Ohio 30/70 Proportioner Anesthesia Machine

WLMD ID: alth
The first commercially available proportioning device was the Quantiflex Monitored Dial Mixer (MDM) by Fraser Sweatman. Introduced in 1972, it was used in place of a flowmeter bank to administer nitrous oxide (N2O) and oxygen (O2) at total gas flow rates between 1 and 20 liters per minute (lpm), in any proportion from 30 to 100 percent oxygen. It simplified the administration of specific concentrations of oxygen and nitrous oxide and acted as a safety component, to help prevent the administration of less than 30% oxygen to the patient.

In 1978, Ohio Medical Products introduced a new anesthesia machine with a built-in proportioner. The 30/70 Proportioner allowed for the administration of 30 to 100 percent O2 at total flow rates between 3 to 16 lpm. It included two flowmeters; one for N2O and one for O2. Below the flowmeters are two dials. One dial was for the total flow of gas, and the other set the percentage of oxygen to be administered. The ‘proportioner’ automatically adjusted the flow of both gases proportionally. This allowed the anesthesiologist to adjust the flowrate with a single dial and not affect the gas concentration. Likewise, the concentration could be adjusted using a single dial without affecting the flowrate.

Additional safety features of the Ohio 30/70 Proportioner Anesthesia Machine included an automatic shut-off of N2O if the flow of oxygen stopped, and an alarm that sounded if oxygen pressure dipped below 30 pounds per square inch (psi).

Catalog Record: Ohio 30/70 Proportioner Anesthesia Machine

Access Key: alth

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

Title: Ohio 30/70 proportioner anesthesia machine.

Corporate Author: Ohio Medical Products.

Title variation: Alt Title
Title: Ohio 30/70 proportioner machine.

Title variation: Alt Title
Title: Ohio 30/70 proportioner.

Publisher: Madison, Wisconsin : Ohio Medical Products, [between 1978-1994].

Physical Descript: 1 anesthesia machine : metals, plastics, glass, rubber ; 170 x 112 x 101 cm.

Subject: Anesthesia Machines.
Subject: Anesthesia, Inhalation – instrumentation.
Subject: Equipment Safety.
Subject: Oxygen – instrumentation.
Subject: Nitrous Oxide.

Note Type: General
Notes: The early year in the date range for the possible year of manufacture of this
machine is based on the earliest found mentiion of the 30/70 proportioner for
nitrous oxide and oxygen (a 1978 advertisement). An Ohio Air/Oxygen
Proportioner was introduced before the 30/70 proportioner for nitrous oxide
and oxygen. The end year is a generous estimate based on a date written on a
maintenance sticker that is on the machine (Nov 1994). The date range could
change if documentation that indicates the dates should be corrected is
discovered.

Note Type: Citation
Notes: Dorsch JA, Dorsch SE. The anesthesia machine. Understanding Anesthesia
Equipment: Construction, Care and Complications. Baltimore: Williams &
Wilkins; 1984:59-65.

Note Type: Citation
Notes: The new Ohio 30/70 Proportioner anesthesia machine [advertisement].
Anesthesiology. April, 1978;48(4):14-15 of advertisements.

Note Type: Citation
Notes: Ohio 30/70 Proportioner anesthesia machine [borchure]. Madison, Wisconsin:
Ohio Medical Products; 1983. [The following text is stamped on the front of
this brochure, “APR – 1987 [new line] DR. DORSCH [new line] ANESTHESIA DEPT. “]

Note Type: Citation
Notes: Ohio 30/70 Proportioner Anesthesia Machine : OM: Operation Maintenance.
Madison, Wisconsin: Ohio Medical Products; [around 1980?].

Note Type: Citation
Notes: Ohio product specifications: 37/70 Proportioner Anesthesia Machine. Madison,
Wisconsin: Ohio Medical Products; 1979.

Note Type: Citation
Notes: Rendell-Baker L. Problems with anesthetic gas machines and their solutions.
In: Rendell-aker L, ed. Problems with Anesthetic and Respiratroy Therapy
Equipment. Boston: Little, Brown and Company; 1982:37.

Note Type: Physical Description
Notes: One table top anesthesia machine; The measurements in the physical
description field include the machine with the breathing system (ventilator
and carbon dioxide absorber); Without the breathing system the machines
measures approximately 170 x 80 x 67 cm; Two stainless steel shelves form the
highest part of the machines; On each shelf is a black plate with white
lettering, marked, “NOT FOR PATIENT USE”; Below the lowest shelf and above
the table top, from left to right, is the rectangular “proportioner,” a
square manometer pressure guage (for blood pressure measurement), and a
backbar with two vaporizers; The proportioner has a built in nitrous oxide
flowmeter (in blue) and oxygen flowmeter (in green); Below the flowmeters is
a flow dial marked, “TOTAL FLOW LPM,” and an oxygen concentration dial,
marked, “% OXYGEN CONCENTRATION”; Two pressure guages are visible at the back
and just above, the table top; One is for nitrous oxide and one is for
oxygen; The vaporizers attached to the back bar are an Ethrane vaporizer and
a Forane vaporizer, both manufactured by Ohio Medical Products; Yokes for two
nitrous oxide tanks are located on the left side of the machine and yokes for
two oxygen tank are located on the right side of the machine; On the back are
two yokes for oxygen tanks; Below the table top is space, with a single
drawer on the based of the machine; A stainless steel surface covers the top
of the drawer, The drawer and legs are pained a clay, or orange-brown, color;
The machine is on four wheels; Attached to a pole on the left side of the
machine is an Ohio V5A Anesthesia Ventilator and a Ohio carbon dioxide
absorber; Marked on a plate on the front of the machine is, “Ohio 30/70 [new
line] PROPORTIONER [new line] ANESTHESIA MACHINE; On a label on the back of
the machine is marked, “STOCK NUMBER [new line] 216-6193-800 [new line]
SERIAL NUMBER [new line] B[???]FK00070 [new line] Ohio Medical Products [new
line] A DIVISION OF AIRCO INC [new line] MADISON, WISCONSIN 53707; A
non-Ohio piece of equipment is also attached to the pole with the ventilator
and carbon dioxide absorber; It is a North American Drager DPM-S (Drager
pressure monitor); It is blue and black in color; A bright yellow/green
sticker is attached to the front of the table-top, and is marked with
“Biomedical Maintenance [new line] safety check [new line] Nov 1994”.

Note Type: Reproduction
Notes: Photographed by Mr. Steve Donisch in January of 2015.

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

Note Type: Historical
Notes: The first commercially available proportioning device was the Quantiflex Monitored Dial Mixer (MDM) by Fraser Sweatman. Introduced in 1972, it was used in place of a flowmeter bank to administer nitrous oxide (N2O) and oxygen (O2) at total gas flow rates between 1 and 20 liters per minute (lpm), in any proportion from 30 to 100 percent oxygen. It simplified the administration of specific concentrations of oxygen and nitrous oxide and acted as a safety component, to help prevent the administration of less than 30% oxygen to the patient.

In 1978, Ohio Medical Products introduced a new anesthesia machine with a built-in proportioner. The 30/70 Proportioner allowed for the administration of 30 to 100 percent O2 at total flow rates between 3 to 16 lpm. It included two flowmeters; one for N2O and one for O2. Below the flowmeters are two dials. One dial was for the total flow of gas, and the other set the percentage of oxygen to be administered. The ‘proportioner’ automatically adjusted the flow of both gases proportionally. This allowed the anesthesiologist to adjust the flowrate with a single dial and not affect the gas concentration. Likewise, the concentration could be adjusted using a single dial without affecting the flowrate.

Additional safety features of the Ohio 30/70 Proportioner Anesthesia Machine included an automatic shut-off of N2O if the flow of oxygen stopped, and an alarm that sounded if oxygen pressure dipped below 30 pounds per square inch (psi).

Note Type: Publication
Notes: About Ohio Medical. Ohio Medical Corporation website. https://www.ohiomedical.
com/about/. Accessed March 20, 2015.

Note Type: Reproduction
Notes: Selected for the WLM website (noted March 24, 2015).