Titration of Mechanical Insufflation–Exsufflation Optimal Pressure Combinations in Neuromuscular Diseases by Flow/Pressure Waveform Analysis

IntroductionThe aim of this study was to assess several air-pressure settings for MI–E to determine their effect on peak cough flow (PCF), and to compare the best pressures with those are more common used in the literature (±40 cmH₂O) in patients with neuromuscular disorders (NMD).MethodsAdults with NMD in whom MI–E was indicated were recruited. Assisted PCF was measured by an external pneumotachograph. The protocol included 9 PCF measures per patient: 1 baseline (non-assisted), 4 with increasing inspiratory pressures without negative pressure (10, 20, 30 and 40 cmH₂O or maximum tolerated), and then 4 adding expiratory pressures (?10, ?20, ?30 and ?40 cmH₂O or maximum tolerated) with maximum inspiratory pressure previously achieved.ResultsTwenty one patients were included, 61% with amyotrophic lateral sclerosis (ALS). Mean PCFs with recommended pressures (±40 cmH₂O) were lower than the scored in the individualized steps of the titration protocol (197.7 ± 67 l/min vs 214.2 ± 60 l/min, p < 0.05). Regarding subgroups, mean PCF_max values in ALS patients with bulbar symptoms were significantly higher than those achieved with recommended pressures (163.6 ± 80 vs 189 ± 66 l/min, p < 0.05).ConclusionThe PCF_max obtained with the protocol did not always match the recommended settings. It may be advisable to perform MI–E titration assessed by non-invasive PCF monitoring in patients with NMD, especially in ALS with bulbar involvement to improve the therapy detecting airway collapse induced by high pressures.     

压力控制容量保证模式用于老年患者术中机械通气的Meta分析

目的 系统评价压力控制容量保证模式（PCV-VG）用于老年患者术中机械通气的有效性和安全性。
方法 计算机检索PubMed、Web of Science、The Cochrane Library、中国期刊全文数据库（CNKI）、万方和维普数据库,检索PCV-VG用于老年患者术中机械通气的随机对照试验（RCT）,检索时限均从建库至2022年1月31日。由2名研究者独立筛选文献、提取资料并评价纳入研究的偏倚风险后,采用RevMan 5.4软件进行Meta分析。
结果 共纳入12篇文献,共计患者749例,PCV-VG组374例,对照组375例。术中机械通气时两组PaO₂（MD=5.32 mmHg,95%CI -0.55～11.18,P=0.08）、PaCO₂（MD=0.12 mmHg,95%CI -0.18～0.41,P=0.43）差异无统计学意义。与对照组比较,PCV-VG组术中机械通气时气道峰压（Ppeak）明显下降（MD=-3.40 cmH₂O,95%CI -4.69～-2.12,P<0.001）,肺动态顺应性（Cdyn）明显升高（MD=3.85 ml/cmH₂O,95%CI 2.46～5.25,P<0.001）。术中机械通气时两组MAP（MD=-0.22 mmHg,95%CI -1.45～1.01,P=0.72）差异无统计学意义。
结论 PCV-VG用于老年患者术中机械通气时,可以降低老年患者Ppeak、提高Cdyn,但不影响PaO₂、PaCO₂和MAP。     

A comparison of pressure-controlled and volume-controlled ventilation for laparoscopic cholecystectomy

The potential advantages of pressure‐controlled over volume‐controlled ventilation during laparoscopic surgery have yet to be proven. We randomly assigned 42 patients with BMI < 30 kg.m^?2 scheduled for laparoscopic cholecystectomy to receive either pressure‐ or volume‐controlled ventilation. Compared with volume‐controlled ventilation, pressure‐controlled ventilation resulted in a significant decrease in mean (SD) peak airway pressure at 10 min (20.4 (2.7) vs 24.0 (4.7) cmH₂O, p = 0.004) and 30 min (20.7 (3.0) vs 23.9 (4.9) cmH₂O, p = 0.015) and an increase in mean airway pressure at 10 min (10.5 (0.9) vs 9.6 (1.1) cmH₂O, p = 0.007) and 30 min (10.5 (1.1) vs 9.6 (1.2) cmH₂O, p = 0.016) after the start of surgery. Gas exchange and haemodynamic stability were similar. We conclude that pressure‐controlled ventilation is a safe alternative and offers some advantages to volume‐controlled ventilation during laparoscopic cholecystectomy in non‐obese patients.     

The association of postoperative pulmonary complications in 109,360 patients with pressure‐controlled or volume‐controlled ventilation

We thought that the rate of postoperative pulmonary complications might be higher after pressure‐controlled ventilation than after volume‐controlled ventilation. We analysed peri‐operative data recorded for 109,360 adults, whose lungs were mechanically ventilated during surgery at three hospitals in Massachusetts, USA. We used multivariable regression and propensity score matching. Postoperative pulmonary complications were more common after pressure‐controlled ventilation, odds ratio (95%CI) 1.29 (1.21–1.37), p < 0.001. Tidal volumes and driving pressures were more varied with pressure‐controlled ventilation compared with volume‐controlled ventilation: mean (SD) variance from the median 1.61 (1.36) ml.kg^?1 vs. 1.23 (1.11) ml.kg^?1, p < 0.001; and 3.91 (3.47) cmH₂O vs. 3.40 (2.69) cmH₂O, p < 0.001. The odds ratio (95%CI) of pulmonary complications after pressure‐controlled ventilation compared with volume‐controlled ventilation at positive end‐expiratory pressures < 5 cmH₂O was 1.40 (1.26–1.55) and 1.20 (1.11–1.31) when ≥ 5 cmH₂O, both p < 0.001, a relative risk ratio of 1.17 (1.03–1.33), p = 0.023. The odds ratio (95%CI) of pulmonary complications after pressure‐controlled ventilation compared with volume‐controlled ventilation at driving pressures of < 19 cmH₂O was 1.37 (1.27–1.48), p < 0.001, and 1.16 (1.04–1.30) when ≥ 19 cmH₂O, p = 0.011, a relative risk ratio of 1.18 (1.07–1.30), p = 0.016. Our data support volume‐controlled ventilation during surgery, particularly for patients more likely to suffer postoperative pulmonary complications.     

Impact of Interface Type on Noninvasive Ventilation Efficacy in Patients With Neuromuscular Disease: A Randomized Cross-Over Trial

Background and objectiveAround 25% of patients with neuro-muscular diseases (NMD) are treated by home noninvasive ventilation (NIV) through an oronasal mask. However, there is growing evidence that nasal masks require lower NIV pressures and result in fewer residual obstructive events. We hypothesized that nasal masks would improve efficacy and reduce side effects compared to oronasal masks in this population.Methodsopen label, cross-over, randomized, study in 2 tertiary care hospitals. Patients with NMD treated by home NIV were randomized for one-week periods to nasal and oronasal interfaces respectively (cross-over). At the end of each period, nocturnal polygraphy (monitoring mouth opening) under NIV, synchronized with transcutaneous partial pressure in CO₂ (tcCO₂) was performed. Data were collected from the NIV built-in software and NIV side-effects were collected. Intention-to-treat and per protocol analyses were performed. The primary outcome was mean nocturnal SpO₂. The secondary outcomes were: percentage of sleep with SpO₂ < 90%, oxygen desaturation index (ODI), mean tcCO₂, mean duration of mouth opening during sleep, level of non-intentional leaks and side-effects.ResultsThirty patients with NMD were included. There were no between-group differences for either the primary or secondary outcomes. Post hoc comparisons showed that changing between interfaces reduced NIV efficacy: mean nocturnal SpO₂ (p = 0.04), ODI (p = 0.01), mean tcCO2 (p = 0.048), side-effects (p = 0.008).ConclusionNasal masks did not improve NIV efficacy or reduce side effects compared to oronasal masks in patients with NMD treated by home NIV. The efficacy of NIV is reduced during the transition to another interface, requiring close monitoring.Registration number: NCT03458507.     

Lung-protective ventilation during Trendelenburg pneumoperitoneum surgery: A randomized clinical trial

Study objectiveTo assess the effects of a protective ventilation strategy during Trendelenburg pneumoperitoneum surgery on postoperative oxygenation.DesignsParallel-group, randomized trial.SettingOperating room of a university hospital, Italy.PatientsMorbidly obese patients undergoing Trendelenburg pneumoperitoneum gynaecological surgery.InterventionsParticipants were randomized to standard (SV: tidal volume = 10 ml/kg of predicted body weight, PEEP = 5 cmH₂O) or protective (PV: tidal volume = 6 ml/kg of predicted body weight, PEEP = 10 cmH₂O, recruitment maneuvers) ventilation during anesthesia.MeasurementsPrimary outcome was PaO₂/FiO₂ one hour after extubation. Secondary outcomes included day-1 PaO₂/FiO₂, day-2 respiratory function and intraoperative respiratory/lung mechanics, assessed through esophageal manometry, end-expiratory lung volume (EELV) measurement and pressure-volume curves.Main resultsSixty patients were analyzed (31 in SV group, 29 in PV group). Median [IqR] tidal volume was 350 ml [300–360] in PV group and 525 [500–575] in SV group. Median PaO₂/FiO₂ one hour after extubation was 280 mmHg [246–364] in PV group vs. 298 [250–343] in SV group (p = 0.64). Day-1 PaO₂/FiO_2, day-2 forced vital capacity, FEV-1 and Tiffenau Index were not different between groups (all p > 0.10). Intraoperatively, 59% of patients showed complete airway closure during pneumoperitoneum, without difference between groups: median airway opening pressure was 17 cmH₂O. In PV group, airway and transpulmonary driving pressure were lower (12 ± 5 cmH₂O vs. 17 ± 7, p < 0.001; 9 ± 4 vs. 13 ± 7, p < 0.001), PaCO₂ and respiratory rate were higher (48 ± 8 mmHg vs. 42 ± 12, p < 0.001; 23 ± 5 breaths/min vs. 16 ± 4, p < 0.001). Intraoperative EELV was similar between PV and SV group (1193 ± 258 ml vs. 1207 ± 368, p = 0.80); ratio of tidal volume to EELV was lower in PV group (0.45 ± 0.12 vs. 0.32 ± 0.09, p < 0.001).ConclusionsIn obese patients undergoing Trendelenburg pneumoperitoneum surgery, PV did not improve postoperative oxygenation nor day-2 respiratory function. PV was associated with intraoperative respiratory mechanics indicating less injurious ventilation. The high prevalence of complete airway closure may have affected study results.Trial registrationProspectively registered on http://clinicaltrials.gov NCT03157479 on May 17th, 2017.     

Changes in ventilator settings and ventilation–induced lung injury in burn patients—A systematic review

ObjectiveVentilation strategies aiming at prevention of ventilator–induced lung injury (VILI), including low tidal volumes (V_T) and use of positive end–expiratory pressures (PEEP) are increasingly used in critically ill patients. It is uncertain whether ventilation practices changed in a similar way in burn patients. Our objective was to describe applied ventilator settings and their relation to development of VILI in burn patients.Data SourcesSystematic search of the literature in PubMed and EMBASE using MeSH, EMTREE terms and keywords referring to burn or inhalation injury and mechanical ventilation.Study selectionStudies reporting ventilator settings in adult or pediatric burn or inhalation injury patients receiving mechanical ventilation during the ICU stay.Data extractionTwo authors independently screened abstracts of identified studies for eligibility and performed data extraction.Data synthesisThe search identified 35 eligible studies. V_T declined from 14 ml/kg in studies performed before to around 8 ml/kg predicted body weight in studies performed after 2006. Low-PEEP levels (<10 cmH₂O) were reported in 70% of studies, with no changes over time. Peak inspiratory pressure (PIP) values above 35 cmH₂O were frequently reported. Nevertheless, 75% of the studies conducted in the last decade used limited maximum airway pressures (≤35 cmH₂O) compared to 45% of studies conducted prior to 2006. Occurrence of barotrauma, reported in 45% of the studies, ranged from 0 to 29%, and was more frequent in patients ventilated with higher compared to lower airway pressures.ConclusionThis systematic review shows noticeable trends of ventilatory management in burn patients that mirrors those in critically ill non-burn patients. Variability in available ventilator data precluded us from drawing firm conclusions on the association between ventilator settings and the occurrence of VILI in burn patients.     

The Tulip GT® airway versus the facemask and Guedel airway: a randomised,controlled, cross‐over study by Basic Life Support‐trained airway providers in anaesthetised patients

We performed a randomised, controlled, cross‐over study of lung ventilation by Basic Life Support‐trained providers using either the Tulip GT^® airway or a facemask with a Guedel airway in 60 anaesthetised patients. Successful ventilation was achieved if the provider produced an end‐tidal CO₂ > 3.5 kPa and a tidal volume > 250 ml in two of the first three breaths, within 60 sec and within two attempts. Fifty‐seven (95%) providers achieved successful ventilation using the Tulip GT compared with 35 (58%) using the facemask (p < 0.0001). Comparing the Tulip GT and facemask, the mean (SD) end‐tidal CO₂ was 5.0 (0.7) kPa vs 2.5 (1.5) kPa, tidal volume was 494 (175) ml vs 286 (186) ml and peak inspiratory pressure was 18.3 (3.4) cmH₂O vs 13.6 (7) cmH₂O respectively (all p < 0.0001). Forty‐seven (78%) users favoured the Tulip GT airway. These results are similar to a previous manikin study using the same protocol, suggesting a close correlation between human and manikin studies for this airway device. We conclude that the Tulip GT should be considered as an adjunct to airway management both within and outside hospitals when ventilation is being undertaken by Basic Life Support‐trained airway providers.     

A clinical trial of volume- versus pressure-controlled intraoperative ventilation during laparoscopic bariatric surgeries

BackgroundIntra-operative ventilation is often challenging in patients with morbid obesity undergoing bariatric surgery.ObjectivesTo test the noninferiority of pressure-controlled ventilation (PCV) to volume-controlled ventilation (VCV) in respiratory mechanics.SettingBariatric Surgery Center, Iran.MethodsIn a randomized open-labeled clinical trial, 66 individuals with morbid obesity undergoing laparoscopic bariatric surgeries underwent intraoperative ventilation with either PCV or VCV. The measurements taken were peak and mean airway pressures (H₂O), partial pressure of arterial oxygen (PaO₂), partial pressure of arterial carbon dioxide (PaCO₂) and end-tidal carbon dioxide (CO₂). We additionally collected pulse-oximetric oxygen saturation, inspiratory concentration of oxygen (FiO₂), and hemodynamic variables. Data were analyzed with repeated measures over the time of intubation, after peritoneal insufflation, and every 15 minutes, thereafter up to one hour.ResultsPCV mode was successful to sustain adequate ventilation in 97% of the patients, which was similar to the 94% success rate of the VCV mode. Peak airway pressure increased 6 cmH₂O and end-tidal CO₂ rose by 5 mm Hg after abdominal insufflation in both groups (P = .850 and .376). Alveolar-arterial oxygen gradient similarly increased within 30 minutes after tracheal intubation both in PCV and VCV groups, with small trend of being higher in the VCV group. The ratio of dead space to tidal volumes (VD/VT) did not have a meaningful change (P = .724).ConclusionPCV was noninferior to VCV during laparoscopic bariatric surgery. Either mode of ventilation could be alternatively used during the anesthesia care of these patients.     

Laparoscopic sleeve gastrectomy for the treatment of idiopathic intracranial hypertension in patients with severe obesity

BackgroundSevere obesity is a major risk factor for idiopathic intracranial hypertension (IIH). Data on the role of bariatric surgery for the treatment of this condition are scarce.ObjectiveTo evaluate the effectiveness of laparoscopic sleeve gastrectomy (LSG) on treating IIH in severely obese patients.SettingTwo university bariatric surgery centers.MethodsProspectively collected data from consecutive patients undergoing LSG were retrospectively analyzed. Patients with IIH and referred by neuroophthalmologists for bariatric surgery were included in the analysis.ResultsFifteen female patients with IIH underwent LSG (median age: 31 yr). Median preoperative body mass index was 42.1 kg/m². Preoperatively, 14 patients (93.3%) had chronic headaches, 8 (53.3%) pulsatile tinnitus, and 1 (6.6%) epistaxis episodes. Ophthalmologic assessment showed bilateral papilledema in all patients, of whom 13 had visual symptoms. Median initial cerebrospinal fluid opening pressure was 31 cmH₂ O (range: 25–50 cmH₂ O); 4 patients required repeated decompressing lumbar punctures (1 ventriculoperitoneal shunt). LSG was successfully performed in all patients. No patients were lost to follow-up. Mean excess weight loss was and 87.4% and 88.1% 1 and 2 years after LSG, respectively. Headaches totally resolved in 13 patients (93.3%) and improved in 1 (P < .001). Pulsatile tinnitus (P = .013), epistaxis, visual symptoms (P < .001), and papilledema (P < .001) significantly resolved. Medication was stopped in 14 patients (93.3%). Two years after LSG, IIH outcomes for 7 patients reaching this time point remained unchanged.ConclusionThis study suggests that LSG is effective for severely obese patients with IIH, resulting in complete remission or significant improvement of their symptoms as well as medication discontinuation.     

Effects of scoliosis on respiratory muscle strength in patients with neuromuscular disorders

Background contextNeuromuscular disorders (NMD) are characterized by loss of lung volume and respiratory muscle weakness, but the effects of scoliosis on lung function are unclear.PurposeTo compare pulmonary function and respiratory muscle strength in patients with NMD with and without scoliosis as well as in healthy controls.Study design/settingProspective comparison of pulmonary function testing and respiratory muscle strength were made at the pediatric pulmonology and cardiopulmonary rehabilitation units of a university hospital.Patient sampleTwenty-two patients with NMD and scoliosis, 17 patients with NMD without scoliosis, and 24 age- and sex-matched healthy controls. Outcome measures were compared in patients with NMD with and without scoliosis and healthy subjects using Student t test, Mann-Whitney U test, chi-square test, one-way analysis of variance (ANOVA), Kruskal-Wallis one-way ANOVA, Pearson correlation coefficients, and Spearman rank correlation, as appropriate.Outcome measures1) Pulmonary function: forced vital capacity (FVC), forced expiratory volume in 1 second (FEV₁), peak expiratory flow rate (PEF), forced expiratory flow between 25% and 75% of FVC (FEF_25–75%), and maximum expiratory flows at 75%, 50%, and 25% of FVC (MEF₇₅, MEF₅₀, and MEF₂₅, respectively); 2) oxygen saturation: pulse oxymeter reading; and 3) respiratory muscle strength: maximal inspiratory mouth pressure (MIP) and maximal expiratory mouth pressure (MEP).MethodsPulmonary function, oxygen saturation, MIP, and MEP were measured and compared in patients with NMD, patients with and without scoliosis, and in healthy subjects.ResultsThe patients with NMD, both with and without scoliosis, had significantly lower PEF, MIP, MEP, % predicted MIP (%MIP), and % predicted MEP (%MEP) than those of healthy subjects (p<.05). The patients with NMD and scoliosis had significantly lower values than those with NMD without scoliosis and controls (p<.05) for FVC, FEV₁, and FEF_25–75%.ConclusionBoth inspiratory and expiratory muscle strength were diminished in patients with NMD compared with healthy controls. Significant differences were also noted in pulmonary function in patients with NMD with or without scoliosis. This suggests that NMD may impact respiratory function independently of the effects of scoliosis. Clinicians treating patients with NMD should be aware of the possibility of compromised respiratory function in these patients to address possible complications.     

Comparison of the Mapleson C system and adult and paediatric self-inflating bags for delivering guideline-consistent ventilation during simulated adult cardiopulmonary resuscitation

There is a discrepancy between resuscitation teaching and witnessed clinical practice. Furthermore, deleterious outcomes are associated with hyperventilation. We therefore conducted a manikin‐based study of a simulated cardiac arrest to evaluate the ability of three ventilating devices to provide guideline‐consistent ventilation. Mean (SD) minute ventilation was reduced with the paediatric self‐inflating bag (7.0 (3.2) l.min^?1) compared with the Mapleson C system (9.8 (3.5) l.min^?1) and adult self‐inflating bag (9.7 (4.2) l.min^?1; p = 0.003). Tidal volume was also lower with the paediatric self‐inflating bag (391 (52) ml) compared with the others (582 (87) ml and 625 (103) ml, respectively; p < 0.001), as was peak airway pressure (14.5 (5.2) cmH₂O vs 20.7 (9.0) cmH₂O and 30.3 (11.4) cmH₂O, respectively; p < 0.001). Participants hyperventilated patients’ lungs in simulated cardiac arrest with all three devices. The paediatric self‐inflating bag delivered the most guideline‐consistent ventilation. Its use in adult cardiopulmonary resuscitation may ensure delivery of more guideline‐consistent ventilation in patients with tracheal intubation.     

Patient Preference for ln-Exsufflation for Secretion Management with Spinal Cord Injury

Abstract

An important aspect of respiratory management in patients with acute spinal cord injury (SCI) is the elimination of secretions. Methods utilized for secretion management in patients with SCI includes endotracheal suctioning and mechanical in-exsufflation (MI-E). Surveyed here is a group of patients with SCI who have had experience with both endotracheal suctioning and MI-E via tracheostomy, to determine patient opinions and experiences regarding the 2 techniques. The survey was administered to 18 patients with traumatic SCI, with an average age of 34. 72% were ASIA A, 22% percent were ASIA B, and 6% were ASIA C, with neurological level of injury ranging from C-1-T-3. Results indicate that patients found MI-E significantly less irritating (p < 0.001 ), less painful (p < 0.001 ), less tiring (p = 0.01 ), and less uncomfortable (p < 0.001) than endotracheal suctioning. In a direct comparison, 89% of patients preferred mechanical in-exsufflation to suctioning. In addition, 89% of patients found MI-E faster, 78% found MI-E more convenient, and 72% found MI-E more effective than suctioning. This study demonstrates that all measured aspects of patient experience are more positive for MI-E than for endotracheal suctioning.     

Restoration of pulmonary compliance after laparoscopic surgery using a simple alveolar recruitment maneuver

Study ObjectiveTo test the hypothesis that a pulmonary maneuver designed to recruit additional alveoli (thereby decreasing atelectasis) applied before extubation can restore pulmonary compliance to baseline values.DesignCohort study.SettingOperating room of a university hospital.Patients20 ASA physical status I and II patients scheduled to undergo laparoscopic radical nephrectomy.InterventionsParticipants received a balanced general anesthesia using intermittent positive pressure ventilation. A pulmonary recruitment maneuver was performed as a single manual inflation of the lungs to 40 cm H₂O, maintained for 10 seconds after release of pneumoperitoneum.MeasurementsRespiratory mechanics including dynamic compliance were measured continuously using the VenTrak respiratory mechanics monitor (VenTrak; Novametrix, Wallingford, CT, USA). Respiratory measures were recorded together with arterial blood gases after induction (T1), with the patient placed in the lateral “jackknife” position (T2), 10 and 120 minutes after CO₂ insufflation (T3 and T4), immediately after desufflation in the lateral and supine positions (T5 and T6), and 10 minutes after a pulmonary recruitment maneuver at the conclusion of surgery (T7). Outcome data were analyzed using analysis of variance for repeated measures; P < 0.05 was defined as statistically significant.Main ResultsOn average, compliance decreased from an initial value of 63.5 to 52.6 mL/cmH₂O when patients were turned from the supine to the lateral position (T1 vs. T2; P < 0.001), and decreased further to 31.07 mL/cmH₂O after CO₂ insufflation (T2 vs. T3; P < 0.001). Compliance increased to 50.8 mL/cmH₂O after desufflation and 54.4 mL/cmH₂O after turning the patient to the supine position, but did not return to baseline levels until after performance of the pulmonary recruitment maneuver, 64.3 mL/cmH₂O (T6 vs. T7; P < 0.001, and T1 vs. T7; P = 0.73).ConclusionsRespiratory mechanics do not fully return to baseline levels after desufflation following laparoscopy; however, lung compliance can be fully restored using a simple alveolar recruitment maneuver.     

ProSeal?-Kehlkopfmaske in normalgewichtigen und adip?sen Patienten

Background

Most of the data on combining pressure-controlled ventilation (PCV) with positive end-expiratory pressure (PEEP) come from studies with an endotracheal tube (ETT) whereas data on utilization of PEEP with a laryngeal mask airway (LMA) are limited. The LMA-ProSeal? (PLMA) forms a more effective seal of the airway than the LMA-Classic? (CLMA). The application of PEEP when PCV is used with the PLMA could have an impact on oxygenation in adult patients.

Methods

For this study 148 patients with an mean age of 44 years (range18?C65 years) and mean weight of 86?kg (range 49?C120?kg) were recruited in 2 groups: group?N _(Normal): body-mass index (BMI) <30?kg/m² and group?O _(Obesity) BMI ??30 and <36?kg/m². Cardiovascular and pulmonary disease and a history of smoking were exclusion criteria in addition to the usual LMA contraindications. The bispectral index-guided (BIS) anesthesia technique was used with propofol, fentanyl, and remifentanil without muscle relaxants. Measurement of PLMA seal pressure served as recruitment maneuver and PCV was randomly combined with 0?cmH₂O, 5?cmH₂O or 8?cmH₂O PEEP. An arterial blood gas sample was taken 50?min after induction of anesthesia under an inspiratory oxygen fraction (F_IO₂₎ of 0.3. In the first part partial oxygen pressure (p_aO₂) under 0?cmH₂O was compared with p_aO₂ under 5?cmH₂O and in the second part p_aO₂ under 5?cmH₂O was compared with p_aO₂ under 8?cmH₂O. A significant difference was set as p<0.025.

Results

The PLMA could be placed after 3 attempts in 147 patients. The mean seal pressure was in the range of 24?C30?cm?H₂O. Application of randomized PEEP was possible in all patients and ventilation was comparable between corresponding groups. In group?N no differences were found in part?1 (139±28 vs. 141±28?mmHg, p=0.88) or part?2 (127±24 vs. 134±26?mmHg, p=0.35). In group?O there was a significant difference in p_aO₂ in part?1 (75±12 vs. 94±18?mmHg, p=0.02) but not in part?2 (92±21 vs. 103±18?mmHg, p=0.04).

Conclusions

The application of PEEP when PCV is used with the PLMA results in improved oxygenation in obese patients with a BMI ??30 and <36?kg/m² but not in normal weight patients. Alveolar recruitment produced by seal pressure measurements below 30?cm?H₂O was sufficient to produce a clinically significant improvement in oxygenation in most obese patients and there was a significant improvement of oxygenation with PEEP=5?cmH₂O. Both findings are in contrast to findings of studies using an ETT which suggests that higher pressures (40?cmH₂O) are needed for recruitment of collapsed alveoli and higher PEEP (10?cmH₂O) is needed to produce a clinically significant improvement in oxygenation in obese patients. The results of this study support data showing that the consequences of bronchopulmonary airway reactions known to occur with an ETT are less pronounced or absent when an LMA is used.     

Impact of changes of positive end-expiratory pressure on functional residual capacity at low tidal volume ventilation during general anesthesia

Purpose

Several reports in the literature have described the effects of positive end-expiratory pressure (PEEP) level upon functional residual capacity (FRC) in ventilated patients during general anesthesia. This study compares FRC in mechanically low tidal volume ventilation with different PEEP levels during upper abdominal surgery.

Methods

Before induction of anesthesia (awake) for nine patients with upper abdominal surgery, a tight-seal facemask was applied with 2?cmH₂O pressure support ventilation and 100?% O₂ during FRC measurements conducted on patients in a supine position. After tracheal intubation, lungs were ventilated with bilevel airway pressure with a volume guarantee (7?ml/kg predicted body weight) and with an inspired oxygen fraction (FIO₂) of 0.4. PEEP levels of 0, 5, and 10?cmH₂O were used. Each level of 5 and 10?cmH₂O PEEP was maintained for 2?h. FRC was measured at each PEEP level.

Results

FRC awake was significantly higher than that at PEEP 0?cmH₂O (P?<?0.01). FRC at PEEP 0?cmH₂O was significantly lower than that at 10?cmH₂O (P?<?0.01). PaO₂/FIO₂ awake was significantly higher than that for PEEP 0?cmH₂O (P?<?0.01). PaO₂/FIO₂ at PEEP 0?cmH₂O was significantly lower than that for PEEP 5?cmH₂O or PEEP 10?cmH₂O (P?<?0.01). Furthermore, PEEP 0?cmH₂O, PEEP 5?cmH₂O after 2?h, and PEEP 10?cmH₂O after 2?h were correlated with FRC (R?=?0.671, P?<?0.01) and PaO₂/FIO₂ (R?=?0.642, P?<?0.01).

Conclusions

Results suggest that PEEP at 10?cmH₂O is necessary to maintain lung function if low tidal volume ventilation is used during upper abdominal surgery.     

Effect of PEEP on regional ventilation during laparoscopic surgery monitored by electrical impedance tomography

Background: Anesthesia per se and pneumoperitoneum during laparoscopic surgery lead to atelectasis and impairment of oxygenation. We hypothesized that a ventilation with positive end‐expiratory pressure (PEEP) during general anesthesia and laparoscopic surgery leads to a more homogeneous ventilation distribution as determined by electrical impedance tomography (EIT). Furthermore, we supposed that PEEP ventilation in lung‐healthy patients would improve the parameters of oxygenation and respiratory compliance. Methods: Thirty‐two patients scheduled to undergo laparoscopic cholecystectomy were randomly assigned to be ventilated with ZEEP (0 cmH₂O) or with PEEP (10 cmH₂O) and a subsequent recruitment maneuver. Differences in regional ventilation were analyzed by the EIT‐based center‐of‐ventilation index (COV), which quantifies the distribution of ventilation and indicates ventilation shifts. Results: Higher amount of ventilation was examined in the dorsal parts of the lungs in the PEEP group. Throughout the application of PEEP, a lower shift of ventilation was found, whereas after the induction of anesthesia, a remarkable ventral shift of ventilation in ZEEP‐ventilated patients (COV: ZEEP, 40.6 ± 2.4%; PEEP, 46.5 ± 3.5%; P<0.001) was observed. Compared with the PEEP group, ZEEP caused a ventral misalignment of ventilation during pneumoperitoneum (COV: ZEEP, 41.6 ± 2.4%; PEEP, 44 ± 2.7%; P=0.013). Throughout the study, there were significant differences in the parameters of oxygenation and respiratory compliance with improved values in PEEP‐ventilated patients. Conclusion: The effect of anesthesia, pneumoperitoneum, and different PEEP levels can be evaluated by EIT‐based COV monitoring. An initial recruitment maneuver and a PEEP of 10 cmH₂O preserved homogeneous regional ventilation during laparoscopic surgery in most, but not all, patients and improved oxygenation and respiratory compliance.     

Effect of Ono-EI-600 elastase inhibitor on high-tidal-volume-induced lung injury in rats

We tested the effect of Ono-EI-600, an elastase inhibitor that suppresses cytokine release, on ventilator-induced lung injury in a rat model. After Wistar rats (aged 8–11 weeks) were anesthetized and tracheostomized, they were randomly assigned to four groups: high tidal volume (V_T) group (H group: n = 10) receiving peak inspiratory pressure (PIP) 30 cmH₂O for 240 min; high V_T with drug group (HD group: n = 10) receiving the same ventilation settings as H group and also intravenous infusion 10 mg·kg⁻¹·h⁻¹ of Ono-EI-600 during the protocol; the lower V_T group (L group: n = 5) receiving PIP 10 cmH₂O for 240 min; and control group (C group: n = 5) receiving the same ventilation as L group for 30 min. The cytokine levels (IL-6 and CINC-1) in the bronchoalveolar lavage fluid (BALF) of the H group were significantly higher than those of the C and L groups (P < 0.05). However, for the H and HD groups, no differences were found in arterial blood gas data, cytokine levels in BALF, and histological injury scores. Our experiment provided no evidence that elastase inhibitor Ono-EI-600 protects against lung injury induced by high V_T ventilation.     

Abdominal functional electrical stimulation to enhance mechanical insufflation-exsufflation

Context: Respiratory complications, attributed to the build-up of secretions in the airway, are a leading cause of rehospitalisation for the tetraplegic population. Previously, we observed that the application of Abdominal Functional Electrical Stimulation (AFES) improved cough function and increased demand for secretion removal, suggesting AFES may aid secretion clearance. Clinically, secretion clearance is commonly achieved by using Mechanical insufflation-exsufflation (MI-E) to simulate a cough. In this study the feasibility of combining AFES with MI-E is evaluated.

Findings: AFES was successfully combined with MI-E at eight fortnightly assessment sessions conducted with one sub-acute participant with tetraplegia. By using the signal from a pressure sensor, integrated with the MI-E device, AFES was correctly applied in synchrony with MI-E with an accuracy of 96.7%. Acute increases in exhaled volume and peak flow were observed during AFES assisted MI-E, compared to MI-E alone, at six of eight assessment sessions.

Conclusion: The successful integration of AFES with MI-E at eight assessment sessions demonstrates the feasibility of this technique. The acute increases in respiratory function observed at the majority of assessment sessions generate the hypothesis that AFES assisted MI-E may be more effective for secretion clearance than MI-E alone.