Postgradulate Medical Journal (August 1972) 48, 507-513.

Artificial ventilation, prolonged endotracheal intubation andtracheostomy in paediatric surgery

W. J. GLOVERM.B., B.Ch., F.F.A.R.C.S., D.Obst.R.C.O.G.

Hospitalfor Sick Children, Great Ormond Street, London, W.C. 1

THE young infant has much less respiratory reservethan older children and adults; for example, hisresting oxygen consumption, per unit of body weight,is twice that of the adult, 7 ml/kg/min compared with3-5 ml/kg/min. The diameters of distal airways re-main constant from birth until about 5 years of ageand only then increase in size (Hogg et al., 1970).Consequently, infants and young children have ahigh peripheral airways resistance and a greatertendency to airways occlusion than older children.The average newborn infant has about twice the

surface for heat loss for each kilogram of tissuecompared with the average adult (Cross, 1965). Ifthe infant is placed in a cool environment his meta-bolism increases to attempt to maintain his bodytemperature. This increase in metabolism in turnincreases his oxygen consumption and minutevolume. Nursing an infant in a cool environmentplaces an additional demand on the respiratorysystem. In an infant already in respiratory distressthis could result in respiratory insufficiency. Theimportance of conserving heat in the care of illinfants is therefore of the utmost importance.

In infants, as in adults, the cause of respiratoryinsufficiency may be decreased respiratory move-ments or pulmonary complications or a combina-tion of both. For the reasons given above, however,infants will reach a state of respiratory insufficiencymore readily than older children.

Essential features of a paediatric ventilator(1) Tidal volumeThe tidal volume of an infant varies inversely with

the respiratory rate and ranges from about 10 to 30ml in patients of about 3.5 kg. The ventilator mustdeliver volumes in this range to the patient. Thevolume indicated by a spirometer placed in the con-ventional position in the expiratory limb of a circuitdoes not represent the patient's minute volume.The figure obtained from the spirometer must becorrected to allow for compression of the gas in thepatient circuit. Gas compressed in the circuit oninspiration will re-expand during expiration when thepressure falls and contribute with the expired gas

from the patient to the reading on the spirometer(Glover, 1965). The volume of the circuit, the peakinspiratory pressure reached in the circuit, and thefrequency of ventilation determine the size of thiscompressibility factor. The discrepancy between thepatient's minute volume and spirometer reading willtherefore be greatest in infants requiring high in-spiratory pressures.

(2) PressureThe inspiratory pressure required to ventilate the

infant lung varies considerably. It will be less than10 cm H20 if the lungs are normal and it may be ashigh as 50 cm H20 in infants with pulmonary oedemaand bronchiolitis. It is therefore essential to be ableto apply pressures of this order when the clinicalcondition requires it.

(3) Accurate control of inspired oxygenIn patients of all ages there is a danger of pul-

monary damage if oxygen concentrations above 500are administered for a number of days.Young animals exposed to 100% oxygen at 1

atmosphere die in 72-96 hours. At autopsy the lungsare large, dark, heavy and liver-like in appearance.Man appears less susceptible and human volunteersshowed a fall in pulmonary diffusion capacity after30 hr exposure to 98% oxygen at 1 atmosphere anda fall in vital capacity after 60 hr exposure (Caldwellet al., 1966).

It is well known that high percentages of oxygenadministered to premature infants may result inblindness due to retrolental fibroplasia. This com-plication may arise if the Pao2 is above 150 mmHgin the retinal vessels. If the oxygen tension in thearterial blood is monitored from the umbilical arteryin the immediate newborn period lower values willbe obtained than exist in the vessels perfusing theeye and brain. This is due to shunting from right-to-left via the ductus arteriosus. Where a considerableright-to-left shunt exists, as in respiratory distress,a Pao2 of 60-90 mmHg in the umbilical artery bloodsample may be acceptable (Baum & Tizard, 1970).

In the care of ill patients there should be no

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hesitation in raising the inspired oxygen concentra-tion as much as is necessary to maintain acceptablearterial oxygen tensions. Retrolental fibroplasia willnot occur unless the arterial oxygen tension is abnor-mally high and the danger of pulmonary damagefrom the high inspired oxygen concentration is notacute enough to outweigh the serious and im-mediate consequences of severe oxygen desatura-tion.

It is therefore essential to be able to controlaccurately the percentage oxygen delivered by a ven-tilator. The inspired oxygen concentration should inaddition be checked regularly with an oxygen analy-ser. When oxygen-rich mixtures are administered it isalso necessary to check the arterial oxygen tension.

(4) HumidificationSince the artificial airway (endotracheal tube or

tracheostomy) by-passes the patient's humidifyingmechanism, the nose, it is essential to humidify theinspired gas. This aspect is often overlooked in con-sidering the merits of various ventilators. In infantsit is of even greater importance because the inspissa-tion of secretions resulting from the inspiration ofdry gas readily blocks the narrow airways of thepatient and also the lumen of the endotracheal ortracheostomy tube. We should try to achieve a rela-tive humidity of 700 or more in order to maintainciliary activity, as a low relative humidity has aretarding effect on ciliary motion (Dalhamn, 1956).

There are three methods of increasing the watercontent in the inspired air and only brief commentsare made on them here:

(a) Standard humidification. This involves the heat-ing of water over which gas is passed to the patient.If the water in the humidifier is kept at about 55° Cthen all vegetative organisms are killed. This elimi-nates an important source of proliferation of bac-teria. The disadvantage of this method is that thetemperature of the inspired gas falls as it passes alongthe inspiratory tubing to the patient. It is desirableto keep the temperature at the patient end of thetubing at approximately 35°C in young infants and33°C in older children. In young infants humidifiedgas is a potent factor in maintaining body tempera-ture as the patient does not have to produce watervapour from his respiratory tract and thereby loseheat.

(b) Compressed air nebulizer. This gives a variabledroplet size and a high proportion of the dropletsmay be comparatively large. Droplets greater than10 ,u are deposited in the upper trachea. The outputfrom compressed air nebulizers is low even with highgas flow rates. With low gas flow rates as used inpaediatric practice the output may be extremelysmall (Fenstermaker, 1970).

(c) Ultrasonic niebilizer. These are extremely effec-

tive provided an artificial airway is in place. If thepatient is breathing through his nose then neitherultrasonic nor compressed air nebulizers are effec-tive because the nose filters out the droplets (Wolfs-dorf, Swift & Avery, 1969). When however an endo-tracheal or tracheostomy tube is in place, the outputfrom the nebulizer must be carefully controlled as itis easy to overload an infant's lungs with fluid.Saline is more dangerous than water in this respectand consequently distilled water should be used(Modell et al., 1968).An important disadvantage of both compressed

air and ultrasonic nebulizers is the possible trans-mission of bacteria to the patient (Moffet & Allan,1967). Any device producing mists is liable to dis-seminate quantities of bacteria. The smaller particlesproduced by ultrasonic nebulizers are particularlydangerous as they penetrate deeply into the lungswhere pulmonary clearance mechanisms may not beefficient.Few ventilators will meet all four criteria described

above. The clinician in choosing a machine mustbear in mind the nature of the clinical problems withwhich he will be confronted in order that he maymake the best choice for his particular purpose.

ManagementContinuous nursing supervision is essential in this

work. The objective in mechanical ventilation is tomaintain the patient's arterial Po2 and Pco, nearphysiological levels and this is most easily achievedby taking complete control of the patient's respira-tion.The use of patient-triggered ventilators would

seem attractive but in practice in infants breathingrapidly it can be extremely difficult to achieve satis-factory patient-triggering. Under-ventilation willthen occur.

If one ventilates children satisfactorily so that thePao2 and Paco2 are approximately normal then thepatient will follow the cycling of the ventilator andcease making his own efforts. There are three excep-tions to this generalization:

(1) If the patient is in pain following surgery thenan analgesic such as morphine is required to gaincontrol.

(2) If an infant is hungry then a feed is requiredto establish control.

(3) If there are large right-to-left shunts causingarterial oxygen desaturation as in respiratory distresssyndrome or pneumonia then mechanical ventilationwill not correct the blood gases and the patient tendsto 'fight the ventilator'. When this occurs respiratorydepressants such as morphine or muscle relaxantssuch as curare are required.

In general however, control of respiration call beaccomplished without resorting to drugs.

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Treatment of respiratory insufficiency in paediatric surgery 509

The avoidance of muscle relaxant drugs in themanagement of these patients ensures that a patientwho is being under-ventilated will attempt tobreathe spontaneously. When a patient ceases tofollow the ventilator one should assume that he isnot being adequately ventilated until proved other-wise. There may be several reasons for under-ventilation; secretions in the airway, collapse of alobe of a lung, pneumothorax, an accidental changein the settings of the ventilator, or a fault in theventilator. All these possibilities should be checkedbefore resorting to drugs.When putting an infant on a ventilator one must

consider the rate, volume and pressures to be used.

RateInfants in respiratory distress have a very high

respiratory rate because it is easier for the infant toincrease his rate of respiration than his depth ofrespiration. It is not necessary in mechanical venti-lation to follow this pattern as rates of ventilationnear the physiological range are satisfactory, i.e.30-40/min. It may be that this slower rate of venti-lation may result in more even distribution of gas,especially in diseased lungs, but this is difficult toprove in clinical practice.

Minute volumeThe difficulties encountered in attempting to study

the normal ventilation in the newborn have beenstated in detail by Cross (1965). The effect of a coldenvironment in causing an increase in ventilation inthe newborn has already been mentioned.There are probably wide variations from infant to

infant. A useful average figure to take is 600 ml asthe minute volume with a tidal volume of 15 ml ata respiratory rate of 40/min in an infant weighing3'5 kg. It must be appreciated that this is a meanfigure.Having decided on a particular minute volume, the

measurement of the minute volume produced by theventilator presents problems. The errors involved inusing a spirometer have been described earlier.Accurate measurements of tidal and minute volumescan be obtained by using a pneumotachograph whichmeasures flow and this can be integrated with timeto measure volume. However, to do this an airtightfit is required around the endotracheal or tracheo-stomy tube and this is not advisable in clinical prac-tice for the reasons given later. In addition, suchinstruments require careful calibration and are fairlydifficult to use in everyday practice.

In clinical practice it is more useful to assess thepatient's colour and the adequacy of movement ofthe chest wall as one would do in anaesthesia.Blood gas analysis can then be done to confirm theadequacy of ventilation. Provided the peripheral

circulation is good, a capillary sample from a heelprick is satisfactory. When the peripheral circulationis poor, a peripheral arterial sample should be takenif the umbilical artery is not available.

PressureAs stated earlier, the pressure required to ventilate

the lung will vary considerably depending on the air-way resistance and lung compliance.The correct pressure in a particular patient is the

pressure which will produce adequate tidal volumes.High pressures are not dangerous provided they arenecessary because the pressure is largely dissipated inovercoming the high airway resistance. They wouldbe dangerous if applied to the normal lung becauseof the likelihood of producing a pneumothorax or ofimpairing pulmonary blood flow.

Discontinuation of mechanical ventilationOnce the respiratory insufficiency which created

the need for mechanical ventilation is no longerpresent there is generally no difficulty in removingthe patient from the ventilator. A useful method is totry the patient off the ventilator on an oxygen-enriched mixture for progressively longer periodsuntil he is completely off. This may be achieved about24 hr after commencing withdrawal. A patient whois unable to tolerate near-normal inspired oxygenconcentrations while on the ventilator is unlikely tobe able to do without the ventilator.

ComplicationsThe means of minimizing most complications

have already been dealt with. If a pneumothoraxoccurs, a chest drain connected to an under-waterseal should be inserted and positive pressure ventila-tion continued. This complication should be veryuncommon if correct pressures are used.The danger of cross-infection by the ventilator

can be avoided by sterilizing the patient circuit afteruse.

In infants with a very high airway resistance it isnecessary, as already described, to use pressures of40 cm H20 or more to inflate the lungs. In suchpatients the lungs become over-inflated because thereis insufficient motive force to expel the air throughthe narrow airways during expiration (Barnes et al.,1969). Discontinuing mechanical ventilation in thesepatients often takes several weeks. This complicationis only seen in infants with a high airway resistanceand has not been observed apart from this.

Prolonged endotracheal intubation and tracheostomyPositive pressure ventilation of the lungs requires

the insertion of an artificial airway, either an endo-tracheal tube or a tracheostomy tube. The preciserole of endotracheal intubation or tracheostomy in

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the care of these patients has aroused considerablecontroversy over the past 9 years.The most commonly used polymer for endotra-

cheal or tracheostomy tubes is polyvinyl chloride(PVC). When formed by itself into a device it is hard,brittle, inflexible and translucent. The heat used toform the device tends to cause thermal degradation.This is shown by a yellowing of the material.

In order to confer flexibility, various materialsknown as plasticizers are used and to retard thermaldegradation various materials known as stabilizersare used (Guess, 1970).

Guess & Stetson (1968) identified a toxic substancewhich leached out of some PVC materials whenthese were inserted in rabbit muscle. Necrosis oc-curred in the muscle around the plastic insert. Thissubstance was an organotin compound which is oneof the most widely used stabilizers. Most manufac-turers have now ceased using organotin compoundsfor this purpose and substituted epoxydized soya oilas a stabilizer. Users must however realize that thereare various additives in PVC tubes and that not allmanufacturers' products contain the same sub-stances.

In the case of tracheostomy or endotracheal tubesno satisfactory test has yet been published that re-veals the subtle effects of these devices upon mucoustissues (Guess, 1970).

Prolonged endotracheal intubation

Management and complicationsNasotracheal intubation is generally preferred to

oral intubation as it is easier to fix the nasal tube tothe face. There is then less danger of the ventilatortubing dislodging the endotracheal tube.

In all patients, every complication of an artificialairway, whether it is an endotracheal or a tracheo-stomy tube, must be regarded as extremely serious.Consequently, it is of the utmost importance to ob-serve the following details:

(I) Incorrect length of endotracheal tube. As theinfant's head may be flexed or extended in the day-to-day care of the patient, there will be some move-ment of the endotracheal tube up and down thetrachea. The length of the tube must therefore bedetermined fairly precisely to avoid, on the one hand,endobronchial intubation and, on the other, dis-lodgement of the tube from the trachea. A usefulmethod is to insert the tube via the nose until the tipof the tube is almost at the glottis; the tube is thencut to allow an appropriate length to pass the larynxand reach the mid-point of the trachea.

(2) Kinking. The most likely site at which kinkingoccurs is when a redundant length of tube protrudesfrom the nostril. The comparatively heavy connec-tions to a ventilator will cause it to kink at this point

and this is a further reason for ensuring that the tubeis the correct length.

(3) Erosion of ala or septum of nose. If the tubepresses on the edge of the nostril or septum, erosioncan appear within 24 hr. If the pressure isnot relieved,erosion through the lateral wall of the nose or theseptum can occur in a few days. Considerable careis required in avoiding this complication. The tubeshould be fixed in such a way that it protrudes down-wards from the nostril and therefore does not presson the edge of the nostril.

(4) Blockage of the tube. This is a serious andcommon occurrence if care is not taken to ensuregood humidification and regular aspiration of thetube. Instruction must be given to the nurse to ensurethat she passes the suction catheter all the waythrough the tube to the trachea.

(5) Sub-glottic oedema and sub-glottic stenosis.This has been the most serious of all complicationsand in the early reports it appeared in almost allseries. The incidence was low, 5% in some series,and this encouraged the view that this complicationwas preventable. A widely held current view is thatthe tubes used in a few cases in the earlier serieswere too large.The endotracheal tube, unlike tubes in the urethra

or oesophagus must pass a non-distensible area atthe level of the cricoid cartilage. Prolonged pressureon the mucosa at this level leads to ischaemia, oede-ma and ultimately, fibrosis. Treatment of a severestenosis is extremely difficult and a long-term tracheo-stomy is usually the unfortunate result.

In paediatric anaesthetic practice one normallyuses the largest tube which will easily pass the larynxin order to have an airtight fit. While this is satisfac-tory for periods of a few hours, it is probable that inprolonged use (over 24 hr) some degree of oedemaand ischaemia occurs. Stocks (1970) therefore recom-mends that the correct size of tube is 0.5 mm internaldiameter less than the size which gives an airtightfit. A useful guide for the inexperienced is that whenpositive pressure is applied to the tube to inflate thelungs an audible leak occurs around the tube atlaryngeal level. It is this leak which leads to difficultyin using the pneumotachograph referred to earlier.

TracheostomyIn the past decade, while experience has built up

with prolonged endotracheal intubation, themanagement of tracheostomy has improved con-siderably. Complications such as death during theoperative procedure, blockage or dislodgement ofthe tracheostomy tube, pneumothorax, trachealstenosis and delayed decannulation are largely pre-ventable (Fearon, 1962: Holinger, Brown & Maurizi,1965: Aberdeen, 1965: Glover, 1970). Attention todetail is as important as in prolonged endotracheal

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Treatment of respiratory insufficiency in paediatric surgery 511

intubation because complications, which are on thewhole preventable, are serious.

TechniqueAnaesthesia. Tracheostomy in young children used

to be performed as an emergency, often under localanaesthesia, and quite often in the ward rather thanin the operating theatre. This resulted in a highoperative mortality from asphyxia. Today thenormal practice is to administer a general anaestheticvia an endotracheal tube. This ensures a good airwayand a well-oxygenated motionless patient so that aplanned operation can take place without haste.

In an emergency situation an endotracheal tubecan be passed in the ward and the tracheostomy canthen take place as a planned procedure in theoperating theatre.

Surgical aspects. There are two points to observe:(1) The first tracheal ring should be left intact as

division of it can lead to perichondritis and sub-glottic stenosis (Watts, 1963).

(2) No cartilage should be excised in the infanttrachea. If cartilage is excised it does not regenerateand healing is by fibrous tissue with consequentnarrowing (Watts, 1963).

These points can be met by making a vertical in-cision in the mid-line of the trachea through thethird and fourth (Holinger, et al., 1965) or third,fourth and fifth tracheal rings (Aberdeen, 1968).After insertion of the tube it is important to flexthe neck fully when tying the tapes as the distancefrom the tracheostomy to the posterior aspect of theneck is minimal in this position. Failure to do thiswill result in the tapes being comparatively loose withconsequent danger of dislodgement of the tube post-operatively.

Tracheostomy tube. Most centres now use plastictracheostomy tubes in infants. The tube designed byAberdeen (1965) has been very satisfactory (Stool,Campbell & Johnson, 1968; Talbert & Haller, 1968).Tubes of this type adapt to the individual infant'strachea and therefore do not cause excessive pressureat any point. Silver cannulae with a removable innertube are unnecessary. The purpose of the inner tubeis to enable a blocked tube to be cleared. Humi-dification, which is essential for the reasons alreadydescribed, eliminates the need for an inner tube.Furthermore, a rigid tube must always producepressure at certain points as it cannot adapt to theindividual trachea. This pressure may occur on atracheal ring with consequent erosion of it and col-lapse of the trachea leading to decannulation diffi-culties. Pressure may also occur at the tip of thetube causing ulceration of the wall of the trachea.An important point about tracheostomy tubes in

infants and young children is that an inflatable cuffis unnecessary. By putting in the largest tracheo-

stomy tube that will comfortably fit the trachea, onehas a sufficiently leak-proof fit to be satisfactoryclinically, thereby enabling quite high inflating pres-sures to be used. There is ample evidence now thatinflatable cuffs increase the incidence of tracheatrauma (Stiles, 1965: Davidson et al., 1971).Management. As in prolonged endotracheal in-

tubation, continuous nursing supervision and goodhumidification are essential. If the patient showssigns of respiratory embarrassment after the trache-ostomy tube is in place one must exclude the possi-bility of a pneumothorax.

Changing the tracheostomy tube. If humidificationis adequate it is seldom necessary to change thetube. It may be changed once per week to enablecomplete toilet to be done to the stoma. In the first3 days it should not be changed outside the operat-ing theatre as it may be extremely difficult to replaceit before a track has formed.

Prevention of infection. The danger of infection isgreatest in premature babies. If a tracheostomy isperformed on such an infant the greatest care mustbe taken to avoid infection, e.g. sterile gloves shouldbe worn when inserting the sterile suction catheterinto the trachea. In infants even a few weeks oldthere is much less danger from this source. Manyinfants of this age already carry pathogens such asP. aeruginosa or coagulase-positive staphylococci intheir nose, throat or rectum. It is almost inevitablethat these organisms will be isolated, within a fewdays, from the tracheal aspirate. Such patients donot show signs of clinical infection and it is not neces-sary to treat them with antibiotics in such circum-stances. A 'no-touch' technique should be usedwhen introducing the sterile catheter to aspirate thetrachea of these older infants, i.e. the part of thecatheter introduced into the trachea need not behandled.

Decannulation. If tracheostomy has been per-formed as described and if a plastic tracheostomytube has been used, then, provided the upper airwaywas normal before the tracheostomy was done, onedoes not anticipate difficulty in decannulation.Damage to the first ring of the trachea is the com-monest cause of decannulation difficulty. It is ofcourse essential, before attempting decannulation,to ensure that the infant is in a satisfactory condition,i.e. secretions should be minimal and cardiac failureor other causes of respiratory difficulty should havebeen eliminated.Young infants often do not breathe normally

after decannulation. This may be because co-ordination between the larynx and respiration is lost.For example, the cords may remain in apposition oninspiration and as a result the infant struggles for airand becomes cyanosed as the stoma closes. Onemethod of attempting to overcome this problem is to

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sedate the infant fairly heavily with morphine (0-2mg/kg) before decannulation. The sedated infantusually continues to sleep, the stoma closes graduallyand more and more air enters via the normal airway.When the sedation has worn off respiration isusually well established by the normal route and thestoma may be almost closed.There is one important point to note. If in spite

of sedation an infant shows signs of obstructedrespiration as the stoma closes then one must assumethat there is an organic obstruction until provedotherwise. The tracheostomy tube should be re-placed and, under full general anaesthesia, an endo-scopy should be performed to exclude such things asgranulations or a mucosal flap at the site of thestoma.

The choice of airway. Many infants and youngchildren in several centres have been managed byeither prolonged endotracheal intubation or bytracheostomy. The supervision and the generaltechniques are similar for both methods and simplemistakes can easily be fatal in these ill patients,whichever method is used.An endotracheal tube seems to be more difficult

to manage from the nursing point of view and is lesspleasant for the patient. The danger of erosion of thenose is a constant anxiety and becomes more diffi-cult to avoid as time goes on. The serious complica-tion of sub-glottic stenosis although probably re-lated mainly to the use of too large a tube may alsohave some relation to the duration of intubation.It would seem therefore that the case for intubationbecomes weaker the longer the tube is required.A tracheostomy does, of course, involve a small

operation and a scar on the neck. In a few patientsthere will be decannulation difficulties if the opera-tion has been performed at too high a level and in afew patients granulations may form in the tracheaat the stoma.

If a patient requires an artificial airway for a fewdays it seems reasonable to use an endotracheal tube.If at the end of this time the patient is not improvingit is probably best to do a tracheostomy at that stage.Both endotracheal intubation and tracheostomy

have made considerable contributions to the care ofill patients and each method should be regarded ascomplementing the other rather than excluding it.

The role of mechanical ventilation in paediatricsurgeryAlthough the causes of respiratory insufficiency

are many and varied, mechanical ventilation isalways in a supportive role while the basic cause isbeing treated. It follows that if the basic cause is notsuccessfully treated then mechanical ventilation willmerely delay the probable fatal outcome.

In the author's experience, the best results asso-

ciated with mechanical ventilation have been ininfants and children undergoing cardiac surgery.In this group of patients we are dealing with respira-tory insufficiency secondary to cardiac failure orventilation/perfusion upsets of a transitory nature inthe lung following cardiac surgery. It is logical togive mechanical support in such conditions and,provided the surgery itself has been successful, thenartificial ventilation is usually necessary for a fewdays only leading to full recovery.

In neonatal surgery of the oesophagus, repair ofdiaphragmatic hernia or surgery of the intestines,mechanical ventilation when required is less reward-ing for various reasons.

(a) In an otherwise normal infant undergoingoesophageal or intestinal surgery, mechanical venti-lation is rarely necessary immediately postopera-tively. If it does become necessary a few days later,it will probably be the result of serious complicationssuch as severe peritonitis from a leaking intestinalanastomosis or pneumonia secondary to an exten-sive leak from the oesophageal anastomosis. Earlyand successful surgery may be necessary to avoid afatal outcome from these complications. In thesecircumstances mechanical ventilation will be in asupportive role and survival will depend on thesuccess of the surgical management.

(b) In congenital diaphragmatic hernia, artificialventilation is often necessary before and aftersurgery. In such infants, requiring artificial ventila-tion within a few hours of birth, results are poor.The contralateral lung may be hypoplastic in addi-tion to severe hypoplasia of the lung on the affectedside. In addition, there are probably severe ventila-tion/perfusion upsets in the lung as these infantsmay remain seriously desaturated even when venti-lated with 100% oxygen.

(c) Some neonates requiring surgery may bepremature and therefore may require artificial venti-lation immediately postoperatively. Such patientsmay have respiratory distress syndrome associatedwith their prematurity. Results will vary in thisgroup depending on the degree of prematurity, theseverity of the RDS and the extent of the surgery.

It is the policy in some centres to ventilate a highproportion of neonates in the immediate post-operative period. This will give a much higher per-centage survival in the total results and must beremembered when interpreting those results.

In conclusion, it can be said that in the total fieldof paediatric surgery mechanical ventilation has animportant supportive role to play. This supportiverole must be stressed otherwise too much may beexpected from it.The nature of the underlying condition necessitat-

ing artificial ventilation will usually determine theoutcome.

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