Changes In Respiratory Mechanics Research Articles

Effects of prone positioning on lung mechanical power components in patients with acute respiratory distress syndrome: a physiologic study

BackgroundProne positioning (PP) homogenizes ventilation distribution and may limit ventilator-induced lung injury (VILI) in patients with moderate to severe acute respiratory distress syndrome (ARDS). The static and dynamic components of ventilation that may cause VILI have been aggregated in mechanical power, considered a unifying driver of VILI. PP may affect mechanical power components differently due to changes in respiratory mechanics; however, the effects of PP on lung mechanical power components are unclear. This study aimed to compare the following parameters during supine positioning (SP) and PP: lung total elastic power and its components (elastic static power and elastic dynamic power) and these variables normalized to end-expiratory lung volume (EELV).MethodsThis prospective physiologic study included 55 patients with moderate to severe ARDS. Lung total elastic power and its static and dynamic components were compared during SP and PP using an esophageal pressure-guided ventilation strategy. In SP, the esophageal pressure-guided ventilation strategy was further compared with an oxygenation-guided ventilation strategy defined as baseline SP. The primary endpoint was the effect of PP on lung total elastic power non-normalized and normalized to EELV. Secondary endpoints were the effects of PP and ventilation strategies on lung elastic static and dynamic power components non-normalized and normalized to EELV, respiratory mechanics, gas exchange, and hemodynamic parameters.ResultsLung total elastic power (median [interquartile range]) was lower during PP compared with SP (6.7 [4.9–10.6] versus 11.0 [6.6–14.8] J/min; P < 0.001) non-normalized and normalized to EELV (3.2 [2.1–5.0] versus 5.3 [3.3–7.5] J/min/L; P < 0.001). Comparing PP with SP, transpulmonary pressures and EELV did not significantly differ despite lower positive end-expiratory pressure and plateau airway pressure, thereby reducing non-normalized and normalized lung elastic static power in PP. PP improved gas exchange, cardiac output, and increased oxygen delivery compared with SP.ConclusionsIn patients with moderate to severe ARDS, PP reduced lung total elastic and elastic static power compared with SP regardless of EELV normalization because comparable transpulmonary pressures and EELV were achieved at lower airway pressures. This resulted in improved gas exchange, hemodynamics, and oxygen delivery.Trial registration: German Clinical Trials Register (DRKS00017449). Registered June 27, 2019. https://drks.de/search/en/trial/DRKS00017449

Comparison of volume-controlled ventilation and pressure-limited ventilation in laparoscopic appendicectomy - a randomized controlled clinical trial

Background: Laparoscopic appendicectomy is a widely performed surgery globally, offering notable benefits such as reduced postoperative pain, quicker mobility, and shorter hospital stays. Aims and Objectives: The study aimed to assess the changes in respiratory mechanics and compare the outcomes of volume-controlled and pressure-limited ventilation (PLV) in patients undergoing laparoscopic appendectomy. Materials and Methods: This randomized, prospective, single-blinded control study was conducted at K.A.P.V. Government Medical College, Tiruchirapalli, on 60 ASA I and II patients scheduled to undergo laparoscopic appendicectomy under general anesthesia. The patients were randomly divided into two groups (volume-controlled ventilation [VCV] group and the PLV group) of 30 patients. A patient’s history includes age, sex, history of diabetes, hypertension, or any cardiovascular disease, respiratory tract infection, wheezing or chronic chest infections, seizures, neuromuscular disease or weakness, etc. Results: There was no significant difference in gender, age, or body mass index between groups. There is no significant difference in the mean arterial pressure or ETCO2 between groups at various intervals. There was a significant difference in the mean heart rate between the VCV and the PLV groups at 5 and 20 min after induction. There was a significant difference in the peak airway pressure, dynamic compliance, and airway resistance between the VCV group and the PLV group at 10 min after induction (T1), 5 min after pneumoperitoneum (T2), 10 min after pneumoperitoneum (T3), and immediately after Trendelenburg position (T4). Conclusion: The airway resistance and peak airway pressure do not increase, and the dynamic compliance was improved in the PLV during laparoscopic appendicectomy.

Intra-breath changes in respiratory mechanics are sensitive to history of respiratory illness in preschool children: the SEPAGES cohort

BackgroundIntra-breath oscillometry has been proposed as a sensitive means of detecting airway obstruction in young children. We aimed to assess the impact of early life wheezing and lower respiratory tract illness on lung function, using both standard and intra-breath oscillometry in 3 year old children.MethodsHistory of doctor-diagnosed asthma, wheezing, bronchiolitis and bronchitis and hospitalisation for respiratory problems were assessed by questionnaires in 384 population-based children. Association of respiratory history with standard and intra-breath oscillometry parameters, including resistance at 7 Hz (R7), frequency-dependence of resistance (R7 − 19), reactance at 7 Hz (X7), area of the reactance curve (AX), end-inspiratory and end-expiratory R (ReI, ReE) and X (XeI, XeE), and volume-dependence of resistance (ΔR = ReE-ReI) was estimated by linear regression adjusted on confounders.ResultsAmong the 320 children who accepted the oscillometry test, 281 (88%) performed 3 technically acceptable and reproducible standard oscillometry measurements and 251 children also performed one intra-breath oscillometry measurement. Asthma was associated with higher ReI, ReE, ΔR and R7 and wheezing was associated with higher ΔR. Bronchiolitis was associated with higher R7 and AX and lower XeI and bronchitis with higher ReI. No statistically significant association was observed for hospitalisation.ConclusionsOur findings confirm the good success rate of oscillometry in 3-year-old children and indicate an association between a history of early-life wheezing and lower respiratory tract illness and lower lung function as assessed by both standard and intra-breath oscillometry. Our study supports the relevance of using intra-breath oscillometry parameters as sensitive outcome measures in preschool children in epidemiological cohorts.

Complications of Peritoneal Dialysis Part I: Mechanical Complications.

Peritoneal dialysis (PD) is a form of KRT that offers flexibility and autonomy to patients with ESKD. It is associated with lower costs compared with hemodialysis in many countries. However, it can be associated with unexpected interruptions to or discontinuation of therapy. Timely diagnosis and resolution are required to minimize preventable modality change to hemodialysis. This review covers mechanical complications, including leaks, PD hydrothorax, hernias, dialysate flow problems, PD-related pain, and changes in respiratory mechanics. Most mechanical complications occur early, either as a result of PD catheter insertion or the introduction of dialysate and consequent increased intra-abdominal pressure. Late mechanical complications can also occur and may require different treatment.

Force adaptation through the intravenous route in naïve mice

Aim of the study: Force adaptation is a process whereby the contractile capacity of the airway smooth muscle increases during a sustained contraction (aka tone). Tone also increases the response to a nebulized challenge with methacholine in vivo, presumably through force adaptation. Yet, due to its patchy pattern of deposition, nebulized methacholine often spurs small airway narrowing heterogeneity and closure, two important enhancers of the methacholine response. This raises the possibility that the potentiating effect of tone on the methacholine response is not due to force adaptation but by furthering heterogeneity and closure. Herein, methacholine was delivered homogenously through the intravenous (i.v.) route. Materials and Methods: Female and male BALB/c mice were subjected to one of two i.v. methacholine challenges, each of the same cumulative dose but starting by a 20-min period either with or without tone induced by serial i.v. boluses. Changes in respiratory mechanics were monitored throughout by oscillometry, and the response after the final dose was compared between the two challenges to assess the effect of tone. Results: For the elastance of the respiratory system (Ers), tone potentiated the methacholine response by 64 and 405% in females (37.4 ± 10.7 vs. 61.5 ± 15.1 cmH2O/mL; p = 0.01) and males (33.0 ± 14.3 vs. 166.7 ± 60.6 cmH2O/mL; p = 0.0004), respectively. For the resistance of the respiratory system (Rrs), tone potentiated the methacholine response by 129 and 225% in females (9.7 ± 3.5 vs. 22.2 ± 4.3 cmH2O·s/mL; p = 0.0003) and males (10.7 ± 3.1 vs. 34.7 ± 7.9 cmH2O·s/mL; p < 0.0001), respectively. Conclusions: As previously reported with nebulized challenges, tone increases the response to i.v. methacholine in both sexes; albeit sexual dimorphisms were obvious regarding the relative resistive versus elastic nature of this potentiation. This represents further support that tone increases the lung response to methacholine through force adaptation.

Factors associated with decreased compliance after on-site extracorporeal membrane oxygenation cannulation for acute respiratory distress syndrome: A retrospective, observational cohort study

BackgroundExtracorporeal membrane oxygenation (ECMO) for acute respiratory distress syndrome (ARDS) is systematically associated with decreased respiratory system compliance (CRS). It remains unclear whether transportation to the referral ECMO center, changes in ventilatory mode or settings to achieve ultra-protective ventilation, or the natural evolution of ARDS drives this change in respiratory mechanics. Herein, we assessed the precise moment when CRS decreases after ECMO cannulation and identified factors associated with decreased CRS. MethodsTo rule out the effect of transportation and the different modes of ventilation on CRS, we conducted a retrospective, single-center, observational cohort study from January 2013 to May 2020, on 22 patients with severe ARDS requiring on-site ECMO and ventilated in pressure-controlled mode to achieve ultra-protective ventilation. CRS was assessed at different time points ranging from 12 h before ECMO cannulation to 72 h after ECMO cannulation. The primary outcome was the relative change in CRS between 3 h before and 3 h after ECMO cannulation. The secondary outcomes included variables associated with the relative changes in CRS within the first 3 h after ECMO cannulation and the relative changes in CRS at each time point. ResultsCRS decreased within the first 3 h after ECMO cannulation (−28.3%, 95% confidence interval [CI]: −38.8 to −17.9, P<0.001), while the decrease was mild before and after these first 3 h after ECMO cannulation. To achieve ultra-protective ventilation, respiratory rate decreased in the mean by –13 breaths/min (95% CI: −15 to −11) and driving pressure by −8.3 cmH2O (95% CI: −11.2 to −5.3), resulting in decreased tidal volume by −3.3 mL/kg of predicted body weight (95% CI: −3.9 to −2.6) as compared to before ECMO cannulation (P <0.001 for all). Plateau pressure reduction, driving pressure reduction, and tidal volume reduction were significantly associated with decreased CRS after ECMO cannulation, whereas neither respiratory rate, positive end-expiratory pressure, inspired fraction of oxygen, fluid balance, nor mean airway pressure was associated with decreased CRS. ConclusionsDecreased driving pressure resulting in lower tidal volume to achieve ultra-protective ventilation after ECMO cannulation was associated with a marked decrease in CRS in ARDS patients with on-site ECMO cannulation.

Changes in respiratory mechanics in response to crystalloid infusions in extremely premature infants.

Extremely premature infants are at a higher risk of developing respiratory distress syndrome and circulatory impairments in the first few weeks of life. Administration of normal saline boluses to manage hypotension is a common practice in preterm infants. As a crystalloid, a substantial proportion might leak into the interstitium; most consequently the lungs in the preterm cohorts, putatively affecting ventilation. We downloaded and analyzed ventilator mechanics data in infants managed by conventional mechanical ventilation and administered normal saline bolus for clinical reasons. Data were downloaded for 30 min prebolus, 60 min during the bolus followed by 30 min postbolus. Sixteen infants (mean gestational age 25.2 ± 1 wk and birth weight 620 ± 60 g) were administered 10 mL/kg normal saline over 60 min. The most common clinical indication for saline was hypotension. No significant increase was noted in mean blood pressure after the saline bolus. A significant reduction in pulmonary compliance (mL/cmH2O/kg) was noted (0.43 ± 0.07 vs. 0.38 ± 0.07 vs. 0.33 ± 0.07, P = 0.003, ANOVA). This was accompanied by an elevation in the required peak inspiratory pressure to deliver set volume-guarantee (19 ± 2 vs. 22 ± 2 vs. 22 ± 3 mmHg, P < 0.0001, ANOVA), resulting in a higher respiratory severity score. Normal saline infusion therapy was associated with adverse pulmonary mechanics. Relevant pathophysiologic mechanisms might include translocation of fluid across pulmonary capillaries affected by low vascular tone and heightened permeability in extremes of prematurity, back-pressure effects from raised left atrial volume due to immature left-ventricular myocardium; complemented by the effect of cytokine release from positive pressure ventilation.NEW & NOTEWORTHY Administration of saline boluses is common in premature infants although hypovolemia is an uncommon underlying cause of hypotension. This crystalloid can redistribute into pulmonary interstitial space. In the presence of an immature myocardium and diastolic dysfunction, excess fluid can also be "edemagenic." This study on extremely premature infants (25 wk gestation) noted adverse influence on respiratory physiology after saline infusion. Clinicians need to choose judiciously and reconsider routine use of saline boluses in premature infants.

Changes in Respiratory Mechanics With Trunk Inclination Differs Between Patients With ARDS With and Without Obesity

Studies investigating the effect of trunk inclination on respiratory mechanics in mechanically ventilated patients with ARDS have reported postural differences in partition respiratory mechanics. Compared with more upright positions, the supine-flat position provided lower lung and chest wall elastance, allowing reduced driving pressures and end-inspiratory transpulmonary pressure. However, the effect of trunk inclination on respiratory mechanics in patients with obesity and ARDS is uncertain. Does the effect of change in posture on partition respiratory mechanics differ between patients with ARDS with and without obesity? In this single-center study, patients with ARDS with and without obesity were randomized into two 15-minute steps in which trunk inclination was changed from semi-recumbent (40° head up) to supine-flat (0°), or vice versa. At the end of each step partition respiratory mechanics, airway opening pressure and arterial blood gases were measured. Paired t test was used to examine respiratory mechanics and blood gas variables in each group. Forty consecutive patients were enrolled. Twenty were obese (BMI, 38.4 [34.5-42.3]), and 20 were non-obese (BMI, 26.6 [25.2-28.5]). In the patients with obesity, lung and chest wall elastance, driving pressure, inspiratory transpulmonary pressure, Paco2, and ventilatory ratio were lower supine than semi-recumbent (P< .001). Airways resistance was greater supine (P= .006). In the patients without obesity, only chest wall elastance was lower in supine vssemi-recumbent (P< .001). In mechanically ventilated patients with ARDS and obesity, supine posture provided lower lung and chest wall elastance, and better CO2 clearance, than the semi-recumbent posture. This study was registered with Australian New Zealand Clinical Trials Registry (ACTRN12623000794606).

Establishment of a digital remote platform for respiratory support and intelligent early warning in intensive care units

During the disease progression or treatment of critically ill patients with lung injury, the changes in respiratory mechanics are continuous and dynamic. Establishing a digital platform for respiratory support in the ICU, which enables the continuous recording, dynamic analysis, and real-time alerting of numerical and waveform data from mechanical ventilation, can help intensivists improve their understanding of "dynamic respiratory mechanics", improve respiratory therapy and patient outcomes, as well as reduce workload and increase work efficiency. The construction of a dedicated database for mechanical ventilation, based on ventilator waveforms provides essential data support for projects such as respiratory mechanics data algorithm models. This will facilitate the establishment of an auxiliary decision-making system, enable the realization of intelligent mechanical ventilation, and create a new era of dynamic respiratory mechanics.

Effect of preoperative pulmonary hemodynamic and cardiopulmonary bypass on lung function in children with congenital heart disease

In children with congenital heart disease (CHD), pulmonary blood flow (Qp) contributes to alterations of pulmonary mechanics and gas exchange, while cardiopulmonary bypass (CPB) induces lung edema. We aimed to determine the effect of hemodynamics on lung function and lung epithelial lining fluid (ELF) biomarkers in biventricular CHD children undergoing CPB. CHD children were classified as high Qp (n = 43) and low Qp (n = 17), according to preoperative cardiac morphology and arterial oxygen saturation. We measured ELF surfactant protein B (SP-B) and myeloperoxidase activity (MPO) as indexes of lung inflammation and ELF albumin as index of alveolar capillary leak in tracheal aspirate (TA) samples collected before surgery and in 6 hourly intervals within 24 h after surgery. At the same time points, we recorded dynamic compliance and oxygenation index (OI). The same biomarkers were measured in TA samples collected from 16 infants with no cardiorespiratory diseases at the time of endotracheal intubation for elective surgery. Preoperative ELF biomarkers in CHD children were significantly increased than those found in controls. In the high Qp, ELF MPO and SP-B peaked 6 h after surgery and tended to decrease afterward, while they tended to increase within the first 24 h in the low Qp. ELF albumin peaked 6 h after surgery and decreased afterwards in both CHD groups. Dynamic compliance/kg and OI significantly improved after surgery only in the High Qp. Conclusion: In CHD children, lung mechanics, OI, and ELF biomarkers were significantly affected by CPB, according to the preoperative pulmonary hemodynamics.What is Known:• Congenital heart disease children, before cardiopulmonary run, exhibit changes in respiratory mechanics, gas exchange, and lung inflammatory biomarkers that are related to the preoperative pulmonary hemodynamics.• Cardiopulmonary bypass induces alteration of lung function and epithelial lining fluid biomarkers according to preoperative hemodynamics.What is New:• Our findings can help to identify children with congenital heart disease at high risk of postoperative lung injury who may benefit of tailored intensive care strategies, such as non-invasive ventilation techniques, fluid management, and anti-inflammatory drugs that can improve cardiopulmonary interaction in the perioperative period.

Unilateral acute lung injury in pig: a promising animal model

BackgroundAcute lung injury (ALI) occurs in 23% unilateral. Models of unilateral ALI were developed and used previously without clearly demonstrating the strictly unilateral nature and severity of lung injury by the key parameters characterizing ALI as defined by the American Thoracic Society (ATS). Thus, the use of unilateral ALI remained rare despite the innovative approach. Therefore, we developed a unilateral model of ALI and focused on the crucial parameters characterizing ALI. This model can serve for direct comparisons between the injured and intact lungs within single animals, thus, reducing the number of animals required for valid experimental conclusions.MethodsWe established the model in nine pigs, followed by an evaluation of key parameters in six pigs (main study). Pigs were ventilated using an adapted left double-lumen tube for lung separation and two ventilators. ALI was induced in the left lung with cyclic rinsing (NaCl 0.9% + Triton® X-100), after which pigs were ventilated for different time spans to test for the timing of ALI onset. Ventilatory and metabolic parameters were evaluated, and bronchoalveolar lavage (BAL) was performed for measurements of inflammatory mediators. Finally, histopathological specimens were collected and examined in respect of characteristics defining the lung injury score (LIS) as suggested by the ATS.ResultsAfter adjustments of the model (n = 9) we were able to induce strictly left unilateral ALI in all six pigs of the evaluation study. The median lung injury score was 0.72 (IQR 0.62–0.79) in the left lung vs 0.14 (IQR 0.14–0.16; p < 0.05) in the right lung, confirming unilateral ALI. A significant and sustained drop in pulmonary compliance (Cdyn) of the left lung occurred immediately, whereas Cdyn of the right lung remained unchanged (p < 0.05). BAL fluid concentrations of interleukin-6 and -8 were increased in both lungs.ConclusionsWe established a model of unilateral ALI in pigs, confirmed by histopathology, and typical changes in respiratory mechanics and an inflammatory response. This thoroughly evaluated model could serve as a basis for future studies and for comparing pathophysiological and pharmacological changes in the uninjured and injured lung within the same animal.

Dynamic evaluation of the pulmonary protective effects of prone position ventilation via respiratory mechanics for patients with moderate to severe acute respiratory distress syndrome.

BackgroundPatients with moderate to severe acute respiratory distress syndrome (ARDS) have been recommended to receive prone position ventilation (PPV). However, the dynamic changes in respiratory mechanics during PPV and their relationship with the prognosis have not been sufficiently evaluated. In addition, the impact of using neuromuscular blocking agents (NMBAs) during PPV on respiratory mechanics is not clear enough. Thus, the study aims to investigate the above-mentioned issues.MethodsA prospective cohort study was conducted on 22 patients with moderate to severe ARDS who received PPV in the intensive care unit (ICU) of the First Affiliated Hospital of Guangzhou Medical University. A multifunctional gastric tube was used to measure the patients’ respiratory mechanics during supine position ventilation (SPV), early PPV (PPV within 4 h of initiation), and middle/late PPV (more than 6 h after the initiation of PPV). Longitudinal data were analyzed with generalized estimating equations (GEE).ResultsCompared with SPV, the esophageal pressure swings (ΔPes) measured during the PPV was significantly higher (SPV 7.46 vs. early PPV 8.00 vs. middle/late PPV 8.30 cmH2O respectively; PSPV vs. middle/late PPV =0.025<0.05). A stratified analysis by patients’ outcome showed that the peak airway pressure (Ppeak), ΔPes and respiration rate (RR) in the death group were significantly higher than survival group. On the contrary, the tidal volume (Vt), diaphragmatic electromyogram (EMGdi) and PaO2/FiO2 ratio (PFR) in the death group were significantly lower than survival group. Notably, the ΔPes and transpulmonary driving pressure (DPL) were significantly lower in the patients treated with NMBAs (7.08 vs. 8.76 cmH2O ΔPes; P<0.01), (14.82 vs. 18.08 cmH2O DPL; P<0.001).ConclusionsDuring the transition from SPV to early PPV and then to middle/late PPV, the ΔPes in the PPV were greater than SPV and it fluctuated within a normal range while oxygenation improved significantly in all patients. The Ppeak, ΔPes and RR in the death group were significantly higher than survival group. When NMBAs were used, the ΔPes, inspiratory transpulmonary pressure (PLei), driving pressure (DP) and DPL were significantly decreased, suggesting that the rational combination of NMBAs and PPV may exert a synergistic protective effect on the lungs.

Impact of Forced Exhalation Maneuvers During Spirometry on Airway Resistance Measured by Oscillometry in Healthy Children.

To analyze the impact of repeated forced spirometry maneuvers on oscillometry parameters of healthy children. This is a cross-sectional study with healthy children (6-12 y old) from schools in Florianopolis-SC/Brazil. Good health condition was confirmed through questionnaires, health history, and normal spirometry. Spirometry maneuvers and impulse oscillometry were conducted according to the American Thoracic Society guidelines. The school children were grouped according to the number of spirometry maneuvers performed: 1) 3 maneuvers; 2) 4 maneuvers and 3) 5 to 8 maneuvers. The following oscillometry values were considered: at rest (T0); after the first spirometry maneuver (T1); and after the last maneuver (T2), according to the groups' allocation. The mixed model ANOVA was applied to verify the interaction of oscillometry parameters in all 3 moments and groups. The Friedman test was used for analysis of Fres (p < 0.05). In 149 school children (mean age: 9.13 y old ± 1.98), there was a significant increase in Z5, R5, R20, and X5 values at rest and after the first spirometry maneuver, and values at rest and after the last maneuver in all groups. The effects on analyzed variables were significant in Z5 (F: 12.35; gl: 2; p < 0.001), R5 (F: 11.14; df: 2, p < 0.001), R20 (F:7.53; df: 2, p < 0.001), and X5 (F: 4.30; df: 2, p = 0.014). There were changes in respiratory mechanics after spirometry, like the increase in baseline Z5, R5, R20, and X5 after the first forced spirometry maneuver, and in comparison to the last maneuver obtained.

Therapeutic hypothermia attenuates physiologic, histologic, and metabolomic markers of injury in a porcine model of acute respiratory distress syndrome.

Acute respiratory distress syndrome (ARDS) is a lung injury characterized by noncardiogenic pulmonary edema and hypoxic respiratory failure. The purpose of this study was to investigate the effects of therapeutic hypothermia on short‐term experimental ARDS. Twenty adult female Yorkshire pigs were divided into four groups (n = 5 each): normothermic control (C), normothermic injured (I), hypothermic control (HC), and hypothermic injured (HI). Acute respiratory distress syndrome was induced experimentally via intrapulmonary injection of oleic acid. Target core temperature was achieved in the HI group within 1 h of injury induction. Cardiorespiratory, histologic, cytokine, and metabolomic data were collected on all animals prior to and following injury/sham. All data were collected for approximately 12 h from the beginning of the study until euthanasia. Therapeutic hypothermia reduced injury in the HI compared to the I group (histological injury score = 0.51 ± 0.18 vs. 0.76 ± 0.06; p = 0.02) with no change in gas exchange. All groups expressed distinct phenotypes, with a reduction in pro‐inflammatory metabolites, an increase in anti‐inflammatory metabolites, and a reduction in inflammatory cytokines observed in the HI group compared to the I group. Changes to respiratory system mechanics in the injured groups were due to increases in lung elastance (E) and resistance (R) (ΔE from pre‐injury = 46 ± 14 cmH2O L−1, p < 0.0001; ΔR from pre‐injury: 3 ± 2 cmH2O L−1 s−, p = 0.30) rather than changes to the chest wall (ΔE from pre‐injury: 0.7 ± 1.6 cmH2O L−1, p = 0.99; ΔR from pre‐injury: 0.6 ± 0.1 cmH2O L−1 s−, p = 0.01). Both control groups had no change in respiratory mechanics. In conclusion, therapeutic hypothermia can reduce markers of injury and inflammation associated with experimentally induced short‐term ARDS.

Intra-breath changes in respiratory mechanics assessed from multi-frequency oscillometry measurements

Objective. Recent studies in respiratory system impedance (Zrs) with single-frequency oscillometry have demonstrated the utility of novel intra-breath measures of Zrs in the detection of pathological alterations in respiratory mechanics. In the present work, we addressed the feasibility of extracting intra-breath information from Zrs data sets obtained with conventional oscillometry. Approach. Multi-frequency recordings obtained in a pulmonology practice were re-analysed to track the 11 Hz component of Zrs during normal breathing and compare the intra-breath measures to that obtained with a single 10 Hz signal in the same subjects. A nonlinear model was employed to simulate changes in Zrs in the breathing cycle. The values of resistance (R) and reactance (X) at end expiration and end inspiration and their corresponding differences (ΔR and ΔX) were compared. Main results. All intra-breath measures exhibited similar mean values at 10 and 11 Hz in each subject; however, the variabilities were higher at 11 Hz, especially for ΔR and ΔX. The poorer quality of the 11 Hz data was primarily caused by the overlapping of modulation side lobes of adjacent oscillation frequencies. This cross-talk was enhanced by double breathing frequency components due to flow nonlinearities. Significance. Retrospective intra-breath assessment of large or special data bases of conventional oscillometry can be performed to better characterise respiratory mechanics in different populations and disease groups. The results also have implications in the optimum design of multiple-frequency oscillometry (avoidance of densely spaced frequencies) and the use of filtering procedures that preserve the intra-breath modulation information.

Effect of acetylcysteine solution combined with fiberoptic bronchoscopy alveolar lavage in elderly patients with severe ventilator-associated pneumonia

&#x0D; &#x0D; &#x0D; &#x0D; Purpose: To explore the effect of acetylcysteine solution combined with fiberoptic bronchoscopy alveolar lavage in elderly patients with severe ventilator-associated pneumonia (VAP).&#x0D; Methods: A total of 120 elderly patients with severe VAP admitted to Department of Critical Care Medicine, the First Affiliated Hospital of Xinjiang Medical University in the past two years were selected for this study. They were randomized into groups A and B. Group B underwent fiberoptic bronchoscopy alveolar lavage for 7 days, group A received acetylcysteine solution plus. Clinical pulmonary infection score (CPIS), respiratory mechanics changes, blood gas levels, inflammatory factor levels, antibiotic use time and mechanical ventilation time were compared.&#x0D; Results: Compared to group B, group A witnessed a lower CPIS, an evidently superior dynamic lung compliance (Cdyn), and worse for other respiratory mechanics indices (p &lt; 0.001). After treatment, the partial pressure of blood oxygen (PaO2) and oxygenation index (PaO2/FiO2) saw a surge; the partial pressure of carbon dioxide (PaCO2) tapered off, and the levels of inflammatory factors witnessed a slump in group A than compared with those for group B (p &lt; 0.001). A shorter antibiotic use time and mechanical ventilation time was observed in group A compared with group B (p &lt; 0.001).&#x0D; Conclusion: Acetylcysteine solution combined with fiberoptic bronchoscopy alveolar lavage yields a promising outcome in notably ameliorating CPIS, respiratory mechanics indicators and blood gas levels, driving down the level of inflammatory factors and diminishing treatment time in elderly patients with severe VAP.&#x0D; &#x0D; &#x0D; &#x0D;

Respiratory consequences of obesity and diabetes

While sustained hyperglicemia affects the smooth muscle tone and the elastin-collagen network, the effect of diabetes mellitus on the function and structure of the airways and the lung parenchyma has not been characterized, and the confounding influence of obesity has not been elucidated. To reveal the separate and additive roles of diabetes mellitus and obesity on the respiratory function. Non-obese mechanically ventilated patients were categorized as control non-diabetic (n = 80) and diabetic (n = 35) groups. Obese patients with (n = 33) or without (n = 47) associated diabetes were also enrolled. Forced oscillation technique was applied to measure airway resistance (Raw), tissue damping (G), and tissue elastance (H). Capnography was utilized to determine phase 3 slopes and ventilation dead space parameters. Arterial and central venous blood samples were analyzed to assess intrapulmonary shunt fraction (Qs/Qt) and the lung oxygenation index (PaO2/FiO2). Diabetes without obesity increased the Raw (7.4 ± 5 cmH2O.s/l vs. 3.0 ± 1.7 cmH2O.s/l), G (11.3 ± 4.9 cmH2O/l vs. 6.2 ± 2.4 cmH2O/l), and H (32.3 ± 12.0 cmH2O/l vs. 25.1 ± 6.9 cmH2O/l, (p<0.001 for all), compared with the corresponding control groups. Capnographic phase 3 slope was increased in diabetes without significant changes in PaO2/FiO2 or Qs/Qt. While similar detrimental changes in respiratory mechanics and alveolar heterogeneity were observed in obese patients without diabetes, these alterations also compromised gas exchange. The intrinsic mechanical abnormalities in the airways and lung tissue induced by diabetes are counterbalanced by hypoxic pulmonary vasoconstriction, thereby maintaining intrapulmonary shunt fraction and oxygenation ability of the lungs. Orv Hetil. 2022; 163(2): 63-73.

Comparison of respiratory muscle strength through manovacuometry in the early postoperative period of bariatric surgery by laparotomy and laparoscopy.

surgical treatment of obesity causes important changes in respiratory mechanics. Comparatively analyze respiratory muscle strength in post bariatric patients underwent to gastric bypass by laparotomy and laparoscopy during hospital stay. observational study with a non-randomized longitudinal design, of a quantitative character. Data were collected from 60 patients with BMI 40Kg/m2, divided in laparotomy group (n=30) and laparoscopy group (n=30). Smokers, patients with previous lung diseases and those unable to perform the exam correctly were excluded. Both groups were evaluated at immediate postoperative, first and second postoperative days with manovacuometry for respiratory muscle strength and visual analogue pain scale. the sample was homogeneous in age, sex and BMI. Reduction in maximal respiratory pressures was observed after surgery for those operated on by laparotomy, no return to baseline values on discharge day on the second postoperative day. This group had also more severe pain and longer operative time. There was no difference in respiratory pressure measurements after surgery in the laparoscopy group. conventional bariatric surgery reduces muscle strength in the postoperative period and leads to more intense pain during hospitalization when compared to the laparoscopy group.

FUNCTIONAL LIMITATIONS ARISING FROM CHANGES IN RESPIRATORY MECHANICS IN CHRONIC OBSTRUCTIVE PULMONARY DYSFUNCTION

(INTRODUCTION) chronic obstructive pulmonary disease is a common preventable and treatable disease where an obstruction leads to various respiratory changes such as impaired airflow, leading to several changes occurring in the mechanics of the respiratory muscles, alters the conformation of the chest and diaphragm, mainly causing dyspnea and limitations as limitations. This research aims to correlate limitations according to changes in respiratory mechanics. (MATERIALS AND METHODS) the present is an integrative literature review, for the search for articles were used as databases PUBMED and SCIELO, studies were included without distinction of language and year, published and indexed in the databases free of charge and in full, studies that associated COPD with other respiratory diseases were excluded, studies where the reserves had undergone lung surgery, and studies that did not bring complete results. (RESULTS) 52 studies were found in total, 15 duplicates were excluded, in the first selection stage 19 studies were excluded, in the second stage 10 studies were excluded, thus the review sample of 9 studies, of the clinical trial type. (CONCLUDING REMARKS) Among the most prevalent limitations we saw low tolerance and resistance to physical exercises, limitations to perform activities of daily living, leading to dyspnea and dysfunction of the respiratory muscles, affecting the happy quality of life.

Acute hypercapnic respiratory failure and its management on the acute medical take.

Acute hypercapnic respiratory failure accounts for 50 000 hospital admissions each year in the UK. This article discusses the pathophysiology and common causes of acute hypercapnic respiratory failure, and provides practical considerations for patient management in acute medical settings. Non-invasive ventilation for persistent acute hypercapnic respiratory failure is widely recognised to improve patient outcomes and reduce mortality. National audits highlight a need to improve patients' overall care and outcomes through appropriate patient selection and treatment initiation. Multidisciplinary involvement is essential, as this underpins inpatient care and follow up after hospital discharge. New non-invasive ventilation modalities may offer better patient comfort and compensate better for sleep-related changes in respiratory mechanics. Emerging therapies, such as nasal high flow, may offer an alternative treatment approach in those who cannot tolerate non-invasive ventilation, but more research is required to completely understand its effectiveness in treating acute hypercapnic respiratory failure.