Document:

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                                                                   Exhibit 10.15

                     [Letterhead of Rotech Healthcare Inc.]

                                                                 October 30,2002
Albert Prast
400 Lakewood Drive
Winter Park, Florida 32789

     Re: Agreement with Respect to Rights Upon Termination of Employment

Dear Albert:

     Rotech Healthcare, Inc., a Delaware corporation (the "Company" or
"Rotech"), is pleased to offer you the following agreement with respect to your
rights upon the termination of your employment with the Company.

     1. Upon the termination of employment by you for Good Reason or by the
Company without Cause (as those terms are defined below), the Company shall (a)
pay to you, with your final paycheck, any base salary or bonus earned by you but
not yet paid as of the date of the termination of your employment; (b) fully
reimburse you for all reimbursable expenses; (c) pay to you in a lump sum no
later than twenty (20) days after the termination of your employment, an amount
equal to the sum of (i) one hundred fifty percent (150%) of your annual base
salary (measured as of the time of the termination of your employment and
without mitigation due to any remuneration or other compensation earned by you
following such termination of employment), and (ii) an amount equal to the bonus
paid to you for performance in 2001 (excluding bankruptcy retention related
bonuses); and (d) continue your medical coverage under the Company's group
health plan in accordance with the Consolidated Omnibus Budget Reconciliation
Act ("COBRA") for a period of eighteen (18) months from the date of the
termination of your employment by directly paying the monthly premiums on your
behalf during such period. Your entitlement to the severance pay and other
termination benefits provided for in this Paragraph 1 are conditioned upon your
(A) providing a general release in favor of Rotech, in a form approved by the
Company, of any and all claims arising out of, relating to or concerning your
employment or the termination of your employment with the Company and (B)
material compliance with the Confidentiality and Inventions Rights Agreement
annexed to this letter as Exhibit A.

     2. Wherever reference is made in this letter agreement to the termination
of your employment by the Company being with or without Cause, "Cause" shall
include, without limitation, the termination of your employment with the
Company due to the occurrence of one or more of the following events as
determined by a majority vote of the Board of Directors: (a) your conviction or
your entry of a plea of guilty or nolo contendere to any felony, (b) your
engagement in conduct constituting breach of fiduciary duty, willful misconduct
or gross negligence relating to the Company or the performance of your duties
(including intentional acts of employment discrimination or sexual harassment)
or fraud which have a significant adverse effect on the Company, (c) your
willful failure to follow a reasonable and lawful written

    2600 Technology Drive, Suite 300 . Orlando, Florida 32804 . 407-822-4600

<PAGE>

directive of the Chief Executive Officer or the Board of Directors (which shall
be capable of being performed by you with reasonable effort), (d) your
deliberate and continued failure to perform your material duties, and (e) your
intentional disparagement of the Company or any of its affiliate, subsidiary or
parent companies or any of their collective executives, shareholders, directors,
or officers in any written or oral communication; provided, however, that you
shall receive thirty (30) days' prior written notice that the Board of Directors
intends to meet to consider your termination for Cause and specifying the
actions allegedly constituting Cause.

     3. For purposes of this letter agreement, "Good Reason" shall mean the
occurrence of one or more of the following events: (a) the Company's failure to
pay your base salary, earned bonus or additional earned compensation or its
failure to continue your benefits, perquisites or related benefits, (b) a
decrease in your base salary, (c) without your written consent, requiring you to
regularly report to work at a facility more than fifty (50) miles from the
location of your employment at the time of the execution of this letter
agreement, (d) without your written consent, the directing to you of any duties
or responsibilities which are materially inconsistent with your
responsibilities, positions and/or titles, (e) without your written consent, a
material reduction in your title, duties, positions or responsibilities, or (f)
without your written consent the failure by the Company to continue in effect
any employee benefit or compensation plan including, but not limited to, any
life insurance plan, health insurance plan and accidental death or disability
plan in which you participate unless (1) such benefit or compensation plan, life
insurance plan, health insurance plan or related covenant, or accidental death
or disability plan or similar plan or benefit is replaced with a comparable plan
in which you will participate or which will provide you with comparable
benefits, or (2) the Company requests that you seek comparable coverage under
another such plan(s) and the Company reimburses you in full, on an after-tax
basis (taking into consideration all net Federal, State and local income taxes),
for such coverage. In the event you believe Good Reason to exist, then you must
provide the Company with written notice no later than ninety (90) days after
such event or condition you claim constitutes Good Reason occurs specifying the
bases for your belief that Good Reason exists. If the Company shall not have
cured or eliminated the event constituting Good Reason within thirty (30) days
after receipt of your written notice, upon expiration of such 30-day period,
your employment hereunder shall automatically be terminated.

4. You acknowledge, and by your signature hereby confirm, that the Company has
agreed to provide you with the benefits and payments provided for herein in
consideration for your agreement to be bound by the terms of the Confidentiality
and Inventions Rights Agreement annexed hereto as Exhibit A and that such
benefits serve as sufficient consideration therefore.

                                       2

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If the foregoing correctly sets forth our understanding, please sign two (2)
copies of this letter and return it to the undersigned, whereupon this letter
shall constitute a binding agreement between you and the Company.

                                  Very truly yours,

                                  Rotech Healthcare, Inc.

                                  By: /s/ Guy P. Sansone
                                  Name:  Guy P. Sansone
                                  Title: Interim Co-CEO & President

Accepted and Agreed:

/s/ Albert Prast
Albert Prast

                                       3<PAGE>
                                                                     Exhibit 4.6

                 FIFTH AMENDMENT TO CREDIT AGREEMENT AND WAIVER

      THIS FIFTH AMENDMENT TO CREDIT AGREEMENT AND WAIVER (this "Amendment"),
dated as of February 6, 2003, is entered into among (1) ALPHA TECHNOLOGIES
GROUP, INC., a Delaware corporation (the "Borrower"), (2) the Lenders party to
the Credit Agreement referred to below and (3) UNION BANK OF CALIFORNIA, N.A.,
as administrative agent for the Lenders (in such capacity, the "Agent").

                                    RECITALS

      A. The Borrower, the Lenders and the Agent previously entered into that
certain Credit Agreement dated as of December 26, 2000, as amended by that
certain Amendment to Credit Agreement and Waiver dated as of January 28, 2002,
that certain Second Amendment to Credit Agreement and Waiver dated as of March
4, 2002, that certain Third Amendment to Credit Agreement and Waiver dated as of
July 24, 2002 and that certain Fourth Amendment to Credit Agreement dated as of
September 27, 2002 (as amended, the "Credit Agreement"). Capitalized terms used
herein and not defined shall have the meanings assigned to them in the Credit
Agreement.

      B. The Borrower has informed the Agent and the Lenders that it is in
default of the Maximum Leverage Ratio covenant contained in Section 6.1(a) and
the Fixed Charge Coverage Ratio covenant contained in Section 6.1(b) of the
Credit Agreement for its First Quarter End 2003.

      C. In connection therewith, the Borrower has requested that the Lenders
(i) waive such Events of Default and (ii) modify the Maximum Leverage Ratio and
Fixed Charge Coverage Ratio covenants for certain periods, as more fully set
forth herein. The Lenders have agreed to grant such waiver and make such
changes, in each case subject to the terms and conditions set forth herein.

      D. As of the date hereof, prior to the effectiveness of this Amendment,
(i) the aggregate principal amount of Revolving Loans outstanding under the
Credit Agreement is $3,200,000 and (ii) aggregate principal amount of Term Loans
outstanding under the Credit Agreement is $20,900,000. The Aggregate Revolving
Loan Commitment is $5,000,000. There are no Letters of Credit outstanding.

      NOW, THEREFORE, in consideration of the premises and the mutual covenants
herein contained, the parties hereto hereby agree as follows:

      SECTION 1. Amendments to Credit Agreement. The Credit Agreement is hereby
amended as follows effective as of the date first set forth above, subject to
satisfaction of the conditions precedent set forth in Section 3 below:

      (a) Section 6.1(a) of the Credit Agreement is restated in its entirety to
read as follows:
<PAGE>
      "(a) Maximum Leverage Ratio. Permit the Maximum Leverage Ratio, as of the
end of any fiscal quarter of the Borrower, to exceed the following levels for
the periods indicated:

<TABLE>
<CAPTION>
              Period                                               Ratio
              ------                                               -----
<S>                                                                <C>
              Third Quarter End 2002                               5.00:1
              Fiscal Year End 2002                                 4.45:1
              First Quarter End 2003                               4.70:1
              Second Quarter End 2003                              4.95:1
              Third Quarter End 2003                               4.90:1
              Fiscal Year End 2003                                 4.50:1
              First Quarter End 2004 through and                   1.85:1
              including Fiscal Year End 2004
              First Quarter End 2005 and thereafter                1.75:1
</TABLE>

; provided, that for purposes of calculating the covenant in this Section 6.1(a)
only, the definition of `EBITDA' shall be deemed to read as follows:

            `EBITDA': for the Borrower and its Subsidiaries on a consolidated
      basis, for the fiscal quarter most recently ended and the immediately
      preceding three fiscal quarters, Net Income after eliminating
      extraordinary gains and losses, plus, without duplication, (i) provisions
      for income taxes, (ii) depreciation and amortization, (iii) Interest
      Expense, (iv) loan fees paid in connection with the Loan Documents
      (including (x) the effect, if any, of execution of warrant agreements in
      connection with the Loan Documents and (y) the amendment and waiver fee
      paid pursuant to the Third Amendment, the amendment fee paid pursuant to
      Section 3 of the Fourth Amendment and the amendment and waiver fee paid
      pursuant to Section 3 of the Fifth Amendment), (v) $250,000 in
      Restructuring Charges for Fiscal Year 2002 and (vi) the amount of any
      annual impairment charges taken by the Borrower in connection with FAS
      Rule 142."

      (b) Section 6.1(b) of the Credit Agreement is restated in its entirety to
read as follows:

      "(b) Fixed Charge Coverage Ratio. Permit the Fixed Charge Coverage Ratio,
as of the end of any fiscal quarter of the Borrower, to be less than the
following levels for the periods indicated:
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<TABLE>
<CAPTION>
              Period                                               Ratio
              ------                                               -----
<S>                                                                <C>
              Third Quarter End 2002                               1.15:1
              Fiscal Year End 2002                                 1.00:1
              Second Quarter End 2003                              0.95:1
              Third Quarter End 2003                               1.10:1
              Fiscal Year End 2003                                 1.15:1
              First Quarter End 2004 through and                   0.80:1
              including Fiscal Year End 2004
              First Quarter End 2005 and thereafter                0.85:1
</TABLE>

; provided, that for purposes of calculating the covenant in this Section 6.1(b)
only,

(i) the Fixed Charge Coverage Ratio for Fiscal Year End 2002 shall be based on
the fiscal quarter most recently ended and the immediately preceding two fiscal
quarters only, without reference to any other fiscal quarter, and the Fixed
Charge Coverage Ratio for each of Second Quarter End 2003, Third Quarter End
2003 and Fiscal Year End 2003 shall be based on such respective fiscal quarter
only, without reference to any other fiscal quarter; and

(ii) the definition of `EBITDA' shall be deemed to read as follows:

            `EBITDA': for the Borrower and its Subsidiaries on a consolidated
      basis, for the fiscal quarter most recently ended and the immediately
      preceding three fiscal quarters, Net Income after eliminating
      extraordinary gains and losses, plus, without duplication, (i) provisions
      for income taxes, (ii) depreciation and amortization, (iii) Interest
      Expense, (iv) loan fees paid in connection with the Loan Documents
      (including (x) the effect, if any, of execution of warrant agreements in
      connection with the Loan Documents and (y) the amendment and waiver fee
      paid pursuant to the Third Amendment, the amendment fee paid pursuant to
      Section 3 of the Fourth Amendment and the amendment and waiver fee paid
      pursuant to Section 3 of the Fifth Amendment), (v) $250,000 in
      Restructuring Charges for Fiscal Year 2002 and (vi) the amount of any
      annual impairment charges taken by the Borrower in connection with FAS
      Rule 142."

      (c) Section 6.1(d) of the Credit Agreement is restated in its entirety to
read as follows:

      "(d) Minimum Net Worth. Permit Net Worth of the Borrower and its
Subsidiaries on a consolidated basis, as of the end of any fiscal quarter of the
Borrower, to be less than $33,050,000 plus (i) with respect to each fiscal
quarter of the Borrower ending on or after First Quarter End 2001, 75% of any
Net Income as revealed by the Borrower's financial statements
<PAGE>
for such fiscal quarter, such increase to become effective upon receipt of such
financial statements, plus (ii) 100% of the Net Proceeds of each Equity Offering
consummated after the date hereof, such increase to become effective
immediately, less the amount of any Permitted Stock Repurchase, such decrease to
become effective immediately, minus (iii) the amount of any charge to the
Borrower as a result of issuance of warrant agreements in connection with the
Loan Documents, minus (iv) the amount of any annual impairment charges taken by
the Borrower in connection with FAS Rule 142."

      SECTION 2. Waivers.

      (a) Section 6.1(a) of the Credit Agreement requires that the Maximum
Leverage Ratio not exceed 4.15:1.00 for First Quarter End 2003. The Borrower has
informed the Agent and the Lenders that its Maximum Leverage Ratio for such
period was 4.68:1.00. As a result of such noncompliance, an Event of Default has
occurred and is continuing under the Credit Agreement. At the Borrower's
request, the Lenders agree to waive such Event of Default, subject to the terms
and conditions set forth herein.

      (b) Section 6.1(b) of the Credit Agreement requires that the Fixed Charge
Coverage Ratio not be less than 1.00:1.00 for First Quarter End 2003. The
Borrower has informed the Agent and the Lenders that its Fixed Charge Coverage
Ratio for such period was 0.87:1.00. As a result of such noncompliance, an Event
of Default has occurred and is continuing under the Credit Agreement. At the
Borrower's request, the Lenders agree to waive such Event of Default, subject to
the terms and conditions set forth herein.

      (c) The foregoing waivers are given in this instance only. The foregoing
waivers shall not be construed as a waiver of or consent to any violation of, or
deviation from, any other term or condition of the Credit Agreement or any other
Loan Document, nor shall such waivers be construed to evidence the willingness
of the Agent or the Lenders to give any other or additional waiver, whether in
similar or different circumstances.

      SECTION 3. Conditions Precedent. This Amendment shall become effective as
of the date first set forth above upon receipt by the Agent of the following:

      (a) this Amendment, duly executed by the Borrower and the Majority
Lenders;

      (b) evidence of the Guarantors' consent to this Amendment, substantially
in the form of Exhibit A hereto;

      (c) an amendment fee equal to twenty basis points on the sum of the
outstanding Term Loans and the Aggregate Revolving Commitment, which is $51,800,
in immediately available funds, to be shared pro rata by the Lenders executing
this Amendment on or before the date hereof, and all outstanding fees and
expenses of the Agent including legal fees incurred in connection with the
negotiation, drafting and execution of this Amendment to the extent requested by
the Agent to be paid in connection herewith; and

      (d) such other documents, agreements and opinions as the Agent or any
Lender may request.
<PAGE>
      SECTION 4. Reference to and Effect on the Credit Agreement and the Other
Loan Documents.(a) Upon the effectiveness of this Amendment, each reference in
the Credit Agreement to "this Agreement," "hereunder," "hereof" or words of like
import referring to the Credit Agreement, and each reference in the other Loan
Documents to "the Credit Agreement," "thereunder," "thereof" or words of like
import referring to the Credit Agreement, shall mean and be a reference to the
Credit Agreement, as amended hereby.

      (b) Except as specifically amended herein, the Credit Agreement and all
other Loan Documents are and shall continue to be in full force and effect and
are hereby in all respects ratified and confirmed.

      (c) The execution, delivery and effectiveness of this Amendment shall not
operate as a waiver of any right, power or remedy of the Agent or the Lenders
under the Credit Agreement or any other Loan Documents, nor constitute a waiver
of any provision of the Credit Agreement or any other Loan Documents, except as
specifically set forth herein.

      SECTION 5. Representations and Warranties. The Borrower hereby represents
and warrants, for the benefit of the Lenders and the Agent, as follows: (i) the
Borrower has all requisite power and authority under applicable law and under
its charter documents to execute, deliver and perform this Amendment, and to
perform the Credit Agreement as amended hereby; (ii) all actions, waivers and
consents (corporate, regulatory and otherwise) necessary or appropriate for the
Borrower to execute, deliver and perform this Amendment, and to perform the
Credit Agreement as amended hereby, have been taken and/or received; (iii) this
Amendment, and the Credit Agreement, as amended by this Amendment, constitute
the legal, valid and binding obligation of the Borrower enforceable against it
in accordance with the terms hereof; (iv) the execution, delivery and
performance of this Amendment, and the performance of the Credit Agreement, as
amended hereby, will not (a) violate or contravene any material Requirement of
Law, (b) result in any material breach or violation of, or constitute a material
default under, any agreement or instrument by which the Borrower or any of its
property may be bound, or (c) result in or require the creation of any Lien upon
or with respect to any properties of the Borrower, whether such properties are
now owned or hereafter acquired; (v) the representations and warranties
contained in the Credit Agreement and the other Loan Documents are correct in
all material respects on and as of the date of this Amendment, after giving
effect to the same, as though made on and as of such date; and (vi) except as
discussed in Section 2 of this Amendment, no Default has occurred and is
continuing.

      SECTION 6. Execution in Counterparts. This Amendment may be executed in
any number of counterparts and by different parties hereto in separate
counterparts, each of which when so executed and delivered shall be deemed to be
an original and all of which taken together shall constitute but one and the
same agreement. Delivery of an executed counterpart of a signature page to this
Amendment by telecopier shall be effective as delivery of a manually executed
counterpart of this Amendment.

      SECTION 7. Governing Law. THIS AMENDMENT AND THE RIGHTS AND OBLIGATIONS OF
THE PARTIES UNDER THIS AMENDMENT SHALL BE GOVERNED BY, AND CONSTRUED AND
INTERPRETED IN ACCORDANCE WITH,
<PAGE>
THE LAW OF THE STATE OF CALIFORNIA (WITHOUT REFERENCE TO ITS CHOICE OF LAW
RULES).
<PAGE>
      IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
duly executed and delivered by their proper and duly authorized officers as of
the day and year first above written.

                                      ALPHA TECHNOLOGIES GROUP, INC.

                                      By:  /s/ Lawrence Butler
                                           -------------------------------------
                                      Name:  Lawrence Butler
                                             -----------------------------------
                                      Title:  Chief Executive Officer
                                              ----------------------------------

                                      UNION BANK OF CALIFORNIA, N.A., as Agent
                                      and as a Lender

                                      By:  /s/ Cecilia M. Valente
                                           -------------------------------------
                                      Name: Cecilia M. Valente
                                      Title: Senior Vice President

                                      CALIFORNIA BANK & TRUST, as a Lender

                                      By:  /s/ Robert K. Chaulk
                                           -------------------------------------
                                      Name:  Robert K. Chaulk
                                             -----------------------------------
                                      Title:   Senior Vice President
                                               ---------------------------------

                                      IBM CREDIT CORPORATION, as a Lender

                                      By:  /s/ Thomas Harahan
                                           -------------------------------------
                                      Name:  Thomas Harahan
                                             -----------------------------------
                                      Title:  Manager
                                              ----------------------------------

                                      MANUFACTURERS BANK
                                      A California Banking Corporation, as a
                                      Lender

                                      By:  /s/ Karen J. Kearney
                                           -------------------------------------
                                      Name:  Karen J. Kearney
                                             -----------------------------------
                                      Title:  Vice President
                                              ----------------------------------

                                      S-1
<PAGE>
                                      U.S. BANK NATIONAL ASSOCIATION, as a
                                      Lender

                                      By:  /s/ E. C. Hengeveld
                                           -------------------------------------
                                      Name:  E. C. Hengeveld
                                             -----------------------------------
                                      Title:  Vice President
                                              ----------------------------------

                                      S-2

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