Comprehensive Clinical Guide: CO₂ Laser Applications from Pigment Disorders to Skin Rejuvenation

CO₂ laser is a powerful and versatile tool in dermatology, applicable to pigmentation treatment, scar management, tattoo removal, and skin rejuvenation. Each patient is unique; treatment plans should be individualized. This guide consolidates extensive clinical insights, protocols, and operational details, offering a practical reference for clinicians and practitioners.

I. CO₂ Laser Applications in Pigment Disorders

(A) Freckle Treatment

1. Background:
   Since six years ago, CO₂ laser has been used effectively to treat superficial pigmentation such as freckles and sunspots. While many focus on new devices, CO₂ laser’s flexible parameter adjustments remain invaluable.
2. Typical Cases:
   • An art teacher showed poor response after 3-4 phototherapy sessions but achieved significant improvement with a single CO₂ laser treatment, maintaining good results at 8-year follow-up.
   • A 12-year-old patient demonstrated that CO₂ laser is suitable for adolescent freckles, requiring 1-2 annual maintenance treatments.
3. Equipment Advantages:
   Unlike fixed-parameter Q-switched lasers or IPL, CO₂ laser allows adjustable energy, pulse width, and depth.

(B) Energy Adjustment and Thermal Damage Control

1. Parameter Tuning:
   • Basic test: Use A4 paper; adjust energy to just yellow (no penetration).
   • Advanced test: Use single-layer tissue paper; adjust pulse width until paper only yellows, no charring.
2. Thermal Damage Control:
   • 30 ms interval: causes mild carbonization without penetration, suitable for epidermal pigments with rapid hand movement or raising the handpiece; also reduces energy needed.
   • 15 ms interval: thermal damage heavier; generally not recommended.
3. Clinical Usage:
   Approximately 80% of pigment patients use CO₂ laser in combination.

(C) Suitable Treatment Areas

• Ideal for delicate sites such as around the eyes and mouth.

(D) Post-Treatment Pigmentation and Recurrence

1. Pigmentation Control:
   If skin barrier remains intact, pigmentation rarely occurs. In about 10% of patients with barrier damage, localized pigmentation appears—observed during a 9-day no-redness period and partially at 3 months.
2. Recurrence Pattern:
   Recurrence is inevitable but manageable; three-year follow-up shows results within normal relapse range; nine-year data confirm stability.

(E) Combined Microneedling Application After Laser

1. Postoperative Protocols:
   • Option A: MEBO moist burn ointment sealed with mask plus plastic wrap for heat dissipation.
   • Option B: Epidermal growth factor plus microneedling to promote repair.
2. Microneedling Advantages:
   • Superior hydration compared to skin boosters, ideal for dry regions like Yunnan.
   • Accelerates scab shedding within one week, preventing pigmentation.
   • Addresses post-laser dullness; also effective after IPL.
3. Critical Window:
   Within two weeks post-treatment is key to prevent cumulative pigmentation.

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II. Senile (Age) Spot Treatment

(A) Overview

1. Pathology:
   Senile spots are hyperkeratotic lesions with relatively inert tissue.
2. Clinical Features:
   Some spots retain activity; treatment timing depends on pigment changes (“darker now” or “wait a bit”).
3. Common Misconceptions:
   Treatment is often seen as simple but requires differentiation of various types.

(B) Treatment Principles

1. Choose methods based on keratinization and pigment depth.
2. Device selection includes CO₂ laser, IPL (phototherapy), 532 nm and 755/694 nm lasers, each requiring tailored use.
3. Assess skin conditions: hydration, texture, dermal depth.

(C) Keratinization and Treatment

1. Severe Keratinization:
   Thickened or sunken skin due to necrosis, dryness, and poor metabolism; treat with CO₂ laser vaporization.
2. Mild Keratinization:
   No obvious thickening but pigment variation; subdivided into deep pigment and shallow pigment types.

(D) Pigment Depth and Treatment

1. Deep Pigment Type:
   IPL is effective with low pigmentation risk; use shielding boards to protect surrounding skin; high energy may cause immediate epidermal disruption.
2. Shallow Pigment Type:
   May have vascular components; IPL alone often ineffective.
   Strategy: fractional laser scanning followed by IPL. IPL induces less pigmentation.

(E) Specific Strategies

1. Four-step decision: assess keratinization (heavy/light), pigment depth (deep/shallow), skin barrier function, then select combined treatment.
2. Special technique: fractional laser puncture before IPL.
3. Hydration levels (especially high-altitude patients) affect outcomes.

(F) Hand Senile Spot Treatment

1. Limited skin appendages and poor repair capacity.
2. High risk of pigment loss or scarring.
3. Avoid forced scab removal; gentle cotton swab test for energy; avoid excessive ablation.
4. Postcare: MEBO moist burn ointment plus enhanced hydration.

(G) CO₂ Laser Application in Senile Spots

1. Use short pulse width to avoid prolonged thermal damage.
2. Cover treatment area beyond lesion margins.
3. Uniform movement avoids focal over-damage.
4. Concave scars can be “filled” by secondary laser treatment.
5. Master energy-movement speed coordination through practice.

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III. Congenital Melanocytic Nevus (CMN) Treatment

(A) Medical Dilemma and Patient Experience

1. Surgeons hesitate to recommend lasers (incomplete removal) and surgery (high risk), limiting patient options.
2. Case: 2016 child with lip nevus treated unsuccessfully in 2-3 hospitals.

(B) Case Study

1. After multiple visits and internal debate, CO₂ laser was tried.
2. Parents informed about hypertrophic scar risk, but lighter than original pigment.

(C) Technical Details

1. Preserve lip red zone moisture retention; abrade to papillary dermis.
2. Papillary dermis is vascular-rich and relatively safe depth.
3. CO₂ laser skills improved over 7 years; better outcomes now.

(D) Outcomes and Follow-up

1. Minimal visible scars post retreatment; microscopic pore changes remain.
2. Complete pigment removal documented; family agreed to case publication.

(E) Innovations in Treatment

1. Use foot pedal frequency control (5-10 Hz) replacing continuous irradiation.
2. “Rapid pulsed” firing (3-4 short pulses) minimizes thermal damage.
3. Manual pulse intervals significantly reduce heat injury.

(F) Key Points in Abrasion

1. Confirm depth involving vascular structures and skin appendages.
2. Repair capacity guides abrasion depth.
3. Control exudate and infection during wound care.

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IV. Tattoo Removal Treatment

(A) Standard Protocol

1. Fractional laser is the standard to avoid scarring and blistering.
2. Expert consensus and standards remain lacking.

(B) Mechanism

1. Carbon pigment heats explosively; heat buildup causes subcutaneous damage.
2. Fractional laser channels dissipate heat, protecting tissue.

(C) Operational Tips

1. Ensure laser reaches pigment layer — visible sparks (“fireworks” effect).
2. Avoid insufficient depth and incorrect energy.

(D) Treatment Details

1. Use super-pulse mode with shortest intervals to minimize heat injury.
2. Bleeding indicates dermal penetration; thermal damage differs from conventional pigment treatments.

(E) Combined Treatments

1. Three-step: fractional laser pretreatment → 755 nm laser + 20-min cold compress → 1064 nm laser second treatment.
2. Monitor carbonization; increase sessions as needed.
3. Use 755 nm for superficial pigment, 1064 nm for deeper pigment.

(F) Complex Case Handling

1. Combine abrasion, dense fractional laser for scar repair, and laser pigment removal.
2. Focus inflammation control in hypertrophic scar phase; morphology repair in stable phase.

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V. CO₂ Laser in Scar Ablation and Regeneration

(A) Depressed Scar Treatment

1. Depressed scars are absolute indication for fractional laser; differentiate from hypertrophic scars.
2. Regeneration depends on undamaged surrounding tissue.
3. Maintain fractional spot spacing (~1.5-1.8 mm) to avoid complete necrosis.
4. Use lower energy than for hypertrophic scars.

(B) Acne Scar Treatment

1. All acne scars treated via “abrasion + regeneration”.
2. Wide shallow scars: fractional laser (diameter >3 mm, depth <1 mm).
3. Ice pick scars: mechanical abrasion (diameter <1 mm, depth >2 mm).
4. Traditional mechanical abrasion superior but requires 1-2 weeks dressing.
5. Scar shape reflects tension direction; abrasion combined with tissue release.
6. Cup-shaped scars require full-caliber abrasion; edges heavier.
7. Warn patients erythema phase is more obvious than pigmentation.
8. Post-abrasion combine silicone dressings with plastic wrap.

(C) Burn Scar Treatment

1. Dermal loss causes depressions from collagen/elastin deficiency.
2. Combine fractional laser/microneedling, nano-fat grafting, and mesotherapy.
3. Early treatment preferred; includes skin prep, cosmetic suturing, botulinum toxin, pressure garments.

(D) Ablation vs. Carbonization

1. Control irradiation time (~0.3 s/spot) to achieve ablation without carbonization.
2. High-quality CO₂ lasers produce clean ablation; poor devices cause carbonization.
3. Follow “three-fast principle”: fast positioning, fast action, fast withdrawal.

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VI. CO₂ Laser in Skin Rejuvenation

(A) Modes

1. Resurfacing mode for pore-free zones: energy 40-50 mJ.
2. Fractional mode for sebaceous glands: energy 100-120 mJ.
3. Ideal endpoint: uniform micro-bleeding spots, not isolated white spots.

(B) Effects on Sebaceous Glands

1. Penetrate 1.5-2 mm to reach sebaceous glands.
2. Oily skin: energy >100 mJ, 1.5 mm spacing.
3. Post-treatment salicylic acid prolongs effects.

(C) Tightening Effect

1. 120 mJ repeated 3 times (~6 passes) gives noticeable tightening.
2. Best for thick stratum corneum, oily skin.
3. Prevent prolonged erythema (3-6 months).

(D) Melasma and Pigmentation Treatment

1. Select patients with large pores, good barrier; avoid dry/sensitive skin.
2. Use 40-50 mJ balancing safety and effect.

(E) Combined Treatments

1. Laser microchannels plus acids (salicylic/fruit acid).
2. Micropores enhance topical absorption; apply meds within 30 minutes.

(F) Summary

1. “Damage-regeneration” is treatment core.
2. Domestic CO₂ lasers match imported when thermal damage well controlled.
3. Precise thermal control expands indications.

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VII. Post-Class Q&A: Practical Insights for Clinicians

(1) Medications After Fractional Laser

• Use Yifu and MEBO ointment immediately; expensive depigmentation products unnecessary.
• This combo optimizes pigment treatment cost-effectively.

(2) Depression Abrasion

• Energy >5 mJ, pulse width <20 ms reduces carbonization.
• Single-pass smoothing ideal.
• Standard glass CO₂ fractional lasers sufficient; RF upgrades optional.

(3) Syringoma Treatment

• Avoid large-area abrasion; precise point treatment on central ducts.
• Multiple sessions needed; combine abrasion with manual fractional laser.

(4) 1064 nm Laser

• Effective for narrow, deep acne pits.
• High energy & frequency; early bleeding more, but faster recovery.
• Evaluate skin tension; botulinum toxin aids in tense skin.

(5) Pigmentation Treatment

• Focus on repair; microneedling or skin boosters preferred.
• IPL for inflammatory acne only.
• Lasers do not directly target pigmentation.

(6) Fractional Laser Erosion Prevention

• Clean, disinfect strictly; compress dressings if heavy exudate.
• Maintain reasonable treatment spacing.
• Proper technique minimizes infection and scarring.

(7) MEBO vs. Yifu

• MEBO during immediate post-treatment heat dissipation and evening.
• Yifu during crusting phase (72 hours post), daytime care.
• Alternate morning/evening after three days for moist healing synergy.

(8) Acid Treatment After Fractional Laser

• Large white frost areas require cleaning; scattered frost does not.

(9) Senile Spot Treatment Parameters

• Fractional laser spacing <1.0 mm; IPL spacing ~1.2 mm.
• Acute phase (0-3 days): keep dry, MEBO only if redness; avoid erythromycin ointment.
• Repair phase: start growth factors, MEBO at night; monitor contraction.

(10) Device Parameter Tuning

• First reduce pulse width, then adjust interval; test on paper.
• Avoid carbonization; common issue with domestic devices.

(11) Advice for Young Doctors

• Practice first, theory later.
• Gain clinical experience to understand device principles.
• Develop personalized protocols.
• Philosophy: “Get started, then refine.”

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Final Thoughts

CO₂ laser treatments demand precise control, careful patient selection, and combined modality approaches for best results. Mastery comes from ongoing practice and attention to technical nuances. With this knowledge, clinicians can confidently address a broad spectrum of dermatological challenges—from pigmentation and scars to rejuvenation—delivering safe, effective, and lasting outcomes.