Body Temperature - What You've Been Taught is Wrong! (Strong Exam)

A discussion of the assessment and interpretation of body temperature, including problems with thermometer inaccuracies, and common myths about normal temperature and the definition of a fever.
@0:00 Introduction
@0:31 Thermometers and their accuracy
@4:21 Normal range of temperature and definition of a fever
@10:38 Etiologies of fevers and hypothermia
@12:06 Common pitfalls/mistakes
References:
Cutuli SL, et al. Accuracy of non-invasive body temperature measurement methods in adult patients admitted to the intensive care unit: a systematic review and meta-analysis. Crit Care Resusc. 2023; 23:6-13.
Niven DJ, et al. Accuracy of peripheral thermometers for estimating temperature. Ann Intern Med. 2015;163:768-77.
Sund-Levander M, Forsberg C, Wahren LK. Normal oral, rectal, tympanic and axillary body temperature in adult men and women: a systematic literature review. Scand J Caring Sci. 2002; 16:122-8.
Protsiv M, et al. Decreasing human body temperature in the United States since the industrial revolution. Elife. 2020;7:9:e49555.
Pecoraro V, et al. The diagnostic accuracy of digital, infrared and mercury-in-glass thermometers in measuring body temperature: a systematic review and network meta-analysis. Intern Emerg Med. 2021; 16:1071-83.
Mah AJ, et al. Studying the accuracy and function of different thermometry techniques for measuring body temperature. Biology. 2021; 10:1327.
Mackowiak PA, Wasserman SS, Levine MM. A critical appraisal of 98.6 degrees F, the upper limit of the normal body temperature, and other legacies of Carl Reinhold August Wunderlich. JAMA. 1992; 268:1578-80.
Mackowiak PA, Worden G. Carl Reinhold August Wunderlich and the evolution of clinical thermometry. Clin Infect Dis. 1994; 18:458-67.
#physicalexam #osce

[@StrongMed]

Frustratingly, there was an on-screen typo in the first version of this video that I published 18 hrs ago. It may have been a minor issue, but if I didn't fix it, it would annoy me every time someone commented on it in the future. Thus, here is the corrected version. Thanks to @ellertt for pointing it out. There's still a great (IMHO) one-off video coming next Sunday, which as I posted before, has cameos from my 2 favorite people in the world! (And definitely has no typos in it)

[@fajraouihedi5895]

Thanks for the great job

[@warxdrum]

hi, not sure if this is a European or Austrian thing. i learned that main body temp should be 36.5 °C. i myself have always had 35.5 °C and learned that a fever is more than 1 °C up from your usual temperature. not sure where my mother took that from. nobody tested me for hypothyroidism although my body temp was low.

[@fjs1111]

"Thermistor" based thermometers... Sounds like Doctor Strong likes a bit of electrical engineering on the side? 🙂

[@trishoconnor2169]

I have hypothyroidism, and even with medication, my temperature is rarely above 97°F, often 95° or even a bit lower. (95° is usually considered hypothermia.) I have often had the experience of health care professionals who were not already acquainted with me looking at the thermometer and saying "That can't be right," until I tell them I typically run low. I can tell a lot about how helpful they will be to me from how seriously they take my report of my experience. Fortunately, when I was diagnosed with Hodgkins Lymphoma (since cured), my oncologist and his nurses were very good about listening to the patient and putting those self-reports into the big picture. When I first started chemo, they told me their usual rule of thumb for what temperature to call, 24/7 (I think 101°). I asked if it should be any different given my tendency to "run low," and after checking my recent measurement, they settled on 99° as my "call the doctor" temp while on chemo. By the way, I've done immersion in a cold pool and my temp measured as low as 92.4°, and I was still not showing the other signs of hypothermia like clumsiness or confusion. Apparently, my body has gotten pretty used to being cold!

[@claysweetser4106]

I'm curious what the difference between your "true" core body temperature and the one estimated using peripheral readings is. As a layperson, I've always been under the impression that the non-peripheral cells in one's body can really only operate within a certain range, and that outside of that range things start going wrong on a fundamental level; chemical reactions occur too infrequently or frequently, cell walls deform, cellular machinery fails, etc.

[@trishoconnor2169]

@@claysweetser4106 Well, as a fellow medical layperson, I can't speak to what the cell walls are doing, but I can tell you that I have significant fatigue that increased to a disabling level after my stem cell transplant. It wouldn't surprise me at all if my low body temperature is connected with that.

[@malaikamillions]

I have yet to get a diagnosis for my chronic low body temperature which also comes with the symptom cluster associated with hypothyroidism. What is boggling is that when I’m suffering any kind of infection, my body temperature plummets to 95 and much lower. No one can tell me why. You seem to indicate yours raises with ailment, so perhaps my temperature plummeting to hypothermic degree is unique to my other mutant manifestations, like every blood pressure machine sometimes registering zero blood pressure on occasion. It’s baffling when regular diagnostic criteria doesn’t apply, never mind having the opposite reaction to every drug. - La La La Life of a mutant.

[@claysweetser4106]

@@malaikamillions Who knows, maybe you'll manifest some cool mutant superpower, like being able to freeze objects with a touch or something.

[@alakborwen]

My normal temperature usually runs around 96.8F (I was curious on one of my vacation weeks a few years ago and took my temperature three times a day (8am, noon, and 8pm) and then took the average of that and got the 96.8. Whenever I go to the doctor with a fever (usually I’ll wait to see if it gets up to 99.9 before I go) I usually have to argue with the person taking my temperature when they tell me I don’t have a fever, they never want to listen to me when I try to explain that my temperature runs low. It gets very annoying when I’m not feeling well.

[@StrongMed]

That does sound frustrating. Just politely refer them to this video. ;)

[@EKimatH]

What a blessing this video is! A few weeks ago a vsauce short (are people getting hotter? No, they’re getting colder.) video stuck the question in my brain and I couldn’t for the life of me find anything that I could conclusively take as relevant information. It’s so difficult to have hyper specific obscure questions about a field you know nothing about, I am so glad to have ran into this video by complete coincidence. I was sent to your channel by HTCT Ann Reardon,band I am leaving a comment and liking this video to let the algorithm know! Cheers!

[@lmagoddess]

This is so true. Early in covid my work set up a temp guideline of 99.5 F as not allowed to work. Seemed reasonable, until I went in to work and was winded climbing stairs but had a temp of 95.4, so I started work. I felt a little off and a coworker said I didn't look normal. He said I looked "pale but red cheeked." Went back up stairs to HR and couldn't catch my breath but temp was the same so HR gave me the choice of staying or getting tested. My temp went down to 98 something and the clinic nurse was flat rude when I told her my temp runs 1-2 ° low. "That's what everyone says, but at least you got out of work for a few hrs, right?" Her sneer made it clear she wasn't joking. She also was rough with the swab and had both sides of my nose bleeding and me yelling at her from the pain. She "yelled back it wasn't that bad!" And left to run the test. She did not return but the clinic doctor did, she gave me tissues for my bloody nose and explained that I yes I did test positive for covid and also influenza A. She even apologized for the nurses behavior. I must have been running on adrenaline because by the time I had arrived home I felt like death warmed over.

[@hvymtal8566]

At my ambulance company we use the no-contact style. I swear half of them read somewhere between 97.3 and 97.6 F regardless of where you take the temp or what the actual peripheral temp is.

[@WVgirl1959]

Yes, that's why I guard my glass mercury thermometer with my life. 😊

[@anniekate76]

Validation! I have felt before like I had a fever with chills and aches and just feeling feverish, but my actual temperature in the 99F point something range and so was too low for anyone to label it that way!

[@karenmsuk]

Baseline readings are something I do at home, same site, same thermometer, same time of day. I drive my daughter nuts but she has tri and bigeminy so her stats need to be tracked no matter what our last ER doctor told me.

[@jayaramchandrasekar5846]

Great video thanks! I'm definitely guilty of thinking about fever as only 100.5 F and you bring a great argument to change that behavior and trust our patients who have a lower temp

[@mopeyhat6361]

If you can't find any other documentation on the thermometer's reported accuracy, I wouldn't be surprised if it was coming straight from the technical specs of the thermister or other sensor

[@magnanimus9692]

Good points, thanks for the info

[@anthonybevers6066]

The only time I was not hypothermic on a no touch thermometer was when I had a 104 fever (oral) when I got dengue. My temp then was 98.3 on that no touch device.

[@Anggelos876]

Very interesting

[@alirezazakaie1106]

Thank you...we are waiting for new videos

[@caterscarrots3407]

I can attest to the fact that we have different average body temperatures per individual. My mom runs low and my dad runs high(I know that because I remember one time when my mom and I tested our temperatures and I was about 1 degree higher than she was and my dad always feels warm to hug regardless of whether or not he's sick). I'm right at the 98.6 F average. I don't know how much it changes with my cycle, haven't tracked that cause I haven't had to(not trying to get pregnant, not even having sex, so no need to know exactly when that post-ovulatory spike is). For me, there's a difference between mildly elevated temperature due to your normal cold virus and a true fever. Mildly elevated temperature, my head will feel a bit hot, but I'll otherwise feel normal(this is complicated by the fact that I get headaches and the pain from headaches also will cause my head to feel a bit hot, even if my body temperature isn't elevated). True fever, like with the possible COVID I had back in January 2020, I feel a full thermal inversion, with my head, hands, and feet all being hot and my core feeling cold and I'm never comfortable, too warm with a blanket, too cold without.

[@tittytwister8317]

Thank you for the stellar video as always Dr. Strong. would you mind covering Homan's sign if that's possible? In my medical school and during my training at the university hospital it was a very heavily emphasized maneuver and we were taught that not performing it / not reporting doing it is a mistake. however, I read some articles back in the day arguing that's it is useless at best and harmful at worst. Thank you Dr. Strong.

[@partofaheart]

commenting for support

[@dizzyboy92]

I eagerly wait your abdominal exam video.

[@StrongMed]

Spoiler alert: Around half of the maneuvers in the traditionally taught abdominal exam has either no evidence to support them, or has evidence specifically against them.

[@kowalskiplota634]

​@@StrongMed our whole lives have been a lie?

[@StrongMed]

If the physical exam has been your "whole life", then I'm sorry to say this, but yes. ;)

[@joesshows6793]

Ann sent me

[@Respectable_Username]

I'm curious, with smartwatches increasingly containing temperature sensors, would/should docs take the historic readings from a regularly warn watch into account during hospital scenarios, or is the watch too inaccurate for the trend line observed to be useful?

[@StrongMed]

I don't know of any studies that have independent confirmed these devices' accuracy in a "real world" scenario, so that would be my first big question. Also, although in a prior video on body temperature I suggested tracking temperatures in individuals over time to more accurately identify when a specific person's temperature falls above their own normal range, I don't know of any studies that have looked at the clinical utility of such an approach. So in short, the ability of a smartwatch to measure temperature seems at best unproven.

[@Streetpfosten]

Now do one on when and how to lower a fever. Lots to cover there as well!

[@zuhairyassin505]

medicine does not make sense at all

[@kitefan1]

Being a mechanical sort, I used to think medicine was a science. Age of Enlightenment medical models or hypotheses of humans, like Harvey on heart circulation were pretty mechanical, which the basis of the circulatory system is. So, as far as I can tell, as a non-medical, all of the traditional disease categories are based on symptoms. The only thing that I see that Diabetes Type 1 and Type 2 have in common is that they involve insulin and that blood sugars are affected by food intake and activities. The causes at the beginning are completely different. But it humans are also biological. Bio things are very complicated, change constantly and each human is a closed system that argues. The blood is a mixture of multiple fluid and particle-ish substances that change as they circulate around. So yeah, heart pumps blood, but blood is even more difficult than pond water to pump. I can take a pond pump apart and clean out the weeds, mud, rock, plastic bags or whatever and repair the broken bits then all good for a while. Before X-Ray no-one could see inside people at all without making incisions and before anesthetic that was very difficult so all of the diagnoses were derived from watching what effected the humans and autopsying the deceased ones. It was only in 1981 that natriuretic factor that promotes kidney excretion of salt and water, in rats, was first reported (Humans followed, of course.) Medicine uses scientific tools to see what properties the human has a point in time. They are still diagnosing what is inside the opaque, very complicated skin and using those clues to figure out how to treat the problem. Often, they are still treating the symptoms to make our lives better.