670 Proc. roy. Soc. Med. Volume 69 September 1976
~ ~ . _g;lL.
REFERENCES Coplans M P (1976) Anwsthesla 31,430 Gordon M & Sellr S (1971) Antsthesta 26, 199 Jacobse E, Skovated P & Thomsen K A (1972) Acta oto-laryngologica (Stockholm) 74, 346 Oulton J L & Donald D M (1971) Anusthesiology 35, 540 Pollard B J (1968) Anasthesia 23,534 Sanchez (1971) Revue de laryngologle, otologle, rhinologie (Bordeaux) 92, 323 Tonkin J (1967) Journal of the Oto-laryngological Society of Australia 2, 81
Fig 1 Long cuffed 5 mm nasotracheal tube (Portex)
this tube were superior to those produced using a 5 mm tube which was narrow bore throughout its length. This suggested that the blood gases might reach an unsatisfactory level with the narrow bore tube, and this was substantiated by Jacobsen etal. (1972). In our unit we used the Pollard tube but found that the bulky oral portion rendered difficult laryngoscopy more difficult and that the tube offered considerable obstruction to the surgeon. A nasal tube afforded much better operating conditions, since it lay consistently between the arytenoids thus impeding surgical access to a minimum, but presented two disadvantages: First, the longest uncut tube was only just long enough for nasal use in small adults; secondly, we confirmed the finding of Jacobsen et al. and were able to demonstrate Pco2 increases of 4.0 kPa following manual ventilation with a high flow-rate on the Mapleson A circuit. To solve the first problem Portex manufactured a 5 mm plastic cuffed tube of sufficient length to allow the cuff to lie well into the trachea when the tube was passed nasally (Fig 1); the cuff was short to prevent ballooning of its upper end into the surgical field. To conquer the second drawback we used manual ventilation through a circle system with CO2 absorption; a compression rate of 12 per minute (6 litres N20, 3 litres OD) consistently resulted in a Pco2 level very close to its prepremedication value. The anesthetic agents used were thiopentone, succinylcholine intermittently, and halothane, and the nose was sprayed with 10% cocaine. This combination was sufficiently flexible to allow continued viewing by the surgeon after removal of the tube with spontaneous ventilation, should this prove necessary. Generally, however, the entire larynx could be examined by gentle displacement of the tube using microsurgical cupped forceps. Whilst the technique described is not ideal for every case of laryngeal examination, it nevertheless provides excellent operating conditions with complete airway protection for the majority of adults undergoing microlaryngeal surgery or biopsy. [For a fuller account of this work see Coplans
1976.]
Mr R F McNab Jones (St Bartholomew's Hospital, London ECI)
Summary of Hazards of Endoscopy
The hazards of endoscopy may be man made or due to natural causes.
Man-made Hazards Lighting systems: For many years the lighting system, bulbs and connecting flexes used for the instruments were fragile and erratic, and gave only modest illumination at the end of a 35 cm cesophagoscope. Modern fibre-optic systems are a great improvement in every way. Design of endoscopes: These sometimes enhanced the dangers of operation. In particular, the cut back beak of the Negus endoscopes is particularly likely to catch, ruck up, and perforate the posterior pharyngeal- wall, especially if osteophytes are present (Fig 1). The Mosher instrument is safer. ig>. .. ,.,,
u..
....................i.......................
... *..~ ~~~~~~~~~~~~~~~.. ....:. .. ..
~~~~~~~~~~~..
...
...
Fig I Negus endoscope in situ
..:
9~ ~ . 9 i }
Section ofLaryngology with Section of Anasthetics 671
Anaesthesia: Modern developments have been helpful to the surgeon but inexpert anesthesia may still p'resent difficulties by damage to teeth, pharynx or larynx, or by over-inflation of the cuff on an endotracheal tube. In rare cases the stomach may be inflated by mistake and can even perforate, releasing anesthetic gases into the peritoneal cavity (Fig 2). Natural Hazards Anatomical difficulties: These include: (1) Awkward dentition with caps and expensive bridgework. (2) Kyphoscoliosis of the cervical and thoracic spine. (3) Osteoarthritic changes in the cervical spine especially when associated with
,,::...
...l
.....:.-......l_. . ._
_
X-'
Fig 3 Barium swallow showing pouch with healedfistula
awkward problems (Fig 4). Adequate preoperative X-rays, careful choice of instruments and the best available expertise give the greatest chance of a ~~~~~successful conclusion. This is not a field for
beginners.
Fig 2 Gas in peritoneal cavity
atherosclerosis of the vertebral arteries. Prolonged hyperextension of the neck in the latter group of patients may precipitate a cerebrovascular accident.
::
Pathological difficulties: Strictures, ulcers, neoplasms and diverticula may all increase the ---/ difficulties of endoscopy and the dangers of instrumentation. Careful preoperative barium swallow studies are invaluable in these cases. Fig 3 shows a barium study done after an unsuccessful endoscopy and demonstrates the healed fistula in the fundus of the previously unsuspected hypopharyngeal pouch. Foreign bodies are found in children, the inebriated, and the mentally deranged. Their variety is infinite but safety pins probably present the most Fig 4 Safety pin at cardia
672 Proc. roy. Soc. Med. Volume 69 September 1976 Golden Rulesfor Endoscopy The following Golden Rules are suggested for these propedures: (1) Careful preparation of patient, X-rays and instruments. (2) Obtain the best available anesthetist. (3) Use skill not strength. (4) Biopsy, dilatation and intubation with care. (5) Avoid prolonged procedures. Adherence to these rules should reduce complications in these operations which are still too frequent for complacence.
Dr D W Bethune (Department of Anasthesia, Papworth Hospital, Papworth Everard, Cambridge, CB3 8RE) A Hazard of Bronchoscopy when Using the Injector Technique to Maintain Ventilation The technique of using a high pressure jet oxygen
directed down the open end of a bronchoscope as described by Saunders (1967) has enabled adequate ventilation to be maintained during operative bronchoscopy. ......
....... ........
.......
OUT OF
BRONCHOSCOPE
111TO ^6 __STEv5 :
We explored methods of using side arm suction to scavenge this expired volume. The original side arm of the Negus bronchoscope can be used as the scavenging port or special adaptors can be fitted to some other bronchoscopes. Using a piped vacuum point a scavenging flow of 40 litres/min is achieved through the side arm of the Negus bronchoscope. Experimental bacteriological studies using a model lung at a tidal volume of 700 ml demonstrated that the scavenging system reduced the dispersal of bacteria by 90 %. Flow studies (Fig 1) indicated that on our test lung the scavenging system prevents expiratory flow out of the end of the bronchoscope at tidal volumes of up to 500 ml, and with larger tidal volumes there is a greatly reduced expiratory flow. As long as the proximal end of the bronchoscope is unobstructed the scavenging flow of 40 litres/min enters through this opening and there is no possibility of producing a subatmospheric pressure in the lungs. It is therefore vital, as with the original technique, that the system is designed to prevent any possibility of obstruction to the proximal end of the bronchoscope.
VOLUME
..TIDAL
60
4
..
20 "::ETar1_
COMPLIANCE OF TEST LUNG 0055 CmH20/L/Sec. LITRES/Cm H20 AIMY RESISTANCE Fig 1 Flow traces with and without scavenging. Two respiratory cycles are shownfor each of three tidal volumes. Thefirst cycle ofeach par Is without scavenging; the second cycle is with a scavengingflow of40 litres per minute
The establishment of normal ventilation volumes through the bronchoscope means that the operator Is exposed to a considerable volume of expired air, during each expiratory phase. This represents a potential hazard in the transmission of infection from the patient to the operator, as well as proving somewhat uncomfortable.
The scavenging system described reduces the potential bacteriological hazard and greatly increases the operator's comfort. REFERENCE Saunduu R D (1967) Delaware Medical Journal 39, 170