PULMONARY PROBLEMS (RESUSCITATION PHASE 0 - 48 hours) Continued

II_d. restrictive chest wall burn

Pathophysiology:

Respiratory excursion can be markedly impaired by a burn to the chest wall.⁹ The process is most evident with a circumferential third degree burn. The loss of elasticity in the chest wall due to the burn tissue will markedly increase the work of breathing required to maintain functional residual capacity and an adequate tidal volume. As more subeschar edema develops, compressing the chest wall, the end-expiratory intrathoracic volume begins to decrease. Edema from a second degree burn is also sufficient to alter lung mechanics. The loose aureolar tissue in the auxilla and lateral chest wall will sequester large amounts of edema fluid, leading to a very heavy tense chest wall. Full thickness burns produce a more severe limitation because tissue expansion is markedly impaired and intrathoracic volume becomes compressed. The result is a significant V/Q mismatch, atelectasis, and hypoventilation. Maximum respiratory effort is frequently required just to maintain adequate gas exchange. Any process that compromises the necessary increase in inspiratory force and muscle activity, such as hypoxia, hypovolemia, pain, or sedation, will accentuate the severity of lung dysfunction.

Diagnosis:

A deep burn to the chest wall, especially involving the entire anterolateral chest wall is at high risk for becoming restrictive as fluid resuscitation proceeds.  This process plus signs of chest wall restriction is diagnostic.

Figure 13:  Restructive Chest Wall Burn

Legend: The restriction to ventilation is further compromised by the abdominal burn that diminishes the movement of the diaphragm.

Treatment:

The three main treatment principles are: a) recognize the problem; b) control the tissue edema process (elevation of upper body if hemodynamically stable); and c) surgically decompress the chest wall constriction.

The surgical decompression entails incision completely through the burn eschar to viable tissue.²¹  An incision to superficial will not correct the restriction.  The standard incisions include vertical incisions down both anterior auxillary lines then a subcostal incision to connect the vertical incisions.  This process separates the constricting chest wall burn from the chest wall muscle function.

The skin vessels are coagulated with a deep burn so the only bleeding is usually from the viable tissue beneath.  Packing the incision with microcrystalline collagen helps control hemostasis.  Electrocautery may be needed.

In general, the procedure can be safely performed at the bedside as minimal pain is encountered due to the damage to the nerve ending.

Escharotomies are usually not required in partial thickness burns unless massive edema develops tightening the eschar until restriction develops.

Figure 14:  Escharotomy

Legend: The standard escharotomy incision lines are shown

Figure 15:  Chest Wall Escharotomy

Legend: Note the incision must extend to normal tissue

Figure 16:  Massive Chest Wall Edema

Legend: A restriction develops late in the resuscitation period due to massive edema

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