxus—a pathological condition in which the pulse wave weakens at the height of inspiration, up to complete disappearance.

Asphyctic and terminal stages

The key marker of the transition of croup to the asphyctic stage is a change in the patient's behavior: marked motor agitation develops, accompanied by a panicky fear of death.

If assistance is not provided, the terminal stage ensues:

1. The patient becomes completely exhausted, and agitation is replaced by absolute adynamia.
2. The breathing pattern changes: it becomes superficial, very rapid, and no longer as noisy.
3. The skin is covered with a sticky, cold sweat, and deep cyanosis develops—the so-called "lead pallor".
4. Body temperature drops sharply, the gaze becomes dull, and the pupils dilate (mydriasis).

The terminal phase ends with the development of seizures and respiratory arrest. In some cases, death occurs unnoticed, without a preceding seizure syndrome.

Descending croup: a diagnostic trap

Descending croup occurs when fibrinous deposits migrate into the lower sections of the respiratory tract. This form is characterized by extremely high mortality (nearly 100%) due to occlusion of the bronchioles and alveoli. Against the background of total obstruction, tracheotomy brings no relief.

The insidious nature of the descending form lies in the fact that typical manifestations of laryngeal stenosis are neutralized. Symptoms of cardiovascular failure, pallor, apathy, and severe dyspnea come to the fore.

It is important for the physician to distinguish this condition from severe pneumonia. In descending croup, radiological signs of pneumonia are absent. On percussion over the lung fields, the sound remains clear (no areas of dullness). However, auscultation reveals a sharp weakening of breath sounds—they are barely conducted to the lower divisions. Instrumentally, the diagnosis is confirmed by laryngoscopy, revealing fibrinous membranes on the vocal cords.

Complications and outcomes

The main specific complication of croup is acute respiratory failure due to mechanical blockage of the laryngeal and tracheobronchial lumen by membranes.

Secondary complications are often associated with the addition of bacterial microflora (streptococci, staphylococci, Haemophilus influenzae), leading to bronchopneumonia and tracheobronchitis. In adult patients, severe hypoxia provokes decompensation of chronic diseases, including heart failure, coronary artery disease, and diabetes mellitus.

Survival depends on how quickly diphtheria antitoxic serum was administered and a tracheotomy was performed. The risk of iatrogenic complications must be considered: anaphylactic shock is possible with serum administration, and arterial bleeding or reflex cardiac arrest with surgical intervention.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

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• Specific complications: myocarditis, polyneuropathies, and infectious-toxic shock
• Nasal diphtheria: differentiation of toxic and non-toxic forms
• The course of diphtheria infection in partially immune (vaccinated) individuals

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