<PAGE>   1
                                                                   EXHIBIT 10.13

      SILICON VALLEY BANK

      AMENDMENT TO LOAN AGREEMENT

BORROWER:              VITALCOM INC., A DELAWARE CORPORATION

ADDRESS:               15222 DEL AMO AVENUE
                       TUSTIN, CA  92780

DATE:                  DECEMBER 31, 1998

THIS AMENDMENT TO LOAN AGREEMENT is entered into between SILICON VALLEY BANK
("Silicon") and the. borrower named above (the "Borrower").

        The Parties agree to amend the Loan and Security Agreement between them
dated February 26, 1993, as amended by that Amendment to Loan Agreement dated
December 21, 1993, as amended by that Amendment to Loan Agreement dated April
27, 1994, as amended by that Amendment to Loan Agreement dated May 5, 1995, as
amended by that Amendment to Loan Agreement dated May 30, 1995, as amended by
that Amendment to Loan Agreement dated December 27, 1995, as amended by that
Amendment to Loan Agreement dated August 6, 1996, as amended by that Amendment
to Loan Agreement dated September 25, 1996, as amended by that Amendment to Loan
Agreement dated August 6, 1997 (the "August 1997 Amendment"), and as otherwise
amended from time to time (the "Loan Agreement"; terms defined in the Loan
Agreement are used herein as therein defined), as follows, effective as of the
date hereof. The Maturity Date set forth in the August 1997 Amendment was August
5, 1998, and effective upon such date the Loan Agreement was terminated.
Effective as of the date hereof, the Loan Agreement is considered to be revived
and in full force and effect.

        1. AMENDED SCHEDULE. The Schedule to the Loan Agreement is amended,
effective as of the date hereof to read as set forth on the Amended Schedule
attached hereto.

        2. MODIFIED SECTION 2.2. Section 2.2 of the Loan Agreement is hereby
deleted in its entirety and replaced with the following:

        "2.2 CONDITIONAL GRANT OF SECURITY INTEREST IN COLLATERAL. Upon the
        making of any Loans, the following shall be considered to be immediately
        and fully effective, without any further action on the part of Silicon
        or Borrower: Borrower hereby grants Silicon a continuing security
        interest in all of Borrower's interest in the Collateral (as defined
        below in Section 2.2A) as security for all Obligations (such grant of a
        security interest is referred to herein as the "Grant"). Notwithstanding
        the foregoing, no Loans shall be made unless and until Silicon has
        acquired a perfected security interest in the Collateral, including but
        not limited to the filing of any UCC-1 financing statements as required
        by Silicon in its discretion. Borrower agrees to take such actions and
        execute such documentation as Silicon determines is necessary or
        desirable in order to allow Silicon to perfect its security interest in
        the Collateral at such time as the Grant becomes effective.


<PAGE>   2


        2.2A COLLATERAL. The following is referred to as the "Collateral": (a)
        All accounts, contract rights, chattel paper, letters of credit,
        documents, securities, money, and instruments, and all other obligations
        now or in the future owing to the Borrower; (b) All inventory, goods,
        merchandise, materials, raw materials, work in process, finished goods,
        farm products, advertising, packaging and shipping materials, supplies,
        and all other tangible personal property which is held for sale or lease
        or furnished under contracts of service or consumed in the Borrower's
        business, and all warehouse receipts and other documents; *All books and
        records, whether stored on computers or otherwise maintained; and **All
        substitutions, additions and accessions to any of the foregoing, and all
        products, proceeds and insurance proceeds of the foregoing, and all
        guaranties of and security for the foregoing; and all books and records
        relating to any of the foregoing.

        * (c)

        ** (d)

        3. SECTION 3.7 OF THE LOAN AGREEMENT. Section 3.7 of the Loan Agreement
is hereby amended in its entirety to read as follows:

        "3.7 FINANCIAL CONDITION AND STATEMENTS. All financial statements now or
        in the future delivered to Silicon have been, and will be, prepared in
        conformity with generally accepted accounting principles and now and in
        the future will completely and accurately reflect the financial
        condition of the Borrower, at the times and for the periods therein
        stated subject to normal year-end adjustments. Since the last date
        covered by any such statement, there has been no material adverse change
        in the financial condition or business of the Borrower. The Borrower is
        now and will continue to be solvent. The Borrower will provide Silicon:
        (i) Within 30 days after the end of each calendar month in which, as of
        the end of such month, Borrower's Liquidity (as defined below). is less
        than $8,000,000, a monthly financial statement prepared by Borrower and
        a Compliance Certificate in such form as Silicon shall reasonably
        specify, signed by the Chief Financial Officer of the Borrower,
        certifying that throughout such month the Borrower was in full
        compliance with all of the terms and conditions of this Agreement, and
        setting forth calculations showing compliance with the financial
        covenants set forth on the Schedule and such other information as
        Silicon shall reasonably request (a "Compliance Certificate"); (ii)
        Within 10 days after the earlier of the date the report l0-Q is filed or
        is required to be filed with the Securities and Exchange Commission
        ("SEC") with respect to Borrower, such l0-Q report, a quarterly
        financial statement prepared by Borrower, and a Compliance Certificate
        for such quarter; (iii) within 10 days after the earlier of the date the
        report l0-K is filed or is required to be filed with the Securities and
        Exchange Commission with respect to Borrower, such 10-K report, complete
        annual financial statements, certified by Deloitte & Touche or other
        independent certified public accountants acceptable to Silicon, and a
        Compliance Certificate for the quarter then ended; provided, however,
        with respect to the 10-Q and 10-K reports referred to above, if (x)
        Borrower applies for and obtains an extension from the SEC for the
        delivery of such reports to the SEC, (y) Borrower provides Silicon with
        evidence of the SEC's grant of such extension, and (z) such extension is
        not 30 days beyond the regular submission date for such reports, then
        the required dates for the submission of financial information and
        reports set forth in this Section 3.7 shall be deemed to be modified to
        the date of the extension so granted by the SEC*. As used herein,
        "Liquidity" means the sum of (i)

<PAGE>   3




        Borrower's cash and marketable securities, plus (ii) the amount
        available for Borrower to borrow under this Agreement.

        * ; AND WITHIN 20 DAYS AFTER THE END OF EACH CALENDAR MONTH IN WHICH, AT
        ANY TIME DURING SUCH MONTH THERE WERE ANY OBLIGATIONS OUTSTANDING, (a) A
        BORROWING BASE CERTIFICATE SIGNED BY THE CHIEF EXECUTIVE OFFICER,
        PRESIDENT, CHIEF FINANCIAL OFFICER OR CONTROLLER OF BORROWER IN FORM AND
        SUBSTANCE ACCEPTABLE TO SILICON, (b) AN ACCOUNTS RECEIVABLE AGING FOR
        SUCH MONTH, AGED BY INVOICE DATE, (c) AN ACCOUNTS PAYABLE AGING FOR SUCH
        MONTH, AGED BY INVOICE DATE, AND (d) OUTSTANDING OR HELD CHECK
        REGISTERS, IF ANY, WITH RESPECT TO SUCH MONTH"

        4. SECTION 4.5 OF THE LOAN AGREEMENT. Section 4.5 of the Loan Agreement
hereby amended in its entirety to read as follows:

        "4.5 ACCESS TO COLLATERAL, BOOKS AND RECORDS. At all reasonable times,
        and upon * notice, Silicon, or its agents, shall have the right to
        inspect the Collateral, and the right to audit and copy the Borrower's
        accounting books and records and Borrower's books and records relating
        to the Collateral. Silicon shall take reasonable steps to keep
        confidential all information obtained in any such inspection or audit,
        but Silicon shall have the right to disclose any such information to its
        auditors, regulatory agencies, and attorneys, and pursuant to any
        subpoena or other legal process. **foregoing audits shall be ***.
        Notwithstanding the foregoing, after the occurrence of an Event of
        Default, all audits shall be at the Borrower's expense ****

        * THREE BUSINESS DAYS'

        ** ALL COSTS OF THE

        *** PAID EQUALLY BY BORROWER AND SILICON, AND SILICON MAY CHARGE
        BORROWER'S PORTION THEREOF TO ANY ACCOUNT OF BORROWER MAINTAINED WITH
        SILICON, PROVIDED THAT SUCH AUDITS SHALL ONLY BE CONDUCTED IF THERE HAVE
        BEEN ANY LOANS MADE AT ANY TIME HEREUNDER, AND THE FIRST SUCH AUDIT
        SHALL BE CONDUCTED WITHIN 90 DAYS OF THE MAKING OF THE FIRST LOAN HERE
        UNDER.

        **** AND MAY BE PERFORMED ON ONE BUSINESS DAY'S NOTICE."

        5. MODIFICATION TO SECTION 4.6. Section 4.6 of the Loan Agreement is
hereby amended in its entirety to read as follows:

        "4.6 NEGATIVE COVENANTS. Except as may be permitted in the Schedule
        hereto, the Borrower shall not, without Silicon's prior written consent,
        do any of the following: (i) acquire any assets outside the ordinary
        course of business for an aggregate purchase price exceeding 25% of
        Borrower's Tangible Net Worth (as defined in the Schedule) as of the end
        of the month prior to the effective date of the acquisition; (ii) enter
        into any other transaction outside the ordinary course of business
        (except as permitted by the other provisions of this Section); (iii)
        sell or transfer any Collateral, except for the sale of finished
        inventory in the ordinary course of the Borrower's business, and except
        for the sale of obsolete or unneeded equipment in the ordinary course of
        business * ; (iv) make any loans of any money or any other assets; (v)
        incur any debts, outside the ordinary course of business, which would
        have a material, adverse effect on the Borrower or on the prospect of
        repayment of the Obligations; (vi) guarantee or otherwise become liable
        with respect to the obligations of another party or entity; (vii) pay or
        declare any dividends on the Borrowers stock (except for dividends
        payable solely in stock of the Borrower); (viii) redeem, retire,
        purchase or otherwise acquire, directly or indirectly, any of the
        Borrowers stock; (ix) make any change in the Borrowers capital structure
        which has a material

<PAGE>   4




        adverse effect on the Borrower or on the prospect of repayment of the
        Obligations; or (x) dissolve or elect to dissolve. Transactions
        permitted by the foregoing provisions of this Section are only permitted
        if no Event of Default and no event which (with notice or passage of
        time or both) would constitute an Event of Default would occur as a
        result of such transaction. **

        * OR LICENSE TECHNOLOGY OR PRODUCTS IN THE ORDINARY COURSE OF BORROWER'S
        BUSINESS

        ** NOTWITHSTANDING ANYTHING TO THE CONTRARY CONTAINED IN THIS AGREEMENT,
        BORROWER MAY MERGE OR CONSOLIDATE WITH ANOTHER CORPORATION IF AND ONLY
        IF (I) BORROWER IS THE SURVIVING CORPORATION, AND (II) NO EVENT OF
        DEFAULT, NOR ANY EVENT OR CONDITION WHICH (WITH NOTICE OR PASSAGE OF
        TIME OR BOTH) WOULD CONSTITUTE AND EVENT OF DEFAULT, EXISTS IMMEDIATELY
        PRIOR TO, OR WOULD EXIST IMMEDIATELY SUBSEQUENT TO, SUCH TRANSACTION.

        6. REFERENCES IN LOAN AGREEMENT. Until such time as the Grant has become
effective, Borrower and Silicon hereby agree that all references to the security
interest or lien of Silicon in the Collateral are deemed not to be in effect;
provided that, upon the effectiveness of the Grant, such provisions and such
references shall immediately be deemed to be in full force and effect, without
any further action or notice by Silicon or Borrower.

        7. NEGATIVE PLEDGE AGREEMENT. Concurrently herewith, Borrower shall
execute Silicon's form of Negative Pledge Agreement, pursuant to which Borrower
agrees not to sell, transfer, assign, mortgage, pledge, lease, grant a security
interest in, or encumber any of Borrower's assets other than the Collateral.

        8. GENERAL PROVISIONS. This Amendment, the Loan Agreement, any prior
written amendments to the Loan Agreement signed by Silicon and the Borrower, and
the other written documents and agreements between Silicon and the Borrower set
forth in full all of the representations and agreements of the parties with
respect to the subject matter hereof and supersede all prior discussions,
representations, agreements and understandings between the parties with respect
to the subject hereof. Except as herein expressly amended, all of the terms and
provisions of the Loan Agreement, and all other documents and agreements between
Silicon and the Borrower shall continue in full force and effect and the same
are hereby ratified and confirmed. This Amendment shall be controlling in the
event of any conflicts between any prior written agreements and amendments
between Silicon and the Borrower, on the one hand, and this Amendment.

  Borrower:                                       Silicon:

  VITALCOM INC                                    SILICON VALLEY BANK

    By   s/  Frank T. Sample                      By  s/  
        -------------------------------               --------------------------
          President and CEO                       Title:   Vice President

    By   s/  Shelley B. Thunen
        -------------------------------
        Secretary



<PAGE>   5


                   INTEREST RATE SUPPLEMENT TO LOAN AGREEMENT


        This Interest Rate Supplement to Loan Agreement (this "Supplement")
dated December ___ 1998, is a supplement to the Loan and Security Agreement (the
"Loan Agreement") between Silicon Valley Bank ("Bank") and VitalCom Inc.
("Borrower") dated February 26 1993, as amended from time to time, including but
not limited to that certain Amendment to Loan and Security Agreement dated
approximately even date herewith. This Supplement forms a part of and is
incorporated into the Loan Agreement.

        1. Definitions.

        "Business Day" means a day of the year (a) that is not a Saturday,
Sunday or other day on which banks in the State of California or the City of
London, United Kingdom are authorized or required to close and (b) on which
dealings are carried on in the interbank market in which Bank customarily
participates.

        "Interest Period" means for each LIBOR Rate Advance, a penod of
approximately one, two, three or six months, provided that the last day of an
Interest Period for a LIBOR Rate Advance shall be determined in accordance with
the practices of the LIBOR interbank market as from time to time in effect,
provided, further, in all cases such period shall expire not later than the
applicable Maturity Date.

        "Interest Rate" shall mean as to: (a) Prime Rate Advances, a rate equal
to the Prime Rate; and (b) LIBOR Rate Advances, a rate of 2.75% per annum in
excess of the LIBOR Rate (based on the LIBOR Rate applicable for the Interest
Period selected by the Borrower).

        "LIBOR Base Rate" means, for any Interest Period for a LIBOR Rate
Advance, the rate of interest per annum determined by Bank to be the per annum
rate of interest as which deposits in United States Dollars are offered to Bank
in the London interbank market in which Bank customarily participates at 11:00
A.M. (local time in such interbank market) two (2) Business Days before the
first day of such Interest Period for a period approximately equal to such
Interest Period and in an amount approximately equal to the amount of such
Advance.

        "LIBOR Rate" shall mean, for any Interest Period for a LIBOR Rate
Advance, a rate per annum (rounded upwards, if necessary, to the nearest 1/16 of
1%) equal to (i) the LIBOR Base Rate for such Interest Period divided by (ii) 1
minus the Reserve Requirement for such Interest Period.

        "LIBOR Rate Advances" means any Advances made or a portion thereof on
which interest is payable based on the LIBOR Rate in accordance with the terms
hereof.

        "Prime Rate" means the variable rate of interest per annum, most
recently announced by Bank as its "prime rate," whether or not such announced
rate is the lowest rate available from Bank. The interest rate applicable to the
Prime Rate Advances shall change on each date there is a change in the Prime
Rate.

        "Prime Rate Advances" means any Advances made or a portion thereof on
which interest is payable based on the Prime Rate in accordance with the terms
hereof.

        "Regulatory Change" means, with respect to Bank, any change on or after
the date of this Loan Agreement in United States federal, state or foreign laws
or regulations, including Regulation D, or the adoption or making on or after
such date of any interpretations, directives or requests applying to a class of
lenders including Bank of or under any United States federal or


<PAGE>   6


state, or any foreign, laws or regulations (whether or not having the force of
law) by any court or governmental or monetary authority charged with the
interpretation or administration thereof.

        "Reserve Requirement" means, for any Interest Period, the average
maximum rate at which reserves (including any marginal, supplemental or
emergency reserves) are required to be maintained during such Interest Period
under Regulation D against "Eurocurrency liabilities" (as such term is used in
Regulation D) by member banks of the Federal Reserve System. Without limiting
the effect of the foregoing, the Reserve Requirement shall reflect any other
reserves required to be maintained by Bank by reason of any Regulatory Change
against (i) any category of liabilities which includes deposits by reference to
which the LIBOR Rate is to be determined as provided in the definition of "LIBOR
Base Rate" or (ii) any category of extensions of credit or other assets which
include Advances.

        2. Requests for Advances; Confirmation of Initial Advances.

        Each LIBOR Rate Advance shall be made upon the irrevocable written
request of Borrower received by Bank not later than 11:00 a.m. (Santa Clara,
California time) on the Business Day three (3) Business Days prior to the date
such Advance is to be made. Each such notice shall specify the date such Advance
is to be made, which day shall be a Business Day; the amount of such Advance,
the Interest Period for such Advance, and comply with such other requirements as
Bank determines are reasonable or desirable in connection therewith. The amount
of a LIBOR Rate Advance shall be $500,000 or such greater amount which is an
integral multiple of $50,000.

        Each written request for a LIBOR Rate Advance shall be in the form of a
LIBOR Rate Advance Borrowing Certificate as set forth on Exhibit A, which shall
be duly executed by the Borrower.

        Each Prime Rate Advance shall be made upon the irrevocable written
request of Borrower received by Bank not later than 3 p.m. (Santa Clara,
California time) on the Business Day such Advance is to be made. Each such
notice shall specify the date such Advance is to be made, which day shall be a
Business Day and the amount of such Advance, and comply with such other
requirements as Bank determines are reasonable or desirable in connection
therewith.

        3. Conversion/Continuation of Advances.

        (a) Borrower may from time to time submit in writing a request that
Prime Rate Advances be converted to LIBOR Rate Advances or that any existing
LIBOR Rate Advances continue for an additional Interest Period. Such request
shall specify the amount of the Prime Rate Advances which will constitute LIBOR
Rate Advances (subject to the limits set forth below) and the Interest Period to
be applicable to such LIBOR Rate Advances. Each written request for a conversion
to a LIBOR Rate Advance or a continuation of a LIBOR Rate Advance shall be
substantially in the form of a LIBOR Rate Conversion/Continuation Certificate as
set forth on Exhibit B, which shall be duly executed by the Borrower. Subject to
the terms and conditions contained herein, three (3) Business Days after Bank's
receipt of such a request from Borrower, such Prime Rate Advances shall be
converted to LIBOR Rate Advances or such LIBOR Rate Advances shall continue, as
the case may be provided that:

                (i) No Event of Default or event which with notice or passage of
        time or both would constitute an Event of Default exists;

                (ii) No party hereto shall have sent any notice of termination
        of this Supplement or of the Loan Agreement;



<PAGE>   7



                (iii) Borrower shall have complied with such customary
        procedures as Bank has established from time to time for Borrower's
        requests for LIBOR Rate Advances;

                (iv) The amount of a LIBOR Rate Advance shall be $500,000 or
        such greater amount which is an integral multiple of $50,000; and

                (v) Bank shall have determined that the Interest Period or LIBOR
        Rate is available to Bank which can be readily determined as of the date
        of the request for such LIBOR Rate Advance.

        Any request by Borrower to convert Prime Rate Advances to LIBOR Rate
Advances or continue any existing LIBOR Rate Advances shall be irrevocable.
Notwithstanding anything to the contrary contained herein, Bank shall not be
required to purchase United States Dollar deposits in the London interbank
market or other applicable LIBOR Rate market to fund any LIBOR Rate Advances,
but the provisions hereof shall be deemed to apply as if Bank had purchased such
deposits to fund the LIBOR Rate Advances.

        (b) Any LIBOR Rate Advances shall automatically convert to Prime Rate
Advances upon the last day of the applicable Interest Period, unless Bank has
received and approved a complete and proper request to continue such LIBOR Rate
Advance at least three (3) Business Days prior to such last day in accordance
with the terms hereof. Any LIBOR Rate Advances shall, at Bank's option, convert
to Prime Rate Advances in the event that (i) an Event of Default, or event which
with the notice or passage of time or both would constitute an Event of Default,
shall exist, (ii) this Supplement or the Loan Agreement shall terminate, or
(iii) the aggregate principal amount of the Prime Rate Advances which have
previously been converted to LIBOR Rate Advances, or the aggregate principal
amount of existing LIBOR Rate Advances continued, as the case may be, at the
beginning of an Interest Period shall at any time during such Interest Period
exceeds the Committed Revolving Line. Borrower agrees to pay to Bank, upon
demand by Bank (or Bank may, at its option, charge Borrower's loan account) any
amounts required to compensate Bank for any loss (including loss of anticipated
profits), cost or expense incurred by such person, as a result of the conversion
of LIBOR Rate Advances to Prime Rate Advances pursuant to any of the foregoing.

        (c) On all Advances, interest shall be payable by Borrower to Bank
monthly in arrears not later than the first day of each calendar month at the
applicable Interest Rate, or on such other day of the month as Bank may notify
Borrower from time to time.

        4. Additional Requirements/Provisions Regarding LIBOR Rate Advances;
Etc.

        (a) If for any reason (including voluntary or mandatory prepayment or
acceleration), Bank receives all or part of the principal amount of a LIBOR Rate
Advance prior to the last day of the Interest Period for such Advance, Borrower
shall immediately notify Borrower's account officer at Bank and, on demand by
Bank, pay Bank the amount (if any) by which (i) the additional interest which
would have been payable on the amount so received had it not been received until
the last day of such Interest Period exceeds (ii) the interest which would have
been recoverable by Bank by placing the amount so received on deposit in the
certificate of deposit markets or the offshore currency interbank markets or
United States Treasury investment products, as the case may be, for a period
starting on the date on which it was so received and ending on the last day of
such Interest Period at the interest rate determined by Bank in its reasonable
discretion. Bank's determination as to such amount shall be conclusive absent
manifest error.

(b) Borrower shall pay to Bank, upon demand by Bank, from time to time such
amounts as Bank may reasonably determine to be necessary to compensate it for
any reasonable costs incurred by Bank that Bank determines are attributable to
its making or maintaining of any amount receivable by Bank hereunder in respect
of any Advances relating thereto (such increases in costs and

<PAGE>   8


reductions in amounts receivable being herein called "Additional Costs"), in
each case resulting from any Regulatory Change which:

               (i) Changes the basis of taxation of any amounts payable to Bank
        under this Supplement in respect of any Advances (other than changes
        which affect taxes measured by or imposed on the overall net income of
        Bank by the jurisdiction in which such Bank has its principal office);
        or

               (ii) Imposes or modifies any reserve, special deposit or similar
        requirements relating to any extensions of credit or other assets of, or
        any deposits with or other liabilities of Bank (including any Advances
        or any deposits referred to in the definition of "LIBOR Base Rate"); or

               (iii) Imposes any other condition affecting this Supplement (or
        any of such extensions of credit or liabilities).

        Bank will notify Borrower of any event occurring after the date of the
Loan Agreement which will entitle Bank to compensation pursuant to this section
as promptly as practicable after it obtains knowledge thereof and determines to
request such compensation. Bank will furnish Borrower with a statement setting
forth the basis and amount of each request by Bank for compensation under this
Section 4. Determinations and allocations by Bank for purposes of this Section 4
of the effect of any Regulatory Change on its costs of maintaining its
obligations to make Advances or of making or maintaining Advances or on amounts
receivable by it in respect of Advances, and of the additional amounts required
to compensate Bank in respect of any Additional Costs, shall be conclusive
absent manifest error, subject to subsequent verification by the Borrower at the
Borrower's sole cost and expense, after the payment thereof by the Borrower.

        (c) Borrower shall pay to Bank, upon the request of Bank, such amount or
amounts as shall be sufficient (in the sole good faith opinion of such Bank) to
compensate it for any loss, costs or expense incurred by it as a result of any
failure by Borrower to borrow an Advance on the date for such borrowing
specified in the relevant notice of borrowing hereunder.

        (d) If Bank shall determine that the adoption or implementation of any
applicable law, rule, regulation or treaty regarding capital adequacy, or any
change therein, or any change in the interpretation or administration thereof by
any governmental authority, central bank or comparable agency charged with the
interpretation or administration thereof, or compliance by Bank (or its
applicable lending office) with any respect or directive regarding capital
adequacy (whether or not having the force of law) of any such authority, central
bank or comparable agency, has or would have the effect of reducing the rate of
return on capital of Bank or any person or entity controlling Bank (a "Parent")
as a consequence of its obligations hereunder to a level below that which Bank
(or its Parent) could have achieved but for such adoption, change or compliance
(taking into consideration its policies with respect to capital adequacy) by an
amount reasonably deemed by Bank to be material, then from time to time, within
15 days after demand by Bank, Borrower shall pay to Bank such additional amount
or amounts as will compensate Bank for such reduction. A statement of Bank
claiming compensation under this Section and setting forth the additional amount
or amounts to be paid to it hereunder shall be conclusive absent manifest error,
subject to subsequent verification by the Borrower at the Borrower's sole cost
and expense, after the payment thereof by the Borrower.

        (e) If at any time Bank, in its sole and absolute discretion, determines
that: (i) the amount of the LIBOR Rate Advances for periods equal to the
corresponding Interest Periods are not available to Bank in the offshore
currency interbank markets, or (ii) the LIBOR Rate does not accurately reflect
the cost to Bank of lending the LIBOR Rate Advance, then Bank shall promptly
give notice thereof to Borrower, and upon the giving of such notice Bank's
obligation

<PAGE>   9


to make the LIBOR Rate Advances shall terminate, unless Bank and the Borrower
agree in writing to a different interest rate Advances shall terminate, unless
Bank and the Borrower agree in writing to a different interest rate applicable
to LIBOR Rate Advances. If it shall become unlawful for Bank to continue to fund
or maintain any Advances, or to perform its obligations hereunder, upon demand
by Bank, Borrower shall prepay the Advances in full with accrued interest
thereon and all other amounts payable by Borrower hereunder (including, without
limitation, any amount payable in connection with such prepayment pursuant to
Section 4(a)).

        IN WITNESS WHEREOF, the parties hereto have caused this Supplement to be
executed as of the date first above written.

                                     VitalCom Inc.


                                     By:  s/  Frank T. Sample
                                          --------------------------------------
                                     Title:  Chief Executive Officer

                                     By:  s/  Shelley B. Thunen
                                          --------------------------------------
                                     Title:  Chief Financial Officer


<PAGE>   10


                                    EXHIBIT A



                    LIBOR RATE ADVANCE BORROWING CERTIFICATE

        The undersigned hereby certify as follows:

        We, _______________________ and _________________________, are the duly
elected and Acting ______________________ and _______________________,
respectively, of VitalCom Inc. ("Borrower").

        This certificate is delivered pursuant to Section 2 of that certain
Interest Rate Supplement to Agreement together with the Loan and Security
Agreement by and between Borrower and Silicon Valley Bank ("Bank") (the "Loan
Agreement"). The terms used in this Borrowing Certificate which are defined in
the Loan Agreement have the same meaning herein as ascribed to them therein.

        Borrower hereby requests on _____________________________ a LIBOR Rate
Advance (the "Advance") as follows:

        (a) The date on which the Advance is to be made is __________________.

        (b) The amount of the Advance is to be _______________($____________)
        for an Interest Period of [one] [two] [three] [six] month[s].

        All representations and warranties of Borrower stated in the Loan
Agreement are true, correct and complete in all material respects as of the date
of this request for an Advance; provided, however, that those representations
and warranties expressly referring to another date shall be true, correct and
complete in all material respects as of such date.

        IN WITNESS WHEREOF, this Borrowing Base Certificate is executed by
undersigned as of this ____ day of __________________________________.


                                         VitalCom Inc.



                                         By: 
                                             --------------------------
                                         Title: 
                                                -----------------------

                                         By: 
                                             --------------------------
                                         Title: 
                                                -----------------------


<TABLE>
<CAPTION>
FOR INTERNAL BANK USE ONLY
LIBOR PRICING DATE        LIBOR RATE         LIBOR RATE VARIANCE          MATURITY DATE
------------------        ----------         -------------------          -------------
<S>                       <C>                <C>                          <C>
                                                            %
------------------       -----------             ------------             --------------
</TABLE>


<PAGE>   11

                                    EXHIBIT B

                 LIBOR RATE CONVERSION/CONTINUATION CERTIFICATE

        The undersigned hereby certify as follows:

        We, _______________________ and _________________________ are the duly
elected and Acting ______________________ and ________________________,
respectively, of VitalCom Inc. ("Borrower").

        This certificate is delivered pursuant to Section 2 of that certain
Interest Rate Supplement to the Loan and Security Agreement by and between
Borrower and Silicon Valley Bank ("Bank") (the "Loan Agreement"). The terms used
in this LIBOR Rate Conversion/Continuation Certificate which are defined in the
Loan Agreement have the same meaning herein as ascribed to them therein.

        Borrower hereby requests on ______________, a LIBOR Rate Advance ("the
"Advance") as follows:

        (a)     _____ (i)    A rate conversion of an existing Prime
                             Rate Advance from a Prime Rate a LIBOR Rate
                             Advance; or

                _____ (ii)   A continuation of an existing LIBOR Rate Advance 
                             as a LIBOR Rate Advance;

                            [Check (i) or (ii) above]

        (b) The date on which the Advance is to be made is ____________________.

        (c) The amount of the Advance is to be ________________ ($___________),
            for an Interest Period of [one] [two] [three] [six] month[s].

        All representations and warranties of Borrower stated in the Loan
Agreement are true, correct and complete in all material respects as of the date
of this request for a loan; provided, however, that those representations and
warranties expressly referring to another date shall be true, correct and
complete in all material respects as of such date.

        IN WITNESS WHEREOF, this LIBOR Rate Conversion/Continuation Certificate
is executed by the undersigned as of this _____ day of ________________________.


                                         VitalCom Inc.



                                         By: 
                                             --------------------------
                                         Title: 
                                                -----------------------

                                         By: 
                                             --------------------------
                                         Title: 
                                                -----------------------

<TABLE>
<CAPTION>
FOR INTERNAL BANK USE ONLY
LIBOR PRICING DATE        LIBOR RATE        LIBOR RATE VARIANCE           MATURITY DATE
------------------        ----------        -------------------           -------------
<S>                       <C>               <C>                           <             

                                                           %
-----------------        -----------           -------------               -------------


</TABLE>


<PAGE>   12


      SILICON VALLEY BANK

                               AMENDED SCHEDULE TO

                           LOAN AND SECURITY AGREEMENT

BORROWER:              VITALCOM INC., A DELAWARE CORPORATION

ADDRESS:               15222 DEL AMO AVENUE
                       TUSTIN, CA  92780

DATE:                  DECEMBER 31, 1998

CREDIT LIMIT
(Section 1.1):          An amount not to exceed the lesser of:

                        (1) $5,000,000 AT any one time outstanding; or

                        (2) the sum of:

                                (a)     Loans (the "Formula Loans") in an amount
                                        not to exceed 75% of the Net Amount of
                                        Borrower's accounts, which Silicon in
                                        its discretion deems eligible for
                                        borrowing; plus

                                (b)     Loans other than Formula Loans (the
                                        "Non-Formula Loans"), provided that no
                                        Non-Formula Loans may be outstanding
                                        unless the sum of Borrower's cash and
                                        marketable securities equals or exceeds
                                        the greater of (i) $3,000,000, or (ii)
                                        150% of the outstanding amount of
                                        Non-Formula Loans. If at any time the
                                        outstanding Non- Formula Loans exceed
                                        the greater of (i) or (ii) in the
                                        preceding sentence, Borrower shall repay
                                        such excess to Silicon immediately,
                                        without demand.

                        "Net Amount" of an account means the gross amount of the
                        account, minus all applicable sales, use, excise and
                        other similar taxes and minus all discounts, credits and
                        allowances of any nature granted or claimed.

                        Without limiting the fact that the determination of
                        which accounts are eligible for borrowing is a matter of
                        Silicon's discretion, the following will not be deemed
                        eligible for borrowing: accounts outstanding for more
                        than 90 days from the invoice date, accounts subject to
                        any contingencies, accounts owing from any government
                        agency, accounts owing from an account debtor outside
                        the United States (unless pre-approved by Silicon in its
                        discretion, or backed by a letter of credit satisfactory
                        to Silicon, or FCJA insured satisfactory to Silicon),
                        accounts owing from one account debtor to the extent
                        they exceed 25%* of the total eligible accounts
                        outstanding, accounts owing from an affiliate of
                        Borrower, and accounts


<PAGE>   13





                        owing from an account debtor to whom Borrower is or may
                        be liable for goods purchased from such account debtor
                        or otherwise. In addition, if more than 50% of the
                        accounts owing from an account debtor are outstanding
                        more than 90 days from the invoice date or are otherwise
                        not eligible accounts, then all accounts owing from that
                        account debtor will be deemed ineligible for borrowing.
                        * provided that in the case of Datascope Instruments and
                        Quinton Instrument Company as account debtors, this
                        percentage figure shall be 40% 
                        No Loans shall be made to Borrower subsequent to
                        December 31, 1999. Beginning January 1, 2000, and
                        continuing on the first day of each succeeding calendar
                        month, Borrower shall repay the principal amount of the
                        Obligations outstanding on December 31, 1999, in forty
                        eight consecutive installments, consisting of forty
                        seven installments equal to one forty-eighth of such
                        then-outstanding principal amount, and one final
                        installment on December 1, 2003, in the amount of the
                        entire unpaid balance of all Obligations.

LETTERS OF CREDIT       Silicon, in its reasonable discretion, will from time to
                        time during the term of this Agreement issue letters of
                        credit for the account of the Borrower ("Letters of
                        Credit"), in an aggregate amount at any one time
                        outstanding hot to exceed $500,000, upon the request of
                        the Borrower, provided that, on the date the Letters of
                        Credit are to be issued, Borrower has available to it
                        Loans in an amount equal to or greater than the face
                        amount of the Letters of Credit to be issued. Prior to
                        the issuance of any Letters of Credit, Borrower shall
                        execute and deliver to Silicon Applications for Letters
                        of Credit and such other documentation as Silicon shall
                        specify (the "Letter of Credit Documentation"). Fees for
                        the Letters of Credit shall be as provided in the Letter
                        of Credit Documentation. The Credit Limit set forth
                        above and the Loans available under this Agreement at
                        any time shall be reduced by the face amount of Letters
                        of Credit from time to time outstanding.

Interest Rate 
(Section 1.2):          Interest on the Loans shall be paid at a rate equal
                        to the "Interest Rate", as defined in, and pursuant to
                        the terms of,the Interest Rate Supplement to Loan
                        Agreement attached hereto, which is incorporated into
                        and forms an integral part of this Agreement.

                        Interest shall be calculated on the basis of a 360-day
                        year for the actual number of days elapsed.

UNUSED LINE FEE:        In the event, in any fiscal quarter of Borrower (or
                        portion thereof at the beginning and end of the term
                        hereof), the average daily principal balance of the
                        Loans outstanding during such fiscal quarter is less
                        than the amount of the Credit Limit, Borrower shall pay
                        Silicon an unused line fee in an amount equal to 0.25%
                        per annum on the difference between



<PAGE>   14


                        the amount of the Credit Limit and the average daily
                        principal balance of the Loans outstanding during such
                        fiscal quarter, which unused line fee shall be computed
                        and paid quarterly, in arrears, on the first day of the
                        following fiscal quarter.

MATURITY DATE
(Section 5.1):          DECEMBER 1, 2003.

PRIOR NAMES OF 
BORROWER
(Section 3.2).          ACCUCORE, INC., PACIFIC COMMUNICATIONS, INC.

TRADE NAMES OF
BORROWER
(Section 3.2):          ACCUCORE

OTHER LOCATIONS 
AND ADDRESSES
(Section 3.3):          NONE

MATERIAL ADVERSE 
LITIGATION
(Section 3.10):         NONE

NEGATIVE 
COVENANTS-EXCEPTIONS
(Section 4.6):          Without Silicon's prior written consent, Borrower may do
                        the following, provided that, after giving effect
                        thereto, no Event of Default has occurred and no event
                        has occurred which, with notice or passage of time or
                        both, would constitute an Event of Default, and provided
                        that the following are done in compliance with all
                        applicable laws, rules and regulations: (i) repurchase
                        shares of Borrower's stock, provided that the total
                        amount paid by Borrower for such stock does not exceed
                        $250,000 in any fiscal year.

FINANCIAL COVENANTS
    (Section 4.1):      Borrower shall comply with all of the following
                        covenants. Compliance shall be determined as of the end
                        of each calendar quarter, except as otherwise
                        specifically provided below:

QUICK ASSET RATIO:      Borrower shall maintain a ratio of "Quick Assets" to
                        current liabilities of not less than 1.75 to I.

TANGIBLE NET WORTH:     Borrower shall maintain a tangible net worth of not less
                        than $18,000,000.



DEBT TO TANGIBLE
NET WORTH RATIO:        Borrower shall maintain a ratio of total liabilities to
                        tangible net worth of not more than 0.75 to 1.



<PAGE>   15

     PROFITABILITY:     Borrower shall not incur a net loss (after taxes) for:

                        (i) the fiscal year ending December 31, 1998, in excess
                        of $3,250,000; nor

                        (ii) the fiscal year ending December 31, 1999, in excess
                        of $2,000,000.

DEFINITIONS:           "Current assets" and "current liabilities" shall have
                        the meaning ascribed thereto in accordance with
                        generally accepted accounting principles.

                        "Tangible net worth" means the excess of total assets
                        over total liabilities, determined in accordance with
                        generally accepted accounting principles, excluding
                        however all assets which would be classified as
                        intangible assets under generally accepted accounting
                        principles, including without limitation goodwill,
                        licenses, patents, trademarks, trade names, copyrights,
                        and franchises.

                        "Quick Assets" means cash on hand or on deposit in
                        banks, readily marketable securities issued by the
                        United States, readily marketable commercial paper rated
                        "A-1" by Standard & Poor's Corporation (or a similar
                        rating by a similar rating organization), certificates
                        of deposit and banker's acceptances, and accounts
                        receivable (net of allowance for doubtful accounts).

SUBORDINATED DEBT:      "Liabilities(1)", for purposes of the foregoing 
                        covenants, do not include indebtedness which is 
                        subordinated to the indebtedness to Silicon under a 
                        subordination agreement in form specified by Silicon or
                        by language in the instrument evidencing the
                        indebtedness which is acceptable to Silicon."


ACQUISITION-RELATED
NON-CASH CHARGES:       "Net loss", for purposes of the foregoing covenants,
                        shall not include non-cash charges incurred in
                        connection with any acquisition(s) by Borrower of
                        another corporation or asset(s).

OTHER COVENANTS
(Section 4.1):          Borrower shall at all times comply with all of the
                        following additional covenants:

                        1. BANKING RELATIONSHIP. Borrower shall at all times
                        maintain its primary operating banking relationship with
                        Silicon.

                        2. INDEBTEDNESS. Without limiting any of the foregoing
                        terms or provisions of this Agreement, Borrower shall
                        not in the future incur indebtedness for borrowed money,
                        except for (i) indebtedness to Silicon, and (ii)
                        indebtedness incurred in the future for the purchase
                        price of or lease of equipment.


<PAGE>   16


                        3. UCC-1 FINANCING STATEMENTS. Borrower is concurrently
                        delivering to Silicon UCC-l financing statements, and it
                        is understood and agreed that such financing statements
                        shall not be considered effective unless and until the
                        first Grant is effective. At such time Silicon shall be
                        permitted to file such financing statements immediately.

                        4. TERMINATION OF AGREEMENT. Borrower and Silicon hereby
                        agree that this Agreement may be terminated by
                        Borrower's written notice to Silicon when no Obligations
                        are outstanding or otherwise have been paid and
                        performed in full.

                     BORROWER:

                        VITALCOM INC.



                        BY  s/  FRANK T. SAMPLE
                            -------------------------------
                                PRESIDENT AND CEO

                        BY  s/  SHELLEY B. THUNEN
                            -------------------------------
                                SECRETARY

                     SILICON:

                        SILICON VALLEY BANK



                        BY s/  GARY REAGAN
                            -------------------------------
                        TITLE     VICE PRESIDENT



<PAGE>   17




                            NEGATIVE PLEDGE AGREEMENT

        This Negative Pledge Agreement is made as of December 31, 1998 by and
between Vitalcom Inc. ("Borrower") and Silicon Valley Bank ("Silicon").

        In connection with, among other documents, the Loan and Security
Agreement between Borrower and Silicon dated February 26, 1993 (as amended, the
"Loan Agreement; the Loan Agreement and all related instruments, documents and
agreements may be collectively referred to herein as the "Loan Documents"),
Borrower agrees as follows:

        1. Borrower shall not sell, transfer, assign, mortgage, pledge, lease,
grant a security interest in, or encumber any of Borrower's:

        a. Equipment, including without limitation all machinery, fixtures,
trade fixtures, vehicles, furnishings, furniture, materials, tools, machine
tools, office equipment, computers and peripheral devices, appliances,
apparatus, parts, dies, and jigs; or

        b General intangibles, including, but not limited to, deposit accounts,
goodwill, drawings, blueprints, customer lists, security deposits, loan
commitment fees, federal, state and local tax refunds and claims, all rights in
all litigation presently or hereafter pending for any cause or claim (whether in
contract, tort or otherwise), and all judgments now or hereafter arising
therefrom, all claims of Borrower against Silicon, all rights to purchase or
sell real or personal property, all rights as a licensor or licensee of any
kind, all royalties, licenses, processes, telephone numbers, proprietary
information, purchase orders, and all insurance policies and claims (including
without limitation credit, liability, property and other insurance), all other
rights, privileges and franchises of every kind, and all intellectual property,
including, without limitation, the following:

               i. Any and all copyright rights, copyright applications,
copyright registrations and like protections in each work or authorship and
derivative work thereof, whether published or unpublished and whether or not the
same also constitutes a trade secret, now or hereafter existing, created,
acquired or held;

               ii. Any and all trade secrets, and any and all intellectual
property rights in computer software and computer software products now or
hereafter existing, created, acquired or held;

               iii. Any and all design rights which may be available to Borrower
now or hereafter existing, created, acquired or held;

               iv. All patents, patent applications and like protections
including, without limitation, improvements, divisions, continuations, renewals,
reissues, extensions and continuations-in-part of the same, including without
limitation the patents and patent applications;

               v. Any trademark and servicemark rights, whether registered or
not, applications to register and registrations of the same and like
protections, and the entire goodwill of the business of Borrower connected with
and symbolized by such trademarks, including without limitation;


                                              1


<PAGE>   18




               vi. Any and all claims for damages by way of past, present and
future infringements of any of the rights included above, with the right, but
not the obligation, to sue for and collect such damages for said use or
infringement of the intellectual property rights identified above;

               vii. All licenses or other rights to use any of the Copyrights,
Patents or Trademarks, and all license fees and royalties arising from such use
to the extent permitted by such license or rights; and

               viii. All amendments, extensions, renewals and extensions of any
of the Copyrights, Trademarks or Patents; and

               ix. All proceeds and products of the foregoing, including without
limitation all payments under insurance or any indemnity or warranty payable in
respect of any of the foregoing;

        2. It shall be an event of default under the Loan Documents between
Borrower and Silicon if there is a breach of any term of this Negative Pledge
Agreement.

        3. Capitalized terms used but not otherwise defined herein shall have
the same meaning as in the Loan Documents.

BORROWER:

VITALCOM INC.


By:   s/  Shelley B. Thunen
      ----------------------------
Title:   Chief Financial Officer
      ----------------------------


SILICON:

SILICON VALLEY BANK


By:  s/  Gary Reagan
     ---------------------------
Title:  Vice President
        ------------------------


                                        2


<PAGE>   19


                               SILICON VALLEY BANK

CERTIFIED RESOLUTION

BORROWER:              VITALCOM INC., A CORPORATION
                       ORGANIZED UNDER THE LAWS OF THE
                       STATE OF DELAWARE

ADDRESS:               15222 DEL AMO AVENUE
                       TUSTIN, CA 92780

DATE:                  DECEMBER 31, 1998

        I, the undersigned, Secretary or Assistant Secretary of the above-named
borrower, a corporation organized under the laws of the state set forth above,
do hereby certify that the following is a full, true and correct copy of
resolutions duly and regularly adopted by the Board of Directors of said
corporation as required by law, and by the by-laws of said corporation, and that
said resolutions are still in full force and effect and have not been in any way
modified, repealed, rescinded, amended or revoked.

    RESOLVED, that this corporation borrow from Silicon Valley Bank ("Silicon"),
    from time to time, such sum or sums of money as, in the judgment of the
    officer or officers hereinafter authorized hereby, this corporation may
    require.

    RESOLVED FURTHER, that any of the Chairman, President, Chief Executive
    Officer, Chief Financial Officer or Secretary of this corporation be, and he
    or she is hereby authorized, directed and empowered, in the name of this
    corporation, to execute and deliver to Silicon, and Silicon is requested to
    accept, the loan agreements, security agreements, notes, financing
    statements, and other documents and instruments providing for such loans and
    evidencing and/or securing such loans, with interest thereon, and said
    authorized officers are authorized from time to time to execute renewals,
    extensions and/or amendments of said loan agreements, security agreements,
    and other documents and instruments.

    RESOLVED FURTHER, that said authorized officers be and they are hereby
    authorized, directed and empowered, as security for any and all indebtedness
    of this corporation to Silicon, whether arising pursuant to this resolution
    or otherwise, to grant, transfer, pledge, mortgage, assign, or otherwise
    hypothecate to Silicon, or deed in trust for its benefit, any property of
    any and every kind, belonging to this corporation, including, but not
    limited to, any and all real property, accounts, inventory, equipment,
    general intangibles, instruments, documents, chattel paper, notes, money,
    deposit accounts, furniture, fixtures, goods, and other property of every
    kind, and to execute and deliver to Silicon any and all grants, transfers,
    trust receipts, loan or credit agreements, pledge agreements, mortgages,
    deeds of trust, financing statements, security agreements and other
    hypothecation agreements, which said instruments and the note or notes and
    other instruments referred to in the preceding paragraph may contain such
    provisions, covenants, recitals and agreements as Silicon may require and
    said authorized officers may approve, and the execution thereof by said
    authorized officers shall be conclusive evidence of such approval.


                                        1


<PAGE>   20


               The undersigned further hereby certifies that the following
persons are the duly elected and acting officers of the corporation named above
as borrower and that the following are their actual signatures:


<TABLE>
<CAPTION>
      NAMES                              OFFICE(S)                       ACTUAL SIGNATURES
<S>                         <C>                                    <C>

 Frank T. Sample              Chairman of the Board, CEO              s/ Frank T. Sample______

 Shelley B. Thunen           Chief Financial Officer, Secretary      s/  Shelley B. Thunen____
</TABLE>


               IN WITNESS WHEREOF, I have hereunto set my hand as such Secretary
or Assistant Secretary on the date set forth above.




                                                    s/  Shelley B. Thunen
                                                    ----------------------------
                                                          Secretary


                                        2


<PAGE>   21




                                                              THIS SPACE FOR USE
                                                               OF FILING OFFICER

FINANCING STATEMENT - FOLLOW INSTRUCTIONS CAREFULLY
THIS FINANCING STATEMENT IS PRESENTED FOR FILING PURSUANT TO THE UNIFORM
COMMERCIAL CODE AND WILL REMAIN EFFECTIVE, WITH CERTAIN EXCEPTIONS, FOR 5 YEARS
FROM DATE OR FILING.

<TABLE>
<S>                                                <C>
A. NAME & TEL. # OF CONTACT AT FILER(OPTIONAL)     B. FILING OFFICE ACOT. #(OPTIONAL)
  Wendy Huey          310471-3000                              CA SOS
</TABLE>

   RETURN CORY TO: (NAME AND MAILING ADDRESS)


                   Levy, Small & Lallas
                   815 Moraga Drive
                   Los Angeles, CA 90049
                   Ann:  Documentation Dept.

C. OFTIONAL DESIGNATION (IF APPLICABLE): 1/2 LESSORILESSEE L CONSIGNOR/CONSIGNEE

NON-UCC FIL'NG

DEBTOR'S ENTITY'S NAME

VITALCOM INC.
15222 DEL AMO AVENUE
TUSTIN, CA  92780  USA

SECURED PARTY'S ENTITY'S NAME

SILICON VALLEY BANK
3003 TASMAN DRIVE, MAIL SORT NC-661
SANTA CLARA, CA  95054  USA

THIS FINANCING STATEMENT COVERS THE FOLLOWING TYPES OR ITEMS OF PROPERTY:

DEBTOR HEREBY GRANTS SECURED PARTY A SECURITY INTEREST IN ALL OF THE FOLLOWING,
WHETHER NOW OWNED OR HEREAFTER ACQUIRED, AND WHEREVER LOCATED, AS COLLATERAL FOR
THE PAYMENT AND PERFORMANCE OF ALL PRESENT AND FUTURE INDEBTEDNESS, LIABILITIES,
GUARANTEES AND OBLIGATIONS OF DEBTOR TO SECURED PARTY: ALL "ACCOUNTS," AND
"INVENTORY," AS SUCH TERMS ARE DEFINED IN DIVISION 9 OF THE CALIFORNIA UNIFORM
COMMERCIAL CODE IN EFFECT ON THE DATE HEREOF, AND ALL OTHER TYPES OR ITEMS OF
PROPERTY DESCRIBED ON EXHIBIT A HERETO (BUT THIS FINANCING STATEMENT SHALL BE
FULLY EFFECTIVE NOTWITHSTANDING ANY LACK OF ANY EXHIBIT A). DEBTOR IS NOT
AUTHORIZED TO SELL, TRANSFER, OR FURTHER ENCUMBER ANY OF THE FOREGOING
COLLATERAL, EXCEPT FORT THE SALE OF FINISHED INVENTORY IN THE ORDINARY COURSE OF
BUSINESS.



VITALCOM INC.                                 SILICON VALLEY BANK

BY:   S/SHELLEY B. THUNEN                     BY:  S/GARY REAGAN
      ---------------------------                  -------------------------
      CHIEF FINANCIAL OFFICER                       VICE PRESIDENT




<PAGE>   22

                                   EXHIBIT "A"

                  TO FINANCING STATEMENT AND SECURITY AGREEMENT

This FINANCING STATEMENT and SECURITY AGREEMENT covers the following types or
items of property, and the undersigned, VITALCOM INC. ("Debtor") hereby grants
SILICON VALLEY BANK ("Secured Party") a security interest therein as collateral
for the payment and performance of all present and future indebtedness,
liabilities, guarantees and obligations of Debtor to Secured Party. Debtor
agrees that said security interest may be enforced by Secured Party in
accordance with the terms and provisions of all security and other agreements
between Secured Party and Debtor, the California Uniform Commercial Code, or
both (but this document shall be fully effective as a security agreement, even
if there is not other security or other agreement between Secured Party and
Debtor): (a) All accounts, contract rights, chattel paper, letters of credit,
documents, securities, securities accounts, investment property, money, and
instruments, all other obligations now or in the future owing to the Debtor; and
(b) All inventory, goods, merchandise, materials, raw materials, work in
process, finished goods, farm products, advertising, packaging and shipping
materials, supplies, and all other tangible personal property which is held for
sale or lease or furnished under contracts of service or consumed in the
Debtor's business, and all warehouse receipts and other documents; (c) All books
and records, whether stored on computers or otherwise maintained; and (d) All
substitutions, additions and accessions to any of the foregoing, and all
products, proceeds and insurance proceeds of the foregoing, and all guaranties
of and security for the foregoing; and all books and records relating to any of
the foregoing.


                                   VITALCOM INC.


                                   By s/ Shelley B. Thunen
                                      -----------------------------
                                   Title    Chief Financial Officer