Pulmonary Embolism and Gas Exchange.

Acute pulmonary embolism (PE) impairs hemodynamics, gas exchange, and lung mechanical capacity. Considering PE pathophysiology, most attention has been paid to hemodynamic impairment. However, the most prevalent symptoms in PE patients come from gas exchange alterations, which have not been in the spotlight for many years. Pulmonary physiology and consequent gas exchange impairment play a pivotal role in the high risk of death from PE. In this review, we will look at the pathophysiology of PE, from the vascular occlusion to the resultant heterogeneity in pulmonary perfusion and gas exchange impairment, discussing in detail its causes and consequences.

Oxygenation index and NT-proBNP as predictors of pulmonary hypertension and ventilation/perfusion mismatch in acute pulmonary embolism.

Introduction: The magnitude of pulmonary artery pressure (PAP) and the extent of ventilation/perfusion (V/Q) mismatch are essential for assessing the prognosis of acute pulmonary embolism (APE). We aimed to develop a model for predicting the status of the pulmonary circulation and arterial gas exchange functions using serum levels of cardiac biomarkers and arterial oxygenation index (OI) values. Materials and methods: This single-center, retrospective observational cohort study included 224 patients with APE. Multivariate linear regression and Poisson regression were used to test the statistical association between cardiac biomarkers, OI, PAP, and V/Q mismatch. Diagnostic efficiency was calculated from a receiver operating characteristic (ROC) curve. Results: Serum levels of troponin I (TNI), N-terminal pro-brain natriuretic peptide (NT-proBNP), and arterial OI magnitude significantly correlated with PAP and V/Q mismatches (P < 0.05). Multivariate linear regression showed that NT-proBNP serum levels (ß = 0.002, P < 0.001) and OI values (ß = -0.022, P = 0.001) significantly influenced PAP. Arterial OI (ß = -0.039, P < 0.001) had a significant influence on the percentage of pulmonary vascular obstruction (PVO) as determined by perfusion scanning. Poisson regression showed that OI (odds ratio: 0.995, p < 0.001) was a predictor of the number of lung segments with V/Q mismatches. ROC area under the curve (AUC) values of NT-proBNP and OI predicting pulmonary hypertension were 0.716 and 0.730, respectively, and for V/Q mismatch scanning, the results were 0.601 and 0.634, respectively. Conclusion: Arterial OI and serum levels of cardiac biomarkers may be used as indicators of pulmonary hypertension and V/Q mismatch.

Endotheliitis, Shunts, and Ventilation-Perfusion Mismatch in Coronavirus Disease 2019: A Literature Review of Disease Mechanisms.

The severe acute respiratory syndrome coronavirus 2 pandemic has continued to impact global health. However, while immunity acquired by vaccines has been developed, 40% of the world's population has still not been vaccinated. Economic problems associated with acquiring novel therapies, misinformation, and differences in treatment protocols have generated catastrophic results, especially in low-resource countries. Understanding the pathophysiological aspects of coronavirus disease and the therapeutic strategies that have been validated to date is essential for successful medical care. In this review, I summarize the historical aspects of the virus, molecules involved in infecting the host, and consequences of viral interactions with and in tissues.

Platypnea-orthodeoxia syndrome in a patient with ongoing COVID-19.

SARS-CoV-2 infection of the vascular endothelium causes excessive vasodilation. It is important in the rehabilitation of patients with COVID-19 to recognize that increased blood flow in lung lesions at the base of the lung due to vasodilation may cause V/Q mismatch and result in platypnea-orthodeoxia syndrome.

Ventilatory constraint is more severe in walking than cycling in patients with COPD.

Due to its effectivity in assessing functional capacity and adding prognostic information to the staging of chronic obstructive pulmonary disease (COPD) patients, the 6-min walk test (6MWT) is extensively used in clinical evaluation. Currently, there is little information about the physiological response this test elicits in patients, especially when compared to cardiopulmonary exercise test (CPET). The aim of the study was to compare ventilatory and metabolic responses between these tests commonly used for the assessment of clinical outcome. A group of 20 patients with moderate to very severe COPD were tested for their pulmonary function (flow-volume curve, static lung volumes), occlusion mouth pressures and breath-by-breath measurement of flow, volumes, and oxygen (O2) and carbon dioxide (CO2) concentration during the 6MWT and CPET. All parameters measured during both exercise tests were assessed over the throughout of the tests and compared between each other at specified time points. Serially measured inspiratory vital capacity (IVC) decreased more rapidly and extensively during the walk-test (p â€‹< â€‹0,0001). This was accompanied by a limited increase in tidal volume (VT) and minute ventilation (VE), which were significantly lower in the course of the 6MWT (p â€‹= â€‹0,0003 and p â€‹= â€‹0,0097, respectively). We also noticed a significant decrease in hemoglobin oxygen saturation (SpO2) during the 6MWT which was correlated to percent decrease in IVC (p â€‹= â€‹0,0206). Over the course of the 6MWT, oxygen consumption (VO2) and VT reached plateau within 2 â€‹min, while carbon dioxide production (VCO2) and VE within 3 â€‹min. During CPET, VO2, VCO2 and VE rose continuously, while VT reached plateau within 4 â€‹min. The 6MWT seems to be a rather endurance-based test associated with more pronounced dynamic lung hyperinflation and mechanical constraint of ventilation in comparison to cycling.

Non-intubated Thoracoscopic Surgery-Tips and Tricks From Anesthesiological Aspects: A Mini Review.

BACKGROUND: In the last few decades, surgical techniques have been developed in thoracic surgery, and minimally invasive strategies such as multi-and uniportal video-assisted thoracic surgery (VATS) have become more favorable even for major pulmonary resections. With this surgical evolution, the aesthetic approach has also changed, and a paradigm shift has occurred. The traditional conception of general anesthesia, muscle relaxation, and intubation has been re-evaluated, and spontaneous breathing plays a central role in our practice by performing non-intubated thoracoscopic surgeries (NITS-VATS). METHODS: We performed a computerized search of the medical literature (PubMed, Google Scholar, Scopus) to identify relevant articles in non-intubated thoracoscopic surgery using the following terms [(non-intubated) OR (non-intubated) OR (awake) OR (tubeless) OR (regional anesthesia)] AND [(VATS) OR (NIVATS)], as well as their Medical Subject Headings (MeSH) terms. RESULTS: Based on the outcomes of the reviewed literature and our practice, it seems that pathophysiological concerns can be overcome by proper surgical and anesthetic management. All risks are compensated by the advantageous physiological changes that result in better patient outcomes. With the maintenance of spontaneous breathing, the incidence of potential adverse effects of mechanical ventilation, such as ventilator-induced lung injury and consequent postoperative pulmonary complications, can be reduced. The avoidance of muscle relaxants also results in the maintenance of contraction of the dependent hemidiaphragm and lower airway pressure levels, which may lead to better ventilation-perfusion matching. These techniques can be challenging for surgeons as well as for anesthetists; hence, a good knowledge of physiological and pathophysiological changes, clear inclusion and exclusion and intraoperative conversion criteria, and good communication between team members are essential. CONCLUSION: NITS-VATS seems to be a feasible and safe method in selected patients with evolving importance as a part of the minimally invasive surgical and anesthetic conception and has a role in reducing perioperative complications, which is crucial in the thoracic surgical patient population.

Anesthesia for Endoscopy.

Anesthesia for endoscopic surgery can be challenging depending on surgical manipulations and patient comorbidity. Anesthetists must understand the possible systemic changes and complications that are associated with endoscopic surgery. Pneumoperitoneum induces vasoconstriction, reduces cardiac output, and decreases functional residual capacity in the cardiopulmonary system. Both hypoventilation caused by the thoracoscopic procedure and CO2 insufflation increase Paco2. To prevent the problems associated with high Paco2, monitoring of end-tidal CO2 (ETco2) and capability of positive pressure ventilation are crucial. Sudden changes of ETco2 should be monitored closely. Endoscopic surgery should be a less invasive procedure; however, appropriate analgesia remains necessary.