Lung Mechanical Parameters Research Articles

Effect of mechanical ventilation guided by transpulmonary pressure in acute respiratory distress syndrome patients: a systematic review and meta-analysis of randomized control trials.

This study aimed to investigate the effect of mechanical ventilation guided by transpulmonary pressure in patients diagnosed with acute respiratory distress syndrome (ARDS). Randomized control trials of ARDS patients that received mechanical ventilation guided by transpulmonary pressure vs. mechanical ventilation guided by traditional lung protective ventilation strategies in adults were retrieved by two reviewers independently from PubMed, EMBASE, The Cochrane Library, The China National Knowledge Infrastructure, and WanFang database before October 2022. The protocol has been registered on PROSPERO (CRD42022307816). The primary outcome was mortality. The secondary outcomes included mechanical ventilation days, oxygenation function and ventilation parameters, hemodynamics, and cytokines level. Thirteen articles (819 patients) were finally included through our search strategy. The total mortality (RR, 0.68; 95% CI, 0.54-0.85; p = 0.0006) and mechanical ventilation days (MD, -2.77; 95% CI, -4.60 - -0.94; p = 0.003) reduced when compared with the control group. Patients in the transpulmonary pressure group had higher oxygen index (MD, 40.74; 95% CI 9.81-71.68, p = 0.010) and lung compliance (MD, 7.98; 95% CI 4.55-11.41, p < 0.00001). Positive end-expiratory pressure (PEEP) was higher in the transpulmonary pressure group (MD, 5.47; 95% CI, 3.59 - 7.35; p < 0.00001). The Interlukin-6 (IL-6) level in the control group decreased obviously compared with that in the transpulmonary pressure group (SMD, -2.03; 95% CI, -3.50 - -0.56; p = 0.007). Mechanical ventilation guided by transpulmonary pressure tended to have a beneficial prognosis on ARDS patients. Oxygenation and lung mechanics parameters were also improved. The clinical effect of mechanical ventilation directed by transpulmonary pressure was superior to the traditional lung protective ventilation strategies in ARDS patients.

Cardiovascular effects of exercise induced dynamic hyperinflation in COPD patients-Dynamically hyperinflated and non-hyperinflated subgroups.

An increase in respiratory rate and expiratory flow limitation can facilitate dynamic hyperinflation (DH), which may cause an element of the intrathoracic pressure in connection with the worsening of venous return, with negative effect on stroke volume (SV) and cardiac output (CO). It has been unclassified, whether poor circulatory adaptation to exercise can be attributed to DH or poor cardio-vascular performance itself in COPD. Only a subset of COPD patients exhibit dynamic hyperinflation during exercise. We designed a study to show how lung mechanical and cardiovascular parameters change in hyperinflated and non-hyperinflated COPD patients during exercise with a new experimental set-up. Thirty-three COPD patients with similar severity of COPD and left ventricular performance (20 men, 13 women, mean±SD age: 65,36±6,95 years) participated. We measured the cardiovascular parameters with a non-invasive device (Finometer-pro) including the left ventricular ejection time index (LVETi) and estimated the change of DH with inspiratory capacity (IC) manoeuvres during exercise. Twenty-one subjects exhibited DH (DH group) and 12 did not (non-DH group). The measurement results were given in mean ± SD and difference between the values measured during maximal load and rest also (ΔX = Xmax.load-Xrest). ΔSV and ΔCO were significantly higher in non-DH vs. DH patients (ΔSV: non-DH 9,7 ± 13,22 ml vs. DH -3,6 ± 14,34 ml, p = 0.0142; ΔCO: non-DH 2,26 ± 1,46 l/min vs. DH 0,88 ± 1,35 l/min, p = 0.0024). LVETi was not different between the two groups. Calculated oxygen delivery (DO2) during maximal load was significantly higher in non-DH group. We concluded that worse cardiovascular adaptation to exercise of COPD patients can be associated with exercise-induced DH in a similar cardiovascular aged COPD group.

Model-Based Estimation of Inspiratory Effort Using Surface EMG.

The quantification of inspiratory patient effort in assisted mechanical ventilation is essential for the adjustment of ventilatory assistance and for assessing patient-ventilator interaction. The inspiratory effort is usually measured via the respiratory muscle pressure (P mus) derived from esophageal pressure (P es) measurements. As yet, no reliable non-invasive and unobtrusive alternatives exist to continuously quantify P mus. We propose a model-based approach to estimate P mus non-invasively during assisted ventilation using surface electromyographic (sEMG) measurements. The method combines the sEMG and ventilator signals to determine the lung elastance and resistance as well as the neuromechanical coupling of the respiratory muscles via a novel regression technique. Using the equation of motion, an estimate for P mus can then be calculated directly from the lung mechanical parameters and the pneumatic ventilator signals. The method was applied to data recorded from a total of 43 ventilated patients and validated against P es-derived P mus. Patient effort was quantified via the P mus pressure-time-product (PTP). The sEMG-derived PTP estimated using the proposed method was highly correlated to P es-derived PTP ([Formula: see text]), and the breath-wise deviation between the two quantities was [Formula: see text]. The estimated, sEMG-derived P mus is closely related to the P es-based reference and allows to reliably quantify inspiratory effort. The proposed technique provides a valuable tool for physicians to assess patients undergoing assisted mechanical ventilation and, thus, may support clinical decision making.

217.9: Activation of Angiotensin-converting Enzyme 2 (ACE2) Modulates Lung Mechanics in a Brain Death Model and Attenuates Pulmonary Edema After Rat Lung Transplantation

Introduction: Lung transplantation is a therapeutic option established worldwide for end-stage lung diseases. However, as most donors evolve with brain death (BD), the donated lung may have been compromised. In view of the participation of the renin angiotensin system (RAS) and the use of angiotensin-converting enzyme 2 (ACE2) activators in several pathological processes, it was investigated how diminazene aceturate (DIZE), an ACE2 activator, modulates hemodynamic and blood gas changes, as well as lung function following transplantation in rats. Method: Male Lewis rats were randomly distributed in the following experimental groups: intact, brain death (BD) and BD + diminazene aceturate (BD+DIZE). The last two groups were submitted to brain death process, treated with saline (0.9%) or DIZE (15 mg/kg-1) and kept on mechanical ventilation for 6 hours (donor). After this period, cardiopulmonary block extraction and left unilateral transplantation (LTx) with independent graft ventilation was performed, followed by 2h reperfusion. Hemodynamics (mean arterial pressure - MAP), blood gas analysis, lung mechanics, and pulmonary edema were evaluated. Results are presented as S.E.M. (ANOVA; Tukey; p<0.05). (Approval # CEUA/FMUSP - 1630/2021). Results: The administration of DIZE, 3 hours after BD, prevented the increase in the MAP (210’ after BD-induction: BD – 110 ± 12 mmHg; n=5; BD+DIZE – 40 ± 12 mmHg; n=4/ p=0.0001) without associated blood gas and metabolic alterations. Changes in lung mechanics, such as decreased tissue damping (G) and histeresivity (n) followed by increased respiratory system compliance (Crs), were associated with BD+DIZE (G - 0,25 ± 0,03 cmH2O/mL; Crs - 0,71 ± 0,03 mL/cmH2O; n – 0,14 ± 0,008) compared to intact (G - 0,40 ± 0,02 cmH2O/mL, p = 0.01; Crs – 0,64 ± 0,01 mL/cmH2O, p = 0.02; n - 0,26 ± 0,01, p = 0.004) and BD groups (G – 0,41± 0,05 cmH2O/mL, p = 0.02; Crs – 0,61 ± 0,01 mL/cmH2O, p = 0.01; n - 0,25 ± 0,008, p = 0.01) (Figure 1). After LTx, MAP, gas exchange function, and lung mechanical parameters, were not different among the 3 groups (p>0.05). On the other hand, the DIZE treatment was capable to reduce wet-to-dry weight ratio (INTACT – 1,87 ± 0,13; BD – 2,59 ± 0,14; BD+DIZE – 1,93 ± 0,15/ p=0.01) (Figure 2). Conclusion: Our data suggests that activation of ACE2 is able to modulate donor hemodynamic and lung mechanical parameters, probably reducing tissue resistance and improving airflow in the peripheral airways, converging to a decrease in ventilation heterogeneity in the sudden onset model of brain death. Our data also indicates that DIZE attenuates pulmonary edema on grafts from BD donors after lung transplantation. Keywords: Diminazene aceturate. Renin-angiotensin system. Brain death. Lung mechanics. Lung transplantation.CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico.

Monitoring respiratory mechanics by oscillometry in COVID-19 patients receiving non-invasive respiratory support.

BackgroundNon-invasive ventilation (NIV) has been increasingly used in COVID-19 patients. The limited physiological monitoring and the unavailability of respiratory mechanic measures, usually obtainable during invasive ventilation, is a limitation of NIV for ARDS and COVID-19 patients management.ObjectivesThis pilot study was aimed to evaluate the feasibility of non-invasively monitoring respiratory mechanics by oscillometry in COVID-19 patients with moderate-severe acute respiratory distress syndrome (ARDS) receiving NIV.Method15 COVID-19 patients affected by moderate-severe ARDS at the RICU (Respiratory Intensive Care Unit) of the University hospital of Cattinara, Trieste, Italy were recruited. Patients underwent oscillometry tests during short periods of spontaneous breathing between NIV sessions.ResultsOscillometry proved to be feasible, reproducible and well-tolerated by patients. At admission, 8 of the 15 patients showed oscillometry parameters within the normal range which further slightly improved before discharge. At discharge, four patients had still abnormal respiratory mechanics, not exclusively linked to pre-existing respiratory comorbidities. Lung mechanics parameters were not correlated with oxygenation.ConclusionsOur results suggest that lung mechanics provide complementary information for improving patients phenotyping and personalisation of treatments during NIV in COVID 19 patients, especially in the presence of respiratory comorbidities where deterioration of lung mechanics may be less coupled with changes in oxygenation and more difficult to identify. Oscillometry may provide a valuable tool for monitoring lung mechanics in COVID 19 patients receiving NIV.

A model-based approach to generating annotated pressure support waveforms

Large numbers of asynchronies during pressure support ventilation cause discomfort and higher work of breathing in the patient, and are associated with an increased mortality. There is a need for real-time decision support to detect asynchronies and assist the clinician towards lung-protective ventilation. Machine learning techniques have been proposed to detect asynchronies, but they require large datasets with sufficient data diversity, sample size, and quality for training purposes. In this work, we propose a method for generating a large, realistic and labeled, synthetic dataset for training and validating machine learning algorithms to detect a wide variety of asynchrony types. We take a model-based approach in which we adapt a non-linear lung-airway model for use in a diverse patient group and add a first-order ventilator model to generate labeled pressure, flow, and volume waveforms of pressure support ventilation. The model was able to reproduce basic measured lung mechanics parameters. Experienced clinicians were not able to differentiate between the simulated waveforms and clinical data (P = 0.44 by Fisher’s exact test). The detection performance of the machine learning trained on clinical data gave an overall comparable true positive rate on clinical data and on simulated data (an overall true positive rate of 94.3% and positive predictive value of 93.5% on simulated data and a true positive rate of 98% and positive predictive value of 98% on clinical data). Our findings demonstrate that it is possible to generate labeled pressure and flow waveforms with different types of asynchronies.

Comparative Study Between Action Vitamin C vs. Action of Nitric Oxide in Prolonged Ventilation in Respiratory Failure Patients Due to ARDS

Introduction: Recent meta-analysis prove that vitamin C shorten the duration of mechanical ventilation and accelerate weaning from ventilator especially in prolonged ventilated patients. Nitric oxide considered a relatively old drug used for long time in this issue. Aim: To compare the effect of either vitamin C or nitric oxide on improvement of general condition of the patients, improvement lung mechanics, early weaning from prolonged ventilation and mortality rates. Material and Methods: This a prospective double-blind study done in King Abdul-Aziz specialist hospital between September 2020 and December 2021 in the intensive care unit on 60 patients had difficult weaning after ventilation for &gt;10 days due to Acute Respiratory Distress Syndrome (ARDS) and still showing full criteria of ARDS. Allocated randomly in two groups 30 patients in each. All patients in both groups continued on the same protocol of ventilation. Group A received Nitric Oxide (NO) while group B received vitamin C intravenous. The duration of the study last 16 days. during this period, APCH II score, Hemodynamics, Chest X-ray, hypoxic index, lung compliance, Recruitment maneuver, arterial blood saturation, Lactic Acid Dehydrogenase (LDH), C-reactive protein used as indicator for improvement. Number of patients weaned from the ventilator and patients died also recorded. &gt;Results: Showed significant improvement in the general condition between patients of group B compared to group A which monitored by number of patients had both APACH II score &lt;10 and had normal core temperature. Significant improvement in lung condition between patients of group B compared to group A which monitored clinically by number of patients had arterial oxygen saturation &gt;95, hypoxic index &gt;300, better lung compliance, responder to recruitment maneuver. And monitored radiologically by significant higher number of patients in group B had parenchymatous lung infiltrate in chest X-ray less than one quadrant infiltration compared to group A. And monitored laboratory by significant higher number of patients had lower level of LDH from (100-200 U/L) and CRP (201-300) mg/L in group B compared to group A. There was significant higher number of patients weaned from the ventilator in group B compared to group A. There was significant lower morbidity between patients of group B compared to group A. No significant difference was found in mortality rates. Conclusion: Vitamin C significantly improve the general condition of the patients, improve all parameters of lung mechanics and accelerate weaning from ventilators in prolonged ventilated patients compared to nitric oxide.

Photodynamic Therapy in the Extracellular Matrix of Mouse Lungs: Preliminary Results of an Alternative Tissue Sterilization Process

Lung transplantation is one of the most difficult and delicate procedures among organ transplants. For the success of the procedure and survival of the new organ, the sterilization step for acellular lungs prior to recellularization is important to ensure that they are free of any risk of transmitting infections from the donor to the recipient subject. However, there are no available information concerning the lung mechanical parameters after sterilizing photodynamic therapy. The aim of this study was to evaluate the extracellular matrix (ECM) and lung mechanical parameters of decellularized lungs undergoing sterilizing photodynamic therapy (PDT). Besides, we also analyzed the lung after controlled infection with C. albicans in order to evaluate the effectiveness of PDT. The lung mechanical evaluation parameters, resistance ( R L ) and elastance ( E L ), exhibited no significant differences between groups. In addition, there were no PDT-induced changes in lung properties, with maintenance of the viscoelastic behavior of the lung scaffold after 1 h exposure to PDT. The ECM components remained virtually unchanged in the acellular lungs of both groups. We also showed that there was a reduction in fungal infection population after 45 minutes of PDT. However, more studies should be performed to establish and verify the effectiveness of PDT as a possible means for sterilizing lung scaffolds. This manuscript was presented as a master thesis of Nadua Apostólico at the postgraduate program in rehabilitation sciences, University Nove de Julho—UNINOVE.

Lung mechanics and respiratory morbidities in school-age children born moderate-to-late preterm.

Late and moderate prematurity may have an impact on pulmonary function during childhood. The present study aimed to investigate lung mechanics in school-age children born moderate-to-late preterm (MLPT). Children aged 5-10 years were enrolled in this case-control study. Lung function and bronchodilator response were assessed by impulse oscillometry (IOS) at two hospital-based specialized clinics. A structured questionnaire was employed to assess respiratory morbidities. A total of 123 children was divided into two groups: case (MLPT) n = 52 and control (children born at term) n = 71. The results showed no difference between groups in mean baseline IOS variables: R5 0.80 ± 0.20 vs 0.82 ± 0.22 kPa/L/s, p = 0.594, R20 0.54 ± 0.13 vs 0.55 ± 0.13 kPa/L/s, p = 0.732, R5-R20 0.26 ± 0.12 vs 0.27 ± 0.15 kPa/L/s, p = 0.615, X5 -0.29 ± 0.01 vs -0.29 ± 0.1 kPa/L/s, p = 0.990, Fres 21.1 ± 3.3 vs 21.7 ± 3.1 L/s, p = 0.380, and AX 2.7 ± 3.36 vs 2.5 ± 1.31 kPa/L/s, p = 0.626. Bronchodilator response and the occurrence of respiratory morbidities after birth were also similar between groups. This study found lung mechanics parameters to be similar in school-age children born MLPT and those born at term, suggesting that pulmonary plasticity continues to occur in children up to school age. Late and moderate prematurity is associated with an increased risk of reduced pulmonary function during childhood. Follow-up reports in adolescents and adults born MLPT are scarce but have indicated pulmonary plasticity with normalization of airway function. Our results show that the lung function in school-age children born MLPT is similar to that of children born at term.

Effect of Retrograde Autologous Blood Priming of Cardiopulmonary Bypass on Hemodynamic Parameters and Pulmonary Mechanics in Pediatric Cardiac Surgery: A Randomized Clinical Study

The present study aimed to assess the impact of retrograde autologous priming (RAP) on hemodynamics and pulmonary mechanics in children subjected to cardiothoracic surgery. This prospective randomized study analyzed the clinical records of 124 children with risk adjustment in congenital heart surgery-1 left to right lesions subjected to cardiac surgery. They comprised 64 patients in RAP group and 60 patients in the conventional priming group. The preoperative, intraoperative and postoperative data of the studied patients were reported. The outcome measures included hematocrit (Hct) value, blood gases, lung mechanics parameters, transfusion needs, ICU stay, postoperative complications and mortality. Preoperatively, there were no significant differences between the studied groups regarding the demographic data, underlying lesions, laboratory data, blood gases and pulmonary mechanics parameters. Intraoperatively, RAP group patients had significantly lower amount of blood loss, less frequent need to packed red blood cells (RBC)s transfusion and better Hct values when compared with the control group. Postoperatively, RAP group patients had significantly higher Hct% at ICU arrival, significantly better pulmonary mechanics parameters and significantly shorter duration on mechanical ventilation. RAP in children older than 12 months subjected to cardiac surgery for risk adjustment in congenital heart surgery-1 left to right lesions is associated with less transfusion needs and better pulmonary mechanics.

Cheek support affects lung mechanics measurements of tidal-based spontaneous breathing

Background and Objective: Patients are required to support their cheeks during breath-occluding lung function tests. This prevents cheek expansion which would alter pressure measured at the mouth, and, consequently, lung mechanics measurements. To date, the effect of cheek support on airway resistance measurements has been assessed. However other lung mechanics have not been studied as thoroughly, and no algorithm to account for the effect of missing cheek support on lung mechanics measurements has been developed.Methods: Lung mechanics were assessed with a breath occlusion test during light panting in healthy subjects with and without cheek support in a body plethysmograph. Average model-based airway resistance, lung elastance, and a parameter representing the viscoelastic were measured. Results were compared to quantify the effect of cheek support on these three parameters.Results: In the nine healthy subjects (5 Female, 4 Male) recruited for this study, all mechanics tended to be underestimated when cheeks were unsupported. Changes in elastance, resistance, and viscoelastic parameter ranged between 1.6–66.8 %, -4.5–21.8 %, and -4.7–68.2 %, respectively, when cheek support was added. The underestimation was due to reduced mouth pressure during cheek expansion when the breath was occluded. The variance of lung mechanics parameters did not change with cheek support in all subjects.Conclusions: The error in lung mechanics measurement caused by unsupported cheeks was subject dependent. Hence, no rule-of-thumb could be identified to reconstruct missing cheek support. For correct lung mechanics measurements during breath-occluding lung tests, patients must have adequate cheek support.Abbreviations:ROCC: Occlusion resistance; COPD: Chronic Obstructive Pulmonary Disorder; SB: spontaneous breathing.

P2Y12 Receptor Antagonist Clopidogrel Attenuates Lung Inflammation Triggered by Silica Particles.

Silicosis is an occupational lung disease caused by inhalation of silica particles. It is characterized by intense lung inflammation, with progressive and irreversible fibrosis, leading to impaired lung function. Purinergic signaling modulates silica-induced lung inflammation and fibrosis through P2X7 receptor. In the present study, we investigate the role of P2Y12, the G-protein-coupled subfamily prototype of P2 receptor class in silicosis. To that end, BALB/c mice received an intratracheal injection of PBS or silica particles (20 mg), without or with P2Y12 receptor blockade by clopidogrel (20 mg/kg body weight by gavage every 48 h) – groups CTRL, SIL, and SIL + Clopi, respectively. After 14 days, lung mechanics were determined by the end-inflation occlusion method. Lung histology was analyzed, and lung parenchyma production of nitric oxide and cytokines (IL-1β, IL-6, TNF-α, and TGF-β) were determined. Silica injection reduced animal survival and increased all lung mechanical parameters in relation to CTRL, followed by diffuse lung parenchyma inflammation, increased neutrophil infiltration, collagen deposition and increased pro-inflammatory and pro-fibrogenic cytokine secretion, as well as increased nitrite production. Clopidogrel treatment prevented silica-induced changes in lung function, and significantly reduced lung inflammation, fibrosis, as well as cytokine and nitrite production. These data suggest that inhibition of P2Y12 signaling improves silica-induced lung inflammation, preventing lung functional changes and mortality. Our results corroborate previous observations of silica-induced lung changes and expand the understanding of purinergic signaling in this process.

A Pilot Bench Study of Decision Support for Proportional Assist Ventilation.

The purpose was to develop a bench setup for testing a decision support system (DSS) for proportional assist ventilation (PAV). The test setup was based on a patient simulator connected to a mechanical ventilator with the DSS measurement sensors connected to the respiratory circuit. A test case was developed with parameters of lung mechanics reflecting a patient with mild acute respiratory distress syndrome. Five experiments were performed starting at different levels of percentage support (%Supp) and continuing until the DSS advised to remain at current settings. Final advice ranged from %Supp of 50-70%, indicating some dependence of baseline level, but with resulting patient effort estimates indicating that this may not be clinically important. Further studies are required of test cases reflecting different patient types and in patients.

Oxidative imbalance in mice intoxicated by microcystin-LR can be minimized

Microcystins-LR (MC-LR) is a cyanotoxin produced by cyanobacteria. We evaluated the antioxidant potential of LASSBio-596 (LB-596, inhibitor of phosphodiesterases 4 and 5), per os, and biochemical markers involved in lung and liver injury induced by exposure to sublethal dose of MC-LR. Fifty male Swiss mice received an intraperitoneal injection of 60 μL of saline (CTRL group, n = 20) or a sublethal dose of MC-LR (40 μg/kg, TOX group, n = 20). After 6 h the animals received either saline (TOX and CTRL groups) or LB-596 (50 mg/kg, TOX + LASS group, n = 10) by gavage. At 6 h after exposure, respiratory mechanics was evaluated in 10 CTRL and 10 TOX mice: there was a significant increase of all lung mechanics parameters (static elastance, viscoelastic component of elastance and lung resistive and viscoelastic/inhomogeneous pressures) in TOX compared to CTRL. 8 h after saline or MC-LR administration, i.e., 2 h after treatment with LB-596, blood serum levels of alanine aminotransferase and aspartate aminotransferase, activity of superoxide dismutase, catalase, and content of malondialdehyde and carbonyl in lung and liver, NADPH oxidase 2 and 4 mRNA expressions, dual oxidase enzyme activity and H2O2 generation were analyzed in lung homogenates. All parameters were significantly higher in TOX than in the other groups. There was no significant difference between CTRL and TOX + LASS. MC-LR deteriorated lung and liver functions and induced redox imbalance in them, which was prevented by oral administration of LB-596.

Heterogeneous pattern of differences in respiratory parameters between elderly with either good or poor FEV1

BackgroundThe relationship of spirometric values to other respiratory and functional parameters in advanced age is not well studied. We assessed this relationship in elderly subjects with either good or poor spirometric parameters to reveal whether different domains of lung function show comparable differences between the two groups.MethodsAmong subjects of the population-based KORA-Age cohort (n = 935, 65-90y; 51% male) two groups were selected from either the lower (LED; n = 51) or the upper (UED; n = 72) end of the FEV1 distribution. All subjects did not have a history of lung disease and were non-smokers at the time of the study. Measurements included spirometry, body plethysmography, diffusing capacity for NO and CO, respiratory pump function and exhaled NO (FeNO). In addition, 6-min walking distance as a functional overall measure, as well as telomere length of blood leukocytes and serum 8-hydroxydeoxyguanosine (8-OHdG) as potential markers of overall biological ageing and stress were determined.ResultsIn the majority of parameters, LED subjects showed significantly impaired values compared to UED subjects. Differences in spirometric parameters, airway resistance and respiratory pump function ranged between 10% and more than 90% in terms of predicted values. In contrast, volume-related CO and NO diffusing capacity showed differences between groups of lower than 5%, while telomere length, 8-OHdG and FeNO were similar. This was reflected in the differences in “functional age” as derived from prediction equations.ConclusionsIn elderly subjects without a history of lung disease differences in spirometric parameters were associated with differences in other lung-mechanical parameters including body plethysmography but not with differences in volume-corrected gas exchange measures. Thus, the concept of a general “lung age” as suggested by the widespread use of this term in connection with spirometry should be considered with caution.

Effects and mechanisms of high-volume hemofiltration on endotoxin-induced acute lung injury of piglets

Objective: To compare the effects of high-volume hemofiltration (HVHF) and continuous veno-venous hemofiltration (CVVH) on cardiopulmonary functions, lung fluid balance, lung damage and cytokine expression in endotoxin-induced acute lung injury piglet model, and to further evaluate the value of high-volume hemofiltration in acute lung injury. Method: Eighteen piglets were randomly divided into the control group (6 piglets), the CVVH group (6 piglets) and the HVHF group (6 piglets). By general anesthesia, the intravenous infusion of 0.15 mg/kg endotoxin were received in all the animals and induced acute lung injury.High-volume hemofiltration and continuous veno-venous hemofiltration were addressed to different groups.Subsequently, hemodynamic parameters (heart rate, mean arterial blood pressure, central venous pressure, pulse contour cardiac index, systemic venous resistance index and extravascular lung water index) as well as gas exchange and lung mechanics parameters (respiratory rate, partial pressure of carbon dioxide, partial pressure of oxygen/fraction of inspired oxygen, dynamic lung compliance and airway resistance) were intermittently measured.Lung tissues were collected for further analysis (the lung wet-to-dry weight ratio, lung injury scoring). The plasma protein levels of cytokines (interleukin(IL) -6, 10 and tumor necrosis factors alpha(TNF-α)) were also assessed.Two-way analysis of variance (ANOVA) and Bonferroni post-test were conducted to identify significant differences among the control, CVVH and HVHF group. Result: Compared with CVVH, HVHF had the capacity to improve significantly the index of Cdyn(HVHF (2.3±0.5) vs. CVVH (1.5±0.5) ml/(cmH(2)O·kg), 1 cmH(2)O=0.098 kPa, P<0.05)and Rrs(HVHF (22.0±1.9) vs.CVVH (29.5±1.5) cmH(2)O/(L·s), P<0.05)at the time of 6 h, and decreased lung water accumulation(index of EVLWI in HVHF (22.7±2.1) vs.CVVH (39.5±2.6) ml/m(2,) P<0.01) at the time of 6 h, and the plasma concentration of cytokines(IL-6, IL-10, TNF-α)in the HVHF group had an obvious decline compared with those in the CVVH group at the time of 6 h( (200±55) vs. (280±61), (74±17) vs. (102±21), (54±13) vs. (73±21) pg/ml, all P<0.05). The lung injury scoring of HVHF group was significantly lower than those of CVVH group((7.8±1.9) vs. (11.3±2.2) scores, P<0.05). Although the plasma concentration of cytokines(IL-6, IL-10, TNF-α) in the CVVH group were lower than those in the control group at the time of 6 h((374±55), (137±25), (98±17) pg/ml, all P<0.05), the indexes of respiratory function were not improved (all P<0.05). Conclusion: Different doses hemofiltration can reduce plasma inflammatory mediators indicators in piglets.Early high volume hemofiltration can improve respiratory function of piglets with endotoxin-induced acute lung injury and reduce lung injury pathological score.

The impact of bilateral vagotomy on the physostigmine-induced airway constriction in ferrets

Vagal innervations have a great role in the respiratory function and are the main route of signal transmission from respiratory neural centers into the trachea and others conducting airways.We have investigated the role of central mechanisms related to vagal neural pathways and the cholinergic outflow in tracheobronchial smooth muscle tone and lung mechanics parameters.Parameters of lung mechanics such as lung resistance (RL), dynamic compliance (Cdyn) and pressure in bypassed tracheal segment (Ptseg) were measured before and after vagotomy and asphyxia test. Before vagotomy (BV), the control measurements were obtained and physostigmine was administered systemically, in increasing dose 10, 40 and 100μg/kg body weight (bw) with 15min interval between doses. After vagotomy (AV), administration of physostigmine with the same doses as BV has been done and the asphyxia challenge was conducted as per study protocol. The values of Ptseg and RL after physostigmine administration, BV vs. AV, respectively, at maximal dose of 100μg/kg bw were 32.5±3.3cm H2O, and 10.6±1.5cm H2O (p<0.0001); 0.16±0.04cm H2O/mL/s, and 0.067±0.006cm H2O/mL/s AV (P<0.05). The Cydn values were affected after physostigmine administration only at the lowest dose of 10μg/kg bw, and BV was 0.75±0.05mL/cm H2O vs. 0.53±0.04mL/cm H2O AV (P<0.004).Cholinergic outflow produced increases in tracheal tone, lung resistance and a decrease in dynamic compliance before, but not after vagotomy. Our results show the high impact of central neuronal mechanism in parameters of lung mechanics and respiration.This study indicates that vagal nerves have a crucial role, in the transmission of impulses initiated from central nervous system, in regulating the respiration by contraction or relaxation of airway smooth muscle tone.

The role of ventilation mode using a laryngeal mask airway during gynecological laparoscopy on lung mechanics, hemodynamic response and blood gas analysis

There are two methods for ventilation in gynecological laparoscopy: volume-controlled ventilation (VCV) and pressure-controlled ventilation (PCV). To compare the lung mechanics, hemodynamic response and arterial blood gas analysis and gas exchange of two modes of VCV and PCV using laryngeal mask airway (LMA) at different time intervals. Sixty infertile women referred for diagnostic laparoscopy, based on ventilation mode, were randomly divided into two groups of VCV (tidal volume: 10 ml/kg) and PCV. In the PCV group, ventilation was initiated with a peak airway pressure (tidal volume: 10 ml/kg, upper limit: 35 cm H2O). In both groups, the arterial blood samples were taken in several time intervals (5, 10 and 15 min after LMA insertion) for blood gas evaluation. Also the lung mechanics parameters were continuously monitored and were recorded at different time intervals. There were no significant differences for patient's age, weight, height and BMI in two groups. The peak and plateau airway pressure were significantly higher in VCV group compared to PCV group 5 and 10 min after insertion of LMA. PaO2 was significantly higher after 10 and 15 min in VCV group compared to PCV group (p=0.005 and p=0.03, respectively). PaCO2 showed significant increase after 5 min in PCV group, but the differences were not significant after 10 and 15 min in two groups. The end tidal CO2 showed significant increase after 10 and 15 min in VCV compared to PCV group. Both VCV and PCV seem to be suitable for gynecological laparoscopy. However, airway pressures are significantly lower in PCV compared to VCV.

Exposure to urban PM1 in rats: development of bronchial inflammation and airway hyperresponsiveness.

BackgroundSeveral epidemiological and laboratory studies have evidenced the fact that atmospheric particulate matter (PM) increases the risk of respiratory morbidity. It is well known that the smallest fraction of PM (PM1 - particulate matter having a diameter below 1 μm) penetrates the deepest into the airways. The ratio of the different size fractions in PM is highly variable, but in industrial areas PM1 can be significant. Despite these facts, the health effects of PM1 have been poorly investigated and air quality standards are based on PM10 and PM2.5 (PM having diameters below 10 μm and 2.5 μm, respectively) concentrations. Therefore, this study aimed at determining whether exposure to ambient PM1 at a near alert threshold level for PM10 has respiratory consequences in rats.MethodsRats were either exposed for 6 weeks to 100 μg/m3 (alert threshold level for PM10 in Hungary) urban submicron aerosol, or were kept in room air. End-expiratory lung volume, airway resistance (Raw) and respiratory tissue mechanics were measured. Respiratory mechanics were measured under baseline conditions and following intravenous methacholine challenges to characterize the development of airway hyperresponsiveness (AH). Bronchoalveolar lavage fluid (BALF) was analyzed and lung histology was performed.ResultsNo significant differences were detected in lung volume and mechanical parameters at baseline. However, the exposed rats exhibited significantly greater MCh-induced responses in Raw, demonstrating the progression of AH. The associated bronchial inflammation was evidenced by the accumulation of inflammatory cells in BALF and by lung histology.ConclusionsOur findings suggest that exposure to concentrated ambient PM1 (mass concentration at the threshold level for PM10) leads to the development of mild respiratory symptoms in healthy adult rats, which may suggest a need for the reconsideration of threshold limits for airborne PM1.

The clinical effect of airway pressure release ventilation for acute lung injury/acute respiratory distress syndrome

To evaluate the effect of airway pressure release ventilation (APRV) in patients with acute lung injury/acute respiratory distress syndrome (ALI/ARDS), to evaluate the extent of ventilator-induced lung injury (VILI), and to explore its possible mechanism. A prospective study was conducted in the Department of Critical Care Medicine of the First Hospital of Hebei Medical University from December 2010 to February 2012. The patients with ALI/ARDS were enrolled. They were randomly divided into two groups. The patients in APRV group were given APRV pattern, while those in control group were given lung protection ventilation, synchronized intermittent mandatory ventilation with positive end-expiratory pressure (SIMV+PEEP). All patients were treated with AVEA ventilator. The parameters such as airway peak pressure (Ppeak), mean airway pressure (Pmean), pulse oxygen saturation (SpO2), mean arterial pressure (MAP), heart rate (HR), central venous pressure (CVP), arterial blood gas, urine output (UO), the usage of sedation and muscle relaxation drugs were recorded. AVEA ventilator "turning point (Pflex) operation" was used to describe the quasi-static pressure volume curve (P-V curve). High and low inflection point (UIP, LIP) and triangular Pflex volume (Vdelta) were automatically measured and calculated. The ventilation parameters were set, and the 24-hour P-V curve was recorded again in order to be compared with subsequent results. Venous blood was collected before treatment, 24 hours and 48 hours after ventilation to measure lung surfactant protein D (SP-D) and large molecular mucus in saliva (KL-6) by enzyme linked immunosorbent assay (ELISA), and the correlation between the above two parameters and prognosis on 28 days was analyzed by multinomial logistic regression. Twenty-six patients with ALI/ARDS were enrolled, and 22 of them completed the test with 10 in APRV group and 12 in control group. The basic parameters and P-V curves between two groups were similar before the test. After 24 hours and 48 hours, mechanical ventilation was given in both groups. The patients' oxygenation was improved significantly, though there were no significant changes in hemodynamic parameters. The Pmean (cmH2O, 1 cmH2O = 0.098 kPa) in APRV group was significantly higher than that in control group (24 hours: 24.20±4.59 vs. 17.50±3.48, P < 0.01; 48 hours: 18.10±4.30 vs. 15.00±2.59, P < 0.05). After ventilation for 24 hours, the ratio of patients with increased Vdelta in APRV group was higher than that in control group (90% vs. 75%), but without statistical difference (P > 0.05). The SP-D level (μg/L) in serum in APRV group showed a tendency of increase (increased from 19.70±7.34 to 27.61±10.21, P < 0.05), in contrast there was a tendency of decrease in control group (decreased from 21.83±7.31 to 16.58±2.90, P > 0.05), the difference between the two groups was statistically significant (P < 0.05). After 48-hour ventilation, SP-D in APRV group was decreased, but no change was found in control group, and no significant difference was found as compared with that of the control group (16.45±8.17 vs. 17.20±4.59, P > 0.05). There was no significant difference in serum KL-6 between the two groups before and after ventilation. The SP-D and KL-6 levels in serum were unrelated with 28-day survival rate of the patients. The odds ratio (OR) of SP-D were 0.900 [95% confidence interval (95%CI) = 0.719-1.125], 1.054 (95%CI = 0.878-1.266), 1.143 (95%CI = 0.957-1.365), and the OR of KL-6 were 1.356 (95%CI = 0.668-2.754), 0.658 (95%CI = 0.161-2.685), 0.915 (95%CI = 0.350-2.394) before the test, 24 hours and 48 hours after ventilation (all P > 0.05). APRV was similar to lung protective ventilation strategy in oxygenation and improvements in the lung mechanics parameters. APRV with a higher Pmean can recruit alveolar more effectively, and it had no impact on hemo-dynamics, but might exacerbate VILI.