Biomedical Engineering Reference
In-Depth Information
(
A
)
(
B
)
Figure 6.43
(
A
) With more advanced photodamage, full treatment with CO
2
laser is performed (two or three passes) and then erbium laser is used to remove layer
of thermal necrosis and selectively sculpt tissue. (
B
) This technique reduces residual erythema, quickens healing, and results in enhanced clinical results,
as seen 2 months postoperatively. CO
2
laser provides tissue tightening periorbitally and on cheeks, whereas erbium laser sculpts deep lines of upper lip, glabella,
and forehead.
erythema were signifi cantly less for the side treated with the
combination CO
2
-Er:YAG as compared with the side treated
with CO
2
laser alone (Figs 6.43 and 6.44). Moreover, this ben-
efi cial effect on postoperative healing was accomplished
without compromising clinical effi cacy. Biopsies taken at 2-3
days, 1 week, and 4-8 weeks showed that thermal necrosis
was greatly reduced by adding the erbium laser treatment,
speeding healing by 2-3 days without compromising new
collagen production. In addition, infl ammation was reduced
at 1 week, and angiogenesis was decreased at 1-8 weeks,
refl ecting the decreased erythema that was seen clinically
(Figs 6.45 and 6.46).
McDaniel et al. compared resurfacing of the upper lip using a
CO
2
laser alone (UltraPulse 5000-C, two passes, 300 mJ, 95 W,
CPG density 6, spot diameter 2.25 mm, 7.5 J/cm
2
) with the com-
bination of the same CO
2
laser treatment followed by three passes
with a short-pulsed Er:YAG laser (7-mm spot, 2 J, 5.2 J/cm
2
).
Medium-to-deep (class III) rhytides were improved with both
techniques. However, the duration of postoperative crusting,
swelling, and pruritus was signifi cantly reduced at the sites
treated with the CO
2
-Er:YAG laser combination (32).
Collagen (skin) tightening occurs as a heat-related
phenomenon, resulting in correction of loose tissue
and atrophic scars.
●
The fi rst pass causes an epidermal-dermal split that
allows easy and complete removal of the epidermis
with a single pass.
●
The Er:YAG laser is unique in the following ways:
●
Minimal residual thermal damage or tissue heating
occurs.
●
This pure-ablation laser continues to ablate with each
pass and does not reach an ablation plateau with depth.
Only minimal tissue water is required for laser-tissue
interaction.
●
The most successful use of lasers for resurfacing would uti-
lize each laser to take advantage of its unique benefi t and to
eliminate the disadvantages of each as much as possible.
Accordingly, the following protocols are followed for early
photodamage and for moderate to advanced photodamage.
Early Photodamage and Superficial Scars
When treating early photodamage or when patients desire a
more superfi cial treatment allowing early return to work and
as little healing time as possible (Fig. 6.47), the laser surgeon
performs the following steps:
protocols for combination
co
2
-
:yag laser treatment
Both the CO
2
laser and the Er:YAG laser have unique qualities
that can be exploited during resurfacing. The CO
2
laser is
unique in the following ways:
e
r
1. The epidermis is removed with a single pass of the
CO
2
laser, usually with a density overlap of 20-30%.
This can be accomplished very effi ciently with the
CO
2
laser, and biopsy studies have shown 0-10
Hemostasis is achieved.
●
A plateau of ablation is reached, limiting resurfacing
depth if proper treatment protocols are followed.
m
of residual thermal necrosis with this single pass.
μ
●
