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CLINICAL INVESTIGATION
Year : 2007  |  Volume : 51  |  Issue : 6  |  Page : 505-509 Table of Contents     

Cricoid pressure: a survey of its practice in India


1 MD, DNB, Assistant Professor, Department of Anaesthesia, Christian Medical College, Vellore-632004, Tamilnadu, India
2 MD, Assistant Professor, Department of Anaesthesia, Christian Medical College, Vellore-632004, Tamilnadu, India
3 M.Sc, Statistician, Department of Anaesthesia, Christian Medical College, Vellore-632004, Tamilnadu, India
4 DA MD,Assistant Professor, Department of Anaesthesia, Christian Medical College, Vellore-632004, Tamilnadu, India
5 DA MD, Professor, Department of Anaesthesia, Christian Medical College, Vellore-632004, Tamilnadu, India

Date of Acceptance25-Oct-2007
Date of Web Publication20-Mar-2010

Correspondence Address:
B S Krishnan
Department of Anaesthesia, Christian Medical College, Vellore-632004, Tamilnadu
India
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Source of Support: None, Conflict of Interest: None


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Cricoid pressure (CP) application is performed by most anaesthesiologists during a rapid sequence intubation as a day to day routine; but very few anaesthetists have adequate knowledge or have been given proper instructions of the technique.
We conducted a survey of knowledge and practice regarding cricoid pressure application in 360 anaesthesiologists who attended the Annual Scientific meeting of the Indian Society of Anaesthesiologists in 2003.
There was a uniform lack of knowledge in most participants with widely varying practices being followed. Participants had experienced a high incidence of regurgitation (30%) and difficulty in tracheal intubation (57%) during application of cricoid pressure during their practice. We concluded that a proper technique of application of CP must be emphasized and demonstrated during the training programme for anaesthesiologists and an equal importance in training must be given to the non anaesthetic assistant who performs the maneuver in most instances in our country.

Keywords: Cricoid pressure, Knowledge, Training


How to cite this article:
Krishnan B S, Sanjib D A, Harikrishna D, Rajlakshmi B, Unnikrishnan, Korula G. Cricoid pressure: a survey of its practice in India. Indian J Anaesth 2007;51:505-9

How to cite this URL:
Krishnan B S, Sanjib D A, Harikrishna D, Rajlakshmi B, Unnikrishnan, Korula G. Cricoid pressure: a survey of its practice in India. Indian J Anaesth [serial online] 2007 [cited 2020 Oct 28];51:505-9. Available from: https://www.ijaweb.org/text.asp?2007/51/6/505/61188


   Introduction Top


Cricoid pressure (CP) was initially described by Sellick as a simple method to protect patients from re­gurgitation of gastric contents during the time of intuba­tion [1] . To practice safe and effective use of this maneu­ver requires training and knowledge of the related anatomy, physiology and the technique of application of cricoid pressure along with its associated complications. Though there continues to be controversy regarding the efficacy of CP and its safety, it is still a standard prac­tice of most anaesthesiologists. Various studies assess­ing knowledge of practitioners regarding CP and the ef­fect of training on them have been done. The uniform conclusion in all these studies was that theoretical knowl­edge of CP was poor in all categories of tested people including anaesthesiologists. These studies included anaesthesiologists in Sweden [2] and anaesthetic assis­tants in the UK. Neither of these studies documented whether cricoid pressure had been taught to them as an independent skill or not. We decided to test knowledge and practice of CP by anaesthesiologists in India and ascertain as to whether simple teaching of CP would reduce complications associated with this maneuver.


   Methods Top


This survey was conducted by means of a ques­tionnaire at the Annual Scientific Meeting of the Indian Society ofAnaesthesiologists in 2003.Atotal of 360 par­ticipants including anaesthesiologists in medical institu­tions and private practitioners were asked to fill up the questionnaire and return it. The questionnaire is shown in [Table 1]. The results were analyzed using SPSS ver­sion 11. Comparison of proportions in various groups was done using Chi-Square analysis. A P value of less than 0.05 was considered as statistically significant.


   Results Top


A total of 360 persons were interviewed by a ques­tionnaire. The results of the questionnaire are shown in [Table 1]. Eighty seven percent of the participants had given cricoid pressure before while 13 % had never ever used cricoid pressure. Though 83% of anaesthesiologists had been taught how to apply CP, only 71% of the par­ticipants routinely used CP for all full stomach patients. Even among those who used CP correct technique and proper knowledge about CP was lacking. Thirty six per­cent of anaesthesiologists routinely ventilated patients with a bag and mask during application of Sellick's ma­neuver and 19% did not aspirate nasogastric tubes present in patients with full stomach prior to rapid sequence in­tubation. Most personnel thought it was sufficient to start application of CP at induction of anaesthesia. The question as to how much force was to be applied during CP was answered with a variety of answers with 28% us­ing classical teachings of 30-40N. Twenty percent did not answer this question probably as they did not know the answer. Only 18% felt it necessary to check the position of the endotracheal tube prior to releasing CP. Most felt it was sufficient to release CP after inflating the cuff. This lack of knowledge and practice was re­flected by the fact that 30% had witnessed regurgitation during intubation of a full stomach patient, and 57% had experienced difficulty during intubation with the concur­rent application of CP. To add to problems of lack of knowledge among anaesthesiologists it was seen that in 66% of cases the person applying CP was an assistant.

One hundred twenty eight of the participants out of a total of 360 had less than 5 years experience whereas the remaining people were evenly distributed in the groups of 5-10, 11-15, 16-20 and more than 20 years experi­ence.


   Discussion Top


Most studies on practices of anaesthesiologists re­garding cricoid pressure application show a uniform poor theoretical knowledge among all categories of people and unacceptable variation in performance of the ma­neuver, which often leaves the patient at risk. This has been seen in surveys conducted among anaesthesiologists practicing in the UK, USA [3] and Sweden [2] . Simple rigs and laryngotracheal models were used in these studies to assess forces applied during CP and whether training sessions would improve the performance of anaesthesiologists.

This survey among Indian population was done to determine whether practices here differed from those in western countries. Very few centers in our country have models where CP application can be practiced to indi­cate forces that are to be used and we did not conduct a practical assessment of the performance by anaesthesiologists. The following questions were ad­dressed through the questionnaire.

Does experience in terms of number of years of practicing anaesthesia make a difference on the theo­retical knowledge or practicalities of application of CP?

Anaesthesiologists with experience of 16-20 years were more likely to initiate CP application correctly i.e. prior to induction of anaesthesia (38%) versus 19% of anaesthesiologists with less than 5 years experience. This was statistically significant (P=0.005). In none of the other groups was this found to be significant.

Classical teachings of CP tell anaesthesiologists to apply between 30-40N forces for occlusion of the oe­sophagus [1] . This has recently been contested by many articles suggesting forces ranging from 10-30N. Vanner initiallystaged the amount of pressure to be applied, based on a cadaver study. He advocated an initial pressure of 20N for awake patients and 30N after the loss of con­sciousness in subjects. Subsequently in 1999 he suggested that the initial pressure be decreased to 10N in awake subjects and then slowly increased to 30N as the patient lost consciousness. [4],[5] . He recommended CP to be re­leased once tracheal intubation was confirmed.

The [Table 1] reveals the pattern of application of force during sellick's maneuver based on the number of years of experience. A significant number of younger anaesthesiologists (<5 years experience) felt that a force of 20-40N would be appropriate compared to anaesthesiologists with >15 years experience who felt that the force required was outside this range of 20­40N. This is probably because there is a lot more em­phasis in recent years on actual force required than pre­viously when CP was just introduced into clinical prac­tice. In southern Sweden two-thirds of the subjects (69%) had never heard of any recommended level of force to be used for application of CP and only 17% could quote a specific force to be used. This, though, half of the sub­jects had been formally educated and 42% instructed or trained by a more experienced colleague [2] .

Irrespective of the number of years of experience, the common misconception uniformly in all groups was that CP could be released once the endotracheal tube cuff was inflated. Most anaesthesiologists did not feel it necessary to check the position of the tube to confirm tracheal intubation prior to releasing pressure. This mis­conception can only be corrected by teaching anaesthesiologists correct protocols for application of CP.

In all the more experienced groups a high percent­age of anaesthesiologists were found to routinely mask ventilate patients while applying CP. Only 25% of those with < 5 years experience routinely mask ventilated their patients compared to 41% in the 11-15 years experience group (P = 0.029), 48% in the 16-20 year group (P = 0.002) and 40% in the group with > 20 experience group (P = 0.039).

Both the groups with 16-20 years experience (60%) and the > 20years experienced group (60%) usually re­moved an existing nasogastric tube before rapid sequence intubation of a patient compared to 35% of those with < 5 years experience (P = 0.001). This is probably due to the fact that older teachings of CP application suggested that the presence of a nasogastric tube was probably an interference in the effectiveness of CP in occluding the oesophagus. Sellick suggested removing the nasogastric tube during CP, as he felt there was an increased risk of regurgitation by tripping both upper and lower esoph­ageal sphincters. The nasogastric tube would also inter­fere with esophageal compression during the maneuver [1] .However recent radiological studies show that efficacy of CP may even be increased in the pres­ence of a nasogastric tube, occupying the part of the esophageal lumen normally not obliterated by CP 4,6 .

These differences between the more experienced and less experienced anaesthesiologists in their approach to CP application also manifested in a high incidence of regurgitation witnessed by 40% in the 11-15 years group (P=0.005) and 46% in the 16-20 year group (P = 0.001) compared to 20% in the group with < 5 years experi­ence. Whether this paradoxically higher incidence of regurgitation seen in the experienced groups is inspite of their experience and because of the simple fact of the number of years of practice they have done or because of inadequate teaching cannot be determined from this data.

Does teaching of application of CP result in better patient management?

Out of the 360 participants of the survey a total of 311 had used CP application at some time in their ca­reers. These 311 were taken into consideration for fur­ther analysis; 278 of them had been taught how to apply CPwhereas the remaining 33 had not been taught. [Table 2] shows the two groups to be comparable with respect to the total number of years of experience they had and yet a significant number of those who had not been taught CP had witnessed regurgitation (47%) whereas only 26% of those who had been taught had witnessed regurgita­tion of gastric fluids. (P =0.01).This gives an impression that teaching of CP application protects patients from gastric fluid aspiration. In this questionnaire the respon­dent was most likely to be situated at the head end of the patient intubating the patient and the actual person ap­plying CP was likely to be an assistant who might have been taught or not. Sixty six of respondents said that an anaesthetic assistant usually applied CP, hence teaching of the anaesthesiologists per se is unlikely to be of help unless the information is passed on to the assistant.

In 1983 a study conducted on operating theatre per­sonnel in UK and the USA showed that 70% had expe­rienced a problem with the application of CP which ex­posed the patient to risks of regurgitation. Ten percent had witnessed regurgitation in that group [3] . This contrasts with our experience where upto 47% had witnessed re­gurgitation. The reason for this could be many; starting with the forces used in the application of CP to the tech­nique involved. The most common problem encountered during application of CP is a difficult airway due to the distortion of upper airway. Problems associated include difficult laryngoscope placement, pharyngeal compres­sion, and laryngeal distortion. It has been seen that in­cremental cricoid forces when applied on awake sub­jects lead to difficulty in breathing in half of them [7] . En­doscopic studies assessing the effect of CP on the cri­coid cartilage and vocal cords show that at forces of upto 44N difficulty in ventilation was present in 50% of subjects and vocal cord closure occurred in 60%. Fail­ure of ventilation was lower at 20N than at 44N [8] . Case reports of complete airway obstruction at 45N have been reported [7] . Complete airway occlusion in 11% of sub­jects along with a decrease in mean expired tidal volume and an increase in peak inspiratory pressure have been reported [9] .The data representing the additional risk posed by CP in terms of failed airway management is minimal. In obstetrics cases incidences of failed intubation range from 1: 300 [10] to 1: 500 [11] , but numbers specifically due to application of CP are not known. These data highlight the importance of a proper technique of CP application to prevent airway difficulties during intubation of full stomach patients.

The question as to whether CP does prevent aspi­ration of gastric contents has not been answered in the absence of randomized clinical trials. Studies on ana­tomical aspects and physiological effects of CP do not show proven benefit by the application of CP in all in­stances. The controversies on this issue have been dealt with in two separate reviews by Brimacombe [12] in 1997 and subsequently by Sanjib DA [13] in 2006. The method of application of CP suggested by Vanner [5] et al, of us­ing an initial pressure of 10N in the awake patient and gradually increasing it to a maximum of 30N after the patient loses consciousness is recommended . It is im­portant to remember the possible complications and side effects of CP during its application and realize that to achieve the above pressures on a consistent basis, train­ing is necessary.

Does training makes a difference to the force ap­plied during CP? The answer seems to be yes. A single training session using mannequins has shown to cause marked improvement in performance. [4] The use of simple instructions in an understandable form about the required force and use of simulators for practical training improves performance further. [15] Additional sessions may not pro­vide further improvement. [14] The ability of participants to apply correct cricoid force has been seen to be re­tained by upto 72% of anaesthesia personnel 14-21 days after a single training session.

After instruction and practice, all type of person­nel including anaesthesiology residents, registered nurse anaesthetists and others are able to learn the recom­mended amount of applied pressure and are able to re­tain this knowledge for upto 3 months after. [16] It has been suggested that models can be used every 3-6 months by anaesthesia personnel to refresh their technique of application of CP. Practicing on weighing scales is an­other method by which the range of forces can become within 5N above or below the target force. [5] Apractical approach regarding the force to be applied during CP is to remember that the force required to produce pain over the bridge of the nose provides approximately 40N. [12] This is another useful method of practicing CP applica­tion in a country where resources are meager but man­power abounds.

In conclusion there is a uniform lack of knowledge in all categories of anaesthesiologists in India irrespec­tive of the number of years of experience they have. In countries like ours where there is a lack of teaching mannequins and laryngo-tracheal models oral teaching practices have to be improved. Theoretical knowledge may go a long way in improving patient management especially if passed on to anaesthetic assistants who would in all probability be applying CP.

 
   References Top

1.Sellick BA. Cricoid pressure to control regurgitation of stom­ach contents during induction of anaesthesia. Lancet 1961; 2:404-6.  Back to cited text no. 1  [PUBMED]    
2.Schmidt A, Akeson J. Practice and knowledge of cricoid pres­sure in southern Sweden. Acta Anaesthesiol Scand 2001; 45:1210-4.  Back to cited text no. 2  [PUBMED]  [FULLTEXT]  
3.Howells TH, Chamney AR, Wraight WJ, Simons RS. The ap­plication of cricoid pressure.An assessment and a survey of its practice. Anaesthesia 1983; 38:457-60.  Back to cited text no. 3  [PUBMED]    
4.Vanner RG, Pryle BJ. Regurgitation and oesophageal rupture with cricoid pressure: a cadaver study.Anaesthesia 1992; 47:732­5.  Back to cited text no. 4  [PUBMED]    
5.Vanner RG, Asai T. Safe use of cricoid pressure. Anaesthesia 1999; 54:1-3.  Back to cited text no. 5  [PUBMED]  [FULLTEXT]  
6.Vanner RG, Pryle BJ. Nasogastric tubes and cricoid pressure. Anaesthesia 1993; 48:1112-3  Back to cited text no. 6      
7.Vanner RG. Tolerance of cricoid pressure by conscious volun­teers. Int J Obstet Anesth 1992; 1:195-8.  Back to cited text no. 7  [PUBMED]    
8.Mac GPJH, Ball DR. The effect of cricoid pressure on the cricoid cartilage and vocal cords: an endoscopic study in anaes­thetized patients. Anaesthesia 2000; 55:263-8.  Back to cited text no. 8      
9.Allman KG. The effect of cricoid pressure application on air­way patency. J Clin Anesth 1995; 7:197-9.  Back to cited text no. 9  [PUBMED]  [FULLTEXT]  
10.Lyons G. Failed intubation. Six years'experience in a teaching maternity unit. Anaesthesia 1985; 40:759-62.  Back to cited text no. 10  [PUBMED]    
11.Davies JM, Weeks S, Crone LA, Pavlin E. Difficult intubation in the parturient. Can J Anaesth 1989; 36:668-74.  Back to cited text no. 11  [PUBMED]    
12.Brimacombe JR, Berry AM. Cricoid pressure. Can J Anaesth 1997; 44:414-25.  Back to cited text no. 12  [PUBMED]    
13.Sanjib DA, Krishnan.B.S. The Cricoid Pressure: A review. In­dian Journal ofAnaesthesia 2006; 50:12-20.  Back to cited text no. 13      
14.Ashurst N, Rout CC, Rocke DA, Gouws E. Use of a mechani­cal simulator for training in applying cricoid pressure. Br J Anaesth 1996; 77:468-72.  Back to cited text no. 14  [PUBMED]  [FULLTEXT]  
15.Meek T, Gittins N, Duggan JE. Cricoid pressure: knowledge and performance amongst anaesthetic assistants. Anaesthesia 1999; 54:59-62.  Back to cited text no. 15  [PUBMED]  [FULLTEXT]  
16.Herman NL, Carter B, Van Decar TK. Cricoid pressure: teach­ing the recommended level.AnesthAnalg 1996; 83:859-63.  Back to cited text no. 16      


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