|Year : 2007 | Volume
| Issue : 6 | Page : 505-509
Cricoid pressure: a survey of its practice in India
BS Krishnan1, DA Sanjib2, D Harikrishna2, B Rajlakshmi3, Unnikrishnan4, Grace Korula5
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 Acceptance||25-Oct-2007|
|Date of Web Publication||20-Mar-2010|
B S Krishnan
Department of Anaesthesia, Christian Medical College, Vellore-632004, Tamilnadu
Source of Support: None, Conflict of Interest: None
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|| |
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  . 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  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|| |
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|| |
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|| |
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  and Sweden  . 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  . 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. , . 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  .
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  .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  . 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  . 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  . Case reports of complete airway obstruction at 45N have been reported  . 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  .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  to 1: 500  , 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  in 1997 and subsequently by Sanjib DA  in 2006. The method of application of CP suggested by Vanner  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.  The use of simple instructions in an understandable form about the required force and use of simulators for practical training improves performance further.  Additional sessions may not provide further improvement.  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.  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.  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.  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.
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