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laryngology > Lasers and Airway Surgery > Flashcards

Lasers and Airway Surgery Flashcards

1
Q

What does LASER stand for?

A

Light amplification by Stimulated Emission of Radiation

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2
Q

What does chromophore mean?

A

Chromophore is a material, present either endogenous in tissues or exogenous, which absorbs particular wavelengths depending on its absorption coefficient

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3
Q

What are the features that are unique to laser light

A

“MUCH”

M: Monochromatic (= single wavelength)
U: Unidirectional light travel (“Collimated”, no divergence)
C: Coherent - Temporal (waves oscillate in phase) and Spatial (photons equal and parallel along wavefront)
H: High intensity

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4
Q

Describe the physics of laser light emission. How does it work?

A
  • Electrons orbit around a nucleus at stable energy level
  • Photon bumps electron into a higher energy level, putting it in an excited/unstable state
  • If struck by a second photon, the unstable electron emits 2 identical photons (= STIMULATED EMISSION) - these have identical wavelengths, direction, and travel (= laser liight characteristics)
  • Each emitted photon stimulates emission of further identical photons in a cascading effect
  1. HIGH REFLECTANCE MIRROR: This will perpetuate cascade by directing photons back through laser medium
  2. PARTIALLY TRANSMISSIVE MIRROR: This allows transmission of small amount of coherent (in-phase) photons (= “laser beam”)
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5
Q

What are the 6 required components for production of laser light?

A
  1. POWER SOURCE (electrical current)
  2. STIMULATION
  3. ACTIVE LASER MEDIUM (Contained in optical/resonant chamber)
    - Solid cystal (e.g. ruby, Nd:Yag - neodymium-doped yttrium aluminum garnet)
    - Liquid (e.g. dyes)
    - Gas (e.g. CO2, helium, neon)
    - Semiconductor (e.g. GaAs)
  4. FRONT AND REAR MIRRORS
    - High reflectance: amplification
    - Partially transmissive: emission
  5. OUTPUT COUPLER/DELIVERY SYSTEM
    - Fiberoptic (most common)
    - Articulated arm (e.g. CO2)
  6. LASER BEAM
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6
Q

What elements of laser light are variable/adjustable?

A
  1. Power wattage (least important)
  2. Spot size (mm^2) - can be modified by changing focal length OR working distance
  3. Exposure time and frequency

Others:
1. Fluence - energy density = total energy (power density) per unit of area
2. Irradiance - power density per unit of area

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7
Q

Define irradiance vs. fluence

A

Irradiance:
- = Power density = power (watts = J/sec) / Spot size (cm^3)

Fluence:
- = Energy deensity = power density x time = J/cm^3

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8
Q

What are the different energy effects that laser light can have on tissue?

A
  1. Photodynamic effect (low): Activate biochemical substances; penetrates 300-500µm
  2. Electromagnetic effect (low): Stimulates biologic tissue; penetrates 300-500µm
  3. Thermal effect (low): Denatures biologic proteins; penetrates 300-500µm
  4. Thermal effect (medium): Coagulates biologic tissues; penetrates 500-600µm (60-70degC)
  5. Thermal effect (high): Vaporize biologic tissues; penetrates ≥600µm (100degC)
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9
Q

What are the tissue effects at various temperatures?

A
  1. 60-65 degC = Denaturation of proteins
  2. 100 degC = H2O vaporized
  3. > 100degC = Smoke, gas, carbon produced.
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10
Q

What are the three main things that determine the tissue effect of the laser?

A
  1. Laser type
  2. Tissue type
  3. Pulse vs. continuous wave of laser
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11
Q

What are 4 ways that tissue responds to energy (ie. laser energy)?

Another way to ask: What are the 4 tissue effects of lasers?

A
  1. Reflection
  2. Absorption
  3. Transmission
  4. Scatter/diffraction

“RATS”

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12
Q

What are the zones of wound injury in lasers?

A
  1. Zone of Tissue Vaporization: A few flakes of carbon debris
  2. Zone of Thermal necrosis: Small vessels, nerves, and lymphatics are sealed
  3. Zone of Thermal conductivity and repair

Vancouver 187

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13
Q

Describe the various beam/pulse structures a laser can have, and examples of each.

A
  1. PULSED VS. CONTINUOUS
    - Pulsed permits heat dissipation –> minimizes thermal damage to surrounding tissue
    - e.g. Pulsed: Pulsed dye
    - e.g. Continuous: CO2, Nd:YAG
  2. ABLATIVE VS. NON-ABLATIVE
    - Ablative coagulates and causes tissue necrosis
    - Non-ablative heats dermis without epidermal destruction
    - E.g. Ablative: CO2, Er:YAG
    - E.g. Non-ablative: Pulsed-dye, Nd:YAG
  3. CONFLUENT VS. FRACTIONED
    - Confluent produces single wide burn area (~crop circle)
    - Fractionated produces many small burn areas (~lawn aeration) - results in less scarring and pigment changes
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14
Q

What are the benefits of fractionated laser beam? List 4

A
  1. Intervening epithelial islands allows for faster healing
  2. Reduced scarring
  3. Reduced hypopigmentation
  4. Minimize thermal damage to surrounding tissue
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15
Q

What is the Super Pulse Peak?

A

Term that describes the point where high peak power exceeds the vaporization threshold
- Superpulsed laser (905nm) produces high powered light in billionth-of-a-second pulses
- High power with deep penetration, short duration
- Short duration allows for thermal relaxation time of the tissues –> tissue cooling and less thermal damage overall

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16
Q

List the full names of the following common laser acronyms below:
1. Ar-PDL
2. KTP
3. FL-PDL
4. Nd:YAG
5. Ho:YAG
6. Er:YAG
7. Thu:YAG

A
  1. Ar-PDL - Argon pulsed-dye laser
  2. KTP - Potassium-titanyl-phosphate
  3. FL-PDL - Flash lamp pulsed-dye laser
  4. Nd:YAG - Neodynium:Ytrium-Aluminum-Garnet
  5. Ho:YAG - Holmium:YAG
  6. Er:YAG - Erbium:YAG
  7. Thu:YAG - Thulium:YAG
17
Q

For each of the following lasers, discuss the wavelength, color, depth, chromophore, and application in ENT, and disadvantages where applicable:
1. Argon
2. Ar-PDL
3. KTP
4. FL-PDL
5. Nd:YAG
6. Ho:YAG
7. Er:YAG
8. Thu-YAG
9. CO2
10. Blue Laser (Photoangiolytic laser)

A

1nm = 0.001µm
1000nm = 1 µm
(Convert µm to nm by x1000)

ARGON:
1. Wave: 488 and 514nm (blue-green)
2. Depth: 0.8mm
3. Chromo: Hgb (red)
4. Application:
- Stapedotomy most common - need to place drop of blood on stapes to initiate absorption of laser energy, b/c argon reflects off white tissue (ie. bone)
- Pigmented lesions (since absorbed by Hgb)
- Argon lasers transmits through clear fluids (e.g. vitreous)

AR-PDL:
1. Wave: Argon 514nm, PDL 630 nm (tunable red) - targets the 630nm
2. Depth: 0.8mm
3. Chromo: Hgb (red)
4. Application:
- Photodynamic therapy for malignant tumors after IV injection of photosensitizer hematoporphyrin derivative (absorbs at 630nm red light) – this hematoporphyrin goes into tissues but stays longer in neoplastic tissue, so after a few days the concentration is higher in tumor and low in normal cells

KTP:
1. Wave: 532nm (green)
2. Depth: 0.9nm
3. Chromo: Hgb
4. Application:
- Similar to Argon but more strongly absorbed by Hgb
- Coagulation, debulking (e.g. larynx, nasal polyps) - less sticky for coagulation compared to CO2
- Tonsillectomy, pigmented dermal lesions
- Chronic ear surgery (e.g. removal hyperplastic infected mucosa, disarticulating stapes suprastructure in complete cholesteatoma removal, removal of middle ear implants)
- Fiberoptic use

FL-PDL:
1. Wave: 585nm (blue green)
2. Depth: 2-4mm
3. Chromo: Oxyhemoglobin (absorption peak 577nm)
4. Application:
- Pigmented vascular lesions (e.g. capillary malformations, hemangiomas, port-wine stains, vocal fold ectasias, vascular polyps, etc.)

Nd:YAG:
1. Wave: 1064nm
2. Depth 2-4mm (deep zone of coagulation)
3. Chromo: Hemoglobin; weakly by water
4. Disadvantages: Less predictable depth of tissue penetration, widespread tissue damage, lacks precision
5. Application:
- Pigmented vascular lesions (e.g. venous malformation, lymphatic malformations)
- HHT
- Coagulation and debulking (e.g. obstructive tracheobronchial lesions, obstructing esophageal lesions, oral cavity/oropharynx tumors
- Transmits through clear fluids, e.g. can be used in bladder
- Can be used through fiberoptic lasers

Ho:YAG:
1. Wave: 2100nm
2. Depth: 0.4µm
3. Chromo: Water
4. Application:
- Sinus surgery (good hemostasis, soft bone ablation is readily controlled) - howevere increases post-op edema

Er:YAG:
1. Wave: 2940nm
2. Depth: < 2µm
3. Chromo: Water
4. Application (very clean incisions with minimal thermal damage; not suitable for highly vascular tissue)
- Skin resurfacing of wrinkles
- Rhinophyma
- Ear/Stapes surgery (bone)

Thu:YAG:
1. Wave: 2013nm
2. Depth
3. Chromo: Water
4. Disadvantages: More ablative than photoangiolytic lasers (e.g. PDL/KTP) causing more periphreal damage such as delicate vocal fold epithelium and SLP layers
5. Application: Simiilar to CO2 laser
- TORS

CO2:
1. Wave: 10600nm (invisible)
2. Depth: 0.03mm
3. Chromo: Water
4. Application: Wide versatility due to minimal adjacent thermal effects, laser independent of tissue color
- Coagulate and necrosis (e.g. papilloma/RRP, SGS, larynx, mucosa, stapes)
- Rhinophyma
- Skin resurfacing
- Very wide range: polyps, leukoplakia, papillomas, ysts, granulomas, benign larynx conditions, webs, SGS, bilateral VF immobility, cordotomy, arytenoidectomy, capillary hemangiomas, etc.

BLUE LASER:
1. Wave: Between 400-500nm
2. Chromophore: Hgb
3. Application - Photoangiolytic laser, similar to KTP

18
Q

What are the wavelengths of the Sclerolaser and Q-switch ruby laser?

A

Sclerolaser = 600nm (orange)
Q-switch Ruby = 694nm (Red)

19
Q

What are the typical laser settings for stapes and laryngeal surgery?

A
  • 1-3W power
  • 0.1-0.5msec pulse
  • Small spot size
20
Q

Describe the required elements of safety protocol for laser use

A

A. EYES
1. Laser goggles for everyone in room
2. Moist gauze over patient’s eyes

B. SKIN
1. Damp towels over all exposed patient skin

C. AIR
1. 2 suctions for smoke evac
2. Special laser mask if risk of aerosolized particles (e.g. HPV)

D. ANESTHESIA
1. Non-flammable gas (e.g. Halothane)
2. Minimize O2 (< 40%)
3. No nitrous
4. Non-flammatory ETT (e.g. silicone, stainless steel)

E. INSTRUMENT/PREP:
1. No plastic instruments
2. Dulled/non-reflective material
3. Alcohol-free prep
4. Water on set-up
5. Pre-test laser accuracy on a wet tongue depressor

F. ROOM:
1. Sign on door indicating laser use
2. Controlled entry/exit
3. Metal garbage can with lid in room
4. Fire extinguisher in room
5. Constant communication (“Laser on, Laser off”)

G. ADMINISTRATION:
1. Standard operating procedures
2. Trained staff in laser
3. Continued education

21
Q

What are 11 things that should be done with a tube fire during laser laryngoscopy?

A
  1. Alert anesthesia
  2. Stop ALL gases including Oxygen!!
  3. Disconnect circuit at ETT side (always do this before removal)
  4. Remove damaged ET tube and throw in cold water, examine tube for any possible other parts missing
  5. Douse the fire with saline in the airway
  6. Mask ventilate with 100% O2 (unless concern there is more material in airway)
  7. Reintubate ASAP with patient paralyzed to facilitate ease of intubation
  8. Intraoperative bronchoscopy to remove any charred debris and assess extent of damage
  9. Intravenous steroids and antibiotics
  10. ICU monitoring with delayed extubation and high humidity oxygen, PPI ± tracheostomy ± antibiotics
  11. Re-examination of subglottis and trachea in 3-5 days to assess extent of further airway compromise
22
Q

How do you prevent airway fire when using a laser?

A

A. Reduce the flammability of the ETT
1. Laser guarded/resistant tubes (wavelength specific)
2. Never use polyvinyl ET tubes (not laser resistant, produces toxins if catches fire)
3. Do not wrap polyvinyl tubes (used to be recommended but now NOT)
4. Cuff of ETT has to be inflated with saline + methylene blue (double cuff)
5. Saline soaked pledgets in the subglottis to protect ETT cuff
6. Use microlaryngeal operating platform to further protect the cuff (i.e. shield below the fold that is being lasered)
7. Pre-operative plan and checklist for airway fires

B. Reduce fuel (ie. oxygen) for potential fire
1. FiO2 < 30%
2. Avoid N2O (nitrous oxide) and volatile anesthetics
3. Use TIVA
4. Intermittent extubation
5. Jet ventilation

23
Q

How do you control / manage the airway when using laser?

A
  1. Tracheostomy
  2. Jet ventilation
    - Subglottic (Mon-jet/Hunsaker) ventilation tube
    - Supraglottic jet ventilation (via port within laryngoscope or attached to laryngoscope)
  3. Intubation with a laser guarded tube
  4. Intermittent extubation
  5. Spontaneous respiration (harder in adults)
24
Q

What are the surgical risks of microlaryngoscopy?

A
  1. Airway scarring
  2. Dental damage
  3. Lingual artery/nerve compression (10-20%) - altered taste and sensation
  4. Anterior glottic web
  5. Pneumothorax
  6. Tracheal rupture
  7. Arytenoid dislocation
  8. Esophageal/hypopharyngeal perforation
25
Q

What are the risks of jet ventilation?

A
  1. Pneumothorax/ pneumomediastinum
  2. Hypoventilation/hypercarbia
  3. Abdominal distention
  4. Distal seeding of HPV lesions
  5. Decreased cardiac output and venous return
  6. Egress - increased retained volume, increased CO2
  7. Death
26
Q

Describe the post-operative care after phonomicrosurgical procedures. What are causes of post-op dysphonia and what is the management?

A
  1. Voice rest (2-14 days, depending on procedure)
  2. Hydration
  3. Reflux treatment
  4. Strobe/scope patient at the end of voice rest (if adequate epithelial coverage –> light voice use –> gradual return to normal voice use)

Post-operative dysphonia:
A. Causes:
- Vocal fold scar
- Dependent edema
- Granulation tissue
- Failure ot microflap
- Recurrence of pathology
- Unreasonable expectations of patient

B. Treatment (according to etiology)
1. PPI
2. Steroid injections
3. Voice rest
4. Revision surgery
5. Voice therapy

laryngology (8 decks)

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