Mechanical ventilation is an importmant life-sustaining treatment for patients with acute respiratory distress syndrome. Its clinical outcomes depend on patients’ characteristics of lung recruitment. Estimation of lung recruitment characteristics is valuable for the determination of ventilatory maneurvers and ventilator parameters. There is no easily-used, bedside method to assess lung recruitment characteristics. The present paper proposed a method to estimate lung recruitment characteristics from the static pressure-volume curve of lungs. The method was evaluated by comparing with published experimental data. Results of lung recruitment derived from the presented method were in high agreement with the published data, suggesting that the proposed method is capable to estimate lung recruitment characteristics. Since some advanced ventilators are capable to measure the static pressure-volume curve automatedly, the presented method is potential to be used at bedside, and it is helpful for clinicians to individualize ventilatory manuevers and the correpsonding ventilator parameters.
Objective To investigate the titration of best positive end-expiratory pressure (Best PEEP) based on mechanical power (MP) and transpulmonary pressure monitoring during lung reexpansion in patients with acute respiratory distress syndrome (ARDS), and to analyze the value of both in evaluating the prognosis of ARDS patients.Methods ARDS patients treated in the intensive care Unit of the First Affiliated Hospital of Jinzhou Medical University from September 2021 to March 2023 were selected and divided into survival group and death group according to the 28-day mortality rate. After full sedation, esophageal pressure tube was inserted through the nasal passage, and lung recruitment maneuvers (RM) was performed by incremental PEEP method. The Best PEEP method was titrated based on MP and transpulmonary pressure. Pearson correlation analysis was used to analyze the correlation between MP at RM 30 min and 2 h and transpulmonary pressure. The changes of clinical indicators at 30 minutes and 2 hours after RM were compared between the two groups with different outcomes. Receiver operating characteristic (ROC) curve was used to analyze the predictive value of 2 h MP and transpulmonary pressure for 28-day mortality in ARDS patients. Results MP and transpulmonary pressure in the survival group decreased significantly at 30 min and 2 h, while MP and transpulmonary pressure in the death group showed a significant upward trend (P < 0.05). The Best PEEP and RR at 30 min and 2 h of the RM in the survival group were lower than those in the death group (P < 0.05). Pearson correlation analysis showed that MP at RM 30 min and 2 h was significantly correlated with transpulmonary pressure (r = 0.710 and 0.804, P < 0.05). The area under the ROC curve of MP and transpulmonary pressure were 0.812 and 0.795, respectively. 95% confidencial interval: 0.704 - 0.920 and 0.687 - 0.903 (P < 0.05); The sensitivity was 86.95% and 82.50%, respectively. The specificity were 76.67% and 59.40%; The positive predictive values were 0.851 and 0.688; The negative predictive values were 0.793 and 0.759; The optimal cut-off values were 15.5 and 17.5, respectively. RM 2 h MP and transpulmonary pressure have good predictive value for 28-day mortality in ARDS patients. Conclusion Monitoring MP and transpulmonary pressure during lung recruitment maneuver can effectively guide the titration of Best PEEP in ARDS patients, and both have good evaluation value for the prognosis of ARDS patients.
Objective To investigate the guiding value of bedside lung ultrasound and lung stretch index for optimal positive end-expiratory pressure (PEEP) in lung recruitment of patients with acute respiratory distress syndrome (ARDS). Methods From February 2020 to October 2023, 90 patients with ARDS requiring invasive mechanical ventilation were selected from the Department of Critical Care Medicine, the Second Affiliated Hospital of Zhengzhou University. According to the setting method of PEEP after lung recruitment, they were randomly divided into an ultrasound group (45 cases) and a stretch group (45 cases). Both groups were treated with PEEP incremental method for lung recruitment, and the ultrasound group was treated with bedside ultrasound-guided method to set PEEP after lung recruitment. PEEP was set by lung stretch index method in the stretch group. The dynamic changes of oxygenation index (PaO2/FiO2), dynamic compliance (Cdyn), mean airway pressure and peak airway pressure were monitored before lung recruitment and 15 min, 1 h, 6 h and 24 h after lung recruitment. Heart rate, mean arterial pressure and central venous pressure were monitored before and 24 h after lung recruitment in the two groups. The optimal PEEP value and the corresponding volume at the end of recruitment were explored. The mechanical ventilation time, ICU hospitalization time, incidence of barotrauma, incidence of extrapulmonary organ failure, and 28-day mortality were recorded as well. Results After lung recruitment, the oxygenation index, Cdyn, mean airway pressure, and peak airway pressure in the ultrasound group were higher than those in the stretch group at 15 min, 1 h, 6 h, and 24 h after recruitment (all P<0.05). There was no significant difference in heart rate, mean arterial pressure or central venous pressure between the two groups at 24 h after lung recruitment (all P>0.05). After lung recruitment, the optimal PEEP value and the corresponding volume at the end of recruitment in the ultrasound group were higher than those in the distraction group (both P<0.05). The mechanical ventilation time and ICU stay in the ultrasound group were shorter than those in the stretch group (both P<0.05). There was no significant difference in the incidence of barotrauma, extrapulmonary organ failure rate or 28-day mortality between the two groups (all P>0.05). Conclusions Both bedside lung ultrasound-guided PEEP and lung stretch index-guided PEEP can improve oxygenation and respiratory compliance, and have no adverse effects on hemodynamics. Bedside lung ultrasound-guided PEEP can make the alveoli fully expand, which is more conducive to improving patients’ oxygenation and respiratory compliance, and the guiding value is higher than the lung stretch index.