Effector mechanisms in the baroreceptor control of blood pressure.

While the effects of changing heart rate and systemic vascular resistance have been generally understood and appreciated, the effects of changes in left ventricular contractility on end-systolic volume may have been less understood and appreciated and the effects of changes in venous capacitance on end-diastolic volume may have been unknown to many readers. Herein, we have provided a brief review for the medical student and beginning graduate student highlighting these sometimes-complex relationships.

Technical Report: Reducing Lens Fogging Associated with Patient Mask Wearing with Heated Diagnostic Fundoscopy Lenses.

Significance: Severe acute respiratory syndrome coronavirus 2 has indirectly created challenges to the ophthalmic retinal examinations because of lens fogging related to patients wearing masks. To date, there are no objective data on the degree of diagnostic ophthalmic lens fogging associated with mask wearing or on the effectiveness of proposed solutions to ophthalmologic lens fogging.

Purpose: The purposes of this study were to investigate the degree of ophthalmologic lens fogging in patients wearing masks and to assess the efficacy lens warming in reducing lens fogging and facilitating ophthalmologic retinal examinations.

Cardiopulmonary physiology: why the heart and lungs are inextricably linked.

Because the heart and lungs are confined within the thoracic cavity, understanding their interactions is integral for studying each system. Such interactions include changes in external constraint to the heart, blood volume redistribution (venous return), direct ventricular interaction (DVI), and left ventricular (LV) afterload. During mechanical ventilation, these interactions can be amplified and result in reduced cardiac output.

A pharmacologic activator of endothelial KCa channels increases systemic conductance and reduces arterial pressure in an anesthetized pig model.

SKA-31, an activator of endothelial KCa2.3 and KCa3.1 channels, reduces systemic blood pressure in mice and dogs, however, its effects in larger mammals are not well known.

Corresponding Ganglion Cell Atrophy in Patients With Postgeniculate Homonymous Visual Field Loss.

Background: The goal of our study was to look for the presence of homonymous ganglion cell layer-inner plexiform layer complex (GCL-IPL) thinning using spectral-domain optical coherence tomography (SD-OCT) in patients with a history of adult-onset injury to the postgeniculate pathways with rigorous radiological exclusion of geniculate and pregeniculate pathology.

Methods: We performed a retrospective review of twenty-two patients (ages 24-75 y, 6 men, 16 women) with homonymous visual field (VF) defects secondary to postgeniculate injury examining the GCL-IPL with SD-OCT. An additional fifteen patients (ages 28-85 y, 5 men, 10 women) with no visual pathway pathology served as controls.

Expanding application of the Wiggers diagram to teach cardiovascular physiology.

Dr. Carl Wiggers' careful observations have provided a meaningful resource for students to learn how the heart works. Throughout the many years from his initial reports, the Wiggers diagram has been used, in various degrees of complexity, as a fundamental tool for cardiovascular instruction.

High-frequency oscillatory ventilation versus conventional ventilation: hemodynamic effects on lung and heart.

Abstract High-frequency oscillatory ventilation (HFOV) may improve gas exchange in patients who are inadequately ventilated by conventional mechanical ventilation (CV); however, the hemodynamic consequences of switching to HFOV remain unclear. We compared the effects of CV and HFOV on pulmonary vascular conductance and left ventricular (LV) preload and performance at different airway and filling pressures. In anesthetized dogs, we measured LV dimensions, aortic and pulmonary artery (PA) flow, and mean airway ( AW) and pericardial pressures.

Mechanism of loss of consciousness during vascular neck restraint.

Vascular neck restraint (VNR) is a technique that police officers may employ to control combative individuals. As the mechanism of unconsciousness is not completely understood, we tested the hypothesis that VNR simply compresses the carotid arteries, thereby decreasing middle cerebral artery blood flow. Twenty-four healthy police officers (age 35 ± 4 yr) were studied.

Volume loading reduces pulmonary vascular resistance in ventilated animals with acute lung injury: evaluation of RV afterload.

During mechanical ventilation, increased pulmonary vascular resistance (PVR) may decrease right ventricular (RV) performance. We hypothesized that volume loading, by reducing PVR, and, therefore, RV afterload, can limit this effect. Deep anesthesia was induced in 16 mongrel dogs (8 oleic acid-induced acute lung injury and 8 controls).

Inconsistencies between actual and estimated blood alcohol concentrations in a field study of college students: do students really know how much they drink?

Background: Alcohol use by college students is commonly measured through the use of surveys. The validity of such data hinge on the assumption that students are aware of how much alcohol they actually consume. Recent studies call this assumption into question.

College students lack knowledge of standard drink volumes: implications for definitions of risky drinking based on survey data.

Background: College students tend to pour single servings of beer and liquor that are larger than commonly used standards. The reasons for this are unknown. Students might overpour because they lack knowledge of standard serving sizes.

RV filling modulates LV function by direct ventricular interaction during mechanical ventilation.

During mechanical ventilation, phasic changes in systemic venous return modulate right ventricular output but may also affect left ventricular function by direct ventricular interaction. In 13 anesthetized, closed-chest, normal dogs, we measured inferior vena cava flow and left and right ventricular dimensions and output during mechanical ventilation, during an inspiratory hold, and (during apnea) vena caval constriction and abdominal compression. During a single ventilation cycle preceded by apnea, positive pressure inspiration decreased caval flow and right ventricular dimension; the transseptal pressure gradient increased, the septum shifted rightward, reflecting an increased left ventricular volume (the anteroposterior diameter did not change); and stroke volume increased.

Ventricular interaction during mechanical ventilation in closed-chest anesthetized dogs.

The cardiac effects of positive pressure ventilation and positive end-expiratory pressure are incompletely understood. External constraint due to increased intrathoracic pressure decreases left ventricular end-diastolic volume; the effects on venous return and ventricular interaction are less clear. Phasic changes in inferior vena caval flow, end-diastolic ventricular dimensions and output were measured in seven anesthetized, ventilated normal dogs.