1. According to the study narrative and Figure 1 in the Flannigan et al. (2014)
ID: 3204184 • Letter: 1
Question
1. According to the study narrative and Figure 1 in the Flannigan et al. (2014) study, does the APLS UK formula under- or overestimate the weight of children younger than 1 year of age? Provide a rationale for your answer.
2. Using the values a = 3.161 and b = 0.502 with the novel formula in Figure 1 , what is the predicted weight in kilograms (kg) for a child at 9 months of age? Show your calculations.
3. Using the values a = 3.161 and b = 0.502 with the novel formula in Figure 1 , what is the predicted weight in kilograms for a child at 2 months of age? Show your calculations.
4. In Figure 2 , the formula for calculating y (weight in kg) is Weight in kg = (0.176 × Age in months) + 7.241. Identify the y intercept and the slope in this formula.
Introduction Medications and other therapies often necessitate knowing a patient's weight. However a child may be admitted to a pediatric intensive care unit (PICU) without a known weight and instability and on-going resuscitation may prevent obtaining this needed weight Clinicians would benefit from a tool that could accurately estimate a patient's weight when such information is unavailable. Thus Flannigan et al. (2014) conducted a retro- spective observational study for the purpose of determining "if the revised APLS UK Advanced Paediatric Life Support United Kingdom) formulae for estimating weight are appropriate for use in the paediatric care population in the United Kingdom" (Flannigan et al., 2014, p. 927). The sample included 10,081 children (5,622 males and 4,459 females) who ranged from term-corrected age to 15 years of age, admitted to the PICU during a 5-year period. Because this was a retrospective study, no geographic location, race, and ethnicity data were collected for the sample. A paired samples t-test was used to compare mean sample weights with the APLS UK formula weight. The "APLS UK formula weight F (0.05 x age in months) 4' significantly overestimates the mean weight of children under 1 year admitted to PICU by between 10% and 25.4%" (Flannigan et al, 2014, p 928). Therefore, the researchers concluded that the APLS UK formulas were not appropri- ate for estimating the weight of children admitted to the PICU Relevant Study Results Simple linear regression was used to produce novel formulae for the prediction of the mean weight specifically for the PICU population" (Flannigan et al., 2014, p. 927). The three novel formulas are presented in Figures 1, 2, and 3, respectively. The new formulas calculations are more complex than the APLS UK formulas. "Although a good estimate of mean weight can be obtained by our newly derived formula, reliance on mean weight alone will still result in significant error as the weights of children admitted to PICU in each age and sex gender group have a large standard deviation...Therefore as soon as possible after admission a weight should be obtained, e.g., using a weight be (Flannigan et al., 2014, p. 929)Explanation / Answer
1. The APLS UK formula overestimates the weight of children younger than 1 year of age.
The formula is .05 x age in months + 4".
The formula assums that the minimum weight of a child when born (age is 0 months) is 4 lb. But it is possible that the minimum weight is less than 4 lb. The figure 1 also denotes that the actual weight can be very low, much below 4 lb. Also, the figure shows that for any specific age, the weight calculated by APLS formula is very high compared to the actual weight. Infact, it is consistently higher than actual weight. The narrative also mentions that the weight using this formula is 10% to 25% higher. Thus, we can say that APLS UK formula overestimates the weight of children younger than 1 year of age.
2. The novel formula in Figure 1 is as follows
weight = (.502 x age in months) + 3.161"
When a child is 9 months of age
The predicted weight is .502 x9 + 3.161"
= 4.518 + 3.161 = 7.68" or 7.68 lb
1 lb = 0.453592 kg
Therefore, 7.68 lb = 3.483589 kg or 3.484 kg (Answer)
3. The novel formula in Figure 1 is as follows
weight = (.502 x age in months) + 3.161"
When a child is 2 months of age
The predicted weight is .502 x2 + 3.161"
= 1.004 + 3.161 = 4.17" or 4.17 lb
1 lb = 0.453592 kg
Therefore, 4.17 lb = 1.89148 kg or 1.892 kg (Answer)
4. In Figure 2 , the formula for calculating y (weight in kg) is Weight in kg = (0.176 × Age in months) + 7.241.
The formula can be written as y = (slope x age in months) + y intercept
y intercept is the weight in kg when age is zero
Here, y intercept = 7.241 (Answer)
Slope is the increase in weight for each month of increase in age
Here, slope = 0.176 (Answer)
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