Pressure never sucks, pressure only pushes: a physiological exploration of the pushing power of pressure.

The movement of air into and out of the lungs is facilitated by changes in pressure within the thoracic cavity relative to atmospheric pressure, as well as the resistance encountered by airways. In this process, the movement of air into and out of the lungs is driven by pressure gradients established by changes in lung volume and intra-alveolar pressure. However, pressure never sucks! The concept that pressure never sucks, pressure only pushes encapsulates a fundamental principle in the behavior of gases. This concept challenges common misconceptions about pressure, shedding light on the dynamic forces that govern the movement of gases. In this Illumination, we explore the essence of this concept and its applications in pulmonary ventilation. Pressure is one of the most important concepts in physics and physiology. Atmospheric pressure at sea level is equal to 1 atmosphere or around 101,325 Pascal [Pa (1 Pa = 1 N/m2)]. This huge pressure is pushing down on everything all the time. However, this pressure is difficult to understand because we do not often observe the power of this incredible force. We used five readily available, simple, and inexpensive demonstrations to introduce the physics and power of pressure. This extraordinarily complex physics concept was approached in a straightforward and inexpensive manner while still providing an understanding of the fundamental concepts. These simple demonstrations introduced basic concepts and addressed common misconceptions about pressure.NEW & NOTEWORTHY The concept that pressure never sucks, pressure only pushes challenges common misconceptions about pressure, shedding light on the dynamic forces that govern the movement of gases. In this Illumination, we will explore the essence of this concept and its applications in pulmonary ventilation. Specifically, we used five readily available, simple, inexpensive demonstrations to introduce the physics and power of pressure.

We used to get money to teach students, now we teach students to get money: medical education has become a market with credentials not knowledge the commodity!

Preclinical medical education has lost its way. In fact, it seems that preclinical medical education has forgotten its mission and has become focused on assembly line efficiency and profits. Administrators and students are increasingly considering preclinical medical education as a market with credentials (access to USMLE Step 1 or COMLEX Level 1) the commodity and students the consumers. Consider that, once banned, for-profit medical schools are on the rise in the United States. In response to these changes, medical schools are adopting corporate models, cutting costs, and seeking profit-making opportunities. One example is the broadcasting of content to multiple sites and satellite campuses. In addition, the customers need to feel satisfied with the educational experience bought for them at high tuition costs. However, providing students with what they want often happens at the expense of what they need, and administrators engage in subtle pandering to students. Furthermore, although the pursuit of credentials is understandable, a university is more than a factory that produces diplomas and careers. Universities exist to educate, discover, and impart knowledge while impacting our ways of living and thinking. In this context, universities exist for the greater good and betterment of societies. The "corporatization" of medical education and satisfying the customer creates an environment where a university is selling socioeconomic stability, professional status, and success, rather than a setting for the formation of character, intellect, and critical thinking. Our hope is that administrators, educators, and students will reconnect to the greater purpose and value of learning.NEW & NOTEWORTHY We should be preparing future physicians to deliver the care we want to receive as patients. This requires training in communication, collaboration, inquiry, discovery, and innovation while developing the habits of the mind and heart that advance the practice of medicine and the health of the public. However, the current "corporatization" of medical education is failing to accomplish this outcome. Specifically, medical schools are adopting corporate models, cutting costs, and seeking profit-making opportunities without improving what goes on in the classroom. Our hope is that we will reconnect to the greater purpose and value of learning.

"Seeing red" reflects hemoglobin's saturation state: a discovery-based activity for understanding the science of pulse oximetry.

Pulse oximetry has become the standard of care in operating rooms, intensive care units, and hospitals worldwide. A pulse oximeter continuously and noninvasively monitors the functional oxygen saturation of hemoglobin in arterial blood ([Formula: see text]). [Formula: see text] is so important in medical care that it is often regarded as a fifth vital sign. Before pulse oximetry, arterial puncture for blood gas analysis was the only method available to determine [Formula: see text] and to identify the presence of hypoxemia. Pulse oximetry is based on the principle that oxygenated hemoglobin (O2Hb) absorbs more near-infrared light than deoxyhemoglobin (HHb) and HHb absorbs more red light than O2Hb. It is important to understand the principles of pulse oximetry, how the equipment works, and its limitations to interpret the information it provides. Accordingly, we used colored balloons to introduce the physics of how a pulse oximeter detects and measures oxyhemoglobin and deoxyhemoglobin in pulsatile (arterial) and nonpulsatile (venous and capillary) blood. The foundations of oximetry started in the 1700s with Johann Lambert (1728-1777). We approached this complex physics in a straightforward way while still providing an understanding of the fundamental concepts developed by Johann Lambert in 1760.NEW & NOTEWORTHY Educators must go beyond teaching the facts and encourage students to think, investigate, and appreciate the subject matter in a broader framework. To achieve these goals, we used a simple and inexpensive experimental approach to introduce the physics of how a pulse oximeter detects and measures oxyhemoglobin and deoxyhemoglobin in blood. We approached this complex physics in a straightforward way while still providing an understanding of the fundamental concepts developed by Johann Lambert in 1760.

Critical skill of teaching: learning the cognitive and emotional states of our students during class.

There has been an increased reliance on prerecorded lectures as a source of learning in place of live lectures in higher education. However, we must appreciate that our students send countless intended and unintended messages during class that relate to their cognitive and emotional states. Shaping productive learning experiences requires understanding their cognitive and emotional states by interpreting their statements, actions, and body language in real time. This can only occur with face-to-face instruction and makes it possible to tailor the class to the students' needs. Becoming aware of the students' cognitive and emotional state by listening and learning their body language is fundamental to teaching, as it will alert educators to cognitive effort and attention, surprise, or uncertainty, as well as a range of emotions, including confusion. Without an understanding of the students cognitive and emotional states, we lose our ability to structure conversations or to reinforce difficult concepts and important ideas in real time. We also lose our ability to adjust on the fly and modify instruction on the basis of the needs of our students. Thus, learning the cognitive and emotional states of our students during class is an essential skill of teaching and the critical means that a teacher uses to promote understanding and positive attitudes about education.

The racist "one drop rule" influencing science: it is time to stop teaching "race corrections" in medicine.

Glomerular filtration rate (GFR) is a key index of renal function. The classic method for assessing GFR is the clearance of inulin. Several current methods using isotopic (125I-iothalamate, 51Cr-EDTA, or 99Tc-DTPA) or nonisotopic (iohexol or iothalamate) markers are available. Clinically, GFR is estimated (eGFR) from serum creatinine or cystatin C levels. Estimated GFR based on creatinine and/or cystatin are less accurate than measured GFR. The creatinine-based equations calculate higher eGFR values (suggesting better kidney function) for black individuals. This upward adjustment for all black individuals is embedded in eGFR calculations on the belief of higher serum creatinine concentrations among black individuals than among white individuals. Thus "race-corrected" eGFR has become a widely accepted and scientifically valid procedure. However, race is not a genetic or biological category. Rather, race is a social construction defined by region-specific cultural and historical ideas. Furthermore, there is no accepted scientific method for classifying people as black or white individuals. Studies typically rely on self-identification of race. However, any person in the United States with any known black ancestry is considered to be a black individual. This is known as the "one-drop rule," meaning that a single drop of "black blood" makes anyone a black individual. It does not matter if an individual has 50%, 25%, 5%, or 0.5% African ancestry. The limited accuracy and reliability of this approach would not be allowed for any other scientific variable. Admixture and migration have produced such broad variations that race categories should not be used as experimental variables.

Spinal cord injury alters purinergic neurotransmission to mesenteric arteries in rats.

Complications associated with spinal cord injury (SCI) result from unregulated reflexes below the lesion level. Understanding neurotransmission distal to the SCI could improve quality of life by mitigating complications. The long-term impact of SCI on neurovascular transmission is poorly understood, but reduced sympathetic activity below the site of SCI enhances arterial neurotransmission (1). We studied sympathetic neurovascular transmission using a rat model of long-term paraplegia (T2-3) and tetraplegia (C6-7). Sixteen weeks after SCI, T2-3 and C6-7 rats had lower blood pressure (BP) than sham rats (103 ± 2 and 97 ± 4 vs. 117 ± 6 mmHg, P < 0.05). T2-3 rats had tachycardia (410 ± 6 beats/min), and C6-7 rats had bradycardia (299 ± 10 beats/min) compared with intact rats (321 ± 4 beats/min, P < 0.05). Purinergic excitatory junction potentials (EJPs) were measured in mesenteric arteries (MA) using microlectrodes, and norepinephrine (NE) release was measured using amperometry. NE release was similar in all groups, while EJP frequency-response curves from T2-3 and C6-7 rats were left-shifted vs. sham rats. EJPs in T2-3 and C6-7 rats showed facilitation followed by run-down during stimulation trains (10 Hz, 50 stimuli). MA reactivity to exogenous NE and ATP was similar in all rats. In T2-3 and C6-7 rats, NE content was increased in left cardiac ventricles compared with intact rats, but was not changed in MA, kidney, or spleen. Our data indicate that peripheral purinergic, but not adrenergic, neurotransmission increases following SCI via enhanced ATP release from periarterial nerves. Sympathetic BP support is reduced after SCI, but improving neurotransmitter release might maintain cardiovascular stability in individuals living with SCI.NEW & NOTEWORTHY This study revealed increased purinergic, but not noradrenergic, neurotransmission to mesenteric arteries in rats with spinal cord injury (SCI). An increased releasable pool of ATP in periarterial sympathetic nerves may contribute to autonomic dysreflexia following SCI, suggesting that purinergic neurotransmission may be a therapeutic target for maintaining stable blood pressure in individuals living with SCI. The selective increase in ATP release suggests that ATP and norepinephrine may be stored in separate synaptic vesicles in periarterial sympathetic varicosities.

Electrify your class with a simple battery: battery demonstration of electrocardiogram vectors.

William Arthur Ward stated, "The mediocre teacher tells. The good teacher explains. The superior teacher demonstrates. The great teacher inspires." Discovery experimentation is an inductive method that demonstrates and inspires by creating an interest in determining the underlining basis of a phenomenon. This experiential approach also fosters motivation and enhances learning. Starting with what the student knows augments this approach. By starting with what the student already knows, the student can consciously and explicitly link the subsequent new information with previous knowledge. Accordingly, we used a simple battery as an analogy for electrocardiogram vectors to introduce the theoretical physics of how the heart produces voltages that are detectable at the body surface. This extraordinarily complex physics was approached in a straightforward and inexpensive way while still providing an understanding of the fundamental concepts developed by Willem Einthoven in 1895.

First African-American to hold a medical degree: brief history of James McCune Smith, abolitionist, educator, and physician.

Dr. James McCune Smith, the first African-American to obtain a medical degree, has a remarkable legacy of historical proportions, yet his immense impact on society remains relatively unknown. He may be most celebrated for his effectiveness in abolitionist politics, however, his pioneering influence in medicine is equally remarkable. As examples, McCune Smith pioneered the use of medically based statistics to challenge the notion of African-American racial inferiority. He scientifically challenged the racial theories promoted in Thomas Jefferson's Notes on the State of Virginia (Jefferson T., 1832), and he was a harsh critic of phrenology (study of the shape and size of the cranium as a supposed indication of character and mental abilities). Furthermore, notwithstanding being denied entry to America's universities and medical societies because of his race, McCune Smith became a giving physician to orphans, an accomplished statistician, medical author, and social activist who worked to end slavery. His pioneering work debunked doubts about the ability of African-Americans to transition into free society. Specifically, he used his training in medicine and statistics to refute the arguments of slave owners and prominent thought leaders that African-Americans were inferior and that slaves were better off than free African-Americans or white urban laborers. Frederick Douglass, narrator of the Anti-Slavery Movement, cited Dr. James McCune Smith as the single most important influence on his life. Dr. McCune Smith, along with Frederick Douglass, Gerrit Smith, John Brown and other intellectual pioneers of the time, were instrumental in making the elimination of slavery possible.

Science reflects history as society influences science: brief history of "race," "race correction," and the spirometer.

Spirometers are used globally to diagnose respiratory diseases, and most commercially available spirometers "correct" for race. "Race correction" is built into the software of spirometers. To evaluate pulmonary function and to make recordings, the operator must enter the subject's race. In fact, the Joint Working Party of the American Thoracic Society/European Respiratory Society recommends the use of race- and ethnic-specific reference values. In the United States, spirometers apply correction factors of 10-15% for individuals labeled "Black" and 4-6% for people labeled "Asian." Thus race is purported to be a biologically important and scientifically valid category. However, history suggests that race corrections may represent an implicit bias, discrimination, and racism. Furthermore, this practice masks economic and environmental factors. The flawed logic of innate, racial difference is also considered with disability estimates, preemployment physicals, and clinical diagnoses that rely on the spirometer. Thomas Jefferson's Notes on the State of Virginia (1832) may have initiated this mistaken belief by noting deficiencies of the "pulmonary apparatus" of blacks. Plantation physicians used Jefferson's statement to support slavery, believing that forced labor was a way to "vitalize the blood" of deficient black slaves. Samuel Cartwright, a Southern physician and slave holder, was the first to use spirometry to record deficiencies in pulmonary function of blacks. A massive study by Benjamin Apthorp Gould (1869) during the Civil War validated his results. The history of slavery created an environment where racial difference in lung capacity become so widely accepted that race correction became a scientifically valid procedure.

Humor, laughter, learning, and health! A brief review.

Human emotions, such as anxiety, depression, fear, joy, and laughter, profoundly affect psychological and physiological processes. These emotions form a set of basic, evolved functions that are shared by all humans. Laughter is part of a universal language of basic emotions that all humans recognize. Health care providers and educators may utilize the power of laughter to improve health and enhance teaching and learning. This is an important consideration because teaching is not just about content: it is also about forming relationships and strengthening human connections. In this context, when used effectively, humor is documented to build relationships and enhance performance. Specifically, humor improves student performance by attracting and sustaining attention, reducing anxiety, enhancing participation, and increasing motivation. Moreover, humor stimulates multiple physiological systems that decrease levels of stress hormones, such as cortisol and epinephrine, and increase the activation of the mesolimbic dopaminergic reward system. To achieve these benefits, it is important to use humor that is relevant to the course content and not disparaging toward others. Self-effacing humor illustrates to students that the teacher is comfortable making mistakes and sharing these experiences with the classroom. In this brief review, we discuss the history and relationship between humor, laughing, learning, and health with an emphasis on the powerful, universal language of laughter.

Intellectual development is positively related to intrinsic motivation and course grades for female but not male students.

We hypothesized that the intellectual development of students, i.e., their beliefs about the nature of knowledge and learning, affects their intrinsic motivation and class performance. Specifically, we hypothesized that students with low intellectual development (i.e., the naive beliefs that knowledge is simple, absolute, and certain) have low intrinsic motivation and low class performance, whereas students with high intellectual development (i.e., more sophisticated beliefs that knowledge is complex, tentative, and evolving) have high intrinsic motivation and class performance. To test this hypothesis, we administered the Learning Context Questionnaire to measure intellectual development. In addition, we administered the Intrinsic Motivation Inventory to assess our students' intrinsic motivation. Furthermore, we performed regression analyses between intellectual development with both intrinsic motivation and class performance. The results document a positive relationship among intellectual development, intrinsic motivation, and class performance for female students only. In sharp contrast, there was a negative relationship between intellectual development, intrinsic motivation, and class performance for male students. The slope comparisons documented significant differences in the slopes relating intellectual development, intrinsic motivation, and class performance between female and male students. Thus, female students with more sophisticated beliefs that knowledge is personally constructed, complex, and evolving had higher intrinsic motivation and class performance. In contrast, male students with the naive beliefs that the structure of knowledge is simple, absolute, and certain had higher levels of intrinsic motivation and class performance. The results suggest that sex influences intellectual development, which has an effect on intrinsic motivation for learning a specific topic.

Cardiac electrophysiology and the susceptibility to sustained ventricular tachycardia in intact, conscious mice.

Cardiac electrophysiological dysfunction is a major cause of death in humans. Accordingly, electrophysiological testing is routinely performed in intact, conscious, humans to evaluate arrhythmias and disorders of cardiac conduction. However, to date, in vivo electrophysiological studies in mice are limited to anesthetized open-chest or closed-chest preparations. However, cardiac electrophysiology in anesthetized mice or mice with surgical trauma may not adequately represent what occurs in conscious mice. Accordingly, an intact, conscious murine model of cardiac electrophysiology has the potential to be of major importance for advancing the concepts and methods that drive cardiovascular therapies. Therefore, we describe, for the first time, the use of an intact, conscious, murine model of cardiac electrophysiology. The conscious mouse model permits measurements of atrioventricular interval, sinus cycle length, sinus node recovery time (SNRT), SNRT corrected for spontaneous sinus cycle, Wenckebach cycle length, the ventricular effective refractory period (VERP) and the electrical stimulation threshold to induce sustained ventricular tachyarrhythmias in an intact, complex model free of the confounding influences of anesthetics and surgical trauma. This is an important consideration because anesthesia and surgical trauma markedly reduced cardiac output and heart rate as well as altered cardiac electrophysiology parameters. Most importantly, anesthesia and surgical trauma significantly increased the VERP and virtually eliminated the ability to induce sustained ventricular tachyarrhythmias. Accordingly, the methodology allows for the accurate documentation of cardiac electrophysiology in complex, conscious mice and may be adopted for advancing the concepts and ideas that drive cardiovascular research.

The flipped exam: creating an environment in which students discover for themselves the concepts and principles we want them to learn.

Students are naturally curious and inquisitive with powerful intrinsic motives to probe, learn, and understand their world. Accordingly, class activities must capitalize on this inherently energetic and curious nature so that learning becomes a lifelong activity where students take initiative for learning, are skilled in learning, and want to learn new things. This report describes a student-centered class activity, the "flipped exam," designed to achieve this goal. The flipped exam was a collaborative, group effort, and learning was interactive. It included a significant proportion (∼30-35%) of material not covered in class. This required students to actively search for content and context, dynamically making connections between what they knew and what they learned, grappling with complexity, uncertainty, and ambiguity, and finally discovering answers to important questions. Accordingly, the need or desire to know was the catalyst for meaningful learning. Student assessment was determined by behavioral noncognitive parameters that were based on the observation of the student and the student's work as well as cognitive parameters (i.e., the student's score on the examination). It is our view that the flipped exam provided a student-centered activity in which students discovered, because of the need to know and opportunities for discussion, the important concepts and principles we wanted them to learn.

Cardiac output, at rest and during exercise, before and during myocardial ischemia, reperfusion, and infarction in conscious mice.

Multiple systems and regulatory strategies interact to control cardiac homeostasis. In fact, regulated systems, feedback controls, and redundant control mechanisms dominate in whole animals. Accordingly, molecular and cellular tools and techniques must be utilized in complex models with multiple systems and regulatory strategies to fully appreciate the physiological context. Currently, these techniques are mainly performed under conditions remote from the normal in vivo condition; thus, the extrapolation of molecular changes to the in vivo situation and the facilitation of translational aspect of the findings are limited. A major obstacle has been the reliance on preparations that do not mimic the clinical or physiological situation. This is particularly true regarding measurements of cardiac function in mice. To address these concerns, we used a permanently implanted Doppler ultrasonic flow probe on the ascending aorta and coronary artery occluder for repeated measurements of ascending aortic blood flow (cardiac output) in conscious mice, at rest and during exercise, before and during coronary artery occlusion/reperfusion and infarction. The conscious mouse model permits detailed monitoring of within-animal changes in cardiac function during myocardial ischemia, reperfusion, and infarction in an intact, complex model free of the confounding influences of anesthetics, surgical trauma, and restraint stress. Results from this study suggest that previous protocols may have overestimated resting baseline values and underestimated cardiac output reserve. Using these procedures in currently available spontaneous or engineered mouse mutants has the potential to be of major importance for advancing the concepts and methods that drive cardiovascular research.

Higher levels of intrinsic motivation are related to higher levels of class performance for male but not female students.

Our students are naturally curious, with powerful intrinsic motives to understand their world. Accordingly, we, as teachers, must capitalize on this inherently active and curious nature so that learning becomes a lifelong activity where students take initiative for learning, are skilled in learning, and want to learn new things. Achieving this goal requires an understanding of student attitudes, beliefs, characteristics, and motivations. To achieve this goal, we administered the intrinsic motivation inventory (IMI) to assess our students' interest and enjoyment, perceived choice, and perceived competence while taking our undergraduate exercise physiology class (46 students; 20 female students and 26 male students). The interest and enjoyment subscale is considered the self-reported measure of intrinsic motivation. The perceived choice and perceived competence concepts are theorized to be positive predictors of both self-reported and behavioral measures of intrinsic motivation. Our results documented a significant increase in course grade with an increase in survey score for the interest and enjoyment subscale of the IMI when female and male students were combined. Specifically, each increase in survey score for the interest and enjoyment subscale of the IMI was associated with a significant (P < 0.05) increase of 3.9% in course grade. However, the increase in survey score was associated with a significantly greater (P < 0.05) increase in course grade for male (6.1%) compared with female (0.3%) students. These results have implications for both classroom practice and educational reform policies.