AMENDMENT NO. 1 TO THE
                                CREDIT AGREEMENT


                                                    Dated as of January 24, 1997

                  AMENDMENT NO. 1 TO THE CREDIT AGREEMENT, among MEDIQ/PRN LIFE
SUPPORT SERVICES, INC., a Delaware corporation (the "Borrower"), MEDIQ
INCORPORATED, a Delaware corporation ("MEDIQ"), PRN HOLDINGS, INC., a Delaware
corporation (together with MEDIQ, the "Parent Guarantors"), the banks, financial
institutions and other institutional lenders parties to the Credit Agreement
referred to below (collectively, the "Lenders") and Banque Nationale de Paris as
administrative agent (the "Administrative Agent") for the Lenders and
NationsBank N.A., as documentation agent (the "Documentation Agent").

                  PRELIMINARY STATEMENTS:

                  (1) The Borrower, the Parent Guarantors, the Lenders, the
Administrative Agent and the Documentation Agent have entered into a Credit
Agreement dated as of October 1, 1996 (the "Credit Agreement"). Capitalized
terms not otherwise defined in this Amendment have the same meanings as
specified in the Credit Agreement.

                  (2) The Borrower seeks to acquire Universal Hospital Services,
Inc., a Minnesota corporation ("UHS"), (the "UHS Acquisition") and, in order to
finance, together with advances under the existing Facilities, such acquisition,
has requested that certain Lenders (the "Affected Lenders" or the "Incremental
Term B Lenders") increase their Commitments under the Term B Facility (the
"Incremental Term B Commitments") and the Working Capital Facility, and amend
certain provisions of the Credit Agreement in order to provide such financing
and for certain other purposes.

                  (3) The Required Lenders and the Affected Lenders are, on the
terms and conditions stated below, willing to grant the request of the Borrower
and the Borrower and such Lenders have agreed to amend the Credit Agreement as
hereinafter set forth.

                  SECTION 1. Amendments to the Credit Agreement. The Credit
Agreement is, effective as of the date hereof and subject to the satisfaction of
the conditions precedent set forth in Section 2(a) hereof, hereby amended as
follows:


                    (a) Section 1.01 is amended by inserting therein the
               following definitions in appropriate alphabetical order:

                         "'BERS' means Biomedical Equipment Rental and Sales,
                    Inc., a Subsidiary of UHS.

                         "'UHS' means Universal Hospital Services, Inc., a
                    Minnesota corporation.

                         "'UHS Acquisition' means the acquisition of the common
                    stock of UHS by the Borrower or any of the Borrower's
                    Ongoing Subsidiaries, as permitted under this Agreement."

                                       

<PAGE>

                         "'UHS Acquisition Closing Date' means any Business Day
                    on which the UHS Acquisition occurs."

                  (b) The definition of "Acquisition Facility Sublimit" in
              Section 1.01 is amended by deleting clause (iii) thereof and
              substituting therefor the following:

                  "(iii) the excess of the aggregate amount of Subordinated
                  Notes outstanding at such time over the principal amount of
                  the NutraMax Note to the extent secured by the NutraMax Letter
                  of Credit multiplied by 66%."

                  (c) The definition of "Borrower's Account" is amended by
              deleting therefrom the account number "200877-001-91" and
              substituting therefor the account number "202330-001-77".

                  (d) The definition of "EBITDA" is amended by inserting
              immediately before the proviso thereto the following:

                  "and (g) all one-time expenses of the Borrower and its
                  Affiliates incurred in connection with the UHS Acquisition for
                  severance expenses, lease related expenses and facility
                  closure expenses".

                  (e) The definition of "Leverage Ratio" is amended (i) by
              inserting in the seventh line thereof, immediately preceding the
              words ", so long as", the phrase "multiplied by 66%", and (ii) by
              adding at the end thereof the following: ",except with respect to
              the UHS Acquisition, in which case the 12-month trailing EBITDA of
              UHS shall be adjusted for the EBITDA of BERS included in such
              calculation for the period of time that said EBITDA of BERS is not
              actually reflected in the aforesaid EBITDA of UHS, in which case
              such EBITDA of UHS shall be the pro forma EBITDA of UHS and BERS
              for such period."

                  (f) The definition of "Senior Leverage Ratio" is amended by
              adding at the end thereof the following: ",except with respect to
              the UHS Acquisition, in which case the 12-month trailing EBITDA of
              UHS shall be adjusted for the EBITDA of BERS included in such
              calculation for the period of time that said EBITDA of BERS is not
              actually reflected in the aforesaid EBITDA of UHS, in which case
              such EBITDA of UHS shall be the pro forma EBITDA of UHS and BERS
              for such period."

                  (g) The definition of "Term B Borrowing" is amended by adding
              at the end thereof the following:

                  "and Incremental Term B Advances made on the UHS Acquisition
                  Closing Date."

                  (h) Section 2.01(b) is amended by (i) inserting "(i)"
              immediately after the heading "The Term B Advances" and (ii)
              adding a new clause (ii) at the end thereof to read as follows:

                           "(ii) Each Incremental Term B Lender severally
                  agrees, on the terms and conditions hereinafter set forth, to
                  make a single advance to the Borrower on the UHS Acquisition
                  Closing Date in an amount not to exceed such Incremental Term
                  B Lender's Incremental Term B Commitment as set forth in
                  Schedule I hereto (each such advance being an "Incremental
                  Term B Advance"). Such Term B Borrowing shall consist of
                  Incremental Term B Advances made simultaneously by the
                  Incremental Term B Lenders ratably according to their
                  Incremental Term B Commitments. Amounts borrowed under this
                  Section 2.01(b)(ii) and repaid or prepaid may not be
                  reborrowed."

                  (i) The table contained in Section 2.04(a) is amended by (i)
              deleting each figure "8,500,000" therein and substituting for each
              such figure the figure "13,000,000" and (ii) deleting each figure
              "15,000,000" therein and substituting for each such figure the
              figure "21,750,000".


                                       2
<PAGE>


                  (j) Section 2.14(a) is amended by adding at the end thereof
              the following:

                  "and, on the UHS Acquisition Closing Date, an aggregate amount
                  of up to $45,000,000 of Incremental Term B Advances to finance
                  a portion of the UHS Acquisition".

                  (k) Section 2.14(c) is amended by inserting therein,
              immediately after "Section 5.01(p)", the following:

                  ", to provide up to $5,000,000 of the financing for the UHS
                  Acquisition".

                  (l) Section 4.01(i) is amended by inserting therein,
              immediately after "provided that", the following:

                  ", other than with respect to the UHS Acquisition as permitted
                  under Section 5.02(f)(i),".

                  (m) Section 5.01(n) is amended by substituting for the date
              "November 15, 1996" the phrase "the date that is 45 days following
              the UHS Acquisition Closing Date" and by adding after the phrase
              "the Term B Facilities " the parenthetical "(including the
              Incremental Term B Advances)".

                  (n) Section 5.02(b)(ii)(B) is amended by deleting therein the
              figure "$100,000,000" and substituting therefor the figure
              "$140,000,000".

                  (o) Section 5.02(b)(ii) is amended by adding at the end
              thereof a new subsection (H) to read as follows:

                  "intercompany Debt owed to the Borrower in connection with the
                  UHS Acquisition, so long as such Debt is evidenced by an
                  intercompany note in form and substance satisfactory to the
                  Administrative Agent, and".

                  (p) Section 5.02(f)(i) is amended (i) by inserting in the
              second line thereof, immediately following "Acquisition Advances",
              the following ", Working Capital Advances, Incremental Term B
              Advances" and (ii) by inserting therein, immediately before
              "provided that", the following:

                  "or constituting the purchase of at least 90% of the common
                  stock of UHS in a transaction approved by the Board of
                  Directors of UHS so long as UHS becomes a wholly owned
                  Subsidiary of the Borrower on the UHS Acquisition Closing Date
                  in a transaction approved by the Board of Directors of UHS or
                  constituting the payment of consideration for the merger of
                  UHS and the Borrower or a wholly owned Subsidiary of the
                  Borrower,"

                  (q) Section 5.02(f)(i)(2) is amended by adding at the end
              thereof the following:

                  "except with respect to the UHS Acquisition, in which case
                  such Leverage Ratio shall not be more than 3.75 to 1.0".

                  (r) Section 5.02(f)(i)(3) is amended by adding at the end
              thereof the following:

                  "except with respect to the UHS Acquisition, in which case
                  such amount shall not exceed 6.5 multiplied by the 12-month
                  trailing EBITDA of UHS (adjusted for the EBITDA of BERS
                  included in such calculation for the period of time
                  that said EBITDA of BERS is not actually reflected in the
                  aforesaid EBITDA of UHS, in which case such EBITDA of UHS
                  shall be the pro forma EBITDA of UHS and BERS for such
                  period)".

                  (s) Section 5.02(f)(i)(4) is amended by (i) deleting therefrom
              the following:

                                       3
<PAGE>
 

                  "shall not exceed $100,000,000"

             and (ii) adding at the end thereof the following:

                  "plus the aggregate amount of Advances made by the Lenders and
                  used for all such Investments outstanding at any time on and
                  after the UHS Acquisition Closing Date shall not exceed
                  $140,000,000."

                  (t) Section 5.04(f) is amended by inserting in the eighth line
              thereof immediately after the word "Investments" the following: ",
              except with respect to the UHS Acquisition, in which case the
              12-month trailing EBITDA of UHS shall be adjusted for the EBITDA
              of BERS included in such calculation for the period of time that
              said EBITDA of BERS is not actually reflected in the aforesaid
              EBITDA of UHS, in which case such EBITDA of UHS shall be the pro
              forma EBITDA of UHS and BERS for such period."

                  (u) Schedule 1 is supplemented by adding with respect to the
              Working Capital Commitment of each of BNP and NationsBank,
              $2,500,000, and adding Incremental Term B Commitments for each of
              BNP and NationsBank, in the amount of $22,500,000.

                  SECTION 2. Conditions of Effectiveness. (a) This Amendment
shall become effective as of the date first above written when, and only when,
the Administrative Agent shall have received (x) counterparts of this Amendment
executed by the Borrower, the Required Lenders and each Affected Lender, or, as
to any of the Lenders, advice satisfactory to the Administrative Agent that such
Lender has executed this Amendment and (y) for the ratable account of the
Lenders, 1/10% of the sum of the Term A Advances, the Term B Advances, the
Acquisition Commitments and the Working Capital Commitments as such Advances and
Commitments shall be outstanding immediately prior to the effectiveness of this
Amendment (i.e. $260,000). The effectiveness of this Amendment is conditioned
upon the accuracy of the factual matters described herein. This Amendment is
subject to the provisions of Section 9.01 of the Credit Agreement.

                  (b) This Amendment shall be null and void and of no effect if,
on or before April 23, 1997 (or such later date before July 15, 1997 as the
Affected Lenders may consent to in writing), the following conditions shall not
have been satisfied:

                  (1) The Administrative Agent shall not have additionally
              received all of the following documents, each such document
              (unless otherwise specified) dated the date of receipt thereof by
              the Administrative Agent (unless otherwise specified) and in
              sufficient copies for each Lender, in form and substance
              satisfactory to the Administrative Agent (unless otherwise
              specified):

                         (i) Certified copies of (x) the resolutions of the
                    Board of Directors of (A) the Borrower approving this
                    Amendment, the Collateral Documents, amendments or
                    supplements thereto contemplated hereby and the matters
                    contemplated hereby and thereby and (B) each other Loan
                    Party evidencing approval of the Consent, the Collateral
                    Documents, amendments or supplements thereto contemplated
                    hereby and the matters contemplated hereby and thereby and
                    (y) all documents evidencing other necessary corporate
                    action and governmental approvals, if any, with respect to
                    this Amendment, the Consent, the Collateral Documents,
                    amendments or supplements thereto contemplated hereby and
                    the matters contemplated hereby and thereby;

                         (ii) A certificate of the Secretary or an Assistant
                    Secretary of the Borrower and each other Loan Party
                    certifying the names and true signatures of the officers of
                    the Borrower and such other Loan Party authorized to sign
                    this Amendment, the Consent, the Collateral Documents,
                    amendments or supplements thereto contemplated hereby to any
                    of which they are or are to be a party and the other
                    documents to be delivered hereunder and thereunder;


                                       4
<PAGE>


                         (iii) Counterparts of a consent with respect to this
                    Amendment No. 1, in form satisfactory to the Administrative
                    Agent, executed by each of the Loan Parties (other than the
                    Borrower);

                         (iv) A favorable opinion of Drinker, Biddle & Reath,
                    counsel for the Loan Parties, as to such matters as the
                    Administrative Agent may reasonably request;

                         (v) A certificate signed by a duly authorized officer
                    of the Borrower stating that:

                             (x) The representations and warranties contained in
                       the Loan Documents as amended hereby, Section 3 hereof,
                       and in each of the Collateral Documents and amendments
                       and supplements thereto delivered pursuant to this
                       Section 2 are correct on and as of the date of such
                       certificate as though made on and as of such date other
                       than any such representations or warranties that, by
                       their terms, refer to a date other than the date of such
                       certificate; and

                             (y) No event has occurred and is continuing that
                       constitutes a Default; and

                         (vi) Notes payable to the order of the Affected
                    Lenders; and

                             (2) Each of the following conditions shall have 
                       been satisfied:

                                    (i) The Borrower and any additional Loan
                           Party, as appropriate, shall have delivered all such
                           documents, agreements, certificates or instruments as
                           shall be required or as the Administrative Agent
                           shall have requested pursuant to Section 5.01(o);

                                    (ii) All governmental and third party
                           consents and approvals necessary in connection with
                           the UHS Acquisition shall have been obtained and
                           remain in effect, and all applicable waiting periods
                           shall have expired without any action being taken by
                           any competent authority, and no law or regulation
                           shall be applicable which, in the case of any of the
                           foregoing, restrains, prevents or imposes materially
                           adverse conditions upon the rights of any Loan Party
                           to transfer or otherwise dispose of shares of UHS
                           acquired in the tender offer, if applicable, the
                           exercise by any transferee of any Loan Party of all
                           ownership rights with respect to the shares of UHS
                           stock acquired in connection with any such tender
                           offer or otherwise owned by any Loan Party, or the
                           consummation of a merger if not completed prior to
                           the UHS Acquisition Closing Date;

                                    (iii) All Advances made by the Lender
                           Parties shall be in compliance with Regulations G, T,
                           U and X of the Board of Governors of the Federal
                           Reserve System; and

                                    (iv) The Borrower shall have retained
                           Murray, Devine & Co. to prepare and deliver a letter
                           attesting to the Solvency of the Borrower after
                           giving effect to the acquisition of UHS.

     SECTION 3. Representations and Warranties of the Borrower. The Borrower
represents and warrants as follows:

                  (a) The Borrower is a corporation duly organized, validly
         existing and in good standing under the laws of the jurisdiction
         indicated in the recital of the parties to this Amendment.

                  (b) The execution, delivery and performance by each Loan Party
         of this Amendment and the Loan Documents, as amended hereby, to which
         it is or is to be a party, and the consummation of the transactions
         contemplated hereby, are within such Loan Party's corporate powers,
         have been duly authorized by all necessary corporate

                                       5
<PAGE>


         action and do not (i) contravene each such Loan Party's charter or
         by-laws, (ii) violate any law (including, without limitation, the
         Securities Exchange Act of 1934, as amended, and the Racketeer
         Influenced and Corrupt Organizations Chapter of the Organized Crime
         Control Act of 1970), rule or regulation (including, without
         limitation, Regulation X of the Board of Governors of the Federal
         Reserve System), or any order, writ, judgment, injunction, decree,
         determination or award, binding on or affecting any Loan Party or any
         of its Subsidiaries or any of their properties, (iii) conflict with or
         result in the breach of, or constitute a default under, any contract,
         loan agreement, indenture, mortgage, deed of trust, lease or other
         instrument binding on or affecting any Loan Party, any of their
         Subsidiaries or any of their properties or (iv) except for the Liens
         created under the Collateral Documents, as amended hereby, or any
         amendments or supplements thereto contemplated hereby, result in or
         require the creation or imposition of any Lien upon or with respect to
         any of the properties of any Loan Party or any of its Subsidiaries.

                  (c) No authorization or approval or other action by, and no
         notice to or filing with, any governmental authority or regulatory body
         or any other third party is required for the due execution, delivery,
         recordation, filing or performance by any Loan Party of this Amendment,
         any of the Collateral Documents or any amendments or supplements
         thereto contemplated hereby to which each such Loan Party is or is to
         be a party, or any of the Loan Documents, as amended hereby, to which
         it is or is to be a party except for such approvals as shall have been
         obtained by the UHS Acquisition Closing Date.

                  (d) This Amendment and each of the Collateral Documents and
         amendments and supplements thereto contemplated hereby to which each
         Loan Party is a party have been duly executed and delivered by each
         such Loan Party. This Amendment and each of the other Loan Documents,
         as amended hereby, to which each Loan Party is a party are, and each of
         the other Collateral Documents and amendments and supplements thereto
         contemplated hereby to which each such Loan Party is or is to be a
         party, when delivered hereunder, will be, legal, valid and binding
         obligations of each such Loan Party, enforceable against each such Loan
         Party in accordance with their respective terms, including as to each
         entity that shall become a Loan Party on the UHS Acquisition Closing
         Date, as to each such Loan Party on the UHS Acquisition Closing Date.

                  (e) There is no action, suit, investigation, litigation or
         proceeding affecting any Loan Party or any of their Subsidiaries
         (including, without limitation, any Environmental Action) pending or
         threatened before any court, governmental agency or arbitrator that (i)
         would be reasonably likely to have a Material Adverse Effect or (ii)
         purports to affect the legality, validity or enforceability of this
         Amendment, the Collateral Documents, any amendments or supplements
         thereto contemplated hereby or any of the other Loan Documents, as
         amended hereby, or the consummation of any of the transactions
         contemplated hereby.


                                       6

<PAGE>

                  (f) As of the UHS Acquisition Closing Date, the Collateral
         Documents and amendments or supplements thereto consisting of security
         agreements or mortgages to which any Loan Party is or is to be a party,
         when delivered hereunder, will create valid and perfected first
         priority liens and security interests in and to the Collateral covered
         thereby, securing the payment of the Secured Obligations (in each case,
         as defined in such Collateral Documents or amendment or supplement
         thereto); and the execution, delivery and performance of this
         Amendment, each of the Collateral Documents and any amendments or
         supplements thereto contemplated hereby do not adversely affect the
         Liens created under any of the Collateral Documents.

                  SECTION 4. Reference to and Effect on the Loan Documents. (a)
On and after 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 Notes and each of
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 by this Amendment.

                  (b) The Credit Agreement, the Notes and each of the other Loan
         Documents, as specifically amended by this Amendment, are and shall
         continue to be in full force and effect and are hereby in all respects
         ratified and confirmed. Without limiting the generality of the
         foregoing, the Collateral Documents and all of the Collateral described
         therein do and shall continue to secure the payment of all Obligations
         of the Loan Parties under the Loan Documents, in each case as amended
         by this Amendment.

                  (c) The execution, delivery and effectiveness of this
         Amendment shall not, except as expressly provided herein, operate as a
         waiver of any right, power or remedy of any Lender or the Agent under
         any of the Loan Documents, nor constitute a waiver of any provision of
         any of the Loan Documents.

                  (d) Except as otherwise provided in this Amendment, from and
         after the UHS Acquisition Closing Date, all references to (i) Term B
         Lenders shall include the Incremental Term B Lenders, (ii) Term B
         Advances shall include all Term B Advances made by the Incremental Term
         B Lenders and (iii) Term B Commitments shall mean the Incremental Term
         B Commitments of the Incremental Term B Lenders hereunder.

         SECTION 5. Costs, Expenses. The Borrower agrees to pay on demand all
costs and expenses of the Agent in connection with the preparation, execution,
delivery and administration, modification and amendment of this Amendment, and
the other instruments and documents to be delivered hereunder (including,
without limitation, the reasonable fees and expenses of counsel for the Agent)
in accordance with the terms of Section 9.04 of the Credit Agreement.

         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 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.


                                       7
<PAGE>


         SECTION 7. Governing Law. This Amendment shall be governed by, and
construed in accordance with, the laws of the State of New York.

         IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
executed by their respective officers thereunto duly authorized, as of the date
first above written.

                                          MEDIQ/PRN LIFE SUPPORT
                                             SERVICES, INC.


                                          By /s/
                                             ----------------------------------
                                             Title:


                                          BANQUE NATIONALE DE PARIS, as
                                            Administrative Agent and as Lender


                                          By /s/
                                             -----------------------------------
                                             Title:


                                          By /s/
                                             -----------------------------------
                                             Title:


                                          NATIONSBANK, N.A., as
                                            Documentation Agent and as Lender


                                          By /s/
                                             ----------------------------------=
                                             Title:



                                       8
<PAGE>
                                          

                                          THE FIRST NATIONAL BANK OF BOSTON


                                          By /s/
                                            ------------------------------------
                                            Title:


                                          CAISSE NATIONALE DE CREDIT AGRICOLE


                                          By /s/
                                             -----------------------------------
                                             Title:


                                          CREDITANSTALT CORPORATE FINANCE, INC.


                                          By /s/
                                             -----------------------------------
                                             Title:


                                          By /s/
                                             -----------------------------------
                                             Title:


                                          FIRST SOURCE FINANCIAL, LLP
                                          By: First Source Financial, Inc.
                                              as Agent/Manager

                                          By /s/
                                             -----------------------------------
                                             Title:


                                          METROPOLITAN LIFE INSURANCE COMPANY


                                          By /s/
                                            ------------------------------------
                                            Title:




                                       9
<PAGE>


                                          

                                          LASALLE NATIONAL BANK


                                          By /s/
                                             -----------------------------------
                                             Title:


                                          MASSACHUSETTS MUTUAL LIFE
                                          INSURANCE COMPANY


                                          By /s/
                                             -----------------------------------
                                             Title:


                                          MELLON BANK, N.A.


                                          By /s/
                                             -----------------------------------
                                              Title:


                                          MERRILL LYNCH SENIOR FLOATING
                                          RATE FUND, INC.


                                          By /s/
                                             -----------------------------------
                                             Title:


                                          PILGRIM AMERICA PRIME RATE TRUST


                                          By /s/
                                             -----------------------------------
                                             Title:


                                          SUMMIT BANK


                                          By /s/
                                             -----------------------------------
                                             Title:




                                       10
<PAGE>


                                          

                                          USTRUST


                                          By /s/
                                             -----------------------------------
                                             Title:


                                          VAN KAMPEN AMERICAN CAPITAL
                                          PRIME RATE INCOME TRUST


                                          By /s/
                                             -----------------------------------
                                             Title:


                                          RESTRUCTURED OBLIGATIONS
                                          BACKED BY SENIOR ASSETS B.V.

                                          By its Managing Director, ABN
                                          TRUSTCOMPANY (NEDERLAND) B.V.


                                          By /s/
                                             -----------------------------------
                                             Title:

                                          By /s/
                                             -----------------------------------
                                             Title:


                                          MERRILL LYNCH PRIME RATE PORTFOLIO


                                          By /s/
                                             -----------------------------------
                                             Title:


                                          SENIOR DEBT PORTFOLIO

                                          By Boston Management and Research, as
                                          Investment Advisor


                                          By /s/
                                             -----------------------------------
                                             Title:


                                       11
<PAGE>


                                          


                                          CERES FINANCE LTD.


                                          By /s/
                                             -----------------------------------
                                             Title:


                                          CAPTIVA FINANCE LTD.


                                          By /s/
                                             -----------------------------------
                                             Title:




                                          AMARA-1 FINANCE LTD.


                                          By /s/
                                             -----------------------------------
                                             Title:


                                          AMARA-2 FINANCE LTD.


                                          By /s/
                                             -----------------------------------
                                             Title:

                                          
                                          MERRILL LYNCH PRIME RATE PORTFOLIO

                                          By Merrill Lynch Asset Management,
                                          L.P., as Investment Advisor


                                          By /s/
                                             -----------------------------------
                                             Title:

                                       12