MedMath 2.0

A medical calculator for the Palm OS ® Platform

Instructions

Screen shotMedMath is a medical calculator for the Palm OS ® Platform. It is designed for rapid calculation of common equations used in adult internal medicine. It is capable of calculating complex quantities (e.g. Dubois formula for Body Surface Area) without resorting to external libraries such as MathLib. For certain quantities, alternate units can easily be selected.

MedMath is largely self-explanatory. On startup, a list of formulas is displayed. Different categories of formulas may be viewed using the pop-up trigger at the upper right corner of the screen. Tapping the menu silkscreen button reveals options for selecting United States (US) units vs. Système Internationale (SI) units, and for clearing the "Last Used" list of equations.

After a formula from the list is selected, the calculation form appears. Simply fill in the numeric fields using Graffiti or the onscreen numeric keypad. The up and down arrow buttons on the keypad move the cursor from field to field; a field may also be selected by tapping directly on it. The units for some quantities may be displayed within selection boxes; tapping on these boxes brings up a pop-up menu of other units that may be used instead. Note that the formula at the top of the calculation form is always shown using US units.

Special buttons:

  • C (Clear): clears the field under the cursor.
  • Backspace: deletes the digit to the left of the cursor.
  • Reset All: clears the form and re-loads default values, if any.
  • Calculate: calculates the desired quantity; all numeric fields must be filled. Please note that range-checking is not provided, except to prevent division by zero. If you enter physiologically unreasonable values, don't be surprised to see physiologically unreasonable answers. Be careful with the units!  Asterisks (***) are shown if the answer overflows.
  • Info: displays a screen giving background information about the formula being used. Most of the formulas are documented with references.
  • Close: returns to the formula list.

Formulas currently supported by MedMath:

  • A-a O2 Gradient
  • Absolute Neutrophil Count
  • Anion Gap (Serum)
  • Anion Gap (Urine)
  • Basal Energy Expenditure
  • Body Mass Index
  • Body Surface Area (Dubois)
  • Cardiac Output (Fick)
  • Corrected QT (QTc)
  • Corrected Serum Calcium
  • Corrected Serum Phenytoin
  • Corrected Serum Sodium
  • Creatinine Clearance (Cockcroft-Gault)
  • Creatinine Clearance (measured)
  • Dosing Calculator
  • Fractional Excretion of Sodium
  • Glomerular Filtration Rate (MDRD)
  • Henderson-Hasselbalch Equation
  • Hepatitis Discriminant Function
  • Ideal Body Weight
  • Kt/V (Daugirdas)
  • LDL
  • Likelihood Ratios
  • Mean Arterial Pressure
  • MELD (Mayo Endstage Liver Disease) Score
  • Number Needed to Treat
  • Osmolality (Serum)
  • Osmotic Gap (Stool)
  • Parkland Formula
  • Peak flow, predicted (Nunn-Gregg)
  • Pediatric Maintenance Fluids
  • PELD (Pediatric Endstage Liver Disease) Score
  • Posttest Probability (Sensitivity/Specificity)
  • Posttest Probability (Likelihood Ratios)
  • Reticulocyte Index
  • Transtubular Potassium Gradient
  • Water Deficit
  • Winters' Formula

Prominent features of MedMath include:

  • Formulas sorted by category
  • Consistent, straightforward user interface
  • Onscreen numeric keypad with backspace button
  • Global selection of US or SI units
  • Onscreen individual unit selection from pop-up menus
  • Information screens providing tips on equation usage and references
  • Program keeps track of the last 10 equations used
  • Editable "Favorites" category
  • No external programs or libraries required
  • State of the program is saved on exit
  • Runs on all Palm platforms, including Palm OS 1.0, without external libraries

Requirements

Palm OS 1.0 or higher.

MedMath occupies less than 50K of memory.

Download / Installation

Download the zip file for MedMath version 2.0 here.

Unzip the 'MedMath.prc' file from the archive and HotSync it to your Palm device using your favorite install tool.

Availability

MedMath is free for non-commercial distribution.  Redistributions should include this documentation with its copyright notices. The source code for MedMath is not publicly available.

E-mail bug reports, comments, suggestions, etc. to the address listed at the end of this document; be sure to include "MedMath" in the subject line. I am interested in suggestions for additional formulas and features, as well as for more suitable references.

Background

I wrote MedMath during my third year of residency in internal medicine at the Hospital of the University of Pennsylvania (HUP). At HUP, I also designed the OncoTrials project, an automated multicenter cancer clinical trials database (the project has fallen by the wayside since I left).

MedMath was implemented in C using prc-tools, a free compiler tool chain, and pilrc, a free resource compiler. Floating point display methods were adapted from public code by Jim Berry.  Math routines were modified from logf and powf routines originally developed at SunPro and currently found in many C math libraries.

MedMath is rated5 Cowsby TUCOWS.

For something completely different, check out the freeware puzzle game Traffic!, my first program for the Palm OS Platform.

Related Links

I am not associated with any of the sites below.

Medical Equations:

Palm-Based Medical Calculators:

  • Archimedes by Skyscape
  • MedCalc by Mathias Tschopp, M.D. A very comprehensive free calculator with an interface similar to MedMath's.
  • MediCalc (GCC) by David Monbaron
  • Medical Mathpad (MathPad) by Vince Iannelli, M.D.

Other Handheld Platforms:

  • Medikit for Psion 5 / EPOC by Jonathan Perry, M.D.

Web-Based Medical Calculators:

History

v. 1.0

11/12/99
  • First public release

v. 1.01

11/28/99
  • Fixes for international users:
    • Selecting long category names in the pop-up category menu causes the French Palm OS to crash. The categories of "Lab Correction" and "Measurement" have been renamed to "Lab" and "Measures."
    • Program now reads the numeric format in the system preferences to determine whether the decimal separator is a period or a comma.

v. 1.1

1/9/2000
  • Added Evidence-Based Medicine (EBM) formulas: Posttest Probability (Bayes Theorem, Fagan Nomogram), Likelihood Ratios, Number Needed to Treat
  • Fixed bug in displaying answer units when SI Units are the default

v. 1.2

5/17/2001
  • Added LDL, cardiac output (Fick), predicted peak flows, MELD (Mayo Endstage Liver Disease) score, GFR (MDRD formula), and Kt/V (Daugridas formula).
  • Recompiled using SDK 3.5, fixing several display bugs that occur in Palm OS 3.5 and higher.
  • Fixed bugs that were reported only in debug ROMs of Palm Emulator.
  • Added editable "Favorites" category.
  • Renamed "Cockcroft-Gault Eqn" to "Cr Clearance (Cockcroft-Gault)" after some confusion regarding this item.
  • Color icon

v. 1.21

7/7/2002
  • Clarification of MELD scores; MedMath now calculates both the original Mayo score (for prognostic information) and UNOS score (for transplant allocation).
  • Recompiled using SDK 4.
  • Fixed several overflow bugs.

v. 2.0

1/4/2004
  • Added dosing calculator, PELD (Pediatric Endstage Liver Disease) score, Parkland Formula, Pediatric Maintenance Fluids.
  • More robust display overflow detection; asterisks shown if numeric overflow.
  • Answers cleared if invalid inputs and calculate button is pressed.
  • Units independently configurable for height and weight.
  • Undo/cut/copy/paste supported on calculation screen.
  • Internal changes to increase efficiency while minimizing footprint.
  • Minor interface changes for compliance with PalmSource UI guidelines.
  • High resolution color icon added.
  • Text added describing age range for Nunn and Gregg peak flow prediction formula (don't use it for kids!)
  • Recompiled using SDK 5.0r3 and pilrc 3.1.
  • Updated copyright notice.

Legalese

MedMath is Copyright © 1999-2004 by Phillip Cheng, M.D.
All rights reserved.

Permission to use, copy, and distribute this software and its documentation for any non-commercial purpose, without fee, and without a written agreement is hereby granted, provided that the above copyright notice and this permission notice is included in all copies or substantial portions of the Software. For commercial usage, please contact the author.

Extensive effort has been exerted to make this software as accurate as possible. However, the accuracy and completeness of the information provided by this software cannot be guaranteed. This software is to be used as a guide only, and health care professionals should use sound clinical judgment and individualize therapy to each specific patient care situation.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

MedMath modifies math routines developed at SunPro.  The copyright notice for these routines follows:

 ====================================================
 Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 
 Developed at SunPro, a Sun Microsystems, Inc. business.
 Permission to use, copy, modify, and distribute this
 software is freely granted, provided that this notice
 is preserved.
 ====================================================

Phillip Cheng, M.D. (pcheng@post.harvard.edu)

Last updated 01/19/2004