Analysis of thermometer types and basic knowledge about body temperature measurement

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Analysis of thermometer types and basic knowledge about body temperature measurement I. Origin and types of thermometers The first use of thermometers in clinical settings dates back to the 18th century, when the Dutch scientist Burghavé invented the mercury thermometer. In 1851, the German scientist Windlich discovered that certain diseases were associated with specific changes in body temperature. In 1867, hospitals in Britain began using thermometers for routine temperature measurement. Currently, in addition to mercury thermometers, there are also various types of thermometers developed based on different principles, such as electronic thermometers, ear thermometers, infrared thermometers, and liquid crystal thermometers. 　　A mercury thermometer is made of glass and contains mercury; based on the principle that mercury expands as temperature rises, the mercury column rises as the temperature increases. Temperature is directly proportional to the rise in the mercury column. Its advantages are relatively high accuracy and low cost. The test range for adults is 35.0–42.0°C, while for premature infants it is 32.0–42.0°C. The disadvantages are that it is troublesome to check the results, it is fragile, and mercury can evaporate at room temperature once it leaks out, causing nerve poisoning. The United States no longer produces mercury thermometers. 　　Electronic thermometers allow for digital reading, which is quite convenient. There are two types: actual-measurement electronic thermometers and predictive electronic thermometers. The former, like mercury thermometers, requires 5 to 10 minutes for measurement and features accuracy and safety ； The latter has the drawbacks mentioned earlier and is not suitable for home use. 　　Infrared thermometers were widely used during the SARS outbreak; they come in the form of ear-mounted infrared thermometers or infrared forehead scanners. The measurement time is 1 to 3 seconds, making them fast and safe to use. However, there is a narrow area just in front of and below the eardrum, making it difficult for infrared rays to reach that area. As a result, the measurement values can be inaccurate, with the error increasing as the age of the person being measured decreases. 　　A liquid crystal thermometer is a new product of the 21st century; it is a thermometer made from liquid crystals that takes only 4–5 seconds to measure body temperature in the armpit. It is accurate and safe, but its price is high. 　　Thermometers are widely used in medical practices, and they are also very useful household medical devices; it’s best to buy one as a spare. II. Factors Affecting Body Temperature Measurement (1) Physiological factors Body temperature measurement is influenced by various physiological factors, such as age ； Women’s menstrual period and pregnancy ； Individual differences ； Whether there was movement, eating, bathing, mental state, etc., during the testing. (II) Other factors Test site: Thermometers measure the temperature of the body surface. Since different parts of the body surface dissipate heat at varying rates, the readings will differ when measuring the armpit, neck, mouth, rectum, vagina, eardrum, groin, forehead, and other areas. It can be 0.2–0.4 lower in the armpit compared to the mouth℃ ； The temperature in the armpit can be 0.4–0.8°C lower than that in the rectum. 　　Duration of the test: In principle, the armpit test should last for 10 minutes. 　　Testing method: The location, angle, and way of holding the thermometer. 　　As mentioned above, thermometer readings are affected by various factors; therefore, the results of temperature measurements represent only relative temperatures, not absolute temperatures. As a general rule, in a healthy state, the body temperature should be measured 2–3 times at the same time and at the same site while in a quiet state, using the same thermometer; the average value of these readings represents the normal body temperature. If the normal body temperature is 36.5°C and there are no factors affecting it, but it suddenly rises to 36.9°C – although this is still below the normal level of 37.0°C – it is necessary to monitor closely by taking measurements every 2–3 hours to see if it continues to rise. III. Structure of electronic thermometers 1. Temperature sensor. This is a key component. 2. Amplification circuit 3. Analog-to-digital converter A/D 4. Digital display section: usually an LCD display component 5. Power supply section IV. Standard steps for measuring body temperature (I) Ear temperature 1. Normal range: 35.7℃~37.9℃ 2. Measurement time: 1-15 seconds 3. Measurement steps: (1) Press the power button to ensure that the “ready indicator” is displayed. Press the slider button; the probe extends and automatically fits a rubber sleeve. Check whether the sleeve is damaged; if it is not damaged, take the temperature measurement within 30 seconds. (2) Under 3 years old: Pull the ears downward and backward, then insert the ear thermometer probe into the ear. Ages 3 and above (including adults): Pull the ears upward and backward. Place the probe tightly inside the ear canal, press the temperature measurement button for one second; when a single long \"beep\" sound is heard, release the button to complete the temperature measurement. (3) Remove the ear thermometer, quickly retract the slider, the rubber sleeve will automatically detach from the probe, and then read the temperature. 4. Precautions: (1) Pay attention to cleaning earwax in order to obtain accurate measurements. (2) After using the ear thermometer, the rubber sleeve should be discarded and not reused to avoid cross-infection. (3) If the measured body temperature is below 35°C, it may be due to improper use of the ear thermometer. (II) Forehead temperature: 1. Normal range: 35.0°C–37.0°C. 2. Measurement time: 1–15 seconds. 3. Measurement steps: (1) A room temperature correction must be performed first, that is, the value is converted to a core body temperature according to the instructions provided with the forehead thermometer. (2) The tester must be in a resting state with a dry forehead. (3) Place the forehead thermometer about 2-5 centimeters in front of the forehead, press the button to take a reading, until the color changes or the temperature value appears. 4. Precautions (1) The normal temperature standard varies depending on the brand. (2) Room temperature, exercise, or whether the forehead is dry can affect the accuracy of the measurement. Note: Do not let the infrared beam of the forehead thermometer come into contact with the examinee’s eyes. (III) Oral temperature: 1. Normal range: 35.5°C–37.4°C. 2. Measurement time: 3–5 minutes, with 7 minutes being the optimal duration. 3. Measurement steps: (1) Before use, shake the thermometer until its reading is below 35°C. (2) Place the thermometer (strip) under the tongue (hold it there; do not bite down hard or speak). (3) The thermometer should be used for at least 3–5 minutes, while the temperature patch should be used for 2 minutes. (4) Remove the thermometer, read the temperature reading, wipe it clean with toilet paper, and then disinfect it with an alcohol swab (wiping from the tail end toward the mercury end in a circular motion). After removing the temperature strip, wait for 10 seconds, read the temperature, and then discard it. 4. Precautions: (1) Do not measure oral temperature in infants, those with breathing difficulties, those who are unconscious, those with a history of seizures, and those who cannot cooperate. (2) Measurement should be taken 30 minutes after eating, drinking hot beverages, smoking, chewing gum, engaging in strenuous exercise, experiencing emotional excitement, or taking a bath. (3) If using a thermometer strip, hold it by the end and avoid touching the temperature-sensing part of the strip. (IV) Axillary temperature: 1. Normal range: 35.0°C–37.0°C. 2. Measurement time: 5–10 minutes. 3. Measurement steps: (1) Before use, shake the thermometer until its reading is below 35°C. Place the thermometer at the top of the armpit, ensuring that the mercury end is in close contact with the skin there and is held firmly in place to prevent it from shifting or falling out. (2) Measure for 5-10 minutes. (3) Remove the thermometer, read the temperature reading, and wipe it with toilet paper. 4. Precautions: (1) If there is sweat under the armpits, it should be dried before taking the measurement. (2) If the measurement time has not yet elapsed and the arms are released from under the armpits, the measurement must be repeated and the time must be recalculated. (3) Wait 30 minutes after drinking hot beverages, engaging in strenuous exercise, experiencing emotional excitement, or taking a bath before taking the measurement. (V) Rectal temperature: 1. Normal range: 36.2°C–37.9°C. 2. Measurement time: 3–5 minutes. 3. Measurement steps: (1) For infants, use the supine with legs raised position or the prone position; for children and adults, use the lateral position. (2) Before use, shake the thermometer until its reading is below 35°C. Lubricate the mercury bulb end of the rectal thermometer with a lubricant (vaseline or paraffin oil). (3) Gently pull apart the anus, rotate the rectal probe and insert it slowly and carefully; the hand holding the probe should be placed against the buttock to prevent it from slipping or being inserted too deeply. (4) Insertion depth: ★ 1.25 cm for infants. ★ Children: 2.5 cm ★ Adults: 3.5 cm (5) Measurement time: 2–5 minutes. (6) Remove the rectal thermometer, read the temperature data, wipe it clean with toilet paper, and then disinfect it with an alcohol swab (wiping from the tail end toward the mercury end in a circular motion). 4. Precautions (1) Suitable for infants and children under 5 years old. (2) Rectal temperature measurement is contraindicated in patients with diarrhea, as well as those with rectal diseases or who have undergone surgery. (3) Wait 30 minutes after drinking hot beverages, engaging in strenuous exercise, experiencing emotional excitement, or taking a bath before taking the measurement. Remarks: (1) Rectal temperature is suitable for use across all age groups; its measurement results are the closest to core body temperature and are least affected by ambient temperature. However, it is inconvenient to measure, making it unsuitable for screening purposes. Therefore, it is recommended to be used for confirmation when the measurement results obtained by other methods are abnormal or questionable. (2) If the rectal thermometer is contaminated and cannot be seen clearly, wipe it clean with toilet paper first before reading the temperature. Other points to note: (1) Mercury thermometers and electronic mercury thermometers are contact-type thermometers, offering relatively stable accuracy in measuring body temperature. (II) The temperature readings obtained using ear thermometers and forehead thermometers are susceptible to factors such as the measurement distance and humidity; therefore, they are recommended as a quick screening tool for fever. However, when the temperature measurement shows an abnormal result, it is recommended that the user take another reading using a mercury thermometer or an electronic mercury thermometer. (III) If a thermometer needs to be calibrated or there are related issues, relevant information can be found on the website of the Accredited Inspection Bureau under the Ministry of Economy. (IV) The body temperature varies depending on age and the environment, so the values mentioned above are not absolute figures but merely for reference ； There is no fixed value for the so-called normal temperature; it can only be expressed as a range, as it varies depending on gender, age, time of day, and level of activity. (5) Throughout the day, a person’s body temperature is lower in the early morning and slightly higher near evening. After work, as stress decreases and adrenal hormone secretion drops, along with a drop in external temperature, body temperature tends to be lower. Factors such as having just exercised, being exposed to sunlight, wearing too many clothes, being overly tired, or being in a too hot environment can all cause an increase in body temperature. Therefore, if the first measurement yields abnormal results, it is recommended to wait half an hour before taking another reading. ☆Recommended thermometer products: http://www.joyisnow.cn/Product/?HongWaiQianEYuYinCeWenYi-75.html The company maintains strong customer relationships in the fields of medical rehabilitation, competitive sports, and public health; its clients are located across the country and include medical rehabilitation institutions, sanatoriums, sports teams, fitness clubs, community clinics, sports research institutions, and sports academies. 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