Flail chest in a neonate resulting from nonaccidental trauma.

Abstract: The authors present a 21-day-old infant who sustained a flail chest as a result of nonaccidental trauma. Initial treatment included endotracheal intubation and mechanical ventilation for hypoxemic respiratory failure followed by the administration of continuous positive airway pressure by nasal cannula. Further evaluation resulted in the identification of nonaccidental as the mechanism of injury. The pathophysiology of flail chest, its etiology, and treatment options are reviewed. In the absence of a documented history of significant thoracic injury or the presence of metabolic bone disease, nonaccidental trauma is the most likely diagnosis in infants and children with a flail chest.

Key Words: flail chest, nonaccidental trauma, child abuse, shaken baby syndrome 

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Flail chest refers to a segment of the chest wall that is isolated from the remainder of the thoracic cavity due to multiple rib fractures. It occurs most commonly as the result of traumatic injury, has been estimated to affect 1 in 13 patients with fractured ribs, and even with modern therapy remains a potential source of morbidity and mortality. (1-3) When compared with the adult trauma population, flail chest is far less common in infants and children. (4,5) Due to the substantial force necessary to produce flail injuries, pediatric patients with such injuries are at high risk for having associated injuries to underlying structures such as the pulmonary parenchyma. (6) The majority of cases of pediatric flail chest result from accidental injuries such as motor vehicle accidents and falls or metabolic bone diseases such as osteogenesis imperfecta. (2,5,7-10) We report a case of nonaccidental injury to an infant resulting in flail chest. We are not aware of previous reports of flail chest in a neonate without associated metabolic bone disorders such as osteogenesis imperfecta.

Case Report

Review of this patient's hospital records and presentation of this case report were approved by the Institutional Review Board of the University of Missouri. A 21-day-old, 3.52 kg, previously healthy male infant was admitted to our Pediatric ICU after evaluation and treatment at an outside hospital for respiratory failure. The patient presented to the outside facility with severe intercostal and substernal retractions, grunting, nasal flaring, paradoxical movement of a segment of the left chest, and crepitus over the anterior and lateral left chest wall. A chest x-ray at the outside hospital revealed multiple rib fractures on the left side involving ribs 2 to 9 with a 3 rib flail segment, and a small area of pulmonary contusion under the flail segment. Additional injuries included a distal femur fracture and a fracture of the right ischium. The patient's head was atraumatic and an ophthalmologic examination was negative for retinal hemorrhages. Computed tomography scan of the head was negative. The parents denied any history of trauma or abuse. The Division of Family Services (DFS) was contacted to investigate the situation and the child was taken into DFS custody. The patient was placed on 100% oxygen by mask and plans were made to transport him to our hospital. During transportation, progressive oxygen desaturation, despite the administration of 100% oxygen by mask, necessitated endotracheal intubation and positive pressure ventilation. After arrival at our institution, sedation and analgesia during mechanical ventilation were provided by a continuous infusion of fentanyl at 2 [micro]g/kg/h with intermittent doses of midazolam (0.1 mg/kg) every 1 hour as needed. Initial ventilatory requirements included a PEEP of 7 cm[H.sub.2]O and an [F.sub.i][O.sub.2] of 0.8. The initial chest x-ray confirmed the rib fractures that were noted at the outside hospital and demonstrated the left-sided pulmonary contusions. Mechanical ventilation with a PEEP of 7 cm[H.sub.2]O was continued for the first 4 hospital days. On hospital Day 4, ceftriaxone was started for thick, tan, tracheal secretions, the culture of which subsequently grew Staphylococcus aureus and Branhamella catarrhalis. A genetics consult was obtained which concluded that the fractures and this patient's clinical course were not consistent with osteogenesis imperfecta. On hospital Day 5, the PEEP was decreased to 6 cm[H.sub.2]O which maintained an adequate oxygenation with a [F.sub.i][O.sub.2] of 0.3. The PEEP was decreased to 5 and then to 4 cm[H.sub.2]O on hospital Day 6. The ventilator rate was weaned and the infant's trachea was extubated on hospital Day 6. As there remained some paradoxical motion of the left chest segment, continuous positive airway pressure (CPAP) was applied using a nasal cannula. On hospital Day 7, IV fluids and enteral Dobhoff feedings were stopped and the patient was allowed to feed by mouth. Subsequent investigation and questioning led to the father's admission that he had thought that the infant was choking and attempted to push on his chest to clear the airway. The father demonstrated that he had actually also encircled the infant's chest with both of his hands and delivered several chest compressions. Over hospital Days 6 to 11, the CPAP flow was weaned and on hospital Day 12, the infant was weaned to room air with an oxygen saturation of 100%. Although the flail segment was still present, there was less paradoxical movement and repeated chest radiography showed early callus formation over some of the anterior ribs. The patient was discharged to foster care on hospital Day 12.

Discussion

Flail chest is a rare, but serious, sequela of blunt chest wall injuries, occurring in 5 to 13% of patients with thoracic trauma. (7) Flail chest is defined as the paradoxical motion of a segment of the chest wall in a spontaneously breathing patient, resulting from anterior and posterior fractures of 3 or more adjacent ribs. It occurs most commonly in thoracic compression injuries in which the force applied on the rib cage is greater than the strength of the thoracic cage. (7) In flail chest, a negative force is generated beneath the flail segment during inspiration, resulting in the segment being pulled inward by the negative intrathoracic pressure. Likewise, with expiration, the positive pressures cause the segment to extend outward. (7) Studies have shown that the ribs are most susceptible to fracture at a location 60 degrees rotated posteriorly from the sternum. However, ribs subjected to lateral or anteroposterior compression may fracture posteriorly. (7)

Respiratory compromise may occur either from the alteration in pulmonary dynamics related to the flail segment or associated trauma to the underlying pulmonary parenchyma. The alteration in chest wall mechanics causes a decrease in tidal volume and cough efficacy thus predisposing the patient to the retention of secretions, atelectasis, pneumonia and respiratory failure. (7,10) In addition, inspiratory muscles must shorten more for a given tidal volume thereby increasing the work of breathing. (11) These changes in respiratory function are further aggravated by pain from the multiple rib fractures and by the relative cartilaginous nature of the neonatal chest wall. (12)

Flail chest in children has been documented less frequently than injury to the underlying structures, including the lungs, heart, and mediastinum. This is likely due to the increased compliance of the thoracic cage of infants and children or possibly due to the inaccuracy of interpretation of chest x-rays, as greenstick rib fractures may be initially missed. (4,5,10) Due to the significant force required to cause a flail chest in an infant or child, one must also maintain a high index of suspicion for associated intrathoracic injuries in these patients. In addition, the soft chest wall may offer less protection and allow direct transfer of energy to the lung parenchyma and other intrathoracic structures. (5,6)

Before the mid-1950s, external chest wall stabilization was the primary treatment modality of flail chest. Following the introduction of routine use of positive pressure ventilation in the mid 1950s until 1975, early endotracheal intubation and ventilation were considered the gold standard of treatment. (1,13,14) However, in 1975, Trinkle et al concluded that many patients with flail chest could be managed in a manner similar to that used in the treatment of pulmonary contusion with a regimen that included analgesia, supplemental oxygen, strict maintenance of intravascular volume, CPAP, and tracheobronchial toilet. (13-16) Today, there remain 2 major schools of thought regarding the therapy of flail chest, including treatment as outlined by Trinkle et al or routine endotracheal intubation and mechanical ventilation. (7,10,17,18) More recently, a third option has been offered that includes surgical stabilization of the flail segment with internal fixation, which may result in a shorter duration of mechanical ventilation and decreased hospital stay, although there are no reports of the use of this technique in infants and children (15,19) The most widely accepted approach today remains conservative management with mechanical ventilation reserved for patients with pulmonary insufficiency or failure after adequate analgesia. Given our patient's progressive hypoxemia and respiratory insufficiency, we chose to proceed with endotracheal intubation and mechanical ventilation, although CPAP or bilevel positive airway pressure (BiPAP) may offer an alternative to endotracheal intubation in select patients. (20)

Little has been written to indicate how therapy for flail chest may be different in the pediatric population. Because the pediatric thoracic cage is not as calcified, and thus more compliant, considerable force must be applied to the pediatric rib cage for flail chest to occur. (6,7,10) Pediatric patients with flail chest are more likely to have sustained serious trauma to the underlying thoracic structures, and experimental studies have demonstrated that pulmonary contusions, as was seen in our patient, may occur from the direct compression of the chest wall. (7,14) In such circumstances, respiratory insufficiency may be further compromised by the contusion. (1,10,15) As a result of these confounding injuries, it is likely that infants and children with a flail chest injury may be less likely to respond to conservative therapy and more likely to require mechanical ventilation. Given the rarity of such injuries in the pediatric patient, as was suspected and later confirmed in our patient, nonaccidental trauma should always be evaluated in an infant with a flail chest.

References

1. Freedland M, Wilson RF, Bender JS, et al. The management of flail chest injuries: factors affecting outcome. J Trauma 1990;30:1460-1468.

2. Rielly JP, Brant ML, Mattox KL, et al. Thoracic trauma in children. J Trauma 1993;34:329-331.

3. Shorr RM, Crittenden M, Indeck M, et al. Blunt thoracic trauma: analysis of 515 patients. Ann Surg 1987;206:200-205.

4. Meller JL, Little AG, Shermeta DW. Thoracic trauma in children. Pediatrics 1984;74:813-819.

5. Nakayama DK, Ramenofsky MI, Rowe MI. Chest injuries in childhood. Ann Surg 1989;210:770-775.

6. Garcia VF, Gotschall CS, Eichelberger MR, et al. Rib fractures in children: a marker of severe trauma. J Trauma 1990;30:695-700.

7. Wanek S, Mayberry JC. Blunt thoracic trauma: flail chest, pulmonary contusion, and blast injury. Crit Care Clin 2004;20:71-81.

8. Balci AE, Kazez A, Eren S, et al. Blunt thoracic trauma in children: review of 137 cases. Eur J Cardiothorac Surg 2004;26:387-392.

9. Cardenas N, Manrique TA, Catlin EA. Flail chest in the newborn: a complication of osteogenesis imperfecta. Clin Pediatr (Phila) 1988;27:161-162.

10. Smyth BT. Chest trauma in children. J Pediatr Surg 1979;14:41-47.

11. Tzelepis GE, McCool FD, Hoppin FG Jr. Chest wall distortion in patients with flail chest. Amer Rev Resp Dis 1989;140:31-37.

12. Cappello M, Yuehua C, De Troyer A. Respiratory muscle response to flail chest. Am J Respir Crit Care Med 1996;153:1897-1901.

13. Richardson JD, Adams L, Flint LM. Selective management of flail chest and pulmonary contusion. Ann Surg 1982;196:481-487.

14. Trinkle JK, Richardson JD, Franz JL. Management of flail chest without mechanical ventilation. Ann Thorac Surg 1975;19:355-363.

15. Voggenreiter G, Neudeck F, Aufmkolk M, et al. Operative chest wall stabilization in flail chest: outcomes of patients with or without pulmonary contusion. J Am Coll Surg 1998;187:130-138.

16. Pierson DJ. Indications for mechanical ventilation in adults with acute respiratory failure. Respir Care 2002;47:249-262.

17. Velmahos GC, Vassiliu P, Chan LS, et al. Influence of flail chest on outcome among patients with severe thoracic cage trauma. Int Surg 2002;87:240-244.

18. Sladen A, Aldredge CF, Albarran R. PEEP vs ZEEP in the treatment of flail chest injuries. Crit Care Med 1973;1:187-191.

19. Ahmed Z, Mohyuddin Z. Management of flail chest injury: internal fixation versus endotracheal intubation and ventilation. J Thorac Cardiovasc Surg 1995;110:1676-1680.

20. Abisheganaden J, Chee CB, Wang YT. Use of bilevel positive airway pressure ventilatory support for pathological flail chest complicating multiple myeloma. Eur Respir J 1998;12:238-239.

Christopher L. Gipson, BS and Joseph D. Tobias, MD

From the School of Medicine, and the Departments of Anesthesiology and Child Health, University of Missouri, Columbia, MO.

Reprint requests to Joseph D. Tobias, MD, Vice-Chairman, Department of Anesthesiology, Chief, Division of Pediatric Anesthesiology, Russell and Mary Shelden Chair in Pediatric Intensive Care Medicine, Professor of Anesthesiology and Child Health, University of Missouri, Department of Anesthesiology, 3W40H. One Hospital Drive, Columbia, MO 65212. Email: [e-mail]

Accepted January 25, 2006

RELATED ARTICLE: Key Points

* Flail chest occurs most commonly as the result of traumatic injury, has been estimated to affect 1 in 13 patients with fractured ribs, and even with modern therapy can be a source of morbidity and mortality.

* Due to the substantial force necessary to produce flail chest injuries, pediatric patients with such injuries are at high risk for having associated injuries to underlying structures such as the pulmonary parenchyma.

* Respiratory compromise associated with a flail chest may occur either from the alteration in pulmonary dynamics related to the flail segment or associated trauma to the underlying pulmonary parenchyma.

* Given the rarity of such injuries in the pediatric patient, in the absence of an appropriate explanation such as a significant traumatic event, non-accidental trauma (child abuse) should be suspected in an infant with a flail chest.