<PAGE>   1

                                                                  EXHIBIT 99.3

                              SILICON VALLEY BANK

                          AMENDMENT TO LOAN AGREEMENT


BORROWER:      VITALCOM INC., A DELAWARE CORPORATION (FORMERLY KNOWN AS
               ACCUCORE, INC., SUCCESSOR BY MERGER TO PACIFIC COMMUNICATIONS,
               INC., A CALIFORNIA CORPORATION)

ADDRESS:       15222 Del Amo Avenue Tustin, CA 92780

Date:          August 6,1996


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 (the "December 1995
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
December 1995 Amendment was May 5, 1996, 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 on the date hereof, to read as set forth on the Schedule 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
         occurrence of an Event of Default arising from the Borrower's non-
         compliance with any of the financial covenants set forth in the Loan
         Agreement while any monetary Obligations are outstanding (the "Granting
         Condition"), the following shall considered to be immediately and fully
         effective at such time, without any further action on the part of
         Silicon or Borrower: Borrower hereby grants Silicon a continuing
         security interest in all of the 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").  Until such time that the Granting Condition has occurred,
         the Grant shall not be considered effective.  Borrower agrees to take
         such actions and execute such documentation as Silicon determines is
         necessary or desirable in order to effectuate



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SILICON VALLEY BANK                                 AMENDMENT TO LOAN AGREEMENT



         the Grant and to allow Silicon to perfect its security interest in the
         Collateral at such time as the Grant becomes effective.

         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 5 business, and all warehouse receipts and
         other documents; and (c) All 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;
         (d) All general intangibles including, but not limited to, deposit
         accounts, goodwill, names, trade names, trademarks and the goodwill of
         the business symbolized thereby, trade secrets, drawings, blueprints,
         customer lists, patents, patent applications, copyrights, 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), and all other rights, privileges and franchises of every
         kind; (e) All books and records, whether stored on computers or
         otherwise maintained; and (f) 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."
        
     3.  MODIFICATION TO SECTION 3.7.  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 the earlier of (A) 45 days after the end of
         each quarter or (B) 5 days after the earlier of the date the report
         10-Q is filed or is required to be filed with the Securities and
         Exchange Commission ("SEC") with respect to Borrower, such 10-Q report,
         a quarterly 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 quarter 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
         (the "Compliance Certificate"); (iii) within the earlier of (A) 90 days
         after the end of Borrower's fiscal year or (B) 5 days after the earlier
         of the date the report 10-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



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SILICON VALLEY BANK                                 AMENDMENT TO LOAN AGREEMENT


         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."
         
     4.  REFERENCES IN LOAN AGREEMENT; ETC.  Until such time that 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 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.

     5.  FEE.  It is acknowledged that Borrower has paid to Silicon a fee in the
amount of $8,250 in connection with this Amendment, which shall be in addition
to all interest and all other fees payable to Silicon and shall be 
non-refundable.  At such time that any Loans are made hereunder, Borrower shall,
prior to Silicon's making of any such Loan, pay to Silicon a further fee of
$8,250, which shall be in addition to all interest and all other fees payable to
Silicon and shall be non-refundable.

     6.  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., a Delaware corporation      SILICON VALLEY BANK


By /s/ DAVID L. SCHLOTTERBECK              /s/ K. CHAMBERLIN for Bonnie J. Renta
-----------------------------              -------------------------------------
President or Vice President                    V.P.


By /s/ SHELLEY B. THUNEN
-----------------------------
Secretary or Ass't Secretary



                                      (3)




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SILICON VALLEY BANK                                  SCHEDULE TO LOAN AGREEMENT



                              SILICON VALLEY BANK

                                  SCHEDULE TO

                          LOAN AND SECURITY AGREEMENT

BORROWER:      VITALCOM INC., A DELAWARE CORPORATION (FORMERLY KNOWN AS
               ACCUCORE, INC., SUCCESSOR BY MERGER TO PACIFIC COMMUNICATIONS,
               INC., A CALIFORNIA CORPORATION)

ADDRESS:       15222 DEL AMO AVENUE
               TUSTIN, CA 92780

DATE:          AUGUST 6,1996
                              
CREDIT LIMIT                      An amount equal to $5,000,000.
(Section 1.1):
                         
  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 not to exceed $250,000, 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):    A rate equal to the "Prime Rate" in effect
                                  from time to time.  Interest shall be
                                  calculated on the basis of a 360-day year for
                                  the actual number of days elapsed. "Prime
                                  Rate" means the rate announced from time to
                                  time by Silicon as its "prime rate;" it is a
                                  base rate upon which other rates charged by
                                  Silicon are based, and it is not necessarily
                                  the best rate available at Silicon.  The
                                  interest rate applicable to the Obligations
                                  shall change on each date there is a change in
                                  the Prime Rate.



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SILICON VALLEY BANK                                 SCHEDULE TO LOAN AGREEMENT



LOAN ORIGINATION FEE              Per the Amendment to Loan Agreement of even
(Section 1.3):                    date. (Section 3.10):
                    
MATURITY DATE                     AUGUST 5, 1997.                 
(Section 5.1):                                                     
                                                               
PRIOR NAMES OF BORROWER           ACCUCORE, INC., PACIFIC COMMUNICATIONS, INC.
(Section 3.2):                                                     
                                                                   
TRADE NAMES OF BORROWER           ACCUCORE                        
(Section 3.2):                                                     
                                                                   
OTHER LOCATIONS AND ADDRESSES     NONE                            
(Section 3.3):
                                                                   
MATERIAL ADVERSE LITIGATION       NONE                            
                                                    
NEGATIVE COVENANTS-EXCEPTIONS     Without Silicon's prior written consent,
(Section 4.6):                    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               Borrower shall comply with all of the
(Section 4.1):                    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 2.00 to 1.
                       
    TANGIBLE NET WORTH:           Borrower shall maintain a tangible net worth
                                  of not less than $25,000,000.
                       
    DEBT TO TANGIBLE NET          Borrower shall maintain a ratio of total
    WORTH RATIO:                  liabilities to tangible net worth of not more
                                  than 1.00 to 1.
                       
    PROFITABILITY:                Borrower shall not incur a loss (after taxes)
                                  for any fiscal quarter, other than in a single
                                  fiscal quarter during any calendar year in
                                  which Borrower shall not incur a loss (after
                                  taxes) in an amount greater than $500,000.
                       
    DEFINITIONS:                  "Current assets," and "current liabilities"
                                  shall have the meanings ascribed to them 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



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SILICON VALLEY BANK                                  SCHEDULE TO LOAN AGREEMENT


                                  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" 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.

OTHER COVENANTS                   Borrower shall at all times comply with all of
(Section 4.1):                    the following additional covenants:
                                      
                                  1.  BANKING RELATIONSHIP.  Borrower shall at
                                      all times maintain its primary operating
                                      banking relationship with Silicon.

                                  2. 30 DAY CLEAN-UP PERIOD.  Borrower shall
                                      have no monetary Obligations outstanding
                                      for a period of 30 consecutive days during
                                      the term hereof.  
                                     
                                  3. 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.  

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

                                  5.  TERMINATION OR 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/ DAVID L. SCHLOTTERBECK
                                        -----------------------------
                                          President or Vice President


                                        By /s/ SHELLEY B. THUNEN
                                        -----------------------------
                                         Secretary or Ass't Secretary


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<PAGE>   7
SILICON VALLEY BANK                                  SCHEDULE TO LOAN AGREEMENT




                              SILICON VALLEY BANK

                         AMENDMENT TO LOAN AGREEMENT


BORROWER:     VITALCOM INC., A DELAWARE CORPORATION

ADDRESS:      15222 DEL AMO AVENUE TUSTIN, CA 92780

DATE:         SEPTEMBER 25, 1996


        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 (the "December 1995
Amendment"), as amended by that Amendment to Loan Agreement dated August 6,
1996 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.

        1.  AMENDED FINANCIAL COVENANTS.  The section of the Schedule to the
Loan Agreement entitled "Financial Covenants (Section 4.1)" is amended
effective as of the date hereof to read as follows:

    "FINANCIAL COVENANTS          Borrower shall comply with all of the
    (Section 4.1):                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 2.00 to 1.
                           
    TANGIBLE NET WORTH:           Borrower shall maintain a tangible net worth
                                  of not less than $22,500,000.
                           
    DEBT TO TANGIBLE              Borrower shall maintain a ratio of total
    NET WORTH RATIO:              liabilities to tangible net worth of not more
                                  than 1.00 to 1.
                           
                           
    MINIMUM CASH COVERAGE:        Borrower shall maintain an aggregate total of
                                  cash and marketable securities (valued at
                                  market value) in an amount at



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SILICON VALLEY BANK                                 AMENDMENT TO LOAN AGREEMENT





                                  least equal to the product of two times the
                                  maximum amount of the Credit Limit.

    DEFINITIONS:                  "Current assets," and "current liabilities"
                                  shall have the meanings ascribed to them 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" 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."

        2.  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., a Delaware corporation          SILICON VALLEY BANK


By /s/ DAVID L. SCHLOTTERBECK                   By /s/ K. CHAMBERLIN
-----------------------------                   ---------------------------
President or Vice President                        V.P.


By /s/ SHELLEY B. THUNEN
-----------------------------
Secretary or Ass't Secretary



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