Overview
Definition:
Apneic oxygenation is the phenomenon of providing supplemental oxygen during an apneic period, typically during tracheal intubation, by passing air through the upper airway and into the lungs via passive diffusion
Cricoid pressure, also known as Sellick's maneuver, is the external pressure applied to the cricoid cartilage to occlude the esophagus and prevent gastroesophageal reflux and aspiration during induction of anesthesia and intubation.
Epidemiology:
Rapid sequence intubation (RSI) is frequently performed in pediatric emergencies and anesthesia
While specific incidence data for the use of apneic oxygenation and cricoid pressure in pediatrics varies, these techniques are considered standard of care in many institutions for managing the pediatric airway during RSI.
Clinical Significance:
Effective apneic oxygenation extends the safe apneic interval, providing crucial time for intubation, especially in neonates and infants where hypoxemia develops rapidly
Cricoid pressure aims to reduce the risk of aspiration, a serious complication during airway manipulation
Both are critical components of safe pediatric RSI, directly impacting patient outcomes and reducing morbidity and mortality.
Apneic Oxygenation Technique
Principle:
During apnea, oxygen can diffuse from the alveoli into the bloodstream, and nitrogen can diffuse from the blood into the alveoli, creating a slight positive pressure gradient that maintains a slow but continuous flow of oxygenated air into the lungs
This process is facilitated by the upper airway providing a conduit for oxygen flow.
Application In Pediatrics:
In pediatric RSI, once paralysis is achieved and before attempting intubation, a high-flow oxygen source (e.g., nasal cannula, nasopharyngeal airway, or simple oxygen mask) is maintained at the nares or mouth
This allows for passive oxygenation during the intubation attempt.
Benefits:
Prolongs safe apneic time by delaying desaturation
Reduces the urgency of intubation, potentially leading to a less traumatic procedure
Provides a buffer against hypoxemia, especially in neonates and infants who have higher metabolic rates and lower functional residual capacity.
Limitations And Risks:
Does not prevent hypoventilation or CO2 accumulation
May not be effective in patients with significant airway obstruction or facial trauma
Risk of gastric distension if oxygen flow is too vigorous or if insufflation occurs.
Cricoid Pressure Technique
Principle:
The cricoid cartilage is the only complete cartilaginous ring of the trachea and is situated just above the esophagus
Applying firm pressure (10-20 Newtons, approximately 1-2 kg force) to the cricoid ring with the thumb and forefinger can compress the esophagus against the vertebral bodies, occluding it.
Application In Pediatrics:
Applied immediately after the induction agent is administered and before laryngoscopy begins
Pressure is maintained throughout laryngoscopy and intubation
Removed only after the endotracheal tube is confirmed in place and the cuff is inflated, or if visualization of the glottis is significantly impaired.
Indications In Pediatrics:
Recommended in all pediatric patients undergoing RSI, particularly those with a full stomach, gastroesophageal reflux, hiatal hernia, or morbid obesity
Also considered in emergent situations where aspiration risk is high.
Controversies And Disadvantages:
Can impair laryngeal view, making intubation more difficult
May cause patient discomfort or pain
Potential for esophageal rupture or tracheal injury if excessive force is applied
Evidence supporting its routine use in all pediatric RSI cases is debated, with some guidelines recommending against it if it impedes intubation.
Current Recommendations:
The American Society of Anesthesiologists (ASA) and other professional bodies suggest using cricoid pressure cautiously, applying it only when necessary and ceasing if it obstructs the airway
The decision to use it should be individualized based on the patient's risk factors for aspiration.
Pediatric Rsi Considerations
Age Differences:
Neonates and infants have different airway anatomy and physiology: smaller airways, larger tongue-to-mouth ratio, higher metabolic rate, and shorter apneic times
These factors make them more susceptible to hypoxemia and aspiration.
Drug Selection And Dosing:
Pediatric RSI drug choices (sedatives, paralytics) differ from adults and depend on age, weight, and clinical condition
Dosing must be precise to avoid adverse effects
Ketamine and succinylcholine are often used in pediatrics, but with careful consideration of contraindications.
Airway Device Selection:
Appropriate endotracheal tube size is crucial and often estimated by age or internal diameter
Laryngoscope blade selection (e.g., Miller blade for anterior larynx) is also important.
Monitoring:
Continuous pulse oximetry, capnography, and ECG are essential
Frequent checks of vital signs and neuromuscular blockade are necessary.
Diagnostic Approach
History Taking:
Assess for risk factors of difficult airway (e.g., craniofacial abnormalities, previous airway surgery, syndromes)
Inquire about feeding history, time of last oral intake, and presence of gastroesophageal reflux disease (GERD) or hiatal hernia.
Physical Examination:
Evaluate for signs of difficult airway: limited neck extension, macroglossia, receding jaw, prominent teeth
Assess for airway patency and signs of distress
Full stomach assessment is crucial.
Investigations:
Generally, no specific investigations are required pre-RSI in an emergency
However, for elective RSI, airway imaging or fiberoptic assessment may be considered in select cases with suspected anatomical difficulties
Fasting status is paramount.
Differential Diagnosis:
Not directly applicable for the techniques themselves, but the decision to perform RSI is based on differential diagnoses leading to the need for airway protection or definitive airway management (e.g., severe respiratory failure, anaphylaxis, status epilepticus, sepsis with hypoperfusion, trauma).
Management
Initial Management:
Pre-oxygenation with 100% oxygen for 3-5 minutes to maximize oxygen reserves
Application of cricoid pressure if indicated, followed by administration of induction agent and neuromuscular blocker.
Intubation Procedure:
Attempt intubation using appropriate laryngoscopy technique
Maintain apneic oxygenation throughout the attempt
Release cricoid pressure only after tube placement is confirmed and cuff is inflated, or if visualization is severely compromised.
Confirmation Of Tube Placement:
Visual confirmation of ETT passing through vocal cords
Presence of chest rise
Auscultation of bilateral breath sounds
Crucially, end-tidal CO2 detection (capnography) is the gold standard.
Post Intubation Care:
Secure the endotracheal tube
Connect to mechanical ventilation
Continuous monitoring of vital signs, oxygenation, and ventilation
Assess for potential complications.
Complications
Early Complications:
Hypoxemia due to failed intubation or inadequate apneic oxygenation
Aspiration of gastric contents leading to chemical pneumonitis
Esophageal intubation
Dental trauma
Mucosal injury
Laryngeal/tracheal trauma
Bronchospasm
Hypoventilation
Hypotension.
Late Complications:
Subglottic stenosis
Vocal cord paralysis
Post-extubation stridor
Pneumonia
Acute respiratory distress syndrome (ARDS) secondary to aspiration.
Prevention Strategies:
Thorough pre-procedure assessment
Appropriate pre-oxygenation
Judicious use of induction agents and paralytics
Careful laryngoscopy technique
Correct sizing of ETT
Confirmation of tube placement with capnography
Judicious and appropriate use of cricoid pressure
Early recognition and management of desaturation.
Key Points
Exam Focus:
Understand the physiological basis of apneic oxygenation and the mechanism of cricoid pressure
Know the indications, contraindications, and risks associated with both
Differentiate pediatric airway anatomy and physiology from adults
Recognize the importance of capnography for ETT confirmation
Be aware of drug choices and dosing for pediatric RSI.
Clinical Pearls:
Always pre-oxygenate vigorously
Maintain high-flow oxygen during apnea
Use cricoid pressure judiciously, and be prepared to release it if it impedes intubation
Confirm ETT placement with capnography, not just auscultation
Prepare for failed intubation and have a clear rescue plan
Pediatric airways are small
avoid excessive force.
Common Mistakes:
Inadequate pre-oxygenation
Insufficient or absent apneic oxygenation
Excessive or continuous cricoid pressure that obstructs the airway
Failure to confirm ETT placement with capnography
Using adult dosing or drug choices in children
Forgetting to remove cricoid pressure after tube confirmation and cuff inflation.