tracheostomy was based on a variety of indications and not solely on a prediction of prolonged ventilator dependence. Full thickness head and facial burns were present in 87% of the subjects and tracheostomies were inserted through a burn wound in 61% of the procedures. Tracheostomy resulted in significant improvement in respiratory compliance and PaO2/FiO2 ratio at 24 hours post procedure and there were no tracheostomy related complications, wound site infections or airway losses after tracheostomy. The incidence of pneumonia was not specifically studied, but 23/38 (55%) had positive sputum cultures consistent with bacterial colonization post tracheostomy. Tracheostomy in burned children was therefore felt to be safe and advantageous, especially from the perspective of ease of mechanical ventilation, and airway security.

To summarize, earlier tracheostomy offers the advantages of better pulmonary toilet and ease of suctioning, better ventilation mechanics and possibly easier weaning, greater patient comfort with less need for sedation, and greater airway security. The disadvantages are that it is an invasive procedure with a low but recognized incidence of significant tracheal and laryngeal complications. The only randomized prospective study to date found no specific benefit to early tracheostomy, but importantly, could not cite any major adverse sequelae associated with this approach. Most likely, prolonged translaryngeal intubation followed by a tracheostomy is the least desirable scenario and should be avoided whenever possible. Patients with severe neck or facial burns or swelling, patients who are likely to need prolonged ventilator support based on advanced age, presence of large burns, and smoke inhalation and pediatric burn patients particularly those with significant burns or extensive facial burns, where securing an airway is considerably more difficult, represent the preferred patient groups in which to consider early tracheostomy.

Fig. 2. Standard escharotomy incisions have been augmented with additional incisions to form a “checkerboard” pattern

pansion. This occurs because of edema formation underneath the inelastic full-thickness eschar enveloping the chest limits thoracic expansion. Typically, this will become apparent as manual ventilation with a Laerdal bag will feel “tight”. Alternatively, for patients on a ventilator, progressively rising airway pressures and end-tidal CO2 and decreasing tidal volumes may be observed. Bedside chest escharotomy is usually immediately therapeutic but it is preferable to perform the escharotomy prophylacticaly in anticipation of this scenario. The author’s approach is to begin with longitudinal incisions along the anterior axillary line, bilaterally, connecting these with a horizontal incision at the costal margin to make an “H” pattern (Fig. 2). Additional vertical and horizontal incisions may be added if needed in a “checkerboard” pattern. Escharotomies must extend just past the edge of the burn and should include the abdomen if it is involved. Other causes of impaired ventilation and worsening chest compliance such as endotracheal tube obstruction or a tension pneumothorax should always be ruled out.

Chest escharotomy

Following airway stabilization the next respiratory priority is to ensure adequate ventilation. Full thickness circumferential or near circumferential burns of the chest and/or abdomen may restrict chest ex-

Bronchial hygiene and chest physiotherapy

Bronchial hygiene and chest physiotherapy are important adjunctive therapies in any intubated and mechanically ventilated patient, but these are par-

ticularly important interventions in a burn patient with smoke inhalation. It is essential to mobilize and clear the airways of the copious secretions, sloughing mucosa and particulate carbonaceous debris that commonly follows an inhalation injury. Retention of these airway obstructants will inevitably result in atelectasis and pneumonia. Mlcak et al. have extensively described techniques of bronchial hygiene [1, 17].

Therapeutic coughing involves stimulation of the cough reflex. Non intubated patients are encouraged by the physiotherapist to voluntarily perform a series of smaller to larger coughs which may be augmented by tracheal massage by the physiotherapist. Intubated patients may have a cough stimulated by transiently altering the balloon cuff pressure or by tracheal suctioning. Chest physiotherapy also includes regular (q1–2 hourly) changes in position for intubated ventilated patients to promote postural drainage, combined with percussion, vibration, and shaking of the chest. Unique to the burn patient is the need to respect skin graft and donor sites, which can affect the intensity of chest physiotherapy. Early ambulation and upright positioning is highly beneficial as it promotes better expansion of the lungs, and maintenanceofrespiratorymuscletoneandstrength. Mlcak has even described upright chair positioning of patients on continuous ventilatory support [1, 17].

Finally, fiberoptic bronchoscopy may be used in a therapeutic fashion to irrigate, loosen, and then remove by suctioning retained cast and airway debris in the primary and secondary bronchi. This approach is mainly used in patients with severe inhalation injury and copious secretions with heavy carbonaceous deposits.

Inhaled heparin/N-acetylcystine (HeparinNAC)

This inhalational therapy is used in numerous Burn Centres for patients with inhalation injury. Following smoke inhalation, airways become progressively obstructed due to mucosal edema and the formation of occlusive casts containing fibrin, cellular debris, mucus and polymorphoneuclear leukocysts [18, 19]. Populations of alveoli distal to the occluded airways are hypoventilated and when combined with region-

al vasodilation caused by inflammatory mediators, results in ventilation perfusion mismatch and increased shunt fraction creating hypoxemia. Other populations of alveoli with patent airways may be subjected to hyperinflation causing mechanical trauma which augments the inflammatory response induced by exposure of the airways to the toxins in smoke. This inflammatory response is characterized by a neutrophil chemotaxis and activation and local production of oxygen-free radicals which propagate pulmonary microvascular injury and further lung damage [20–22].

Inhaled heparin-NAC is intended to act not only as a mucolytic agent to break down and loosen the obstructing casts but also to harness NAC’s capabilities as a free radical scavenger [23]. Animal experiments determined that a heparin infusion reduced tracheobronchial casts, minimized barotrauma and pulmonary edema, and improved oxygenation after smoke inhalation injury. Further animal experimentation in an ovine model of inhalation injury also found that the combination of heparin and dimethyl sulfoxide (a free-radical scavenger) produced improved oxygenation, reduction in peak inspiratory pressures and improved survival [25].

Three human trials of heparin-NAC, following smoke inhalation have been reported (Table 2). All are retrospective and involve either historical or contemporaneous non-randomized control groups. The studies all differ slightly in the treatment regimen: dosages of heparin differ slightly (5000 units vs. 10,000 units), Albuterol is sometimes given in combination with the heparin-NAC, and Heparin and NAC are either given separately or in combination. The studies by Desai et al. (in children) [26] and Miller et al. [20] (in adults) were positive and found benefit from heparin-NAC. Although both studies used historical controls, all patients in both of these studies had bronchoscopy-confirmed smoke inhalation and all patients were mechanically ventilated. The study by Miller et al. [20] provides the most detailed analysis of the beneficial outcomes in the heparinNAC treated patients which included significant reductions in the lung injury score, significantly improved respiratory resistance and lung compliance measurements, and significantly less hypoxemia and a survival benefit compared to untreated controls. In contrast, the study by Holt et al. [27] found no benefit