Endotracheal tube cuff pressure: need for precise measurement

Original Article

Endotrache al tube cuff pre ssure :

ne e d for pre cise me asure me nt

Department of Anesthesiology, Faculdade de Medicina,

Universidade Estadual Paulista, Botucatu, Brazil

INTRODUCTION

High co mpliance endo tracheal tubes cuffs are used to prevent gas leak and also pulmo nary aspiratio n in mechanically ventilated patients. Ho wever, the use o f the usual cuff inflatio n vo lumes pro duces transmissio n o f the pressure directly to the tracheal wall aro und the cuffs. W hen the cuff pressure is o ver 4 0 cmH2O , which is the perfusio n pressure o f the tracheal muco sa a nd sub muc o sa ,1 lo ss o f muc o sa l c ilia r,2 ,3 ulceratio n, bleeding ,3 tracheal steno sis,4 and tracheo eso phageal fistula5 may o ccur.

Altho ugh deleterio us co nsequences have decreased with the ro utine use o f high-vo lume, lo w -p re ssure c uffs,6 c o mp lic a tio ns suc h a s tra c he a l ste no sis ma y still o c c ur.5 ,6 During anesthesia, it sho uld be co nsidered that nitro us o xide, a co mmo nly used g aseo us anesthetic, diffuses easily to the endo tracheal tube cuffs, increasing the cuff pressure.7

Endo tracheal tube cuff pressures are no t ro utinely measured8 and previo us studies have demo nstrated that cuff palpatio n is insufficient to detect high cuff pressures.9

In this study, we tested the hypo thesis that endo tracheal tube cuff pressure is ro utinely high (abo ve 4 0 cmH2O ) and that mo st pro fessio nals

ABSTRACT

CON TEX T: High co mpliance endo tracheal tubes cuffs are used to prevent gas leak and also pulmo nary aspiratio n in mechanically ventilated patients. Ho wever, the use o f the usual cuff inflatio n vo lumes may cause tracheal damage.

OBJECTIVE: W e tested the hypo thesis that endo tracheal tube cuff pressures are ro utinely high (abo ve 4 0 cmH2O ) in the Po st Anesthesia Care Unit (PACU) o r Intensive Care Units (ICU).

DESIGN : Cro ss-sectio nal study.

SETTIN G: Post anesthesia care unit and intensive care unit.

PARTICIPAN TS: W e measured endo tracheal tubes cuff pressure in 8 5 adult patients, as fo llo ws: G 1 (n = 3 1 ) patients fro m the ICU; G 2 (n = 3 2 ) patients fro m the PACU, after anesthesia with nitro us o xide; G 3 (n = 2 2 ) patients fro m the PACU, after anesthesia witho ut nitro us o xide. Intracuff pressure was measured using a mano meter (Mallinckro dt, USA). G as was remo ved as necessary to adjust cuff pressure to 3 0 cmH2O .

M AIN M EASUREM EN TS: Endotracheal tube cuff pressure.

RESULTS: High cuff pressure (> 4 0 cmH2O ) was o bserved in 9 0 .6 % patients o f G 2 , 5 4 .8 % o f G 1 and 4 5 .4 % o f G 3 (P < 0 .0 0 1 ). The vo lume remo ved fro m the cuff in G 2 was higher than G 3 (P < 0 .0 5 ).

CON CLUSION: Endo tracheal tubes cuff pressures in ICU and PACU are ro utinely high and significant higher when nitro us o xide is used. Endo tracheal tubes cuff pressure sho uld be ro utinely measured to minimize tracheal trauma.

that wo rk in the o perating ro o m o r Intensive Care Units are unaware o f the pro blem. W e underto o k a study to examine the frequency o f high cuff pressures in Po st Anesthesia Care Units and Intensive Care Units.

METHODS

After appro val fro m the Ethics Co mmittee, we measured endo tracheal tube cuffs pressures in 8 5 patients, as fo llo ws:

G ro up 1 : 3 1 patients admitted into the Intensive Care Unit (ICU);

G ro up 2 : 3 2 patients admitted into the Po st Anesthesia Care Unit (PACU), after anesthesia with nitro us o xide;

G ro up 3 : 2 2 patients admitted into the PACU, after anesthesia witho ut nitro us o xide. O nly adult patients that had been intubated by so meo ne o ther than the autho rs were eligible fo r inc lusio n in the stud y. Pa tie nts w ith tracheo to mies, laryngeal disease o r laryngeal surgery were excluded. The sizes o f the lo w-pressure high-co mpliance cuffed endo tracheal tubes ranged fro m 7 .0 to 9 .0 mm in internal diameter and cuff tube inflation was under control o f the anesthesio lo gist in the o peratio n ro o m, o r the intensive care specialist in the ICU.

In o rder to measure endo tracheal tube cuff pressure, a hand-held battery-o perated digital ma no me te r P-V G a ug e ma nufa c ture d b y Mallinckro dt (USA) was used. The age, weight, heig ht and sex o f the patients, and also the inte rna l d ia me te r a nd ma nufa c ture r o f the

e nd o tra c he a l tub e s w e re lo g g e d . Air w a s remo ved as necessary to adjust cuff pressure to an acceptable level (3 0 cmH2O ) at the time o f measurement.

Statistical Metho ds. Data o btained were co mpared using chi-squared test and variance analysis. The relatio nship between the vo lume o f remo ved a ir a nd c uff pressure wa s a lso o bserved, by means o f regressio n analysis. Data were repo rted as means, standard deviatio n o r mo de. Pro bability levels less than 0 .0 5 were co nsidered significant.

RESULTS

We fo und no differences amo ng the gro ups acco rding to anthro po metry o r sex (Table 1 ). High cuff pressures (> 4 0 cmH2O ) were fo und in 9 0 .6 % o f patients in G 2 , 5 4 .8 % in G 1 , and 4 5 .4 % in G 3 (P < 0 .0 0 1 ). Endo tracheal tube cuff pressure sho wed sig nificant differences between the gro ups, with G 2 > G 1 = G 3 (P < 0 .0 5 ), and was higher than the tracheal capillary pressure (4 0 cmH2O ) in all gro ups (Table 2 and Figure). There was also a significant difference between the gro ups in relatio n to air remo ved fro m the cuff (P < 0 .0 5 ). It was o bserved that little g a s ne e d e d to b e re mo ve d fro m endo tracheal tube cuffs to reduce cuff pressure to acceptable levels (3 0 cmH2O ) (Table 1 ). The greatest vo lume remo ved fro m the cuff was 1 0 cm3 (G 1 ) and the least was 0 .5 cm3 (G 3 ). There w a s a line a r re la tio nship b e tw e e n vo lume remo ved and cuff pressures in G 1 (r = 0 .9 3 ; P <

Table 1 - Distribution of sex and anthropometric variables and air volume removed from the cuff. G roups

Data ICU PACU with N2O PACU without N2O P-value

Patients 31 32 22 > 0 .5 0

Age, years 4 8 (1 8 ) 4 7 (1 8 ) 4 7 (1 9 ) > 0 .1 0

Sex (M/ F) 1 9 / 1 2 1 7 / 1 5 1 0 / 1 2 > 0 .5 0

Weight, kg 7 0 (1 5 ) 6 8 (1 3 ) 6 5 (1 6 ) > 0 .5 0

Height, m 1 .6 8 (0 .1 0 ) 1 .6 6 (0 .1 1 ) 1 .6 4 (0 .0 8 ) > 0 .1 0

Air volume removed from the cuff, cm3 2 .3 (1 .9 ) 2 .5 (2 .1 ) 0 .9 (0 .7 ) < 0 .0 5

0 .0 0 1 ), G 2 (r = 0 .7 4 ; P < 0 .0 0 1 ), and G 3 (r = 0 .7 2 ; P < 0 .0 0 1 ).

Endo tracheal tube size ranged fro m 7 .0 to 9 .0 mm internal diameter (Table 3 ), with no sig nificant difference amo ng the g ro ups (P > 0 .1 0 ). It was o nly po ssible to standardize the endo tracheal tubes used in O R (G 2 and G 3 ), in which high-vo lume, lo w-pressure endo tracheal tub e s fro m the sa me ma nufa c ture r (Rusc h, Uruguay) were always emplo yed. In ICU’s (G 1 ), endo tracheal tubes fro m Rusch (Uruguay) were also used the mo st (7 7 .4 %), but high-vo lume lo w-p re ssure e nd o tra c he a l tub e s fro m o the r manufacturers were also emplo yed.

DISCUSSION

The results o f the present study sho wed that there was high pressure in endo tracheal tube cuffs in mo st o f G 2 , tho se patients who were submitted to nitro us o xide during anesthesia, sho wing the impo rtance o f fast diffusio n o f this gas into the air-filled cuff. The co ntro l o f cuff pressure should be performed, if not continuously,

at least intermittently during anesthesia.

O n the o ther hand, high endo tracheal tube cuff pressure was also impo rtant in ICU patients (G 1 ) and tho se that did no t receive nitro us o xide during a nesthesia (G 3 ), co nfirming the lo w accuracy of cuff pressure estimation by palpation, even amo ng experienced anesthesio lo gists.9

The re ha ve b e e n d e sc rip tio ns o f the o ccurrence o f tracheal sequelae, seco ndary to endo tra c hea l tub e c uff hig h pressure, sinc e mechanical ventilatio n was intro duced in 1 9 5 0 . The first endo tracheal tube cuffs used were made o f lo w-co mpliance latex rubber, requiring high pressure levels to seal the tracheal lumen. Since the end o f the 1 9 7 0 ’s, these endo tracheal tube cuffs have been replaced by o nes made o f high-co mpliance plastic. Thus, higher air vo lumes can be injected with o nly small pressure increases, decreasing the incidence o f tracheal lesio ns.5 ,1 0 Lo w-pressure endo tracheal tube cuffs present wider suppo rt surfaces o n the tracheal muco sa tha n hig h-pre ssure o ne s, a nd the re fo re the pressure exerted by the fo rmer is lo wer.7

Despite the use o f lo w-pressure c uffed endo tra chea l tub es, po st-intub a tio n tra chea l steno sis is still repo rted in the literature.4

The characteristics o f tracheal muco sa, which is fo rmed by ciliated pseudo -stratified e p ithe lium, ma ke it ve ry se nsitive to the endo tracheal tube cuffs. Thus, pressure exerted

Table 3 - Endotracheal tube sizes (internal diameter) Tube size (mm)

G roup n 7 .0 7 .5 8 .0 8 .5 9 .0 Mean Mode

G 1 31 0 9 11 7 4 8.3 8.0

G 2 32 1 3 14 12 2 8.4 8.0

G 3 22 0 0 11 10 1 8.2 8.0

P > 0 .1 0

Table 2 - Endotracheal tube cuff pressure (cmH2O)

G roups

ICU PACU with N2O PACU without N2O

6 9 (7 0 ) 1 0 6 * (6 6 ) 6 0 .5 (3 8 )

(8 to 3 0 4 ) (1 5 to 2 8 7 ) (1 8 to 1 4 0 )

* Values are mean, standard deviation and range. P < 0 .0 5 [G 2 >(G 1 =G 3 )]

Figure - Endotracheal tube cuff pressure in the three

groups: mean and standard deviation and indica-tive limit value for tracheal capillary pressure. * p < 0.05:G2>(G1=G3).

G1 - ICU G2 - with N

2O

G3 - without N

2O

Limit value *

C

u

ff

P

re

ss

u

re

(

cm

H2

O

)

by the cuff o n the tracheal muco sa seems to be the main cause o f po st-intubatio n sequelae.1 ,4 ,5 ,1 1 -1 3

Ischemic damage o f the trachea depends o n the balance between muco sal perfusio n pressure and the pressure exerted by the cuff. W hen the cuff pressure exceeds tracheal muco sal perfusio n pressure, inductio n o f ischemia and/ o r necro sis will just be a questio n o f time.1 Tracheitis witho ut ulceration is the initial lesion that occurs, followed by muco sal denudatio n and expo sure o f trachea cartilage.1 O ther asso ciated facto rs can increase the inc id e nc e o f p o st-intub a tio n tra c he a l co mplicatio ns, even with cuff pressures that appear no t be excessive o n the tracheal muco sa. Amo ng these facto rs are included the decrease in muco sal blo o d flo w pro duced by hypo tensio n, sho ck and anemia,2 and lo w o xygen delivery to tracheal tissue, pro duced by hypo xemia, anemia and metabo lic acido sis.1 2 Additio nal mechanical facto rs, such as the placement o f naso gastric tubes, seem to increase the risk o f develo ping tracheoesophageal fistulas in patients under long-time tracheal intubatio n.4

W e o bserved that little gas needs to be remo ved fro m endo tracheal tube cuffs to reduce their pressure. This suggests that lo w-pressure, high-vo lume cuffs are filled to a lo w co mpliance po int o f the pressure-vo lume curve o f the cuff, when co nfined within a trachea.8 So me autho rs observed that high-compliance endotracheal tube cuff pressure increases very slo wly, between pressures o f 1 0 and 2 0 cmH2O , after which the additio n o f small vo lumes increases the cuff pressure substantially.8

The demo nstratio n o f the lo w accuracy o f fing er palpatio n estimates fo r cuff pressure9 makes it essential to measure endo tracheal tubes cuff pressure frequently, by using a more objective appro ach. During anesthesia with nitro us o xide, cuff pressure measurements beco me mandato ry due to the high pressure levels reached.7

Mo re recently, it has been pro po sed that endo tracheal tubes sho uld be used that pro vide pressure relief valves allo wing nitro us o xide d iffusio n w he n c uff p re ssure s e xc e e d 4 0 cmH2O .

1 4 -1 6

Unfo rtunately, the high co st o f these endo tracheal tubes make them impracticable fo r

frequent use.

W e reco mmend ro utine adjustment o f cuff pressures to o btain the lo west pressure co nsistent with a llo wing a sea l b etween tra c hea a nd e nd o tra c he a l tub e s. Ho w e ve r, p ro b le ms attributable to insufficient cuff inflatio n have been repo rted.1 7 These include leaking o f the tidal vo lume supplied by the ventilato ry system and micro -aspiratio ns o f o ro pharyngeal secretio ns tha t c o uld pro duc e no so c o mia l pulmo na ry infectio ns.18

CONCLUSION

Endotracheal tube cuff pressures in Intensive Care Units and Po st Anesthesia Care Units are ro utinely high and are significantly higher when nitro us o xide is used. Endo tracheal tube cuff pressures sho uld b e ro utinely mea sured b y mano metry to minimize trauma to the tracheal muco sa and surro unding structures.

REFERENCES

1. No rdin V. The trachea and cuff induced tracheal injury. Acta Oto laryngo l 1977;71(suppl 345):7-71.

2. Klaine r SA, Turnd o rf H, Wu HW. Surfac e alte ratio ns d ue to endo tracheal intubatio n. Am J Med 1975;58:674–83.

3. Martins RHG, Braz JRC, Bretan O. Lesõ es preco ces da intubação traqueal. Rev Bras Oto rrino laringo l 1995;61:343-8.

4. Berlauk J. Pro lo nged endo tracheal intubatio n vs. tracheo sto my. Crit Care Med 1986;14:742-6.

5. Stauffer J, Olsen D, Petty HT. Co mplicatio ns and co nsequences o f endo tracheal intubatio n and tracheo sto my. Am J Med 1981;70:65-76. 6. Te m p e lho ff G, Carto n M, Cannam e l A. Co m p lic atio ns laringo tracheales de l’intubatio n: étude pro spective sur 128 patients de réanimatio n co ntro lés par fibro sco pie à 24h à 1 mo is. Reanim So ins Intens Med Urg 1986;2:264-9.

7. Stanley TH, Kamamura R, Serio us C. Effects o f nitro us o xide o n vo lume and pressure o f endo tracheal tube cuff. Anesthesio lo gy 1974;41:256-61.

8. Byrd RA, Mascia MF. What is the endo tracheal tube cuff pressure in a cro ss-sectio n o f intubated patients? Anesthesio lo gy 1996;85(suppl 3A):982.

9. Fernandez R, Blanch L, Mancebo J, Bo nso ms N. Endo tracheal tube cuff pressure assessment: pitfalls o f finger estimatio n and need fo r o bjective measurement. Crit Care Med 1990;18:1423-6.

10. Lewis F, Schlo bo hm R, Tho mas A. Preventio n o f co mplicatio ns fro m pro lo nged tracheal intubatio n. Am J Surg 1978;135:452-7. 11. Do brin P, Canfield T. Cuffed endo tracheal tubes: muco sal pressures

and tracheal wall blo o d flo w. Am J Surg 1977;133:562-8.

13. Jo h S, Matsuura H, Ko tani Y, et al. Change in tracheal blo o d flo w d uring e nd o trac he al intub atio n. Ac ta Anae s the s io l Sc and 1987;31:300-6.

14. Brand t L. Pre ve ntio n o f nitro us o xid e ind uc e d inc re ase in endo tracheal tube cuff pressure. Anesth Analg 1991;72:262-70. 15. Fill DM, Do sch MP, Bruni RM. Rediffusio n o f nitro us o xide prevents

increase in endo tracheal tube cuff pressure. J Am Asso c Nurse Anesth 1994;62:77-91.

16. Bo uflers E, Menu H, Gérard A, Maslo wski D, Reyfo rd H, Guermo uche T. Étude co mparative des pressio ns au niveau du ballo net temo in d e d e ux typ e s d e so nd e s d ’intub atio n. Cahie rs Ane sthe sio l 1996;44:499-502.

17. Metha S, Mickiewicz M. Wo rk practices relating to intubatio n and asso ciated pro cedures in intensive care units in Sweden. Acta Anesthesio l Scand 1986;30:637-40.

18. To bin MJ, Grenvik A. No so co mial lung infectio n and its diagno sis. Crit Care Med 1984;12:191-6.

Ack now ledgement: W e thank Pro f. Dr. Paulo Ro berto Curi fo r statistical advice and analysis.

José Reina ldo Cerqueira Bra z - MD, PhD. Department o f Anesthesio lo gy, Faculty o f Medicine o f Universidade Estadual Paulista. Bo tucatu, Brazil.

Lais Helena Camacho N avarro- Undergraduate medical student of Universidade Estadual Paulista. Botucatu, Brazil.

Ieda Ha rumi Ta k a ta - MD. Department o f

Anesthesio lo gy, Faculty o f Medicine, Universidade Estadual Paulista. Bo tucatu, Brazil.

Pa ulo N a scimento Júnior - MD, PhD. Department o f Anesthesio lo gy, Faculty o f Medicine, Universidade Estadual Paulista. Bo tucatu, Brazil.

Sources of funding: Research sponsored by PIBIC/ CNPq.

Conflict of interest: No t declared

La st received: 2 2 April 1 9 9 9

Accepted: 1 4 May 1 9 9 9

Address for correspondence:

Jo sé Reinaldo Cerqueira Braz

Faculdade de Medicina de Bo tucatu - UNESP Departamento de Anestesio lo gia

Rubião Júnio r/ SP - Brasil - CEP 1 8 6 1 8 -9 7 0 Email: jbraz@ fmb.unesp.br

RESUMO

CON TEX TO: Tubo s traqueais co m balo nete de alta co mplacência são utilizado s para prevenção de vazamento de gás e de aspiração pulmo nar em pacientes submetido s à ventilação mecânica. Entretanto , o vo lume de insuflação habitual gera uma pressão do balo nete que se transmite diretamente à parede traqueal e po de causar lesõ es. OBJETIVO: Testar a hipó tese de que as pressõ es no balo nete do tubo traqueal geralmente estão elevadas (acima de 4 0 cmH2O ) na Sala de Recuperação Pó s-anestésica (SRPA) o u nas Unidades de Terapia Intensiva (UTI). TIPO DE ESTUDO: Estudo de seção transversal. LOCAL: Sala de recuperação pós-anestésica e unidade de terapia intensiva. PARTICIPAN TES: Medimos a pressão no balonete do tubo traqueal em 8 5 pacientes adulto s, sendo : G 1 (n=3 1 ) pacientes da UTI; G 2 (n=3 2 ) pacientes da SRPA, apó s anestesia co m ó xido nitroso; G 3 (n=2 ) pacientes da SRPA, após anestesia sem óxido nitroso. A pressão no balonete foi medida utilizando-se um manômetro (Mallinkrodt, USA). Q uando necessário, retirou-se gás para ajustar a pressão no balonete até 3 0 cmH2O .

VARIÁVEIS ESTUDADAS: Pressão do balo nete do tubo traqueal. RESULTADOS: Fo ram o bservadas pressõ es elevadas no balo nete do tubo traqueal em 9 0 ,6 % do s pacientes de G 2 , 5 4 ,8 % de G 1 e 4 5 ,4 % de G 3 (P < 0 ,0 0 1 ). CON CLUSÕES: As pressõ es no balo nete do tubo traqueal na UTI e na SRPA estão elevadas ro tineiramente e são significativamente mais altas quando se utiliza ó xido nitro so . A pressão no balo nete do tubo traqueal deve ser medida ro tineiramente para minimizar o trauma traqueal.