Use Of Airway Pressure Release Ventilation Research Articles

Awareness and practice of airway pressure release ventilation mode in acute respiratory distress syndrome patients among nurses in Saudi Arabia

BackgroundThis study aimed to assess the knowledge and current practice of using the airway pressure release ventilation (APRV) mode with acute respiratory distress syndrome (ARDS) patients and identify barriers to not using this mode of ventilation among nurses who work in critical areas in Saudi Arabia.MethodsBetween December 2022 and April 2023, a cross-sectional online survey was disseminated to nurses working in critical care areas in Saudi Arabia. The characteristics of the respondents were analyzed using descriptive statistics. Percentages and frequencies were used to report categorical variables.ResultsOverall, 1,002 nurses responded to the online survey, of whom 592 (59.1%) were female. Only 248 (24.7%) nurses had ever used APRV mode, whereas only 229 (22.8%) received training on APRV mode. Moreover, 602 (60.0%) nurses did not know whether APRV was utilized in their hospital. Additionally, 658 (65.6%) nurses did not know whether APRV mode was managed using a standard protocol. Prone positioning was the highest recommended intervention by 444 (43.8%) when a conventional MV failed to improve oxygenation in patients with ARDS. 323 (32.2%) respondents stated that the P-high should be set equal to the plateau pressure on a conventional ventilator, while 400 (39.9%) said that the P-low should match PEEP from a conventional ventilator. Almost half of the respondents (446, 44.5%) stated that the T-high should be set between 4 and 6 s, while 415 (41.4%) said that the T-low should be set at 0.4 to 0.8 s. Over half of the nurses (540, 53.9%) thought that the maximum allowed tidal volume during the release phase should be 4–6 ml/kg. Moreover, 475 (47.4%) believed that the maximum allowed P-high setting should be 35 cm H2O. One-third of the responders (329, 32.8%) stated that when weaning patients with ARDS while in APRV mode, the P-high should be reduced gradually to reach a target of 10 cm H2O. However, 444 (44.3%) thought that the T-high should be gradually increased to reach a target of 10 s. Half of the responders (556, 55.5%) felt that the criteria to switch the patient to continuous positive airway pressure (CPAP) were for the patient to have an FiO2 ≤ 0.4, P-high ≤ 10 cm H2O, and T-high ≥ 10 s. Lack of training was the most common barrier to not using APRV by 615 (61.4%).ConclusionThe majority of nurses who work in critical care units have not received sufficient training in APRV mode. A significant discrepancy was observed regarding the clinical application and management of APRV parameters. Inadequate training was the most frequently reported barrier to the use of APRV in patients with ARDS.

Comparison of Airway Pressure Release Ventilation to High-Frequency Oscillatory Ventilation in Neonates with Refractory Respiratory Failure.

Background Airway pressure release ventilation (APRV) is a relatively new mode of ventilation in neonates. We hypothesize that APRV is an effective rescue mode in infants failing conventional ventilation and it is comparable in survival rates to rescue with high-frequency oscillatory ventilation (HFOV). Methods This is a 6-year retrospective cohort study of infants that failed synchronized intermittent mandatory ventilation (SIMV) and were rescued with either APRV or HFOV. For comparison, we divided infants into two groups (28-37 and >37 weeks) based on their corrected gestational age (CGA) at failure of SIMV. Results Ninety infants were included in the study. Infants rescued with APRV (n = 46) had similar survival rates to those rescued with HFOV (n = 44)—28-37 weeks CGA (APRV 78% vs. HFOV 84%, p = 0.68) and >37 weeks CGA (APRV 76% vs. HFOV 72%, p = 0.74). Use of APRV was not associated with an increase in pneumothorax (APRV 0% and HFOV 10%, p = 0.31, in 28-37 weeks CGA, and APRV 0% and HFOV 4%, p = 0.22, in >37 weeks CGA). Conclusion APRV can be effectively used to rescue infants with refractory respiratory failure on SIMV. When compared to HFOV, rescue with APRV is not associated with an increase in mortality or pneumothorax.

Airway pressure release ventilation in mechanically ventilated patients with COVID-19: a multicenter observational study

BackgroundEvidence prior to the coronavirus disease 2019 (COVID-19) pandemic suggested that, compared with conventional ventilation strategies, airway pressure release ventilation (APRV) can improve oxygenation and reduce mortality in patients with acute respiratory distress syndrome. We aimed to assess the association between APRV use and clinical outcomes among adult patients receiving mechanical ventilation for COVID-19 and hypothesized that APRV use would be associated with improved survival compared with conventional ventilation.MethodsA total of 25 patients with COVID-19 pneumonitis was admitted to intensive care units (ICUs) for invasive ventilation in Perth, Western Australia, between February and May 2020. Eleven of these patients received APRV. The primary outcome was survival to day 90. Secondary outcomes were ventilation-free survival days to day 90, mechanical complications from ventilation, and number of days ventilated.ResultsPatients who received APRV had a lower probability of survival than did those on other forms of ventilation (hazard ratio, 0.17; 95% confidence interval, 0.03–0.89; P=0.036). This finding was independent of indices of severity of illness to predict the use of APRV. Patients who received APRV also had fewer ventilator-free survival days up to 90 days after initiation of ventilation compared to patients who did not receive APRV, and survivors who received APRV had fewer ventilator-free days than survivors who received other forms of ventilation. There were no differences in mechanical complications according to mode of ventilation.ConclusionsBased on the findings of this study, we urge caution with the use of APRV in COVID-19.

A Pilot Study of Patients With COVID–19-Related Respiratory Failure Utilizing Airway Pressure Release Ventilation (APRV)

ABSTRACT Background Pneumonia leading to acute respiratory distress syndrome (ARDS) is one of the devastating consequences of coronavirus disease 2019 (COVID-19). Airway pressure release ventilation (APRV) has been described as beneficial in acute lung injury and ARDS. We hypothesized that utilizing APRV would be advantageous in the COVID-19 ARDS population. Methods Prospective, observational, single-center study. Data were extracted on demographics, vasopressors, sedatives, analgesics, and oxygenation (PaO2/FiO2). A generalized linear mixed models analysis was performed to compare low tidal volume ventilation (LTV) with APRV for patients who required intubation due to ARDS from COVID-19 and who were managed with at least 48 consecutive hours of APRV in our surgical intensive care unit (SICU). Results Twelve patients met criteria; two were on APRV mode from admission to the SICU and were not included in the study. Ten patients were analyzed and were primarily male (70%), average age of 64.5 ± 12.9 years, and 70% were obese (average body mass index of 30.6 ± 8.0 kg/m2). There were no smokers in the sample, but two patients presented with underlying lung pathology. APRV was shown to significantly increase the PaO2/FiO2 ratio by 30% (5% to 61%) (p = 0.05) and was associated with up to a 12% (−26% to 5%) reduction in the level of FiO2 and reduction in the use of vasopressor support (−59% [−83% to −2%]), sedatives (−15% [−29% to 2%]), and analgesics (−16% [−38% to 12%]). Conclusions This pilot study showed that APRV was associated with decreases in FiO2, vasopressors, sedatives, and analgesic requirements with an increase in PaO2/FiO2 ratio. In the current pandemic, where providers are grappling with ways to manage COVID-19 ARDS, APRV may be the optimal ventilator mode. Prospective randomized studies are required to validate whether use of APRV in the COVID-19 population leads to improved oxygenation and a subsequent decrease of ventilator days and length of stay.

Management of primary blast lung injury: a comparison of airway pressure release versus low tidal volume ventilation

BackgroundPrimary blast lung injury (PBLI) presents as a syndrome of respiratory distress and haemoptysis resulting from explosive shock wave exposure and is a frequent cause of mortality and morbidity in both military conflicts and terrorist attacks. The optimal mode of mechanical ventilation for managing PBLI is not currently known, and clinical trials in humans are impossible due to the sporadic and violent nature of the disease.MethodsA high-fidelity multi-organ computational simulator of PBLI pathophysiology was configured to replicate data from 14 PBLI casualties from the conflict in Afghanistan. Adaptive and responsive ventilatory protocols implementing low tidal volume (LTV) ventilation and airway pressure release ventilation (APRV) were applied to each simulated patient for 24 h, allowing direct quantitative comparison of their effects on gas exchange, ventilatory parameters, haemodynamics, extravascular lung water and indices of ventilator-induced lung injury.ResultsThe simulated patients responded well to both ventilation strategies. Post 24-h investigation period, the APRV arm had similar PF ratios (137 mmHg vs 157 mmHg), lower sub-injury threshold levels of mechanical power (11.9 J/min vs 20.7 J/min) and lower levels of extravascular lung water (501 ml vs 600 ml) compared to conventional LTV. Driving pressure was higher in the APRV group (11.9 cmH2O vs 8.6 cmH2O), but still significantly less than levels associated with increased mortality.ConclusionsAppropriate use of APRV may offer casualties with PBLI important mortality-related benefits and should be considered for management of this challenging patient group.

Airway Pressure Release Ventilation: A Review of the Evidence, Theoretical Benefits, and Alternative Titration Strategies.

Objective:To review the theoretical benefits of airway pressure release ventilation (APRV), summarize the evidence for its use in clinical practice, and discuss different titration strategies.Data Source:Published randomized controlled trials in humans, observational human studies, animal studies, review articles, ventilator textbooks, and editorials.Data Summary:Airway pressure release ventilation optimizes alveolar recruitment, reduces airway pressures, allows for spontaneous breathing, and offers many hemodynamic benefits. Despite these physiologic advantages, there are inconsistent data to support the use of APRV over other modes of ventilation. There is considerable heterogeneity in the application of APRV among providers and a shortage of information describing initiation and titration strategies. To date, no direct comparison studies of APRV strategies have been performed. This review describes 2 common management approaches that bedside providers can use to optimally tailor APRV to their patients.Conclusion:Airway pressure release ventilation remains a form of mechanical ventilation primarily used for refractory hypoxemia. It offers unique physiological advantages over other ventilatory modes, and providers must be familiar with different titration methods. Given its inconsistent outcome data and heterogeneous use in practice, future trials should directly compare APRV strategies to determine the optimal management approach.

88 A Retrospective Review of the Use of Airway Pressure Release Ventilation (APRV) in the Burn Operating Room

Airway Pressure Release Ventilation (APRV) is the preferred mode of mechanical ventilation for the initial treatment of inhalation injury at our burn center. APRV improves alveolar recruitment, thus improving oxygenation. However, general anesthesia cannot be administered when patients are on APRV, resulting in frequent interruptions in the circuit and subsequent alveolar derecruitment with prolonged periods of sub-optimal ventilation post-operatively. Total IV anesthesia (TIVA) allows for the continued use of APRV perioperatively. The purpose of this study was to assess the safety and efficacy of APRV during surgery. This was a retrospective chart review of patients that remained on APRV during surgery over a 3-year period. Demographic, injury, ventilator, and outcome data were collected. Pre (PRE) and post-operative (POST) FIO2, Rate (set & spontaneous), Tidal Volume (TV), Minute Volume (MV), P High/Low, T High/Low, and Mean Airway Pressures (MAP) were compared for each surgery. The charts of 55 patients were reviewed, mean age was 45 years, the majority were male (75%) and 9% had pre-existing pulmonary disease. The most common mechanism was flame/flash (67%) with total body surface area (TBSA) burned ranging from 0 - 92% (M 42%). Concomitant inhalation injury was present for 58% of patients. Total ventilator days (M 42.2, ±35.7), total APRV days (M 16, ±12.9). Total number of surgeries (M 9.4, ±7.94), total number of surgeries on APRV (M 3.4, ±2.65). There were 38 patients with complete PRE and POST ventilator data. Surgery 1 on APRV; there were no significant differences for FIO2, Rate, TV, MV, P High/Low, T High, MAP; POST T Low was lower (M 0.8) when compared to PRE (M 0.9), (p=0.0005). Surgery 2 (n=35), POST mean FIO2 requirements were higher; PRE (0.47) vs POST (0.57), (p=.0358). Surgery 3 (n=25) average TV was lower POST-OP; PRE-OP (630) vs POST (523), (p=.005). There were no significant differences between PRE and POST requirements for patients on APRV during surgeries 4 (n=16) and 5 (=13). No patients suffered complications pre, peri or post-operatively when on APRV. Overall inpatient mortality was 35%. Of survivors, 92% required transfer to a post-acute care facility. APRV can be continued intra-operatively with the use of TIVA. This retrospective study demonstrates that TIVA and intra-operative APRV are safe and effective. TIVA allows the continued use of APRV intra-operatively in burn patients requiring aggressive ventilator support.

Should Airway Pressure Release Ventilation Be the Primary Mode in ARDS?

Airway pressure release ventilation (APRV) was originally described as a mode to treat lung-injured patients with the goal to maintain a level of airway pressure that would not depress the cardiac function, deliver mechanical breaths without excessive airway pressure, and to allow unrestricted spontaneous ventilation. Indeed, based on its design, APRV has technological features that serve the goals of safety and comfort. Animal studies suggest that APRV leads to alveolar stability and recruitment which result in less lung injury. These features are sought in patients at risk for lung injury or with ARDS. APRV allows unrestricted spontaneous ventilation, which is welcome in the era of less sedation and increased patient mobility (the effects in terms of lung injury remain to be explored). However, we must highlight that the performance of APRV is dependent on the operator-selected settings and the ventilator's performance. The clinician must select the appropriate settings in order to make effective the imputed benefits. This is a challenge when the ventilator's performance is not uniform, and the outcomes depend on high precision settings (very short expiratory time), where small variations can lead to undesired outcomes (de-recruitment or large tidal volumes leading to lung injury). Finally, we do not have evidence that APRV (as originally described) improves relevant clinical outcomes of patients with ARDS. For APRV to become the primary mode of ventilation for ARDS, it will require development of sound protocols and technological enhancements to ensure its performance and safety. For now, APRV does have a greater potential for adversely affecting patient outcome than improving it; unless definitive data are forthcoming demonstrating outcome benefits from the use of APRV in ARDS, there is no reason to consider this approach to ventilatory support.

A huge ovarian tumor: Perioperative ventilation challenges

Introduction: Huge ovarian tumors can compromise respiratory functions in various ways leading to a challenging ventilation management. case report: We report a case of a young lady with a huge ovarian tumor (17 kg) posted for tumor resection, which was initially intubated and required high ventilator setting using airway pressure release ventilation (APrV) mode in the intensive care unit (IcU) for respiratory failure secondary to concomitant splinting of diaphragm, pleural effusion and pneumonia. Herein, we described our successful use of APrV extended into the intraoperative period of the tumor resection in order to maintain an adequate oxygenation and ventilation. As the operating room (Or) ventilator is not equipped with APrV as a mode of ventilation, there were several practical challenges we faced. Firstly, we had to transport the IcU ventilator to the Or with the patient. Due to the inability to deliver inhaled anesthetic while the patient was connected to the

Hemodynamic changes in child acute respiratory distress syndrome with airway pressure release ventilation: a case series.

Airway pressure release ventilation (APRV) is widely used in adult critical care settings. However, information on the use of APRV in the pediatric population is limited. All patients admitted to the medical-surgical pediatric intensive care unit with a diagnosis of acute respiratory distress syndrome (ARDS) who received APRV for at least 12 h between 2007 and 2009 were reviewed. Thirteen patients with a variety of etiologies of ARDS were included, with a mean weight of 18.2 ± 15.0 kg, a mean age of 68 ± 57 months and a predicted mortality (based on Pediatric Index of Mortality version 2) of 23.9 ± 13.8%. Patients were placed on APRV for a median of 4 days (range 1-10 days). There was no change in blood gas parameters after 1 h or 12 h of APRV when compared with pre-APRV. There was no statistical difference in hemodynamic parameters, including mean arterial blood pressure, central venous blood pressure and heart rate, while the patients were on APRV. APRV could be safely used in pediatric ARDS patients, without significant hemodynamic compromise or side effects.

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Introduction: Acute respiratory failure (ARF) is one of the most common causes for admission to pediatric intensive care units. Children who have reversible lung disease with life threatening hypoxia or hypercarbia are candidates for extracorporeal membrane oxygenation, (ECMO) which ensures gas exchange while limiting ventilator induced injury. The ventilator is often put on rest settings which can lead to pulmonary derecruitment. High pressure recruitment efforts are needed before separation from ECMO. Airway Pressure Release Ventilation (APRV) can promote lung recruitment and maintenance of functional residual capacity (FRC), preparing the lungs for resumption of function after separation from ECMO. We propose that APRV can be used for lung recruitment and maintenance or aeration in non-spontaneous breathing children on ECMO for ARF. Here we report 3 children with ARF requiring VA ECMO who had radiologic and physiologic evidence of derecruitment on rest settings. APRV was able to provide recruitment on CXR. Patient 1: 6 week old male with pertussis requiring ECMO had peak inspiratory pressure (PIP) 26 cm H2O resulting in effective tidal volume (Vteff) 2 mL/kg after 22 days on ECMO. He was on APRV for 7 days; subsequently on PC he had a PIP 30 cm H2O and Vteff 8mL/kg. He was decannulated on ECMO day 29. Patient 2: 5 year old male with group A strep sepsis and pulmonary hemorrhage who required 9 days of ECMO. Initially on ECMO with pressure control (PC) ventilation he had Vteff of 2 mL/kg with PIP 22 cm H2O. After recruitment with APRV he resumed PC and with Vteff 6 mL/kg and PIP 22 cm H2O. Patient 3: 28 month old female with a history of heart transplant and ARF due to RSV who had 13 days of ECMO. The patient was on PC with Vteff 1.7 mL/kg and PIP 20 cm H2O before APRV. Before separation from ECMO she was transitioned from APRV to PC and was receiving 7 mL/kg TV with PIP 30 cm H2O. This novel use of APRV in non-spontaneously breathing children with ARF requiring ECMO facilitated pulmonary recruitment and separation from ECMO. There were no adverse events related to APRV. More research is needed to determine the best methods of ventilation in patients with ARF on ECMO.

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Introduction: Airway pressure release ventilation (APRV) has been used extensively in adult patients with acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). Purported advantages of APRV include increase in mean airway pressure (MAP), decrease in peak inspiratory pressures (PIP), and ability to spontaneously ventilate. It has not been studied extensively in pediatrics especially in the infant population with ALI/ARDS. We demonstrate two patients in which the APRV strategy was used to improve refractory hypoxemia (patient 1) and perform lung recruitment while on extra-corporeal membrane oxygenation (ECMO) (patient 2). Methods: Retrospective review of two patients’ charts; one in the Neonatal ICU and another in the Pediatric ICU. The patient’s ventilator modes, settings, blood gas measurements and radiographic imaging were analyzed. Results: Two patients’ charts were reviewed in whom APRV was used for refractory hypoxemia and to perform lung recruitment. Patient 1 was a 6 month old 3.9 kg ex-24 week preemie with recurrent bouts of necrotizing enterocolitis requiring bowel resection, status post stricturoplasty who was kept intubated post-op and returned to the NICU. During the procedure her PIP was 21 mm Hg, positive end expiratory pressure (PEEP) of 4, rate of 16 bpm, and FiO2 of 38% with SpO2 of 100% that delivered a MAP of 10.4 mm Hg. Venous blood gas at the end of the case demonstrated a pH 7.36, pCO2 45, pO2 37, HCO3 25, Lactate 1.9. Initially in the NICU her ventilator was set in pressure cycled assist controlled (PC/AC) with a rate of PIP 19, PEEP of 5, rate, rate of 33 bpm, PIP and FiO2 21% with SpO2 of 95% that delivered a MAP of 7 mm Hg. Over the next 26 hours she developed progressive hypoxemia requiring up titration in her PIP (26 mm Hg), PEEP (7 mm Hg) and FiO2 (85%) delivering a MAP of 12 mm Hg with SpO2 of 80–85%. Chest x-ray demonstrated a right upper lobe atelectasis along with low lung volumes. She was switched to APRV with a pressure high (PHIGH) of 25 mm Hg, pressure low (PLOW) of 0 mm Hg, time high (THIGH) of 2 seconds and time low (TLOW) of 0.2 seconds with MAP of 22 mm Hg, FiO2 40% with SpO2 97%. Chest radiography demonstrated improved aeration within approximately 1 hour of APRV initiation. She subsequently self extubated after 47 hours on APRV to 2 liters nasal cannula and remained extubated. Patient 2 was a 1 month old 5 kg male with a giant omphalocele who developed renal failure, volume overload and progressive respiratory failure requiring endotracheal intubation and eventual veno-venous (VV) ECMO. He was kept on rest lung settings PIP 25 mm Hg, PEEP 9 mm Hg, FiO2 40% and rate of 10 with a MAP of 11 mm Hg. He was on full VV-ECMO support with a flow of 760 mL/min and sweep gas of 0.8 L/min. His chest x-rays demonstrated bilaterally opacified lung fields with no expiratory tidal volumes. He was placed on APRV on post-ECMO day 6 at settings of pressure high (PHIGH) of 20 mm Hg, pressure low (PLOW) of 2 mm Hg, time high (THIGH) of 4 seconds and time low (TLOW) of 0.35 seconds with MAP of 18 mm Hg, while still on ECMO support. His lungs began to show aeration and evidence of recruitment at 12 hours on APRV with marked improvement in his lung aeration. He continued on APRV for 48 hours and then was transitioned to conventional ventilation. Conclusions: APRV is a useful ventilator strategy in cases of refractory hypoxemia and de-recruited lungs. We demonstrate the safe use of APRV in two patients less than 1 year of age with improvement in oxygenation and lung recruitment. Advantages of APRV were mentioned above. The disadvantages include air trapping and CO2 retention. While the disadvantages can be mostly mitigated with titration of the APRV settings, additional studies are needed to demonstrate efficacy and safety along with formulation of age appropriate pressure and time settings.

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Introduction: The use of airway pressure release ventilation (APRV) has been well characterized in patients with Acute Lung Injury, Acute Respiratory Distress Syndrome, and atelectasis after major surgeries. APRV allows for the minimization of pulmonary barotrauma and facilitates lung-protective inverse-ratio ventilatory strategies in patients with significant injury who may not tolerate inverted ratios in other ventilation modes. We report the successful use of APRV for surgical site protection in a case of membranous tracheal injury requiring surgical repair and postoperative non-ventilatory extracorporeal membrane oxygenation (ECMO) support. A 57 year-old male with a past history significant for esophageal adenocarcinoma s/p robotically assisted esophogectomy presented as a transfer from outside hospital on post operative day 8 after bronchoscopy demonstrated a 7mm perforation in the left main-stem bronchus and multiple punctate perforations of the carina extending into the proximal right main-stem bronchus. A 37-French left double lumen tube was placed to maintain ventilation distal to these defects, and the patient was taken to the operating room for emergent surgical repair and veno-venous ECMO cannulation. Surgical repair was acheived using a combination of autologous pericardial patch and serratus muscle flap, and the patient was admitted to the ICU for management of non-ventilatory ECMO. His lungs were initially managed for 48 hours with a closed 5cm H2O CPAP circuit, with initiation of APRV ventilation on postoperative day 3. Initial CXR demonstrated complete opacification of bilateral lung fields, and initial tidal volumes were 35-50 cc using a P-high of 15 cm H20 and P-low of 5cm H2O. Inverse-ratio ventilation was achieved at 7:1 using a T-high of 5 seconds, and T-low of 0.7 seconds. Peak airway pressures were maintained below 20cm H2O for 48 hours after resumption of ventilation and below 25cm H2O for an additional 48 hours. Mean airway pressures were consistently 10-11cm H2O during the first 48 hours after resumption of ventilation, and peaked at 16cm H2O on postoperative day 6. Respiratory parameters normalized by 96 hours after resumption of ventilation with the patient spontaneously ventilating in excess of 8cc/kg, and ECMO was de-cannulated. Chest radiography on postoperative day 6 demonstrated clear bilateral lung fields, and bronchoscopy demonstrated patent and intact surgical repairs to the membranous trachea. The patient tolerated this ventilatory strategy well, never developed any signs of acute lung injury, and sedation was weaned sufficiently by postoperative day 4 for him to meaningfully interact with his family. The use of inverse-ratio ventilation with APRV in this case provided an ideal management strategy to minimize barotrauma on surgical airway repairs while recruiting previously non-ventilated lungs after ECMO.

Management of acute respiratory distress syndrome in a French Bulldog using airway pressure release ventilation

To describe the successful clinical management of a dog with acute respiratory distress syndrome (ARDS) using airway pressure release ventilation (APRV). An 18-month-old female French Bulldog was presented for routine ovariohysterectomy and correction of brachycephalic airway obstruction syndrome. Following the surgical procedures, the dog developed aspiration pneumonia and ARDS. Her clinical condition failed to improve with conventional pressure-support mechanical ventilation and she was subsequently managed with APRV. She recovered fully and exhibited no clinical or radiographic abnormalities during follow-up examinations. This is the first reported use of APRV to manage refractory hypoxemia associated with ARDS in a dog. This alternative mode of mechanical ventilation can be considered a feasible alternative in canine patients with ARDS.

Airway Pressure Release Ventilation: A Neonatal Case Series and Review of Current Pediatric Practice

The use of airway pressure release ventilation (APRV) in very low birth weight infants is limited. To report the authors' institutional experience and to review the current literature regarding the use of APRV in pediatric populations. Neonates <1500 g ventilated using APRV from 2005 to 2006 at McMaster Children's Hospital (Hamilton, Ontario) were retrospectively reviewed. Publications describing APRV in children from 1987 to 2011 were reviewed. Five infants, 24 to 28 weeks' gestational age, were ventilated using APRV. Indications for APRV were refractory hypoxemia (n=3), ventilatory dyssynchrony (n=1) and minimizing sedatives (n=1). All infants appeared to tolerate APRV well with no recorded adverse events. Current pediatric evidence regarding APRV is primarily observational. Published experience reveals that APRV settings in pediatrics often approximate those used in adults, thus deviating from the original guidelines recommended in children. Clinical outcomes, such as oxygenation, ventilation and sedation requirements, are inconsistent. APRV is primarily used as a rescue ventilation mode in children. Neonatal evidence is limited; however, the present study indicates that APRV is feasible in very low birth weight infants. There are unique considerations when applying this mode in small infants. Further research is necessary to confirm whether APRV is a safe and effective ventilation strategy in this population.

Use of Airway Pressure Release Ventilation is Associated With a Reduced Incidence of Ventilator-Associated Pneumonia in Patients With Pulmonary Contusion

Past studies suggest that airway pressure release ventilation (APRV) is associated with reduced sedative requirements and increased recruitment of atelectatic lung, two factors that might reduce the risk for ventilator-associated pneumonia (VAP). We investigated whether APRV might be associated with a decreased risk for VAP in patients with pulmonary contusion. Retrospective cohort study. Of 286, 64 (22%) patients requiring mechanical ventilation for >48 hours met criteria for pulmonary contusion and were the basis for this study. Subjects with pulmonary contusion had a significantly higher rate of VAP than other trauma patients, [VAP rate contusion patients: 18.3/1,000, non-contusion patients: 7.7/1,000, incidence rate ratio 2.37 (95% confidence interval [CI], 1.11-4.97), p=0.025]. Univariate analysis showed that APRV (hazard ratio, 0.15 [0.03-0.72; p=0.018]) was associated with a decreased incidence of VAP. Cox proportional hazards regression, using propensity scores for APRV to control for confounding, supported a protective effect of APRV from VAP (hazard ratio, 0.10 [95% CI, 0.02-0.58]; p=0.01). Pao2/FiO2 ratios were higher during APRV compared with conventional ventilation (p<0.001). Subjects attained the goal Sedation Agitation Score for an increased percentage of time during APRV (median [interquartile range (IQR)] 72.7% [33-100] of the time) compared with conventional ventilation (47.2% [0-100], p=0.044), however, dose of sedatives was not different between these subjects. APRV was not associated with hospital mortality (odds ratio 0.57 [95% CI, 0.06-5.5]; p=0.63) or ventilator-free days (No APRV 15.4 vs. APRV 13.7 days, p=0.49). Use of APRV in patients with pulmonary contusion is associated with a reduced risk for VAP.

Feasibility of airway pressure release ventilation in infants with near end stage- neonatal bronchopulmonary dysplasia

Background: Ventilated premature infants with severe, advanced bronchopulmonary dysplasia (BPD) often require high mean airway pressure (MAP) and FiO2 to maintain acceptable gas exchange using conventional mechanical ventilation techniques such as synchronized intermittent mandatory ventilation (SIMV). In addition, they are at risk to develop ep isodes of severe respiratory failure (BPD spells). We report our experience with airway pressure release ventilation (APRV), a ventilation modality which allows spontaneous respiration during a relatively long high pressure phase followed by a shorter release period allowing for CO2 removal from the conducting airways. Despite the higher MAP, the unique APRV flow pattern is thought to decrease volutrauma. Objective: To determine the feasibility and safety of APRV in neonates with severe BPD. Design/methods: Approval for this retrospective review was obtained from Childrens Hospital Los Angeles (CHLA) Institutional Review Board. Patients with advanced BPD treated in the Newborn and Infant Critical Care Unit at CHLA that received APRV at the discretion of the attending neonatologist for develo ping severe respiratory failure between May 2004 and June 2005 were identified and their medical records reviewed. Results: Nine patients were placed on APRV using the AVEA ventilator (CareFusion, San Diego, CA). Eight infants were former extremely premature infants with severe BPD and 1 infant was born at term infant with suspected surfactant protein-B defi ciency. Mean gestational and postmenstrual age was 26.7± 4.9 and 50.5± 9.8 weeks, respectively at the time of initiation of APRV. The duration of APRV was 17.5± 11.9 days. On APRV, patients received higher MAP (29 vs. 15 cm H2O; p < 0.001) and lower FiO2 (0.5 vs. 0.3; p = 0.38) compared to SIMV with pressure support, high-frequency oscillatory ventilation or high-frequency jet ventilation. Seven of the 9 patients had clinical improv ement on APRV within 3 days defined by fewer episodes of severe desaturation, variability in FiO2, and vasopressor/inotrope support. In addition, none of th e infants received pharmacological neuromuscular blockade after the initiation of APRV. Despite the higher MAP, patients did not develop air-leaks and remained hemodynamically stable with normal blood pressure and urine output. Conclusions: These preliminary data indicate that infants with severe BPD tolerate the use of APRV without apparent adverse effects. However, it remains unclear whether APRV is indeed safe and beneficial in former very preterm neonates with seve re BDP and episodes of respiratory failure. Randomized controlled studies are required to determine the safety, efficacy and l ong-term morbidities of this mode of ventilation in neonates.

Preliminary Experience with Airway Pressure Release Ventilation in a Trauma/Surgical Intensive Care Unit

Airway pressure-release ventilation (APRV) is a pressure-limited, time-cycled mode of mechanical ventilation. The purpose of this study was to evaluate our initial experience with the use of APRV in acutely injured, ventilated patients. Since March 2003, APRV has been used selectively in adult trauma patients with or at risk for acute lung injury/acute respiratory distress syndrome. Data were obtained before and during the 72 hours after switching to APRV. A retrospective analysis of these data was then performed. Complete data were available on 46 of 60 patients (77%) for the first 72 hours of APRV. Before APRV, the average Pao2/Fio2 ratio was 243 and the average peak airway pressure was 28 cm H2O. Peak airway pressure decreased 19% (p = 0.001), Pao2/Fio2 improved by 23% (p = 0.017) and release tidal volumes improved by 13% (p = 0.020) over the course of the analysis. APRV significantly improved oxygenation by alveolar recruitment and allowed for a reduction in peak airway pressures. This relatively new modality had favorable results and appears to be an effective alternative for lung recruitment in traumatically injured patients at risk for acute lung injury/acute respiratory distress syndrome.

Other approaches to open-lung ventilation: Airway pressure release ventilation

To review the use of airway pressure release ventilation (APRV) in the treatment of acute lung injury/acute respiratory distress syndrome. Published animal studies, human studies, and review articles of APRV. APRV has been successfully used in neonatal, pediatric, and adult forms of respiratory failure. Experimental and clinical use of APRV has been shown to facilitate spontaneous breathing and is associated with decreased peak airway pressures and improved oxygenation/ventilation when compared with conventional ventilation. Additionally, improvements in hemodynamic parameters, splanchnic perfusion, and reduced sedation/neuromuscular blocker requirements have been reported. APRV may offer potential clinical advantages for ventilator management of acute lung injury/acute respiratory distress syndrome and may be considered as an alternative "open lung approach" to mechanical ventilation. Whether APRV reduces mortality or increases ventilator-free days compared with a conventional volume-cycled "lung protective" strategy will require future randomized, controlled trials.

Airway pressure release ventilation in the acute respiratory distress syndrome following traumatic injury.

Respiratory insufficiency that occurs following a traumatic injury is due to both mechanical and physiological disruption of pulmonary integrity. Although an overall decrease in pulmonary compliance (Δ V/Δ P) is a component of acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS)*, this may not be a homogeneous process. Changes in compliance may actually occur at varying degrees throughout the lung parenchyma in a heterogeneous fashion. Attempting to open or recruit collapsed alveoli without causing lung injury by overdistention or stretch of alveoli with more normal compliance remains a clinical challenge. Airway pressure release ventilation (APRV) is a ventilator mode that incorporates features that optimize the spectrum of alveolar mechanics present in ARDS/ALI. In the past, the focus on ventilator support was on conforming the patient to the ventilator; alternatively, APRV accommodates the patient's breathing pattern and superimposes ventilation onto a pressure framework to support spontaneous breathing, 1 - 3 and thereby conforms the ventilator to the patient. APRV differs from other modes of positive-pressure ventilation in that it delivers a continuous positive airway pressure (CPAP) that releases periodically to augment CO 2 exchange. The patient's breathing is spontaneous and unrestricted throughout the entire ventilator cycle, allowing infinite inspiratory/expiratory ratios. Studies have shown that APRV can augment ventilation with lower pulmonary artery pressures and improved efficiency compared to traditional modes of ventilatory support; these elements may reduce the risk of ventilator-associated lung injury while improving oxygenation. After a brief review of the incidence and outcome of traumatic ARDS, we will present basic concepts of ventilator management with APRV and then will address the use of APRV in the patient with respiratory failure secondary to trauma.