Ain-Shams Journal of Anaesthesiology

ORIGINAL ARTICLE
Year
: 2017  |  Volume : 10  |  Issue : 1  |  Page : 20--27

Efficacy and safety of single versus repeated stepwise cycling recruitment maneuver during one-lung ventilation in patients with normal pulmonary function undergoing video-assisted thoracoscopic lung surgery: a randomized, controlled trial


Elokda A Sherif1, Arafa A Rasha2, Gamil Khaled3,  
1 Department of Anesthesia, ICU & Pain Management, Ain Shams University, Cairo, Egypt
2 Department of Anesthesia, Cairo University, Cairo, Egypt
3 Department of Anesthesia & Pain Management, National Cancer Institute, Cairo University, Cairo, Egypt

Correspondence Address:
Elokda A Sherif
Department of Anesthesia, Dallah Hospital, Al-nakheel District, PO Box 87833, Riyadh 11652
Egypt

Abstract

Background One-lung ventilation (OLV)-associated hypoxemia is a major concern and a challenge for the anesthesiologist. Lung recruitment maneuvers (RMs) are ventilator strategies in which the main goal is to restore the functional residual capacity and improve arterial oxygenation. Hemodynamic side effects are mainly associated with ‘fast’ RM not with ‘slow’ cycling RM and their effects are self-limited; therefore, they must be performed repetitively. Aim The aim of this study was to evaluate the efficacy and safety of single versus repeated stepwise cycling RMs during OLV in patients with normal lung function. Settings and design The study design is a randomized, double-blinded, controlled one. Patients and methods Sixty adult patients of ASA I–II who were scheduled for elective thoracoscopic lung surgery were randomized into groups C, single recruitment maneuver (SRM), and repeated recruitment maneuver (RRM) comprising 20 patients each. Group C patients received standard ventilation protocol: volume-controlled ventilation mode, VT 6 ml/kg, I : E ratio 1 : 2, positive end expiratory pressure (PEEP) 5 cmH2O, and respiratory rate 10–12 breaths/min. SRM patients received standard ventilation protocol with one alveolar RM 10 min after initiation of OLV with a PEEP of 10 cmH2O until end of surgery. RRM patients received standard ventilation protocol with first RM 10 min after initiation of OLV and then repeated every 30 min during OLV and a PEEP of 10 cmH2O until end of surgery. The following were assessed: hemodynamic parameters – heart rate, mean arterial blood pressure, and central venous pressure; respiratory mechanical parameters – peak airway pressure (Paw-peak), plateau pressure (Paw-plat), and static lung compliance; and oxygenation parameters – partial arterial oxygen tension (PaO2), PaO2/FiO2, and oxygen saturation (SpO2). Results PaO2 and PaO2/FiO2 ratio increased in the SRM and RRM groups after RM from T2 (10 min after first RM) to T4 (45 min from first RM), with a significant difference compared with group C (P<0.05). Peak and plateau airway pressures declined in the SRM and RRM groups after RM from T2 to T4, with a significant difference when compared with group C (P<0.05). Static lung compliance increased in the SRM and RRM groups after RM, with a significant difference among the groups (P<0.05). Conclusion Single or repeated cycling RM was considered effective with high safety profile in patients with normal pulmonary function undergoing thoracoscopic lung surgery using OLV.



How to cite this article:
Sherif EA, Rasha AA, Khaled G. Efficacy and safety of single versus repeated stepwise cycling recruitment maneuver during one-lung ventilation in patients with normal pulmonary function undergoing video-assisted thoracoscopic lung surgery: a randomized, controlled trial.Ain-Shams J Anaesthesiol 2017;10:20-27


How to cite this URL:
Sherif EA, Rasha AA, Khaled G. Efficacy and safety of single versus repeated stepwise cycling recruitment maneuver during one-lung ventilation in patients with normal pulmonary function undergoing video-assisted thoracoscopic lung surgery: a randomized, controlled trial. Ain-Shams J Anaesthesiol [serial online] 2017 [cited 2018 Oct 16 ];10:20-27
Available from: http://www.asja.eg.net/text.asp?2017/10/1/20/238456


Full Text



 Introduction



Video-assisted thoracoscopic lung resection or lobectomy indicates exclusion of the nondependent lung from ventilation − that is, one-lung ventilation (OLV) − to optimize the surgical field, facilitate the resection, and reduce the surgical time [1],[2]. OLV was first described in 1932 by Gale and Waters [3], who used a single-light tube that was inserted into the right or the left main stem bronchus.

Situations in which OLV are indicated can be classified as follows: to separate both lungs, such as in case of hemothorax, massive hemorrhage, bronchopleural fistulae, and unilateral pulmonary diseases, or to facilitate surgical procedures such as pneumonectomies, lobectomies, thoracoscopies, and esophageal resection [4]. Intraoperative hypoxemia during OLV is observed in ∼1–27% of patients despite the use of high inspiratory oxygen fraction (FiO2) [5],[6]. The incidence of this hypoxemia is affected by many factors − for example, ventilator settings used, the type of surgery performed, the patient’s position during surgery, and anesthesiologist’s experience in OLV thoracic anesthesia [7].

Lung collapse is a well-known anesthesia-induced complication that has been observed in ∼90% of patients undergoing general anesthesia. It usually starts with induction of anesthesia and may persist for several hours postoperatively. Its mechanism is multifactorial, and hence it can be due to loss of respiratory muscle tone by anesthetic drugs, surfactant inactivation by anesthetics, or high FiO2 used during induction of anesthesia [8].

OLV-associated hypoxemia is usually due to increased intrapulmonary shunt that results from ventilation/perfusion (V/Q) mismatch due to residual perfusion in the nondependent collapsed lung and insufficient oxygenation of blood in a telectatic and poorly ventilated areas of the dependent ventilated lung [9]. Lung recruitment maneuvers (RMs) are ventilator strategies in which the main goal is to restore the functional residual capacity to normalize lung function and to avoid the pathogenesis of ventilator-induced lung injury [10]. These maneuvers are based on the premise described by Lachmann a few decades ago, taking into account the Young–Laplace equation states: the lungs can be opened by applying high pressures in the airways and then keeping them open in time by using enough positive end expiratory pressure (PEEP) [11].

There are two basic types of RMs:The continuous positive airway pressure (CPAP) maneuvers, which consist of application of high continuous positive pressure in the airways for few seconds (10–40 s) in a breathless patient [12].The cycling maneuvers, in which airway pressure is increased in a stepwise pattern during the respiratory cycle [13].

The management of OLV has been changed over the last decades. In the early days of thoracic anesthesia, knowledge and an awareness of ventilator-induced lung injury were rare, and hence ventilation with high VT and FiO2 without PEEP was applied [14]. Later on, low tidal volumes and PEEP of no more than 5 cmH2O became popular, whereas RM was still considered a rescue intervention in case of severe hypoxemia [15]. Alveolar recruitment per se is a rapid phenomenon that happens quickly during the intervention. Shear stress within fragile lung tissue and hemodynamic side effects are mainly associated with ‘fast’ RM and not with ‘slow’ cycling RM [16].

One-step sustained inflation maneuvers are more harmful compared with cycling stepwise RM because they abruptly change pressure and volumes within lungs [17]. The number of RM needed to be applied during thoracic surgery and OLV depends on the efficiency of such maneuvers and the level of PEEP chosen, which should be higher than lung’s closing pressure to keep the lungs ‘open’ [18]. Many studies concluded that RM effects are self-limited, and therefore RMs must be performed repetitively [19]. Therefore, the rational stands behind this study was to investigate and evaluate both the efficacy and safety of single versus repeated stepwise cycling RMs during OLV in patients with normal lung function.

 Patients and methods



Study groups

The medical ethical committee of Dallah Hospital, Riyadh, Kingdom of Saudi Arabia, approved the study protocol and then written informed consent was obtained from all patients before enrollment into the study. Sixty (n=60) adult male and female patients of American Society of Anesthesiologist (ASA) physical status I–II scheduled for elective video-assisted thoracoscopic lung surgery (resection or lobectomy) during the period from May 2014 to April 2015 were included in the study. The patients were enrolled into one of the three randomized, double-blind, controlled study groups using a computer-generated randomization schedule and sealed opaque envelopes.

Patients were eligible for inclusion if they were between 25 and 60 years of age and had normal pulmonary function tests. They were excluded from the study if they had any of the following: previous lung surgery, chronic obstructive pulmonary disease, restrictive lung disease, bronchial asthma, home oxygen therapy, contralateral lung bullae, uncompensated cardiac disease (NYHA class III or IV), hemodynamic instability, and increased intracranial pressure. In addition, any patient who developed hemodynamic instability [mean arterial blood pressure (MAP)<60 mmHg] or desaturation (SpO2<90%) during recruitment procedure was excluded from the study.

Patients were randomly divided into three groups: the control group (group C, n=20), the single recruitment maneuver group (group SRM, n=20), and the repeated recruitment maneuver group (group RRM, n=20). All patients were premedicated with midazolam 0.05 mg/kg intramuscularly 1 h before shifting to the operating theater. Group C patients received the standard ventilation protocol as follows: volume-controlled ventilation mode, with VT 6 ml/kg of ideal body weight, inspiratory : expiratory ratio 1 : 2, a PEEP of 5 cmH2O, and respiratory rate 10–12 breaths/min that was adjusted to keep end-tidal carbon dioxide tension (EtCO2) between 35 and 40 mmHg. Patients in group SRM received the standard ventilation protocol with one alveolar RM performed 10 min after initiation of OLV for the dependent lung and PEEP was set at 10 cmH2O after RM until the end of surgery and extubation. Group RRM received the standard ventilation protocol with first alveolar RM 10 min after initiation of OLV and then repeated every 30 min during the OLV for the dependent lung and PEEP was set at 10 cmH2O until end of surgery and extubation.

Anesthetic technique

On arrival of the patient to the operating theater and before induction of anesthesia, all standard monitors were applied, including heart rate (HR), ECG, oxygen saturation (SpO2), end-tidal CO2, arterial blood pressure (systolic, diastolic, and MAP), and temperature. In addition to these monitors, both neuromuscular monitoring, train of four (TOF), and bipolar BIS electrodes (BIS QUATRO-BX13366; Aspect Medical Systems Inc., Chicago, Illinois, USA) were applied to the patient. After induction of anesthesia, arterial catheter was inserted in the radial artery for continuous blood pressure monitoring and frequent blood gas analysis. Initial readings of all these monitors were taken and recorded before starting any drug infusion.

Anesthesia was induced by means of intravenous remifentanil (1 μg/kg) over 30–60 s, followed by propofol (1–2 mg/kg). Intubation was facilitated with rocuronium bromide at a dose of 0.6 mg/kg, and a left-sided double-lumen endobroncheal tube (Mallinckrodt Medical Ltd, Athlone, Ireland) size 39 F or 37 Fr for male or female patients, respectively, was inserted. The position of double-lumen endobroncheal tube was confirmed using a fiberoptic bronchoscope. A triple-lumen internal jugular venous catheter was inserted under complete aseptic conditions. Anesthesia was maintained with continuous infusion of remifentanil (0.25 μg/kg/min), sevoflurane 1–2% MAC, and inspired oxygen fraction of 1.0. Anesthesia was titrated to keep the ‘BIS’ value within the range (40–50). Muscle relaxation was monitored with ‘TOF’ every 10 min, and rocuronium infusion from 0.3 to 0.6 mg/kg/h was administered and adjusted to maintain 1–2 responses to ‘TOF’ stimulation. Lungs were mechanically ventilated to maintain normocapnia (EtCO2 35–40 mmHg). All surgical procedures were performed by the same surgeon who was blinded to the study.

All vital signs were continuously monitored and recorded at specific time intervals after induction of anesthesia until the end of surgery and extubation. After patient positioning, the endobroncheal tube location was confirmed with the fiberoptic bronchoscope. All patients were anesthetized by one anesthetist who was not involved in the study and was instructed to follow the study design. Lactated Ringer’s solution was set at a rate of 10 ml/kg/h as a baseline infusion in all groups to assure hemodynamic stability. Additional solutions were infused if required.

Alveolar recruitment maneuver

Dräger anesthesia machine (Zeus Turbovent; Dräger and Siemens Company, Lubeck, Germany) was used in this study. This machine had both volume and pressure modes of ventilation in addition to measuring lung compliance. The recruitment was performed by shifting the ventilation mode to pressure-controlled ventilation. The driving pressure (Paw-plat-PEEP) was adjusted to maintain a tidal volume identical to the volume given during volume-controlled ventilation mode. Although driving pressure was kept constant, the external PEEP was progressively increased in stepwise increments of 5 cmH2O every minute until reaching 15 cmH2O, and then the driving pressure was increased to a final Paw-plat of 40 cmH2O. The 40/15 cmH2O recruitment pressure was applied for 1 min, and then the standard ventilation was resumed but with a PEEP of 10 cmH2O to keep the recruited alveoli opened. For safety, the peak inspiratory pressure of the ventilator was limited to 45 cmH2O.

At the end of surgery, two-lung ventilation (TLV) was re-established using the standard ventilation setting, except that the PEEP was set at 10 cmH2O. All anesthetic agents were discontinued and the patients were ventilated with 100% oxygen. The residual effect of rocuronium was reversed with neostigmine at a dose of 40 μg/kg and atropine sulfate 20 μg/kg. Thereafter, the patients were extubated after regaining their spontaneous breathing and transferred to the postanesthesia care unit (PACU) for routine follow-up. Postoperative analgesia was started with pethidine 50 mg intramuscularly every 8 h and paracetamol infusion 1 g every 6 h to keep visual analogue scale score of 4 or less. The patients were discharged to the ward after fulfilling the recovery discharge criteria. Chest radiograph was performed 2 h postoperatively and 24 h later to exclude any adverse effects of the RM.

Data for assessment

Hemodynamic parameters: HR, MAP, and central venous pressure.Respiratory mechanical parameters: peak airway pressure (Paw-peak), plateau pressure (Paw-plat), and static lung compliance.Oxygenation parameters: partial arterial oxygen tension (PaO2), PaO2/FiO2, and oxygen saturation (SpO2).

All these measurements were performed at the following time intervals: T0 (baseline), during TLV before positioning; T1, 10 min after initiation of OLV; T2, 10 min after first RM; T3, 30 min after first RM; T4, 45 min after first RM; T5, 60 min after first RM; and T6, at the end of surgery with TLV. Additional blood gases analysis was performed in the PACU at 30 min and 1 h after surgery.

The primary outcome for the current study was to evaluate the efficacy of repeated stepwise cycling RM on gas exchange and respiratory mechanics, and the secondary outcome was to assure pulmonary and extrapulmonary safety of this maneuver. The pulmonary safety will be assessed by performing arterial blood gas analysis and chest radiography in the recovery room to detect hypoxia or pneumothorax if present, whereas the extrapulmonary safety was assessed by monitoring the vital signs for the presence of hypotension or any arrhythmia.

Statistical analysis and sample size

Sample size calculation was performed guided by power of 80%, confidence level of 95%, and Z score of 1.96 together with an accepted margin of error of 5% and expected outcome percentage of the trials used. Accordingly, the total sample calculated was 60 patients divided into three equal groups. Analysis of data was performed with IBM computer using SPSS (Statistical Package for Social Science version 16; SPSS Inc., Chicago, Illinois, USA). Quantitative variables were presented as mean±SD and range. Qualitative variables were presented as number and percentage (%), and the one-way analysis of variance (ANOVA) test was used to compare more than two groups as regards quantitative variables. The paired t-test was used to compare quantitative variables within each group. A P value less than 0.05 was considered statistically significant.

 Results



Of 70 patients considered eligible for this study, 10 patients were not included in the study because of either the presence of one or more of the exclusion criteria or refusal to participate in the study. Only 60 patients were involved and their data were analyzed in this study.

The results of this study showed that there was no significant difference among the three study groups as regards patients’ characteristics and operative data ([Table 1]).{Table 1}

Arterial oxygenation

The current study demonstrated that there was a significant reduction in PaO2 and PaO2/FiO2 ratio after initiating OLV in all groups at T1 when compared with baseline values at T0, with a significant difference using the paired t-test (P<0.05) ([Figure 1] and [Figure 2]). This decline was maintained throughout the study in the control group (group C) but was increased again in both the SRM and RRM groups after performing the RM without reaching the baseline readings starting from T2 to T4, with a significant difference when compared with the control group using the one-way ANOVA test (P<0.05) ([Figure 1] and [Figure 2]). Both parameters started to decrease again in the SRM group at T5 when compared with RRM group, with a significant difference using the one-way ANOVA test (P<0.05) ([Figure 1] and [Figure 2]).{Figure 1}{Figure 2}

As regards oxygen saturation, the results documented that there were no significant differences neither inside each group after and before initiation of OLV using the paired t-test (P>0.05) nor among the study groups at all time intervals using the one-way ANOVA test (P>0.05) ([Table 2]).{Table 2}

Respiratory mechanical parameters

Peak and plateau airway pressures were increased dramatically in all study groups after initiation of OLV at T1 when compared with baseline readings at T0, with a significant difference using the paired t-test (P<0.05) ([Figure 3] and [Figure 4]). This increase was maintained throughout OLV in group C but was declined in both the SRM and RRM groups after application of RM without reaching the baseline readings from T2 to T4, with a significant difference when compared with group C (P<0.05). At T5, peak and plateau pressures started to increase again in the SRM group compared with the RRM group, with a significant difference in between the two groups using the one-way ANOVA test ([Figure 3] and [Figure 4]).{Figure 3}{Figure 4}

As regards static lung compliance, the results showed that there was a sudden decrease in all study groups after initiation of OLV at T1 compared with the baseline values at T0, with a significant difference using the paired t-test (P<0.05) ([Table 3]). However, it started to increase again in both the SRM and RRM groups after application of RM, while stayed low in the control group (groupC) during the whole study, with a significant difference among the groups using the one-way ANOVA test (P<0.05). At T5, the compliance declined again in the SRM group, whereas it remained high in the RRM group, with a significant difference when compared together (P<0.05) ([Table 3]).{Table 3}

Hemodynamic parameters

The results of current study showed that there was no significant difference among the study groups in terms of MAP, HR, or central venous pressure using the one-way ANOVA test (P>0.05) ([Table 4],[Table 5],[Table 6]). Moreover, there was no significant difference within each study group before and after application of RM using the paired t-test ([Table 4],[Table 5],[Table 6]).{Table 4}{Table 5}{Table 6}

Postoperative complications

In terms of postoperative complications (hypoxia, infection, or pneumothorax), this study documented that there was no significant difference between the study groups using the one-way ANOVA test (P>0.05).

 Discussion



Efficacy of the recruitment maneuver

Intraoperative hypoxemia (SaO2<90% or PaO2<60 mmHg) during OLV is considered a major concern and a great challenge for the anesthesiologist [20]. Recently, because of improvements in anesthetic and lung isolation techniques, together with the use of recent anesthetic drugs with minimal effects on hypoxic pulmonary vasoconstriction, the incidence of intraoperative hypoxemia was decreased to 1% [21]. Intraoperative hypoxemia during OLV is mostly due to atelectasis, which causes a ventilation/perfusion mismatch and a left-to-right shunt [22]. This OLV-induced atelectasis could be reversed or prevented using alveolar RM, as evidenced from previous studies [23],[24].

The current study showed that application of cycling RM, followed by 10 mmHg PEEP, effectively increased the intraoperative PaO2 and PaO2/FiO2 ratio during OLV in both the SRM and RRM groups when compared with standard ventilation protocol in group C. This improvement was sustained until 45 min after initiation of OLV and then decreased again in the SRM group, whereas it sustained high in the RRM group. After restoration of TLV, the values of both PaO2 and PaO2/FiO2 were raised up to levels before initiation of OLV.

This study demonstrated that there was no difference in peripheral oxygen saturation among the study groups (P>0.05) despite the changes in both PaO2 and PaO2/FiO2 ratio. This can be explained by the plateau of oxyhemoglobin dissociation curve near 100% saturation.

In the present study, there was a significant increase in both peak and plateau pressures in all groups immediately after initiation of OLV. However, after application of RM, they started to decrease gradually in both the SRM and RRM groups with a significant difference when compared with group C (P<0.05). This improvement was temporary until 45 min after RM in the SRM group, whereas maintained throughout OLV in the RRM group, with a significant difference (P<0.05). These changes in airway pressures were associated with changes in static lung compliance among the study groups. The compliance was decreased in all groups after starting OLV and then began to improve after application of RM in both the SRM and RRM groups with a significant difference when compared with the control group (P<0.05). This improvement was temporary in the SRM group for 45 min only, whereas it remained high in the RRM group with a significant difference (P<0.05).

A previous study by Slinger [25] recommended to keep both plateau and peak airway pressure below 25 and 35 cmH2O, respectively, to minimize the risk for lung injury. In our study, these pressures were below the recommended values during OLV; this can explain why we did not detect any evidence of significant lung injury on postoperative chest radiographs.

The results of our study are in accordance with the results of a recent randomized study by Unzueta et al. [26], who showed that application of RM was associated with improvement in arterial oxygenation and decreases in dead space in patients undergoing OLV. In another prospective randomized study, application of cycling RM in the dependent lung with driving pressure (Paw-Pplat)/PEEP of 40/20 cmH2O for 12 min in patients undergoing open lung surgery was associated with increased PaO2 and compliance during OLV in the treated group compared with the control group [27].

These results are in agreement with the results of a recent study that investigated the effects of pre-emptive alveolar recruitment strategy on arterial oxygenation during OLV with different tidal volumes in patients undergoing wedge resection with video-assisted thoracostomy and concluded that pre-emptive alveolar recruitment strategy together with low tidal volume and 8 cmH2O PEEP can improve arterial oxygenation and static lung compliance without increasing the risk for lung injury [28]. In contrast with our study, in another study conducted on 41 patients undergoing thoracic procedures with OLV, the authors found that application of PEEP 5 and 10 cmH2O sequentially failed to improve arterial oxygenation when compared with pre-PEEP values [29]. This difference can be explained by the small sample size for that study.

The results of our study are in agreement with many other studies that showed a decreasing trend in Paw-peak and Paw-plat as well as increased lung compliance after successful alveolar recruitment [30],[31],[32]. However, Hedenstierna and Tenling [33] observed that there were no significant differences as regards Paw-peak and Paw-plat after alveolar RM with a peak inspiratory pressure of 40 cmH2O and a PEEP of 20 cmH2O during OLV at a 8 ml/kg tidal volume and a 5 cmH2O PEEP, but they did observe a significant reduction in the static respiratory elastance. This can be attributed to the fact that, in our study, the RM was performed in a stepwise manner and was gradual.

Safety of the recruitment maneuver

The hemodynamic tolerance is related to the patient’s preload status and is rarely a problem in normovolemic patients. We found that the use of either single or repeated cycling RM was associated neither with hemodynamic impairment nor with higher intraoperative fluid requirements. Our results are in agreement with the results of another study that investigated the effects of single versus repeated vital capacity maneuver on arterial oxygenation and compliance in obese patients undergoing laparoscopic bariatric surgery, and the authors concluded that there were no significant differences between the groups in terms of HR and MAP throughout the study [34]. In contrast with our study, Jauncey-Cooke et al. [35] recorded that a RM was associated with harmful hemodynamic effects that were justified by high PEEP that decreased the venous return and consequently decreased the blood pressure that responded well to fluid boluses. This study demonstrated that there was no significant difference among the three study groups in the PACU as regards arterial oxygenation and chest radiographs for atelectasis, infection, or pneumothorax. These results were also confirmed by some other studies [36],[37].

 Conclusion



Primarily in patients with normal preoperative lung function we found that application of either single or repeated cycling RM was associated with improved intraoperative arterial oxygenation and hemodynamic stability. In addition, there was no significant difference as regards postoperative pulmonary complications among the study groups.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

1Plummer S, Hartley M, Vaughan RS. Anaesthesia for telescopic procedures in the thorax. Br J Anaesth 1998; 80:223–234.
2Szegedi LL. Pathophysiology of one-lung ventilation. Anesthesiol Clin N Am 2001; 19:435–453.
3Gale JW, Waters RM. Closed endobroncheal anesthesia in thoracic surgery: preliminary report. J Thorac Surg 1932; 1:432–437.
4Ost D. Independent lung ventilation. Clin Chest Med 1996; 17:591–601.
5Lesser T, Schubert H, Klinzing S. Determination of the side separated pulmonary right-to-left shunt volume. J Med Invest 2008; 55:44–50.
6Schwarzkopf K, Schreiber T, Preussler NP, Gaser E, Huter L, Bauer R et al. Lung perfusion, shunt fraction, and oxygenation during one lung ventilation in pigs: the effects of desflurane, isoflurane, and propofol. J Cardiothorac Vasc Anesth 2003; 17:73–75.
7Ishikawa S, Losher J. One-lung ventilation and arterial oxygenation. Curr Opin Anesth 2011; 24:24–31.
8Tusman G, Belda JF. Treatment of anesthesia- induced lung collapse with lung recruitment maneuvers Curr Anaesth Crit Care 2010; 21:244–249.
9Kozian A, Schilling T, Schutze H, Senturk M, Hachenberg T, Hedenstierna G. Effects of alveolar maneuver and low-tidal volume ventilation on lung density distribution. Anesthesiology 2011; 114:1009–1010.
10Karzai W, Schwarzkoph K. Hypoxemia during one-lung ventilation: prediction, prevention and treatment. Anesthesiology 2009; 110:1402–1411.
11Brodsky JB, Fitzmaurice B. Modern anesthetic techniques for thoracic operations. World J Surg 2001; 25:162–166.
12Licker M, Diaper J, Villiger Y, Spiliopoulos A, Licker V, Robert J, Tschopp JM. Impact of intraoperative lung-protective interventions in patients undergoing lung cancer surgery. Crit Care 2009; 13:R41.
13Kozian A, Schilling T, Rocken C, Breitling C, Hachenberg T, Hedenstierna G. Increased alveolar damage after mechanical ventilation in a porcine model of thoracic surgery. J Cardiothorac Vasc Anesth 2010; 24:617–623.
14Schilling T, Kozian A, Huth C, Buhling F, Kretzschmar M, Welte T, Hachenberg T. The pulmonary immune effects of mechanical ventilation in patients undergoing thoracic surgery. Anesth Analg 2005; 101:957–965.
15Fernandez- Perez ER, Keegan MT, Brown DR, Hubmayr RD, Gajic O. Intraoperative tidal volume as a risk factor for respiratory failure after pneumonectomy. Anesthesiology 2006; 105:14–18.
16Tusman G, Bohm S, Suarez-Sipmann F. Alveolar recruitment maneuvers for one-lung ventilation during thoracic anesthesia. Curr Anesthesiol Rep 2014; 4:160–169.
17Lachman B. Open up the lung and keep the lungs open. Intensive Care Med 1992; 18:319–321.
18Rothen HU, Sporre B, Engberg G, Wegenius G, Hedenstiema G. Reexpansion and atelectasis during general anaesthesia: a computed tomography study. Br J Anaesth 1993; 71:788–795.
19Rothen HU, Sporre B, Engberg G, Wegenius G, Hedenstiema G. Reexpansion of atelectasis during general anesthesia may have a prolonged effect. Acta Anesthesiol Scand 1995; 39:118–125.
20Karzai W, Schwarzkopf K. Hypoxemia during one-lung ventilation: prediction, prevention, and treatment. Anesthesiology 2009; 110:1402–1411.
21Brodsky JB, Lemmens HJ. Left double-lumen tubes: clinical experience with 1170 patients. J Cardiothorac Vasc Anesth 2003; 17:289–298.
22Dunn PF. Physiology of the lateral decubitus position and one-lung ventilation. Int Anesthesiol Clin 2000; 38:25–53.
23Lapinsky SE, Mehta S. Bench-to-bedside review: recruitment and recruiting maneuvers. Crit Care 2005; 9:60–65.
24Maggiore SM, Lellouche F, Pigeot J, Taille S, Deye N, Durrmeyer X et al. Prevention of endotracheal suctioning-induced alveolar derecruitment in acute lung injury. Am J Respir Crit Care Med 2003; 167:1215–1224.
25Slinger P. Pro: low tidal volume is indicated during one-lung ventilation. Anesth Analg 2006; 103:268–270.
26Unzueta C, Tusman G, Suarez-Sipmann F, Bohm SH, Moral V. Alveolar recruitment improves ventilation during thoracic surgery: a randomized controlled trial. Br J Anaesth 2012; 108:517–524.
27Park SH, Jeon YT, Hwang JH, Park HP. A preemptive alveolar recruitment strategy before one-lung ventilation improves arterial oxygenation in patients undergoing thoracic surgery: a prospective randomized study. Eur J Anaesthesiol 2011; 28:298–302.
28Jung JD, Kim SH, Yu BS, Kim HJ. Effects of a preemptive alveolar recruitment strategy on arterial oxygenation during one-lung ventilation with different tidal volumes in patients with normal pulmonary function test. Korean J Anesthesiol 2014; 67:96–102.
29Hoftman N, Canales C, Leduc M, Mahajan A. Positive end expiratory pressure during one-lung ventilation: selecting ideal patients and ventilator settings with the aim of improving arterial oxygenation. Ann Card Anaesth 2011; 14:183–187.
30Cinnella G, Grasso S, Natale C, Sollitto F, Cacciapaglia M, Angiolollo M et al. Physiological effects of a lung-recruiting strategy applied during one-lung ventilation. Acta Anesthesiol Scand 2008; 52:766–775.
31Park SH, Jeon YT, Hwang JW, Do SH, Park HP. A preemptive alveolar recruitment strategy before one-lung ventilation improves arterial oxygenation in patients undergoing thoracic surgery: a prospective randomised study. Eur J Anesthesiol 2011; 28:298–302.
32Kozian A, Schilling T, Schutze H, Senturk M, Hachenberg T, Hedenstierna G. Ventilatory protective strategies during thoracic surgery: effects of alveolar recruitment maneuver and low-tidal volume ventilation on lung density distribution. Anesthesiology 2011; 114:1025–1035.
33Hedenstierna G, Tenling A. The lung during and after thoracic anesthesia. Curr Opin Anesthesiol 2005; 18:23–28.
34Ahmed WG, Abu-Elnasr NE, Ghoneim SH. The effects of single vs. repeated vital capacity maneuver on arterial oxygenation and compliance in obese patients presenting for laparoscopic bariatric surgery. Ain Sham J Anesthesiol 2012; 5-1:121–132.
35Jauncey-Cooke JI, Bogossian F, East CE. Lung recruitment − a guide for clinicians. Aust Crit Care 2009; 22:155–162.
36Sprung J, Whalen FX, Comfere T, Bonsnjak ZJ, Bajzer Z, Gajic O et al. Alveolar recruitment and arterial desflurane concentration during bariatric surgery. Anesth Anal 2009; 107:120–127.
37Weingarten TN, Whalen FX, Warner DO, Gajic O, Schears GJ, Snyder MR et al. Comparison of two ventilatory strategies in elderly patients undergoing major abdominal surgery. BJA 2010; 104:16–22.