Receipt of high-frequency ventilation is associated with acute kidney injury in very preterm neonates.

BACKGROUND: High-frequency ventilation (HFV) is frequently used in critically ill preterm neonates. We aimed to determine the incidence of acute kidney injury (AKI) in neonates less than 29 weeks gestation who received HFV in the first week of life and to determine if the rates of AKI differed in those who received other forms of respiratory support. METHODS: This retrospective cohort study of 24 international, level III/IV neonatal intensive care units (NICUs) included neonates less than 29 weeks gestation from the AWAKEN study database. Exclusion criteria included the following: no intravenous fluids ≥ 48 h, admission ≥ 14 days of life, congenital heart disease requiring surgical repair at < 7 days of life, lethal chromosomal anomaly, death within 48 h, severe congenital kidney abnormalities, inability to determine AKI status, insufficient data on ventilation, and when the diagnosis of early AKI was unable to be made. Subjects were grouped into three groups based on ventilation modes (CPAP/no ventilation, conventional ventilation, and HFV). RESULTS: The incidence of AKI was highest in the CPAP/no ventilation group, followed by HFV, followed by conventional ventilation (CPAP/no ventilation 48.5% vs. HFV 42.6% vs. conventional ventilation 28.4% (p = 0.009). An increased risk for AKI was found for those on HFV compared to CPAP/no ventilation (HR = 2.65; 95% CI:1.22-5.73). CONCLUSIONS: HFV is associated with AKI in the first week of life. Neonates on HFV should be screened for AKI. The reasons for this association are not clear. Further studies should evaluate the relationship between ventilator strategies and AKI in premature neonates. A higher resolution version of the Graphical abstract is available as Supplementary information.

Venovenous extracorporeal membrane oxygenation for respiratory failure refractory to high frequency percussive ventilation.

BACKGROUND: High frequency percussive ventilation (HFPV) has demonstrated improvements in gas exchange, but not in clinical outcomes. OBJECTIVES: We utilize HFPV in patients failing conventional ventilation (CV), with rescue venovenous extracorporeal membrane oxygenation (VV ECMO) reserved for failure of HFPV, and we describe our experience with such a strategy. METHODS: All adult patients (age >18 years) placed on HFPV for failure of CV at a single institution over a 10-year period were included. Those maintained on HFPV were compared to those that failed HFPV and required VV ECMO. Survival was compared to expected survival after upfront VV ECMO as estimated by VV ECMO risk prediction models. RESULTS: Sixty-four patients were placed on HFPV for failure of CV over a 10-year period. After HFPV initiation, the P/F ratio rose from 76mmHg to 153.3mmHg in the 69 % of patients successfully maintained on HFPV. The P/F ratio only rose from 60.3mmHg to 67mmHg in the other 31 % of patients, and they underwent rescue ECMO with the P/F ratio rising to 261.6mmHg. The P/F ratio continued to improve in HFPV patients, while it declined in ECMO patients, such that at 24 h, the P/F ratio was greater in HFPV patients. The strongest independent predictor of failure of HFPV requiring rescue VV ECMO was a lower pO2 (p = .055). Overall in-hospital survival (59.4 %) was similar to that expected with upfront ECMO (RESP score: 57 %). CONCLUSIONS: HFPV demonstrated significant and sustained improvements in gas exchange and may obviate the need for ECMO and its associated complications.

The outcome of high-frequency oscillatory ventilation in pediatric patients with acute respiratory distress syndrome in an intensive care unit.

BACKGROUND: In adults with acute respiratory distress syndrome (ARDS), high-frequency oscillatory ventilation (HFOV) has been associated with higher mortality rates. Therefore, its use in children with ARDS is still controversial. OBJECTIVES: Evaluate the overall mortality of HFOV in children with ARDS and explore mortality-related risk factors; compare the outcome of using HFOV post-endotracheal intubation early (≤24 hours) versus late (≤24 hours). DESIGN: Retrospective (medical record review) SETTING: Pediatric intensive care unit in a tertiary care center in Saudi Arabia. PATIENTS AND METHODS: Data were collected from medical records of all pediatric patients with ARDS aged one week to 14 years, who were admitted to the pediatric intensive care unit (PICU) from January 2016-June 2019 and who required HFOV. MAIN OUTCOME MEASURES: PICU mortality. SAMPLE SIZE AND CHARACTERISTICS: 135 ARDS patients including 74 females (54.8%), and 61 males (45.2%), with a median age (interquar-tile range) of 35 (72) months. RESULTS: The overall mortality rate was 60.0% (81/135), and most died in the first 28 days in the PICU (91.3%, 74/8). Of non-survivors, 75.3% (61/81) were immunocompromised, and 24.7% (20/81) were immuno-competent patients, 52 (64.2%) received inotropic support, 40 (49.4%) had a bone-marrow transplant (BMT) before HFOV initiation. Although the prone position was used in 20.7% (28/135) to improve the survival rate post-HFOV ventilation, only 28.6% (8/28) survived. In addition, altered code status or chemotherapy reported a significant association with mortality (P<.05). Interestingly, early HFOV initiation (≤24 hours) did not seem to have a high impact on survival compared to late initiation (>24 hours); (57.4% vs. 42.6%, P=.721). CONCLUSION: Immunocompromised and oncology patients, including post-BMT, reported poorer outcomes, and neither the prone position nor early use of HFOV improved outcomes. However, it is recommended to replicate the study in a larger cohort to generalize the results. LIMITATIONS: Retrospective single-center study.

A review of the utility of high-frequency oscillatory ventilation in burn and trauma ICU patients.

PURPOSE OF REVIEW: The purpose was to examine the utility of high-frequency oscillatory ventilation (HFOV) in trauma and burn ICU patients who require mechanical ventilation, and provide recommendations on its use. RECENT FINDINGS: HFOV may be beneficial in burn patients with smoke inhalation injury with or without acute lung injury/acute respiratory distress syndrome (ARDS), as it improves oxygenation and minimizes ventilator-induced lung injury. It also may have a role in improving oxygenation in trauma patients with blast lung injury, pulmonary contusions, pneumothorax with massive air leak, and ARDS; however, the mortality benefit is unknown. SUMMARY: Although some studies have shown promise and improved outcomes associated with HFOV, we recommend its use as a rescue modality for patients who have failed conventional ventilation.

High-Frequency Oscillatory Ventilation for Refractory Hypoxemia in Severe COVID-19 Pneumonia: A Small Case Series.

BACKGROUND COVID-19 continues to place a tremendous burden on the healthcare system, with most deaths resulting from respiratory failure. Management strategies have varied, but the mortality rate for mechanically ventilated patients remains high. Conventional management with ARDSnet ventilation can improve outcomes but alternative and adjunct treatments continue to be explored. High-frequency oscillatory ventilation (HFOV), a modality now rarely used in adult critical care medicine, may offer an alternative treatment option by maximizing lung protection and limiting oxygen toxicity in critically ill patients failing conventional ventilator strategies. CASE REPORT We present 3 patients with severe acute respiratory distress syndrome (ARDS) and sepsis due to COVID-19 who all improved clinically after transitioning from conventional ventilation to HFOV. Two patients developed refractory hypoxemia with hemodynamic instability and multiple organ failure requiring vasopressor support and renal replacement therapy. After failing to improve with all available therapies, both patients stabilized and ultimately improved after being placed on HFOV. The third patient developed severe volutrauma/barotrauma despite extreme lung protection and ARDSnet ventilation. He showed improvement in oxygenation and signs of lung trauma slowly improved after initiating HFOV. All 3 patients were ultimately liberated from mechanical ventilation and discharged from the hospital to return to functional independence. CONCLUSIONS Our experience suggests that HFOV offers advantages in the management of certain critically ill patients with ARDS due to COVID-19 pneumonia and might be considered in cases refractory to standard management strategies.

Non-invasive respiratory support for the management of transient tachypnea of the newborn.

BACKGROUND: Transient tachypnea of the newborn (TTN) is characterized by tachypnea and signs of respiratory distress. Transient tachypnea typically appears within the first two hours of life in term and late preterm newborns. Supportive management might be sufficient. Non-invasive (i.e. without endotracheal intubation) respiratory support may, however, be administered to reduce respiratory distress during TTN. In addition, non-invasive respiratory support might improve clearance of lung liquid thus reducing the effort required to breathe, improving respiratory distress and potentially reducing the duration of tachypnea. OBJECTIVES: To assess benefits and harms of non-invasive respiratory support for the management of transient tachypnea of the newborn. SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2019, Issue 2), MEDLINE (1996 to 19 February 2019), Embase (1980 to 19 February 2019) and CINAHL (1982 to 19 February 2019). We applied no language restrictions. We searched clinical trial registries for ongoing studies. SELECTION CRITERIA: Randomized controlled trials, quasi-randomized controlled trials and cluster trials on non-invasive respiratory support provided to infants born at 34 weeks' gestational age or more and less than three days of age with transient tachypnea of the newborn. DATA COLLECTION AND ANALYSIS: For each of the included trials, two review authors independently extracted data (e.g. number of participants, birth weight, gestational age, duration of oxygen therapy, need for continuous positive airway pressure [CPAP] and need for mechanical ventilation, duration of mechanical ventilation, etc.) and assessed the risk of bias (e.g. adequacy of randomization, blinding, completeness of follow-up). The primary outcomes considered in this review were need for mechanical ventilation and pneumothorax. We used the GRADE approach to assess the certainty of evidence. MAIN RESULTS: We included three trials (150 infants) comparing either CPAP to free-flow oxygen, nasal intermittent mandatory ventilation to nasal CPAP, or nasal high-frequency percussive ventilation versus nasal CPAP. Due to these different comparisons and to high clinical heterogeneity in the baseline clinical characteristics, we did not pool the three studies. The use of CPAP versus free oxygen did not improve the primary outcomes of this review: need for mechanical ventilation (risk ratio [RR] 0.30, 95% confidence interval [CI] 0.01 to 6.99; 1 study, 64 participants); and pneumothorax (not estimable, no cases occurred). Among secondary outcomes, CPAP reduced the duration of tachypnea as compared to free oxygen (mean difference [MD] -21.10 hours, 95% CI -22.92 to -19.28; 1 study, 64 participants). Nasal intermittent ventilation did not reduce the need for mechanical ventilation as compared with CPAP (RR 4.00, 95% CI 0.49 to 32.72; 1 study, 40 participants) or the incidence of pneumothorax (RR 1.00, 95% CI 0.07 to 14.90; 1 study, 40 participants); duration of tachypnea did not differ (MD 4.30, 95% CI -19.14 to 27.74; 1 study, 40 participants). In the study comparing nasal high-frequency ventilation to CPAP, no cases of mechanical ventilation of pneumothorax occurred (not estimable; 1 study, 46 participants); duration of tachypnea was reduced in the nasal high-frequency ventilation group (MD -4.53, 95% CI -5.64 to -3.42; 1 study, 46 participants). The quality of the evidence was very low due to the imprecision of the estimates and unclear risk of bias for detection bias and high risk of bias for reporting bias. Tests for heterogeneity were not applicable for any of the analyses as no studies were pooled. Two trials are ongoing. AUTHORS' CONCLUSIONS: There is insufficient evidence to establish the benefit and harms of non-invasive respiratory support in the management of transient tachypnea of the newborn. Though two of the included trials showed a shorter duration of tachypnea, clinically relevant outcomes did not differ amongst the groups. Given the limited and low quality of the evidence available, it was impossible to determine whether non-invasive respiratory support was safe or effective for the treatment of transient tachypnea of the newborn.

DCO2/PaCO2 correlation on high-frequency oscillatory ventilation combined with volume guarantee using increasing frequencies in an animal model.

To examine the correlation DCO2/PaCO2 on high-frequency oscillatory ventilation (HFOV) combined with volume guarantee (VG) throughout increasing frequencies in two different respiratory conditions, physiological and low compliance. Neonatal animal model was used, before and after a bronchoalveolar lavage (BAL). HFOV combined with VG was used. The frequency was increased from 10 to 20 Hz, and high-frequency tidal volume (VThf) was gradually decreased maintaining a constant DCO2. Arterial partial pressure of carbon dioxide (PaCO2) was evaluated after each frequency and VThf change. Six 2-day-old piglets were studied. A linear decrease in PaCO2 was observed throughout increasing frequencies in both respiratory conditions while maintaining a constant DCO2, showing a significant difference between the initial PaCO2 (at 10 Hz) and the PaCO2 obtained at 18 and 20 Hz. A new DCO2 equation (corrected DCO2) was calculated in order to better define the correlation between DCO2 and the observed PaCO2.Conclusion: The correlation DCO2/PaCO2 throughout increasing frequencies is not linear, showing a greater CO2 elimination efficiency at higher frequencies, in spite of maintaining a constant DCO2. So, using frequencies close to the resonant frequency of the respiratory system on HFOV combined with VG, optimizes the efficiency of gas exchange.What is Known: • The efficacy of CO2removal during high-frequency oscillatory ventilation (HFOV), described as the diffusion coefficient of CO2(DCO2) is related to the square of the high-frequency tidal volume (VThf) and the frequency (f), expressed as DCO2= VThf2× f.What is New: • The correlation between DCO2and PaCO2throughout increasing frequencies is not linear, showing a greater CO2elimination efficiency at higher frequencies. So, using very high frequencies on HFOV combined with volume guarantee optimizes the efficiency of gas exchange allowing to minimize lung injury.

Current views of complications associated with neonatal ventilation.

Infants born prematurely require external respiratory support device like ventilation for the purpose of life saving. However, these ventilation machines have complications that sometimes unfortunately result in morbidity. New ventilation techniques have been developed to prevent morbidity, but have yet to be fully evaluated. The present review article would discuss current aspects of this life saving gear especially for pediatric patients in clinical setting. Besides basic ventilation apparatus, advancements in the filed like proportional assist ventilation, volume targeted ventilation would be discussed.

An Asian multicenter retrospective study on persistent pulmonary hypertension of the newborn: incidence, etiology, diagnosis, treatment and outcome.

Objectives: To explore the incidence, etiologies, diagnostic methods, treatment options and outcomes in neonates with persistent pulmonary hypertension of the newborn (PPHN) and to identify mortality risk factors in a study from six Asian countries.Methods: A retrospective chart review of patients with documented PPHN from seven centers in six Asian countries (Japan, Kuwait, India, Pakistan, Singapore, and Thailand) between 1 January, 2014 and 31 December, 2016, was performed.Results: A total of 369 PPHN infants were identified. The incidence of PPHN ranged from 1.2 to 4.6 per 1000 live births. The all-cause mortality rate was 20.6% (76 of 369). Meconium aspiration syndrome was the primary cause of PPHN (24.1%). In most cases (84.8%) echocardiography was used to establish the diagnosis of PPHN. Sildenafil was the most commonly used pulmonary vasodilator (51.2%). Multivariate multiple regression analysis indicated gestational age <34 weeks (adjusted odds ratio (OR) = 3.27; 95% CI 1.56-6.74), congenital diaphragmatic hernia (CDH)/lung hypoplasia (LH) (adjusted OR = 6.13 (95% CI 2.28-16.42)), treatment with high frequency oscillation ventilation (HFOV) with or without inhaled nitric oxide (iNO) (adjusted OR = 3.11 (95% CI 1.52-6.34)), and inotropic agents (adjusted OR = 9.43 (95% CI 2.71-32.83)) were independently associated with increased risk of death.Conclusions: The incidence of PPHN in the current study was higher than in western settings. Birth weight, gestational age, CDH/LH, HFOV/iNO, and inotropic agents were significant mortality risk factors.

High-Frequency Oscillatory Ventilation and Ventilator-Induced Lung Injury: Size Does Matter.

OBJECTIVES: The theoretical basis for minimizing tidal volume during high-frequency oscillatory ventilation may not be appropriate when lung tissue stretch occurs heterogeneously and/or rapidly. The objective of this study was to assess the extent to which increased ventilation heterogeneity may contribute to ventilator-induced lung injury during high-frequency oscillatory ventilation in adults compared with neonates on the basis of lung size, using a computational model of human lungs. DESIGN: Computational modeling study. SETTING: Research laboratory. SUBJECTS: High-fidelity, 3D computational models of human lungs, scaled to various sizes representative of neonates, children, and adults, with varying injury severity. All models were generated from one thoracic CT image of a healthy adult male. INTERVENTIONS: Oscillatory ventilation was simulated in each lung model at frequencies ranging from 0.2 to 40 Hz. Sinusoidal flow oscillations were delivered at the airway opening of each model and distributed through the lungs according to regional parenchymal mechanics. MEASUREMENTS AND MAIN RESULTS: Acinar flow heterogeneity was assessed by the coefficient of variation in flow magnitudes across all acini in each model. High-frequency oscillatory ventilation simulations demonstrated increasing heterogeneity of regional parenchymal flow with increasing lung size, with decreasing ratio of deadspace to total acinar volume, and with increasing frequency above lung corner frequency and resonant frequency. Potential for resonant amplification was greatest in injured adult-sized lungs with higher regional quality factors indicating the presence of underdamped lung regions. CONCLUSIONS: The potential for ventilator-induced lung injury during high-frequency oscillatory ventilation is enhanced at frequencies above lung corner frequency or resonant frequency despite reduced tidal volumes, especially in adults, due to regional amplification of heterogeneous flow. Measurements of corner frequency and resonant frequency should be considered during high-frequency oscillatory ventilation management.

Tension pneumoperitoneum caused by rupture of intraabdominal soft tissue emphysema in a child supported with high-frequency oscillatory ventilation: a case report.

BACKGROUND: We reported a case with tension pneumoperitoneum while being on high-frequency oscillatory ventilation. CASE PRESENTATION: A 12-month-old Thai girl presented with acute respiratory distress syndrome, septic shock, and bacterial pneumonia. Although supported with mechanical ventilation, she still had severe hypoxia. She was then transitioned to high-frequency oscillatory ventilation. During a weaning period on day 7, she developed left tension pneumothorax requiring intercostal drainage and a markedly large amount of pneumoperitoneum. In spite of a bedside abdominocentesis, her abdomen was still tense and her hemodynamics was unstable. Subsequently, to exclude hollow viscus perforation, diaphragmatic injury caused by intercostal drainage, or abdominal compartment syndrome, she was transferred for surgery. There was no intestinal perforation. Postoperatively, she was on oxygen therapy, on chest physical therapy, and kept hemodynamically stable until she had recovered. CONCLUSION: A case of tension pneumoperitoneum probably caused by high-frequency oscillatory ventilation was reported. Awareness of this condition should be included in the differential diagnosis.

Inflammatory lung injury in rabbits: effects of high-frequency oscillatory ventilation in the prone position.

OBJECTIVE: To compare the effects that prone and supine positioning during high-frequency oscillatory ventilation (HFOV) have on oxygenation and lung inflammation, histological injury, and oxidative stress in a rabbit model of acute lung injury (ALI). METHODS: Thirty male Norfolk white rabbits were induced to ALI by tracheal saline lavage (30 mL/kg, 38°C). The injury was induced during conventional mechanical ventilation, and ALI was considered confirmed when a PaO2/FiO2 ratio < 100 mmHg was reached. Rabbits were randomly divided into two groups: HFOV in the supine position (SP group, n = 15); and HFOV with prone positioning (PP group, n = 15). For HFOV, the mean airway pressure was initially set at 16 cmH2O. At 30, 60, and 90 min after the start of the HFOV protocol, the mean airway pressure was reduced to 14, 12, and 10 cmH2O, respectively. At 120 min, the animals were returned to or remained in the supine position for an extra 30 min. We evaluated oxygenation indices and histological lung injury scores, as well as TNF-α levels in BAL fluid and lung tissue. RESULTS: After ALI induction, all of the animals showed significant hypoxemia, decreased respiratory system compliance, decreased oxygenation, and increased mean airway pressure in comparison with the baseline values. There were no statistically significant differences between the two groups, at any of the time points evaluated, in terms of the PaO2 or oxygenation index. However, TNF-α levels in BAL fluid were significantly lower in the PP group than in the SP group, as were histological lung injury scores. CONCLUSIONS: Prone positioning appears to attenuate inflammatory and histological lung injury during HFOV in rabbits with ALI.

Use of very low tidal volumes during high-frequency ventilation reduces ventilator lung injury.

The use of volume guarantee (VG) on high-frequency oscillatory ventilation (HFOV) allows to use fixed very low high-frequency tidal volume (VThf), maintaining adequate CO2 removal while potentially reducing the risk of ventilator-induced lung injury. OBJECTIVE: To demonstrate that the use of very low VThf can be protective compared with standard VThf on HFOV combined with VG in a neonatal animal model. STUDY DESIGN: Experimental study in 2-day-old piglets with induced respiratory distress syndrome ventilated with two different HFOV strategies combined with VG (10 Hz with high VThf versus 20 Hz with very low VThf at similar PaCO2). After 12 h of mechanical ventilation, the pulmonary histologic pattern was analyzed. RESULTS: We found in the 10 Hz group with the higher VThf compared with the 20 Hz and very low VThf group more evident and more severe histological lesions with inflammatory infiltrate within the alveolar wall and alveolar space, as well as large areas of parenchyma consolidation and areas of alveolar hemorrhage in the more severe cases. CONCLUSION: The use of very low VThf compared with higher VThf at similar CO2 removal reduces lung injury in a neonatal animal model of lung injury after prolonged mechanical ventilation with HFOV combined with VG.

Lung Lavage with Dilute Surfactant vs. Bolus Surfactant for Meconium Aspiration Syndrome.

OBJECTIVE: To compare the effectiveness of lung lavage with surfactant vs. bolus surfactant treatment in meconium aspiration syndrome (MAS). PATIENTS AND METHODS: This randomized controlled trial included newborns ventilated with MAS. In lavage group (n = 17) 30 ml/kg of diluted porcine surfactant was instilled into the lung. In bolus group (n = 16) porcine surfactant (100 mg/kg) was administered as bolus. Respiratory outcomes and mortality were compared between groups. RESULTS: Duration of respiratory support was found to be similar between lavage and bolus groups (3 vs. 3.5 days, p = 0.36). Death or requirement for extracorporeal membrane oxygenation (ECMO) was 12% vs. 6%; respectively (RR: 2, 95% CI 0.16-24.48; p = 1.0). Duration of oxygen therapy, high-frequency ventilation or inhaled nitric oxide requirement did not differ among the groups. CONCLUSION: Lung lavage did not show any advantage over bolus therapy on duration of respiratory support. The incidence of pneumothorax and surfactant re-administration decreased nonsignificantly in lavage group. CLINICAL TRIAL REGISTRATION: We registered the trial to ClinicalTrials.gov (http://clinicaltrials.gov) under identifier NCT02041546. REGISTRY NAME: Lung Lavage With Dilute Poractant Alfa for Meconium Aspiration Syndrome.

Predictors of Respiratory Improvement 1 Week after Ligation of Patent Ductus Arteriosus in Preterm Infants.

OBJECTIVE: To characterize preterm infants that demonstrates respiratory improvement 7 days after ligation of a patent ductus arteriosus (PDA). STUDY DESIGN: We performed a 2-phase study of preterm infants (birthweight <1500 g between 2010 and 2016). We first did a retrospective analysis using regression modeling of ligation population. We then performed a case-control study comparing a ligation group with infants matched by gestational age, postnatal age, and preligation respiratory condition (ventilator mode, mean airway pressure [MAP], and fraction of inspired oxygen [FiO2]). Respiratory improvement was defined as either extubation, downgrading of ventilatory mode, reduction in MAP >25%, or decrease in FiO2 >25%. RESULTS: Forty-five (42%) of 107 preterm infants (gestational age 25.5 ± 1.7 weeks) with ligation showed respiratory improvement at 7 days. Infants on high frequency ventilation (HFV) were more likely to have respiratory improvement (aOR 5.03, 95% CI [1.14-22.18]). In matched-control analysis of 89 pairs, there was no difference in respiratory improvement. Among infants on HFV, the ligation group had an increase in MAP during 3 days prior to ligation. For infants on conventional ventilation, the ligation group had higher MAP and FiO2 than the control group during the first 2-3 postoperative days. CONCLUSIONS: Among infants undergoing PDA ligation, those on HFV were more likely to have respiratory improvement in the first week, possibly because of the prevention of further respiratory deterioration. For infants on conventional ventilation, ligation was associated with higher respiratory support in the immediate postligation period without respiratory benefits at 7 days. As HFV was used as a rescue mode, our findings suggest that those with worse lung disease may achieve greater short term benefit from PDA ligation.

Ambient Noise Production by High-Frequency Neonatal Ventilators.

OBJECTIVE: To assess sound levels of 4 high-frequency neonatal ventilators to determine whether there is a safety benefit in using modern high-frequency ventilators compared with older models. STUDY DESIGN: We performed a bench study comparing noise production of the Sensormedics 3100A Oscillator, Bunnell Life Pulse Jet Ventilators Model 203 and Model 204, and Dräger VN500 in high-frequency mode. A wide range of ventilation settings was examined. All measurements were performed in triplicate using a high-fidelity sound meter, with data analyzed using ANOVA and regression analyses. RESULTS: The Dräger ventilator was quietest overall, with average sound levels of 49.8 ± 0.49 dB across all settings. The average noise from the Sensormedics was 53.6 ± 2.01 dB, for Bunnell Model 203 was 54.1 ± 1.09 dB, and for Bunnell Model 204 was 53.7 ± 1.45 dB. Adjustments made to frequency/rate and mean airway pressure/positive end-expiratory pressure had minimal effect on noise, and increasing amplitude/peak inspiratory pressure resulted in significantly more noise by all ventilators. At all settings, the Sensormedics and Bunnell ventilators were louder than the Dräger, and the difference became greater as amplitude/peak inspiratory pressure was increased. CONCLUSIONS: The Dräger VN500 in high-frequency mode produces significantly less noise that both the Sensormedics and Bunnell ventilators. These data suggest that using the Dräger VN500 as a high-frequency ventilator may reduce the potential for adverse outcomes created by ventilator noise.

A neonate with tracheobronchial cobblestone mucosa presenting with acute severe hypercapnia.

Liu Y, Ly Li, Hu YL. A neonate with tracheobronchial cobblestone mucosa presenting with acute severe hypercapnia. Turk J Pediatr 2019; 61: 971-974. Here, we describe the case of a neonate suffering from respiratory distress complicated by pulmonary hemorrhage shortly after birth. The neonate experienced repeated dyspnea and acute severe hypercapnia (160-100 mmHg) that began on the 7th day after birth during invasive mechanical ventilation. Rescue high frequency oscillatory ventilation played a key role in maintaining gas exchange during these episodes. Subsequent bronchoscopy revealed tracheobronchial edematous mucosa with a cobblestone pattern, which we believe is the first report of this condition in neonates. Protrusion of the diffuse edematous mucosa led to airway stenosis and respiratory distress. Lesions of the tracheal mucosa should therefore be considered as one potential cause of neonatal respiratory distress.

Inflammatory lung injury in rabbits: effects of high-frequency oscillatory ventilation in the prone position / Lesão inflamatória pulmonar em coelhos: efeitos da ventilação oscilatória de alta frequência em posição prona

ABSTRACT Objective: To compare the effects that prone and supine positioning during high-frequency oscillatory ventilation (HFOV) have on oxygenation and lung inflammation, histological injury, and oxidative stress in a rabbit model of acute lung injury (ALI). Methods: Thirty male Norfolk white rabbits were induced to ALI by tracheal saline lavage (30 mL/kg, 38°C). The injury was induced during conventional mechanical ventilation, and ALI was considered confirmed when a PaO2/FiO2 ratio < 100 mmHg was reached. Rabbits were randomly divided into two groups: HFOV in the supine position (SP group, n = 15); and HFOV with prone positioning (PP group, n = 15). For HFOV, the mean airway pressure was initially set at 16 cmH2O. At 30, 60, and 90 min after the start of the HFOV protocol, the mean airway pressure was reduced to 14, 12, and 10 cmH2O, respectively. At 120 min, the animals were returned to or remained in the supine position for an extra 30 min. We evaluated oxygenation indices and histological lung injury scores, as well as TNF-α levels in BAL fluid and lung tissue. Results: After ALI induction, all of the animals showed significant hypoxemia, decreased respiratory system compliance, decreased oxygenation, and increased mean airway pressure in comparison with the baseline values. There were no statistically significant differences between the two groups, at any of the time points evaluated, in terms of the PaO2 or oxygenation index. However, TNF-α levels in BAL fluid were significantly lower in the PP group than in the SP group, as were histological lung injury scores. Conclusions: Prone positioning appears to attenuate inflammatory and histological lung injury during HFOV in rabbits with ALI.

RESUMO Objetivo: Comparar os efeitos das posições prona e supina durante ventilação oscilatória de alta frequência (VOAF) sobre oxigenação e inflamação pulmonar, lesão histológica e estresse oxidativo em um modelo de lesão pulmonar aguda (LPA) em coelhos. Métodos: Trinta coelhos Norfolk machos brancos foram submetidos à LPA por meio de lavagem traqueal com salina (30 ml/kg, 38°C). A lesão foi induzida durante a ventilação mecânica convencional, e a LPA foi considerada confirmada na presença de relação PaO2/FiO2 < 100 mmHg. Os coelhos foram aleatoriamente divididos em dois grupos: VOAF em posição supina (grupo PS, n = 15); e VOAF em posição prona (grupo PP, n = 15). Para a VOAF, a pressão média das vias aéreas foi inicialmente estabelecida em 16 cmH2O. No 30º, 60º e 90º min após o início do protocolo de VOAF, a pressão média das vias aéreas foi reduzida para 14, 12 e 10 cmH2O, respectivamente. No 120º min, os animais foram recolocados ou permaneceram na posição supina por mais 30 min. Foram avaliados os índices de oxigenação e escores histológicos de lesão pulmonar, bem como os níveis de TNF-α em lavado broncoalveolar e tecido pulmonar. Resultados: Após a indução da LPA, todos os animais apresentaram hipoxemia significativa, diminuição da complacência do sistema respiratório, diminuição da oxigenação e aumento da pressão média das vias aéreas em comparação aos valores basais. Não houve diferenças estatisticamente significativas entre os dois grupos, em nenhum dos momentos avaliados, quanto a PaO2 e índice de oxigenação. Entretanto, os níveis de TNF-α no lavado broncoalveolar foram significativamente menores no grupo PP que no grupo PS, assim como os escores histológicos de lesão pulmonar. Conclusões: A posição prona parece atenuar a lesão pulmonar inflamatória e histológica durante a VOAF em coelhos com LPA.

Pneumoperitoneum in a neonate weighing less than 500 g. What do we really know about it?

Pneumoperitoneum in preterm infants is a surgical emergency as it is usually indicative of intestinal perforation. Rare cases of idiopathic pneumoperitoneum have been described in the literature, the underlying causes and pathophysiology of which remain uncertain. We present a case of pneumoperitoneum in an extremely preterm infant with severe growth restriction. This occurred while she was receiving high frequency oscillatory ventilation. She had respiratory distress syndrome with pulmonary interstitial emphysema. The pneumoperitoneum occurred in isolation. Despite the insertion of two surgical drains and two exploratory laparotomies in which no obvious intestinal perforation was noted, the free air in the abdomen reaccumulated. A decision was made to manage it conservatively. She was successfully extubated on the fourth week of life and the pneumoperitoneum resolved spontaneously. She was discharged home on day 136 of life. This case highlights our limited understanding of the intricate physiology of extremely low birthweight preterm neonates.