Vital signs in hospital patients: a systematic review

International Journal of Nursing Studies 38 (2001) 643–650

Vital signs in hospital patients: a systematic review David Evans*, Brent Hodgkinson, Judith Berry The Joanna Briggs Institute, Margaret Graham Building, Royal Adelaide Hospital, North Terrace, Adelaide 5000, Australia Received 14 January 2000; accepted 10 November 2000

Abstract Objectives: This review was initiated to identify the best available evidence on vital sign measurements in hospital patients. Method: Inclusion Criteria – Studies that evaluated some aspect of vital signs. Search – Covered all major databases and the references of identified studies. Data Analysis. because of the nature of identified studies, data were summarised using narrative rather than statistical methods. Results: A total of 737 papers of which 69 met the inclusion criteria. Conclusion: This review has highlighted a need for further investigation of issues related to the role, nature and optimal practice of monitoring patient vital signs. # 2001 Elsevier Science Ltd. All rights reserved. Keywords: Vital signs; Observations; Systematic review

1. Introduction Vital signs are an important component of monitoring the patient’s progress during hospitalisation as they allow for the prompt detection of delayed recovery or adverse events. These vital signs, or patient observations, traditionally consist of blood pressure, temperature, pulse rate and respiratory rate. While the measurement of vital signs has become an accepted component of any hospitalisation, the optimal practice is yet to be determined. An initial search of the literature indicated that there was a vast number of published articles relating to this topic; however there had been no previous attempt to review systematically this literature. This review was initiated to identify and summarise the best available evidence relating to the use of vital signs by nurses to monitor hospital patients.

patient vital signs and to summarise the findings of relevant studies. The specific objectives of this review were to determine: * * *

the measurements that constitute patient vital signs, the optimal frequency for monitoring vital signs, and limitations of vital signs measurements.

The objective of this review was to present the best available information related to the monitoring of

2.1.1. Criteria for considering studies for this review Population: Studies which included neonatal, paediatric or adult hospital patients. Intervention: Those related to the determination of optimal frequency of measurement, their limitations and what measurements are needed to ensure patient safety or adequate monitoring. Outcomes: Those related to accuracy, the required frequency or the need for vital signs. Study design: The initial search of the literature highlighted a lack of rigorous research on many aspects of vital signs, therefore this review considered all papers addressing some aspect of vital signs measurement to ensure all issues of importance were identified. Exclusions: Non-English language reports.

*Corresponding author. Tel.: +61-08-8303-4880; fax: +6108-8303-4881. E-mail address: [email protected] (D. Evans).

2.1.2. Search strategy The search sought to identify both published and unpublished studies. An initial limited search of

2. Method 2.1. Objectives

0020-7489/01/$ - see front matter # 2001 Elsevier Science Ltd. All rights reserved. PII: S 0 0 2 0 - 7 4 8 9 ( 0 0 ) 0 0 1 1 9 - X

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databases was conducted to identify optimal search terms, which were then used during a comprehensive search. The initial search terms were: vital NEAR sign* and observation*. The second search terms, which were adapted for each specific database, included: * * * * * * * * * * * * * *

heart rate determination blood pressure determination body temperature determination respiratory rate determination vital signs monitoring physiological nursing pulse evaluation body temperature blood AND pressure in ti respiratory in ti pulse in ti temperature in ti vital AND sign* in ti observation* in ti

Databases searched were CINAHL, MEDLINE, Psyclit, Current Contents, Cochrane Library and Embase. Databases searched for unpublished papers included Dissertation Abstracts International and Proceedings. The bibliographies of all retrieved papers were checked for additional studies. All identified abstracts were assessed and the full report was retrieved for any that appeared to meet the inclusion criteria. Studies identified during bibliography list searches were assessed for relevance to the review based on the title of the paper. 2.1.3. Critical appraisal and data synthesis Methodological quality was assessed using a checklist which was developed based on the work of Cochrane Collaboration (Mulrow and Oxman, 1997) and Centre for Reviews and Dissemination (NHS Centre for Reviews and Dissemination, 1996). Data were extracted using a data extraction tool that was developed and tested prior to use. As the topic was conceptually very broad and studies identified addressed many different aspects of vital signs, statistical pooling of results was not attempted. Results were summarised in narrative form, identifying emerging themes, issues of importance, limitations, or gaps in the available research. An initial search of the literature demonstrated that there would be difficulties in summarising findings from existing studies because of issues such as *

* *

the small number of studies that addressed the broader issues of vital sign measurement, the variable quality of studies, the great variety of research methods that have been utilised,

*

*

the different populations and health care settings used to evaluate vital signs, and the great variety of outcomes that have been used to evaluate vital signs.

However, systematic reviews provide a comprehensive, rigorous and reproducible method to summarise the best evidence on a topic. While systematic reviews have focused primarily on randomised controlled trials, the review methodology can also be used to identify, appraise and summarise studies using a variety of research designs. This review was therefore conducted to bring together the many diverse studies that could contribute potentially important evidence on which clinical practice could be based and help provide a focus for future research.

3. Results The search of the literature identified 737 papers that referred to vital signs or to the determination of temperature, blood pressure, respiratory rate or pulse rate. Of these papers, 356 appeared to meet the inclusion criteria and so were retrieved, of which 69 papers are cited in this report. Two hundred and eighty-seven papers were excluded because they did not meet the inclusion criteria, were discussion papers and contained no original data, or were literature reviews. 3.1. The 5th vital sign Traditionally, vital signs have consisted of temperature, pulse, respiratory rate and blood pressure. However, it has been suggested that these four parameters could be supplemented with other measurements such as nutritional status, smoking status, spirometry and pulse oximetry. Nutritional status, including the calculation of the person’s body mass index, has been proposed as a vital sign for the elderly (Yen, 1992; Cope, 1994). The basis for this recommendation is the fact that inadequate nutritional intake is a problem for both the elderly and the sick, and that regular assessment may aid in the identification and management of this problem. However this recommendation is based on expert opinion and there is currently no research to demonstrate that regular nutritional assessment will result in improved patient outcomes. One expert opinion paper suggested that spirometry is an important measurement that should be included as a vital sign during the initial ‘work-up’ of patients (Petty, 1994). This was based on the fact that spirometry can provide a snap-shot of the person’s pulmonary function and can aid in the disclosure of moderate to advanced degrees of airflow obstruction. However, there is

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currently no research to show that this will influence patient management or improve patient outcomes. Orthostatic, or postural, changes to blood pressure and heart rate, have been used as indicators of intravascular volume status in the emergency department, and has been proposed as another possible addition to vital sign measurements. Orthostatic vital signs is the measurement of heart rate and blood pressure when the person is in a lying position and then while standing, to detect any position-related changes, and are viewed as positive if the *

*

*

heart rate increases by more than 20 beats per minute; systolic blood pressure decreases by more than 10 mmHg; or diastolic blood pressure decreases by more than 10 mmHg (Koziol-McLain et al., 1991).

However, one observational study of 132 patients presenting to an emergency department found 43% of the orthostatic vital signs were positive (Koziol-McLain et al., 1991). Another study found orthostatic vital signs were not sensitive enough to detect reliably an acute 450 ml blood loss in 100 blood donors (Baraff and Schriger, 1992). These studies suggest that the routine use of orthostatic vital signs to detect a reduced intravascular volume is unreliable and therefore is not likely to be a useful addition to the traditional vital signs. Pulse oximetry is perhaps the most commonly recommended addition to the traditional vital signs. It has been suggested that in the newborn, skin colour alone is an inadequate indicator of oxygenation and that pulse oximetry will provide important information for clinicians (Katzman et al., 1995). It has been recommended for use in situations such as pulmonary outpatient departments, for patients receiving oxygen therapy and those with moderate to severe pulmonary disease who have borderline hypoxaemia (Neff, 1988). However, an observational study in a pulmonary outpatients department, suggested pulse oximetry was not very useful in terms of the management of this group of patients, in that the impaired respiratory function of patients was already known to health care workers (Loggan et al., 1988). Descriptive studies suggest that pulse oximetry is useful during the insertion of invasive lines in premedicated cardiac surgical patients (Hensley et al., 1986), and with post-operative patients, as hypoxaemia can occur during the transfer from theatre to the recovery unit (Tyler et al., 1985). Studies evaluating the use of pulse oximetry in the emergency department found that it significantly changed medical treatment (Mower et al., 1995, 1997), and has therefore been recommend for all acutely ill patients presenting at

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emergency departments (Holburn and Allen, 1989). One before and after study found that the introduction of pulse oximetry in the emergency department resulted in a 37% reduction in the number of arterial blood gas analyses (ABG) and a 56% reduction in the number of cases involving three or more ABG, without any increase in the number of adverse events (Kellerman et al., 1991). A controlled trial evaluating the value of pulse oximetry in children presenting at an emergency department with wheezing, suggested it was a reliable adjunct to ambulatory emergency care in terms of predicting the need for hospitalisation (Rosen et al., 1989). No study was identified that evaluated the effect and usefulness of pulse oximetry in a general hospital ward. Smoking status has also been recommended as an important vital sign (Robinson et al., 1995). This study, based in a family practice centre, found that the documentation of a patient’s smoking status, with the aid of a ‘‘smoking is a vital sign’’ stamp, significantly increased the likelihood that the physician and nurse would discuss the patients smoking habit. It also dramatically increased the likelihood of the physician advising the patient to quit smoking. One editorial comment supporting the elevation of smoking assessment to the priority status of a vital sign suggested it would be an important first step in a coordinated action plan to aggressively confront smoking (Fiore, 1991). However, these papers do not argue for a 4-hourly monitoring of smoking status, rather that cigarette smoking should be assessed on the patient’s initial encounter with the doctor or nurse, and so encourage the incorporation of counselling and advice into the care provided. 3.2. Frequency There is only limited information regarding the frequency with which vital signs should be monitored and much of this is based on surveys of nurses, clinical practice reports and expert opinion. The frequency of monitoring post-operative vital signs following the patients return to the ward from the recovery unit has been the subject of some investigation. One observational study of 250 surgical patients suggested that recording vital sign measurements every 15 min, which is common practice in some hospitals, is not necessary (Davis, 1990). A similar study of 766 post-operative patients supported this reduction in initial vital sign monitoring (Schumacher, 1995). These studies recommended the vital sign monitoring frequency for patients returning to the ward as follows: * * * *

every every every every

15 min  1 30 min  2 60 min  1 4h4

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These two studies found that for most patients, vital signs remained within normal limits during the postoperative period, and that hypotension was the most commonly identified problem. However, it was noted that the reduced frequency of vital sign measurements delayed detection of problems for two patients (Schumacher, 1995). Structured interviews conducted with 50 registered nurses found that all nurses did half hourly vital sign measurements for 4 h following discharge from the recovery unit and believed this was prescribed by ward or hospital policy (Botti and Hunt, 1994). A small number of these nurses admitted to taking these half-hourly measurements on patients who they believed did not require frequent observation. Another survey of 80 nurses suggested that the measurement of vital signs has become a routine procedure unrelated to perceived individual patient needs (Burroughs and Hoffbrand, 1990). A practice report described changes to the monitoring of vital signs during blood transfusions (Roach, 1995). The paper reported a change in the taking of vital signs every 15 min for the first hour, then every 30 min till transfusion was complete, to the reduced rate of observing the patient for first 5–15 min and taking vital signs only at commencement, at 15 min and on completion of the transfusion. The authors claim this reduction in vital sign measurements did not compromise safe practice. However, no studies were identified to provide research evidence to support this type of practice change. 3.3. Limitations of vital signs Some information identified during the search suggested that there are limitations to the usefulness of vital sign measurements, and many factors have been identified that influence the reliability and accuracy of these measurements. 1. Pulse rate measurement: There has been little research evaluating pulse rate measurement. A study evaluating apical pulse rate measurement in infants found a difference of 6 beats per minute between sleeping and awake states (Margolius et al., 1991). Another study found that in the presence of atrial fibrillation, 86% of nurses underestimated the pulse rate (Sneed and Hollerbach, 1992). No studies were identified that evaluated pulse rate as an indicator of serious illness. 2. Respiratory rate measurement: Studies have also suggested that the value of respiratory rate measurement is limited. An observational study that sought to identify markers of serious illness in infants under 6 months on presentation to hospital, found rapid respiratory rates were not very useful (Hewson et al., 1990). This study found that some healthy babies aged 2 weeks to 4–5 months consistently breathed at 70–100 breaths per

minute while at rest and awake, thereby limiting the usefulness of a cut-off value of 50 breaths per minute as a indicator of respiratory dysfunction. A similar study in adults, comparing respiratory rates and oxygen saturation, found that only 33% of people with an oxygen saturation below 90% had an increased respiratory rate (Mower et al., 1996). Several studies have also highlighted limitations of respiratory rate associated with inaccurate measurement. A descriptive study comparing the measurement of respiratory rate for 15 s compared to a minute found that rates commonly differed between count periods (Hooker et al., 1989). Similar results in children have also been reported when a 30 and 60 s count period was used, with the 60 s period resulting in the least variability (Simoes et al., 1991). One descriptive study found that respiratory rates counted in babies using a stethoscope were 20–50% higher than those counted from beside the cot (Hewson et al., 1990), and another study of infants found that factors such as agitation, upper respiratory tract infection and age of infants between 2 and 11 months increased variation in the respiratory rate measurement (Simoes et al., 1991). 3. Blood pressure measurement: A large number of studies have addressed many components of blood pressure measurement, particularly in regard to factors that can influence measurement accuracy. Studies have demonstrated that many factors can contribute to inaccurate measurements such as inappropriate cuff size (Nielsen and Janniche, 1974; Nielsen et al., 1983; Geddes and Tivey, 1976; Geddes and Whistler, 1978; van Montfrans et al., 1987; Burch and Shewey, 1973; Maxwell et al., 1982; Manning et al., 1983), site of measurement (Tachovsky, 1985; Forsberg et al., 1970; Hocken, 1967), position of arm (Webster et al., 1984; Mitchell et al., 1964), position of the person during measurement (Newton, 1981; Fleming et al., 1983), use of the bell or the diaphragm of stethoscope (Mauro, 1988; Prineas and Jacobs, 1983) and talking during measurement (Hellmann and Grimm, 1984). In addition to these many factors that influence blood pressure measurement accuracy, another study found that nurses often do not follow recommended techniques (Bogan et al., 1993). It is therefore not surprising that a descriptive study concluded that only 3% of general practitioners and 2% of nurses obtained reliable blood pressure measurements (Villegas et al., 1995). However, two studies found that education programs increased agreement between blood pressure readings and significantly reduced difference in technique (Sherwitz et al., 1982). Studies have also demonstrated that patient factors can influence the accuracy of measures. One descriptive study identified falsely elevated blood pressure and pulse rates on surgical patients following admission to hospital (O’Dell, 1974). These elevated readings decreased over the first 6 h of admission, suggesting that

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the initial vital signs may be inappropriate to use as baseline values for comparison of subsequent changes. This ‘white coat hypertension’ has been reported in many community-based studies of adults (Mancia et al., 1983; Watson et al., 1987; Mancia et al., 1987; Lerman et al., 1989; Pickering et al., 1988) and children (Hornsby et al., 1991). While the magnitude of the increase can be as great as 75 mmHg (Mancia et al., 1983), repeat measurements have been shown to overcome this problem (Brueren et al., 1996; Burstyn et al., 1981; Carey et al., 1976). These studies suggest that single blood pressure measurements will not be a reliable basis for treatment. A retrospective study of all vital sign parameters in patients with severe thoracoabdominal injury found that normal or stabilised post-injury vital signs did not signify the absence of a life-threatening haemorrhage (Luna et al., 1989). 4. Temperature measurement: The largest number of studies identified during the review addressed the measurement of temperature. Studies have demonstrated that the insertion time used during the measurement of oral temperatures has a significant impact on measurement accuracy (Coggon and Vessey, 1976; Nichols and Fielding, 1969; Nichols, 1972). While these studies suggest an insertion time of 6–7 min is required to ensure an accurate measurement, a survey of nurses found that 37% left the thermometers in place for less than a minute (Graves and Markarian, 1980). Accuracy of tympanic temperature measurements are also influenced by a variety of factors such as environmental temperature (Zehner and Terndrup, 1991; Doyle et al., 1992), cerumen (Hasel and Erickson, 1995; Doezema et al., 1995) and operator technique (Pransky, 1991; Terndrup and Rajik, 1992).

4. Implications for practice While there is considerable research addressing specific aspects of vital sign measurement, there has been little attempt to address the larger contextual issues. It would appear from the identified papers that other measures might be useful additions to the traditional four vital sign parameters. However, much of this support is based on limited research evidence or expert opinion. In the research reviewed, the only parameters that have been shown to change practice are pulse oximetry and smoking status. There is evidence to suggest that in some situations pulse oximetry is useful for detecting a deterioration in physiological function that might otherwise be missed by health care workers. This early detection has resulted in changed patient management and a reduction in the number of investigations undertaken. On this basis, pulse oximetry could be considered as the fifth vital sign parameter, and be used in situations where assessment

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of oxygenation is critical, such as the peri-operative period, during and following anaesthetics, during insertion of central venous lines, and as part of the assessment of any potentially seriously ill person. However, there is currently little research evidence to show that the routine measurement of pulse oximetry on all hospital patients will result in changed patient management or improved patient outcomes. Smoking status has been shown to be a useful measure during the initial encounter with the patient. While it does not meet the traditional concept of signs that represent vital physiologic functions and would be inappropriate to be measured routinely, smoking status may have a role in some situations. During the admission of patients to hospital, or during outpatient and community-based patient assessment, smoking status would likely provide important information that may influence patient management by encouraging the provision of appropriate health information and education. In reviewing the studies and reports related to the optimal frequency of vital sign measurement, little useful information was identified because it has received only limited attention. The few studies that evaluated a reduction in the frequency of vital sign measurements report only minor and superficial change during the care of a specific group of patients. To date, the frequency of vital signs in clinical practice is based on either expert opinion or tradition, rather than research evidence. Vital signs have also been shown to be of only limited value for the detection of serious illness in adults, children and infants. Descriptive studies have shown that normal vital sign parameters do not necessarily indicate normal physiologic function. Added to this, many factors related to operator technique can also influence measurement accuracy, with some studies suggesting that health care workers do not always follow the recommended practice. However, there appears to have been no evaluation on the usefulness of vital signs as indicators of deteriorating physiological status when the parameters change suddenly from previously stable values. The technique used in monitoring vital signs has been shown to influence measurement accuracy. However, studies have also demonstrated that education programs are effective in reducing differences in blood pressure measurement technique. This suggests that health care workers should be trained to perform patient observations in a standardised manner to minimise differences due to technique.

5. Implications for research While there is a wealth of research on specific aspects of blood pressure and temperature measurement, the more important questions on the role, the nature and the

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optimal practice of vital sign measurement have not been asked. On this basis, there is an urgent need for rigorous evaluation of most aspects of vital sign measurement as used for hospital patients. One important area not addressed in the studies reviewed is that of the role of advanced technology in vital signs measurement. Currently available devices can monitor a range of physiological parameters, can alarm for changing status and some can print reports or graphical trends of these parameters. These devices have the potential to produce significant changes to clinical practices. Some of these advanced technologies are now employed in some clinical areas, but this is based more on the availability of the equipment than on a demonstrated usefulness or an ability to improve care delivery, patient outcomes or cost. This issue has not been seriously addressed in the health care literature. There is some evidence to suggest that visual observation may be appropriate for the monitoring of patient status and progress. However, this is based on a practice report and currently it has not been rigorously evaluated. This would suggest a need to evaluate visual observation as an alternative to vital sign measurement to determine its role and impact on patient safety. Many studies have demonstrated that techniques used by health care workers often contribute to inaccurate measurements. While education has been shown to improve blood pressure measurement technique, there is little other information on how best to correct this problem. This highlights the need for further investigation on how to ensure accuracy of vital signs as measured by health care workers.

6. Conclusion This review has highlighted the lack of research on many important issues related to vital signs such as the role, nature and optimal practice of vital sign measurement. This would suggest that much of current practice of vital sign measurement is based more on tradition and expert opinion, than on research evidence. Current evidence suggests that smoking status and pulse oximetry may be useful additions to the traditional vital signs. Smoking status has been shown to influence practice during the initial encounter between patient and health care worker in terms of improving the provision of appropriate counseling and education. Pulse oximetry has also been shown to change practice, and on this basis would be an appropriate adjunct to traditional parameters in situations where assessment of patient status is critical. In concluding this review, it is recommended that further research be initiated into the broader issues of vital sign measurement, to ensure the most useful parameters are monitored, at an appropriate frequency,

using accurate techniques. These investigations will help minimise practices based more on ritual than on research evidence.

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