Initiation Of High-frequency Oscillatory Ventilation Research Articles

Lung behavior during a staircase high-frequency oscillatory ventilation recruitment maneuver

BackgroundLung volume optimization maneuvers (LVOM) are necessary to make physiologic use of high-frequency oscillatory ventilation (HFOV), but lung behavior during such maneuvers has not been studied to determine lung volume changes after initiation of HFOV, to quantify recruitment versus derecruitment during the LVOM and to calculate the time to stabilization after a pressure change.MethodsWe performed a secondary analysis of prospectively collected data in subjects < 18 years on HFOV. Uncalibrated respiratory inductance plethysmography (RIP) tracings were used to quantify lung recruitment and derecruitment during the LVOM inflation and deflation. The time constant was calculated according to the Niemann model.ResultsRIP data of 51 subjects (median age 3.5 [1.7–13.3] months) with moderate-to-severe pediatric acute respiratory distress syndrome (PARDS) in 85.4% were analyzed. Lung recruitment and derecruitment occurred during the LVOM inflation phase upon start of HFOV and between and within pressure changes. At 90% of maximum inflation pressure, lung derecruitment already started during the deflation phase. Time to stable lung volume (time constant) could only be calculated in 26.2% of all pressure changes during the inflation and in 21.4% during the deflation phase, independent of continuous distending pressure (CDP). Inability to calculate the time constant was due to lack of stabilization of the RIP signal or no change in any direction.ConclusionsSignificant heterogeneity in lung behavior during a staircase incremental–decremental LVOM occurred, underscoring the need for higher initial inflation pressures when transitioning from conventional mechanical ventilation (CMV) and a longer time between pressure changes to allow for equilibration.

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

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. 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). Retrospective (medical record review) SETTING: Pediatric intensive care unit in a tertiary care center in Saudi Arabia. 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. PICU mortality. 135 ARDS patients including 74 females (54.8%), and 61 males (45.2%), with a median age (interquar-tile range) of 35 (72) months. 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). 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. Retrospective single-center study.

Evaluation of High-Frequency Oscillatory Ventilation as a Rescue Strategy in Respiratory Failure.

The use of high-frequency oscillatory ventilation (HFOV) is backed by sound physiologic rationale, but clinical data on the elective use of HFOV have been largely disappointing. Nonetheless, HFOV is still occasionally used as a rescue mode in patients with severe hypoxemia. The evidence that supports this practice is sparse. This was a retrospective single-center analysis that involved subjects admitted to the medical ICU at Cleveland Clinic, Cleveland, Ohio. We included all adult patients (ages > 18 y) who received rescue HFOV between January 1, 2010, and December 31, 2018, and analyzed their clinical outcomes. A total of 48 subjects were included in the analysis. The most common primary diagnosis was pneumonia (n = 33 [68.8%]), followed by aspiration (n = 6 [12.5%]) and diffuse alveolar hemorrhage (n = 2 [4.2%]). Switching to HFOV improved oxygenation but also increased vasopressor requirements at 3 h. The mortality rate of the study population was 92% (44/48). Our study did not support utilization of HFOV as a "last-ditch" rescue measure in subjects with respiratory failure. The delayed timing of HFOV initiation and its detrimental hemodynamic effects are among the potential reasons for the high mortality rate.

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.

Use of high frequency oscillatory ventilator in neonates with respiratory failure: the clinical practice in Taiwan and early multimodal outcome prediction

High-frequency oscillatory ventilation (HFOV) can be a rescue for neonates with refractory respiratory failure or an early elective therapy for preterm infants with severe respiratory distress syndrome (RDS). However, little is known about the current evolution and therapeutic limitations of HFOV. We therefore aimed to describe its use in clinical practice and predict the risk of mortality for neonates receiving HFOV. A retrospective observational study of all neonates treated with HFOV in a quaternary referral NICU between January 2007 and December 2016 was conducted. We classified these patients into five subgroups based on primary respiratory diagnoses. We performed the logistic regression and decision tree regression analyses to identify independent factors of 30-day mortality following HFOV. A total of 1125 patients who were ever supported on HFOV were enrolled, of whom 64.1% received HFOV as a rescue therapy, 27.2% received it as an elective therapy, and 8.7% received it for air leak. An average oxygenation index (OI) greater than 25 in the first 24 hours after the initiation of HFOV and patients with secondary pulmonary hypertension were found to have the greatest risk of in-hospital mortality (p < 0.0001). The overall in-hospital mortality rate was 25.8% (290/1125). Decision tree regression analysis revealed that neonates with refractory respiratory failure who had a pre-HFOV OI value higher than 20.5 and OI values higher than 21.5, 23.5 and 34 at 2 hours, 6 hours, and 12 hours after the use of HFOV, respectively, had a significantly increased risk of 30-day mortality. We identified the predictors and cutoff points of OI before and after the initiation of HFOV in neonates with respiratory failure, which can be clinically used as a reference for 30-day mortality. Further efforts are still needed to optimize the outcomes.

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.MethodsThis 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.ResultsOf 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.ConclusionsSurvival 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: still a role?

In light of emerging data from clinical trials, the place of high-frequency oscillatory ventilation (HFOV) in the management of acute respiratory distress syndrome (ARDS) is uncertain. This review provides an overview of these new clinical data and also explores new areas of investigation for HFOV in adults. While prior meta-analyses suggested benefit for HFOV, updated systematic reviews published this year, which include two large recent clinical trials, now show no statistically significant impact of HFOV on mortality in adults with ARDS. It is possible that HFOV would be safer and more effective with a more individualized approach to setting mean airway pressure (mPaw). Possible techniques to achieve this include titrating mPaw in response to oxygenation or hemodynamic changes after HFOV initiation, by measuring respiratory system impedance, or by following echocardiographic changes. Although not first-line, HFOV remains a tool in the armamentarium of the intensivist managing the patient with severe ARDS and refractory hypoxemia. A refinement in the approach to delivering HFOV is warranted, with more attention paid to its adverse hemodynamic consequences.

Use of Sedation and Neuromuscular Blockers in Critically Ill Adults Receiving High-Frequency Oscillatory Ventilation

Nearly all patients receive sedation and neuromuscular blockers (NMBs) during high-frequency oscillatory ventilation (HFOV). To describe analgo-sedation and NMB use prior to and during HFOV in adults with acute respiratory distress syndrome. Retrospective single-center study of 131 consecutive adults whose care was managed with HFOV from 2002 to 2011. During the first 4 days of HFOV, 89% and 95% of patients received sedation and opioids, respectively. Upon HFOV initiation, 119 (90.8%) patients received fentanyl doses higher than 200 µg/h; of these, 48 also received more than 20 mg/h of midazolam. Analgo-sedation doses increased significantly over time such that doses were double by day 3. Factors independently associated with fentanyl doses higher than 200 µg/h were NMB ever used (OR 4.43; 95% CI 1.26-15.65, p = 0.02), pH less than 7.15 (OR 2.08; 95% CI 1.22-3.5, p = 0.007), worsening partial pressure of oxygen/fraction of inspired oxygen (OR 1.05; 95% CI 1.00-1.10, p = 0.04), and Acute Physiology and Chronic Health Evaluation (APACHE) II score (OR 0.87; 95% CI 0.79-0.97, p = 0.009). Deep sedation was commonly administered when NMBs were not being used, with 99.2% of sedation-agitation scores of 1 or 2. Eighty-six patients (65.6%) received NMBs and use was greatest on day 1 (59.5%). Train-of-Four was measured every hour for 53.4% of patients; 29.2% of the measurements were 0 of 4. NMB use declined over the 10-year study period. High analgo-sedation doses were associated with APACHE II scores, worsening gas exchange, and NMB use. Two thirds of patients received NMBs; use was highest on day 1 and subsequently declined. The percentage of patients who received NMB during HFOV in our study was lower than that previously reported. Future research should evaluate patient outcomes with and without use of NMBs, as well as the potential to manage patients with less sedation.

Early application of high frequency oscillatory ventilation in ‘H1N1 influenza’ related ARDS is associated with better outcome: a retrospective study

Dear Editor, High frequency oscillatory ventilation (HFOV) is an accepted therapy for refractory hypoxemia in acute respiratory distress syndrome (ARDS). There is a paucity of data for use of HFOV for 2009 H1N1 influenza ARDS and whether early application of HFOV decreases mortality in this subgroup of patients with severe ARDS. We performed a retrospective analysis of 19 patients who received HFOV as a rescue therapy for 2009 H1N1 influenza with severe ARDS to study the outcome predictors. Deenanath Mangeshkar Hospital ethics committee has approved use of HFOV as a rescue therapy in severe ARDS and consent was obtained from next of kin. Inclusion criteria were the presence of severe ARDS (PaO2/FiO2 100) due to H1N1 influenza virus infection, the application of a maximal support of conventional mechanical ventilation (PEEP equal or greater than 12 cm H2O), and the use of HFOV as a rescue therapy. Patients who received HFOV treatment for less than 24 h were excluded from the analysis. Out of the 19 patients studied, 10 survived (52 %). Patients were divided into survivors and non-survivors Demographic variables, baseline gas exchange and ventilation variables were comparable. Average age and APACHE II score were 30.21 ± 9.60 years 13.25 ± 1.90, respectively. Average tidal volume and plateau pressure on conventional ventilation prior to initiation of HFOV were 6.12 ± 1.26 ml/kg of predicted body weight and 27.21 ± 3.85 cm H2O, respectively. In the whole cohort there was a significant improvement in PaO2/FiO2 at 24 h, after initiation of HFOV (77.89 ± 32.50 vs. 121.78 ± 37.94, p = 0.005). Earlier application of HFOV was the only significant independent predictor of survival (p = 0.045) on multivariate logistic regression analysis. Survival odds ratio was 7.05 (95 % CI, 1.04–47.78) for every day of reduced conventional ventilation. Cox regression analysis of survival rates adjusted for APACHE II score, oxygenation index and time from symptom onset to hospital contact indicated a decrease in survival with increasing duration of conventional ventilation (Fig. 1, Table 1). Our findings are in general agreement with the literature on ARDS in adults. Terragni et al. [1] has shown that even with a lung protective strategy, ventilator induced lung injury is possible. Matthias David et al., had suggested that, an increased conventional ventilation period of more then 3 days prior to HFOV was associated with higher mortality [2]. A recent meta-analysis had reaffirmed this suggestion [3]. However, Casper Bollen et al, [4] had suggested that prolonged conventional ventilation prior to HFOV is not associated with higher mortality. Patients in this case series, randomized to the HFOV group had received conventional ventilation at higher tidal volumes (9.30 ± 2.20 ml/kg of predicted body weight), prior to initiation of HFOV. Limiting the duration of volume controlled ventilation before HFOV may confer a benefit by pre-empting ventilator induced lung injury in these patients. A limitation of our case series is a small sample size. However, it may provide useful insight into management of severe ARDS related to

High-Frequency Oscillatory Ventilators in Burn Patients

The objective of the study is to review a single institution's experience with high-frequency oscillatory ventilation (HFOV) and compare patient characteristics, outcomes, and complications with other reported studies of HFOV use in burn patients with acute respiratory distress syndrome and respiratory failure. This study is a retrospective chart review of the burn patients treated with HFOV in Pediatric Burn Unit at Riley Hospital for Children from October 1996 to April 2007. Patient data were collected, including demographics, percentage of TBSA burn, percentage of full-thickness burn, mechanisms of burn, settings on conventional mechanical ventilation and HFOV, and blood gas data before initiation of HFOV and at 1, 3, 6, 12, 24, 72 (3 days), 120 (5 days), 168 (7 days), 240 (10 days), and 336 hours (14 days). Length of stay, mortality, and complications were also included. HFOV was used 24 times in 21 patients between October 1996 and April 2007 with a mean age of 10 ± 11 years. At initiation of HFOV, the PaO2/FiO2 and oxygenation index values were 109 ± 26 and 36 ± 12, respectively. At stop, the PaO2/FiO2 improved to 166 ± 24 with an average increase from before HFOV of 57 ± 39 (P < .002). At 5 days of HFOV, oxygenation index improved to 14.1 ± 1.7 (P < .02) but did not significantly improve at discontinuation of HFOV at 28.8 ± 6.2 (P = .11). The mortality rate during admission to the burn unit was 29%. Barotrauma occurred in 38% of patients during HFOV. Severe hypercapnea was present briefly in 49% of patients, and this was refractory to standard treatment in 19%. In our experience, HFOV in severe burn patients has significant, early, and sustained improvement in oxygenation. Earlier institution of HFOV seems to significantly lower rates of barotraumas.

High-frequency oscillatory ventilation after cardiac surgery: a treatment for all ages

In a recent issue of Critical Care, Bojan and colleagues [1] reported their experience with early initiation of highfrequency oscillatory ventilation (HFOV) in pediatric cardiac surgery that demonstrated shorter mechanical ventilation times and intensive care stays. Acute lung injury is common in adult patients undergoing surgery, yet there is scant reporting of the intraoperative utility of HFOV [2]. We initiated HFOV in a 49-year-old morbidly obese (body mass index of 69 kg/m 2 ) man who had aortic stenosis, pulmonary hypertension, and decompensated congestive heart failure and who was undergoing aortic valve replacement. Separation from cardiopulmonary bypass (CPB) with inverse-ratio pressure-control ventilation – fraction of inspired oxygen (FiO 2 ) of 1.0 and positive end-expiratory pressure (PEEP) of 18 cm H 2 O – failed because of hypoxia, defi ned as an arterial partial pressure of oxygen (PaO 2 ) of 64 mm Hg. HFOV was initiated (mean pressure airway of 33 cm H 2 O and FiO 2 of 1.0), yielding a PaO 2 of 74 mm Hg and allowing CPB separation. Th e patient was transitioned to conventional ventilation on postoperative day 3 and was extubated on postoperative day 5. Th is adult patient benefi ted from HFOV, as did the pediatric population of Bojan and colleagues. Continuous positive intrathoracic pressure is a concern as it may impede venous return and thereby limit cardiac output (CO) [3]. However, the transition from ventilation with PEEP to HFOV usually results in signifi cant changes in oxygenation/ventilation but not in CO [4]. In patients with pulmonary hypertension, HFOV has been demonstrated to increase CO and decrease pulmonary vascular resistance [5]. For our patient, HFOV allowed improved oxygenation without aff ecting hemodynamics. HFOV may be a safe and eff ective therapy to improve oxygenation/ventilation in patients undergoing cardiac surgery and possibly is underused because of unfounded hemodynamic concerns. HFOV needs exploration as a rescue tool after CPB for patients with hypoxia.

Resolution of Organ Functional Scores to Predict the Outcome in Adult Acute Respiratory Distress Syndrome Patients Receiving High-Frequency Oscillatory Ventilation

High-frequency oscillatory ventilation (HFOV) may be used as a rescue therapy for adults with acute respiratory distress syndrome who have failed conventional ventilation (CV). We undertook a prospective study to investigate the determinants of mortality and the sequential evolution of organ failures in HFOV-treated adult acute respiratory distress syndrome patients. The indication for HFOV was severe oxygenation failure (PaO2/FiO2 <120 mm Hg) while receiving aggressive CV support (defined by either PaO2 ≤65 mm Hg with FiO2 ≥0.6 when positive end-expiratory pressures >10 cmH2O or plateau airway pressure ≥35 cm H2O). Demographic, clinical, and physiologic data were collected prospectively (May 2007-July 2009). Organ System Failure (OSF), Sequential Organ Failure Assessment (SOFA), and Multiple Organ Dysfunction (MOD) scores were recorded during and after HFOV application. Additional outcome measures included HFOV successful weaning rate, cause of failure, complications, survival rate, and cause of death. The intensive care unit mortality rate was 62% (21 of 34). Survivors had a significantly shorter CV time before HFOV than nonsurvivors (32.8 hours ± 16.7 hours vs. 47.9 hours ± 26.2 hours, p = 0.049). Survivors had significantly lower baseline lung injury scores, OSF, SOFA, and MOD scores than nonsurvivors. After HFOV, the OSF, SOFA, and MOD scores were significantly decreased for survivors, particularly from day 3 onward. Survivors had early improvements in OSF scores after HFOV application. Organ failure system scoring may be used for deciding on HFOV initiation and for evaluating the effects of HFOV.

Comparison of four methods of lung volume recruitment during high frequency oscillatory ventilation

To compare four methods of volume recruitment upon initiation of high frequency oscillatory ventilation (HFOV). Anesthetized intubated neonatal piglets (n = 10) underwent repeated saline lavage, followed by conventional mechanical ventilation (CMV). After transition to HFOV at a mean airway pressure 8 cmH2O above CMV (P(basal)), four methods of lung volume recruitment were tested in each animal in random order: Escalating--step-wise pressure increments over 6 min to a peak mean airway pressure 12 cmH2O above P(basal); Sustained dynamic inflation (DI)--a 20 s inflation to the same peak pressure; DI repeated six times for 1 s; Standard--mean airway pressure set directly at P(basal). After each recruitment method, HFOV continued at P(basal) for 15 min. Thoracic gas volume and distribution of aeration were determined by single slice computed tomography, and oxygenation by arterial blood gas sampling. Escalating recruitment resulted in the greatest thoracic gas volume 15 min post recruitment [77 +/- 3.3% of total lung capacity vs. 70 +/- 4.2% (Sustained DI), 65 +/- 3.5% (Repeated DI),63 +/- 5.1% (Standard); mean +/- SEM; P = 0.042, ANOVA]. All methods resulted in a reduction in non-aerated lung, with the greatest redistribution to normally aerated lung being with Escalating recruitment. Oxygenation 15 min post recruitment was better with the Escalating method than with Repeated DI or Standard recruitment (pO2 307 +/- 41 vs. 159 +/- 36 vs. 134 +/- 39 mmHg, respectively; P = 0.016, ANOVA). Escalating recruitment produced the greatest increase in lung volume and resolution of atelectasis, and is recommended for lung volume recruitment upon initiation of HFOV.

A Brief Report: The Use of High-Frequency Oscillatory Ventilation for Severe Pulmonary Contusion

Severe pulmonary contusions are a common cause of acute respiratory distress syndrome (ARDS) and are associated with significant morbidity. High frequency oscillatory ventilation (HFOV) is a ventilatory mode that employs a lung protective strategy consistent with the ARDSNet low tidal volume ventilation strategy and may result in reduced morbidity. The objective of this report is to examine the impact of HFOV on blunt trauma patients with severe pulmonary contusions who failed or were at a high risk of failing conventional mechanical ventilation. We undertook a retrospective chart review of all patients at our institution who received HFOV for severe pulmonary contusions. Patients were placed on HFOV when their mean airway pressure (mP(aw)) surpassed 30 cm H2O and their FIO2 was greater than 0.6. Baseline demographic data including injury severity score (ISS), length of time requiring HFOV, total ventilator days, and inhospital mortality were collected. Serial determinations of oxygenation index (OI) and the PaO2/FIO2 ratio (P/F) were made up to 72 hours after initiation of HFOV. A linear mixed model was used to analyze the slope (beta) of the regression line of P/F versus time and that of OI versus time. Seventeen patients were identified who underwent HFOV for ARDS due primarily to pulmonary contusions. Mean ISS was 36.6, mean APACHE II score was 21.7, and the mean time before initiation of HFOV was 2.0 days. P/F increased significantly after HFOV was initiated (beta = 12.1; 95% confidence interval 7.9 to 16.4, p < 0.001). OI significantly decreased after HFOV implementation (beta = -1.8; 95% confidence interval -2.3 to -1.3, p < 0.001). Mortality rate was 17.6%. The early use of HFOV appears to be safe and efficacious in blunt trauma patients sustaining pulmonary contusions, and results in a rapid improvement in OI and the P/F ratio.

High frequency oscillatory ventilation for respiratory failure due to RSV bronchiolitis

ObjectiveTo describe the time course of high frequency oscillatory ventilation (HFOV) in respiratory syncytial virus (RSV) bronchiolitis.DesignRetrospective charts review.SettingA tertiary paediatric intensive care unit.Patients and participantsInfants with respiratory failure due to RSV infection.InterventionHFOV.Measurements and resultsPattern 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) cmH2O during HFOVi (P < 0.05), then decreased to 11.1(1.3) at HFOVe (P < 0.05). Mean FiO2 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) cmH2O (HFOVi) to 21.1 (7.7) P < 0.05 (HFOVe) while mean (SD) PaCO2 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.ConclusionRSV induced respiratory failure with hypercapnia can be managed with HFOV using high mean airway pressure and large pressure swings while preserving spontaneous breathing.

PH: an overlooked criterion for success in high-frequency oscillatory ventilation in acute respiratory distress syndrome?

High-frequency oscillatory ventilation (HFOV) is used for patients with refractory hypoxia and or severe oxygenation failure in our ICU. There is a unit policy regarding the timing of initiation of HFOV, and all patients were initiated with a single static recruitment manoeuvre and then managed according to local guidelines. The aim of this study was to understand which ventilatory parameters best predicted successful outcome following HFOV.

High-frequency oscillatory ventilation in pediatric patients with acute respiratory failure

To evaluate the effectiveness of high-frequency oscillatory ventilation (HFOV) in pediatric patients with acute respiratory failure, failing conventional ventilation. A prospective, clinical study. Tertiary care pediatric intensive care unit. Twenty pediatric patients (ages 12 days to 5 yrs) with acute respiratory failure (pneumonia, 14; sepsis with acute respiratory distress syndrome, 3; pulmonary edema as a complication of upper airway obstruction, 2; salicylate intoxication with acute respiratory distress syndrome, 1), failing conventional ventilation (median alveolar-arterial oxygen difference [P(A-a)O2] 578 [489-624] torr, median oxygenation index 26 [21-32]. HFOV was instituted after a median length of conventional ventilation of 15.5 (3.3-43.5) hrs. Ventilator settings, arterial blood gases, oxygenation index, and P(A-a)O2 were recorded before HFOV (0 hrs) and at predetermined intervals during HFOV and compared using the one-way Friedman rank-sum procedure and a two-tailed Wilcoxon matched-pairs test. Initiation of HFOV caused a significant decrease in FiO2 at 1 hr that continued to 24 hrs (p <or= .04). In all patients, target ventilation was achieved, and 19 had improved oxygenation. After 1 hr, PaCO2 significantly decreased (p = .002) and remained within the target range thereafter. There were significant decreases in P(A-a)O2 and oxygenation index at 1 and 4 hrs, respectively, that were sustained up to 12 hrs (p <or= .04). No significant complications associated with HFOV were detected. Fifteen patients (75%) survived to hospital discharge. Only one patient died from respiratory failure. In pediatric patients with acute respiratory failure, failing conventional ventilation, HFOV improves gas exchange in a rapid and sustained fashion. However, randomized controlled trials are needed to identify its benefits over conventional modes of mechanical ventilation.

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

IntroductionWith 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.MethodsAn 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.ResultsUsing 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.ConclusionThe 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.

Effect of a lung recruitment maneuver by high-frequency oscillatory ventilation in experimental acute lung injury on organ blood flow in pigs

IntroductionThe objective was to study the effects of a lung recruitment procedure by stepwise increases of mean airway pressure upon organ blood flow and hemodynamics during high-frequency oscillatory ventilation (HFOV) versus pressure-controlled ventilation (PCV) in experimental lung injury.MethodsLung damage was induced by repeated lung lavages in seven anesthetized pigs (23–26 kg). In randomized order, HFOV and PCV were performed with a fixed sequence of mean airway pressure increases (20, 25, and 30 mbar every 30 minutes). The transpulmonary pressure, systemic hemodynamics, intracranial pressure, cerebral perfusion pressure, organ blood flow (fluorescent microspheres), arterial and mixed venous blood gases, and calculated pulmonary shunt were determined at each mean airway pressure setting.ResultsThe transpulmonary pressure increased during lung recruitment (HFOV, from 15 ± 3 mbar to 22 ± 2 mbar, P < 0.05; PCV, from 15 ± 3 mbar to 23 ± 2 mbar, P < 0.05), and high airway pressures resulted in elevated left ventricular end-diastolic pressure (HFOV, from 3 ± 1 mmHg to 6 ± 3 mmHg, P < 0.05; PCV, from 2 ± 1 mmHg to 7 ± 3 mmHg, P < 0.05), pulmonary artery occlusion pressure (HFOV, from 12 ± 2 mmHg to 16 ± 2 mmHg, P < 0.05; PCV, from 13 ± 2 mmHg to 15 ± 2 mmHg, P < 0.05), and intracranial pressure (HFOV, from 14 ± 2 mmHg to 16 ± 2 mmHg, P < 0.05; PCV, from 15 ± 3 mmHg to 17 ± 2 mmHg, P < 0.05). Simultaneously, the mean arterial pressure (HFOV, from 89 ± 7 mmHg to 79 ± 9 mmHg, P < 0.05; PCV, from 91 ± 8 mmHg to 81 ± 8 mmHg, P < 0.05), cardiac output (HFOV, from 3.9 ± 0.4 l/minute to 3.5 ± 0.3 l/minute, P < 0.05; PCV, from 3.8 ± 0.6 l/minute to 3.4 ± 0.3 l/minute, P < 0.05), and stroke volume (HFOV, from 32 ± 7 ml to 28 ± 5 ml, P < 0.05; PCV, from 31 ± 2 ml to 26 ± 4 ml, P < 0.05) decreased. Blood flows to the heart, brain, kidneys and jejunum were maintained. Oxygenation improved and the pulmonary shunt fraction decreased below 10% (HFOV, P < 0.05; PCV, P < 0.05). We detected no differences between HFOV and PCV at comparable transpulmonary pressures.ConclusionA typical recruitment procedure at the initiation of HFOV improved oxygenation but also decreased systemic hemodynamics at high transpulmonary pressures when no changes of vasoactive drugs and fluid management were performed. Blood flow to the organs was not affected during lung recruitment. These effects were independent of the ventilator mode applied.

Use of high-frequency oscillatory ventilation in burn patients

Patients with major burn injuries frequently develop acute respiratory distress syndrome (ARDS). High-frequency oscillatory ventilation (HFOV) has been used successfully in our regional burn center since 1999 for the management of oxygenation failure secondary to ARDS and as a method of intraoperative ventilation to allow surgical burn wound excision to proceed, despite the presence of severe ARDS. The objective of this article is to review the use of HFOV in burn patients, with an emphasis on the indications and selection criteria for the initiation of HFOV, special considerations for patients with smoke inhalation injury, and our approach to intra-operative HFOV. Adult regional burn center in a university-affiliated tertiary care hospital. We have now used HFOV in 36 severely burned patients, 33% of whom had an associated smoke inhalation injury. HFOV produced significant improvements in oxygenation among burn patients with oxygenation failure secondary to ARDS. HFOV produced a slower and less robust reversal of oxygenation failure in those with smoke inhalation compared with patients with burns alone. HFOV has been used intraoperatively for 33 procedures in 18 patients without complications. HFOV has been an indispensable ventilation modality in our burn center, and has played an important role in reversing oxygenation failure in patients with ARDS and in facilitating early excision and closure of the burn wound in these patients.