Airway Management and Intubation Lecture Notes

Oropharyngeal Airway (OPA) Overview

• Definition and Purpose: The OPA is an airway adjunct used primarily to displace the tongue and maintain a patent airway. The tongue is identified as the most common cause of airway obstruction.

• Sizing and Measurement:     * OPAs are not universal in size; they range from neonatal to very large adults and come in various colors corresponding to sizes.     * Measurement Procedure: To select the correct size, measure the device from the corner of the patient's mouth to the tip of the earlobe.

• Insertion Techniques:     * Sideways Method: Insert the OPA sideways until resistance is met, then rotate it downward and push it the rest of the way.     * Upside Down Method: Insert the OPA completely upside down until resistance is felt, then perform a $180^{\circ}$ rotation to tuck it behind the jaw.     * Contraindication for Straight Insertion: Pushing the device straight back is avoided because it can shove the tongue further into the posterior pharynx, worsening the obstruction.

• Critical Patient Requirement:     * Patients must be unconscious or lack a gag reflex.     * The end of the OPA sits near the uvula, which is the source of the gag reflex.     * Stimulating the gag reflex in a conscious or semi-conscious patient will lead to vomiting and potential aspiration, which fails to protect the airway.

Nasopharyngeal Airway (NPA) and Nasal Trumpets

• Definition and Sizing: Similar to OPAs, NPAs come in multiple sizes, ranging from small diameters to large "garden hose" sizes.

• Measurement: Measure from the nare (nostril) to the tip of the earlobe.

• Insertion Guidelines:     * Lubrication: Always use water-based lubricant. Oil-based lubricants are prohibited because they are flammable and oxygen is combustible. Medical staff should use clean (non-sterile) technique with gloves.     * Direction: The device must be inserted straight back and slightly downward to reach the airway. Directing it upward can lead to the sinuses, cause pain, and fail to secure the airway.

• Clinical Advantages and Risks:     * Gag Reflex: The NPA slides past the uvula, so it does not typically trigger the gag reflex, allowing it to be used on conscious or semi-conscious patients.     * Duration: It can remain in place for up to $48\,hours$. After this period, the risk of infection or tissue irritation increases, and the device should be replaced—ideally in the opposite nare.     * Suctioning: NPAs are frequently used in patients requiring repeated nasotracheal suctioning. The trumpet acts as a guide, reducing trauma to the vascular nasal mucosa by preventing repeated contact with the sinuses.

• Contraindications and Anatomy:     * Trauma: Avoid use in patients with suspected facial or skull fractures. There is a documented case where an NPA was accidentally inserted into the brain due to unrecognized facial fractures.     * Deviated Septum: Anatomical shifts in the bridge of the nose mean one nare may be significantly smaller than the other. Always select the larger nare for insertion. If a patient has a deviated septum, the rule of alternating nostrils every $48\,hours$ is waived in favor of using the patent side.

The Intubation Process and Rapid Sequence Induction (RSI)

• Risks of Intubation: The most significant risk is cardiac arrest. Other risks include trauma from the procedure and the physiological stress of positive pressure ventilation.

• Preparation (The Intubation Box): Hospitals use standardized "fishing boxes" or tackle boxes that are restocked and sealed with a plastic lock to ensure all necessary supplies are ready for emergency use.

• Preoxygenation and the Oxygen Dissociation Curve:     * The goal is to maximize $PaO_2$ and $SpO_2$ levels before the attempt to buy more time for a safe placement.     * Critical Threshold: On the oxygen-hemoglobin dissociation curve, the major drop-off point occurs at an $SpO_2$ of approximately $90\%$, which corresponds to a $PaO_2$ of $60\,mmHg$.     * During intubation, it is standard practice to turn on the audible pulse oximeter. If the $SpO_2$ drops too low (e.g., below $80\%$ or $75\%$), the attempt must stop to preoxygenate the patient again.

• Pretreatment: This includes clearing the airway of secretions, vomit, or blood via suctioning. If a patient is already on non-invasive ventilation, the $FiO_2$ can be increased to $100\%$ for preoxygenation.

• Pharmacology of RSI:     * Dual Administration: A sedative and a paralytic must be given together. Administering a paralytic without a sedative is unethical as the patient will be awake, feel pain, and be unable to move or communicate.     * Short-Acting Meds: Ideally, drugs used have a fast onset and a short half-life.

Sedatives Used in Airway Management

• Propofol (Diprivan):     * Known as "Milk of Amnesia" due to its white, milky appearance.     * It is the most common sedative for intubation and ICU maintenance drips.     * Effects: Provides hypnosis and amnesia. Famous as the drug associated with the death of Michael Jackson.     * Contraindications: Cannot be used in patients with allergies to eggs or soy.     * Kinetics: Very short half-life of roughly $2.5\,minutes$, allowing for quick waking during extubation trials.

• Etomidate (Amidate):     * Considered the "gold standard" sedative for intubation per the NBRC (National Board for Respiratory Care).     * It has almost no contraindications and a very short half-life.     * Limitation: It is generally used as a one-time bolus/push and is not suitable for continuous sedation drips.

• Ketamine:     * Benefits: Does not cause respiratory depression and acts as a bronchodilator, making it the drug of choice for intubating asthmatic patients.     * Drawbacks: It has a longer half-life. The state the patient is in when given the drug (e.g., panicked or combative) is often the state they return to upon waking ("coming out swinging").     * Interactions: Synergistic effect with PCP (Angel Dust). Combining the two can lead to "superhuman strength," potentially allowing patients to bend CAT scan tables or break bones.

Paralytics (Neuromuscular Blocking Agents)

• Succinylcholine ("Sucks"):     * The gold standard paralytic for RSI due to its extremely short half-life.     * Contraindication: Hyperkalemia (high potassium). Succinylcholine causes a spike in potassium levels. If a patient already has high potassium (e.g., burn victims or renal failure), this can lead to immediate cardiac arrest.

• The "Rhonium" Drugs (Rocuronium, Vecuronium):     * Rocuronium: Used if Succinylcholine is contraindicated (high potassium) as it does not cause a potassium spike.     * Kinetics: They have a significantly longer half-life than most sedatives. Clinical staff must ensure sedation continues long after the paralytic is given to avoid the patient being paralyzed while conscious.

Endotracheal Tube (ETT) Anatomy and Features

• Sizing: ETT sizes refer to the internal diameter (ID) in millimeters, ranging from size $2.0$ (neonatal) to $10.0$ (very large adult).     * Resistance: Smaller tubes result in higher airway resistance ($Raw$). Clinicians aim for the largest tube appropriate for the patient.

• Tube Markings:     * Centimeter Markings: Indicate the depth of the tube. For most adults, a common depth is $23\,cm$ at the lip.     * Radio-opaque Line: A blue or white line running the length of the tube that visible on chest X-rays. In adults, the tip should be $3-5\,cm$ above the carina.

• Safety Features:     * Murphy's Eye: A side hole near the tip that provides a collateral ventilation pathway if the primary distal opening becomes occluded by the tracheal wall or mucus.     * 15 mm Adapter: A universal stovepipe adapter at the top of every tube that fits all ventilators and Ambu bags.

• The Cuff and Pilot Balloon:     * Purpose: The cuff creates a seal for positive pressure ventilation and prevents aspiration.     * Pediatric Anatomy: Infants may use uncuffed tubes because their cricoid cartilage is soft and naturally forms a seal around the tube due to negative pressure during inhalation.     * Integrity Check: To check for leaks, use a syringe to collapse the pilot balloon completely. If it reinflates on its own, there is a leak in the cuff or pilot system.

• Subglottic Port (CASS Tubes): An extra port allowing suctioning of secretions sitting above the cuff. Using these tubes can reduce Ventilator Associated Pneumonia (VAP) rates by approximately $47\%$.

Cuff Pressure Standards

• Thresholds: Pressures must be high enough to seal but low enough to allow capillary blood flow to the trachea.

• Millimeters of Mercury ($mmHg$): Maintain between $20-25\,mmHg$. Pressures exceeding $30\,mmHg$ can cause tissue death (tracheomalacia or fistulas).

• Centimeters of Water ($cmH_2O$): Maintain between $20-30\,cmH_2O$. Manometers used in clinical settings typically use this unit.

Laryngoscopy and Verification Equipment

• Blades:     * Macintosh (Mac): Curved blade; the tip is placed in the vallecula to indirectly lift the epiglottis.     * Miller: Straight blade; used to directly lift the epiglottis. Preferred for infants with floppy airways.

• Technique: The laryngoscope is always held in the left hand regardless of the clinician's dominant hand, as the light and tube guide are designed for right-sided tube insertion.

• Intubation Aids:     * Stylet: Provides rigidity to the bendy ETT. It is shaped like a "hockey stick" to guide the tube into the trachea and is removed once the tube passes the vocal cords.     * Magill Forceps: Curved, serrated tools used to remove foreign bodies (dentures, grapes, mucus plugs) from the upper airway.     * Yankauer: A rigid suction tip used to clear the mouth and posterior pharynx.

• Verification Methods:     * Primary (Immediate): Bilateral chest rise and breath sounds.     * Secondary (CO2 Detection): Colorimetric detector rhyme: "If it's yellow, let it mellow (CO2 present); if it's purple, pull it out (esophageal intubation)."     * Definitive: Chest X-ray to confirm the exact distance from the carina.