Alveolar Recruitment Maneuver Research Articles

Improving Lung Procurement and Utilization Rates Using Clinical Practice Guidelines for Ventilation Management

The utilization of donor's lungs in the US has averaged 21% over the last decade. Alveolar recruitment maneuvers can improve lungs transplanted per donor (LTPD). Donor management goals (DMGs) are endpoints transplant clinicians strive to demonstrate organ recovery from the brain-death process. In a US organ procurement organization (OPO), three recruitment maneuvers (continuous positive airway pressure, step-up PEEP, and inverse ratio ventilation) were trialed against each other. Three years later, the practice of these techniques waned, and a program was created to improve the utilization of the recruitment maneuvers in their clinical practice guidelines (CPGs). An educational activity was performed based on information gathered from a needs assessment questionnaire of the OPO clinicians' experiences with recruitment maneuvers. Afterwards an evaluation completed by the attendees reported perceptions of the intervention. Then, a comparison between organs transplanted per donor (OTPD), DMGs and LTPD were made two months after the intervention and compared to a continuous sample of donors that were managed two months prior. A content analysis of the needs assessment (n=25) demonstrated a need to review the organization's CPGs. After the educational module there was an improvement in, (1) organs transplanted per donor (3.0 vs. 4.21; p = < .01), (2) LTPD (8 of 31 [26%] vs. 14 of 34 [41%]), (3) and comfort levels when utilizing the CPGs. This intervention failed to demonstrate an improved ratio of donors meeting seven of nine DMGs (58% control vs. 56% sample). However, the percent of lung donors meeting lung-specific DMGs in the study sample almost doubled in comparison to the pre-intervention control group (52% vs. 29%). The intent of this scholarship was to show an educational intervention may help remove barriers that limited performing recruitment maneuvers and improve donor management in the perioperative period. Future studies are indicated.

Individualized lung protective ventilation vs. conventional ventilation during general anesthesia in laparoscopic total hysterectomy.

Laparoscopic total hysterectomy is performed by carbon dioxide insufflation, Trendelenburg position and mechanical ventilation of patients under general anesthesia. However, this may induce pulmonary atelectasis and/or hyperdistention of the lungs. Multiple studies have indicated that mechanical ventilation with the use of low tidal volumes, moderate positive end-expiratory pressure (PEEP) and regular alveolar recruitment maneuvers may improve post-operative outcomes. However, the benefits of an individualized level of PEEP have not been clearly established. In the present study, it was hypothesized that a moderate fixed PEEP may not suit all patients and an individually-titrated PEEP during anesthesia may improve the peri-operative pulmonary oxygenation function. The aim of the present study was to compare the pulmonary oxygenation function and post-operative pulmonary complications (PPCs) in patients receiving individualized lung-protective mechanical ventilation (LPV) vs. conventional ventilation (CV) during laparoscopic total hysterectomy. The present study was a randomized double-blinded clinical trial on 87 patients who were randomly divided to receive CV or protective ventilation (PV). An optimal individualized PEEP value was determined using a static pulmonary compliance-directed PEEP titration procedure. Pulmonary oxygenation function, serum inflammatory factors, including interleukin-8 and Clara cell protein 16, the incidence of PPCs and the post-operative length of stay were also determined. Patients in the PV group exhibited improved pulmonary oxygenation function during and after the operation. The total percentage of PPCs during the first 7 days after surgery was significantly lower in the PV group compared with those in the CV group. In conclusion, as compared to CV, intra-operative individualized LPV significantly improved pulmonary oxygenation function and reduced the incidence of PPCs during the first 7 days after laparoscopic total hysterectomy (Clinical trial registration no. ChiCTR1900027738).

Effect of Alveolar Recruitment Maneuver on Postoperative Pain

Effect of Alveolar Recruitment Maneuver on Postoperative Pain

Intraoperative ventilation strategies for obese patients undergoing bariatric surgery: systematic review and meta-analysis

BackgroundObesity is a global epidemic, and it is widely known that increased Body mass index (BMI) is associated with alterations in respiratory mechanics. Bariatric surgery is established as an effective treatment for this condition.ObjectiveTo assess the safety and effectiveness of different ventilation strategies in obese patients undergoing bariatric surgery.MethodsA systematic review of randomized clinical trials aimed at evaluating ventilation strategies for obese patients was carried out. Primary outcomes: in-hospital mortality, adequacy of gas exchange, and respiration mechanics alterations.ResultsFourteen clinical trials with 574 participants were included. When recruitment maneuvers (RM) vs Positive end-expiratory pressure (PEEP) were compared, RM resulted in better oxygenation p = 0.03 (MD 79.93), higher plateau pressure p < 0.00001 (MD 7.30), higher mean airway pressure p < 0.00001 (MD 6.61), and higher compliance p < 0.00001 (MD 21.00); when comparing RM + Zero end-expiratory pressure (ZEEP) vs RM + PEEP 5 or 10 cmH2O, RM associated with PEEP led to better oxygenation p = 0.001 (MD 167.00); when comparing Continuous Positive Airway Pressure (CPAP) 40 cmH2O + PEEP 10 cmH2O vs CPAP 40 cmH2O + PEEP 15 cmH2O, CPAP 40 + PEEP 15 achieved better gas exchange p = 0.003 (MD 36.00) and compliance p = 0.0003 (MD 3.00).ConclusionThere is some evidence that the alveolar recruitment maneuvers associated with PEEP lead to better oxygenation and higher compliance. There is no evidence of differences between pressure control ventilation (PCV) and Volume control ventilation (VCV).

Protective ventilation from ICU to operating room: state of art and new horizons.

The prevention of ventilator-associated lung injury (VALI) and postoperative pulmonary complications (PPC) is of paramount importance for improving outcomes both in the operating room and in the intensive care unit (ICU). Protective respiratory support includes a wide spectrum of interventions to decrease pulmonary stress–strain injuries. The motto ‘low tidal volume for all’ should become routine, both during major surgery and in the ICU, while application of a high positive end-expiratory pressure (PEEP) strategy and of alveolar recruitment maneuvers requires a personalized approach and warrants further investigation. Patient self-inflicted lung injury is an important type of VALI, which should be diagnosed and mitigated at the early stage, during restoration of spontaneous breathing.This narrative review highlights the strategies used for protective positive pressure ventilation. The emerging concepts of damaging energy and power, as well as pathways to personalization of the respiratory settings, are discussed in detail. In the future, individualized approaches to protective ventilation may involve multiple respiratory settings extending beyond low tidal volume and PEEP, implemented in parallel with quantifying the risk of VALI and PPC.

Maintaining spontaneous ventilation during surgery—a review article

Mechanical ventilation is necessary during many surgical procedures, however a paradigm shift in ventilation has taken place in the past decades. There is convincing evidence that neuromuscular blockade and subsequent controlled mechanical ventilation applying intermittent positive pressure, also in patients with non-injured, healthy lungs, may impair the respiratory system, leading to postoperative pulmonary complications (PPCs), resulting in worse clinical outcome, prolonged hospitalization time and increased cost of hospital care. Multifactorial pathophysiology of ventilator induced lung injury (VILI) has been evaluated and a pulmonary protective ventilatory strategy [lung protective ventilation (LPV)], including the use of low tidal volumes [6 mL/kg, ideal body weight (IBW)], moderate or optimal levels of positive end-expiratory pressure (PEEP) and applying regular or targeted alveolar recruitment maneuvers (ARMs), has been developed. Recognizing the role of neuromuscular blockade during general anesthesia and even the importance of avoiding residual neuromuscular blockade in the early postoperative period regarding to postoperative respiratory impairment have become another, newer direction of research. Despite promising and convincing results of recent clinical trials, incidence of PPCs could not be reduced significantly and lung protective ventilation has remained to be a “hot topic” among researchers in the field of anesthesia and critical care. Maintaining spontaneous breathing during general anesthesia has some pathophysiological rationale worth to be dealt with, because it may be one of the options for further improvement. Physiology, advantages, disadvantages and potential role of spontaneous breathing during surgery as compared to intermittent positive pressure ventilation will be described in this article.

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

To investigate the effects of alveolar recruitment maneuver (ARM) during one-lung ventilation (OLV) on end-expiratory lung volume (EELV) of the dependent lung. Patients who were planned to undergo lung resection surgery for lung tumors and needed OLV for at least 1h 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 20min after OLV started (baseline) and 15, 30, 45, 60min after ARM was performed on the dependent lung. 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. 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.

Positive End-Expiratory Pressure (PEEP), Tidal Volume, or Alveolar Recruitment: Which One Does Matter in One-Lung Ventilation?

This review attempts to focus on protective ventilation approaches during one-lung ventilation (OLV) and will summarize recent findings. Recent studies have demonstrated the importance of low tidal volume (low TV) and reduced driving pressure during OLV. Along with low TV, correct use of positive end-expiratory pressure (PEEP) seems to have a vital role in terms of protecting the ventilated lung. PEEP decremental trial and the use of electrical impedance tomography are prominent techniques for individualizing the PEEP. The use of alveolar recruitment maneuvers (ARMs) is furthermore recommended. Nevertheless, there are several studies published considering negative effects of ARM. Although small tidal volumes are highly recommended during OLV, it is not possible for low TV to be beneficial unless an optimal PEEP is applied. Use of ARM is still under debate. Yet, it seems to be the only way for preventing injurious tidal recruitment, which is known to be harmful to the lungs.

Driving pressure y mortalidad en el síndrome de distrés respiratorio agudo

Las actuales guías de manejo del síndrome de distrés respiratorio agudo (SDRA) recomiendan una ventilación protectora: volumen corriente bajo, presión positiva al final de la espiración (PEEP) adecuada y maniobras de reclutamiento alveolar. Sin embargo, estudios recientes han mostrado que la driving pressure podría ser la variable que mejor se correlaciona con la supervivencia en pacientes con SDRA. ABSTRACT Driving pressure and mortality in acute respiratory distress syndrome Current guidelines for ventilation in patients with acute respiratory distress syndrome (ARDS) recommend lung-protective ventilation: use of low tidal volumes, appropiate positive end-expiratory pressure and alveolar recruitment maneuvers. However, recent studies have shown that driving pressure could be the variable that best correlated with survival in patients with ARDS.

A Central and Eastern European Survey On PEEP Titration and Alveolar Recruitment Manoeuvres During Surgery

A Central and Eastern European Survey On PEEP Titration and Alveolar Recruitment Manoeuvres During Surgery

Analysis of the current state of the postoperative pulmonary complications issue in abdominal surgery

Purpose: based on the analysis of the scientific literature data, to determine the relevance of postoperative pulmonary complications (PPCs) issue in abdominal surgery, as well as to examine the causes and modern methods of their development prevention in patients with unaffected lungs.Conclusions. Indicators of PPCs in abdominal surgery range from 17 % to 88 %, and their development leads to an increase in lethality, the cost of treatment, and the length of stay in a medical institution. Mechanical ventilation (MV) is non-physiological and can cause ventilator-associated lung injury (VALI), adversely affects the respiratory muscles, as well as non-respiratory lung function. The above factors are prominent in PPCs development causing an increase in morbidity and mortality in the postoperative period. Extensive open abdominal operations, especially upper abdominal surgical procedures, increase the risk of PPCs development. In the analysis of modern studies, there has been a clear “paradigm shift” from the prevention of death and complications of lung damage to the prevention of respiratory complications development itself. To date, the risk factors have been identified and scales have been developed that allow predicting PPCs development in a timely and reliable manner, one of which is the ARISCAT scale. There are various measures to prevent VALI and PPCs development and the main ones include low respiratory volume, the use of positive end-expiratory pressure (PEEP) and alveolar recruitment maneuvers. The combination of these measures has been termed “protective ventilation”. It has been proved that protective MV during abdominal surgery in patients with unaffected lungs can reduce the risk of PPCs development.

Effect of Intraoperative High Positive End-Expiratory Pressure (PEEP) With Recruitment Maneuvers vs Low PEEP on Postoperative Pulmonary Complications in Obese Patients

An intraoperative higher level of positive end-expiratory positive pressure (PEEP) with alveolar recruitment maneuvers improves respiratory function in obese patients undergoing surgery, but the effect on clinical outcomes is uncertain. To determine whether a higher level of PEEP with alveolar recruitment maneuvers decreases postoperative pulmonary complications in obese patients undergoing surgery compared with a lower level of PEEP. Randomized clinical trial of 2013 adults with body mass indices of 35 or greater and substantial risk for postoperative pulmonary complications who were undergoing noncardiac, nonneurological surgery under general anesthesia. The trial was conducted at 77 sites in 23 countries from July 2014-February 2018; final follow-up: May 2018. Patients were randomized to the high level of PEEP group (n = 989), consisting of a PEEP level of 12 cm H2O with alveolar recruitment maneuvers (a stepwise increase of tidal volume and eventually PEEP) or to the low level of PEEP group (n = 987), consisting of a PEEP level of 4 cm H2O. All patients received volume-controlled ventilation with a tidal volume of 7 mL/kg of predicted body weight. The primary outcome was a composite of pulmonary complications within the first 5 postoperative days, including respiratory failure, acute respiratory distress syndrome, bronchospasm, new pulmonary infiltrates, pulmonary infection, aspiration pneumonitis, pleural effusion, atelectasis, cardiopulmonary edema, and pneumothorax. Among the 9 prespecified secondary outcomes, 3 were intraoperative complications, including hypoxemia (oxygen desaturation with Spo2 ≤92% for >1 minute). Among 2013 adults who were randomized, 1976 (98.2%) completed the trial (mean age, 48.8 years; 1381 [69.9%] women; 1778 [90.1%] underwent abdominal operations). In the intention-to-treat analysis, the primary outcome occurred in 211 of 989 patients (21.3%) in the high level of PEEP group compared with 233 of 987 patients (23.6%) in the low level of PEEP group (difference, -2.3% [95% CI, -5.9% to 1.4%]; risk ratio, 0.93 [95% CI, 0.83 to 1.04]; P = .23). Among the 9 prespecified secondary outcomes, 6 were not significantly different between the high and low level of PEEP groups, and 3 were significantly different, including fewer patients with hypoxemia (5.0% in the high level of PEEP group vs 13.6% in the low level of PEEP group; difference, -8.6% [95% CI, -11.1% to 6.1%]; P < .001). Among obese patients undergoing surgery under general anesthesia, an intraoperative mechanical ventilation strategy with a higher level of PEEP and alveolar recruitment maneuvers, compared with a strategy with a lower level of PEEP, did not reduce postoperative pulmonary complications. ClinicalTrials.gov Identifier: NCT02148692.

Preemptive Alveolar Recruitment Maneuver Followed by PEEP in Obese Patients Undergoing Laparoscopic Gastric Banding. Does it make a Difference? A Randomized Controlled Clinical Study

Background: Impaired respiratory functions during general anesthesia are commonly caused by lung atelectasis more in morbidly obese patients. This occurs more frequently with laparoscopic surgery due to trendelenburg position and pneumoperitoneum. Preemptive recruitment maneuver + PEEP results in the prevention of these changes. Aim: To quantitate the effects of RM and PEEP on intraoperative hypoxemia and respiratory mechanics during laparoscopic gastric banding in obese patients. Study Design: A randomized, double-blinded, controlled study. Method and Materials: Fifty adults ASA I-II, BMI (40-50 kg/m2) for elective laparoscopic gastric banding were randomized into, groups C, and RM, 25 patients each. Group C patients received standard ventilation, VT 6 ml/kg, I: E ratio 1: 2 PEEP 5 cm H2O, and respiratory rate 10-12 breaths/ min. RM patients received standard ventilation with one alveolar recruitment maneuver after mechanical ventilation with PEEP of 15 cm H2O till the end of the surgery. Heart rate, mean blood pressure, respiratory mechanical parameters: peak airway pressure, plateau pressure and end-expiratory lung volume, PaO2, PaO2/FiO2 and (SpO2) were assessed. Results: PaO2 and PaO2/FiO2 ratio increased significantly in the RM group after RM from T2 (before pneumoperitoneum) to T6 (end of surgery) compared with group C (P &lt; 0.001). Peak and plateau airway pressures increased significantly in group C from T2 till T5 (60 min after pneumoperitoneum) compared with the RM group (P &lt; 0.001). End-expiratory lung volume increased significantly in the RM group after RM compared with group C (P&lt;0.001). Conclusion: Preemptive RM with PEEP of 15 cm H2O was effective in preventing pneumoperitoneum-induced intraoperative hypoxemia and respiratory mechanics changes.

The Effects of Alveolar Recruitment Maneuver Versus Low Tidal Volume Ventilation on Oxygenation and Lung Mechanics in Patients Undergoing Laparoscopic Surgeries: A Prospective Randomized Controlled Study

The Effects of Alveolar Recruitment Maneuver Versus Low Tidal Volume Ventilation on Oxygenation and Lung Mechanics in Patients Undergoing Laparoscopic Surgeries: A Prospective Randomized Controlled Study

The Effects of Alveolar Recruitment Maneuver Versus Low Tidal Volume Ventilation on Oxygenation and Lung Mechanics in Patients Undergoing Laparoscopic Surgeries: A Prospective Randomized Controlled Study.

Different ventilatory strategies have been studied to improve gas exchange and compliance of the lungs in patients undergoing laparoscopic surgeries. This study aimed to test the impact of alveolar recruitment maneuver versus low tidal volume ventilation combine with PEEP on arterial oxygenation and lung mechanics in patients undergoing laparoscopic surgeries. Sixty patients were randomly allocated into three equal groups according to the type of ventilation strategy used during surgery. In the control group, patients received conventional volume-controlled ventilation with 10ml/Kg VT and zero PEEP (ZEEP). In group II ( LTV ), patients received low tidal volume ventilation in the form of 6-8 ml/Kg VT and PEEP 5cmH2O. In group III (REC), patients received 6-8 ml/Kg and recruitment maneuvers were done every 10 minutes after intubation till extubation by manual inflation to 40cmH2O peak inspiratory pressure for 15 seconds then the patient was placed back to the same ventilation settings with PEEP of 5cmH2O. The primary outcome is the dynamic compliance. The secondary outcome measures include PaO2, PH, PCO2, SPO2, HR and MAP. Demographic characteristics and duration of surgery were comparable among groups. PaO2 was highly significantly increased (p <0.001) in the recruitment group (Rec) compared to the conventional group (C) and low tidal volume ventilation group (LTV). There was significant increase in dynamic compliance in the recruitment group (REC) compared with the conventional (C) and low tidal volume (LTV) groups. SpO2, PaCO2 showed a highly statistical significance differences between the three ventilated groups. There were no statistically significant differences between the three ventilated groups in terms of PH. There were no statistically significant differences between the three ventilated groups in terms of Mean arterial blood pressure and HR. repeated recruitment maneuvers combined with 5 cm H2O of PEEP increased respiratory system compliance and PaO2 in patients undergoing laparoscopic surgeries without hemodynamics adverse effects.

Efecto de dos maniobras cíclicas de reclutamiento alveolar sobre diversos parámetros de monitoreo microcirculatorio no invasivo en perros

Alveolar recruitment maneuvers (ARM) are important in reversing the formation of perioperative atelectasis; however, its performance is subject to significant hemodynamic changes. The present study evaluated the effect of two cyclic alveolar recruitment protocols, by increasing positive end-expiratory pressure (PEEP), on three parameters of microcirculatory monitoring in 28 anesthetized dogs. Animals were randomly assigned to one of three groups, according to the ARM to be performed, thus: Group 1, short protocol (SP) recruited with PEEP of 10cmH2O; Group 2, long protocol (LP) recruited with PEEP of 20cmH2O; and Group 3, control protocol (CoP) ventilated with PEEP of 0cmH2O. For each maneuver, the central-peripheral temperature gradient (TG), capillary refill time (CRT) and pulse oximetry (SpO2) were evaluated, in four times namely: T1 (Pre-anesthesia), T2 (pre-recruitment), T3 (30 min post-maneuver) and T4 (60 min post-maneuver). In T2, CRT values showed a significant decrease (p<0.05), with respect to baseline time. Subsequently, in the T3, a significant statistical decrease of the TG for the SP group was evident compared to the other treatments; while in the T4 the CRT presented a significant decrease (p<0.05) for LP group versus the other treatments. It is suggested that under the conditions presented here, the protocol of ventilation with PEEP increments of up to 20cmH2O is the ARM of choice as it does not produce alterations of clinical importance in the microcirculatory parameters evaluated.

Changes in stroke volume during an alveolar recruitment maneuvers through a stepwise increase in positive end expiratory pressure and transient continuous positive airway pressure in anesthetized patients. A prospective observational pilot study

Background and Aims:Recruitment maneuvers may be used during anesthesia as part of perioperative protective ventilation strategy. However, the hemodynamic effect of recruitment maneuvers remain poorly documented in this setting.Material and Methods:This was a prospective observational study performed in operating theatre including patients scheduled for major vascular surgery. Patients were monitored with invasive arterial pressure and esophageal doppler. After induction of general anesthesia, before surgery began, preload optimization based on stroke volume (SV) variation following fluid challenge was performed. Then, an alveolar recruitment maneuver (ARM) through stepwise increase in positive end expiratory pressure (PEEP) or continuous positive airway pressure (CPAP) was performed. Hemodynamic data were noted before, during, and after the alveolar recruitment maneuver.Results:ARM through stepwise increase in PEEP and CPAP were applied in 22 and 14 preload independent patients, respectively. Relative changes in SV during ARMs were significantly greater in the ARMCPAP group (-39 ± 20%) as compared to the ARMPEEP group (-15 ± 22%; P = 0.002). The difference (95% CI) in relative decrease in SV between ARMCPAP and ARMPEEP groups was -24% (-38 to -9; P = 0.001). Changes in arterial pressure, cardiac index, pulse pressure variation, peak velocity, and corrected flow time measures were not different between groups.Conclusion:During anesthesia, in preload independent patients, ARMs through CPAP resulted in a significantly greater decrease in SV than stepwise increase in PEEP. During anesthesia, ARM should be used cautiously.

Analysis of different levels of positive end-expiratory pressure during lung retrieval for transplantation: an experimental study.

Atelectasis and inadequate oxygenation in lung donors is a common problem during the retrieval of these organs. Nevertheless, the use of high positive end-expiratory pressure (PEEP) is not habitual during procedures of lung retrieval. Twenty-one Sprague-Dawley male consanguineous rats were used in the study. The animals were divided into 3 groups according to the level of PEEP used: low (2 cmH2O), moderate (5 cmH2O), and high (10 cmH2O). Animals were ventilated with a tidal volume of 6 mL/kg. Before lung removal, the lungs were inspected for the presence of atelectasis. When atelectasis was detected, alveolar recruitment maneuvers were performed. Blood gasometric analysis was performed immediately. Finally, the lungs were retrieved, weighed, and submitted to histological analysis. The animals submitted to higher PEEP showed higher levels of oxygenation with the same tidal volumes PO2=262.14 (PEEP 2), 382.4 (PEEP 5), and 477.0 (PEEP 10). The occurrence of atelectasis was rare in animals with a PEEP of 10 cmH2O, which therefore required less frequent recruitment maneuvers (need for recruitment: PEEP 2=100%, PEEP 5 =100%, and PEEP 10=14.3%). There was no change in hemodynamic stability, occurrence of pulmonary edema, or other histological injuries with the use of high PEEP. The use of high PEEP (10 cmH2O) was feasible and probably a beneficial strategy for the prevention of atelectasis and the optimization of oxygenation during lung retrieval. Clinical studies should be performed to confirm this hypothesis.

Effects of 12 and 17 cmH2O positive end-expiratory pressure applied after alveolar recruitment maneuver on pulmonary gas exchange and compliance in isoflurane-anesthetized horses

ObjectiveTo compare static compliance (Cst) and alveolar–arterial oxygen tension difference [P(a–a)O2] between positive end-expiratory pressures (PEEP) of 7, 12 and 17 cmH2O applied after an alveolar recruitment maneuver (RM) in isoflurane-anesthetized horses. Study designProspective, randomized, clinical study. AnimalsA group of 30 healthy adult horses undergoing arthroscopic surgery. MethodsAnimals in dorsal recumbency and mechanically ventilated with a tidal volume of 14 mL kg−1 and 7 cmH2O PEEP (control; n = 6) were subjected to an RM by increasing PEEP from 7 to 22 cmH2O in 5 cmH2O increments at 5 minute intervals, and then decreased similarly to PEEP of 17 (RM17; n = 8), 12 (RM12; n = 8) or 7 cmH2O (RM7; n = 8). Cst and P(a–a)O2 were assessed prior to (baseline) and after the RM at 5, 10, 15, 20, 40, 60 and 80 minutes after achieving each target PEEP, and during recovery from anesthesia. ResultsPost-RM improvements on P(a–a)O2 were maintained (baseline versus 80 minutes) in RM12 [216 ± 77 mmHg (28.8 ± 10.3 kPa) versus 194 ± 39 mmHg (25.9 ± 5.2 kPa)] and RM17 [180 ± 86 mmHg (24.0 ± 11.6 kPa) versus 136 ± 75 mmHg [18.2 ± 10.0 kPa]). The improvements on Cst were maintained only in RM12 (0.80 ± 0.13 versus 0.98 ± 0.13 mL cmH2O−1 kg−1). No such improvements were observed in RM7 and control. No significant differences were observed between groups during recovery from anesthesia. Conclusionsand clinical relevance The 12 and 17 cmH2O PEEP can be used to maintain the improvements on P(a–a)O2 obtained after an RM. Only 12 cmH2O PEEP maintained the post-RM increase on Cst. Such variables were not influenced by the 7 cmH2O PEEP.

An alveolar recruitment maneuver followed by positive end-expiratory pressure improves lung function in healthy dogs undergoing laparoscopy

ObjectiveTo evaluate the effects of an alveolar recruitment maneuver (ARM) followed by 5 cmH2O positive end-expiratory pressure (PEEP) in dogs undergoing laparoscopy. Study designProspective, randomized clinical study. AnimalsA group of 20 dogs undergoing laparoscopic ovariectomy. MethodsDogs were sedated with acepromazine and methadone intramuscularly; anesthesia was induced with propofol intravenously and maintained with inhaled isoflurane. The following baseline ventilatory setting (BVS) was administered: tidal volume of 12 mL kg–1, inspiratory to expiratory ratio of 1:2, inspiratory pause 25% of inspiratory time, no PEEP and a respiratory rate to maintain end-tidal carbon dioxide tension between 5.3 and 7.3 kPa. Then, 10 minutes after the pneumoperitoneum, 10 dogs (RM) underwent a sustained inflation ARM followed by BVS plus 5 cmH2O PEEP, while 10 dogs (NO-RM) were left with BVS throughout the procedure. Gas exchange and respiratory system mechanics were evaluated before the pneumoperitoneum (PPpre), before ARM (PP10), 30 minutes later (PP30) and 20 minutes after pneumoperitoneum discontinuation (PPpost20). Data were analyzed using anova (p < 0.05). ResultsThe Fshunt at PP30 and PPpost20 was lower (p < 0.001) in the RM (2.3 ± 2.2 and 4.7 ± 3.7%) than in the NO-RM (5.2 ± 2.1 and 11.1 ± 5.2%), and PaO2 at PP30 and PPpost20 was higher (p < 0.001) in the RM (67.3 ± 4.2 and 60.1 ± 9.4 kPa) than in the NO-RM (50.2 ± 7.4 and 45.5 ± 11.1 kPa). Static compliance of the respiratory system at PP30 and PPpost20 was greater (p < 0.001) in the RM (2.4 ± 0.2 and 2.1 ± 0.4 mL cmH2O−1 kg–1) than in the NO-RM (0.9 ± 0.4 and 1.2 ± 0.2 mL cmH2O−1 kg–1). Conclusions and clinical relevanceIn dogs undergoing laparoscopy, ARM followed by 5 cmH2O PEEP improves gas exchange and respiratory system mechanics.