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Understanding the Role of Cricoid Pressure in Preventing Aspiration

Explore the history, principles, and controversies surrounding cricoid pressure to prevent aspiration during anesthesia. Learn how anatomy, physiology, and proper technique play a crucial role.

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Understanding the Role of Cricoid Pressure in Preventing Aspiration

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  1. Does Cricoid PressurePrevent Aspiration?Pro Rakesh B. Vadhera, MD, FRCA, FFARCSI Galveston, Texas

  2. Introduction • “Linchpin” of Rapid Sequence Induction in ObstetricsRozen1981 1 • Aspiration (with or without failed/difficult intubation): one of the main causes of anesthesia related morbidity & mortality 2,3

  3. Anesthesia-Related Deaths During Obstetric Delivery 1979-90 Hawkins 1997 4

  4. Introduction • Over 35 years: • It has become a standard of practice &a fail safe against aspiration • Since wide spread introduction of CP : • a decrease in the incidence of aspiration related mortality • CEMDGB-1988-90 3- no mortality

  5. How and Why?? • History dates back to 1770s, when CP was applied to stop gastric insufflation 5 • Monro 1770: in drowned people - a pressure that should not interrupt laryngeal patency • Hunter 1776 Caution: Pressure should be applied with “judgement” so that “Larynx and trachea remains patent”

  6. How and Why? • Most earlier research was done to prove that pressures below 40 mm Hg does not insufflate stomach: we have forgotten this part of research!!! • 1961: Sellick reintroduced CP, as a mean of preventing the regurgitation 6

  7. Why and Why Not?? • A simple mechanical and, physically, physiologically, and anatomically appropriate maneuver • Concern about it’s efficacy and safety • interfere with airway management • esophageal trauma/rupture • aspiration and • wrong application!!!!!!!!

  8. Physics • If lower as well as upper esophageal sphincters somehow become incompetent • Pressure in stomach is more than pharynx • How can you stop the flow (regurgitation)??? • You can not, except

  9. Physics • How can you stop the regurgitation? • Inside • Outside • Gravity

  10. How can you stop Regurgitation? • Reduce gastric pressure • Increase lower esophageal sphincter as well as barrier pressures • Increase upper esophageal sphincter pressure

  11. Physiology of Regurgitation • Full Stomach (volume and pH) • Increase in IGP • Reduction in LESP • Reduction in UESP • All these forces have to work together • BrP = LESP-IGP

  12. Gastro-esophageal Reflux • Normal physiological consequence of full stomach: reflux relaxation 7,8 • Esophageal pressure rises by 5-10 mm Hg 8 • equals gastric pressure • common cavity • Pathogenesis depends upon • mix factors • vary among individuals • difficult to identify

  13. Gastro-esophageal Reflux • Parturients: 8-13 • GER common • Low/incompetent LESP • 45-85%: h/o heart burns • 80% have GER and incompetent LES • Full stomach • Delayed gastric emptying

  14. IGP • Normally < 7 mm Hg 13 • 25 mm Hg in starved full term supine parturient 13 • Increased to 35 mm Hg when stomach is distended 7 • Additional insults • pressure • succinylcholine

  15. Lower Esophageal Sphincter • LESP is reduced:7-13 • spontaneously in GERD • in patients full stomach • in term parturients • h/o reflux and heart burns • with GA to 7-14 mm Hg, depending upon relaxation 14-16 • with CP: at CF of 20 N 15 17

  16. Upper Esophageal Sphincter • UESP is a “Second Line” defense • UESP normally 38 mm Hg :18is reduced < 10 mm Hg by • induction agents 19 • before loss of consciousness 19 • Laryngoscopy 20 • muscle relaxants 19

  17. Upper Esophageal Sphincter • Regurgitation occurs,if UESP < 25 mm Hg • UESP is restored by CP 18

  18. Application of CP

  19. Anatomy & Physiology of CP • Cricoid Cartilage (CC): • signet shaped ring • horizontal inferiorly • deep vertical lamina • CP • applied to anterior CC • obstructs the opening of esophagus • pushes CC against hypopharynx CPM E

  20. Anatomy & Physiology of CP • CF • Newton (9.81N=2.2lbs) • Esophagus • lower border of CC • opening guarded by • CC anteriorly • Cricopharyngeus muscle posteriorly • UES • 3 cm high pressure zone CPM E

  21. Application of CP Some VariationsHead & Neck PositionSingle Vs Double HandedTime of ApplicationHow much CF ?

  22. Head & Neck Position • Sellick : Tonsillectomy position 6,21 • anterior convexity of cervical spine • stretches esophagus • prevents lateral esophageal displacement • Magill’s position • better for intubation • must avoid flexion of the neck at atlanto-occipital joint 22

  23. Head & Neck Position • No difference in the efficacy of CP in patients WITH or WITHOUT pillow when CF > 15 N is applied.Vanner 1992 13 • Must avoid flexion of neck with CP 23 • Application from left side 24

  24. Time of Application • Apply CP, as Thiopentone is injectedSellick 1961 6 • Fear: application of CP in awake patients • pain • difficulty in breathing • trigger vomiting, retching & coughing

  25. Time of Application • Most discomfort occurs at a CF > 40 N • Most subjects tolerate CF of 20 N • Reduction in UESP commences before loss of consciousness “Must apply CP before loss of consciousness”Vanner 1992 13

  26. Single Vs Double Handed • SHCP • Thumb & middle finger on either side & index finger above • Prevents lateral movement Sellick 6 • Better option in routine circumstancesCook 25-27 Brimacombe 14

  27. Cricoid Force • CF should be such that it • prevents regurgitation • maintains laryngeal patency • Initial recommendations were to use CF of 44 N 28 • pain, retching and vomiting • fear of esophageal trauma • laryngeal patency

  28. Cricoid Force • Current recommendations:29 • 20 N before loss of consciousness • 20 N tolerated by most • Increase to 30 N with loss of consciousness 30 • UESP > IGP • prevents regurgitation, OP of 42 mm Hg • likely to maintain patency • least likely to cause trauma

  29. FEARS

  30. Fears • Airway Management • Aspiration • Esophageal Rupture • too much CP • badly applied CP • timing of CP • Wrong Application

  31. Airway Management • Biggest fear • anatomical distortion • difficult intubation / ventilation • Most of the data collected at > 44 N • Technique???

  32. Airway Management • Vanner 1997 31 • Better view • Backward & upward pressure • 6% chance of improvement by removing CP • Randell 1998 32 • Similar to BURP • 57/68 better view

  33. Airway Management • Learn from history • If you ever reach a scenario • Difficult to ventilate • Judgment says that you have a much better chance of intubation without CP

  34. Aspiration • Reported cases with the use of CP • Seen with • wrong application • CP taken off before securing the airwayHowell 1983 33 • Fault • procedure itself • wrong application • what if did not apply CP?????

  35. Esophageal Trauma/Rupture • Very few cases 34 • Unlikely because of direct pressure • pressure at level of hypopharynx • Only if high pressures develop during application • retching/vomiting

  36. Esophageal Trauma/Rupture • Minimized by • unconsciousness, muscle relaxation and CP to occur synchronously Sellick 1982 35 • no esophageal trauma reported in cadavers, if CF applied < 30 N Vanner 1992 30

  37. Wrong Application???

  38. Wrong Application • Does not mean it’s technique’s fault • Do something to learn the correct technique and teach others • Pediatric scale • Mannequin • Simulator training

  39. Consistent facts • LES/UES is reduced • gastric distension • pregnant women (heart burns/reflux) • anesthetic agents

  40. Consistent facts • CP • is the only “SECOND” line defense • restores UESP • should be applied before loss of consciousness

  41. Consistent facts • 30 N Cricoid Force is adequate • restore UESP • maintains laryngeal patency • Unlikely to cause esophageal trauma • We do not apply CP correctly • but can learn from training • need continuous training

  42. Non-consistent Facts • Airway management more difficult • too much CF • badly applied CP • SHCP may be a better option • Esophageal trauma • Aspiration with CP

  43. Recommendations • Feel for CC • CP must be applied to CC and not thyroid • CC in center (slightly right) • apply backward and upward pressure

  44. Recommendations • Maintain vertebral arch (sniffing position) • Apply correct force • pain on the bridge of the nose • 3-3.2 kg

  45. Case Senario • A pregnant women with h/o of heart burns, who drank wine and took some cocaine comes for a Stat C. section for abruption (and has DIC) • Diabetic, Gastroparesis, ate 2 hours ago, h/o regurgitation on lying flat, receiving heparin, comes for embolectomy

  46. Prevention Prevention Prevention

  47. Thanks

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