Swiss Micros DM41X: Health Calculations
These programs also apply to the HP 41C or almost any emulator. I don't believe that you will need the Extended Functions Module for these programs.
Mean Arterial Pressure
Generally, when we take our blood pressure we get a ratio: systolic blood pressure over diastolic blood pressure. The Mean Arterial Pressure (MAP) can be calculated by the following formula:
MAP = (Systolic BP + 2 × Diastolic BP) ÷ 3
Example:
Systolic BP = 124
Diastolic BP = 86
Result: MAP ≈ 98.6667
Swiss Micros DM41X Program: MAP
01 LBL^T MAP
02 ^T SYS BP?
03 PROMPT
04 ^T DIA BP?
05 PROMPT
06 2
07 *
08 +
09 3
10 /
11 ^T MAP =
12 ARCL X
13 AVIEW
14 RTN
Source:
Lung, Johnny. Respiratory Therapy Formulas and Calculations Respiratory Therapy Zone 2020
Body Surface Area: The Mosteller Formula
There are several ways of calculating BSA (body surface area) which is used as a person's metabolic mass, which in turn is used in other clinical and respiratory calculations such as the cardiac output. Several formulas to estimate BSA exist, including formulas from Haycock, Fujimoto, Body, Du Bois, and Mosteller. The calculations depend on two factors: the person's height in centimeters (cm), and the person's mass in kilograms (kg). The BSA is measured in squared meters (m^2).
The Mosteller formula provides a simple calculation:
BSA ≈ √(mass × height) ÷ 60
The program presented will allow for U.S. units, as amounts are converted when necessary. Using U.S. units, enter height in inches (in) and mass in pounds (lb). The result will be in square feet (ft^2).
Conversions:
1 in = 2.54 cm
2.2406 lb ≈ 1 kg
1 m^2 ≈ 10.7639 ft^2
The program will prompt you "IN/LB? Y=1" if you want to use U.S. units, enter 1 then press [R/S] for yes, entering any other number then [R/S] defaults to SI units. In U.S. units mode, flag 1 is turned on (there will be a 1 indicator on the screen).
Examples:
Height = 70 in (5'10")
Mass = 240 lb
BSA ≈ 24.9589 ft^2
Height = 177.8 cm
Mass = 108.8622 kg
BSA ≈ 2.31874 m^2
Swiss Micros DM41X Program: BSA
01 LBL^T BSA
02 CF 01
03 ^T IN/LB? Y=1
04 PROMPT
05 1
06 X=Y?
07 SF 01
08 ^T HEIGHT?
09 PROMPT
10 FS? 01
11 2.54
12 FS? 01
13 *
14 ^T WEIGHT?
15 PROMPT
16 FS? 01
17 2.2046
18 FS? 01
19 /
20 *
21 SQRT
22 60
23 /
24 ^T BSA=
25 AVIEW
26 PSE
27 PSE
28 FS? 01
29 10.7639
30 FS? 01
31 *
32 FS? 01
33 ^T FT^2:
34 FC? 01
35 ^T M^2:
36 ARCL X
37 AVIEW
38 CF 01
39 RTN
Source:
"Body Surface Area". Wikipedia. Edited July 22, 2021. Accessed on August 9, 2021. https://en.wikipedia.org/wiki/Body_surface_area
Cardiac Output with Fick's Equation
Given the following variables:
VO_2: total oxygen consumption in L/min
CaO_2: arterial oxygen content in ml/L
CvO_2: venous oxygen content in ml/L
HR: heart rate (BPM)
The following can be calculated:
CO: Cardiac Output in l/min
CO = (VO_2 × 100) ÷ ((CaO_2 - CvO-2) × 1000)
SV: Stroke Volume in ml/beat
SV = (CO × 1000) ÷ HR
Example:
Inputs:
VO_2: 248 ml/min
CaO_2: 22% (enter 22)
CvO_2: 18% (enter 18)
HR: 84 BPM
Results:
CO = 6.2000 l/min
SV = 73.8095 ml/beat
Swiss Micros DM41X Program: FICK
01 LBL^T FICK
02 ^T VO.2?
03 PROMPT
04 ^T C.A 0.2 %?
05 PROMPT
06 ^T C.V 0.2 %?
07 PROMPT
08 -
09 1000
10 *
11 /
12 100
13 *
14 STO 01
15 ^T CO =
16 ARCL 01
17 AVIEW
18 STOP
19 1000
20 *
21 ^T HR?
22 PROMPT
23 /
24 STO 02
25 ^T SV =
26 ARCL 02
27 AVIEW
28 RTN
Sources:
"Fick Cardiac Output" HP 67/97 User's Library Solutions: Cardiac. Corvallis, OR. 1976. pp. 20-23 https://literature.hpcalc.org/community/hp6797-ul-cardiac.pdf
"Fick's Cardiac of cardiac output measurement" Deranged Physiology. Updated December 1, 2020. Accessed August 9, 2021. https://derangedphysiology.com/main/cicm-primary-exam/required-reading/cardiovascular-system/Chapter%20811/ficks-principle-cardiac-output-measurement
Download the .raw files here: https://drive.google.com/file/d/1VJCkwSk9QpbBFsxoh6H0G8dRfAuuVU7j/view?usp=sharing
Eddie
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