High-Frequency Percussive Ventilation: An Alternative Mode of Ventilation for Head-Injured Patients With Adult Respiratory Distress Syndrome

Impact of opioid free Anaesthesia versus opioid Anaesthesia on the immediate postoperative oxygenation after bariatric surgery: a prospective observational study

Introduction: Opioid induced respiratory depression (OIRD) is a preventable aetiology of postoperative respiratory depression with 85% of the episodes taking place in the first 24 postoperative hours. Due to altered respiratory functional metrics and frequently coexisting comorbidities, obese patients are at a particularly higher risk for such complications. The present study aimed to assess if an opioid-free anesthesia (OFA) was associated with a reduced immediate postoperative OIRD when compared to Opiod-based anesthesia (OA). Methods: Obese patients presenting for bariatric surgery were consecutively included in a non-randomized fashion. Lung protective ventilation strategies applied in both groups. In the OA group, Sufentanil was used for intraoperative analgesia in a liberal fashion. In the OFA group, patients received a pre-induction dexmedetomidine loading, followed by a lidocaine, ketamine and dexmedetomidine bolus immediately before induction, further maintained throughout the intraoperative period. Plethysmographic saturations were obtained before induction as well as after extubation and in the Post-anesthesia care unit (PACU). Opioid requirement and Postoperative Nausea and Vomiting incidence were similarly registered. Results: Thirty-four patients were included in the OFA group, and 30 in the OA group. No significant anthropometric and comorbidity differences were found between both groups. OFA patients had significantly lower pre-induction saturations after dexmedetomidine loading. No difference was found for post-extubation saturations as well as well as pre-PACU discharge. The need for supplemental oxygen at the PACU was higher in the OA group. Opioid requirement and cumulative consumption (MEDs) were significantly higher with OA. Conclusion: OFA was not associated with significant postoperative saturation changes but led to a lower need of postoperative supplemental oxygen therapy. OA led to higher opioid rescue need. No fatal respiratory complications were registered in both groups in the immediate postoperative period.

Airway pressure release ventilation does not increase intracranial pressure in patients with traumatic brain injury with poor lung compliance

The use of Airway Pressure Release Ventilation (APRV) in patients with traumatic brain injury (TBI) remains controversial. Some believe that elevated mean airway pressures transmitted to the thorax may cause clinically significant increases in Central Venous Pressure (CVP) and intracranial pressure (ICP) from venous congestion. We perform a retrospective review from 2009 to 2015 of traumatically injured patients who were transitioned from traditional ventilator modes to APRV and also had an ICP monitor in place. Fifteen patients undergoing 19 transitions to APRV were identified. Prior to transitioning to APRV the average static and dynamic compliance was 22.9 +/- 5.6 and 16.5 +/- 4.12 mL/cm H2O. There was no statistical difference in ICP, MAP, and CPP prior to and after transition to APRV. There was a statistically significant increase in CVP, PaO2, and P:F ratio. Individually, only 4 patients had ICP values >20 in the first hour after transitioning to APRV and the rate of ICP elevations was similar between the two modes of ventilation. These data show that APRV is a viable mode of ventilation in patients with TBI who have low lung compliance. The increased CVP of this mode of ventilation did not affect ICP or hemodynamic parameters.

The use of high-frequency percussive ventilation after cardiac surgery significantly improves gas exchange without impairment of hemodynamics

Objective

Respiratory failure represents a significant source of morbidity and mortality for surgical patients. High-frequency percussive ventilation (HFPV) is emerging as a potentially effective rescue therapy in patients failing conventional mechanical ventilation (CMV). Use of HFPV is often limited by concerns for potential effects on hemodynamics, which is particularly tenuous in patients immediately after cardiac surgery. In this manuscript we evaluated the effects of HFPV on gas exchange and cardiac hemodynamics in the immediate postoperative period after cardiac surgery, in comparison with CMV.

Methods

Twenty-four consecutive cardiac surgery patients were ventilated in immediate postoperative period with HFPV for two to four hours, then they switched to a CMV using the adaptive support ventilation mode for weaning. Arterial blood gases were performed during the first and second hour on HFPV, and at 45 minutes after initiation of CMV. Respiratory settings and invasive hemodynamic data (mixed venous oxygen saturation, central venous pressure, systemic and pulmonary blood pressure, cardiac output and index) were collected utilizing right heart pulmonary catheter and arterial lines during HFPV and CMV. Primary outcome was improvement in the ratio between partial pressure of oxygen to fraction of inspired oxygen (P/F ratio) and changes in hemodynamics.

Results

Analysis of data for 24 patients revealed a significantly better P/F ratio during the first and second hour on HFPV, compared with a P/F ratio on CMV (420.0 ± 158.8, 459.2 ± 138.5, and 260.2 ± 98.5 respectively, p < 0.05), suggesting much better gas exchange on HFPV than on CMV. Hemodynamics were not affected by the mode of the ventilation.

Conclusions

Improvement in gas exchange, reflected in a significantly improved P/F ratio, wasn't accompanied by worsening in hemodynamic parameters. The significant gains in the P/F ratio were lost when patients were switched to conventional ventilation. This data suggest that HFPV provides significantly better gas exchange compared with CMV and can be safely utilized in postoperative cardiac patients without any significant effect on hemodynamics.

High-Frequency Percussive Ventilation Rescue Therapy in Morbidly Obese Patients Failing Conventional Mechanical Ventilation

BACKGROUND

Morbidly obese patients with respiratory failure who do not improve on conventional mechanical ventilation (CMV) often undergo rescue therapy with extracorporeal membrane oxygenation (ECMO). We describe our experience with high-frequency percussive ventilation (HFPV) as a rescue modality.

METHODS

In a retrospective analysis from 2009 to 2016, 12 morbidly obese patients underwent HFPV after failing to wean from CMV. Data were collected regarding demographics, cause of respiratory failure, ventilation settings, and hospital course outcomes. Our end point data were pre- and post-HFPV partial pressure of arterial oxygen and PaO₂ to fraction of inspired oxygen (PF) ratios measured at initiation, 2, and 24 hours.

RESULTS

Twelve morbidly obese patients required HFPV for respiratory failure. Causes of respiratory failure overlapped and included cardiogenic pulmonary edema (n = 8), pneumonia (n = 5), septic shock (n = 5), and asthma (n = 1). After HFPV initiation, mean fraction of inspired oxygen FiO₂ was tapered from 98% to 82% and 66% at 2 and 24 hours, respectively. Mean PaO₂ increased from 60.9 mm Hg before HFPV to 175.1 mm Hg (P < .05) at initiation of HFPV, then sustained at 129.5 mm Hg (P < .05) and 88.1 mm Hg (P < .005) at 2 and 24 hours, respectively. Mean PF ratio improved from 66.1 before HFPV to 180.3 (P < .05), 181.0 (P < .05) and 148.9 (P < .0005) at initiation, 2, and 24 hours, respectively. The improvement in mean PaO₂ and PF ratios was durable at 24 hours whether or not the patient was returned to CMV (n = 10) or remained on HFPV (n = 2). Survival to discharge was 66.7%.

CONCLUSION

In our cohort of morbidly obese patients, HFPV was successfully utilized as a rescue therapy precluding the need for ECMO. Despite our small sample size, HFPV should be considered as a rescue therapy in morbidly obese patients failing CMV prior to the initiation of ECMO. Our retrospective analysis supports consideration for HFPV as another form of rescue therapy for obese patients with refractory hypoxemia and respiratory failure who are not improving with CMV.

Use of High-Frequency Percussive Ventilation to Expand Organ Donor Pool

A 34-year-old woman was brought in to the emergency department after a motor vehicle accident. She had signs of traumatic head injury with Glasgow Coma Scale score of 3, and her neurological examination was consistent with brain death. She was persistently hypoxic on conventional mechanical ventilation and high-frequency percussive ventilation was initiated. The patient’s oxygenation improved and was sustained long enough to provide time for organ procurement. This is the first case portraying high-frequency percussive ventilation as a bridge for donors failing on conventional mechanical ventilation.

High-frequency percussive ventilation in severe acute respiratory distress syndrome: A single center experience

BACKGROUND

Few studies have investigated high-frequency percussive ventilation (HFPV) in adult patients with acute respiratory distress syndrome (ARDS).

MATERIALS AND METHODS

We retrospectively analyzed data from critically ill-patients with moderate and severe ARDS who received HFPV. Ventilation and oxygenation were governed according to a predefined protocol. HFPV was continued until patients could be switched to conventional ventilation.

RESULTS

A total of 42 patients (20 with pneumonia-related ARDS and 22 non-septic ARDS cases) were evaluable. Baseline demographic characteristics, severity of illness, lung injury score; pH and respiratory variables were comparable between pneumonia and non-sepsis-related ARDS. Within 24 h, HFPV restored normal pH and PaCO2 and considerably improved oxygenation. Oxygenation improved more in non-septic than in pneumonia-related ARDS. Patients with pneumonia-induced ARDS also remained longer HFPV-dependent (7.0 vs. 4.9 days; P < 0.05). Mortality at 30 days was significantly higher in pneumonia-related than in non-sepsis-related ARDS (50% vs. 18%; P = 0.01).

CONCLUSIONS

HFPV caused rapid and sustained improvement of oxygenation and ventilation in patients with moderate to severe ARDS. Less improved oxygenation, longer ventilator dependency and worse survival were observed in pneumonia-related ARDS.

Ventilatory strategies in trauma patients

Lung injury in trauma patients can occur because of direct injury to lung or due to secondary effects of injury elsewhere for example fat embolism from a long bone fracture, or due to response to a systemic insult such as; acute respiratory distress syndrome (ARDS) secondary to sepsis or transfusion related lung injury. There are certain special situations like head injury where the primary culprit is not the lung, but the brain and the ventilator strategy is aimed at preserving the brain tissue and the respiratory system takes a second place. The present article aims to delineate the strategies addressing practical problems and challenges faced by intensivists dealing with trauma patients with or without healthy lungs. The lung protective strategies along with newer trends in ventilation are discussed. Ventilatory management for specific organ system trauma are highlighted and their physiological base is presented.

High-frequency percussive ventilation improves oxygenation and ventilation in pediatric patients with acute respiratory failure

PURPOSE

High-frequency percussive ventilation (HFPV) in pediatrics has been described predominantly in burned patients. We aimed to describe its effectiveness and safety in noninhalational pediatric acute respiratory failure (ARF).

METHODS

We conducted an observational study in a tertiary care pediatric intensive care unit on 31 patients with ARF failing conventional ventilation transitioned to HFPV. Demographics, ventilator settings, oxygenation index, oxygen saturation index, oxygen saturation as measured by pulse oximetry/fraction of inspired oxygen (Fio2), and Pao2/Fio2 were recorded before and during HFPV.

RESULTS

Initiation of HFPV was associated with improvements in oxygenation index, oxygen saturation index, Pao2/Fio2, and oxygen saturation as measured by pulse oximetry/Fio2 as early as 12 hours (P < .05), which continued through 48 hours after transition. Improved oxygenation occurred without an increase in mean airway pressures. Reductions in Paco2 occurred 6 hours after initiation of HFPV and continued through 48 hours (P < .01). Improved gas exchange was accompanied by reduced peak-inflating pressures at all time intervals after initiation of HPFV (P < .01). Vasopressor scores were similar before and after initiation of HFPV in patients requiring vasoactive support. Twenty-six (83.9%) of 31 patients survived to hospital discharge.

CONCLUSIONS

In a heterogeneous population of pediatric ARF failing conventional ventilation, HFPV efficiently improves gas exchange in a lung-protective manner.

[Interaction brain-lungs]

The brain and the lungs interact early and rapidly when hit by a disease process. Often well tolerated by the healthy brain, an impaired respiratory function may deteriorate further a "sick" brain. Hypoxemia is a prognostic factor in the brain-injured patients. At the opposite, an acute brain damage early impacts the lung function. Local brain inflammation spreads rapidly to the lung. It initiates an immunological process weakening the lungs and increasing its susceptibility to infection and mechanical ventilation. Sometimes this process is preceded by a swelling lesion, known as neurogenic pulmonary oedema, resulting from an sympathetic overstimulation which usually follows an intense and brutal surge of intracranial pressure. The management of brain-injured patients has to be directed toward the protection of both the brain and lung. Neuronal preservation is crucial, because of the lack of regenerative potential in the brain, unlike the lung. A compromise must be obtained between the cerebral and pulmonary treatments although they may conflict in some situations.

Acute lung injury in patients with severe brain injury: a double hit model

The presence of pulmonary dysfunction after brain injury is well recognized. Acute lung injury (ALI) occurs in 20% of patients with isolated brain injury and is associated with a poor outcome. The "blast injury" theory, which proposes combined "hydrostatic" and "high permeability" mechanisms for the formation of neurogenic pulmonary edema, has been challenged recently by the observation that a systemic inflammatory response may play an integral role in the development of pulmonary dysfunction associated with brain injury. As a result of the primary cerebral injury, a systemic inflammatory reaction occurs, which induces an alteration in blood-brain barrier permeability and infiltration of activated neutrophils into the lung. This preclinical injury makes the lungs more susceptible to the mechanical stress of an injurious ventilatory strategy. Tight CO2 control is a therapeutic priority in patients with acute brain injury, but the use of high tidal volume ventilation may contribute to the development of ALI. Establishment of a therapeutic regimen that allows the combination of protective ventilation with the prevention of hypercapnia is, therefore, required. Moreover, in patients with brain injury, hypoxemia represents a secondary insult associated with a poor outcome. Optimal oxygenation may be achieved by using an adequate FiO2 and by application of positive end-expiratory pressure (PEEP). PEEP may, however, affect the cerebral circulation by hemodynamic and CO2-mediated mechanisms and the effects of PEEP on cerebral hemodynamics should be monitored in these patients and used to titrate its application.

High-frequency percussive ventilation revisited

High-frequency percussive ventilation (HFPV) has demonstrated a potential role as a rescue option for refractory acute respiratory distress syndrome and as a method for improving inhalation injury outcomes. Nevertheless, there is a lack of literature examining the practical application of HFPV theory toward either improving gas exchange or preventing possible ventilator-induced lung injury. This article will discuss the clinically pertinent aspects of HFPV, inclusive of high- and low-frequency ventilation.

Mechanical ventilation in trauma

PURPOSE OF REVIEW

The purpose of this review is to evaluate new concepts in mechanical ventilation in trauma. We begin with the keystone of physiology prior to embarking on a discussion of several new modes of mechanical ventilation. We will discuss the use of noninvasive ventilation as a mode to prevent intubation and then go on to airway pressure release ventilation, high-frequency oscillatory ventilation, and computer-based, closed loop ventilation.

RECENT FINDINGS

The importance of preventing further injury in mechanical ventilation lies at the heart of the introduction of several new strategies of mechanical ventilation. New modes of ventilation have been developed to provide lung recruitment and alveolar stabilization at the lowest possible pressure.

SUMMARY

The old modes of continuous positive airway pressure and bilevel positive airway pressure have been actively introduced in clinical practice in the case of trauma patients. Used with proper pain management protocols, there has been a decrease in the incidence of intubation in blunt thoracic trauma. Airway pressure release ventilation has been gaining a role in the management of thoracic injury and may lead to less incidence of physiologic trauma to mechanically ventilated patients. High-frequency oscillatory ventilation has been shown to be effective in patient care by its ability to open and recruit the lung in trauma patients and in those with acute respiratory distress syndrome but it may not have a role in patients with inhalational injury. Closed loop ventilation is a technology that may better control major pulmonary parameters and lead to more rapid titration from the ventilator to spontaneous breathing.

Severe hypoxemic respiratory failure: part 1--ventilatory strategies

Approximately 16% of deaths in patients with ARDS results from refractory hypoxemia, which is the inability to achieve adequate arterial oxygenation despite high levels of inspired oxygen or the development of barotrauma. A number of ventilator-focused rescue therapies that can be used when conventional mechanical ventilation does not achieve a specific target level of oxygenation are discussed. A literature search was conducted and narrative review written to summarize the use of high levels of positive end-expiratory pressure, recruitment maneuvers, airway pressure-release ventilation, and high-frequency ventilation. Each therapy reviewed has been reported to improve oxygenation in patients with ARDS. However, none of them have been shown to improve survival when studied in heterogeneous populations of patients with ARDS. Moreover, none of the therapies has been reported to be superior to another for the goal of improving oxygenation. The goal of improving oxygenation must always be balanced against the risk of further lung injury. The optimal time to initiate rescue therapies, if needed, is within 96 h of the onset of ARDS, a time when alveolar recruitment potential is the greatest. A variety of ventilatory approaches are available to improve oxygenation in the setting of refractory hypoxemia and ARDS. Which, if any, of these approaches should be used is often determined by the availability of equipment and clinician bias.

Ventilatory strategies for patients with acute brain injury

PURPOSE OF REVIEW

The ventilation of patients with acute brain injuries can present significant challenges. Frequently, guidelines recommending management strategies for patients with traumatic brain injuries come into conflict with what is now considered best ventilatory practice. In this review, we will explore many of these areas of conflict.

RECENT FINDINGS

The use of ventilatory strategies to control partial pressure of carbon dioxide in patients with traumatic brain injury is associated with the development of acute lung injury. Analysis of the International Mission for Prognosis And Clinical Trial (IMPACT) database has confirmed the association between hypoxia and poor neurological outcome. Although a recent meta-analysis has suggested a survival benefit for steroids in acute lung injury, the use of steroids has been associated with a worsening of outcome in patients with traumatic brain injuries and their effects on the brain have not been fully elucidated.

SUMMARY

There are unlikely to be randomized controlled trials advising how best to ventilate patients with acute brain injuries because of the heterogeneous nature of such injuries. Hypoxia should be avoided. The more widespread use of multimodal brain monitoring, including brain tissue oxygen and cerebral blood flow monitoring, may allow clinicians to tolerate a higher arterial partial pressure of carbon dioxide than has been traditional, allowing a less injurious ventilatory strategy. Modest positive end-expiratory pressure can be used. In severe respiratory failure, most 'rescue' strategies have been attempted in patients with acute brain injuries. Choice of rescue therapy at present is best decided on a case-by-case basis in conjunction with local expertise.

Clinical review: Ventilatory strategies for obstetric, brain-injured and obese patients

The ventilatory management of patients with acute respiratory failure is supported by good evidence, aiming to reduce lung injury by pressure limitation and reducing the duration of ventilatory support by regular assessment for discontinuation. Certain patient groups, however, due to their altered physiology or disease-specific complications, may require some variation in usual ventilatory management. The present manuscript reviews the ventilatory management in three special populations, namely the patient with brain injury, the pregnant patient and the morbidly obese patient.

Acute lung injury in patients with severe brain injury: a double hit model

The presence of pulmonary dysfunction after brain injury is well recognized. Acute lung injury (ALI) occurs in 20% of patients with isolated brain injury and is associated with a poor outcome. The "blast injury" theory, which proposes combined "hydrostatic" and "high permeability" mechanisms for the formation of neurogenic pulmonary edema, has been challenged recently by the observation that a systemic inflammatory response may play an integral role in the development of pulmonary dysfunction associated with brain injury. As a result of the primary cerebral injury, a systemic inflammatory reaction occurs, which induces an alteration in blood-brain barrier permeability and infiltration of activated neutrophils into the lung. This preclinical injury makes the lungs more susceptible to the mechanical stress of an injurious ventilatory strategy. Tight CO2 control is a therapeutic priority in patients with acute brain injury, but the use of high tidal volume ventilation may contribute to the development of ALI. Establishment of a therapeutic regimen that allows the combination of protective ventilation with the prevention of hypercapnia is, therefore, required. Moreover, in patients with brain injury, hypoxemia represents a secondary insult associated with a poor outcome. Optimal oxygenation may be achieved by using an adequate FiO2 and by application of positive end-expiratory pressure (PEEP). PEEP may, however, affect the cerebral circulation by hemodynamic and CO2-mediated mechanisms and the effects of PEEP on cerebral hemodynamics should be monitored in these patients and used to titrate its application.

High-frequency oscillatory ventilation as a rescue therapy for adult trauma patients

BACKGROUND

High-frequency oscillatory ventilation is an alternative ventilation mode that improves oxygenation in trauma patients in whom conventional ventilation strategies have been unsuccessful.

OBJECTIVE

To evaluate the effect of high-frequency oscillatory ventilation on oxygenation, survival, and parameters predictive of survival in trauma patients.

METHODS

A retrospective case series of 24 adult patients admitted to the trauma intensive care unit at a level I trauma center between November 2001 and July 2005 and treated with high-frequency oscillatory ventilation. Survivors and nonsurvivors were compared for mechanism and severity of injury, oxygenation parameters related to high-frequency oscillatory ventilation, and hospital course.

RESULTS

Of the 8577 patients admitted during the study period, acute respiratory distress syndrome developed in 103 (1%). Of those 103 patients, 24 (23%) were treated with high-frequency oscillatory ventilation. Most of the patients treated with high-frequency oscillatory ventilation had sustained blunt trauma (79%). Oxygenation parameters improved significantly with high-frequency oscillatory ventilation in all patients, regardless of survival. Of the 24 patients treated with this ventilation mode, 15 (62%) survived. Survival did not correlate with improved oxygenation parameters but with the number of failed organ systems and injury severity.

CONCLUSION

Although high-frequency oscillatory ventilation improves oxygenation, severity of traumatic injury and organ failure, not respiratory parameters, are predictors of survival. High-frequency oscillatory ventilation should be considered for pulmonary rescue of severely injured patients with acute respiratory distress syndrome.

The role of high frequency oscillatory ventilation in the management of children with severe traumatic brain injury and concomitant lung pathology

OBJECTIVE

To report the use of high frequency oscillatory ventilation (HFOV) in two children with severe traumatic brain injury and concurrent lung pathology where conventional mechanical ventilation was ineffective.

DESIGN

: Case report.

SETTING

Regional intensive care unit in a pediatric teaching hospital.

PATIENTS

Two severely head-injured children (both with postresuscitation Glasgow Coma Scores of 3), one of whom was age 11 yrs and developed an invasive fungal (rhizomucor) pneumonia, while the other age 5 yrs had bilateral lung contusions. Both were treated according to local head injury guidelines, which included conventional ventilation. Despite increasing conventional ventilatory support, CO2 removal became problematic in both cases, making the intracranial pressure control and consequent maintenance of adequate cerebral perfusion pressure difficult. In both patients, a dramatic reduction in intracranial pressure and improvement in cerebral perfusion pressure was observed soon after the use of HFOV. Additionally, inotropic support was weaned by 50% in both children after commencing HFOV. A significant increase in the mean arterial blood pressure occurred in one child with HFOV.

INTERVENTION

Use of HFOV as an alternative to conventional mechanical ventilation.

CONCLUSION

HFOV may have utility in the management of selected cases of severe brain trauma with concurrent lung pathology where conventional ventilation is ineffective.

Neurologic injury and mechanical ventilation

Mechanical ventilation in neurologically injured patients presents a number of unique challenges. Patients who are intubated due to a primary neurologic injury often experience respiratory phenomena secondary to that injury, including elevation of intracranial pressure (ICP) in response to mechanical ventilation and variations in respiratory patterns. These problems often require unique ventilator strategies that are designed to minimize the impact of the ventilator on ICP and brain oxygenation. Balancing the need to maintain brain oxygenation and control of ICP can be complicated by the effects of ventilator management on ICP. We will examine the consequences of ventilator management as they relate to parameters that affect ICP and brain oxygenation in patients who have neurologic injury.

Respiratory care

PURPOSE OF THE REVIEW

Neurosurgical patients frequently develop respiratory complications, adversely affecting neurologic outcome and survival. The review summarizes current literature and management of respiratory complications associated with brain injury.

MAJOR FINDINGS

Respiratory complications are commonly associated with traumatic brain injury and subarachnoid haemorrhage. Lung-protective ventilation with reduced tidal volumes improves outcome in acute lung injury, and should be applied to neurosurgical patients in the absence of increased intracranial pressure. Weaning from the mechanical ventilation should be initiated as soon as possible, although the role of neurological status in the weaning process is not clear. Prevention of pneumonia and aspiration improves survival. In patients with difficult weaning, early bedside percutaneous tracheostomy should be considered.

FURTHER INVESTIGATIONS

Further studies are warranted to elucidate an optimal oxygenation and ventilation in brain-injured patients, weaning strategies, predictors of the failed weaning and extubation, respiratory support in patients with difficulties to wean, and early tracheostomy.

Bench-to-bedside review: brain-lung interaction in the critically ill--a pending issue revisited

Brain and/or lung injury is the most frequent cause of admission to critical care units and patients in this setting frequently develop multiple organ dysfunction with high rates of morbidity and mortality. Mechanical ventilation is commonly used in the management of these critically ill patients and the consequent inflammatory response, together with other physiological factors, is also thought to be involved in distal organ dysfunction. This peripheral imbalance is based on a multiple-pathway cross-talk between the lungs and other organs, including the brain. Interestingly, acute respiratory distress syndrome survivors frequently present some cognitive deterioration at discharge. Such neurological dysfunction might be a secondary marker of injury and the neuroanatomical substrate for downstream impairment of other organs. Brain-lung interactions have received little attention in the literature, but recent evidence suggests that both the lungs and brain are promoters of inflammation through common mediators. This review addresses the current status of evidence regarding brain-lung interactions, their pathways and current interventions in critically ill patients receiving mechanical ventilation.

Atelectatic children treated with intrapulmonary percussive ventilation via a face mask: clinical trial and literature overview

BACKGROUND

Persistent atelectasis in children is lacking a gold standard treatment. Intrapulmonary percussive ventilation (IPV) is presented as a promising chest physiotherapy technique in the treatment of atelectasis. This study aimed to follow the evolution of atelectasis resolution with noninvasive IPV in young children and to detect eventual adverse effects.

METHODS

Six children were hospitalized for respiratory distress with suspicion of atelectasis. A 15 min IPV treatment was immediately started at D1 twice a day for 5 days. Children were free of any other treatment. Chest X-Ray (CXR) was performed on the second day (D2) and was repeated 3 days later (D5). After the study, CXR were retrospectively reviewed by three specialists who had no knowledge of the clinical observations of the patients. They were asked to assess atelectasis by a score between 4 (complete collapse) and 0 (complete resolution). A clinical score on a maximum of 4 points was assessed by appetite deterioration, dyspnoea, mucus production and cough presence at D1 and D5 (1 point per symptom present). Paired t-test compared D1 and D5 results.

RESULTS

All patients returned home after 5 days IPV. SpO2 normalized (93.2 +/- 0.8 to 95.3 +/- 0.8; P = 0.002) and patients all improved clinically (score, 2.8 +/- 0.9 to 0.8 +/- 0.6; P < 0.05). Out of four patients with radiographic evidence of atelectasis, three improved their atelectasis score.

CONCLUSIONS

No side-effect or adverse effect was observed during IPV treatments. IPV was safe and effective in atelectasis resolution in 3/4 of the cases. Patients all recovered a stable clinical state. CXR improved in 4/5 children. They were all discharged home after 5 days of IPV treatment.

High-frequency percussive ventilation in a pediatric patient with hydrocarbon aspiration

INTRODUCTION

To describe ventilator management using a high-frequency percussive ventilator (HFPV), after other modes of mechanical ventilation failed.

DESIGN

Case series.

SETTING

Pediatric intensive care unit.

PATIENTS

Previously healthy 11-month-old male with severe aspiration pneumonitis from mineral oil.

INTERVENTIONS

The patient was initially placed on a conventional ventilator in a pressure-regulated volume-control mode but needed higher-than-normal pressures to maintain adequate ventilation. A decision was made to switch the patient to a pressure-control/pressure-support mode. At the end of the third day of pressure-control/pressure-support mode, a decision was made to attempt airway pressure-release ventilation. During a trial attempt, saturation levels deteriorated and a decision was made to place the patient on a high-frequency oscillator. The patient remained on this mode of ventilation for 6 days. On the sixth day, the chest radiograph showed a worsening of his pneumonia, and the patient started to deteriorate. A decision was made to try the HFPV in an attempt to mobilize secretions and any residual mineral oil. Immediately after initiating the HFPV and for 4 hrs thereafter, large amounts of secretions -- including a thick, oily substance -- were suctioned from the airways. Within 12-24 hrs, oxygenation improved dramatically and Fio2 was weaned. During the next 12 hrs, the patient was weaned off HFPV onto a conventional ventilator, and he was extubated 48 hrs after initiating HFPV.

CONCLUSIONS

In this case, HFPV used as an alternative mode of ventilation successfully mobilized secretions that were otherwise unobtainable and that we believe led to the swift recovery of this child. HFPV should be given consideration as a mode of ventilation when mobilization of secretions is an issue.

Influence of the mode of ventilation on ketamine/xylazine requirements in rabbits

OBJECTIVE

To evaluate the effect of the mode of mechanical ventilation (MV) on the dose of intravenous anesthetic during 3 hours of ketamine/xylazine anesthesia.

STUDY DESIGN

Prospective laboratory study.

ANIMALS

Sixty-one adult male New Zealand White rabbits.

METHODS

Rabbits were anesthetized (ketamine/xylazine 35 + 5 mg kg(-1), IM), the trachea was intubated and randomized to four groups - (1) CMV-1 (n = 14), ventilated with traditional conventional volume-cycled MV [V(T) = 12 mL kg(-1), RR = 20, positive end-expiratory pressure (PEEP) = 0 cmH(2)O]; (2) CMV-2 (n = 13), ventilated with a modern lung-protective regimen of volume-cycled MV (V(T) = 6 mL kg(-1), RR = 40, PEEP = 5 cmH(2)O); (3) HFPV (n = 17) ventilated with high-frequency percussive ventilation [high-frequency oscillations (450 minute(-1)) superimposed on 40 minute(-1) low-frequency respiratory cycles, I:E ratio = 1:1], oscillatory continuous positive airway pressure (CPAP) of 7-10 cmH(2)O, and demand CPAP of 8-10 cmH(2)O. (4) A fourth group, spontaneously ventilating (SV, n = 17), was anesthetized, intubated, but not ventilated mechanically. FiO(2) in all groups was 0.5. Anesthesia was maintained at a surgical plane by IV administration of a ketamine/xylazine mixture (10 + 2 mg kg(-1), as necessary) for 3 hours after intubation. Total dose of xylazine/ketamine administered and the need for yohimbine to facilitate recovery were quantitated.

RESULTS

The total dose of xylazine/ketamine was significantly higher in the HFPV and SV groups compared with CMV-1 (p < 0.01). Fewer animals required yohimbine to reverse anesthesia in the HFPV than CMV-1 group (p < 0.05).

CONCLUSIONS

The HFPV mode of MV led to higher doses of ketamine/xylazine being used than the other modes of MV.

CLINICAL RELEVANCE

In rabbits, anesthetic dose for the maintenance of anesthesia varied with the mode of MV used. Investigators should be aware of the possibility that changing the mode of ventilation may lead to an alteration in the amount of drug required to maintain anesthesia.

Use of high frequency oscillatory ventilation (HFOV) in neurocritical care patients

INTRODUCTION

Adult respiratory distress syndrome (ARDS) can be a common problem associated with the treatment of acute brain injury. High frequency oscillatory ventilation (HFOV) is a developing therapy for the treatment of ARDS in adult patients that can be life saving. However, often patients with acute, severe brain injury demonstrate intracranial hypertension (hICP) due to a variety of injuries (e.g., traumatic brain injury, mass lesion, acute hydrocephalus). There is concern over the use of HFOV due to its effects on intracranial pressure in patients with hICP.

METHODS

Retrospective case series study.

RESULTS

We describe the effects of HFOV on hemodynamics, respiratory function, and intracranial pressure in five patients with acute brain injury being treated for ARDS.

CONCLUSIONS

HFOV did not cause unmanageable or sustained increases in ICP in our series of patients. It appears HFOV may be a relatively safe and effective means of oxygenating patients with severe ARDS and concomitant hICP secondary to acute brain injury.

Efficacy and safety of intrapulmonary percussive ventilation superimposed on conventional ventilation in obese patients with compression atelectasis

PURPOSE

To investigate the efficacy and safety of intrapulmonary percussive ventilation (IPV) in obese patients, we assessed their respiratory and hemodynamic functions during IPV superimposed on conventional ventilation.

MATERIALS AND METHODS

Ten obese patients with acute respiratory failure due to compression atelectasis who had not improved by conventional ventilation were treated with IPV. Hemodynamic parameters, ventilator settings, and intracranial pressure (n = 1) were recorded every hour. Arterial blood gas was analyzed every 3 hours. The efficacy and safety of IPV was assessed at the start of weaning.

RESULTS

Before IPV, Pao(2)/Fio(2) ratio remained low (189 +/- 63 mm Hg), which significantly increased to 243 +/- 67 mm Hg at 3 hours from the initiation of IPV (P < .01). Furthermore, it continuously increased to 280 +/- 50 mm Hg at 24 hours (P < .01). Intrapulmonary percussive ventilation induced significant increase in dynamic compliance from control value of 30 +/- 8 mL/cm H(2)O at 0 hours to 35 +/- 9 mL/cm H(2)O at 12 hours (P < .05) and to 38 +/- 8 mL/cm H(2)O at 24 hours (P < .01). Heart rate and mean arterial pressure were not significantly changed during IPV. Improvement of compression atelectasis was confirmed by their chest computed tomographic scans. Adverse effects such as pneumothorax and intracranial hypertension were not seen.

CONCLUSIONS

These results demonstrated that IPV was effective and safe in improving compression atelectasis without adverse effects in obese patients.

High-frequency percussive ventilation improves oxygenation in trauma patients with acute respiratory distress syndrome: a retrospective review

BACKGROUND

High-frequency percussive ventilation (HFPV), a hybrid of conventional mechanical ventilation and high-frequency oscillatory ventilation, has been used to salvage patients with persistent hypoxemia on conventional mechanical ventilation. We hypothesized that oxygenation would improve in injured patients with severe hypoxemia who were converted to HFPV after initial management with conventional ventilation.

METHODS

Chart review identified patients with acute respiratory distress syndrome (ARDS) managed with HFPV. Oxygenation parameters (oxygenation index, OI; Pao(2)/Fio(2) ratio, P/F) and mean airway pressures (mPaw) were recorded at baseline and at 1 to 4, 8 to 12, and 12 to 24 hours after initiation of HFPV. Values at baseline and each time point after conversion to HFPV were compared by using analysis of variance or Kruskal-Wallis tests.

RESULTS

Twelve patients, over 24 months, were reviewed. Baseline measurements were OI: 42.2 +/- 33, P/F: 70 +/- 31, (median +/- interquartile range), and mPaw: 29 +/- 8 (mean +/- standard deviation) cm H(2)O. After initiation of HFPV, mPaw did not differ from baseline. There was an improvement in OI (P = .01) from baseline at 12 to 24 hours after initiation of HFPV and in P/F at 12 to 24 hours (P = .002) and 8 to 12 hours (P = .001) after initiation of HFPV.

CONCLUSIONS

HFPV may improve oxygenation in patients with ARDS without a concomitant increase in mPaw. A randomized trial of HFPV versus conventional ventilation in trauma patients is needed.

Lung-protective ventilation in neurosurgical patients

PURPOSE OF REVIEW

Concepts of ventilator-induced lung injury have revolutionized our approach to the ventilatory management of patients with acute lung injury and acute respiratory distress syndrome over the past 10 years. The extension of these principles to patients with brain injuries is challenging, as many of them are out of keeping with usual brain-protective management.

RECENT FINDINGS

Many patients with acute lung injury or acute respiratory distress syndrome and an acute brain injury may in fact be managed safely within the confines of a lung-protective strategy. Elevated levels of positive end-expiratory pressure in head-injured patients with acute lung injury or acute respiratory distress syndrome also appear to be safe, particularly when the level is set below that of the intracranial pressure, when patients have a low respiratory system compliance, or when positive end-expiratory pressure results in significant lung volume recruitment. Several novel therapies to minimize ventilator-induced lung injury are currently in the early stages of investigation in neurosurgical patients.

SUMMARY

In many patients with brain injuries and acute lung injury the goals of lung protection can be achieved without threatening cerebral perfusion. In patients with more refractory raised intracranial pressure the optimal balance between brain and lung is not well established. Further research is needed on lung-protective strategies in this vulnerable population.

Mechanical loads modulate tidal volume and lung washout during high-frequency percussive ventilation

High-frequency percussive ventilation (HFPV) has been proved useful in patients with acute respiratory distress syndrome. However, its physiological mechanisms are still poorly understood. The aim of this work is to evaluate the effects of mechanical loading on the tidal volume and lung washout during HFPV. For this purpose a single-compartment mechanical lung simulator, which allows the combination of three elastic and four resistive loads (E and R, respectively), underwent HFPV with constant ventilator settings. With increasing E and decreasing R the tidal volume/cumulative oscillated gas volume ratio fell, while the duration of end-inspiratory plateau/inspiratory time increased. Indeed, an inverse linear relationship was found between these two ratios. Peak and mean pressure in the model decreased linearly with increasing pulsatile volume, the latter to a lesser extent. In conclusion, elastic or resistive loading modulates the mechanical characteristics of the HFPV device but in such a way that washout volume and time allowed for diffusive ventilation vary agonistically.

Non-neurological organ dysfunction in neurocritical care: impact on outcome and etiological considerations

PURPOSE OF REVIEW

Organ dysfunction is an important determinant of outcome in critical care medicine. Patients with life threatening neurologic injury represent a distinct subset of critically ill patients in whom non-neurologic organ dysfunction may develop. In this paper the incidence and impact of non-neurologic organ dysfunction in patients with major neurologic injury will be reviewed. Further, potential etiological considerations will be addressed and management strategies discussed.

RECENT FINDINGS

Non-neurologic organ dysfunction is extremely common in patients with brain injury occurring in 80-90% of patients admitted to intensive-care units. Several studies have now identified this dysfunction as an independent predictor of poor outcome in neurocritical care. This dysfunction may arise as a result of the neurologic injury or secondary to treatment. Massive catecholamine release continues to be the primary etiological theory of non-neurologic organ dysfunction due to brain injury. Currently employed therapies directed at intracranial hypertension such as maintenance of cerebral perfusion pressure and the use of hypothermia or barbiturates predispose non-neurologic organ dysfunction.

SUMMARY

Non-neurologic organ dysfunction is common. This dysfunction independently predicts poor outcome following brain injury and represents a potentially modifiable risk factor. Further study is required to develop optimal management strategies.

High-frequency percussive ventilation

OBJECTIVE

To review the technique and clinical application of high-frequency percussive ventilation in critically ill patients.

DESIGN

Literature search and descriptive review.

RESULTS

High-frequency percussive ventilation is a time-cycled, pressure-limited mode of ventilation that delivers subphysiologic tidal volumes at rates that can exceed 500 breaths/min. It offers the potential advantage over conventional ventilation of providing equal or improved oxygenation and ventilation at lower peak and end-expiratory pressures. This modality has been used to manage severe lung disease in the neonatal and pediatric population, treat inhalation injury in pediatric and adult patients, and as salvage therapy in adult patients with acute respiratory distress syndrome.

CONCLUSIONS

High-frequency percussive ventilation has been shown to provide favorable gas exchange in several well-defined patient populations. It reliably improves oxygenation and provides adequate ventilation at lower peak pressures than conventional ventilation. Adequately powered, randomized, prospective studies demonstrating significant mortality benefit have not yet been performed.