What Is 'Normal?' Evaluating Vital Signs
What Is 'Normal?' Evaluating Vital Signs
The purpose of this review of the evidence was to look to the current literature to determine normative VS values, as well as define abnormal or significant changes in VS. To answer the clinical question, "Among pediatric patient ages 1 through 5 years, what are 'normal' VS parameters?" the authors reviewed a sampling of pediatric textbooks from the nursing and medical disciplines. The current normative HR and RR charts found in medical and nursing textbooks are inconsistent and are largely based on expert opinion (Level VII) and not based on research findings. Blood pressure normative data most frequently cited the Fourth Report (NHBPEP Working Group on High Blood Pressure in Children and Adolescents, 2004). This report was primarily designed for identifying hypertension in children and not to define normative ranges, although there has been some work on defining hypotension. Normative values for vital signs were inconsistent. How those values were reported was also inconsistent, with some values given as ranges and others as means or medians.
The inconsistency and paucity of evidence cited in the development of the VS charts prompted the authors to search for studies designed to establish normative values in children 1 to 5 years of age. The research literature has used descriptive design (Levels V and VI) (Melnyk & Fineout-Overholt, 2011), which can be expected in developing normative charts. Normative charts have been based on a normal distribution of values, but there is inconsistency in the use of 5 and 95 percentiles (versus 2.5 and 90 or 97.5 percentiles) as the cutoff points for normal values. Methods of collecting VS data were inconsistent, despite literature on variations between different methods (Fleming et al., 2011; Park & Menard, 1989; Rusconi et al., 1994). One study measured RR by means of observation of the fully clothed child (Wallis et al., 2005), and a second study listened with a stethoscope to the bare chest wall (Rusconi et al., 1994). The inconsistency in the methods of measuring may introduce systematic error in synthesizing studies to determine normative values. Epidemiological studies of VS parameters have also been criticized for including children with unhealthy characteristics, for example, including hypertensive children in the sample that may increase the upper limits of normal BP (Rosner et al., 2008). A 2011 meta-analysis confirmed the finding of inconsistency across the literature (Fleming et al., 2011). This meta-analysis of the current evidence resulted in parameters that differed from those used in national and international life support guidelines on HR and RR in young children, further indicating more research is needed.
To answer the second clinical question, "Among pediatric patient ages 1 through 5 years, what is a significant clinical change in VS?" the literature on Early Warning Systems was reviewed. The normative VS values were inconsistent across the various systems. Additionally, not all studies sought to identify which items predicted deterioration of health status. When determining what change in VS was predictive of deterioration, tachypnea and respiratory distress were the primary predictors (Haines et al., 2006; Tume, 2007). Tachycardia was a predictor only if fluid status had been addressed (Haines et al., 2006). Blood pressure as a sign of shock was considered a late sign and was not included in one pediatric tool for that reason (Monaghan, 2005). Many early warning tools rely on behavioral changes and the nurses' "worry" over the child as indicators of impending deterioration. Although there is good evidence of the need for screening for hypertension in children, support for the use of BP as a predictor of deterioration is limited due lack of normative data on the low end of BP and the lack of evidence in its usefulness as an early indicator of health status.
Discussion
The purpose of this review of the evidence was to look to the current literature to determine normative VS values, as well as define abnormal or significant changes in VS. To answer the clinical question, "Among pediatric patient ages 1 through 5 years, what are 'normal' VS parameters?" the authors reviewed a sampling of pediatric textbooks from the nursing and medical disciplines. The current normative HR and RR charts found in medical and nursing textbooks are inconsistent and are largely based on expert opinion (Level VII) and not based on research findings. Blood pressure normative data most frequently cited the Fourth Report (NHBPEP Working Group on High Blood Pressure in Children and Adolescents, 2004). This report was primarily designed for identifying hypertension in children and not to define normative ranges, although there has been some work on defining hypotension. Normative values for vital signs were inconsistent. How those values were reported was also inconsistent, with some values given as ranges and others as means or medians.
The inconsistency and paucity of evidence cited in the development of the VS charts prompted the authors to search for studies designed to establish normative values in children 1 to 5 years of age. The research literature has used descriptive design (Levels V and VI) (Melnyk & Fineout-Overholt, 2011), which can be expected in developing normative charts. Normative charts have been based on a normal distribution of values, but there is inconsistency in the use of 5 and 95 percentiles (versus 2.5 and 90 or 97.5 percentiles) as the cutoff points for normal values. Methods of collecting VS data were inconsistent, despite literature on variations between different methods (Fleming et al., 2011; Park & Menard, 1989; Rusconi et al., 1994). One study measured RR by means of observation of the fully clothed child (Wallis et al., 2005), and a second study listened with a stethoscope to the bare chest wall (Rusconi et al., 1994). The inconsistency in the methods of measuring may introduce systematic error in synthesizing studies to determine normative values. Epidemiological studies of VS parameters have also been criticized for including children with unhealthy characteristics, for example, including hypertensive children in the sample that may increase the upper limits of normal BP (Rosner et al., 2008). A 2011 meta-analysis confirmed the finding of inconsistency across the literature (Fleming et al., 2011). This meta-analysis of the current evidence resulted in parameters that differed from those used in national and international life support guidelines on HR and RR in young children, further indicating more research is needed.
To answer the second clinical question, "Among pediatric patient ages 1 through 5 years, what is a significant clinical change in VS?" the literature on Early Warning Systems was reviewed. The normative VS values were inconsistent across the various systems. Additionally, not all studies sought to identify which items predicted deterioration of health status. When determining what change in VS was predictive of deterioration, tachypnea and respiratory distress were the primary predictors (Haines et al., 2006; Tume, 2007). Tachycardia was a predictor only if fluid status had been addressed (Haines et al., 2006). Blood pressure as a sign of shock was considered a late sign and was not included in one pediatric tool for that reason (Monaghan, 2005). Many early warning tools rely on behavioral changes and the nurses' "worry" over the child as indicators of impending deterioration. Although there is good evidence of the need for screening for hypertension in children, support for the use of BP as a predictor of deterioration is limited due lack of normative data on the low end of BP and the lack of evidence in its usefulness as an early indicator of health status.
