Page 631 - Clinical Application of Mechanical Ventilation

Mechanical Ventilation in Nontraditional Settings 597

At an F O of 100%,
2
I
P O 5 (P 2 P H 2 O ) 3 F O 2 PaCO 2
I
2
2
A
B
5 (760 2 47) mm Hg 3 100% 2 40 mm Hg

5 673 mm Hg
Since PaO < P O
2
A
2
Dissolved oxygen at 1 ATA 5 P O 3 0.003
A
2
5 (673 3 0.003) vol%
< 2 vol%
Dissolved oxygen at 3 ATA 5 3 3 2 vol%
< 6 vol%
Indications for HBO
One barometric pressure equals 760 mm of mercury or 33 ft of water. At 33 ft below
Treatment for diver de- the sea level, the total barometric pressure is 1,520 mm Hg (760 mm Hg 3 2).
compression and high-altitude
decompression includes Decompression sickness occurs when a diver surfaces too rapidly. Rapid decom-
recompression quickly in a pression of pressure causes the dissolved gases in blood to form gas bubbles.
hyperbaric chamber followed
by gradual decompression. These bubbles can migrate to different parts of the body, causing moderate to
severe adverse outcomes, ranging from joint pain to paralysis and death. High-
altitude decompression sickness can also occur upon rapid ascent from low al-
titude to high altitude over 18,000 ft (Leach et al., 1998). Treatment for both
conditions includes recompression quickly in a hyperbaric chamber followed by
gradual decompression.
Patients with severe carbon monoxide (CO) poisoning often benefit from HBO.
Mild to moderate CO CO poisoning reduces the oxygen-carrying capacity of hemoglobin, and HBO
poisoning may be treated compensates for this deficiency by increasing the amount of dissolved oxygen.
with 100%-inspired oxygen
until the COHb is less than The symptoms of severe CO poisoning include unconsciousness, convulsions, and
5 vol%. neurological impairment. Mild to moderate CO poisoning may be treated with
100%-inspired oxygen (via a non-rebreathing mask) until the carboxyhemoglobin
(COHb) level is less than 5% (Boutros, 1976). In severe CO poisoning, HBO is
needed to treat acute tissue hypoxia (Leach et al., 1998).
Another indication for HBO is myonecrosis and gas gangrene of soft tissues due
Another indication for
HBO is myonecrosis and gas to clostridial infection. These anaerobic infections (e.g., Clostridium perfringens)
gangrene of soft tissues respond to HBO in some cases because an oxygen-enriched environment hinders
due to anaerobic clostridial
infection. the growth of anaerobic pathogens. HBO is usually used as an adjunctive therapy
to antibiotics, along with abridgement of necrotic soft tissues (Leach et al., 1998).

Endotracheal Tube and Ventilator

For patients requiring an endotracheal tube in the hyperbaric chamber, water (instead
A fluid-filled ET tube of air) is used to filled the cuff of the endotracheal tube. A fluid-filled cuff prevents
cuff prevents overdistension
and rupture of the cuff during overdistension and rupture of the cuff during decompression. Neuromuscular blocking
decompression in a hyperbaric agents have a shorter half-life under hyperbaric conditions. The degree of block must
chamber.
be monitored closely. If necessary, the blocking agents need to be administered at lower
dosages but more frequently (Desola, 1988).

Copyright 2013 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).
Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.