245 - Acquired Lobar Emphysema in Severe BPD: Who, Why, and What can we do about it?

Publication Number: 245.3668

Sara L. Wiener, Children's Hospital of Philadelphia, Bala Cynwyd, PA, United States; Huayan Zhang, Children’s Hospital of Philadelphia-University of Pennsylvania, Philadelphia, PA, United States; Krithika Lingappan, MD, PhD, Children's Hospital of Philadelphia, Philadelphia, PA, United States; Danielle Callaway, University of Texas Southwestern Medical Center, Dallas, TX, United States

Background: Premature babies with severe Bronchopulmonary Dysplasia (BPD) are a heterogeneous group with a variety of phenotypes. Lobar emphysema develops in a subset of babies with severe BPD, possibly due to prolonged exposure to mechanical ventilation leading to severe impairment in lung recruitment and respiratory failure. Studies have shown that surgical resection of the emphysematous lobe may improve outcomes, although there is no standard process to identify candidates who will tolerate and benefit from this procedure.

Objective: To identify contributing factors for the development of lobar emphysema in severe BPD and assess outcomes after surgical lobectomy.

Design/Methods: A chart review was performed on eight infants with grade III BPD from the CHOP N/IICU who had lobar emphysema on imaging and subsequently had lobectomies. Their clinical courses were evaluated, and pertinent imaging and procedures were noted, including SPECT-CT, bronchoscopy, and bronchial balloon occlusion of the affected lobe. Respiratory severity scores (RSS; average FiO2 X mean airway pressure) were calculated before and after lobectomy and compared with a paired two-tailed T-test.

Results: No clear shared contributing factors predisposed to lobar emphysema, though nearly all had evidence of airway malacia on bronchoscopy. All cases demonstrated inability to wean ventilator settings, findings of lobar emphysema, and lung hyperinflation on imaging. Prior to lobectomy, all infants had a SPECT-CT and/or balloon occlusion of the affected lobe. All infants survived at least 1-month post-lobectomy. There was no significant difference in the RSS pre- and post-lobectomy (p=0.109), but the RSS was higher post-procedure in three infants, and two of them died before discharge.

Conclusion(s): In infants with BPD, it is challenging to predict who will develop acquired lobar emphysema. Providers should closely monitor imaging obtained in infants with difficulty weaning support as this may be the first clue pointing to hyperinflation. Although the RSS did not differ significantly pre- and post-lobectomy, reduction of RSS post-procedure may predict the ability to wean support. A high pre-procedure RSS did not predict survival, but values >10 were associated with post-procedure tracheostomy, indicating persistent pathology in the remaining lung. Lobectomy is safe to perform in this patient population, particularly when combined with pre-procedure balloon occlusion or SPECT-CT as an adjunct to screening candidates.

Figure 1: Imaging of Lobar Emphysema
CTA (left) and CXR (right) of patient with left sided lobar emphysema, prior to lobectomy

Table 1: Respiratory Parameters
Ventilator parameters and calculated respiratory severity score (RSS, MAP X FiO2) as indications of underlying respiratory function and pathology before and after lobectomy. The medical chart was reviewed and either the maximal value was taken in the case of PEEP and MAP, or the morning value (~ 8 AM) was extracted for 7 days prior to the procedure and 7 days post procedure. The daily morning data points were averaged to obtain the data above. Use of paralysis includes a paralytic agent with the intention of use for promoting patient stability, not for procedures. Abbreviations: positive end-expiratory pressure (PEEP), mean airway pressure (MAP), fraction of inspired oxygen (FiO2), respiratory severity score (RSS), post-menstrual age (PMA), spontaneous intermittent mandatory ventilation (SIMV), volume diffusive respirator (VDR), pressure control (PC), volume control (VC), high frequency oscillatory ventilation (HFOV).

Figure 2: Respiratory Severity Score Before and After Lobectomy
RSS before is averaged over seven days prior to lobectomy.
RSS one week after is averaged over seven days post lobectomy.
Red line represents deceased by discharge.
RSS compared with paired two-tailed T-test.