Impact of Respiratory Fluctuation on Hemodynamics in Human Cardiovascular System: A 0-1D Multiscale Model

To explore hemodynamic interaction between the human respiratory system (RS) and cardiovascular system (CVS), here we propose an integrated computational model to predict the CVS hemodynamics with consideration of the respiratory fluctuation (RF). A submodule of the intrathoracic pressure (ITP) adjustment is developed and incorporated in a 0-1D multiscale hemodynamic model of the CVS specified for infant, adolescent, and adult individuals. The model is verified to enable reasonable estimation of the blood pressure waveforms accounting for the RF-induced pressure fluctuations in comparison with clinical data. The results show that the negative ITP caused by respiration increases the blood flow rates in superior and inferior vena cavae; the deep breathing improves the venous return in adolescents but has less influence on infants. It is found that a marked reduction in ITP under pathological conditions can excessively increase the flow rates in cavae independent of the individual ages, which may cause the hemodynamic instability and hence increase the risk of heart failure. Our results indicate that the present 0-1D multiscale CVS model incorporated with the RF effect is capable of providing a useful and effective tool to explore the physiological and pathological mechanisms in association with cardiopulmonary interactions and their clinical applications.

Influence of Spontaneous and Mechanical Ventilation on Frequency-Based Measures of Heart Rate Variability

Frequency-based measures of heart rate variability have been shown to be a useful physiological marker in both clinical and research settings providing insight into the functioning of the autonomic nervous system. Ongoing interactions between the autonomic nervous system control of the heart and lung occurs during each ventilation cycle because of their anatomical position within the closed thoracic cavity. Mechanical ventilation and subsequent removal change the normal ventilator mechanics producing alterations in the tidal volume, intrathoracic pressure, and oxygen delivery. A noninvasive method called heart rate variability (HRV) can be used to evaluate this interaction during ventilation and can be quantified by applying frequency-based measures of the variability between heartbeats. Although HRV is a reliable method to measure alteration of the autonomic nervous system (ANS) function and cardiopulmonary interaction, there have been limited reports concerning the changes in the frequency-based measure of HRV during both spontaneous and mechanical ventilation. The purpose of this methodological study is therefore to describe the physiological influence of both spontaneous and mechanical ventilation on frequency-based measures of HRV.

Management of tension gastrothorax: experience from sub-Saharan Africa

Tension gastrothorax is a form of obstructive shock resulting from increased intrathoracic pressure due to a distended herniated stomach. The clinical features of tension gastrothorax are similar to the clinical features of the more common tension pneumothorax. Clinical recognition of this trauma has remained difficult especially in the tropics where most responders are not specialists. We managed a 31-year-old male who, in addition to typical features of obstructive shock secondary to increased intrathoracic pressures, had a recent meal prior to the trauma and a scaphoid abdomen at presentation. We argue that a history of a recent meal before trauma and an unusually scaphoid abdomen could be suggestive of tension gastrothorax and may help to differentiate it from tension pneumothorax. We recommend improved emergency preparedness to help recognise and treat this pathology.

Tachycardia and hypertension enhance tracer efflux from the spinal cord

Background Disruption of cerebrospinal fluid (CSF)/interstitial fluid (ISF) exchange in the spinal cord is likely to contribute to central nervous system (CNS) diseases that involve abnormal fluid accumulation, including spinal cord oedema and syringomyelia. However, the physiological factors that govern fluid transport in the spinal cord are poorly understood. The aims of this study were to determine the effects of cardiac pulsations and respiration on tracer signal increase, indicative of molecular movement following infusion into the spinal cord grey or white matter. Methods In Sprague Dawley rats, physiological parameters were manipulated such that the effects of spontaneous breathing (generating alternating positive and negative intrathoracic pressures), mechanical ventilation (positive intrathoracic pressure only), tachycardia (heart atrial pacing), as well as hypertension (pharmacologically induced) were separately studied. Since fluid outflow from the spinal cord cannot be directly measured, we assessed the molecular movement of fluorescent ovalbumin (AFO-647), visualised by an increase in tracer signal, following injection into the cervicothoracic spinal grey or white matter. Results Tachycardia and hypertension increased AFO-647 tracer efflux, while the concomitant negative and positive intrathoracic pressures generated during spontaneous breathing did not when compared to the positive-pressure ventilated controls. Following AFO-647 tracer injection into the spinal grey matter, increasing blood pressure and heart rate resulted in increased tracer movement away from the injection site compared to the hypotensive, bradycardic animals (hypertension: p = 0.05, tachycardia: p < 0.0001). Similarly, hypertension and tachycardia produced greater movement of AFO-647 tracer longitudinally along the spinal cord following injection into the spinal white matter (p < 0.0001 and p = 0.002, respectively). Tracer efflux was strongly associated with all blood vessel types. Conclusions Arterial pulsations have profound effects on spinal cord interstitial fluid homeostasis, generating greater tracer efflux than intrathoracic pressure changes that occur over the respiratory cycle, demonstrated by increased craniocaudal CSF tracer movement in the spinal cord parenchyma.

Potential targets for preclinical diagnostics of acute kidney injury in covid-19 patients (review of literature)

An relevance of the topic was defined by the high occurrence, unfavorable prognosis, lack of diagnostic techniques for early stages of acute kidney injury (AKI) disclosed in patients with COVID-19 (Coronavirus Disease 2019). Screening of medical literature for selection of AKI preclinical biomarkers was considered as main aim of this review. More than 200 publications from Russian Science Citation Index (RSCI), Scopus, The Cochrane Library, and MEDLINE were reviewed. Such risk factors as hypoxemia, increased intrathoracic pressure associated with Acute Respiratory Distress Syndrome (ARDS), hypertension (HT) involving endothelial dysfunction, and Diabetes mellitus were considered to be associated with AKI. There were explicated cytopathic and immune-mediated (cytokine-induced) mechanisms of COVID-19 associated AKI pathogenesis. Multiple methodological approaches were defined for detection and identification of the biomarkers based on urine proteome and metabolome screening. Perspective ways in the preclinical diagnostics of AKI such as detection of the markers of injury of the hypoxia-sensitive proximal canaliculi and the ATP metabolites that reflect first stages of the energy metabolism disorder in the epithelium lining canaliculi were identified in this study. The instantaneous and non-invasive investigation of different markers was regarded as possible method of the prognostication. The accuracy of the diagnosis on the initial stages of AKI, substantiate for preventive start of therapy, and make projections on the disease`s outcome will be improved due to the identification of high-sensitive specific biomarkers.

Slosh Simulation in a Computer Model of Canine Syringomyelia

The exact pathogenesis of syringomyelia is unknown. Epidural venous distention during raised intrathoracic pressure (Valsalva) may cause impulsive movement of fluid (“slosh”) within the syrinx. Such a slosh mechanism is a proposed cause of syrinx dissection into spinal cord parenchyma resulting in craniocaudal propagation of the cavity. We sought to test the “slosh” hypothesis by epidural excitation of CSF pulse in a computer model of canine syringomyelia. Our previously developed canine syringomyelia computer model was modified to include an epidural pressure pulse. Simulations were run for: cord free of cavities; cord with small syringes at different locations; and cord with a syrinx that was progressively expanding caudally. If small syringes are present, there are peaks of stress at those locations. This effect is most pronounced at the locations at which syringes initially form. When a syrinx is expanding caudally, the peak stress is typically at the caudal end of the syrinx. However, when the syrinx reaches the lumbar region; the stress becomes moderate. The findings support the “slosh” hypothesis, suggesting that small cervical syringes may propagate caudally. However, when the syrinx is large, there is less focal stress, which may explain why a syrinx can rapidly expand but then remain unchanged in shape over years.

The larynx

The larynx, trachea and bronchi develop embryologically from the foregut in the form of an outpouching during the fourth week of gestation. The larynx bridges the gap from the base of the tongue above, to the trachea below lying within the hypopharynx. It sits in the neck spanning the distance from the third to sixth cervical vertebrae. It is a complex respiratory organ composed of a cartilage framework, ligaments, intrinsic and extrinsic muscles and is lined by an epithelial mucous membrane continuous above with the pharynx and below with the trachea. Its primary function is protection of the lower respiratory tract against aspiration. It allows the generation of a high intrathoracic pressure required for coughing, straining and lifting (Valsalva manoeuvre) and phonation. The anatomy of the larynx can either be considered by its surgical division of the supraglottis, glottis and subglottis (these landmarks are important in the consideration of cancer spread).

A rare case of compression atelectasis due to spontaneous diaphragmatic hernia: a case report

Type IV diaphragmatic hernia is a rare case which has various clinical manifestations. The clinical manifestations as a result of protruded organ towards thoracic cavity in diaphragmatic hernia are varied from gastrointestinal symptoms such as epigastric pain, dysphagia and acid reflux. However, in a rare occasion, dyspnea may present as a result of compression atelectasis due to excessive increased in intrathoracic pressure. Here, we report a 57-year-old male patient who had spontaneous diaphragmatic hernia admitted with dyspnea as a chief complaint. This report might add another perspective to the physicians in facing the patient with atelectasis as the result of a high level of lung compression secondary to type IV diaphragmatic hernia.

1130 An Obstructed Morgagni Hernia in Adulthood, Could Regular Cocaine Use Have Exacerbated Symptoms?

Introduction Morgagni hernias are an uncommon form of diaphragmatic hernia, it is rare for them to be diagnosed in adulthood and they are often asymptomatic in this population. Case Report We report a case of a 26-year-old female who used cocaine on a weekly basis who presented to the emergency department with an acutely obstructed right-sided Morgagni’s hernia. She underwent laparotomy which demonstrated transverse colon with ischaemic associated omentum inside the hernia. The hernia was reduced, the ischaemic omentum was excised and the 4x4cm diaphragmatic defect closed with 2-0 ethibond without mesh. Conclusions Following review of the literature, the medical risks of cocaine use are well documented, however they focus on the risks from a pharmacological perspective. Further thought should be given to the effects of inhalant cocaine use and how this may exacerbate herniation from the drastic changes in intrathoracic pressure during inhalation of the substance, this is a new possible risk of cocaine use that is not previously mentioned in the literature and warrants further investigation.

Pneumomediastinum in a cannabis smoker precipitated by vigorous sexual intercourse

Primary pneumomediastinum is the presence of air in the interstitium of the mediastinum. The exact aetiology is unclear; nevertheless, it has been reported more frequently in patients with asthma and in individuals who use recreational drugs. It is commonly preceded by a sharp rise in intrathoracic pressure as in a Valsalva-like manoeuvre. We describe a rare case of severe pneumomediastinum with a small pneumothorax related to cannabis smoking and aggravated by vigorous sexual intercourse. The patient was successfully treated conservatively due to clinical and radiological stability and the absence of secondary cause.