<PAGE>
                                                                    Exhibit 10.6

                     19820 North Creek Parkway, Suite 100
                              Bothell, WA  98011


                                 July 2, 2001

Dr. David Albert
1508 Guilford Lane
Oklahoma City, OK  73120

Dear Dr. Albert:

     In connection with our recent acquisition of VitalCom, Inc. and as a result
of the related consolidation and move of our operations to Tustin, California,
we wish to clarify our severance policy in respect of your continued service as
an employee of Data Critical Corporation (the "Company").  References to "you"
and "Executive" mean Dr. David Albert.

     The Company may not terminate Employee's employment with the Company
without cause unless it provides Employee at least thirty (30) days' advance
written notice of such termination.  In addition, in the event that at any time
prior to December 30, 2001:

          (a)  the Company terminates your employment at any point in time
     without cause, or

          (b)  as a requirement of your continued employment with the Company,
     the Company requires you to permanently relocate to Tustin, California and,
     rather than relocate, you elect to voluntarily terminate your employment
     with the Company (which event shall be deemed a termination without cause),

then in either such case the Company will pay you $17,875 per month (subject to
customary withholding) for a period of two months after such termination in
accordance with the Company's standard payroll procedures.  For purposes of this
letter, "cause" shall mean, the commission of an act of fraud or dishonesty in
the course of your employment with the Company; conviction of a crime
constituting a felony or in respect of any act of fraud, dishonesty or moral
turpitude; failure to perform the duties assigned to you material to the
business conduct of the Company under circumstances in which you knew or should
have reasonably known that such failure would be detrimental to the Company,
unless you remedy such failure not later than 30 days following delivery to you
of a written notice from the Company describing such failure in reasonable
detail.

     The Company and Executive acknowledge that Executive's employment is and
shall continue to be at-will, as defined under applicable law, and that
Executive's employment with the Company may be terminated by either party at any
time for any or no reason, subject to the terms of this letter.  If Executive's
employment terminates for any reason, Executive shall not be entitled to any
payments, benefits, damages, award or compensation other than as provided in
this letter or as otherwise required by law.  Any payments, benefits, damages,
awards, or other compensation provided for hereunder upon any termination hereof
shall be inclusive of (and not additive to) any such amounts required pursuant
to any applicable law. The rights and duties created by this letter may not be
modified in any way except by a written agreement executed by or on behalf of
the
<PAGE>

Board of Directors of the Company.

     The terms of this letter may be amended or waived only with the written
consent of the parties.  This letter constitutes the sole agreement of the
parties and supersedes all oral negotiations and prior writings with respect to
the subject matter hereof.  The validity, interpretation, construction and
performance of this letter agreement shall be governed by the laws of the State
of Washington, without giving effect to the principles of conflict of laws.
This letter agreement may be executed in counterparts, each of which shall be
deemed an original, but all of which together will constitute one and the same
instrument.  Any dispute or claim arising out of or in connection with this
letter agreement will be finally settled by binding arbitration in Seattle,
Washington in accordance with the rules of the American Arbitration Association
by one arbitrator appointed in accordance with said rules. Judgment on the award
rendered by the arbitrator may be entered in any court having jurisdiction
thereof.  Notwithstanding the foregoing, the parties may apply to any court of
competent jurisdiction for preliminary or interim equitable relief, or to compel
arbitration in accordance with this paragraph, without breach of this
arbitration provision.

     Advice of Counsel.  EACH PARTY TO THIS LETTER ACKNOWLEDGES THAT, IN
EXECUTING THIS LETTER, SUCH PARTY HAS HAD THE OPPORTUNITY TO SEEK THE ADVICE OF
INDEPENDENT LEGAL COUNSEL, AND HAS READ AND UNDERSTOOD ALL OF THE TERMS AND
PROVISIONS OF THIS LETTER.  THIS LETTER SHALL NOT BE CONSTRUED AGAINST ANY PARTY
BY REASON OF THE DRAFTING OR PREPARATION HEREOF.


                                 DATA CRITICAL CORPORATION:

                                 By:        /s/ Michael E. Singer
                                    ---------------------------------------
                                 Name:  Michael E. Singer
                                 Title: Executive Vice President, Corporate
                                        Development, Chief Financial Officer

                                 Address:
                                 19820 North Creek Parkway
                                 Suite 100
                                 Bothell, WA  98011


ACKNOWLEDGED AND AGREED:

DR. DAVID ALBERT


Signature:  /s/ David Albert
          ---------------------