Ohio Modulus

WLMD ID: amve

The Ohio Chemical and Manufacturing Company, founded in 1910, evolved through a series of acquisitions and mergers to become one of the dominant makers of anesthesia machines in the world. Its first fully-computerized machine, the Modulus, was introduced in 1979. The name indicated that many of its components were interchangeable. It conformed to a new national standard for anesthesia machine design, ANSI Z-79.8, which ensured that all controls and indicators were easy for the anesthesiologist to see and to reach. But the ability to add numerous optional monitors without plan could defeat that aim. Later models of the machine featured integrated monitors. 

The example of the Modulus shown here was produced in 1983. It had numerous safety features, including separate controls over each anesthetic agent, an oxygen flush valve, a fail-safe system, an ascending bellows ventilator, an oxygen monitor, blood pressure monitor, and alarms. The machine has three vaporizers, for the liquid agents enflurane (Ethrane), isoflurane (Forane) and halothane (Fluothane).  The company changed its name to Ohmeda in 1984.

Catalog Record: Ohio Modulus

Access Key: amve

Accession No.: 2007-05-10-2 G

Title: Modulus anesthetic gas machine / Ohio Medical Products.

Corporate Author: Ohio Medical Products.

Title variation: Alt Title
Title: Ohio Modulus anesthetic gas machine.

Publisher: Madison, Wisconsin : Ohio Medical Products, a division of AIRCO, Inc., [1983?].

Physical Descript: 1 anesthesia machine : metals, plastics, glass ; 170 x 112 x 93 cm.

Subject: Anesthesia Machines.
Subject: Anesthesia, Inhalation – instrumentation.

Note Type: General
Notes: The probable year of manufacture is based on the year that the Ohio 7000
Ventilator was introduced, and on the date that is handwritten on a sticker
placed just below the manufacturer’s plate on the back of the machine. This
sticker has the word, “ACCPTED” printed on it and the date “8-16-83”
handwritten. Of note: The name Ohio Medical Products was changed to Ohmeda in
1984. The oxygen monitor on this machine is marked with the name Ohmeda. .
Also, a GE representative (phone conversation with Daniel Hatlestad on
November 16, 2015) believed that manufacture of the Modulus ceased in 1983.
Mr. Hatlestad also reported that manufacture of the Modulus may have begun as
early as 1978. The date of manufacture could change if documentation or
expert opinion indicate the range should be corrected.

Note Type: Citation
Notes: Modulus Standard Anesthesia Gas Machine Product Specifications [marketing
booklet]. Madison, Wisconsin: Ohio Medical Products; 1979. [“©1979 Airco.
Inc” is printed in small text on the lower left corner of the cover of this

Note Type: Citation
Notes: New products. J Med Eng Technol. 1983;7(3):163-170. [Description of the “new”
Ohio 7000 Electronic Anesthesia Ventilator.]

Note Type: Citation
Notes: Ohio Modulus Anesthesia Gas Machine: OM Operation Maintenance. Madison,
Wisconsin: Ohio Medical Products; [1980]. [“4/80-New”, is printed after
publication numbers on the back cover. The publication year 1980 is based on

Note Type: Citation
Notes: The Ohio Modulus: It will help make your world a lot safer [marketing
booklet]. Madison, Wisconsin: Ohio Medical Products; 1980.

Note Type: Citation
Notes: On October 22, Ohio will make your world a lot safer for you [advertisement].
Anesthesiology. 1979;51(4):15 of advertisements. [The Modulus is not named.
This advertisement invites readers to a new machine’s ‘unveiling’. In
addition to the ‘title’, other text in the ad includes, “That date marks the
start of the American Society of Anesthesiologists Annual Meeting in San
Francisco. And the introduction of a new concept that not only meets te
recently adopted ANSI Z-79.8 standards but sets new standards of its own! …
We cordially invite you to visit us at Booth No. 60. October 22, 1979 at the
ASA Conference. White you are there, you’ll find out how Ohio Medical
Products is translating Z-79.8 from theory into practice.”]

Note Type: Citation
Notes: Where in the world is Ohio? After today, everywhere. Ohmeda. Anesthesiology.
1984;61(2):25 of advertisements. [Announcement of name chage to Ohmeda.]

Note Type: Physical Description
Notes: One cabinet style anesthesia machine with three vaporizers, an oxygen monitor
ventilator and breathing system; Beginning at the upper left of the machine
is a flowmeter bank, or Flow Control Module; It houses the machine ON-OFF
switch, oxygen flush valve, and three flowmeters: one for air, one for
nitrous oxide and one for oxygen; A red DYMO label, with the number “16”, is
located on the lower left of the flowmeter bank; To the right of the flow
meter bank is an upper and lower shelf; Below the lower shelf is a gauge for
manual blood pressure monitoring and a Ohmeda 5120 Oxygen Monitor; “BOC
Health Care” is also marked on the front of the monitor; To the right of the
oxygen monitor is a North American Drager DPM S monitor; A sticker with an
inventory number, 55502, for “ST. LUKES HOSPITAL” is located on the right
side of the DPM S monitor; To the left of the flowmeter bank is a “Ohio 7000
ELECTRONIC ANESTHESIA VENTILATOR”; The ventilator is marked, “Made in U.S.A.”
with “STOCK NUMBER 309-0608-800” and “SERIAL NUMBER CAA L00370”; Also marked
on the ventilator is, “Ohio Medical Products”, and “A DIVISION OF AIRCO, INC.
[new line] MADISON, WISCONSIN 53707″; Below the flowmeter bank are three
Ohio Medical Products vaporizers; From left to right, they are, “VAPORIZER
enflurane vaporizer is marked with serial number BAJJ02329, and model number
“100E”; The isoflurane vaporizer is marked with serial number AKOK0078, and
model number “100E”; The halothane vaporizer is marked with serial number
BAKHO0666; Below the vaporizers and just above the table top, is a row of
pressure gauges for air, nitrous oxide and oxygen; Each has a gauge for
pipeline supply and cylinder supply; To the right of the pressure gauges is
the following, “Modulus™ [new line] ANESTHETIC GAS MACHINE”; Below the
stainless steel table top are three drawers; The drawers and outer shell for
the drawers is painted a dark teal color; The machine is on four wheels;
Mounted to the right of the drawers is a foldable shelf; The machine was
folded in the down position; The preoperative checklist for the machine is in
the 3rd drawer; To the left of the drawers is an area for a common gas outlet
the oxygen monitor port and the noninvasive blood pressure gauge connection;
Mounted on the left side of the machine is the absorber and parts of the
breathing circuit; The absorber is marked “Ohio ANESTHESIA ABSORBER”; It is
also marked with, “U.S. PAT. 3,088,810”, “MODEL NUMBER 21DC” and “SERIAL
NUMBER ACKL00806″; On the back are four yokes for gas cylinders: two for
oxygen, one for nitrous oxide and one for air; One of the oxygen, the nitrous
oxide and the air yokes have extensions for pipeline supplied gas; Marked on
the back is the following, “Ohio [new line] Modulus [new line] ANESTHETIC GAS
MACHINE [new line] SERIAL NUMBER [new line] ABLL00909 [new line] BASIC STOCK
NUMBER [new line] 236-6432-910 [new line] …Ohio Medical Products [new
maintenance inspection history card on the back of the machine lists March,
2000 (“3-00”) as the last date for “Next Service Due”.

Note Type: Reproduction
Notes: Photographed by Mr. Steve Donisch, June 8, 2015.

Note Type: Acquisition
Notes: Donated to the WLM by Jerry Dorsch, MD, and Susan Dorsch, MD.

Note Type: Exhibition
Notes: Selected for the WLM website (noted November 16, 2015).