The term “vital sign” has been assigned to various phenomena with the presumptive intent to emphasize their importance in health care resulting in the emergence of eight vital signs with multiple designations and overlapping terms. This review developed a case definition for vital signs and identified and described the fifth through eighth vital signs. PubMed/Medline, Google and biographical databases were searched using the individual Medical Subject Headings (MeSH) terms, vital sign and fifth, vital sign and sixth, vital sign and seventh, and vital sign eighth. The search was limited to human clinical studies written in English literature from 1957 up until November 30, 2021. Excluded were articles containing the term vital sign if used alone without the qualifier fifth, sixth, seventh, or eighth or about temperature, blood pressure, pulse, and respiratory rate. One hundred ninety-six articles (122 for the fifth vital sign, 71 for the sixth vital sign, two for the seventh vital sign, and one for the eighth vital sign) constituted the final dataset. The vital signs consisted of 35 terms, classified into 17 categories compromising 186 unique papers for each primary authored article with redundant numbered vital signs for glucose, weight, body mass index, and medication compliance. Eleven terms have been named the fifth vital sign, 25 the sixth vital sign, three the seventh, and one as the eighth vital sign. There are four time-honored vital signs based on the case definition, and they represent an objective bedside measurement obtained noninvasively that is essential for life. Based on this case definition, pulse oximetry qualifies as the fifth while end-tidal CO2 and cardiac output as the sixth. Thus, these terms have been misappropriated 31 times. Although important to emphasize in patient care, the remainder are not vital signs and should not be construed in this manner.
