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Previous studies demonstrated that high-frequency oscillatory ventilation (HFOV) begun at birth limits the development of alveolar proteinaceous edema in premature monkeys at risk for hyaline membrane disease (HMD). We hypothesized that exogenous surfactant combined with HFOV would lead to even further reductions in edema. Twenty Macaca nemestrina monkeys were delivered at 134 d gestation (term = 168 d) and treated with either HFOV or conventional mechanical ventilation (CMV) from the first breath; modified bovine surfactant (Survanta [beractant]) was introduced into the trachea over the first few minutes of life. These animals were compared with 20 animals treated with either CMV or HFOV but without surfactant. At 6 h the lung was rapidly frozen in situ during inflation for determination of the volume fraction of alveolar edema. The combined use of surfactant and HFOV from the first breath reduced alveolar proteinaceous edema (3 +/- 1%; mean +/- SEM) from that seen with CMV alone (27 +/- 3%, p < 0.0001), CMV after surfactant (21 +/- 3%, p < 0.0001), and HFOV alone (13 +/- 3%, p < 0.015). We conclude that the use of surfactant with HFOV after premature birth is superior to either surfactant or HFOV alone in reducing lung injury during the first few hours of life. We speculate that this reduction in lung injury may reduce the incidence or severity of bronchopulmonary dysplasia.

Bubble continuous positive airway pressure (B-CPAP) applies small-amplitude, high-frequency oscillations in airway pressure (⌬P aw ) that may improve gas exchange in infants with respiratory disease. We developed a device, high-amplitude B-CPAP (HAB-CPAP), which provides greater ⌬P aw than B-CPAP provides. We studied the effects of different operational parameters on ⌬P aw and volumes of gas delivered to a mechanical infant lung model. In vivo studies tested the hypothesis that HAB-CPAP provides noninvasive respiratory support greater than that provided by B-CPAP. Lavaged juvenile rabbits were stabilized on ventilator nasal CPAP. The animals were then supported at the same mean airway pressure, bias flow, and fraction of inspired oxygen (F i O 2 ) required for stabilization, whereas the bubbler angle was varied in a randomized crossover design at exit angles, relative to vertical, of 0 (HAB-CPAP0; equivalent to conventional B-CPAP), 90 (HAB-CPAP90), and 135°(HAB-CPAP135). Arterial blood gases and pressure-rate product (PRP) were measured after 15 min at each bubbler angle. PaO 2 levels were higher (p Ͻ 0.007) with HAB-CPAP135 than with conventional B-CPAP. PaCO 2 levels did not differ (p ϭ 0.073) among the three bubbler configurations. PRP with HAB-CPAP135 were half of the PRP with HAB-CPAP0 or HAB-CPAP90 (p ϭ 0.001). These results indicate that HAB-CPAP135 provides greater respiratory support than conventional B-CPAP does. (Pediatr Res 67: 624-629, 2010) B ubble-nasal continuous positive airway pressure (BnCPAP) is a form of noninvasive respiratory support that is used frequently as a primary strategy for supporting spontaneously breathing preterm infants at risk of developing respiratory distress syndrome. Compared with intubation and mechanical ventilation, the use of B-CPAP has been associated with lower indicators of acute lung injury (1) and bronchopulmonary dysplasia (2).Recent studies suggest that the bubbling of gas exiting the B-nCPAP circuit at the water seal creates oscillations in airway pressure (⌬P aw ), having broadband high frequencies (3), which may promote airway patency and enhance lung volume and gas exchange in preterm lambs (4). However, a study of 261 consecutively born premature infants revealed that 24% of infants born weighing Ͻ1250 g and 50% of infants weighing Ͻ750 g failed B-nCPAP and required endotracheal intubation and mechanical ventilation (5). In an effort to diminish the potentially deleterious effects of invasive mechanical ventilation (6), we designed a novel device, highamplitude B-CPAP (HAB-CPAP), which, through alterations in angle of gas entry at the water seal, may enhance respiratory efficiency and improve oxygenation when compared with conventional B-nCPAP.In this report, we describe a device that provides ⌬P aw higher in amplitude than B-CPAP. Studies were conducted to determine the effects of bubbler angle and bias flow on ⌬P aw and the amplitude of oscillations in volume (⌬V) delivered to a mechanical model of an infant lung. In addition, studies were con...

A method is described whereby cerebrospinal fluid (CSF) may be sampled repeatedly from awake rats over a period of 1 to 10 wk. Stainless steel or Teflon catheters (22-gauge) were implanted in the cisterna magna of anesthetized rats (n = 19) via a midline hole immediately rostral to the interparietal-occipital suture. Several days later almost simultaneous CSF and blood samples from the same air-breathing animals were slowly drawn into glass capillary tubes. pH was determined immediately by electrode and total CO2 by microgasometer. Because sampling via Tygon microbore tubing attached to the implanted catheters allowed part of CSF CO2 content to be lost through the tube wall, stainless steel tube is preferred to make this connection. For mock CSF, total CO2 calculated from pH and PCO2 values was closely comparable to that directly measured by microgasometer. CSF pH, PCO2, and [HCO-3] in five awake rats were found to be similar to those reported in the literature for the briefly anesthetized rat. The sampling procedure did not of itself significantly alter breathing patterns (n = 14). Thus, chronic CSF sampling is feasible in awake rats for purposes of studies of ventilatory control.