The difficult extubation

Editor's Notes

• #2: How many of us have had a routine extubation go wrong? What’s the first thing we do when first faced with the difficult extubation?
• #3: Today I am going to define such emergencies and hopefully give you ideas of how to treat them
• #4: First I need to remind you that there is a different set of criteria for discontinuing mechanical ventilation vs. extubation. Discontinuing mechanical ventilation is determined by the res….Why was the patient intubated? Has that condition been resolved? If resolved then does the patient have the ability to breathe spontaneously? Has the sedation/anesthesia medication cleared? Have they been allowed to breathe spontaneously? Are the patients hemodynamics and ABG’s stable?
• #5: This slide speaks to the things that need to be assessed prior to an extubation. Westcott and Bendixon in Anesthesiology years ago(1962) defined a maximal inspiratory pressure standard to be at least a pressure change of 20cm H2O to be able to maintain an open pharynx for breathing. There are other studies out there since suggesting that -35cmH2O is needed to adequately cough as well. Vital capacity and Peak expiratory flow also are indicative of whether a pt’s cough is adequate to clear secretions. In an already extubated pt. a PEF of >120l/min is needed and/or a VC of at least 2x the resting or tidal volume. In a fairly recent article (2004), Salam et al show a correlation between these three criteria to the success of extubation.PEP, Cognitive ability and quantity of secretions. In this relatively small study, PEF or Cough Peak flow, cognitive ability and the amount of secretions. The study showed that pts who failed all four parts of the cognitive assessment, had secretions of >2.5 ml/hr, PEF of <60l/min had a 100% rate of extubation failure compared to a failure rate of 4.2% of those without any of these risks. In addition pts with any two risk factors had 3.8 times likelyhood of failing extubation as well. The quantity of sputum suctioned emerged as an independent predictor of extubation outcome though it is the most variable and vulnerable to the operator (RN and RT) and their technique of quantifying. So using secretions as a predictor will be variable from therapist to therapist and institution to institution. However it is wise to use caution when extubating a pt. who has more than 2.5ml of secretions per hour.
• #6: On an experiential note, hardware issues need to be assessed as well. NG/OG tubes occupy the same pharyngeal space. If the jaw is wired in any manner, wire cutters need to be at the bedside for any complication of the airway. And Halo’s or other cervical spine fixation devices could be an issue if the extubation goes awry. Especially in the issue of upper airway obstruction and need for re-intubation.
• #7: Now on to the main theme of this talk. The Top five. Let’s review them one at a time
• #9: The causes of laryngospasm are hysteria, mechanical(somethng even mucous touches the vocal cords and protectively they slam shut), and chemical (noxious gases can cause the vocal cords to close protectivley as well) Can you predict it? No however Since subglottic suctioning does not clear all secretions above the cuff, it is best to extubate patients with a positive pressure breath. This allows the secretions missed by previous subglottic secretions and places the vocal cords in an optimal position for removal of the ETT.
• #10: Laryngospasm is the most frightening emergency of extubation. Pt. gets very panicked and flail around. And there is nothing we can do except to attempt to relax the pt. Sedation can help. Attempting to help with a cough assist may also help. But the main thing is to get the pt. to relax.
• #11: Definition… Can you predict it? Many studies have been done to date to predict those patients who will have post-extubation stridor. First, it has been the standard of most institutions if not all to perform a cuff leak test. This is where the clinician deflates the cuff while giving a positive pressure breath, ventilator or manual, and notes whether a leak around the ETT is present. If the difference between inspiratory volume and expiratory volume is less than 110ml or <15% of insp.vol, it has been considered a failed test. However the studies showing the need have been small (<100 pts). The largest study to date was in Respiratory Care in December 2005 by Kriner et al. In it 462 pts were studied and the cuff leak test was not a reliable predictor. Another study by Maury et al in Critical Care 2004 describes the ETT occlusion test. This test conducted by anesthesiologists, is when the clinician deflates the cuff then occludes the ETT and assesses whether the pt. is able to move air around ETT, inspiratory and expiratory. If not, then the test is a failure. Though this study was positive it also was a small study. And the practice of this method has large risks of aspiration and such sequelae. Again in the study by Kriner et al, the risk of post-extubation stridor was higher in pts. With consistent abrasion-promoting variables specifically prolonged intubation(>6 days), a ratio of ETT size to laryngeal size>45%, and the female sex. Obesity has also been noted as a risk factor of post-extubation stridor.
• #12: When talking about laryngeal stridor one must determine whether or not it truly is laryngeal stridor. Using the jaw thrust manuever or placing the pt. in the sniff position will help distinguish if it is partial obstruction of the upper airway. Also one needs to make sure the secretions have been adequately removed. If by doing this the noise of stridor disappears, you more than likely have upper airway or soft tissue obstruction. Now place a nasal or oral airway to assess whether or not that will help without the manual manipulation. If that doesn’t quite do it, will mask CPAP relieve it, as in OSA pts.
• #15: When talking about laryngeal stridor one must determine whether or not it truly is laryngeal stridor. Using the jaw thrust manuever or placing the pt. in the sniff position will help distinguish if it is partial obstruction of the upper airway. Also one needs to make sure the secretions have been adequately removed. If by doing this the noise of stridor disappears, you more than likely have upper airway or soft tissue obstruction. Now place a nasal or oral airway to assess whether or not that will help without the manual manipulation. If that doesn’t quite do it, will mask CPAP relieve it? as in OSA pts.
• #16: Now that we have determined that it is laryngeal stridor what can we do? Racemic epinephrine/bronchodilators can be given via nebulizers as a first step. If the patient feels relief—wonderful. If patient is still struggling, Heliox can be initiated. Heliox is a mixture of Helium and Oxygen that is less dense than air or O2 and thereby can pass through small airways easier. Remember that a mixture that requires less than 70% Helium loses it efficacy. So this treatment is for those patients who are oxygenating quite well. Heliox use usually buys the time for the vocal folds to be less irritated and decrease in swelling. Most patients can be weaned off it’s use within 8 hours. 4 hrs full continuous use , 4 hrs weaning the amount of Helium. The reason I put sedation on the list is that a patient with stridor, especially a conscience one, is usually very anxious and will probably need some sedation to keep calm. The key is to stay calm so the therapy will be allowed to work. If a tight fitting mask cannot or will not be worn, the patient will need to be re-intubated with hopefully a smaller ETT.
• #17: NO
• #18: These are some causes of acute hypoxemia in the extubated pt. Two types of pulmonary edema may happen. Negative pressure pulmonary edema occurs when a pt generates strong >45cm H2O negative pressure within chest. It can occur with post-laryngospasm pts and in striorous pts as well. This pulmonary edema dissipates rather quickly and the clinician needs to support the patient with increased oxygen needs. Cardiac pulmonary edema can occur with extubation as well. Some CHF pts are very sensitive to any PEEP applied and as little as 5 cmH2O can obscure the fluid status of these patients. Mask CPAP has been used with a great deal of success in such cases. Vomiting with the extubation procedure or shortly thereafter can pose a high risk of aspiration. This cannot be predicted and the clinician must be prepared to position the pt. on their side, turn their head and orally or NT suction pt as quickly as possible. If aspiration has occurred, the oxygenation needs may be increased.
• #19: Defined as an inability to ventilate to maintain a normal pH (7.35-7.45). This can happen rather acutely or take a matter of a few hours. I am not speaking of the respiratory failure that happens over a few days and can be somewhat compensated with a rising HCO3. Can present itself by increased RR, increased WOB (using accessory muscles, posture) and eventually a corresponding decreased SaO2.
• #20: Can you predict it? If you did the assessment of discontinuing mechanical ventilation correctly, this is usually not predictable. Let’s discuss the use of NPPV post-extubation. In Esteban’s study it was discovered that re-intubation was delayed and the mortality of such patients was increased if NPPV was used for the general population. Ferrer’s study came out later and showed that mortality was not increased in their pt. population. However it is noted that Ferrer’s study population was 51% COPD pts. When COPD exacerbation was the cause of the intubation, NPPV has been used successfully to transition the pt. back to their normal respiratory pattern and without the ETT.