LESSON 1
PERFORM PREVENTIVE MAINTENANCE CHECKS AND SERVICES
ON ANESTHESIA APPARATUS
Section I. OPERATIONS
1-1.
GENERAL
The Ohmeda 885A Anesthesia machine is designed for surgery patients that
require some degree of anesthetizing. The Ohmeda 885A delivers the anesthetic agent
to the patient. The anesthetic, either gases or vapors, mixes with oxygen at precise
levels. This is the crucial aspect of anesthesiology. The Model 885 Conversion
Anesthesia Apparatus provides all the minimum essentials for administration of
anesthesia for adults and children. It accommodates large (M and G size) and small (D
and E size) cylinder gas supplies. This lesson starts with the overall theory of
operations for the anesthesia apparatus. This provides the basis for a better
understanding of the types of preventive maintenance checks and services (PMCS) you
must perform.
1-2.
THEORY OF OPERATIONS
Refer to figure 1-1, Adult re-breathing circuit, and figure 1-2, Pediatric partial re-
breathing circuit, when reading this section. Both these circuits consist of two
operational circuits: the delivery circuit and the re-breathing circuit. The delivery circuit
is identical for both; however, due to a child's physiology, the re-breathing circuit is
different. The delivery circuit uses oxygen (O2), a life-support gas, and nitrous oxide
(N2O), a temporary general anesthesia. The delivery circuit routes these gases through
a series of flow meters, regulators, and valves. This reduces the pressure delivered
from the gas cylinders. These monitor the delivery circuit so that the patient's inhalation
is not hampered by too much pressure within the system. This is discussed in
paragraph "a" below. A pure flow of oxygen picks up additional anesthetic vapors in the
vaporizer. It then combines with the oxygen-nitrous oxide flow to achieve the desired
ratio of oxygen and anesthetic for the patient. The new mixture flows on to the patient
through the closed re-breathing circuit. Both types of re-breathing circuits are discussed
in paragraphs b and c below.
MD0353
1-2