Silent hypoxia in COVID-19: pathomechanism and possible management strategy

Progress in research on osteoporosis secondary to SARS-CoV-2 infection

The World Health Organization has declared that COVID-19 no longer constitutes a "public health emergency of international concern," yet the long-term impact of SARS-CoV-2 infection on bone health continues to pose new challenges for global public health. In recent years, numerous animal model and clinical studies have revealed that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection can lead to secondary osteoporosis. The mechanisms involved are related to the virus's direct effects on bone tissue, dysregulation of the body's inflammatory response, hypoxia, noncoding RNA imbalance, and metabolic abnormalities. Although these studies have unveiled the connection between SARS-CoV-2 infection and osteoporosis, current research is not comprehensive and in depth. Future studies are needed to evaluate the long-term effects of SARS-CoV-2 on bone density and metabolism, elucidate the specific mechanisms of pathogenesis, and explore potential interventions. This review aims to collate existing research literature on SARS-CoV-2 infection-induced secondary osteoporosis, summarize the underlying mechanisms, and provide direction for future research.

HIF-1α Pathway in COVID-19: A Scoping Review of Its Modulation and Related Treatments

The COVID-19 pandemic, driven by SARS-CoV-2, has led to a global health crisis, highlighting the virus's unique molecular mechanisms that distinguish it from other respiratory pathogens. It is known that the Hypoxia-Inducible Factor 1α (HIF-1α) activates a complex network of intracellular signaling pathways regulating cellular energy metabolism, angiogenesis, and cell survival, contributing to the wide range of clinical manifestations of COVID-19, including Post-Acute COVID-19 Syndrome (PACS). Emerging evidence suggests that dysregulation of HIF-1α is a key driver of systemic inflammation, silent hypoxia, and pathological tissue remodeling in both the acute and post-acute phases of the disease. This scoping review was conducted following PRISMA-ScR guidelines and registered in INPLASY. It involved a literature search in Scopus and PubMed, supplemented by manual reference screening, with study selection facilitated by Rayyan software. Our analysis clarifies the dual role of HIF-1α, which may either worsen inflammatory responses and viral persistence or support adaptive mechanisms that reduce cellular damage. The potential for targeting HIF-1α therapeutically in COVID-19 is complex, requiring further investigation to clarify its precise role and translational applications. This review deepens the molecular understanding of SARS-CoV-2-induced cellular and tissue dysfunction in hypoxia, offering insights for improving clinical management strategies and addressing long-term sequelae.

Acute COVID-19 and LongCOVID syndrome - molecular implications for therapeutic strategies - review

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has been recognized not only for its acute effects but also for its ability to cause LongCOVID Syndrome (LCS), a condition characterized by persistent symptoms affecting multiple organ systems. This review examines the molecular and immunological mechanisms underlying LCS, with a particular focus on autophagy inhibition, chronic inflammation, oxidative, nitrosative and calcium stress, viral persistence and autoimmunology. Potential pathophysiological mechanisms involved in LCS include (1) autoimmune activation, (2) latent viral persistence, where SARS-CoV-2 continues to influence host metabolism, (3) reactivation of latent pathogens such as Epstein-Barr virus (EBV) or cytomegalovirus (CMV), exacerbating immune and metabolic dysregulation, and (4) possible persistent metabolic and inflammatory dysregulation, where the body fails to restore post-infection homeostasis. The manipulation of cellular pathways by SARS-CoV-2 proteins is a critical aspect of the virus' ability to evade immune clearance and establish long-term dysfunction. Viral proteins such as NSP13, ORF3a and ORF8 have been shown to disrupt autophagy, thereby impairing viral clearance and promoting immune evasion. In addition, mitochondrial dysfunction, dysregulated calcium signaling, oxidative stress, chronic HIF-1α activation and Nrf2 inhibition create a self-sustaining inflammatory feedback loop that contributes to tissue damage and persistent symptoms. Therefore understanding the molecular basis of LCS is critical for the development of effective therapeutic strategies. Targeting autophagy and Nrf2 activation, glycolysis inhibition, and restoration calcium homeostasis may provide novel strategies to mitigate the long-term consequences of SARS-CoV-2 infection. Future research should focus on personalized therapeutic interventions based on the dominant molecular perturbations in individual patients.

Understanding chronic inflammation: couplings between cytokines, ROS, NO, Cai 2+, HIF-1α, Nrf2 and autophagy

Chronic inflammation is an important component of many diseases, including autoimmune diseases, intracellular infections, dysbiosis and degenerative diseases. An important element of this state is the mainly positive feedback between inflammatory cytokines, reactive oxygen species (ROS), nitric oxide (NO), increased intracellular calcium, hypoxia-inducible factor 1-alpha (HIF-1α) stabilisation and mitochondrial oxidative stress, which, under normal conditions, enhance the response against pathogens. Autophagy and the nuclear factor erythroid 2-related factor 2 (Nrf2)-mediated antioxidant response are mainly negatively coupled with the above-mentioned elements to maintain the defence response at a level appropriate to the severity of the infection. The current review is the first attempt to build a multidimensional model of cellular self-regulation of chronic inflammation. It describes the feedbacks involved in the inflammatory response and explains the possible pathways by which inflammation becomes chronic. The multiplicity of positive feedbacks suggests that symptomatic treatment of chronic inflammation should focus on inhibiting multiple positive feedbacks to effectively suppress all dysregulated elements including inflammation, oxidative stress, calcium stress, mito-stress and other metabolic disturbances.

Chest computed tomography and plain radiographs demonstrate vascular distribution and characteristics in COVID-19 lung disease - a pulmonary vasculopathy

Introduction

Early in the COVID-19 pandemic, CT was demonstrated as a sensitive tool for diagnosing COVID-19. We undertook a detailed study of CT scans in COVID-19 patients to characterise disease distribution within lung parenchyma, respiratory airways, and pulmonary vasculature, aiming to delineate underlying disease processes.

Methods

We characterised acute phase chest CT of 40 participants with COVID-19 from the REACT study, 31 with CT pulmonary angiography (CTPA), 4 with intravenous contrast enhanced CT and 5 with non-intravenous contrast enhanced CT. Participants had neither been vaccinated nor received systemic steroids. We further correlated the distribution of lung parenchymal damage on CT with contemporaneous chest radiographs.

Results

Parenchymal lung damage was found in all subjects. However, airways inflammation was present in only 23% (9) and limited to small areas. Notably, vascular abnormalities were dominant and characterised by dilated peripheral pulmonary vessels supplying areas of lung damage in a gravity-dependent distribution bilaterally in 95% (38), basally in 90% (36), peripherally in 92.5% (37), and posteriorly in 90% (36). Macrothrombosis was demonstrated in 23% (7) of CTPAs. Wedge-shaped peripheral lung damage, resembling areas of pulmonary vascular congestion, were distinct in 53% (21) with or without visible macrothrombosis. Pleural effusions were seen in 28% (11). Notably, lung opacification distribution in 98% of the plain radiographs matched distribution on CT (39).

Conclusion

Our study frames COVID-19 as a pulmonary vasculopathy rather than a more conventional pneumonia which may be important not only for guiding mechanistic study design but also for the development of novel targeted therapeutics.

Supplemental oxygen prescriptions after hospitalization for coronavirus disease 2019

BACKGROUND

The role of home oxygen therapy for patients recovering from Coronavirus Disease 2019 (COVID-19) pneumonia, characterized by impaired gas exchange, is not well-defined.

OBJECTIVES

To compare the characteristics, duration, odds of receiving, and continuing to receive home oxygen prescriptions between patients discharged home after COVID-19 pneumonia hospitalization and those discharged after non-COVID-19 pneumonia.

METHODS

From April 2020 to March 2021, 52,951 patients with COVID-19 pneumonia (53.6 % women, 64 % White) were identified, and from January 2019 to December 2019, 26,701 patients with non-COVID pneumonia (53.9 % women, 76.7 % White) were identified, using the Optum Clinformatics Data Mart Database. New oxygen prescriptions were identified through Healthcare Common Procedure Coding Systems codes. Propensity score matching adjusted for confounders, and Cox regression analysis was conducted to compare post-discharge oxygen use.

RESULTS

Following hospitalization, oxygen was prescribed to 52,951 patients with COVID-19 pneumonia and 26,701 patients with non-COVID pneumonia in the United States. The COVID-19 pneumonia group were four times more likely to be prescribed supplemental oxygen compared to the non-COVID-19 pneumonia group (OR 4.22; 95 % confidence interval [CI] 3.76-4.74). This trend persisted in sensitivity analyses: ICU patients (OR 4.05; 95 % CI 3.36-4.88) and those who received both ICU admission and mechanical ventilation (OR 3.84; 95 % CI 2.32-6.37). Hispanic patients had the highest likelihood of receiving a supplemental oxygen prescription after discharge (OR 6.75; 95 % CI 5.03-9.05).

CONCLUSIONS

Post-hospitalization, one in five patients with COVID-19 received prescriptions for supplemental oxygen, which was significantly higher than the proportion of patients with non-COVID-19 pneumonia.

Neurological, psychological, psychosocial complications of long-COVID and their management

Since it first appeared, Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has had a significant and lasting negative impact on the health and economies of millions of individuals all over the globe. At the level of individual health too, many patients are not recovering fully and experiencing a long-term condition now commonly termed 'long-COVID'. Long-COVID is a collection of symptoms which must last more than 12 weeks following initial COVID infection, and which cannot be adequately explained by alternate diagnoses. The neurological and psychosocial impact of long-COVID is itself now a global health crisis and therefore preventing, diagnosing, and managing these patients is of paramount importance. This review focuses primarily on: neurological functioning deficits; mental health impacts; long-term mood problems; and associated psychosocial issues, among patients suffering from long-COVID with an eye towards the neurological basis of these symptoms. A concise account of the clinical relevance of the neurological and psychosocial impacts of long-COVID, the effects on long-term morbidity, and varied approaches in managing patients with significant chronic neurological symptoms and conditions was extracted from the literature, analysed and reported. A comprehensive account of plausible pathophysiological mechanisms involved in the development of long-COVID, its management, and future research needs have been discussed.

Retrospective longitudinal study on the long-term impact of COVID-19 infection on polysomnographic evaluation in patients with Prader-Willi syndrome

BACKGROUND

To evaluate the impact of coronavirus disease 2019 (COVID-19) on polysomnographic evaluation in patients with Prader-Willi syndrome (PWS).

PATIENTS AND METHODS

A retrospective cohort study of two consecutive overnight polysomnograms (PSG) in 92 PWS patients (mean age 9.1, range 3.1-22 years). 57/92 participants (35 female) had a COVID-19 infection between the two consecutive examinations. 35 patients (21 female) had no infection (control group). Distribution of genetics was as follows: 13/57 (22.8%) deletion, 19/57 (33.3%) uniparental disomy, 2/57 (3,5%) imprinting defect, 3/57 (5.3%) non-deletion, 20/57 (35.1%) diagnosed by analyses of the methylation pattern of chromosome 15q11-13. Mean time interval between COVID-19 infection and post-COVID-19 evaluation was 96.2 days.

RESULTS

Course of COVID-19 infection was asymptomatic 8/82 (9.8%), mild 63/82 (76.8%), medium 11/84 (13.4%). The five most frequently experienced symptoms in PWS patients were fever (56.1%); headache (45.1%); cold (42.7%); cough (31.7%) and body aches (21.95%). PWS patients who had COVID-19 infection had significantly lower mean oxygen saturation (SpO2) measured by pulse oximetry (post 94.8% vs. pre 95.7%, p = 0.001), lower detected lowermost SpO2 (post 86.2 vs. pre 87.3%, p = 0.003), and higher occurrence of hypopnoea (post 13.9 vs. pre 10.7, p = 0.001). Time in optimal SpO2 (95-100%) decreased significantly (post 54.3% vs. pre 73.8%, p = 0.001), whereas an increase was observed in time in suboptimal SpO2 (90-95%) (post 45.5% vs. 25.8%, p = 0.001) and in time in poor SpO2 (< 90%) (post 0.7% vs. pre 0.2%, p = 0.030). Body-Mass-Index (BMI)-SDS for PWS showed no differences between the groups at any time. BMI-SDS-differences showed no influence on differences in SpO2 evaluations. In the genetic subgroup with deletion there was a statistically significant effect on an increased number of OSA (p = 0.027). The genetic subgroup with uniparental disomy (UPD) was associated with a reduced risk of higher HF (p = 0.035) and less hypopnea (p = 0.011).

CONCLUSION

PWS patients predominantly experienced only mild to medium symptoms during COVID-19 infection without necessity of hospitalisation. However, on average three months after infection, differences in PSG evaluations were still apparent, manifesting in lower SpO2 and more frequent hypopnea. A long-lasting impairment of the pulmonary system due to the COVID-19 infection might be responsible.

Incidence and predictive factors of hyperventilation syndrome in patients after COVID 19 pneumonia: a prospective cohort study

Background

This study investigates the incidence and predictive factors of Hyperventilation Syndrome (HVS) in patients after COVID 19 pneumonia, addressing the clinical overlap between these conditions.

Methods

A one-month prospective study was conducted, tracking survivors of COVID-19 pneumonia. Patients were evaluated for ongoing clinical status, including HVS and post-traumatic syndrome disorder (PTSD), using clinical questionnaires, mMRC, Post-COVID-19 Functional Status (PCFS) Score, Nijmegen score, and PTSD Checklist for DSM-5 questionnaire.

Results

Our study included 222 patients (median age: 57 years, male predominance 62.6%). Somatic comorbidities, primarily metabolic disorders, were reported in 71.2% of cases. The majority had severe or critical infection forms (78.4%), and 91.9% experienced acute symptoms, with 86.5% having three or more symptom clusters. At one month follow-up, dyspnea (52.9%) and asthenia (21.7%) persisted. Functional limitations (PCFS Grade > 2) were observed in 19.6% of patients. The overall incidence of HVS was 158 per 1000 patients, and PTSD was 445 per 1000 patients. Multivariate logistic regression identified cognitive impairment (acute phase), persistent weight loss (post-COVID-19 phase), PCFS grade > 2, and PTSD as independent factors for developing HVS, with relative risks (RRs) of 3.47 (95%CI [1.48-8.31]; p = 0.004), 11.87 (95%CI [1.25-112.88]; p = 0.031), 3.24 (95%CI [1.34-7.86]; p = 0.009), and 5.98 (95%CI [2.27-15.77]; p < 0.001), respectively.

Conclusion

HVS is prevalent in the post-COVID-19 phase, affecting 15.6 % of survivors. Identified predictive factors suggest the convergence of psychosomatic pathophysiological mechanisms. Further research is crucial for a detailed understanding of these mechanisms in long COVID-19 patients.

Blood oxygenation state in COVID-19 patients: Unexplored role of 2,3-bisphosphoglycerate

BACKGROUND

COVID-19 reduces lung functionality causing a decrease of blood oxygen levels (hypoxemia) often related to a decreased cellular oxygenation (hypoxia). Besides lung injury, other factors are implicated in the regulation of oxygen availability such as pH, partial arterial carbon dioxide tension (PaCO2), temperature, and erythrocytic 2,3-bisphosphoglycerate (2,3-BPG) levels, all factors affecting hemoglobin saturation curve. However, few data are currently available regarding the 2,3-BPG modulation in SARS-CoV-2 affected patients at the hospital admission.

MATERIAL AND METHODS

Sixty-eight COVID-19 patients were enrolled at hospital admission. The lung involvement was quantified using chest-Computer Tomography (CT) analysed with automatic software (CALIPER). Haemoglobin concentrations, glycemia, and routine analysis were evaluated in the whole blood, while partial arterial oxygen tension (PaO2), PaCO2, pH, and HCO3- were assessed by arterial blood gas analysis. 2,3-BPG levels were assessed by specific immunoenzymatic assays in RBCs.

RESULTS

A higher percentage of interstitial lung disease (ILD) and vascular pulmonary-related structure (VRS) volume on chest-CT quantified with CALIPER had been found in COVID-19 patients with a worse disease outcome (R = 0.4342; and R = 0.3641, respectively). Furthermore, patients with lower PaO2 showed an imbalanced acid-base equilibrium (pH, p = 0.0208; PaCO2, p = 0.0496) and a higher 2,3-BPG levels (p = 0.0221). The 2,3-BPG levels were also lower in patients with metabolic alkalosis (p = 0.0012 vs. no alkalosis; and p = 0.0383 vs. respiratory alkalosis).

CONCLUSIONS

Overall, the data reveal a different pattern of activation of blood oxygenation compensatory mechanisms reflecting a different course of the COVID-19 disease specifically focusing on 2,3-BPG modulation.

Does COVID-19 Trigger the Risk for the Development of Parkinson's Disease? Therapeutic Potential of Vitamin C

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes coronavirus disease 2019 (COVID-19), which was proclaimed a pandemic by the World Health Organization (WHO) in March 2020. There is mounting evidence that older patients with multimorbidity are more susceptible to COVID-19 complications than are younger, healthy people. Having neuroinvasive potential, SARS-CoV-2 infection may increase susceptibility toward the development of Parkinson's disease (PD), a progressive neurodegenerative disorder with extensive motor deficits. PD is characterized by the aggregation of α-synuclein in the form of Lewy bodies and the loss of dopaminergic neurons in the dorsal striatum and substantia nigra pars compacta (SNpc) of the nigrostriatal pathway in the brain. Increasing reports suggest that SARS-CoV-2 infection is linked with the worsening of motor and non-motor symptoms with high rates of hospitalization and mortality in PD patients. Common pathological changes in both diseases involve oxidative stress, mitochondrial dysfunction, neuroinflammation, and neurodegeneration. COVID-19 exacerbates the damage ensuing from the dysregulation of those processes, furthering neurological complications, and increasing the severity of PD symptomatology. Phytochemicals have antioxidant, anti-inflammatory, and anti-apoptotic properties. Vitamin C supplementation is found to ameliorate the common pathological changes in both diseases to some extent. This review aims to present the available evidence on the association between COVID-19 and PD, and discusses the therapeutic potential of vitamin C for its better management.

V-V ECMO for severe Chlamydia psittaci pneumonia presenting with sudden cardiac arrest: A case report and literature review

RATIONALE

Psittacosis, also known as parrot fever, is an infectious disease caused by Chlamydia psittaci, which can lead to C psittaci pneumonia. Clinical manifestations are highly nonspecific, which can vary from asymptomatic infection to severe pneumonia and even death.

PATIENT CONCERNS

In this case presentation, we reported one 65-year-old male case of C psittaci pneumonia who was admitted to our hospital on December 2, 2022 due to the chief complaints of poor appetite and fatigue for 3 days as the clinical manifestations. He denied contact with birds but admitted riding horses 1 week ago.

DIAGNOSES

Chlamydia psittaci pneumonia of patient was confirmed through metagenomic sequencing of bronchoalveolar lavage fluid under bronchoscopy.

INTERVENTION

Patient was treated with V-V ECMO, invasive mechanical ventilation and CRRT.

OUTCOMES

On December 12, the patient was successfully weaned off V-V ECMO and discharged on December 20, 2022. During postoperative follow-up, CT scan in a local hospital revealed the infiltrative lesions of the lung were absent.

LESSONS

This case prompts that metagenomic next-generation sequencing is a feasible diagnostic tool for psittacosis, which can rapidly worsen and even cause sudden cardiac arrest. V-V ECMO might be a viable emergency therapeutic option.

Evaluating Personalized Add-On Ayurveda Therapy in Oxygen-Dependent Diabetic COVID-19 Patients: A 60-Day Study of Symptoms, Inflammation, and Radiological Changes

Background Effective management of both acute and post-acute sequelae of SARS-CoV-2 is essential, particularly for type 2 diabetes mellitus (T2DM) patients, who are at increased risk of severe pro-inflammatory responses and complications. Persistent symptoms and residual lung and cardiovascular damage in post-coronavirus disease (COVID-19) individuals highlight the need for comprehensive long-term treatment strategies. Conventional treatments, including Remdesivir and glucocorticoids, have limitations, suggesting that further investigation into Ayurvedic therapies could be beneficial, though controlled trials are currently limited. Objectives Evaluate the effectiveness and safety of Ayurveda with the standard of care (SOC) versus SOC in improving symptoms, moderating immune responses (interleukin-6 (IL-6), C-reactive protein (CRP), neutrophil-lymphocyte ratio (NLR), and radiological outcomes in oxygen-dependent, high-risk, non-vaccinated type 2 diabetes COVID-19 patients over 60 days, and thus addressing their heightened vulnerability to severe infections. Methods A controlled trial with 50 diabetic COVID-19 patients, aged 18-80, with an NLR of >= 4, primarily on Remdesivir, was assigned to Group 1 (Add-on Ayurveda+SOC, n=30) or Group 2 (SOC, n=20) based on their voluntary choice with follow-up on days 14, 28, and 60. Parametric outcomes in group analysis were assessed with robust regression and non-parametric outcomes with Cochran-Mantel-Haenszel, log-rank test, and chi-square tests at 95% confidence interval (CI). Results Group 1 exhibited statistically significant improvements in fever, cough, diarrhea, as well as NLR, IL-6, and CRP by 14 days, and in anosmia, loss of taste, shortness of breath, general weakness, and headache by 60 days. Though the sample size is small, notable improvements can be seen in troponin levels in Group 1 at 28 and 60 days. High-resolution computer tomography COVID-19 reporting and data system (HRCT CO-RADS) scores improved more slowly in Group 2 than in Group 1. Survival rates were 96.4% for Group 1 and 90% for Group 2. Numbers were too small for reliable comparisons at 60 days.  Conclusion The add-on Ayurveda group showed a better symptomatic response, and faster normalization in inflammatory markers, including IL-6 and NLR by 14 days, and cardiac markers by 28 days. Minimal clinical and no laboratory adverse events were observed. This study supports the need for a randomized, double-blind trial.

Pragmatic approach to mobilizing individuals with critical illness due to COVID-19: clinical perspective

PURPOSE

To provide pragmatic guidance for acute rehabilitation management and implementation of early mobility for individuals with critical illness due to COVID-19.

METHODS

Clinical perspective developed through reflective clinical practice and narrative review of best available evidence.

RESULTS

Current clinical practice guidelines do not provide guidance for implementation of early mobility interventions for individuals with critical illness due to COVID-19 who require enhanced ventilatory support or support of inhaled pulmonary artery vasodilators. Many individuals who may benefit from implementation of early mobility interventions are excluded by strict interpretation of current guidelines.

CONCLUSIONS

Risk vs benefit of implementing early mobility interventions in individuals with critical illness due to COVID-19 can be mitigated through coordinated efforts of interdisciplinary teams to promote shared decision-making through therapeutic alliances with patients and their families. Clinicians must clearly define the goals of care, understand the limitations of monitoring equipment in the intensive care unit, prepare to titrate levels of oxygen based on an individual's physiologic response to mobility interventions, and help individuals maintain external goal-directed focus of attention to optimize outcomes of early mobility interventions.

The regulatory effects of mesedin and beditin alpha2-adrenoblockers on the functional activity of the nervous, cardiovascular, and endocrine systems in rats under the hypoxic conditions

One of the reasons of the development of pathologies causing death is hypoxia. The purposes of this study were (1) to study some physiological and biochemical mechanisms of α2-adrenoblockers, which ensure the tissue resistance increase to hypoxia; (2) to offer new drugs contributing to the increase of tissues' stability towards the hypoxic affection; and (3) to submit new medications to surpass by their anti-hypoxic activity of those already used in modern medicine and have some advantages. The reactivity of postsynaptic vascular α2-adrenoceptors was determined on the damaged spinal cord expressed by the blood pressure increase in response to intravenous administration of azepexole that selectively binds to α2-adrenoceptors. Determination of the systemic hemodynamic values and the vascular resistance to the blood flow was performed by the method with plastic microspheres of marked isotopes. pO2 in the blood and the oxygen-transporting function were determined in a sample of 0.1 ml of blood in 30, 90, and 180 min after the α2-adrenoblockers' injections. It has been found that one of the major hemodynamic effects of mesedin and beditin was an improvement in cardiac output, as well as a prolonged increase in coronary blood flow and vasodilation of the heart vessels. Some anti-hypoxic mechanisms of the studied α2-adrenoblockers are an improvement of blood oxygen-transporting function followed by tissue oxygenation and the increased level of corticosterone and resistance to hypoxia. Revealing the mechanisms of action of the postsynaptic α2-adrenoceptors suggests that mesedin and beditin are potentially effective therapeutic means for many hypoxic conditions.

Impacts of SARS-CoV-2 on brain renin angiotensin system related signaling and its subsequent complications on brain: A theoretical perspective

Cellular ACE2 (cACE2), a vital component of the renin-angiotensin system (RAS), possesses catalytic activity to maintain AngII and Ang 1-7 balance, which is necessary to prevent harmful effects of AngII/AT2R and promote protective pathways of Ang (1-7)/MasR and Ang (1-7)/AT2R. Hemostasis of the brain-RAS is essential for maintaining normal central nervous system (CNS) function. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a viral disease that causes multi-organ dysfunction. SARS-CoV-2 mainly uses cACE2 to enter the cells and cause its downregulation. This, in turn, prevents the conversion of Ang II to Ang (1-7) and disrupts the normal balance of brain-RAS. Brain-RAS disturbances give rise to one of the pathological pathways in which SARS-CoV-2 suppresses neuroprotective pathways and induces inflammatory cytokines and reactive oxygen species. Finally, these impairments lead to neuroinflammation, neuronal injury, and neurological complications. In conclusion, the influence of RAS on various processes within the brain has significant implications for the neurological manifestations associated with COVID-19. These effects include sensory disturbances, such as olfactory and gustatory dysfunctions, as well as cerebrovascular and brain stem-related disorders, all of which are intertwined with disruptions in the RAS homeostasis of the brain.

Exploring the bias: how skin color influences oxygen saturation readings via Monte Carlo simulations

Significance

Our goal is to understand the root cause of reported oxygen saturation (SpO 2 ) overestimation in heavily pigmented skin types to devise solutions toward enabling equity in pulse oximeter designs.

Aim

We aim to gain theoretical insights into the effect of skin tone onSpO 2 - R curves using a three-dimensional, four-layer tissue model representing a finger.

Approach

A finger tissue model, comprising the epidermis, dermis, two arteries, and a bone, was developed using a Monte Carlo-based approach in the MCmatlab software. Two skin tones-light and dark-were simulated by adjusting the absorption and scattering properties within the epidermal layer. Following this,SpO 2 - R curves were generated in various tissue configurations, including transmission and reflection modes using red and infrared wavelengths. In addition, the influence of source-detector (SD) separation distances on both light and dark skin tissue models was studied.

Results

In transmission mode,SpO 2 - R curves did not deviate with changes in skin tones because both pulsatile and non-pulsatile terms experienced equal attenuation at red and infrared wavelengths. However, in reflection mode, measurable variations inSpO 2 - R curves were evident. This was due to differential attenuation of the red components, which resulted in a lower perfusion index at the red wavelength in darker skin. As the SD separation increased, the effect of skin tone onSpO 2 - R curves in reflection mode became less pronounced, with the largest SD separation exhibiting effects similar to those observed in transmission mode.

Conclusions

Monte Carlo simulations have demonstrated that different light pathlengths within the tissue contribute to the overestimation ofSpO 2 in people with darker skin in reflection mode pulse oximetry. Increasing the SD separation may mitigate the effect of skin tone onSpO 2 readings. These trends were not observed in transmission mode; however, further planned research using more complex models of the tissue is essential.

Evaluation of the predictors and frequency of silent hypoxemia in COVID-19 patients and the gap between pulse oximeter and arterial blood gas levels: A cross-sectional study

Background

Silent hypoxemia is when patients do not experience breathing difficulty in the presence of alarmingly low O2 saturation. It could cause rapid deterioration and higher mortality rates among patients, so prompt detection and identifying predictive factors could result in significantly better outcomes. This study aims to document the evidence of silent hypoxemia in patients with COVID-19 and its clinical features.

Methods

A total of 78 hospitalized, nonintubated patients with confirmed COVID-19 infection were included in this study. Their O2 saturation was measured with a pulse oximeter (PO), and arterial blood gas (ABG) was taken. Demographic and clinical features were recorded. The Borg scale was used to evaluate dyspnea status, and patients with a score of less than two accompanied by O2 saturation of less than 94% were labeled as silent hypoxic. Univariate analysis was utilized to evaluate the correlation between variables and their odds ratio (OR) and 95% confidence interval (CI).

Results

Silent hypoxemia was observed in 20 (25.6%) of the participants. The average difference between the PO and ABG methods was 4.36 ± 3.43. Based on regression analysis, dyspnea and respiratory rate demonstrated a statistically significant correlation with the O2 saturation difference between PO and ABG (OR: 2.05; p = 0.026; 95% CI: 0.248-3.847 and OR: 0.144; p = 0.048, 95% CI: 0.001-0.286). Furthermore, the Borg scale (OR: 0.29; p = 0.009; 95% CI: 0.116-0.740) had a significant reverse correlation with silent hypoxia.

Conclusions

Silent hypoxemia can be a possible complication that affects some COVID-19 patients. Further care should be bestowed upon the younger population and those with underlying neurological or mental illnesses. Furthermore, the respiratory rate, pulse oximeter, and arterial blood gas O2 levels should be considered alongside each other.

Effect and mechanism of quercetin or quercetin-containing formulas against COVID-19: From bench to bedside

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused the global coronavirus disease 2019 (COVID-19) pandemic since 2019. Immunopathogenesis and thromboembolic events are central to its pathogenesis. Quercetin exhibits several beneficial activities against COVID-19, including antiviral, anti-inflammatory, immunomodulatory, antioxidative, and antithrombotic effects. Although several reviews have been published, these reviews are incomplete from the viewpoint of translational medicine. The authors comprehensively evaluated the evidence of quercetin against COVID-19, both basically and clinically, to apply quercetin and/or its derivatives in the future. The authors searched the PubMed, Embase, and the Cochrane Library databases without any restrictions. The search terms included COVID-19, SARS-CoV-2, quercetin, antiviral, anti-inflammatory, immunomodulatory, thrombosis, embolism, oxidative, and microbiota. The references of relevant articles were also reviewed. All authors independently screened and reviewed the quality of each included manuscript. The Cochrane Risk of Bias Tool, version 2 (RoB 2) was used to assess the quality of the included randomized controlled trials (RCTs). All selected studies were discussed monthly. The effectiveness of quercetin against COVID-19 is not solid due to methodological flaws in the clinical trials. High-quality studies are also required for quercetin-containing traditional Chinese medicines. The low bioavailability and highly variable pharmacokinetics of quercetin hinder its clinical applications. Its positive impact on immunomodulation through reverting dysbiosis of gut microbiota still lacks robust evidence. Quercetin against COVID-19 does not have tough clinical evidence. Strategies to improve its bioavailability and/or to develop its effective derivatives are needed. Well-designed RCTs are also crucial to confirm their effectiveness in the future.

Pulse oximeter bench tests under different simulated skin tones

Pulse oximeters' (POs) varying performance based on skin tones has been highly publicised. Compared to arterial blood gas analysis, POs tend to overestimate oxygen saturation (SpO2) values for people with darker skin (occult hypoxemia). The objective is to develop a test bench for assessing commercial home and hospital-based POs in controlled laboratory conditions. A laboratory simulator was used to mimic different SpO2 values (~ 70 to 100%). Different neutral density and synthetic melanin filters were used to reproduce low signal and varying melanin attenuation levels. Six devices consisting of commercial home (Biolight, N = 13; ChoiceMMed, N = 18; MedLinket, N = 9) and hospital-based (Masimo Radical 7 with Neo L, N = 1; GE B450 Masimo SET with LNCS Neo L, N = 1; Nonin 9550 Onyx II™, N = 1) POs were reviewed and their response documented. Significant variations were observed in the recorded SpO2 values among different POs when exposed to identical simulated signals. Differences were greatest for lower SpO2 (< 80%) where empirical data is limited. All PO responses under low signal and melanin attenuation did not change across various simulated SpO2 values. The bench tests do not provide conclusive evidence that melanin does not affect in vivo SpO2 measurements. Research in the areas of instrument calibration, theory and design needs to be further developed.

Cross-Validation of Metabolic Phenotypes in SARS-CoV-2 Infected Subpopulations Using Targeted Liquid Chromatography-Mass Spectrometry (LC-MS)

To ensure biological validity in metabolic phenotyping, findings must be replicated in independent sample sets. Targeted workflows have long been heralded as ideal platforms for such validation due to their robust quantitative capability. We evaluated the capability of liquid chromatography-mass spectrometry (LC-MS) assays targeting organic acids and bile acids to validate metabolic phenotypes of SARS-CoV-2 infection. Two independent sample sets were collected: (1) Australia: plasma, SARS-CoV-2 positive (n = 20), noninfected healthy controls (n = 22) and COVID-19 disease-like symptoms but negative for SARS-CoV-2 infection (n = 22). (2) Spain: serum, SARS-CoV-2 positive (n = 33) and noninfected healthy controls (n = 39). Multivariate modeling using orthogonal projections to latent structures discriminant analyses (OPLS-DA) classified healthy controls from SARS-CoV-2 positive (Australia; R2 = 0.17, ROC-AUC = 1; Spain R2 = 0.20, ROC-AUC = 1). Univariate analyses revealed 23 significantly different (p < 0.05) metabolites between healthy controls and SARS-CoV-2 positive individuals across both cohorts. Significant metabolites revealed consistent perturbations in cellular energy metabolism (pyruvic acid, and 2-oxoglutaric acid), oxidative stress (lactic acid, 2-hydroxybutyric acid), hypoxia (2-hydroxyglutaric acid, 5-aminolevulinic acid), liver activity (primary bile acids), and host-gut microbial cometabolism (hippuric acid, phenylpropionic acid, indole-3-propionic acid). These data support targeted LC-MS metabolic phenotyping workflows for biological validation in independent sample sets.

Meta-analysis of the serum/plasma proteome identifies significant associations between COVID-19 with Alzheimer's/Parkinson's diseases

In recent years, we have seen the widespread devastations and serious health complications manifested by COVID-19 globally. Although we have effectively controlled the pandemic, uncertainties persist regarding its potential long-term effects, including prolonged neurological issues. To gain comprehensive insights, we conducted a meta-analysis of mass spectrometry-based proteomics data retrieved from different studies with a total of 538 COVID-19 patients and 523 healthy controls. The meta-analysis revealed that top-enriched pathways were associated with neurological disorders, including Alzheimer's (AD) and Parkinson's disease (PD). Further analysis confirmed a direct correlation in the expression patterns of 24 proteins involved in Alzheimer's and 23 proteins in Parkinson's disease with COVID-19. Protein-protein interaction network and cluster analysis identified SNCA as a hub protein, a known biomarker for Parkinson's disease, in both AD and PD. To the best of our knowledge, this is the first meta-analysis study providing proteomic profiling evidence linking COVID-19 to neurological complications.

SARS-CoV-2 and its Multifaceted Impact on Bone Health: Mechanisms and Clinical Evidence

PURPOSE OF REVIEW

SARS-CoV-2 infection, the culprit of the COVID-19 pandemic, has been associated with significant long-term effects on various organ systems, including bone health. This review explores the current understanding of the impacts of SARS-CoV-2 infection on bone health and its potential long-term consequences.

RECENT FINDINGS

As part of the post-acute sequelae of SARS-CoV-2 infection, bone health changes are affected by COVID-19 both directly and indirectly, with multiple potential mechanisms and risk factors involved. In vitro and preclinical studies suggest that SARS-CoV-2 may directly infect bone marrow cells, leading to alterations in bone structure and osteoclast numbers. The virus can also trigger a robust inflammatory response, often referred to as a "cytokine storm", which can stimulate osteoclast activity and contribute to bone loss. Clinical evidence suggests that SARS-CoV-2 may lead to hypocalcemia, altered bone turnover markers, and a high prevalence of vertebral fractures. Furthermore, disease severity has been correlated with a decrease in bone mineral density. Indirect effects of SARS-CoV-2 on bone health, mediated through muscle weakness, mechanical unloading, nutritional deficiencies, and corticosteroid use, also contribute to the long-term consequences. The interplay of concurrent conditions such as diabetes, obesity, and kidney dysfunction with SARS-CoV-2 infection further complicates the disease's impact on bone health. SARS-CoV-2 infection directly and indirectly affects bone health, leading to potential long-term consequences. This review article is part of a series of multiple manuscripts designed to determine the utility of using artificial intelligence for writing scientific reviews.

COVID-19 and Bone Loss: A Review of Risk Factors, Mechanisms, and Future Directions

PURPOSE OF REVIEW

SARS-CoV-2 drove the catastrophic global phenomenon of the COVID-19 pandemic resulting in a multitude of systemic health issues, including bone loss. The purpose of this review is to summarize recent findings related to bone loss and potential mechanisms.

RECENT FINDINGS

The early clinical evidence indicates an increase in vertebral fractures, hypocalcemia, vitamin D deficiencies, and a loss in BMD among COVID-19 patients. Additionally, lower BMD is associated with more severe SARS-CoV-2 infection. Preclinical models have shown bone loss and increased osteoclastogenesis. The bone loss associated with SARS-CoV-2 infection could be the result of many factors that directly affect the bone such as higher inflammation, activation of the NLRP3 inflammasome, recruitment of Th17 cells, the hypoxic environment, and changes in RANKL/OPG signaling. Additionally, SARS-CoV-2 infection can exert indirect effects on the skeleton, as mechanical unloading may occur with severe disease (e.g., bed rest) or with BMI loss and muscle wasting that has also been shown to occur with SARS-CoV-2 infection. Muscle wasting can also cause systemic issues that may influence the bone. Medications used to treat SARS-CoV-2 infection also have a negative effect on the bone. Lastly, SARS-CoV-2 infection may also worsen conditions such as diabetes and negatively affect kidney function, all of which could contribute to bone loss and increased fracture risk. SARS-CoV-2 can negatively affect the bone through multiple direct and indirect mechanisms. Future work will be needed to determine what patient populations are at risk of COVID-19-related increases in fracture risk, the mechanisms behind bone loss, and therapeutic options. This review article is part of a series of multiple manuscripts designed to determine the utility of using artificial intelligence for writing scientific reviews.

SARS-CoV-2 Infection to Premature Neuronal Aging and Neurodegenerative Diseases: Is there any Connection with Hypoxia?

The pandemic of coronavirus disease-2019 (COVID-19), caused by SARS-CoV-2, has become a global concern as it leads to a spectrum of mild to severe symptoms and increases death tolls around the world. Severe COVID-19 results in acute respiratory distress syndrome, hypoxia, and multi- organ dysfunction. However, the long-term effects of post-COVID-19 infection are still unknown. Based on the emerging evidence, there is a high possibility that COVID-19 infection accelerates premature neuronal aging and increases the risk of age-related neurodegenerative diseases in mild to severely infected patients during the post-COVID period. Several studies correlate COVID-19 infection with neuronal effects, though the mechanism through which they contribute to the aggravation of neuroinflammation and neurodegeneration is still under investigation. SARS-CoV-2 predominantly targets pulmonary tissues and interferes with gas exchange, leading to systemic hypoxia. The neurons in the brain require a constant supply of oxygen for their proper functioning, suggesting that they are more vulnerable to any alteration in oxygen saturation level that results in neuronal injury with or without neuroinflammation. We hypothesize that hypoxia is one of the major clinical manifestations of severe SARS-CoV-2 infection; it directly or indirectly contributes to premature neuronal aging, neuroinflammation, and neurodegeneration by altering the expression of various genes responsible for the survival of the cells. This review focuses on the interplay between COVID-19 infection, hypoxia, premature neuronal aging, and neurodegenerative diseases and provides a novel insight into the molecular mechanisms of neurodegeneration.

Respiratory rate‑oxygenation (ROX) index for predicting high-flow nasal cannula failure in patients with and without COVID-19

BACKGROUND

The predictive value of the respiratory rate‑oxygenation (ROX) index for a high-flow nasal cannula (HFNC) in patients with COVID-19 with acute hypoxemic respiratory failure (AHRF) may differ from patients without COVID-19 with AHRF, but these patients have not yet been compared. We compared the diagnostic accuracy of the ROX index for HFNC failure in patients with AHRF with and without COVID-19 during acute emergency department (ED) visits.

METHODS

We performed a retrospective analysis of patients with AHRF treated with an HFNC in an ED between October 2020 and April 2022. The ROX index was calculated at 1, 2, 4, 6, 12, and 24 h after HFNC placement. The primary outcome was the failure of the HFNC, which was defined as the need for subsequent intubation or death within 72 h. A receiver operating characteristic (ROC) curve was used to evaluate discriminative power of the ROX index for HFNC failure.

RESULTS

Among 448 patients with AHRF treated with an HFNC in an ED, 78 (17.4%) patients were confirmed to have COVID-19. There was no significant difference in the HFNC failure rates between the non-COVID-19 and COVID-19 groups (29.5% vs. 33.3%, p = 0.498). The median ROX index was higher in the non-COVID-19 group than in the COVID-19 group at all time points. The prognostic power of the ROX index for HFNC failure as evaluated by the area under the ROC curve was generally higher in the COVID-19 group (0.73-0.83) than the non-COVID-19 group (0.62-0.75). The timing of the highest prognostic value of the ROX index for HFNC failure was at 4 h for the non-COVID-19 group, whereas in the COVID-19 group, its performance remained consistent from 1 h to 6 h. The optimal cutoff values were 6.48 and 5.79 for the non-COVID-19 and COVID-19 groups, respectively.

CONCLUSIONS

The ROX index had an acceptable discriminative power for predicting HFNC failure in patients with AHRF with and without COVID-19 in the ED. However, the higher ROX index thresholds than those in previous publications involving intensive care unit (ICU) patients suggest the need for careful monitoring and establishment of a new threshold for patients admitted outside the ICU.

Large-scale Implementation of a COVID-19 Remote Patient Monitoring Program

Introduction

We implemented a large-scale remote patient monitoring (RPM) program for patients diagnosed with coronavirus 2019 (COVID-19) at a not-for-profit regional healthcare system. In this retrospective observational study, patients from nine emergency department (ED) sites were provided a pulse oximeter and enrolled onto a monitoring platform upon discharge.

Methods

The RPM team captured oxygen saturation (SpO2), heart rate, temperature, and symptom progression data over a 16-day monitoring period, and the team engaged patients via video call, phone call, and chat within the platform. Abnormal vital signs were flagged by the RPM team, with escalation to in-person care and return to ED as appropriate. Our primary outcome was to describe study characteristics: patients enrolled in the COVID-19 RPM program; engagement metrics; and physiologic and symptomatic data trends. Our secondary outcomes were return-to-ED rate and subsequent readmission rate.

Results

Between December 2020-August 2021, a total of 3,457 patients were referred, and 1,779 successfully transmitted at least one point of data. Patients on COVID-19 RPM were associated with a lower 30-day return-to-ED rate (6.2%) than those not on RPM (14.9%), with capture of higher acuity patients (47.7% of RPM 30-day returnees were subsequently hospitalized vs 34.8% of non-RPM returnees).

Conclusion

Our program, one of the largest studies to date that captures both physiologic and symptomatic data, may inform others who look to implement a program of similar scope. We also share lessons learned regarding barriers and disparities in enrollment and discuss implications for RPM in other acute disease states.

Sensitivity of cognitive function tests to acute hypoxia in healthy subjects: a systematic literature review

Acute exposure to hypoxia can lead to cognitive impairment. Therefore, hypoxia may become a safety concern for occupational or recreational settings at altitude. Cognitive tests are used as a tool to assess the degree to which hypoxia affects cognitive performance. However, so many different cognitive tests are used that comparing studies is challenging. This structured literature evaluation provides an overview of the different cognitive tests used to assess the effects of acute hypoxia on cognitive performance in healthy volunteers. Less frequently used similar cognitive tests were clustered and classified into domains. Subsequently, the different cognitive test clusters were compared for sensitivity to different levels of oxygen saturation. A total of 38 articles complied with the selection criteria, covering 86 different cognitive tests. The tests and clusters showed that the most consistent effects of acute hypoxia were found with the Stroop test (where 42% of studies demonstrated significant abnormalities). The most sensitive clusters were auditory/verbal memory: delayed recognition (83%); evoked potentials (60%); visual/spatial delayed recognition (50%); and sustained attention (47%). Attention tasks were not particularly sensitive to acute hypoxia (impairments in 0%-47% of studies). A significant hypoxia level-response relationship was found for the Stroop test (p = 0.001), as well as three clusters in the executive domain: inhibition (p = 0.034), reasoning/association (p = 0.019), and working memory (p = 0.024). This relationship shows a higher test sensitivity at more severe levels of hypoxia, predominantly below 80% saturation. No significant influence of barometric pressure could be identified in the limited number of studies where this was varied. This review suggests that complex and executive functions are particularly sensitive to hypoxia. Moreover, this literature evaluation provides the first step towards standardization of cognitive testing, which is crucial for a better understanding of the effects of acute hypoxia on cognition.

[Saturation index and fraction of inspired oxygen as a predictor in COVID-19]

Background

Coronavirus disease leads to silent hypoxia, ARDS, and organ failure. The saturation and fraction of inspired oxygen have been related to the degree of lung damage, can be considered as a monitoring tool for lung function during hospitalization and a predictor of mortality in patients with pneumonia by COVID-19.

Objective

To evaluate the usefulness of the oxygen saturation index and fraction of inspired oxygen as a predictor of mortality in patients with COVID-19 pneumonia.

Material and methods

A retrospective, longitudinal, analytical study. Files of eligible patients with a diagnosis of SARS-CoV-2 pneumonia were admitted to HGR No.2, complete file, recording of oxygen saturation and inspired fraction of oxygen, were included. Patients dependent on supplemental oxygen, who did not require supplemental oxygen during their hospitalization, incomplete records, patients who have died from non-pulmonary causes, were excluded.

Results

A sample of 175 files with a diagnosis of pneumonia with SARS-CoV-2 was obtained. A logistic regression model was performed including age over 60 years BE of 2.68, with CI (1.09-6.5), DM2 with a BE of 2.35 with CI (0.99-5.59), HTA with a BE of 0.80, with CI (0.32-2.02), SAFI index less than 310 with a BE of 6.63, with a CI (2.64-16.65), endotracheal intubation with a BE 48.43, and a CI (2.64-16.65).

Conclusion

The SpO2/Fio2 index can be used for continuous monitoring of lung function in patients with COVID-19 pneumonia, in an accessible, easy and economical way. A relationship with mortality was obtained in patients with SpO2/FiO2 less than 310 associated with other factors.

The Mechanisms of Ferroptosis Under Hypoxia

Ferroptosis is a new form of programmed cell death, which is characterized by the iron-dependent accumulation of lipid peroxidation and increase of ROS, resulting in oxidative stress and cell death. Iron, lipid, and multiple signaling pathways precisely control the occurrence and implementation of ferroptosis. The pathways mainly include Nrf2/HO-1 signaling pathway, p62/Keap1/Nrf2 signaling pathway. Activating p62/Keap1/Nrf2 signaling pathway inhibits ferroptosis. Nrf2/HO-1 signaling pathway promotes ferroptosis. Furthermore, some factors also participate in the occurrence of ferroptosis under hypoxia, such as HIF-1, NCOA4, DMT1. Meanwhile, ferroptosis is related with hypoxia-related diseases, such as MIRI, cancers, and AKI. Accordingly, ferroptosis appears to be a therapeutic target for hypoxia-related diseases.

Mesenchymal Stem Cells in the Treatment of COVID-19

Since the emergence of the coronavirus disease 2019 (COVID-19) pandemic, many lives have been tragically lost to severe infections. The COVID-19 impact extends beyond the respiratory system, affecting various organs and functions. In severe cases, it can progress to acute respiratory distress syndrome (ARDS) and multi-organ failure, often fueled by an excessive immune response known as a cytokine storm. Mesenchymal stem cells (MSCs) have considerable potential because they can mitigate inflammation, modulate immune responses, and promote tissue regeneration. Accumulating evidence underscores the efficacy and safety of MSCs in treating severe COVID-19 and ARDS. Nonetheless, critical aspects, such as optimal routes of MSC administration, appropriate dosage, treatment intervals, management of extrapulmonary complications, and potential pediatric applications, warrant further exploration. These research avenues hold promise for enriching our understanding and refining the application of MSCs in confronting the multifaceted challenges posed by COVID-19.

Mild hypoxia-induced structural and functional changes of the hippocampal network

Hypoxia causes structural and functional changes in several brain regions, including the oxygen-concentration-sensitive hippocampus. We investigated the consequences of mild short-term hypoxia on rat hippocampus in vivo. The hypoxic group was treated with 16% O2 for 1 h, and the control group with 21% O2. Using a combination of Gallyas silver impregnation histochemistry revealing damaged neurons and interneuron-specific immunohistochemistry, we found that somatostatin-expressing inhibitory neurons in the hilus were injured. We used 32-channel silicon probe arrays to record network oscillations and unit activity from the hippocampal layers under anaesthesia. There were no changes in the frequency power of slow, theta, beta, or gamma bands, but we found a significant increase in the frequency of slow oscillation (2.1-2.2 Hz) at 16% O2 compared to 21% O2. In the hilus region, the firing frequency of unidentified interneurons decreased. In the CA3 region, the firing frequency of some unidentified interneurons decreased while the activity of other interneurons increased. The activity of pyramidal cells increased both in the CA1 and CA3 regions. In addition, the regularity of CA1, CA3 pyramidal cells' and CA3 type II and hilar interneuron activity has significantly changed in hypoxic conditions. In summary, a low O2 environment caused profound changes in the state of hippocampal excitatory and inhibitory neurons and network activity, indicating potential changes in information processing caused by mild short-term hypoxia.

Wavelet Analysis of Respiratory Muscle sEMG Signals during the Physiological Breakpoint of Static Dry End-Expiratory Breath-Holding in Naive Apneists: A Pilot Study

The wavelet spectral characteristics of three respiratory muscle signals (scalenus (SC), parasternal intercostal (IC), and rectus abdominis (RA)) and one locomotor muscle (brachioradialis (BR)) were analyzed in the time-frequency (T-F) domain during voluntary breath-holding (BH), with a focus on the physiological breakpoint that is commonly considered the first involuntary breathing movement (IBM) that signals the end of the easy-going phase of BH. The study was performed for an end-expiratory BH physiological breaking point maneuver on twelve healthy, physically active, naive breath-holders/apneists (six professional athletes; six recreational athletes, and two individuals in the post-COVID-19 period) using surface electromyography (sEMG). We observed individual effects that were dependent on muscle oxygenation and each person's fitness, which were consistent with the mechanism of motor unit (MU) recruitment and the transition of slow-twitch oxidative (type 1) to fast-twitch glycolytic (type 2) muscle fibers. Professional athletes had longer BH durations (BHDs) and strong hypercapnic responses regarding the expiratory RA muscle, which is activated abruptly at higher BHDs in a person-specific range below 250 Hz and is dependent on the BHD. This is in contrast with recreational athletes, who had strong hypoxic responses regarding inspiratory IC muscle, which is activated faster and gradually in the frequency range of 250-450 Hz (independent of the person and BHD). This pilot study preliminarily indicates that it is possible to noninvasively assess the physiological characteristics of skeletal muscles, especially oxygenation, and improve physical fitness tests by determining the T-F features of elevated myoelectric IC and RA activity during BH.

Mitochondria in hypoxic pulmonary hypertension, roles and the potential targets

Mitochondria are the centrol hub for cellular energy metabolisms. They regulate fuel metabolism by oxygen levels, participate in physiological signaling pathways, and act as oxygen sensors. Once oxygen deprived, the fuel utilizations can be switched from mitochondrial oxidative phosphorylation to glycolysis for ATP production. Notably, mitochondria can also adapt to hypoxia by making various functional and phenotypes changes to meet the demanding of oxygen levels. Hypoxic pulmonary hypertension is a life-threatening disease, but its exact pathgenesis mechanism is still unclear and there is no effective treatment available until now. Ample of evidence indicated that mitochondria play key factor in the development of hypoxic pulmonary hypertension. By hypoxia-inducible factors, multiple cells sense and transmit hypoxia signals, which then control the expression of various metabolic genes. This activation of hypoxia-inducible factors considered associations with crosstalk between hypoxia and altered mitochondrial metabolism, which plays an important role in the development of hypoxic pulmonary hypertension. Here, we review the molecular mechanisms of how hypoxia affects mitochondrial function, including mitochondrial biosynthesis, reactive oxygen homeostasis, and mitochondrial dynamics, to explore the potential of improving mitochondrial function as a strategy for treating hypoxic pulmonary hypertension.

Iron and iron-related proteins in COVID-19

COVID-19 can cause detrimental effects on health. Vaccines have helped in reducing disease severity and transmission but their long-term effects on health and effectiveness against future viral variants remain unknown. COVID-19 pathogenesis involves alteration in iron homeostasis. Thus, a contextual understanding of iron-related parameters would be very valuable for disease prognosis and therapeutics.Accordingly, we reviewed the status of iron and iron-related proteins in COVID-19. Iron-associated alterations in COVID-19 reported hitherto include anemia of inflammation, low levels of serum iron (hypoferremia), transferrin and transferrin saturation, and high levels of serum ferritin (hyperferritinemia), hepcidin, lipocalin-2, catalytic iron, and soluble transferrin receptor (in ICU patients). Hemoglobin levels can be low or normal, and compromised hemoglobin function has been proposed. Membrane-bound transferrin receptor may facilitate viral entry, so it acts as a potential target for antiviral therapy. Lactoferrin can provide natural defense by preventing viral entry and/or inhibiting viral replication. Serum iron and ferritin levels can predict COVID-19-related hospitalization, severity, and mortality. Serum hepcidin and ferritin/transferrin ratio can predict COVID-19 severity. Here, serum levels of these iron-related parameters are provided, caveats of iron chelation for therapy are discussed and the interplay of these iron-related parameters in COVID-19 is explained.This synopsis is crucial as it clearly presents the iron picture of COVID-19. The information may assist in disease prognosis and/or in formulating iron-related adjunctive strategies that can help reduce infection/inflammation and better manage COVID-19 caused by future variants. Indeed, the current picture will augment as more is revealed about these iron-related parameters in COVID-19.

Investigating the accuracy of blood oxygen saturation measurements in common consumer smartwatches

Blood oxygen saturation (SpO2) is an important measurement for monitoring patients with acute and chronic conditions that are associated with low blood oxygen levels. While smartwatches may provide a new method for continuous and unobtrusive SpO2 monitoring, it is necessary to understand their accuracy and limitations to ensure that they are used in a fit-for-purpose manner. To determine whether the accuracy of and ability to take SpO2 measurements from consumer smartwatches is different by device type and/or by skin tone, our study recruited patients aged 18-85 years old, with and without chronic pulmonary disease, who were able to provide informed consent. The mean absolute error (MAE), mean directional error (MDE) and root mean squared error (RMSE) were used to evaluate the accuracy of the smartwatches as compared to a clinical grade pulse oximeter. The percent of data unobtainable due to inability of the smartwatch to record SpO2 (missingness) was used to evaluate the measurability of SpO2 from the smartwatches. Skin tones were quantified based on the Fitzpatrick (FP) scale and Individual Typology Angle (ITA), a continuous measure of skin tone. A total of 49 individuals (18 female) were enrolled and completed the study. Using a clinical-grade pulse oximeter as the reference standard, there were statistically significant differences in accuracy between devices, with Apple Watch Series 7 having measurements closest to the reference standard (MAE = 2.2%, MDE = -0.4%, RMSE = 2.9%) and the Garmin Venu 2s having measurements farthest from the reference standard (MAE = 5.8%, MDE = 5.5%, RMSE = 6.7%). There were also significant differences in measurability across devices, with the highest data presence from the Apple Watch Series 7 (88.9% of attempted measurements were successful) and the highest data missingness from the Withings ScanWatch (only 69.5% of attempted measurements were successful). The MAE, RMSE and missingness did not vary significantly across FP skin tone groups, however, there may be a relationship between FP skin tone and MDE (intercept = 0.04, beta coefficient = 0.47, p = 0.04). No statistically significant difference was found between skin tone as measured by ITA and MAE, MDE, RMSE or missingness.

Analysis of Ischemia-Modified Albumin (IMA) and Coagulation Parameters in Patients with SARS-CoV-2 Pneumonia

BACKGROUND

Coronavirus disease 2019 (COVID-19) is a systemic disease which causes an increased inclination to thrombosis by leading to coagulation system activation and endothelial dysfunction. Our objective in this study is to determine whether ischemia-modified albumin (IMA) can be used as a new marker in patients with COVID-19 for evaluating the increased coagulation risk, pneumonic infiltration, and thus, prognosis.

METHODS

Our study included 59 patients with COVID-19 compatible pneumonic infiltration on lung computed tomography (CT) who applied to and were hospitalized in the Internal Diseases Outpatient Clinic, then followed up and treated, as well as 29 healthy individuals with a negative COVID-19 rRT-PCR test without any additional disease. Hemogram, coagulation, routine biochemistry, and serum IMA activity parameters were studied.

RESULTS

In our study, the higher serum IMA level in COVID-19 patients with pneumonic infiltration compared to that of the healthy control group was found to be statistically significant. No significant correlation was found between the serum IMA levels and the coagulation and inflammation parameters in the 59 COVID-19 patients included.

CONCLUSIONS

Serum IMA levels in COVID-19 patients with pneumonic infiltration on CT were found to be higher than in the control group. Examination of biochemical parameters, especially thrombotic parameters that affect prognosis such as IMA, can be a guide in estimating pneumonic infiltration.

Can affinity of hemoglobin to oxygen to be a prognostic marker in critically ill COVID-19 patients?

Background

This study's objective is to determine the slope of the hemoglobin oxygen dissociation curve in critically ill patients who have COVID-19 along with blood gas measurements and how mortality might be impacted by this circumstance.

Aim

It has been reported that the hemoglobin oxygen dissociation curve is not different from healthy patients in COVID-19. However, there are insufficient data on the behavior of the curve in patients who require intensive care.

Patients and Methods

This retrospective study was conducted between 01.03.2021 and 01.07.2021 with patients who were followed up due to COVID-19 in adult intensive care unit. P50 and lactate value obtained from in vitro calculated blood gas analysis. The survival status of the patients was recorded.

Results

The mean P50 value at the admission of nonsurvivors was significantly higher than survivors. In correlation analysis, a significant positive correlation was seen between P50, mortality, and lactate level at admission. SpO₂, PaO₂/FiO₂ ratio, and length of stay in intensive care unit were significantly negatively correlated with P50 levels.

Conclusion

A right shift in the hemoglobin oxygen dissociation curve is associated with mortality. Lactate levels were also associated with a right shift. Prospective experimental studies are needed to provide a better understanding of this process.

Plasma proteomics of SARS-CoV-2 infection and severity reveals impact on Alzheimer's and coronary disease pathways

Identification of proteins dysregulated by COVID-19 infection is critically important for better understanding of its pathophysiology, building prognostic models, and identifying new targets. Plasma proteomic profiling of 4,301 proteins was performed in two independent datasets and tested for the association for three COVID-19 outcomes (infection, ventilation, and death). We identified 1,449 proteins consistently associated in both datasets with any of these three outcomes. We subsequently created highly accurate models that distinctively predict infection, ventilation, and death. These proteins were enriched in specific biological processes including cytokine signaling, Alzheimer's disease, and coronary artery disease. Mendelian randomization and gene network analyses identified eight causal proteins and 141 highly connected hub proteins including 35 with known drug targets. Our findings provide distinctive prognostic biomarkers for two severe COVID-19 outcomes, reveal their relationship to Alzheimer's disease and coronary artery disease, and identify potential therapeutic targets for COVID-19 outcomes.

Ferroptosis Regulated by Hypoxia in Cells

Ferroptosis is an oxidative damage-related, iron-dependent regulated cell death with intracellular lipid peroxide accumulation, which is associated with many physiological and pathological processes. It exhibits unique features that are morphologically, biochemically, and immunologically distinct from other regulated cell death forms. Ferroptosis is regulated by iron metabolism, lipid metabolism, anti-oxidant defense systems, as well as various signal pathways. Hypoxia, which is found in a group of physiological and pathological conditions, can affect multiple cellular functions by activation of the hypoxia-inducible factor (HIF) signaling and other mechanisms. Emerging evidence demonstrated that hypoxia regulates ferroptosis in certain cell types and conditions. In this review, we summarize the basic mechanisms and regulations of ferroptosis and hypoxia, as well as the regulation of ferroptosis by hypoxia in physiological and pathological conditions, which may contribute to the numerous diseases therapies.

Unraveling the Underlying Molecular Mechanism of 'Silent Hypoxia' in COVID-19 Patients Suggests a Central Role for Angiotensin II Modulation of the AT1R-Hypoxia-Inducible Factor Signaling Pathway

A few days after being infected with SARS-CoV-2, a fraction of people remain asymptomatic but suffer from a decrease in arterial oxygen saturation in the absence of apparent dyspnea. In light of our clinical investigation on the modulation of molecules belonging to the renin angiotensin system (RAS) in COVID-19 patients, we propose a model that explains 'silent hypoxia'. The RAS imbalance caused by SARS-CoV-2 results in an accumulation of angiotensin 2 (Ang II), which activates the angiotensin 2 type 1 receptor (AT1R) and triggers a harmful cascade of intracellular signals leading to the nuclear translocation of the hypoxia-inducible factor (HIF)-1α. HIF-1α transactivates many genes including the angiotensin-converting enzyme 1 (ACE1), while at the same time, ACE2 is downregulated. A growing number of cells is maintained in a hypoxic condition that is self-sustained by the presence of the virus and the ACE1/ACE2 ratio imbalance. This is associated with a progressive worsening of the patient's biological parameters including decreased oxygen saturation, without further clinical manifestations. When too many cells activate the Ang II-AT1R-HIF-1α axis, there is a 'hypoxic spillover', which marks the tipping point between 'silent' and symptomatic hypoxia in the patient. Immediate ventilation is required to prevent the 'hypoxic spillover'.

Electrical stimulation to regain lower extremity muscle perfusion and endurance in patients with post-acute sequelae of SARS CoV-2: A randomized controlled trial

Muscle deconditioning and impaired vascular function in the lower extremities (LE) are among the long-term symptoms experienced by COVID-19 patients with a history of severe illness. These symptoms are part of the post-acute sequelae of Sars-CoV-2 (PASC) and currently lack evidence-based treatment. To investigate the efficacy of lower extremity electrical stimulation (E-Stim) in addressing PASC-related muscle deconditioning, we conducted a double-blinded randomized controlled trial. Eighteen (n = 18) patients with LE muscle deconditioning were randomly assigned to either the intervention (IG) or the control (CG) group, resulting in 36 LE being assessed. Both groups received daily 1 h E-Stim on both gastrocnemius muscles for 4 weeks, with the device functional in the IG and nonfunctional in the CG. Changes in plantar oxyhemoglobin (OxyHb) and gastrocnemius muscle endurance (GNMe) in response to 4 weeks of daily 1 h E-Stim were assessed. At each study visit, outcomes were measured at onset (t₀ ), 60 min (t₆₀ ), and 10 min after E-Stim therapy (t₇₀ ) by recording ΔOxyHb with near-infrared spectroscopy. ΔGNMe was measured with surface electromyography at two time intervals: 0-5 min (Intv₁ ) and: 55-60 min (Intv₂ ). Baseline OxyHb decreased in both groups at t₆₀ (IG: p = 0.046; CG: p = 0.026) and t₇₀ (IG = p = 0.021; CG: p = 0.060) from t₀ . At 4 weeks, the IG's OxyHb increased from t₆₀ to t₇₀ (p < 0.001), while the CG's decreased (p = 0.003). The IG had higher ΔOxyHb values than the CG at t₇₀ (p = 0.004). Baseline GNMe did not increase in either group from Intv₁ to Intv₂ . At 4 weeks, the IG's GNMe increased (p = 0.031), whereas the CG did not change. There was a significant association between ΔOxyHb and ΔGNMe (r = 0.628, p = 0.003) at 4 weeks in the IG. In conclusion, E-Stim can improve muscle perfusion and muscle endurance in individuals with PASC experiencing LE muscle deconditioning.

The hypoxia-age-shock index at triage to predict the outcomes of Covid-19 patients

STUDY OBJECTIVE

The coronavirus disease 2019 (COVID-19) outbreak has caused a severe burden on medical professionals, as the rapid disposition of patients is important. Therefore, we aimed to develop a new clinical assessment tool based on the shock index (SI) and age-shock index (ASI). We proposed the hypoxia-age-shock index (HASI) and determined the usability of triage for COVID-19 infected patients in the first scene.

METHODS

The predictive power for three indexes on mortality, intensive care unit (ICU) admission, and endotracheal intubation rate was evaluated using the receiver operating curve (ROC). We used DeLong's method for comparing the ROCs.

RESULTS

The area under the curve (AUC) for ROC on mortality for SI, ASI, and HASI were 0.546, 0.771, and 0.773, respectively. The AUC on ICU admission mortality for SI, ASI, and HASI were 0.581, 0.700, and 0.743, respectively. The AUC for intubation for SI, ASI, and HASI were 0.592, 0.708, and 0.757, respectively. The AUC differences between HASI and SI showed statistically significant (P = 0.001) results on mortality, ICU admission, and intubation. Additionally, statistically significant results were found for the AUC difference between the HASI and ASI on ICU admission and intubation (P = 0.001 and P = 0.004, respectively).

CONCLUSION

HASI can provide a better prediction compared to ASI on ICU admission and endotracheal intubation. HASI was more sensitive in mortality, ICU admission, and intubation prediction than the ASI.

Investigating the possible mechanisms of autonomic dysfunction post-COVID-19

Patients with long COVID suffer from many neurological manifestations that persist for 3 months following infection by SARS-CoV-2. Autonomic dysfunction (AD) or dysautonomia is one complication of long COVID that causes patients to experience fatigue, dizziness, syncope, dyspnea, orthostatic intolerance, nausea, vomiting, and heart palpitations. The pathophysiology behind AD onset post-COVID is largely unknown. As such, this review aims to highlight the potential mechanisms by which AD occurs in patients with long COVID. The first proposed mechanism includes the direct invasion of the hypothalamus or the medulla by SARS-CoV-2. Entry to these autonomic centers may occur through the neuronal or hematogenous routes. However, evidence so far indicates that neurological manifestations such as AD are caused indirectly. Another mechanism is autoimmunity whereby autoantibodies against different receptors and glycoproteins expressed on cellular membranes are produced. Additionally, persistent inflammation and hypoxia can work separately or together to promote sympathetic overactivation in a bidirectional interaction. Renin-angiotensin system imbalance can also drive AD in long COVID through the downregulation of relevant receptors and formation of autoantibodies. Understanding the pathophysiology of AD post-COVID-19 may help provide early diagnosis and better therapy for patients.

Same but Different-ECMO in COVID-19 and ARDS of Other Etiologies. Comparison of Survival Outcomes and Management in Different ARDS Groups

Background: COVID-19 has led to increased numbers of patients in need of venovenous extracorporeal membrane oxygenation (ECMO) support, but knowledge on management in comparison to acute respiratory distress syndrome (ARDS) of other etiologies is still lacking. We analyzed venovenous ECMO management and survival outcomes in patients with COVID-19 in comparison to influenza ARDS and pulmonary ARDS of other origin. Results: Retrospective analysis of prospective venovenous ECMO registry-based data collection was performed. One hundred consecutive venovenous ECMO patients with severe ARDS were included (41 COVID-19, 24 influenza A, 35 ARDS of other etiologies). Patients with COVID-19 had higher BMI (body mass index), lower SOFA (Sequential Organ Failure Assessment) and APACHE II (Acute Physiology and Chronic Health Evaluation II) scores, lower C-reactive protein and procalcitonin levels and less vasoactive support at ECMO initiation. Significantly more patients were mechanically ventilated for more than 7 days prior to ECMO initiation in the COVID-19 group, however they were ventilated with lower tidal volumes and more often received additional rescue therapies prior to and on ECMO. COVID-19 patients had significantly more barotrauma and thrombotic events on ECMO. There were no differences in weaning of ECMO, however duration of ECMO runs and ICU length of stay was significantly longer in the COVID-19 group. The leading cause of death in the COVID-19 group was irreversible respiratory failure, while uncontrolled sepsis and multiorgan failure were leading causes in the other 2 groups. All patients who survived ICU treatment were discharged out of hospital, and there were no differences in survival among groups at 180 days. Conclusions: Survival outcomes of venovenous ECMO patients do not differ between COVID-19 and ARDS of other pulmonary etiologies. ARDS guidelines were in greater proportion adhered to in COVID-19 patients, with, however, longer time to ECMO initiation. COVID-19 ARDS seems specific as a more single-organ disease with longer ECMO duration and irreversible respiratory failure as a main cause of ICU mortality.

Mechanisms, Effects, and Management of Neurological Complications of Post-Acute Sequelae of COVID-19 (NC-PASC)

With a growing number of patients entering the recovery phase following infection with SARS-CoV-2, understanding the long-term neurological consequences of the disease is important to their care. The neurological complications of post-acute sequelae of SARS-CoV-2 infection (NC-PASC) represent a myriad of symptoms including headaches, brain fog, numbness/tingling, and other neurological symptoms that many people report long after their acute infection has resolved. Emerging reports are being published concerning COVID-19 and its chronic effects, yet limited knowledge of disease mechanisms has challenged therapeutic efforts. To address these issues, we review broadly the literature spanning 2020-2022 concerning the proposed mechanisms underlying NC-PASC, outline the long-term neurological sequelae associated with COVID-19, and discuss potential clinical interventions.

Liver injury in COVID-19: Clinical features, potential mechanisms, risk factors and clinical treatments

The coronavirus disease 2019 (COVID-19) pandemic has been a serious threat to global health for nearly 3 years. In addition to pulmonary complications, liver injury is not uncommon in patients with novel COVID-19. Although the prevalence of liver injury varies widely among COVID-19 patients, its incidence is significantly increased in severe cases. Hence, there is an urgent need to understand liver injury caused by COVID-19. Clinical features of liver injury include detectable liver function abnormalities and liver imaging changes. Liver function tests, computed tomography scans, and ultrasound can help evaluate liver injury. Risk factors for liver injury in patients with COVID-19 include male sex, preexisting liver disease including liver transplantation and chronic liver disease, diabetes, obesity, and hypertension. To date, the mechanism of COVID-19-related liver injury is not fully understood. Its pathophysiological basis can generally be explained by systemic inflammatory response, hypoxic damage, ischemia-reperfusion injury, and drug side effects. In this review, we systematically summarize the existing literature on liver injury caused by COVID-19, including clinical features, underlying mechanisms, and potential risk factors. Finally, we discuss clinical management and provide recommendations for the care of patients with liver injury.

COVID-19 as a Risk Factor for Alzheimer's Disease

Severe acute respiratory disease coronavirus 2 (SARS-CoV-2) is responsible for the coronavirus disease 2019 (COVID-19) pandemic. Although a primarily respiratory disease, recent reports indicate that it also affects the central nervous system (CNS). Over 25% of COVID-19 patients report neurological symptoms such as memory loss, anosmia, hyposmia, confusion, and headaches. The neurological outcomes may be a result of viral entry into the CNS and/or resulting neuroinflammation, both of which underlie an elevated risk for Alzheimer's disease (AD). Herein, we ask: Is COVID-19 a risk factor for AD? To answer, we identify the literature and review mechanisms by which COVID-19-mediated neuroinflammation can contribute to the development of AD, evaluate the effects of acute versus chronic phases of infection, and lastly, discuss potential therapeutics to address the rising rates of COVID-19 neurological sequelae.

Prediction of low pulse oxygen saturation in COVID-19 using remote monitoring post hospital discharge

BACKGROUND

Monitoring systems have been developed during the COVID-19 pandemic enabling clinicians to remotely monitor physiological measures including pulse oxygen saturation (SpO₂), heart rate (HR), and breathlessness in patients after discharge from hospital. These data may be leveraged to understand how symptoms vary over time in COVID-19 patients. There is also potential to use remote monitoring systems to predict clinical deterioration allowing early identification of patients in need of intervention.

METHODS

A remote monitoring system was used to monitor 209 patients diagnosed with COVID-19 in the period following hospital discharge. This system consisted of a patient-facing app paired with a Bluetooth-enabled pulse oximeter (measuring SpO₂ and HR) linked to a secure portal where data were available for clinical review. Breathlessness score was entered manually to the app. Clinical teams were alerted automatically when SpO₂ < 94 %. In this study, data recorded during the initial ten days of monitoring were retrospectively examined, and a random forest model was developed to predict SpO₂ < 94 % on a given day using SpO₂ and HR data from the two previous days and day of discharge.

RESULTS

Over the 10-day monitoring period, mean SpO₂ and HR increased significantly, while breathlessness decreased. The coefficient of variation in SpO₂, HR and breathlessness also decreased over the monitoring period. The model predicted SpO₂ alerts (SpO₂ < 94 %) with a mean cross-validated. sensitivity of 66 ± 18.57 %, specificity of 88.31 ± 10.97 % and area under the receiver operating characteristic of 0.80 ± 0.11. Patient age and sex were not significantly associated with the occurrence of asymptomatic SpO₂ alerts.

CONCLUSION

Results indicate that SpO₂ alerts (SpO₂ < 94 %) on a given day can be predicted using SpO₂ and heart rate data captured on the two preceding days via remote monitoring. The methods presented may help early identification of patients with COVID-19 at risk of clinical deterioration using remote monitoring.