A preterm baby boy was born in good condition at 31+5 weeks gestation with a birth weight of 1956 g, following a precipitous labour with no prolonged rupture of membranes and no opportunity for administration of antenatal steroids to mother. Following admission to the neonatal unit, he developed respiratory distress and was commenced on nasal continuous positive airway pressure (CPAP) of 6 cm of water. At 24 hours of age, he developed a left-sided tension pneumothorax (figure 1), requiring endotracheal intubation and insertion of a chest drain. He received two doses of surfactant and was extubated onto CPAP on day 3. There was reaccumulation of the pneumothorax on day 4, which was subsequently drained. He remained self-ventilating in air in the second week of life. From day 15 to day 30, he required humidified high flow nasal cannula oxygen (fractional inspired oxygen up to 0.4), in view of marked subcostal and intercostal recession, intolerance to handling and a compensated respiratory acidosis on capillary blood gases. Figure 2 is the chest radiograph undertaken in the third week of life.
What is the most likely diagnosis in this case?
Congenital pulmonary airway malformation (CPAM)
Respiratory distress syndrome
Pulmonary interstitial emphysema (PIE)
Congenital diaphragmatic hernia
Which of the following is not an effective option for treatment of this condition?
Lateral decubitus with affected side down
High frequency oscillatory ventilation (HFOV)
Selective main bronchial intubation of contralateral lung (which is not affected)
Which of the following statements is false about this condition?
Complications can include other air leak syndromes
Most neonates presenting with this condition have been mechanically ventilated
Diagnosis is usually made on a chest radiograph
Surfactant therapy has been associated with an increase in this condition
Air embolism can be a fatal complication
Questions Answers can be found on page 2
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ANSWERS TO THE QUESTIONS ON PAGE 1
Question 1: the correct answer is C
The most likely diagnosis is PIE. There are features of unilateral PIE on the left side. PIE presents with linear and cyst-like radiolucencies on the chest radiograph, which follow the pattern of bronchovascular sheaths.1 It can affect one or multiple lobes and can be unilateral or bilateral. Unilateral PIE produces overexpansion of the affected side with contralateral mediastinal shift. PIE can be differentiated from other conditions on chest radiographs. CPAM may show up as a mass containing air-filled cysts. Respiratory distress syndrome can show air bronchograms which follow the pattern of the bronchial tree. A pneumatocoele is a gas-filled cyst which develops from ventilator-induced injury or as a sequelae of pneumonia. A congenital diaphragmatic hernia shows bowel loops in the chest cavity of the affected side and the tip of the nasogastric tube can be seen within the chest cavity if the stomach is also involved.
Question 2: the correct answer is E
The management of PIE can be challenging and is mainly supportive. The aim is to adequately ventilate non-affected areas of the lung, while avoiding overventilation of affected regions, which may lead to complications like air bullae, air leak and pneumothoraces. This can be achieved by avoiding excessive ventilation by reducing the overall mean airway pressure through reducing peak inspiratory pressure and inspiratory time to generate a suitable peak expiratory pressure.2 Switching from conventional to high frequency oscillatory ventilation can facilitate this.3 4 Lateral decubitus position with the affected side down in unilateral PIE or the worse side down in bilateral PIE is helpful as it aids plugging of the over-distended areas and aerating the contralateral lung.5 Chest physiotherapy is not very useful for this condition and should be kept to a minimum. In some situations, steroid therapy may be of benefit.6 In unilateral cases, selective main bronchial intubation of the contralateral lung or selective occlusion of the affected lung can be undertaken.7–9 In persistent unifocal cases, surgical lobectomy may be required.10 11
Question 3: the correct answer is D
PIE usually develops in preterm infants and is associated with mechanical ventilation. It has also been reported in the absence of mechanical ventilation, where babies have been spontaneously breathing or on CPAP.12–15 PIE refers to the collection of gas in the perivascular and peribronchial spaces due to rupture at bronchioalveolar junctions. The lungs in PIE are overdistended due to air leak but less compliant. Gas exchange is affected by the increased distance between the pulmonary vascular bed and the air spaces. Very low birth weight (<1500 g), high ventilator pressures and oxygen therapy are associations and the lung injury can occur due to barotrauma or volutrauma.16 17 It generally develops in babies who have respiratory distress syndrome, meconium aspiration syndrome, pneumonia and sepsis. Incorrect positioning of the endotracheal tube may predispose to localised PIE.18 These situations can result in complications such as pneumothorax, and sometimes it is only after its drainage that the changes of PIE are apparent on the chest radiograph. The use of expectant surfactant therapy in many of these conditions has resulted in improved compliance in the preterm lung and reduced the incidence of PIE. As PIE is the collection of air in the interstitial spaces, extension of this air leak can result in pneumothorax, pneumomediastinum or air embolism. Diagnosis of PIE is possible on chest radiographs. In case of any diagnostic dilemma, CT imaging of the chest would aid in diagnosing PIE, particularly where changes are persistent and surgical intervention is being considered.10 19
Contributors SR identified this patient, drafted, reviewed and approved the final manuscript.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.