Smoke inhalation injury refers to the chemical and thermal injury of the respiratory tract, as well as systemic toxicity, arising from inhalation of various irritants found in smoke. Either occupational or accidental exposure (fires, blast injuries, excessive steam, etc.) may be responsible for this type of injury. Symptoms range from mild bronchial irritation to life-threatening hypoxia and respiratory insufficiency. A thorough clinical assessment is the most important step in the diagnostic workup, followed by laboratory and imaging studies.
Smoke inhalation injury is roughly defined as the injury of the bronchial tree and the respiratory system developing as a result of inhalation of particulate matter (soot) and chemical or thermal irritants found in smoke and accounts for up to 10,000 deaths every year in the United States [1]. Some of the most important compounds responsible for this type of injury are carbon monoxide (CO), hydrogen cyanide (HCN), free oxygen radicals (reactive oxygen species, or ROS), sulfur dioxide (SO2), benzene and other aromatic hydrocarbons, as well as ammonia (NH3) [2] [3] [4]. Despite their increasing concentrations in the industrial setting and markedly higher occupational exposure, inhalation of smoke during fires is the predominant mode of smoke related injury, as extensive nasopharyngeal irritation promotes breathing through the mouth and subsequent introduction of large amounts of smoke directly into the bronchial tree [1]. The clinical presentation depends on the amount of smoke inhaled, the concentration of gasses found in the smoke, and the ability of the individual's respiratory tract to cope with chemical and thermal injury [1] [2]. In most cases, mucosal edema and irritation eventually result in stridor, hoarseness, dyspnea, hypoxia, and tachypnea, whereas accompanying burns on the face and surrounding area is quite common [1] [3]. The presence of soot in the nasopharynx and sputum has also been documented as an important finding [3]. Loss of consciousness and respiratory insufficiency are signs of life-threatening smoke inhalation injury, in which case rapid therapeutic measures (mainly in the form of cessation of exposure to smoke) are mandatory [3] [4] [5].
The need for rapid treatment necessitates a prompt clinical workup by the physician, but in order to gain sufficient evidence for a presumptive diagnosis, a detailed patient history, and a thorough physical examination must be performed. As many patients develop altered consciousness and confusion, a heterogeneous anamnesis (friends, relatives, or coworkers who were exposed together with the patient) can be of great help in identifying the circumstances that preceded the development of symptoms [4]. Furthermore, findings such as facial burns, soot in the nasopharynx and sputum, as well as voice changes are highly indicative signs of smoke inhalation injury, which is why the role of a proper physical exam must not be overlooked [1]. As soon as clinical suspicion is raised, both laboratory and imaging studies should be performed [3] [6]. A complete blood count (CBC), pulse oximetry, and arterial blood gas (ABG) analysis are vital for evaluating the status of tissue perfusion and oxygen content, whereas computed tomography (CT) of the thorax is the recommended imaging modality [1] [3] [4] [5]. Pulmonary function testing (spirometry), electrocardiography (ECG), and measurements of carboxyhemoglobin are also a part of the initial workup, but in order to make a definite diagnosis and establish the severity of smoke inhalation injury, fiberoptic bronchoscopy (FOP), although being an invasive procedure, is the gold standard [2] [6].