Ventilation-perfusion Mismatch Research Articles

Whole lung lavage: considerations from the anesthesiology perspective.

Whole lung lavage (WLL) remains the standard treatment for pulmonary alveolar proteinosis (PAP). The procedure involves meticulous preparation, including a multidisciplinary team and appropriate facilities, to ensure patient safety and procedural success. Effective anesthesia management is essential to allow for successful completion of the procedure and prevent complications. Effective anesthesia management, including total intravenous anesthesia (TIVA) and careful intraoperative monitoring, is essential to prevent complications such as hypoxemia and fluid overload. Proper airway control with a double-lumen tube, careful positioning, and continuous monitoring during the lavage phase are key to minimizing risks. Challenges such as fluid spillage and ventilation-perfusion mismatch must be managed proactively with techniques such as fiberoptic bronchoscopy and recruitment maneuvers. In cases of severe hypoxemia, advanced options like extra-corporeal membrane oxygenation (ECMO) or sequential lavage may be required. WLL is a pivotal treatment for PAP, offering significant relief and improvement for many patients despite the challenges in standardizing the procedure due to the rare nature of the condition. Involvement of a multidisciplinary team involving pulmonologist, anesthesiologist, critical care personnel, operating room personnel and in some cases and centers, cardiothoracic surgeon and perfusionist is critical to the success of the procedure.

Pathophysiological Markers of Acute Respiratory Distress Syndrome Severity Are Correlated With Ventilation-Perfusion Mismatch Measured by Electrical Impedance Tomography.

Pulmonary ventilation/perfusion (V/Q) mismatch measured by electrical impedance tomography (EIT) is associated with the outcome of patients with the acute respiratory distress syndrome (ARDS), but the underlying pathophysiological mechanisms have not been fully elucidated. The present study aimed to verify the correlation between relevant pathophysiological markers of ARDS severity and V/Q mismatch. Prospective observational study. General ICU of a university-affiliated hospital. Deeply sedated intubated adult patients with ARDS under controlled mechanical ventilation. Measures of V/Q mismatch by EIT, respiratory mechanics, gas exchange, lung imaging, and plasma biomarkers. Unmatched V/Q units were assessed by EIT as the fraction of ventilated nonperfused plus perfused nonventilated lung units. At the same time, plasma biomarkers with proven prognostic and mechanistic significance for ARDS (carbonic anhydrase 9 [CA9], hypoxia-inducible factor 1 [HIF1], receptor for advanced glycation endproducts [RAGE], angiopoietin 2 [ANG2], gas exchange, respiratory mechanics, and quantitative chest CT scans were measured. Twenty-five intubated ARDS patients were included with median unmatched V/Q units of 37.1% (29.2-49.2%). Unmatched V/Q units were correlated with plasma levels of CA9 (rho = 0.47; p = 0.01), HIF1 (rho = 0.40; p = 0.05), RAGE (rho = 0.46; p = 0.02), and ANG2 (rho = 0.42; p = 0.03). Additionally, unmatched V/Q units correlated with plateau pressure (r = 0.38; p = 0.05) and with the number of quadrants involved on chest radiograph (r = 0.73; p < 0.01). Regional unmatched V/Q units were correlated with the corresponding fraction of poorly aerated lung tissue (r = 0.62; p = 0.01) and of lung tissue weight (rho: 0.51; p = 0.04) measured by CT scan. In ARDS patients, unmatched V/Q units are correlated with pathophysiological markers of lung epithelial and endothelial dysfunction, increased lung stress, and lung edema. Unmatched V/Q units could represent a comprehensive marker of ARDS severity, reflecting the complex organ pathophysiology and reinforcing their prognostic significance.

Advances in Physiological Research: Consideration on Arterial Hypercapnia in Acute Cardiogenic Pulmonary Edema (ACPE)

The causes of hypercapnia in Acute Cardiogenic Pulmonary Edema are still unknown. Our hypothesis recognizes an alteration of the ventilation-perfusion ratio in the apical areas of the lung as the major cause. The redistribution of blood to the apical lung zone in hypertensive pulmonary circulation determines an excess of perfusion compared to ventilation and consequently hypercapnia. Our suggestion might be in favor of Bilevel-PAP over Continuous Positive Airway Pressure (CPAP) as the first line of therapy.

Pulmonary Shunt in Critical Care: A Comprehensive Review of Pathophysiology, Diagnosis, and Management Strategies.

Pulmonary shunt, an abnormal passage of blood through the pulmonary circulation without adequate gas exchange, poses significant challenges in critical care. This comprehensive review explores the pathophysiology, diagnostic approaches, and management strategies associated with pulmonary shunt. Pulmonary shunts are classified into anatomical and physiological types, each with distinct mechanisms and implications for gas exchange. Anatomical shunts result from structural heart defects, while physiological shunts arise from ventilation-perfusion (V/Q) mismatches. Both conditions can significantly impair oxygenation and contribute to multi-organ dysfunction. This review delves into various diagnostic modalities, including clinical assessment, imaging techniques such as chest X-ray and CT scans, and advanced diagnostic methods such as V/Q scanning and echocardiography. Challenges in diagnosing pulmonary shunt are discussed, emphasizing the limitations of current tools and the need for accurate differentiation of shunt types. Management strategies are examined, covering pharmacological interventions, non-pharmacological treatments such as mechanical ventilation and prone positioning, and surgical options. Emerging therapies and innovations in treatment are also highlighted. Special considerations are given to different patient populations, including pediatric and elderly patients and those with multiple comorbidities. This review concludes with an analysis of the prognosis and outcomes associated with pulmonary shunt, focusing on short-term and long-term impacts on survival and quality of life. This review aims to enhance understanding and guide effective management practices for pulmonary shunt in critical care settings by synthesizing current knowledge and identifying areas for further research.

Absolute values of regional ventilation-perfusion mismatch in patients with ARDS monitored by electrical impedance tomography and the role of dead space and shunt compensation

BackgroundAssessment of regional ventilation/perfusion (V′/Q) mismatch using electrical impedance tomography (EIT) represents a promising advancement for personalized management of the acute respiratory distress syndrome (ARDS). However, accuracy is still hindered by the need for invasive monitoring to calibrate ventilation and perfusion. Here, we propose a non-invasive correction that uses only EIT data and characterized patients with more pronounced compensation of V′/Q mismatch.MethodsWe enrolled twenty-one ARDS patients on controlled mechanical ventilation. Cardiac output was measured invasively, and ventilation and perfusion were assessed by EIT. Relative V′/Q maps by EIT were calibrated to absolute values using the minute ventilation to invasive cardiac output (MV/CO) ratio (V′/Q-ABS), left unadjusted (V′/Q-REL), or corrected by MV/CO ratio derived from EIT data (V′/Q-CORR). The ratio between ventilation to dependent regions and perfusion reaching shunted units (VD′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{V}}_{{\ ext{D}}}^{\\prime }$$\\end{document}/QSHUNT) was calculated as an index of more effective hypoxic pulmonary vasoconstriction. The ratio between perfusion to non-dependent regions and ventilation to dead space units (QND/VDS′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{V}}_{{{\ ext{DS}}}}^{\\prime }$$\\end{document}) was calculated as an index of hypocapnic pneumoconstriction.ResultsOur calibration factor correlated with invasive MV/CO (r = 0.65, p < 0.001), showed good accuracy and no apparent bias. Compared to V′/Q-ABS, V′/Q-REL maps overestimated ventilation (p = 0.013) and perfusion (p = 0.002) to low V′/Q units and underestimated ventilation (p = 0.011) and perfusion (p = 0.008) to high V′/Q units. The heterogeneity of ventilation and perfusion reaching different V′/Q compartments was underestimated. V′/Q-CORR maps eliminated all these differences with V′/Q-ABS (p > 0.05). Higher VD′/QSHUNT\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$V_{D}^{\\prime } /Q_{SHUNT}$$\\end{document} correlated with higher PaO2/FiO2 (r = 0.49, p = 0.025) and lower shunt fraction (ρ = − 0.59, p = 0.005). Higher QND/VDS′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Q_{ND} /V_{DS}^{\\prime }$$\\end{document} correlated with lower PEEP (ρ = − 0.62, p = 0.003) and plateau pressure (ρ = − 0.59, p = 0.005). Lower values of both indexes were associated with less ventilator-free days (p = 0.05 and p = 0.03, respectively).ConclusionsRegional V′/Q maps calibrated with a non-invasive EIT-only method closely approximate the ones obtained with invasive monitoring. Higher efficiency of shunt compensation improves oxygenation while compensation of dead space is less needed at lower airway pressure. Patients with more effective compensation mechanisms could have better outcomes.

Respiratory management of acute chest syndrome in children with sickle cell disease.

Acute chest syndrome (ACS) is a leading cause of respiratory distress and hospitalisation in children with sickle cell disease (SCD). The aetiology is multifactorial and includes fat embolism, venous thromboembolism, alveolar hypoventilation and respiratory infections, with the latter being particularly common in children. These triggers contribute to a vicious cycle of erythrocyte sickling, adhesion to the endothelium, haemolysis, vaso-occlusion and ventilation-perfusion mismatch in the lungs, resulting in the clinical manifestations of ACS. The clinical presentation includes fever, chest pain, dyspnoea, cough, wheeze and hypoxia, accompanied by a new pulmonary infiltrate on chest radiography. Respiratory symptoms may overlap with those of acute asthma, which may be difficult to distinguish. Patients with ACS may deteriorate rapidly; thus prevention, early recognition and aggressive, multidisciplinary team management is essential. In this narrative review, we highlight the current evidence regarding the epidemiology, pathophysiology, treatment and preventative strategies for ACS, focusing on the aspects of major interest for the paediatric pulmonologist and multidisciplinary team who manage children with SCD.

Immediate cardiopulmonary responses to consecutive pulmonary embolism: a randomized, controlled, experimental study

BackgroundAcute pulmonary embolism (PE) induces ventilation-perfusion mismatch and hypoxia and increases pulmonary pressure and right ventricular (RV) afterload, entailing potentially fatal RV failure within a short timeframe. Cardiopulmonary factors may respond differently to increased clot burden. We aimed to elucidate immediate cardiopulmonary responses during successive PE episodes in a porcine model.MethodsThis was a randomized, controlled, blinded study of repeated measurements. Twelve pigs were randomly assigned to receive sham procedures or consecutive PEs every 15 min until doubling of mean pulmonary pressure. Cardiopulmonary assessments were conducted at 1, 2, 5, and 13 min after each PE using pressure-volume loops, invasive pressures, and arterial and mixed venous blood gas analyses. ANOVA and mixed-model statistical analyses were applied.ResultsPulmonary pressures increased after the initial PE administration (p < 0.0001), with a higher pulmonary pressure change compared to pressure change observed after the following PEs. Conversely, RV arterial elastance and pulmonary vascular resistance was not increased after the first PE, but after three PEs an increase was observed (p = 0.0103 and p = 0.0015, respectively). RV dilatation occurred following initial PEs, while RV ejection fraction declined after the third PE (p = 0.004). RV coupling exhibited a decreasing trend from the first PE (p = 0.095), despite increased mechanical work (p = 0.003). Ventilatory variables displayed more incremental changes with successive PEs.ConclusionIn an experimental model of consecutive PE, RV afterload elevation and dysfunction manifested after the third PE, in contrast to pulmonary pressure that increased after the first PE. Ventilatory variables exhibited a more direct association with clot burden.

Computational Decision Support for PE Diagnosis based on Ventilation Perfusion Ratio.

The aim of this study is to investigate whether computer-aided, semi-automated 3D lung lobe quantification can support decision-making on PE diagnosis based on the ventilation-perfusion ratio in clinical practice. A study cohort of 100 patients (39 male, 61 female, age 64.8±15.8 years) underwent ventilation/perfusion single photon emission computed tomography (V/Q-SPECT/CT) to exclude acute PE on SPECT/CT OPTIMA NM/CT 640 (GE Healthcare). Two 3D lung lobe quantification software tools (Q. Lung: Xeleris 4.0, GE Healthcare and LLQ: Hermes Hybrid 3D Lung Lobar Quantification, Hermes Medical Solutions) were used to evaluate the numerical lobar ventilation/perfusion ratio (VQR) and lobar volume/perfusion ratio (VPR). A test of linearity and equivalence of the two 3D software tools was performed using Pearson, Spearman, quadratic weighted kappa and the mean squared deviation for VPR/VQR. An algorithm was developed that identified PE candidates using ROC analysis. The agreement between the PE findings of an experienced nuclear medicine expert and the calculated PE candidates was represented by the magnitude of the YOUDEN index (J) and the size of the area under the receiver operating curve (AUC). Both 3D software tools showed good comparability. The YOUDEN index for QLUNG(VPR/VQR)/LLQ(VPR/VQR) was in the range from 0.2 to 0.5. The mean AUC averaged over all lung lobes for QLUNG(VPR) was 0.66, CI95%: ±14.0%, for QLUNG(VQR) 0.66, CI95%: ±13.3%, for LLQ(VPR) 0.64, CI95%: ±14.7% and for LLQ(VQR) 0.65, CI95%: ±13.1%. This study reveals that 3D software tools are feasible for numerical PE detection. The clinical decision can be supported by using a numerical algorithm based on ROC analysis.

Physics-based in silico modelling of microvascular pulmonary perfusion in COVID-19.

Due to its ability to induce heterogenous, patient-specific damage in pulmonary alveoli and capillaries, COVID-19 poses challenges in defining a uniform profile to elucidate infection across all patients. Computational models that integrate changes in ventilation and perfusion with heterogeneous damage profiles offer valuable insights into the impact of COVID-19 on pulmonary health. This study aims to develop an in silico hypothesis-testing platform specifically focused on studying microvascular pulmonary perfusion in COVID-19-infected lungs. Through this platform, we explore the effects of various acinar-level pulmonary perfusion abnormalities on global lung function. Our modelling approach simulates changes in pulmonary perfusion and the resulting mismatch of ventilation and perfusion in COVID-19-afflicted lungs. Using this coupled modelling platform, we conducted multiple simulations to assess different scenarios of perfusion abnormalities in COVID-19-infected lungs. The simulation results showed an overall decrease in ventilation-perfusion (V/Q) ratio with inclusion of various types of perfusion abnormalities such as hypoperfusion with and without microangiopathy. This model serves as a foundation for comprehending and comparing the spectrum of findings associated with COVID-19 in the lung, paving the way for patient-specific modelling of microscale lung damage in emerging pulmonary pathologies like COVID-19.

Temporal effects of caffeine on intrapulmonary shunt in preterm ventilated infants.

We hypothesized that caffeine would be associated with a transient reduction in the right-to-left shunt and VA/Q. We aimed to explore the temporal effects of caffeine on right-to-left shunt, ventilation perfusion ratio (VA/Q) and shift of the oxyhaemoglobin dissociation curve (ODC) in premature ventilated infants. Retrospective cohort study at a tertiary neonatal unit of infants born at less than 31weeks of gestation that were mechanically ventilated on day three of life. The non-invasive method of the ODC was used to determine the right-to-left shunt, VA/Q and shift before and at 1, 4 and 20 h after a maintenance dose of caffeine citrate. A total of 21 infants were included with a median (range) gestational age of 27 (23.7-30.7) weeks. The median shunt percentage was significantly reduced, compared to baseline at 1 h (8 (range: 7-9) % vs. 4 (range: 0-6) %, p=0.042) and 4 h post caffeine administration (8 (range: 7-9) % vs. 0 (range: 0-3) %, p=0.042), but the VA/Q and the right shift of the ODC did not differ significantly between these time points. At 20 h, there were no significant differences between these indices compared to baseline values. Caffeine led to a transient decrease in intrapulmonary shunt from one to 4 h after administration and this may be due to its diuretic action.

The Pathophysiology of Scoliosis Across the Spectrum of Human Physiological Systems

Scoliosis is a medical condition characterized by an abnormal lateral curvature of the spine. It can lead to various health issues, affecting mobility, respiratory function, and overall quality of life. There are several types of scoliosis, including idiopathic, congenital, neuromuscular, degenerative, and functional. The severity of scoliosis is measured by the degree of spinal curvature, typically expressed in degrees through a system known as the Cobb angle. Early detection and intervention are fundamental in managing scoliosis, as more severe forms may necessitate bracing or surgical intervention. Healthcare professionals must understand the different types of scoliosis and their unique characteristics to tailor appropriate treatment plans.Scoliosis can significantly impact various physiological systems, including the circulatory, digestive, endocrine, integumentary, lymphatic, muscular, nervous, and respiratory systems. In the circulatory system, scoliosis can cause hemodynamic changes, impaired venous return, cardiac strain, and pulmonary complications. In the digestive system, scoliosis can lead to gastric displacement, impaired intra-abdominal pressure, gastroesophageal reflux, and nutritional implications. The endocrine system can be affected by scoliosis, leading to neuroendocrine dysregulation, growth hormone abnormalities, cortisol dysregulation, and impact on thyroid function. Scoliosis can also affect the integumentary system, leading to pressure ulcers, altered skin sensation, and hygiene challenges. In the lymphatic system, scoliosis can cause lymphatic obstruction, impaired immune response, altered inflammatory responses, fibrosis, and secondary lymphedema. Scoliosis can affect the muscular system, leading to muscle imbalance, myofascial pain, respiratory muscle weakness, and mobility issues. The nervous system can also be impacted by scoliosis, leading to neural compression, central nervous system impact, neurological dysfunction, and coordination challenges. In the respiratory system, scoliosis can cause thoracic deformities, reduced lung compliance, ventilation-perfusion mismatch, respiratory muscle weakness, increased work of breathing (WOB), and an increased risk of respiratory infections.Recognizing and addressing the interplay between scoliosis and these physiological systems is integral for healthcare professionals to provide comprehensive care to individuals with scoliosis.Current research on scoliosis has made progress in diagnostic tools and techniques, including the use of imaging methods like MRI and X-ray, wearable sensors, and 3D reconstruction techniques for better evaluation of spinal motion and function, along with treatment strategies like Schroth exercises and braces, and management measures for respiratory and circulatory problems. However, there are limitations to current studies, such as the heterogeneity of scoliosis, compartmentalized approaches, limited longitudinal studies, reliance on retrospective data, and the need for standardized measures and diagnostic criteria. Future research prospects include advancements in genetic research, biomechanics, artificial intelligence and machine learning, longitudinal studies, non-invasive treatments, and multidisciplinary collaborations among researchers, clinicians, and technologists.

Individualized estimation of arterial carbon dioxide partial pressure using machine learning in children receiving mechanical ventilation

BackgroundMeasuring arterial partial pressure of carbon dioxide (PaCO2) is crucial for proper mechanical ventilation, but the current sampling method is invasive. End-tidal carbon dioxide (EtCO2) has been used as a surrogate, which can be measured non-invasively, but its limited accuracy is due to ventilation-perfusion mismatch. This study aimed to develop a non-invasive PaCO2 estimation model using machine learning.MethodsThis retrospective observational study included pediatric patients (< 18 years) admitted to the pediatric intensive care unit of a tertiary children’s hospital and received mechanical ventilation between January 2021 and June 2022. Clinical information, including mechanical ventilation parameters and laboratory test results, was used for machine learning. Linear regression, multilayer perceptron, and extreme gradient boosting were implemented. The dataset was divided into 7:3 ratios for training and testing. Model performance was assessed using the R2 value.ResultsWe analyzed total 2,427 measurements from 32 patients. The median (interquartile range) age was 16 (12−19.5) months, and 74.1% were female. The PaCO2 and EtCO2 were 63 (50−83) mmHg and 43 (35−54) mmHg, respectively. A significant discrepancy of 19 (12–31) mmHg existed between EtCO2 and the measured PaCO2. The R2 coefficient of determination for the developed models was 0.799 for the linear regression model, 0.851 for the multilayer perceptron model, and 0.877 for the extreme gradient boosting model. The correlations with PaCO2 were higher in all three models compared to EtCO2.ConclusionsWe developed machine learning models to non-invasively estimate PaCO2 in pediatric patients receiving mechanical ventilation, demonstrating acceptable performance. Further research is needed to improve reliability and external validation.

Assessing the pulmonary vascular responsiveness to oxygen with proton MRI.

Ventilation-perfusion matching occurs passively and is also actively regulated through hypoxic pulmonary vasoconstriction (HPV). The extent of HPV activity in humans, particularly normal subjects, is uncertain. Current evaluation of HPV assesses changes in ventilation-perfusion relationships/pulmonary vascular resistance with hypoxia and is invasive, or unsuitable for patients because of safety concerns. We used a noninvasive imaging-based approach to quantify the pulmonary vascular response to oxygen as a metric of HPV by measuring perfusion changes between breathing 21% and 30%O2 using arterial spin labeling (ASL) MRI. We hypothesized that the differences between 21% and 30%O2 images reflecting HPV release would be 1) significantly greater than the differences without [Formula: see text] changes (e.g., 21-21% and 30-30%O2) and 2) negatively associated with ventilation-perfusion mismatch. Perfusion was quantified in the right lung in normoxia (baseline), after 15 min of 30% O2 breathing (hyperoxia) and 15 min normoxic recovery (recovery) in healthy subjects (7 M, 7 F; age = 41.4 ± 19.6 yr). Normalized, smoothed, and registered pairs of perfusion images were subtracted and the mean square difference (MSD) was calculated. Separately, regional alveolar ventilation and perfusion were quantified from specific ventilation, proton density, and ASL imaging; the spatial variance of ventilation-perfusion (σ2V̇a/Q̇) distributions was calculated. The O2-responsive MSD was reproducible (R2 = 0.94, P < 0.0001) and greater (0.16 ± 0.06, P < 0.0001) than that from subtracted images collected under the same [Formula: see text] (baseline = 0.09 ± 0.04, hyperoxia = 0.08 ± 0.04, recovery = 0.08 ± 0.03), which were not different from one another (P = 0.2). The O2-responsive MSD was correlated with σ2V̇a/Q̇ (R2 = 0.47, P = 0.007). These data suggest that active HPV optimizes ventilation-perfusion matching in normal subjects. This noninvasive approach could be applied to patients with different disease phenotypes to assess HPV and ventilation-perfusion mismatch.NEW & NOTEWORTHY We developed a new proton MRI method to noninvasively quantify the pulmonary vascular response to oxygen. Using a hyperoxic stimulus to release HPV, we quantified the resulting redistribution of perfusion. The differences between normoxic and hyperoxic images were greater than those between images without [Formula: see text] changes and negatively correlated with ventilation-perfusion mismatch. This suggests that active HPV optimizes ventilation-perfusion matching in normal subjects. This approach is suitable for assessing patients with different disease phenotypes.

Ventilation Management in a Patient with Ventilation–Perfusion Mismatch in the Early Phase of Lung Injury and during the Recovery

Chest trauma is one of the most serious and difficult injuries, with various complications that can lead to ventilation–perfusion (V/Q) mismatch and systemic hypoxia. We are presenting a case of a 53-year-old male with no chronic therapy who was admitted to the Intensive Care Unit due to severe respiratory failure after chest trauma. He developed a right-sided pneumothorax, and then a thoracic drain was placed. On admission, the patient was hemodynamically unstable and tachypneic. He was intubated and mechanically ventilated, febrile (38.9 °C) and unconscious. A lung CT showed massive non-ventilated areas, predominantly in the right lung, guiding repeated therapeutic and diagnostic bronchoalveolar lavages. He was ventilated with PEEP of 10 cmH2O with a FiO2 of 0.6–0.8. Empirical broad-spectrum antimicrobial therapy was immediately initiated. Both high FiO2 and moderate PEEP were maintained and adjusted according to the current blood gas values and oxygen saturation. He was weaned from mechanical ventilation, and non-invasive oxygenation was continued. After Stenotrophomonas maltophilia was identified and treated with sulfamethoxazole/trimethoprim, a regression of lung infiltrates was observed. In conclusion, both ventilatory and antibiotic therapy were needed to improve the oxygenation and outcome of the patient with S. maltophilia pneumonia and V/Q mismatch.

Dynamic model of the influence of gravity, ventilation with positive and negative pressure on ventilation-perfusion ratio in lungs

Dynamic model of the influence of gravity, ventilation with positive and negative pressure on ventilation-perfusion ratio in lungs

The study of respiratory function of the lungs in patients with Bronchial Asthma

The article discusses the possibilities of functional assessment of the state of the respiratory function of the lungs in patients with bronchial asthma.The purpose of the study: a comparative assessment of the information content of capnometry, spirometry, the method of multiple breath nitrogen washout and the diffusion test in patients with asthma.Results and conclusions: 2 groups of patients were examined: I — 30 patients with asthma of 3–4 degrees of severity, II — 30 healthy volunteers. Capnometry showed a statistically significant increase in the slope of the alveolar phase in patients with asthma compared to the control group with quiet breathing, both before and after the use of a bronchodilator. According to spirometry data, in patients, the FEV1 /FVC ratio was statistically significantly lower compared to the control group, both before and after bronchodilator use. In a comparative analysis of the diffusion capacity of the lungs, there was a trend towards lower DLCO values in patients with asthma. A statistically significant difference was obtained in relation to the lung clearance index between the group of patients with asthma and the control group, in which the index was significantly lower. There were no statistically significant differences between the FRC (%) estimates obtained using the diffusion test and the method of the multiple breath nitrogen washout in patients with asthma. Thus, the informative methods in patients with asthma were not only the method of spirometry, but also the method of capnometry and the method of multiple breath nitrogen washout, which revealed uneven ventilation and distribution of ventilation-perfusion ratios in the lungs.

Three-dimensional analysis reveals a high incidence of lung adenocarcinoma in the upper region.

The lung is a unique organ with a ventilation-perfusion mismatch, which can cause inhomogeneous incidence rates of lung cancer depending on the location in the lung. We aimed to evaluate the incidence of lung adenocarcinoma in each lobe by analyzing the incidence per unit volume, to evaluate the incidence without being affected by differences in the size of each lobe or in the size of the lungs between individuals. The number of adenocarcinomas in each lobe was counted. Lung volumes were measured using a three-dimensional computer workstation. The tumor incidence per unit volume was analyzed based on the number of tumors in each lobe. The number of tumors per unit volume was 0.467 in the right upper lobe (RUL), 0.182 in the right middle lobe, 0.209 in the right lower lobe, 0.306 in the left upper segment (LUS), 0.083 in the left lingular segment, and 0.169 in the left lower lobe. The tumor incidence rate of RUL + LUS was 2.269 times that of the other lobes, a value that was significantly higher when using the bootstrap method (p < 0.001). The incidence of adenocarcinoma per unit volume in both upper lobes was higher than that in other lobes.

Chemical-computational comparison of organometallic complexes in oxygen carriers and their incidence on blood color

Blood typically carries small amounts of molecular oxygen (O2) dissolved in the plasma and large amounts chemically combined with hemoglobin. Partial pressure depends only on physically dissolved oxygen, which determines how much oxygen will combine with hemoglobin. The blood needs an O2 carrier in humans because this gas is not sufficiently soluble in the blood plasma to satisfy the body's requirement. At 37 ºC, a liter of blood only dissolves 2.3 mL of O2. However, one liter of blood contains 150 g of hemoglobin, and since each gram of hemoglobin dissolves 1.34 mL of O2, 200 mL of O2 are transported per liter of blood. This quantity is 87 times more than what plasma could carry by itself. Without an O2 carrier like hemoglobin, blood would have to circulate 87 times faster, requiring a high-pressure pump, turbulent flow, and a considerable ventilation-perfusion mismatch. This is why other transporter molecules exist in various organisms, giving each of them a representative color. This is how it is in the human being that blood is red; in spiders, crustaceans, mollusks, octopuses, and squids, the blood is blue; in some segmented worms, some leeches, and some marine worms, there is green blood; finally, in marine worms and brachiopods, the blood is violet.

Effects of early versus delayed application of prone position on ventilation–perfusion mismatch in patients with acute respiratory distress syndrome: a prospective observational study

BackgroundProne position has been shown to improve oxygenation and survival in patients with early acute respiratory distress syndrome (ARDS). These beneficial effects are partly mediated by improved ventilation/perfusion (V/Q) distribution. Few studies have investigated the impact of early versus delayed proning on V/Q distribution in patients with ARDS. The aim of this study was to assess the regional ventilation and perfusion distribution in early versus persistent ARDS after prone position.MethodsThis is a prospective, observational study from June 30, 2021, to October 1, 2022 at the medical ICU in Zhongda Hospital, Southeast University. Fifty-seven consecutive adult patients with moderate-to-severe ARDS ventilated in supine and prone position. Electrical impedance tomography was used to study V/Q distribution in the supine position and 12 h after a prone session.ResultsOf the 57 patients, 33 were early ARDS (≤ 7 days) and 24 were persistent ARDS (> 7 days). Oxygenation significantly improved after proning in early ARDS (157 [121, 191] vs. 190 [164, 245] mm Hg, p < 0.001), whereas no significant change was found in persistent ARDS patients (168 [136, 232] vs.177 [155, 232] mm Hg, p = 0.10). Compared to supine position, prone reduced V/Q mismatch in early ARDS (28.7 [24.6, 35.4] vs. 22.8 [20.0, 26.8] %, p < 0.001), but increased V/Q mismatch in persistent ARDS (23.8 [19.8, 28.6] vs. 30.3 [24.5, 33.3] %, p = 0.006). In early ARDS, proning significantly reduced shunt in the dorsal region and dead space in the ventral region. In persistent ARDS, proning increased global shunt. A significant correlation was found between duration of ARDS onset to proning and the change in V/Q distribution (r = 0.54, p < 0.001).ConclusionsProne position significantly reduced V/Q mismatch in patients with early ARDS, while it increased V/Q mismatch in persistent ARDS patients.Trial registration ClinicalTrials.gov (NCT05207267, principal investigator Ling Liu, date of registration 2021.08.20).

Presence of procoagulant peripheral blood mononuclear cells in severe COVID-19 patients relate to ventilation perfusion mismatch and precede pulmonary embolism

PurposePulmonary emboli (PE) contribute substantially to coronavirus disease 2019 (COVID-19) related mortality and morbidity. Immune cell-mediated hyperinflammation drives the procoagulant state in COVID-19 patients, resulting in immunothrombosis. To study the role of peripheral blood mononuclear cells (PBMC) in the procoagulant state of COVID-19 patients, we performed a functional bioassay and related outcomes to the occurrence of PE. Secondary aims were to relate this functional assay to plasma D-dimer levels, ventilation perfusion mismatch and TF expression on monocyte subsets. MethodsPBMC from an ICU biobank were obtained from 20 patients with a computed tomography angiograph (CTA) proven PE and compared to 15 COVID-19 controls without a proven PE. Functional procoagulant properties of PBMC were measured using a modified fibrin generation time (MC-FGT) assay. Tissue factor (TF) expression on monocyte subsets were measured by flow cytometry. Additional clinical data were obtained from patient records including end-tidal to arterial carbon dioxide gradient. ResultsMC-FGT levels were highest in the samples taken closest to the PE detection, similar to the end-tidal to arterial carbon dioxide gradient (ETCO2 – PaCO2), a measurement to quantify ventilation-perfusion mismatch. In patients without proven PE, peak MC-FGT relates to an increase in end-tidal to arterial carbon dioxide gradient. We identified non-classical, CD16 positive monocytes as the subset with increased TF expression. ConclusionWe show that the procoagulant state of PBMC could aid in early detection of PE in COVID-19 ICU patients. Combined with end-tidal to ETCO2 – PaCO2 gradient, these tests could improve early detection of PE on the ICU.