<PAGE>

                                                                   EXHIBIT 10.37

[MPT LOGO]

          MEDICAL PROPERTIES TRUST

February 28, 2005

Prem Reddy, M.D., Chairman
Mr. Lex Reddy, President & CEO
Desert Valley Health System, Inc.
16850 Bear Valley Road
Victorville, CA 93292

         RE:      COMMITMENT LETTER FOR EXPANSION FUNDING FOR VICTORVILLE,
                  CALIFORNIA HOSPITAL FACILITY

Dear Sirs:


MPT Operating Partnership, L.P. and MPT of Victorville, LLC, (collectively,
"MPT"), are pleased to extend a commitment to Desert Valley Hospital, Inc.,
("DESERT VALLEY" also sometimes referred to herein as "LESSEE") respecting the
financing of certain improvements to and expansions (the "Expansion") of
certain real estate and improvements (the "Real Estate") in Victorville,
California, which Real Estate is subject to a lease agreement of even date
herewith (the "Lease"). MPT's commitment to provide all or any portion of the
Commitment Amount (as hereinafter defined) for the purpose of financing for the
Expansion (the "Financing") shall be contingent upon and subject to: (i) the
approval of the Financing by the Board of Directors of Medical Properties
Trust, Inc.: (ii) MPT being satisfied with all aspects of the proposed
Expansion as provided in the Development Agreement (as herein defined): and
(iii) such other conditions as are described herein or as are customary in
similar transactions.

                                    ARTICLE I

                                  BASIC TERMS

SECTION 1.1 BASIC TRANSACTION: Subject to the conditions set forth herein. MPT
hereby commits to fund, and DESERT VALLEY hereby commits to draw and use, up to
Twenty Million Dollars ($20,000,000) (the "Commitment Amount"), for the purpose
of financing the costs and expenses of the Expansion. The Expansion shall be
treated as a Capital Addition under the Lease in accordance with the terms set
forth in Section 10.3(b) through Section 10.3(d) of the Lease. DESERT VALLEY
agrees that, subject to the MPT terms hereof, MPT shall be the exclusive source
of financing for the Expansion.

SECTION 1.2 COMMENCEMENT DATE: MPT and DESERT VALLEY agree that, subject to the
conditions set forth herein. MPT shall begin funding, and DESERT VALLEY shall
begin drawing upon, the Commitment Amount within twelve (12) months after the
date hereof (the "Development Period") in accordance with the disbursement
schedule to be provided in a definitive development agreement approved by MPT
(the "Development Agreement"). Accordingly, DESERT VALLEY


<PAGE>

shall use its best efforts to propose a form of Development Agreement for the
Expansion no later than thirty (30) days prior to the expiration of the
Development Period.

                                   ARTICLE II

                            ADDITIONAL REQUIREMENTS

SECTION 2.1 NON-REFUNDABLE COMMITMENT FEE: Upon receipt and approval of the
Development Agreement, DESERT VALLEY shall pay MPT a commitment fee in cash
equal to One-Half of One Percent (.5%) of the maximum Commitment Amount (the
"Commitment Fee"); provided, however, that the Commitment Fee shall be adjusted,
following full and final funding of the Expansion, to equal One-Half of One
Percent (.5%) of the actual amount funded (the "Adjusted Commitment Fee").
Except for any adjustments to the Commitment Fee that may result from funding
less than the maximum Commitment Amount, the Commitment Fee shall be
non-refundable. In the event that DESERT VALLEY fails to provide a Development
Agreement to MPT prior to the expiration of the Development Period, MPT shall
have no further liability or obligation to provide the Financing.

SECTION 2.2 EXPENSES: DESERT VALLEY shall reimburse MPT for all of its costs and
expenses in connection with the Financing.

SECTION 2.3 SIGNS: MPT shall have the right to erect a sign at the Facility,
approved by DESERT VALLEY, which such approval shall not be unreasonably
withheld, stating that the Real Estate is owned, and that the Expansion is being
financed, by MPT.

                                   ARTICLE III

                               GENERAL CONDITIONS

SECTION 3.1 ENTIRE AGREEMENT, MODIFICATIONS, AND AMENDMENTS: This Commitment
Letter contains the entire agreement of LESSEE and MPT with respect to the
Financing and supersedes any prior or contemporaneous understanding or
commitment. MPT has made no representations to LESSEE relating to the Financing
that are not set forth in this Commitment Letter. No changes in this Commitment
Letter shall be binding unless in writing and executed by the party against whom
enforcement of the change is sought.

SECTION 3.2 TIME: Time is of the essence with respect to all dates and periods
of time set forth in this Commitment Letter.

SECTION 3.3 ACCEPTANCE OF COMMITMENT: Upon return by LESSEE of a fully-executed
copy of this Commitment Letter, this Commitment Letter will constitute an
agreement of the parties to the terms and conditions set forth above.

SECTION 3.4 PRIOR COMMITMENT LETTERS SUPERSEDED: This Commitment Letter
supersedes and cancels all prior oral and written commitments made by and
between MPT and LESSEE with respect to the Expansion and/or the Financing.


<PAGE>

SECTION 3.5 MPT SECURITIES OFFERING: Notwithstanding any other agreement of the
parties, in connection with public offering or private placement of its
securities or any third-party financing, MPT may disclose that it has entered
into this Commitment Letter with DESERT VALLEY and may provide other information
regarding DESERT VALLEY, the Real Estate, the Expansion; and the Financing to
its current or proposed investors in such public offering or private offering of
its securities and to any third-party lender.

Section 3.6 ASSIGNMENT: This Commitment Letter, and all rights of the parties
hereunder, shall not be assigned by any party without the prior written
approval of the other parties; provided, however, that any party may assign its
rights and obligations hereunder to any entity controlling, controlled by, or
under common control with the other. No such assignment, however, shall relieve
any party of any liability hereunder.

Section 3.7 GOVERNING LAW: This Commitment Letter shall be governed by the laws
of the State of Alabama.

Please indicate acceptance of the terms and conditions set forth in this
Commitment Letter by signing a copy of this Commitment Letter below. This
Commitment Letter may be executed in any number of counterparts, each of which
so executed shall be deemed an original, but all such counterparts shall
together constitute but one and the same agreement.

                        Sincerely,

                        MPT OPERATING PARTNERSHIP, L.P.



                        By: /s/ Emmett E. McLean
                            ----------------------------------------------------
                            Emmett E. McLean
                            Executive Vice President and Chief Operating Officer

                        MPT OF VICTORVILLE, LLC,
                        BY MPT OPERATING PARTNERSHIP, L.P.
                        ITS SOLE MEMBER



                        By: /s/ Emmett E. McLean
                            ----------------------------------------------------
                            Emmett E. McLean
                            Executive Vice President and Chief Operating Officer


                        Accepted and Agreed to this 28th day of February, 2005:



                        DESERT VALLEY HOSPITAL, INC.



                        By: /s/ Lex Reddy
                            --------------------------
                        Its: President