Mechanical ventilation after cardiac arrest: protecting the brain by protecting the lungs.

Objective: To assess the compliance with a lung protective ventilation strategy and to evaluate the relationship with prognosis in patients with acute respiratory distress syndrome (ARDS). Methods: In the prospective multicenter cohort study (CHARDS), patients with ARDS undergoing invasive mechanical ventilation were enrolled to collect essential information, mechanical ventilation data, and prognostic data. Compliance was operationally defined as tidal volume ≤7 ml/kg predicted body weight (PBW) or plateau pressure ≤30 cmH2O or driving pressure≤15 cmH2O. Tidal volume data collected 7 days prior to ventilation after ARDS diagnosis were categorized into four groups: standard group (Group A, 100% compliance), non-standard group (Group B, 50%-99% compliance, Group C,1%-49% compliance,and Group D,totally non-compliant). Plateau pressure and drive pressure measurements were recorded on the first day. Stepwise regression, specifically Logistics regression, was used to identify the factors influencing ICU survival. Results: A total of 449 ARDS patients with invasive mechanical ventilation were included; the proportion of mild, moderate, and severe patients was 71 (15.8%), 198 (44.1%) and 180 (40.1%), respectively. During the first 7 days, a total of 2880 tidal volume measurements were recorded with an average tidal volume of (6.89±1.93) ml/kg PBW. Of these measurements, 53.2% were found to be≤7 ml/kg PBW. The rates of compliance with lung protective mechanical ventilation were 29.8% (134/449), 24.5% (110/449), 23.6% (106/449), and 22% (99/449) in groups A, B, C, and D, respectively. In the standard group, the tidal volume for mild ARDS patients was 18.3%(13/71), while it was 81.7%(58/71)in the non-standard group. Similarly, in patients with moderate ARDS, the tidal volume was 25.8% (51/198) in the standard group, while it was 74.2% (147/198) in the non-standard group. Finally, in patients with severe ARDS, the tidal volume was 38.9% (70/180) in the standard group, while it was 61.1% (110/180) in the non-standard group. Notably, the compliance rate was higher in patients with moderate and severe ARDS in group A compared to patients with mild and moderate ARDS (18.3% vs. 25.8% vs. 38.9%, χ2=13.124, P=0.001). Plateau pressure was recorded in 221 patients, 95.9% (212/221) patients with plateau pressure≤30 cmH2O, and driving pressure was recorded in 207 patients, 77.8% (161/207) patients with a driving pressure ≤15 cmH2O.During the first 7 days, the mortality rate in the intensive care unit (ICU) was lower in the tidal volume standard group compared to the non-standard group (34.6% vs. 51.3%, χ2=10.464, P=0.001). In addition, the in-hospital mortality rate was lower in the standard group compared to the non-standard group (39.8% vs. 57%, χ2=11.016, P=0.001).The results of the subgroup analysis showed that the mortality rates of moderate and severe ARDS patients in the standard group were significantly lower than those in the non-standard group, both in the ICU and in the hospital (all P<0.05). However, there was no statistically significant difference in mortality among mild ARDS patients (all P>0.05). Conclusions: There was high compliance with recommended lung protective mechanical ventilation strategies in ARDS patients, with slightly lower compliance in patients with mild ARDS, and high compliance rates for plateau and drive pressures. The tidal volume full compliance group had a lower mortality than the non-compliance group, and showed a similar trend in the moderate-to-severe ARDS subgroup, but there was no significant correlation between compliance and prognosis in patients with mild ARDS subgroup.

Objective To explore the impact of lung-protective mechanical ventilation (low tidal volume and optimal positive end-expiratory pressure (PEEP) on cerebral perfusion pressure (CPP) and cerebral oxygen metabolism.Methods Forty patients with severe cerebral injury along with respiratory failure were randomly assigned into two groups:lung-protective ventilation group A and conventional ventilation group B.Group A was planned to prescribe tidal volume 6 ～ 8 mL/kg,initial FiO240％,PEEP gradually increasing from 2 cmH2O to matched with FiO2 elevation,but the FiO2 was kept at permissive lower level.Group B was formulated with tidal volume 8 ～ 12 mL/kg,PEEP stepwise increasing from 0 2 cmH2O to match with FiO2 elevation,but PEEP was kept at permissive lower pressure.The intracranial pressure (ICP),mean arterial pressure (MAP),CPP,arterial and jugular venous blood gas were monitored.Results PEEP (8.2±3.32 cmH2O),ICP (19.7 ±3.6 mmHg),PaCO2 (54±7.3 mmHg),jugular venous carbon dioxide partial pressure (PjV CO2,56.7 ± 9.6 mmHg) in group A were higher than those (5.7±2.3 cmH2O,16.9±3.8 mmHg,41 ±5.2 mmHg,49.8 ±6.9 mmHg) in group B (P＜ 0.05 or P ＜ 0.01).VT,FiO2 in the group A were lower than those in the group B.There were no differences in PaO2/FiO2,jugular venous oxygen saturation (SjVO2),MAP,and CPP between two groups.PaCO2 were significantly correlated with CPP (r =0.368,P =0.019) while there was no correlation with ICP,PaO2,SjVO2,PjVCO2 (all P ＞0.05).CPP (69.7 ± 12.3 mmHg) was higher in case of PaCO2 (46 ～60mmHg) than those (61.5 ±9.1 mmHg) in case of PaCO2 (35 ～45 mmHg).There was correlation between PEEP and ICP (r =0.436,P =0.005).When PEEP was divided into three groups:≤52 cmH2O,6 ～ 102 cmH2O and ＞ 102 cmH2O,ICPs were different one another among three groups.When PEEP ＞ 102 cmH2O,it had a distinguished negative correlation with CPP (r =-0.395,P =0.017),while PEEP ≤ 102 cmH2O,CPP presented decreasing tendency.SjVO2 correlated with PaO2 (r =0.403,P =0.014) and PjVCO2 (r =-0.502,P =0.001) respectively.There were no significant relationships between SjVO2 and CPP,ICP,MAP,PEEP,respectively.Conclusions Lung-protective mechanical ventilation was relatively safer in patients with severe cerebral injury compared with conventional mechanical ventilation.Mild PaCO2 elevation (46 ～ 60 mmHg) combined with higher PEEP (＜ 102 cmH2O) did not decrease CPP.There was no difference in SjVO2 between the two modes of mechanical ventilation,suggesting no changes in cerebral metabolism occurred. Key words: Cerebral injury; Cerebral perfusion pressure; Jugular venous oxygen saturation; Respiratory failure ; Mechanical ventilation ; Acute lung injury ; Tidal volume ; Blood gas analysis ; Positive end-expiratory pressure

Lung-protective Ventilation for Acute Respiratory Distress Syndrome.

Counterpoint: Is Pressure Assist-Control Preferred Over Volume Assist-Control Mode for Lung Protective Ventilation in Patients With ARDS? No

Acute lung injury (ALI) affects an estimated 190,000 persons per year in U.S. intensive care units (ICUs), but little is known about its prevalence in the emergency department (ED). The objective was to describe the prevalence of ALI among mechanically ventilated adult nontrauma patients in the ED. The hypothesis was that the prevalence of ALI in adult ED patients would be low. This was a retrospective cohort study of admitted nontrauma patients presenting to an academic ED. Two trained investigators abstracted data from patient records using a standardized form. The use of mechanical ventilation in the ED was identified in two phases. First, all ED patients were screened for the current procedural terminology (CPT) code for endotracheal intubation (CPT 31500) from January 1, 2003, to December 31, 2006. Second, each patient record was reviewed to verify the use of mechanical ventilation. ALI was defined in accordance with a modified version of the American-European Consensus Conference criteria as: 1) hypoxemia defined as PaO(2) /FiO(2) ratio ≤300 mm Hg on all arterial blood gases (ABGs) in the ED and the first 24 hours of admission, 2) the presence of bilateral infiltrates on chest radiograph, and 3) the absence of left atrial hypertension. Data are presented in absolute numbers and percentages. Interobserver agreement was evaluated using the kappa statistic. Of the 552 patients who received mechanical ventilation in the ED and were subsequently admitted, a total of 134 (24.3%, 95% confidence interval [CI] = 20.8% to 28.0%) met hypoxemia criteria. Of these, 34 had evidence of left atrial hypertension, 52 did not have chest radiograph findings consistent with ALI, and two did not have a chest radiograph performed; the remaining 46 met ALI criteria. An additional two patients who died in the ED had clinical evidence of ALI. Thus, 48 of 552, or 8.7% (95% CI = 6.6% to 11.3%), met criteria for ALI. The kappa value for determination of ALI was 0.84 (95% CI = 0.54 to 1.0). The prevalence of ALI was nearly 9% in adult nontrauma patients receiving mechanical ventilation in the ED. Further study is required to determine which types of patients present to the ED with ALI, the extent to which lung protective ventilation is used, and the need for ED ventilator management algorithms.

POINT: Should Computerized Protocols Replace Physicians for Managing Mechanical Ventilation? Yes

What is the Ideal Tidal Volume During One-Lung Ventilation?

Acute Renal Failure and Mechanical Ventilation: Reality or Myth?

The cardiovascular effects of positive pressure ventilation

The lung-protective mechanical ventilation strategy has been standard practice for management of acute respiratory distress syndrome (ARDS) for more than a decade. Observational data, small randomized studies and two recent systematic reviews suggest that lung protective ventilation is both safe and potentially beneficial in patients who do not have ARDS at the onset of mechanical ventilation. Principles of lung-protective ventilation include: a) prevention of volutrauma (tidal volume 4 to 8 ml/kg predicted body weight with plateau pressure <30 cmH2O); b) prevention of atelectasis (positive end-expiratory pressure ≥5 cmH2O, as needed recruitment maneuvers); c) adequate ventilation (respiratory rate 20 to 35 breaths per minute); and d) prevention of hyperoxia (titrate inspired oxygen concentration to peripheral oxygen saturation (SpO2) levels of 88 to 95%). Most patients tolerate lung protective mechanical ventilation well without the need for excessive sedation. Patients with a stiff chest wall may tolerate higher plateau pressure targets (approximately 35 cmH2O) while those with severe ARDS and ventilator asynchrony may require a short-term neuromuscular blockade. Given the difficulty in timely identification of patients with or at risk of ARDS and both the safety and potential benefit in patients without ARDS, lung-protective mechanical ventilation is recommended as an initial approach to mechanical ventilation in both perioperative and critical care settings.

Background Pulmonary complications are major cause of postoperative mortality. Many factors aggravate pulmonary complications(PPC). Lung protective ventilation strategy prevents pulmonary complications to some extent. Objective To know if lung protective ventilation strategies can improve clinical outcomes of patients with high risk factors. Content To explain if lung protective ventilation strategies can improve clinical outcomes of patients with high risk factors like smoking, advanced age, pulmonary hypertension, chronic obstructive pulmonary disease(COPD), cardiac and neurologic diseases, and so on. Trend In patients with acute respiratory distress syndrome(ARDS), ventilation with low tidal volumes and high level of positive end expiratory pressure(PEEP) are recommended, and intraoperative ventilation should continue the settings applied on the ICU. In other critically ill patients, the evidence for the benefits of low tidal volume ventilation is growing. Low tidal volumes could cause excessive hypercapnia. High level of PEEP could cause dynamic hyperinflation, increased intracranial pressure and increased incidence of hemodynamic instability. We should not use lung protective ventilation strategies blindly. In patients with comorbidities, further research is necessary to find out whether lung protective ventilation should be adopted. Key words: Lung protective ventilation strategies; Postoperative pulmonary complications

Therapeutic Value of a Lung Protective Ventilation Strategy in Acute Lung Injury

Role of Helmet-Delivered Noninvasive Pressure Support Ventilation in COVID-19 Patients

To evaluate the impact of an emergency department mechanical ventilation protocol on clinical outcomes and adherence to lung-protective ventilation in patients with acute respiratory distress syndrome. Quasi-experimental, before-after trial. Emergency department and ICUs of an academic center. Mechanically ventilated emergency department patients experiencing acute respiratory distress syndrome while in the emergency department or after admission to the ICU. An emergency department ventilator protocol which targeted variables in need of quality improvement, as identified by prior work: 1) lung-protective tidal volume, 2) appropriate setting of positive end-expiratory pressure, 3) oxygen weaning, and 4) head-of-bed elevation. A total of 229 patients (186 preintervention group, 43 intervention group) were studied. In the emergency department, the intervention was associated with significant changes (p < 0.01 for all) in tidal volume, positive end-expiratory pressure, respiratory rate, oxygen administration, and head-of-bed elevation. There was a reduction in emergency department tidal volume from 8.1 mL/kg predicted body weight (7.0-9.1) to 6.4 mL/kg predicted body weight (6.1-6.7) and an increase in lung-protective ventilation from 11.1% to 61.5%, p value of less than 0.01. The intervention was associated with a reduction in mortality from 54.8% to 39.5% (odds ratio, 0.38; 95% CI, 0.17-0.83; p = 0.02) and a 3.9 day increase in ventilator-free days, p value equals to 0.01. This before-after study of mechanically ventilated patients with acute respiratory distress syndrome demonstrates that implementing a mechanical ventilator protocol in the emergency department is feasible and associated with improved clinical outcomes.

Background: Lung protective strategy in acute respiratory distress syndrome (ARDS) patients is based on low tidal volume (VT), lower end-inspiratory (plateau) pressure and higher positive end-expiratory pressure (PEEP). But to predict body weight adjusted tidal volume, heterogeneous pathology of the lung in ARDS with different respiratory system compliance (CRS) is not considered. In driving pressure (ΔP=VT / CRS) tidal volume (VT) is normalized to functional lung size. It is unclear whether mechanical ventilation targeting driving pressure (ΔP) is more effective than low tidal volume ventilation (LTVV) in patients with ARDS. Materials and Methods: An open labelled randomized controlled trial was conducted at Intensive Care Unit of Dhaka Medical College Hospital, a tertiary care referral hospital over 12 months from March 2021 to February 2022. Ninety two patients with ARDS, defined by the Berlin criteria, requiring mechanical ventilation were randomized to 1:1 ratio after enrollment in the study using simple random sampling, one group receiving targeted driving pressure (ΔP) that is &lt;/=14cm of H2O ventilation another group receiving low tidal volume ventilation (LTVV) that is 4-6ml/kg PBW. Results: The study found no significant differences between the two groups in terms of clinical variables and laboratory parameters (p &gt; 0.05), except for the duration of mechanical ventilation (MV), which was significantly shorter in the Targeted ΔP group (p&lt;0.05). Aspiration pneumonia was the most common cause of ARDS, occurring in 34.8% of the Targeted ΔP group and 39.1% of the LTVV group. The Targeted ΔP group demonstrated a significant increase in mean respiratory system compliance compared to the LTVV group (p&lt;0.001), and a significantly shorter length of ICU stay (p &lt;0.001). Additionally, the PaO2/FiO2 ratio was significantly higher in the Targeted ΔP group on Days 3, 5, and 7 (p&lt;0.05). Mean exhaled tidal volume was also significantly higher in the Targeted ΔP group on these days (p&lt;0.05). In the Targeted ΔP group, mean driving pressure significantly decreased on Days 3, 5, and 7 (p &lt;0.001), along with a significant reduction in mean plateau pressure (PPlt) (p &lt;0.001). Mean positive end-expiratory pressure (PEEP) significantly decreased on Days 3, 5, and 7 (p &lt;0.001). Respiratory rate significantly decreased on Day 7 (p &lt;0.05). Mean set tidal volume (VT) significantly increased on Days 3, 5, and 7 (p &lt;0.001). Moreover, the 28-day mortality incidence was significantly lower in the Targeted ΔP group compared to the LTVV group (8.7% vs. 26.1%, p &lt;0.05). Conclusion: Targeted Driving pressure (ΔP) guided ventilation offers significant clinical benefits over LTVV in managing ARDS patients in terms of increased respiratory system compliance (CRS), shorter lengths of hospital and ICU stays, and lower in-hospital mortality. Bangladesh Crit Care J September 2024; 12 (2): 81-88