Inhalation injury and respiratory burns

A concomitant inhalation injury, compounding a cutaneous burn, has a greater effect on mortality than either the age of the patient or the total body surface area of the burn. Inhalation injuries are associated with a reported mortality of 45 to 78 per cent, and mortality has been shown to be 20 to 40 per cent greater in patients with a combined cutaneous burn and inhalation injury than in patients with similar burns but without an inhalation injury ( Herodoo.ef a/ 1985).

True respiratory burns of the lower pulmonary tree are rare, generally occurring only with inhalation of superheated steam. Moist air has 4000 times the heat-carrying capacity of dry air and interferes with the ability of the upper respiratory tract mucosa to dissipate heat efficiently. What is commonly thought of as an inhalation injury is generally smoke inhalation or carbon monoxide poisoning or both. These result in hypoxemia associated with bronchospasm and bronchorrhea.

Incomplete products of combustion, such as aldehydes, nitrogen dioxide, and hydrochloric acid, can cause direct parenchymal lung damage. Plastics and petroleum-based products such as polyvinyl chloride can release extremely toxic agents (e.g. benzene, phosgene, and isocyanates). These small smoke particles may cause damage either as direct irritants or as a mechanism for transmission of heat.

Carbon monoxide, which has an affinity for hemoglobin 200 times that of oxygen, will seriously impair oxygen delivery to the tissues. Carboxyhemoglobin levels of less than 15 per cent do not generally alter clinical outcome significantly; however, levels greater than 40 per cent are often associated with neurological or mental status changes. Treatment consists of the administration of high-flow oxygen, with or without intubation and hyperbaric oxygen. The concentration of carboxyhemoglobin is reduced by 50 per cent for each 40-min period of treatment with high-flow oxygen.

Pulmonary injury resulting from smoke inhalation results in histological and physiological changes in pulmonary function. The most prominent is an early marked increase in extravascular lung water. The severity and duration, usually from 24 h to 5 days, depends on the nature of the inhalation injury and the presence or absence of an associated cutaneous burn injury. An inflammatory exudate, containing high concentrations of thromboxane A 2 and glucuronidase, rapidly forms in the tracheobronchial tree. The end result of this cascade is progressive airway obstruction. Neutrophils present in the lung at the time of injury are trapped; additional neutrophils are recruited to the lung by release of chemotactic factors produced by stimulated pulmonary macrophages. Release of the oxygen free radicals and proteolytic enzymes results in fibronectin degradation and interstitial matrix disruption.

Coping with Asthma

Coping with Asthma

If you suffer with asthma, you will no doubt be familiar with the uncomfortable sensations as your bronchial tubes begin to narrow and your muscles around them start to tighten. A sticky mucus known as phlegm begins to produce and increase within your bronchial tubes and you begin to wheeze, cough and struggle to breathe.

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