High-frequency oscillatory ventilation in children: a single-center experience of 53 cases

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.

The effect of high-frequency oscillatory ventilation or airway pressure release ventilation on children with acute respiratory distress syndrome as a rescue therapy

BACKGROUND

To investigate the effects of high-frequency oscillatory ventilation (HFOV) or airway pressure release ventilation (APRV) as a rescue therapy on children with moderate and severe acute respiratory distress syndrome (ARDS).

METHODS

We retrospectively enrolled 47 children with ARDS who were transitioned from synchronized intermittent mandatory ventilation (SIMV) to either HFOV or APRV for 48 h or longer after failure of SIMV. The parameters of demographic data, arterial blood gases, ventilator settings, oxygenation index (OI), and PaO₂/FiO₂ (PF) ratio during the first 48 h of HFOV and APRV were recorded.

RESULTS

There was no significant difference between the HFOV and APRV groups with survival rates of 60% and 72.7%, respectively. Compared to pre-transition, the mean airway pressures at 2 and 48 h after transition were higher in both groups (P<0.01), and the PF ratio at 2 and 48 h in both modes was significantly improved (P<0.001). PF ratio and PaCO₂ have significant differences at 48 h between two groups. The OI at 2 h after transition had no improvement in either group and was substantially lower at 48 h relative to the pre-transition level (P<0.001) in both groups. At 48 h after the transition to both HFOV and APRV, the survivors had lower mean airway pressures, higher PF ratios, and a lower OIs than non-survivors (P<0.01).

CONCLUSIONS

There was no significant difference on the survival rates of HFOV and APRV application as a rescue therapy for ARDS, but improved oxygenation at 48 h reliably discriminated survivors from non-survivors in both groups.

Outcomes of Severe PARDS on High-Frequency Oscillatory Ventilation - A Single Centre Experience

OBJECTIVE

To describe experience with high-frequency oscillatory ventilation (HFOV) in children with acute respiratory distress syndrome (ARDS) transitioned from conventional mechanical ventilation (CMV) due to refractory hypoxemia and to assess factors associated with survival and also compare outcomes of patients who were managed with early HFOV (within 24 h of intubation) vs. late HFOV.

METHODS

This retrospective, observational study was conducted in a tertiary care hospital's pediatric intensive care unit. Thirty-four children with pediatric acute respiratory distress syndrome (PARDS) managed with HFOV were included.

RESULTS

Of 34 children with PARDS managed with HFOV after failure of conventional ventilation to improve oxygenation, 8 survived. Improvement in the Oxygenation Index (OI) at 48 h of initiation of HFOV along with percent increase in PaO₂/FiO₂ (P/F ratio) at 24 h of HFOV were predictors of survival. The response to HFOV, based on OI and P/F ratio, between 24 and 48 h of ventilation identified potential survivors. Also, lower positive end-expiratory pressure (PEEP) on CMV and shorter duration of CMV before initiation of HFOV were associated with survival.

CONCLUSIONS

Survival in pediatric ARDS patients treated with HFOV could be predicted by using trends of OI - with survivors showing a more rapid decline in OI between 24 and 48 h of initiation compared to non-survivors.

High-Frequency Oscillatory Ventilation Use and Severe Pediatric ARDS in the Pediatric Hematopoietic Cell Transplant Recipient

INTRODUCTION

The effectiveness of high-frequency oscillatory ventilation (HFOV) in the pediatric hematopoietic cell transplant patient has not been established. We sought to identify current practice patterns of HFOV, investigate parameters during HFOV and their association with mortality, and compare the use of HFOV to conventional mechanical ventilation in severe pediatric ARDS.

METHODS

This is a retrospective analysis of a multi-center database of pediatric and young adult allogeneic hematopoietic cell transplant subjects requiring invasive mechanical ventilation for critical illness from 2009 through 2014. Twelve United States pediatric centers contributed data. Continuous variables were compared using a Wilcoxon rank-sum test or a Kruskal-Wallis analysis. For categorical variables, univariate analysis with logistic regression was performed.

RESULTS

The database contains 222 patients, of which 85 subjects were managed with HFOV. Of this HFOV cohort, the overall pediatric ICU survival was 23.5% (n = 20). HFOV survivors were transitioned to HFOV at a lower oxygenation index than nonsurvivors (25.6, interquartile range 21.1-36.8, vs 37.2, interquartile range 26.5-52.2, P = .046). Survivors were transitioned to HFOV earlier in the course of mechanical ventilation, (day 0 vs day 2, P = .002). No subject survived who was transitioned to HFOV after 1 week of invasive mechanical ventilation. We compared subjects with severe pediatric ARDS treated only with conventional mechanical ventilation versus early HFOV (within 2 d of invasive mechanical ventilation) versus late HFOV. There was a trend toward difference in survival (conventional mechanical ventilation 24%, early HFOV 30%, and late HFOV 9%, P = .08).

CONCLUSIONS

In this large database of pediatric allogeneic hematopoietic cell transplant subjects who had acute respiratory failure requiring invasive mechanical ventilation for critical illness with severe pediatric ARDS, early use of HFOV was associated with improved survival compared to late implementation of HFOV, and the subjects had outcomes similar to those treated only with conventional mechanical ventilation.

High-Frequency Oscillatory Ventilation in Pediatric Acute Lung Injury: A Multicenter International Experience

OBJECTIVE

We aim to describe current clinical practice, the past decade of experience and factors related to improved outcomes for pediatric patients receiving high-frequency oscillatory ventilation. We have also modeled predictive factors that could help stratify mortality risk and guide future high-frequency oscillatory ventilation practice.

DESIGN

Multicenter retrospective, observational questionnaire study.

SETTING

Seven PICUs.

PATIENTS

Demographic, disease factor, and ventilatory and outcome data were collected, and 328 patients from 2009 to 2010 were included in this analysis.

INTERVENTIONS

None.

MEASUREMENT AND MAIN RESULTS

Patients were classified into six cohorts based on underlying diagnosis. We used univariate analysis to identify factors associated with mortality risk and multivariate logistic regression to identify independent predictors of mortality risk. An oxygenation index greater than 35 and immunocompromise exhibited the greatest predictive power (p < 0.0001) for increased mortality risk, and respiratory syncytial virus was associated with lowest mortality risk (p = 0.003). Differences in mortality risk as a function of oxygenation index were highly dependent on primary underlying condition. A trend toward an increase in oscillator amplitude and frequency was observed when compared with historical data.

CONCLUSIONS

Given the number of centers and subjects included in the database, these findings provide a robust description of current practice regarding the use of high-frequency oscillatory ventilation for pediatric hypoxic respiratory failure. Patients with severe hypoxic respiratory failure and immunocompromise had the highest mortality risk, and those with respiratory syncytial virus had the lowest. A means of identifying the risk of 30-day mortality for subjects can be obtained by identifying the underlying disease and oxygenation index on conventional ventilation preceding the initiation of high-frequency oscillatory ventilation.

Is there still a role for high-frequency oscillatory ventilation in neonates, children and adults?

Critically ill patients with respiratory pathology often require mechanical ventilation and while low tidal volume ventilation has become the mainstay of treatment, achieving adequate gas exchange may not be attainable with conventional ventilator modalities. In attempt to achieve gas exchange goals and also mitigate lung injury, high frequency ventilation is often implemented which couples low tidal volumes with sustained mean airway pressure. This manuscript presents the physiology of high-frequency oscillatory ventilation, reviews the currently available data on its use and provides strategies and approaches for this mode of ventilation.

High-frequency oscillation ventilation for hypercapnic failure of conventional ventilation in pulmonary acute respiratory distress syndrome

Introduction

High-frequency oscillation ventilation (HFOV) is regarded as particularly lung protective. Recently, HFOV has been shown to be not beneficial for acute respiratory distress syndrome (ARDS) patients in general. Due to its special physical effects, it could be beneficial, however, in inhomogeneous ARDS. This study evaluates the effect of HFOV on PaCO₂ removal in hypercapnic patients with ARDS of pulmonary origin.

Methods

Between October 2010 and June 2014 patients with ARDS of pulmonary origin with PaO₂/FiO₂ ratio >60 mmHg, but respiratory acidosis (pH <7.26) under optimized protective ventilation were switched to HFOV, using moderate airway pressure (adopting the mean airway pressure of the prior ventilation). Data from these patients were analyzed retrospectively; PaCO₂ and pH before, 1 h and 24 h after the start of HFOV were compared.

Results

Twenty-six patients with PaO₂/FiO₂ ratio 139 ± 49 and respiratory acidosis (PaCO₂ 68 ± 12 mmHg) were put on HFOV after 17 ± 22 h of conventional ventilation. Mean airway pressure was 19 cm H₂O (15 to 28). PaCO₂ decreased significantly: after 1 hour the mean difference was −14 ± 10 mmHg; P <0.01 and after 24 hours −17 ± 12 mmHg; P <0.01; n = 24. CO₂ clearance improved in all but two patients; in those, extracorporeal lung support was initiated. Oxygenation remained unchanged after 1 h and slightly increased after 24 h. No complications related to HFOV were observed. Twenty-two patients improved and could be weaned from HFOV. Twenty patients (77%) were alive on day 30.

Conclusions

HFOV could be a useful alternative in patients with ARDS of pulmonary origin with hypercapnic failure of lung-protective conventional ventilation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-0935-4) contains supplementary material, which is available to authorized users.

High-frequency oscillatory ventilation for cardiac surgery children with severe acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) in children after open heart surgery, although uncommon, can be a significant source of morbidity. Because high-frequency oscillatory ventilation (HFOV) had been used successfully with pediatric patients who had no congenital heart defects, this therapy was used in our unit. This report aims to describe a single-center experience with HFOV in the management of ARDS after open heart surgery with respect to mortality. This retrospective clinical study was conducted in a pediatric intensive care unit. From October 2008 to August 2012, 64 of 10,843 patients with refractory ARDS who underwent corrective surgery at our institution were ventilated with HFOV. Patients with significant uncorrected residual lesions were not included. No interventions were performed. The patients were followed up until hospital discharge. The main outcome measure was survival to hospital discharge. Severe ARDS was defined as acute-onset pulmonary failure with bilateral pulmonary infiltrates and an oxygenation index (OI) higher than 13 despite maximal ventilator settings. The indication for HFOV was acute severe ARDS unresponsive to optimal conventional treatment. The variables recorded and subjected to multivariate analysis were patient demographics, underlying disease, clinical data, and ventilator parameters and their association with hospital mortality. Nearly 10,843 patients underwent surgery during the study period, and the ARDS incidence rate was 0.76 % (83/10,843), with 64 patients (77 %, 64/83) receiving HFOV. No significant changes in systemic or central venous pressure were associated with initiation and maintenance of HFOV. The complications during HFOV included pneumothorax for 22 patients. The overall in-hospital mortality rate was 39 % (25/64). Multiple regression analyses indicated that pulmonary hypertension and recurrent respiratory tract infections (RRTIs) before surgery were independent predictors of in-hospital mortality. The findings show that HFOV is an effective and safe method for ventilating severe ARDS patients after corrective cardiac surgery. Pulmonary hypertension and RRTIs before surgery were risk factors for in-hospital mortality.

High-frequency oscillatory ventilation in children with acute respiratory distress syndrome: experience of a pediatric intensive care unit

OBJECTIVE

To describe the effects of high-frequency oscillatory ventilation (HFOV) as a rescue ventilatory support in pediatric patients with acute respiratory distress syndrome (ARDS).

METHODS

Twenty-five children (1 month < age < 17 years) admitted to a university hospital pediatric intensive care unit (ICU) with ARDS and submitted to HFOV for a minimum of 48 hours after failure of conventional mechanical ventilation were assessed.

RESULTS

Twenty eight days after the onset of ARDS, the mortality rate was 52% (13/25). Over the course of 48 hours, the use of HFOV reduced the oxygenation index [38 (31-50) vs. 17 (10-27)] and increased the ratio of partial arterial pressure O2 and fraction of inspired O2 [65 [44-80) vs. 152 (106-213)]. Arterial CO2 partial pressure [54 (45-74) vs. 48 (39-58) mmHg] remained unchanged. The mean airway pressure ranged between 23 and 29 cmH2O. HFOV did not compromise hemodynamics, and a reduction in heart rate was observed (141±32 vs. 119±22 beats/min), whereas mean arterial pressure (66±20 vs. 71±17 mmHg) and inotropic score [44 (17-130) vs. 20 (16-75)] remained stable during this period. No survivors were dependent on oxygen.

CONCLUSION

HFOV improves oxygenation in pediatric patients with ARDS and severe hypoxemia refractory to conventional ventilatory support.

High-frequency oscillatory ventilation in children: a 10-year experience

OBJECTIVES

The aim of the study was to describe the experience with high-frequency oscillatory ventilation (HFOV) in a Portuguese Pediatric Critical Care Unit, and to evaluate whether HFOV allowed improvement in oxygenation and ventilation.

METHODS

This was a retrospective observational cohort study of children ventilated by HFOV between January, 2002 and December, 2011. The following parameters were recorded: demographic and clinical data, and blood gases and ventilatory parameters during the first 48 hours of HFOV.

RESULTS

80 children were included, with a median age of 1.5 months (min: one week; max: 36 months). Pneumonia (n=50; 62.5%) and bronchiolitis (n=18; 22.5%) were the main diagnoses. Approximately 40% (n=32) of the patients developed acute respiratory distress syndrome (ARDS). Conventional mechanical ventilation was used in 68 (85%) of patients prior to HFOV. All patients who started HFOV had hypoxemia, and 56 (70%) also presented persistent hypercapnia. Two hours after starting HFOV, a significant improvement in SatO2/FiO2 ratio (128±0.63 vs. 163±0.72; p<0.001) that was sustained up to 24 hours of HFOV and a decrease in FiO2 were observed. Since the beginning of HFOV, the mean PCO2 significantly decreased (87±33 vs. 66±25; p<0.001), and the pH significantly improved (7.21±0.17 vs. 7.32±0.15; p<0.001). Overall survival was 83.8%.

CONCLUSIONS

HFOV enabled an improvement in hypercapnia and oxygenation. It is a safe option for the treatment of ARDS and severe small airway diseases.

Nontraditional modes of mechanical ventilation: progress or distraction?

As technology continues to develop, a wide range of novel and nontraditional modes of mechanical ventilation have become available for the management of critically ill patients. Proportional assist ventilation, neurally adjusted ventilatory assist and adaptive support ventilation are three novel modes of ventilation, which attempt to optimize patient-ventilator synchrony. Improved interactions between patient and ventilator may be important in improving clinical outcomes. Another important priority for mechanically ventilated patients is lung protection, and nontraditional modes of ventilation that may be implemented to minimize ventilator-associated lung injury include airway pressure release ventilation and high-frequency ventilation. Novel and nontraditional modes of ventilation may represent important tools in the critical care environment; however, continued investigation is needed to determine the overall impact of these various approaches on outcomes for mechanically ventilated patients.

High-frequency oscillatory ventilation in pediatric acute hypoxemic respiratory failure: disease-specific morbidity survival analysis

Background

Multiple ventilatory strategies for acute hypoxemic respiratory failure (AHRF) in children have been advocated, including high-frequency oscillatory ventilation (HFOV). Despite the frequent deployment of HFOV, randomized controlled trials remain elusive and currently there are no pediatric trials looking at its use. Our longitudinal study analyzed the predictive clinical outcome of HFOV in pediatric AHRF given disease-specific morbidity.

Methods

A retrospective 8-year review on pediatric intensive care unit admissions with AHRF ventilated by HFOV was performed. Primary outcomes included survival, morbidity, length of stay (LOS), and factors associated with survival or mortality.

Results

A total of 102 patients underwent HFOV with a 66 % overall survival rate. Survivors had a greater LOS than nonsurvivors (p = 0.001). Mortality odds ratio (OR) for patients without bronchiolitis was 8.19 (CI = 1.02, 65.43), and without pneumonia it was 3.07 (CI = 1.12, 8.39). A lower oxygenation index (OI) after HFOV commencement and at subsequent time points analyzed predicted survival. After 24 h, mortality was associated with an OI > 35 [OR = 31.11 (CI = 3.25, 297.98)]. Sepsis-related mortality was associated with a higher baseline FiO₂ (0.88 vs. 0.65), higher OI (42 vs. 22), and augmented metabolic acidosis (pH of 7.25 vs. 7.32) evaluated 4 h on HFOV (p < 0.05).

Conclusion

High-frequency oscillatory ventilation may be safely utilized. It has a 66 % overall survival rate in pediatric AHRF of various etiologies. Patients with morbidity limited to the respiratory system and optimized oxygenation indices are most likely to survive on HFOV.

The use of high frequency oscillatory ventilation in a pediatric oncology intensive care unit

BACKGROUND

High frequency oscillatory ventilation (HFOV) has been successfully used in the management of acute respiratory distress syndrome (ARDS) in children. The aim of our study is to determine its effectiveness in pediatric patients with cancer or post hematopoietic stem cell transplantation (HSCT) diagnosed with ARDS.

PROCEDURE

A retrospective case review, in a pediatric intensive care unit (PICU) in a tertiary-care oncology center in Amman, Jordan. Patients included were children with cancer and/or receiving allogeneic HSCT who were diagnosed with ARDS and placed on HFOV from January 2007 to February 2009.

RESULTS

Data from 12 pediatric oncology patients on HFOV were analyzed for demographics, oncological diagnosis, PRISM III scores, ventilator settings before switching to HFOV and 24 hours after switching, complications, and outcomes. Alveolar-arterial oxygen (A-a) gradient and oxygen index (OI) were calculated, and pressure of arterial CO(2) (PaCO(2) ) was measured before and 24 hours after switching. Endpoints were successful extubation and discharge, or death while intubated. After 24 hours on HFOV, the A-a gradient decreased significantly in all patients (from a median of 564-267 torr; P=0.001). OI decreased in all but two patients who died (median 17); PaCO(2) decrease was not significant. Five patients died (two of them post-HSCT) and the 7 (58%) survivors were weaned from HFOV (median, 9 days) and discharged.

CONCLUSIONS

HFOV improves gas exchange and is useful in managing critically ill children with cancer and post-HSCT patients who develop ARDS.

Pediatric acute respiratory failure: areas of debate in the pediatric critical care setting

Pediatric intensive care units across the world care for large numbers of mechanically ventilated infants and children on a daily basis, yet management of these patients is far from standardized. This lack of standardization may be a necessity in certain situations given variation between underlying disease processes, pathophysiology, response to therapy and available resources. However, there are many situations in which similar patients are managed differently across pediatric intensive care units simply because there are a shortage of available data to guide the management of these critically ill infants and children. Thus, a large fraction of pediatric critical care involves a combination of institutional preference, individual experience, opinion and extrapolation of adult data.

Acute lung injury in children: therapeutic practice and feasibility of international clinical trials

OBJECTIVES

To describe mechanical ventilation strategies in acute lung injury and to estimate the number of eligible patients for clinical trials on mechanical ventilation management. In contrast to adult medicine, there are few clinical trials to guide mechanical ventilation management in children with acute lung injury.

DESIGN

A cross-sectional study for six 24-hr periods from June to November 2007.

SETTING

Fifty-nine pediatric intensive care units in 12 countries in North America and Europe.

PATIENTS

We identified children meeting acute lung injury criteria and collected detailed information on illness severity, mechanical ventilatory support, and use of adjunctive therapies.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of 3823 patients screened, 414 (10.8%) were diagnosed with acute lung injury by their treating physician, but only 165 (4.3%) patients met prestablished inclusion/exclusion criteria to this trial and, therefore, would have been eligible for a clinical trial. Of these, 124 (75.2%) received conventional mechanical ventilation, 27 (16.4%) received high-frequency oscillatory ventilation, and 14 (8.5%) received noninvasive mechanical ventilation. In the conventional mechanical ventilation group, 43.5% were ventilated in a pressure control mode with a mean tidal volume of 8.3 ± 3.3 mL/kg; and there was no clear relationship between positive end-expiratory pressure and Fio2 delivery in the conventional mechanical ventilation group. Use of adjunctive treatments, including nitric oxide, prone positioning, surfactant, hemofiltration, recruitment maneuvers, steroids, bronchodilators, and fluid restriction, was highly variable.

CONCLUSIONS

Our study reveals inconsistent mechanical ventilation practice and use of adjunctive therapies in children with acute lung injury. Pediatric clinical trials assessing mechanical ventilation management are needed to generate evidence to optimize outcomes. We estimate that a large number of centers (∼60) are needed to conduct such trials; it is imperative, therefore, to bring about international collaboration.

High frequency oscillatory ventilation for respiratory failure due to RSV bronchiolitis

OBJECTIVE

To describe the time course of high frequency oscillatory ventilation (HFOV) in respiratory syncytial virus (RSV) bronchiolitis.

DESIGN

Retrospective charts review.

SETTING

A tertiary paediatric intensive care unit.

PATIENTS AND PARTICIPANTS

Infants with respiratory failure due to RSV infection.

INTERVENTION

HFOV.

MEASUREMENTS AND RESULTS

Pattern of lung disease, ventilatory settings, blood gases, infant's vital parameters, sedation and analgesia during the periods of conventional mechanical ventilation (CMV, 6 infants), after initiation of HFOV (HFOVi, 9 infants), in the middle of its course (HFOVm), at the end (HFOVe) and after extubation (Post-Extub) were compared. All infants showed a predominant overexpanded lung pattern. Mean airway pressure was raised from a mean (SD) 12.5 (2.0) during CMV to 18.9 (2.7) cmH(2)O during HFOVi (P < 0.05), then decreased to 11.1(1.3) at HFOVe (P < 0.05). Mean FiO(2) was reduced from 0.68 (0.18) (CMV) to 0.59 (0.14) (HFOVi) then to 0.29 (0.06) (P < 0.05) at HFOVe and mean peak to peak pressure from 44.9 (12.4) cmH(2)O (HFOVi) to 21.1 (7.7) P < 0.05 (HFOVe) while mean (SD) PaCO(2) showed a trend to decrease from 72 (22) (CMV) to 47 (8) mmHg (HFVOe) and mean infants respiratory rate a trend to increase from 20 (11) (HFOVi) to 34 (14) (HFOVe) breaths/min. With usual doses of sedatives and opiates, no infant was paralysed and all were extubated to CPAP or supplemental oxygen after a mean of 120 h.

CONCLUSION

RSV induced respiratory failure with hypercapnia can be managed with HFOV using high mean airway pressure and large pressure swings while preserving spontaneous breathing.

High frequency oscillatory ventilation in children: experience of a medical center in Taiwan

BACKGROUND/PURPOSE

Data about the effectiveness of high frequency oscillatory ventilation (HFOV) in children with respiratory failure are limited. This study investigated the efficacy and prognostic factors of this treatment.

METHODS

Children between 2 months and 18 years of age who received HFOV between January 2000 and September 2006 in a tertiary care center were enrolled in this retrospective study.

RESULTS

Thirty-six HFOV treatments were given to 33 patients (twice in one patient and three times in another patient) at a mean age of 5.4 +/- 5.0 years. HFOV was used as a rescue after conventional mechanical ventilation (CMV) for 4.4 +/- 4.2 days. The mean duration of HFOV was 7.6 +/- 7.9 days. The most common indication for HFOV was oxygenation failure, which was due to pneumonia with acute respiratory distress syndrome in 15 (45.5%), severe lobar pneumonia in nine (27.3%), pulmonary hemorrhage in eight (24.2%) and pneumothorax in one (3%). PaCO2 was significantly improved 4 hours after HFOV and the PaO2/FiO2 ratio increased significantly 12 hours later. The oxygenation index and alveolar-arterial oxygen difference P(A-a)O2, however, did not change markedly. Four (12%) patients needed further extracorporeal life support and two of these survived. The overall survival rate was 45.5%. Patients with heavier body weight (p less than 0.05) and of the male gender (p less than 0.05) had a higher risk of mortality.

CONCLUSION

As a relatively late rescue therapy after failure of CMV, HFOV may improve PaCO2 and PaO2/FiO2 in children with respiratory failure. However, it carries an increased mortality rate in patients with heavier body weight and male gender.

Imposed work of breathing during high-frequency oscillatory ventilation: a bench study

Introduction

The ventilator and the endotracheal tube impose additional workload in mechanically ventilated patients breathing spontaneously. The total work of breathing (WOB) includes elastic and resistive work. In a bench test we assessed the imposed WOB using 3100 A/3100 B SensorMedics high-frequency oscillatory ventilators.

Methods

A computer-controlled piston-driven test lung was used to simulate a spontaneously breathing patient. The test lung was connected to a high-frequency oscillatory ventilation (HFOV) ventilator by an endotracheal tube. The inspiratory and expiratory airway flows and pressures at various places were sampled. The spontaneous breath rate and volume, tube size and ventilator settings were simulated as representative of the newborn to adult range. The fresh gas flow rate was set at a low and a high level. The imposed WOB was calculated using the Campbell diagram.

Results

In the simulations for newborns (assumed body weight 3.5 kg) and infants (assumed body weight 10 kg) the imposed WOB (mean ± standard deviation) was 0.22 ± 0.07 and 0.87 ± 0.25 J/l, respectively. Comparison of the imposed WOB in low and high fresh gas flow rate measurements yielded values of 1.63 ± 0.32 and 0.96 ± 0.24 J/l (P = 0.01) in small children (assumed body weight 25 kg), of 1.81 ± 0.30 and 1.10 ± 0.27 J/l (P < 0.001) in large children (assumed body weight 40 kg), and of 1.95 ± 0.31 and 1.12 ± 0.34 J/l (P < 0.01) in adults (assumed body weight 70 kg). High peak inspiratory flow and low fresh gas flow rate significantly increased the imposed WOB. Mean airway pressure in the breathing circuit decreased dramatically during spontaneous breathing, most markedly at the low fresh gas flow rate. This led to ventilator shut-off when the inspiratory flow exceeded the fresh gas flow.

Conclusion

Spontaneous breathing during HFOV resulted in considerable imposed WOB in pediatric and adult simulations, explaining the discomfort seen in those patients breathing spontaneously during HFOV. The level of imposed WOB was lower in the newborn and infant simulations, explaining why these patients tolerate spontaneous breathing during HFOV well. A high fresh gas flow rate reduced the imposed WOB. These findings suggest the need for a demand flow system based on patient need allowing spontaneous breathing during HFOV.

Unloading work of breathing during high-frequency oscillatory ventilation: a bench study

Introduction

With the 3100B high-frequency oscillatory ventilator (SensorMedics, Yorba Linda, CA, USA), patients' spontaneous breathing efforts result in a high level of imposed work of breathing (WOB). Therefore, spontaneous breathing often has to be suppressed during high-frequency oscillatory ventilation (HFOV). A demand-flow system was designed to reduce imposed WOB.

Methods

An external gas flow controller (demand-flow system) accommodates the ventilator fresh gas flow during spontaneous breathing simulation. A control algorithm detects breathing effort and regulates the demand-flow valve. The effectiveness of this system has been evaluated in a bench test. The Campbell diagram and pressure time product (PTP) are used to quantify the imposed workload.

Results

Using the demand-flow system, imposed WOB is considerably reduced. The demand-flow system reduces inspiratory imposed WOB by 30% to 56% and inspiratory imposed PTP by 38% to 59% compared to continuous fresh gas flow. Expiratory imposed WOB was decreased as well by 12% to 49%. In simulations of shallow to normal breathing for an adult, imposed WOB is 0.5 J l^-1 at maximum. Fluctuations in mean airway pressure on account of spontaneous breathing are markedly reduced.

Conclusion

The use of the demand-flow system during HFOV results in a reduction of both imposed WOB and fluctuation in mean airway pressure. The level of imposed WOB was reduced to the physiological range of WOB. Potentially, this makes maintenance of spontaneous breathing during HFOV possible and easier in a clinical setting. Early initiation of HFOV seems more possible with this system and the possibility of weaning of patients directly on a high-frequency oscillatory ventilator is not excluded either.

Year in review 2005: Critical Care--respirology: mechanical ventilation, infection, monitoring, and education

We summarize all original research in the field of respiratory intensive care medicine published in 2005 in Critical Care. Twenty-seven articles were grouped into the following categories and subcategories to facilitate rapid overview: mechanical ventilation (physiology, spontaneous breathing during mechanical ventilation, high frequency oscillatory ventilation, side effects of mechanical ventilation, sedation, and prone positioning); infection (pneumonia and sepsis); monitoring (ventilatory monitoring, pulmonary artery catheter and pulse oxymeter); and education (training and health outcome).

The role of high-frequency oscillatory ventilation in paediatric intensive care

Mechanical ventilation during acute respiratory failure in children is associated with development of ventilator-induced lung injury. Experimental models of mechanical ventilation that limit phasic changes in lung volumes and prevent alveolar overdistension appear to be less damaging to the lung. High-frequency oscillatory ventilation, using very small tidal volumes and relatively high end-expiratory lung volumes, provides a safe and effective means of delivering mechanical ventilatory support with the prospect of reducing the development of ventilator-induced lung injury. Despite theoretical advantages and convincing laboratory data, however, the use of high-frequency oscillatory ventilation in the paediatric population has not yet been associated with significant improvements in clinically significant outcome measures.