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                                                                     Exhibit 4.2




                         CERTIFICATE OF DESIGNATIONS OF
                      SERIES I CONVERTIBLE PREFERRED STOCK
                                       OF
                            DIAMETRICS MEDICAL, INC.
                             a Minnesota corporation

      The undersigned, being the duly elected and acting Chief Executive Officer
of Diametrics Medical, Inc., a Minnesota corporation (the "CORPORATION"), hereby
certifies that pursuant to the authority contained in Article 3 of the
Corporation's Amended and Restated Articles of Incorporation, as amended, and in
accordance with the provisions of Minnesota Statutes, Section 302A.401, Subd.
3(b), the Corporation's Board of Directors has adopted the following resolutions
creating a series of its Preferred Stock designated as Series I Convertible
Preferred Stock:

      WHEREAS, the Corporation's Amended and Restated Articles of Incorporation
provides for a class of shares known as Preferred Stock, issuable from time to
time in one or more series; and

      WHEREAS, the Board of Directors of the Corporation is authorized to
determine or alter the rights, preferences, privileges and restrictions granted
to or imposed upon any wholly unissued shares of Preferred Stock, to fix the
number of shares constituting any such series, and to determine the designation
thereof, or any of any of them.

      NOW, THEREFORE, BE IT RESOLVED, that the Board of Directors hereby fixes
and determines the designations of, the number of shares constituting, and the
rights, preferences, privileges and restrictions relating to, a new series of
Preferred Stock as follows:

      (a) Designation. The series of Preferred Stock is hereby designated Series
I Convertible Preferred Stock (the "SERIES I PREFERRED STOCK").

      (b) Authorized Shares. The number of authorized shares constituting the
Series I Preferred Stock shall be 13,794 shares of such series.

      (c) Dividends. Subject to the prior rights of holders of all classes of
stock at the time outstanding having prior rights as to dividends, the holder of
the Series I Preferred Stock shall be entitled to receive, when, as and if
declared by the Board of Directors, out of any assets of the Corporation legally
available therefor, such dividends as may be declared from time to time by the
Board of Directors.

      (d) Liquidation Preference.

            (i) Preference upon Liquidation, Dissolution or Winding Up. In the
event of any dissolution or winding up of the Corporation, whether voluntary or
involuntary, holders of each outstanding share of Series I Preferred Stock shall
be entitled to be paid, together with the holders of each outstanding share of
Series H Preferred Stock issued by the Corporation ("SERIES H PREFERRED STOCK"),
on a pro rata basis, first out of the assets of the Corporation available for
distribution to shareholders, whether such assets are capital, surplus or
earnings, an amount equal to the greater of (A) an amount equal to $100 (the
"SERIES I PURCHASE PRICE") per share of Series

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I Preferred Stock held (as adjusted for any stock splits, stock dividends or
recapitalizations of the Series I Preferred Stock) and any declared but unpaid
dividends on such share, and (B) the amount such holders would be entitled to
receive had such holders converted such shares of Series I Preferred Stock into
shares of Common Stock in accordance with paragraph (f) hereof immediately prior
to such distribution, before any payment shall be made to the holders of the
Common Stock, or any other stock of the Corporation ranking junior to the Series
I Preferred Stock and the Series H Preferred Stock with regard to any
distribution of assets upon liquidation, dissolution or winding up of the
Corporation. The holders of the Series I Preferred Stock and the Series H
Preferred Stock shall be entitled to share ratably, in accordance with the
respective preferential amounts payable on such stock, in any distribution which
is not sufficient to pay in full the aggregate of the amounts payable thereon.
If, upon any liquidation, dissolution or winding up of the Corporation, the
assets to be distributed to the holders of the Series I Preferred Stock and the
Series H Preferred Stock shall be insufficient to permit payment to such
shareholders of the full preferential amounts aforesaid, then all of the assets
of the Corporation available for distribution to shareholders shall be
distributed to the holders of Series I Preferred Stock and the Series H
Preferred Stock, on a pro rata basis. Each holder of the Series I Preferred
Stock shall be entitled to receive that portion of the assets available for
distribution as the number of outstanding shares of Series I Preferred Stock
held by such holder bears to the total number of shares of Series I Preferred
Stock and Series H Preferred Stock then outstanding. Such payment shall
constitute payment in full to the holders of the Series I Preferred Stock upon
the liquidation, dissolution or winding up of the Corporation. After such
payment shall have been made in full, or funds necessary for such payment shall
have been set aside by the Corporation in trust for the account of the holders
of Series I Preferred Stock, so as to be available for such payment, such
holders of Series I Preferred Stock shall be entitled to no further
participation in the distribution of the assets of the Corporation.

            (ii) Consolidation, Merger and Other Corporate Events. A
consolidation or merger of the Corporation (except into or with a subsidiary
corporation) or a sale, lease, mortgage, pledge, exchange, transfer or other
disposition of all or substantially all of the assets of the Corporation or any
reclassification of the stock of the Corporation (other than a change in par
value or from no par to par, or from par to no par or as the result of an event
described in subsections (iv) through (vii) of paragraph (f)), shall be regarded
as a liquidation, dissolution or winding up of the affairs of the Corporation
within the meaning of this paragraph (d). In no event shall the issuance of new
classes of stock, whether senior, junior or on a parity with the Series I
Preferred Stock, be deemed a "reclassification" under or otherwise limited by
the terms hereof.

            (iii) Distribution of Cash and Other Assets. In the event of a
liquidation, dissolution or winding up of the Corporation resulting in the
availability of assets other than cash for distribution to the holders of the
Series I Preferred Stock, the holders of the Series I Preferred Stock shall be
entitled to a distribution of cash and/or assets equal to the value of the
liquidation preference stated in subsection (i) of this paragraph (d), which
valuation shall be made solely by the Board of Directors, and provided that such
Board of Directors was acting in good faith, shall be conclusive.

            (iv) Distribution to Junior Security Holders. After the payment or
distribution to the holders of the Series I Preferred Stock of the full
preferential amounts aforesaid, the

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holders of the Common Stock then outstanding, or any other stock of the
Corporation ranking as to assets upon liquidation, dissolution or winding up of
the Corporation junior to the Series I Preferred Stock, shall be entitled to
receive ratably all of the remaining assets of the Corporation.

            (v) Preference; Priority. References to a stock that is "SENIOR" to,
on a "PARITY" with or "JUNIOR" to other stock as to liquidation shall refer,
respectively, to rights of priority of one series or class of stock over another
in the distribution of assets on any liquidation, dissolution or winding up of
the Corporation. The Series I Preferred Stock shall be on a parity with the
Series H Preferred Stock and senior to the Common Stock of the Corporation, all
other series of Preferred Stock of the Corporation and any other capital stock
of the Corporation now or hereafter authorized.

      (e) Voting Rights. (i) Except as otherwise expressly provided herein or by
law, the holder of each share of Series I Preferred Stock shall have the right
to one vote for each share of Common Stock into which such Series I Preferred
Stock could then be converted, and with respect to such vote, such holder shall
have full voting rights and powers equal to the voting rights and powers of the
holders of Common Stock, and shall be entitled, notwithstanding any provision
hereof, to notice of any shareholders' meeting in accordance with the Bylaws of
the Corporation, and shall be entitled to vote, together with holders of Common
Stock, with respect to any question upon which holders of Common Stock have the
right to vote. Fractional votes shall not, however, be permitted and any
fractional voting rights available on an as-converted basis (after aggregating
all shares into which shares of Series I Preferred Stock held by each holder
could be converted) shall be rounded to the nearest whole number (with one-half
being rounded upward).

            (ii) Notwithstanding the foregoing, upon the approval of the holders
of a majority of the then outstanding shares of Series I Preferred Stock, the
voting rights of the Series I Preferred Stock shall automatically be amended
such that, except (A) as otherwise required by law or (B) with respect to the
matters set forth in Section (e)(iii) below), the holder of shares of Series I
Preferred Stock shall not have the right to vote on matters that come before the
shareholders.

            (iii) The Corporation shall not, without first obtaining the
approval of the holders of a majority of the then outstanding shares of Series I
Preferred Stock:

                        (A) alter or change the rights, preferences or
      privileges of the shares of Series I Preferred Stock so as to affect
      adversely the shares of such series, by way of merger or otherwise; or

                        (B) increase or decrease (other than by conversion or in
      accordance with this Certificate of Designation) the total number of
      authorized shares of Series I Preferred Stock.

      (f) Conversion Rights. The holders of Series I Preferred Stock will have
the following conversion rights:

            (i) Right to Convert. Subject to and in compliance with the
provisions of this paragraph (f), any issued and outstanding shares of Series I
Preferred Stock may, at the option of

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the holder, be converted at any time or from time to time into fully paid and
nonassessable shares of Common Stock at the conversion rate in effect at the
time of conversion, determined as provided herein.

            (ii) Mechanics of Conversion. Before any holder of Series I
Preferred Stock shall be entitled to convert the same into shares of Common
Stock, he shall surrender the certificate or certificates therefor, duly
endorsed, at the office of the Corporation or of any transfer agent for the
Common Stock, and shall give written notice to the Corporation at such office
that he elects to convert the same and shall state therein the number of shares
of Series I Preferred Stock being converted. Thereupon, the Corporation shall
promptly issue and deliver at such office to such holder of Series I Preferred
Stock a certificate or certificates for the number of shares of Common Stock to
which he shall be entitled. Such conversion shall be deemed to have been made
immediately prior to the close of business on the date of such surrender of the
shares of Series I Preferred Stock to be converted, and the person or persons
entitled to receive the shares of Common Stock issuable upon such conversion
shall be treated for all purposes as the record holder or holders of such shares
of Common Stock on such date.

            (iii) Conversion Price. The number of shares into which one share of
Series I Preferred Stock shall be convertible shall be determined by dividing
the Series I Purchase Price by the then existing Conversion Price (as set forth
below), which shall be subject to adjustment from time to time in certain
instances, as provided below in this paragraph (f). The "CONVERSION PRICE" per
share for the Series I Preferred Stock shall be equal to $0.0001 per share.

            (iv) Adjustment for Stock Splits and Combinations. If the
Corporation shall at any time, or from time to time after the date Series I
Preferred Stock is first issued ("THE ORIGINAL ISSUANCE DATE"), effect a
subdivision of the outstanding Common Stock, the Conversion Price in effect
immediately prior thereto shall be proportionately decreased, and conversely, if
the Corporation shall at any time or from time to time after the Original
Issuance Date combine the outstanding shares of Common Stock, the Conversion
Price then in effect immediately before the combination shall be proportionately
increased. Any adjustment under this paragraph (f)(iv) shall become effective at
the close of business on the date the subdivision or combination becomes
effective.

            (v) Adjustment for Certain Dividends and Distributions. In the event
the Corporation at any time, or from time to time after the Original Issuance
Date, shall make or issue, or fix a record date for the determination of holders
of Common Stock entitled to receive, a dividend or other distribution payable in
additional shares of Common Stock, then and in each such event the Conversion
Price for the Series I Preferred Stock then in effect shall be decreased as of
the time of such issuance or, in the event such a record date shall have been
fixed, as of the close of business on such record date, by multiplying the
Conversion Price for such Series I Preferred Stock then in effect by a fraction:

                        (A) the numerator of which shall be the total number of
      shares of Common Stock issued and outstanding immediately prior to the
      time of such issuance or the close of business on such record date, and


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                        (B) the denominator of which shall be the total number
      of shares of Common Stock issued and outstanding immediately prior to the
      time of such issuance or the close of business on such record date plus
      the number of shares of Common Stock issuable in payment of such dividend
      or distribution;

provided, however, if such record date shall have been fixed and such dividend
is not fully paid or if such distribution is not fully made on the date fixed
therefor, the Conversion Price for the Series I Preferred Stock shall be
recomputed accordingly as of the close of business on such record date and
thereafter, the Conversion Price for the Series I Preferred Stock shall be
adjusted pursuant to this paragraph (f)(v) as of the time of actual payment of
such dividends or distributions.

            (vi) Adjustments for Other Dividends and Distributions. In the event
the Corporation at any time or from time to time after the Original Issuance
Date shall make or issue, or fix a record date for the determination of holders
of Common Stock entitled to receive, a dividend or other distribution payable in
securities of the Corporation other than shares of Common Stock, then and in
each such event provision shall be made so that the holders of such Series I
Preferred Stock shall receive upon conversion thereof in addition to the number
of shares of Common Stock receivable thereupon, the amount of securities of the
Corporation that they would have received had their Series I Preferred Stock
been converted into Common Stock on the date of such event and had thereafter,
during the period from the date of such event to and including the conversion
date, retained such securities receivable by them as aforesaid during such
period giving application to all adjustments called for during such period under
this paragraph (f) with respect to the rights of the holders of the Series I
Preferred Stock.

            (vii) Adjustment for Reclassification Exchange or Substitution. If
the Common Stock issuable upon the conversion of the Series I Preferred Stock
shall be changed into the same or a different number of shares of any class or
classes of stock, whether by capital reorganization, reclassification or
otherwise (other than a subdivision or combination of shares or stock dividend
provided for above, or a reorganization, merger, consolidation or sale of assets
provided for elsewhere in this paragraph (f)), then and in each such event the
holder of each share of Series I Preferred Stock shall have the right thereafter
to convert such share into the kind and amount of shares of stock and other
securities and property receivable upon such reorganization, reclassification or
other change, by holders of the number of shares of Common Stock into which such
shares of Series I Preferred Stock might have been converted immediately prior
to such reorganization, reclassification, or change, all subject to further
adjustment as provided herein.

            (viii) Adjustment for Issuances of Additional Stock. In the event
the Corporation at any time, or from time to time after the Original Issuance
Date, shall issue any shares of Common Stock (including shares of Common Stock
deemed to have been issued pursuant to Section (f)(ix) below) after the Original
Issuance Date (the "ADDITIONAL STOCK"), then and in each such event the
Conversion Price for the Series I Preferred Stock then in effect shall be
decreased as of the time of such issuance by multiplying the Conversion Price
for such Series I Preferred Stock then in effect by a fraction:


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                        (A) the numerator of which shall be the total number of
      shares of Common Stock issued and outstanding immediately prior to the
      time of such issuance (including shares of Common Stock deemed issued
      pursuant to Section (f)(ix) below) (the "OUTSTANDING COMMON"), and

                        (B) the denominator of which shall be the total number
      of shares of Outstanding Common plus the number of shares of such
      Additional Stock;

No adjustment to the Conversion Price shall be made pursuant to this Section
(f)(viii) on account of any issuance of Additional Stock that is consummated on
a date on which the Corporation's equity market capitalization, as obtained from
Bloomberg Financial Services or another similar service, exceeds $15,000,000 as
of the close of trading on each of the ten (10) consecutive trading days prior
to such date.

            (ix) Deemed Issuances of Common Stock. In the case of the issuance
after the Original Issuance Date of securities or rights convertible into, or
entitling the holder thereof to receive directly or indirectly, additional
shares of Common Stock (the "Common Stock Equivalents"), the following
provisions shall apply for all purposes of Section (f)(viii) and this Section
(f)(ix):

                        (A) The aggregate maximum number of shares of Common
      Stock deliverable upon conversion, exchange or exercise (assuming the
      satisfaction of any conditions to convertibility, exchangeability or
      exercisability, including, without limitation, the passage of time, but
      without taking into account potential antidilution adjustments) of any
      Common Stock Equivalents and subsequent conversion, exchange or exercise
      thereof shall be deemed to have been issued at the time such securities
      were issued or such Common Stock Equivalents were issued.

                        (B) In the event of any change in the number of shares
      of Common Stock deliverable upon conversion, exchange or exercise of any
      Common Stock Equivalents including, but not limited to, a change resulting
      from the antidilution provisions thereof, the Conversion Price for the
      Series I Preferred Stock, to the extent in any way affected by or computed
      using such Common Stock Equivalents, shall be recomputed to reflect such
      change, but no further adjustment shall be made for the actual issuance of
      Common Stock upon the conversion, exchange or exercise of such Common
      Stock Equivalents.

                        (C) Upon the termination or expiration of the
      convertibility, exchangeability or exercisability of any Common Stock
      Equivalents, the Conversion Price for the Series I Preferred Stock, to the
      extent in any way affected by or computed using such Common Stock
      Equivalents, shall be recomputed to reflect the issuance of only the
      number of shares of Common Stock (and Common Stock Equivalents that remain
      convertible, exchangeable or exercisable) actually issued upon the
      conversion, exchange or exercise of such Common Stock Equivalents.

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                        (D) The number of shares of Common Stock deemed issued
      pursuant to Section (f)(ix)(A) shall be appropriately adjusted to reflect
      any change, termination or expiration of the type described in either
      Section (f)(ix)(B) or (f)(ix)(C).

            (x) No Increased Conversion Price. Notwithstanding any other
provisions of Section (f)(viii) or this Section (f)(ix), except to the limited
extent provided for in Sections (f)(ix)(B) and (f)(ix)(C), no adjustment of the
Conversion Price pursuant to Section (f)(viii) or this Section (f)(ix) shall
have the effect of increasing the Conversion Price above the Conversion Price in
effect immediately prior to such adjustment.

            (xi) Reorganization, Mergers, Consolidations or Sales of Assets. If
at any time or from time to time there shall be a capital reorganization of the
Common Stock (other than a subdivision, combination, reclassification or
exchange of shares provided for elsewhere in this paragraph (f)) or a merger or
consolidation of the Corporation with or into another corporation, or the sale
of all or substantially all of the Corporation's properties and assets to any
other person, then, as a part of such reorganization, merger, consolidation or
sale, provision shall be made so that the holders of the Series I Preferred
Stock shall thereafter be entitled to receive upon conversion of such Series I
Preferred Stock, the number of shares of stock or other securities or property
of the Corporation or of the successor corporation resulting from such merger or
consolidation or sale, to which a holder of Common Stock deliverable upon
conversion would have been entitled on such capital reorganization, merger,
consolidation or sale. In any such case, appropriate adjustment shall be made in
the application of the provisions of this paragraph (f) with respect to the
rights of the holders of the Series I Preferred Stock after the reorganization,
merger, consolidation or sale to the end that the provisions of this paragraph
(f) (including adjustment of the Conversion Price then in effect and the number
of shares purchasable upon conversion of the Series I Preferred Stock) shall be
applicable after that event as nearly equivalent as may be practicable.

            (xii) Certificate of Adjustment. In each case of an adjustment or
readjustment of the Conversion Price for the number of shares of Common Stock or
other securities issuable upon conversion of the Series I Preferred Stock, the
Corporation shall compute such adjustment or readjustment in accordance herewith
and the Corporation's Chief Financial Officer shall prepare and sign a
certificate showing such adjustment or readjustment, and shall mail such
certificate by first class mail, postage prepaid, to each registered holder of
the Series I Preferred Stock at the holder's address as shown in the
Corporation's books. The certificate shall set forth such adjustment or
readjustment, showing in detail the facts upon which such adjustment or
readjustment is based.

            (xiii) Notices of Record Date. In the event of (A) any taking by the
Corporation of a record of the holders of any class or series of securities for
the purpose of determining the holders thereof who are entitled to receive any
dividend or other distribution or (B) any reclassification or recapitalization
of the capital stock of the Corporation, any merger or consolidation of the
Corporation or any transfer of all or substantially all of the assets of the
Corporation to any other corporation, entity or person, or any voluntary or
involuntary dissolution, liquidation or winding up of the Corporation, the
Corporation shall mail to each holder of Series I Preferred Stock at least 10
days prior to the record date specified therein, a notice specifying (1) the
date on which any such record is to be taken for the purpose of such

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dividend or distribution and a description of such dividend or distribution, (2)
the date on which any such reorganization, reclassification, transfer,
consolidation, merger, dissolution, liquidation or winding up is expected to
become effective and (3) the time, if any is to be fixed, as to when the holders
of record of Common Stock (or other securities) shall be entitled to exchange
their shares, of Common Stock (or other securities) for securities or other
property deliverable upon such reorganization, reclassification, transfer,
consolidation, merger, dissolution, liquidation or winding up.

            (xiv) Fractional Shares. No fractional shares of Common Stock shall
be issued upon conversion of the Series I Preferred Stock. In lieu of any
fractional shares to which the holder would otherwise be entitled, the
Corporation shall pay cash equal to the product of such fraction multiplied by
the fair market value of one share of the Corporation's Common Stock on the date
of conversion, as determined in good faith by the Board of Directors.

            (xv) Reservation of Stock Issuable Upon Conversion. The Corporation
shall at all times reserve and keep available out of its authorized but unissued
shares of Common Stock, solely for the purpose of effecting the conversion of
the shares of the Series I Preferred Stock, such number of its shares of Common
Stock as shall from time to time be sufficient to effect the conversion of all
outstanding shares of Series I Preferred Stock, and if at any time the number of
authorized but unissued shares of Common Stock shall not be sufficient to effect
the conversion of all then outstanding shares of Series I Preferred Stock, the
Corporation will take such corporate action as may, in the opinion of its
counsel, be necessary to increase its authorized but unissued shares of Common
Stock to such number of shares as shall be sufficient for such purpose.

            (xvi) Notices. Any notice required by the provisions of this
paragraph (f) to be given to the holders of shares of Series I Preferred Stock
shall be deemed given (A) if deposited in the United States mail, postage
prepaid, or (B) if given by any other reliable or generally accepted means
(including by facsimile or by a nationally recognized overnight courier
service), in each case addressed to each holder of record at his address (or
facsimile number) appearing on the books of the Corporation.

            (xvii) Payment of Taxes. The Corporation will pay all transfer taxes
and other governmental charges that may be imposed in respect of the issue or
delivery of shares of Common Stock upon conversion of shares of Series I
Preferred Stock.

      (g) No Reissuance of Preferred Stock. Any shares of Series I Preferred
Stock acquired by the Corporation by reason of purchase, conversion or otherwise
shall be canceled, retired and eliminated from the shares of Series I Preferred
Stock that the Corporation shall be authorized to issue. All such shares shall
upon their cancellation become authorized but unissued shares of Preferred Stock
and may be reissued as part of a new series of Preferred Stock subject to the
conditions and restrictions on issuance set forth in the Articles of
Incorporation or in any certificate of designation creating a series of
Preferred Stock or any similar stock or as otherwise required by law.

      (h) Severability. If any right, preference or limitation of the Series I
Preferred Stock set forth herein is invalid, unlawful or incapable of being
enforced by reason of any rule, law or

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public policy, all other rights, preferences and limitations set forth herein
that can be given effect without the invalid, unlawful or unenforceable right,
preference or limitation shall nevertheless remain in full force and effect, and
no right, preference or limitation herein shall be deemed dependent upon any
other such right, preference or limitation unless so expressed herein.

      IN WITNESS WHEREOF, Diametrics Medical, Inc. has caused this Certificate
of Designations of Series I Preferred Stock to be executed by W. Bruce Comer
III, its Chief Executive Officer, this 5th day of December, 2005.

                                    /s/ W. Bruce Comer
                                    -------------------------------------------
                                    W. Bruce Comer III, Chief Executive Officer




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