Restoration of Pulmonary Compliance after Laparoscopic Gynecologic Surgery Using a Recruitment Maneuver.

BACKGROUND/OBJECTIVES: This study aimed to investigate the hypothesis that an alveolar recruitment maneuver can restore lung compliance to initial values after laparoscopic gynecological surgery. METHODS: A total of 31 patients who underwent laparoscopic gynecological surgery were enrolled. Protective mechanical ventilation was applied, and the radial artery was catheterized in all patients. An alveolar recruitment maneuver (incremental and decremental positive end-expiratory pressure) was applied ten minutes after the release of pneumoperitoneum. The respiratory mechanics and blood gas results were recorded at eight different time points: after induction of anesthesia (T1), in the lithotomy position (T2), in the Trendelenburg position (T3), 10 and 90 min after insufflation of carbon dioxide (T4 and T5), in the supine position (T6), after desufflation (T7), and 10 min after an alveolar recruitment maneuver at the end of surgery (T8). RESULTS: Pneumoperitoneum and the Trendelenburg position caused a decline of 15 units in compliance (T7 vs. T1; p < 0.05) compared to baseline. After the alveolar recruitment maneuver, compliance increased by 17.5% compared with the mean value of compliance at time T1 (T8 vs. T1; p < 0.05). The recruitment maneuver had favorable results in patients with low initial compliance (41.5 mL/cmH2O, IQR: 9.75 mL/cmH2O), high Body Mass Index 30.32 kg/m2 (IQR: 1.05 kg/m2), and high initial plateau airway pressure (16.5 cmH2O, IQR: 0.75 cmH2O). CONCLUSIONS: Lung compliance does not return to initial values after performing laparoscopic gynecological procedures. However, after the release of pneumoperitoneum, an alveolar recruitment maneuver is beneficial as it improves compliance and gas exchange.

The Effect of Recruitment Maneuver on Static Lung Compliance in Patients Undergoing General Anesthesia for Laparoscopic Cholecystectomy: A Single-Centre Prospective Clinical Intervention Study.

Background and Objectives: The aim of this study was to examine whether the use of an alveolar recruitment maneuver (RM) leads to a significant increase in static lung compliance (Cstat) and an improvement in gas exchange in patients undergoing laparoscopic cholecystectomy. Material and Methods: A clinical prospective intervention study was conducted. Patients were divided into two groups according to their body mass index (BMI): normal-weight (group I) and pre-obese and obese grade I (group II). Lung mechanics were monitored (Cstat, dynamic compliance-Cdin, peak pressure-Ppeak, plateau pressure-Pplat, driving pressure-DP) alongside gas exchange, and hemodynamic changes (heart rate-HR, mean arterial pressure-MAP) at six time points: T1 (induction of anesthesia), T2 (formation of pneumoperitoneum), T3 (RM with a PEEP of 5 cm H2O), T4 (RM with a PEEP of 7 cm H2O), T5 (desufflation), and T6 (RM at the end). The RM was performed by increasing the peak pressure by +5 cm of H2O at an equal inspiration-to-expiration ratio (I/E = 1:1) and applying a PEEP of 5 and 7 cm of H2O. Results: Out of 96 patients, 33 belonged to group I and 63 to group II. An increase in Cstat values occurred after all three RMs. At each time point, the Cstat value was measured higher in group I than in group II. A higher increase in Cstat was observed in group II after the second and third RM. Cstat values were higher at the end of the surgical procedure compared to values after the induction of anesthesia. The RM led to a significant increase in PaO2 in both groups without changes in HR or MAP. Conclusions: During laparoscopic cholecystectomy, the application of RM leads to a significant increase in Cstat and an improvement in gas exchange. The prevention of atelectasis during anesthesia should be initiated immediately after the induction of anesthesia, using protective mechanical ventilation and RM.

Diagnostic accuracy of the peripheral venous pressure variation induced by an alveolar recruitment maneuver to predict fluid responsiveness during high-risk abdominal surgery.

BACKGROUND: In patients undergoing high-risk surgery, it is recommended to titrate fluid administration using stroke volume or a dynamic variable of fluid responsiveness (FR). However, this strategy usually requires the use of a hemodynamic monitor and/or an arterial catheter. Recently, it has been shown that variations of central venous pressure (ΔCVP) during an alveolar recruitment maneuver (ARM) can predict FR and that there is a correlation between CVP and peripheral venous pressure (PVP). This prospective study tested the hypothesis that variations of PVP (ΔPVP) induced by an ARM could predict FR. METHODS: We studied 60 consecutive patients scheduled for high-risk abdominal surgery, excluding those with preoperative cardiac arrhythmias or right ventricular dysfunction. All patients had a peripheral venous catheter, a central venous catheter and a radial arterial catheter linked to a pulse contour monitoring device. PVP was always measured via an 18-gauge catheter inserted at the antecubital fossa. Then an ARM consisting of a standardized gas insufflation to reach a plateau of 30 cmH2O for 30 s was performed before skin incision. Invasive mean arterial pressure (MAP), pulse pressure, heart rate, CVP, PVP, pulse pressure variation (PPV), and stroke volume index (SVI) were recorded before ARM (T1), at the end of ARM (T2), before volume expansion (T3), and one minute after volume expansion (T4). Receiver-operating curves (ROC) analysis with the corresponding grey zone approach were performed to assess the ability of ∆PVP (index test) to predict FR, defined as an ≥ 10% increase in SVI following the administration of a 4 ml/kg balanced crystalloid solution over 5 min. RESULTS: ∆PVP during ARM predicted FR with an area under the ROC curve of 0.76 (95%CI, 0.63 to 0.86). The optimal threshold determined by the Youden Index was a ∆PVP value of 5 mmHg (95%CI, 4 to 6) with a sensitivity of 66% (95%CI, 47 to 81) and a specificity of 82% (95%CI, 63 to 94). The AUC's for predicting FR were not different between ΔPVP, ΔCVP, and PPV. CONCLUSION: During high-risk abdominal surgery, ∆PVP induced by an ARM can moderately predict FR. Nevertheless, other hemodynamic variables did not perform better.

Effects of a stepwise alveolar recruitment maneuver on lung volume distribution in dogs assessed by computed tomography.

Background: Pulmonary atelectasis is a commonly occurs during anesthesia. In these cases, mechanical ventilation (MV) associated with alveolar recruitment maneuvers (ARMs) and positive end-expiratory pressure (PEEP) is indicated to reverse the condition, ensure adequate gas exchange and improve oxygenation. ARMs can trigger volutrauma, barotrauma, and atelectrauma. Therefore, computed tomography (CT) is the gold-standard method for monitoring lung aeration after ARM. Objective: To evaluate lung volume distribution after stepwise ARMs using computed tomography (CT). Methods: Twelve dogs weighing 24.0 ± 6.0 kg, aged 3 ± 1 years, of both sexes and different breeds, underwent orchiectomy or ovariohysterectomy. The animals were anesthetized and ventilated in volume-controlled mode. ARMs were then initiated by positive end-expiratory pressure (PEEP) titration (5, 10, 15, and 20 cmH2O). CT scans, cardiovascular parameters, and ventilatory mechanics were evaluated at all time points. Data were assessed for normality using the Shapiro-Wilk test and a two-way analysis of variance, followed by a post-hoc Bonferroni test to identify differences between time points. Statistical significance was attributed to a value of p of <0.05. Results: CT demonstrated that the ARMs increased ventilation throughout the lung, including the dependent regions, with volumes that increased and decreased proportionally with PEEP titration. When they reached PEEP 10 and 5 cmH2O descending (d), they remained significantly higher than those in PEEP 0 cmH2O (baseline). Static compliance improved about 40% at PEEP 10d and PEEP 5d compared to baseline. There was an increase in heart rate (HR) from PEEP 15 increasing (i) (74.5%) to PEEP 10d (54.8%) compared to baseline. Mean arterial blood pressure (MABP) decreased approximately 9% from PEEP 15i to PEEP 15d compared to baseline. Conclusion: Lung attenuation and regional and global volumes assessed by CT showed that maximum pulmonary aeration distribution followed by PEEP titration occurred at PEEP 20 cmH2O, maintaining the lungs normoaerated and without hyperaeration.

Corrigendum: Intraoperative protective mechanical ventilation in dogs: A randomized clinical trial.

[This corrects the article DOI: 10.3389/fvets.2022.842613.].

The optimal PEEP after alveolar recruitment maneuver assessed by electrical impedance tomography in healthy horses.

Background: Electrical impedance tomography (EIT) has been an essential tool for assessing pulmonary ventilation in several situations, such as the alveolar recruitment maneuver (ARM) in PEEP titration to maintain the lungs open after atelectasis reversion. In the same way as in humans and dogs, in horses, this tool has been widely used to assess pulmonary aeration undergoing anesthesia, mechanical ventilation, recruitment maneuver, standing horses, or specific procedures. Objectives: The present study aimed to evaluate the distribution of regional ventilation during ARM based on lung monitoring assessment by EIT, with a focus on better recruitment associated with less or no overdistention. Methods: Fourteen horses of 306 ± 21 kg undergoing isoflurane anesthesia in dorsal recumbency were used. The animals were mechanically ventilated with a tidal volume of 14 ml kg-1 and a respiratory rate of 7-9. An alveolar recruitment maneuver was instituted, increasing the PEEP by five cmH2O every 5 min until 32 cmH2O and decreasing it by five cmH2O every 5 min to 7 cmH2O. At each step of PEEP, arterial blood samples were collected for blood gas analysis, EIT images, hemodynamic, and respiratory mechanics. Results: Associated with the CoV-DV increase, there was a significant decrease in the DSS during the ARM and a significant increase in the NSS when PEEP was applied above 12 cmH2O compared to baseline. The ComplROI showed a significant increase in the dependent area and a significant decrease in the non-dependent area during ARM, and both were compared to their baseline values. The driving pressure decreased significantly during the ARM, and Cst, PaO2, and PaO2/FiO2 ratio increased significantly. The VD/VT decreased significantly at DEPEEP17 and DEPEEP12. There was an HR increase at INPEEP27, INPEEP 32, and DEPEEP17 (p < 0.0001; p < 0.0001; and p < 0.05, respectively), those values being above the normal reference range for the species. The SAP, MAP, DAP, CI, and DO2I significantly decreased INPEEP32 (p < 0.05). Conclusion: The ARM by PEEP titration applied in the present study showed better ventilation distribution associated with better aeration in the dependent lung areas, with minimal overdistention between PEEP 17 and 12 cmH2O decreasing step. Those changes were also followed by improvements in static and regional compliance associated with increased oxygenation and pulmonary ventilation. ARM promoted a transitory decrease in arterial blood pressure and depression in CI with a concomitant drop in oxygen delivery, which should be best investigated before its routine use in clinical cases.

Effect of Low or High Pressure Alveolar Recruitment Maneuver on Postoperative Pain and Quality of Recovery in Patients with Obesity Undergoing Laparoscopic Sleeve Gastrectomy.

Background: This study aimed to evaluate whether a low- or high-pressure alveolar recruitment maneuver (ARM) might reduce postoperative pain and improve the quality of recovery after laparoscopic bariatric surgery. Methods: 90 patients with a body mass index > 30 kg/m2 scheduled for laparoscopic sleeve gastrectomy were randomly assigned to control (n = 30), low ARM (n = 30), or high ARM groups (n = 30). For the low and high ARM groups, ARM was repeated five times to hold the peak airway pressure at 30 cmH2O and 60 cmH2O for 5 s, respectively, before removal of the trocar. Conventional methods to reduce post-laparoscopic pain, such as intraperitoneal saline irrigation, hemovac drainage, and gentle abdominal compression were performed in all patients, regardless of the assigned group. Results: Shoulder and surgical site pain scores 24 h postoperatively and rescue meperidine requirement were similar between the groups (p = 0.141, 0.101, and 0.82, respectively). The quality of recovery 40 (QoR40) score 24 h postoperatively was similar between the groups (p = 0.755). Postoperative pulmonary complications were similar between the groups (p = 0.124). Conclusion: Application of a low- or high-pressure ARM in addition to conventional methods to remove remnant peritoneal CO2 gas did not reduce postoperative shoulder or surgical site pain or improve the quality of recovery after laparoscopic sleeve gastrectomy.

Lung aeration and volumes following alveolar recruitment maneuvers with three airway pressures in healthy anesthetized and mechanically ventilated Beagle dogs.

OBJECTIVE: To compare the effects of three recruitment airway pressures (RPaw) on lung aeration and volumes in mechanically ventilated dogs during propofol anesthesia. STUDY DESIGN: Prospective, crossover randomized experimental study. ANIMALS: A total of eight healthy anesthetized experimental Beagle dogs in dorsal recumbency. METHODS: Dogs were mechanically ventilated with a tidal volume of 15 mL kg-1 and zero positive end-expiratory pressure and 100% oxygen. Three maneuvers consisting of a 30 second inspiration at RPaws of 15 (RPaw15), 25 (RPaw25) and 35 (RPaw35) cmH2O were performed randomly, 15 minutes apart. Changes in lung aeration and lung deformation were compared with end-expiratory baseline (before the application of each RPaw) and between-RPaws using computed tomography scans and calculations of global lung strain. Between-group comparisons were performed with one-way anova for repeated measures followed by Tukey test for multiple comparisons. A p value < 0.05 was considered significant. RESULTS: The amount of nonaeration was minimal (<1%) at baseline and not different with the application of the RPaws. The amount of hypoaeration and normoaeration during baseline decreased with all RPaws (p < 0.001). There was no difference between RPaws regarding hypoaeration (all p > 0.999), whereas normoaeration was higher at RPaw15 than RPaw25 and RPaw35 (p < 0.009). Compared with baseline, the fraction of hyperaerated alveoli increased with each RPaw (p < 0.001) and was lower during RPaw15 than RPaw25 and RPaw35 (both p ≤ 0.007). Global lung strain was lower during RPaw15 than at higher RPaw (p < 0.001). CONCLUSIONS AND CLINICAL RELEVANCE: A RPaw of 15 cmH2O for 30 seconds was the recommended RPaw because it was as effective at reversing hypoaeration as RPaws of 25 and 35 cmH2O but with less hyperaeration and potential for overdistension of the lungs in this particular population of dogs with negligible atelectasis.

Intraoperative Protective Mechanical Ventilation in Dogs: A Randomized Clinical Trial.

Objective: To evaluate gas exchange, respiratory mechanics, and hemodynamic impact of mechanical ventilation with low tidal volume (VT) in dogs with the use of positive end-expiratory pressure (PEEP) or preceded by alveolar recruitment maneuver (ARM). Study Design: Prospective randomized clinical trial. Animals: Twenty-one healthy client-owned mesocephalic healthy dogs, 1-7 years old, weighing 10-20 kg, and body condition scores 4-6/9 admitted for periodontal treatment. Methods: Isoflurane-anesthetized dogs in dorsal recumbency were ventilated until 1 h with a volume-controlled ventilation mode using 8 mL kg-1 of VT. The dogs were distributed in 2 groups: in the ARM group, PEEP starts in 0 cmH2O, increasing gradually 5 cmH2O every 3 min, until reach 15 cmH2O and decreasing in the same steps until 5 cmH2O, maintaining this value until the end; and PEEP group, in which the pressure 5 cmH2O was instituted from the beginning of anesthesia and maintained the same level up to the end of the anesthesia. Cardiopulmonary, metabolic, oxygenation parameters, and respiratory mechanics were recorded after the anesthesia induction (baseline-BL), 15, 45, and 75 min after BL and during the recovery. Results: The ARM increased the static compliance (Cst) (15 min after baseline) when compared with baseline moment (24.9 ± 5.8 mL cmH20-1 vs. 20.7 ± 5.4 mL cmH20-1-p = 0.0364), oxygenation index (PaO2/FIO2) (505.6 ± 59.2 mmHg vs. 461.2 ± 41.0 mmHg-p = 0.0453) and reduced the shunt fraction (3.4 ± 2.4% vs. 5.5 ± 1.6%-p = 0.062). In the PEEP group, no statistical differences were observed concerning the variables evaluated. At the beginning of the evaluation, the driving pressure (DP) before ARM was significantly greater than all other evaluation time points (6.9 ± 1.8 cmH20). Conclusions and Clinical Relevance: The use of 8 mL kg-1 of VT and 5 cmH20 PEEP without ARM maintain adequate oxygenation and mechanical ventilation in dental surgeries for up to 1 h. The use of ARM slightly improved compliance and oxygenation during the maneuver.

Effects of individualized positive end-expiratory pressure combined with recruitment maneuver on intraoperative ventilation during abdominal surgery: a systematic review and network meta-analysis of randomized controlled trials.

Low tidal volume ventilation strategy may lead to atelectasis without proper positive end-expiratory pressure (PEEP) and recruitment maneuver (RM) settings. RM followed by individualized PEEP was a new method to optimize the intraoperative pulmonary function. We conducted a systematic review and network meta-analysis of randomized clinical trials to compare the effects of individualized PEEP + RM on intraoperative pulmonary function and hemodynamic with other PEEP and RM settings. The primary outcomes were intraoperative oxygenation index and dynamic compliance, while the secondary outcomes were intraoperative heart rate and mean arterial pressure. In total, we identified 15 clinical trials containing 36 randomized groups with 3634 participants. Ventilation strategies were divided into eight groups by four PEEP (L: low, M: moderate, H: high, and I: individualized) and two RM (yes or no) settings. The main results showed that IPEEP + RM group was superior to all other groups regarding to both oxygenation index and dynamic compliance. LPEEP group was inferior to LPEEP + RM, MPEEP, MPEEP + RM, and IPEEP + RM in terms of oxygenation index and LPEEP + RM, MPEEP, MPEEP + RM, HPEEP + RM, IPEEP, and IPEEP + RM in terms of dynamic compliance. All comparisons were similar for secondary outcomes. Our analysis suggested that individualized PEEP and RM may be the optimal low tidal volume ventilation strategy at present, while low PEEP without RM is not suggested.

Comparison of Positive End-Expiratory Pressure versus Tidal Volume-Induced Ventilator-Driven Alveolar Recruitment Maneuver in Robotic Prostatectomy: A Randomized Controlled Study.

BACKGROUND: We evaluated the pulmonary effects of two ventilator-driven alveolar recruitment maneuver (ARM) methods during laparoscopic surgery. METHODS: Sixty-four patients undergoing robotic prostatectomy were randomized into two groups: incrementally increasing positive end-expiratory pressure in a stepwise manner (PEEP group) versus tidal volume (VT group). We performed each ARM after induction of anesthesia in the supine position (T1), after pneumoperitoneum in the Trendelenburg position (T2), and after peritoneum desufflation in the supine position (T3). The primary outcome was change in end-expiratory lung impedance (EELI) before and 5 min after ARM at T3, measured by electrical impedance tomography. RESULTS: The PEEP group showed significantly higher increasing EELI 5 min after ARM than the VT group at T1 and T3 (median [IQR] 460 [180,800] vs. 200 [80,315], p = 0.002 and 280 [170,420] vs. 95 [55,175], p = 0.004, respectively; PEEP group vs. VT group). The PEEP group showed significantly higher lung compliance and lower driving pressure at T1 and T3. However, there was no significant difference in EELI change, lung compliance, or driving pressure after ARM at T2. CONCLUSIONS: The ventilator-driven ARM by the increasing PEEP method led to greater improvements in lung compliance at the end of laparoscopic surgery than the increasing VT method.

The Nature of Recruitment and De-Recruitment and Its Implications for Management of ARDS.

Recruitment maneuvers in ARDS are used to improve oxygenation and lung mechanics by applying high airway pressures to reopen collapsed or obstructed peripheral airways and alveoli. In the early 1990s, recruitment maneuvers became a central feature of a variant form of lung-protective ventilation known as open-lung ventilation. This strategy is based on the belief that repetitive opening and closing of distal airspaces induces shear injury and therefore contributes both to ventilator-induced lung injury and ARDS-associated mortality. However, the largest multi-center randomized controlled trial of open-lung ventilation in moderate to severe ARDS reported that recruitment maneuver plateau pressures of 50-60 cm H2O were associated with significantly higher mortality compared to traditional lung-protective ventilation. Despite being based on well conducted preclinical and clinical recruitment maneuver studies, the higher mortality associated with the open-lung ventilation strategy requires re-examining the assumptions and conclusions drawn from those previous studies. This narrative review examines the evidence used to design recruitment maneuver strategies. We also review the radiologic, rheologic, and histopathologic evidence regarding the nature of lung injury and the phenomena of recruitment and de-recruitment as it informs our perceptions of recruitment potential in ARDS. Major lung-protective ventilation clinical trial data and other clinical data are also examined to assess the practical necessity of recruitment maneuvers in ARDS and whether a subset of cases might benefit from pursuing recruitment maneuver therapy. Finally, a less a radical approach to recruitment maneuvers is offered that might achieve the goals of recruitment maneuvers with less risk of harm.

Evaluation of alveolar recruitment maneuver on respiratory resistance during general anesthesia: a prospective observational study.

BACKGROUND: Alveolar 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. METHODS: After 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's t-tests, and p < 0.05 was considered statistically significant. RESULTS: We 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. CONCLUSION: The recruitment maneuver decreased respiratory resistance and increased lung compliance during mechanical ventilation. TRIAL REGISTRATION: Name 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.

Effects of an Alveolar Recruitment Maneuver During Lung Protective Ventilation on Postoperative Pulmonary Complications in Elderly Patients Undergoing Laparoscopy.

PURPOSE: Controversy remains over whether alveolar recruitment maneuvers (ARMs) can reduce postoperative pulmonary complications. We hypothesized that performing an ARM in addition to lung protective ventilation (LPV) could improve intraoperative arterial oxygenation and postoperative pulmonary complications (PPCs) in elderly patients undergoing laparoscopy in the Trendelenburg position. PATIENTS AND METHODS: Sixty-two patients (aged 65-85) scheduled for laparoscopic low anterior resection were randomized to receive LPV only (LPV group, n = 32) or LPV with an ARM (ARM group, n = 30). LPV was set to a tidal volume of 6 mL/kg with a positive end expiratory pressure (PEEP) of 5 cmH2O. The ARM was performed by serially increasing the PEEP to 10 cmH2O for 3 breaths, 15 cmH2O for 3 breaths, then 20 cmH2O for 10 breaths, both immediately before and after abdominal insufflation. The primary end-point was the frequency of PPCs such as desaturation (SpO2 <90%), atelectasis, and pneumonia. Secondary end-points were changes in intraoperative respiratory and gas exchange parameters and hemodynamic variables. RESULTS: One patient in the LPV group experienced desaturation on the first postoperative day. The frequency of chest X-ray abnormalities such as atelectasis or pleural effusion was comparable between groups (6 (19%) and 5 (17%) patients, respectively, P = 0.676). Changes in other respiratory, gas exchange and hemodynamic parameters over time were not significantly different between the groups. However, vasopressor requirements during surgery were higher in the ARM than the LPV group (9 (30%) and 2 (6%) patients, respectively, P = 0.014). CONCLUSION: This study suggests that performing an ARM during LPV may not improve postoperative respiratory outcomes and intraoperative oxygenation compared to LPV alone in geriatric patients undergoing laparoscopy in the Trendelenburg position. In addition, since the ARM could cause a significant deterioration in hemodynamic parameters, applying ARM to elderly patients should be carefully considered.

Effects of alveolar recruitment maneuver on end-expiratory lung volume during one-lung ventilation.

PURPOSE: To investigate the effects of alveolar recruitment maneuver (ARM) during one-lung ventilation (OLV) on end-expiratory lung volume (EELV) of the dependent lung. METHODS: Patients who were planned to undergo lung resection surgery for lung tumors and needed OLV for at least 1 h were included in the study. After turning the patients into the lateral position under total intravenous anesthesia, OLV was commenced using a double-lumen endobronchial tube. EELV was measured using the nitrogen washout technique at 20 min after OLV started (baseline) and 15, 30, 45, 60 min after ARM was performed on the dependent lung. RESULTS: Among 42 patients who completed the study, EELV increased at 15 min after ARM by 20% or greater compared with baseline in 21 patients (responders). Responders were significantly shorter in height (158 vs. 165 cm, p = 0.01) and had smaller preoperative functional residual capacity (2.99L vs. 3.65L, p = 0.02) than non-responders. Before ARM, responders had significantly higher driving pressure (14.2 vs. 12.4 cmH2O, p = 0.01) and lower respiratory system compliance (23.6 vs. 31.4 ml/cmH2O, p = 0.0002) than non-responders. Driving pressure temporarily dropped after ARM in responders, while no significant change was observed in non-responders. Fourteen out of 21 responders kept EELV 20% or more increased EELV than baseline at 60 min after ARM. CONCLUSION: EELV of the dependent lung was increased by 20% or greater in half of the patients responding to ARM. The increased volume of the dependent lung caused by ARM was maintained for 60 min in two-thirds of the responders.

Effects of pneumoperitoneum and of an alveolar recruitment maneuver followed by positive end-expiratory pressure on cardiopulmonary function in sheep anesthetized with isoflurane-fentanyl.

OBJECTIVE: To investigate the effects of pneumoperitoneum alone or combined with an alveolar recruitment maneuver (ARM) followed by positive end-expiratory pressure (PEEP) on cardiopulmonary function in sheep. STUDY DESIGN: Prospective, randomized, crossover study. ANIMALS: A total of nine adult sheep (36-52 kg). METHODS: Sheep were administered three treatments (≥10-day intervals) during isoflurane-fentanyl anesthesia and volume-controlled ventilation (tidal volume: 12 mL kg-1) with oxygen: CONTROL (no intervention); PNEUMO (120 minutes of CO2 pneumoperitoneum); PNEUMOARM/PEEP (PNEUMO protocol with an ARM instituted after 60 minutes of pneumoperitoneum). The ARM (5 cmH2O increases in PEEP of 1 minute duration until 20 cmH2O of PEEP) was followed by 10 cmH2O of PEEP until the end of anesthesia. Cardiopulmonary data were recorded until 30 minutes after abdominal deflation. RESULTS: PaO2 was decreased from 435-462 mmHg (58.0-61.6 kPa) (range of mean values in CONTROL) to 377-397 mmHg (50.3-52.9 kPa) in PNEUMO (p < 0.05). Quasistatic compliance (Cqst, mL cmH2O-1 kg-1) was decreased from 0.85-0.92 in CONTROL to 0.52-0.58 in PNEUMO. PaO2 increased from 383-385 mmHg (51.1-51.3 kPa) in PNEUMO to 429-444 mmHg (57.2-59.2 kPa) in PNEUMOARM/PEEP (p < 0.05) and Cqst increased from 0.52-0.53 in PNEUMO to 0.70-0.74 in PNEUMOARM/PEEP. Abdominal deflation in PNEUMO did not restore PaO2 and Cqst to control values. Cardiac index (L minute-1 m2) decreased from 4.80-4.70 in CONTROL to 3.45-3.74 in PNEUMO and 3.63-3.76 in PNEUMOARM/PEEP. Compared with controls, ARM/PEEP with pneumoperitoneum decreased mean arterial pressure from 81 to 68 mmHg and increased mean pulmonary artery pressure from 10 to 16 mmHg. CONCLUSIONS AND CLINICAL RELEVANCE: Abdominal deflation did not reverse the pulmonary function impairment associated with pneumoperitoneum. The ARM/PEEP improved respiratory compliance and reversed the oxygenation impairment induced by pneumoperitoneum with acceptable hemodynamic changes in healthy sheep.

Safety and effectiveness of alveolar recruitment maneuvers and positive end-expiratory pressure during general anesthesia for cesarean section: a prospective, randomized trial.

INTRODUCTION: During cesarean section, the supine position reduces functional residual capacity and worsens lung compliance. We tested the hypothesis that alveolar recruitment maneuvers and positive end-expiratory pressure improve lung compliance in women undergoing general anesthesia for cesarean section. METHODS: Ninety women undergoing cesarean section were randomly assigned to one of two groups in a prospective, double-blind trial. In the alveolar recruitment maneuver group, pressure-control ventilation was used and inspiratory time was increased to 50% after delivery; positive end-expiratory pressure was increased to 20cmH2O and peak airway inspiratory pressure gradually increased to 45-50cmH2O. Volume-control ventilation was then used with low tidal volumes (6mL/kg) and positive end-expiratory pressure was reduced stepwise to 8cmH2O. In the control group, alveolar recruitment maneuvers were not used. Data were collected before and 3, 10 and 20min after the alveolar recruitment maneuver, before extubation and postoperatively at 10 and 20min. RESULTS: Dynamic compliance, peak airway inspiratory pressure, PaO2 and PaO2/FiO2 were significantly different in the alveolar recruitment maneuver group compared to controls at all time points during surgery except at baseline. Oxygen saturation was significantly greater in the alveolar recruitment maneuver group at 10 and 20min and before extubation. Dynamic compliance was 29.7-42.5% higher and peak airway inspiratory pressure 3.6-10.2% lower in the alveolar recruitment maneuver group compared to controls. The PaO2, PaO2/FiO2 and oxygen saturation were higher (9.4-12%, 10.3-11.9% and 0.4-1.3%, respectively) in the alveolar recruitment maneuver group. Postoperatively, PaO2 and oxygen saturation were significantly higher in the alveolar recruitment maneuver group compared to controls (PaO2 9.2% at 10min and 8.4% at 20min, oxygen saturation 0.8% at 10min and 1.1% at 20min). There were no significant differences in hemodynamic stability or adverse events between groups. CONCLUSION: Compared to standard care, the alveolar recruitment maneuver with positive end-expiratory pressure and low tidal volumes appears safe and effective in improving lung compliance and both intraoperative and postoperative oxygenation in women undergoing general anesthesia for elective cesarean section.

Effects of intraoperative protective lung ventilation on postoperative pulmonary complications in patients with laparoscopic surgery: prospective, randomized and controlled trial.

BACKGROUND: Respiratory functions are usually impaired during pneumoperitoneum for laparoscopic surgery. This randomized, controlled and single-blinded study was performed to evaluate whether intraoperative protective lung ventilation influences postoperative pulmonary complications after laparoscopic hepatobiliary surgery. METHODS: Sixty-two patients were randomized to receive either conventional ventilation with alveolar recruitment maneuver (tidal volume of 10 ml/kg with inspiratory pressure of 40 cmH2O for 30 s after the end of pneumoperitoneum, group R), or protective lung ventilation (low tidal volume of 6 ml/kg with positive end-expiratory pressure [PEEP] of 5 cmH2O, group P). Induction and maintenance of anesthesia were done with balanced anesthesia. Respiratory complications such as atelectasis, pneumonia or desaturation were observed postoperatively. The length of hospital stay, arterial blood gas analysis, peak inspiratory pressure and hemodynamic variables were also recorded. Results are presented as mean ± SD or number of patients (%). RESULTS: Postoperative pulmonary complications (P = 0.023) and desaturation below 90 % (P = 0.016) occurred less frequently in group P than in group R. Eight patients of group R and 3 patients of group P showed atelectasis. Pneumonia was diagnosed in 1 patient of group R. No differences were observed in the length of hospital stay, arterial blood gas analysis (pH, PaO2, PaCO2 and PAO2) and hemodynamic variables except PAO2, AaDO2 and peak inspiratory pressure between the two groups. CONCLUSION: Protective lung ventilation (low tidal volume with PEEP) during pneumoperitoneum was associated with less incidences of pulmonary complications than conventional ventilation with alveolar recruitment maneuver after laparoscopic hepatobiliary surgery.

Difference of Short Term Survival in Patients with ARDS According to Responsiveness to Alveolar Recruitment / 결핵

BACKGROUND: Lung protective strategies, using low tidal volume in ARDS, improve survival rate in ARDS. However, low tidal volume ventilation may promote alveolar de-recruitment. Therefore, alveolar recruitment is necessary to maintain arterial oxygenation and to prevent repetitive opening and closure of collapsed alveoli in lung protective strategies. There has been a recent report describing improvement in arterial oxygenation with use of recruitment maneuver. However, impact of recruitment on outcome of ARDS is unknown. We evaluated whether short-term survival difference existed in patients with ARDS, who were performed alveolar recruitment maneuver(ARM) and prone position, according to response of alveolar recruitment or not. METHODS: All patients who were diagnosed with ADRS and received mechanical ventilation were included. ARM were sustained inflation(35-45 cmH2O CPAP for 30-40 sec.) or increasing level of PEEP. If these methods were ineffective, alveolar recruitment with prone position was done for at least 10 hours. PaO2/FiO2(P/F) ratio was determined before and at 0.5 and 2 hours after ARM. We defined a responder if the P/F ratio was increased over 50% of baseline value. We compared 10-days and 30-days survival rate between responders and non-responders. RESULTS: 20 patients(M:F=12:8, 63 +/- 14 age) were included. Among them, 12 patients were responders and 8 patients were non-responders. In responders, P/F ratio was increased from 92 +/- 25 mmHg to 244 +/- 85 mmHg. In non-responders, P/F ratio increased from 138 +/- 37 mmHg to 163 +/- 60 mmHg. Among non-responders, P/F ratio was improved over 50% in 2 patients after prone position. Overall, 14 patients were responders after ARM and prone position. The 10-days and 30-days survival rate in responders was significantly higher than in non-responders(86%, 57% in responders and 33%, 0% in non-responders)(p<0.05). There was no significant difference between responders and non-responders in age(71 +/- 11, 60 +/- 14), lung injury score(2.8 +/- 0.2, 2.9 +/- 0.45), simplified acute physiology score(SAPS) II (35 +/- 4.6, 34 +/- 5.7), positive end-positive pressure level(15.6 +/- 1.9 cmH2O, 14.5 +/- 2.1 cmH2O). CONCLUSION: ARM may improve arterial oxygenation in some patients with ARDS. These responders in patients with ARDS showed significant higher 10-days and 30-days survival rate than non-responders patients with alveolar recruitment.