|
UNDERSTANDING EQUIPMENT Face Mask: Delivery of positive pressure ventilation by means of a face mask (or bag-valve-mask device) is an essential skill to develop. The rim of the mask is soft and form-fitting and by pressing it firmly against the face an airtight seal is made. The mask is attached to a breathing circuit including an oxygen bag. When pressure in the mask increases by squeezing the inflated oxygen bag, air flows through the upper airway into the lungs. When the bag is empty or you stop squeezing it, air will flow out the lungs through the nose and mouth into the mask. Successful ventilation requires both an air-tight mask fit and a patent airway. Without an airtight seal between the skin of the patient’s face and the mask, sufficient pressure to inflate the lungs (or for that matter the ventilation bag) will not develop. Leak is the most common problem in delivering face mask ventilation and can be avoided or resolved by proper technique. If you have an assistant who can squeeze the ventilation bag for you, use two hands to secure an air-tight seal. The thumbs hold the mask down while the fingertips or knuckles displace the jaw forward and upward (lift and protrude the jaw to prevent or alleviate airway obstruction by the tongue). The one handed technique is achieved by using the right hand to generate positive pressure by squeezing the bag using the left thumb and index finger to secure the mask (by pushing downward). The middle and ring finger grasp the mandible (and not the soft tissue of the chin) to extend the atlanto-occipital joint (the neck). The little finger is positioned under the angle of the jaw and thrusts it anteriorly. Signs of successful seal and ventilation include: * a foggy mask * the rising of the chest with delivery of positive pressure * breath sounds on auscultation * a firm/taught/full bag * return carbon dioxide on exhalation capnography. Oropharyngeal airway (OPA) – A curved piece of plastic inserted over the tongue that creates an air passage way between the mouth and the posterior pharyngeal wall. Useful when the tongue and/or epiglottis fall back against the posterior pharynx in anesthetized or unconscious patients obstructing the flow of air. The preferred technique is to use a tongue blade to depress the tongue and then insert the airway posteriorly. An alternate technique is to insert the oral airway upside down until the soft palate is reached. Rotate the device 180 degrees and slip it over the tongue. Be sure not to use the airway to push the tongue backward and block, rather than clear, the airway. This device is poorly tolerated in conscious patients and may induce gagging, vomiting and aspiration. Nasopharyngeal airway – Also known as trumpets, nasopharyngeal airways are inserted through one nostril to create an air passage between the nose and the nasopharynx. The NPA is preferred to the OPA in conscious patients because it is better tolerated and less likely to induce a gag reflex. The length of the nasal airway can be estimated as the distance from the nares to the meatus of the ears and is usually 2-4 cm longer than the oral airway. Any tube inserted through the nose should be well lubricated and advanced at an angle perpendicular to the face (remember: the floor of the nose is the roof of the mouth!). Use a nostril that is unobstructed. While nasopharyngeal airways are better tolerated than oropharyngeal airways in awake or lightly anesthetized patients, they are contraindicated in patients who are anticoagulated, patients with basilar skull fractures, patients with nasal infectios and deformities as well as in children (because of risk of epistaxis). If the nasopharyngeal tube is visible in the posterior oropharynx, it may provide safe passage of an nasogastric tube (NG tube) in a patient with maxillofacial fractures. deflated laryngeal mask airwayLaryngeal Mask Airway (LMA) – The LMA is a cuff device that provides sufficient seal to allow for positive pressure ventilation to be delivered. It is particularly useful in maintaining an airway in anesthetized patients when endotracheal intubation is not desired or during emergency situations in which mask ventilation is not possible or intubation and/or ventilation fails. An LMA is a wide bore tube, with a connector at its proximal end (that can be connected to a breathing circuit)and with an elliptical cuff at its distal end. When inflated, the elliptical cuff forms a low pressure seal around the entrance into the larynx. The LMA comes in a variety of pediatric and adult sizes and successful insertion requires appropriate size selection. Laryngoscope – A laryngoscope is a rigid instrument used to examine the larynx and to facilitate intubation of the trachea. It is composed of two separate parts: the handle (which also contains the battery) and the blade, which is used to move the tongue and soft tissues aside to reveal a view of the larynx. To this end, an incandescent bulb can be found on the blade tip - it turns on when the blade is attached to the handle and locked into the 90 degree position to illuminate the larynx. blades and handle The two most commonly used blades in the United States are the Macintosh, which is curved, and the Miller, which is straight. Both blades come in a variety of sizes. The choice of blade depends on personal preference and patient anatomy. The laryngoscope is held in your NON-DOMINANT HAND (if you are right handed, resist the temptation to hold the laryngoscope in your right hand!). Carefully introduce the blade into the right side of the mouth. Regardless of which blade is used, IT MUST NEVER PRESS AGAINST THE TEETH or dental trauma will result. The tongue is then swept to the left and up into the floor of the pharynx by the blade’s flange. Laryngoscope with Macintosh Blade The curved Macintosh blade is inserted past the tongue into the vallecula (at the base of the tongue). Providing sufficient lifting force in parallel with the handle, yet avoiding posterior rotation that causes the blade to press against the teeth, pressure is applied deep in the vallecular space by the tip of the blade immediately anterior to the epiglottis, which flips out of the visual field to expose the laryngeal opening. The straight Miller blade is inserted deep into the oropharynx, PAST the epiglottis. Providing sufficient lifting force in parallel with the handle, yet avoiding posterior rotation that causes the blade to press against the teeth, under direct vision, the blade is slowly withdrawn. It will slip over the anterior larynx and come to a position at which it holds the epiglottis flat against the tongue and anterior pharynx, exposing a view of the larynx. blades and handle With either blade, the handle is raised up and away from the patient in a plane perpendicular to the patient’s mandible. Avoid trapping a lip between the teeth and the blade and AVOID using the teeth as leverage. Endotracheal Tube – Endotracheal tubes are most commonly made from polyvinyl chloride, with a radiopaque line from top to bottom, standard size connectors (for anesthesia machines, ventilators, or bag-mask devices, a high pressure/low volume inflatable balloon, and a hole at the beveled, distal end (known as Murphy’s eye). Tubes come in a number of sizes, usually designated in millimeters of internal diameter. The choice of ETT size is always a compromise between choosing the largest size to maximize flow and minimize airway resistance and the smallest size to minimize airway trauma. Once a view of the larynx is obtained via laryngoscopy, the ETT is introduced with the dominant hand through the right side of the mouth. Directly observe the tip of the tube passing into the larynx, between the abducted cords. Pass the tube 1 cm through the cords. Double lumen endotracheal tubes are designed so that one lung may be isolated from the other to facilitate selective ventilation of one lung or surgery within a hemithorax. Stylet – A stylet is a long, bendable rod that can be inserted into an endotracheal tube to facilitate intubation. It is placed into the tube prior to laryngoscopy and then the tube (with the stylet in it) is bent to resemble a hockey stick. After insertion of the tube into the trachea, the stylet is removed. Styletteendotracheal tube with stylet Bougie – The Bougie is a straight, semi-rigid stylette-like device with a bent tip that can be used when intubation is (or is predicted to be) difficult. During laryngoscopy, the bougie is carefully advanced into the larynx and through the cords until the tip enters a mainstem broncus. While maintaining the laryngoscope and Bougie in position, an assistant threads an ETT over the end of the bougie, into the larynx. Once the ETT is in place, the bougie is removed. http://www.healthsystem.virginia.edu/Internet/Anesthesiology-Elective/airway/equipment.cfm |