Evaluation of lung volumes and gas exchange in surfactant-deficient rabbits between variable and fixed servo pressures during high-frequency jet ventilation.

OBJECTIVE: To investigate a novel servo pressure (SP) setting during high-frequency jet ventilation (HFJV) for a lung protective strategy in a neonatal model of acute respiratory distress. STUDY DESIGN: Comparison of efficacy between variable (standard) and fixed SP settings in a randomized animal study using rabbits (n = 10, mean weight = 1.80 kg) with surfactant deficiency by repeated lung lavages. RESULTS: Rabbits in the fixed SP group had greater peak inspiratory pressure, SP, minute volume, pH, and PaO2, and lower PaCO2 after lung lavage than the variable SP group. Lung volume monitoring with electrical impedance tomography showed that fixed SP reduced the decline of the global lung tidal variation at 30 min after lung lavage (-17.4% from baseline before lavage) compared to variable SP (-44.9%). CONCLUSION: HFJV with fixed SP significantly improved gas exchange and lung volumes compared to variable SP. Applying a fixed SP may have important clinical implications for patients receiving HFJV.

Surfactant therapy for COVID-19 related ARDS: a retrospective case-control pilot study.

BACKGROUND: COVID-19 causes acute respiratory distress syndrome (ARDS) and depletes the lungs of surfactant, leading to prolonged mechanical ventilation and death. The feasibility and safety of surfactant delivery in COVID-19 ARDS patients have not been established. METHODS: We performed retrospective analyses of data from patients receiving off-label use of exogenous natural surfactant during the COVID-19 pandemic. Seven COVID-19 PCR positive ARDS patients received liquid Curosurf (720 mg) in 150 ml normal saline, divided into five 30 ml aliquots) and delivered via a bronchoscope into second-generation bronchi. Patients were matched with 14 comparable subjects receiving supportive care for ARDS during the same time period. Feasibility and safety were examined as well as the duration of mechanical ventilation and mortality. RESULTS: Patients showed no evidence of acute decompensation following surfactant installation into minor bronchi. Cox regression showed a reduction of 28-days mortality within the surfactant group, though not significant. The surfactant did not increase the duration of ventilation, and health care providers did not convert to COVID-19 positive. CONCLUSIONS: Surfactant delivery through bronchoscopy at a dose of 720 mg in 150 ml normal saline is feasible and safe for COVID-19 ARDS patients and health care providers during the pandemic. Surfactant administration did not cause acute decompensation, may reduce mortality and mechanical ventilation duration in COVID-19 ARDS patients. This study supports the future performance of randomized clinical trials evaluating the efficacy of meticulous sub-bronchial lavage with surfactant as treatment for patients with COVID-19 ARDS.

A pilot study to assess short-term physiologic outcomes of transitioning infants with severe bronchopulmonary dysplasia from ICU to two subacute ventilators.

INTRODUCTION: This study was designed to evaluate short-term physiologic outcomes of transitioning neonates with bronchopulmonary dysplasia (BPD) from intensive care unit (ICU) ventilators to both the Trilogy 202 (Philips Healthcare, Andover, MA) and LTV 1200 (CareFusion, Yorba Linda, CA) subacute ventilators. METHODS: Six infants with BPD requiring tracheostomies for support with a neonatal-specific ICU ventilator underwent placement of esophageal balloon catheters, airway pressure transducers, flow sensors, oxygen saturation (SpO2), and end tidal carbon dioxide (PETCO2) monitors. Noninvasive gas exchange, airflow, and airway and esophageal pressures (PES) were recorded following 20 min on the ICU ventilator. The infants were placed on the Trilogy 202 and LTV 1200 ventilators in random order at identical settings as the ICU ventilator. We measured noninvasive gas exchange, pressure-rate product (respiratory rate × ΔPES), ventilator response times, and the percentage of spontaneous breaths that triggered the ventilator at 20 min in each subject while being supported with each of the different subacute ventilators. RESULTS: The mean (SD) weight of the six infants was 4.983 (0.56) kg. There were no differences in heart rate (p = 0.51) or SpO2 (p = 0.97) but lower PETCO2, ΔPES, respiratory rate, pressure rate-product, response times, and greater percentage of subject initiated breaths that triggered the ventilator (p < 0.05) was observed with the Trilogy 202 than the LTV 1200. All six infants transitioned successfully from the ICU ventilator to the Trilogy 202 ventilator. CONCLUSION: In this small group of infants with BPD, the Trilogy 202 ventilator performed better than the LTV 1200. The improved subject efforts, per cent subject triggering, and response times observed with the Trilogy are likely related to differences in triggering algorithms, location of triggering mechanisms, and gas delivery system performance within the ventilators. These pilot data may be useful for informing future clinical study design and understanding differences in the level of support provided by different subacute ventilators in infants with BPD.

Spirometry-Assisted High Resolution Chest Computed Tomography in Children: Is it Worth the Effort?

BACKGROUND: Image quality of high resolution chest computed tomographies (HRCTs) depends on adequate breath holds at end inspiration and end expiration. We hypothesized that implementation of spirometry-assisted breath holds in children undergoing HRCTs would improve image quality over that obtained with voluntary breath holds by decreasing motion artifact and atelectasis. METHODS: This is a retrospective case-control study of HRCTs obtained at a tertiary care children's hospital before and after implementation of a spirometry-assisted CT protocol, in which children ≥8 years of age are first trained in supine slow vital capacity maneuvers and then repeat the maneuvers in the CT scanner, coached by a respiratory therapist. Spirometry-assisted CT scans (cases) were matched by age, gender and diagnosis (cystic fibrosis vs other) to CT scans obtained with voluntary breath holds in the 6 years before implementation of the spirometry assistance protocol (controls), and evaluated by 2 blinded pediatric radiologists. RESULTS: Among both cases and controls (N = 50 each), 10 carried the diagnosis of cystic fibrosis and 40 had other diagnoses. Mean age was 12.9 years (range: 7.5-20.1) among cases and 13.0 (7.1-19.7) among controls. Mean (SD) inspiratory image density among cases was -852 (37) Hounsfield units (HU) and -828 (43) among controls (p = 0.006). Mean (SD) expiratory image density was -629 (95) HU among cases and -688 (83) HU among controls (p = 0.002). Mean (SD) change in image density between inspiratory and expiratory images was +222 (85) HU among cases and +140 (76) HU among controls (p < 0.001). Motion artifact was present on inspiratory images in 5 cases and 9 controls (p = 0.39 by Fisher's exact test), and on expiratory images in 20 cases and 18 controls (p > 0.80). Atelectasis was present on inspiratory images in 8 cases and 9 controls and on expiratory images in 9 cases and 10 controls (p > 0.80). CONCLUSIONS: Spirometry-assisted CTs had a significantly greater difference in lung density between inspiratory and expiratory scans than those performed with voluntary breath holds, likely improving the ability to detect air trapping. No appreciable difference in image quality was detected for the presence of motion artifact or atelectasis.

Effective gas exchange in paralyzed juvenile rabbits using simple, inexpensive respiratory support devices.

We have developed two devices: a high-amplitude bubble continuous positive airway pressure (HAB-CPAP) and an inexpensive bubble intermittent mandatory ventilator (B-IMV) to test the hypotheses that simple, inexpensive devices can provide gas exchange similar to that of bubble CPAP (B-CPAP) and conventional mechanical ventilation (CMV). Twelve paralyzed juvenile rabbits were intubated, stabilized on CMV, and then switched to CPAP. On identical mean airway pressures (MAPs), animals were unable to maintain pulse oximeter oxygen saturation (SpO2) >80% on conventional B-CPAP, but all animals oxygenated well (97.3 ± 2.1%) on HAB-CPAP. In fact, arterial partial pressures of O2 (Pao2) were higher during HAB-CPAP than during CMV (p = 0.01). After repeated lung lavages, arterial partial pressures of CO2 (Paco2) were lower with B-IMV than with CMV (p < 0.0001), despite identical ventilator settings. In lavaged animals, when HAB-CPAP was compared with CMV at the same MAP and 100% O2, no differences were observed in Pao2, but Paco2 levels were higher with HAB-CPAP (70 ± 7 versus 50 ± 5 mm Hg; p < 0.05). Arterial blood pressures were not impaired by HAB-CPAP or B-IMV. The results confirm that simple inexpensive devices can provide respiratory support in the face of severe lung disease and could extend the use of respiratory support for preterm infants into severely resource-limited settings.

The effects of flexible bronchoscopy on mechanical ventilation in a pediatric lung model.

BACKGROUND: Flexible bronchoscopy performed through endotracheal tubes (ETTs) in children receiving mechanical ventilation can significantly impact ventilation, but the magnitude of this impact has not been established. We used a lung model to simulate mechanical ventilation in a range of child sizes in order to determine how the insertion of pediatric flexible bronchoscopes into ETTs alters ventilatory parameters, especially tidal volume (Vt) and peak inspiratory pressure (PIP), in both healthy and diseased lungs. METHODS: We simulated five child sizes based on weight, and evaluated 22 bronchoscope/ETT combinations, first in pressure control (PC) ventilation mode and then in volume control (VC) ventilation mode. The combinations ranged from the 2.2-mm (bronchoscope outer diameter)/3.0-mm (ETT inner diameter) to 5.0-mm bronchoscope/8.0-mm ETT. The primary outcome measures were decrease in Vt after bronchoscope insertion during PC ventilation and increase in PIP during VC ventilation. RESULTS: In the PC ventilator mode, Vt decreased by > 50% with nine of the combinations, while during VC ventilation, PIP increased by >or= 20 cm H(2)O with seven combinations. The 2.2-mm bronchoscope/3.0-mm ETT, 2.8-mm bronchoscope/5.0-mm ETT, and 3.6-mm bronchoscope/5.0-mm ETT combinations severely impaired ventilation, while the 3.6-mm bronchoscope/4.5-mm ETT, 5.0-mm bronchoscope/6.5-mm ETT, and 5.0-mm bronchoscope/7.0-mm ETT combinations were incompatible with adequate ventilation. CONCLUSIONS: The insertion of bronchoscopes into ETTs can lead to clinically relevant decreases in Vt when in the PC ventilator mode and large increases in PIP during VC ventilation. The minimum bronchoscope/ETT diameter difference required to maintain adequate ventilation increases with child size.