- Email: [email protected]
FURTHER STUDIES ON TRANSTRACHEAL VENTILATION: THE INFLUENCE OF UPPER AIRWAY OBSTRUCTION ON THE PATTERNS OF PRESSURE AND VOLUME CHANGES
Brit. f. Atuusth. (1973), 45,733
FURTHER STUDIES ON TRANSTRACHEAL VENTILATION: THE INFLUENCE OF UPPER AIRWAY OBSTRUCTION ON THE PATTERNS OF PRESSURE AND VOLUME CHANGES K. CHAKRAVARTY, P. S. NARAYANAN AND W. E. SPOEREL SUMMARY
A new method of obtaining intermittent positive pressure ventilation by inserting a needle into the trachea and utilizing the jet principle has been developed recently in our Institution (Spoerel, Narayanan and Singh, 1971). It has been shown that using a 16-gauge needle as a jet with an oxygen pressure of 50 Lb./sqin., satisfactory pulmonary ventilation can be achieved in an adult patient. This method of ventilation has been advocated for resuscitation (Jacobs, 1972) in situations where immediate endotracheal intubation may not be possible and in anaesthesia for direct laryngoscopy (Spoerel, Singh and Sawhney, 1972; Spoerel and Greenway, 1973). Transtracheal ventilation is now being employed frequently by us for the purposes of resuscitation and during anaesthesia for direct laryngoscopy and oesophagoscopy. Many of these patients have varying degrees of upper airway obstruction and careful adjustments are needed in the setting of the ventilatory pattern. In order to find out how the patterns of pressure and volume are influenced by the presence of an obstruction in the proximal or upper airway during transtracheal ventilation, these parameters were studied in a model.
distance of 5 cm from its open end. A screw clamp was fixed on the rubber tube at 2 cm from its open end. The screw was turned gradually to constrict the tube up to a size of about 7 mm in internal diameter, simulating the glottic opening. The jet was connected to a Bird Mark II ventilator attached to the central pipeline (60 Lb./sqjn.). Built-in pressure gauges in a Bird Mark II ventilator and in the training thorax indicated the jet pressure and intrapulmonary pressure respectively. A 16-gauge needle introduced into the airway tube 2 cm proximal to the entry of jet was connected to a Statham transducer and pressure recorder in order to record the pressure proximal to the jet. A similar arrangement was used to obtain pressures in the airway tube distally at a point 1 cm from its junction with the training thorax; the pressure recorded here was identical to that inside the lung model. The arrangement is shown schematically in figure 1. The ventilator controls were adjusted to produce a standard pattern of ventilation. When the system reached a steady state, pressure recordings were obtained from the airway tube proximal and distal to the jet as described. Volume changes in the lung were calculated from the pressure readings after
METHOD
A Draeger training thorax was used as a lung model which was connected to a rubber tube, 15 cm in length and 10 mm in internal diameter representing the tracheobronchial airway. The jet needle (16 gauge) was introduced into the rubber tube at a
K. CHAKRAVABTV, DJL, FJ\AJLOS.(I), Department of Anaesthesiology; P. S. NARAYANAN, ALS., FJI.CS^ENG),
FJtas.(KDiN), Department of Thoracic Surgery, Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry-d, India; W. E. SPOEHEL, MJ>.» FJLCPJCC),
Department of Anaesthesiology, University of Western Ontario, London, f d
Downloaded from http://bja.oxfordjournals.org/ at Carleton University on June 12, 2015
The influence of partial obstruction of the upper airway on the pressure and volume changes during transtracheal ventilation has been studied on a model. It was found that obstruction of the airway proximal to the jet tends to increase the time required for inflation and deflation of the lung and also produces a higher inflation pressure, all proportional to the severity of the obstruction. While the tidal exchange remains largely unaffected, there will be hyperinflation of the lung with an increased functional residual volume. Careful adjustment of the pattern of ventilation is necessary for the safe use of transtracheal ventilation with upper airway obstruction, particularly when such obstruction is produced by stenosing lesions or by instrumentation during laryngoscopy or oesophagoscopy.
BRITISH JOURNAL OF ANAESTHESIA
734 having measured the compliance under static conditions. The obstruction in the proximal airway was increased by tightening the screw clamp further and changes in pressures and volumes were determined with different degrees of obstruction.
IO 8
X
E
6 -
UJ
+2"
J E T ON
JETOFF
1
7I
4 cc
o -J 3 /) - 2 4 UJ a: 6 a.
1\
•
•
•
i
•
i
i
y^
i
i
IO TIME IN SECONDS JET OFF
JET ON
O
i
i
15
JET ON
5 IO 15 TIME IN SECONDS
FIG. 1A. Typical pressure changes during respiratory cycle in model: Upper tracing, proximal airway (part F in fig. 1); lower tracing, distal airway (part G in fig. 1).
Lb/sq.in., applied to die jet, the pressure tracing in figure 2A was obtained proximal to the jet (part F, fig. 1). In figure 2B an obstruction of the inlet (part A in fig. 1) was produced by seven screw turns on the clamp (part H in fig. 1). This obstruction caused an increase in the initial negative pressure proximal to the jet (part F in fig. 1) and a much higher rise in pressure early in the expiratory phase with a much slower return of the pressure to the baseline. TO PIPE-LINE O , SUPPLY (80 US.j.q.ln.5
FIG. 1. The experimental arrangement. A-B=Tubc connected to Model Lung C D=Pressure gauge in the model showing intrapulmonary pressure. E=Jet needle 16 gauge and its connections. F=Point of measurement of proximal airway pressure. G=Point of measurement of distal airway pressure. H = Screw clamp. I=Pressure gauge in Bird ventilator representing jet pressure.
When the jet is turned "off" the pressure in the lung will rapidly fall to zero, while the gas emerging from the lung causes a sharp rise in pressure with a subsequent rapid fall to the baseline, proximal to the jet. With a ventilating pattern of an inspiratory phase ("jet on") of 1 second and expiratory phase of 3 seconds ("jet off") and a pressure of 40
i A>
"312 x 10 e 6 E, 6 4
UJ
(0 O co 2
-
-
1B1
/ ( L # f c / - / - / - /
1- r
1- 3 1
/--/
-
1 =
-
f 1.11
P / . ;-/
Mr
A.
1... s
1 ; . i 1 1 1.1-1
trf? T^" 7- / 1
-
v-
/V
Y.
a.
/-
t i t -
\'-,
-hr,
>•/••:
. _ \i
-1
IV-i-
. V-
1
,v
it:v
1
. 1 1..
V
. . 11 . m
100
s
Downloaded from http://bja.oxfordjournals.org/ at Carleton University on June 12, 2015
When the jet is turned "on", the pressure proximal to the jet (part F, fig. 1) becomes initially slighdy negative then rises to a slightly positive plateau (fig. 1A, upper tracing). At the same time, the pressure distal to the jet rapidly rises to a plateau (fig. 1A, lower tracing). The difference between the pressure plateaus proximal and distal to the jet will remain constant as long as die jet is "on"; its magnitude is a measure of the force generated by die jet. The height of the pressure plateau proximal to the jet is determined by the resistance to the out-flow of excess gas from die lung.
i
•
;
o
RESULTS
JET ON \
... IO
TIME IN SECONDS
FIG. 2. Pressure in proximal airway: Jet pressure 40 Lb./sq.in. inspiration:expiration 1:3 sec A = N o obstruction. B=Severe obstruction in proximal airway (seven screw turns on clamp).
Distal to the jet, i.e., inside the lung model, me pressure rose to 10 mm Hg during inspiration ("jet on") with an early return to baseline in expiration
735
FURTHER STUDIES ON TRANSTRACHEAL VENTILATION t o X SO
^ M
i i ••• i <-•
FIG. 3. Pressure in distal airway with same respiratory pattern as in figure 2. A=No obstruction. B = Moderate obstruction (five turns on screw clamp). C=Severe obstruction (seven turns on screw clamp). Note rise in peak inflation pressure and end-expiratory pressure and delayed inspiration and expiration.
I JO
5 is UJ
10
iin o'
10
fT~ ITTTrrTTT IO O
S
10
O
IO
TIME IN SECONDS
f
model has a linear compliance, the volume changes could be calculated from the pressure changes in the model lung (manometer D in fig. 1). With the changes shown in figures 3 and 4 the tidal volume remained unchanged when an obstruction was introduced, while the peak inspiratory volume increased corresponding to the increase in the residual volume at the end of the expiratory phase (table I). Supraglottic obstruction of the airway is common in anaesthetized patients and figure 5 shows a tracing: of the tracheal pressure. A rise in the peak pressure and an elevation of the end-expiratory pressure occurred when the jaw was relaxed, similar to the changes observed in our model; pulling the jaw forward corrected these changes.
FIG. 4. Pressure in distal airway with inspiration :expiration 2:2 sec. A = N o obstruction. B=Moderate obstruction and C = Severe obstruction, as in figure 3.
I 2% iu IS
I" s © IO O
S IO O TIME IN SECONDS
obstruction (fig. 4A), the introduction of obstruction (five screw turns in fig. 4B and seven screw turns in fig. 4c) showed a slower rise to a higher peak inflation pressure and an increase in the pressure at the end of expiration similar to figure 3. Since the Draeger training thorax used as lung
03 iN3Wf1SlSNI NOHJ.C
FIG. 5. Tracheal pressure tracing in patient during transtracheal ventilation under general anaesthesia. A=Chin held forward. B=Chin relaxed. Paper speed, 2 mm/sec.
TABLE I. This shows the effects of proximal airway obstruction on volume changes in the model lung. Note increase in peak inspiratory volume corresponding to increase in residual volume while the tidal volume remains unchanged.
State of proximal airway Standard (as in fig. 3A) Obstruction (as in fig. 3B) Obstruction (as in fig. 3c) Standard (as in fig. 4A) Obstruction (as in fig. 4c)
Calculated Calculated peak increase Calculated inspiratory in residual tidal volume volume volume (ml) (ml) (ml) 400
0
400
440
40
400
480
80
400
400
0
400
560
160
400
Downloaded from http://bja.oxfordjournals.org/ at Carleton University on June 12, 2015
("jet off") as shown in figure 3A. A moderate obstruction proximal to the jet produced by five screw turns on the clamp (part H in fig. 1) raised the inflation pressure to 13 mm Hg and prolonged the expiration so that the pressure returned barely to the baseline before the next inspiration occurred (fig. 3B). With a further increase in the obstruction by two additional screw turns the pressure in the lung model rose to 14 mm Hg (fig. 3c). The fall in pressure was still slower and a positive pressure of 4 mm Hg was still present when the next respiratory cycle started. Figure 4 shows the same sequence as in figure 3, except that the inspiration and expiration were set at 2 seconds each. Compared with the tracing without
BRITISH JOURNAL OF ANAESTHESIA
736
the point of entry of the jet into the trachea will offer a resistance to the entrainment of flow. ConseThe injector is a constant pressure generator and the pressure generated is determined by the force quently the negative pressure above the jet will be of the jet and the cross-sectional area of the tube greater but the inflation of the lungs slower since into which the jet discharges (Mushin et al, 1969; the entrainment volume is reduced. If the obstruction Spoerel and Grant, 1971). In transtracheal ventilation offers resistance to expiration, the pressure plateau the injector principle is directly applied to the trachea will rise further corresponding to the resistance to (Spoerel, Narayanan and Singh, 1971; Jacobs, 1972); the "leak-out" flow. When the jet is turned off, a the pulmonary inflation pressure is determined by partial obstruction will offer resistance to the expirathe size of the transtracheal needle acting as a jet, tory flow: the pressure in the lung falls more graduthe pressure applied to it, and the cross-sectional ally and a longer rime is required to deflate the lung area of the trachea. When the jet is turned on, the completely. With a fixed expiratory time, the pressure lungs are inflated by gas emerging from the jet as in the trachea and lungs may still be elevated when well as gas entrained through the upper airway by the next inspiration occurs. Our model experiments the negative pressure generated proximal to the jet. have shown that such an elevated end-expiratory As inflation proceeds, the entrainment flow gradually pressure results in an increase in the residual volume falls as the pressure in the lungs rises until the force of the lung without a change in the tidal volume. generated by the jet is equal to the pressure in the It is conceivable that with severe airway obstruction lung; further gas flow from the jet will now leak a dangerous overinflation and possible rupture of out of the upper airway while a pressure plateau the lung can occur, unless these problems are avoided is maintained in the lung. When the jet is turned by a suitable reduction of the pressure applied to off, pressure in the trachea will equalize and gas the jet and by allowing a sufficiently long expiratory will emerge from the upper airway until the lung time. pressure has returned to atmospheric pressure. Airway obstruction occurs frequently in clinical circumstances and its effect on the flow dynamics in The volume changes can be observed on a spirometric tracing attached to an endotracheal tube the airway requires careful evaluation when transending above the point of entrance of the trans- tracheal ventilation is to be used safely. Soft tissue tracheal jet; in this way the volume of entrainment obstruction above the larynx is not likely to create can be estimated, while the volume change in the problems; such obstruction offers only moderate spirometer during the leak out phase represents the resistance to expiration. Stenosing lesions of the volume flow emerging from the jet (fig. 6). Without larynx and the upper trachea are of greater signiobstruction, the entrainment contributed about 40% ficance and must be approached cautiously. Larynof the tidal volume (Spoerel, Narayanan and Singh, geal spasm may generate a high resistance to expira1971). A partial obstruction of the airway above tion, although we do not know what pressure would be required to overcome the obstruction to outflow BfOOin this condition. Complete obstruction of the outflow can be produced during the introduction of a scope into the oropharynx. Clinical experience has shown that during laryngoscopy and oesophagoscopy, a severe degree of obstruction can be produced inadvertently when the instrument is introduced into the oropharyngeal airway. For these procedures, the patient's muscles should be adequately relaxed to facilitate the introduction and to avoid active closure of the larynx. It is advisable in laryngoscopies to interrupt the ventilation whilst the instrument is being introduced lOOO and to resume ventilation once the glottis is properly I a s TIME IN SECOND* exposed (Spoerel and Greenway, 1973). Fio. 6. Spirometer tracing of one respiratory cycle during In our hands, transtracheal ventilation has proved transtracheal ventilation. Spirometer connected to cuffed endotracheal tube ^n
Downloaded from http://bja.oxfordjournals.org/ at Carleton University on June 12, 2015
737
FURTHER STUDIES ON TRANSTRACHEAL VENTILATION properly, and is situated freely in the lumen of the trachea. Careful attention must be paid to the first inflation, observing the inspiratory expansion of the chest as well as the subsequent expiration. If the expiration is prolonged, a long expiratory time must be set on a mechanical ventilator such as the Bird Mark n , or it may be preferable to use a hand valve to interrupt the jet while carefully observing the patient's chest movements. ACKNOWLEDGEMENTS
REFERENCES
Jacobs, H. B. (1972). Emergency percutaneous transtracheal catheter and ventilator. J. Trauma, 12, 50. Mushin, W. W., Rendell-Baker, L., Thompson, P. W., and Mapleson, W. W. (1969). Automatic Ventilation of the Lungs (2nd edn.). Oxford and Edinburgh: Blackwell. Spoerel, W. E., and Grant, P. A. (1971). Ventilation during bronchoscopy. Canad. Anaesth. Soc. J., 18, 178. Greenway, R. E. (1973). Jet ventilation during endolaryngeal surgery under general anaesthesia. Canad. Anaesth. Soc. % 20, 369. Narayanan, P. S., and Singh, N. P. (1971). Transtracheal ventilation. Brit. J. Anaesth., 43, 932. Singh, N. P., and Sawhney, K. L. (1972). Transtracheale Beatmung fur endolaryngeale Eingriffe Der Anaesthetist., 21, 59.
NOUVELLES ETUDES SUR LA VENTILATION TRANSTRACHEALE: L'INFLUENCE DE L'OBSTRUCTION DES VOtES AERIENNES SUPERIEURES EXERCEE SUR LES TYPES DE VARIATION DE LA PRESSION ET DU VOLUME SOMMATRB
On a etudif d'apres un modele l'influence de Pobstruction partklle des voies aeriennes superieures, exercee sur les variations de pression et de volume1 au cours de la ventilation transtracheale. On a trouve que robstruction de la voie aerienne proximate au jet a tendance a augmenter le temps necessaire au gonflement et au dtfonflement du poumon et produit egalement une pression d'insufflation plus ilevee, proportionnelle a la gravitf de 1'obstniction. Alors que l'echange d"air courant n'est pas du tout effecti,
WETTERE UNTERSUCHUNGEN OBER TRANSTRACHEALE BEATMUNG: DER EINFLUSS EINER VERLEGUNG DER OBEREN LUFTWEGE AUF DIE ABLAUFE DER VERANDERUNGEN VON DRUCK UND VOLUMEN ZUSAMMENFASSUNG
An einem Modell wurde der Einfluss teilweiser Verlegung der oberen Luftwege auf die Ver&nderungen von Druck und Volumen im Verlaufe transtrachealer Beatmung untersucht. Es zeigte sich dabei, dafl eine Veriegung der Luftwege proximal des Strahles dazu tendiert, die fur die Beluftung und Entluftung der Lunge erfbrderiiche Zeit zu verlSngern. Sie bewirkt ferner eincn hoheren Einatmungsdruck. Alle diese Werte sind proportional zur Schwere der Obstruktion. WShrend die zeitliche Vertoderung weithin unbeeinfhisst bleibt, entsteht eine Hyperinflation der Lunge mit einem gestelgerten funktionellen Residualvolumen. Eine sorgfaltige Anpassung des Beatmungsablaufes ist daher fflr die sichere Anwendung der transtrachealen Beatmung bei Veriegungen der oberen Luftwege notwendig. Dies ist insbesondere dann der Fall, wenn eine derartige Obstruktion hervorgerufen wird durch stenosierende Laeskmen oder durch eine entsprechende Instrumentation wBhrend der Laryngoskopie oder Oesophagoskopie. NUEVOS ESTUDIOS DE LA VENTTLACION TRANSTRAQUEAL: LA INFLUENCIA DE LA OBSTRUCCION DE LAS VIAS RESPIRATORIAS ALTAS SOBRE LOS PATRONES DE LOS CAMBIOS DE PRESION Y VOLUMEN RESUMEN
Se ha estudiado en un modelo la influencia de la obstruoci6n prcial de las vias respiratorias superiores sobre los cambios de presi6n y volumen durante la venrilacion transtraqueal. Se descubri6 qiie la obstruccion de las vias aireas proximales a la salida tiende a aumentar el tiempo requerido para la insuflacion del pulm6n y su vaciamiento, produciendo una mayor presion de insuflaci6n, siempre en proporci6n con el grado de obstruccion. Mientras que el valor del ritmo permanece inalterodo, habrA una hiperinsuflacion del pulmon con aumento del volumen residual funcionaL Se necesita un ajuste cuidadoso de los patrones de ventilacion para el uso seguro de la ventilaci6n transtraqueal con una obstruccion de las vfas aereas altas, especialmente cuando esta obstmccion es producida por lesiones estenosantes o por instrumentos durante la laringoscopia o esofagoscopia.
Downloaded from http://bja.oxfordjournals.org/ at Carleton University on June 12, 2015
We arc thankful to Dr M. Balasubrahmanyan (Principal, JTPMER) for his permission to utilize all the facilities available in the Institution for the purpose of this investigation and its publication. Shri Md. Mobideen Basha (Technician in the Department of Thoracic Surgery, JTPMBR) has given us valuable technical assistance for which we are obliged. We also thank the Department of Medical Illustration and Photography of JTPMER, Shri S. Jagedeesh and many other colleagues for their kind help.
il eziste une hyperinsufflation du poumon avec un volume fonctionnel et residuel augmented D est necessaire de faire un reglage soigneux des types de ventilation pour une utilisation sure de la ventilation transtracheale avec obstruction de la voie aerienne superieure, surtout si une telle obstruction est produite par des lesions stenosantes ou par rinstrumentation pendant la laryngoscopie ou roesophagoscopie.
FURTHER STUDIES ON TRANSTRACHEAL VENTILATION: THE INFLUENCE OF UPPER AIRWAY OBSTRUCTION ON THE PATTERNS OF PRESSURE AND VOLUME CHANGES K. CHAKRAVARTY, P. S. NARAYANAN AND W. E. SPOEREL SUMMARY
A new method of obtaining intermittent positive pressure ventilation by inserting a needle into the trachea and utilizing the jet principle has been developed recently in our Institution (Spoerel, Narayanan and Singh, 1971). It has been shown that using a 16-gauge needle as a jet with an oxygen pressure of 50 Lb./sqin., satisfactory pulmonary ventilation can be achieved in an adult patient. This method of ventilation has been advocated for resuscitation (Jacobs, 1972) in situations where immediate endotracheal intubation may not be possible and in anaesthesia for direct laryngoscopy (Spoerel, Singh and Sawhney, 1972; Spoerel and Greenway, 1973). Transtracheal ventilation is now being employed frequently by us for the purposes of resuscitation and during anaesthesia for direct laryngoscopy and oesophagoscopy. Many of these patients have varying degrees of upper airway obstruction and careful adjustments are needed in the setting of the ventilatory pattern. In order to find out how the patterns of pressure and volume are influenced by the presence of an obstruction in the proximal or upper airway during transtracheal ventilation, these parameters were studied in a model.
distance of 5 cm from its open end. A screw clamp was fixed on the rubber tube at 2 cm from its open end. The screw was turned gradually to constrict the tube up to a size of about 7 mm in internal diameter, simulating the glottic opening. The jet was connected to a Bird Mark II ventilator attached to the central pipeline (60 Lb./sqjn.). Built-in pressure gauges in a Bird Mark II ventilator and in the training thorax indicated the jet pressure and intrapulmonary pressure respectively. A 16-gauge needle introduced into the airway tube 2 cm proximal to the entry of jet was connected to a Statham transducer and pressure recorder in order to record the pressure proximal to the jet. A similar arrangement was used to obtain pressures in the airway tube distally at a point 1 cm from its junction with the training thorax; the pressure recorded here was identical to that inside the lung model. The arrangement is shown schematically in figure 1. The ventilator controls were adjusted to produce a standard pattern of ventilation. When the system reached a steady state, pressure recordings were obtained from the airway tube proximal and distal to the jet as described. Volume changes in the lung were calculated from the pressure readings after
METHOD
A Draeger training thorax was used as a lung model which was connected to a rubber tube, 15 cm in length and 10 mm in internal diameter representing the tracheobronchial airway. The jet needle (16 gauge) was introduced into the rubber tube at a
K. CHAKRAVABTV, DJL, FJ\AJLOS.(I), Department of Anaesthesiology; P. S. NARAYANAN, ALS., FJI.CS^ENG),
FJtas.(KDiN), Department of Thoracic Surgery, Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry-d, India; W. E. SPOEHEL, MJ>.» FJLCPJCC),
Department of Anaesthesiology, University of Western Ontario, London, f d
Downloaded from http://bja.oxfordjournals.org/ at Carleton University on June 12, 2015
The influence of partial obstruction of the upper airway on the pressure and volume changes during transtracheal ventilation has been studied on a model. It was found that obstruction of the airway proximal to the jet tends to increase the time required for inflation and deflation of the lung and also produces a higher inflation pressure, all proportional to the severity of the obstruction. While the tidal exchange remains largely unaffected, there will be hyperinflation of the lung with an increased functional residual volume. Careful adjustment of the pattern of ventilation is necessary for the safe use of transtracheal ventilation with upper airway obstruction, particularly when such obstruction is produced by stenosing lesions or by instrumentation during laryngoscopy or oesophagoscopy.
BRITISH JOURNAL OF ANAESTHESIA
734 having measured the compliance under static conditions. The obstruction in the proximal airway was increased by tightening the screw clamp further and changes in pressures and volumes were determined with different degrees of obstruction.
IO 8
X
E
6 -
UJ
+2"
J E T ON
JETOFF
1
7I
4 cc
o -J 3 /) - 2 4 UJ a: 6 a.
1\
•
•
•
i
•
i
i
y^
i
i
IO TIME IN SECONDS JET OFF
JET ON
O
i
i
15
JET ON
5 IO 15 TIME IN SECONDS
FIG. 1A. Typical pressure changes during respiratory cycle in model: Upper tracing, proximal airway (part F in fig. 1); lower tracing, distal airway (part G in fig. 1).
Lb/sq.in., applied to die jet, the pressure tracing in figure 2A was obtained proximal to the jet (part F, fig. 1). In figure 2B an obstruction of the inlet (part A in fig. 1) was produced by seven screw turns on the clamp (part H in fig. 1). This obstruction caused an increase in the initial negative pressure proximal to the jet (part F in fig. 1) and a much higher rise in pressure early in the expiratory phase with a much slower return of the pressure to the baseline. TO PIPE-LINE O , SUPPLY (80 US.j.q.ln.5
FIG. 1. The experimental arrangement. A-B=Tubc connected to Model Lung C D=Pressure gauge in the model showing intrapulmonary pressure. E=Jet needle 16 gauge and its connections. F=Point of measurement of proximal airway pressure. G=Point of measurement of distal airway pressure. H = Screw clamp. I=Pressure gauge in Bird ventilator representing jet pressure.
When the jet is turned "off" the pressure in the lung will rapidly fall to zero, while the gas emerging from the lung causes a sharp rise in pressure with a subsequent rapid fall to the baseline, proximal to the jet. With a ventilating pattern of an inspiratory phase ("jet on") of 1 second and expiratory phase of 3 seconds ("jet off") and a pressure of 40
i A>
"312 x 10 e 6 E, 6 4
UJ
(0 O co 2
-
-
1B1
/ ( L # f c / - / - / - /
1- r
1- 3 1
/--/
-
1 =
-
f 1.11
P / . ;-/
Mr
A.
1... s
1 ; . i 1 1 1.1-1
trf? T^" 7- / 1
-
v-
/V
Y.
a.
/-
t i t -
\'-,
-hr,
>•/••:
. _ \i
-1
IV-i-
. V-
1
,v
it:v
1
. 1 1..
V
. . 11 . m
100
s
Downloaded from http://bja.oxfordjournals.org/ at Carleton University on June 12, 2015
When the jet is turned "on", the pressure proximal to the jet (part F, fig. 1) becomes initially slighdy negative then rises to a slightly positive plateau (fig. 1A, upper tracing). At the same time, the pressure distal to the jet rapidly rises to a plateau (fig. 1A, lower tracing). The difference between the pressure plateaus proximal and distal to the jet will remain constant as long as die jet is "on"; its magnitude is a measure of the force generated by die jet. The height of the pressure plateau proximal to the jet is determined by the resistance to the out-flow of excess gas from die lung.
i
•
;
o
RESULTS
JET ON \
... IO
TIME IN SECONDS
FIG. 2. Pressure in proximal airway: Jet pressure 40 Lb./sq.in. inspiration:expiration 1:3 sec A = N o obstruction. B=Severe obstruction in proximal airway (seven screw turns on clamp).
Distal to the jet, i.e., inside the lung model, me pressure rose to 10 mm Hg during inspiration ("jet on") with an early return to baseline in expiration
735
FURTHER STUDIES ON TRANSTRACHEAL VENTILATION t o X SO
^ M
i i ••• i <-•
FIG. 3. Pressure in distal airway with same respiratory pattern as in figure 2. A=No obstruction. B = Moderate obstruction (five turns on screw clamp). C=Severe obstruction (seven turns on screw clamp). Note rise in peak inflation pressure and end-expiratory pressure and delayed inspiration and expiration.
I JO
5 is UJ
10
iin o'
10
fT~ ITTTrrTTT IO O
S
10
O
IO
TIME IN SECONDS
f
model has a linear compliance, the volume changes could be calculated from the pressure changes in the model lung (manometer D in fig. 1). With the changes shown in figures 3 and 4 the tidal volume remained unchanged when an obstruction was introduced, while the peak inspiratory volume increased corresponding to the increase in the residual volume at the end of the expiratory phase (table I). Supraglottic obstruction of the airway is common in anaesthetized patients and figure 5 shows a tracing: of the tracheal pressure. A rise in the peak pressure and an elevation of the end-expiratory pressure occurred when the jaw was relaxed, similar to the changes observed in our model; pulling the jaw forward corrected these changes.
FIG. 4. Pressure in distal airway with inspiration :expiration 2:2 sec. A = N o obstruction. B=Moderate obstruction and C = Severe obstruction, as in figure 3.
I 2% iu IS
I" s © IO O
S IO O TIME IN SECONDS
obstruction (fig. 4A), the introduction of obstruction (five screw turns in fig. 4B and seven screw turns in fig. 4c) showed a slower rise to a higher peak inflation pressure and an increase in the pressure at the end of expiration similar to figure 3. Since the Draeger training thorax used as lung
03 iN3Wf1SlSNI NOHJ.C
FIG. 5. Tracheal pressure tracing in patient during transtracheal ventilation under general anaesthesia. A=Chin held forward. B=Chin relaxed. Paper speed, 2 mm/sec.
TABLE I. This shows the effects of proximal airway obstruction on volume changes in the model lung. Note increase in peak inspiratory volume corresponding to increase in residual volume while the tidal volume remains unchanged.
State of proximal airway Standard (as in fig. 3A) Obstruction (as in fig. 3B) Obstruction (as in fig. 3c) Standard (as in fig. 4A) Obstruction (as in fig. 4c)
Calculated Calculated peak increase Calculated inspiratory in residual tidal volume volume volume (ml) (ml) (ml) 400
0
400
440
40
400
480
80
400
400
0
400
560
160
400
Downloaded from http://bja.oxfordjournals.org/ at Carleton University on June 12, 2015
("jet off") as shown in figure 3A. A moderate obstruction proximal to the jet produced by five screw turns on the clamp (part H in fig. 1) raised the inflation pressure to 13 mm Hg and prolonged the expiration so that the pressure returned barely to the baseline before the next inspiration occurred (fig. 3B). With a further increase in the obstruction by two additional screw turns the pressure in the lung model rose to 14 mm Hg (fig. 3c). The fall in pressure was still slower and a positive pressure of 4 mm Hg was still present when the next respiratory cycle started. Figure 4 shows the same sequence as in figure 3, except that the inspiration and expiration were set at 2 seconds each. Compared with the tracing without
BRITISH JOURNAL OF ANAESTHESIA
736
the point of entry of the jet into the trachea will offer a resistance to the entrainment of flow. ConseThe injector is a constant pressure generator and the pressure generated is determined by the force quently the negative pressure above the jet will be of the jet and the cross-sectional area of the tube greater but the inflation of the lungs slower since into which the jet discharges (Mushin et al, 1969; the entrainment volume is reduced. If the obstruction Spoerel and Grant, 1971). In transtracheal ventilation offers resistance to expiration, the pressure plateau the injector principle is directly applied to the trachea will rise further corresponding to the resistance to (Spoerel, Narayanan and Singh, 1971; Jacobs, 1972); the "leak-out" flow. When the jet is turned off, a the pulmonary inflation pressure is determined by partial obstruction will offer resistance to the expirathe size of the transtracheal needle acting as a jet, tory flow: the pressure in the lung falls more graduthe pressure applied to it, and the cross-sectional ally and a longer rime is required to deflate the lung area of the trachea. When the jet is turned on, the completely. With a fixed expiratory time, the pressure lungs are inflated by gas emerging from the jet as in the trachea and lungs may still be elevated when well as gas entrained through the upper airway by the next inspiration occurs. Our model experiments the negative pressure generated proximal to the jet. have shown that such an elevated end-expiratory As inflation proceeds, the entrainment flow gradually pressure results in an increase in the residual volume falls as the pressure in the lungs rises until the force of the lung without a change in the tidal volume. generated by the jet is equal to the pressure in the It is conceivable that with severe airway obstruction lung; further gas flow from the jet will now leak a dangerous overinflation and possible rupture of out of the upper airway while a pressure plateau the lung can occur, unless these problems are avoided is maintained in the lung. When the jet is turned by a suitable reduction of the pressure applied to off, pressure in the trachea will equalize and gas the jet and by allowing a sufficiently long expiratory will emerge from the upper airway until the lung time. pressure has returned to atmospheric pressure. Airway obstruction occurs frequently in clinical circumstances and its effect on the flow dynamics in The volume changes can be observed on a spirometric tracing attached to an endotracheal tube the airway requires careful evaluation when transending above the point of entrance of the trans- tracheal ventilation is to be used safely. Soft tissue tracheal jet; in this way the volume of entrainment obstruction above the larynx is not likely to create can be estimated, while the volume change in the problems; such obstruction offers only moderate spirometer during the leak out phase represents the resistance to expiration. Stenosing lesions of the volume flow emerging from the jet (fig. 6). Without larynx and the upper trachea are of greater signiobstruction, the entrainment contributed about 40% ficance and must be approached cautiously. Larynof the tidal volume (Spoerel, Narayanan and Singh, geal spasm may generate a high resistance to expira1971). A partial obstruction of the airway above tion, although we do not know what pressure would be required to overcome the obstruction to outflow BfOOin this condition. Complete obstruction of the outflow can be produced during the introduction of a scope into the oropharynx. Clinical experience has shown that during laryngoscopy and oesophagoscopy, a severe degree of obstruction can be produced inadvertently when the instrument is introduced into the oropharyngeal airway. For these procedures, the patient's muscles should be adequately relaxed to facilitate the introduction and to avoid active closure of the larynx. It is advisable in laryngoscopies to interrupt the ventilation whilst the instrument is being introduced lOOO and to resume ventilation once the glottis is properly I a s TIME IN SECOND* exposed (Spoerel and Greenway, 1973). Fio. 6. Spirometer tracing of one respiratory cycle during In our hands, transtracheal ventilation has proved transtracheal ventilation. Spirometer connected to cuffed endotracheal tube ^n
Downloaded from http://bja.oxfordjournals.org/ at Carleton University on June 12, 2015
737
FURTHER STUDIES ON TRANSTRACHEAL VENTILATION properly, and is situated freely in the lumen of the trachea. Careful attention must be paid to the first inflation, observing the inspiratory expansion of the chest as well as the subsequent expiration. If the expiration is prolonged, a long expiratory time must be set on a mechanical ventilator such as the Bird Mark n , or it may be preferable to use a hand valve to interrupt the jet while carefully observing the patient's chest movements. ACKNOWLEDGEMENTS
REFERENCES
Jacobs, H. B. (1972). Emergency percutaneous transtracheal catheter and ventilator. J. Trauma, 12, 50. Mushin, W. W., Rendell-Baker, L., Thompson, P. W., and Mapleson, W. W. (1969). Automatic Ventilation of the Lungs (2nd edn.). Oxford and Edinburgh: Blackwell. Spoerel, W. E., and Grant, P. A. (1971). Ventilation during bronchoscopy. Canad. Anaesth. Soc. J., 18, 178. Greenway, R. E. (1973). Jet ventilation during endolaryngeal surgery under general anaesthesia. Canad. Anaesth. Soc. % 20, 369. Narayanan, P. S., and Singh, N. P. (1971). Transtracheal ventilation. Brit. J. Anaesth., 43, 932. Singh, N. P., and Sawhney, K. L. (1972). Transtracheale Beatmung fur endolaryngeale Eingriffe Der Anaesthetist., 21, 59.
NOUVELLES ETUDES SUR LA VENTILATION TRANSTRACHEALE: L'INFLUENCE DE L'OBSTRUCTION DES VOtES AERIENNES SUPERIEURES EXERCEE SUR LES TYPES DE VARIATION DE LA PRESSION ET DU VOLUME SOMMATRB
On a etudif d'apres un modele l'influence de Pobstruction partklle des voies aeriennes superieures, exercee sur les variations de pression et de volume1 au cours de la ventilation transtracheale. On a trouve que robstruction de la voie aerienne proximate au jet a tendance a augmenter le temps necessaire au gonflement et au dtfonflement du poumon et produit egalement une pression d'insufflation plus ilevee, proportionnelle a la gravitf de 1'obstniction. Alors que l'echange d"air courant n'est pas du tout effecti,
WETTERE UNTERSUCHUNGEN OBER TRANSTRACHEALE BEATMUNG: DER EINFLUSS EINER VERLEGUNG DER OBEREN LUFTWEGE AUF DIE ABLAUFE DER VERANDERUNGEN VON DRUCK UND VOLUMEN ZUSAMMENFASSUNG
An einem Modell wurde der Einfluss teilweiser Verlegung der oberen Luftwege auf die Ver&nderungen von Druck und Volumen im Verlaufe transtrachealer Beatmung untersucht. Es zeigte sich dabei, dafl eine Veriegung der Luftwege proximal des Strahles dazu tendiert, die fur die Beluftung und Entluftung der Lunge erfbrderiiche Zeit zu verlSngern. Sie bewirkt ferner eincn hoheren Einatmungsdruck. Alle diese Werte sind proportional zur Schwere der Obstruktion. WShrend die zeitliche Vertoderung weithin unbeeinfhisst bleibt, entsteht eine Hyperinflation der Lunge mit einem gestelgerten funktionellen Residualvolumen. Eine sorgfaltige Anpassung des Beatmungsablaufes ist daher fflr die sichere Anwendung der transtrachealen Beatmung bei Veriegungen der oberen Luftwege notwendig. Dies ist insbesondere dann der Fall, wenn eine derartige Obstruktion hervorgerufen wird durch stenosierende Laeskmen oder durch eine entsprechende Instrumentation wBhrend der Laryngoskopie oder Oesophagoskopie. NUEVOS ESTUDIOS DE LA VENTTLACION TRANSTRAQUEAL: LA INFLUENCIA DE LA OBSTRUCCION DE LAS VIAS RESPIRATORIAS ALTAS SOBRE LOS PATRONES DE LOS CAMBIOS DE PRESION Y VOLUMEN RESUMEN
Se ha estudiado en un modelo la influencia de la obstruoci6n prcial de las vias respiratorias superiores sobre los cambios de presi6n y volumen durante la venrilacion transtraqueal. Se descubri6 qiie la obstruccion de las vias aireas proximales a la salida tiende a aumentar el tiempo requerido para la insuflacion del pulm6n y su vaciamiento, produciendo una mayor presion de insuflaci6n, siempre en proporci6n con el grado de obstruccion. Mientras que el valor del ritmo permanece inalterodo, habrA una hiperinsuflacion del pulmon con aumento del volumen residual funcionaL Se necesita un ajuste cuidadoso de los patrones de ventilacion para el uso seguro de la ventilaci6n transtraqueal con una obstruccion de las vfas aereas altas, especialmente cuando esta obstmccion es producida por lesiones estenosantes o por instrumentos durante la laringoscopia o esofagoscopia.
Downloaded from http://bja.oxfordjournals.org/ at Carleton University on June 12, 2015
We arc thankful to Dr M. Balasubrahmanyan (Principal, JTPMER) for his permission to utilize all the facilities available in the Institution for the purpose of this investigation and its publication. Shri Md. Mobideen Basha (Technician in the Department of Thoracic Surgery, JTPMBR) has given us valuable technical assistance for which we are obliged. We also thank the Department of Medical Illustration and Photography of JTPMER, Shri S. Jagedeesh and many other colleagues for their kind help.
il eziste une hyperinsufflation du poumon avec un volume fonctionnel et residuel augmented D est necessaire de faire un reglage soigneux des types de ventilation pour une utilisation sure de la ventilation transtracheale avec obstruction de la voie aerienne superieure, surtout si une telle obstruction est produite par des lesions stenosantes ou par rinstrumentation pendant la laryngoscopie ou roesophagoscopie.