Ultrasound-guided versus conventional lung recruitment manoeuvres in thoracic surgery: a randomised controlled study

Lung recruitment manoeuvres (RMs) during mechanical ventilation may reduce atelectasis, however, the optimal recruitment strategy for patients undergoing thoracic surgery remains unknown. Our study was designed to investigate whether ultrasound-guided lung RMs is superior to conventional RMs in reducing perioperative atelectasis during thoracic surgery with one-lung ventilation. We conducted a randomised controlled clinical trial from August 2022 to September 2022. Sixty patients scheduled for video-assisted thoracoscopic surgery (VATS) under general anaesthesia were enrolled. Subjects were randomly divided into the ultrasound-guided RMs group (manual inflation guided by lung ultrasound) or conventional RMs group (manual inflation with 30 cmH2O pressure). Lung ultrasound were performed at three predefined time points (1 min after anaesthetic induction; after RMs at the end of surgery; before discharge from postanesthesia care unit [PACU]). The primary outcome was lung ultrasound score before discharge from the PACU after extubation. In the early postoperative period, lung aeration deteriorated in both groups even after lung RMs. However, ultrasound-guided lung RMs had significantly lower lung ultrasound scores when compared with conventional RMs in bilateral lungs (2.0 [0.8-4.0] vs. 8.0 [3.8-10.3], P < 0.01) at the end of surgery, which remained before patients discharged from the PACU. Accordingly, the lower incidence of atelectasis was found in ultrasound-guided RMs group than in conventional RMs group (7% vs. 53%; P < 0.01) at the end of surgery. Ultrasound-guided RMs is superior to conventional RMs in improving lung aeration and reducing the incidence of lung atelectasis at early postoperative period in patients undergoing VATS. The study protocol was approved by the Institutional Review Board of the Fudan University Shanghai Cancer Center (No. 220,825,810; date of approval: August 5, 2022) and registered on Chinese Clinical Trial Registry (registration number: ChiCTR2200062761).

One-Lung Ventilation and Postoperative Pulmonary Complications After Major Lung Resection Surgery. A Multicenter Randomized Controlled Trial

OBJECTIVES

The effect of one-lung ventilation (OLV) strategy based on low tidal volume (TV), application of positive end-expiratory pressure (PEEP), and alveolar recruitment maneuvers (ARM) to reduce postoperative acute respiratory distress syndrome (ARDS) and pulmonary complications (PPCs) compared with higher TV without PEEP and ARM strategy in adult patients undergoing lobectomy or pneumonectomy has not been well established.

DESIGN

Multicenter, randomized, single-blind, controlled trial.

SETTING

Sixteen Italian hospitals.

PARTICIPANTS

A total of 880 patients undergoing elective major lung resection.

INTERVENTIONS

Patients were randomized to receive lower tidal volume (LTV group: 4 mL/kg predicted body weight, PEEP of 5 cmH2O, and ARMs) or higher tidal volume (HTL group: 6 mL/kg predicted body weight, no PEEP, and no ARMs). After OLV, until extubation, both groups were ventilated using a tidal volume of 8 mL/kg and a PEEP value of 5 cmH2O. The primary outcome was the incidence of in-hospital ARDS. Secondary outcomes were the in-hospital rate of PPCs, major cardiovascular events, unplanned intensive care unit (ICU) admission, in-hospital mortality, ICU length of stay, and in-hospital length of stay.

MEASUREMENTS AND MAIN RESULTS

ARDS occurred in 3 of 438 patients (0.7%, 95% CI 0.1-2.0) and in 1 of 442 patients (0.2%, 95% CI 0-1.4) in the LTV and HTV group, respectively (Risk ratio: 3.03 95% CI 0.32-29, p = 0.372). Pulmonary complications occurred in 125 of 438 patients (28.5%, 95% CI 24.5-32.9) and in 136 of 442 patients (30.8%, 95% CI 26.6-35.2) in the LTV and HTV group, respectively (risk ratio: 0.93, 95% CI 0.76-1.14, p = 0.507). The incidence of major complications, in-hospital mortality, and unplanned ICU admission, ICU and in-hospital length of stay were comparable in both groups.

CONCLUSIONS

In conclusion, among adult patients undergoing elective lung resection, an OLV with lower tidal volume, PEEP 5 cmH2O, and ARMs and a higher tidal volume strategy resulted in low ARDS incidence and comparable postoperative complications, in-hospital length of stay, and mortality.

Effect of permissive hypercarbia on lung oxygenation during one-lung ventilation and postoperative pulmonary complications in patients undergoing thoracic surgery: A prospective randomised controlled trial

BACKGROUND

The effect of hypercarbia on lung oxygenation during thoracic surgery remains unclear.

OBJECTIVE

To investigate the effect of hypercarbia on lung oxygenation during one-lung ventilation in patients undergoing thoracic surgery and evaluate the incidence of postoperative pulmonary complications.

DESIGN

Prospective randomised controlled trial.

SETTING

A tertiary university hospital in the Republic of Korea from November 2019 to December 2020.

PATIENTS

Two hundred and ninety-seven patients with American Society of Anaesthesiologists physical status II to III, scheduled to undergo elective lung resection surgery.

INTERVENTION

Patients were randomly assigned to Group 40, 50, or 60. An autoflow ventilation mode with a lung protective ventilation strategy was applied to all patients. Respiratory rate was adjusted to maintain a partial pressure of arterial carbon dioxide of 40 ± 5 mmHg in Group 40, 50 ± 5 mmHg in Group 50 and 60 ± 5 mmHg in Group 60 during one-lung ventilation and at the end of surgery.

MAIN OUTCOME MEASURES

The primary outcome was the arterial oxygen partial pressure/fractional inspired oxygen ratio after 60 min of one-lung ventilation.

RESULTS

Data from 262 patients were analysed. The partial pressure/fractional inspired oxygen ratio was significantly higher in Group 50 and Group 60 than in Group 40 (269.4 vs. 262.9 vs. 214.4; P  < 0.001) but was not significantly different between Group 50 and Group 60. The incidence of postoperative pulmonary complications was comparable among the three groups.

CONCLUSION

Permissive hypercarbia improved lung oxygenation during one-lung ventilation without increasing the risk of postoperative pulmonary complications or the length of hospital stay.

TRIAL REGISTRATION

NCT04175379.

Ventilation during Lung Resection and Critical Care: Comparative Clinical Outcomes

Recent evidence suggests that outcomes do not meaningfully differ between thoracic surgery patients who are ventilated with a low or higher tidal volume and the effects of low versus higher positive end-expiratory pressure are unclear.

Clinical guide to perioperative management for videothoracoscopy lung resection (Section of Cardiac, Vascular and Thoracic Anesthesia, SEDAR; Spanish Society of Thoracic Surgery, SECT; Spanish Society of Physiotherapy)

The introduction of video-assisted thoracoscopic (VATS) techniques has led to a new approach in thoracic surgery. VATS is performed by inserting a thoracoscope through a small incisions in the chest wall, thus maximizing the preservation of muscle and tissue. Because of its low rate of morbidity and mortality, VATS is currently the technique of choice in most thoracic procedures. Lung resection by VATS reduces prolonged air leaks, arrhythmia, pneumonia, postoperative pain and inflammatory markers. This reduction in postoperative complications shortens hospital length of stay, and is particularly beneficial in high-risk patients with low tolerance to thoracotomy. Compared with conventional thoracotomy, the oncological results of VATS surgery are similar or even superior to those of open surgery. This aim of this multidisciplinary position statement produced by the thoracic surgery working group of the Spanish Society of Anesthesiology and Reanimation (SEDAR), the Spanish Society of Thoracic Surgery (SECT), and the Spanish Association of Physiotherapy (AEF) is to standardize and disseminate a series of perioperative anaesthesia management guidelines for patients undergoing VATS lung resection surgery. Each recommendation is based on an in-depth review of the available literature by the authors. In this document, the care of patients undergoing VATS surgery is organized in sections, starting with the surgical approach, and followed by the three pillars of anaesthesia management: preoperative, intraoperative, and postoperative anaesthesia.

The role of mechanical ventilation in primary graft dysfunction in the postoperative lung transplant recipient: A single center study and literature review

Background

Primary graft dysfunction (PGD) is still a major complication in patients undergoing lung transplantation (LTx). Much is unknown about the effect of postoperative mechanical ventilation on outcomes, with debate on the best approach to ventilation.

Aim/Purpose

The goal of this study was to generate hypotheses on the association between postoperative mechanical ventilation settings and allograft size matching in PGD development.

Method

This is a retrospective study of LTx patients between September 2011 and September 2018 (n = 116). PGD was assessed according to the International Society of Heart and Lung Transplantation (ISHLT) criteria. Data were collected from medical records, including chest x‐ray assessments, blood gas analysis, mechanical ventilator parameters and spirometry.

Results

Positive end‐expiratory pressures (PEEP) of 5 cm H₂O were correlated with lower rates of grade 3 PGD. Graft size was important as tidal volumes calculated according to the recipient yielded greater rates of PGD when low volumes were used, a correlation that was lost when donor metrics were used.

Conclusion

Our results highlight a need for greater investigation of the role donor characteristics play in determining post‐operative ventilation of a lung transplant recipient. The mechanical ventilation settings on postoperative LTx recipients may have an implication for the development of acute graft dysfunction. Severe PGD was associated with the use of a PEEP higher than 5 and lower tidal volumes and oversized lungs were associated with lower long‐term mortality. Lack of association between ventilatory settings and survival may point to the importance of other variables than ventilation in the development of PGD.

Recommendations of the Society of Thoracic Surgery and the Section of Cardiothoracic and Vascular Surgery of the Spanish Society of Anesthesia, Resuscitation and Pain Therapy, for patients undergoing lung surgery included in an intensified recovery program

In recent years, multidisciplinary programs have been implemented that include different actions during the pre, intra and postoperative period, aimed at reducing perioperative stress and therefore improving the results of patients undergoing surgical interventions. Initially, these programs were developed for colorectal surgery and from there they have been extended to other surgeries. Thoracic surgery, considered highly complex, like other surgeries with a high postoperative morbidity and mortality rate, may be one of the specialties that most benefit from the implementation of these programs. This review presents the recommendations made by different specialties involved in the perioperative care of patients who require resection of a lung tumor. Meta-analyzes, systematic reviews, randomized and non-randomized controlled studies, and retrospective studies conducted in patients undergoing this type of intervention have been taken into account in preparing the recommendations presented in this guide. The GRADE scale has been used to classify the recommendations, assessing on the one hand the level of evidence published on each specific aspect and, on the other hand, the strength of the recommendation with which the authors propose its application. The recommendations considered most important for this type of surgery are those that refer to pre-habilitation, minimization of surgical aggression, excellence in the management of perioperative pain and postoperative care aimed at providing rapid postoperative rehabilitation.

Clinical guide to perioperative management for videothoracoscopy lung resection (Section of Cardiac, Vascular and Thoracic Anesthesia, SEDAR; Spanish Society of Thoracic Surgery, SECT; Spanish Society of Physiotherapy)

The introduction of video-assisted thoracoscopic (VATS) techniques has led to a new approach in thoracic surgery. VATS is performed by inserting a thoracoscope through a small incisions in the chest wall, thus maximizing the preservation of muscle and tissue. Because of its low rate of morbidity and mortality, VATS is currently the technique of choice in most thoracic procedures. Lung resection by VATS reduces prolonged air leaks, arrhythmia, pneumonia, postoperative pain and inflammatory markers. This reduction in postoperative complications shortens hospital length of stay, and is particularly beneficial in high-risk patients with low tolerance to thoracotomy. Compared with conventional thoracotomy, the oncological results of VATS surgery are similar or even superior to those of open surgery. This aim of this multidisciplinary position statement produced by the thoracic surgery working group of the Spanish Society of Anesthesiology and Reanimation (SEDAR), the Spanish Society of Thoracic Surgery (SECT), and the Spanish Association of Physiotherapy (AEF) is to standardize and disseminate a series of perioperative anaesthesia management guidelines for patients undergoing VATS lung resection surgery. Each recommendation is based on an in-depth review of the available literature by the authors. In this document, the care of patients undergoing VATS surgery is organized in sections, starting with the surgical approach, and followed by the three pillars of anaesthesia management: preoperative, intraoperative, and postoperative anaesthesia.

Recommendations of the Society of Thoracic Surgery and the Section of Cardiothoracic and Vascular Surgery of the Spanish Society of Anesthesia, Resuscitation and Pain Therapy, for patients undergoing lung surgery included in an intensified recovery program

In recent years, multidisciplinary programs have been implemented that include different actions during the pre, intra and postoperative period, aimed at reducing perioperative stress and therefore improving the results of patients undergoing surgical interventions. Initially, these programs were developed for colorectal surgery and from there they have been extended to other surgeries. Thoracic surgery, considered highly complex, like other surgeries with a high postoperative morbidity and mortality rate, may be one of the specialties that most benefit from the implementation of these programs. This review presents the recommendations made by different specialties involved in the perioperative care of patients who require resection of a lung tumor. Meta-analyses, systematic reviews, randomized and non-randomized controlled studies, and retrospective studies conducted in patients undergoing this type of intervention have been taken into account in preparing the recommendations presented in this guide. The GRADE scale has been used to classify the recommendations, assessing on the one hand the level of evidence published on each specific aspect and, on the other hand, the strength of the recommendation with which the authors propose its application. The recommendations considered most important for this type of surgery are those that refer to pre-habilitation, minimization of surgical aggression, excellence in the management of perioperative pain and postoperative care aimed at providing rapid postoperative rehabilitation.

Recruitment maneuvers in patients undergoing thoracic surgery: a meta-analysis

OBJECTIVE

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 thoracic surgery. This meta-analysis of randomized controlled trials (RCTs) is to evaluate the effectiveness and safety of recruitment maneuvers in patients undergoing thoracic surgery.

METHODS

We performed a literature search on the PubMed, Embase, and Cochrane Library databases and the ClinicalTrials.gov registry for trials published before April 2021. We investigated postoperative pulmonary atelectasis incidence, intrapulmonary shunt fraction, static lung compliance, and mean arterial pressure.

RESULTS

Six RCTs involving 526 patients were reviewed. Patients receiving a recruitment maneuver exhibited a significant decrease in intrapulmonary shunt fraction [weighted mean difference (WMD) - 0.02, 95% CI - 0.03 to - 0.01], improved static lung compliance (WMD 2.16; 95% CI 1.14-3.18), and PaO₂/FIO₂ ratio (WMD 31.31; 95% CI 12.11-50.52) without a significant difference in mean arterial pressure (WMD - 0.64; 95% CI - 4.92 to 3.64). The incidence pulmonary atelectasis favored recruitment maneuver group, but was not statistically significant (RR 0.55; 95% CI 0.27-1.12).

CONCLUSIONS

Recruitment maneuvers may be a viable treatment for reducing intra-pulmonary shunt and improving static lung compliance and PaO₂/FIO₂ ratio without the disturbance of hemodynamics in patients undergoing thoracic surgery.

[Intraoperative Ventilation Approaches to One-lung Ventilation]

The management of thoracic surgery patients is challenging to the anesthetist, since one-lung ventilation (OLV) includes at least two major conditions: sufficient oxygenation and lung protection. The first is mainly because the ventilation of one lung is stopped while perfusion to that lung continues; the latter is related to the fact that the whole ventilation is applied to only a single lung. Recommendations for maintaining the oxygenation and methods of lung protection may contradict each other (e. g. high vs. low inspiratory oxygen fraction (FiO₂), high vs. low tidal volume, etc.). Therefore, a high degree of pathophysiological understanding and manual skills are required in the management of these patients.In light of recent clinical studies, this review focuses on a current protective strategy for OLV, which includes a possible decrease in FiO₂, lowered V_T, the application of positive end-expiratory pressure (PEEP) to the dependent and continuous positive airway pressure (CPAP) to the non-dependent lung and alveolar recruitment manoeuvres as well. Other approaches such as the choice of anaesthetics, remote ischemic preconditioning, fluid management and pain therapy can support the success of ventilatory strategy. The present work describes new developments that may change the classical approach in this respect.

Protective mechanical ventilation with optimal PEEP during RARP improves oxygenation and pulmonary indexes

BACKGROUND

This trial aimed to evaluate the effects of a protective ventilation strategy on oxygenation/pulmonary indexes in patients undergoing robot-assisted radical prostatectomy (RARP) in the steep Trendelenburg position.

METHODS

In phase 1, the most optimal positive end-expiratory pressure (PEEP) was determined in 25 patients at 11 cmH₂O. In phase 2, 64 patients were randomized to the traditional ventilation group with tidal volume (VT) of 9 ml/kg of predicted body weight (PBW) and the protective ventilation group with VT of 7 ml/kg of PBW with optimal PEEP and recruitment maneuvers (RMs). The primary endpoint was the intraoperative and postoperative PaO₂/FiO₂. The secondary endpoints were the PaCO₂, SpO₂, modified clinical pulmonary infection score (mCPIS), and the rate of complications in the postoperative period.

RESULTS

Compared with controls, PaO₂/FiO₂ in the protective group increased after the second RM (P=0.018), and the difference remained until postoperative day 3 (P=0.043). PaCO₂ showed transient accumulation in the protective group after the first RM (T2), but this phenomenon disappeared with time. SpO₂ in the protective group was significantly higher during the first three postoperative days. Lung compliance was significantly improved after the second RM in the protective group (P=0.025). The mCPIS was lower in the protective group on postoperative day 3 (0.59 (1.09) vs. 1.46 (1.27), P=0.010).

CONCLUSION

A protective ventilation strategy with lower VT combined with optimal PEEP and RMs could improve oxygenation and reduce mCPIS in patients undergoing RARP.

TRIAL REGISTRATION

ChiCTR ChiCTR1800015626 . Registered on 12 April 2018.

Repeated intermittent hypoxic stimuli to operative lung reduce hypoxemia during subsequent one-lung ventilation for thoracoscopic surgery: A randomized controlled trial

Background

An intervention to potentiate hypoxic pulmonary vasoconstriction may reduce intrapulmonary shunt and hypoxemia during one-lung ventilation. Previous animal studies reported that repeated intermittent hypoxic stimuli potentiated hypoxic pulmonary vasoconstriction, but no clinical study has examined the effects of this intervention on hypoxemia during one-lung ventilation. We thus performed a single-center, parallel-group, double-blind, randomized controlled trial to investigate whether repeated intermittent hypoxic stimuli to the operative lung reduce hypoxemia during the subsequent one-lung ventilation for thoracoscopic surgery.

Methods

Patients undergoing one-lung ventilation were randomized into two groups (n = 68 each). Before one-lung ventilation, in the intermittent hypoxia group, the nondependent lung was not ventilated for 2 min and then ventilated for 2 min while the dependent lung was continuously ventilated. This was repeated five times. In the continuous normoxia group, both lungs were ventilated for 20 min. We measured SpO₂, PaO₂, FiO₂, PaCO₂, SaO₂, and central venous oxygen saturation during one-lung ventilation. The primary outcome was the number of patients with hypoxemia defined as a SpO₂ <95% during one-lung ventilation, which was analyzed with a chi-squared test.

Results

Hypoxemia was less frequent in the intermittent hypoxia group than in the continuous normoxia group during OLV [6/68 (8.8%) vs 17/68 (25.0%), risk ratio (95% CI) 0.35 (0.15–0.84), p = 0.012]. The PaO₂ (p = 0.008 for 30 min and 0.007 for 60 min) and PaO₂/FiO₂ (p = 0.008 for both) were higher 30 and 60 min after starting one-lung ventilation, and the alveolar-arterial pressure gradient (p = 0.010) and shunt index (p = 0.008) were lower 30 min after starting one-lung ventilation in the intermittent hypoxia group than in the continuous normoxia group. Postoperative adverse events did not differ significantly between groups.

Conclusions

Repeated intermittent hypoxic stimuli to the operative lung seemed to potentiate hypoxic pulmonary vasoconstriction, and thus reduced hypoxemia during the subsequent one-lung ventilation.

Guidelines on enhanced recovery after pulmonary lobectomy

OBJECTIVE

To establish recommendations for optimisation of the management of patients undergoing pulmonary lobectomy, particularly Enhanced Recovery After Surgery (ERAS).

DESIGN

A consensus committee of 13 experts from the French Society of Anaesthesia and Intensive Care Medicine (Soci,t, franOaise d'anesth,sie et de r,animation, SFAR) and the French Society of Thoracic and Cardiovascular Surgery (Soci,t, franOaise de chirurgie thoracique et cardiovasculaire, SFCTCV) was convened. A formal conflict-of-interest policy was developed at the onset of the process and enforced throughout. The entire guidelines process was conducted independently of any industry funding. The authors were advised to follow the principles of the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system to guide assessment of quality of evidence.

METHODS

Five domains were defined: 1) patient pathway and patient information; 2) preoperative management and rehabilitation; 3) anaesthesia and analgesia for lobectomy; 4) surgical strategy for lobectomy; and 5) enhanced recovery after surgery. For each domain, the objective of the recommendations was to address a number of questions formulated according to the PICO model (Population, Intervention, Comparison, Outcome). An extensive literature search on these questions was carried out and analysed using the GRADE® methodology. Recommendations were formulated according to the GRADE® methodology, and were then voted by all experts according to the GRADE grid method.

RESULTS

The SFAR/SFCTCV guideline panel provided 32 recommendations on the management of patients undergoing pulmonary lobectomy. After two voting rounds and several amendments, a strong consensus was reached for 31 of the 32 recommendations and a moderate consensus was reached for the last recommendation. Seven of these recommendations present a high level of evidence (GRADE 1+), 23 have a moderate level of evidence (18 GRADE 2+ and 5 GRADE 2-), and 2 correspond to expert opinions. Finally, no recommendation was provided for 2 of the questions.

CONCLUSIONS

A strong consensus was expressed by the experts to provide recommendations to optimise the whole perioperative management of patients undergoing pulmonary lobectomy.

Intraoperative Anesthetic Management of the Thoracic Patient

The intraoperative anesthetic management for thoracic surgery can impact a patient's postoperative course, especially in patients with significant lung disease. One-lung ventilation poses an inherent risk to patients, including hypoxemia, acute lung injury, and right ventricular dysfunction. Patient-specific ventilator management strategies during one-lung ventilation can reduce postoperative morbidity.

CPAP Effects on Oxygen Delivery in One-Lung Ventilation During Minimally Invasive Surgical Ablation for Atrial Fibrillation in The Supine Position

OBJECTIVE

In minimally invasive surgical ablation for atrial fibrillation during video-assisted thoracoscopy surgery, one-lung ventilation (OLV) with a double- lumen tube is commonly employed. In contrast with the majority of thoracic procedures, the patient lies supine; thus, the protective effect of gravity is lost and intrapulmonary shunt remains high. To decrease intrapulmonary shunt and to increase oxygenation, many strategies are utilized: high inspiratory fraction of oxygen (F_IO₂), positive end-expiratory pressure on the ventilated lung, and continuous positive airway pressure (CPAP) on the deflated lung.

DESIGN

The authors performed a prospective, single- center, randomized study to evaluate the effect of additional CPAP in the nonventilated lung on oxygen delivery during surgical ablation for atrial fibrillation via video-assisted thoracoscopy in the supine position.

SETTING

University hospital Centro Cardiologico Monzino IRCCS, Milano, Italy.

PARTICIPANTS

Twenty-two patients scheduled for minimally invasive surgical ablation for atrial fibrillation.

INTERVENTIONS

The patients underwent pressure-controlled ventilation, adjusting inspiratory pressure to obtain a tidal volume of 7 mL/kg while keeping F_IO₂ constantly 1.0, a respiratory rate to maintain arterial partial pressure of carbon dioxide (PaCO₂) between 35 and 40 mmHg, and positive end-expiratory pressure of 5 cmH₂O. During OLV, inspiratory pressure was reduced to obtain a tidal volume of 5 mL/kg, maintaining F_IO₂ of 1.0, a respiratory rate to maintain PaCO₂ between 35 and 40 mmHg with capnothorax of 10 cmH₂O. The patients were then randomized into the CPAP group (CPAP 10 cmH₂0 on deflated lung) and NO CPAP group. Inotropic agents (dopamine or dobutamine) were used if cardiac index fell below 1.5 L/min/m².

MEASUREMENTS AND MAIN RESULTS

Twenty-two patients were enrolled, randomized, and completed the study. Median age was 62 years. The difference in arterial partial pressure of oxygen between the 2 groups was shy of significance, p = 0.16. Cardiac index progressively increased during OLV until the end of the procedure in both groups (p < 0.01) and was maintained above 1.5 mL/min/m² during the whole study time. Arterial oxygen content remained stable during the entire procedure in both groups (p = 0.27). Oxygen delivery index (DO₂I) increased significantly during the procedure (p < 0.01); nevertheless, the difference in DO₂I between the CPAP and NO CPAP group was nonsignificant (p = 0.61). Intrapulmonary shunt (Q_s/Q_t) increased during OLV (p < 0.01 for the time effect) and remained high until total lung ventilation was reintroduced. No difference in Q_s/Q_t was observed between the CPAP and NO CPAP groups (p = 0.98). Similarly, mean pulmonary artery pressure increased significantly during OLV and remained high at the end of the procedure in both groups (time effect p < 0.01).

CONCLUSIONS

During OLV for atrial fibrillation surgical ablation in the supine position, CPAP on the deflated lung seemed to be ineffective to reduce Q_s/Q_t or to increase arterial partial pressure of oxygen and DO₂I, provided cardiac output was maintained above 1.5 L/min/m².

Driving pressure guided ventilation

Protective ventilation is a prevailing ventilatory strategy these days and is comprised of small tidal volume, limited inspiratory pressure, and application of positive end-expiratory pressure (PEEP). However, several retrospective studies recently suggested that tidal volume, inspiratory pressure, and PEEP are not related to patient outcomes, or only related when they influence the driving pressure. Therefore, this review introduces the concept of driving pressure and looks into the possibility of driving pressure-guided ventilation as a new ventilatory strategy, especially in thoracic surgery where postoperative pulmonary complications are common, and thus, lung protection is of utmost importance.

Lung recruitment maneuvers: opening the door to a hidden enemy

Recruitment manoeuvres (RM) are common practice in anaesthesiology; however, they can have adverse effects. We present an unforeseen complication in a patient undergoing surgical resection of a bronchial tumour who presented cardiac arrest due to pulseless electrical activity immediately after RMs. A transoesophageal echocardiogram performed after return of spontaneous circulation showed a patent foramen ovale (PFO), left ventricular dysfunction with segmental changes, and air in the left ventricle, leading to suspicion of paradoxical air embolism. The contractility changes normalised spontaneously, and postoperative evolution was uneventful. RMs cause changes in intracavitary pressures that can lead to opening of a PFO (present in up to 30% of the population) and reversal of the physiological left-right shunt. Transoesophageal echocardiography facilitated immediate diagnosis and follow-up.

Protective ventilation with high versus low positive end-expiratory pressure during one-lung ventilation for thoracic surgery (PROTHOR): study protocol for a randomized controlled trial

BACKGROUND

Postoperative pulmonary complications (PPC) may result in longer duration of in-hospital stay and even mortality. Both thoracic surgery and intraoperative mechanical ventilation settings add considerably to the risk of PPC. It is unclear if one-lung ventilation (OLV) for thoracic surgery with a strategy of intraoperative high positive end-expiratory pressure (PEEP) and recruitment maneuvers (RM) reduces PPC, compared to low PEEP without RM.

METHODS

PROTHOR is an international, multicenter, randomized, controlled, assessor-blinded, two-arm trial initiated by investigators of the PROtective VEntilation NETwork. In total, 2378 patients will be randomly assigned to one of two different intraoperative mechanical ventilation strategies. Investigators screen patients aged 18 years or older, scheduled for open thoracic or video-assisted thoracoscopic surgery under general anesthesia requiring OLV, with a maximal body mass index of 35 kg/m2, and a planned duration of surgery of more than 60 min. Further, the expected duration of OLV shall be longer than two-lung ventilation, and lung separation is planned with a double lumen tube. Patients will be randomly assigned to PEEP of 10 cmH2O with lung RM, or PEEP of 5 cmH2O without RM. During two-lung ventilation tidal volume is set at 7 mL/kg predicted body weight and, during OLV, it will be decreased to 5 mL/kg. The occurrence of PPC will be recorded as a collapsed composite of single adverse pulmonary events and represents the primary endpoint.

DISCUSSION

PROTHOR is the first randomized controlled trial in patients undergoing thoracic surgery with OLV that is adequately powered to compare the effects of intraoperative high PEEP with RM versus low PEEP without RM on PPC. The results of the PROTHOR trial will support anesthesiologists in their decision to set intraoperative PEEP during protective ventilation for OLV in thoracic surgery.

TRIAL REGISTRATION

The trial was registered in clinicaltrials.gov ( NCT02963025 ) on 15 November 2016.

Optimal PEEP during one-lung ventilation with capnothorax: An experimental study

BACKGROUND

One-lung ventilation (OLV) with induced capnothorax carries the risk of severely impaired ventilation and circulation. Optimal PEEP may mitigate the physiological perturbations during these conditions.

METHODS

Right-sided OLV with capnothorax (16 cm H₂ O) on the left side was initiated in eight anesthetized, muscle-relaxed piglets. A recruitment maneuver and a decremental PEEP titration from PEEP 20 cm H₂ O to zero end-expiratory pressure (ZEEP) was performed. Regional ventilation and perfusion were studied with electrical impedance tomography and computer tomography of the chest was used. End-expiratory lung volume and hemodynamics were recorded and.

RESULTS

PaO₂ peaked at PEEP 12 cm H₂ O (49 ± 14 kPa) and decreased to 11 ± 5 kPa at ZEEP (P < 0.001). PaCO₂ was 9.5 ± 1.3 kPa at 20 cm H₂ O PEEP and did not change when PEEP step-wise was reduced to 12 cm H₂ O PaCO_2. At lower PEEP, PaCO₂ increased markedly. The ventilatory driving pressure was lowest at PEEP 14 cm H₂ O (19.6 ± 5.8 cm H₂ O) and increased to 38.3 ± 6.1 cm H₂ O at ZEEP (P < 0.001). When reducing PEEP below 12-14 cm H₂ O ventilation shifted from the dependent to the nondependent regions of the ventilated lung (P = 0.003), and perfusion shifted from the ventilated to the nonventilated lung (P = 0.02).

CONCLUSION

Optimal PEEP was 12-18 cm H₂ O and probably relates to capnothorax insufflation pressure. With suboptimal PEEP, ventilation/perfusion mismatch in the ventilated lung and redistribution of blood flow to the nonventilated lung occurred.

Management of 1-Lung Ventilation-Variation and Trends in Clinical Practice: A Report From the Multicenter Perioperative Outcomes Group

BACKGROUND

Lung-protective ventilation (LPV) has been demonstrated to improve clinical outcomes in surgical patients. There are very limited data on the current use of LPV for patients undergoing 1-lung ventilation (1LV) despite evidence that 1LV may be a particularly important setting for its use. In this multicenter study, we report trends in ventilation practice for patients undergoing 1LV.

METHODS

The Multicenter Perioperative Outcomes Group database was used to identify patients undergoing 1LV. We retrieved and calculated median initial and overall tidal volume (VT) for the cohort and for high-risk subgroups (female sex, obesity [body mass index >30 kg/m], and short stature), percentage of patients receiving positive end-expiratory pressure (PEEP) ≥5 cm H2O, LPV during 1LV (VT ≤ 6 mL/kg predicted body weight [PBW] and PEEP ≥5 cm H2O), and ventilator driving pressure (ΔP; plateau airway pressure - PEEP).

RESULTS

Data from 5609 patients across 4 institutions were included in the analysis. Median VT was calculated for each case and since the data were normally distributed, the mean is reported for the entire cohort and subgroups. Mean of median VT during 1LV for the cohort was 6.49 ± 1.82 mL/kg PBW. VT (mL/kg PBW) for high-risk subgroups was significantly higher; 6.86 ± 1.97 for body mass index ≥30 kg/m, 7.05 ± 1.92 for female patients, and 7.33 ± 2.01 for short stature patients. Mean of the median VT declined significantly over the study period (from 6.88 to 5.72; P < .001), and the proportion of patients receiving LPV increased significantly over the study period (from 9.1% to 54.6%; P < .001). These changes coincided with a significant decrease in ΔP during the study period, from 19.4 cm H2O during period 1 to 17.3 cm H2O in period 12 (P = .003).

CONCLUSIONS

Despite a growing awareness of the importance of protective ventilation, a large proportion of patients undergoing 1LV continue to receive VT PEEP levels outside of recommended thresholds. Moreover, VT remains higher and LPV less common in high-risk subgroups, potentially placing them at elevated risk for iatrogenic lung injury.

Peep titration based on the open lung approach during one lung ventilation in thoracic surgery: a physiological study

BACKGROUND

During thoracic surgery in lateral decubitus, one lung ventilation (OLV) may impair respiratory mechanics and gas exchange. We tested a strategy based on an open lung approach (OLA) consisting in lung recruitment immediately followed by a decremental positive-end expiratory pressure (PEEP) titration to the best respiratory system compliance (C_RS) and separately quantified the elastic properties of the lung and the chest wall. Our hypothesis was that this approach would improve gas exchange. Further, we were interested in documenting the impact of the OLA on partitioned respiratory system mechanics.

METHODS

In thirteen patients undergoing upper left lobectomy we studied lung and chest wall mechanics, transpulmonary pressure (P_L), respiratory system and transpulmonary driving pressure (ΔP_RS and ΔP_L), gas exchange and hemodynamics at two time-points (a) during OLV at zero end-expiratory pressure (OLV_pre-OLA) and (b) after the application of the open-lung strategy (OLV_post-OLA).

RESULTS

The external PEEP selected through the OLA was 6 ± 0.8 cmH₂O. As compared to OLV_pre-OLA, the PaO₂/FiO₂ ratio went from 205 ± 73 to 313 ± 86 (p = .05) and C_L increased from 56 ± 18 ml/cmH₂O to 71 ± 12 ml/cmH₂O (p = .0013), without changes in C_CW. Both ΔP_RS and ΔP_L decreased from 9.2 ± 0.4 cmH₂O to 6.8 ± 0.6 cmH₂O and from 8.1 ± 0.5 cmH₂O to 5.7 ± 0.5 cmH₂O, (p = .001 and p = .015 vs OLV_pre-OLA), respectively. Hemodynamic parameters remained stable throughout the study period.

CONCLUSIONS

In our patients, the OLA strategy performed during OLV improved oxygenation and increased C_L and had no clinically significant hemodynamic effects. Although our study was not specifically designed to study ΔP_RS and ΔP_L, we observed a parallel reduction of both after the OLA.

TRIAL REGISTRATION

TRN: ClinicalTrials.gov , NCT03435523 , retrospectively registered, Feb 14 2018.

Perioperative lung protective ventilation

Perioperative lung injury is a major source of postoperative morbidity, excess healthcare use, and avoidable mortality. Many potential inciting factors can lead to this condition, including intraoperative ventilator induced lung injury. Questions exist as to whether protective ventilation strategies used in the intensive care unit for patients with acute respiratory distress syndrome are equally beneficial for surgical patients, most of whom do not present with any pre-existing lung pathology. Studied both individually and in combination as a package of intraoperative lung protective ventilation, the use of low tidal volumes, moderate positive end expiratory pressure, and recruitment maneuvers have been shown to improve oxygenation and pulmonary physiology and to reduce postoperative pulmonary complications in at risk patient groups. Further work is needed to define the potential contributions of alternative ventilator strategies, limiting excessive intraoperative oxygen supplementation, use of non-invasive techniques in the postoperative period, and personalized mechanical ventilation. Although the weight of evidence strongly suggests a role for lung protective ventilation in moderate risk patient groups, definitive evidence of its benefit for the general surgical population does not exist. However, given the shift in understanding of what is needed for adequate oxygenation and ventilation under anesthesia, the largely historical arguments against the use of intraoperative lung protective ventilation may soon be outdated, on the basis of its expanding track record of safety and efficacy in multiple settings.

Effect of combining a recruitment maneuver with protective ventilation on inflammatory responses in video-assisted thoracoscopic lobectomy: a randomized controlled trial

BACKGROUND

We hypothesized that the addition of a recruitment maneuver to protective ventilation (PVRM) would result in lower pulmonary and systemic inflammatory responses than traditional ventilation or protective ventilation (PV) alone in patients undergoing lung surgery.

METHODS

Sixty patients who underwent scheduled thoracoscopic lobectomy were randomly assigned to three groups: traditional ventilation, PV, or PVRM. Ventilations were performed using a tidal volume of 10 mL/kg for the traditional ventilation group and either 8 mL/kg (two-lung) or 6 mL/kg (one-lung, OLV) with a positive end-expiratory pressure of 5 cm H₂O for the PV and PVRM groups. The RM was performed 10 min after the start of OLV. Fiberoptic bronchoalveolar lavage (BAL) was performed twice in dependent and non-dependent lungs: before the start and immediately after the end of OLV. Blood samples were collected at the same time points. The levels of cytokines, including TNF-α, IL-1β, IL-6, IL-8, and IL-10, were measured.

RESULTS

After OLV, the level of TNF-α in the BAL fluid of dependent lungs was significantly higher in the PV than in the PVRM group (P = 0.049), whereas IL-1β, IL-6, IL-8, and IL-10 levels were not significantly different among the groups. In non-dependent lung BAL fluid, no cytokines were significantly different among the groups. After OLV, IL-10 serum levels were significantly higher in the traditional ventilation than in the PVRM group (P = 0.027).

CONCLUSIONS

Lower inflammatory responses in the ventilated lung and serum were observed with PVRM than with traditional ventilation or PV alone. Larger multi-center clinical trials are warranted to confirm the effects of different ventilatory strategies on postoperative outcomes.

New evidence in one-lung ventilation

Mechanical ventilation in thoracic surgery has undergone significant changes in recent years due to the implementation of the protective ventilation. This review will analyze recent ventilatory strategies in one-lung ventilation. A MEDLINE research was performed using Mesh term "One-Lung Ventilation" including randomized clinical trials, metanalysis, reviews and systematic reviews published in the last 6 years. Search was performed on 21st March 2017. A total of 75 articles were initially found. After title and abstract review 14 articles were included. Protective ventilation is not simply synonymous of low tidal volume ventilation, but it also includes routine use of PEEP and alveolar recruitment maneuver. New techniques are still in discussion namely PEEP adjustment, ratio inspiration:expiration, ideal type of anesthesia during one-lung ventilation and hypercapnic ventilation.

Recruitment manoeuvres in anaesthesia: How many more excuses are there not to use them?

Pulmonary recruitment manoeuvres (RM) are intended to reopen collapsed lung areas. RMs are present in nature as a physiological mechanism to get a newborn to open their lungs for the first time at birth, and we also use them, in our usual anaesthesiological clinical practice, after induction or during general anaesthesia when a patient is desaturated. However, there is much confusion in clinical practice regarding their safety, the best way to perform them, when to do them, in which patients they are indicated, and in those where they are totally contraindicated. There are important differences between RM in the patient with adult respiratory distress syndrome, and in a healthy patient during general anaesthesia. Our intention is to review, from a clinical and practical point of view, the use of RM, specifically in anaesthesia.

Interaction between peri-operative blood transfusion, tidal volume, airway pressure and postoperative ARDS: an individual patient data meta-analysis

Background

Transfusion of blood products and mechanical ventilation with injurious settings are considered risk factors for postoperative lung injury in surgical Patients.

Methods

A systematic review and individual patient data meta-analysis was done to determine the independent effects of peri-operative transfusion of blood products, intra-operative tidal volume and airway pressure in adult patients undergoing mechanical ventilation for general surgery, as well as their interactions on the occurrence of postoperative acute respiratory distress syndrome (ARDS). Observational studies and randomized trials were identified by a systematic search of MEDLINE, CINAHL, Web of Science, and CENTRAL and screened for inclusion into a meta-analysis. Individual patient data were obtained from the corresponding authors. Patients were stratified according to whether they received transfusion in the peri-operative period [red blood cell concentrates (RBC) and/or fresh frozen plasma (FFP)], tidal volume size [≤7 mL/kg predicted body weight (PBW), 7-10 and >10 mL/kg PBW] and airway pressure level used during surgery (≤15, 15-20 and >20 cmH₂O). The primary outcome was development of postoperative ARDS.

Results

Seventeen investigations were included (3,659 patients). Postoperative ARDS occurred in 40 (7.2%) patients who received at least one blood product compared to 40 patients (2.5%) who did not [adjusted hazard ratio (HR), 2.32; 95% confidence interval (CI), 1.25-4.33; P=0.008]. Incidence of postoperative ARDS was highest in patients ventilated with tidal volumes of >10 mL/kg PBW and having airway pressures of >20 cmH₂O receiving both RBC and FFP, and lowest in patients ventilated with tidal volume of ≤7 mL/kg PBW and having airway pressures of ≤15 cmH₂O with no transfusion. There was a significant interaction between transfusion and airway pressure level (P=0.002) on the risk of postoperative ARDS.

Conclusions

Peri-operative transfusion of blood products is associated with an increased risk of postoperative ARDS, which seems more dependent on airway pressure than tidal volume size.

One-lung Ventilation for Thoracic Surgery: Current Perspectives

One-lung ventilation (OLV) is an anesthesiological technique that is increasingly being used beyond thoracic surgery. This requires specific skills and knowledge about airway management, maintenance of gas exchange and prevention of acute lung injury. Sometimes maintaining adequate gas exchange and minimizing acute lung injury may be opposing processes. Parameters validated for OLV titration still have not been found, but a multimodal approach based on low tidal volume, end-expiratory pressure application and alveolar recruitment maneuvers is considered the best way to ensure protective ventilation and reduce lung damage. The purpose of this review is to analyze all these factors using the latest scientific evidence and the opinions of the most influential authors.

Open lung approach versus standard protective strategies: Effects on driving pressure and ventilatory efficiency during anesthesia - A pilot, randomized controlled trial

BACKGROUND

Low tidal volume (VT) during anesthesia minimizes lung injury but may be associated to a decrease in functional lung volume impairing lung mechanics and efficiency. Lung recruitment (RM) can restore lung volume but this may critically depend on the post-RM selected PEEP. This study was a randomized, two parallel arm, open study whose primary outcome was to compare the effects on driving pressure of adding a RM to low-VT ventilation, with or without an individualized post-RM PEEP in patients without known previous lung disease during anesthesia.

METHODS

Consecutive patients scheduled for major abdominal surgery were submitted to low-VT ventilation (6 ml·kg-1) and standard PEEP of 5 cmH2O (pre-RM, n = 36). After 30 min estabilization all patients received a RM and were randomly allocated to either continue with the same PEEP (RM-5 group, n = 18) or to an individualized open-lung PEEP (OL-PEEP) (Open Lung Approach, OLA group, n = 18) defined as the level resulting in maximal Cdyn during a decremental PEEP trial. We compared the effects on driving pressure and lung efficiency measured by volumetric capnography.

RESULTS

OL-PEEP was found at 8±2 cmH2O. 36 patients were included in the final analysis. When compared with pre-RM, OLA resulted in a 22% increase in compliance and a 28% decrease in driving pressure when compared to pre-RM. These parameters did not improve in the RM-5. The trend of the DP was significantly different between the OLA and RM-5 groups (p = 0.002). VDalv/VTalv was significantly lower in the OLA group after the RM (p = 0.035).

CONCLUSIONS

Lung recruitment applied during low-VT ventilation improves driving pressure and lung efficiency only when applied as an open-lung strategy with an individualized PEEP in patients without lung diseases undergoing major abdominal surgery.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02798133.

[Anesthesia in thoracic surgery]

Thoracic surgery represents a special challenge for anesthesia and requires a high level of human and material resources. Accurate knowledge of the pathophysiology is essential for selection of the anesthetic procedure, the separation of the lungs, monitoring and treatment of hemodynamics as well as for postoperative follow-up care. The increasing number of thoracic interventions and patients who are often suffering from complex diseases require close interdisciplinary cooperation between surgeons, anesthesiologists and intensive care specialists. In addition to the anesthetic techniques particular attention must be paid to the prevention of perioperative complications that can have a relevant effect on patient outcome. In particular hypoxemia during one-lung ventilation influences postoperative morbidity and mortality. Protective pulmonary ventilation strategies play an important role in prevention of postoperative acute lung injury.

Diagnosis Accuracy of Mean Arterial Pressure Variation during a Lung Recruitment Maneuver to Predict Fluid Responsiveness in Thoracic Surgery with One-Lung Ventilation

Background. Lung recruitment maneuver (LRM) during thoracic surgery can reduce systemic venous return and resulting drop in systemic blood pressure depends on the patient's fluid status. We hypothesized that changes in systemic blood pressure during the transition in LRM from one-lung ventilation (OLV) to two-lung ventilation (TLV) may provide an index to predict fluid responsiveness. Methods. Hemodynamic parameters were measured before LRM (T0); after LRM at the time of the lowest mean arterial blood pressure (MAP) (T1) and at 3 minutes (T2); before fluid administration (T3); and 5 minutes after ending it (T4). If the stroke volume index increased by >25% following 10 mL/kg colloid administration for 30 minutes, then the patients were assigned to responder group. Results. Changes in MAP, central venous pressure (CVP), and stroke volume variation (SVV) between T0 and T1 were significantly larger in responders. Areas under the curve for change in MAP, CVP, and SVV were 0.852, 0.759, and 0.820, respectively; the optimal threshold values for distinguishment of responders were 9.5 mmHg, 0.5 mmHg, and 3.5%, respectively. Conclusions. The change in the MAP associated with LRM at the OLV to TLV conversion appears to be a useful indicator of fluid responsiveness after thoracic surgery. Trial Registration. This trial is registered at Clinical Research Information Service with KCT0000774.

Fast track in thoracic surgery and anaesthesia: update of concepts

PURPOSE OF REVIEW

Update of key elements on enhanced recovery after thoracic anaesthesia and surgery.

RECENT FINDINGS

Pathways to enhance recovery after thoracic surgery ('fast-track') aim to improve response to lung surgery, reduction of postoperative pulmonary complications, and restore patient's vital function. Uncomplicated recovery after lung surgery reduces morbidity, hospital stay, and costs. Video-assisted thoracoscopic surgery is a major part of enhanced recovery minimizing tissue injury and stress response. Maintaining patient's physiology throughout perioperative processes by optimized anaesthesiological management and effective pain control present a crucial role in improving outcome.

SUMMARY

The concept of enhanced recovery ('fast-track') after thoracic surgery and anaesthesia was developed in recent years making allowance to the increased number of video-assisted parenchymal lung resections in managing primary lung cancer. Current studies promote the benefit in thoracic surgical patients, if an established departmental protocol-based algorithm is implemented.

Comparison of pressure-controlled ventilation with volume-controlled ventilation during one-lung ventilation: a systematic review and meta-analysis

BACKGROUND

Not only arterial hypoxemia but acute lung injury also has become the major concerns of one-lung ventilation (OLV). The use of pressure-controlled ventilation (PCV) for OLV offers the potential advantages of lower airway pressure and intrapulmonary shunt, which result in a reduced risk of barotrauma and improved oxygenation, respectively.

METHODS

We searched Medline, Embase, the Cochrane central register of controlled trials and KoreaMedto find publications comparing the effects of PCV with those of volume-controlled ventilation (VCV) during intraoperative OLV in adults. A meta-analysis of randomized controlled trials was performed using the Cochrane Review Methods.

RESULTS

Six studies (259 participants) were included. The PaO2/FiO2 ratio in PCV was higher than in VCV [weighted mean difference (WMD) = 11.04 mmHg, 95 % confidence interval (CI) = 0.30 to 21.77, P = 0.04, I(2) = 3 %] and peak inspiratory pressure was significantly lower in PCV (WMD = -4.91 cm H2O, 95 % CI = -7.30 to -2.53, P < 0.0001, I (2) = 91 %). No differences in PaCO2, tidal volume, heart rate and blood pressure were observed. There were also no differences incompliance, plateau and mean airway pressure.

CONCLUSIONS

Our meta-analysis provided the evidence of improved oxygenation in PCV. However, it is difficult to draw any definitive conclusions due to the fact that the duration of ventilation in the studies reviewed was insufficient to reveal clinically relevant benefits or disadvantages of PCV. Significantly lower peak inspiratory pressure is the advantage of PCV.

How to minimise ventilator-induced lung injury in transplanted lungs: The role of protective ventilation and other strategies

Lung transplantation is the treatment of choice for end-stage pulmonary diseases. In order to avoid or reduce pulmonary and systemic complications, mechanical ventilator settings have an important role in each stage of lung transplantation. In this respect, the use of mechanical ventilation with a tidal volume of 6 to 8 ml  kg(-1) predicted body weight, positive end-expiratory pressure of 6 to 8 cmH2O and a plateau pressure lower than 30 cmH2O has been suggested for the donor during surgery, and for the recipient both during and after surgery. For the present review, we systematically searched the PubMed database for articles published from 2000 to 2014 using the following keywords: lung transplantation, protective mechanical ventilation, lung donor, extracorporeal membrane oxygenation, recruitment manoeuvres, extracorporeal CO2 removal and noninvasive ventilation.

Volumetric capnography: lessons from the past and current clinical applications

Dead space is an important component of ventilation–perfusion abnormalities. Measurement of dead space has diagnostic, prognostic and therapeutic applications. In the intensive care unit (ICU) dead space measurement can be used to guide therapy for patients with acute respiratory distress syndrome (ARDS); in the emergency department it can guide thrombolytic therapy for pulmonary embolism; in peri-operative patients it can indicate the success of recruitment maneuvers. A newly available technique called volumetric capnography (Vcap) allows measurement of physiological and alveolar dead space on a regular basis at the bedside. We discuss the components of dead space, explain important differences between the Bohr and Enghoff approaches, discuss the clinical significance of arterial to end-tidal CO₂ gradient and finally summarize potential clinical indications for Vcap measurements in the emergency room, operating room and ICU.

Association between driving pressure and development of postoperative pulmonary complications in patients undergoing mechanical ventilation for general anaesthesia: a meta-analysis of individual patient data

BACKGROUND

Protective mechanical ventilation strategies using low tidal volume or high levels of positive end-expiratory pressure (PEEP) improve outcomes for patients who have had surgery. The role of the driving pressure, which is the difference between the plateau pressure and the level of positive end-expiratory pressure is not known. We investigated the association of tidal volume, the level of PEEP, and driving pressure during intraoperative ventilation with the development of postoperative pulmonary complications.

METHODS

We did a meta-analysis of individual patient data from randomised controlled trials of protective ventilation during general anesthaesia for surgery published up to July 30, 2015. The main outcome was development of postoperative pulmonary complications (postoperative lung injury, pulmonary infection, or barotrauma).

FINDINGS

We included data from 17 randomised controlled trials, including 2250 patients. Multivariate analysis suggested that driving pressure was associated with the development of postoperative pulmonary complications (odds ratio [OR] for one unit increase of driving pressure 1·16, 95% CI 1·13-1·19; p<0·0001), whereas we detected no association for tidal volume (1·05, 0·98-1·13; p=0·179). PEEP did not have a large enough effect in univariate analysis to warrant inclusion in the multivariate analysis. In a mediator analysis, driving pressure was the only significant mediator of the effects of protective ventilation on development of pulmonary complications (p=0·027). In two studies that compared low with high PEEP during low tidal volume ventilation, an increase in the level of PEEP that resulted in an increase in driving pressure was associated with more postoperative pulmonary complications (OR 3·11, 95% CI 1·39-6·96; p=0·006).

INTERPRETATION

In patients having surgery, intraoperative high driving pressure and changes in the level of PEEP that result in an increase of driving pressure are associated with more postoperative pulmonary complications. However, a randomised controlled trial comparing ventilation based on driving pressure with usual care is needed to confirm these findings.

FUNDING

None.