LASER BRONCHOSCOPY

Notes for a talk at the Radiation Therapy Conference-City of Hope February 16 1990.

I have been unable to find any accurate figures on what % of lung cancers cause major bronchial obstruction, but certainly the figure must be very high. Adeno, large cell and bronchioloalveolar carcinoma all arise peripherally and usually do not obstruct central bronchi until far advanced. Squamous carcinoma often arises centrally and often obstructs major bronchi. Once growth into the lumen of the bronchus begins, there is a preferential endobronchial growth, so that the tumor will protrude out of the bronchus containing the primary growth to obstruct adjacent major bronchi, and eventually the trachea. Cough and hemoptysis result, and can be debilatating. Increasing luminal obstruction results in wheezing, shortness of breath and , with the onset of occlusion, distal atalectasis, obstructive pneumonitis and cavitation. Sepsis and massive hemoptysis are terminal events. It is axiomatic that essentially all patients who are long term smokers and have significant COPD. Further loss of function by obstruction of bronchi serving functioning lung tissue can worsen dyspnea and precipitate respiratory failure.

While oat cell carcinomas also have a central distribution, they less often cause obstructive problems. In any case, obstruction is usually manangeable with radiation and chemotherapy and seldom represents an indication for laser ablation in my experience. External beam radiation therapy is presently the first line therapy of obstructive lung cancer. It has a high incidence of success, but it also has a number of disadvantages. It cannot treat, in an urgent fashion, severe respiratory failure 2nd to obstruction. Swelling of tumor can temporarily exaccerbate obstruction on initiation of treatment in some cases. Retreatment with radiation therapy is usually not feasible. While most cancers with central obstruction are unresectable at presentation, occasionally, slow growing carcinomas or bronchial adenomas can be resected by pneumonectomy or sleeve resections. Occasionally cryotherapy, balloon dilatation and forceps debulking can be efficatious. Again, I can find no good statistics regarding the % of successful reopening of bronchi by radiation therapy. In my personal experience, would estimate 60-70% Recurrence and reobstruction is common. Management of radioresistant obstruction, recurrent obtruction after rorx and acute obstruction that will not allow time for radiation effect were difficult problems before the introduction of laser bronchoscopy by Dumon. Such obstructions can be removed piecemeal with a rigid bronchoscope and forceps as detailed in a large series recently reported by Grillo et. al from Massachusetts General Hospital. Such forceps removal is, in my experience, a hazardous proceedure, during which, bleeding can become a major problem. Even a small amount of clot can close the residual lumen and result in asphyxiation.

There is nothing mystical about laser bronchoscopy. The laser is merely an adjunctive tool that permits the ablation of tumor or scar tissue under controlled circumstances with a minimum of bleeding.

L.A.S.E.R.

Light Amplification by Stimulated Emission of Radiation

was first produced by Maiman in 1960. Stimulated emission is a process whereby an atom in an excited state returns to the ground state, after an interaction with an incident wave of wavelength corresponding to the absorption energy wavelength. The net result of such interaction will be two waves of the same wavelength traveling in the same direction, and in phase with one another.

Laser components:

  1. Active Medium- the atoms capable of being stimulated e.g.CO2, YAG (a crystal of Yttrium- Aluminum-Garnet doped with Neodymium ions),argon gas,dye etc. are contained in a
  2. Resonator- the chamber that contains the active medium into which the
  3. Pump-provides the energy input to stimulate emission from the active medium, thus producing photons of light which are focused by
  4. Total and Partial Reflectors- at each end of the resonator.

The laser beam of intense , coherent light exits through the opening in the partial reflector.

The biologic effect of the laser is dependent on the intensity, duration and wavelegnth of the beam directed to the tissue. The wavelength of the beam is monochromatic and varies with the active medium. Absorption of laser light can be enhanced by photosensitizers, such as hematoporphyrin derivative (HPD). Lasers can be classified by the active medium:

  • CO2= infrared 10,600 nm . This wavelength is absorbed by water and accordingly there is very little penetration depth. It is suitable only for small lesions e.g. larynx. In addition it cannot be transmitted down a fiberoptic fiber. The optical coupling to a rigid bronchoscope is therefore, complicated and expensive. It is also inefective in coagulation of vessels >2mm in diameter.
  • Argon= blue-green , absorbed by chromagens melanin and hemoglobin. Can be transmitted via fiberoptics. Primary use is retinal and for port-wine angiomas.
  • Argon Dye=tuneable wavelength at low power, but fiberoptic capable, and displays high absorption by hematoporphyrin derivative (HPD) which makes it ideal for treatment of superficial lesions that concentrate HPD such as bronchogenic carcinoma.
  • YAG= near infra-red 1060 nm. Poor absorption in water and hemoglobin means deep penetration. This property, combined with fiberoptic compatability and high power >100 watt/sec, make the YAG laser a powerful tool, to coagulate at low power, or vaporize at high power , bulky endobronchial tumors.

LASER FACILITY

Pre-operative Evaluation

  • PFTs with flow volume loops
  • MRI superior to CT
  • Coagulation Panel
  • Ventilation-perfusion scan

General anaesthesia

  • FIO2 must be kept below 40% because of the risk of endobronchial fire
  • Avoid curare,pavulon because of post-operative respiratory depression.
  • Non flammable anaesthetic gases are mandatory.
  • An anesthesiologist experienced in the technique is important.
  • Oximetry monitoring is mandatory.
  • All persons in the room must wear protective glasses to avoid the risk of laser eye injury.
  • Plumbing- increased water for machine cooling
  • Electrical- special generator for high power needs.
  • RN Laser safety nurse
  • Laser operation-fiber bundle repair
  • Laser- $200,000maintainance- backup?

Equipment

  • Dumon rigid laser bronchoscope with ventilating port, laser channel and suction channel.
  • Disposable large bore suction catheters.
  • Biopsy forceps with telescope.
  • Flexible bronchoscope.
  • Endobrochial balloon catheters in case of massive hemorrhage.

TECHNIQUE

It is my practice to examine the patient with a flexible bronchoscope under local anaesthesia. to assess whether the anatomy is suitable for laser ablation. In the ideal situation, there is a high grade, but not complete, obstruction of the trachea or a main stem bronchus. Extrinsic compression is not manageable by laser ablation. If the lumen is completely obstructed, and the distal bronchus cannot be visualized, a number of problems arise. First, there is the danger ofstraying out of the lumen and perforating the bronchus, esophagus or major vessel. Second, the operator does not know how long the tumor obstruction is, nor whether distal bronchi are patent. Finally, tumors in either of the upper lobes can be technically impossible to ablate with the laser. If the patient is a reasonable candidate, he is transfered to a hospital with YAG laser equipment. Under general anaesthesia, the patient is intubated with the Dumon bronchoscope and the anaeshesia machine is connected to the ventilating attachment. The pharynx is packed with a moist guaze pack and the nares with vaseline gauze to produce a closed system. The patients eyes are securely covered by moist pads.

All OR personnel must wear protective eyewear.The door is locked and any windows covered. A sign warning that no entry is permitted is placed on the door. The laser fiber is then introduced and the aiming system checked. A ruby laser beam marks the target.

Continuous air flow through the laser fiber must be ensured to prevent overheating and damage to the fiber. Oxygen concentration must be kept below 40% to avoid the hazard of endobronchial fire or explosion. Inadvertant firing of the laser inside the working channel of the fiberoptic scope will destroy the instrument.The laser is set at 25 watts and 1/2 second burst duration.The plastic suction catheter is introduced through the suction lumen and suction checked.The visible tumor is coagulated using the low power setting and then vaporized at 50watts . Higher power 100 watt settings have resulted in pulmonary artery perforations and exsanguination. Smoke, clots and debris are removed with the sucker. Necrotic tumor can be removed with large biopsy forceps. Manipulation of the scope, the suction catheter, the laser fiber and the forceps is cumbersome and sometimes passage of a flexible bronchoscope facilitates aiming ot the laser fiber. Once the obstruction is relieved, distal mucous secretions are aspirated and the bronchi lavaged. The remnant of the tumor is then ablated as completely as possible. This can be a tedious process especially if the tumor is vascular. Dilute epinephrine is usually effective as a hemostatic agent. Even small amounts of clot can precipitate lethal airway obstruction. In this case the bronchoscope is passed distally to ensure ventilation and to tamponade the bleeding site. The operator must at all times visualize the cross sectional anatomy surrounding the bronchus and at all costs avoid the laser beam penetrating beyond the bronchial lumen in areas where large pulmonary artery branches pass over.

It has been my practice to leave the patient intubated at the end of the proceedure and ventilate overnight. If reexpansion of obstructed lung does not occur, follow up bronchoscopy for removal of necrotic debris and clots is indicated. Nebulized xylocaine is helpful in controlling cough.

HPD- Phototherapy- I have no personal experience with the use of phototherapy. It has the advantage of being technically simpler than YAG laser endoscopy. It can be performed under local anaesthesia, using a flexible bronchoscope, in a short period of time, by an endoscopist without special skills. Disadvantages include the possibility of severe skin reactions if the patient is non-compliant in avoiding sunlight for a period of time following injection of HPD, and delay in achieving the therapeutic result. Also, follow=up bronchoscopies to remove necrotic tissue are sometimes required. Phototherapy is optimal for small tumors and in situ cancer. The Ohio State University experience demonstrates that YAG laser ablation and HPD phototherapy are complementary rather than competitive and can often be used in series to achieve maximum palliation.

Technique: HPD 2.5-5.0 mg/kg 3-5 days pre-op

General anaesthesia

Flexible bronchoscopy 630 nm therapeutic light focused on tumor via an argon pumped tunable dye laser

INDICATIONS:

  • 1. Obstructive unresectable bronchogenic carcinoma

    • a. acute respiratory distress-previously untreated

    b. recurrent following radiation therapy

  • 2. Obstruction by metastasis
  • 3. Unresectable bronchial adenoma
  • 4. Assess resectability of tumors ( e.g. a tumor presenting in the trachea may be polypoid arising in the right upper lobe and be resectable)
  • 5. Improve conditions of surgery by preliminary relief of obstruction
  • 6. Stop hemorrhage from tumor or other disease
  • 7. Open a channel for brachytherapy or phototherapy
  • 8. Open benign stricture
  • 9. Tracheostomy granulations
  • 10. Foreign body
  • 11. Broncholithiasis

COMPLICATIONS:

  • 1. The most frequent problem is failure to achieve an adequate airway. This is usually a result of poor selection. Upper lobe lesions, especially the RUL are difficult to open because acute angle of takeoff from the RMB cannot be achieved with current fiberoptic equipment. If the lumen is completely occluded, it can sometimes be very difficult to safely open. Furthermore, the situation distally is unknown. It is disappointing to spend a number of hours opening a main bronchus only to find that distal bronchi are extrinsically compressed or filled with unmanageable tumor.
  • 2. Hemorrhage is a common problem, but fortunately is usually mild and represents only a nuisance. Fatal hemorrhage is rare if power settings are kept low and due caution to restrict the laser beam to tumor is exercised.
  • 3. Asphyxia is usually a consequence of bleeding. It has been observed that 100cc of blood is sufficient to pack the airway with fatal result. An even smaller quantity will suffice to occlude a tight stenosis in the trachea.
  • 4. Tracheoesophageal fistula can occur in LMB or tracheal lesions.
  • 5. Mediastinal emphysema.
  • 6. Delayed hemorrhage is a known complication of YAG laser, phototherapy and radiation therapy. It occurs a few weeks after treatment and probably results from necrosis of tumor that had invaded a nearby pulmonary artery. Such invasion, noted best by MRI, should raise a red flag in the therapists mind.
  • 7. Endobronchial fire can occur with O2 concentrations greater than 40%
  • 8. Eye injury to the patient or OR staff can be caused by violation of safety precautions.

RESULTS

The large experience of Dumon in France has been repeated in numerous centers in Italy, Boston, Detroit, Rochester, Los Angeles and San Diego. None of the data is in the form of controlled prospective studies. Selection factors make it hard to compare results at different institutions. Clear trends emerge clearly from the published case material.

MORTALITY

is less than 2% in the immediate perioperative period.

  • EXCELLENT results are obtained in approximately 50% of cases. Best results are in patients with tracheal or main bronchial lesions that are non-occlusive and involve single, short segments. Improvement is mainly in symptoms, although some improvements in PFTs can be documented.
  • FAIR results with incomplete relief of symptoms occur in another 25%.
  • POOR results are unfortunately not unusual and reflect advanced disease and improper selection. Closer surveillance of lung cancer patients, and a more liberal attitude to bronchoscopy when recurrent disease is suspected, might identify patients at an earlier stage, where disease is more treatable. Even highly successful airway re-opening will be of no avail if distal lung is destroyed or blood vessels are occluded. Atalectasis of lung tissue for more than 3 months is an unfavorable prognostic factor.

SURVIVAL

is approxiately 4-6 mo with YAG laser therapy alone

RECURRENCE

of obstruction is common requiring addiational laser'sessions. Only 25-30% of patients are alive without need for additional therapy at 4 mo.

ADJUVANT THERAPYis therefore required for maximum palliative effect.

BRACHYTHERAPY

has been shown to extend survival beyond a mean of 6 months

PHOTOTHERAPY

can also be used to extend the palliative effect of the YAG laser.


Frederic W. Grannis Jr. M.D
If you have trouble contacting me with the address above, I may also be reached at 76516,2333@compuserve.com and at fgrannis@cris.com

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