Alveolar recruitment strategy improves arterial oxygenation after cardiopulmonary bypass

Recruitment maneuvers to reduce pulmonary atelectasis after cardiac surgery: A meta-analysis of randomized trials

BACKGROUND

Pulmonary atelectasis is a common postoperative complication that may lead to intrapulmonary shunt, refractory hypoxemia, and respiratory distress. Recruitment maneuvers may relieve pulmonary atelectasis in patients undergoing cardiac surgery. We conducted a meta-analysis of randomized controlled trials to evaluate the effectiveness of recruitment maneuvers in these patients.

METHODS

We conducted a search in PubMed, Embase, Cochrane Library, and the ClinicalTrials.gov registry for trials published before March 2020. Individual effect sizes were standardized, and a meta-analysis was performed to calculate a pooled effect size by using random-effects models. Pulmonary atelectasis was assessed postoperatively. Secondary outcomes included hypoxic events, arterial oxygen tension (Pao₂)/inspired oxygen fraction (Fio₂) ratio, cardiac index, mean arterial pressure, and postoperative complications including pneumothorax and pneumonia.

RESULTS

We reviewed 16 trials involving 1455 patients. Patients receiving recruitment maneuvers had a reduced incidence of pulmonary atelectasis (group with recruited pressure >40 cmH₂O: risk ratio [RR], 0.20; 95% confidence interval [CI], 0.07-0.57; group with recruited pressure <40 cmH₂O: RR, 0.54; 95% CI, 0.33-0.89), reduced incidence of hypoxic events (RR, 0.23; 95% CI, 0.14-0.37), reduced incidence of pneumonia (RR, 0.42; 95% CI, 0.18-0.95), and improved Pao₂/Fio₂ ratio (weighted mean difference [WMD]; 58.87, 95% CI, 31.24-86.50) without disturbing the cardiac index (WMD, 0.22; 95% CI, -0.18 to 0.61) or mean arterial pressure (WMD, -0.30, 95% CI, -3.19 to 2.59) as compared with those who received conventional mechanical ventilation. The incidence of pneumothorax was nonsignificant between the groups.

CONCLUSIONS

Recruitment maneuvers may reduce postoperative pulmonary atelectasis, hypoxic events, and pneumonia and improve Pao₂/Fio₂ ratios without hemodynamic disturbance in patients undergoing cardiac surgery.

Lung ultrasound evaluation of incremental PEEP recruitment maneuver in children undergoing cardiac surgery

AIM

To explore the effect of incremental positive end-expiratory pressure recruitment maneuver (iPEEPRM) in children with congenital heart diseases (CHDs) using lung ultrasound.

METHODS

Thirty-six children aged 3 months to 5 years scheduled for cardiac surgery participated. iPEEPRM was performed with PEEP stepwise increase (0-5-10-15 cmH₂ O) and decrease at the same rate before and after surgery. Atelectatic areas, ultrasound scores, arterial oxygen pressure (PaO₂ ), and respiratory system dynamic compliance per kilogram body weight (CDyn/kg) were analyzed before and after iPEEPRM. The primary outcome is the incidence of atelectasis. Secondary outcomes are oxygenation, ventilation, CDyn/kg, and atelectasis area.

RESULTS

iPEEPRM was successfully applied in 92% (33/36) children before surgery and 71% (24/34) children after surgery. The incidence of atelectasis was significantly reduced by iPEEPRM from 76% to 15% before surgery and from 92% to 38% after surgery, respectively (P < .001). Before surgery, iPEEPRM significantly reduced atelectatic areas and ultrasound scores: 32.5 (0-128.1) mm² vs 0 (0-0) mm² and 8 (3-12) vs 2 (0-4). PaO₂ and CDyn/kg were significantly increased after iPEEPRM: 243 (129-275) mm Hg vs 278 (207-323) mm Hg and 0.6 (0.4-0.7) mL/cmH₂ O/kg vs 0.8 (0.6-1.0) mL/cmH₂ O/kg. After surgery, iPEEPRM significantly reduced atelectatic areas and ultrasound scores: 45.7 (13.1-115.8) mm² vs 0 (0-34.7) mm² , and 9 (6-12) vs 3 (0-5). PaO₂ and CDyn/kg were also significantly increased after iPEEPRM.

CONCLUSIONS

iPEEPRM effectively reduced atelectasis, improved lung aeration, oxygenation, and CDyn/kg in children undergoing cardiac surgery.

Temporal Changes in Ventilator Settings in Patients With Uninjured Lungs: A Systematic Review

In patients with uninjured lungs, increasing evidence indicates that tidal volume (VT) reduction improves outcomes in the intensive care unit (ICU) and in the operating room (OR). However, the degree to which this evidence has translated to clinical changes in ventilator settings for patients with uninjured lungs is unknown. To clarify whether ventilator settings have changed, we searched MEDLINE, Cochrane Central Register of Controlled Trials, and Web of Science for publications on invasive ventilation in ICUs or ORs, excluding those on patients <18 years of age or those with >25% of patients with acute respiratory distress syndrome (ARDS). Our primary end point was temporal change in VT over time. Secondary end points were changes in maximum airway pressure, mean airway pressure, positive end-expiratory pressure, inspiratory oxygen fraction, development of ARDS (ICU studies only), and postoperative pulmonary complications (OR studies only) determined using correlation analysis and linear regression. We identified 96 ICU and 96 OR studies comprising 130,316 patients from 1975 to 2014 and observed that in the ICU, VT size decreased annually by 0.16 mL/kg (-0.19 to -0.12 mL/kg) (P < .001), while positive end-expiratory pressure increased by an average of 0.1 mbar/y (0.02-0.17 mbar/y) (P = .017). In the OR, VT size decreased by 0.09 mL/kg per year (-0.14 to -0.04 mL/kg per year) (P < .001). The change in VTs leveled off in 1995. Other intraoperative ventilator settings did not change in the study period. Incidences of ARDS (ICU studies) and postoperative pulmonary complications (OR studies) also did not change over time. We found that, during a 39-year period, from 1975 to 2014, VTs in clinical studies on mechanical ventilation have decreased significantly in the ICU and in the OR.

Ventilation strategies with different inhaled Oxygen conceNTration during CardioPulmonary Bypass in cardiac surgery (VONTCPB): study protocol for a randomized controlled trial

Background

There is no consensus on the ventilation management during cardiopulmonary bypass (CPB), and the anesthesiologists or the surgeons usually ventilate the lungs with different ventilation strategies or keep them static. Better outcomes are more likely to occur when the ventilation is administered during CPB according to the existing literatures. However, the use of high fraction of inspired oxygen (FiO₂) is debatable in cardiac surgery. And the potential effects of strategies combining low tidal volume (V_T) ventilation with different FiO₂ during CPB on postoperative pulmonary complications (PPCs) are unclear.

Design

The VONTCPB trial is a single-center, prospective, double-blinded, randomized, controlled trial. We are going to recruit total 420 elective cardiac surgery patients with median sternotomy under CPB, who will be equally randomized into three different ventilation strategy groups: NoV, LOV and HOV. (1) The NoV group receives no mechanical ventilation during CPB; (2) the LOV group receives a low V_T of 3-4 ml/kg of ideal body weight (IBW) with the respiratory rate (RR) of 10–12 acts/min, and the positive end-expiratory pressure (PEEP) of 5–8 cmH₂O during CPB; the FiO₂ is 30%; (3) the HOV group receives a low V_T of 3-4 ml/kg of IBW with the RR of 10–12 acts/min, and the PEEP of 5–8 cmH₂O during CPB; the FiO₂ is 80%. The primary endpoints are the incidence of the composite of PPCs and the PPCs score. The secondary endpoints refer to the incidence of the oxygenation index (PaO₂/FiO₂ ratio) < 300 mmHg at three time points (the moment arriving in the ICU, 6 and 12 h after arrival in the ICU), the surgical incision healing grade, the intubation time, the stay of ICU, the length of hospital stay, and mortality at 30 days after the surgery.

Discussion

The VONTCPB trial is the first study to assess the effects of strategies combining low tidal volume (V_T) ventilation with different FiO₂ during CPB on patients’ outcomes.

Trial registration

ChiCTR1800015261. Registered on 20 March 2018.

Electronic supplementary material

The online version of this article (10.1186/s13063-019-3335-2) contains supplementary material, which is available to authorized users.

Low tidal volume mechanical ventilation against no ventilation during cardiopulmonary bypass heart surgery (MECANO): study protocol for a randomized controlled trial

Background

Postoperative pulmonary complications are a leading cause of morbidity and mortality after cardiac surgery. There are no recommendations on mechanical ventilation associated with cardiopulmonary bypass (CPB) during surgery and anesthesiologists perform either no ventilation (noV) at all during CPB or maintain low tidal volume (LTV) ventilation. Indirect evidence points towards better pulmonary outcomes when LTV is performed but no large-scale prospective trial has yet been published in cardiac surgery.

Design

The MECANO trial is a single-center, double-blind, randomized, controlled trial comparing two mechanical ventilation strategies, noV and LTV, during cardiac surgery with CPB. In total, 1500 patients are expected to be included, without any restrictions. They will be randomized between noV and LTV on a 1:1 ratio. The noV group will receive no ventilation during CPB. The LTV group will receive 5 breaths/minute with a tidal volume of 3 mL/kg and positive end-expiratory pressure of 5 cmH2O. The primary endpoint will be a composite of all-cause mortality, early respiratory failure defined as a ratio of partial pressure of oxygen/fraction of inspired oxygen <200 mmHg at 1 hour after arrival in the ICU, heavy oxygenation support (defined as a patient requiring either non-invasive ventilation, mechanical ventilation or high-flow oxygen) at 2 days after arrival in the ICU or ventilator-acquired pneumonia defined by the Center of Disease Control. Lung recruitment maneuvers will be performed in the noV and LTV groups at the end of surgery and at arrival in ICU with an insufflation at +30 cmH20 for 5 seconds. Secondary endpoints are those composing the primary endpoint with the addition of pneumothorax, CPB duration, quantity of postoperative bleeding, red blood cell transfusions, revision surgery requirements, length of stay in the ICU and in the hospital and total hospitalization costs. Patients will be followed until hospital discharge.

Discussion

The MECANO trial is the first of its kind to compare in a double-blind design, a no-ventilation to a low-tidal volume strategy for mechanical ventilation during cardiac surgery with CPB, with a primary composite outcome including death, respiratory failure and postoperative pneumonia.

Trial registration

ClinicalTrials.gov, NCT03098524. Registered on 27 February 2017.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-017-2321-9) contains supplementary material, which is available to authorized users.

Different strategies for mechanical VENTilation during CardioPulmonary Bypass (CPBVENT 2014): study protocol for a randomized controlled trial

Background

There is no consensus on which lung-protective strategies should be used in cardiac surgery patients. Sparse and small randomized clinical and animal trials suggest that maintaining mechanical ventilation during cardiopulmonary bypass is protective on the lungs. Unfortunately, such evidence is weak as it comes from surrogate and minor clinical endpoints mainly limited to elective coronary surgery. According to the available data in the academic literature, an unquestionable standardized strategy of lung protection during cardiopulmonary bypass cannot be recommended. The purpose of the CPBVENT study is to investigate the effectiveness of different strategies of mechanical ventilation during cardiopulmonary bypass on postoperative pulmonary function and complications.

Methods/design

The CPBVENT study is a single-blind, multicenter, randomized controlled trial. We are going to enroll 870 patients undergoing elective cardiac surgery with planned use of cardiopulmonary bypass. Patients will be randomized into three groups: (1) no mechanical ventilation during cardiopulmonary bypass, (2) continuous positive airway pressure of 5 cmH₂O during cardiopulmonary bypass, (3) respiratory rate of 5 acts/min with a tidal volume of 2–3 ml/Kg of ideal body weight and positive end-expiratory pressure of 3–5 cmH₂O during cardiopulmonary bypass. The primary endpoint will be the incidence of a PaO₂/FiO₂ ratio <200 until the time of discharge from the intensive care unit. The secondary endpoints will be the incidence of postoperative pulmonary complications and 30-day mortality. Patients will be followed-up for 12 months after the date of randomization.

Discussion

The CPBVENT trial will establish whether, and how, different ventilator strategies during cardiopulmonary bypass will have an impact on postoperative pulmonary complications and outcomes of patients undergoing cardiac surgery.

Trial registration

ClinicalTrials.gov, ID: NCT02090205. Registered on 8 March 2014.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-017-2008-2) contains supplementary material, which is available to authorized users.

Ventilation during cardiopulmonary bypass for prevention of respiratory insufficiency: A meta-analysis of randomized controlled trials

BACKGROUND

Cardiopulmonary bypass (CPB) is necessary for most cardiac surgery, which may lead to postoperative lung injury. The objective of this paper is to systematically evaluate whether ventilation during CPB would benefit patients undergoing cardiac surgery.

METHODS

We searched randomized controlled trials (RCTs) through PubMed, Embase, and Cochrane Library from inception to October 2016. Eligible studies compared clinical outcomes of ventilation versus nonventilation during CPB in patients undergoing cardiac surgery. The primary outcome includes oxygenation index (PaO2/FiO2 ratio) or alveolar to arterial oxygen tension difference (AaDO2) immediately after weaning from bypass. The secondary outcomes include postoperative pulmonary complications (PPCs), shunt fraction (Qs/Qt), hospital stay, and AaDO2 4 hours after CPB.

RESULTS

Seventeen trials with 1162 patients were included in this meta-analysis. Ventilation during CPB significantly increased post-CPB PaO2/FiO2 ratio (mean difference [MD] = 21.84; 95% confidence interval [CI] = 1.30 to 42.37; P = 0.04; I = 75%) and reduced post-CPB AaDO2 (MD = -50.17; 95% CI = -71.36 to -28.99; P <0.00001; I = 74%). Qs/Qt immediately after weaning from CPB showed a significant difference between groups (MD = -3.24; 95% CI = -4.48 to -2.01; P <0.00001; I = 0%). Incidence of PPCs (odds ratio [OR] = 0.79; 95% CI = 0.42 to 1.48; P = 0.46; I = 37%) and hospital stay (MD = 0.09; 95% CI = -23 to 0.41; P = 0.58; I = 37%) did not differ significantly between groups.

CONCLUSION

Ventilation during CPB might improve post-CPB oxygenation and gas exchange in patients who underwent cardiac surgery. However, there is no sufficient evidence to show that ventilation during CPB could influence long-term prognosis of these patients. The beneficial effects of ventilation during CPB are requisite to be evaluated in powerful and well-designed RCTs.

Changes in Stroke Volume Induced by Lung Recruitment Maneuver Predict Fluid Responsiveness in Mechanically Ventilated Patients in the Operating Room

Background

Lung recruitment maneuver induces a decrease in stroke volume, which is more pronounced in hypovolemic patients. The authors hypothesized that the magnitude of stroke volume reduction through lung recruitment maneuver could predict preload responsiveness.

Methods

Twenty-eight mechanically ventilated patients with low tidal volume during general anesthesia were included. Heart rate, mean arterial pressure, stroke volume, and pulse pressure variations were recorded before lung recruitment maneuver (application of continuous positive airway pressure of 30 cm H2O for 30 s), during lung recruitment maneuver when stroke volume reached its minimal value, and before and after volume expansion (250 ml saline, 0.9%, infused during 10 min). Patients were considered as responders to fluid administration if stroke volume increased greater than or equal to 10%.

Results

Sixteen patients were responders. Lung recruitment maneuver induced a significant decrease in mean arterial pressure and stroke volume in both responders and nonresponders. Changes in stroke volume induced by lung recruitment maneuver were correlated with those induced by volume expansion (r2 = 0.56; P &lt; 0.0001). A 30% decrease in stroke volume during lung recruitment maneuver predicted fluid responsiveness with a sensitivity of 88% (95% CI, 62 to 98) and a specificity of 92% (95% CI, 62 to 99). Pulse pressure variations more than 6% before lung recruitment maneuver discriminated responders with a sensitivity of 69% (95% CI, 41 to 89) and a specificity of 75% (95% CI, 42 to 95). The area under receiver operating curves generated for changes in stroke volume induced by lung recruitment maneuver (0.96; 95% CI, 0.81 to 0.99) was significantly higher than that for pulse pressure variations (0.72; 95% CI, 0.52 to 0.88; P &lt; 0.05).

Conclusions

The authors’ study suggests that the magnitude of stroke volume decrease during lung recruitment maneuver could predict preload responsiveness in mechanically ventilated patients in the operating room.

Carbon dioxide pneumothorax occurring during laparoscopy-assisted gastrectomy due to a congenital diaphragmatic defect: a case report

During laparoscopic surgery, carbon dioxide (CO2) pneumothorax can develop due to a congenital defect in the diaphragm. We present a case of a spontaneous massive left-sided pneumothorax that occurred during laparoscopy-assisted gastrectomy, because of an escape of intraperitoneal CO2 gas, under pressure, into the pleural cavity through a congenital defect in the esophageal hiatus of the left diaphragm. This was confirmed on intraoperative chest radiography and laparoscopic inspection. This CO2 pneumothorax caused tolerable hemodynamic and respiratory consequences, and was rapidly reversible after release of the pneumoperitoneum. Thus, a conservative approach was adopted, and the remainder of the surgery was completed, laparoscopically. Due to the high solubility of CO2 gas and the extra-pulmonary mechanism, CO2 pneumothorax with otherwise hemodynamically stable conditions can be managed by conservative modalities, avoiding unnecessary chest tube insertion or conversion to an open procedure.

Respiratory function during anesthesia: effects on gas exchange

Anaesthesia causes a respiratory impairment, whether the patient is breathing spontaneously or is ventilated mechanically. This impairment impedes the matching of alveolar ventilation and perfusion and thus the oxygenation of arterial blood. A triggering factor is loss of muscle tone that causes a fall in the resting lung volume, functional residual capacity. This fall promotes airway closure and gas adsorption, leading eventually to alveolar collapse, that is, atelectasis. The higher the oxygen concentration, the faster will the gas be adsorbed and the aleveoli collapse. Preoxygenation is a major cause of atelectasis and continuing use of high oxygen concentration maintains or increases the lung collapse, that typically is 10% or more of the lung tissue. It can exceed 25% to 40%. Perfusion of the atelectasis causes shunt and cyclic airway closure causes regions with low ventilation/perfusion ratios, that add to impaired oxygenation. Ventilation with positive end-expiratory pressure reduces the atelectasis but oxygenation need not improve, because of shift of blood flow down the lung to any remaining atelectatic tissue. Inflation of the lung to an airway pressure of 40 cmH2O recruits almost all collapsed lung and the lung remains open if ventilation is with moderate oxygen concentration (< 40%) but recollapses within a few minutes if ventilation is with 100% oxygen. Severe obesity increases the lung collapse and obstructive lung disease and one-lung anesthesia increase the mismatch of ventilation and perfusion. CO2 pneumoperitoneum increases atelectasis formation but not shunt, likely explained by enhanced hypoxic pulmonary vasoconstriction by CO2. Atelectasis may persist in the postoperative period and contribute to pneumonia.

Effects of fluid load on cardiovascular function during stepwise lung recruitment manoeuvre in healthy dogs

The aim of this study was to evaluate the effects of a stepwise lung recruitment manoeuvre (RM) on cardiac output (CO) in mechanically ventilated dogs, with or without a previous fluid load. Eight healthy adult Beagle dogs were enrolled in a prospective crossover study. Following sedation with dexmedetomidine and methadone, anaesthesia was induced with propofol and maintained with isoflurane. CO (thermodilution method) and direct arterial blood pressure were monitored. The dogs were mechanically ventilated in a volume-controlled mode (tidal volume, VT = 10 mL/kg; positive end-expiratory pressure [PEEP] = 0 cm H2O) until normocapnia was achieved (end tidal CO2 35-45 mmHg). The RM was then performed in a pressure-controlled mode, with progressive increases of the PEEP and end-inspiratory pressure of 5 cm H2O, until 15 cm H2O and 30 cm H2O were reached, respectively. After the RM, the ventilatory mode was returned to volume-control, and the PEEP was sequentially decreased to 10, 5 and 0 cm H2O. Baseline ventilation was maintained for 30 min. Next, 10 mL/kg of lactated Ringer's solution was administered within 10 min, prior to a second RM. The CO was determined before each RM (baseline) and at each pressure step. A repeated measures ANOVA test was used to compare data. Compared to baseline, CO decreased during the RM in both groups. However, there was a significantly higher CO during the second RM at the highest pressure step (P<0.05) and during all decreasing pressure steps (P<0.05). In conclusion, a previous crystalloid fluid load could reduce the impact of a RM on CO in healthy dogs.

PEEP-ZEEP technique: cardiorespiratory repercussions in mechanically ventilated patients submitted to a coronary artery bypass graft surgery

BACKGROUND

The PEEP-ZEEP technique is previously described as a lung inflation through a positive pressure enhancement at the end of expiration (PEEP), followed by rapid lung deflation with an abrupt reduction in the PEEP to 0 cmH2O (ZEEP), associated to a manual bilateral thoracic compression.

AIM

To analyze PEEP-ZEEP technique's repercussions on the cardio-respiratory system in immediate postoperative artery graft bypass patients.

METHODS

15 patients submitted to a coronary artery bypass graft surgery (CABG) were enrolled prospectively, before, 10 minutes and 30 minutes after the technique. Patients were curarized, intubated, and mechanically ventilated. To perform PEEP-ZEEP technique, saline solution was instilled into their orotracheal tube than the patient was reconnected to the ventilator. Afterwards, the PEEP was increased to 15 cmH2O throughout 5 ventilatory cycles and than the PEEP was rapidly reduced to 0 cmH2O along with manual bilateral thoracic compression. At the end of the procedure, tracheal suction was accomplished.

RESULTS

The inspiratory peak and plateau pressures increased during the procedure (p < 0.001) compared with other pressures during the assessment periods; however, they were within lung safe limits. The expiratory flow before the procedure were 33 ± 7.87 L/min, increasing significantly during the procedure to 60 ± 6.54 L/min (p < 0.001), diminishing to 35 ± 8.17 L/min at 10 minutes and to 36 ± 8.48 L/min at 30 minutes. Hemodynamic and oxygenation variables were not altered.

CONCLUSION

The PEEP-ZEEP technique seems to be safe, without alterations on hemodynamic variables, produces elevated expiratory flow and seems to be an alternative technique for the removal of bronchial secretions in patients submitted to a CABG.

Evaluation of transoperatory ventilation modalities by a questionnaire

BACKGROUND AND OBJECTIVES

Anesthesia devices have been making it possible to reduce the physiological repercussions and problems caused by mechanical ventilation. The objective of this study was to evaluate, retrospectively, ventilatory methods and support resources used by a group of anesthesiologists in patients without prior lung damage in the intraoperative period.

METHODS

A non-identifiable questionnaire composed of 27 questions was applied to a group of anesthesiologists and anesthesiology residents who work at different private hospitals in the city of São Paulo. The questionnaires were applied over a 15-day period. Ventilation patterns, positive end-expiratory pressure (PEEP), alveolar recruitment maneuvers, and the calculation of the tidal volume used with tracheal intubation were observed.

RESULTS

Participants were predominantly males, 40.5% bearing the Anesthesiology Superior Title (TSA), and the majority concluded their residency less than 10 years ago. Most anesthesiologists used PEEP, between 5 and 10 cmH(2)O, routinely. Fresh gas flow above 1,000 mL.min(-1) is still used by most anesthesiologists. Alveolar recruitment maneuvers were performed by 80% of those interviewed, shortly after intubation and before removing the ET tube with the most common strategy insufflation with 40 cmH(2)O for 15 seconds. As for strategies to protect ventilation, only 30% used a tidal volume with less than 7 mL.kg(-1) with inspired oxygen fraction between 40% and 60%.

CONCLUSIONS

This descriptive study allows us to state that in the hospitals evaluated the majority of anesthesiologists uses resources to minimize eventual repercussions of controlled mechanical ventilation. This data can orient the development of continuing medical education programs in mechanical ventilation associated with anesthesia aiming to safety and improvement of patient care.

Prevention and reversal of lung collapse during the intra-operative period

General anaesthesia induces ventilation/perfusion mismatch by lung collapse. Such lung collapse predisposes patients to preoperative complications since it can persist for several hours or days after surgery. Atelectasis can be partially prevented by using continuous positive airway pressure (CPAP) and/or by lowering FiO2 during anaesthesia induction. However, these manoeuvres are dangerous for patients presenting with challenging airway or ventilator conditions. Lung recruitment manoeuvres (RMs) are ventilatory strategies that aim to restore the aeration of normal lungs. They consist of a brief and controlled increment in airway pressure to open up collapsed areas of the lungs and sufficient positive end-expiratory pressure (PEEP) to keep them open afterward. The application of RMs during anaesthesia normalises lung function along the intraoperative period. There is physiological evidence that patients of all ages and any kind of surgery benefit from such an active intervention. The effect of RMs on patient outcome in the postoperative period is, however, not yet known.

CPAP of 10 cmH2O during cardiopulmonary bypass followed by an alveolar recruitment manoeuvre does not improve post-bypass oxygenation compared to a recruitment manoeuvre alone in children

This randomised controlled study assessed whether continuous positive airway pressure (CPAP) of 10 cmH2O during cardiopulmonary bypass improves post-bypass oxygenation in children compared with no CPAP during bypass. We studied children with a ventricular septal defect. CPAP of 10 cmH2O was applied during bypass in the CPAP group (n=24), whereas the lungs were left deflated in the control group (n=20). In both groups, an alveolar recruitment maneuver was performed by applying positive pressure of 30 to 40 cmH2O for five seconds before weaning from bypass. Postoperative ventilation had the peak inflation pressure set to produce an expired tidal volume of 8 ml/kg with positive end expiratory pressure of 5 cmH2O. Arterial blood gas and haemodynamic measurements were performed at skin incision, five minutes after weaning from bypass, five minutes after chest closure and four hours after arrival in the intensive care unit. In four children CPAP was discontinued because it adversely affected the operating field. There was no difference in demographic characteristics, haemodynamic data, bypass time and operation time. No difference was observed between the groups with respect to pH, PaO2, P(A-a) DO2, PaCO2, and ETCO2 at each time. Variability in the data was greater than expected, leading to a decrease in the expected power of the study. CPAP at 10 cmH2O during bypass was not found to improve the post-bypass oxygenation as compared with leaving the lung deflated during bypass in children undergoing ventricular septal defect repair who had an alveolar recruitment maneuver at the end of bypass.

[Peri-operative atelectasis and alveolar recruitment manoeuvres]

Respiratory complications are a significant cause of post-operative morbidity and mortality. Peri-operative atelectasis, in particular, affects 90% of surgical patients and its effects can be prolonged, due to changes in respiratory mechanics, pulmonary circulation and hypoxaemia. Alveolar collapse is caused by certain predisposing factors, mainly by compression and absorption mechanisms. To prevent or treat these atelectasis several therapeutic strategies have been proposed, such as alveolar recruitment manoeuvres, which has become popular in the last few years. Its application in patients with alveolar collapse, but without a previous significant acute lung lesion, has some special features, therefore its use is not free of uncertainties and complications. This review describes the frequency, pathophysiology, importance and treatment of peri-operative atelectasis. Special attention is paid to treatment with recruitment manoeuvres, with the purpose of providing a basis for the their rational and appropriate use.

Alveolar recruitment strategy during cardiopulmonary bypass does not improve postoperative gas exchange and lung function

Pulmonary dysfunction with impairment of lung function and oxygenation is one of the most serious problems in the early postoperative period after cardiac surgery. In this study we investigated the effect of alveolar recruitment strategy during cardiopulmonary bypass on postoperative gas exchange and lung function. This prospective randomized study included 32 patients undergoing elective myocardial revascularization with cardiopulmonary bypass. In 16 patients 5 cm H(2)O of positive end-expiratory pressure was applied after intubation and maintained until extubation (Group I). In the other 16 patients (group II) a positive end expiratory pressure (PEEP) of 5 cm H(2)O was maintained as well but was increased to 14 cm H(2)O every 20 min for 2 min during cross clamp. Measurements were taken preoperatively, before skin incision, before and after (3, 24, 48 h) cardiopulmonary bypass and before discharge (6th postoperative day). Postoperative gas exchange, extravascular lung water and lung function showed no significant difference between the groups. Postoperative pulmonary function variables were lower in both groups compared to baseline values. In patients with normal preoperative pulmonary function, application of an alveolar recruitment strategy during cardiopulmonary bypass does not improve postoperative gas exchange and lung function after cardiac surgery.

Comparison of monitoring performance of Bioreactance vs. pulse contour during lung recruitment maneuvers

INTRODUCTION

This study was designed to test the hypothesis of equivalence in cardiac output (CO) and stroke volume (SV) monitoring capabilities of two devices: non invasive transthoracic bioreactance (NICOM), and a pulse contour analysis (PICCO PC) coupled to transpulmonary thermodilution (PICCO TD).

METHODS

We included consecutive patients of a single ICU following cardiac surgery. Continuous minute-by-minute hemodynamic variables obtained from NICOM and PICCO PC were recorded and compared in 20 patients at baseline, during a lung recruitment maneuver (20 cmH2O of PEEP) and following withdrawal of PEEP. PICCO TD measurements were also determined. We evaluated the accuracy of these two technologies at baseline using PICCO TD as reference and we estimated the precision by the fluctuation around the mean value (2SD/mean). Then, we assessed time response, amplitude response and reliability for detecting expected decreases when PEEP was applied. Type I and type II errors were analyzed.

RESULTS

CO values (PICCO TD) ranged from 1.6 to 8.0 L.min-1. At baseline, CO values were comparable for NICOM, PICCO PC and PICCO TD: 5.0 +/- 1.2, 4.7 +/- 1.4 and 4.6 +/- 1.3 L.min.-1, respectively (NS). Limits of agreements with PICCO TD were 1.52 L.min.-1 for NICOM and 1.77 L.min.-1 for PICCO PC, NS. The 95% statistical power gives an equivalence with a threshold of 0.52 L.min.-1 for NICOM vs. PICCO PC. The CO precision was 6 +/- 3% and 6 +/- 5% for NICOM and PICCO PC, respectively, NS. When PEEP was applied, CO was reduced by 33 +/- 12%, 31 +/- 14% and 32 +/- 13%, for NICOM, PICCO PC and PICCO TD, respectively (NS). Time response was 3.2 +/- 0.7 minute for NICOM vs. 2 +/- 0.5 minute for PICCO PC (NS). SV results were comparable to those for CO.

CONCLUSIONS

Although limited to 20 patients, this study has enough power to show comparable CO and SV monitoring capabilities of Bioreactance and pulse contour analysis calibrated by transpulmonary thermodilution.

Effects of early vital capacity maneuver on respiratory variables during multivessel off-pump coronary artery bypass graft surgery

OBJECTIVES

Despite avoiding cardiopulmonary bypass, similar degrees of pulmonary impairment compared with on-pump coronary artery bypass surgery have been demonstrated in patients undergoing off-pump coronary artery bypass graft surgery (OPCAB) compared with on-pump coronary artery bypass surgery. To investigate the effects of an early vital capacity maneuver (VCM) on intrapulmonary shunt (Qs/Qt), oxygenation, and pulmonary outcome in OPCAB.

DESIGN

Prospective, randomized, controlled, double-blind clinical trial.

SETTING

Cardiothoracic operating room and intensive care unit (ICU) of a university hospital.

PATIENTS

Fifty patients scheduled for OPCAB were randomized to treatment with VCM or none.

INTERVENTIONS

After sternotomy, VCM was performed by inflating the lungs to 40 cm H2O and holding this pressure for 10 seconds.

MEASUREMENTS AND MAIN RESULTS

Qs/Qt, Pao2/Fio2 (P/F) ratio, and dynamic and static pulmonary compliances were measured before induction of anesthesia (T0), 15 minutes after tracheal intubation (T1), during Y-graft construction (T2), 15 minutes after completion of grafting (T3), 15 minutes after sternal closure (T4), and 3 hours after arrival at the ICU (T5). Qs/Qt was lower and P/F ratio was higher in the VCM group at T2 through T5. Pulmonary compliances were also higher in the VCM group at T4 and T5. Patients in the VCM group were extubated earlier.

CONCLUSIONS

The beneficial effects of an early VCM on Qs/Qt persisted into the period of ICU care, with an improvement in P/F ratio and preserved pulmonary compliances, leading to a shorter time to extubation.

[Atelectasis in general anesthesia and alveolar recruitment strategies]

Atelectasis occurs in most patients during general anesthesia and is the main cause of hypoxemia. The objective of this review is to examine the causes and diagnosis of atelectasis and the different strategies for reducing or preventing this complication and improving oxygenation. Pulmonary atelectasis is mainly caused by 3 factors: compression, gas absorption, and lack of surfactant. Compression and gas absorption are, however, the 2 most commonly implicated factors. Lung collapse is accentuated if pure oxygen is inhaled during induction or if the patient is morbidly obese. Laparoscopic, thoracic, and upper abdominal interventions also carry risk of lung collapse. Various techniques may be used to prevent atelectasis or to reopen collapsed lung tissue. These include using positive end-expiratory pressure or a high tidal volume-thus providing a higher airway pressure (vital capacity maneuver)-or both in combination. Alveolar recruitment strategies have been tried in bariatric surgery, single-lung ventilation, laparoscopy, and adult respiratory distress syndrome. Their application has reduced or prevented atelectasis, thereby reducing postoperative pulmonary complications.

Postoperative study of vital capacity and ventilation measurements following elective craniotomy

CONTEXT AND OBJECTIVE

Changes in pulmonary function commonly occur after general surgery. The aims were to evaluate vital capacity, tidal volume and respiratory frequency among patients undergoing elective craniotomy and to determine possible correlations of these parameters with surgery duration and etiology for neurosurgery.

DESIGN AND SETTING

Prospective, open study at a tertiary university hospital.

METHODS

Twenty-six patients underwent elective craniotomy for aneurysm clipping (11) or tumor resection (15). Vital capacity (VC), tidal volume (TV), minute volume (VE) and respiratory rate were determined before the operation and on the first to fourth postoperative days.

RESULTS

There were significant decreases of 25% in VC, 22% in TV and 12% in VE (p < 0.05) and no significant increase in respiratory frequency (5%) on the first postoperative day. VE returned to baseline on the second postoperative day and TV on the third postoperative day, while VC was 8% lower on the fourth postoperative day, compared with before the operation (p < 0.05). VC reduction was significantly greater in patients undergoing aneurysm clipping (43%) than in patients undergoing tumor resection (14%) when surgery duration was more than four hours (p < 0.05), with no significant change when surgery duration was less than four hours.

CONCLUSION

Reductions in VC, TV and VE were observed during the postoperative period in patients undergoing aneurysm clipping or tumor resection. The reductions in VC and TV were greater in patients undergoing craniotomy due to aneurysm and with longer surgery duration.

Oxygenation and release of inflammatory mediators after off-pump compared with after on-pump coronary artery bypass surgery

BACKGROUND

In a previous study, we showed that oxygenation was impaired for up to 5 day after conventional coronary artery bypass grafting (CABG). As cardiopulmonary bypass (CPB) may have a detrimental effect on pulmonary function, we hypothesized that coronary revascularization grafting without the use of CPB (OPCAB) would affect post-operative oxygenation and release of inflammatory mediators less compared with CABG.

METHODS

Low-risk patients scheduled for elective coronary revascularization were randomly assigned to one of two groups (CABG, n = 17 or OPCAB, n = 18). Two parameters of oxygenation, shunt (%) and ventilation-perfusions mismatch, described as DeltaPO(2) (kPa), were estimated for up to 5 days post-operatively. Systemic release of interleukin (IL)-6, -8 and -10, C-reactive protein (CRP) and neutrophils were measured in peripheral blood samples for up to 3 days post-operatively. The lungs participation in the cytokine response was evaluated from mixed venous blood samples taken within the first 16 h post-operatively.

RESULTS

OPCAB was followed by a higher shunt (P = 0.047), with no difference (P = 0.47) in the deterioration of DeltaPO(2) between the groups. OPCAB was followed by an attenuated systemic release of IL-8 (P = 0.041) and IL-10 (P = 0.006), while the release of IL-6 (P = 0.94), CRP (P = 0.121) and neutrophils (P = 0.078) did not differ between the groups. Indications of an uptake of cytokines in the lungs were found after OPCAB.

CONCLUSIONS

When comparing OPCAB with CABG, oxygenation was more affected and only part of the systemic inflammatory response was attenuated.

Chest physiotherapy prolongs duration of ventilation in the critically ill ventilated for more than 48 hours

OBJECTIVE

This study aimed to determine the impact of providing chest physiotherapy after routine clinical assessment on the duration of mechanical ventilation, outcome and intensive care length of stay.

DESIGN AND SETTING

Single-centre, single-blind, prospective, randomised, controlled trial in a university hospital general intensive care unit.

PATIENTS AND PARTICIPANTS

180 patients requiring mechanical ventilation for more than 48 h.

INTERVENTIONS

Patients randomly allocated, one group receiving physiotherapy as deemed appropriate by physiotherapists after routine daily assessments and another group acting as controls were limited to receiving decubitus care and tracheal suctioning.

MEASUREMENTS AND RESULTS

Primary endpoints were initial time to become ventilator-free, secondary endpoints included intensive care unit (ICU) and hospital mortality and ICU length of stay. Kaplan-Meier analysis censored for death revealed a significant prolongation of median time to become ventilator-free among patients receiving physiotherapy (p=0.047). The time taken for 50% of patients (median time) to become ventilator-free was 15 and 11 days, respectively, for physiotherapy and control groups. There were no differences between groups in ICU or hospital mortality rates, or length of ICU stay. The number of patients needing re-ventilation for respiratory reasons was similar in both groups.

The Pulmonary and Hemodynamic Effects of Two Different Recruitment Maneuvers After Cardiac Surgery

BACKGROUND

The aim of our study was to evaluate the pulmonary and hemodynamic effects of two different recruitment maneuvers after open heart surgery.

METHODS

Sixty patients undergoing coronary artery bypass surgery were randomized into three groups after operation: recruitment maneuver with continuous positive airway pressure (CPAP) (CPAP-40 group, n = 20), recruitment by positive end-expiratory pressure (PEEP) (PEEP-20 group, n = 20), and 5 cm H2O PEEP (PEEP-5 group, n = 20). In the CPAP-40 group, 40 cm H2O peak inspiratory pressure was applied for 30 s, then PEEP was reduced to 20 cm H2O and ventilation was continued with baseline variables with PEEP decreased until the best Pao2 was achieved. In the PEEP-20 group, 20 cm H2O PEEP was set for 2 min, tidal volume was adjusted to achieve a peak inspiratory airway pressure of 40 cm H2O during the maneuver, then PEEP was decreased until the best Pao2 had been achieved. In the PEEP-5 group, 5 cm H2O PEEP was applied postoperatively.

RESULTS

The mean arterial blood pressure of the CPAP-40 group was lower than that of the PEEP-20 (P < 0.01) and PEEP-5 groups (P < 0.01) during the interventions. Oxygenation was higher in both recruitment groups than in the PEEP-5 group during the mechanical ventilation period. There was no significant difference among the groups beyond that period. The atelectasis score of the PEEP-5 group (1.3 +/- 0.9) on postoperative day 1 was higher than that of the CPAP-40 (0.65 +/- 0.6; P = 0.01) and PEEP-20 (0.65 +/- 0.5; P = 0.01) groups.

CONCLUSIONS

The recruitment techniques with postmaneuver PEEP increased oxygenation and decreased atelectasis equally, whereas PEEP-20 provided more stable hemodynamic conditions than the CPAP maneuver.

Hemodynamic effect of sustained pulmonary hyperinflation in patients after cardiac surgery: open vs. closed chest

BACKGROUND

In a previous study, we showed that sustained pulmonary hyperinflation, i.e. a lung recruitment maneuver, after closure of the chest in patients undergoing cardiac surgery had significantly negative effects on the central hemodynamics. As elevated pleural pressure is believed to be a major cause of this cardiovascular impairment, we hypothesized that performing the sustained pulmonary hyperinflation under open chest conditions would affect the circulation less.

METHODS

Patients undergoing cardiac by-pass surgery were included and sustained pulmonary hyperinflations (40 cmH(2)O airway pressure for 15 s) were performed immediately before and after closure of the sternum. Pulse contour cardiac output, heart rate, mean arterial pressure and pulse pressure variation were measured before, during and 1 min after the hyperinflations. Left ventricular dimensions were measured using trans-esophageal echocardiography.

RESULTS

Cardiac output (CO) and mean arterial blood pressure (MAP) decreased significantly during the sustained pulmonary hyperinflation both with an open and closed chest (in parenthesis): CO by 50 (45)% and MAP by 19 (24)%. The left ventricular end-diastolic area was significantly reduced by 24 (33)%. One minute after the hyperinflation, all measured variables had returned to baseline values. No significant differences in the measured variables were found between the two conditions before, during or 1 min after the hyperinflation.

CONCLUSION

Contrary to our hypothesis, sustained pulmonary hyperinflations with the chest open, i.e. before sternal closure, had similar negative effects on central hemodynamics as those performed with the chest closed, i.e. after sternal closure.

Open lung ventilation does not increase right ventricular outflow impedance: An echo-Doppler study

OBJECTIVE

Ventilation according to the open lung concept (OLC) consists of recruitment maneuvers, followed by low tidal volume and elevated positive end-expiratory pressure (PEEP). Elevated PEEP is associated with an increased right ventricular afterload. We investigated the effect of OLC ventilation on right ventricular outflow impedance during inspiration and expiration in patients after cardiac surgery using transesophageal echo-Doppler.

DESIGN

A prospective, single-center, crossover, randomized, controlled clinical study.

SETTING

Cardiothoracic intensive care unit of a university hospital.

PATIENTS

Twenty-eight patients scheduled for elective cardiac surgery with cardiopulmonary bypass.

INTERVENTIONS

In the intensive care unit, each patient was ventilated for approximately 30 mins according to both OLC and conventional ventilation. During OLC ventilation, recruitment maneuvers were applied until PaO2/FiO2 was >375 torr (50 kPa); during conventional ventilation no recruitment maneuvers were performed.

MEASUREMENTS AND MAIN RESULTS

Transesophageal echo-Doppler measurements were performed at end-inspiration and end-expiration in a steady-state condition, 20 mins after initiation of a ventilation strategy. Mean acceleration of flow was determined in the long axis of the pulmonary artery in a transverse axis view. During OLC ventilation, a total PEEP of 14 +/- 4 cm H2O was applied vs. 5 cm H2O during conventional ventilation. Mean acceleration during expiration was comparable between groups. During inspiration, OLC ventilation did not cause a decrease of mean acceleration compared with expiration, whereas this did occur during conventional ventilation.

CONCLUSIONS

Despite the use of elevated PEEP levels, ventilation according to OLC does not change right ventricular outflow impedance during expiration and decreases right ventricular outflow impedance during inspiration.

Study of respiratory muscle strength, vital capacity, and ventilometry in the postoperative period of spinal surgery by posterior access

STUDY DESIGN

Prospective.

OBJECTIVE

To analyze tidal volume (TV), minute volume (VE), respiratory frequency (f), vital capacity (VC), maximal inspiratory (PImax), and expiratory (PEmax) pressures in patients submitted to spinal surgery for tumor or herniated disc by posterior access, and to investigate a possible association of respiratory function with surgery duration, site of surgical access, and diagnosis.

SUMMARY OF BACKGROUND DATA

A reduction in pulmonary volumes is usually seen in patients submitted to thoracic or upper abdominal surgery, and recent studies have demonstrated such alterations during the postoperative period in patients submitted to craniotomy.

METHODS

A total of 45 patients (mean age, 42 +/- 14 years) were submitted to spinal surgery in an University Hospital, and TV, VC, MV, f, PImax, and PEmax were measured in the preoperative period, and in the first and second postoperative days.

RESULTS

Patients submitted to spinal surgery showed a decrease in the first and second postoperative days in VC, respectively (17% and 10%), TV (18% and 13%), PImax (17% and 12%), PEmax (12% and 7%), and an increase in f (18% and 12%) (P < 0.05). Reduction in TV, VC, PImax, and PEmax and the increase in f were associated with surgical time > or =240 minutes, diagnosis of tumor, and cervicothoracic surgical access (P < 0.05).

CONCLUSIONS

Alterations in the respiratory function in the postoperative period of elective spinal surgery by posterior access for tumor removal or herniated disc were related to surgical time > or =240 minutes, tumor, or cervicothoracic surgical access.

Effects of alveolar recruitment on arterial oxygenation in patients after cardiac surgery: a prospective, randomized, controlled clinical trial

OBJECTIVE

Pulmonary atelectasis and hypoxemia remain considerable problems after cardiac surgery. The objective of this study was to determine the efficacy of consecutive vital capacity maneuvers (C-VCMs) to improve oxygenation in patients after cardiac surgery.

STUDY DESIGN

Randomized, controlled clinical trial.

SETTING

Tertiary referral teaching center.

PARTICIPANTS

Ninety-five patients requiring elective cardiac surgery with cardiopulmonary bypass (CPB).

INTERVENTION

Patients were randomly allocated to either C-VCM or control groups. In the C-VCM group, lung inflation at pressure of 35 cmH(2)O was sustained for 15 seconds before separation from CPB and at 30 cmH(2)O for 5 seconds after admission to the intensive care unit (ICU).

MEASUREMENTS AND MAIN RESULTS

The primary outcome was the ratio of arterial oxygen tension to inspired oxygen fraction measured at the following predetermined time intervals: after induction of anesthesia, 15 minutes after separation from CPB, after admission to the ICU, after 3 hours of positive-pressure ventilation, after extubation, and before ICU discharge. C-VCM resulted in better arterial oxygenation extending from the immediate postoperative period to approximately 24 hours after surgery at the time of ICU discharge. There were no significant adverse events related to C-VCM application.

CONCLUSION

C-VCM is an effective method to reduce hypoxemia associated with the formation of atelectasis after cardiac surgery with CPB.

Effect of Lung Ventilation With 50% Oxygen in Air or Nitrous Oxide Versus 100% Oxygen on Oxygenation Index After Cardiopulmonary Bypass

OBJECTIVE

This study was designed to assess the use of 100% oxygen or 50% oxygen in air or nitrous oxide after cardiopulmonary bypass (CPB) on atelectasis, as evidenced by the oxygenation index (PaO2/F(I)O2), after coronary artery bypass graft (CABG) surgery.

DESIGN

Prospective, randomized clinical study.

SETTING

University teaching hospital.

PARTICIPANT

Thirty-six adult patients undergoing CABG surgery.

INTERVENTIONS

Patients either received 50% O2 in air (50% O2 group), 50% O2 in N2O (50% N2O group), or 100% O2 (100% O2 group) after CPB.

MEASUREMENTS AND MAIN RESULTS

Apart from demographic and perioperative clinical data, extubation time, mediastinal drainage, and pulmonary complications were also recorded. After CPB, arterial blood gases done at various time points until 3 hours postextubation and oxygenation index were calculated. No significant differences were noted in demographic and perioperative data except preoperative hemoglobin and fluid use. Significant deterioration in arterial oxygenation was noted in the 100% O2 group from the baseline value, whereas significant improvement was seen in the 50% O2 group at 4 time points from baseline value and at all time points from the 100% O2 group. After initial deterioration in oxygenation, no further change was evident in the 50% N2O group. Furthermore, there was a greater increase in the oxygenation index as compared with the 100% O2 group. Time to extubation was also longer in the 100% O2 group than the 50% O2 group.

CONCLUSION

Significant deterioration in arterial oxygenation and an increase in the extubation time occurred with the use of 100% O2 after CPB, whereas better oxygenation was evident with the use of 50% O2 in air.

Central hemodynamics during lung recruitment maneuvers at hypovolemia, normovolemia and hypervolemia. A study by echocardiography and continuous pulmonary artery flow measurements in lung-injured pigs

OBJECTIVE

The impact of lung-recruitment maneuvers on heart function at different volemic levels has not been studied in detail. We therefore investigated the effect on central hemodynamics of lung recruitment maneuvers at hypovolemia, normovolemia and hypervolemia in experimental lung injury.

DESIGN

Randomized, controlled, cross-over experimental study.

SETTING

Animal laboratory at a university hospital.

PARTICIPANTS

Eleven anesthetized and lung-lavaged pigs.

INTERVENTION

The animals were randomized to 10-s lung recruitment maneuvers followed by 30-s maneuvers (40 cm H(2)O airway pressure) or vice versa, performed under hypovolemia, normovolemia and hypervolemia.

MEASUREMENTS AND MAIN RESULTS

Left-ventricular end-diastolic diameter and cardiac output were measured before, during, and 1 min and 5 min after the lung recruitment maneuver and left-ventricular eccentricity index was calculated for before and during the maneuver. Cardiac output and left-ventricular end-diastolic diameter (within parentheses) decreased significantly during both the 10-s and 30-s lung recruitment maneuvers at hypovolemia, by a mean of 89% (35) and 92% (33), at normovolemia by 75% (33) and 86% (32), and at hypervolemia by 56% (32) and 64% (43), respectively. At hypovolemia, cardiac output was increased above baseline 1-5 min following the 30-s maneuver. Left-ventricular eccentricity index increased significantly during the maneuver, indicating right ventricular dysfunction.

CONCLUSIONS

In this animal lung injury model, lung recruitment maneuvers significantly decreased left-ventricular end-diastolic volume and cardiac output at hypovolemia. Hypervolemia did partly counteract this compromise. In addition, a marked right-ventricular dysfunction during the maneuver was found.

Rekrutierungsmanöver bei Patienten mit Lungenversagen

Recruitment maneuvers have been proposed as an adjunct to mechanical ventilation to re-expand collapsed lung regions. Although, in most patients recruitment maneuvers improve gas exchange a controversial discussion on recruitment maneuvers remains. This article reviews the physiological and patho-physiological backgrounds of recruitment maneuvers. The different recruitment maneuvers and possible monitoring are discussed as well as the influence of recruitment on other organs. Furthermore, we discuss whether recruitment maneuvers are useful if patients with acute lung injury or acute respiratory distress syndrome are ventilated with a lung-protective strategy.

Lung recruitment during mechanical positive pressure ventilation in the PICU: what can be learned from the literature?

A literature review was conducted to assess the evidence for recruitment manoeuvres used in conventional mechanical positive pressure ventilation. A total of 61 studies on recruitment manoeuvres were identified: 13 experimental, 31 ICU, 6 PICU and 12 anaesthesia studies. Recruitment appears to be a continuous process during inspiration and expiration and is determined by peak inspiratory pressure (PIP) and positive end expiratory pressure (PEEP). Single or repeated recruitment manoeuvres may result in a statistically significant increase in oxygenation; however, this is short lasting and clinically irrelevant, especially in late ARDS and pneumonia. Temporary PIP elevation may be effective but only after PEEP loss (for example disconnection and tracheal suctioning). Continuous PEEP elevation and prone positioning can increase P(a)O2 significantly. Adverse haemodynamic or barotrauma effects are reported in various studies. No data exist on the effect of recruitment manoeuvres on mortality, morbidity, length of stay or duration of mechanical ventilation. Although recruitment manoeuvres can improve oxygenation, they can potentially increase lung injury, which eventually determines outcome. Based on the presently available literature, prone position and sufficient PEEP as part of a lung protective ventilation strategy seem to be the safest and most effective recruitment manoeuvres. As paediatric physiology is essentially different from adult, paediatric studies are needed to determine the role of recruitment manoeuvres in the PICU.

The effect of positive end-expiratory pressure level on peak expiratory flow during manual hyperinflation

Including positive end-expiratory pressure (PEEP) in the manual resuscitation bag (MRB) may render manual hyperinflation (MHI) ineffective as a secretion maneuver technique in mechanically ventilated patients. In this study we aimed to determine the effect of increased PEEP or decreased compliance on peak expiratory flow rate (PEF) during MHI. A blinded, randomized study was performed on a lung simulator by 10 physiotherapists experienced in MHI and intensive care practice. PEEP levels of 0-15 cm H(2)O, compliance levels of 0.05 and 0.02 L/cm H(2)O, and MRB type were randomized. The Mapleson-C MRB generated significantly higher PEF (P < 0.01, d = 2.72) when compared with the Laerdal MRB for all levels of PEEP. In normal compliance (0.05 L/cm H(2)O) there was a significant decrease in PEF (P < 0.01, d = 1.45) for a PEEP more than 10 cm H(2)O in the Mapleson-C circuit. The Laerdal MRB at PEEP levels of more than 10 cm H(2)O did not generate a PEF that is theoretically capable of producing two-phase gas-liquid flow and, consequently, mobilizing pulmonary secretions. If MHI is indicated as a result of mucous plugging, the Mapleson-C MRB may be the most effective method of secretion mobilization.

The lung during and after thoracic anaesthesia

PURPOSE OF REVIEW

Increased awareness of widespread atelectasis and deoxygenation after cardiac surgery, and in the ventilated lung during one-lung anaesthesia, has prompted many studies on recruitment of collapsed tissue and other methods to treat hypoxia in the perioperative period. It is therefore time to summarize what benefits might come from such manoeuvres.

RECENT FINDINGS

Major findings are that recruitment by different, often vigorous inflation of the lungs improves oxygenation and that this can also be seen when a recruitment manoeuvre is done of the ventilated lung in one-lung anaesthesia. The inspired oxygen fraction seems to be an important determinant of how long the recruitment persists.

SUMMARY

Recruitment manoeuvres are highly efficient in improving oxygenation but often for a limited period. So they have to be repeated. To what extent they may affect hospital stay and other variables of outcome, remains to be shown.

Both lung recruitment maneuver and PEEP are needed to increase oxygenation and lung volume after cardiac surgery

BACKGROUND

Patients ventilated after cardiac surgery commonly have impaired oxygenation, mainly due to lung collapse. We have previously found that PaO2 and end-expiratory lung volume (EELV) were increased by a lung recruitment maneuver (LRM) followed by positive end-expiratory pressure (PEEP). The aim of this study was to evaluate whether only PEEP or only a LRM could give similar effects.

METHODS

Thirty circulatory stable patients (aged 55-79 years) mechanically ventilated after cardiac surgery were randomized to receive LRM (four 10-s insufflations to an airway pressure of 45 cmH2O) and zero end-expiratory pressure (LRM-group), PEEP 12 cmH2O (PEEP-group) or LRM in combination with PEEP 12 cmH2O (LRM + PEEP-group). The set end-expiratory pressure was kept for 75 min. Before, during and after the intervention, EELV (SF6 washout technique) and blood gases were measured.

RESULTS

Initial EELV and PaO2 were similar in all groups. In the LRM-group, PaO2 and EELV increased transiently (P < 0.0001), but returned at 5 min to the initial values. In the PEEP-group, PaO2 did not change but EELV increased to 155 +/- 27% of the initial value (P < 0.0001). In the LRM+PEEP-group, PaO2 and EELV increased to 212 +/- 66% and 178 +/- 31% of the initial values (P < 0.0001), respectively, and were maintained during PEEP application.

CONCLUSION

In patients ventilated after cardiac surgery: (1) PEEP increased lung volume but not PaO2, (2) a lung recruitment maneuver without subsequent PEEP had no sustained effect, and (3) both a lung recruitment maneuver and PEEP were needed to increase and maintain the increased lung volume and PaO2.

Clinical review: the implications of experimental and clinical studies of recruitment maneuvers in acute lung injury

Mechanical ventilation can cause and perpetuate lung injury if alveolar overdistension, cyclic collapse, and reopening of alveolar units occur. The use of low tidal volume and limited airway pressure has improved survival in patients with acute lung injury or acute respiratory distress syndrome. The use of recruitment maneuvers has been proposed as an adjunct to mechanical ventilation to re-expand collapsed lung tissue. Many investigators have studied the benefits of recruitment maneuvers in healthy anesthetized patients and in patients ventilated with low positive end-expiratory pressure. However, it is unclear whether recruitment maneuvers are useful when patients with acute lung injury or acute respiratory distress syndrome are ventilated with high positive end-expiratory pressure, and in the presence of lung fibrosis or a stiff chest wall. Moreover, it is unclear whether the use of high airway pressures during recruitment maneuvers can cause bacterial translocation. This article reviews the intrinsic mechanisms of mechanical stress, the controversy regarding clinical use of recruitment maneuvers, and the interactions between lung infection and application of high intrathoracic pressures.