Lower Airway Pressures Research Articles

Ventilatory choices for intubated patients during helicopter stretcher winching

The winching of intubated patients on a stretcher into a helicopter is a rare event. Intermittent positive pressure ventilation is mandatory, which can either be performed manually with a self-inflating bag, or automatically using a portable ventilator. Theoretically automatic ventilation would provide improved oxygenation, more stable arterial carbon dioxide levels and a reduced risk of airway disconnection. Furthermore, the stretcher attendant may better perform winching procedures with higher situational awareness, contributing to crew and patient safety. However ventilator failure, and the diagnosis and management of such, is of concern. The aim of this study is to compare automatic against manual ventilation during intubated helicopter stretcher winching. The trial had two phases. Initially a static winch on a hoist simulator was performed, followed by live winching into a helicopter. All stretcher attendants performed two winches with an intubated manikin. During one winch, the manikin was manually ventilated, and an automatic ventilator was used for the other. Airway pressures were measured. Automatic ventilation did not fail. Compared with automatic ventilation, manual ventilation displayed significant pauses, inconsistent rates and both high and low airway pressures. Automatic ventilation permitted better situational awareness and performance in winching manoeuvres. One airway disconnection occurred during manual ventilation. During helicopter winching, automatic ventilation is superior in providing controlled, consistent and reliable ventilation for intubated patients. The stretcher attendant is also able to provide more attention to the winching manoeuvres with subsequent safety gains. The risk of automatic ventilator failure is low.

Risk Factors for Pediatric Extubation Failure: The Importance of Respiratory Muscle Strength.

Respiratory muscle weakness frequently develops during mechanical ventilation, although in children there are limited data about its prevalence and whether it is associated with extubation outcomes. We sought to identify risk factors for pediatric extubation failure, with specific attention to respiratory muscle strength. Secondary analysis of prospectively collected data. Tertiary care PICU. Four hundred nine mechanically ventilated children. Respiratory measurements using esophageal manometry and respiratory inductance plethysmography were made preextubation during airway occlusion and on continuous positive airway pressure of 5 and pressure support of 10 above positive end-expiratory pressure 5 cm H2O, as well as 5 and 60 minutes postextubation. Thirty-four patients (8.3%) were reintubated within 48 hours of extubation. Reintubation risk factors included lower maximum airway pressure during airway occlusion (aPiMax) preextubation, longer length of ventilation, postextubation upper airway obstruction, high respiratory effort postextubation (pressure rate product, pressure time product, tension time index), and high postextubation phase angle. Nearly 35% of children had diminished respiratory muscle strength (aPiMax ≤ 30 cm H2O) at the time of extubation, and were nearly three times more likely to be reintubated than those with preserved strength (aPiMax > 30 cm H2O; 14% vs 5.5%; p = 0.006). Reintubation rates exceeded 20% when children with low aPiMax had moderately elevated effort after extubation (pressure rate product > 500), whereas children with preserved aPiMax had reintubation rates greater than 20% only when postextubation effort was very high (pressure rate product > 1,000). When children developed postextubation upper airway obstruction, reintubation rates were 47.4% for those with low aPiMax compared to 15.4% for those with preserved aPiMax (p = 0.02). Multivariable risk factors for reintubation included acute neurologic disease, lower aPiMax, postextubation upper airway obstruction, higher preextubation positive end-expiratory pressure, higher postextubation pressure rate product, and lower height. Neuromuscular weakness at the time of extubation was common in children and was independently associated with reintubation, particularly when postextubation effort was high.

Impact of Low Tidal Volumes During One-Lung Ventilation. A Meta-Analysis of Randomized Controlled Trials

The link between ventilation strategies and perioperative outcomes remains one of the fundamental paradigms of thoracic anaesthesia. During one-lung ventilation (OLV), one lung is excluded from gas exchange and ventilation is directed at the dependent lung. The authors hypothesised that the use of low tidal volumes (VT) during OLV provides adequate gas exchange and improves postoperative outcome. Meta-analysis of randomized clinical trials. Thoracic surgery. Patients undergoing OLV. None. The authors performed a meta-analysis of all randomized trials on low versus high VT during OLV in patients undergoing thoracic surgery. Outcomes of the study were gas exchange and airway pressures during and after OLV, postoperative pulmonary complications (PPCs), and hospital stay (HLOS). Fourteen randomized trials were selected, but only a few of them contained one outcome of interest. Low VT was associated with lower arterial oxygen tension, lower airway pressures, and higher arterial carbon dioxide tension at specific time points during OLV. Low VT was associated with preserved gas exchange after OLV, lower incidence of pulmonary infiltrations, and acute respiratory distress syndrome. Incidences of PPCs and HLOS were similar. The use of low VT reduces airway pressure but worsens gas exchange during OLV. Preservation of postoperative oxygenation and reduction in infiltrates suggest a lung-protective modality with no demonstrable impact on PPCs and HLOS.

Experimental study on effect of airway pressure on cardiopulmonary resuscitation

To observe the effect of different airway pressure on ventilation, organ perfusion and return of spontaneous circulation (ROSC) of cardiac arrest (CA) pigs during cardiopulmonary resuscitation (CPR), and to explore the possible beneficial mechanism of positive airway pressure during CPR. Twenty healthy landrace pigs of clean grade were divided into low airway pressure group (LP group, n = 10) and high airway pressure group (HP group, n = 10) with random number table. The model of ventricular fibrillation (VF) was reproduced by electrical stimulation, and mechanical chest compressions and mechanical ventilation (volume-controlled mode, tidal volume 7 mL/kg, frequency 10 times/min) were performed after 8 minutes of untreated VF. Positive end expiratory pressure (PEEP) in LP group and HP group was set to 0 cmH2O and 6 cmH2O (1 cmH2O = 0.098 kPa) respectively. Up to three times of 100 J biphasic defibrillation was delivered after 10 minutes of CPR. The ROSC of animals were observed, and the respiratory parameters, arterial and venous blood gas and hemodynamic parameters were recorded at baseline, 5 minutes and 10 minutes of CPR. The number of animals with ROSC in the HP group was significantly more than that in the LP group (8 vs. 3, P < 0.05). Intrathoracic pressure during chest compression relaxation was negative in the HP group, and its absolute value was significantly lower than that in LP group at the same time [intrathoracic negative pressure peak (cmH2O): -4.7±2.2 vs. -10.8±3.5 at 5 minutes, -3.9±2.8 vs. -6.5±3.4 at 10 minutes], however, there was significantly difference only at 5 minutes of CPR (P < 0.01). Intrathoracic pressure variation during CPR period in the HP group were significantly higher than those in the LP group (cmH2O: 22.5±7.9 vs. 14.2±4.4 at 5 minutes, 23.1±6.4 vs. 12.9±5.1 at 10 minutes, both P < 0.01). Compared to the LP group, arterial partial pressure of oxygen [PaO2 (mmHg, 1 mmHg = 0.133 kPa): 81.5±10.7 vs. 68.0±12.1], venous oxygen saturation (SvO2: 0.493±0.109 vs. 0.394±0.061) at 5 minutes of CPR, and PaO2 (mmHg: 77.5±13.4 vs. 63.3±10.5), arterial pH (7.28±0.09 vs 7.23±0.11), SvO2 (0.458±0.096 vs. 0.352±0.078), aortic blood pressure [AoP (mmHg): 39.7±9.5 vs. 34.0±6.9], coronary perfusion pressure [CPP (mmHg): 25.2±9.6 vs. 19.0±7.6], and carotid artery flow (mL/min: 44±16 vs. 37±14) at 10 minutes of CPR in the HP group were significantly higher (all P < 0.05). Arterial partial pressure of carbon dioxide (PaCO2) in the HP group was significantly lower than that in the LP group at 10 minutes of CPR (mmHg: 60.1±9.7 vs. 67.8±8.6, P < 0.05). Compared to low airway pressure, a certain degree of positive airway pressure can still maintain the negative intrathoracic pressure during relaxation of chest compressions of CPR, while increase the degree of intrathoracic pressure variation. Positive airway pressure can improve oxygenation and hemodynamics during CPR, and is helpful to ROSC.

Effects of pressure support and pressure-controlled ventilation on lung damage in a model of mild extrapulmonary acute lung injury with intra-abdominal hypertension.

Intra-abdominal hypertension (IAH) may co-occur with the acute respiratory distress syndrome (ARDS), with significant impact on morbidity and mortality. Lung-protective controlled mechanical ventilation with low tidal volume and positive end-expiratory pressure (PEEP) has been recommended in ARDS. However, mechanical ventilation with spontaneous breathing activity may be beneficial to lung function and reduce lung damage in mild ARDS. We hypothesized that preserving spontaneous breathing activity during pressure support ventilation (PSV) would improve respiratory function and minimize ventilator-induced lung injury (VILI) compared to pressure-controlled ventilation (PCV) in mild extrapulmonary acute lung injury (ALI) with IAH. Thirty Wistar rats (334±55g) received Escherichia coli lipopolysaccharide intraperitoneally (1000μg) to induce mild extrapulmonary ALI. After 24h, animals were anesthetized and randomized to receive PCV or PSV. They were then further randomized into subgroups without or with IAH (15 mmHg) and ventilated with PCV or PSV (PEEP = 5cmH2O, driving pressure adjusted to achieve tidal volume = 6mL/kg) for 1h. Six of the 30 rats were used for molecular biology analysis and were not mechanically ventilated. The main outcome was the effect of PCV versus PSV on mRNA expression of interleukin (IL)-6 in lung tissue. Regardless of whether IAH was present, PSV resulted in lower mean airway pressure (with no differences in peak airway or peak and mean transpulmonary pressures) and less mRNA expression of biomarkers associated with lung inflammation (IL-6) and fibrogenesis (type III procollagen) than PCV. In the presence of IAH, PSV improved oxygenation; decreased alveolar collapse, interstitial edema, and diffuse alveolar damage; and increased expression of surfactant protein B as compared to PCV. In this experimental model of mild extrapulmonary ALI associated with IAH, PSV compared to PCV improved lung function and morphology and reduced type 2 epithelial cell damage.

Elevated Mean Airway Pressure and Central Venous Pressure in the First Day of Mechanical Ventilation Indicated Poor Outcome.

The relationship between respiratory mechanical parameters and hemodynamic variables remains unclear. This study was performed to determine whether mean airway pressure and central venous pressure in the first day of mechanical ventilation are associated with patient outcomes. Retrospective first 24-hour comparison during ICU stay. The Department of Critical Care Medicine of Peking Union Medical College Hospital. Patients with mechanical ventilation. None. The clinical data of patients who received mechanical ventilation, especially respiratory and hemodynamic data, were collected and analyzed. In terms of the hemodynamic and perfusion data, the nonsurvivors group (177/2,208) had higher heart rate, respiratory rate, central venous pressure, and lactates and a lower perfusion index and P(v-a)CO2 (p < 0.05). In terms of respiratory condition, mean airway pressure, peak airway pressure, positive end-expiratory pressure, driving pressure, and inspiratory time/total respiration time of nonsurvivors were significantly higher, and arterial oxygen pressure and dynamic compliance worsened and were lower than the survivors (p < 0.05). Increased central venous pressure (odds ratio, 1.125; 95% CI, 1.069-1.184; p < 0.001) and elevated mean airway pressure (odds ratio, 1.125; 95% CI, 1.069-1.184; p < 0.001) were independently associated with 28-day mortality. The area under receiver operating characteristic demonstrated that central venous pressure and mean airway pressure were measured at 0.795 (95% CI, 0.654-0.757) and 0.833 (95% CI, 0.608-0.699), respectively. Based on the cutoff of central venous pressure and mean airway pressure, all of the participants were divided into the following groups: low central venous pressure and mean airway pressure, only high central venous pressure or mean airway pressure, or high central venous pressure and mean airway pressure. Post hoc tests showed significant differences among these three groups based on 28-day survival (log rank [Mantel-Cox], 131.931; p < 0.001). During the first 24 hours of mechanical ventilation, patients with elevated mean airway pressure and elevated central venous pressure had worse outcomes.

Low flow veno-venous extracorporeal CO2 removal for acute hypercapnic respiratory failure.

Ventilation with low tidal volume and airway pressure results in a survival benefit in ARDS patients. Previous research suggests that avoiding mechanical ventilation altogether may be beneficial in some cases of respiratory failure. Our hypothesis was that low flow veno-venous extracorporeal CO2 removal (ECCO2R) enables maintenance of a lung protective ventilation strategy or awake spontaneous ventilation despite severe hypercapnic respiratory failure (HRF). Twenty patients with HRF were investigated while mechanically ventilated (N.=14) or breathing spontaneously close to respiratory exhaustion (N.=6). Low flow ECCO2R was performed using a hemoperfusion device with a polypropylene gas-exchanger. Causes of HRF were severe ARDS (N.=11), COPD (N.=4), chronic lung transplant rejection (N.=3) and cystic fibrosis (N.=2). During the first 8h of ECCO2R, PaCO2 decreased from 10.6 (9.3-12.9) to 7.9 (7.3-9.3) kPa (P<0.001) and pH increased from 7.23 (7.09-7.40) to 7.36 (7.27-7.41) (P<0.05). Thereafter, steady state was achieved while maintaining lung protective tidal volume (4.7 (3.8-6.5) mL/kg) and peak ventilator pressure (28 (27-30) mbar at 24 h). During the first 48 h, thrombocyte count decreased by 52% (P<0.01), Fibrinogen by 38% (P<0.05). Intubation could be avoided in all spontaneously breathing patients. In 4/6 high blood flow extracorporeal circulation was required due to increased oxygen demand. 6/14 mechanically ventilated patients recovered from respiratory support. Our results suggest that in mechanically ventilated patients with HRF, low flow ECCO2R supports the maintenance of lung protective tidal volume and peak ventilator pressure. In selected awake patients with acute HRF, it may be a novel treatment approach to avoid mechanical ventilation, hence preventing ventilator- and sedation-associated morbidity and mortality.

The clinical application of high frequency oscillatory ventilation in children

High-frequency ventilation (HFV) is theoretically an ideal ventilatory mode for lung protection.It also delivers extremely small tidal volumes near to or less than the anatomically invalid cavity (about 2ml/kg) at very high respiratory frequencies (recognized ventilation frequency about 4 times more than the normal range). Compared to the conventional mechanical ventilation, HFV makes use of lung-open mode, with low tidal volume, low airway pressure, low thoracic pressure and end-exhaling pressure effect, which can avoid recruitment/derecruitment of alveoli to reduce pressure injuries on lung tissue and airway.Nowadays, more and more critical care practitioners implement this ventilation mode.We reviewed the principles, classification, parameters, and clinical indications of HFV in this article. Key words: High frequency ventilation; Ventilation principle; Technical parameters; Clinical application,

Comparison of actual and ideal body weight for selection of appropriate size of ProSeal™ laryngeal mask airway in overweight and obese patients: A prospective, randomised study.

Background and Aims:The ProSeal™ laryngeal mask airway (PLMA) has advantages of providing better cuff seal and the presence of a gastric drain tube. The manufacturer recommends actual body weight (ABW) for size selection. Pharyngeal area reduces with increase in body mass index (BMI); hence, in overweight patients, PLMA selected on ABW may not fit well. We hypothesised that the ideal body weight (IBW) would be more appropriate in size selection of PLMA.Methods:This randomised, single-blind study included 124 patients of 20–60 years and American Society of Anesthesiologists Class I–II, with BMI >25. Patients were randomly divided into two groups. In Group ABW, PLMA was selected based on ABW (62 patients) and in Group IBW, PLMA was selected based on IBW (62 patients). The primary outcome was the first-attempt insertion success rate. Oropharyngeal air leaks, gastric air leaks, drain tube air leaks, insertion difficulty scores and postoperative complications were assessed. Fibre-optic view (Grade I–IV) was assessed for proper placement by a blinded assessor. Statistical analyses were performed using Chi-square test or Fisher's exact test.Results:First-attempt insertion success rate and overall insertion success rates were similar in both the groups. Group IBW patients had significantly less resistance during insertion, lower peak airway pressures, successful nasogastric tube insertions, better fibre-optic views and less post-operative complications. Oropharyngeal leak pressure and instrumentation used for insertion were comparable.Conclusion:IBW is preferable for the size selection of the PLMA in overweight and obese patients compared to the ABW.

The Efficacy Of Non Inflatable Cuff (I-gel and SLIPA) Versus Inflatable Cuff(Soft Seal LMA) Supraglottic Airways In Paralyzed Adult Patients

Aim: To compare the efficacy of non-inflatable cuff supraglottic airways (I-gel and SLIPA) to inflatable cuff soft seal Laryngeal mask airway (SSLMA) in patients requiring general anesthesia and controlled ventilation during elective surgical procedures. Patients and methods: An experimental study design was used, with comparison of three groups of patients using i-gel, SLIPA and SSLMA. Patients with risk of gastro esophageal reflux were excluded. Ease of insertion, quality of seal, effective ventilation, hemodynamic responses, side effects and surgical time were assessed. An Oropharyngeal sealing pressure or ‘leak’ test was performed with the airway devices to quantify the efficacy of the seal with the patient airway. Airway sealing pressure tests claimed to be excellent for clinical purposes. Results: Overall success of insertion was 100% in i-gel, 97.5% and 95% in SSLMA and SLIPA respectively. The i-gel permitted ventilation with a significantly high tidal volume (485 ± 82 ml) at a significantly low peak airway pressure (12 ± 3 cmH2O) and a significantly high leak pressure (26 ± 6.3 cmH2O). All groups show stable hemodynamic responses to insertion and removal of the devices. Insertion time was significantly shorter with i-gel (15 ± 2.5 sec.) compared to SLIPA and SSLMA, 22 ± 4.6 sec. and 19 ± 3.85 sec, respectively. Sore throat was significantly high in SSLMA 30%. Whereas, blood traces on the device and gastric air insufflations were highly significant with SLIPA 8% and 10% respectively. Conclusion: The three disposable SGAs proved to be suitable for controlled ventilation during elective short surgical operations. The i-gel provides effective ventilation with minimal side effects. Whereas, SLIPA is associated with a high incidence of gastric air insufflations, The Soft Seal LMA provides high leakage volume and incidence of sore throat postoperatively.

Comparison of volume controlled ventilation and pressure controlled ventilation in patients undergoing robot-assisted pelvic surgeries: An open-label trial.

Background and Aims:Although volume controlled ventilation (VCV) has been the traditional mode of ventilation in robotic surgery, recently pressure controlled ventilation (PCV) has been used more frequently. However, evidence on whether PCV is superior to VCV is still lacking. We intended to compare the effects of VCV and PCV on respiratory mechanics and haemodynamic in patients undergoing robotic surgeries in steep Trendelenburg position.Methods:This prospective, randomized trial was conducted on sixty patients between 20 and 70 years belonging to the American Society of Anesthesiologist Physical Status I–II. Patients were randomly assigned to VCV group (n = 30), where VCV mode was maintained through anaesthesia, or the PCV group (n = 30), where ventilation mode was changed to PCV after the establishment of 40° Trendelenburg position and pneumoperitoneum. Respiratory (peak and mean airway pressure [APpeak, APmean], dynamic lung compliance [Cdyn] and arterial blood gas analysis) and haemodynamics variables (heart rate, mean blood pressure [MBP] central venous pressure) were measured at baseline (T1), post-Trendelenburg position at 60 min (T2), 120 min (T3) and after resuming supine position (T4).Results:Demographic profile, haemodynamic variables, oxygen saturation and minute ventilation (MV) were comparable between two groups. Despite similar values of APmean, APpeak was significantly higher in VCV group at T2 and T3 as compared to PCV group (P < 0.001). Cdyn and PaCO2 were also better in PCV group than in VCV group (P < 0.001 and 0.045, respectively).Conclusion:PCV should be preferred in robotic pelvic surgeries as it offers lower airway pressures, greater Cdyn and a better-preserved ventilation-perfusion matching for the same levels of MV.

Approach to the Patient with Acute Respiratory Failure

Acute respiratory failure (ARF) is a common reason for admission to the intensive care unit (ICU), and is associated with significant morbidity and mortality. Failure of one or more components of the respiratory system can lead to hypoxemia, hypercabia, or both. Initial evaluation of patients with ARF should include physical examination, chest imaging, and arterial blood gases (ABG) sampling. As ARF is often a life-threatening emergency, a patient’s oxygenation and ventilation will need to be supported at the same time that diagnostic and therapeutic interventions are planned. The priorities for early treatment are essentially those of basic life support: airway and breathing. The first step is to assess a patient’s airway and ascertain that it is patent. This is followed by efforts to support both oxygenation and ventilation. This can include non-invasive or invasive mechanical ventilatory support. As with all interventions, there are risks inherent in the use of mechanical ventilation, which may be minimized by the use of lung protective ventilation (i.e., with low tidal volumes and airway pressures). Finally, due to the potential complications associated with mechanical ventilation, it is important to regularly assess whether a patient continues to require the assistance of the ventilator, and to liberate patients from mechanical ventilation at the earliest opportunity when clinically safe and feasible to do so. Figures depict pressure-time curve. Tables list the clinical causes of hypoxemic respiratory failure, oxygen delivery devices, indications for noninvasive positive pressure support, common causes of abnormal respiratory mechanics, and common causes of acute respiratory distress syndrome (ARDS). This review contains 2 highly rendered figures, 5 tables, and 86 references.

Low Positive Airway Pressure without Positive End-Expiratory Pressure Decreases Blood Loss during Hepatectomy in Living Liver Donors

Background/Aims: Despite the development of strategies to minimize blood loss during hepatectomy challenges remain. Our aim was to determine whether low positive airway pressure (PAP) without positive end-expiratory pressure (PEEP) could minimize blood loss during hepatectomy. Methods: Forty-one living liver donors who underwent extended left lobectomy or right lobectomy between December 2012 and November 2013 were retrospectively analyzed. In the standard PAP group (n = 18), tidal volume was 8-10 ml/kg, respiratory rate was 10-12/min and PEEP was maintained at 5 cm H₂O. In the low PAP group (n = 23), tidal volume was reduced to 5 ml/kg, respiratory rate was increased to 15/min and PEEP maintained at 0 cm H₂O. Low central venous pressure (CVP) was maintained during surgery in all cases. Results: The low PAP group had significantly less blood loss (p = 0.0075) and shorter operation time (p = 0.0303) than the standard PAP group. In multiple regression analysis, ventilation mode and median CVP were found to be determining factors for blood loss. In no case did the ventilation mode affect perioperative management. Conclusions: Low PAP without PEEP is a safe mechanical ventilation mode that might help minimize blood loss along with CVP monitoring during hepatectomy.

Effects of pressure-controlled and volume-controlled ventilation on respiratory mechanics and systemic stress response during prone position.

BackgroundProne position during general anesthesia for special surgical operations may be related with increased airway pressure, decreased pulmonary and thoracic compliance that may be explained by restriction of chest expansion and compression of abdomen. The optimum ventilation mode for anesthetized patients on prone position was not described and studies comparing volume-controlled ventilation (VCV) and pressure-controlled ventilation (PCV) during prone position are limited. We hypothesized that PCV instead of VCV during prone position could achieve lower airway pressures and reduce the systemic stress response. In this study, we aimed to compare the effects of PCV and VCV modes during prone position on respiratory mechanics, oxygenation, and hemodynamics, as well as blood cortisol and insulin levels, which has not been investigated before.MethodsFifty-four ASA I-II patients, 18–70 years of age, who underwent percutaneous nephrolithotomy on prone position, were randomly selected to receive either the PCV (Group PC, n = 27) or VCV (Group VC, n = 27) under general anesthesia with sevoflurane and fentanyl. Blood sampling was made for baseline arterial blood gases (ABG), cortisol, insulin, and glucose levels. After anesthesia induction and endotracheal intubation, patients in Group PC were given pressure support to form 8 mL/kg tidal volume and patients in Group VC was maintained at 8 mL/kg tidal volume calculated using predicted body weight. All patients were maintained with 5 cmH2O PEEP. Respiratory parameters were recorded during supine and prone position. Assessment of ABG and sampling for cortisol, insulin and glucose levels were repeated during surgery and 60 min after extubation.ResultsP-peak and P-plateau levels during supine and prone positions were significantly higher and P-mean and compliance levels during prone position were significantly lower in Group VC when compared with Group PC. Postoperative PaO2 level was significantly higher in Group PC compared with Group VC. Cortisol levels were increased with surgery in both groups (p < 0.05) and decreased to baseline levels in Group PC while remained high in Group VC in the early postoperative period. Cortisol levels were significantly higher in Group VC during surgery and in the early postoperative period compared with Group PC.ConclusionWhen compared with VCV mode, PCV mode is associated with lower P-peak and P-plateau levels during both supine and prone positions, better oxygenation postoperatively, lower blood cortisol levels during surgery in prone position and in the early postoperative period. We concluded that PCV mode might be more appropriate in prone position during anesthesia.

Current status and recognition of high frequency ventilation in acute respiratory distress syndrome

Acute respiratory distress syndrome(ARDS) is a common critical disease in pediatric patients, and mechanical ventilation is one of the most important methods for respiratory support.High frequency oscillation ventilation, which has these characteristics of low tidal volume, low airway pressure, and low alveolar injury, is a safe and effective treatment of ARDS.This article will elaborate about current status and recognition of high frequency ventilation in ARDS. Key words: Acute respiratory distress syndrome; High frequency oscillation ventilation; Child

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.

Neurally adjusted ventilatory assist (NAVA) in preterm newborn infants with respiratory distress syndrome-a randomized controlled trial.

Neurally adjusted ventilatory assist (NAVA) improves patient-ventilator synchrony during invasive ventilation and leads to lower peak inspiratory pressures (PIP) and oxygen requirements. The aim of this trial was to compare NAVA with current standard ventilation in preterm infants in terms of the duration of invasive ventilation. Sixty infants born between 28+0 and 36+6weeks of gestation and requiring invasive ventilation due to neonatal respiratory distress syndrome (RDS) were randomized to conventional ventilation or NAVA. The median durations of invasive ventilation were 34.7h (quartiles 22.8-67.9h) and 25.8h (15.6-52.1h) in the NAVA and control groups, respectively (P=0.21). Lower PIPs were achieved with NAVA (P=0.02), and the rapid reduction in PIP after changing the ventilation mode to NAVA made following the predetermined extubation criteria challenging. The other ventilatory and vital parameters did not differ between the groups. Frequent apneas and persistent pulmonary hypertension were conditions that limited the use of NAVA in 17% of the patients randomized to the NAVA group. Similar cumulative doses of opiates were used in both groups (P=0.71). NAVA was a safe and feasible ventilation mode for the majority of preterm infants suffering from RDS, but the traditional extubation criteria were not clinically applicable during NAVA. • NAVA improves patient-ventilator synchrony during invasive ventilation. • Lower airway pressures and oxygen requirements are achieved with NAVA during invasive ventilation in preterm infants by comparison with conventional ventilation. What is new: • Infants suffering from PPHN did not tolerate NAVA in the acute phase of their illness. • The traditional extubation criteria relying on inspiratory pressures and spontaneous breathing efforts were not clinically applicable during NAVA.

An Experimental Study on the Relationship Among Airway Pressure, Pneumoperitoneum Pressure, and Central Venous Pressure in Pure Laparoscopic Hepatectomy.

To determine optimal settings for airway pressure (AWP), pneumoperitoneum pressure (PPP), and central venous pressure (CVP) in pure laparoscopic hepatectomy. High PPP is often employed to control bleeding from the hepatic vein during pure laparoscopic hepatectomy; however, there is a risk of pulmonary gas embolism. We noted that decreases in AWP were often effective. After establishing carbon dioxide pneumoperitoneum in 6 male piglets and maintaining PPP at 25 mmHg, CVP was measured 3 times at each of 9 levels of airway pressure, which was increased in increments of 5 cmH2O from 0 to 40 cmH2O. CVP was measured in the same manner by maintaining PPP at 20, 15, 10, 5, and 0 mmHg, and in laparotomy. Correlation and regression analyses were performed among airway pressure, CVP, and pneumoperitoneum pressure. Positive correlations were observed between AWP and CVP and between PPP and CVP (P < 0.001). Under high airway pressure, CVP was persistently higher than pneumoperitoneum pressure. Under low airway pressure, CVP did not increase or often decreased when PPP was higher than CVP. By increasing pneumoperitoneum pressure, bleeding from the hepatic vein cannot be controlled under high airway pressure, but can be controlled under low airway pressure. However, under low airway pressure, the risk of pulmonary gas embolism increases when PPP is higher than CVP. We consider that reducing AWP is also effective for controlling bleeding from the hepatic vein and safer than increasing pneumoperitoneum pressure.

The optimal combination of mechanical ventilator parameters under general anesthesia in obese patients undergoing laparoscopic surgery

ObjectivePulmonary dysfunction after laparoscopic surgery is commonly seen in the high-risk group of obese patients. To reduce or avoid this complication caused by an improper combination of mechanical ventilation parameters, we conducted the following trial of 3 factors with 3 levels of mechanical ventilation, aimed to obtain the low airway pressure with good ventilator effects. MethodsPatients were randomly allocated as a sample of cases according to the “30≤weight/height2<40” obesity index. Anesthesia machine was checked on the most fundamental respiratory frequency (f), tidal volume (VT), and respiratory ratio (I:E) as the 3 factors of A, B, and C, with 3 levels of f=15, 12, 9 (beats per minute), VT=8, 10, 12 (mL/kg), and I:E=1:2.5, 1:2.0, 1:1.5. By using L9 (34) K=3 repeat, the orthogonal experimental design and analysis table for statistics, testing, and analysis of the factors that affect the respiratory and change at the end of the level of carbon dioxide (PETCO2), peak airway pressure (PIP), mean airway pressure (Pmean), and the end of endogenous airway pressure (PEEPi) are of statistical significance. SPSS 13.0 analysis of variance was used for statistically significant test, with P<.05 and P<.01 as statistically significant differences. ResultsIn this study, a total of 27 cases of laparoscopic surgery were allocated in 9 experimental groups under general anesthesia. Patients' vital signs are stable; SPO2 is 100%. There are different combinations among 3 factors and 3 levels of parameters: (1) the impact on the PETCO2, respiratory frequency (f), and/or VT, choose either level, P<.01 means statistically significant, respiratory ratio (I:E) of either selection, P>.05, not statistically significant; (2) the impact of PIP: respiratory frequency (f) change, P<.05, significant difference, VT and I:E changes, P<.01 means statistically significant; (3) the impact of airway pressure on average (Pmean): 3 factors and 3 levels of selected respiratory parameters, P<.01 means statistically significant. ConclusionThe best combination of respiratory parameters is A3B1C2, that is, f=9beats per minute, VT=8mL/kg, and I:E=1:2.0. That is, neither small tidal volume and faster frequency nor slow frequency large tidal volume is a good choice. To let obese patients under general anesthesia can obtain a lung protective effect of low airway pressure with good ventilation; it is noteworthy that (1) I:E of airway pressure (PIP, Pmean) is the important impact factor for the protection of the lung and (2) I:E of airway pressure (PIP, Pmean) is the factor with opposite properties.