Intubation

Intubation:

Managing the airway: may be one of the most difficult aspects of the entire resuscitation due to the sheer variety of airway difficulties possible, even the most skilled resuscitator can find the task challenging (blood, loosened teeth, vomitus, swollen or distorted landmarks).

The Chin-Lift Maneuver: the rescuer places the tips of the fingers, volar surface superiorly, beneath the pt’s chin. The jaw is lifted gently forward. The pt’s mouth is opened by drawing down on the lower lip with the thumb of the same hand.

The Jaw-Thrust Maneuver: the second choice, again because neck extension is not necessary. Forward traction on the mandible is achieved by using two hands to grasp the mandibular rami and pull them forward.

The Abdominal Thrust: a method to relieve a completely obstructed airway. The technique is commonly referred to as the Heimlich maneuver. The technique is most effective when a solid food bolus obstructs the larynx. Contraindicated in pregnant pt’s and others with protuberant abdomens (a chest thrust similarly to that delivered in closed chest massage may be used instead).

Bag-Valve Mask Ventilation (BVM): often used with an oropharyngeal or nasopharyngeal airway in place. A rescuer who is not skilled with the BVM will achieve much better ventilation with mouth-to-mouth or mouth-to-mask breathing than with a BVM. Achieving adequate tidal volume with BVM ventilation requires a tight mask seal and adequate compression of the bag. The rescuer’s hand must be large enough to apply pressure anteriorly while simultaneously lifting the jaw forward. The thumb and index finger provide anterior pressure while the fifth and fourth fingers lift the jaw. Care must be exercised to deliver an adequate tidal volume by full compression of the bag. Dentures generally should be left in place to help ensure a better seal with the mask. All BVM devices should be attached to a supplemental oxygen source (with a flow rate of 15 L/min) to avoid hypoxia. Pediatric BVM devices should have a minimum volume of 450 mL. Facial hair, obesity, advanced age, edentulousness, and a history of snoring have previously been identified as clinical predictors of difficult BMV. One study found that grade 3 BMV (difficult; defined as requiring 2 operators or being difficult to maintain oxygenation) occurred in 1.4% of pt’s, and grade 4 BMV (impossible to maintain oxygenation) occurred in 0.16% (Anesthesiology 2006;105:885-91)…..Multivariate analysis identified six independent predictors of grade 3 BMV: presence of a beard, age 57 years, history of snoring, obesity (body mass index >30 kg/m2), Mallampati class 3 or 4, and limited ability to actively protrude the mandible. Grade 4 BMV was independently predicted by thyromental distance <6 cm or history of snoring. Independent predictors of grade 3 or 4 BMV and difficult intubation were limited mandibular protrusion, thick or obese neck anatomy, history of sleep apnea or snoring, and obesity.

Intermediate Airways: a midpoint between airway establishment and true airway control (tracheal intubation or tracheotomy). The devices include the esophageal obturator airway (EOA), the esophageal gastric tube airway (EGTA), the laryngeal mask airway (LMA, placed blindly) and the esophageal-tracheal Combitube (ETC, placed blindly) airway. Link Laryngeal Mask & Combitube | Difficult & Failed Airways & Techniques |

Intubation Indications:

Provide patent airway, prevent aspiration (failure or anticipated failure of airway maintenance/ protection), failure of ventilation/ oxygenation, facilitate positive pressure ventilation, when airway maintenance using a mask is difficult, need for prolonged mechanical ventilation.

Apnea –> RR <4.

Acute hypoxemia –> PO2 <55mmHg.

2 key bedside measures to help decide when to intubate a hospitalized pt: FVC & NIF are both handy if evaluating a pt with possible airway obstruction or neuromuscular dz and concerned about impending respiratory failure.

• Negative inspiratory force (NIF) gives info on respiratory muscle strength and reserve (ability to maintain lung expansion and prevent atelectasis), normal is -60 cm H2O, -20 is highly abnormal and indicates need for probable ventilatory support.

• Forced vital capacity (FVC) is usually ~60ml/kg, if <25 then compromised pulmonary function, if <15 it may herald respiratory failure severe enough to require intubation.

• Upper airway obstruction –> Fb aspiration, edema due to anaphylaxis, trauma, inhalational injury or bleeding.

• Acute Respiratory Insufficiency –> PCO2 >50 mmHg. Acute reduction in pH. RR >35. Chest wall trauma (flail chest), to prevent unnecessary chest wall movement.

• Airway protection –> CNS d/o, deep coma, prevention of aspiration pneumonia. Incr ICP to hyperventilate. General anesthesia. Hypothermia (core rewarming).

Equipment: 2 wall suction devices with Yankauer tips, laryngoscope (check lights), appropriate size ET tube with backup 0.5-1 size smaller, + stylet, check integrity of inflatable cuff (no cuff if age <8yo). Bag & Mask Ventilation (BMV) is a prerequisite to using paralytic drugs, optimally done by two people (one to secure face mask with two hands). The standard ET tube is plastic and measures ~ 30 cm. Tube sizing is based on internal diameter (ID), measured in millimeters, and ranges from a 2-20 mm tube, increasing in increments of 0.5 mm. The outer tube diameter is 2 and 4 mm larger than the internal diameter. In emergency intubations, particularly if a difficult intubation is anticipated, many clinicians choose a smaller tube and change to a larger tube later if necessary. One exception is in the burn pt, in whom one places as large a tube as possible on the initial attempt because swelling may prohibit subsequent tube placement. For nasal intubation, a slightly smaller tube (by 0.5 to 1.0 mm) is chosen.

Laryngoscopy: the blade is the tool that controls the tongue by sweeping it to the left. C-Spine motion is similar with Macintosh and Miller blades according to a fluroscopic study on 11 pt’s (Anesthesiology 2007;107:884). Laryngoscopy requires less force in the extension-extension position (neck-extension/atlanto-occipital–extension position, by placing a pillow behind the shoulders) rather than the sniffing position (neck flexion and atlanto-occipital extension, e.g., by placing a pillow behind the head) (Anaesthesia 2008;63:375). See Difficult & Failed Airways & Techniques | See Ventilatory Modes | Extubation |

MacIntosh (Mac) (curved) Blade: designed to fit into the vallecula (cul-de-sac where the epiglottis meets the tongue) in order to lift the epiglottis. Pt’s who are short (<5 feet) or have a thyromental distance 5 cm, the laryngoscopic view, intubation time and % succesfull was significantly better with the MAC2 blade compared to the MAC3 (Anesthesiology 2006;104:1131-6)…..video laryngoscopy eliminates much of this type of view problem.

Miller (straight) Blade: better view, but harder to use. It flattens the tongue and picks up the epiglottis with its tip, this is best for trauma, short necks, high larynxes and obese pt’s. Aim for a max of 30 sec as pt not ventilating during this time.

Re-usable vs Single use: In a large study, single-use metal direct laryngoscope blades outperformed their reusable counterparts (Anesthesiology 2010;112:325)…..Intubation was not successful on the first attempt significantly more often with the reusable blade than with the single-use blade (5.4% vs. 2.8%). Poor Cormack-Lehane glottic views (grade III or IV) were significantly more common with the reusable blade than with the single-use blade (10% vs. 6%)…..The reusable blades provided significantly higher mean light intensity than the single-use blades, but a significantly greater proportion of reusable blades than single-use blades provided low illuminance (<40 lux).

Adult Female –> 7.0-8.5 ETT, ~21cm in length. An ETT with an internal diameter of 7.5 to 8.0 mm is appropriate for most adult females.

Adult Male –> 7.5-9.0 ETT, ~23cm length. A size #9 is 2X normal airway resistance, 4X the work of breathing if use size #7. An ETT size 8-8.5 mm is appropriate for most adult males.

Estimate of ETT size: Internal Diameter (mm) of cuffed ET = (age in yr/4) + 3. May also may use size (width) of pt’s fifth digit as a guide, which usually is sufficiently accurate. Cuffed ETT can be used safely in all children according to the AHA 2005 guidelines.

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