Approach Considerations
Admission/transfer to a neonatal intensive care unit (NICU) is indicated for infants with pulmonary interstitial emphysema (PIE). A thoracentesis set should be readily available due to the possibility of air leak, including pneumothorax and pneumopericardium.
Different treatment modalities have been used to manage PIE, with variable success.
Although the primary risk factor for PIE, prematurity, is rarely preventable, attention should be given to the use of as little mechanical ventilatory support as is necessary for the infant's very fragile lungs. An often-used strategy is to reduce the inspiratory time and/or decrease pressure along with adjusting the positive-end expiratory pressure (PEEP) enough to stent the airway will allow better emptying of the alveoli during expiration. [1] Close clinical observation by monitoring oxygen need, work of breathing and perfusion status, as well as judicious analysis of blood gas and chest x-ray, are essential to determine an optimal PEEP for a particular infant.
Because pneumothorax is a known complication of PIE, anticipatory guidance for this possibility should be provided for all those caring for the infant. Appropriate personnel should be readily available to address this complication.
In addition to pulmonary treatment, the overall importance of appropriate nutritional management of these ill newborns cannot be overstressed. Most of these infants are treated with total parenteral nutrition, and their nutritional needs require diligent attention.
All infants with PIE need to be under the care of a neonatologist. In some cases, pediatric pulmonology and pediatric surgery consultations are appropriate.
Lateral Decubitus Positioning
Lateral decubitus positioning is a conservative approach that has been used successfully in infants with pulmonary interstitial emphysema (PIE), and it is most effective in infants with unilateral PIE. In different case studies of lateral decubitus positioning as a treatment of unilateral PIE in infants, PIE resolved in 48 hours to 6 days with minimal recurrence and a low failure rate. Thus, lateral decubitus positioning should be considered as an early first-line therapy in the management of unilateral PIE; it has also been used successfully for patients with bilateral PIE when one side is more significantly affected.
Place the infant in the lateral decubitus position, with the affected lung dependent. This therapy can result in plugging of dependent airways and improved oxygenation of the nondependent lung. The latter allows for an overall decrease in ventilatory settings. The combination of the above factors helps in resolving PIE. [31]
Selective Main Bronchial Intubation and Occlusion
Many case reports detail successful treatment of infants with severe localized pulmonary interstitial emphysema (PIE) by selective intubation of the contralateral bronchus. [32, 33, 34] This maneuver decompresses the overdistended lung tissue and avoids exposing it to high positive inflationary pressures. Selective bronchial intubation of the right main bronchus is not a difficult procedure; the left side may be more difficult.
This procedure uses an endotracheal tube of the same diameter as for a regular intubation. However, the tube is inserted 2-4 cm beyond its usual position. It is introduced with the bevel on the end of the tube positioned so that the long part of the tube is toward the bronchus to be intubated. This increases the chance of the tube entering the correct bronchus as it is advanced into the airway. Turning the infant's head to the left or right moves the tip of the endotracheal tube to the contralateral side of the trachea and may help in selective tube placement.
Weintraub et al described a method for left selective bronchus intubation using a regular Portex endotracheal tube in which an elliptical hole 1 cm in length has been cut through half the circumference about 0.5 cm above the tip of the oblique distal end. [34] By directing the side with the elliptical hole to the left lung, left selective bronchus intubation can be easily and repeatedly accomplished.
Another method of selective intubation is the use of a small fiberoptic bronchoscope to direct the endotracheal tube tip into the desired bronchus. Selective intubation under fluoroscopy can also be considered.
Potential complications of selective intubation/ventilation include the following:
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Atelectasis in the affected lung
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Injury to the bronchial mucosa, with subsequent scarring and stenosis
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Acute hypoventilation or hypoxemia if ventilating one lung is inadequate
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Excessive secretions
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Hyperinflation of the intubated (nonoccluded) lung
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Upper lobe collapse when intubating the right lung
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Bradycardia
Despite the potential risks, selective bronchial intubation is a desirable alternative to lobectomy in a patient with persistent, severe localized PIE that is causing a mediastinal shift and compression atelectasis that is refractory to conservative management. This procedure should be attempted before any surgical intervention.
High-Frequency Ventilation
Keszler et al found that high-frequency ventilation was safe and more effective than rapid-rate conventional ventilation in the treatment of newborns with pulmonary interstitial emphysema (PIE). [35] In their study of 144 newborns with PIE, the use of high-frequency ventilation resulted in similar oxygenation and ventilation obtained at lower peak and mean airway pressures. These results suggested that less air would leak into the interstitial spaces in these infants.
Similar effects can be achieved by use of high-frequency oscillatory ventilation (HFOV). A study by Clark et al demonstrated the efficacy of HFOV in 27 low birth weight infants who developed PIE and respiratory failure while on conventional ventilation. [36] Overall survival in nonseptic patients was 80%. Surviving patients showed continued improvement in oxygenation and ventilation at an increasingly lower fraction of inspired oxygen (FiO2) and proximal airway pressure with resolution of PIE, whereas nonsurvivors progressively developed chronic respiratory insufficiency with continued PIE from which recovery was not possible. [36]
The investigators hypothesized that interstitial air leak is decreased during HFOV because adequate ventilation is provided at lower peak distal airway pressures. [36] Although this mode of ventilation has inherent risks, it can be a very effective tool for experienced clinicians to treat severe diffuse PIE. Note that care must be taken in smaller infants who require a high amplitude to ventilate, because the active exhalation during HFOV may cause small airway collapse and exacerbate gas trapping.
Squires et al also found that low oscillatory frequency of HFOV had some benefits for preterm infants with severe PIE. [37] After transition to low-frequency HFOV, physiologic responses were seen in both unilateral and bilateral PIE, in particular a rapid and sustained improvement in oxygenation in the bilateral group. [37]
Lobectomy
Lobectomy is indicated in a small number of patients with localized pulmonary interstitial emphysema (PIE) in whom spontaneous regression is not occurring and medical management has failed. [38, 39, 40] However, a case report exists of the spontaneous resolution of diffuse persistent PIE with pneumomediastinum, supporting the consideration of a nonsurgical approach in a stable infant with persistent PIE. [41] Thus, clear guidelines for surgical intervention in PIE are difficult to establish. In general, lobectomy should be reserved for infants in whom the risks of recurring complications outweigh those of surgery. Lobectomy seems most helpful in infants who develop severe lobar emphysema.
Other Treatment Modalities
Case reports and/or case series describe a variety of other approaches for the management of pulmonary interstitial emphysema (PIE), including the following:
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Chest physiotherapy with intermittent 100% oxygen in localized and persistent compressive PIE [43]
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Multiple pleurotomies [46]
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Heliox with inhaled nitric oxide [47]
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Percutaneous catheter insertion [4]
Despite the success claimed by the authors of these reports, the efficacy of the treatment modalities they discussed seem questionable. With advancements in respiratory care, these treatment modalities are rarely used.
Prevention of Pulmonary Interstitial Emphysema
Surfactant
Prophylactic surfactant administration to infants (< 30-32 weeks' gestation) judged to be at risk of developing respiratory distress syndrome (RDS) compared with selective use of surfactant in infants with established RDS has been demonstrated to decrease the risk of PIE. [48]
Meta-analysis of early surfactant replacement therapy with brief ventilation compared with later, selective surfactant replacement and continued mechanical ventilation suggests a trend toward a reduced incidence of air leak syndromes in premature infants in the early surfactant group. [49] Early surfactant treatment, less invasive ventilatory support, or both could be responsible factors for the observed beneficial trend. [49]
According to one report, in infants with RDS, multiple doses of animal-derived surfactant extract resulted in greater improvements in oxygenation and ventilatory requirements, a decreased risk of pneumothorax, and a trend toward improved survival. [50]
High-frequency ventilation
In a study comparing high-frequency positive pressure ventilation (HFPPV) to conventional mechanical ventilation (CMV), Pohlandt et al reported a reduction in the risk of PIE with HFPPV. [51] A meta-analysis by Greenough et al demonstrated that, compared to CMV, HFPPV was associated with a reduction in the risk of air leak, primarily pneumothorax, but not for PIE (typical relative risk [RR] for pneumothorax was 0.69; 95% confidence interval [CI]: 0.51-0.93). [52]
A review of different trials of elective high-frequency oscillatory ventilation (HFOV) versus CMV for acute pulmonary dysfunction in preterm infants suggested there may be an increase in the incidence of air leak syndromes, including but not limited to PIE in the HFOV group. [53]
In contrast, a prospective randomized multicenter study of HFOV versus CMV in premature infants with RDS showed no difference in the incidence of PIE. [24] Limited data regarding rescue HFOV for pulmonary dysfunction in the preterm infant also showed no difference in the rate of PIE. [54] Similarly, Cochrane reviews of trials of elective high-frequency jet ventilation (HFJV) versus CMV for RDS demonstrated no significant difference in the incidence of air leak syndrome in the individual trials or in the overall analysis. [55]
In summary, the available literature suggests elective or rescue high-frequency ventilation does not prevent the development of PIE.
Other considerations
Different modes of CMV do not appear to affect the risk of PIE. Goel at al showed that the rate of PIE was significantly less while delivering nasal continuous positive airway pressure (CPAP) in the mask group as compared to cannula group (4.9% vs 17.5%; RR: 0.28, 95% CI: 0.08-0.96; P = 0.03). [56]
Although data are limited on the benefit of volume-targeted ventilation strategies, some data appear to be promising regarding volume-targeted ventilation to prevent PIE. Stefanescu et al reported that rates of PIE were lower among infants treated with volume guarantee pressure support ventilation versus pressure-controlled ventilation (odds ratio: 0.6; 95% confidence limits: 0.4, 0.8). [57] However, McCallion et al found no significant difference in the rate of PIE either in a pooled analysis within subgroups or the overall pooled analysis of trials comparing volume-targeted versus pressure-limited ventilation in the neonate. [58]
Avoid the use of high peak inspiratory pressure (PIP). Carefully monitor the PIP (watch the manometer) during manual ventilation.
Long-Term Monitoring
Monitoring for physical and psychomotor development in a neonatal follow-up care program or equivalent program is important, because most infants with pulmonary interstitial emphysema (PIE) are premature and are at risk for developmental delay. In addition, PIE has been associated with increased risks of intraventricular hemorrhage (IVH) and periventricular leukomalacia (PVL), which also raise the risks of developmental delay in these infants.
Patients with chronic lung disease (CLD) may need pediatric pulmonology follow-up care. Note that the available literature remains unclear regarding the role of bronchodilator agents in preventing or treating CLD in preterm infants; in addition, no specific trials appear to have studied the use of these agents for managing CLD in this population. [59]
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This radiograph, obtained from a 1-day-old premature infant at 24 weeks' gestation, shows bilateral pulmonary interstitial emphysema (PIE). Linear radiolucencies extending up to the lung periphery are visible.
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This radiograph, obtained from a premature infant at 26 weeks' gestation, shows characteristic radiographic changes of pulmonary interstitial emphysema (PIE) of the right lung.
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This radiograph shows pneumothorax and pulmonary interstitial emphysema (PIE) on the right side. Interstitial air prevents collapse of the underlying lung by a tension pneumothorax. In such cases, extreme caution is required during drainage of a pneumothorax to avoid perforation of the underlying lung.
