Mechanical ventilation in critically ill burned patients with inhalation


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The therapeutic approach to critically ill patients with inhalation burns is based on maintaining airway patency through intubation and mechanical ventilation in severe cases.

Mechanical ventilation is a treatment option for those patients who have suffered a critical inhalation burn.

Inhalation injury generally occurs in the context of a multisystem setting with burns, carbon monoxide poisoning, and cyanide toxicity. Ultimately it results from the inhalation of very hot gas and incomplete combustion products, usually during a fire.

2% of patients with burns have inhalation injuries, being more frequent the greater the burned body surface. In burned patients, inhalation injury is a fundamental determinant of increased morbidity and mortality, being responsible for half of the deaths of burned patients.

Airway and lung damage depends on the components of inhaled smoke, the degree of exposure, and the body’s response.

respiratory injury

mechanic ventilation

Injury due to heat and toxic gases causes upper airway edema with clinical obstruction. These symptoms are greater the younger the patient is and generally appear in the first 12-18 hours, although the onset of symptoms can be delayed up to 72 hours

Respiratory injury is the leading cause of immediate death. We distinguish several types:

  • Thermal injury: According to this report from the Aragonese Institute of Health Sciences, heat injury is usually limited to the oropharynx due to the reflex closure of the glottis and the high thermal dissipation power of these tissues.
  • Injury due to inhalation of products of the composition: the water-soluble gases react with the water in the mucous membranes, releasing strong acids and alkalis, producing edema and bronchospasm. The poorly soluble gases cause injuries in the most distal areas. The main toxic product of combustion is carbon monoxide. Another toxic gas of clinical relevance is hydrogen cyanide.
  • Pulmonary injury of endogenous origin: patients with extensive burns may develop progressive respiratory failure after the initial phase, even if they do not present direct damage to the airway by inhalation.

Diagnosis

Diagnosis of inhalation injury is, according to this study by the Complutense University of Madrid, above all clinical. It should be suspected when the patient is unconscious in a closed space where there has been a fire or hot gas leak.

On physical examination, suspicious signs include burning nose hair, dark sputum, burning of the face and nostrils, cough, hoarseness, and wheezing.

It is important to explore the oropharynx to assess the alteration of the mucosa. Complementary diagnostic methods help assess pulmonary and systemic damage. However, none of them is specific enough or allows a diagnosis to be established.

Treatment

Nurse collecting medical material in a sternotomy surgery

Most manifestations of lung injury appear after several hours of latency. For this reason, it is very important that in the event of any anomaly, mechanical ventilation should be performed.

However, there is no specific treatment for critically ill patients with inhalation burns. The therapeutic approach is based on maintaining airway patency through intubation and mechanical ventilation in severe cases, lung cleansing, and administration of antibiotics if there is infection.

Intubation and mechanical ventilation

Intubation is necessary in up to 50% of patients with inhalation injuries. Severe cases require, as we have seen, early intubation with a large caliber tube to:

  • Keep the airway patent.
  • Avoid aspiration.
  • Allow the elimination of secretions and plugs of mucus.
  • Help ventilation.

In cases where intubation is done late when the patient has severe airway edema, it can make intubation impossible or have to resort to tracheostomy.

Mechanical ventilation should be aimed at maintaining oxygenation and ventilation, avoiding ventilation-induced damage, using, depending on the degree of lung damage, conventional ventilation with permissive hypercapnia, nitric oxide inhalation, high-frequency ventilation, and extracorporeal membrane oxygenation.

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