Keywords
Electrical Impedance Tomography (EIT), Penumatocele, Paediatric
Intensive Care, Pneumococcal pneumonia, Pediatric acute respiratory
distress syndrome (pARDS)
To the Editor,
A previously healthy 4-year-old male child, weighing 12 kg, was admitted
to our PICU for pneumococcal pneumonia complicated by right lower lobe
empyema. The disease quickly progressed to severe pediatric acute
respiratory distress syndrome (PARDS) and the patient was placed
initially on conventional protective mechanical ventilation, then
High-Frequency Oscillatory Ventilation (HFOV) and finally supported with
Veno-Venous Extracorporeal Membrane Oxygenation in light of the
impossibility of correcting the hypoxemia. In order to optimize Positive
End-Expiratory Pressure (PEEP), during the phase of recovery from ECMO
run we performed an Electrical Impedance Tomography (EIT) guided
decremental PEEP trial from 14 cmH2O to 8 cmH2O in 2 cmH2O steps, with
each level maintained for 10 minutes1. Introduced to
the medical community for the first time in the late 1980s, EIT utilizes
alterations in electrical impedance between air-filled and tissue or
fluid-filled compartments to delineate and measure regional lung volume
distribution at the patient’s bedside. A fundamental tenet of EIT’s
approach to ventilation monitoring is not only mitigating global
overdistension or collapse but also emphasizing regional
characteristics. While its efficacy in the adult population has been
extensively validated and established, its application in pediatric
patients remains an area of ongoing investigation2. In
our case, measurements were conducted using the PulmoVista 500 system
(Dräger Medical, Lübeck, Germany) (Figure 1). Significantly, during the
trial we were able to identify a region with ventilation delay (RVD)
appearing at PEEP 14cmH2O. RVD refers to the delay between the onset of
inspiration in the entire lung and the impedance curve specific to a
particular region. As a result, RVD is usually used to identify lung
regions experiencing delayed expansion3. In our case,
owing to prior pulmonary tomographic imaging (Figure 2), the region of
RVD was interpreted not merely as ventilation inhomogeneity but as the
air-flow manifestation corresponding to a pneumatocele in the basal
right lung. The presence of pneumatocele presents a challenge for
clinicians managing patients on invasive ventilation. Due to their
increased compliance and valve-like properties, insufficient ventilation
characterized by excessively high PEEP levels carries the risk of
pneumatocele overdistension, potentially resulting in rupture and/or
formation of bronchopleural fistulas4. Conversely, an
excessively conservative approach may contribute to generalized lung
derecruitment, contributing to worsening the hypoxemia. Considering this
insight, we successfully determined with EIT the optimal PEEP level to
obtain either a reduction of alveolar dead space and the pneumatocele
detente, minimizing the risk of ropture and developing a bronchopleural
fistula.
Managing mechanical ventilation in patients with severe PARDS, requiring
VV ECMO, and presenting with pneumatocele, poses considerable
challenges. However, as illustrated in the described case, EIT was
instrumental in determining the optimal PEEP level to optimize
ventilation and minimize pneumatocele-related risks, improving patient
management and outcomes.