Lung protective ventilation in patients undergoing major surgery: a systematic review incorporating a Bayesian approach

Impact of Lower Tidal Volumes During One-Lung Ventilation: A 2022 Update of the Meta-analysis of Randomized Controlled Trials

OBJECTIVES

To clarify the influence of lower tidal volume (4-7 mL/kg) compared with higher tidal volume (8-15 mL/kg) during one-lung ventilation (OLV) on gas exchange and postoperative clinical outcome.

DESIGN

Meta-analysis of randomized trials.

SETTING

Thoracic surgery.

PARTICIPANTS

Patients receiving OLV.

INTERVENTIONS

Lower tidal volume during OLV.

MEASUREMENTS AND MAIN RESULTS

Primary outcome was PaO2-to-the oxygen fraction (PaO2/FIO2) ratio at the end of the surgery, after the reinstitution of two-lung ventilation. Secondary endpoints included perioperative changes in PaO2/FIO2 ratio and carbon dioxide (PaCO2) tension, airway pressure, the incidence of postoperative pulmonary complications, arrhythmia, and length of hospital stay. Seventeen randomized controlled trials (1,463 patients) were selected. Overall analysis showed that the use of low tidal volume during OLV was associated with a significantly higher PaO2/FIO2 ratio 15 minutes after the start of OLV and at the end of surgery (mean difference 33.7 mmHg [p = 0.02] and mean difference 18.59 mmHg [p < 0.001], respectively). The low tidal volume also was associated with higher PaCO2 values 15 minutes and 60 minutes after the start of OLV and with lower airway pressure, which was maintained during two-lung ventilation after surgery. Moreover, the application of lower tidal volume was associated with fewer postoperative pulmonary complications (odds ratio 0.50; p < 0.001) and arrhythmias (odds ratio 0.58; p = 0.009), with no difference in length of hospital stay.

CONCLUSIONS

The use of lower tidal volume, a component of protective OLV, increases the PaO2/FIO2 ratio, reduces the incidence of postoperative pulmonary complications, and should be considered strongly in daily practice.

The PANDORA Study: Prevalence and Outcome of Acute Hypoxemic Respiratory Failure in the Pre-COVID-19 Era

OBJECTIVES:

To establish the epidemiological characteristics, ventilator management, and outcomes in patients with acute hypoxemic respiratory failure (AHRF), with or without acute respiratory distress syndrome (ARDS), in the era of lung-protective mechanical ventilation (MV).

DESIGN:

A 6-month prospective, epidemiological, observational study.

SETTING:

A network of 22 multidisciplinary ICUs in Spain.

PATIENTS:

Consecutive mechanically ventilated patients with AHRF (defined as Pao₂/Fio₂ ≤ 300 mm Hg on positive end-expiratory pressure [PEEP] ≥ 5 cm H₂O and Fio₂ ≥ 0.3) and followed-up until hospital discharge.

INTERVENTIONS:

None.

MEASUREMENTS AND MAIN RESULTS:

Primary outcomes were prevalence of AHRF and ICU mortality. Secondary outcomes included prevalence of ARDS, ventilatory management, and use of adjunctive therapies. During the study period, 9,803 patients were admitted: 4,456 (45.5%) received MV, 1,271 (13%) met AHRF criteria (1,241 were included into the study: 333 [26.8%] met Berlin ARDS criteria and 908 [73.2%] did not). At baseline, tidal volume was 6.9 ± 1.1 mL/kg predicted body weight, PEEP 8.4 ± 3.1 cm H₂O, Fio₂ 0.63 ± 0.22, and plateau pressure 21.5 ± 5.4 cm H₂O. ARDS patients received higher Fio₂ and PEEP than non-ARDS (0.75 ± 0.22 vs 0.59 ± 0.20 cm H₂O and 10.3 ± 3.4 vs 7.7 ± 2.6 cm H₂O, respectively [p < 0.0001]). Adjunctive therapies were rarely used in non-ARDS patients. Patients without ARDS had higher ventilator-free days than ARDS (12.2 ± 11.6 vs 9.3 ± 9.7 d; p < 0.001). All-cause ICU mortality was similar in AHRF with or without ARDS (34.8% [95% CI, 29.7–40.2] vs 35.5% [95% CI, 32.3–38.7]; p = 0.837).

CONCLUSIONS:

AHRF without ARDS is a very common syndrome in the ICU with a high mortality that requires specific studies into its epidemiology and ventilatory management. We found that the prevalence of ARDS was much lower than reported in recent observational studies.

Individualized Mechanical power-based ventilation strategy for acute respiratory failure formalized by finite mixture modeling and dynamic treatment regimen

BACKGROUND

Mechanical ventilation (MV) is the key to the successful treatment of acute respiratory failure (ARF) in the intensive care unit (ICU). The study aims to formalize the concept of individualized MV strategy with finite mixture modeling (FMM) and dynamic treatment regime (DTR).

METHODS

ARF patients requiring MV for over 48 h from 2008 to 2019 were included. FMM was conducted to identify classes of ARF. Static and dynamic mechanical power (MP_static and MP_dynamic) and relevant clinical variables were calculated/collected from hours 0 to 48 at an interval of 8 h. Δ M P was calculated as the difference between actual and optimal MP.

FINDINGS

A total of 8768 patients were included for analysis with a mortality rate of 27%. FFM identified three classes of ARF, namely, the class 1 (baseline), class 2 (critical) and class 3 (refractory respiratory failure). The effect size of MP_static on mortality is the smallest in class 1 (HR for every 5 Joules/min increase: 1.29; 95% CI: 1.15 to 1.45; p < 0.001) and the largest in class 3 (HR for every 5 Joules/min increase: 1.83; 95% CI: 1.52 to 2.20; p < 0.001).

INTERPRETATION

MP has differing therapeutic effects for subtypes of ARF. Optimal MP estimated by DTR model may help to improve survival outcome.

FUNDING

The study was funded by Health Science and Technology Plan of Zhejiang Province (2021KY745), Key Research & Development project of Zhejiang Province (2021C03071) and Yilu "Gexin" - Fluid Therapy Research Fund Project (YLGX-ZZ-2,020,005).

Comparing outcomes of mechanical ventilation with high vs. moderate tidal volumes in tracheostomized patients with spinal cord injury in acute inpatient rehabilitation setting: a retrospective cohort study

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

The primary objective of this study was to evaluate safety and efficacy of higher tidal volumes (HVt) compared to moderate Vt (MVt) in people with spinal cord injury (SCI) admitted to acute inpatient rehabilitation (AIR) facility on mechanical ventilation via tracheostomy.

SETTING

AIR facility in the United States.

METHODS

Eighty-four adults with SCI were divided into MVt group if maximum Vt received in AIR was <15 ml/kg predicted body weight (PBW) and HVt group if maximum Vt was >15 ml/kg PBW. Primary outcomes were incidence of pneumonia and composite pulmonary adverse events (pneumonia, weaning failure, or acute care transfers due to respiratory complications). Secondary outcomes were AIR preweaning days defined as time from AIR admission to beginning of weaning, weaning days defined as days from start to end of weaning, and AIR ventilator days calculated as days on ventilator from AIR admission to discharge.

RESULTS

MVt was utilized in 50 patients and HVt was utilized in 34 patients. The risk of pneumonia in HVt group was 4.3 times higher [95% confidence interval (CI): 1.5-12] compared to MVt group. Odds of pulmonary adverse events in HVt group was 5.4 times higher (CI: 1.8-17) compared to MVt group. There was no difference in preweaning days, weaning days, or AIR ventilator days between the two groups.

CONCLUSIONS

Our data suggest that HVt is associated with increased risk of pneumonia and higher odds of pulmonary adverse events in tracheostomized patients with SCI which warrants further investigation.

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

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

Driving Pressure During General Anesthesia for Open Abdominal Surgery (DESIGNATION): study protocol of a randomized clinical trial

BACKGROUND

Intraoperative driving pressure (ΔP) is associated with development of postoperative pulmonary complications (PPC). When tidal volume (V_T) is kept constant, ΔP may change according to positive end-expiratory pressure (PEEP)-induced changes in lung aeration. ΔP may decrease if PEEP leads to a recruitment of collapsed lung tissue but will increase if PEEP mainly causes pulmonary overdistension. This study tests the hypothesis that individualized high PEEP, when compared to fixed low PEEP, protects against PPC in patients undergoing open abdominal surgery.

METHODS

The "Driving prESsure durIng GeNeral AnesThesIa for Open abdomiNal surgery trial" (DESIGNATION) is an international, multicenter, two-group, double-blind randomized clinical superiority trial. A total of 1468 patients will be randomly assigned to one of the two intraoperative ventilation strategies. Investigators screen patients aged ≥ 18 years and with a body mass index ≤ 40 kg/m², scheduled for open abdominal surgery and at risk for PPC. Patients either receive an intraoperative ventilation strategy with individualized high PEEP with recruitment maneuvers (RM) ("individualized high PEEP") or one in which PEEP of 5 cm H₂O without RM is used ("low PEEP"). In the "individualized high PEEP" group, PEEP is set at the level at which ΔP is lowest. In both groups of the trial, V_T is kept at 8 mL/kg predicted body weight. The primary endpoint is the occurrence of PPC, recorded as a collapsed composite of adverse pulmonary events.

DISCUSSION

DESIGNATION will be the first randomized clinical trial that is adequately powered to compare the effects of individualized high PEEP with RM versus fixed low PEEP without RM on the occurrence of PPC after open abdominal surgery. The results of DESIGNATION will support anesthesiologists in their decisions regarding PEEP settings during open abdominal surgery.

TRIAL REGISTRATION

Clinicaltrials.gov, NCT03884543. Registered on 21 March 2019.

Cumulative oxygen deficit is a novel predictor for the timing of invasive mechanical ventilation in COVID-19 patients with respiratory distress

BACKGROUND AND OBJECTIVES

The timing of invasive mechanical ventilation (IMV) is controversial in COVID-19 patients with acute respiratory hypoxemia. The study aimed to develop a novel predictor called cumulative oxygen deficit (COD) for the risk stratification.

METHODS

The study was conducted in four designated hospitals for treating COVID-19 patients in Jingmen, Wuhan, from January to March 2020. COD was defined to account for both the magnitude and duration of hypoxemia. A higher value of COD indicated more oxygen deficit. The predictive performance of COD was calculated in multivariable Cox regression models.

RESULTS

A number of 111 patients including 80 in the non-IMV group and 31 in the IMV group were included. Patients with IMV had substantially lower PaO₂ (62 (49, 89) vs. 90.5 (68, 125.25) mmHg; p < 0.001), and higher COD (-6.87 (-29.36, 52.38) vs. -231.68 (-1040.78, 119.83) mmHg·day) than patients without IMV. As compared to patients with COD < 0, patients with COD > 30 mmHg·day had higher risk of fatality (HR: 3.79, 95% CI [2.57-16.93]; p = 0.037), and those with COD > 50 mmHg·day were 10 times more likely to die (HR: 10.45, 95% CI [1.28-85.37]; p = 0.029).

CONCLUSIONS

The study developed a novel predictor COD which considered both magnitude and duration of hypoxemia, to assist risk stratification of COVID-19 patients with acute respiratory distress.

Mechanical power normalized to predicted body weight as a predictor of mortality in patients with acute respiratory distress syndrome

PURPOSE

Protective mechanical ventilation based on multiple ventilator parameters such as tidal volume, plateau pressure, and driving pressure has been widely used in acute respiratory distress syndrome (ARDS). More recently, mechanical power (MP) was found to be associated with mortality. The study aimed to investigate whether MP normalized to predicted body weight (norMP) was superior to other ventilator variables and to prove that the discrimination power cannot be further improved with a sophisticated machine learning method.

METHODS

The study included individual patient data from eight randomized controlled trials conducted by the ARDSNet. The data was split 3:1 into training and testing subsamples. The discrimination of each ventilator variable was calculated in the testing subsample using the area under receiver operating characteristic curve. The gradient boosting machine was used to examine whether the discrimination could be further improved.

RESULTS

A total of 5159 patients with acute onset ARDS were included for analysis. The discrimination of norMP in predicting mortality was significantly better than the absolute MP (p = 0.011 for DeLong's test). The gradient boosting machine was not able to improve the discrimination as compared to norMP (p = 0.913 for DeLong's test). The multivariable regression model showed a significant interaction between norMP and ARDS severity (p < 0.05). While the norMP was not significantly associated with mortality outcome (OR 0.99; 95% CI 0.91-1.07; p = 0.862) in patients with mild ARDS, it was associated with increased risk of mortality in moderate (OR 1.11; 95% CI 1.02-1.23; p = 0.021) and severe (OR 1.13; 95% CI 1.03-1.24; p < 0.008) ARDS.

CONCLUSIONS

The study showed that norMP was a good ventilator variable associated with mortality, and its predictive discrimination cannot be further improved with a sophisticated machine learning method. Further experimental trials are needed to investigate whether adjusting ventilator variables according to norMP will significantly improve clinical outcomes.

Individualised perioperative open-lung approach versus standard protective ventilation in abdominal surgery (iPROVE): a randomised controlled trial

BACKGROUND

The effects of individualised perioperative lung-protective ventilation (based on the open-lung approach [OLA]) on postoperative complications is unknown. We aimed to investigate the effects of intraoperative and postoperative ventilatory management in patients scheduled for abdominal surgery, compared with standard protective ventilation.

METHODS

We did this prospective, multicentre, randomised controlled trial in 21 teaching hospitals in Spain. We enrolled patients who were aged 18 years or older, were scheduled to have abdominal surgery with an expected time of longer than 2 h, had intermediate-to-high-risk of developing postoperative pulmonary complications, and who had a body-mass index less than 35 kg/m². Patients were randomly assigned (1:1:1:1) online to receive one of four lung-protective ventilation strategies using low tidal volume plus positive end-expiratory pressure (PEEP): open-lung approach (OLA)-iCPAP (individualised intraoperative ventilation [individualised PEEP after a lung recruitment manoeuvre] plus individualised postoperative continuous positive airway pressure [CPAP]), OLA-CPAP (intraoperative individualised ventilation plus postoperative CPAP), STD-CPAP (standard intraoperative ventilation plus postoperative CPAP), or STD-O₂ (standard intraoperative ventilation plus standard postoperative oxygen therapy). Patients were masked to treatment allocation. Investigators were not masked in the operating and postoperative rooms; after 24 h, data were given to a second investigator who was masked to allocations. The primary outcome was a composite of pulmonary and systemic complications during the first 7 postoperative days. We did the primary analysis using the modified intention-to-treat population. This trial is registered with ClinicalTrials.gov, number NCT02158923.

FINDINGS

Between Jan 2, 2015, and May 18, 2016, we enrolled 1012 eligible patients. Data were available for 967 patients, whom we included in the final analysis. Risk of pulmonary and systemic complications did not differ for patients in OLA-iCPAP (110 [46%] of 241, relative risk 0·89 [95% CI 0·74-1·07; p=0·25]), OLA-CPAP (111 [47%] of 238, 0·91 [0·76-1·09; p=0·35]), or STD-CPAP groups (118 [48%] of 244, 0·95 [0·80-1·14; p=0·65]) when compared with patients in the STD-O₂ group (125 [51%] of 244). Intraoperatively, PEEP was increased in 69 (14%) of patients in the standard perioperative ventilation groups because of hypoxaemia, and no patients from either of the OLA groups required rescue manoeuvres.

INTERPRETATION

In patients who have major abdominal surgery, the different perioperative open lung approaches tested in this study did not reduce the risk of postoperative complications when compared with standard lung-protective mechanical ventilation.

FUNDING

Instituto de Salud Carlos III of the Spanish Ministry of Economy and Competitiveness, and Grants Programme of the European Society of Anaesthesiology.

Prophylactic penehyclidine inhalation for prevention of postoperative pulmonary complications in high-risk patients: study protocol of a randomized controlled trial

Background

Postoperative pulmonary complications (PPCs) are major causes of morbidity, mortality, and prolonged hospital stay in patients after surgery. Using effective strategies to prevent its occurrence is essential to improve outcome. However, despite various efforts, the incidence of PPCs remains elevated in high-risk patients. Anticholinergic inhalation is used to reduce high airway resistance and improve pulmonary function; it may be helpful to decrease the risk of PPCs. Penehyclidine is a long-acting anticholinergic agent which selectively blocks M1 and M3 receptors. We hypothesize that, in high-risk patients, prophylactic penehyclidine inhalation may decrease the incidence of PPCs.

Methods

This is a randomized, double-blind, placebo-controlled trial with two parallel arms. A total of 864 patients at high risk of PPCs will be enrolled and randomized to receive prophylactic inhalation of either penehyclidine or placebo (water for injection). Study drug inhalation will be administered from the night (7 pm) before surgery until the second day after surgery, in an interval of every 12 hours. The primary outcome is the incidence of PPCs within 30 days after surgery. Secondary outcomes include the time to onset of PPCs (from end of surgery to first diagnosis of PPCs), the number of PPCs (indicates the number of diagnosed individual PPCs), the incidence of postoperative extrapulmonary complications, the length of stay in hospital after surgery, and the 30-day all-cause mortality.

Discussion

Results of the present study will provide evidence to guide clinical practice in using prophylactic inhalation of an anticholinergic to prevent PPCs in high-risk patients.

Trial registration

The study was registered prospectively in Chinese Clinical Trial Registry (www.chictr.org.cn, ChiCTR-IPC-15006603) on 14 May 2015 and retrospectively in ClinicalTrials.gov (NCT02644876) on 30 December 2015.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-017-2315-7) contains supplementary material, which is available to authorized users.

The Society for Translational Medicine: clinical practice guidelines for mechanical ventilation management for patients undergoing lobectomy

Patients undergoing lobectomy are at significantly increased risk of lung injury. One-lung ventilation is the most commonly used technique to maintain ventilation and oxygenation during the operation. It is a challenge to choose an appropriate mechanical ventilation strategy to minimize the lung injury and other adverse clinical outcomes. In order to understand the available evidence, a systematic review was conducted including the following topics: (I) protective ventilation (PV); (II) mode of mechanical ventilation [e.g., volume controlled (VCV) versus pressure controlled (PCV)]; (III) use of therapeutic hypercapnia; (IV) use of alveolar recruitment (open-lung) strategy; (V) pre-and post-operative application of positive end expiratory pressure (PEEP); (VI) Inspired Oxygen concentration; (VII) Non-intubated thoracoscopic lobectomy; and (VIII) adjuvant pharmacologic options. The recommendations of class II are non-intubated thoracoscopic lobectomy may be an alternative to conventional one-lung ventilation in selected patients. The recommendations of class IIa are: (I) Therapeutic hypercapnia to maintain a partial pressure of carbon dioxide at 50-70 mmHg is reasonable for patients undergoing pulmonary lobectomy with one-lung ventilation; (II) PV with a tidal volume of 6 mL/kg and PEEP of 5 cmH₂O are reasonable methods, based on current evidence; (III) alveolar recruitment [open lung ventilation (OLV)] may be beneficial in patients undergoing lobectomy with one-lung ventilation; (IV) PCV is recommended over VCV for patients undergoing lung resection; (V) pre- and post-operative CPAP can improve short-term oxygenation in patients undergoing lobectomy with one-lung ventilation; (VI) controlled mechanical ventilation with I:E ratio of 1:1 is reasonable in patients undergoing one-lung ventilation; (VII) use of lowest inspired oxygen concentration to maintain satisfactory arterial oxygen saturation is reasonable based on physiologic principles; (VIII) Adjuvant drugs such as nebulized budesonide, intravenous sivelestat and ulinastatin are reasonable and can be used to attenuate inflammatory response.

Mechanical Ventilation during Extracorporeal Membrane Oxygenation in Patients with Acute Severe Respiratory Failure

Conventionally, a substantial number of patients with acute respiratory failure require mechanical ventilation (MV) to avert catastrophe of hypoxemia and hypercapnia. However, mechanical ventilation per se can cause lung injury, accelerating the disease progression. Extracorporeal membrane oxygenation (ECMO) provides an alternative to rescue patients with severe respiratory failure that conventional mechanical ventilation fails to maintain adequate gas exchange. The physiology behind ECMO and its interaction with MV were reviewed. Next, we discussed the timing of ECMO initiation based on the risks and benefits of ECMO. During the running of ECMO, the protective ventilation strategy can be employed without worrying about catastrophic hypoxemia and carbon dioxide retention. There is a large body of evidence showing that protective ventilation with low tidal volume, high positive end-expiratory pressure, and prone positioning can provide benefits on mortality outcome. More recently, there is an increasing popularity on the use of awake and spontaneous breathing for patients undergoing ECMO, which is thought to be beneficial in terms of rehabilitation.

Adult patient with pulmonary agenesis: focusing on one-lung ventilation during general anesthesia

Congenital pulmonary agenesis is a rare condition with high mortality. Mechanical ventilation in these patients is challenging and there has no such case been reported in the literature. We reported a 61-year-old female with lung agenesis who presented to our hospital with pneumonia and pelvic mass. In the past, she had undergone repairing of atrial septal defect and mitral valve forming surgery at 6-year-old. Thereafter she had remained asymptomatic until this time of hospital admission. The patient underwent operation for the pelvic mass with one-lung ventilation (OLV) under general anesthesia. We highlighted the use of protective ventilation (PV) strategy during OLV.