Drug dose rate calculator

A drug dosage calculation system includes a hand held, battery operated computing device for use by nurses and other clinical personnel to make calculations pertaining to the drug administration rate and the corresponding flow rate settings of IV systems that are used for intravenous administration of fluids to a patient. Flow rate setting, drug dose rate, drug amount and the amount of IV solution into which the drug is diluted are the primary variables used in such calculations. A keyboard is used to supply data to a computation device that computes the unknown quantity. A display device displays the data input to the computer and also displays data calculated for the unknown variable.

BACKGROUND OF THE INVENTION 
This invention relates generally to apparatus and methods for administering 
drugs and other substances intravenously into a patient. The invention 
relates more particularly to apparatus and methods for assuring that a 
prescribed dosage is actually administered to the patient. 
There are significant difficulties in assuring administration of prescribed 
dosages to patients. The difficulties arise from the various units in 
which prescriptions are given and from the units that define the dosage 
rates that are administered by typical intravenous equipment. Drug 
administration rates are commonly prescribed in milligrams, micrograms or 
UNITS per unit of time. A UNIT is a measure of an amount of a drug. The 
time is usually given in hours or minutes. The patient's body weight in 
kilograms or pounds may be a factor in the drug administration rate. The 
patient's body surface area, commonly given in square meters, may also be 
considered in determining the drug administration rate. 
Actual drug administration rates are determined by a pump setting that is 
normally a certain number of drops per minute or cubic centimeters per 
hour. A physician will normally prescribe a drug administration rate in 
units of measure with which he is familiar or in units recommended by the 
drug's manufacturer. The nurse or other technician who actually sets the 
pump rate must convert the prescribed drug administration rate into an 
appropriate number of drops per minute or cubic centimeters per hour so 
that the pump may be set at a value appropriate for delivering the 
prescribed amount of drug to the patient. 
Present methods for determining the pump rates include hand calculations 
and calculations using general purpose calculators. These methods are 
subject to error with results that are sometimes catastrophic. 
Therefore, there is a need in the art for a simple, reliable device for 
calculating drug dose rates to facilitate administration of prescribed 
dosages. 
SUMMARY OF THE INVENTION 
The present invention provides a drug dosage calculation system and method 
that overcomes the deficiencies of prior systems and methods. The 
invention comprises a hand held, battery operated computing device for use 
by nurses and other clinical personnel to make calculations pertaining to 
the drug administration rate and the corresponding pump settings of IV 
pumps that are used for intravenous administration of fluids to a patient. 
The operational features of the computing device according to the 
invention are self explanatory and fail-safe so that improper dosage 
calculations cannot be made. 
The computing device according to the invention accepts input values for 
three of four variables used in determining the amount of drug to be 
administered to the patient. These variables are pump setting, drug dose 
rate, drug amount and the amount of IV solution into which the drug is 
diluted. 
A drug dosage calculation system according to the invention for calculating 
a variable selected from the group consisting of the pump setting, 
intravenous solution volume, drug dose rate and drug quantity when three 
of the variables are known for intravenous administration of drugs or the 
like to a patient by means of a pump and a catheter connected to the pump, 
comprises: a computation device; keyboard means for inputting data for 
three of the variables to the computation device; and display means for 
displaying the data input to the computing means and for displaying data 
calculated for the previously unknown variable. 
The keyboard in the system of the invention includes a first set of keys 
connected to the computation device for supplying signals thereto 
indicative of the pump setting, intravenous solution volume, drug dose 
rate and drug quantity variables; a second set of keys connected to the 
computation device for supplying signals thereto indicative of the 
numerical value of the selected variable; and a third set of keys 
connected to the computation device for supplying signals thereto 
indicative of the units of the selected variable. The computing device may 
provide an output to a valve for controlling the rate of fluid flow from a 
source of fluid. 
The method of the invention for determining one of the variables selected 
from the group consisting of the pump setting, intravenous solution 
volume, drug dose rate and drug quantity when three of the variables are 
known for intravenous administration of drugs or the like to a patient by 
means of a pump and a catheter connected to the pump, comprises the steps 
of: supplying data indicative of the known variables to a computation 
device; supplying data indicative of the numerical values of the known 
variables to the computation device; supplying data indicative of the 
units of the known variables to the computation device; supplying data 
indicative of selected units of the unknown variable to the computation 
device; and computing the previously unknown variable.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1, a drug administration rate calculator 110 according to 
the invention includes a keyboard 112 and a display 114 mounted in a case 
116. The keyboard 112 and the display 114 are connected to a computation 
system 118, shown in FIGS. 4 and 5. The display 114 is preferably a liquid 
crystal display well known in the art, and the keyboard 112 may be any 
suitable data entry device well known in the art for inputting data to 
electronic calculators and computers. The computation system 118 
preferably comprises well-known CMOS technology so that it can operate for 
extended periods of time on the power available from conventional 
batteries (not shown). 
Still referring to FIG. 1, the keyboard 112 has keys for each of the 
variables that are considered in intravenous administration of a drug to a 
patient. The drug administration rate calculator 110 permits selection of 
the unknown variable and its units, where there is a choice of units, so 
that the numerical value of the unknown may be calculated. The labeling of 
these variable keys and the units for the variables are summarized in 
TABLE I below. 
TABLE 1 
______________________________________ 
KEYBOARD VARIABLE AND UNIT KEYS 
Key Label Key Variable Units 
______________________________________ 
PUMP Pump Setting cc/hr, drops/min 
DDR Drug Dose Rate .mu.g, kg, mg per hr 
or per min, per m.sup.2 
or per kg, if specified 
DRUG Drug Amount .mu.g, mg or UNITS 
IV SOL IV solution Volume 
cc 
BSA Body Surface Area 
m.sup.2 
WT Body Weight kg, lb 
HT Body height cm, inches 
DROPS Drops of Drug Drops/cc 
______________________________________ 
The pump setting variable should be understood to include any means for 
controlling the flow of drug to a patient. For example, in some systems it 
is necessary to control the setting of a valve (not shown) to regulate the 
flow of fluid from a container above the patient. The height differential 
supplies the pressure necessary for the fluid to enter the patient's body 
so that pumping is unnecessary. 
The PUMP, DDR, DRUG and IV SOL keys are the primary variables that are 
considered in intravenous drug administration. The remaining variables 
sometimes must be used to provide data necessary for determining some of 
the primary variables. For example, the patient's body surface area may be 
calculated from the empirical formula 
EQU BSA=0.007184W.sup.0.425 H.sup.0.725, 
where BSA is the body surface area, W is the patient's body weight in 
pounds and H is the patient's height in inches. The empirical formula for 
calculating the body surface area is preferably included in the software 
as explained subsequently. 
The keyboard 112 and display 114 are preferably arranged so that LCD 
annunciators correspond to the keys. The annunciators indicate the units 
of the variables. After the drug administration rate calculator 110 is 
turned on, the annunciators for the four primary keys turned on. The 
keyboard 112 includes a number pad that has a decimal point and digit keys 
0-9, a clear key C and a compute key, labeled COMP. 
In order to input data for a known variable, the user first presses the key 
corresponding to the variable and then depresses keys to input the 
numerical value of the variable. The user must next depress a key to 
select the units for the variable if there is a choice of units available. 
After the input sequence is complete, the numerical value and the units of 
the variable last input are displayed on the LCD display 114. The 
variables may be input to the drug administration rate calculator 110 in 
any desired order. Any time a variable key is depressed, previous 
numerical values of that variable clear from the display 114. The display 
114 then displays a flashing legend that identifies the variable; all 
permissible units for the variable are displayed; and all data that was 
completely entered with numerical values and units is maintained in a 
memory stack within the computational system until a new complete set of 
data for that variable is entered via the keyboard 112. 
The primary purpose of the drug administration rate calculator 110 is to 
determine the pump setting value from a given drug dose rate. Occasionally 
it will be necessary to calculate the drug dose rate from the pump 
setting, and sometimes it is necessary to calculate the amount of drug or 
intravenous solution to be used. Calculation of the body surface area from 
the weight and height is a convenience feature of the drug administration 
rate calculator 110, but is not an essential function of the device. Body 
surface areas may be obtained from tables of such data for any given 
height and weight, rather than being computed. 
The drug administration rate calculator 110 will not store values entered 
for all four primary variables. For example, if the operator enters data 
for all four variables from the keyboard, either the drug dose rate or the 
pump setting will clear from the display. The drug administration rate 
calculator 110 accepts entered values of three of the primary variables 
and then calculates the fourth primary variable. 
The hardware included in the drug administration rate calculator 110 
includes a microcomputer 130 connected to the keyboard 112 to receive 
inputs therefrom. The microcomputer 130 preferably includes either an 
Hitachi model HD63P01M1, an Hitachi HD6301 or other similar device. The 
microcomputer 130 provides outputs to a pair of display drivers 132 and 
134 which drive the segments of the display 114. The drivers 132 and 134 
are preferably Hitachi HD63602 integrated circuits or the equivalent. The 
microcomputer 130 and the display drivers 132 and 134 receive power from a 
power supply 135, shown in FIG. 3. A power control circuit 136, shown in 
FIG. 2 supplies a low voltage warning signal if the voltage drops below a 
predetermined value and turns the power supply 135 off after it has been 
on for a predetermined time. 
As shown schematically in FIG. 4, the keyboard 112 is a 5.times.8 matrix. 
The elements of the matrix include the variables of TABLE I, the units of 
the variables, the numeric keypad and the compute key. In the exemplary 
embodiment of FIG. 4, the eight columns of the keyboard 112 are input to 
port 1 of the microcomputer 130. Port 1 includes the pins 13-20 of the 
microcomputer 130. Each of the pins represents a bit of the signal sent 
between the microcomputer 130 and the keyboard 112. For example, pin 13 
corresponds to port 1, bit 0; pin 14 corresponds to port 1, bit 1, etc. 
The five rows of the keyboard 112 are connected to port 2 of the 
microcomputer 130. Port 2 includes pins 8-12. Pin 8 corresponds to port 2, 
bit 0; pin 9 corresponds to port 2, bit 1, etc. 
The keyboard 112 addresses the microcomputer 130 by providing low signals 
on the lines which intersect in the matrix. For example, depression of the 
key corresponding to the patient's body weight, provides low signals to 
port 1, bit 2 and port 2, bit 4 of the microcomputer 130. The WT light of 
the keyboard 112 then lights up. If the user then depresses the key to 
indicate that the units of the patient's height are inches, the 
microcomputer 130 receives low signals at port 1, bit 4 and port 2, bit 2 
to light up the IN light on the keyboard 112. Resistors 140-144 are 
connected to pins 8-12, respectively, to bring unaddressed lines between 
port 2 and the keyboard 112 to logic high states. 
The microcomputer 130 includes a first group of pins numbered 1-20 and 
second group of pins numbered 30-40. The pins 8-12 and 13-20 form the 
first and second output ports previously described. Pin 1 is connected to 
ground. Pins 2 and 3 are connected across a crystal oscillator 150, which 
supplies 4 MHz clock signals to the microcomputer 130. Pin 4 is a 
non-maskable interrupt input not used in the present invention and 
therefore tied high by a 100 K.OMEGA. resistor 162. Pin 5 is an interrupt 
request input that receives a signal warning of low power supply voltage. 
Pin 6 is a reset input for reapplying power to the microcomputer 130 after 
an interruption. Pin 7 is a standby input that receives a signal for 
placing the microcomputer 130 in a standby mode to conserve power. 
The second group of pins includes an eight bit output port 3 that has bits 
numbered P.sub.30 through P.sub.37, where P.sub.30 means port 3, bit 0. 
Port 3, bit 0 is connected to port 2, bit 0 to activate the keyboard 112 
after the drug administration rate calculator 110 has been turned on or 
reset. Port 3, bit 1 is outputs a signal for initiating the standby mode. 
Port 3, bit 4 and port 3, bit 5 are chip select outputs for selecting 
which of the two display drivers 132 and 134 will receive data from the 
microcomputer 130. Port 3, bit 6 outputs a signal indicating that the 
microcomputer 130 is ready to accept inputs from the keyboard 112. The 
second group of pins further includes an eight bit output port 4 that has 
bits numbered P.sub.40 through P.sub.47 that supply data to the display 
drivers 132 and 134. 
Referring to FIG. 3, the power supply 135 that preferably includes a low 
drop out voltage regulator 164 such as a National Semiconductor model LM 
2931. The voltage regulator 164 receives voltage from any convenient 
source, such as a combination of batteries that outputs about 7.5 volts. 
The voltage regulator 164 preferably regulates the voltage down to 5.2 
volt and provides an output of about 5.0 volts between an output terminal 
and ground. The output voltage may be taken across a capacitor 165, which 
preferably has a capacitance of about 22 .mu.F. 
The drug administration rate calculator 110 preferably includes the power 
control circuit 136 of FIG. 2A for controlling application of power to the 
microcomputer 130. The power control circuit 136 includes a transistor 168 
having its base connected to receive the output of the power supply 135 
through a resistor 169, which preferably has a resistance of about 100 
K.OMEGA.. The emitter of the transistor 168 is connected to a 6 volt 
V.sub.cc source. The collector is grounded through a resistor 171 of about 
560 K.OMEGA.. 
The collector is also connected to a 100 k.OMEGA. resistor, which is 
connected to input pins 12 and 13 of a NAND gate 170. Pin 13 of the NAND 
gate 170 is connected to input pin 5 of the microcomputer 130. When the 
voltage from collector to base of the transistor 168 drops to about 0.7 
volt, the transistor 168 turns off and provides a low signal to input pin 
5 of the microcomputer 130, which then turns off. An output pin 11 of the 
NAND gate 170 is connected to pin 36 of the microcomputer 130 to control 
entry of the microcomputer 130 into a standby mode. 
Referring to FIG. 2B, a second NAND gate 172 has input terminals 8 and 9 
connected to ground through a resistor 171, which is preferably about 560 
K.OMEGA.. The input terminals 8 and 9 are also connected to the anodes of 
a plurality of diodes 175A-175H, which have their anodes connected to 
eight columns of the display 112 as shown in FIG. 4. 
The NAND gate 172 provides an output through a resistance 173 of about 330 
k.OMEGA. to an input terminal 1 of a flip flop 174 formed of a pair of 
NAND gates 176 and 177 connected as an RS latch. An input 6 of the NAND 
gate 177 is connected to inputs 8 and 9 of the NAND gate 172, which also 
receive inputs from pin 37 of the microcomputer 130. An output 3 of the 
NAND gate 176 is connected to an input 5 of the NAND gate 177, and an 
output 4 of the NAND gate 177 is connected to an input 2 of the NAND gate 
176. The inputs of the flip flop are normally high and must be pulsed to 
zero to change the state of the flip flop outputs. The output of the flip 
flop 174 is taken at pin 3 of the NAND gate 176 and is connected to input 
pin 7 of the microcomputer 130. The output of the flip flop 174 is also 
connected to input pin 6 of the microcomputer 130 through a resistor 178 
of about 100 K.OMEGA.. The junction of the resistor 178 and pin 6 of the 
microcomputer 130 is grounded through a capacitor 179 of about 1.0 .mu.F. 
If the power supply 135 is providing adequate power so that the transistor 
168 is conducting, the microcomputer 130 is on and outputs a signal to 
input pin 8 of the NAND gate to indicate that the drug administration rate 
calculator 110 is ready for operation. After the drug administration rate 
calculator 110 has been on for a predetermined time, such as twenty 
seconds, the output of the NAND gate, which is connected to the standby 
input of the microcomputer, goes low. The microcomputer 130 then goes into 
a standby mode until it is reset. 
Each of the drivers 132 and 134 is capable of driving 208 segments of the 
display 114. A segment is any portion of the LCD display array that lights 
up at one time in response to a single signal from one of the drivers 132 
and 134. Each numeral of the display 114 is seven segments. The letters 
indicating the drug dose rate are one segment. Two drivers are required 
because the display 114 has more than 104 segments. The drivers 132 and 
134 are each separate computers that store and output data. The drivers 
132 and 134 get data from the microcomputer 130 and output the last 
information received. The drivers 132 and 134 update the display 114 at a 
rate of 130 times per second, which provides convenient reading of the 
display 114. 
The voltages output from the drivers 132 and 134 to the display 114 may be 
adjusted by adjusting the resistance of trimmer resistors 182 and 184 
connected between the power supply 135 and the power input pins of the 
drivers 132 and 134 respectively. The display 114 is preferably a 
multiplex LCD display, which is well-known in the art. Four different 
common lines connected to pins 23-26 of the drivers 132 and 134 drive the 
display 114 in a time domain. 
Port 4 of the microcomputer 130 outputs data to the driver selected by 
means of one of the chip select lines in port 3 described above. Except 
for the chip select lines, the connections between the drivers 132 and 134 
and the microcomputer are identical. Port 3 provides reset, standby, ready 
and clock signals to the driver whose chip select line has been brought 
low by the microcomputer 130. 
Operation of the drug administration rate calculator 110 is initiated by 
turning on the start switch 180 to start the sequence of steps shown in 
FIG. 6A. All of the display 114, the lights for the pump setting, the drug 
dose rate, drug and IV solution are turned on at the beginning of the 
sequence. The drug administration rate calculator 110 then waits for a 
keystroke to select one of the variables PS, DDR, D, IV SOL, DROPS, the 
body weight or the body height. The variables may be entered in any order. 
Variable selection should be done at the next keystroke. 
Referring to FIG. 7, the drug administration rate calculator 110 may be 
connected to a valve 200, which is preferably an electrically controlled 
solenoid valve. The valve 200 is in fluid communication with a source 202 
of pressurized fluid to regulate the flow of the pressurized fluid to the 
patient. The fluid may be pressurized by a pump 204 or it may be 
pressurized by a height differential between the fluid source and the 
point of insertion of the IV tube into the patient. 
Pump Setting Routine 
If the operator depresses the pump setting key, the drug administration 
rate calculator 110 enters the routine shown in FIG. 6B. The PS light 
flashes and the cc/hr and drops/min segments of the display 114 are 
lighted. After a key is depressed, the microcomputer compares the D, DDR 
and IV SOL numbers to zero. If all these numbers are nonzero, the DDR 
numbers are cleared from the memory and from the display 114. The units of 
the DDR are maintained. The drug administration rate calculator 110 then 
waits for a keystroke, which causes the microcomputer 130 to jump to the 
compute, cc/hr, drop/min, clear, number, pump setting, wrong units or any 
other function sequences shown in the lower half of FIG. 6B. 
If the next keystroke is the compute command, the pump setting number from 
the memory is displayed and the microcomputer 130 goes to a compute 
routine described subsequently with reference to FIG. 6K. 
If the cc/hr key is depressed, the cc/hr segments of the display 114 light 
up and the PS light stops flashing. The pump set segments of the display 
114 are lighted, and then the microcomputer goes to the main sequence of 
FIG. 6A and awaits a keystroke, which ordinarily will be a number. 
If the key for drops/min is depressed, then the corresponding portion of 
the display 114 is lighted. The pump setting light stops flashing and the 
pump setting from the memory is displayed. The microcomputer goes to the 
main sequence of FIG. A and awaits a keystroke, which ordinarily will be a 
number. 
If the operator wishes to abort the sequence, the clear key is depressed, 
which causes all numbers and units to clear from the display 114. The drug 
administration rate calculator 110 then awaits a keystroke indicating 
further instructions. 
If a number key is depressed, the segments of the display 114 corresponding 
to the number are lighted and the cc/hr and drops/min units are flashed to 
indicate that the available choices for the units of pump setting. After 
selection of units for pump setting, the process goes to another branch of 
the sequence described subsequently. If keys for the wrong units or for 
the pump setting are depressed, the program goes to point A of the pump 
setting routine and awaits a keystroke. 
If the key for any other function not described above was depressed the 
program goes to the corresponding routine. 
Drug Dose Rate Routine 
If the operator selects the drug dose rate from the main sequence of FIG. 
6A, the microprocessor 130 goes to the drug dose rate routine shown in 
FIG. 6C. After a key is depressed, the microcomputer compares the D, PS 
and IV SOL numbers to zero. If any of the numbers are not zero, then the 
microcomputer 130 clears the PS numbers and flashes the PS light. The drug 
administration rate calculator 110 then awaits a keystroke, which will 
cause the microcomputer 130 to jump to either the clear, compute, numbers, 
micrograms, milligrams, units or any other function sequences shown in the 
lower half of FIG. 6C. 
Depression of the clear key causes the microcomputer 130 to return to the 
main sequence of FIG. 6A to await another keystroke. 
Depression of the compute key causes the number for the drug dose rate from 
memory to be displayed and the DDR light to stop flashing and causes the 
microcomputer 130 to go to the compute routine. 
Depression of any other function key causes the microcomputer 130 to go to 
the routine for the selected function. 
Depression of a number key causes the segments of the display 114 
corresponding to the number to light up. The drug administration rate 
calculator 110 then awaits another keystroke. If another number key is 
depressed, the number is displayed and the drug administration rate 
calculator 110 again awaits another keystroke. After the numbers are 
entered, the milligram, microgram and UNITS lights are flashed to indicate 
the possible units for the drug dose rate. The selected unit is displayed, 
and then the microcomputer 130 goes to part C of the drug dose rate 
routine shown in the lower right corner of FIG. 6C The lights for 
kilograms, hours, square meters and minutes are flashed so that the user 
can enter data related to the weight or body surface area of the patient 
and the selected time units. 
If the wrong units or the DDR keys are depressed, the microcomputer 130 
goes to point B of the DDR routine and awaits a keystroke. 
Referring to FIG. 6D, if the KG key are depressed as one of the units of 
the drug dose rate, then KG is displayed and the program continues to the 
sequence E of FIG. 6D. The display segments of HR and MIN flash, and the 
drug administration rate calculator 110 awaits a keystroke to select the 
time unit before jumping to the compute, clear, wrong units, DDR, other 
function, HR or MIN sequences shown in the lower portion of FIG. 6D. 
If the M.sup.2 key is depressed, M.sup.2 is displayed and sequence E is 
repeated. 
If the HR key is depressed, KG and M.sup.2 are turned off and HR is 
displayed. The drug dose rate from the memory is displayed and the 
microcomputer returns to the main sequence. 
If the MIN key is depressed, KG and M.sup.2 are turned off and MIN is 
displayed. The drug dose rate from the memory is displayed and the 
microcomputer returns to the main sequence. 
Drug Routine 
Depression of the drug key in the main sequence causes the microcomputer 
130 to enter the drug routine shown in FIG. 6E. After a key is depressed, 
the microcomputer compares the D, PS and IV SOL numbers to zero. If any of 
the numbers are not zero, then the microcomputer 130 clears the PS numbers 
and flashes the PS light. The drug administration rate calculator 110 then 
awaits a keystroke to select one of the computer, number, milligrams, 
micrograms, UNITS or any other function sequences shown in the lower 
portion of FIG. 6E. 
The compute and any other function sequences for the drug routine are the 
same as for the routines described previously. 
Depression of the number keys for the drug amount causes the gram, 
microgram, milligram and UNITS keys to flash, and causes the microcomputer 
130 to jump to one of the sequences for displaying the selected unit for 
the drug amount. 
If any of the keys for selecting units for the drug amount are depressed, 
the selected unit is displayed before the microcomputer 130 returns to the 
main sequence of FIG. 6A. 
IV Routine 
Selection of the IV routine from the main sequence causes the microcomputer 
130 to execute the sequence shown in FIG. 6F. After a key is depressed, 
the microcomputer compares the D, DDR and IV SOL numbers to zero. If all 
these numbers are nonzero, the DDR numbers are cleared from the memory and 
from the display 114. The light IV SOL is flashed and the "cc" units are 
displayed. If some of the numbers are not zero, the microcomputer 130 
clears the pump setting number before the light IV SOL is flashed and the 
"cc" units are displayed. The 110 then awaits a keystroke to select one of 
the clear, compute, any other function, number, wrong units, CC or IV SOL 
sequences shown in the lower portion of FIG. 6F for execution. The clear, 
compute and any other function sequences have been previously described. 
Depression of the number keys to enter a number for the amount of IV 
solution causes the number to be displayed and the "C" to flash. The 
microcomputer 130 then is prepared to jump to the CC sequence. 
Depression of the CC key causes the CC segment of the display to light and 
causes the IV SOL light to stop flashing. The amount of IV solution is 
displayed and stored before the microcomputer returns to the main 
sequence. 
Depression of the IV SOL key or a key for an incorrect unit causes the 
microcomputer to go to point H of the IV routine and await a keystroke. 
Body Surface Area Routine 
If it is necessary to calculate the patient's body surface area (BSA), then 
the BSA key is depressed to start the body surface area routine of FIG. 
6G. The BSA light is flashed, and the display 114 is cleared of numbers. 
The segment M.sup.2 for the units of body surface is displayed, and the 
110 awaits a keystroke to select one of the branches for compute, clear, 
BSA, wrong units, number, M.sup.2 or any other function. 
If a number key is depressed, the number is displayed, and the units 
M.sup.2 are flashed before the program jumps to the M.sup.2 branch. The 
microcomputer checks to see if the display 114 reads zero. If the display 
114 does not read zero, it is cleared before the sequence continues. After 
ascertaining that the display 114 reads zero, the 110 causes the display 
to light the segments for M.sup.2 and stops flashing the BSA light. The 
microcomputer then clears the patient's height and weight data and returns 
to the main sequence. 
Weight Routine 
If it is necessary to enter the patient's weight, the user depresses the WT 
key, which causes the microcomputer the execute the sequence shown in FIG. 
6H. The WT light is flashed, and the numbers are cleared from the display 
114. The units LB and KG are displayed, and the 110 awaits a keystroke 
indicating which of the compute, clear, weight, number, LB, KG wrong units 
or any other function branches of FIG. 6H are to be executed. 
Depression of the compute, clear or any other function keys causes the 
execution of steps similar to those described above. 
Depression of a number key causes the number to be displayed. After the 
numbers are entered into the 110, the lights for pounds and kilograms are 
flashed; and the microcomputer 130 jumps to either the pounds or kilograms 
sequence of FIG. 6H. 
The pounds sequence displays LBS and stops flashing the WT light. The 
microcomputer 130 compares the body weight area in the memory to zero. If 
the BSA data is zero and the light is not zero, then the microcomputer 130 
computes the BSA as a function of weight and height by a predetermined 
algorithm. The calculated BSA is displayed, and the microcomputer 130 
returns to the main sequence. If the BSA is not zero, the microcomputer 
130 clears the previous value and then proceeds to calculate the BSA as 
described above. If the height is zero, then the microcomputer 130 goes to 
the main sequence so that the height routine may be executed if the 
operator desires. 
Depression of the weight key or wrong units causes the microcomputer to go 
to point J of the weight routine to await a keystroke. 
Height Routine 
If is necessary to enter the patient's height into the 110, the HT key is 
depressed, which causes the HT light to flash. The units centimeter and 
inches are displayed, and the 110 awaits a keystroke to indicate which 
branch of the compute, clear, number, IN, CM, wrong units, height or any 
other function sequences to execute. The clear, compute and any other 
function sequences are similar to those described above. Depressing the 
height key or the wrong units will cause the microcomputer to go to point 
K of the height routine to await another keystroke. 
Depressing the number key causes the number to be displayed. After all of 
the numbers for the height are entered into the 110, the units IN and CM 
flash; and the microcomputer jumps to one of the sequences selected by 
depressing the IN or CM keys. If the IN key is depressed, the display 114 
114 stops flashing and the number and units are displayed. The 
microcomputer checks to see if the BSA is zero. If the BSA is zero, the 
microcomputer continues to execute steps to calculate the BSA. If the BSA 
is not zero, then the previous value is cleared so that a new value can be 
computed. The microcomputer 130 then checks the weight data. If the weight 
is zero, then the microcomputer goes to the main sequence so that the 
weight may be entered into the 110 if the operator so desires. If the 
weight is not zero, then the microcomputer computes the BSA and displays 
the calculated value in square meters before returning to the main 
sequence. 
Drops Routine 
Selection of the drops routine from the main sequence causes the 
microcomputer to execute the sequence shown in FIG. 6J. The numbers are 
cleared from the display 114, and the D/CC light is flashed. The system 
then awaits a keystroke for instructions regarding which of the compute, 
clear, number, D/CC, drops, wrong units or any other function branches to 
execute. 
The compute, any other function and clear branches function similarly to 
those previously described. Depression of the keys for drops or incorrect 
units causes the microcomputer to go to point L of the drops routine. 
Depression of a number key causes the number to be displayed. After all of 
the numbers for the drops have been entered, the microcomputer jumps to 
the D/CC sequence to calculate the amount of drug per cubic centimeter of 
IV solution. The first step of the D/CC sequence is to check for numbers. 
The D/CC segment of the display 114 is lighted, and the drops light stop 
flashing. The amount of drug per cubic centimeter is stored and displayed 
before the microcomputer 130 returns to the main sequence. 
Compute Routine 
Depression of the compute key causes the 110 to execute the sequence of 
steps shown in FIG. 6K. The flow chart includes several flags to related 
to the units or status of the variables and functions. These flags are 
summarized in Table II to facilitate understanding of the compute routine. 
TABLE II 
______________________________________ 
Flow Chart Flags 
DPM = status of pump setting 
= 0, undefined 
= 1, drops/min 
= 2, cc/hr 
DCC = drops/cc status of drops/cc function 
= 0, undefined (implied cc/hr) 
= 1, drops/cc specified 
DDU = drug dose rate units 
= 0, undefined 
= 1, UNITS 
= 2, .mu.g 
= 3, mg 
DU = drug unit status 
= 0, undefined 
= 1, UNITS 
= 2, .mu.g 
= 3, mg 
= 4, grams 
H = height function status 
= 0, not specified 
= 1, inches 
= 2, cm 
B = BSA status 
= 0, not specified 
= 1, input 
= 2., computed 
W = weight status 
= 0, not specified 
= 1, pounds 
= 2, grams 
= 3, kg 
DDK = M.sup.2 or kg or blank for DDR 
= 0, undefined 
= 1, kg 
= 2, M.sup.2 
= 3, blank 
DDT = drug dose rate time 
= 0, undefined 
= 1, hr 
= 2, min 
______________________________________ 
The microcomputer 130 first checks the status of the pump setting and the 
drops setting. If the pump setting is not in drops per minute and the 
drops/cc are not specified, then the display 114 flashes "ID", displays 
"PS" and "D" and waits for a keystroke. If the keystroke clears the pump 
setting or the drug setting, then the flashing ceases. If the keystroke 
does not clear the pump setting or the drug then the 110 awaits another 
keystroke that will clear either the pump setting or the drug amount. 
After the "ID" flashing ceases, the microcomputer executes a branch of the 
program described subsequently. 
If the pump setting is in drops per minute and the drops/cc are specified, 
then the sequence continues, and the microcomputer determines whether the 
kilograms of body weight are to be considered in subsequent calculations 
of the drug dose rate. If the kilograms of body weight are to be 
considered, then the microcomputer 130 tests to determine whether data for 
the patient's weight has been entered into the 110. If the weight has not 
been entered, then "ID" is flashed and the 110 awaits a keystroke to clear 
the W and DDR settings. 
If the weight has been specified, the 110 checks the status of the BSA. If 
the BSA has not been specified, then "ID" flashes, and DDR and BSA are 
displayed. The system then awaits a keystroke to clear the DDR, BSA, HT 
and WT. If the BSA has been input or computed, the microcomputer 130 
determines the status of the D/CC. If D/CC=0 then the microcomputer checks 
the status of the drug units and the weight and height of the patient. 
The microcomputer 130 then determines which of the four primary variables 
is zero while the other three are not zero and calculates the previously 
unknown variable. The subroutines for calculating the pump setting, the 
drug dose rate, the drug amount and the amount of IV solution are shown in 
FIG. 6L. These are standard types of computational subroutines using 
formulas and constants stored in the memory for calculating the unknown 
variable. 
Although the invention has been described with reference to a specific 
preferred embodiment, it should be understood that modifications may be 
made to the preferred embodiment without departing from the spirit of the 
invention. Accordingly, the invention encompasses the subject matter of 
the appended claims, which distinctly point out the invention, and 
equivalents thereof.