High Frequency Positive Pressure Ventilation Research Articles

A randomized controlled comparison of three modes of ventilation during cardiopulmonary bypass on oxygenation in pediatric patients with pulmonary hypertension undergoing congenital heart surgeries

ABSTRACT Background Several studies have attempted to improve post bypass oxygenation, decrease extravascular total lung water volume, utilizing continuous positive airway pressure (CPAP) and high-frequency ventilation (HFV) during cardiopulmonary bypass (CPB). Aims To assess the influence of various ventilation modes during CPB on direct pulmonary artery systolic pressure and post bypass oxygenation in pediatric patients with moderate to severe pulmonary hypertension undergoing corrective cardiac surgeries. Methods Included in the study were 24 patients aged 4 months to 6 years, suffering from moderate to severe pulmonary hypertension, undergoing elective corrective cardiac surgeries for atrial septal defect (ASD) or ventricular septal defect (VSD) or atrioventricular canal defects (AVC) (ASA II and III). Group A patients (n = 8) received high-frequency positive pressure ventilation during cardiopulmonary bypass, Group B patients (n = 8) received continuous positive, while group C patients (n = 8) disconnected from the ventilation (passive deflation) (control group). Results There was no statistically significant difference regarding the pulmonary artery systolic pressure (PASP) and pulmonary artery systolic pressure to systemic systolic blood pressure (PASP/SSBP Ratio) at t1, t2, and t3 between the three groups. Conclusion After cadiopulmonary bypass, no significant changes in pulmonary artery pressure was observed in pediatric patients, regardless of the ventilation mode utilized during cardiopulmonary bypass. Conversely, the pulmonary outcomes; delivered Oxygen (DA-aO2), arterial oxygen tension (paO2) and paO2/FiO2 (p/f ratio) and lung ultrasound (LUS) were significantly improved when comparing continuous positive airway pressure (CPAP) with high frequency positive pressure ventilation (HFPPV) and passive deflation during cardiopulmonary bypass.

High-Frequency Positive Pressure Ventilation as Primary Rescue Strategy for Patients with Congenital Diaphragmatic Hernia: A Comparison to High-Frequency Oscillatory Ventilation.

The aim of this article was to evaluate high-frequency positive pressure ventilation (HFPPV) compared with high-frequency oscillatory ventilation (HFOV) as a rescue ventilation strategy for patients with congenital diaphragmatic hernia (CDH). HFPPV is a pressure-controlled conventional ventilation method utilizing high respiratory rate and low positive end-expiratory pressure. Seventy-seven patients diagnosed with CDH from January 2005 to September 2019 who were treated with stepwise progression from HFPPV to HFOV versus only HFOV were included. Fisher's exact test and the Kruskal-Wallis test were used to compare outcomes. Patients treated with HFPPV + HFOV had higher survival to discharge (80 vs. 50%, p = 0.007) and to surgical intervention (95.6 vs. 68.8%, p = 0.003), with average age at repair 2 days earlier (p = 0.004). Need for extracorporeal membrane oxygenation (p = 0.490), inhaled nitric oxide (p = 0.585), supplemental oxygen (p = 0.341), and pulmonary hypertension medications (p = 0.381) were similar. In CDH patients who fail respiratory support with conventional ventilation, HFPPV may be used as an intermediary mode of rescue ventilation prior to HFOV without adverse effects. · HFPPV may be used as an intermediary mode of rescue ventilation prior to HFOV without adverse effect.. · HFPPV is more widely available and can mitigate the limitations faced when using HFOV.. · HFPPV allows for intra- or interhospital transfer of neonates with CDH..

High-Frequency Ventilation in the Treatment of Acute Respiratory Failure

The need for respiratory therapy can reach 90% depending on the category of the intensive care unit and intensive care unit (ICU). Currently is a wide selection of respiratory therapy methods, including fully controlled mechanical ventilation and assist ventilation. The widespread use of mechanical ventilation and its varieties significantly reduced the mortality of ICU patients. However, the mortality of patients from acute respiratory distress syndrome, nosocomial pneumonia, and newborns with respiratory disorders remains high. High-frequency mechanical ventilation (HFMV) is an alternative treatment for severe respiratory failure, but the frequency of use is not yet sufficient. Three main types of HF ventilation is currently available: high-frequency positive pressure ventilation (HFPPV), high-frequency jet ventilation (HFJV) and high-frequency oscillatory ventilation (HFOV). There is an opportunity to choose a specific mode which will be most applicable for a particular patient. The use of the HFOV method allows the successful treatment of newborns with severe respiratory failure due to primary surfactant deficiency, meconial aspiration or multiple organ failure. Recently high amount of publications appeared on the possibilities of non-invasive HFMV in both adult patients and in pediatrics. This mini-review is devoted to this problem.

ПРИМЕНЕНИЕ ВЫСОКОЧАСТОТНОЙ ИСКУССТВЕННОЙ ВЕНТИЛЯЦИИ ЛЕГКИХ В РОДИЛЬНОМ ЗАЛЕ У НЕДОНОШЕННЫХ НОВОРОЖДЕННЫХ ДЕТЕЙ С РЕСПИРАТОРНЫМ ДИСТРЕСС-СИНДРОМОМ

Objective of the research: comparison of two methods of initial respiratory support: high-frequency positive pressure ventilation (HFPPV) and conventional mechanical ventilation (CMV) in extremely low birth weight (ELBW) infants. Materials and methods: prospective, randomized, pilot study, carried out in one level III perinatal center. Thirty-two ELBW babies was randomly separated in two groups: group A – HFPPV (n=17), group B – CMV (n=15). Results: the recovery time for heart rate more than 100 beats per minute in group A was faster than in group B (33,9 seconds vs. 79,2 seconds, p=0,002). Maximum FiO2 for the period of staying in hospital was significantly higher in group B (0,37 vs. 0,73, p<0,001). Mortality in CMV group was significantly higher (0% versus 27%, p=0,038). Conclusion: HFPPV in the delivery room in ELBW babies effectively restores heart rate, reduces the risk of lungs injury and the risk of death before discharge from the hospital.

Synchronized mechanical ventilation for respiratory support in newborn infants.

During synchronised mechanical ventilation, positive airway pressure and spontaneous inspiration coincide. If synchronous ventilation is provoked, adequate gas exchange should be achieved at lower peak airway pressures, potentially reducing baro/volutrauma, air leak and bronchopulmonary dysplasia. Synchronous ventilation can potentially be achieved by manipulation of rate and inspiratory time during conventional ventilation and employment of patient-triggered ventilation. To compare the efficacy of:(i) synchronised mechanical ventilation, delivered as high-frequency positive pressure ventilation (HFPPV) or patient-triggered ventilation (assist control ventilation (ACV) and synchronous intermittent mandatory ventilation (SIMV)), with conventional ventilation or high-frequency oscillation (HFO);(ii) different types of triggered ventilation (ACV, SIMV, pressure-regulated volume control ventilation (PRVCV), SIMV with pressure support (PS) and pressure support ventilation (PSV)). We used the standard search strategy of the Cochrane Neonatal Review group to search the Cochrane Central Register of Controlled Trials (CENTRAL 2016, Issue 5), MEDLINE via PubMed (1966 to June 5 2016), EMBASE (1980 to June 5 2016), and CINAHL (1982 to June 5 2016). We also searched clinical trials databases, conference proceedings, and the reference lists of retrieved articles for randomised controlled trials and quasi-randomised trials. Randomised or quasi-randomised clinical trials comparing synchronised ventilation delivered as HFPPV to CMV, or ACV/SIMV to CMV or HFO in neonates. Randomised trials comparing different triggered ventilation modes (ACV, SIMV, SIMV plus PS, PRVCV and PSV) in neonates. Data were collected regarding clinical outcomes including mortality, air leaks (pneumothorax or pulmonary interstitial emphysema (PIE)), severe intraventricular haemorrhage (grades 3 and 4), bronchopulmonary dysplasia (BPD) (oxygen dependency beyond 28 days), moderate/severe BPD (oxygen/respiratory support dependency beyond 36 weeks' postmenstrual age (PMA) and duration of weaning/ventilation.Eight comparisons were made: (i) HFPPV versus CMV; (ii) ACV/SIMV versus CMV; (iii) SIMV or SIMV + PS versus HFO; iv) ACV versus SIMV; (v) SIMV plus PS versus SIMV; vi) SIMV versus PRVCV; vii) SIMV vs PSV; viii) ACV versus PSV. Data analysis was conducted using relative risk for categorical outcomes, mean difference for outcomes measured on a continuous scale. Twenty-two studies are included in this review. The meta-analysis demonstrates that HFPPV compared to CMV was associated with a reduction in the risk of air leak (typical relative risk (RR) for pneumothorax was 0.69, 95% confidence interval (CI) 0.51 to 0.93). ACV/SIMV compared to CMV was associated with a shorter duration of ventilation (mean difference (MD) -38.3 hours, 95% CI -53.90 to -22.69). SIMV or SIMV + PS was associated with a greater risk of moderate/severe BPD compared to HFO (RR 1.33, 95% CI 1.07 to 1.65) and a longer duration of mechanical ventilation compared to HFO (MD 1.89 days, 95% CI 1.04 to 2.74).ACV compared to SIMV was associated with a trend to a shorter duration of weaning (MD -42.38 hours, 95% CI -94.35 to 9.60). Neither HFPPV nor triggered ventilation was associated with a significant reduction in the incidence of BPD. There was a non-significant trend towards a lower mortality rate using HFPPV versus CMV and a non-significant trend towards a higher mortality rate using triggered ventilation versus CMV. No disadvantage of HFPPV or triggered ventilation was noted regarding other outcomes. Compared to conventional ventilation, benefit is demonstrated for both HFPPV and triggered ventilation with regard to a reduction in air leak and a shorter duration of ventilation, respectively. In none of the trials was complex respiratory monitoring undertaken and thus it is not possible to conclude that the mechanism of producing those benefits is by provocation of synchronised ventilation. Triggered ventilation in the form of SIMV ± PS resulted in a greater risk of BPD and duration of ventilation compared to HFO. Optimisation of trigger and ventilator design with respect to respiratory diagnosis is encouraged before embarking on further trials. It is essential that newer forms of triggered ventilation are tested in randomised trials that are adequately powered to assess long-term outcomes before they are incorporated into routine clinical practice.

Synchronized mechanical ventilation for respiratory support in newborn infants.

During synchronised mechanical ventilation, positive airway pressure and spontaneous inspiration coincide. If synchronous ventilation is provoked, adequate gas exchange should be achieved at lower peak airway pressures, potentially reducing baro/volutrauma, air leak and bronchopulmonary dysplasia. Synchronous ventilation can potentially be achieved by manipulation of rate and inspiratory time during conventional ventilation and employment of patient-triggered ventilation. To compare the efficacy of:(i) synchronised mechanical ventilation, delivered as high-frequency positive pressure ventilation (HFPPV) or patient-triggered ventilation (assist control ventilation (ACV) and synchronous intermittent mandatory ventilation (SIMV)), with conventional ventilation or high-frequency oscillation (HFO);(ii) different types of triggered ventilation (ACV, SIMV, pressure-regulated volume control ventilation (PRVCV), SIMV with pressure support (PS) and pressure support ventilation (PSV)). We used the standard search strategy of the Cochrane Neonatal Review group to search the Cochrane Central Register of Controlled Trials (CENTRAL 2016, Issue 5), MEDLINE via PubMed (1966 to June 5 2016), EMBASE (1980 to June 5 2016), and CINAHL (1982 to June 5 2016). We also searched clinical trials databases, conference proceedings, and the reference lists of retrieved articles for randomised controlled trials and quasi-randomised trials. Randomised or quasi-randomised clinical trials comparing synchronised ventilation delivered as HFPPV to CMV, or ACV/SIMV to CMV or HFO in neonates. Randomised trials comparing different triggered ventilation modes (ACV, SIMV, SIMV plus PS, PRVCV and PSV) in neonates. Data were collected regarding clinical outcomes including mortality, air leaks (pneumothorax or pulmonary interstitial emphysema (PIE)), severe intraventricular haemorrhage (grades 3 and 4), bronchopulmonary dysplasia (BPD) (oxygen dependency beyond 28 days), moderate/severe BPD (oxygen/respiratory support dependency beyond 36 weeks' postmenstrual age (PMA) and duration of weaning/ventilation.Eight comparisons were made: (i) HFPPV versus CMV; (ii) ACV/SIMV versus CMV; (iii) SIMV or SIMV + PS versus HFO; iv) ACV versus SIMV; (v) SIMV plus PS versus SIMV; vi) SIMV versus PRVCV; vii) SIMV vs PSV; viii) ACV versus PSV. Data analysis was conducted using relative risk for categorical outcomes, mean difference for outcomes measured on a continuous scale. Twenty-two studies are included in this review. The meta-analysis demonstrates that HFPPV compared to CMV was associated with a reduction in the risk of air leak (typical relative risk (RR) for pneumothorax was 0.69, 95% confidence interval (CI) 0.51 to 0.93). ACV/SIMV compared to CMV was associated with a shorter duration of ventilation (mean difference (MD) -38.3 hours, 95% CI -53.90 to -22.69). SIMV or SIMV + PS was associated with a greater risk of moderate/severe BPD compared to HFO (RR 1.33, 95% CI 1.07 to 1.65) and a longer duration of mechanical ventilation compared to HFO (MD 1.89 days, 95% CI 1.04 to 2.74).ACV compared to SIMV was associated with a trend to a shorter duration of weaning (MD -42.38 hours, 95% CI -94.35 to 9.60). Neither HFPPV nor triggered ventilation was associated with a significant reduction in the incidence of BPD. There was a non-significant trend towards a lower mortality rate using HFPPV versus CMV and a non-significant trend towards a higher mortality rate using triggered ventilation versus CMV. No disadvantage of HFPPV or triggered ventilation was noted regarding other outcomes. Compared to conventional ventilation, benefit is demonstrated for both HFPPV and triggered ventilation with regard to a reduction in air leak and a shorter duration of ventilation, respectively. In none of the trials was complex respiratory monitoring undertaken and thus it is not possible to conclude that the mechanism of producing those benefits is by provocation of synchronised ventilation. Triggered ventilation in the form of SIMV ± PS resulted in a greater risk of BPD and duration of ventilation compared to HFO. Optimisation of trigger and ventilator design with respect to respiratory diagnosis is encouraged before embarking on further trials. It is essential that newer forms of triggered ventilation are tested in randomised trials that are adequately powered to assess long-term outcomes before they are incorporated into routine clinical practice.

Physiologic effects and regional ventilation of high-frequency positive-pressure ventilation using a conventional ventilator in a severe ARDS animal model associated with an inspiratory pause or recruitment maneuvers

Protective mechanical ventilation (MV) in ARDS is based on reduced stretch of pulmonary tissue, sometimes resulting in severe hypoventilation that can be avoided when using high respiratory rate. High-frequency positive-pressure ventilation (HFPPV) has not been fully explored, especially when associated with other strategies aiming to avoid hypercapnia.

Comparative study of the non-dependent continuous positive pressure ventilation and high-frequency positive-pressure ventilation during one-lung ventilation for video-assisted thoracoscopic surgery

The application of volume controlled high-frequency positive-pressure ventilation (HFPPV) to the non-dependent lung (NL) may have comparable effects to continuous positive-airway pressure (CPAP) on the surgical conditions during one-lung ventilation (OLV) for video-assisted thoracoscopic surgery (VATS). After local Ethics Committee approval and informed consent, we randomly allocated 30 patients scheduled for elective VATS after the first 15min of OLV to ventilate the NL with CPAP of 2cm H(2)O (NL-CPAP(2)) and HFPPV using tidal volume 2ml/kg, inspiratory to expiratory ratio <0.3 and respiratory rate 60/min (NL-HFPPV) for 30min, each in a randomized crossover order. Intraoperative adequacy of surgical conditions was evaluated using a visual analog scale and the changes in hemodynamic and arterial oxygen were recorded. The application of NL-CPAP(2) and NL-HFPPV resulted in more improved arterial oxygenation than during OLV for VATS (P<0.001). The operative field was much better during the application of NL-CPAP(2) than during NL-HFPPV (P<0.001). We concluded that the application of CPAP to the NL during OLV offers good quality of operative field and improved arterial oxygenation for VATS.

Inversed ratio ventilation as an rescue option for ventilation of very premature infants

Objective: We report on three very premature infants who were treated with inverse ratio ventilation (IRV) using a high ventilation frequency (˜60/min) as a rescue method for oxygenation. IRV has become a popular mode of ventilation in adults, but has not been used in premature infants so far. The idea of using IRV stems from a concern of possible ventilator-induced lung injury using high peak pressures to generate higher mean inspiration pressures. Using IRV creates the possibility to increase tidal volumes, overcome the critical opening pressure during inspiration and better alveolar recruitment without increasing the peak pressure. Patients: Three extremely premature infants with a birth weight ranging from 640g and 990g. All of them could not be ventilated adequately with conventional ventilation neither with high frequency oscillation. They were treated with high frequency inverse ratio ventilation. Measurements and main result: At our NICU oxygen saturation, paO2, paCO2 were measured on a regular basis and ventilation modified accordingly. When our standard ventilation schemes failed, high frequency inverse ration ventilation was used a rescue method. When this failed IRV was used as a rescue method. All infants had significant benefit of our IVR ventilation scheme. Conclusion: It seems that in our setting we were able to combine the benefits of pcIRV and of high frequency positive pressure ventilation. The IRV scheme was well tolerated without additional sedation or relaxation needed. All three infants left our NICU without radiological signs of severe BPD. Further studies are needed to describe the possible beneficial role of high frequency pcIRV in premature infants with respiratory failure

Effects of Nondependent Lung Ventilation With Continuous Positive-Pressure Ventilation and High-Frequency Positive-Pressure Ventilation on Right-Ventricular Function During 1-Lung Ventilation

Background. The application of volume-controlled high frequency positive pressure ventilation (HFPPV) to the nondependent lung (NL) may have comparable effects to continuous positive airway pressure (CPAP) on the right ventricular (RV) function, oxygenation, and surgical conditions during one lung ventilation (OLV) for thoracotomy. Methods. After local ethics committee approval and informed consent, 75 patients scheduled for elective thoracotomy using OLV were randomly allocated to receive nondependent lung either CPAP 2 (CPAP2; n=25) or 5 (CPAP5; n=25) cm H2O pressure setting of the device or HFPPV using VT 3 mL-1, I: E ratio <0.3 and R.R 60/min (HFPPV; n=25), followed 15 min of OLV. Intraoperative changes in RV ejection fraction (REF), end-diastolic volume (RVEDVI) and stroke work (RVSWI), stroke volume (SVI), oxygen delivery (DO2), and uptake (VO2) indices and shunt fraction (Qs: Qt) were recorded without any surgical manipulation of the lung. Results. The application of NL-HFPPV resulted in improved REF by 33%, SVI and DO2 (P < 0.01) and reduced RVEDVI, RVSWI, PVRI, oxygen uptake, and shunt fraction by 24.8% (P < 0.01) than in the NL-CPAP groups. Conclusion. We concluded that the use of NL-HFPPV is a feasible option and offers improved RV function and oxygenation during OLV for open thoracotomy.

A Comparison between High Frequency Positive Pressure Ventilation and Intermittent Positive Pressure Ventilation during Closed Mitral Valvotomy

Background: Patients with tight mitral stenosis usually suffer low cardiac output symptoms and elevated pulmonary vascular resistance. They may be candidates for the use of high frequency positive pressure ventilation (HFPPV). We aimed to compare HFPPV with intermittent positive pressure ventilation (IPPV) in patients subjected to closed mitral valvotomy (CMV). Methods: Twenty-four patients subjected to closed mitral valvotomy were randomly allocated to ventilation with IPPV or HFPPV. The minute volume in the IPPV group was given as a tidal volume of 10 ml/kg and a respiratory rate of 14 breaths/min, while in the HFPPV it was given as a tidal volume of 3 ml/kg and a respiratory rate of 60 breaths/min. Heart rate, arterial blood pressure, right atrial pressure (RAP), O2 saturation (SpO2), end-tidal CO2 (PeCO2), arterial CO2 tension (PaCO2) and arterial O2 tension (PaO2) were recorded during the procedure. In addition, interferences to correct hypoxaemia were recorded. Dead space fraction was calculated. Results: RAP decreased significantly during surgery in HFPPV group when compared to IPPV group. Interferences with manual ventilation to correct hypoxaemia were less frequent in HFPPV group compared to IPPV group. In each group dead space fraction increased significantly during surgery when compared to the baseline values. Surgeon's complaint was more frequent in IPPV group. Conclusion: The use of HFPPV during closed mitral valvotomy provides a safe alternative to the conventional IPPV with possible better right side unloading, less hypoxic episodes and better surgical conditions.

Synchronized mechanical ventilation for respiratory support in newborn infants.

During synchronized mechanical ventilation, positive airway pressure and spontaneous inspiration coincide. Thus, if synchronous ventilation is provoked, it is likely that adequate gas exchange should be achieved at lower peak airway pressures, reducing barotrauma and hence airleak and chronic lung disease. Synchronous ventilation can be achieved by manipulation of rate and inspiratory time during conventional ventilation and employment of patient assisted ventilation. To compare (i) the efficacy of synchronized mechanical ventilation, delivered as high frequency positive pressure ventilation or triggered ventilation (patient triggered ventilation (PTV) or synchronous intermittent mandatory ventilation (SIMV)) with conventional ventilation (ii) different types of triggered ventilation Searches were made from 1985-2000 of the Oxford Database of Perinatal Trials, Medline (MeSH terms: mechanical ventilation; triggered ventilation; newborn infant); previous reviews, abstracts, symposia proceedings, hand searching of journals in the English language and contacting expert informants. Randomized or quasi randomized clinical trials comparing synchronized ventilation delivered as high frequency positive pressure ventilation (HFPPV) or triggered ventilation (PTV/SIMV) to conventional mechanical ventilation (CMV) in neonates. Randomized trials comparing different triggered ventilation modes (PTV and SIMV) in neonates. Data regarding clinical outcomes including mortality, airleaks (pneumothorax or pulmonary interstitial emphysema (PIE)), severe intracerebral haemorrhage (grades 3 and 4), chronic lung disease (oxygen dependency beyond 28 days) and duration of weaning/ventilation. Data subdivided into three groups: (i) HFPPV vs CMV; (ii) PTV/SIMV vs CMV; (iii) PTV vs SIMV. Data analysis was conducted according to the standards of the Neonatal Cochrane Review Group. The meta-analysis demonstrates that HFPPV compared to CMV was associated with a reduction in the risk of airleak (typical relative risk for pneumothorax was 0.69 (95% CI 0.51, 0.93). PTV/SIMV compared to CMV was associated with a shorter duration of ventilation (weighted mean difference -31.8 hours, 95% CI -54.1, -9.6). PTV compared to SIMV was associated with a trend to a shorter duration of weaning (weighted mean difference -42.4 hours, 95% CI -94.4, 9.6). No disadvantage to HFPPV or triggered ventilation was noted regarding other outcomes but neither ventilatory mode was associated with a significant reduction in the incidence of chronic lung disease. Compared to conventional ventilation, benefit is demonstrated for both HFPPV and triggered ventilation with regard to a reduction in airleak and a shorter duration of ventilation respectively. In none of the trials was complex respiratory monitoring undertaken and thus it is not possible to conclude that the mechanism of producing those benefits is by provocation of synchronized ventilation. Further trials are needed to determine whether synchronized ventilation is associated with other benefits but optimization of trigger and ventilator design with respect to respiratory diagnosis is encouraged before embarking on further trials.

High-Frequency Ventilation for a Child with Traumatic Bronchial Rupture

Trauma to the intrathoracic tracheobronchial tree is a rare, but usually fatal, injury in childhood (l), and it can result from severe blunt thoracic trauma to the upper part of the chest. When a bronchopleural fistula (BPF) in a child is associated with massive air leakage and tension pneumothorax, immediate thoracotomy for surgical correction of the airway disruption may be lifesaving (2). However, emergency thoracotomy can be difficult in a patient who is hypoxic and hypercarbic due to a lack of adequate ventilation caused by the same tracheobronchial injury. We present an extremely serious case of BPF in which one of the large bronchi was torn and where ventilation was made possible only by the use of highfrequency positive pressure ventilation (HFPPV).

Ventilation techniques to minimize circulatory depression in rabbits with surfactant deficient lungs

Changes in aortic blood flow were measured in rabbits with both normal and surfactant depleted lungs in order to elucidate the effect of different modes of ventilation on the circulation while optimizing arterial oxygenation (PaO2). Conventional mechanical ventilation (CMV), reversed inspiratory to expiratory ratio of CMV (IRV), high frequency positive pressure ventilation (HFV), and high frequency oscillation (HFO) were used. Normocapnia was maintained throughout during different modes of ventilation. In normal lungs the aortic blood flow during IRV was significantly lower with similar levels of PaCO2 compared with CMV, HFV, and HFO. In lavaged lungs, without positive end-expiratory pressure (PEEP), the aortic blood flow during CMV was significantly higher than with other modes of ventilation. When 10 cm H2O of PEEP was applied, the PaO2 increased maximally to normal values at all modes of ventilation, but the aortic blood flow was significantly reduced (P < 0.05) during CMV and IRV compared to HFV and HFO. The aortic blood flows at 5 cm H2O of PEEP were very similar during CMV, HFV, and HFO but significantly reduced during IRV. This study showed that at an optimal arterial oxygenation with higher PEEP levels, maintenance of aortic blood flow was maximal during HFV and HFO.

Multicentre randomised controlled trial of high against low frequency positive pressure ventilation. Oxford Region Controlled Trial of Artificial Ventilation OCTAVE Study Group.

A total of 346 infants aged less than 72 hours were randomly allocated to be treated either by high frequency positive pressure ventilation (HFPPV; rate fixed at 60/minute throughout treatment and initial inspiratory:expiratory (I:E) ratio 1:2, increased to 1:1 if necessary) or by low frequency positive pressure ventilation (LFPPV; rate less than or equal to 40/minute and initial I:E ratio usually 1:1, both decreasing during weaning). The main hypotheses were that HFPPV reduces pneumothorax, chronic lung disease and death before discharge in all infants, as well as those with hyaline membrane disease, and that it reduces the incidence of later neurodevelopmental complications in infants of less than 33 weeks' gestation. Among all the infants the rate of pneumothorax was 19% in the HFPPV group and 26% in the LFPPV group (p = 0.13; odds ratio 0.7, 95% confidence intervals (CI) 0.4 to 1.1); there was no difference in mortality or the incidence of chronic lung disease. In infants of less than 33 weeks' gestation there were no differences in adverse neurodevelopmental outcomes. Among the subgroup of 237 infants with hyaline membrane disease, median fractional inspired oxygen at the time of entry to the trial was 0.6 in the HFPPV group and 0.7 in the LFPPV group, indicating that many had moderately severe disease. In patients with hyaline membrane disease HFPPV was associated with a lower rate of pneumothorax (18% in the HFPPV group compared with 33% in the LFPPV group, p = 0.013, odds ratio 0.5, 95% CI 0.3 to 0.8, with no differences in mortality, or in duration of intubation or supplementary oxygen in survivors. As used in this study, HFPPV was the preferred ventilator regimen for infants with hyaline membrane disease.

A Comparison of Two-Lung High Frequency Positive Pressure Ventilation and One-Lung Ventilation plus 5 cm H2O Non-Ventilated Lung CPAP, in Patients Undergoing Anaesthesia for Oesophagectomy

A randomised prospective controlled study was conducted during a one-year period on patients scheduled for oesophagectomy via a right thoracotomy approach. Twenty-two patients received one-lung ventilation (OLV group) and twenty patients received high frequency positive pressure ventilation (HFPPV group). Episodic hypoxaemia (SaO2 less than 90% for greater than 30 seconds, FiO2 1.0) occurred in eleven patients in the OLV group and six patients in the HFPPV group. No patient in the HFPPV group had a severe desaturation episode (SaO2 less than 80%, FiO2 1.0) compared with nine patients in the OLV group (P less than 0.05). The mean peak inspiratory pressure and average mean airway pressure were significantly lower in the HFPPV group 28.8 (SD 7.7) and 7.2 (SD 2.4) cm H2O respectively, compared with the OLV group, 40.0 (SD 9.9) and 11.9 (SD 4.9) cm H2O (P less than 0.05). Two-lung high frequency positive pressure ventilation has some advantages over one-lung ventilation during the thoracotomy phase of oesophagectomy because it is easy to administer, does not significantly compromise the surgical exposure and is associated with fewer severe undesirable physiological disturbances.

An experimental study of different ventilatory modes in piglets in severe respiratory distress induced by surfactant depletion

In 19 anesthetized piglets 3 ventilatory modes were studied after inducing pulmonary insufficiency by bronchoalveolar lavage by the method of Lachmann. The lavage model was considered suitable for reproduction of severe respiratory distress. This model was reproducible and stable with respect to alveolar collapse, decrease in static chest-lung compliance and increase in extravascular lung water. The ventilatory modes studied were volume-controlled intermittent positive-pressure ventilation (IPPV), pressure-controlled inverse ratio ventilation (IRV), and pressure-controlled high-frequency positive-pressure ventilation (HFPPV). The 3 ventilatory modes were used in random sequence for at least 30 min to produce a ventilatory steady state. Ventilation with no PEEP, permitting alveolar collapse, was interposed between each experimental mode. The ability to open collapsed alveoli, i.e. alveolar recruitment, was different. The recruitment rate for IPPV was 74%, but for IRV and HFPPV it was 95%, respectively. Although IRV provided the best PaO2, this was at the expense of high airway pressures with circulatory interference and reduced oxygen transport. In contrast to this, HFPPV provided lower airway pressures, less circulatory interference and improved oxygen transport. In the clinical setting there might be negative effects on vital organs and functions unless the ventilatory modes are continuously and cautiously adapted to the individual requirements in different phases of severe respiratory distress. Therefore, one ventilatory strategy could be to "open the airways" with IRV, but then switch to HFPPV in an attempt to maintain the airways open with lesser risk of barotrauma and with improved oxygen transport.

An experimental randomized study of six different ventilatory modes in a piglet model with normal lungs

A randomized study of 6 ventilatory modes was made in 7 piglets with normal lungs. Using a Servo HFV 970 (prototype system) and a Servo ventilator 900 C the ventilatory modes examined were as follows: SV-20V, i.e. volume-controlled intermittent positive-pressure ventilation (IPPV); SV-20VIosc, i.e. volume-controlled ventilation (IPPV) with superimposed inspiratory oscillations; and SV-20VEf, i.e. volume-controlled ventilation (IPPV) with expiratory flush of fresh gas; HFV-60 denotes low-compressive high-frequency positive-pressure ventilation (HFPPV) and HVF-20 denotes low-compressive volume-controlled intermittent positive-pressure ventilation; and SV-20P denotes pressure-controlled intermittent positive-pressure ventilation. With all modes of ventilation a PEEP of 7.5 cm H2O was used. In the abbreviations used, the number denotes the ventilatory frequency in breaths per minute (bpm). HFV indicates that all gas was delivered via the HFV 970 unit. The ventilatory modes described above were applied randomly for at least 30 min, aiming for a normoventilatory steady state. The HFV-60 and the HFV-20 modes gave lower peak airway pressures, 12-13 cm H2O compared to approximately 17 cm H2O for the other ventilatory modes. Also the mean airway pressures were lower with the HFV modes 8-9 cm H2O compared to 11-14 cm H2O for the other modes. The gas distribution was evaluated by N2 wash-out and a modified lung clearance index. All modes showed N2 wash-out according to a two-compartment model. The SV-20P mode had the fastest wash-out, but the HFV-60 and HFV-20 ventilatory modes also showed a faster N2 wash-out than the others.(ABSTRACT TRUNCATED AT 250 WORDS)

Randomised trial of patient triggered ventilation versus high frequency positive pressure ventilation in acute respiratory distress

Synchronous respiration during mechanical ventilation of preterm neonates with acute respiratory distress is extremely beneficial as it improves oxygenation and is associated with a very low incidence of pneumothorax. We have assessed which form of ventilation: patient triggered ventilation (PTV) or high frequency positive pressure ventilation (HFPPV) is most successful in provoking this beneficial respiratory interaction, synchrony. Preterm infants of less than 4 hours of age and gestational age greater than or equal to 27 weeks were entered into a randomised controlled trial. Thirteen patients received PTV, median gestational age 30 weeks (range 27-36) and 36 HFPPV, median gestational age, 29 weeks (range 27-40). HFPPV was delivered by Sechrist ventilators at rates between 61 and 120 breaths/minute. Patient triggered ventilation was delivered by an SLE ventilator and an airway pressure trigger was used. Inflation times during PTV were between 0.2 and 0.45 seconds. HFPPV provoked synchrony which persisted until extubation in 25 patients, but PTV provoked persistent synchrony only in four patients (p less than 0.05). No infant developed a pneumothorax. Eleven of 36 patients became asynchronous on HFPPV and 5 of 13 on PTV. In addition, four patients on PTV developed recurrent apnoea with deteriorating blood gases. Thus, 11 of 36 patients on HFPPV and 9 of 13 on PTV required transfer to conventional ventilation (p less than 0.05). Transfer occurred at a median of 30 hours (range 6-84) on HFPPV and 1 hour (range 1-25) on PTV, p less than 0.01. Infants who required transfer from the randomised mode of ventilation required a longer period of intubation (median 174 hours, range 30-2928) compared to 38 hours (range 1.5-456) for successful cases, regardless of randomisation (p less than 0.01). This study demonstrates PTV is significantly less successful in promoting synchrony than HFPPV. We therefore conclude HFPPV is a more useful form of respiratory support than PTV for preterm infants with acute respiratory distress.

Circulatory effects of fast ventilator rates in preterm infants.

High frequency positive pressure ventilation has been suggested to result in a lower incidence of respiratory complications in preterm infants with idiopathic respiratory distress syndrome compared with ventilation at conventional rates. A possible disadvantage is compromise of the infant's cardiovascular condition secondary to inadvertent positive end expiratory pressure (PEEP). In a group of 20 such infants treated with high frequency positive pressure ventilation (rates of up to 100/minute) and analysed, changes in arterial blood pressure and cerebral blood flow velocity were largely influenced by changes in arterial blood gases, and no effect could be attributed to inadvertent PEEP. In addition, the observed fall in both arterial carbon dioxide and oxygen tensions could be readily predicted for theoretical reasons. Under certain conditions at the fastest rates used, cerebral blood flow velocity was significantly influenced by changes in blood pressure, which may indicate impaired cerebrovascular regulation. Though other factors (such as the severity of the infants' illness or the use of paralysis) may have been responsible for this apparent blood pressure passivity, the role of high frequency positive pressure ventilation in such infants warrants further study.