For Dr. Mitch only

See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/26863638

Comparison of different Methods. of ventilation via cannula cricothyroidotomy in a trachea-lung model

Article in BJA British Journal of Anaesthesia · September 2009

DOI: 10.1093/bja/aep264 · Source: PubMed

CITATIONS

10

READS

33

3 authors, including:

Jonathan P Thompson

University of Leicester

103 PUBLICATIONS 1,918 CITATIONS

SEE PROFILE

All content following this page was uploaded by Jonathan P Thompson on 23 May 2016.

The user has requested enhancement of the downloaded file. All in-text references underlined in blue are added to the original document and are linked to publications on ResearchGate, letting you access and read them immediately.

Comparison of different methods of ventilation via cannula cricothyroidotomy in a trachea – lung model

†

N. J. Flint1*, W. C. Russell1 and J. P. Thompson2

1 Department of Anaesthesia, Critical Care and Pain Management, University Hospitals of Leicester NHS

Trust, Leicester Royal Infirmary, Leicester LE1 5WW, UK. 2 Department of Cardiovascular Sciences, Clinical

Division of Anaesthesia, Critical Care and Pain Management, University of Leicester and University

Hospitals of Leicester NHS Trust, Leicester Royal Infirmary, Leicester LE1 5WW, UK

*Corresponding author. E-mail: [email protected]

Background. Cannula cricothyroidotomy is recommended in recent guidelines as a rescue

intervention in the ‘cannot-intubate cannot-ventilate’ scenario. Several methods of providing

ventilation via a cannula cricothyroidotomy have been described, but there are no data compar-

ing these methods and using cannulae of differing diameters.

Methods. Using a bench-top trachea – lung model (comprising a Siemens test lung attached to

commercially available breathing system tubing), we compared delivered minute volumes (MVs)

for five methods of ventilation administered through cannulae of diameters 20, 16, 14, and

13 G. The ventilation methods were: an ENK oxygen flow modulator, a Manujet, a self-inflating

resuscitation bag, the oxygen flush of an anaesthetic machine, and oxygen from a wall-mounted

flow meter attached via a three-way tap to the cannula. All experiments were performed

with and without a proximal 2.5 mm diameter constriction to simulate partial upper airway

obstruction.

Results. MVs increased with increasing cannula diameter. In the absence of a proximal constric-

tion, MVs delivered via a 20 G cannula were ,1 litre min21 with all devices; only the Manujet

delivered MVs .2 litre min21, at cannula sizes of �16 G. MVs were greater in the presence of a proximal constriction, but did not exceed 4 litre min

21 using the low-pressure devices.

Conclusions. Extrapolated to the clinical situation, these data suggest that low-pressure devices

will not deliver adequate MVs via a cannula cricothroidotomy and should no longer be advocated.

Purpose-made devices should be available in all areas where anaesthesia is administered or

airway interventions are performed.

Br J Anaesth 2009; 103: 891–5

Keywords: airway, obstruction; equipment, breathing systems; ventilation, transtracheal

Accepted for publication: August 10, 2009

Failure to intubate and to ventilate a patient’s lungs with

oxygen [the cannot-intubate cannot-ventilate (CICV) scen-

ario] can have devastating consequences. This situation is

fortunately rare (with a quoted incidence of 1 in 10 000

general anaesthetics) 1

but is life threatening, and rapid

action is required to prevent hypoxic brain injury, cardiac

arrest, or death. This has led to the publication of guidelines

for the management of the CICV situation. 2 3

The United

Kingdom Difficult Airway Society (DAS) recommends two

options: the use of cannula cricothyroidotomy or surgical

cricothyroidotomy. 3

Surgical cricothyroidotomy has been

advocated as the procedure of choice in pre-hospital care; 4

however, many anaesthetists prefer transtracheal cannula

techniques with which they may be more familiar. 5

There is

little consensus as to the optimal cannula size, although the

DAS guidelines suggest that a ‘large’ cannula should be

used. 3

Previous investigators have commonly used a 14 G

cannula, 6 7

but there are few comparative published data on

which to base recommendations.

In addition to siting a cannula cricothyroidotomy, a

means of ventilation is required. Several purpose-

† Presented in part to the Anaesthetic Research Society Meeting,

Loughborough, UK, November 2005.

# The Author [2009]. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved.

For Permissions, please email: [email protected]

British Journal of Anaesthesia 103 (6): 891–5 (2009)

doi:10.1093/bja/aep264 Advance Access publication September 29, 2009

by guest on O ctober 20, 2015

http://bja.oxfordjournals.org/ D

ow nloaded from

manufactured devices are now available, but several other

improvised systems have been described and rec-

ommended 8 – 11

and included in resuscitation manuals. 10

The DAS recommend the use of ‘a high-pressure device

capable of delivering a high minute volume’ (MV); though

they do not state what this MV should be. 3

There are few

data directly comparing the different available systems.

The primary aim of this study was to assess the minute

ventilation delivered by different systems described for ven-

tilation through a cannula cricothyroidotomy using cannulae

of different diameters. Upper airway obstruction is a

common contributor to the CICV scenario and so a second-

ary aim was to assess minute ventilation in the presence or

absence of a simulated proximal airway constriction.

Methods

A simple physical model (Fig. 1) was used, based on the

one previously described. 12

This comprised a 210 mm

length of corrugated plastic anaesthetic breathing system

tubing (22 mm internal diameter), connected to a test lung

(Siemens test lung 190, Siemens Medical Solutions,

Bracknell, UK) which had a static compliance of 24 ml

kPa 21

. The proximal end of the ‘trachea’ was open to

atmosphere via a tracheal tube connector. During each

experiment, an i.v. cannula of varying size (13 – 20 G) was

inserted up to its hub through the wall of the hollow tube

60 mm from the proximal end and secured in place. The

i.v. cannulae were 20, 16, and 14 G (Abbocath Ireland

Ltd, Sligo, Ireland) and 13 G (Ravussin cannula, VBM

Medical, Sultz, Germany); the lengths of these cannulae

were 32, 51, 51, and 63 mm, respectively. MV was deter-

mined using a Wright respirometer connected in series at

the junction of the model trachea and test lung. The respi-

rometer was calibrated before the study against an industry

standard Biotek VT plus gas flow analyser (Biotek

Instruments, Winooski, VT, USA).

Five devices were compared. These were two purpose-

manufactured commercially available devices: the ENK

oxygen flow modulator (Cook, Bjaeverskov, Denmark)

and the Manujet (VBM Medical), and three systems

which are ‘improvised’ but have been described

previously. 8 – 10

The ENK (Fig. 2) and Manujet both

connect to the piped oxygen supply at 4 bar. The ENK

allows the oxygen flow to be controlled manually (by

occlusion of a number of its five side openings); it was

connected to the cannula using the ‘Luer lock’ tubing sup-

plied with the device. The Manujet is a high-pressure gas

injecting device (similar to a Sanders injector) but in

addition the driving pressure can be altered; in this study,

the Manujet was connected to piped oxygen at 4 bar, its

pressure reducing valve set to maximum pressure and con-

nected to the device via the luer lock tubing provided. The

‘improvised’ systems were:

(i) A self-inflating resuscitation bag (Laerdal Medical

Ltd, Orpington, UK) connected to the cannula via a 5

mm tracheal tube connector and connected to wall

oxygen via a flow regulator set at 15 litre min 21

(Fig. 2).

(ii) The oxygen flush from a Blease Frontline 560 anaes-

thetic machine (Blease UK, Chesham, UK) connected

to the cannula via oxygen tubing.

(iii) An improvised three-way tap device (Fig. 2) con-

nected to the cannula via oxygen tubing and con-

nected to wall oxygen via a flow regulator set at 15

litre min 21

, as described in the UK Resuscitation

Council Advanced Life Support Course manual. 10

Oxygen pipeline pressures and delivered flow rates were

measured by the Medical Physics Department using a

Biotek VT plus gas flow analyser. Ventilation was deliv-

ered via all devices at a rate of 20 min 21

with an inspira-

tory time of 1 s. In each case, ventilation was administered

for at least 20 s and the system allowed to stabilize before

measurements of MV were made. MV was recorded six

times in random order for each combination of device and

cannula. All measurements were made over a duration of

60 s and the Wright respirometer dial was concealed from

the investigator throughout each experiment. The diameter

Adjustable restriction (8 or 2.5 mm)

Flow monitor (Wright respirometer)

Test lung22 mm

Cannula (13–20 G)

210 mm10 mm

Fig 1 The trachea – lung model.

Fig 2 From left to right, ENK flow modulator, self-inflating bag, and

three-way tap connections.

Flint et al.

892

by guest on O ctober 20, 2015

http://bja.oxfordjournals.org/ D

ow nloaded from

of the proximal trachea tube connector was 8 mm and in

order to investigate the effect of an upper airway stenosis

on delivered MV, all experiments were repeated after sub-

stituting this for a tracheal tube connector of 2.5 mm

diameter.

Results

Recorded MVs varied significantly according to the type

of device, the size of cannula, and the presence or absence

of a constriction proximal to the cannula. MV increased

with increasing cannula size with all devices, although

there were large differences between devices in delivered

MV at a given cannula size. MV was generally increased

in the presence of a proximal constriction.

At an airway diameter of 8 mm (no constriction) MV

was low, with only the Manujet producing MV .2 litre

min 21

, and at a cannula diameter �20 G (Table 1). The ENK and three-way tap device produced no measurable

MV with either of the two smallest cannulae and achieved

above 1 litre min 21

only with the 13 G cannula. Neither

of the two low-pressure devices (oxygen flush and self-

inflating bag) were able to generate a measurable MV

regardless of cannula size.

Measurements of delivered pipeline pressures confirmed

a mean pressure of 406 kPa (data not shown) except the

machine O2 flush, which was 47 kPa.

In the presence of a simulated proximal airway constric-

tion (2.5 mm diameter), delivered MV was greater

(Table 2): MV .2 litre min 21

was recorded with all

devices via the 13 G cannula. However, at a cannula diam-

eter ,13 G, the self-inflating bag recorded no minute ven-

tilation, and the oxygen flush produced minimal or no

ventilation at a cannula diameter �14 G. The Manujet pro- duced MV .10 litre min

21 for all but the smallest

cannula, and both the Manujet and three-way tap produced

MV .2 litre min 21

at all cannula diameters.

Discussion

In this bench-top model, we found large differences

between delivered MV with different ventilation devices.

As expected, increasing cannula size was associated with

substantial increases in MV for a given device. At an

upper airway diameter of 8 mm, simulating a clear airway,

only the high-pressure devices delivered any recordable

MV; only the Manujet delivered an MV .2 litre min 21

and required a cannula size of �16 G to achieve this. The presence of a proximal constriction in the model to simu-

late upper airway obstruction also increased the delivered

MV, which is consistent with previous work using high-

frequency jet ventilation in a similar model. 13

However,

MV was negligible at an upper airway diameter of 2.5 mm

using the oxygen flush or self-inflating bag with cannula

sizes of ,14 or 13 G, respectively. Irrespective of upper

airway diameter, no device produced above 3 litre min 21

with the 20 G cannula.

These results compare broadly with previous investi-

gations which have found flow rates of 2.5 – 6.0 litre

min 21

using a 14 G cannula delivered via a ‘transtracheal’

model similar to the one used here. 6 7

Precise comparisons

are difficult because the studies differed in the gas delivery

systems, the precise method and configuration of the venti-

lating device and cannulae, and the presence or absence of

a test-lung. Previous studies have investigated different

individual devices and routes of ventilation, although this

is the first comparative study of available devices. Marr

and Yamamoto 9

found no difference in ventilation

volumes between catheters of different size when venti-

lation was delivered using a self-inflating bag. This study

had several limitations including that no lung-tracheal

model was incorporated, and the authors inferred gas

delivery from the displacement of water. Nevertheless,

they concluded and recommended that transtracheal venti-

lation is feasible using a self-inflating bag. Our data con-

tradict this and are consistent with the more sophisticated

models previously described.

Previous authors have commented on constriction of the

upper airway in the CICV scenario and concluded that

there is a critical diameter below which obstruction to

expiration occurs 12 14

and that passive expiration is likely

to occur despite a seemingly obstructed upper airway. 15 16

Our data suggest that upper airway obstruction is likely to

increase delivered MV when delivered manually via a cri-

cothyroid cannula. This is consistent with previous work

showing that distal airway pressures increase during

high-frequency jet ventilation delivered below a small

constriction of the proximal airway, 12 17

because of

Table 1 Mean (SD) MVs (litre min 21

) for each device across the range of

cannula sizes with a proximal airway diameter of 8 mm (‘no constriction’)

20 G 16 G 14 G 13 G

Manujet 0.89 (0.1) 2.43 (0.2) 3.38 (0.2) 10.55 (0.7)

Three-way tap 0.00 0.00 0.80 (0.1) 1.67 (0.5)

ENK 0.00 0.00 0.39 (0.1) 1.14 (0.2)

Oxygen flush 0.00 0.00 0.00 0.00

Self-inflating

bag

0.00 0.00 0.00 0.00

Table 2 Mean (SD) MVs (litre min 21

) for each device across the range of

cannula sizes with a proximal airway diameter of 2.5 mm (‘upper airway

constriction’)

20 G 16 G 14 G 13 G

Manujet 2.12 (0.1) 10.28 (0.2) 12.55 (0.2) 15.73 (0.2)

Three-way tap 2.93 (0.2) 3.72 (0.4) 5.25 (0.3) 6.07 (0.8)

ENK 1.15 (0.3) 2.00 (0.3) 3.12 (0.4) 6.08 (0.7)

Oxygen flush 0.00 0.70 (0.0) 3.10 (0.1) 3.90 (0.1)

Self-inflating

bag

0.00 0.00 0.00 2.17 (0.3)

Comparison of devices for cannula ventilation

893

by guest on O ctober 20, 2015

http://bja.oxfordjournals.org/ D

ow nloaded from

impedance to expiratory gas flow. To assess this risk, we

measured the peak (112 mbar) and mean (46 mbar) pressures

generated using the Manujet via a 13 G cannula with a 2.5

mm constriction. The effects of an immobile, rigid stenosis

as used in this model may be greater than those of a flaccid,

mobile, or semi-rigid upper airway obstruction, which is a

more likely scenario in clinical practice. Practitioners should

be aware of the potential for pulmonary barotrauma when

using this technique and specifically the importance of

allowing time for expiration, to prevent breath stacking.

Clearly, extrapolation of the precise values obtained

from this model to clinical practice should be made with

caution. Gas flow through the tracheobronchial tree in

humans during artificial ventilation depends on many

factors, including lung and thoracic compliance, airway

resistance, pressure and flow characteristics of the venti-

lation device and its airway conduit, route of delivery of

ventilation, pharmacological factors, and anatomical

abnormalities of the respiratory tract. However, this

trachea – lung model was of similar dimensions and the

test lung of similar compliance to that of an adult human.

It should be noted that the cannulae were of differing

lengths and different diameter. According to the Hagen –

Poiseuille equation, flow rates decrease with increased

catheter length, but this cannot be avoided in the clinical

situation; other authors have considered cannula length to

be insignificant in practice. 9

Furthermore, the primary aim

of the study was to compare the performance of the

devices in a stable laboratory situation. The Wright respi-

rometer has a tendency to underread at low volumes due

to inertia; however, the absolute values obtained using the

Wright respirometer were consistent, reproducible, and

were compared before the series of experiments against

the Biotek, an industry-standard gas flow analyser. On the

basis of previous data showing optimal I:E ratios for low-

and high-pressure systems, 18

we used a ventilatory rate of

20 min 21

and inspiratory time of 1 s, which would also be

appropriate in clinical practice. Our choice of cannula size

was determined partly by the range commonly available,

and which are likely to be accessible in the emergency

situation. We included a small (20 G) cannula for com-

parison as these are often used to instil local anaesthetics

and are readily available. We limited our study to devices

well described in the literature, resuscitation guidelines, in

the DAS guidelines, or both. Other available devices not

advocated in the DAS guidelines [e.g. the Quicktrach

(VBM Medical)] were not studied.

It is important to remember that the MV required for

effective ventilation and resuscitation in a CICV situation

is not clearly established. The primary aim during a CICV

situation is to deliver oxygen to the lungs (rather than

striving to achieve normal minute ventilation); however, a

greater MV will lead to a more rapid reversal of hypoxia.

Equally, since this scenario is likely to be associated with

a variable degree of hypercapnia, acidaemia, and hypoxaemia,

MVs in excess of basal physiological values may be

required. ‘Adequate’ MV has been defined as 7 19

or 4 litre

min 21

in the short term, if metabolic requirements are

low; 18

Zornow and colleagues 20

demonstrated that it was

possible to reverse hypoxia and hypercarbia in 22 kg

swine within 1 min with an MV of 7.8 litre min 21

.

Notwithstanding the limitations of our model, there were

clear differences between different devices and cannula

sizes. Only the Manujet in conjunction with a larger bore

cannula was able to consistently deliver MV that might be

considered adequate. In the presence of a proximal con-

striction of 2.5 mm diameter, MVs were greater, but absol-

ute values were still dependent on the device used and

cannula size. In general, only the high-pressure devices

(Manujet, ENK, and three-way tap) are likely to be able to

produce adequate ventilation.

In conclusion, these data suggest that in the absence of a

significant upper airway obstruction or stenosis, the Manujet

is the only device of those tested likely to deliver adequate

minute ventilation, and this depends on using as large a diam-

eter cannula as possible. In the presence of significant upper

airway obstruction, distal effective ventilation is augmented

and clinicians should be aware of the potential for pulmonary

barotrauma and hence the requirement for an appropriate

expiration time. Of the ad hoc devices, the simple three-way

tap and oxygen tubing performed best. In all cases, a cannula

of �14 G is recommended. Although the oxygen flush and self-inflating bag should be immediately available at every

location where anaesthesia is administered, they failed to

produce any effective ventilation. In the emergency situation,

hypoxia (and to a lesser extent hypercarbia) must be reversed

as rapidly as possible; therefore, low-pressure devices should

no longer be advocated. Furthermore, we suggest that

although ad hoc devices may be useful in the emergency situ-

ation, purpose-made devices that use a high-pressure oxygen

supply should be available in all areas where anaesthesia or

airway interventions are performed.

Funding

No external funding.

References 1 Benumof JL, Scheller MS. The importance of transtracheal jet

ventilation in the management of the difficult airway. Anesthesiology 1989; 71: 769 – 78

2 Crosby ET, Cooper RM, Douglas MJ, et al. The unanticipated diffi- cult airway with recommendations for management. Can J

Anaesth 1998; 45: 757 – 76 3 Henderson JJ, Popat MT, Latto IP, Pearce AC. Difficult Airway

Society guidelines for management of the unanticipated difficult intubation. Anaesthesia 2004; 59: 675 – 94

4 Scrase I, Woolard M. Needle vs. surgical cricothyroidotomy: a

short cut to effective ventilation. Anaesthesia 2006; 61: 662 – 74 5 Ratanayake B, Langford RM. A survey of emergency airway man-

agement in the United Kingdom. Anaesthesia 1996; 51: 908 – 11

Flint et al.

894

by guest on O ctober 20, 2015

http://bja.oxfordjournals.org/ D

ow nloaded from

6 Morley D, Thorpe CM. Apparatus for emergency transtracheal ventilation. Anaesth Intensive Care 1997; 25: 675 – 8

7 Ryder IG, Paoloni CCE, Harle CC. Emergency transtracheal ven- tilation: assessment of breathing systems chosen by anaesthetists.

Anaesthesia 1996; 51: 764 – 8 8 Gaughan SD, Benumof JL, Ozaki GT. Can an anaesthetic machine

flush valve provide for effective jet ventilation? Anesth Analg 1993; 76: 800 – 8

9 Marr JK, Yamamoto LG. Gas flow rates through transtracheal ventilation catheters. Am J Emerg Med 2004; 22: 264 – 6

10 Resuscitation Council (UK). Advanced Life Support Course Manual, 5th Edn. London: Resuscitation Council (UK), 2006

11 Bould MD, Bearfield P. Techniques for emergency ventilation

through a needle cricothyroidotomy. Anaesthesia 2008; 63: 535 – 9 12 Buczkowski PW, Fombon FN, Russell WC, Thompson JP. Effects

of helium on high frequency jet ventilation in a model of upper airway stenosis. Br J Anaesth 2005; 95: 710 – 5

13 Buczkowski PW, Fombon FN, Lin ES, Russell WC, Thompson JP.

Air entrainment during high-frequency jet ventilation in a model of upper tracheal stenosis. Br J Anaesth 2007; 99: 891 – 7

14 Dworkin R, Benumof JL, Benumof R, et al. The effective tracheal diameter that causes air trapping during jet ventilation. J Cardiothorac Anesth 1990; 4: 731 – 6

15 Farmery AD. Physics and physiology. In: Calder I, Pearce A, eds.

Core Topics in Airway Management. Cambridge: Cambridge University Press, 2005; 35 – 42

16 Smith RB, Babinski M, Klain M, et al. Percutaneous transtracheal ventilation. JACEP 1976; 5: 765 – 70

17 Ng A, Russell WC, Harvey N, Thompson JP. Comparing methods of administering high-frequency jet ventilation in a model of lar- yngotracheal stenosis. Anesth Analg 2002; 95: 764 – 9

18 Gaughan SD, Ozaki GT, Benumof JL. A comparison in a lung model of low- and high-flow regulators for transtracheal jet venti-

lation. Anesthesiology 1992; 77: 189 – 99 19 Craven RM, Vanner RG. Ventilation of a model lung using various

cricothyrotomy devices. Anaesthesia 2004; 59: 595 – 9 20 Zornow MH, Thomas TC, Scheller MS. The efficacy of three

different methods of transtracheal ventilation. Can J Anaesth 1989;

36: 624 – 8

Comparison of devices for cannula ventilation

895

by guest on O ctober 20, 2015

http://bja.oxfordjournals.org/ D

ow nloaded from

View publication statsView publication stats