THERAPEUTIC SYSTEMS
The traditional method of administering hyperbaric therapy is
with the use of a multiplace chamber that accommodates two or more persons ( Fig.
70-5
). Size may vary from a small, portable two-person chamber used for
transporting patients in the field to one 20 or more feet in diameter in which up
to a dozen patients may be comfortably admitted in addition to tenders. The largest
multiple chamber ever built was a 20-m-diameter sphere that could be compressed to
3 ATA.[4]
Multiplace chambers are compressed with
air, and the patient breathes O2
with a head tent ( Fig.
70-6
), facemask, or endotracheal tube. Because of immediate access to
the patient by accompanying nursing personnel or physicians, monitoring is relatively
straightforward. Intravenous lines can be inserted during treatment, and airway
management, including suctioning, can be performed. As already pointed out, surgery
has even been performed inside multiplace hyperbaric chambers. However, operation
of these chambers is complex. They have a large space requirement for installation
and are costly.
The other type of chamber is a monoplace chamber that is large
enough to accommodate only one patient ( Fig.
70-7
); a tender can be used only with a small child. The chamber wall
in most types is manufactured of Plexiglas to facilitate close observation of the
patient. The chamber is usually compressed with 100% O2
. The advantage
of monoplace chambers is their relatively low cost and ease of installation. The
chamber may be put into use merely by connecting the O2
inlet to the hospital
supply, although some modification of the main supply piping may be required to accommodate
large flow rates. Operation of the chamber is relatively simple, but it has the
disadvantage of less flexibility. The patient inside the chamber at pressure cannot
be evaluated "hands on," monitoring is
Figure 70-6
Head tent circuit for use in a multiplace chamber. Fresh
gas (100% O2
) flows at a constant rate (>30 L/min) through the head
tent. Exhaust gas may be either vented outside the chamber or recirculated through
a CO2
scrubber. The sample line attached to the exhaust hose allows monitoring
of the patient's breathing gas.
Figure 70-7
Monoplace chamber. This type of chamber has room for
one patient or a tender with a small child. The chamber's atmosphere is 100% O2
.
The chamber is constructed of transparent Plexiglas to allow observation. Through-hull
penetrators in the door can be used for monitoring, administration of intravenous
fluid, and control of a ventilator inside the chamber.
somewhat more remote, and emergency care of the airway cannot be provided. The development
of pneumothorax, particularly tension pneumothorax, through rare, can be fatal because
of the impossibility of inserting a chest tube before decompression. A minor disadvantage
of these chambers is that the ambient pressure limit is 3 ATA, and for practical
reasons, treatment times are limited. Moreover, the need for intermittent periods
of air breathing to decrease the risk of O2
toxicity (see later) requires
the installation of an additional gas delivery system. Nevertheless, monoplace technology
now permits the administration of intravenous fluids from outside the chamber, invasive
intravascular monitoring, mechanical ventilation, and the use of pleural drainage
systems incorporating regulated suction. Additional details have been published
by Weaver and Strauss.[145]
[146]
Many chambers are now also equipped with mask systems from which the patient may
intermittently breathe air (called "BIBS" for built-in breathing system), thereby
permitting the administration of U.S. Navy treatment tables for decompression illness
(see later).
