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BackgroundThe peak inspiratory pressure (PIP) is crucial in mechanical ventilation with supraglottic airway device (SAD). Pressure-controlled ventilation volume-guaranteed (PCV-VG), delivering a preset tidal volume with the lowest required airway pressure, is being increasingly used during general anesthesia. In this study, we compared respiratory mechanics and circulatory parameters between volume-controlled ventilation (VCV) and PCV-VG in elderly patients undergoing laparoscopic surgery using the laryngeal mask airway supreme (LMA).MethodsEighty participants scheduled for laparoscopic surgery were enrolled in this prospective, randomized clinical trial. The participants were randomly assigned to receive VCV or PCV-VG. PIP, dynamic compliance (Cdyn) and mean inspiratory pressure (Pmean) were recorded at 5 min after induction of anesthesia (T1), 5 min after pneumoperitoneum(T2), 30 and 60 min after pneumoperitoneum (T3 and T4). Data including other respiratory variables, hemodynamic variables, and arterial blood gases were also collected. The difference in PIP between VCV and PCV-VG was assessed as the primary outcome.ResultsPIP was significantly lower at T2, T3, and T4 in both groups compared with T1 (allP P P P ConclusionIn elderly patients who underwent laparoscopic surgery using an LMA, PCV-VG was superior to VCV in its ability to provide ventilation with lower peak inspiratory pressure and greater dynamic compliance.

Background During lumbar spine surgery, patients are placed in the prone position for surgical access. The prone position has various effects on cardiac and pulmonary function, including a decreased cardiac index (CI), decreased dynamic lung compliance (Cdyn), and increased peak inspiratory pressure (Ppeak). In this study, we compared the volume-controlled ventilation mode (VCV) and pressure-controlled ventilation with volume guaranteed mode (PCV-VG) based on hemodynamic and pulmonary variables in the prone position during lumbar spine surgery. Methods Thirty-six patients scheduled for lumbar spine surgery in the prone position were enrolled in this prospective, randomized clinical trial. The patients were randomly assigned to receive VCV or PCV-VG. Hemodynamic variables, respiratory variables, and arterial blood gases were measured in the supine position 15 min after the induction of anesthesia, 15 min after placement in the prone position, 30 min after placement in the prone position, and 15 min after placement in the supine position at the end of anesthesia. Results The hemodynamic variables and arterial blood gas results did not differ significantly between the two groups. Lower Ppeak values were observed in the PCV-VG group than in the VCV group (p = 0.045). The Cdyn values in the VCV group were lower than those in the PCV-VG group (p = 0.040). Conclusion PCV-VG led to lower Ppeak and improved Cdyn values compared with VCV, showing that it may be a favorable alternative mode of mechanical ventilation for patients in the prone position during lumbar spine surgery. Trial registration The study was retrospectively registered at ClinicalTrials.gov (NCT 03571854). The initial registration date was 6/18/2018.

BackgroundAlveolar recruitment maneuvers enable easily reopening nonaerated lung regions via a transient elevation in transpulmonary pressure. To evaluate the effect of these maneuvers on respiratory resistance, we used an oscillatory technique during mechanical ventilation. This study was conducted to assess the effect of the alveolar recruitment maneuvers on respiratory resistance under routine anesthesia. We hypothesized that respiratory resistance at 5 Hz (R5) after the maneuver would be decreased after the lung aeration.MethodsAfter receiving the ethics committee’s approval, we enrolled 33 patients who were classified with an American Society of Anesthesiologists physical status of 1, 2 or 3 and were undergoing general anesthesia for transurethral resection of a bladder tumor within a 12-month period from 2017 to 2018. The recruitment maneuver was performed 30 min after endotracheal intubation. The maneuver consisted of sustained manual inflation of the anesthesia reservoir bag to a peak inspiratory pressure of 40 cmH2O for 15 s, including 5 s of gradually increasing the peak inspiratory pressure. Respiratory resistance was measured using the forced oscillation technique before and after the maneuver, and the mean R5 was calculated during the expiratory phase. The respiratory resistance and ventilator parameter results were analyzed using paired Student’st-tests, andp ResultsWe analyzed 31 patients (25 men and 6 women). R5 was 7.3 ± 1.6 cmH2O/L/sec before the recruitment maneuver during mechanical ventilation and was significantly decreased to 6.4 ± 1.7 cmH2O/L/sec after the maneuver. Peak inspiratory pressure and plateau pressure were significantly decreased, and pulmonary compliance was increased, although the values were not clinically relevant.ConclusionThe recruitment maneuver decreased respiratory resistance and increased lung compliance during mechanical ventilation.Trial registrationName of registry: Japan Medical Association Center for Clinical Trials.Trial registration number: reference JMA-IIA00136.Date of registration: 2 September 2013.URL of trial registry record:https://dbcentre3.jmacct.med.or.jp/JMACTR/App/JMACTRE02_04/JMACTRE02_04.aspx?kbn=3&seqno=3582

Indexación: Scopus. This work was supported by CONICYT #1160631 (Dr. Cruces) and CONICYT. #11160463 (Dr. Diaz) grants. These grants were involved in design of the study, collection of data, writing the manuscript and manuscript language edition services. Background: Positive end-expiratory pressure (PEEP) has been demonstrated to decrease ventilator-induced lung injury in patients under mechanical ventilation (MV) for acute respiratory failure. Recently, some studies have proposed some beneficial effects of PEEP in ventilated patients without lung injury. The influence of PEEP on respiratory mechanics in children is not well known. Our aim was to determine the effects on respiratory mechanics of setting PEEP at 5 cmH2O in anesthetized healthy children. Methods: Patients younger than 15 years old without history of lung injury scheduled for elective surgery gave informed consent and were enrolled in the study. After usual care for general anesthesia, patients were placed on volume controlled MV. Two sets of respiratory mechanics studies were performed using inspiratory and expiratory breath hold, with PEEP 0 and 5 cmH2O. The maximum inspiratory and expiratory flow (QI and QE) as well as peak inspiratory pressure (PIP), plateau pressure (PPL) and total PEEP (tPEEP) were measured. Respiratory system compliance (CRS), inspiratory and expiratory resistances (RawI and RawE) and time constants (KTI and KTE) were calculated. Data were expressed as median and interquartile range (IQR). Wilcoxon sign test and Spearman's analysis were used. Significance was set at P < 0.05. Results: We included 30 patients, median age 39 (15-61.3) months old, 60% male. When PEEP increased, PIP increased from 12 (11,14) to 15.5 (14,18), and CRS increased from 0.9 (0.9,1.2) to 1.2 (0.9,1.4) mL·kg- 1·cmH2O- 1; additionally, when PEEP increased, driving pressure decreased from 6.8 (5.9,8.1) to 5.8 (4.7,7.1) cmH2O, and QE decreased from 13.8 (11.8,18.7) to 11.7 (9.1,13.5) L·min- 1 (all P < 0.01). There were no significant changes in resistance and QI. Conclusions: Analysis of respiratory mechanics in anesthetized healthy children shows that PEEP at 5 cmH2O places the respiratory system in a better position in the P/V curve. A better understanding of lung mechanics may lead to changes in the traditional ventilatory approach, limiting injury associated with MV. © 2018 The Author(s). https://bmcanesthesiol.biomedcentral.com/articles/10.1186/s12871-018-0611-8

BackgroundThis study were designed to investigate the usefulness of the videolaryngoscope-guided insertion technique compared with the standard digital technique for the insertion success rate and insertion conditions of the Proseal™ laryngeal mask airway (PLMA).MethodsProspective, one hundred and nineteen patients (ASA I–II, aged 18–65 yr) were randomly divided for PLMA insertion using the videolaryngoscope-guided technique or the standard digital technique. The PLMA was inserted according to the manufacturer’s instructions in the standard digital technique group. The videolaryngoscope-guided technique was performed a C-MAC® videolaryngoscope with D-Blade, under gentle videolaryngoscope guidance, the epiglottis was lifted, and the PLMA was advanced until the tip of the distal cuff reached the oesophagus inlet. The number of insertion attempts, insertion time, oropharyngeal leak pressure, leak volume, fiberoptic bronchoscopic view, peak inspiratory pressure, ease of gastric tube placement, hemodynamic changes, visible blood on PLMA and postoperative airway morbidity were recorded.ResultsThe first-attempt success rate (the primary outcome) was higher in the videolaryngoscope-guided technique than in the standard digital technique (p = 0.029). The effect size values with 95% confidence interval were 0.19 (0.01–0.36) for the first and second attempts, 0.09 (− 0.08–0.27) for the first and third attempts, and not computed for the second and third attempts by the groups, respectively.ConclusionVideolaryngoscope-guided insertion technique can be a help in case of difficult positioning of a PLMA and can improve the PLMA performance in some conditions. We suggest that the videolaryngoscope-guided technique may be a useful technique if the digital technique fails.Trial registrationClinicalTrials.govNCT03852589 date of registration: February 22th 2019.

Background Electrical impedance tomography (EIT) is a tool to monitor regional ventilation distribution in patient’s lungs under general anesthesia. The objective of this study was to assess the regional ventilation distribution using different driving pressures (DP) during high frequency jet ventilation (HFJV). Methods Prospective, observational, cross-over study. Patients undergoing rigid bronchoscopy were ventilated HFJV with DP 1.5 and 2.5 atm. Hemodynamic and ventilation parameters, as well as ventilation in different regions of the lungs in percentage of total ventilation, assessed by EIT, were recorded. Results Thirty-six patients scheduled for elective rigid bronchoscopy. The final analysis included thirty patients. There was no significant difference in systolic, diastolic and mean arterial blood pressure, heart rate, and peripheral saturation between the two groups. Peak inspiratory pressure, mean inspiratory pressure, tidal volume, and minute volume significantly increased in the second, compared to the first intervention group. Furthermore, there were no statistically significant differences between each time profiles in all ROI regions in EIT. Conclusions In our study intraoperative EIT was an effective method of functional monitoring of the lungs during HFJV for rigid bronchoscopy procedure. Lower driving pressure was as effective in providing sufficient ventilation distribution through the lungs as the higher driving pressure but characterized by lower airway pressure. Trial registration The study was registered on ClinicalTrials.gov under no. NCT02997072.

Background Lung protective mechanical ventilation with limited peak inspiratory pressure has been shown to affect cardiac output in patients with ARDS. However, little is known about the impact of lung protective mechanical ventilation on regional perfusion, especially when associated with moderate permissive respiratory acidosis. We hypothesized that lung protective mechanical ventilation with limited peak inspiratory pressure and moderate respiratory acidosis results in an increased cardiac output but unequal distribution of blood flow to the different organs of pigs with oleic-acid induced ARDS. Methods Twelve pigs were enrolled, 3 died during instrumentation and induction of lung injury. Thus, 9 animals received pressure controlled mechanical ventilation with a PEEP of 5 cmH2O and limited peak inspiratory pressure (17 ± 4 cmH2O) versus increased peak inspiratory pressure (23 ± 6 cmH2O) in a crossover-randomized design and were analyzed. The sequence of limited versus increased peak inspiratory pressure was randomized using sealed envelopes. Systemic and regional hemodynamics were determined by double indicator dilution technique and colored microspheres, respectively. The paired student t–test and the Wilcoxon test were used to compare normally and not normally distributed data, respectively. Results Mechanical ventilation with limited inspiratory pressure resulted in moderate hypercapnia and respiratory acidosis (PaCO2 71 ± 12 vs. 46 ± 9 mmHg, and pH 7.27 ± 0.05 vs. 7.38 ± 0.04, p < 0.001, respectively), increased cardiac output (140 ± 32 vs. 110 ± 22 ml/min/kg, p

Background Not only arterial hypoxemia but acute lung injury also has become the major concerns of one-lung ventilation (OLV). The use of pressure-controlled ventilation (PCV) for OLV offers the potential advantages of lower airway pressure and intrapulmonary shunt, which result in a reduced risk of barotrauma and improved oxygenation, respectively. Methods We searched Medline, Embase, the Cochrane central register of controlled trials and KoreaMedto find publications comparing the effects of PCV with those of volume-controlled ventilation (VCV) during intraoperative OLV in adults. A meta-analysis of randomized controlled trials was performed using the Cochrane Review Methods. Results Six studies (259 participants) were included. The PaO2/FiO2 ratio in PCV was higher than in VCV [weighted mean difference (WMD) = 11.04 mmHg, 95 % confidence interval (CI) = 0.30 to 21.77, P = 0.04, I2 = 3 %] and peak inspiratory pressure was significantly lower in PCV (WMD = −4.91 cm H2O, 95 % CI = −7.30 to –2.53, P

BackgroundHyperinflation (HI) is performed following open endotracheal suctioning (OES), whose goals include: to stimulate a cough, recover oxygenation and improve compliance. However, it may also induce unintended consequences, including: lung stress and strain, failure to maintain high distending pressure, and subsequently cycling recruitment and derecruitment. Here, our aim was to investigate the effects of hyperinflation after repeated OES on sequential alteration of arterial oxygenation and lung injury profile using a saline lavage-induced surfactant depleted ARDS rabbit model.MethodsBriefly, 30 Japanese White Rabbits were anesthetized and ventilated in pressure-controlled setting with a tidal volume of 6-8 ml/kg. Animals were divided into four groups, i.e.; Control, ARDS, OES, and HI. Saline-lavage-induced lung injury was induced except for Control group. Thereafter, rabbits were ventilated with positive-end expiratory pressure (PEEP) at 10 cm H2O. The ARDS group received ventilation with the same PEEP without derecruitment. As intervention, OES and HI were performed in ARDS animals. OES was performed for 15 seconds at 150 mm Hg, whereas HI was performed with PEEP at 0 cm H2O and peak inspiratory pressure at +5 cm H2O for a minute. Total duration of the experiment was for 3 hours. OES and HI were performed every 15 minutes from beginning of the protocol.ResultsPaO2 was maintained at about 400 mm Hg in both control and ARDS groups for the duration of this study, while in both OES and HI groups, PaO2 decreased continuously up to 3 hours, dropped to a mean (±SD) of 226 ± 28.9 and 97.0 ± 30.7 mmHg at 3 h, respectively. HI group had the lowest PaO2 in the present investigation. Histological lung injury score was the highest in HI group than other three groups. Pulmonary TNF-α and IL-8 levels were the highest in HI group compared to other groups, but without significant alterations at circulatory level in all the experimental groups.ConclusionsWe show in the present study that hyperinflation following repeated OES deteriorate arterial oxygenation and the severity of lung injury in a rabbit model of ARDS undergoing mechanical ventilation., Research article

Background We have proved that hypercapnic acidosis (a PaCO2 of 80-100 mmHg) protects against ventilator-induced lung injury in rats. However, there remains uncertainty regarding the appropriate target PaCO2 or if greater CO2 “doses” (PaCO2 > 100 mmHg) demonstrate this effect. We wished to determine whether severe acute hypercapnic acidosis can reduce stretch-induced injury, as well as the role of nuclear factor-κB (NF-κB) in the effects of acute hypercapnic acidosis. Methods Fifty-four rats were ventilated for 4 hours with a pressure-controlled ventilation mode set at a peak inspiratory pressure (PIP) of 30 cmH2O. A gas mixture of carbon dioxide with oxygen (FiCO2 = 4-5%, FiCO2 = 11-12% or FiCO2 = 16-17%; FiO2 = 0.7; balance N2) was immediately administered to maintain the target PaCO2 in the NC (a PaCO2 of 35-45 mmHg), MHA (a PaCO2 of 80-100 mmHg) and SHA (a PaCO2 of 130-150 mmHg) groups. Nine normal or non-ventilated rats served as controls. The hemodynamics, gas exchange and inflammatory parameters were measured. The role of NF-κB pathway in hypercapnic acidosis-mediated protection from high-pressure stretch injury was then determined. Results In the NC group, high-pressure ventilation resulted in a decrease in PaO2/FiO2 from 415.6 (37.1) mmHg to 179.1 (23.5) mmHg (p

Background Recent evidence suggests that the use of low tidal volume ventilation with the application of positive end-expiratory pressure (PEEP) may benefit patients at risk of respiratory complications during general anaesthesia. However current Australian practice in this area is unknown. Methods To describe current practice of intraoperative ventilation with regard to tidal volume and application of PEEP, we performed a multicentre audit in patients undergoing general anaesthesia across eight teaching hospitals in Melbourne, Australia. Results We obtained information including demographic characteristics, type of surgery, tidal volume and the use of PEEP in a consecutive cohort of 272 patients. The median age was 56 (IQR 42–69) years; 150 (55%) were male. Most common diagnostic groups were general surgery (31%), orthopaedic surgery (20%) and neurosurgery (9.6%). Mean FiO2 was 0.6 (IQR 0.5-0.7). Median tidal volume was 500 ml (IQR 450-550). PEEP was used in 54% of patients with a median value of 5.0 cmH2O (IQR 4.0-5.0) and median tidal volume corrected for predicted body weight was 9.5 ml/kg (IQR 8.5-10.4). Median peak inspiratory pressure was 18 cmH2O (IQR 15–22). In a cohort of patients considered at risk for respiratory complications, the median tidal volume was still 9.8 ml/kg (IQR 8.6-10.7) and PEEP was applied in 66% of patients with a median value of 5 cmH20 (IQR 4–5). On multivariate analyses positive predictors of tidal volume size included male sex (p

Background The impact of anesthetic equipment on clinical practice parameters associated with development of acute respiratory distress syndrome (ARDS) has not been extensively studied. We hypothesized a change in anesthesia machines would be associated with parameters associated with lower rates of ARDS. Methods We performed a retrospective cohort study on a subset of data used to evaluate intraoperative ventilation. Patients included adults receiving a non-cardiac, non-thoracic, non-transplant, non-trauma, general anesthetic between 2/1/05, and 3/31/09 at the University of Michigan. Existing anesthesia machines (Narkomed IIb, Drager) were exchanged for new equipment (Aisys, General Electric). The initial subset compared the characteristics of patients anesthetized between 12/1/06 and 1/31/07 (pre) with those between 4/1/07 and 5/30/07 (post). An extended subset examined cases two years pre and post exchange. Using the standard predicted body weight (PBW), we calculated and compared the tidal volume (total Vt and mL/kg PBW) as well as positive end-expiratory pressure (PEEP), peak inspiratory pressure (PIP), Delta P (PIP-PEEP), and FiO2. Results A total of 1,414 patients were included in the 2-month pre group and 1,635 patients included in the post group. Comparison of ventilation characteristics found statistically significant differences in median (pre v post): PIP (26 ± 6 v 21 ± 6 cmH2O,p

To evaluate changes in intraocular pressure (IOP) and intracerebral pressure (ICP) reflected by the optic nerve sheath diameter (ONSD) in patients undergoing robotic-assisted laparoscopic prostatectomy (RALP) in permanent 45° steep Trendelenburg position (STP). Fifty-one patients undergoing RALP under a standardised anaesthesia. IOP was perioperatively measured in awake patients (T0) and IOP and ONSD 20 min after induction of anaesthesia (T1), after insufflation of the abdomen in supine position (T2), after 30 min in STP (T3), when controlling Santorini’s plexus in STP (T4) and before awakening while supine (T5). We investigated the influence of respiratory and circulatory parameters as well as patient-specific and time-dependent factors on IOP and ONSD. Average IOP values (mmHg) were T0 = 19.9, T1 = 15.9, T2 = 20.1, T3 = 30.7, T4 = 33.9 and T5 = 21.8. IOP was 14.0 ± 7.47 mmHg (mean ± SD) higher at T4 than T0 (p = 0.013). Univariate mixed effects models showed peak inspiratory pressure (PIP) and mean arterial blood pressure (MAP) to be significant predictors for IOP increase. Mean ONSD values (mm) were T1 = 5.88, T2 = 6.08, T3 = 6.07, T4 = 6.04 and T5 = 5.96. The ONSD remained permanently >6.0 mm during RALP. Patients aged