Sunday, October 24, 2021

Swiss Micros DM41X: Health Calculations

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