Respiratory Mechanical Parameters Research Articles

Esophageal pressure monitoring and its clinical significance in severe blast lung injury.

The incidence of blast lung injury (BLI) has been escalating annually due to military conflicts and industrial accidents. Currently, research into these injuries predominantly uses animal models. Despite the availability of various models, there remains a scarcity of studies focused on monitoring respiratory mechanics post-BLI. Consequently, our objective was to develop a model for monitoring esophageal pressure (Pes) following BLI using a biological shock tube (BST), aimed at providing immediate and precise monitoring of respiratory mechanics parameters post-injury. Six pigs were subjected to BLI using a BST, during which Pes was monitored. We assessed vital signs; conducted blood gas analysis, hemodynamics evaluations, and lung ultrasound; and measured respiratory mechanics before and after the inflicted injury. Furthermore, the gross anatomy of the lungs 3h post-injury was examined, and hematoxylin and eosin staining was conducted on the injured lung tissues for further analysis. The pressure in the experimental section of the BST reached 402.52 ± 17.95KPa, with a peak pressure duration of 53.22 ± 1.69ms. All six pigs exhibited an anatomical lung injury score ≥3, and pathology revealed classic signs of severe BLI. Post-injury vital signs showed an increase in HR and SI, along with a decrease in MAP (p < 0.05). Blood gas analyses indicated elevated levels of Lac, CO2-GAP, A-aDO2, HB, and HCT and reduced levels of DO2, OI, SaO2, and OER (p < 0.05). Hemodynamics and lung ultrasonography findings showed increased ELWI, PVPI, SVRI, and lung ultrasonography scores and decreased CI, SVI, GEDI, and ITBI (p < 0.05). Analysis of respiratory mechanics revealed increased Ppeak, Pplat, Driving P, MAP, PEF, Ri, lung elastance, MP, Ptp, Ppeak - Pplat, and ΔPes, while Cdyn, Cstat, and time constant were reduced (p < 0.05). We have successfully developed a novel respiratory mechanics monitoring model for severe BLI. This model is reliable, repeatable, stable, effective, and user-friendly. Pes monitoring offers a non-invasive and straightforward alternative to blood gas analysis, facilitating early clinical decision-making. Our animal study lays the groundwork for the early diagnosis and management of severe BLI in clinical settings.

Ex Vivo Porcine Experimental Model for Studying and Teaching Lung Mechanics.

Mechanical ventilation is widely used and requires specific knowledge for understanding and management. Health professionals in this field may feel insecure and lack knowledge because of inadequate training and teaching methods. Therefore, the objective of this article is to outline the steps involved in generating an ex vivo porcine lung model to be used in the future, to study and teach lung mechanics. To generate the model, five porcine lungs were carefully removed from the thorax following the guidelines of the Animal Research Ethics Committee with adequate care and were connected to the mechanical ventilator through a tracheal cannula. These lungs were then subjected to the alveolar recruitment maneuver. Respiratory mechanics parameters were recorded, and video cameras were used to obtain videos of the lungs during this process. This process was repeated for five consecutive days. When not used, the lungs were kept refrigerated. The model showed different lung mechanics after the alveolar recruitment maneuver every day; not being influenced by the days, only by the maneuver. Therefore, we conclude that the ex vivo lung model can provide a better understanding of lung mechanics and its effects, and even of the alveolar recruitment maneuver through visual feedback during all stages of the process.

Effects of Levosimendan on Diaphragmatic Dysfunction in Patients with Sepsis.

In this study, our aim was to examine the effects of levosimendan on diaphragmatic dysfunction in patients with sepsis, as well as assess its impact on respiratory muscle contractility and the outcome of weaning. This was a single-blind, randomized, controlled trial. Patients with diaphragmatic dysfunction and failure of spontaneous breathing trials (SBT) were randomly and equally assigned to the experimental and control groups. The experimental group received levosimendan at a loading dose of 6 μg/kg for 10 minutes, followed by a continuous infusion at 0.2 μg/kg/min. The control group received an equivalent dose of a placebo. The pre- and post-administration respiratory mechanics parameters of the patients were recorded. Evaluation of the effect of levosimendan on patients with sepsis-induced diaphragm dysfunction comprised arterial blood gas analysis as well as ultrasound measurements of diaphragm excursion (DE), diaphragm thickness (DT), diaphragm thickening fraction (TFdi), and diaphragm-rapid shallow breathing index (D-RSBI). Forty-four patients were enrolled in the study. We found that post-administration of levosimendan, the patients' tidal volume (GCSMV) increased, while the D-RSBI decreased, and the partial pressure of carbon dioxide (PACO2) decreased when compared to the pre-administration levels. Additionally, following levosimendan administration, patients showed increased DE and pressure support (PS) when compared to before administration (1.14 ± 0.177 vs. 1.22 ± 0.170 cm and 0.248 ± 0.03 vs. 0.284 ± 0.06, respectively), and decreased D-RSBI (22.76 ± 6.14 vs. 20.06 ± 6.04, respectively), all of which were statistically significant (P < 0.05). In contrast, in the control group of patients, there were no statistically significant differences in the post-administration levels of DE, TFdi, and D-RSBI as compared to the pre-administration period (P > 0.05). Furthermore, in terms of weaning outcomes, we did not find any statistically significant difference in the number of patients in the two groups who eventually underwent weaning (P = 0.545). In this study, we found that levosimendan enhanced diaphragm contractile function. However, further investigations are required to explore its effect on weaning outcomes in patients undergoing mechanical ventilation.

Parâmetros do sistema respiratório em crianças com fibrose cística de baixa gravidade: há acometimento precoce em relação a pares saudáveis?

ABSTRACT Objective: To compare and analyze pulmonary function and respiratory mechanics parameters between healthy children and children with cystic fibrosis. Methods: This cross-sectional analytical study included healthy children (HSG) and children with cystic fibrosis (CFG), aged 6–13 years, from teaching institutions and a reference center for cystic fibrosis in Florianópolis/SC, Brazil. The patients were paired by age and sex. Initially, an anthropometric evaluation was undertaken to pair the sample characteristics in both groups; the medical records of CFG were consulted for bacterial colonization, genotype, and disease severity (Schwachman-Doershuk Score — SDS) data. Spirometry and impulse oscillometry were used to assess pulmonary function. Results: In total, 110 children were included, 55 in each group. In the CFG group, 58.2% were classified as excellent by SDS, 49.1% showed the ΔF508 heterozygotic genotype, and 67.3% were colonized by some pathogens. Statistical analysis revealed significant differences between both groups (p&lt;0.05) in most pulmonary function parameters and respiratory mechanics. Conclusions: Children with cystic fibrosis showed obstructive ventilatory disorders and compromised peripheral airways compared with healthy children. These findings reinforce the early changes in pulmonary function and mechanics associated with this disease.

Optimal positive end-expiratory pressure titration of intraoperative mechanical ventilation in different operative positions of female patients under general anesthesia

ObjectiveThis study aimed to compare the effectiveness and safety of different titrated methods used to determine individual positive end-expiratory pressure (PEEP) for intraoperative mechanical ventilation in female patients undergoing general anesthesia in different operative positions, and provide reference ranges of optimal PEEP values based on the titration. MethodsA total of 123 female patients who underwent elective open abdominal surgery under general anesthesia were included in this study. After endotracheal intubation, patients' body position was adjusted to the supine position, Trendelenburg positions at 10° and 20° respectively. PEEP was titrated from 20 cmH2O to 4 cmH2O, decreasing by 2 cmH2O every 1 min. Electrical impedance tomography (EIT), hemodynamic and respiratory mechanics parameters were continuously monitored and recorded. Optimal PEEP values and reference ranges were respectively calculated based on optimal EIT parameters, mean arterial pressure (MAP), and lung dynamic compliance (Cdyn). ResultsEIT-guided optimal PEEP was found to have higher values than those of the MAP-guided and Cdyn-guided methods for all three body positions (P < 0.001), and it was observed to more significantly inhibit hemodynamics (P < 0.05). The variable coefficients of EIT-guided optimal PEEP values were smaller than those of the other two methods, and this technique could provide better ventilation uniformity for dorsal/ventral lung fields and better balance for pulmonary atelectasis/collapse. The 95% reference ranges of EIT-guided optimal PEEP values were 4.6–13.8 cmH2O, 7.0–15.0 cmH2O and 8.6–17.0 cmH2O for the supine position, Trendelenburg 10°, and Trendelenburg 20° positions, respectively. ConclusionEIT-guided optimal PEEP titration was found to be a superior method for lung protective ventilation in different operative positions under general anesthesia. The calculated reference ranges of PEEP values based on the EIT-guided method can be used as a reference for intraoperative mechanical ventilation.

Elastic power, a novel predictor of the severity and prognosis of ARDS

PurposeTo explore the predictive value of the new comprehensive respiratory mechanics parameters elastic power (EP) and elastic power normalized to the compliance (Cst-EP) in the evaluation of the severity and 28-day prognosis of ARDS patients. MethodsThe MIMIC-III database was used to identify ARDS patients under invasive mechanical ventilation for at least 48 h. Their baseline data and ventilatory variables were collected. EP, elastic energy, driving pressure and mechanical power were calculated according to the corresponding formulas. Their value in assessing the severity of ARDS was evaluated. The correlation between Cst-EP and 28-day prognosis of ARDS patients was analyzed. ResultsEP was independently associated with the severity of the ARDS and the odds ratio (OR) was 1.301 [95% CI (1.190–1.423), p < 0.001]. It has higher accuracy for the severity of ARDS, with an optimal cut-off value of 14.6 J/min. The Cst-EP was significantly associated with increased risk of death and the hazard ratio (HR) per 100 J/min × cmH2O/ml × 10−3 was 1.169 [95% CI (1.093–1.250), p < 0.001]. In addition, the 28-day cumulative survival rate of the high Cst-EP group was significantly lower than that of the low Cst-EP group. ConclusionEP can be used to predict the severity of ARDS, and Cst-EP is associated with mortality during controlled mechanical ventilation in ARDS.

Efficacy and Safety Evaluation of Different Maintenance Dose Regimens of Caffeine Citrate in the Treatment of Primary Apnea in Preterm Infants

We have investigated the efficacy and safety of different maintenance doses of caffeine citrate in the treatment of primary apnea in preterm infants. To this end, apneic premature infants were treated with 5 mg/kg (low dose) or 10 mg/kg (high dose) caffeine citrate, and the frequency of apnea at 48 h and 72 h, improvement of clinical symptoms, respiratory mechanics parameters related to lung function, and blood gas analysis indexes were compared between the two groups, and safety was evaluated. The frequency of apnea at 48 h and 72 h was significantly lower in the high-dose group than in the low-dose group, and the difference was statistically significant (P &lt; 0.05). The time to resolution of apnea, the time to mechanical ventilation, and the time to citrate use were significantly shorter in the high-dose group than in the low-dose group (P &lt; 0.05). The tidal volume and peak expiratory flow values were significantly higher in the high-dose group than in the low-dose group (P &lt; 0.05). The oxygen partial pressure and pulse oximetry levels in the blood gas analysis indexes of the high-dose group were significantly higher than those of the low-dose group, and the partial pressure of carbon dioxide level was significantly lower than that of the low-dose group, with statistically significant differences (P &lt; 0.05). The safety evaluation results showed no significant difference in the rate of adverse reactions and short-term complications between the high-dose group and the low-dose group (P &gt; 0.05). Caffeine citrate at a maintenance dose of 10 mg/kg can effectively reduce the frequency of apnea, shorten the improvement time of clinical symptoms, and improve the lung function and blood gas analysis level of children with a high safety profile.

Development and validation of a mechanical power-oriented nomogram model for predicting the risk of weaning failure in mechanically ventilated patients: an analysis using the data from MIMIC-IV

To develop and validate a mechanical power (MP)-oriented nomogram prediction model of weaning failure in mechanically ventilated patients. Patients who underwent invasive mechanical ventilation (IMV) for more than 24 hours and were weaned using a T-tube ventilation strategy were collected from the Medical Information Mart for Intensive Care-IV v1.0 (MIMIC-IV v1.0) database. Demographic information and comorbidities, respiratory mechanics parameters 4 hours before the first spontaneous breathing trial (SBT), laboratory parameters preceding the SBT, vital signs and blood gas analysis during SBT, length of intensive care unit (ICU) stay and IMV duration were collected and all eligible patients were enrolled into the model group. Lasso method was used to screen the risk factors affecting weaning outcomes, which were included in the multivariate Logistic regression analysis. R software was used to construct the nomogram prediction model and build the dynamic web page nomogram. The discrimination and accuracy of the nomogram were assessed by receiver operator characteristic curve (ROC curve) and calibration curves, and the clinical validity was assessed by decision curve analysis (DCA). The data of patients undergoing mechanical ventilation hospitalized in ICU of the First People's Hospital of Lianyungang City and the Second People's Hospital of Lianyungang City from November 2021 to October 2022 were prospectively collected to externally validate the model. A total of 3 695 mechanically ventilated patients were included in the model group, and the weaning failure rate was 38.5% (1 421/3 695). Lasso regression analysis finally screened out six variables, including positive end-expiratory pressure (PEEP), MP, dynamic lung compliance (Cdyn), inspired oxygen concentration (FiO2), length of ICU stay and IMV duration, with coefficients of 0.144, 0.047, -0.032, 0.027, 0.090 and 0.098, respectively. Logistic regression analysis showed that the six variables were all independent risk factors for predicting weaning failure risk [odds ratio (OR) and 95% confidence interval (95%CI) were 1.155 (1.111-1.200), 1.048 (1.031-1.066), 0.968 (0.963-0.974), 1.028 (1.017-1.038), 1.095 (1.076-1.113), and 1.103 (1.070-1.137), all P < 0.01]. The MP-oriented nomogram prediction model of weaning failure in mechanically ventilated patients showed accurate discrimination both in the model group and external validation group, with area under the ROC curve (AUC) and 95%CI of 0.832 (0.819-0.845) and 0.879 (0.833-0.925), respectively. Furthermore, its predictive accuracy was significantly higher than that of individual indicators such as MP, Cdyn, and PEEP. Calibration curves showed good correlation between predicted and observed outcomes. DCA indicated that the nomogram model had high net benefits, and was clinically beneficial. The MP-oriented nomogram prediction model of weaning failure accurately predicts the risk of weaning failure in mechanical ventilation patients and provides valuable information for clinicians making decisions on weaning.

Effect of neurally adjusted ventilatory assist ventilation in severe neurological cerebrovascular diseases patients undergoing mechanical ventilation

To explore the prognostic effect and safety of neurally adjusted ventilatory assist (NAVA) mode on the patients with severe neurological cerebrovascular disease undergoing mechanical ventilation. A prospective study was conducted. Fifty-four patients with cerebrovascular disease undergoing mechanical ventilation admitted to the neurosurgery intensive care unit (NSICU) of the First Affiliated Hospital of Wannan Medical College (Yijishan Hospital) from December 2020 to May 2022 were enrolled. They were divided into NAVA group and pressure support ventilation (PSV) group by computer random number generator with 27 patients in each group. The ventilation time of the two groups was ≥ 72 hours. The general basic data of the two groups were recorded. The time without mechanical ventilation 28 days after enrollment, total length of mechanical ventilation, survival rate of 90 days after enrollment, length of NSICU stay, total length of hospital stay, NSICU mortality, in-hospital mortality, Glasgow outcome score (GOS), complications related to mechanical ventilation, and changes of respiratory mechanics indexes, arterial blood gases, vital signs, and diaphragm function indexes were observed. The time without mechanical ventilation 28 days after enrollment in the NAVA group was significantly longer than that in the PSV group [days: 22 (15, 26) vs. 6 (0, 23), P < 0.05]. However, there were no significant differences in the total length of mechanical ventilation, 90-day survival rate, length of NSICU stay, total length of hospital stay, NSICU mortality, in-hospital mortality, GOS score, and incidence of mechanical ventilator-related complications between the two groups. In terms of respiratory mechanics parameters, the expiratory tidal volume (VTe) on 3 days after mechanical ventilation of patients in the NAVA group was significantly lower than that on 1 day and 2 days, and significantly lower than that in the PSV group [mL: 411.0 (385.2, 492.6) vs. 489.0 (451.8, 529.4), P < 0.01]. Minute ventilation (MV) at 2 days and 3 days in the NAVA group was significantly higher than that at 1 day, and significantly higher than that in the PSV group at 2 days [L/min: 9.8 (8.4, 10.9) vs. 7.8 (6.5, 9.8), P < 0.01], while there was no significant change of MV in the PSV group. At 1 day, peak airway pressure (Ppeak) and mean airway pressure (Pmean) in the NAVA group were significantly lower than those in the PSV group [Ppeak (cmH2O, 1 cmH2O ≈ 0.098 kPa): 14.0 (12.2, 17.0) vs. 16.6 (15.0, 17.4), Pmean (cmH2O): 7.0 (6.2, 7.9) vs. 8.0 (7.0, 8.2), both P < 0.05]. However, there was no significant difference in the Ppeak or Pmean at 2 days and 3 days between the two groups. In terms of arterial blood gas, there was no significant difference in pH value between the two groups, but with the extension of mechanical ventilation time, the pH value at 3 days of the two groups was significantly higher than that at 1 day. Arterial partial pressure of oxygen (PaO2) at 1 day in the NAVA group was significantly lower than that in the PSV group [mmHg (1 mmHg ≈ 0.133 kPa): 122.01±37.77 vs. 144.10±40.39, P < 0.05], but there was no significant difference in PaO2 at 2 days and 3 days between the two groups. There was no significant difference in arterial partial pressure of carbon dioxide (PaCO2) or oxygenation index (PaO2/FiO2) between the two groups. In terms of vital signs, the respiratory rate (RR) at 1, 2, and 3 days of the NAVA group was significantly higher than that of the PSV group [times/min: 19.2 (16.0, 25.2) vs. 15.0 (14.4, 17.0) at 1 day, 21.4 (16.4, 26.0) vs. 15.8 (14.0, 18.6) at 2 days, 20.6 (17.0, 23.0) vs. 16.7 (15.0, 19.0) at 3 days, all P < 0.01]. In terms of diaphragm function, end-inspiratory diaphragm thickness (DTei) at 3 days in the NAVA group was significantly higher than that in the PSV group [cm: 0.26 (0.22, 0.29) vs. 0.22 (0.19, 0.26), P < 0.05]. There was no significant difference in end-expiratory diaphragm thickness (DTee) between the two groups. The diaphragm thickening fraction (DTF) at 2 days and 3 days in the NAVA group was significantly higher than that in the PSV group [(35.18±12.09)% vs. (26.88±8.33)% at 2 days, (35.54±13.40)% vs. (24.39±9.16)% at 3 days, both P < 0.05]. NAVA mode can be applied in patients with neuro-severe cerebrovascular disease, which can prolong the time without mechanical ventilation support and make patients obtain better lung protective ventilation. At the same time, it has certain advantages in avoiding ventilator-associated diaphragm dysfunction and improving diaphragm function.

Physiological Regulation of Pulmonary Microcirculation under Mechanical Ventilation at Different Cardiac Outputs and Positive End-Expiratory Pressures in a Porcine Model.

This study was performed to visualize the hemodynamic effects of pulmonary microcirculation and ventilation/perfusion (V/Q) matching after mechanical ventilation under different cardiac outputs and positive end-expiratory pressures (PEEPs). Ten experimental pigs were randomly divided into high and low tidal volume groups, and ventilation/perfusion were measured by electrical impedance tomography (EIT) at different PEEPs. Then, all the pigs were redivided into high cardiac output (CO) and low CO groups and measured by EIT at different PEEP levels with a low tidal volume. Additionally, sidestream dark field (SDF) was used to measure pulmonary microcirculation. Hemodynamic parameters and respiratory mechanics parameters were recorded. As PEEP increased at high tidal volume, blood flow was impaired at a higher PEEP (20 cmH2O) compared with low tidal volume (shunt: 30.01 ± 0.69% vs. 17.95 ± 0.72%; V/Q ratio: 65.12 ± 1.97% vs. 76.57 ± 1.25%, p &lt; 0.01). Low tidal volume combined with an appropriate PEEP is the best option from the match between ventilation and pulmonary blood flow. Increasing PEEP can solve the problem of excessive shunt at high CO, and the V/Q ratio tends to match. At low CO, the increased dead space can reach as high as 64.64 ± 7.13% when PEEP = 20 cmH2O. With increasing PEEP, the microcirculation index deteriorates, including total vessel density (TVD), proportion of perfused vessel (PPV), perfused vessel density (PVD), and microcirculatory flow index (MFI). The periodic collapse of pulmonary capillaries or interruption of blood flow obviously occurred with high PEEP. The hemodynamic parameters indicated that the transpulmonary capillary wall pressure (Pcap) of the low CO group was negative at PEEP = 5 cmH2O, which determines the opening and closing of the pulmonary microcirculation and controls lung perfusion and the production of extravascular lung water. Therefore, it is essential to couple macrocirculation and pulmonary microcirculation during mechanical ventilation by improving shunting and optimizing Pcap.

Different positive end expiratory pressure and tidal volume controls on lung protection and inflammatory factors during surgical anesthesia.

Mechanical ventilation can lead to the severe impairment of the metabolic pathway of alveolar surfactants, inactivating alveolar surfactants and significantly reducing lung-chest compliance. The cardiopulmonary function of elderly patients usually reduced to a certain extent, and there are lung complications after surgical anesthesia, just like lung barotrauma caused by mechanical ventilation, atelectasis and postoperative hypoxemia. To investigate the effects of different positive end expiratory pressures (PEEPs) and tidal volumes (VTs) on respiratory function, the degree of the inflammatory response and hemodynamic indexes in patients undergoing surgery under general anesthesia. A total of 120 patients undergoing surgery for gastric or colon cancer under general anesthesia in Xinghua People's Hospital from January 2017 to January 2021 were randomly divided into Group A and Group B, with 60 cases in each group. The ventilation mode in Group A was VT (6.0 mL/kg) + PEEP (5.0 cmH2O), while that in Group B was VT (6.0 mL/kg) + PEEP (8.0 cmH2O). Blood gas parameters, respiratory mechanical parameters, inflammatory response indicators, hemodynamic indicators and related complications were compared between the two groups. There were no significant differences in PaCO2, PaO2, oxygen or the examined indexes at T0 between group A and group B (P > 0.05). The measured PaO2 value of patients in group A at T3 was higher than that in group B, and the difference was significant (P < 0.05). There were no significant differences in peak airway pressure (Ppeak), mean airway pressure or dynamic pulmonary compliance (Cdyn) at T0 between group A and group B (P > 0.05). The measured Ppeak value of patients in group A at T1 was higher than that in group B, and the difference was significant (P < 0.05). The measured Cdyn value at T1 and T2 was greater than that in group B (P < 0.05). Before surgery, there were no significant differences in tumor necrosis factor-α (TNF-α), interleukin (IL)-6 or IL-10 between group A and group B (P > 0.05). After 4 h, the measured values of TNF-α and IL-6 in group A were lower than those in group B, and the differences were significant (P < 0.05). The IL-10 Level in group A was higher than that in group B (P < 0.05). At T0, there were no significant differences in cardiac output, cardiac index (CI), stroke volume index (SVI) or mean arterial pressure between group A and group B (P > 0.05). The measured values of CI and SVI at T2 in patients in group A were higher than those in group B, and the differences were significant (P < 0.05). For patients undergoing surgery for gastric or colon cancer under general anesthesia, the VT (6.0 mL/kg) + PEEP (5.0 cmH2O) regimen was more effective than the VT (6.0 mL/kg) + PEEP (8.0 cmH2O) regimen in protecting the lung function and ventilatory function of patients, and it had better effects on maintaining hemodynamic stability and reducing inflammatory reactions.

Distinct type I collagen alterations cause intrinsic lung and respiratory defects of variable severity in mouse models of osteogenesis imperfecta.

Type I collagen alterations cause osteogenesis imperfecta (OI), a connective tissue disorder characterized by severe bone fragility. Patients with OI can suffer from significant pulmonary manifestations including severe respiratory distress in the neonatal period and a progressive decline in respiratory function in adulthood. We and others have shown intrinsic lung defects in some mouse models of OI. In this large study, we performed histological, histomorphometric, microcomputed tomography and invasive studies on oim/+, Col1a2+/G610C , CrtapKO and oim/oim mice, mimicking mild to moderate to severe OI, with the overall goal of determining the extent of their pulmonary and respiratory mechanics defects and whether these defects correlate with the skeletal disease severity and affect each sex equally. Although with variable severity, OI lung histology consistently showed alveolar simplification with enlarged acinar airspace and reduced alveolar surface. Numerous respiratory mechanics parameters, including respiratory system resistance and elastance, tissue damping, inspiratory capacity, total lung capacity, and others, were significantly and similarly impacted in CrtapKO and oim/oim but not in oim/+ or Col1a2+/G610C compared to control mice. Our data indicate that the impact of type I collagen alterations and OI on lung morphology and function positively correlate with the severity of the extracellular matrix deficiency. Moreover, the respiratory defects were more pronounced in male compared to female mice. It will be important to determine whether our observations in mice translate to OI patients and to dissect the respective contribution of intrinsic lung defects vs. extrinsic skeletal defects to impaired lung function in OI. KEY POINTS: Different type I collagen alterations in mouse models of osteogenesis imperfecta (OI) cause similar abnormal lung histology, with alveolar simplification and reduced alveolar surface, reminiscent of emphysema. Several respiratory mechanics parameters are altered in mouse models of OI. The impact of type I collagen alterations and OI on lung morphology and function positively correlate with the severity of the extracellular matrix deficiency. Respiratory defects were more pronounced in male compared to female mice. It will be important to determine whether our observations in mice translate to OI patients and to dissect the respective contribution of intrinsic lung defects vs. extrinsic skeletal defects to impaired lung function in OI.

Sequential treatment of severe pneumonia with respiratory failure and its influence on respiratory mechanical parameters and hemodynamics.

BACKGROUNDThe pathophysiological characteristics of severe pneumonia complicated by respiratory failure comprise pulmonary parenchymal changes leading to ventilation imbalance, alveolar capillary injury, pulmonary edema, refractory hypoxemia, and reduced lung compliance. Prolonged hypoxia can cause acid-base balance disorder, peripheral circulatory failure, blood-pressure reduction, arrhythmia, and other adverse consequences.AIMTo investigate sequential mechanical ventilation’s effect on severe pneumonia complicated by respiratory failure. METHODSWe selected 108 patients with severe pneumonia complicated by respiratory failure who underwent mechanical ventilation between January 2018 and September 2020 at the Luhe Hospital’s Intensive Care Unit and divided them into sequential and regular groups according to a randomized trial, with each group comprising 54 patients. The sequential group received invasive and non-invasive sequential mechanical ventilation, whereas the regular group received invasive mechanical ventilation. Blood-gas parameters, hemodynamic parameters, respiratory mechanical parameters, inflammatory factors, and treatment outcomes were compared between the two groups before and after mechanical-ventilation treatment. RESULTSThe arterial oxygen partial pressure and stroke volume variation values of the sequential group at 24, 48, and 72 h of treatment were higher than those of the conventional group (P < 0.05). The carbon dioxide partial pressure value of the sequential group at 72 h of treatment and the Raw value of the treatment group at 24 and 48 h were lower than those of the conventional group (P < 0.05). The pH value of the sequential group at 24 and 72 h of treatment, the central venous pressure value of the treatment at 24 h, and the Cst value of the treatment at 24 and 48 h were higher than those of the conventional group (P < 0.05). The tidal volume in the sequential group at 24 h of treatment was higher than that in the conventional group (P < 0.05), the measured values of interleukin-6 and tumor necrosis factor-α in the sequential group at 72 h of treatment were lower than those in the conventional group (P < 0.05), and the total time of mechanical ventilation in the sequential group was shorter than that in the conventional group, with a statistically significant difference (P < 0.05).CONCLUSIONTreating severe pneumonia complicated by respiratory failure with sequential mechanical ventilation is more effective in improving respiratory system compliance, reducing inflammatory response, maintaining hemodynamic stability, and improving patient blood-gas levels; however, from this study’s perspective, it cannot reduce patient mortality.

Effect of respiratory mechanics-guided sedation strategy on diaphragm function in mechanical ventilated patients with chronic obstructive pulmonary disease

To investigate the effects of respiratory mechanics-guided sedation strategy on diaphragm function in chronic obstructive pulmonary disease (COPD) patients treated with mechanical ventilation (MV). A prospective study was conducted. Patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD) received invasive MV who were admitted to the Affiliated Huxi Hospital of Jining Medical University from May 2020 to May 2021 were enrolled. The patients were divided into observational group and control group by random number table method. All patients were intubated for MV, and received bronchodilators, glucocorticoid, anti-infectives, expectorant, nutritional support, analgesia and sedation. The sedatives were dexmedetomidine combined with propofol, and the analgesics were sufentanil in both groups. Respiratory mechanics monitoring was performed every 6 hours in the observational group, and the depth of sedation was adjusted according to the parameters of respiratory mechanics: when airway resistance (Raw) > 20 cmH2O×L-1×s-1, deep sedation was given to maintain Richmond agitation-sedation scale (RASS) ≤ -3; when the Raw was 10-20 cmH2O×L-1×s-1, the initial depth of sedation maintained to reach the RASS score of -2-0; when Raw < 10 cmH2O×L-1×s-1, withdrawn the sedation, or given light sedation, and maintained the RASS score of -2-0. While the control group received light sedation. The patients' diaphragmatic excursions (DE) was measured by bedside ultrasound, tidal volume (VT) and respiratory rate (RR) were recorded, and the diaphragmatic rapid shallow breathing index (D-RSBI, D-RSBI = RR/DE) and diaphragmatic excursion efficiency (DEE, DEE = VT/DE) were calculated. The differences in DE, D-RSBI, and DEE before and 3 days and 5 days of treatment between the two groups were compared. The difference in the RASS score within 3 days of sedation between the two groups was compared. The differences in the duration of MV and 28-day mortality between the two groups were compared. A total of 96 patients were selected. Six patients were excluded due to delirium or the duration of MV shorter than 3 days. Finally, 90 patients were enrolled, with 46 in the observational group, and 44 in the control group. There were no statistically significant differences in DE, D-RSBI or DEE before treatment between the two groups. After treatment, D-RSBI in both groups was gradually decreased, and DEE was gradually increased with time. The D-RSBI at 3 days and 5 days of treatment in the observational group were significantly lower than those in the control group (times×min-1×mm-1: 1.73±0.48 vs. 1.96±0.35 at 3 days, 1.45±0.64 vs. 1.72±0.40 at 5 days, both P < 0.05), and DEE were significantly higher than those in the control group (mL/mm: 19.7±4.3 vs. 17.1±3.9 at 3 days, 25.8±5.6 vs. 22.9±5.4 at 5 days, both P < 0.05). There was no significant difference in DE at all time points between the two groups. The RASS scores within 2 hours of sedation in the observational group were significantly lower than those in the control group (1 day: -3.78±0.92 vs. -2.34±0.68, 2 days: -2.87±1.04 vs. -2.43±0.79, both P < 0.05), while no statistical difference at 3 days was found between the two groups. The duration of MV in the observational group was significantly shorter than that in the control group (days: 5.78±2.01 vs. 6.84±2.27, P < 0.05). One patient died in each of the control group and the observational group, and there was no significant difference in the 28-day mortality between the two groups (2.3% vs. 2.2%, P > 0.05). For AECOPD patients undergoing MV, respiratory mechanics-guided sedation strategy can reduce D-RSBI, increase DEE, shorten the duration of MV, and have a certain protective effect on the diaphragm.

Full Assessment of Lung Mechanics Using Computer-Controlled, Forced Oscillation Technique.

The forced oscillation technique (FOT) is a powerful and accurate method to quantify the mechanical properties of the airways and tissues of the respiratory system. Here we provide a detailed protocol for the measurement of mouse respiratory mechanical parameters. We present a procedure for mouse endotracheal intubation using a handcrafted intubation platform and confirmation module. The FlexiVentFX™ system (Scireq Inc.) is utilized for the thorough assessment of lung function with the FlexiWare™ software serving as a unit for the planning, experimentation, and analysis. The protocol has been standardized and adapted for use by our center for lung-function phenotyping of mouse models generated for the International Mouse Phenotyping Consortium (IMPC). The simplified steps, technical considerations, and integrated hardware-software demonstration make this protocol adaptable and implementable for researchers interested in using FOT for lung-function evaluation. © 2022 The Authors. Current Protocols published by Wiley Periodicals LLC. Support Protocol 1: Assembly of the FlexiVentFX™ system for measurements Support Protocol 2: FlexiWare database management Support Protocol 3: A guide for the construction of intubation platform and confirmation module Basic Protocol 1: Mouse endotracheal intubation Basic Protocol 2: Assessment of mouse basal lung function.

Effect of Driving Pressure-Oriented Ventilation on Patients Undergoing One-Lung Ventilation During Thoracic Surgery: A Systematic Review and Meta-Analysis.

BackgroundHypoxemia and fluctuations in respiratory mechanics parameters are common during one-lung ventilation (OLV) in thoracic surgery. Additionally, the incidence of postoperative pulmonary complications (PPCS) in thoracic surgery is higher than that in other surgeries. Previous studies have demonstrated that driving pressure-oriented ventilation can reduce both mortality in patients with acute respiratory distress syndrome (ARDS) and the incidence of PPCS in patients undergoing general anesthesia. Our aim was to determine whether driving pressure-oriented ventilation improves intraoperative physiology and outcomes in patients undergoing thoracic surgery.MethodsWe searched MEDLINE via PubMed, Embase, Cochrane, Web of Science, and ClinicalTrials.gov and performed a meta-analysis to compare the effects of driving pressure-oriented ventilation with other ventilation strategies on patients undergoing OLV. The primary outcome was the PaO2/FiO2 ratio (P/F ratio) during OLV. The secondary outcomes were the incidence of PPCS during follow-up, compliance of the respiratory system during OLV, and mean arterial pressure during OLV.ResultsThis review included seven studies, with a total of 640 patients. The PaO2/FiO2 ratio was higher during OLV in the driving pressure-oriented ventilation group (mean difference [MD]: 44.96; 95% confidence interval [CI], 24.22–65.70.32; I2: 58%; P < 0.0001). The incidence of PPCS was lower (OR: 0.58; 95% CI, 0.34–0.99; I2: 0%; P = 0.04) and the compliance of the respiratory system was higher (MD: 6.15; 95% CI, 3.97–8.32; I2: 57%; P < 0.00001) in the driving pressure-oriented group during OLV. We did not find a significant difference in the mean arterial pressure between the two groups.ConclusionDriving pressure-oriented ventilation during OLV in patients undergoing thoracic surgery was associated with better perioperative oxygenation, fewer PPCS, and improved compliance of the respiratory system.Systematic Review RegistrationPROSPERO, identifier: CRD42021297063.

Effects of Prone Positioning on Respiratory Mechanics and Oxygenation in Critically Ill Patients With COVID-19 Requiring Venovenous Extracorporeal Membrane Oxygenation.

Background:The effect of prone positioning (PP) on respiratory mechanics remains uncertain in patients with severe acute respiratory distress syndrome (ARDS) requiring venovenous extracorporeal membrane oxygenation (VV-ECMO).Methods:We prospectively analyzed the effects of PP on respiratory mechanics from continuous data with over a thousand time points during 16-h PP sessions in patients with COVID-19 and ARDS under VV-ECMO conditions. The evolution of respiratory mechanical and oxygenation parameters during the PP sessions was evaluated by dividing each PP session into four time quartiles: first quartile: 0–4 h, second quartile: 4–8 h, third quartile: 8–12 h, and fourth quartile: 12–16 h.Results:Overall, 38 PP sessions were performed in 10 patients, with 3 [2–5] PP sessions per patient. Seven (70%) patients were responders to at least one PP session. PP significantly increased the PaO2/FiO2 ratio by 14 ± 21% and compliance by 8 ± 15%, and significantly decreased the oxygenation index by 13 ± 18% and driving pressure by 8 ± 12%. The effects of PP on respiratory mechanics but not on oxygenation persisted after supine repositioning. PP-induced changes in different respiratory mechanical parameters and oxygenation started as early as the first-time quartile, without any difference in PP-induced changes among the different time quartiles. PP-induced changes in driving pressure (−14 ± 14 vs. −6 ± 10%, p = 0.04) and mechanical power (−11 ± 13 vs. −0.1 ± 12%, p = 0.02) were significantly higher in responders (increase in PaO2/FiO2 ratio > 20%) than in non-responder patients.Conclusions:In patients with COVID-19 and severe ARDS, PP under VV-ECMO conditions improved the respiratory mechanical and oxygenation parameters, and the effects of PP on respiratory mechanics persisted after supine repositioning.

Diagnostic value of mechanical power in patients with moderate to severe acute respiratory distress syndrome: an analysis using the data from MIMIC-III

To explore the diagnostic value of mechanical power (MP) in patients with moderate to severe acute respiratory distress syndrome (ARDS) based on the Medical Information Mart for Intensive Care-IIIv1.4 (MIMIC-III v1.4). The information of ARDS patients undergoing invasive mechanical ventilation for no less than 48 hours who were hospitalized at Beth Israel Deaconess Medical Center in Boston, Massachusetts from June 2001 to October 2012 in the MIMIC-III v1.4 were collected. The demographics of patients, disease severity scores, ARDS etiology, prognostic indicators, pre-ventilation arterial blood gas analysis and respiratory parameters within 48 hours of ventilation were extracted. According to the lowest oxygenation index (PaO2/FiO2) before ventilation, the patients were divided into mild to moderate ARDS group (> 150 mmHg, 1 mmHg≈0.133 kPa) and moderate to severe ARDS group (≤ 150 mmHg), and the differences in baseline characteristics between the two groups were compared. The independent predictors associated with the severity of ARDS were analyzed using Logistic regression. The receiver operator characteristic curve (ROC curve) was plotted. The area under ROC curve (AUC) was calculated to evaluate the diagnostic value of MP for moderate to severe ARDS. The Youden index was used to determine the diagnostic threshold of MP for moderate to severe ARDS. According to the cut-off value of MP based on Youden index, all ARDS patients were divided into high and low MP groups. Kaplan-Meier survival curve was used to analyze the 28-day survival status of patients. A total of 403 ARDS patients were enrolled in the study, including 107 subjects with mild to moderate ARDS and 296 with moderate to severe ARDS. There were significant differences in age, sequential organ failure assessment (SOFA) score, the lowest PaO2/FiO2 before ventilation, the last PaO2/FiO2 before ventilation, 28-day mortality, the length of intensive care unit (ICU) stay, duration of mechanical ventilation, lung dynamic compliance (Cdyn) in the second 24 hours of ventilation and positive end-expiratory pressure (PEEP), plateau pressure (Pplat), driving pressure (ΔP), respiratory rate (RR), lung static compliance (Cst), MP, inspired fraction of oxygen (FiO2) within 48 hours of ventilation between the two groups. After adjusting variables such as age, SOFA score, the last PaO2/FiO2 before ventilation, and related respiratory mechanics parameters, multivariate Logistic regression analysis showed that higher ΔP, PEEP and MP, and lower last PaO2/FiO2 before ventilation were independently associated with moderate to severe ARDS [odds ratio (OR) and 95% confidence interval (95%CI) was 1.137 (1.032-1.252), 1.333 (1.139-1.561), 1.102 (1.030-1.179), and 0.996 (0.993-0.998), respectively, all P < 0.01]. The ROC curve analysis showed that the best cut-off value of MP for the diagnosis of moderate to severe ARDS was 18.1 J/min with sensitivity of 81.42% and specificity of 60.75%, and the AUC was 0.745 (95%CI was 0.690-0.799). According to the cut-off value of MP obtained by ROC curve, all ARDS patients were divided into high MP group (> 18.1 J/min) and low MP group (≤ 18.1 J/min). The Kaplan-Meier survival curve showed that the 28-day cumulative survival rate in the high MP group was significantly lower than that in the low MP group (73.8% vs. 85.1%; Log-Rank test: χ2 = 5.660, P = 0.017). MP is an independent predictor of the severity of ARDS, and it can be used to diagnose moderate to severe ARDS.

Effects of Different Levels of Variability and Pressure Support Ventilation on Lung Function in Patients With Mild–Moderate Acute Respiratory Distress Syndrome

Background: Variable pressure support ventilation (vPSV) is an assisted ventilation mode that varies the level of pressure support on a breath-by-breath basis to restore the physiological variability of breathing activity. We aimed to compare the effects of vPSV at different levels of variability and pressure support (ΔPS) in patients with acute respiratory distress syndrome (ARDS).Methods: This study was a crossover randomized clinical trial. We included patients with mild to moderate ARDS already ventilated in conventional pressure support ventilation (PSV). The study consisted of two blocks of interventions, and variability during vPSV was set as the coefficient of variation of the ΔPS level. In the first block, the effects of three levels of variability were tested at constant ΔPS: 0% (PSV0%, conventional PSV), 15% (vPSV15%), and 30% (vPSV30%). In the second block, two levels of variability (0% and variability set to achieve ±5 cmH2O variability) were tested at two ΔPS levels (baseline ΔPS and ΔPS reduced by 5 cmH2O from baseline). The following four ventilation strategies were tested in the second block: PSV with baseline ΔPS and 0% variability (PSVBL) or ±5 cmH2O variability (vPSVBL), PSV with ΔPS reduced by 5 cmH2O and 0% variability (PSV−5) or ±5 cmH2O variability (vPSV−5). Outcomes included gas exchange, respiratory mechanics, and patient-ventilator asynchronies.Results: The study enrolled 20 patients. In the first block of interventions, oxygenation and respiratory mechanics parameters did not differ between vPSV15% and vPSV30% compared with PSV0%. The variability of tidal volume (VT) was higher with vPSV15% and vPSV30% compared with PSV0%. The incidence of asynchronies and the variability of transpulmonary pressure (PL) were higher with vPSV30% compared with PSV0%. In the second block of interventions, different levels of pressure support with and without variability did not change oxygenation. The variability of VT and PL was higher with vPSV−5 compared with PSV−5, but not with vPSVBL compared with PSVBL.Conclusion: In patients with mild-moderate ARDS, the addition of variability did not improve oxygenation at different pressure support levels. Moreover, high variability levels were associated with worse patient-ventilator synchrony.Clinical Trial Registration: www.clinicaltrials.gov, identifier: NCT01683669.

Relationship of respiratory mechanics parameters acquired by forced oscillation technique (FOT) and morphological measurements in BALB/c mice

Relationship of respiratory mechanics parameters acquired by forced oscillation technique (FOT) and morphological measurements in BALB/c mice