Jan Fanta, Lukáš Havluj,

Surgical Clinic of 3rd Medical Faculty of Charles University, Šrobárova 50, Prague 10, CZ

 

ABSTRACT

This article is a general overview of possibillities and indications of lasers in the lung open surgery. It contains contemporary knowledge from lung laser medicine, deals with differences between interactions of CO₂ and Nd:YAG laser on lung tissue. Basic Nd:YAG laser lung procedures are briefly introduced and described.

 

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The endeavour of physicians to use laser technique in medicine dates back to the beginnings when the first ruby laser in the world was designed (physicist Theodore H. Maiman, 1960). In the year 1961 Leon Goldman applied curative laser in dermatology and in the same year Ch. J. Campbell used laser therapy in detachment of the retina. (1,2). In the literature of 1968 - 1972 we can read articles on the first experiments with using the laser in abdominal and thoracic operations. The articles under discussion dealt with the usage of CO2 laser designed for surgical purposes in 1965 and put into clinical practice in 1972 by plastic surgeon Isaac Kaplan. (2). In the year 1972 monofilamental flexible light-conductive fibre was invented and produced. This revolutionary discovery enabled the transmission of Nd: YAG laser beam to any locality in the body accessible to endoscopic instruments. The era of fibro-endoscopy had begun. Peter Kiefhaber managed to stop the bleeding of the stomach mucosa by using the method of gastroscopy and Nd: YAG laser in the year 1975. In the same year J.Christensen carried out complete thoracotomy by using CO2 laser. (3). In 1987 the first positive reports on the usage of Nd: YAG laser in open lung surgery appeared - K.Moghissi (Cottingham), J. Fanta (Prague), M. Tos (Milano). All three clinics, independently, certified the exceptional effects of Nd: YAG laser interaction with lung tissue. As hemo and aerostasis together with Nd: YAG laser are almost perfect, we consider Nd: YAG laser to be a useful and suitable supplement to lung surgical amrmanetarium. 

Nd: YAG (Neodymium: Yttrium Aluminium Garnet) laser is an apparatus which emits the beam with a surprisingly effective result on the lung. In lung operations the Nd: YAG laser is safer and more sophisticated when compared with e.g. CO2 laser. We shall briefly deal with the basic qualities of Nd: YAG and CO2 lasers and introduce their priorities and their insufficiencies. 

In open surgery, nowadays, we mostly work with two types of lasers: CO2 and Nd: YAG laser. The mentioned lasers can be distinguished from each other by different characters of the emitted beam. The wavelength of CO2 laser beam is 10.600 nm and is invisible to the eye. It is absorbed already in small volumes of tissue and hardly penetrates the liquid environment. Therefore it is effective in the mere distance of 0,1 mm - 0,2 mm from the surface. Regarding the small penetration into tissues, CO2 laser has not such coagulation abilities that would predetermine it for operation on such well-perfused organs as lungs and liver. CO2 laser incision is very sharply demarcated, it is clear, delicate but superficial. With its thermic effect CO2 laser beam is able to keep haemostasis in those regions that are interlaced with blood vessels of maximum 0,5 mm in diameter. Here we use high-discharge CO2 laser (80W - 110W); lower class of CO2 lasers (16W - 35W) are not suitable for major intraabdominal and thoracic surgeries. We successfully use CO2 laser when we need to make a very precise, sharply demarcated incision with little thermic penetration into the surrounding; therefore its main indicative domains are plastic surgery and neurosurgery. Besides the little coagulation ability the CO2 laser beam has another disadvantage which limits its use: it is the manner of transmission to the target - CO2 laser beam cannot be transmitted by light-conductive fibre. We transmit the CO2 laser beam to the place of destination by a system of articulated tubes and arms inside which the beam moves by reflection from exactly adjusted mirrors. We need not stress that this is a complicated technical apparatus device which takes up much room in the operating theatre. 

Nd: YAG laser beam, in contradiction to CO2, penetrates deep into tissues and liquid environment makes no impediment for it (is of no barrier to it). By causing coagulative necrosis the laser beam destroys tissues in wide surrounding, and stops the bleeding. It is an excellent destructive device which does not abound in exact incision line; it is rough and more suitable for surface evaporation of tumour tissue. The Nd: YAG laser beam may have 1064nm wave length with output up to 120W, or 1319 nm with output over 50 W. It is also invisible, but, above all, it can be transmitted by flexible light-conductive fibre. The 1064 nm wavelength guarantees that great destructive, coagulative and necrotic effect, coarse (rough) impairment of tissues. If we give preference to the second Nd: YAG laser wave (1319 nm) with its qualities it approaches those of CO2 laser beam. The penetration of this laser through liquid environment is worse, it is absorbed by tissues, the incision is narrower and coagulation properties are worse. That is why rather the 1319 nm wavelength is used and more like a scalpel than a coagulation instrument. The first wave length (1064 nm) has better coagulation qualities than incisive. Lesion caused by 1064 nm wavelength is wide, it does not have sharp borders and induces thermo-destructive changes which afflict extensive surrounding. 

When working with Nd: YAG laser in lung and abdominal surgery we exploit the conversion of light into heat in the interaction of laser beam with tissue (effect usually from 1 ms to 10 seconds). After the incidence on tissue, a part of the laser beam is reflected back from the surface a part is absorbed in the tissue, another part is dispersed and still another penetrates through the tissue. The effect itself, is caused, above all, but the absorbed beam and less by its dispersed part. The part of the reflected beam and the part transmitting a way through the tissue remain with out effect. The size of the destructive changes in tissue is influenced by two factors. Firstly the time (t) and period of irradiation, secondly the output of the laser (W). The cooperation of both mentioned factor results in the temperature of the diathermy of tissue given by the conversion if light into heat. In low outputs of the photic beam and a very short period of irradiation of the tissue, the thermic load need not have a destructive effect. In one-second action of high-output laser, the beam physically (by evaporation) destroys the tissue. 

 

Table no. 1. Dependence of Morphological Changes in Live Tissue on Conversial Temperature 

Temperature	Tissue response
43 - 45 °C	Diathermy without any greater damage ( the exception is: hypothermia )
45 - 60 °C	Decrease of enzymatic activity, tissue oedema.
60 - 65 °C	Denaturation of proteins. Coagulation necrosis.
80 - 100 °C	Denaturation of collagen, violation of cellulous membrane. Carbonisation. Loss of liquids, dehydration and shrinking of tissue.
> 100 °C	Mechanical destruction, ablation, vaporisation.

 

During lung operation it is important to keep the principal of bloodless preparation in the lung parenchyma and, at the same time, not to have the communication between lung tissue and pleural cavity open (to avoid postoperative broncho-pleural fistula). In other words: in lung surgery perfect hemostasis and aerostasis are of prime importance. We usually reach this by careful preparation of the lung parenchyma or, nowadays, by the stapler technique. The beam of Nd: YAG laser causes the most profound biological changes in the lung parenchyma; we were able to observe such changes e.g. in comparing with liver or spleen (2). This beam substitutes the lung surgeon's two mentioned tasks surprisingly well, and it also causes good hemostasis and aerostasis. We had repeatedly proved these effects in the course of two years in animal experimental surgery. After this experimental period the acquired experience was brought into clinical practice. Since 1987 we have performed more than a hundred lung surgeries with Nd: YAG laser in clinical practice; the acquired results correlate with those of foreign laser centres. As we use Nd: YAG laser in lung surgery mainly for secondary tumour diseases and less for benign tumours, we give preference to 1064 nm wave length which secures greater destructive, coagulative and even aerostatic effect. The exact scope of changes in lungs after continual application of Nd: YAG laser is shown in Table no.2. 

 

Table no.2. Histological Changes in Lung with Non-contact Application of Nd: YAG laser 

Wave length	Speed of transfer	Output	Depth of necrosis	Transitory zone	Hyperaemia zone
1 064 nm	5 mm/sec	70 W	4.7 mm	0.3 mm	3.8 mm

 

On the preparations made out after the irradiation of the lung by the mentioned parameters of the laser beam, we can recognise four layers of pathological changes: 

1) Zone of carbonisation, absolutely superficial, up to 0.1 mm; 

2) Zone of necrosis, very deep, exceeding 4.5 mm; 

3) Transient zone, 0.3 mm; 

4) Zone of congested tissue, > 3.5 mm. 

 

The pathological changes intervening into the depth of 8 - 10 mm from the surface (using 70 - 100 W outputs). 

 

On the basis of experimental surgery, and namely from the experience of clinical practice, we can advise with full responsibility indications to such lung operations( with the help of Nd: YAG laser can be performed with ease and, at the same time are safe and profitable for the patient. They are easy and safe because the laser beam allows clear and quiescent surgery, and profitable for the patient because there are only minimal blood losses and minimal consumption of extraneous material (e.g. staples, thread). The operations are more radical and greater sterility is guaranteed (high temperatures of the beam). 

 

Indications for Application of Nd: YAG Laser in Lung Surgery 

The application of laser in medicine was, at the beginning, greatly admired. This usually happens with the arrival of every revolutionary progress, and hope which is theoretically evoked. It was presumed that a " universally insuperable instruments " had been developed with the help of which even the most complicated operations would be performed without any problems or difficulties. The layman supposed that the laser would replace the scalpel and would remove any tumour, that new revolutionary means of surgical treatment of all ailments had been invented. These ideas were very much promoted by the mass media adoration of lasers, including various sci-fi films such as " Stars wars " etc. However, the reality is such more sober and rational. Laser really helps the sick, but the surgeon must know exactly what type of laser is to be used, under what conditions and in what manner. For example, the application of CO2 laser is not ideal for lung surgery. On the other hand, the advantages of Nd: YAG laser can be well applied in this field. On the basis of our own, more than ten years long experience, we introduce those diseases in whose treatment we can suitable combine lung surgery with Nd: YAG laser: 

• Benign lung tumours
• Malignant lung tumours
• Lung metastases
• Lung cysts
• Pneumothorax
• Lung emphysema.  Lung Volume Reduction Surgery (LVRS) 

Benign Lung Tumours 

Benign lung tumours are usually located in the lung periphery, and only very rarely these can be found in the vicinity of lung hilus. Tumours of 1 - 3 cm in size, maximum 5 cm (not bigger), in subpleural or slightly intraparenchymatous location, can be very well indicated for laser extirpation. The greater majority of benign tumours are formed by chondro-hamartoma of the lungs. They can be easily enucleted by the following procedure: we set the Nd: AYG laser to the working regime of continual emission of beam - 1064 nm wave length, 90 - 100 W output at the end of the thread. We use non-contact application of radiation. After having opened the thorax and after a palpation check-up of the tumour location, we capture the area of the lung above the tumour with Duvall forceps and draw up the lung into the operation wound-lesion. The operating group and personnel in the operating theatre protect their eyes with special eyeglasses which absorb wave radiation of 1064 nm. We conduce the laser beam directly above the area of the palpable tumour and successively incise the lung tissue above the tumour by linear irradiation. We proceed slowly, while the tissues blacken, carbonise and the parenchyma dehisces. As the operation proceeding is bloodless, we have a clear overview of the adjacent tissues and this access to the tumour is simple. As soon as we catch sight of the white-yellow, cartilaginous hard surface of the hamartoma, we prolong the laser incision above the upper half of the tumour. Then, with the thumb and the forefinger, we press the soft tissues around the chondro-hamartoma which we then dislodge out of the lung as a " stone from a cherry ". Using the laser, the operation proceeds safely, easily and quickly. There may be slight bleeding from the area of the removed tumour in the lung parenchyma. Therefore we complete the procedure with two or three wide atraumatic stitches. Thus, the operation is finished by inserting the thoracic drain and closing the thoracotomy. Nowadays this operation can also be performed by V.A.T.S. technique (Video Assisted Thoracic Surgery). In such a case we mark the place of the lung lesion, already before the operation by subpleural injecting of blue colour (methylene blue) across the thoracic wall under CT control. Thus, we can more easily identify the location of the tumour in the thoracoscopic picture. 

Malignant Lung Tumours 

Primary lung malignant tumours are not generally indicated for applying the laser. The basic method of choice for malignant tumours still remains the classical lobectomy or pneumonectomy. Here, the laser is of hardly any benefit. The exception can be those situations when we have to transect the lung bridges-bonds) between the lung lobes. The separation of lobes in the split can be carried out with the laser beam. However, these days the quicker and equally reliable stapler technique is used for this performance. The laser beam can alternate with classical surgery in the lung malignity in the cases when we are obliged to perform a limited lung resection in old people whose functional reserve is low. In today's conditions, however, cuneiform resection can be carried out more quickly with the help of staplers than with laser. 

Lung Metastases 

Secondary lung tumours, metastases, are absolute indications for the application of Nd: YAG laser. Such laser benefits have not been observed anywhere else as in these cases. Lung metastases are in most cases located closely under the lung surface, are of small size, in fact quite often, they are dispersed over the lung like minute " poppy seed " focuses which cannot be detected before the operation even by CT examination. These focuses are 1 - 2 mm in size which can easily and quickly be evaporated by Nd:YAG laser of 100 W output in non-contact manner and by continual application. Metastases in sizes from 0.5 cm to 3cm are extirpated not by evaporation but in one piece, so that the samples can be sent for histological examination. We use the same performance and regimen, i.e. 100W at the end of fibre non-contact manner and continual application of laser. The environment of the surface of the metastasis is irradiated and then lightly evaporated with the laser. Thus the metastasis gradually extravasates from the lung, and the destructive changes intervene into the environment as far as 10 mm. The safety line in the environment of the extirpated metastasis caused by the thermo-necrosis is sufficient and radical. In this manner even a greater amount of secondary focuses may be removed from one lung. We have experience with extirpation of 11 metastases in the course of one operation. We operated on 92 patient for lung metastases, from this number 34 were operated on two times and 14 three times and 2 patients were operated on four times in a several years' interval. The survival is five years in 25-45% and ten years in 20% of laser treated patients. For this reason we consider this chapter as exceptionally important. In our country, up to now, the general opinion has been that metastases have hardly any chance of being cured. However, we have recorded especially good results in patients with metastases of primary mesenchymal tumours. We give preference to open surgery to thoracoscopy. We perform sternotomy and bilateral surgeries on right and left lung in the course of one operation. Open surgery allows palpation of the lungs and introduction of light-conductive fibre direct to the place of lung metastasis. Videothoracoscopy does not allow palpative perception which is essential for recognition of more deeply deposited metastases (visceral pleura and lung above the metastasis need not be changed). The compromising metastasis V.A.T.S. method can be chosen only when we face the decision of helping a patient with high operational risk. 

Methodically important warnings for lung surgery with Nd: YAG laser. 

1. At the operation we use separated lung ventilation which allows surgery on asphyxial and exsufflated lung. However, laser surgery is possible even on an expanded lung filled with air. 
2. Laser regimen: Nd: YAG, 1064 nm continual beam, non-contact technique, 80 - 100 W output.
3. We advise to keep a certain safety line beyond which we should not go with the laser. The area of the lung hilum should be considered as "sacred" and laser irradiation ought not to be applied in this location. Large vessels (arteries and veins) and main air passages lead through the lung hilum, their injury can cause serious peroperative complications. Imagining the lung wings, we can see that the safe line leads through the lung parenchyma in the fiction distance of > 5 cm from the trunk hilum of pulmonary artery. We can operate in this area without any risk of injuring the lobar bronchus or vessel. Working with the laser bellow the mentioned borderline is dangerous and demands the responsibility of a very experienced pneumosurgeon. 
4. After the removal of a metastasis bigger than 3-5 cm there remains a carbonised cavity which does not bleed, is dry and impermeable. There is no air escape, the lung breathing is normal and the lung expands. If the transverse diameter of the defect surface is larger than 3 cm, it is advisable to apply two to three atraumatic lung sutures. The lung edges draw together and the carbonised base between the sutures are closed. There is no danger of its detachment or the possibility of serious postoperative haemorrhage in due time (e.g. after 10 days). Minute focuses after evaporation which do not exceed the surface of 5 cm2, need not be safeguarded by intraparenchymal stitches. 
5. The thoracic cavity is always drained by active suction. 

 

Lung Cysts 

Etensive lung cysts which occupy 1/3 of the lobe are extirpated preferably by e.g. stapler technique, or in cases of their being even larger, we perform lobectomy. We can use the laser when the size of the cysts does no surpass approx. 5 cm. Larger cysts can also be removed by the laser, however, the time needed for their enucleation is incomparably longer than the time needed for the same operation performed with staplers. In the extirpation of a cyst we proceed similarly as in the removal of lung metastases. We orient the beam closely into the surrounding of the cyst wall, slowly advancing forward and into depth, and the cyst gradually emerges from the lung. We treat the created defect in the lung, which is nonaerial and bloodless, in the same manner as mentioned above in operations for metastases. 

Pneumothorax 

If we find in the course of videothoracoscopy performed for pneumothorax, cysts or bullae in the lung periphery (in most cases these are located on the apical or apicodorsal segment of upper lobe) we can successfully apply the laser. This procedure is used in those cases when the scope of lung impairment is no extensive, when we find blebs and smaller bullae up to 2-3 cm. These pathological segments are successively resected with laser beam, the sampled tissue is then sent for histological tests. The line of the incision is coagulated with the laser till a layer of carbonised tissue is created. This guarantees nonaeration and haemostasis. We supplement the operation by irradiation of the parietal pleura in the scope of the upper lobe, which induces postoperative pleurodesis (physical principle of pleura "abrasion"). The adjusting regimen of Nd: YAG laser parameters are the same as in other lung surgeries: output 100 W, wave length 1064 nm, continual and non-contact application. 

Lung emphysema. Lung Volume Reduction Surgery (LVRS) 

Since 1995, at many pneumosurgical departments, so called LVRS (Lung Volume Reduction Surgery) operations have been performed for advanced stages of lung emphysema. The principle of this operation is the reduction of those parts of the lungs which are the most affected by hyperinflation. We apply wedge resection in these places usually using the stapler technique as open surgery or videothoracoscopy. In LVRS operations we usually resect the lung apex about 20 - 30% so that the resection line is usually more than 10-15 cm long. The removed volume of the lung amounts up to 70 g of mass. Sporadically the laser is tested as a method of choice; the heat of the beam shrivels the lung parenchyma, causes retraction and reduces the inner area of the lung. Hyperinflated spaces are thus reduced, and in the pathophysiologic image, the exchange of gasses on the alveolo-capilary membrane gradually improves. Although, at our clinic, we have had experience with laser therapy and with LVRS operations, we have not used the laser for this indication up to now. The reasons being: a) laser surgery requires a long-term application on contrary to the stapler technique. b) danger of risking imperfect sealing of the wound area. Stapler resection of the lung is also endoscopicaly easy quick and safe. Our opinion is that using the laser for LVRS is technically possible, but still it is not the ideal solution. However, we do not exclude the combination of stapler technique with laser irradiation of the line where stapler was applied for increasing the air-tightness of the lung. Other procedures are being tested, e.g. employing Ho: YAG (Holmium: YAG) which has more impressive effect in experiments on animals (it causes quicker and more extensive changes in lung) than Nd: YAG laser. Therefore, could be better applied in lung resections theoretically Ho: YAG laser resections for bullae or for lung emphysema than Nd: YAG laser (4). However, this presumption will have to be verified by further clinical tests. 

 

REFERENCES 

1. Choy, D.,S.: History of lasers in medicine. Thorac.Cardiovasc. Surg., 36, June, Suppl.,2: 1988; 114-117. 

2. Fanta, J.: Indikace a operační technika pro Nd:YAG laser v hrudní a v břišní chirurgii. Kandidátská dizertační práce, UK Praha, 1989:8-13. 

3. Christensen, J.: The Sharplan CO2 laser in thoracic surgery. Proceedings of the First International Symposium on Laser Surgery. Jerusalem 1975:19-24. 

4. Brenner, M., Wong., H., Yoong, B., Wang, N.,S., Chen, J.,C., Budd, M., Hamilton, A., Tadir, Y., Mc Kenna,R., Fischel, R.,J., Hugh, J., Tromberg, B., Wilson, A.,E.: Comparison of Ho:YAG versus Nd:YAG thoracoscopic laser treatment of pulmonary bullae in a rabbit model. Journal of Clinical Laser Medicine & Surgery. 15 (3); 1997: 103-108.