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VENTILATION DURING BRONCHOSCOPY WITH AN INJECTOR
Brit. J. Anaesth. (1973), 45,1063
VENTILATION DURING BRONCHOSCOPY WITH AN INJECTOR I. M. BALI, J. W. DUNDEE AND H. M. STEVENSON SUMMARY
Adequate pulmonary ventilation during bronchoscopy under general anaesthesia with a muscle relaxant has presented problems for the anaesthetist and the bronchoscopist. The introduction of the venturi principle for bronchoscopic work by Sanders (1967) has reduced the complicating factors of hypoxia and hypercarbia during this investigation. This paper reports the findings of a study which had the following objectives: (1) To perfect a simple venturi attachment which can be easily attached to and removed from a bronchoscope. (2) To find the concentration of oxygen and inflation pressure generated at the bronchial end of three adult sizes of bronchoscopes without and with the telescopic sight or suction catheter in position. (3) To obtain serial blood-gas and pH measurements during bronchoscopic ventilation with the venturi attachment. APPARATUS
(1) Detachable injector. Figures 1 and 2 show the detachable injector. A cut piece of copper plate with the tip bent at a right-angle was soldered on to an ordinary adjustable Jubilee clip (a size which was seen to fit the bronchoscopes). A 16 s.w.g. intravenous cannula was cut midway to shorten the injector and bent gradually to a right-angle. The butterfly flanges were screwed on to the copper plate. (2) Interruptor. A manual oxygen valve (Monitron Ltd) as shown in figure 3, was attached between the oxygen source and the injector. This proved very efficient for breath-by-breath control of ventilation as judged by the movement of the chest wall.
(3) Source of oxygen. The source of oxygen was the central pipeline supply at a pressure of 4.25 bar (60 Lb/sqin.). Figure 3 shows the safety keyed plug attached to the distal end of the pressure tubing. This system, with a slight modification of an adjustable pressure regulator, can be attached to an oxygen cylinder in the absence of pipeline facilities. EXPERIMENTAL STUDY
Three sizes of Negus bronchoscopes, (1) adult with an internal diameter (i.d.) of 10x8.7 mm and external diameter (o.d.) of 11 mm, (2) small adult with i.d. of 9.0X7.1 mm and o.d. of 10 mm, and (3) adolescent with i.d. of 8.0x6.7 mm and o.d. of 9 mm, were used with the 16 s.w.g. venturi attachment. The concentration of oxygen delivered and the inflation pressure generated were measured at the bronchial end of the bronchoscopes. (1) Oxygen concentration. This was measured by the Beckman paramagnetic oxygen analyser. With each setting three readings were taken, and the mean of the three observations recorded. Table I shows the concentrations achieved with the manual oxygen valve fully on, working at oxygen pipeline pressure of 4.25 bar. Both the telescopic sight and suction tube increased the oxygen concentration delivered at the end of the bronchoscopes. The lowest concentration (40%) was achieved with the adult bronchoscope and this increased as the bore for entrainment of air decreased. (2) Inflation pressure. A simple water manometer I.
M.
BALI,
MJ.,
M.'S.,
J.
W.
DUNDEE, MJ>., PH.D.,
F.F.A.R.C.S., Department of Anaesthetics, The Queen's University of Belfast; H. M. STEVENSON, F.R.OS., The Royal Victoria Hospital, Grosvenor Road, Belfast
Downloaded from http://bja.oxfordjournals.org/ at Cambridge University on July 11, 2015
The assembly of a simple detachable injector apparatus for ventilation during bronchoscopy is described. Using a 16 s.w.g. injector and pipeline oxygen at 4.25 bar (60 Lb/sq.in.), three sizes of Negus bronchoscopes were studied with regard to oxygen concentration and inflation pressure delivered at their bronchial ends. Serial blood-gas measurements in eight patients showed that if the patients were clinically adequately ventilated (by observing the chest movements during inflation) a steady state of Pao,, Pacoj and pH could be maintained.
1064
BRITISH JOURNAL OF ANAESTHESIA was used for measuring the inflation pressures. The side vents at the bronchial end of the bronchoscopes were closed for this pan of the study. As seen in table n , the pressure increased and behaved in a manner similar to that of the oxygen concentrations. TABLE I.
Percentage oxygen concentration.
1
2
3
40 42 46
54 61 76
47 55 63
Negus bronchoscopes Adult Small adult Adolescent
TABLE II.
Inflation pressure at distal end of bronchoscope
(cm/H.O).
Negus bronchoscopes Adult Small adult Adolescent
1
2
3
22.0 22.5 29.0
26.0 26.0 30.0
23.0 23.5 29.5
l=Normal. 2=With telescopic sight in bronchoscope. 3=With suction tube in bronchoscope. CLINICAL TRIAL
Method. This study was done on eight patients premedicated with atropine sulphate 0.6 mg and anaesthetized by intravenous injection of thiopentone or Althesin followed by suxamethonium for a bronFIG. 2. Detachable injector seen in an end-on view. Note choscopy lasting 2-7 minutes. Prcoxygenation was the ease with which a small-sized injector cannula can be not carried out and the lungs were not inflated screwed in place. before the insertion of the bronchoscope. As soon as the bronchoscope was passed between the vocal cords (which took only 5-15 sec, except in Case No. 6 where it took 30 sec), ventilation was commenced at a rate of 15-20 respirations a minute, with an inspiratory period of 1-2 sec. The required frequency and duration of each respiration was judged separately for each patient by observing the movements of the chest walL Permission for radial artery cannulation was obtained and a plastic catheter (18 s.w.g. green Median) inserted under local anaesthesia prior to induction of anaesthesia. A control arterial blood sample was drawn before the induction. The second sample was taken immediately following the muscle fasciculations and before insertion of the bronchoscope; thereafter samples were drawn at 1-minute intervals during the bronchoscopic ventilaFIG. 3. The apparatus for ventilation during bronchoscopy. tion. In one patient (Case No. 5) the arterial mnniiln The manual oxygen valve is for control of frequency and slipped out after the preinduction sample and further duration of ventilation.
Downloaded from http://bja.oxfordjournals.org/ at Cambridge University on July 11, 2015
FIG. 1. Detachable injector as seen in a side view.
l=Nonnal. 2=With telescopic sight in bronchoscope. 3=With suction tube in bronchoscope.
1065
VENTILATION DURING BRONCHOSCOPY WITH AN INJECTOR TABLE III.
Case No. 1 2 3* 4
61 7 8
Pao, Paco,
PH
Pao, Paco,
pH
Pao, Paco,
PH
Pao, Paco, pH Pao, Paco,
Pao, Paco, pH Pao, Paco, pH Pao, Paco,
PH
102 35 7.43 95 44 7.35 87 35 7.43 65 35 7.38 95 33 7.24 95 36 7.46 93 35 7.41 90 24 7.43
73 38 7.40 98 38 7.39 82 33 7.44 65 30 7.39 — — — 85 36.5 7.49 86 37 7.41 86 25 7.45
132 38 7.37 190 40 7.37 97 35 7.39 85 36 7.36 — 86 39 7.39 120 36 7.40 108 32 7.38
132 38 7.37 200 41 7.37 116 37 7.36 150 32 7.38 190 31 7.43 96 37 7.41 — — 114 29 7.39
_ 190 38 7.40 112 43 7.35 150 29 7.41 200 28 7.42 102 38 7.43 146 28 7.46 —
— 190 34 7.43 116 43 7.35 175 25 7.44 195 27.5 7.44 — 158 30 7.46 112 29 7.39
185 30 7.46 112 33 7.38
*Patient was ventilated only 10 times/min. Blood-gas analysis shows hypoventilation. fArterial canmila slipped out. Sampling at 2, 3 and 4 min was done by femora] artery puncture. {Difficulty in passing bronchoscope. A delay of 30 sec was caused.
samples at 2, 3 and 4 min of ventilation were taken from direct puncture of the femoral artery. At the end of the bronchoscopic examination the arterial cannula was removed and firm pressure maintained for 5 min to prevent haematoma formation. The arterial samples were taken in heparinized 2-ml syringes under anaerobic conditions. The syringes were capped and stored in ice. All samples were analysed within 20 min after bronchoscopy. Duplicate measurements were carried out using the Radiometer oxygen electrode type E5046 for arterial oxygen tension and the Radiometer Astrup model AMEI with the Siggaard-Andersen nomogram for pH and Pco2. RESULTS (TABLE III)
Oxygen tension (Pa^). Preinduction oxygen tension ranged from 65 to 102 mm Hg with an average of 90.2 mm Hg. A fall to an average of 82.1 mm Hg was observed after induction. As seen from figure 4 Paoj rose to an average of 116.9 mm Hg after 1 min of bronchoscopic ventilation with the venturi system. A further rise to a mean of 142.4 mm Hg was obtained in 2-min samples. After this the mean Paoj stabilized but some patients showed a further rise.
I r OP
T
I
•'Jp
i
tp
r r •t-t-
H
(VENTILATION UNUTIS
FIG. 4. Mean arterial oxygen, carbon dioxide, and pH values during bronchoscopy. Paoi represented by — . — . — Paooi represented by pH represented by Only two cases, Nos. 7 and 8, were ventilated for 7 min. Their mean arterial values art represented.
Carbon dioxide tension (Paco,)- The average fall of Pacoj after induction was to a value of 33.3 mm Hg from a preinduction level of 34.6 mm Hg. A mean rise 36.5 mm Hg occurred by 1 min which in subsequent samples fell gradually to a
Downloaded from http://bja.oxfordjournals.org/ at Cambridge University on July 11, 2015
5t
Arterial blood-gas values {mm Hg) and pH changes before and during bronchoscopic ventilation taith the venturi attachment. During bronchoscopic ventilation (min) PreAfter induction induction
1066
BRITISH JOURNAL OF ANAESTHESIA
DISCUSSION
Since Sanders (1967) introduced the venturi principle for apnoeic ventilation during bronchoscopy, modifications from simple detachable attachments to permanent alterations in the bronchoscope have been made by various workers including Spoerel (1969,1970), Hart (1970), Bradley, Moyes and Parke (1971), and Fuller, Davies and Stradling (1972). The injector attachment used for the study is easy to fix on to the Negus bronchoscopes, it does not require any major alterations in the equipment, and can be easily adjusted to fit any of the three sizes. Apart from the noise of the venturi there were no objections from the surgeon's viewpoint and the degree of blow-back was not excessive. The use of Bird Mark II ventilator by Spoerel (1969) and the recent addition by Bradley, Moyes and Parke (1971) of a solenoid valve activated by a timing device are two automatic controlling devices for ventilation specially for prolonged bronchoscopic examinations. In the conditions where the authors are working, diagnostic bronchoscopy rarely takes longer than 3-4 min, so that the need for automatic device does not arise. However, they may have a place in prolonged therapeutic procedures. The manual oxygen valve was found to be very easy to use. It gave a complete control of the duration and frequency of respirations which could be altered by judging the adequacy of chest movements. We did not preoxygenate the patients as it was desired to see the efficacy of this apparatus in raising
the arterial oxygen tension. It can be seen from table III that the arterial oxygen tension rose quite quickly over a period of 1 or 2 min, and then stabilized at a new high level. The two patients ventilated for 7 min each did not show any fall in arterial oxygen tension. Komesaroff and McKie (1972) have described a new device called the "Bronchoflator" for ventilation; this entrains minimal quantities of air and provides an oxygen concentration of 60-80%. They also found that when a Sanders injector was used there was a tendency for the arterial oxygen tension to fall and carbon dioxide tension to rise if ventilation was carried on for a long period. In their patients preoxygenation was carried out before ventilation with the venturi system was instituted. The high arterial oxygen tensions could not be maintained because the Sanders attachment gave only 25-35 % oxygen. The rise of arterial carbon dioxide tension in their series is probably accounted for by the fact that the lungs were ventilated at a fixed rate of 12 respirations per minute. Our experience suggests that if the ventilation rate is kept between 15-20 b.p.m., and the adequacy of ventilation is judged by clinical observation of the chest movements, a steady blood-gas level can be maintained. ACKNOWLEDGEMENTS
We are grateful to Mr J. J. Wilson, Medical Physics Technician (Respiratory and Intensive Care Unit), for his help in making the bronchoscopic attachments. We thank Dr W. F. K. Morrow, Consultant Anaesthetist, for his criticism and help in starting this work. We also wish to thank the patients for their co-operation. REFERENCES
Bradley, J. F., Moyes, E. N., and Parke, F. W. (1971). Modification of Sanders' technique of ventilation during bronchoscopy. Thorax, 26, 112. Fuller, W. R., Davies, D. M., and Stradling, P. (1972). Anaesthesia for bronchoscopy prolonged by teaching and photography. Anaesthesia, 27, 292. Hart, S. M. (1970). A further modification of a simple apparatus for pulmonary ventilation during bronchoscopy. Brit. J. Anaesth., 42, 78. Komesaroff, D., and McKie, B. (1972). The Bronchoflator: a new technique for bronchoscopy under general anaesthesia. Brit. J. Anaesth., 44, 1057. Sanders, R_ D. (1967). Two ventilating attachments for bronchoscopes. Delaware med. J., 39, 170. Spoerel, W. E. (1969). Ventilation through an open bronchoscope. Canad. Anaesth. Soc. J^ 16, 61. (1970). A ventilating attachment for the fiber-optic bronchoscope. Anesthesiology, 32, 561.
Downloaded from http://bja.oxfordjournals.org/ at Cambridge University on July 11, 2015
level of 31.5 mm Hg after 4 min of venturi ventilation. Case No. 3, who was deliberately ventilated at 10 times a minute showed a rise of Paoo, from 35 mm Hg at 1 min to 43 mm Hg after 3- and 4-min ventilation; however, the Paoa values in this case remained steady after the initial rise. pH measurements. As seen from figure 4 there was a slight mean rise to 7.42 during induction and a fall by 1 min to an average of 7.38, which is similar to the preinduction value of 7.39. During the subsequent minutes the average pH values rose to 7.41 and 7.42 by 3 and 4 min of ventilation respectively. Figure 4 summarizes the average changes in the measured parameters and shows the efficacy of the method of maintaining Oxygenation with minimal changes in Paooa and pH.
VENTILATION DURING BRONCHOSCOPY WITH AN INJECTOR I. M. BALI, J. W. DUNDEE AND H. M. STEVENSON SUMMARY
Adequate pulmonary ventilation during bronchoscopy under general anaesthesia with a muscle relaxant has presented problems for the anaesthetist and the bronchoscopist. The introduction of the venturi principle for bronchoscopic work by Sanders (1967) has reduced the complicating factors of hypoxia and hypercarbia during this investigation. This paper reports the findings of a study which had the following objectives: (1) To perfect a simple venturi attachment which can be easily attached to and removed from a bronchoscope. (2) To find the concentration of oxygen and inflation pressure generated at the bronchial end of three adult sizes of bronchoscopes without and with the telescopic sight or suction catheter in position. (3) To obtain serial blood-gas and pH measurements during bronchoscopic ventilation with the venturi attachment. APPARATUS
(1) Detachable injector. Figures 1 and 2 show the detachable injector. A cut piece of copper plate with the tip bent at a right-angle was soldered on to an ordinary adjustable Jubilee clip (a size which was seen to fit the bronchoscopes). A 16 s.w.g. intravenous cannula was cut midway to shorten the injector and bent gradually to a right-angle. The butterfly flanges were screwed on to the copper plate. (2) Interruptor. A manual oxygen valve (Monitron Ltd) as shown in figure 3, was attached between the oxygen source and the injector. This proved very efficient for breath-by-breath control of ventilation as judged by the movement of the chest wall.
(3) Source of oxygen. The source of oxygen was the central pipeline supply at a pressure of 4.25 bar (60 Lb/sqin.). Figure 3 shows the safety keyed plug attached to the distal end of the pressure tubing. This system, with a slight modification of an adjustable pressure regulator, can be attached to an oxygen cylinder in the absence of pipeline facilities. EXPERIMENTAL STUDY
Three sizes of Negus bronchoscopes, (1) adult with an internal diameter (i.d.) of 10x8.7 mm and external diameter (o.d.) of 11 mm, (2) small adult with i.d. of 9.0X7.1 mm and o.d. of 10 mm, and (3) adolescent with i.d. of 8.0x6.7 mm and o.d. of 9 mm, were used with the 16 s.w.g. venturi attachment. The concentration of oxygen delivered and the inflation pressure generated were measured at the bronchial end of the bronchoscopes. (1) Oxygen concentration. This was measured by the Beckman paramagnetic oxygen analyser. With each setting three readings were taken, and the mean of the three observations recorded. Table I shows the concentrations achieved with the manual oxygen valve fully on, working at oxygen pipeline pressure of 4.25 bar. Both the telescopic sight and suction tube increased the oxygen concentration delivered at the end of the bronchoscopes. The lowest concentration (40%) was achieved with the adult bronchoscope and this increased as the bore for entrainment of air decreased. (2) Inflation pressure. A simple water manometer I.
M.
BALI,
MJ.,
M.'S.,
J.
W.
DUNDEE, MJ>., PH.D.,
F.F.A.R.C.S., Department of Anaesthetics, The Queen's University of Belfast; H. M. STEVENSON, F.R.OS., The Royal Victoria Hospital, Grosvenor Road, Belfast
Downloaded from http://bja.oxfordjournals.org/ at Cambridge University on July 11, 2015
The assembly of a simple detachable injector apparatus for ventilation during bronchoscopy is described. Using a 16 s.w.g. injector and pipeline oxygen at 4.25 bar (60 Lb/sq.in.), three sizes of Negus bronchoscopes were studied with regard to oxygen concentration and inflation pressure delivered at their bronchial ends. Serial blood-gas measurements in eight patients showed that if the patients were clinically adequately ventilated (by observing the chest movements during inflation) a steady state of Pao,, Pacoj and pH could be maintained.
1064
BRITISH JOURNAL OF ANAESTHESIA was used for measuring the inflation pressures. The side vents at the bronchial end of the bronchoscopes were closed for this pan of the study. As seen in table n , the pressure increased and behaved in a manner similar to that of the oxygen concentrations. TABLE I.
Percentage oxygen concentration.
1
2
3
40 42 46
54 61 76
47 55 63
Negus bronchoscopes Adult Small adult Adolescent
TABLE II.
Inflation pressure at distal end of bronchoscope
(cm/H.O).
Negus bronchoscopes Adult Small adult Adolescent
1
2
3
22.0 22.5 29.0
26.0 26.0 30.0
23.0 23.5 29.5
l=Normal. 2=With telescopic sight in bronchoscope. 3=With suction tube in bronchoscope. CLINICAL TRIAL
Method. This study was done on eight patients premedicated with atropine sulphate 0.6 mg and anaesthetized by intravenous injection of thiopentone or Althesin followed by suxamethonium for a bronFIG. 2. Detachable injector seen in an end-on view. Note choscopy lasting 2-7 minutes. Prcoxygenation was the ease with which a small-sized injector cannula can be not carried out and the lungs were not inflated screwed in place. before the insertion of the bronchoscope. As soon as the bronchoscope was passed between the vocal cords (which took only 5-15 sec, except in Case No. 6 where it took 30 sec), ventilation was commenced at a rate of 15-20 respirations a minute, with an inspiratory period of 1-2 sec. The required frequency and duration of each respiration was judged separately for each patient by observing the movements of the chest walL Permission for radial artery cannulation was obtained and a plastic catheter (18 s.w.g. green Median) inserted under local anaesthesia prior to induction of anaesthesia. A control arterial blood sample was drawn before the induction. The second sample was taken immediately following the muscle fasciculations and before insertion of the bronchoscope; thereafter samples were drawn at 1-minute intervals during the bronchoscopic ventilaFIG. 3. The apparatus for ventilation during bronchoscopy. tion. In one patient (Case No. 5) the arterial mnniiln The manual oxygen valve is for control of frequency and slipped out after the preinduction sample and further duration of ventilation.
Downloaded from http://bja.oxfordjournals.org/ at Cambridge University on July 11, 2015
FIG. 1. Detachable injector as seen in a side view.
l=Nonnal. 2=With telescopic sight in bronchoscope. 3=With suction tube in bronchoscope.
1065
VENTILATION DURING BRONCHOSCOPY WITH AN INJECTOR TABLE III.
Case No. 1 2 3* 4
61 7 8
Pao, Paco,
PH
Pao, Paco,
pH
Pao, Paco,
PH
Pao, Paco, pH Pao, Paco,
Pao, Paco, pH Pao, Paco, pH Pao, Paco,
PH
102 35 7.43 95 44 7.35 87 35 7.43 65 35 7.38 95 33 7.24 95 36 7.46 93 35 7.41 90 24 7.43
73 38 7.40 98 38 7.39 82 33 7.44 65 30 7.39 — — — 85 36.5 7.49 86 37 7.41 86 25 7.45
132 38 7.37 190 40 7.37 97 35 7.39 85 36 7.36 — 86 39 7.39 120 36 7.40 108 32 7.38
132 38 7.37 200 41 7.37 116 37 7.36 150 32 7.38 190 31 7.43 96 37 7.41 — — 114 29 7.39
_ 190 38 7.40 112 43 7.35 150 29 7.41 200 28 7.42 102 38 7.43 146 28 7.46 —
— 190 34 7.43 116 43 7.35 175 25 7.44 195 27.5 7.44 — 158 30 7.46 112 29 7.39
185 30 7.46 112 33 7.38
*Patient was ventilated only 10 times/min. Blood-gas analysis shows hypoventilation. fArterial canmila slipped out. Sampling at 2, 3 and 4 min was done by femora] artery puncture. {Difficulty in passing bronchoscope. A delay of 30 sec was caused.
samples at 2, 3 and 4 min of ventilation were taken from direct puncture of the femoral artery. At the end of the bronchoscopic examination the arterial cannula was removed and firm pressure maintained for 5 min to prevent haematoma formation. The arterial samples were taken in heparinized 2-ml syringes under anaerobic conditions. The syringes were capped and stored in ice. All samples were analysed within 20 min after bronchoscopy. Duplicate measurements were carried out using the Radiometer oxygen electrode type E5046 for arterial oxygen tension and the Radiometer Astrup model AMEI with the Siggaard-Andersen nomogram for pH and Pco2. RESULTS (TABLE III)
Oxygen tension (Pa^). Preinduction oxygen tension ranged from 65 to 102 mm Hg with an average of 90.2 mm Hg. A fall to an average of 82.1 mm Hg was observed after induction. As seen from figure 4 Paoj rose to an average of 116.9 mm Hg after 1 min of bronchoscopic ventilation with the venturi system. A further rise to a mean of 142.4 mm Hg was obtained in 2-min samples. After this the mean Paoj stabilized but some patients showed a further rise.
I r OP
T
I
•'Jp
i
tp
r r •t-t-
H
(VENTILATION UNUTIS
FIG. 4. Mean arterial oxygen, carbon dioxide, and pH values during bronchoscopy. Paoi represented by — . — . — Paooi represented by pH represented by Only two cases, Nos. 7 and 8, were ventilated for 7 min. Their mean arterial values art represented.
Carbon dioxide tension (Paco,)- The average fall of Pacoj after induction was to a value of 33.3 mm Hg from a preinduction level of 34.6 mm Hg. A mean rise 36.5 mm Hg occurred by 1 min which in subsequent samples fell gradually to a
Downloaded from http://bja.oxfordjournals.org/ at Cambridge University on July 11, 2015
5t
Arterial blood-gas values {mm Hg) and pH changes before and during bronchoscopic ventilation taith the venturi attachment. During bronchoscopic ventilation (min) PreAfter induction induction
1066
BRITISH JOURNAL OF ANAESTHESIA
DISCUSSION
Since Sanders (1967) introduced the venturi principle for apnoeic ventilation during bronchoscopy, modifications from simple detachable attachments to permanent alterations in the bronchoscope have been made by various workers including Spoerel (1969,1970), Hart (1970), Bradley, Moyes and Parke (1971), and Fuller, Davies and Stradling (1972). The injector attachment used for the study is easy to fix on to the Negus bronchoscopes, it does not require any major alterations in the equipment, and can be easily adjusted to fit any of the three sizes. Apart from the noise of the venturi there were no objections from the surgeon's viewpoint and the degree of blow-back was not excessive. The use of Bird Mark II ventilator by Spoerel (1969) and the recent addition by Bradley, Moyes and Parke (1971) of a solenoid valve activated by a timing device are two automatic controlling devices for ventilation specially for prolonged bronchoscopic examinations. In the conditions where the authors are working, diagnostic bronchoscopy rarely takes longer than 3-4 min, so that the need for automatic device does not arise. However, they may have a place in prolonged therapeutic procedures. The manual oxygen valve was found to be very easy to use. It gave a complete control of the duration and frequency of respirations which could be altered by judging the adequacy of chest movements. We did not preoxygenate the patients as it was desired to see the efficacy of this apparatus in raising
the arterial oxygen tension. It can be seen from table III that the arterial oxygen tension rose quite quickly over a period of 1 or 2 min, and then stabilized at a new high level. The two patients ventilated for 7 min each did not show any fall in arterial oxygen tension. Komesaroff and McKie (1972) have described a new device called the "Bronchoflator" for ventilation; this entrains minimal quantities of air and provides an oxygen concentration of 60-80%. They also found that when a Sanders injector was used there was a tendency for the arterial oxygen tension to fall and carbon dioxide tension to rise if ventilation was carried on for a long period. In their patients preoxygenation was carried out before ventilation with the venturi system was instituted. The high arterial oxygen tensions could not be maintained because the Sanders attachment gave only 25-35 % oxygen. The rise of arterial carbon dioxide tension in their series is probably accounted for by the fact that the lungs were ventilated at a fixed rate of 12 respirations per minute. Our experience suggests that if the ventilation rate is kept between 15-20 b.p.m., and the adequacy of ventilation is judged by clinical observation of the chest movements, a steady blood-gas level can be maintained. ACKNOWLEDGEMENTS
We are grateful to Mr J. J. Wilson, Medical Physics Technician (Respiratory and Intensive Care Unit), for his help in making the bronchoscopic attachments. We thank Dr W. F. K. Morrow, Consultant Anaesthetist, for his criticism and help in starting this work. We also wish to thank the patients for their co-operation. REFERENCES
Bradley, J. F., Moyes, E. N., and Parke, F. W. (1971). Modification of Sanders' technique of ventilation during bronchoscopy. Thorax, 26, 112. Fuller, W. R., Davies, D. M., and Stradling, P. (1972). Anaesthesia for bronchoscopy prolonged by teaching and photography. Anaesthesia, 27, 292. Hart, S. M. (1970). A further modification of a simple apparatus for pulmonary ventilation during bronchoscopy. Brit. J. Anaesth., 42, 78. Komesaroff, D., and McKie, B. (1972). The Bronchoflator: a new technique for bronchoscopy under general anaesthesia. Brit. J. Anaesth., 44, 1057. Sanders, R_ D. (1967). Two ventilating attachments for bronchoscopes. Delaware med. J., 39, 170. Spoerel, W. E. (1969). Ventilation through an open bronchoscope. Canad. Anaesth. Soc. J^ 16, 61. (1970). A ventilating attachment for the fiber-optic bronchoscope. Anesthesiology, 32, 561.
Downloaded from http://bja.oxfordjournals.org/ at Cambridge University on July 11, 2015
level of 31.5 mm Hg after 4 min of venturi ventilation. Case No. 3, who was deliberately ventilated at 10 times a minute showed a rise of Paoo, from 35 mm Hg at 1 min to 43 mm Hg after 3- and 4-min ventilation; however, the Paoa values in this case remained steady after the initial rise. pH measurements. As seen from figure 4 there was a slight mean rise to 7.42 during induction and a fall by 1 min to an average of 7.38, which is similar to the preinduction value of 7.39. During the subsequent minutes the average pH values rose to 7.41 and 7.42 by 3 and 4 min of ventilation respectively. Figure 4 summarizes the average changes in the measured parameters and shows the efficacy of the method of maintaining Oxygenation with minimal changes in Paooa and pH.