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Mechanical ventilation stands as a life-saving intervention in the management of respiratory failure. However, it carries the risk of ventilator-induced lung injury. Despite the adoption of lung-protective ventilation strategies, including lower tidal volumes and pressure limitations, mortality rates remain high, leaving room for innovative approaches. The concept of mechanical power has emerged as a comprehensive metric encompassing key ventilator parameters associated with the genesis of ventilator-induced lung injury, including volume, pressure, flow, resistance, and respiratory rate. While numerous animal and human studies have linked mechanical power and ventilator-induced lung injury, its practical implementation at the bedside is hindered by calculation challenges, lack of equation consensus, and the absence of an optimal threshold. To overcome the constraints of measuring static respiratory parameters, dynamic mechanical power is proposed for all patients, regardless of their ventilation mode. However, establishing a causal relationship is crucial for its potential implementation, and requires further research. The objective of this review is to explore the role of mechanical power in ventilator-induced lung injury, its association with patient outcomes, and the challenges and potential benefits of implementing a ventilation strategy based on mechanical power.

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Highly trained aerobic athletes progressively use most of their breathing reserve with increased exercise intensity during whole-body exercise. Additionally, females typically present proportionally smaller lungs than males. Therefore, sex, exercise intensity, and breathing reserve use likely influence the volume and time in which respiratory parameters vary between consecutive breaths during whole-body exercise. However, breath-by-breath variability has been scarcely investigated during exercise. Accordingly, we sought to investigate breath-by-breath pulmonary ventilation (V̇E), tidal volume (VT), and respiratory frequency (fR) variability during a maximal treadmill incremental exercise test in 17 females and 18 males highly trained professional endurance runners. The breath-by-breath variability was analyzed by root mean square of successive differences (RMSSD) within 1-minute windows. Females had lower absolute and percent predicted forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) than males, as well as lower height-adjusted absolute FVC than males. V̇E and VT reserve use were similar between the sexes at peak exercise. While RMSSDV̇E and RMSSDfR did not change over exercise (P > 0.05), RMSSDVT progressively decreased (P < 0.001). RMSSDVT was negatively correlated with VT reserve use only in males. Females showed lower RMSSDV̇E than males during the entire exercise test (P < 0.001). At iso-V̇E reserve use, between-sex differences in RMSSDV̇E persisted (P = 0.003). Our findings indicate that exercise intensity decreases VT variability in professional runners, which is linked to VT reserve use in males but not females. Additionally, the female sex lowers V̇E variability regardless of exercise intensity and V̇E reserve use.

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PURPOSE: To compare phase-resolved functional lung (PREFUL) regional ventilation derived from a free breathing 3D UTE radial MRI acquisition to hyperpolarized 129Xe-MRI (Xe-MRI), conventional 2D multi-slice PREFUL MRI, and pulmonary function tests in pediatric cystic fibrosis (CF) lung disease. METHODS: Free-breathing 3D UTE and 2D multi-slice 1H MRI as well as Xe-MRI were acquired in 12 stable pediatric CF patients. Using PREFUL, regional ventilation (RVent) maps were calculated from the free-breathing data. Ventilation defect percentage (VDP) was determined from 3D and 2D RVent maps (2D VDPRVent and 3D VDPRVent, respectively) and Xe-MRI ventilation (VDPXe). VDP was calculated for the whole lung and for eight regions based on left/right, anterior/posterior, and superior/inferior divisions of the lung. Global and regional VDP was compared between the three methods using Bland-Altman analysis, linear mixed model-based correlation, and one-way analysis of variance and multiple comparisons tests. RESULTS: Global 3D VDPRVent, VDPXe, and 2D VDPRVent were all strongly correlated (all R2 > 0.62, p < 0.0001) and showed minimal, non-significant bias (all <2%, p > 0.05). Three dimensional and 2D VDPRVent significantly correlated to VDPXe in most of the separate lung regions (R2 = 0.18-0.74, p < 0.04), but showed lower inter-agreement. The superior/anterior lung regions showed the least agreement between all three methods (all p > 0.12). CONCLUSION: Absolute VDP assessed by 3D UTE PREFUL MRI showed good global agreement with Xe-MRI and 2D multi-slice PREFUL MRI in pediatric CF lung disease. Therefore, 3D UTE PREFUL MRI offers a sensitive and potentially more accessible alternative to Xe-MRI for regional volumetric evaluation of ventilation.

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BACKGROUND: Laparoscopic-assisted radical gastrectomy (LARG) is the standard treatment for early-stage gastric carcinoma (GC). However, the negative impact of this procedure on respiratory function requires the optimized intraoperative management of patients in terms of ventilation. AIM: To investigate the influence of pressure-controlled ventilation volume-guaranteed (PCV-VG) and volume-controlled ventilation (VCV) on blood gas analysis and pulmonary ventilation in patients undergoing LARG for GC based on the lung ultrasound score (LUS). METHODS: The study included 103 patients with GC undergoing LARG from May 2020 to May 2023, with 52 cases undergoing PCV-VG (research group) and 51 cases undergoing VCV (control group). LUS were recorded at the time of entering the operating room (T0), 20 minutes after anesthesia with endotracheal intubation (T1), 30 minutes after artificial pneumoperitoneum (PP) establishment (T2), and 15 minutes after endotracheal tube removal (T5). For blood gas analysis, arterial partial pressure of oxygen (PaO2) and partial pressure of carbon dioxide (PaCO2) were observed. Peak airway pressure (Ppeak), plateau pressure (Pplat), mean airway pressure (Pmean), and dynamic pulmonary compliance (Cdyn) were recorded at T1 and T2, 1 hour after PP establishment (T3), and at the end of the operation (T4). Postoperative pulmonary complications (PPCs) were recorded. Pre- and postoperative serum interleukin (IL)-1ß, IL-6, and tumor necrosis factor-α (TNF-α) were measured by enzyme-linked immunosorbent assay. RESULTS: Compared with those at T0, the whole, anterior, lateral, posterior, upper, lower, left, and right lung LUS of the research group were significantly reduced at T1, T2, and T5; in the control group, the LUS of the whole and partial lung regions (posterior, lower, and right lung) decreased significantly at T2, while at T5, the LUS of the whole and some regions (lateral, lower, and left lung) increased significantly. In comparison with the control group, the whole and regional LUS of the research group were reduced at T1, T2, and T5, with an increase in PaO2, decrease in PaCO2, reduction in Ppeak at T1 to T4, increase in Pmean and Cdyn, and decrease in Pplat at T4, all significant. The research group showed a significantly lower incidence of PPCs than the control group within 3 days postoperatively. Postoperative IL-1ß, IL-6, and TNF-α significantly increased in both groups, with even higher levels in the control group. CONCLUSION: LUS can indicate intraoperative non-uniformity and postural changes in pulmonary ventilation under PCV-VG and VCV. Under the lung protective ventilation strategy, the PCV-VG mode more significantly improved intraoperative lung ventilation in patients undergoing LARG for GC and reduced lung injury-related cytokine production, thereby alleviating lung injury.

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Background: Patients with coronary artery disease (CAD) often experience pulmonary ventilation dysfunction following their initial event. However, there is insufficient research exploring the relationship between this dysfunction and CAD prognosis. Methods: To address this gap, a retrospective observational study was conducted involving 3800 CAD patients without prior pulmonary ventilation disease who underwent cardiopulmonary exercise testing (CPET) during hospitalization between November 2015 and September 2021. The primary endpoint was a composite of major adverse cardiovascular events (MACE), such as death, myocardial infarction (MI), repeat revascularization, and stroke. Propensity score matching (PSM) was used to minimize selection bias between the two groups, with a subgroup analysis stratified by smoking status. Results: The results showed that patients were divided into normal (n = 2159) and abnormal (n = 1641) groups based on their pulmonary ventilation function detected by CPET, with 1469 smokers and 2331 non-smokers. The median follow-up duration was 1237 (25-75% interquartile range 695-1596) days. The primary endpoint occurred in 390 patients (10.26%). 1472 patients in each of the two groups were enrolled in the current analysis after PSM, respectively. However, pulmonary function was not associated with MACE before (hazard ratio (HR) 1.20, 95% confidence interval (95% CI) 0.99-1.47; Log-rank p = 0.069) or after PSM (HR 1.07, 95% CI 0.86-1.34; Log-rank p = 0.545) among the entire population. Nonetheless, pulmonary ventilation dysfunction was significantly associated with an increased risk of MACE in smoking patients (HR 1.65, 95% CI 1.25-2.18; p < 0.001) but not in non-smoking patients (HR 0.81, 95% CI 0.60-1.09; p = 0.159). In addition, there was a significant interaction between current smoking status and pulmonary ventilation dysfunction on MACE (p for interaction < 0.001). Conclusions: Pulmonary ventilation dysfunction identified through CPET was independently associated with long-term poor prognosis in smoking patients with CAD but not in the overall population.

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BACKGROUND: An improper host immune response to Mycoplasma pneumoniae generates excessive inflammation, which leads to the impairment of pulmonary ventilation function (PVF). Azithromycin plus inhaled terbutaline has been used in the treatment of Mycoplasma pneumoniae pneumonia (MPP) in children with impaired pulmonary function, but previous randomized controlled trials (RCTs) showed inconsistent efficacy and safety. This study is aimed to firstly provide a systematic review of the combined therapy. METHODS: This study was registered at the International Prospective Register of Systematic Reviews (PROSPERO CRD42023452139). A PRISMA-compliant systematic review and meta-analysis was performed. Six English and four Chinese databases were comprehensively searched up to June, 2023. RCTs of azithromycin sequential therapy plus inhaled terbutaline were selected. The revised Cochrane risk of bias tool for randomized trials (RoB2) was used to evaluate the methodological quality of all studies, and meta-analysis was performed using Stata 15.0 with planned subgroup and sensitivity analyses. Publication bias was evaluated by a funnel plot and the Harbord' test. Certainty of evidence was assessed using the Grading of Recommendations, Assessment, Development and Evaluation recommendations. RESULTS: A total of 1,938 pediatric patients from 20 RCTs were eventually included. The results of meta-analysis showed that combined therapy was able to significantly increase total effectiveness rate (RR = 1.20, 95%CI 1.15 to 1.25), forced expiratory volume in one second (SMD = 1.14, 95%CIs, 0.98 to 1.29), the ratio of forced expiratory volume in one second/forced vital capacity (SMD = 2.16, 95%CIs, 1.46 to 2.86), peak expiratory flow (SMD = 1.17, 95%CIs, 0.91 to 1.43). The combined therapy was associated with a 23% increased risk of adverse reactions compared to azithromycin therapy alone, but no significant differences were found. Harbord regression showed no publication bias (P = 0.148). The overall quality of the evidence ranged from moderate to very low. CONCLUSIONS: This first systematic review and meta-analysis suggested that azithromycin sequential therapy plus inhaled terbutaline was safe and beneficial for children with MPP. In addition, the combined therapy represented significant improvement of PVF. Due to lack of high-quality evidence, our results should be confirmed by adequately powered RCTs in the future.

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BACKGROUND: Dynamic chest radiography (DCR) is a recently developed functional x-ray imaging technique that detects pulmonary ventilation impairment as a decrease in changes in lung density during respiration. However, the diagnostic performance of DCR is uncertain owing to an insufficient number of clinical cases. One solution is virtual imaging trials (VITs), which is an emerging alternative method for efficiently evaluating medical imaging technology via computer simulation techniques. PURPOSE: This study aimed to estimate the typical threshold thickness of residual normal tissue below which the presence of emphysema may be detected by DCR via VITs using virtual patients with different physiques and a user-defined ground truth. METHODS: Twenty extended cardiac-torso (XCAT) phantoms that exhibited changes in lung density during respiration were generated to simulate virtual patients. To simulate a locally collapsed lung, an air sphere was inserted into each lung regions in the phantom. The XCAT phantom was virtually projected using an x-ray simulator. The respiratory changes in pixel value (ΔPV) were measured on the projected air spheres (simulated lesions) to calculate the percentage of decrease (ΔPV%) relative to ΔPVexp-ins in the absence of an air sphere. The relationship between the amount of residual normal tissue and ΔPV% was fitted to a cubic approximation curve (hereafter, performance curve), and the threshold at which the ΔPV% began to decrease (normal-tissuethre) was determined. The goodness of fit for each performance curve was evaluated according to the coefficient of determination (R2) and the 95% confidence interval derived from the standard errors between the measured and theoretical values corresponding to each performance curve. The ΔPV% was also visualized as a color scaling to validate the results of the VITs in both virtual and clinical patients. RESULTS: For each lung region in all body sizes, the ΔPV% decreased as the amount of residual normal tissue decreased and could be defined as a function of the amount of residual normal tissue in front of and behind the simulated lesions with high R2 values. Meanwhile, the difference between the measured and theoretical values corresponding to each performance curve was only partially included in the 95% confidence interval. The normal-tissuethre values were 146.0, 179.5, and 170.9 mm for the upper, middle, and lower lungs, respectively, which were demonstrated in virtual patients and one real patient, where the value of the residual normal tissue was less than that of normal-tissuethre; any reduction in the residual normal tissue was reflected as a reduced ΔPV and depicted as a reduced color intensity. CONCLUSIONS: The performance of DCR-based pulmonary impairment assessment depends on the amount of residual normal tissue in front of and behind the lesion rather than on the lesion size. The performance curve can be defined as a function of the amount of residual normal tissue in each lung region with a specific threshold of normal tissue remaining where lesions become detectable, shown as a decrease in ΔPV. The results of VITs are expected to accelerate future clinical trials for DCR-based pulmonary function assessment.

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Background: The use of extracorporeal membrane oxygenation (ECMO) technology has significantly decreased mortality rates associated with neonatal pulmonary hypertension and respiratory failure. Prone positioning ventilation (PPV) is a commonly used technique in critically ill infants, designed to improve thoracic pressure gradients, re-expand dorsal lung segments, and increase oxygenation in approximately 70-80% of patients suffering from acute respiratory distress syndrome. This study aimed to evaluate the effects of PPV on pulmonary function in neonates undergoing venous-arterial extracorporeal membrane oxygenation (VA-ECMO). Methods: We conducted a retrospective analysis of clinical data from 17 neonates who received ECMO support in our institution, divided into two groups based on ventilation strategy: ECMO with PPV (ECMO-PPV, n=8) and ECMO with supine positioning ventilation (ECMO-SPV, n=9). Parameters such as the P/F ratio [arterial oxygen partial pressure (PaO2)/fraction of inspired oxygen (FiO2)], oxygenation index (OI), respiratory system compliance (Crs), and airway resistance (RAW) were collected and analyzed at baseline, and at 1, 2, and 3 days post-ECMO initiation. In the ECMO-PPV group, these parameters were also assessed 3 days pre-treatment and 2 hours post-treatment initiation. Results: Initial comparisons between ECMO-PPV and ECMO-SPV groups showed no significant difference in PaO2/FiO2, OI, Crs, or RAW. Throughout the ECMO treatment, both groups demonstrated gradual improvements in PaO2/FiO2 and Crs, and reductions in OI and RAW. Notably, by day 3, the ECMO-PPV group exhibited significant improvements in Crs and RAW compared to the ECMO-SPV group (P<0.05). Specifically, in the ECMO-PPV group, Crs significantly increased and RAW decreased after 2 hours of initiating PPV, with these changes becoming statistically significant by day 3 (Crs P=0.03, RAW P=0.03). No severe PPV-related complications were noted. Conclusions: PPV during neonatal ECMO may improve respiratory compliance and reduce RAW, potentially aiding lung recovery. Our findings suggest PPV as a viable strategy for neonates under ECMO support.

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BACKGROUND: The optimal ventilation modalities to manage out-of-hospital cardiac arrest (OHCA) remain debated. A specific pressure mode called cardio-pulmonary ventilation (CPV) may be used instead of manual bag ventilation (MBV). We sought to analyse the association between mechanical CPV and return of spontaneous circulation (ROSC) in non-traumatic OHCA. METHODS: MBV and CPV were retrospectively identified in patients with non-traumatic OHCA from the Belgian Cardiac Arrest Registry. We used a two-level mixed-effects multivariable logistic regression analysis to determine the association between the ventilation modalities and outcomes. The primary and secondary study criteria were ROSC and survival with a Cerebral Performance Category (CPC) score of 1 or 2 at 30 days. Age, sex, initial rhythm, no-flow duration, low-flow duration, OHCA location, use of a mechanical chest compression device and Rankin status before arrest were used as covariables. RESULTS: Between January 2017 and December 2021, 2566 patients with OHCA who fulfilled the inclusion criteria were included. 298 (11.6%) patients were mechanically ventilated with CPV whereas 2268 were manually ventilated. The use of CPV was associated with greater probability of ROSC both in the unadjusted (odds ratio: 1.28, 95% confidence interval [CI]: 1.01-1.63; p = 0.043) and adjusted analyses (adjusted odds ratio [aOR]: 2.16, 95%CI 1.37-3.41; p = 0.001) but not with a lower CPC score (aOR: 1.44, 95%CI 0.72-2.89; p = 0.31). CONCLUSIONS: Compared with MBV, CPV was associated with an increased risk of ROSC but not with improved an CPC score in patients with OHCA. Prospective randomised trials are needed to challenge these results.

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Introducción: El edema agudo del pulmón es una enfermedad frecuente en los pacientes que se presentan en los servicios de urgencias. Objetivo: Caracterizar a los pacientes con edema agudo del pulmón en el servicio de urgencias. Método: Se realizó un estudio descriptivo y transversal en 37 pacientes con edema agudo del pulmón, que asistieron al cuerpo de guardia del Hospital Clinicoquirúrgico Docente Dr. Joaquín Castillo Duany de Santiago de Cuba, desde enero a noviembre de 2019. Las variables estudiadas fueron edad, sexo, estado al egreso y uso de la ventilación no invasiva. Resultados: No hubo diferencias entre ambos sexos, predominaron los mayores de 60 años, que padecían de hipertensión arterial. Se comprobó el poco uso de la ventilación no invasiva o invasiva. Conclusiones: El edema agudo del pulmón es más frecuente en pacientes mayores de 60 años, sin distinción de sexo. La mayoría lo presenta relacionado con la hipertensión arterial y existe un escaso uso de la ventilación no invasiva en estos casos.

Introduction: Acute pulmonary edema is a frequent disease among patients in emergency services. Objective: To characterize patients with acute pulmonary edema who attended the emergency services. Methods: A descriptive and cross-sectional study of 37 patients with acute pulmonary edema who attended the emergency services of Dr. Joaquín Castillo Duany Teaching Clinical Surgical Hospital in Santiago de Cuba was carried out, from January to November 2019. The studied variables were age, sex, alive or dead when discharged, noninvasive ventilation usage. Results: There were no differences between the sexes; there was a prevalence of patients older than 60 years of age, who suffered from hypertension. It was demonstrated low noninvasive or invasive ventilation usage. Conclusions: Acute pulmonary edema is more frequent among patients older than 60 years of age in both sexes. Most of the patients suffered from hypertension and there was a deficit in the implementation of noninvasive ventilation in these cases.

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Background: Single-photon emission computed tomography (SPECT) ventilation perfusion imaging is the main imaging method for the diagnosis of pulmonary embolism, and its application in the diagnosis and efficacy evaluation of chronic thromboembolic pulmonary hypertension (CTEPH) has been paid more and more attention. In recent years, with the development of computer software technology, ventilation/perfusion (V/Q) imaging quantitative analysis technology has become more and more mature. The objective of this study was to investigate the utility of quantitative analysis of pulmonary V/Q scintigraphy in evaluating the efficacy of balloon pulmonary angioplasty (BPA) in patients with CTEPH. Methods: In this retrospective analysis, we collected data of patients diagnosed with CTEPH who underwent BPA at the China-Japan Friendship Hospital from April 2018 to September 2020. The sample consisted of 23 males and 28 females, with an average age of 55.1±12.7 years. All patients underwent V/Q scintigraphy within one week before surgery, and we reviewed the pulmonary angiography within 1-3 months following the last BPA procedure. We repeated V/Q scintigraphy within 1 week before or after the pulmonary angiography, at the time of collecting clinical and hemodynamic parameters of these patients. We divided the patients into two groups based on the presence of residual pulmonary hypertension post-surgery and compared the pre- and post-operative quantitative pulmonary perfusion defect percentage scores (PPDs%) using the t-test. Results: In all, 102 V/Q scintigraphy scans were performed in 51 patients. The quantitative PPDs% were positively correlated with the hemodynamic indexes mean pulmonary arterial pressure (mPAP), pulmonary vascular resistance (PVR), and mean right ventricular pressure (RVP) (r=0.605, 0.391, and 0.464, respectively, all P<0.001) and negatively correlated with the 6-minute walking distance (6MWD) (r=-0.254, P=0.010). The average preoperative quantitative PPDs% were (49.0±15.6)% which significantly decreased to (33.5±13.9)% after surgery (t=11.249, P<0.001). The preoperative quantitative PPDs% were (54.7±15.7)% and (44.0±13.8)% in the residual pulmonary hypertension group and the non-residual pulmonary hypertension group, respectively (t=2.599, P=0.012). The postoperative quantitative PPDs% were (41.5±12.5)% and (26.3±11.0)%, in the residual pulmonary hypertension group and the non-residual pulmonary hypertension group, respectively (t=4.647, P<0.001). Conclusions: In this study, we found that quantitative analysis of SPECT pulmonary V/Q scintigraphy adequately reflected the pulmonary artery pressure and clinical status in patients with CTEPH. Our results demonstrate its definite utility in predicting residual pulmonary hypertension and in evaluating the postoperative efficacy of BPA in patients with CTEPH.

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Electrical impedance tomography (EIT) is a new method of monitoring non-invasive mechanical ventilation, at the bedside and useful in critically ill patients. It allows lung monitoring of ventilation and perfusion, obtaining images that provide information on lung function. It is based on the physical principle of impedanciometry or the body's ability to conduct an electrical current. Various studies have shown its usefulness both in adults and in pediatrics in respiratory distress syndrome, pneumonia and atelectasis in addition to pulmonary thromboembolism and pulmonary hypertension by also providing information on pulmonary perfusion, and may be very useful in perioperative medicine; especially in pediatrics avoiding repetitive imaging tests with ionizing radiation.

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Sleep-disordered breathing is highly prevalent in individuals with high-level spinal cord injury. In addition, chest mechanics are known to be altered, leading to paradoxical breathing. Here we investigated the interaction between paradoxical breathing and sleep quality in these patients, and its association with measurements of respiratory function, hypercapnic ventilatory response and peak exercise ventilation. Home-based polysomnography was performed in 13 patients with spinal cord injury (C4 to T4) untreated for sleep-disordered breathing. We defined paradoxical breathing as counterphase between thoracic and abdominal movements during slow-wave and rapid eye movement sleep. Sleep quality, pulmonary function, hypercapnic ventilatory responses and peak exercise ventilation were compared between those with and without paradoxical breathing. Half of individuals presented with nocturnal paradoxical breathing. Despite similar age, body mass index, injury level, time since injury, and respiratory function, those with paradoxical breathing had higher apnea-hypopnea index (13 ± 8 versus 5 ± 3 events per hr) and average sleep heart rate (67 ± 12 versus 54 ± 4 bpm; p < 0.05). Moreover, paradoxical breathing was associated with lower hypercapnic ventilatory response (slope: 0.35 ± 0.17 versus 0.96 ± 0.38) and lower peak exercise ventilation (33 ± 4 versus 48 ± 12 L min-1 ; p < 0.05). Nocturnal respiratory muscle desynchronization could play a role in the pathophysiology of sleep apnea, and could relate to low ventilatory responses to both hypercapnia and exercise in high-level spinal cord injury. Polysomnography may be an important diagnostic tool for these patients for whom therapeutic approaches should be considered to treat this abnormality.

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OBJECTIVE: Asthma is a common chronic respiratory diseases, and the relationship between pulmonary ventilation function and the prognosis of patients with suspected asthma is not well understood. This study aims to explore the impact of pulmonary ventilation functions on the prognosis of patients with suspected asthma. METHODS: This retrospective observational study included patients with suspected asthma who were diagnosed and treated at the Guangdong Provincial Hospital of Traditional Chinese Medicine between August 2015 and January 2020. The primary outcome of interest was improvement in asthma symptoms, as measured by bronchial provocation test (BPT) results within one year after diagnosis. The impact of pulmonary ventilation functions on prognosis was explored by multivariable logistic regression analysis. RESULTS: Seventy-two patients were included in the study. Patients with normal (OR = 0.123, p = .004) or generally normal (OR = 0.075, p = .039) pulmonary ventilation function were more likely to achieve improvement in asthma symptoms compared with patients with mild obstruction. There were no significant differences between the improvement and non-improvement groups in baseline characteristics. CONCLUSION: These results suggest that suspected asthma patients with normal or generally normal pulmonary ventilation function are more likely to achieve improvement in asthma symptoms within one year compared to patients with mild obstruction.

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BACKGROUND: Previous studies have shown that the ratio between alveolar volume (VA) and total lung capacity (TLC) reflects ventilation heterogeneity in subjects with chronic obstructive pulmonary disease (COPD). However, the ratio and its correlation to respiratory symptoms had to our knowledge not previously been investigated in subjects with mild chronic airflow obstruction or without airflow obstruction (normal ratio FEV1/VC). The purpose of this study was to investigate potential connection between VA/TLC and respiratory symptoms, smoking habits and lung function parameters in subjects with normal spirometry and with mild chronic airflow obstruction. METHODS: We examined 450 subjects (82 non-smokers with normal spirometry, 298 subjects who smoked or had smoked earlier but had a normal spirometry and 70 subjects with chronical airflow obstruction) with routine lung function tests and a questionnaire regarding respiratory symptoms. RESULTS: This study showed 31 out of 54 subjects with a low VA/TLC had a normal ratio FEV1/VC. Of these subjects, 58.1 % had respiratory symptoms, compared to the group with normal ratio for both VA/TLC and FEV1/VC where 35.8 % had respiratory symptoms (p-value 0.02). CONCLUSION: This study has shown that within the group of subjects with a normal ratio FEV1/VC, those with a decreased ratio VA/TLC had a higher prevalence of respiratory symptoms compared to subjects with a normal VA/TLC ratio. These findings indicate that including the ratio VA/TLC in the evaluation of a pulmonary function test assessment might increase the possibility to identify subjects with early or at risk of lung disease.

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Refined management of mechanically ventilation is an obvious target for improving patient outcomes, but is impeded by the nature of data for study and hypothesis generation. The connections between clinical outcomes and temporal development of iatrogenic injuries current lung-protective ventilator settings remain poorly understood. Analysis of lung-ventilator system (LVS) evolution at relevant timescales is frustrated by data volume and multiple sources of heterogeneity. This work motivates, presents, and validates a computational pipeline for resolving LVS systems into the joint evolution of data-conditioned model parameters and ventilator information. Applied to individuals, the workflow yields a concise low-dimensional representation of LVS behavior expressed in phenotypic breath waveforms suitable for analysis. The effectiveness of this approach is demonstrated through application to multi-day observational series of 35 patients. Individual patient analyses reveal multiple types of patient-oriented dynamics and breath behavior to expose the complexity of LVS evolution; less than 10% of phenotype changes related to ventilator settings changes. Dynamics are shown to including both stable and unstable phenotype transitions as well as both discrete and continuous changes unrelated to ventilator settings. At a cohort scale, 721 phenotypes constructed from individual data are condensed into a set of 16 groups that empirically organize around certain settings (positive end-expository pressure and ventilator mode) and structurally similar pressure-volume loop characterizations. Individual and cohort scale phenotypes, which may be refined by hypothesis-specific constructions, provide a common framework for ongoing temporal analysis and investigation of LVS dynamics.

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BACKGROUND: This study assessed the clinical effects of a ventilatory assist (VA) device in addition to supplemental O2 (VA+O2) on exercise endurance in subjects with severe to very severe COPD managed with long-term oxygen therapy (LTOT). METHODS: This was a crossover clinical feasibility study of the effects of VA+O2 in subjects with severe to very severe COPD managed with LTOT (N = 15). At visit 1, physiologic measures were obtained, and subjects were tested on the cycle ergometer with VA. Peak work rate and flow for continuous supplemental O2/VA+O2 were established. At visit 2, subjects exercised at a constant work rate of 80% peak work rate to maximum endurance after allocation to VA+O2 or O2. Cardiorespiratory variables, work rate, and dyspnea were included to define potential clinical benefits of VA+O2. Data were analyzed using a linear mixed model. RESULTS: Fifteen subjects with COPD (mean ± SD, age 67.9 ± 9.0 y, FEV1 0.89 ± 0.35 observed) completed the study. Exercise duration in minutes was significantly longer with VA+O2 versus O2 (least squares mean [standard error], 12.0 [2.0] vs 6.2 [2.0], P = .01). VA+O2 versus O2 was also associated with significantly greater isotime improvements in Borg dyspnea scores (3.6 [0.5] vs 5.7 [0.5], P < .001), SpO2 (96.9 [0.9] vs 91.4 [0.9], P < .001), leg fatigue scores (3.8 [0.6] vs 5.2 [0.6], P = .008), and breathing frequency (22.8 [0.9] vs 25.8 [0.9] breaths/min, P = .01). There were no differences in heart rate. CONCLUSIONS: In symptomatic subjects with severe to very severe COPD, VA+O2 significantly increased exercise time and improved dyspnea, SpO2 , breathing frequency, and leg fatigue versus O2 alone.

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Objectives: To identify that incidence of pulmonary barotrauma secondary to mechanical ventilation for the management of acute respiratory distress syndrome associated with coronavirus-disease-2019, and to compare it with the incidence of pulmonary barotrauma trauma secondary to mechanical ventilation associated with all the other causes. METHODS: The retrospective case-control study was conducted at the Aga Khan University Hospital, Karachi, and comprised data from October 2020 to March 2021 of patients who underwent mechanical ventilation. The data was divided into two groups. Data of acute respiratory distress syndrome associated with coronavirus-disease-2019 was in group 1, and that of acute respiratory distress syndrome associated with any other cause in control group 2. Medical records were reviewed to obtain demographic and clinical data, while the institutional picture archiving and communication system was used to review radiological images. Data was analysed using SPSS 24. RESULTS: Of the 261 cases, 115(44%) were in group 1; 87(75.6%) males and 28(24.3%) females. There were 146(56%) controls in group 2; 96(65.7%) males and 50(34.2%) females. There were 142(54.4%) subjects aged >60 years; 61(43%) in group 1 and 81(57%) in group 2. The incidence of pulmonary barotrauma in group 1 was 39(34%) and 8(5.5%) in group 2 (p<0.0001). CONCLUSIONS: Mechanical ventilation in the management of acute respiratory distress syndrome associated with coronavirusdisease- 2019 was found to be associated with a significantly higher incidence of pulmonary barotrauma than acute respiratory distress syndrome associated with any other cause.

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