Non-invasive high-frequency ventilation in newborn infants with respiratory distress.

BACKGROUND: Respiratory distress occurs in up to 7% of newborns, with respiratory support (RS) provided invasively via an endotracheal (ET) tube or non-invasively via a nasal interface. Invasive ventilation increases the risk of lung injury and chronic lung disease (CLD). Using non-invasive strategies, with or without minimally invasive surfactant, may reduce the need for mechanical ventilation and the risk of lung damage in newborn infants with respiratory distress. OBJECTIVES: To evaluate the benefits and harms of nasal high-frequency ventilation (nHFV) compared to invasive ventilation via an ET tube or other non-invasive ventilation methods on morbidity and mortality in preterm and term infants with or at risk of respiratory distress. SEARCH METHODS: We searched CENTRAL, MEDLINE, Embase, CINAHL and three trial registries in April 2023. SELECTION CRITERIA: Randomised controlled trials (RCTs), cluster- or quasi-RCTs of nHFV in newborn infants with respiratory distress compared to invasive or non-invasive ventilation. DATA COLLECTION AND ANALYSIS: Two authors independently selected the trials for inclusion, extracted data, assessed the risk of bias, and undertook GRADE assessment. MAIN RESULTS: We identified 33 studies, mostly in low- to middle-income settings, that investigated this therapy in 5068 preterm and 46 term infants. nHFV compared to invasive respiratory therapy for initial RS We are very uncertain whether nHFV reduces mortality before hospital discharge (RR 0.67, 95% CI 0.20 to 2.18; 1 study, 80 infants) or the incidence of CLD (RR 0.38, 95% CI 0.09 to 1.59; 2 studies, 180 infants), both very low-certainty. ET intubation, death or CLD, severe intraventricular haemorrhage (IVH) and neurodevelopmental disability (ND) were not reported. nHFV vs nasal continuous positive airway pressure (nCPAP) used for initial RS We are very uncertain whether nHFV reduces mortality before hospital discharge (RR 1.00, 95% CI 0.41 to 2.41; 4 studies, 531 infants; very low-certainty). nHFV may reduce ET intubation (RR 0.52, 95% CI 0.33 to 0.82; 5 studies, 571 infants), but there may be little or no difference in CLD (RR 1.35, 95% CI 0.80 to 2.27; 4 studies, 481 infants); death or CLD (RR 2.50, 95% CI 0.52 to 12.01; 1 study, 68 participants); or severe IVH (RR 1.17, 95% CI 0.36 to 3.78; 4 studies, 531 infants), all low-certainty evidence. ND was not reported. nHFV vs nasal intermittent positive-pressure ventilation (nIPPV) used for initial RS nHFV may result in little to no difference in mortality before hospital discharge (RR 1.86, 95% CI 0.90 to 3.83; 2 studies, 84 infants; low-certainty). nHFV may have little or no effect in reducing ET intubation (RR 1.33, 95% CI 0.76 to 2.34; 5 studies, 228 infants; low-certainty). There may be a reduction in CLD (RR 0.63, 95% CI 0.42 to 0.95; 5 studies, 307 infants; low-certainty). A single study (36 infants) reported no events for severe IVH. Death or CLD and ND were not reported. nHFV vs high-flow nasal cannula (HFNC) used for initial RS We are very uncertain whether nHFV reduces ET intubation (RR 2.94, 95% CI 0.65 to 13.27; 1 study, 37 infants) or reduces CLD (RR 1.18, 95% CI 0.46 to 2.98; 1 study, 37 participants), both very low-certainty. There were no mortality events before hospital discharge or severe IVH. Other deaths, CLD and ND, were not reported. nHFV vs nCPAP used for RS following planned extubation nHFV probably results in little or no difference in mortality before hospital discharge (RR 0.92, 95% CI 0.52 to 1.64; 6 studies, 1472 infants; moderate-certainty). nHFV may result in a reduction in ET reintubation (RR 0.42, 95% CI 0.35 to 0.51; 11 studies, 1897 infants) and CLD (RR 0.78, 95% CI 0.67 to 0.91; 10 studies, 1829 infants), both low-certainty. nHFV probably has little or no effect on death or CLD (RR 0.90, 95% CI 0.77 to 1.06; 2 studies, 966 infants) and severe IVH (RR 0.80, 95% CI 0.57 to 1.13; 3 studies, 1117 infants), both moderate-certainty. We are very uncertain whether nHFV reduces ND (RR 0.92, 95% CI 0.37 to 2.29; 1 study, 74 infants; very low-certainty). nHFV versus nIPPV used for RS following planned extubation nHFV may have little or no effect on mortality before hospital discharge (RR 1.83, 95% CI 0.70 to 4.79; 2 studies, 984 infants; low-certainty). There is probably a reduction in ET reintubation (RR 0.69, 95% CI 0.54 to 0.89; 6 studies, 1364 infants), but little or no effect on CLD (RR 0.88, 95% CI 0.75 to 1.04; 4 studies, 1236 infants); death or CLD (RR 0.92, 95% CI 0.79 to 1.08; 3 studies, 1070 infants); or severe IVH (RR 0.78, 95% CI 0.55 to 1.10; 4 studies, 1162 infants), all moderate-certainty. One study reported there might be no difference in ND (RR 0.88, 95% CI 0.35 to 2.16; 1 study, 72 infants; low-certainty). nHFV versus nIPPV following initial non-invasive RS failure nHFV may have little or no effect on mortality before hospital discharge (RR 1.44, 95% CI 0.10 to 21.33); or ET intubation (RR 1.23, 95% CI 0.51 to 2.98); or CLD (RR 1.01, 95% CI 0.70 to 1.47); or severe IVH (RR 0.47, 95% CI 0.02 to 10.87); 1 study, 39 participants, all low- or very low-certainty. Other deaths or CLD and ND were not reported. AUTHORS' CONCLUSIONS: For initial RS, we are very uncertain if using nHFV compared to invasive respiratory therapy affects clinical outcomes. However, nHFV may reduce intubation when compared to nCPAP. For planned extubation, nHFV may reduce the risk of reintubation compared to nCPAP and nIPPV. nHFV may reduce the risk of CLD when compared to nCPAP. Following initial non-invasive respiratory support failure, nHFV when compared to nIPPV may result in little to no difference in intubation. Large trials, particularly in high-income settings, are needed to determine the role of nHFV in initial RS and following the failure of other non-invasive respiratory support. Also, the optimal settings of nHVF require further investigation.

Benefits of intratracheal and extrathoracic high-frequency percussive ventilation in a model of capnoperitoneum.

Abdominal inflation with CO2 is used to facilitate laparoscopic surgeries, however, providing adequate mechanical ventilation in this scenario is of major importance during anesthesia management. We characterized high-frequency percussive ventilation (HFPV) in protecting from the gas exchange and respiratory mechanical impairments during capnoperitoneum. In addition, we aimed to assess the difference between conventional pressure-controlled mechanical ventilation (CMV) and HFPV modalities generating the high-frequency signal intratracheally (HFPVi) or extrathoracally (HFPVe). Anesthetized rabbits (n = 16) were mechanically ventilated by random sequences of CMV, HFPVi, and HFPVe. The ventilator superimposed the conventional waveform with two high-frequency signals (5 Hz and 10 Hz) during intratracheal HFPV (HFPVi) and HFPV with extrathoracic application of oscillatory signals through a sealed chest cuirass (HFPVe). Lung oxygenation index ([Formula: see text]/[Formula: see text]), arterial partial pressure of carbon dioxide ([Formula: see text]), intrapulmonary shunt (Qs/Qt), and respiratory mechanics were assessed before abdominal inflation, during capnoperitoneum, and after abdominal deflation. Compared with CMV, HFPVi with additional 5-Hz oscillations during capnoperitoneum resulted in higher [Formula: see text]/[Formula: see text], lower [Formula: see text], and decreased Qs/Qt. These improvements were smaller but remained significant during HFPVi with 10 Hz and HFPVe with either 5 or 10 Hz. The ventilation modes did not protect against capnoperitoneum-induced deteriorations in respiratory tissue mechanics. These findings suggest that high-frequency oscillations combined with conventional pressure-controlled ventilation improved lung oxygenation and CO2 removal in a model of capnoperitoneum. Compared with extrathoracic pressure oscillations, intratracheal generation of oscillatory pressure bursts appeared more effective. These findings may contribute to the optimization of mechanical ventilation during laparoscopic surgery.NEW & NOTEWORTHY The present study examines an alternative and innovative mechanical ventilation modality in improving oxygen delivery, CO2 clearance, and respiratory mechanical abnormalities in a clinically relevant experimental model of capnoperitoneum. Our data reveal that high-frequency oscillations combined with conventional ventilation improve gas exchange, with intratracheal oscillations being more effective than extrathoracic oscillations in this clinically relevant translational model.

Oscillometry for personalizing continuous distending pressure maneuvers: an observational study in extremely preterm infants.

RATIONALE: Lung recruitment and continuous distending pressure (CDP) titration are critical for assuring the efficacy of high-frequency ventilation (HFOV) in preterm infants. The limitation of oxygenation (peripheral oxygen saturation, SpO2) in optimizing CDP calls for evaluating other non-invasive bedside measurements. Respiratory reactance (Xrs) at 10 Hz measured by oscillometry reflects lung volume recruitment and tissue strain. In particular, lung volume recruitment and decreased tissue strain result in increased Xrs values. OBJECTIVES: In extremely preterm infants treated with HFOV as first intention, we aimed to measure the relationship between CDP and Xrs during SpO2-driven CDP optimization. METHODS: In this prospective observational study, extremely preterm infants born before 28 weeks of gestation undergoing SpO2-guided lung recruitment maneuvers were included in the study. SpO2 and Xrs were recorded at each CDP step. The optimal CDP identified by oxygenation (CDPOpt_SpO2) was compared to the CDP providing maximal Xrs on the deflation limb of the recruitment maneuver (CDPXrs). RESULTS: We studied 40 infants (gestational age at birth = 22+ 6-27+ 5 wk; postnatal age = 1-23 days). Measurements were well tolerated and provided reliable results in 96% of cases. On average, Xrs decreased during the inflation limb and increased during the deflation limb. Xrs changes were heterogeneous among the infants for the amount of decrease with increasing CDP, the decrease at the lowest CDP of the deflation limb, and the hysteresis of the Xrs vs. CDP curve. In all but five infants, the hysteresis of the Xrs vs. CDP curve suggested effective lung recruitment. CDPOpt_SpO2 and CDPXrs were highly correlated (ρ = 0.71, p < 0.001) and not statistically different (median difference [range] = -1 [-3; 9] cmH2O). However, CDPXrs were equal to CDPOpt_SpO2 in only 6 infants, greater than CDPOpt_SpO2 in 10, and lower in 24 infants. CONCLUSIONS: The Xrs changes described provide complementary information to oxygenation. Further investigation is warranted to refine recruitment maneuvers and CPD settings in preterm infants.

Impact on cerebral hemodynamics of the use of volume guarantee combined with high frequency oscillatory ventilation in a neonatal animal respiratory distress model.

High-frequency oscillatory ventilation (HFOV) is an alternative to conventional mechanical ventilation (CMV). Recently, the use of volume guarantee (VG) combined with HFOV has been suggested as a safe strategy capable of reducing the damage induced by ventilation in immature lungs. However, the possible impact of this new ventilation technique on cerebral hemodynamics is unknown. To evaluate the cerebral hemodynamics effect of HFOV combined with VG in an experimental animal model of neonatal respiratory distress syndrome (RDS) due to surfactant deficiency compared with HFOV and CMV+VG (control group). Eighteen newborn piglets were randomized, before and after the induction of RDS by bronchoalveolar lavage, into 3 mechanical ventilation groups: CMV, HFOV and HFOV with VG. Changes in cerebral oxygen transport and consumption and cerebral blood flow were analyzed by non-invasive regional cerebral oxygen saturation (CrSO2), jugular venous saturation (SjO2), the calculated cerebral oxygen extraction fraction (COEF), the calculated cerebral fractional tissue oxygen extraction (cFTOE) and direct measurement of carotid artery flow. To analyze the temporal evolution of these variables, a mixed-effects linear regression model was constructed. After randomization, the following statistically significant results were found in every group: a drop in carotid artery flow: at a rate of -1.7 mL/kg/min (95% CI: -2.5 to -0.81; p < 0.001), CrSO2: at a rate of -6.2% (95% CI: -7.9 to -4.4; p < 0.001) and SjO2: at a rate of -20% (95% CI: -26 to -15; p < 0.001), accompanied by an increase in COEF: at a rate of 20% (95% CI: 15 to 26; p < 0.001) and cFTOE: at a rate of 0.07 (95% CI: 0.05 to 0.08; p < 0.001) in all groups. No statistically significant differences were found between the HFOV groups. CONCLUSION: No differences were observed at cerebral hemodynamic between respiratory assistance in HFOV with and without VG, being the latter ventilatory strategy equally safe. WHAT IS KNOWN: • Preterm have a situation of fragility of cerebral perfusion wich means that any mechanical ventilation strategy can have a significant influence. High-frequency oscillatory ventilation (HFOV) is an alternative to conventional mechanical ventilation (CMV). Recently, the use of volume guarantee (VG) combined with HFOV has been suggested as a safe strategy capable of reducing the damage induced by ventilation in immature lungs. Several studies have compared CMV and HFOV and their effects at hemodynamic level. It is known that the use of high mean airway pressure in HFOV can cause an increase in pulmonary vascular resistance with a decrease in thoracic venous return. WHAT IS NEW: • The possible impact of VAFO + VG on cerebral hemodynamics is unknown. Due the lack of studies and the existing controversy, we have carried out this research project in an experimental animal model with the aim of evaluating the cerebral hemodynamic repercussion of the use of VG in HFOV compared to the classic strategy without VG.

[Therapeutic efficacy of volume-guaranteed high frequency oscillation ventilation on respiratory failure in preterm infants with a gestational age of 28-34 weeks: a prospective randomized controlled study]. / 容量保证的高频振荡通气模式对胎龄28~34å‘¨æ—©äº§å„¿å‘¼å¸è¡°ç«­ç–—æ•ˆçš„å‰çž»æ€§éšæœºå¯¹ç §ç ”ç©¶.

OBJECTIVES: To investigate the therapeutic efficacy of volume-guaranteed high frequency oscillation ventilation (HFOV-VG) versus conventional mechanical ventilation (CMV) in the treatment of preterm infants with respiratory failure. METHODS: A prospective study was conducted on 112 preterm infants with respiratory failure (a gestational age of 28-34 weeks) who were admitted to the Department of Neonatology, Jiangyin Hospital Affiliated to Medical School of Southeast University, from October 2018 to December 2022. The infants were randomly divided into an HFOV-VG group (44 infants) and a CMV group (68 infants) using the coin tossing method based on the mode of mechanical ventilation. The therapeutic efficacy was compared between the two groups. RESULTS: After 24 hours of treatment, both the HFOV-VG and CMV groups showed significant improvements in arterial blood pH, partial pressure of oxygen, partial pressure of carbon dioxide, and partial pressure of oxygen/fractional concentration of inspired oxygen ratio (P<0.05), and the HFOV-VG group had better improvements than the CMV group (P<0.05). There were no significant differences between the two groups in the incidence rate of complications, 28-day mortality rate, and length of hospital stay (P>0.05), but the HFOV-VG group had a significantly shorter duration of invasive mechanical ventilation than the CMV group (P<0.05). The follow-up at the corrected age of 6 months showed that there were no significant differences between the two groups in the scores of developmental quotient, gross motor function, fine motor function, adaptive ability, language, and social behavior in the Pediatric Neuropsychological Development Scale (P>0.05). CONCLUSIONS: Compared with CMV mode, HFOV-VG mode improves partial pressure of oxygen and promotes carbon dioxide elimination, thereby enhancing oxygenation and shortening the duration of mechanical ventilation in preterm infants with respiratory failure, while it has no significant impact on short-term neurobehavioral development in these infants.

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.

Benefits of secretion clearance with high frequency percussive ventilation in tracheostomized critically ill patients: a pilot study.

Clearance of secretions remains a challenge in ventilated patients. Despite high-frequency percussive ventilation (HFPV) showing benefits in patients with cystic fibrosis and neuromuscular disorders, very little is known about its effects on other patient categories. Therefore, we designed a physiological pilot study investigating the effects on lung aeration and gas exchange of short HFPV cycles in tracheostomized patients undergoing mechanical ventilation. Electrical impedance tomography (EIT) was recorded at baseline (T0) by a belt wrapped around the patient's chest, followed by the HFPV cycle lasting 10 min. EIT data was collected again after the HFPV cycle (T1) as well as after 1 h (T2) and 3 h (T3) from T0. Variation from baseline of end-expiratory lung impedance (∆EELI), tidal variation (TIV) and global inhomogeneity index (GI) were computed. Arterial blood was also taken for gas analysis. HFPV cycle significantly improved the ∆EELI at T1, T2 and T3 when compared to baseline (p < 0.05 for all comparisons). The ratio between arterial partial pressure and inspired fraction of oxygen (PaO2/FiO2) also increased after the treatment (p < 0.001 for all comparison) whereas TIV (p = 0.132) and GI (p = 0.114) remained unchanged. Short cycles of HFPV superimposed to mechanical ventilation promoted alveolar recruitment, as suggested by improved ∆EELI, and improved oxygenation in tracheostomized patients with high load of secretion.Trial Registration Prospectively registered on www.clinicaltrials.gov (NCT05200507; dated 6th January 2022).

High-frequency ventilation in preterm infants and neonates.

High-frequency ventilation (HFV) has been used as a respiratory support mode for neonates for over 30 years. HFV is characterized by delivering tidal volumes close to or less than the anatomical dead space. Both animal and clinical studies have shown that HFV can effectively restore lung function, and potentially limit ventilator-induced lung injury, which is considered an important risk factor for developing bronchopulmonary dysplasia (BPD). Knowledge of how HFV works, how it influences cardiorespiratory physiology, and how to apply it in daily clinical practice has proven to be essential for its optimal and safe use. We will present important aspects of gas exchange, lung-protective concepts, clinical use, and possible adverse effects of HFV. We also discuss the study results on the use of HFV in respiratory distress syndrome in preterm infants and respiratory failure in term neonates. IMPACT: Knowledge of how HFV works, how it influences cardiorespiratory physiology, and how to apply it in daily clinical practice has proven to be essential for its optimal and safe use. Therefore, we present important aspects of gas exchange, lung-protective concepts, clinical use, and possible adverse effects of HFV. The use of HFV in daily clinical practice in lung recruitment, determination of the optimal continuous distending pressure and frequency, and typical side effects of HFV are discussed. We also present study results on the use of HFV in respiratory distress syndrome in preterm infants and respiratory failure in term neonates.

Therapeutic efficacy of volume-guaranteed high frequency oscillation ventilation on respiratory failure in preterm infants with a gestational age of 28-34 weeks: a prospective randomized controlled study / 中国当代儿科杂志

OBJECTIVES@#To investigate the therapeutic efficacy of volume-guaranteed high frequency oscillation ventilation (HFOV-VG) versus conventional mechanical ventilation (CMV) in the treatment of preterm infants with respiratory failure.@*METHODS@#A prospective study was conducted on 112 preterm infants with respiratory failure (a gestational age of 28-34 weeks) who were admitted to the Department of Neonatology, Jiangyin Hospital Affiliated to Medical School of Southeast University, from October 2018 to December 2022. The infants were randomly divided into an HFOV-VG group (44 infants) and a CMV group (68 infants) using the coin tossing method based on the mode of mechanical ventilation. The therapeutic efficacy was compared between the two groups.@*RESULTS@#After 24 hours of treatment, both the HFOV-VG and CMV groups showed significant improvements in arterial blood pH, partial pressure of oxygen, partial pressure of carbon dioxide, and partial pressure of oxygen/fractional concentration of inspired oxygen ratio (P<0.05), and the HFOV-VG group had better improvements than the CMV group (P<0.05). There were no significant differences between the two groups in the incidence rate of complications, 28-day mortality rate, and length of hospital stay (P>0.05), but the HFOV-VG group had a significantly shorter duration of invasive mechanical ventilation than the CMV group (P<0.05). The follow-up at the corrected age of 6 months showed that there were no significant differences between the two groups in the scores of developmental quotient, gross motor function, fine motor function, adaptive ability, language, and social behavior in the Pediatric Neuropsychological Development Scale (P>0.05).@*CONCLUSIONS@#Compared with CMV mode, HFOV-VG mode improves partial pressure of oxygen and promotes carbon dioxide elimination, thereby enhancing oxygenation and shortening the duration of mechanical ventilation in preterm infants with respiratory failure, while it has no significant impact on short-term neurobehavioral development in these infants.

Lung protection strategy with high-frequency oscillatory ventilation improves respiratory outcomes at two years in preterm respiratory distress syndrome: a before and after, quality improvement study.

INTRODUCTION: Bronchopulmonary dysplasia (BPD) remains one of the major challenges of extreme prematurity. High-frequency oscillatory ventilation (HFOV) with volume guarantee (HFOV-VG) can be used as an early-rescue ventilation to protect developing lungs. However, the studies exploring the impact of this ventilatory strategy on neonatal respiratory morbidity are very limited. This study aimed at documenting the improvement in respiratory outcomes in mechanically ventilated preterm newborns, after the implementation of a new mechanical ventilation respiratory bundle. METHODS: A prospective, quality improvement study was conducted between January 2012 and December 2018 in a third level NICU in Madrid, Spain. Infants born <32 weeks of gestation with severe respiratory distress syndrome (RDS) and requiring invasive mechanical ventilation were included. The intervention consisted of a new ventilation respiratory care bundle, with HFOV as early rescue therapy using low high-frequency tidal volumes (Vthf) and higher frequencies (15-20 Hz). Criteria for HFOV start were impaired oxygenation or ventilation on conventional ventilation, or peak inspiratory pressures >15 cmH2O. Two cohorts of mechanically ventilated patients were compared, cohort 1 (2012-2013, baseline period) and cohort 2 (2016-2018, after implementation of the new bundle). Clinical outcomes at 36 weeks and 2 years of postmenstrual age were compared between the groups. RESULTS: A total of 216 patients were included, the median gestational age was 26 weeks (IQR 25-28) and median birth weight was 895 g (IQR 720-1160). There were no significant differences in survival between the groups, but patients with the protective ventilation strategy (cohort 2) had higher survival without BPD 2-3 (OR 2.93, 95%CI 1.41-6.05). At 2 years of postmenstrual age, patients in cohort 2 also had a higher survival free of baseline respiratory treatment and hospital respiratory admissions than the control group (adjusted OR 2.33, 95%CI 1.10-4.93, p=.03). The results did not suggest significant differences in neurologic development. CONCLUSIONS: In extreme premature related severe respiratory failure, the use of a lung protective HFOV-VG strategy was proven to be a useful quality improvement intervention in our unit, leading to better pulmonary outcomes at 36 weeks and additional improved respiratory prognosis at two years of age.

Use of intraoperative high frequency oscillatory ventilation in neonates with pulmonary hypoplasia.

High-frequency oscillatory ventilation (HFOV) is a ventilatory modality widely used in neonatal intensive care units. Its main indication is restrictive lung pathology with difficult gas exchange using conventional mechanical ventilation (CMV). Patients receiving CMV require high intensity care, and immature lungs can be at risk for barotrauma and volutrauma. The few studies that have explored the use of HFOV in the operating room are mainly limited to HFVO during congenital diaphragmatic hernia repair. Limited experience of this ventilatory method in the operating room may be a disadvantage for the anesthesiologist. However, it is important to remember the benefits of this technique as a lung protection strategy. We report two cases of neonatal pulmonary hypoplasia of different etiology in which good oxygenation and ventilation was achieved with intraoperative HFOV.

Demonstration of mucus simulant clearance in a Bench-Model using acoustic Field-Integrated Intrapulmonary Percussive ventilation.

Intrapulmonary Percussive Ventilation (IPV) is a high-frequency airway clearance technique used to help in mucus transport for mechanically ventilated and unventilated patients. Despite the many years of usage, this technique does not provide clear evidence of its intended efficacy. This is mainly attributable to the lack of in vitro observations that show "mucokinesis" towards the direction of the mouth. In the current manuscript, we demonstrate and subsequently propose a mechanism that details the movement of a mucus simulant in the proximal (towards the mouthpiece) direction. Towards this end, a novel method utilizing a high-frequency acoustic field in addition to the conventional air pulsations brought forth by traditional IPV is proposed. Under these conditions, at certain parameter settings, it is shown that the simulant is broken down into much smaller parts and subsequently pushed in the upstream direction gradually over a period of half-hour.

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.

Oscillation Transmission of Modern High-Frequency Neonatal Ventilators Under Different Lung Mechanics Conditions.

BACKGROUND: High-frequency oscillatory ventilation (HFOV) is widely used in neonatal critical care, and several modern ventilators using different technologies are available to provide HFOV. These devices have different technical characteristics that might interact with patient lung mechanics to influence the effectiveness of ventilation. To verify this, we studied the oscillation transmission of 5 neonatal oscillators in a lung model mimicking the mechanical patterns commonly observed in neonatal practice. METHODS: This was a benchtop, in vitro, physiological, pragmatic study using a model mimicking airways and lung of a 1-kg preterm neonate and the following patterns: normal (compliance: 1.0 mL/cm H2O, resistance: 50 cm H2O/L/s), restrictive (compliance: 0.3 mL/cm H2O, resistance: 50 cm H2O/L/s), and mixed mechanics (compliance: 0.3 mL/cm H2O, resistance: 250 cm H2O/L/s). Several permutations of HFOV parameters (variable mean airway pressure or amplitude or frequency protocols) were tested. Oscillations were measured with a dedicated pressure transducer validated for use during HFOV, and oscillatory pressure ratio (OPR) was calculated to estimate the oscillation transmission. RESULTS: Overall OPR (calculated on all experiments) was significantly different between ventilators and the mechanical patterns (both P < .001). Different ventilators and patterns accounted for 35.6% and 20.6% of the variation in oscillation transmission, respectively. Sub-analyses per changing amplitude or frequency protocols and multivariate regressions showed that VN500 (standardized ß coefficient [St.ß]: 0.548, P < .001) and Fabian HFO (St.ß: 0.421, P < .001; adjusted R2: 0.615) provided the best oscillation transmission. Fabian HFO also delivered oscillations with the lowest variability when increasing amplitude. CONCLUSIONS: In an experimental setting mimicking typical neonatal lung disorders, the oscillation transmission was more dependent on the ventilator model than on the mechanical lung conditions at equal HFOV parameters. Fabian HFO and VN500 provided better oscillation transmission overall, and when increasing amplitude, Fabian HFO delivered oscillations with the lowest variability.

Lung volume distribution in preterm infants on non-invasive high-frequency ventilation.

INTRODUCTION: Non-invasive high-frequency oscillatory ventilation (nHFOV) is an extension of nasal continuous positive airway pressure (nCPAP) support in neonates. We aimed to compare global and regional distribution of lung volumes during nHFOV versus nCPAP. METHODS: In 30 preterm infants enrolled in a randomised crossover trial comparing nHFOV with nCPAP, electrical impedance tomography data were recorded in prone position. For each mode of respiratory support, four episodes of artefact-free tidal ventilation, each comprising 30 consecutive breaths, were extracted. Tidal volumes (VT) in 36 horizontal slices, indicators of ventilation homogeneity and end-expiratory lung impedance (EELI) for the whole lung and for four horizontal regions of interest (non-gravity-dependent to gravity-dependent; EELINGD, EELImidNGD, EELImidGD, EELIGD) were compared between nHFOV and nCPAP. Aeration homogeneity ratio (AHR) was determined by dividing aeration in non-gravity-dependent parts of the lung through gravity-dependent regions. MAIN RESULTS: Overall, 228 recordings were analysed. Relative VT was greater in all but the six most gravity-dependent lung slices during nCPAP (all p<0.05). Indicators of ventilation homogeneity were similar between nHFOV and nCPAP (all p>0.05). Aeration was increased during nHFOV (mean difference (95% CI)=0.4 (0.2 to 0.6) arbitrary units per kilogram (AU/kg), p=0.013), mainly due to an increase in non-gravity-dependent regions of the lung (∆EELINGD=6.9 (0.0 to 13.8) AU/kg, p=0.028; ∆EELImidNGD=6.8 (1.2 to 12.4) AU/kg, p=0.009). Aeration was more homogeneous during nHFOV compared with nCPAP (mean difference (95% CI) in AHR=0.01 (0.00 to 0.02), p=0.0014). CONCLUSION: Although regional ventilation was similar between nHFOV and nCPAP, end-expiratory lung volume was higher and aeration homogeneity was slightly improved during nHFOV. The aeration difference was greatest in non-gravity dependent regions, possibly due to the oscillatory pressure waveform. The clinical importance of these findings is still unclear.

Conventional vs high-frequency ventilation for weaning from total liquid ventilation in lambs.

OBJECTIVE: To compare conventional gas ventilation (GV) and high-frequency oscillatory ventilation (HFOV) for weaning from total liquid ventilation (TLV). METHODS: Sixteen lambs were anesthetized. After 1 h of TLV with perflubron (PFOB), they were assigned to either GV or HFOV for 2 h. Oxygen requirements, electrical impedance tomography and videofluoroscopic sequences, and respiratory system compliance were recorded. RESULTS: The lambs under GV needed less oxygen at 20 min following TLV (40 [25, 45] and 83 [63, 98]%, p = 0.001 under GV and HFOV, respectively). During weaning, tidal volume distribution was increased in the nondependent regions in the GV group compared to baseline (p = 0.046). Furthermore, residual PFOB was observed in the most dependent region. No air was detected by fluoroscopy in that region at the end of expiration in the GV group. CONCLUSION: GV offers a transient advantage over HFOV with regards to oxygenation for TLV weaning.

Lung Recruitment Using High-Frequency Oscillation Volume Guarantee in Preterm Infants with Evolving Bronchopulmonary Dysplasia.

BACKGROUND: Stepwise lung recruitment maneuvers (LRMs) may be used in ventilated preterm infants. However, its use in high-frequency oscillation with volume guarantee (HFO-VG) is not well studied. METHODS: Preterm infants treated with HFO-VG who had LRMs were identified. Patient and respiratory parameters were recorded. RESULTS: Ten infants, median GA 25+6 (IQR 24+2-27+0) weeks, and 21 LRMs were identified. LRMs were performed at a median age of 26 days, with a starting MAP of 16 (14-17) cm H2O and the highest MAP of 23.5 (22.0-24.8) cm H2O. Most (76%) resulted in immediate improved SpO2/FiO2. There were no sustained differences in median oxygen saturation index (8.4 vs. 9, p = 0.09), SpO2/FiO2 (1.8 vs. 1.8, p = 0.8), ∆P (21 vs. 23, p = 0.64), or transcutaneous CO2 (58 vs. 60, p = 0.84) in 24 h before and after LRMs. CONCLUSIONS: In preterm infants with evolving bronchopulmonary dysplasia, LRMs on HFO-VG did not result in sustained improvement to oxygenation or ventilation.

Performance characteristics of high-frequency percussive ventilation under hyperbaric conditions.

Introduction: Safe administration of critical care hyperbaric medicine requires specialized equipment and advanced training. Equipment must be tested in order to evaluate function in the hyperbaric environment. High-frequency percussive ventilation (HFPV) has been used in intensive care settings effectively, but it has never been tested in a hyperbaric chamber. Methods: Following a modified U.S. Navy testing protocol used to evaluate hyperbaric ventilators, we evaluated an HFPV transport ventilator in a multiplace hyperbaric chamber at 1.0, 1.9, and 2.8 atmospheres absolute (ATA). We used a test lung with analytical software for data collection. The ventilator uses simultaneous cyclic pressure-controlled ventilation at a pulsatile flow rate (PFR)/oscillatory continuous positive airway pressure (oCPAP) ratio of 30/10 with a high-frequency oscillation percussive rate of 500 beats per minute. Inspiratory and expiratory times were maintained at two seconds throughout each breathing cycle. Results: During manned studies, the PFR/oCPAP ratios were 26/6, 22/7, and 22.5/8 at an airway resistance of 20cm H2O/L/second and 18/9, 15.2/8.5, and 13.6/7 at an airway resistance of 50 cm/H2O/L/second at 1, 1.9, and 2.8 ATA. The resulting release volumes were 800, 547, and 513 mL at airway resistance of 20 cm H2O/L/sec and 400, 253, and 180 mL at airway resistance of 50 cm/H2O/L/sec at 1, 1.9, and 2.8 ATA. Unmanned testing showed similar changes. The mean airway pressure (MAP) remained stable throughout all test conditions; theoretically, supporting adequate lung recruitment and gas exchange. A case where HFPV was used to treat a patient for CO poisoning was presented to illustrate that HFPV worked well under HBO2 conditions and no complications occurred during HBO2 treatment. Conclusion: The HFPV transport ventilator performed adequately under hyperbaric conditions and should be considered a viable option for hyperbaric critical care. This ventilator has atypical terminology and produces unique pulmonary physiology, thus requiring specialized training prior to use.

Therapeutic effects and outcomes of rescue high-frequency oscillatory ventilation for premature infants with severe refractory respiratory failure.

Despite wide application of high frequency oscillatory ventilation (HFOV) in neonates with respiratory distress, little has been reported about its rescue use in preterm infants. We aimed to evaluate the therapeutic effects of HFOV in preterm neonates with refractory respiratory failure and investigate the independent risk factors of in-hospital mortality. We retrospectively analyzed data collected prospectively (January 2011-December 2018) in four neonatal intensive care units of two tertiary-level medical centers in Taiwan. All premature infants (gestational age 24-34 weeks) receiving HFOV as rescue therapy for refractory respiratory failure were included. A total of 668 preterm neonates with refractory respiratory failure were enrolled. The median (IQR) gestational age and birth weight were 27.3 (25.3-31.0) weeks and 915.0 (710.0-1380.0) g, respectively. Pre-HFOV use of cardiac inotropic agents and inhaled nitric oxide were 70.5% and 23.4%, respectively. The oxygenation index (OI), FiO2, and AaDO2 were markedly increased after HFOV initiation (all p < 0.001), and can be decreased within 24-48 h (all p < 0.001) after use of HFOV. 375 (56.1%) patients had a good response to HFOV within 3 days. The final in-hospital mortality rate was 34.7%. No association was found between specific primary pulmonary disease and survival in multivariate analysis. We found preterm neonates with gestational age < 28 weeks, occurrences of sepsis, severe hypotension, multiple organ dysfunctions, initial higher severity of respiratory failure and response to HFOV within the first 72 h were independently associated with final in-hospital mortality. The mortality rate of preterm neonates with severe respiratory failure remains high after rescue HFOV treatment. Aggressive therapeutic interventions to treat sepsis and prevent organ dysfunctions are the suggested strategies to optimize outcomes.

High frequency percussive ventilation as a rescue mode for refractory status asthmaticus - a case study.

INTRODUCTION: A severe asthma exacerbation is called status asthmaticus when symptoms worsen despite conventional medical treatment in the hospital. If arterial blood gas (ABG) values deteriorate and this is accompanied by respiratory muscle fatigue, the patient will require mechanical ventilation. However, mechanical ventilation of the severe asthmatic presents difficult challenges. CASE STUDY: We report on High Frequency Percussive Ventilation (HFPV) used along with continuous inhaled albuterol and neuromuscular blockade, as rescue therapy for a case of acute, severe asthma that was refractory to conventional treatment and conventional mechanical ventilation. RESULTS: This patient's arterial pH was 6.97 when we initiated HFPV, but ten hours post-intubation her ABG values normalized. She was successfully extubated six days later and discharged from ICU the following day. CONCLUSION: This case describes the successful use of HFPV for a status asthmaticus patient failing conventional mechanical ventilation. We have anecdotal evidence of other medical centers using HFPV for these patients but larger studies are needed to verify its efficacy.