Volume 3, Issue 3, 1999                     ISSN 1329 - 187BestPracticeEvidence Based Practice Information Sheets for Heal...
Studies have demonstrated that in some            of this is based on surveys of nurses, clini-   breaths per minute, ther...
Vital Signs: Blood Pressure                     Cuff Size                                      Bell versus DiaphragmStudie...
Table Two             Recommended Blood Pressure Measurement Technique              Based on published information, below ...
Tympanic TemperatureThere has been considerable research addressing tympanic temperature measurements ranging from theinfl...
Implications For PracticeWhile much research has been undertaken on specific aspects of patient observations, such as the ...
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Vital signs article

  1. 1. Volume 3, Issue 3, 1999 ISSN 1329 - 187BestPracticeEvidence Based Practice Information Sheets for Health Professionals Vital Signs Acknowledgement Levels of Evidence This Best Practice Information Sheet has This Practice Information been based on a systematic review of Sheet Covers The Following All studies were categorised according to the strength of the evidence based on the research relating to vital signs. If you wish Concepts following classification system. to view the primary references on which this information sheet is based, they are Level I available in the systematic review report Evidence obtained from a systematic review of all relevant randomised controlled trials. published by the Joanna Briggs Institute. 1. Vital Signs: General Level II Introduction Issues Evidence obtained from at least one properly designed randomised controlled trial. Patient observations are an important part of nursing care in that they allow the 2. Vital Signs: Respiratory Level III.1 patient’s progress to be monitored and also Evidence obtained from well designed ensure prompt detection of adverse events Rates controlled trials without randomisation. or delayed recovery. Patient observations, Level III.2 or vital signs, traditionally consist of blood Evidence obtained from well designed cohort pressure, temperature, pulse rate and 3. Vital Signs: Pulse Rate or case control analytic studies preferably from more than one center or research respiratory rate. A systematic review was group. recently conducted addressing issues such as the purpose of vital signs, the optimal 4. Vital Signs: Blood Level III.3 frequency with which they should be Evidence obtained from multiple time series Pressure with or without the intervention. Dramatic conducted, what observations constitute results in uncontrolled experiments. vital signs and to identify issues related to the individual measures of temperature, 5. Vital Signs: Temperature Level IV pulse rate, respiratory rate and blood Opinion of respected authorities, based on clinical experience, descriptive studies, or pressure. reports of expert committees. This Best Practice Information Sheet inconsistent and at times inter-changeable. What Constitutes Vital Signs summarises current best evidence on the The term vital signs suggests measurement Traditionally, the term “vital signs” is used topic. In this information sheet, the term of vital or critical physiologic functions, in reference to the measurement of observations refers to patient observations where as the term “observations” implies temperature, respiratory rate, pulse rate in general, while vital signs is used in broader range of measures. While there and blood pressure. However, within the reference specifically to temperature, is no clear definition in the literature, the literature there are suggestions that these pulse, respiration and blood pressure. panel of experts which guided the system- parameters could be supplemented with atic review process argued that observa- other useful measures such as nutritional Vital Signs: General Issues tions is the more appropriate term, in that it more accurately reflects current clinical status, smoking status, spirometr y, practice. This implies that patient obser- orthostatic vital signs and pulse oximetry. Vital Signs versus Observations The measurement of temperature, pulse, vations need not be limited to the tradi- However, only pulse oximetr y and heart rate and blood pressure is termed tional four parameters but supplemented determining a patient’s smoking status have both vital signs and observations. Neither with other measures as indicated by the been shown to actually change the practice have been well defined and their use is patient’s clinical status. of clinicians. volume 3, issue 3, page 1, 1999
  2. 2. Studies have demonstrated that in some of this is based on surveys of nurses, clini- breaths per minute, thereby questioning thesituations pulse oximetry is useful for cal practice reports and expert opinion. value of having a “cut-off” at 50 breathsdetecting a deterioration in physiological Surveys of nurses have shown that many per minute as the indicator of serious res-function that might otherwise be missed. admit to carrying out frequent vital sign piratory illness. It has also been reportedThis has resulted in a reduction in the measurements on patients they believed did that factors such as crying, sleeping, agi-number of investigations undertaken and not require them, and that they had be- tation and age have a significant influencehas changed the planned management of come a routine procedure unrelated to per- on the respiratory rate. As a result of thesepatients. On this basis, pulse oximetry has ceived individual patients needs. and similar studies the value of respira-been recommended as a useful addition tory rate as an indicator of serious illnessto the four traditional measures of Two studies evaluated the impact of reduc- is limited.physiologic status. ing the frequency of post-operative obser- vations, but both involved only minor Vital Signs: Pulse RateThe use of the concept “smoking status is a changes to measurement frequency. One There has been very little researchvital sign” has been evaluated during the practice report describes the change from evaluating the measurement of pulse rates.initial patient encounter and has been 15 and 30 minutely vital sign measurement It is likely, that when heart rate is ofshown to increase the likelihood that during a blood transfusion, to vital signs concern, cardiac monitors are used tocounselling and smoking cessation advice only at commencement, at 15 minutes and determine not only rate, but also rhythm.would be provided by the health care on completion. This report used visual ob- The role of the “pattern of the pulse”, forworker. While this parameter does not fit servation to monitor patient status at other example regular pulse versus irregularwithin the traditional concept of vital signs times during the transfusion, and suggest pulse or strong pulse versus weak pulse,or patient observations, it may still have there was no compromise to safe practice. have not been addressed in the context ofan important role during the initial patient However, the strength of this evidence is vital signs or patient observations. On thisassessment. limited and so cannot be used to justify basis, an important role of pulse rate practice change. The “vital signs” system- monitoring will likely be to identify whenOther proposed vital sign measurements, atic review concluded that there has been more advanced monitoring is required.such as nutritional and orthostatic vital little serious evaluation of the optimal fre-signs, have not been shown to have an quency of patient observations. Measurement of a person’s pulse rate ininfluence on patient management. While the presence of atrial fibrillation wasmany other measures and scales exist, their Vital Signs: Respiratory Rate evaluated and results suggest that pulserole within the framework of patient There is only limited research relating to rate, measured apically using aobservations has yet to be determined. monitoring respiratory rate, and these stethoscope for a 60 second count period,Indeed, in some situations simple visual studies focused on issues such as the is likely to be the most accurate rate. Thisobservation of the patient may be all that inaccuracy of respiratory rate measurement study noted that 86% of nurses under-is required in terms of monitoring the and respiratory rate as a marker for estimated the pulse rate, and that as thepatient’s progress and clinical status, yet respiratory dysfunction. heart rate increased the magnitude of errorthis has still to be addressed. also increased. Another study Inaccuracies in respiratory measurement recommended a 30 second count period have been reported in the literature. One as the most accurate and efficient way ofLimitations study compared respiratory rate counted measuring pulse rate, noting that the 15Based on the findings of a small number using a 15 second count period, to a full second count time was the least accurate.of studies, it appears that vital signs are minute, and found significant differencesquite limited in terms of detecting important A third study found that there was no in the rates. Respiratory rates measurementphysiologic changes. Examples of this advantage in using the longer 60 seconds, in children under five years, for a 30 sec-include: their failure to detect large blood over the 15 or 30 second count periods. ond or 60 second period, suggesting thelosses, to identify serious illness in infants, These researchers suggest that counting an 60 seconds resulted in the least variability.and their inability to detect an inadequate accurate pulse rate may be more difficult Another study found that rapid respiratoryplasma volume in burn injury patients. One than commonly recognised. rates in babies, counted using a stetho-retrospective study of patients with severe scope, were 20% to 50% higher than thosethoracoabdominal injury found that A study assessing infants apical pulse rate counted from beside the cot without the aidnormal or stabilised post injury vital signs using a stethoscope, suggested that length of the stethoscope.did not signify that life threatening of time may not be the primary factor inhaemorrhage was absent. These studies errors, and that like respiratory rate, pulse The value of respiratory rate as an indica-suggest that the usefulness of vital signs is tor of potential respiratory dysfunction has rate also appears to be influenced by infantperhaps more as an indicator for the need been investigated but findings suggest it is states in addition to illness.of further more appropriate investigations. of limited value. One study found that onlyIt is therefore important to note that normal 33% of people presenting to an emergency While these studies have identified that thevital sign parameters do not guarantee a department with a oxygen saturation be- accuracy of pulse rate measurements isstable physiological status. low 90% had an increased respiratory rate. influenced by the number of seconds that An evaluation of respiratory rate for the the pulse is counted, the clinicalFrequency of Vital Signs differentiation of the severity of illness in significance of these findings is unclear. TheThere is only limited information regard- babies under 6 months found it not to be contradictory findings of studies suggesting the frequency with which patient ob- very useful. Approximately half of the ba- that the count period used to determineservation should be undertaken and much bies had a respiratory rate above 50 pulse rate is of only limited significance. volume 3, issue 3, page 2, 1999
  3. 3. Vital Signs: Blood Pressure Cuff Size Bell versus DiaphragmStudies addressing the measurement of The length and width of the inflatable cuff The accuracy of blood pressures measuredblood pressure with a sphygmomanometer (bladder) that is used during the with the bell or the diaphragm of the measurement of blood pressure may be a stethoscope have been investigated. Onehave focused on issues such as the accu- source of error. Much of the research has study found the bell of the stethoscoperacy of indirect blood pressure, palpation focused on cuff width, (the dimension resulted in higher readings than thoseversus auscultation cuff size, position of across along the bladder) as the potential taken using the diaphragm. These resultsarm during measurements and health care source of this error. The standard width of were supported by another study, withworkers technique. currently available cuffs is approximately researchers recommending the use of the 12cm, with both larger and smaller sizes bell for all blood pressure measurements.Direct versus IndirectSeveral studies have compared direct (in- also available. Studies have shown that the Health Care Workers Techniquetra-arterial) and indirect (auscultation) use of a cuff that is too narrow results in The technique used by health care work-measurements of blood pressure. There an overestimation of blood pressure, and ers to measure blood pressure has beenappears to be little significant difference a cuff that is too wide underestimates blood shown to differ from recommended prac-in systolic pressures measured by either pressure. Length of cuff appears to have tice. Using the American Heart Associa-method, with differences ranging from 3 little influence on accuracy. tion Guidelines as the standard, one studymmHg in two studies to 12mmHg in a third. found that 57% of nursing students failedDifferences in diastolic blood pressure are For obese people it has been suggested to comply with these guidelines in areasgreater, and are influenced by the refer- that large cuffs (15cm width) will be such as cuff placement, estimation ofence point that is used. When the phase V required when the person’s arm systolic pressure by palpation, calculationKorotkoff’s sound is used (disappearance circumferences is between 33 –35cm, and of proper inflation pressure, and properof the sound), both methods provide simi- a thigh cuff (18cm width) may be needed stethoscope placement. Another study oflar pressures. However when the phase IV if the arm circumferences is greater than 172 health care workers concluded thatKorotkoff’s sound (muffling), is used, aus- 41cm. However, difficulties in applying nurses and physicians evaluated bloodcultated measurements are significantly thigh cuffs to large arms have been pressure in an inadequate, incorrect and Table One Korotkoff’s Sounds Measurement of blood pressure by auscultation is based on the sounds produced as a result of changes in blood flow, termed Korotkoff’s sounds, and are: 1. Phase I The pressure level at which the first faint, clear tapping sounds are heard, which increase as the cuff is deflated (reference point for systolic BP). 2. Phase II During cuff deflation when a murmur or swishing sounds are heard. 3. Phase III The period during which sounds are crisper and increase in intensity. 4. Phase IV When a distinct, abrupt, muffling of sound is heard 5. Phase V The pressure level when the last sound is heard (reference point for diastolic BP).greater than intra-arterial pressures (see reported. Cuff width may also be important inaccurate way, and that only 3% of gen- when measuring blood pressure in eral practitioners and 2% of nurses ob-table one). A study in children reported neonates and a cuff width equal to tained reliable results. Two studies evalu-the use of either auscultation or palpation ating the impact of education programsoverestimated systolic pressure. See table approximately 50% of the arm on blood pressure measurement, foundtwo for current recommended practice for circumference has been recommended. they increased agreement between the dif-the measurement of blood pressure. ferent blood pressure readings and also Arm and Body Position significantly reduced differences in opera- Comparisons of blood pressures measured tor technique.Palpation versus AuscultationA comparison between systolic blood pres- in the sitting person with their arm sup- Limitations ported horizontally or with the arm rest- A descriptive study of blood pressures insure measurements taken by auscultation ing at their side, have found an average critically ill patients who had suffered aand palpation found both were within 8 difference in systolic pressure of 11mmHg cardiac arrest highlighted some limitationsmmHg. While palpation has been commonly and diastolic pressure of 12mmHg. When to these measurements. Of the 15 patientslimited to the measurement of systolic blood investigated, 5 patients had adequate the arm was placed above or below thepressure, one study reported that diastolic intra-arterial blood pressures, but level of the heart, blood pressure meas-pressures could be accurately palpated us- unreadable cuff pressures. Four patients urements changed by as much as had cuff pressures approaching normal,ing the brachial artery to identify the sharp 20mmHg. As a result of this, it has been but had an inadequate cardiac output. Thisphase IV Korotkoff’s sound, However, the recommended that blood pressures be study suggests that indirect blood pressurevalue of this technique in clinical practice, measurements do not always accurately taken in the sitting position with arm sup-and its accuracy when used by health care ported horizontally at approximately heart reflect haemodynamic status of critically illworkers, has yet to be demonstrated. level. people. volume 3, issue 3, page 3, 1999
  4. 4. Table Two Recommended Blood Pressure Measurement Technique Based on published information, below is a summary of the recommended practice • Patient should be seated and have rested for 5 minutes and have arm supported at heart level. • Appropriate cuff size should be used, and the bladder should nearly (at least 80%) or completely encircle arm. • Patients should not have smoked or ingested caffeine within 30 minutes before measurements. • Measurements should be taken with a mercury sphygmomanometer, a recently calibrated aneroid manometer, or a calibrated electronic device. • Both systolic and diastolic blood pressure should be recorded. • Korotkoff’s phase V (disappearance of sound) should be used for the diastolic reading. • Two or more readings, separated by 2 minutes, should be averaged, and more taken if they differ by more than 5mmHg.Vital Signs : Oral Temperatures thermometers to accurately Studies evaluating measure- record the person’s oralTemperature ments from the different areas temperature. One study foundThe largest volume of research of the mouth recommend using that with healthy adults, usingidentified during the literature either the right or left posterior a two minute insertion timesearch addressed various sublingual pocket, as these resulted in 27% of theaspects of temperature result in higher recorded temperature readings havingmeasurement. These studies temperatures. an error of at least 0.3°C. Ahighlight the large range of study assessing thermometermethods and body sites that Evaluation of the impact of insertion time in afebrile andare used for the measurement oxygen therapy on oral febrile adults, suggested a sixof temperature (see table temperatures have reported minute insertion time as athree). Because of the volume contradictory results regarding compromise between optimalof research, comparisons of its statistical significance, time and clinical practicalitydifferent temperature however no study reported a while another recommended ameasurement methods will be clinically significant effect. seven minute insertion time tosummarised as a separate Similarly, different rates of ensure the majority of afebrilesystematic review. Summarised oxygen flow, from 2 litres to 6 and febrile temperatures arein this practice information litres per minute, and warmed correctly recorded. However, asheet are studies addressing or cooled inspired gas, were survey of nurses showed thataspects of oral, rectal axillary found not to have an influence most left the mercur yand tympanic temperatures. on oral temperature thermometer in the mouth for measurements. Two studies less than 3 minutes.General Issues found that rapid respiratoryWhile much attention has rates had a small influence on Axillary Temperaturefocused on measurement oral temperatures, but these There has been only limited re-accuracy, one study evaluated results were contradicted by search focusing on axillarytouch as a screen for fever and another study that found temperatures. One studyfound that while mothers and neither rapid or deep evaluated axillary temperaturemedical students overestimated breathing, alone or in measurements in elderly fe-the incidence of fever when combination, had any males, and found great varia-using touch, they rarely missed significant effect on oral tion between individuals.its presence in a child. The temperatures. While the mean axillary tem-results of this study perhaps peratures were approximatelychallenge the current focus of Studies have shown that 36°C, the wide range of tem-research on the accuracy of drinking hot or cold water has peratures encountered pre-measurements using tenths of a significant impact on vented the identification of aa degree, when simple touch recorded oral temperatures, single figure that could be con-is an accurate measure for and it has been suggested sidered the “normal” axillaryfever. The use of temperature waiting 15 to 20 minutes after temperature. Another studyas a discharge criterion for an drinks to ensure accuracy. evaluated the influence of in-ambulatory surgical unit has Smoking does not change oral travenous infusions, via upperbeen studied, but results temperature measurements. limbs of neonates, on axillarysuggest it is not useful in temperatures and found theredifferentiating readiness for Researchers have evaluated the was little significance in termsdischarge. time required for mercury of the temperature accuracy. volume 3, issue 3, page 4, 1999
  5. 5. Tympanic TemperatureThere has been considerable research addressing tympanic temperature measurements ranging from theinfluence of infection and cerumen on measurement accuracy, to optimal technique. Studies have evaluatedthe impact of otitis media on tympanic temperatures and suggest it has little effect. While some studies havereported a statistically significant difference in tympanic temperatures between ears in people with unilateralotitis media, this difference was approximately 0.1°C and so of little clinical importance. The presence ofcerumen does influence tympanic temperature readings, and while results are variable, they suggest asignificant proportion of the temperature readings taken from the occluded ear will be more than 0.3°Clower than the ear that is not occluded.Studies evaluating technique suggest an ear tug should be used during the measurement of tympanictemperatures, as this is reported to straighten the external auditory canal. Failure to use the ear tug meansinfrared thermometers are only partially directed at the tympanic membrane. The tug technique in adultshas been described as pulling the pinna (auricle of ear) in an upward and backward direction, and ininfants it is pulling the pinna in a backward direction.Evaluations of the impact of ambient temperatures on tympanic temperatures suggest that while a hotenvironment can significantly affect readings, cold appears to have little effect.Cost analyses of the different temperature measurement methods suggest infrared measurements may bethe most cost effective despite the greater initial costs. These savings are the result of the rapid readingcapabilities of these instruments, and the labour cost savings that result.Rectal TemperatureMany studies have compared the different methods of temperature measurement, and commonly rectaltemperatures are used as the standard comparison. However, these studies will be summarised in a separatesystematic review. The most common reported issue related to rectal temperature measurement is that ofrectal perforation, which appears to be a risk primarily for the newborn and very young. Other reportedcomplications include peritonitis secondary to rectal perforation, and one case of intra-spinal migration ofa rectal thermometer in a two year old, which broke during routine rectal temperature measurement. A tenyear review of hospital records identified 16 children admitted to a surgical unit with broken or retainedrectal thermometers. In response to this problem axillary temperature measurements have been recommendedin preference to the rectal measurements. With the advent of infrared tympanic thermometers, thesecomplications are likely to become less common. Table Three Temperature Measurement The different body areas that have A wide range of instruments have been been used for the measurement of used to measure these temperatures, body temperature include: and include: • mouth • glass mercury thermometer • axilla • electronic thermometer • tympanic membrane • pulmonary artery catheter • rectum • skin surface • endotracheal tube with temperature • pulmonary artery probe • nose • urinary catheter with temperature • groin probe • oesophagus • liquid crystal thermometer strip • trachea • disposable thermometers • urinary bladder • urine • infrared (tympanic) thermometers volume 3, issue 3, page 5, 1999
  6. 6. Implications For PracticeWhile much research has been undertaken on specific aspects of patient observations, such as the accuracy of individualmeasurements, there is little research addressing the broader issues of the most effective and efficient way to monitor patientprogress. However, there is a need for clinical areas to determine the role of patient observations within their setting, withparticular reference to the four traditional vital sign parameters, to ensure:1. observations are appropriate as determined by the patient’s clinical status;2. available technologies are utilised appropriately, to complement or even replace less effective methods of patient observation; and3. inappropriate observations, based on habit rather than need, should be minimised.Other issues identified during the systematic review that impact on clinical practice include:1. the term “observations” should be used in preference to “vital signs”, as this better reflects the diversity of what may constitute patient monitoring;2. the rectum should not be the first site of choice for the measurement of temperature;3. normal vital sign parameters do not guarantee normal physiologic status;4. education programs will likely be effective in improving health care workers blood pressure measurement technique; and5. while many factors can have a small influence on the accuracy of vital sign measurements, there may be a cumulative effect, and so organisations should promote a standardised method for all measurements. RecommendationsBecause of the lack of evidence relating to most of the broader issues of patient observation, these recommendations havebeen generated by the expert panel, and have been rated level IV evidence (expert opinion)• The specific patient observations, their frequency and duration, should be based on clinical assessment rather than protocol alone.• Patient observations should be performed as often as indicated by the patient’s clinical status.• Beginner practitioners should validate their clinical assessment with a more experienced practitioner.• Vital signs should not be used as a way to ensure frequent visits by the nurse.• When visual checks or inspection of the patient are all that is indicated by the patient’s clinical status, this should be an acceptable form of patient observation.• Health care workers should be trained to perform patient observations in a standardised manner within each institution, and be made aware of the risks and limitations associated with this activity.• Pulse oximetry should be considered a vital sign in situations where accurate assessment and monitoring is critical.Other issues of importance noted by the panel of experts include:• Clinical areas should identify who has responsibility for determining the frequency and nature of patient observations.• Trends in observations will likely be more important than single measures.• What happens to the information after it is collected is as important as the accuracy of individual parameters. AcknowledgementsFor further information contact: This publication was produced based on a• The Joanna Briggs Institute for Evidence Based Nursing and Midwifery, Margaret Graham systematic review of the research literature Building, Royal Adelaide Hospital, North Terrace, South Australia, 5000. undertaken by The Joanna Briggs Institute http://www.joannabriggs.edu.au, ph: (08) 8303 4880, fax: (08) 8303 4881 under the guidance of a review panel of• NHS Centre for Reviews and Dissemination, Subscriptions Department, Pearson Professional, clinical experts, and was led by Mr. David PO Box 77, Fourth Avenue, Harlow CM19 5BQ UK. Evans – Coordinator of Reviews, The Joanna• AHCPR Publications Clearing House, PO Box 8547, Silver Spring, MD 20907 USA. Briggs Institute; Mr. Brent Hodgkinson – Research Officer, The Joanna Briggs Institute; “The procedures described in Best and Ms Judith Berry – Nursing Director, The Practice must only be used by Royal Adelaide Hospital. The Joanna BriggsDisseminated collaboratively by: people who have appropriate Institute would like to acknowledge and expertise in the field to which the thank the review panel members whose procedure relates. The applicability expertise was invaluable throughout this of any information must be activity. The review panel members were: established before relying on it. • Ms Judith Berry While care has been taken to ensure • Ms Heidi Silverston that this edition of Best Practice • Mr Peter Le-Gallou summarises available research and • Ms Deb Henrys expert consensus, any loss, • Ms Kathy Read damage, cost, expense or liability • Ms Lee Hussie suffered or incurred as a result of reliance on these procedures • Ms Sue Edwards (whether arising in contract, • Ms Annette Heinmann negligence or otherwise) is, to the • Ms Hazel Morrison extent permitted by law, excluded”. • Mr Lyell Brougham volume 3, issue 3, page 6, 1999

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