https://doi.org/10.36866/pn.123.28

Dr Katherine MA Rogers, Queen’s University Belfast, UK

Deirdre Boyle, Queen’s University Belfast, UK

Kate Bennett, Queen’s University Belfast, UK

Maggie Bennett, Queen’s University Belfast, UK

Dr Christopher Torrens, Royal College of Surgeons, Dublin, Ireland

Physiology can be quite a numerical subject. We think of rates (heart, respiratory, filtration), volumes (stroke volume, tidal volume, body fluid volume) and concentrations (plasma hormones, intra vs. extracellular Na+ and K+) as we describe the homeostatic mechanisms that control and maintain these values. They provide a framework through which we can talk about hyperkalaemia, hypovolaemia, or tachypnoea; but they also provide a means to look at variation and think about what is “normal”.

Physiology teaching using the “textbook person”

One of the common ideas in physiology is that of the “textbook person”, the archetypal character that exists in textbooks as a paradigm of normality. On first encounter, this sounds a bit like the average person (l’homme moyen) put forward to some controversy by Aldophe Quetelet (1842), but it is not really. Instead, the textbook person is drawn from a much smaller sample size, with very specific criteria – he is male, aged 21-25 and weighs 70 kg and from the repeated observations of one of the authors, he occurs at a rate of ~0.5% in a typical, undergraduate medical cohort. On one hand, the scarcity of such an individual is a positive, allowing for the selection of a single individual from a cohort to embody cardiac output or a similar variable. On the other, it wholly excludes 99.5% of that
population so in those terms what does a statement such as “cardiac output is approximately 5 L/min” actually mean?

For a number of parameters like plasma electrolytes, or glucose and vitamin D, most “normal” values are given as a range. In most cases these are calculated from the mean of a representative sample and the range calculated as plus and minus 1.96 standard deviations from the mean (to include 95% of the population). Since, by definition, 5% of normal values will lie outside the range, these now tend to be referred to as reference ranges rather than normal ranges. This too goes back to Quetelet who showed that many human traits were normally distributed around the mean. Quetelet was an interesting character, not only as a pioneer of statistics but he also developed the idea for body mass index (Eknoyan, 2008).

In a previous edition of Physiology News, Ord (2019) highlighted the differences in cardiovascular variables across childhood, while Strait and Lakatta (2012) have elsewhere highlighted the changes in structure and function that occur in the ageing population. In a population of over 2000 Chinese individuals, Cattermole et al. (2017) highlighted the change in a number of cardiovascular variables including cardiac output across the life course (data shown in Table 1).

Despite this large variation, the idea of a “normal” value can be useful. If we think of our “textbook” cardiac output, we can think of the situations that may alter this and the homeostatic controls that bring it back to normal. Indeed, we often think about cardiac output in terms of changes in exercise and/ or heart failure. However, while physiology is crucial for maintaining our own “normal” values it is also crucial in setting them in the first place, as many variables are dependent on physiology. As depicted in Table 1, age has a significant impact on cardiac output, but, along with other factors, it is also affected by sex, genetics, environment and diet.

Cattermole et al. (2017) showed an apparent sex difference in cardiac output, with male individuals having larger outputs than female individuals. However, this disappeared when corrected for weight;
instead, rather than a sex difference, cardiac output increases as weight increases. The data from weight ranges are also shown (Table 2). Similarly, a supposed sex difference in exercise limitation
has been shown to disappear when lung size is taken into account (Boseman et al., 2017). These data show that a person’s height, weight as well as environment can also impact on other physiological
variables. For example, when considering haemoglobin concentration, altitude is an important consideration. Similarly, the latitude of your population is likely to impact on the “normal” vitamin D levels.

Another example that has raised a lot of media attention recently is that of serum creatinine, used to calculate the estimated glomerular filtration rate (eGFR). Creatinine is a breakdown product of creatine phosphate in muscle. It is released by muscles and filtered and excreted by the kidneys. The serum creatinine measured is therefore a function of how much is produced (the muscle mass) and
how much is cleared (renal filtration), so if it is to tell you anything about glomerular filtration rate (GFR) then it needs to take muscle mass into account. There are a number of algorithms that estimate GFR from serum creatinine but mass (and certainly muscle mass) is rarely available so proxies are employed. Age, sex, and weight can make these estimates more accurate but the inclusion of race in these has recently caused some concern, not least in how a social construct like race impacts on a biological process (Vyas et al., 2020). The inclusion of the race factor leads to a significant increase in the estimated kidney function possibly missing some reduced function, while exclusion of the correction factor may underestimate renal function (Levey et al., 2020).

Crucial here is the lack of a genetic race difference (Birney et al., 2021), highlighted poignantly with the case of the Biggs twins (Edwards, 2018). Any arbitrary creation of groups will lead to perceived differences, but these could easily just be artefacts or the result of confounding biological or sociodemographic factors, just as supposed sex differences discussed above were really an issue of weight or lung size.

If the idea of the textbook person has value as a reference point to help teach physiology, then perhaps it should cease to be the definite article and become a textbook person instead. Whether it persists with the 22-year-old, 70 kg male or we choose instead a 56-year-old, 80 kg female, it does not really matter so long as we keep in mind that it is just one version of normal from a myriad of others on offer.

Integrating equality, diversity and inclusion to the physiology curricula

Educators on healthcare courses need to provide an educational experience that equips students with the knowledge and expertise to (verbally and non-verbally) interact with and care for patients while being mindful and respectful of inclusion, diversity and equality issues. Lots of studies discuss the integration of cultural awareness in nursing and medical education, and such advances in these programmes are widely recognised (Leung et al., 2020), yet most studies focus on the sociology themes of equality, diversity and inclusion (EDI) awareness for healthcare practice.

Perhaps these sociology themes that underpin a significant portion of pre-registration nursing and medical training are not adequate to equip students with the awareness of EDI issues in the clinical setting. Should responsibility also lie within life science components of the curriculum to encourage students to consider the links between cultural EDI issues and a patient’s physiological differences? This is not a new hypothesis – it was cited by Beagan (2003) – but does the fact that we are still discussing it suggest that little progress has been made in the intervening years?

Case-based scenarios are a tried and trusted way to teach students physiology. However, we ought to recognise that the educational scenarios we provide may not represent the diversity of patients our students are likely to care for. In teaching physiology, we need to be reflective and aware of the bias in our stereotyping of patients (Bleakley and Bligh, 2008) and proactively champion EDI. Co-developed real-patient cases, informed by research, should be included to embed EDI in our curricula. Table 3 illustrates how we can tweak aspects of the case study to be more inclusive.

In our physiology teaching we highlight examples of diversity within risk factors during lectures and use them as prompts for more detailed discussions that integrate EDI consideration in tutorials. We also included these differences in risk factors to some of our assessment questions.

We probed the issue of EDI in physiology teaching among nursing and medical students using the following questions (distributed by email). Despite being students on different courses (who have never met) it was interesting to note the similarities in their answers.

Student perspectives

The interviewees are Deirdre Boyle, a final-year nursing student, and Kate Bennett, a year 2 medical student.

Do you think your physiology education has adequately equipped you to deal with issues of EDI in the clinical setting?

Deirdre Boyle (DB): Our life sciences education has given us a good foundation into the awareness of how certain conditions can be more prevalent in various ethnic groups. Distinguishing between genetic input and other determinants of health can then direct how we help to educate and empower our patients, so that better outcomes are achieved.

Kate Bennett (KB): Case-based learning is a new form of teaching and learning introduced by the School of Medicine in September 2020. The cases challenged us as a team to work through clinical scenarios, consider communication with patients and colleagues, and appreciate the individual expectations and lifestyles of each patient. The cases were written to represent the demographic of Northern Ireland (NI). For example, one case focused on phenylketonuria (a particularly prevalent genetic disorder in NI), patients working in agriculture and the implications they face with illness, and the cultural diversity within local communities.

The cases brought prescribing guidelines to life for African/Caribbean patients with hypertension, the consideration of sickle cell anaemia amongst Black, Asian, and minority ethnic (BAME) patients, and
the burden of care that multigenerational families bring to patients.

What can we do differently in physiology teaching that might better equip students for clinical practice today and in the future?

KB: It would be beneficial to develop a greater appreciation for the language barrier often experienced in clinical practice and how this impacts the treatment provided. I would like to learn how clinicians overcome communication difficulties and hear the patients’ perspective in these situations. Furthermore, I would be curious to understand more about the increased impact certain illnesses (such as COVID-19) have on BAME patients.

DB: While genetics may only be one factor in why BAME groups have poorer health outcomes, perhaps delving deeper into the role genetics plays could enhance understanding. Allowing for more discussion of these topics during tutorials would be helpful because these discussions give the vital opportunity to ask questions and independently research evidence-based literature. It would also be useful if lecturers included more recommended reading on the topic. From my experience on clinical placements, the big challenge is language barriers and accessing translation services to assist with the nurse/patient relationship. In clinical practice, I think it will entail things like observing how the multi-disciplinary (MD) teams advise various communities and the resources available.

Are there any aspects or examples of physiology teaching that are notable to you as being useful or highlighted EDI issues?

DB: Our life sciences tutorials provided the opportunity to acknowledge that certain conditions were more (or less) prevalent amongst BAME populations. However, perhaps case studies that facilitated more in-depth discussion would be useful. Due to the nature of my placements thus far I have not encountered much cultural diversity among the patient population. However, previous work experience in a maternity and general hospital in India highlighted the worrying trends of increasing numbers of patients with Type 2 diabetes and its resulting effects if poorly controlled. The rising number of pregnant women presenting with gestational diabetes, and its implication for increased instrumental deliveries and Caesarean sections, along with an increased likelihood of developing Type 2 in the future. Overall, maternal death and infant mortality were at a higher rate than the UK; however, the mortality rate among BAME mothers in the UK is greater than among mothers of non-BAME origin. Topics such as these would be interesting to consider further in our physiology
education.

KB: The family attachment scheme (during which we are assigned a family to work alongside for a year) provided us with the invaluable opportunity to gain perspective on living with chronic illness and what it is like to be a patient in the health service. The scheme allowed us to listen to patients whose experiences were impacted by their community, occupation, education, and family. The scheme was like working through a real- life case study in real time and helped us to apply many aspects of what we learned, but also increased our awareness of the impact of EDI issues as they arise in clinical practice.

Conclusion

The student experience of diversity and inclusion issues in the clinical practice setting is variable. So perhaps, when developing new case studies for teaching bioscience subjects to students on health professions courses, we should garner some co-production elements and include student experiences in our teaching. Using more representative case studies in teaching physiology that illustrate the impact of not only age and sex, but also race and socioeconomic class can help students understand unequal health outcomes. Moving beyond single factors to an intersectional approach highlights important differences between groups that are frequently presented as homogeneous – such as men, women, migrants, and minorities (Kapilashrami and Hankivsky, 2018).

As physiology educators we could be clearer about modifiable and non-modifiable factors that contribute to health and disease. Human physiology is predominantly non-modifiable but is significantly influenced by modifiable factors. We need to help students be more aware of these differences in their clinical practice; making our case studies more diverse is a good place to start.

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