Cricoid PressureDo We Still Need to Push?

Cricoid Cartilage

(from the Greek krikoeides meaning "ring-shaped"), is the only complete ring of cartilage around the trachea.

Cricoid Pressure

• Often performed incorrectly

• Potentially interfering

• Possibly harmful

• Unproven benefit

Cricoid Pressure History

• 1770 (Monroe) prevention of gastric inflation: ventilation for drowning victims

• 1961 (Sellick) occlusion of esophageal lumen to prevent regurgitation & aspiration

with induction of anesthesia

Sellick’s Maneuver

• Goal: Compress esophagus between ring cartilage and cervical vertebral body (C6)

• Technique:

thumb and middle finger on the sides of cricoid cartilage and index finger above to avoid lateral deviation

Sellick’s Study

• Observational: 26 high risk patients

• 3 of 26: immediate reflux of gastric or esophageal contents into pharynx when cricoid pressure was released

Cricoid Anatomy and Location

• Between thyroid and 1st tracheal ring

• Attached by:crico-thyroid ligament & crico-tracheal ligament

• Lies at vertebral level of C5-C6

• Esophagus: posterior to cartilage

• CP: avoid aspiration of regurgitated gastric content

Cricoid Anatomy and Location

• It sits just inferior to the thyroid cartilage in the neck, and is joined to it medially by the median cricothyroid ligament and postero-laterally by the cricothyroid joints. Inferior to it are the rings of cartilage around the trachea (which are not continuous - rather they are C-shaped with a gap posteriorly). The cricoid is joined to the first tracheal ring by the cricotracheal ligament, and this can be felt as a more yielding area between the firm thyroid cartilage and firmer cricoid.

Cricoid Anatomy and Location

• It is also anatomically related to the thyroid gland; although the thyroid isthmus is inferior to it, the two lobes of the thyroid extend superiorly on each side of the cricoid as far as the thyroid cartilage above it.

Cricoid Anatomy and Location

• The posterior part of the cricoid is slightly broader than the anterior and lateral parts, and is called the lamina, while the anterior part is the band; this may be the reason for the common comparison made between the cricoid and a signet ring.

Cricoid Function

• The function of the cricoid is to provide attachments for the various muscles, cartilages, and ligaments involved in opening and closing the airway and in speech production.

• It is made of hyaline cartilage, and so can become calcified or even ossified, particularly in old age.

Clinical Significance

• When intubating a patient under general anesthesia prior to surgery, the anesthesiologist will press on the cricoid cartilage to compress the esophagus behind it so as to prevent gastric reflux from occurring.

• Gastric reflux could cause aspiration if this is not done considering the general anesthesia can cause relaxation of the gastro-esophageal sphincter allowing stomach contents to ascend through the esophagus into the trachea.

Clinical Significance

Often Performed Incorrectly

• Can’t find cricoid

• Not enough pressure

• Start to soon or too early

• Head & Neck position– Originally described as full neck extension without pillow– Currently: Magill’s intubating position

Clinical Significance

Often Performed Incorrectly

• Force - How much?– How do you know

• Timing? - when?– before unconsciousness?

• Single vs. Double handed– BURP?

How Much Force?

• Mean Gastric Pressures– 6mmHg inspiration; 3 mmHg expiration– 11mmHg in pregnancy

• Barrier Pressure– BrP = LESP - GP

• Cricoid Pressure lowers BrP & LESPbut not GP

How Much Force?

• Too much:– Airway obstruction, cricoid occlusion– 20 N = 30%– 30N = 43%– 44N = 50%

• Ventilation Difficulty– 20N = 50%– 44N = 80%

How Much Force?

• Too much:– Impaired laryngoscopy / failed intubation

• Single vs. bimanual• Effect of 10-60N = unpredictable impairment

– Cricoid pressure and BURP worsen laryngoscopic view• Properly performed; no effect on intubation

How Much Force?

• Too much:– Initial recommendation ; 44N

• 1 newton = 1 kg x m/s2 // 9.81 Newtons = resting weight of 1 kg

– Current recommendation on timing:• Conscious: approx. 10N (painful, may cause vomiting)• LOC: approx. 20 - 40 N

• Bridge of Nose: ‘till tears’• Indent a tennis ball

Anatomic Relationship

• Esophagus is displaced lateral to cricoid in 50% of normal adults.

• Bimanual CP increases frequency and degree of lateral displacement 1.5 to 3 x normal

Contraindications

• Active vomiting• Difficult airway• Injury to larynx• Unstable C-spine• Sharp foreign body