Ambulatory physiological monitor with removable disk cartridge and wireless modem

An ambulatory physiological monitor includes a high capacity, plug connectable magnetic disk cartridge for storing physiological data and analysis software. The disk cartridge is easily removable from the monitor and is connectable to a remote computer for analysis of the physiological data using the analysis software stored in the disk cartridge. The ambulatory physiological monitor may include a wireless data modem for communicating with a remote computer system as to the patient's condition through a cellular telephone system. Selected portions of the physiological data or results of analysis of the physiological data may be transmitted to the remote computer system. The monitor may operate in a server mode in which it is controlled by the remote computer system. Updates to the analysis software and remote commands may be sent from the remote computer system to the monitor.

FIELD OF THE INVENTION 
This invention relates to patient monitoring systems and, more 
particularly, to ambulatory physiological monitoring methods and 
apparatus. 
BACKGROUND OF THE INVENTION 
Monitoring of electrocardiography (ECG) data is a useful tool in diagnosing 
the condition of a patient's heart. A prominent type of ECG monitoring is 
Holter monitoring, in which ECG data is acquired continuously over a 24 
hour period. Data acquired by Holter monitoring is useful in identifying 
patients who are at risk of ventricular tachycardia. 
Ambulatory ECG monitors include several electrodes, which are attached to 
the patient, and a miniature recording unit. ECG signals acquired from the 
electrodes are stored by the recording unit for analysis. Typically, the 
recording unit is attached to a belt worn by the patient. The ambulatory 
monitor may be worn by the patient outside the hospital during the 
patient's normal daily routine. 
Prior art ambulatory ECG monitoring systems have utilized several 
approaches for storing the ECG data. Tape-based systems are provided with 
a magnetic tape recorder that records ECG signals acquired from the 
electrodes. Tape-based systems have various drawbacks, including a limited 
frequency response, tape motion error problems and difficulty in encoding 
the occurrence of important events with precision. Solid state ambulatory 
ECG monitors utilize a memory, such as a random access memory (RAM), built 
into the recording unit. Presently available solid state systems must rely 
on data compression to store all the data generated during a recording 
session. The data compression involves a high degree of information loss. 
In addition, data held in the memory may be lost upon an interruption of 
power. An ambulatory medical monitor having a removable RAM package is 
disclosed in U.S. Pat. No. 4,592,018 issued May 27, 1986 to Wiegman. 
An ambulatory physiological monitor containing a high capacity, 
miniaturized magnetic disk storage unit is disclosed in U.S. Pat. No. 
5,228,450 issued Jul. 20, 1993 to Sellers. The disclosed ambulatory 
physiological monitor overcomes the problems associated with tape-based 
and solid state monitors and provides highly satisfactory performance. 
However, the disclosed monitor, as well as all other known prior art 
ambulatory physiological monitors, requires that the monitor be taken to a 
location having a specially adapted computer for analysis of the recorded 
data. The computer is specialized in the sense that it must have an 
adaptor for connection to the ambulatory physiological monitor to access 
the data stored therein and must be loaded with appropriate analysis 
software. In many instances, this process is inconvenient to the patient. 
An ambulatory ECG monitoring system wherein analysis software is stored 
within the ambulatory monitor is disclosed in U.S. Pat. No. 5,205,295 
issued Apr. 27, 1993 to Del Mar et al. 
Telemetry systems have also been utilized for transmitting ECG data from a 
patient to a monitoring location, typically in a hospital. An 
electrocardiographic telemetry and telephone transmission link system is 
disclosed in U.S. Pat. No. 3,882,277 issued May 6, 1975 to DePedro et al. 
A telemetry system which provides medical and location information to a 
host computer including a communication network is disclosed in U.S. Pat. 
No. 5,416,695 issued May 16, 1995 to Stutman et al. Another telemetry 
system which provides medical and location information is disclosed in 
U.S. Pat. No. 5,458,123 issued Oct. 17, 1995 to Unger. Additional 
telemetry systems for transmitting physiological data are disclosed in 
U.S. Pat. Nos. 5,153,584 issued Oct. 6, 1992 to Engira; 5,226,431 issued 
Jul. 13, 1993 to Bible et al; 5,417,222 issued May 23, 1995 to Dempsy et 
al; 5,113,869 issued May 19, 1992 to Nappholz et al; and 5,381,798 issued 
Jan. 17, 1995 to Burrows. 
All of the known telemetry systems have had one or more disadvantages. 
Telemetry systems are typically designed for use within a limited 
geographical area, such as a hospital or the home. Thus, the patient's 
mobility is limited, and data is lost if the patient goes outside the 
coverage area of the system. In addition, such systems transmit raw data 
continuously, thus requiring a dedicated transmission channel. Finally, 
such systems are relatively complex and expensive. 
SUMMARY OF THE INVENTION 
According to a first aspect of the invention, a method for recording and 
analyzing physiological data from a patient is provided. The method 
comprises the steps of attaching an ambulatory physiological monitor 
containing a high capacity, miniaturized magnetic disk cartridge to an 
ambulatory patient, acquiring physiological data from the patient while 
the patient is ambulatory using the ambulatory physiological monitor, 
storing the physiological data acquired from the patient in the disk 
cartridge while the patient is ambulatory, removing the disk cartridge 
from the ambulatory physiological monitor and attaching the disk cartridge 
to a computer, and analyzing the physiological data stored in the disk 
cartridge with the computer. The disk cartridge preferably plugs into 
standard connectors in the ambulatory physiological monitor and in the 
computer. 
According to a further feature of the invention, analysis software may be 
stored in the disk cartridge. When the disk cartridge is attached to the 
computer, at least a portion of the analysis software is transferred from 
the disk cartridge to the computer, and the physiological data is analyzed 
with the analysis software transferred from the disk cartridge to the 
computer. 
According to another aspect of the invention, an ambulatory physiological 
monitor for recording physiological data from a patient for subsequent 
medical diagnosis of the patient is provided. The ambulatory physiological 
monitor comprises a housing, a high capacity, miniaturized magnetic disk 
cartridge located in the housing for storing physiological data and 
analysis software, and a circuit located in the housing for receiving a 
physiological signal representative of a physiological parameter of an 
ambulatory patient from a transducer attached to the ambulatory patient, 
for converting the physiological signal to the physiological data and for 
transferring the physiological data to the disk cartridge. The disk 
cartridge is plug connectable to the monitor and is easily removable from 
the monitor. The disk cartridge containing the physiological data and 
analysis software is plug is connectable to a remote computer for analysis 
of the physiological data using the analysis software in the disk 
cartridge. 
According to a further aspect of the invention, a method for recording and 
analyzing physiological data from a patient is provided. The method 
comprises the steps of attaching an ambulatory physiological monitor 
containing a wireless data modem and a storage device to an ambulatory 
patient, the storage device having analysis software stored therein, 
acquiring physiological data representative of the patient's condition 
while the patient is ambulatory using the ambulatory physiological 
monitor, storing the physiological data acquired from the patient in the 
storage device while the patient is ambulatory, and communicating with a 
remote computer system as to the patient's condition through a cellular 
telephone system using the wireless data modem. 
According to one feature of the invention, the physiological data stored in 
the storage device is analyzed using the analysis software to provide 
physiological information. The physiological information may be 
transmitted to the remote computer system in response to a request from 
the remote computer system, in response to a predetermined event in the 
physiological data or at predetermined intervals. 
According to a further feature of the invention, new analysis software may 
be downloaded from the remote computer system to the ambulatory 
physiological monitor through the cellular telephone system using the 
wireless data modem. The new analysis software may be used to replace, 
modify or supplement the analysis software in the storage device. 
According to a further feature of the invention, a portion of the 
physiological data may be selected based on a predetermined criteria in 
the analysis software. The selected physiological data may be transmitted 
to the remote computer system through the cellular telephone system using 
the wireless data modem. 
According to still another feature of the invention, at least a portion of 
the analysis software may be transmitted to the remote computer system 
through the cellular telephone system using the wireless data modem. The 
analysis software may be used by the remote computer system for analyzing 
physiological data transmitted from the ambulatory physiological monitor. 
According to still another aspect of the invention, an ambulatory 
physiological monitor for recording physiological data from a patient for 
a subsequent medical diagnosis of the patient is provided. The ambulatory 
physiological monitor comprises a housing, a storage device mounted in the 
housing for storing physiological data and analysis software, and a 
circuit mounted in the housing for receiving a physiological signal 
representative of a physiological parameter of an ambulatory patient from 
a transducer attached to the ambulatory patient, for converting the 
physiological signal to physiological data representative of the patient's 
condition and for transferring the physiological data to the storage 
device. The ambulatory physiological monitor further includes a wireless 
data modem mounted in the housing for communicating with a remote computer 
system as to the patient's condition through a cellular telephone system. 
The wireless data modem may comprise a cellular digital packet data modem. 
The storage device may comprise a high capacity, miniaturized magnetic 
disk cartridge.

DETAILED DESCRIPTION 
A perspective view of an ambulatory physiological monitor 10 in accordance 
with the present invention is shown in FIG. 1. The elements of the monitor 
10 are enclosed within a housing 12 which may be fabricated of a plastic 
material such as, for example, GE Noryl 2000. An event button 14, a user 
display 16, a patient connector 18 and an antenna 19 are located at one 
end of housing 12. The patient connector 18 provides an electrical 
connection between the circuitry of the ambulatory physiological monitor 
10 and electrodes or other transducers affixed to the patient for 
monitoring the patient's condition. In a preferred embodiment, the 
ambulatory physiological monitor 10 has a generally rectangular shape with 
a length of about 5.1 inches, a width of about 3.2 inches and a thickness 
of about 1.5 inches. The monitor 10 may conveniently be worn on a 
patient's belt with a suitable attachment, such as a holster 11 shown in 
FIG. 3. In the preferred embodiment, the monitor 10 has a weight of about 
14 ounces. The monitor 10 is carried by an ambulatory patient during the 
patient's normal activities, and the patient's physiological parameters of 
interest are recorded while the patient is ambulatory. 
The user display 16 displays status messages and the time of day. The 
display 16 may be a conventional liquid crystal display (LCD). The event 
button 14 allows the patient to record the time of an event, such as the 
suffering of chest pains, so that the ECG data recorded at that time can 
be marked for closer examination. The antenna 19 is used for wireless 
communication as described below. In a preferred embodiment, the patient 
connector 18 and the antenna 19 are joined in a T-connector mounted in 
housing 12. 
Cross sections of the ambulatory physiological monitor 10 are shown in 
FIGS. 2A-2C. The elements of the monitor 10 include an electronics module 
20, a battery module 22, a display/user interface module 24 and a 
removable disk cartridge 26. The monitor 10 may optionally include a 
wireless data modem 28. The housing 12 includes a removable cover 30 which 
snaps onto the rear of monitor 10. The cover 30 is removed to provide 
access to battery module 22 and to permit removal or installation of disk 
cartridge 26. In the embodiment of FIGS. 2A-2C, the electronics module 
includes printed circuit boards 20A and 20B, and the display/user 
interface module 24 includes a printed circuit board for mounting of event 
button 14, user display 16, connector 18 and antenna 19. The elements of 
the monitor 10 are described in detail below. 
The monitor 10 is used with a set of electrodes or other transducers. For 
most ECG applications, either two or three sets of electrodes are 
employed. As shown in FIG. 3, three sets of electrodes 34A, 34B, 36A, 36B, 
38A and 38B are employed to provide a three-dimensional view of heart 
activity. The three pairs of electrodes provide ECG signals from X, Y and 
Z axes of the patient, respectively. Each electrode is connected to 
monitor 10 via a lead wire 33 and connector 18. The lead wire 33 for 
electrode 38B is shown in phantom in FIG. 3, because the electrode is 
placed on the patient's back. This pattern of electrode replacement 
corresponds to a standard established by the Association for the 
Advancement of Medical Instrumentation (AAMI). A ground electrode 40 is 
also utilized. The electrodes may be conventional ECG silver chloride 
electrodes. As indicated previously, the monitor 10 may be positioned in 
holster 11 for attachment to the patient's belt with belt loops 42. The 
monitor 10 may be worn or carried by the patient in any desired manner 
that does not interfere with recording of physiological data. 
A block diagram of the ambulatory physiological monitor 10 is shown in FIG. 
4. The contacts in patient connector 18 are connected to an analog circuit 
50 in electronics module 20. As indicated above, electrodes attached to 
the patient are electrically connected through connector 18 to the monitor 
10. The analog circuit 50 amplifies and processes ECG signals from the 
patient electrodes. A suitable analog circuit is disclosed in U.S. Pat. 
No. 5,228,450, which is hereby incorporated by reference. The outputs of 
analog circuit 50 are connected to an acquisition processor 52, which 
controls a portion of the monitor operation and converts amplified analog 
ECG signals into digital data words. The acquisition processor 52 is 
connected to a memory 54 which includes a program storage area 56 and a 
data buffer 58. The program storage area 56 is used to store a program for 
controlling operation of the acquisition processor 52. Data buffer 58 
provides temporary storage of ECG data. The acquisition processor 52 is 
connected through an operator interface 60 to event button 14 and user 
display 16. Acquisition processor 52 records the times when the event 
button 14 is activated by the patient. The user display 16 normally 
displays the time of day and can be used to provide other status messages 
to the patient. A real-time clock 62 is connected to acquisition processor 
52. 
A command processor 66 is connected to acquisition processor 52 and to 
memory 54. The command processor 66 is further connected through a PC Card 
interface 70 to disk cartridge 26 and to wireless data modem 28. The PC 
Card interface 70 includes I/O drivers and power supplies for the disk 
cartridge 26 and the wireless data modem 28. The program storage area 56 
is used to store a program for controlling operation of the command 
processor 66. ECG data is transferred at intervals by the command 
processor 66 from data buffer 58 to disk cartridge 26. The command 
processor 66 also controls transmission and reception of information 
through wireless data modem 28 as described below. The command processor 
66 is coupled to a connector 74 which permits serial communication with 
devices such as a printer or an instrument. 
Each of the processors 52 and 66 is preferably implemented as a single chip 
microprocessor. A suitable microprocessor is the type 87C451, manufactured 
by Philips Semiconductor. This device includes an analog-to-digital 
converter which is used by the acquisition processor 52 for converting 
analog ECG signals to digital data words. The memory 54 is preferably 
implemented as flash memory having a capacity of 4 megabytes. The memory 
54 has sufficient capacity to store programs for operation of the 
processors 52 and 66 and for temporary storage of ECG data. Suitable 
memory devices include the Samsung KM29N16000. 
The battery module 22 provides electrical power to electronics module 20, 
disk cartridge 26, wireless data modem 28 and display/user interface 
module 24. As described below, portions of the monitor 10 are powered down 
when not in use to save battery power. In a preferred embodiment, the 
battery module 22 contains four AA alkaline batteries 68 (FIGS. 2A-2C), 
sufficient to power the ambulatory physiological monitor 10 for 24 hour 
operation. 
The disk cartridge 26 is preferably a high capacity, miniaturized disk 
cartridge that is plug connectable in the ambulatory physiological monitor 
10. The disk cartridge may be one that meets the PC Card standard 
developed by the Personal Computer Memory Card Industry Association 
(PCMCIA). The PC Card standard may be used to implement various memory 
devices, including disk drives and flash memories. A perspective view of 
the PC Card configuration of disk cartridge 26 is shown in FIG. 5. The 
module has a generally rectangular configuration, with a connector 76 that 
mates with a fixed connector 78 (FIG. 2A) in the monitor 10. Thus, the 
disk cartridge 26 is easily removable from the monitor 10. PC Card modules 
have dimensions of 54 mm.times.85.6 mm (approximately the size of a credit 
card) and thicknesses of 3.3 mm (Type I), 5.0 mm (Type II) or 10.5 mm 
(Type III). Disk cartridges with capacities up to 500 megabytes are 
available in accordance with the PC Card standard. In a preferred 
embodiment, the monitor 10 utilizes a Type III disk cartridge having a 
capacity of 170 megabytes available from Integral Peripherals. Important 
features of the disk cartridge are that it be sufficiently small to fit in 
the monitor 10, that it have sufficient capacity to store 24 hours of 
uncompressed physiological data and that it be plug connectable to the 
monitor 10. 
In an alternative embodiment, the disk cartridge 26 may be replaced with a 
PC Card module containing flash memory. Flash memory modules configured in 
accordance with the PC Card standard described above are available from 
SanDisk Corporation, as the SDP5 series. Presently available flash memory 
PC Card modules provide up to 40 megabytes of storage capacity. This 
capacity is not sufficient to record 24 hours of uncompressed ECG data. 
However, the flash memory PC Card module can be used in applications where 
less than 24 hour recording is acceptable. It is expected that the storage 
capacity of flash memory PC Card modules will increase in the near future. 
The wireless data modem 28 is preferably one that meets the cellular 
digital packet data (CDPD) standard. The CDPD standard is an industry 
standard that allows the wireless transmission of data over the existing 
cellular networks. Designed to leverage the existing cellular technology 
infrastructure and equipment, CDPD technology utilizes the Internet 
protocol scheme, making it compatible with very large installed base of 
networks and applications. CDPD technology takes advantage of moments 
during usage of a cellular telephone channel when the channel is idle. 
CDPD technology detects and utilizes the idle moments by packaging data in 
small packets and sending it in short bursts during the idle time. CDPD 
radio transceivers are available, for example, from Cincinnati Microwave. 
Preferably, the wireless data modem is configured as a PC Card module as 
described above. In an alternative embodiment, the wireless data modem 28 
may be permanently installed within the ambulatory physiological monitor 
10. The wireless data modem 28 permits transmission and reception of data 
through the cellular telephone network as described below. The wireless 
data modem 28 may be omitted from monitor 10 when wireless communication 
is not required. 
The data buffer 58 is used for temporary storage of ECG data. The data 
buffer 58 permits the command processor 66, PC Card interface 70 and disk 
cartridge 26 to be powered down during a major portion of the 24 hour 
Holter recording session, thus saving battery power. ECG signals from the 
patient electrodes are continuously sampled and converted to digital data 
words (ECG data) by acquisition processor 52. The ECG data is stored by 
acquisition processor 52 in data buffer 58. During this time, the command 
processor 66, PC Card interface 70 and disk cartridge 26 are powered down. 
When the acquisition processor 52 detects that the data buffer 58 is 
nearly full, the command processor 66, PC Card interface 70 and disk 
cartridge 26 are powered on. The command processor 66 then transfers the 
ECG data in the data buffer to the disk cartridge 26. This operation takes 
a relatively short time, typically about 20 seconds. Then, the command 
processor 66, PC Card interface 70 and disk cartridge 26 are again powered 
down, and the acquisition processor 52 continues storing ECG data in the 
data buffer 58. Typically, the transfer of data from data buffer 58 to 
disk cartridge 26 is repeated on the order of once every 80 minutes. As a 
result, the battery module 22 has sufficient capacity for operation over a 
24 hour period. It will be understood that the acquisition and storage of 
ECG data in data buffer 58 proceeds without interruption during transfer 
of data from data buffer 58 to disk cartridge 26. Intermittent transfer of 
ECG data to a disk is described in further detail in U.S. Pat. No. 
5,228,450. 
As indicated above, the disk cartridge 26 is removable from the ambulatory 
physiological monitor 10. After recording of the ECG data or other 
physiological data has been completed, typically over a period of 24 
hours, the disk cartridge 26 is removed from the monitor 10 by removing 
connector 76 from its mating connector 78 in monitor 10. Preferably, the 
disk cartridge 26 also stores an analysis program for analysis of the ECG 
data. Techniques for analysis of ECG data are well known to those skilled 
in the art. The disk cartridge containing ECG data and the analysis 
program is taken to a suitable computer 100 as shown in FIG. 6. The 
computer 100 may be any computer having a PC Card slot, including a 
connector for receiving a PC Card module and circuitry for interfacing 
with the PC Card module. The computer 100 is typically a conventional 
personal computer (PC). The computer 100 is not required to have 
pre-installed software for accessing and analyzing the ECG data. The disk 
cartridge 26 is plugged into the PC Card slot in the computer 100. In 
accordance with conventional protocols for interfacing with PC Card 
modules, the computer 100 reads the information on the disk cartridge 26 
and loads relevant portions of the analysis program into its memory. The 
computer 100 then executes the analysis program and analyzes the ECG data 
contained on the disk cartridge 26. 
As indicated above, the computer 100 may be any computer that is equipped 
with a connector and circuitry for operation with a PC Card module that 
meets the PC Card standard described above. Since PC Card modules are 
becoming relatively common, PC's having PC Card slots are also becoming 
common. Thus, the computer 100 is not required to have a connector which 
is specially adapted for connection to the ambulatory physiological 
monitor 10. Furthermore, the computer 10 is not required to have 
pre-installed ECG analysis software. Thus, the ECG data contained on disk 
cartridge 26 can be analyzed on any PC having a PC Card slot, for example 
in a doctor's office, and the patient is not required to travel to a 
location having specialized equipment for analysis of the ECG data. 
A block diagram illustrating use of the wireless data modem 28 is shown in 
FIG. 7. The wireless data modem 28 permits the ambulatory physiological 
monitor 10 to transmit information to a remote computer system 110 and to 
receive information from the remote computer system 110 via a radio link 
112. The wireless data modem 28, having antenna 19, preferably 
communicates through a cellular telephone site 116, having an antenna 118. 
The cellular site 116 is one that is equipped for communication in 
accordance with the cellular digital packet data standard. The cellular 
telephone site 116 communicates with remote computer 110 through the 
public switched telephone network 120. Communication through the telephone 
network 120 may utilize a dial-up line or may utilize the Internet. The 
communication system illustrated in FIG. 7 differs from conventional 
telemetry systems, because information is transmitted and received in 
packets, typically during relatively short time periods. By contrast, 
telemetry systems typically transmit data continuously and thus require a 
dedicated communication channel. The system of FIG. 7 has the advantage 
that communication can occur whenever the patient carrying the monitor 10 
is within range of a cellular telephone site that has CDPD capability. As 
cellular sites with CDPD capability become more widespread, this 
restriction will not be significant. Thus, the patient is not limited as 
to location during a monitoring session. 
Communication between the ambulatory physiological monitor 10 and the 
remote computer system 110 through the wireless modem 28 can be 
implemented in a variety of different ways. The following are examples of 
operations that can be performed. 
1. Selected portions of the ECG data can be transmitted from the monitor 10 
to the remote computer system 110. Selection of data can be based on a 
variety of criteria. For example, a block of ECG data before and after 
activation of the event button by the patient can be transmitted to the 
remote computer system 110. In another approach, the selection of ECG data 
for transmission can be automatic. Thus, when a predefined event occurs in 
the ECG data, a block of ECG data associated with that event is 
transmitted to the remote computer system. In yet another approach, a 
block of ECG data can be transmitted at predefined intervals, such as once 
per hour. In still another approach, the remote computer system 110 can 
transmit a message to the monitor 10 through the wireless data modem 28 
requesting a selected block of ECG data. In response, the selected block 
of ECG data is transmitted to the remote computer system 110. 
2. The command processor 66 in the monitor 10 can analyze all or a portion 
of the ECG data stored on disk cartridge 26 to provide ECG information 
representative of the condition of the patient. The ECG information which 
results from the analysis operation is transmitted to the remote computer 
system 110 through wireless data modem 28. Initiation of analysis by the 
command processor 66 can be automatic or by command from the computer 
system 110. The remote computer system can request that different 
algorithms of the analysis program be executed. Execution of the analysis 
program can also be initiated by activation of the event button, by a 
predefined event in the ECG data or at predefined intervals. 
3. The operating mode of the ambulatory physiological monitor 10 can be 
changed by command from the remote computer system 110 through wireless 
data modem 28. For example, the monitor 10 can be changed from normal to 
high resolution mode by remote command. 
4. The remote computer system 110 can download modifications and additions 
to the software in the monitor 10. Thus, for example, an analysis 
algorithm may be altered, or a new analysis algorithm may be downloaded to 
the monitor 10 through wireless data modem 28. 
5. Analysis routines can be transmitted from the monitor 10 to the remote 
computer system 110 to enable analysis of the ECG data by the remote 
computer system. 
6. The monitor 10 can operate in a server mode in which it is controlled by 
the remote computer system 110. In the server mode, the remote computer 
system 110 has access to the files of monitor 10 and effectively functions 
as a terminal for controlling monitor 10. 
A flow chart of the operations performed by the acquisition processor 52 is 
shown in FIG. 8. As shown in step 200, the acquisition processor 52 
performs power up tests of the monitor 10 and controls the user interface, 
including event button 14 and user display 16. In addition, the 
acquisition processor 52 acquires ECG signals from analog circuit 50, 
converts the signals to ECG data and stores the data in data buffer 58. 
These operations are described in more detail in U.S. Pat. No. 5,228,450. 
The acquisition processor 52 also checks alarm limits with respect to the 
ECG data. For example, the acquisition processor 52 may check the ECG data 
for the occurrence of abnormal heartbeats. In step 202, the acquisition 
processor 52 determines whether the data buffer 58 is nearly full. When 
the data buffer is nearly full, the acquisition processor 52 starts the 
command processor 66 in step 204. The acquisition processor 52 causes the 
command processor 66 and the disk cartridge 26 to be powered up. Then a 
command to transfer ECG data from the data buffer 58 to the disk cartridge 
26 is sent to the command processor 66. Upon completion of the data 
transfer, the command processor 66 notifies the acquisition processor 52 
via a status message if the transfer operation was successful. If the 
acquisition processor determines in step 206 that the command processor 
operation was successful, the acquisition processor 52 returns to step 
202. When the command processor did not successfully transfer ECG data 
from the data buffer 58 to disk cartridge 26, error routines are processed 
by the acquisition processor 52 in step 210. The acquisition processor 
then returns to step 202. 
When the data buffer 58 is not nearly full, as determined in step 202, the 
acquisition processor determines in step 212 whether a call/alarm limit 
has been reached. When a call/alarm limit has been reached, the 
acquisition processor 52 starts the command processor 66 in step 204 and 
sends a command requesting the command processor to execute a call/alarm 
limit routine. This may involve storing the parameters of the call/alarm 
limit on the disk cartridge 26 and/or transmitting a message via the 
wireless data modem 28. When the call/alarm limit has not been reached, 
the acquisition processor 52 determines in step 214 whether a new data 
acquisition program has been received. If a new data acquisition program 
has been received, the new program is loaded into the program storage area 
56 and program execution is initiated in step 216. If loading and 
execution of the new program is determined to be successful in step 218, 
the acquisition processor 52 sends a success status message and a power 
down command to the command processor 66 in step 220. If the new program 
is not successfully loaded, the acquisition processor 52 processes error 
routines in step 222 and returns to step 200 to continue data acquisition 
in accordance with the existing data acquisition program. When a new data 
acquisition program has not been received, the acquisition processor 52 
returns to step 200 and continues with data acquisition in accordance with 
the existing data acquisition program. 
A flow diagram of the operations performed by the wireless data modem 28 is 
shown in FIG. 9. The wireless data modem looks for an incoming call from 
the remote computer system 110 in step 240 and looks for an outgoing call 
from the command processor 66 in step 242. When an incoming call is 
received, the wireless data modem 28 establishes communication with the 
command processor 66 in step 246 and forwards the incoming data to the 
command processor 66. When the wireless data modem 28 identifies an 
outgoing call, communication with the command processor 66 is established 
in step 246. The wireless data modem transmits data received from the 
command processor to the remote computer system 110 as described above. 
When an incoming call or an outgoing call is not in process, the wireless 
data modem is an idle state in which it can identify incoming and outgoing 
calls but is otherwise powered down. 
A flow diagram of the operations performed by the command processor 66 is 
shown in FIGS. 10A-10B. The command processor is normally powered down and 
waiting for commands from the acquisition processor 52 or the wireless 
data modem 28 in step 300. In the idle state, the command processor 66 is 
partially powered on so that it may receive commands from the acquisition 
processor 52 and the wireless data modem 28. When a power up command is 
received in step 302, the command processor 66 performs a power on 
sequence and self test in step 304. 
When a memory full command is identified in step 306, the command processor 
transfers ECG data from data buffer 58 to disk cartridge 26 in step 310. 
If the data transfer is determined in step 328 to be successful, command 
processor returns to step 300 and notifies the acquisition processor 52 
via a status message that the transfer was successfully completed. If the 
data transfer was not successful, the command processor executes an error 
routine in step 330 and returns to step 300. The acquisition processor 52 
is notified by the command processor 66 that the data transfer was not 
successful. 
If an analyze data command is identified in step 320, the requested 
analysis is performed by the command processor 66 in step 322, and the 
results are transferred into a data output area. Output files are built in 
step 324. In step 326, the output file is transmitted via the wireless 
data modem 28 or is written to the disk cartridge 26. The destination of 
the output file depends on the particular command received. When the 
analyze data command is successfully executed, as determined in step 328, 
the command processor 66 returns to step 300 and sends a success status 
message to the acquisition processor 52 or the wireless data modem 28. 
When the analyze data command is not successfully executed, an error 
routine is executed in step 330, and the command processor returns to step 
300. The acquisition processor or the wireless modem is notified that the 
analyze data command was not successfully executed. 
If the command processor 66 identifies a call/alarm limit command in step 
336, any necessary analysis is performed by the command processor in step 
322. The output file is built in step 324, and information regarding the 
call/alarm limit is transmitted via the wireless data modem 28 or is 
written to the disk cartridge 26 in step 326. 
If the command processor 66 identifies a command to process user installed 
command in step 340, the user installed commands are processed in step 
342. User installed commands are commands to the monitor 10 by the remote 
computer system 110. Examples of user installed commands include commands 
to perform heart rate variability analysis and analysis of ECG late 
potentials. After the user installed commands are processed, the command 
processor proceeds to step 328. 
If a server mode command is identified in step 346, the file system in the 
monitor 10 is connected to the external interface in step 350. In the 
server mode, the remote computer system 110 is in control of the 
ambulatory physiological monitor 10. In this mode, the remote computer 
system 110 can, for example, access ECG data and other files in the 
monitor 10, modify the analysis program, alter alarm limits and the like. 
The command processor processes remote procedure calls from the remote 
computer system 110 in step 352 and proceeds to step 328. 
If a load program command is identified in step 360, the program is loaded 
from disk cartridge 26 to memory 54 in step 362. The load program command 
may, for example, be used to load a new or modified program that was 
transferred from the remote computer system 110 to disk cartridge 26 in 
the server mode. The command processor 66 proceeds from step 362 to step 
328. 
If a power down command is identified in step 366, the power down mode is 
entered in step 368. The command processor then returns to step 300 to 
wait for additional commands. 
The ambulatory physiological monitor 10 has been described in connection 
with ECG monitoring using ECG electrodes attached to the patient. It will 
be understood that the ambulatory physiological monitor of the present 
invention can be used for monitoring other physiological parameters of the 
patient. Examples of such parameters include respiration, EEG, blood 
pressure, blood oxygen content and respiration CO.sub.2 content. Different 
types and numbers of transducers may be utilized in connection with 
monitoring the condition of the patient. In general, the monitor of the 
present invention acquires, processes and stores data representative of 
one or more physiological parameters of the patient. The physiological 
parameters may be ECG signals or other physiological parameters. 
While there have been shown and described what are at present considered 
the preferred embodiments of the present invention, it will be obvious to 
those skilled in the art that various changes and modifications may be 
made therein without departing from the scope of the invention as defined 
by the appended claims.