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                                                                    EXHIBIT 4(b)


                         Novametrix Medical Systems Inc.
                               5 Technology Drive
                              Wallingford, CT 06492

                                                   December 17, 2001

Respironics, Inc.
1501 Ardmore Boulevard
Pittsburgh, PA  15221

Ladies and Gentlemen:

         The undersigned understands that Respironics Holdings, Inc. ("Merger
Subsidiary"), a wholly - owned subsidiary of Respironics, Inc. ("Respironics"),
is about to enter into an Agreement and Plan of Merger (the "Merger Agreement")
with Novametrix Medical Systems Inc. ("Novametrix"). The Merger Agreement
provides for the merger of Merger Subsidiary with and into Novametrix (the
"Merger") and the conversion of outstanding shares of Novametrix Common Stock
into Respironics Common Stock in accordance with the formula therein set forth.

         In order to induce Respironics to cause Merger Subsidiary to enter into
the Merger Agreement, and intending to be legally bound hereby, the undersigned
represents, warrants and agrees that at the Novametrix Stockholders Meeting
contemplated by Section 5.02 of the Merger Agreement and any adjournment or
postponement thereof the undersigned will, in person or by proxy, vote or cause
to be voted in favor of the Merger Agreement and the Merger the shares of
Novametrix Common Stock beneficially owned by the undersigned individually or,
to the extent of the undersigned's proportionate voting interest, jointly with
other persons, as well as (to the extent of the undersigned's proportionate
voting interest) any other shares of Novametrix Common Stock over which the
undersigned may hereafter acquire beneficial ownership in such capacities
(collectively, the "Shares"). The undersigned further agrees that the
undersigned will use the undersigned's best efforts to cause any other shares of
Novametrix Common Stock over which the undersigned has or shares voting power to
be voted in favor of the Merger Agreement and the Merger.

         The undersigned further represents, warrants and agrees that until the
earlier of (i) the consummation of the Merger or (ii) the termination of the
Merger Agreement in accordance with its terms, the undersigned will not,
directly or indirectly:

                  (a) vote any of the Shares, or cause or permit any of the
         Shares to be voted in favor of any other merger, consolidation, plan of
         liquidation, sale of assets, reclassification or other transaction
         involving Novametrix or any of its subsidiaries which would have the
         effect of any person other than Respironics or its affiliate acquiring
         control over Novametrix, any of its subsidiaries or any substantial
         portion of the assets of Novametrix or any of its subsidiaries. As used
         herein, the term "control" means (i) the ability to direct the voting
         of 30% or more of the outstanding voting securities of a person having
         ordinary voting power in the election of directors or in the election
         of any other body having similar functions or (ii) the ability to
         direct the management and policies of a person, whether through
         ownership of securities, through any contract, arrangement or
         understanding or otherwise; or
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                  (b) sell or otherwise transfer any of the Shares, or cause or
         permit any of the Shares to be sold or otherwise transferred (i)
         pursuant to any tender offer, exchange offer or similar proposal made
         by any person (other than Respironics or its affiliate), (ii) to any
         person seeking to obtain control of Novametrix, any of its subsidiaries
         or any substantial portion of the assets of Novametrix or any of its
         subsidiaries or to any other person (other than Respironics or its
         affiliate) under circumstances where such sale or transfer may
         reasonably be expected to assist a person seeking to obtain such
         control or (iii) for the principal purpose of avoiding the obligations
         of the undersigned under this agreement.

         It is understood and agreed that this agreement relates solely to the
capacity of the undersigned as a shareholder or other beneficial owner of the
Shares and is not in any way intended to affect the exercise by the undersigned
of the undersigned's responsibilities as a director or officer of Novametrix or
any of its subsidiaries. This agreement will terminate upon the earlier of
consummation of the Merger of the termination of the Merger Agreement in
accordance with the its terms.

                                             Very truly yours,



                                            ----------------------------
Accepted and Agreed to:
RESPIRONICS, INC.


By
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Title
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Date:
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