Pulmonary interstitial emphysema during piston-type high-frequency oscillatory ventilation

Effect of frequency on pressure cost of ventilation and gas exchange in newborns receiving high-frequency oscillatory ventilation

BackgroundWe hypothesized that ventilating at the resonant frequency of the respiratory system optimizes gas exchange while limiting the mechanical stress to the lung in newborns receiving high-frequency oscillatory ventilation (HFOV). We characterized the frequency dependence of oscillatory mechanics, gas exchange, and pressure transmission during HFOV.MethodsWe studied 13 newborn infants with a median (interquartile range) gestational age of 29.3 (26.4-30.4) weeks and body weight of 1.00 (0.84-1.43) kg. Different frequencies (5, 8, 10, 12, and 15 Hz) were tested, keeping carbon dioxide diffusion coefficient (DCO₂) constant. Oscillatory mechanics and transcutaneous blood gas were measured at each frequency. The attenuation of pressure swings (ΔP) from the airways opening to the distal end of the tracheal tube (TT) and to the alveolar compartment was mathematically estimated.ResultsBlood gases were unaffected by frequency. The mean (SD) resonant frequency was 16.6 (3.5) Hz. Damping of ΔP increased with frequency and with lung compliance. ΔP at the distal end of the TT was insensitive to frequency, whereas ΔP at the peripheral level decreased with frequency.ConclusionThere is no optimal frequency for gas exchange when DCO₂ is held constant. Greater attenuation of oscillatory pressure at higher frequencies offers more protection from barotrauma, especially in patients with poor compliance.

Selective unilateral lung ventilation in preterm infants with acquired bullous emphysema: a series of nine cases

BACKGROUND AND AIMS

Immature lungs of preterm infants are particularly prone to overdistension from mechanical ventilation or continuous positive airway pressure. In these infants a localized pulmonary emphysema (PE) can develop. Conventional therapy regimens to resolve this process sometimes fail and especially in the case of bullous emphysema (BE) invasive procedures such as surgical resection of the affected lobe ultimately may be required. In the past few years we have applied selective one-sided lung ventilation, a nearly forgotten therapeutic option, in these infants with acquired BE.

METHODS

Medical charts of preterm infants in two Divisions of Neonatology, born between 1993 and 2010 with acquired BE treated with selective one-sided ventilation were reviewed. Gestational age, clinical presentation, course of disease, associated treatment, duration of ventilation and outcome of one-sided lung ventilation are recorded. Therapy was deemed successful if thereafter chest X-ray showed a permanent resolution of the BE and, in case of BPD, lung appearance was comparable to a grade < III according to Weinstein [Weinstein et al. Pediatr Pulmonol 1994; 18: 284-289].

RESULTS

Overall, nine preterm infants with a gestational age between 24 and 35 weeks and a birth weight between 500 and 3,170 g underwent one-sided lung ventilation. This intervention was started between day 12 and day 35 after birth and was continued for 24 hr to 7 days. In three cases selective intubation was performed on the left side. Two patients needed a second course of one-sided ventilation and one had three courses. Therapy was successful in seven patients, who had no recurrence of BE.

CONCLUSIONS

Selective one-sided intubation is technically challenging, in particular for the left bronchus, but seems to be feasible and helpful. If during selective intubation the affected lung lobe shows complete atelectasis for more than 48 hr the overdistension of airways probably will permanently resolve.

Efficacy of early piston-type high-frequency oscillatory ventilation in infants with respiratory distress syndrome

We investigated whether the combination of surfactant replacement therapy and early application of high-frequency oscillatory ventilation (HFOV) was more effective in patients with respiratory distress syndrome (RDS) than late application of HFOV and conventional mechanical ventilation (CMV). To determine this, we retrospectively reviewed the cases of 126 neonates with RDS who received surfactant replacement therapy within 4 hr after birth. Patients were grouped into those who received HFOV immediately after birth (HFOV group), those who initially were ventilated by CMV and subsequently received HFOV (CMV/HFOV group), and those who did not receive HFOV (CMV group). Changes in respiratory system compliance (Crs), arterial-alveolar oxygen gradient (a/ApO(2)), and mean airway pressure (MAP) were compared. Infants who received HFOV were less mature than those who received CMV. The a/ApO(2) measured immediately after birth before surfactant replacement therapy was significantly lower in the HFOV and CMV/HFOV group than in the CMV group. After 72 hr, the Crs in the HFOV group was higher than in any other group and was significantly higher than the CMV/HFOV group at 48 and 120 hr. These results suggest that initiating HFOV in combination with surfactant replacement therapy immediately after birth provides effective ventilatory support for infants with RDS.

Demonstration of communication between alveolus and interstitium in persistent interstitial pulmonary emphysema: case report

Persistent interstitial pulmonary emphysema (PIPE) is an uncommon complication of premature infants suffering from hyaline membrane disease who have been treated with mechanical ventilation. The presumed mechanism for the development of the disease is via a break in the bronchioalveolar system that allows air to escape into the interstitium. We report a case of a 9-week-old child who developed the localized form of the disease and underwent a lobectomy. Immunohistochemical stains helped to demonstrate the communication between the airway system and interstitium. This report strengthens the theory that the disease develops from airway rupture at the alveolar level.