Everything you need to know about weaning parameters in mechanical ventilation
By the end of the lesson, you will understand which parameters to monitor during a weaning trial.
When deciding whether to extubate a patient, knowing how to monitor appropriate weaning parameters is critical. In this video from our Mechanical Ventilation Essentials course, you'll learn about the four key assessment areas that are vital to a successful extubation, and what to look out for.
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[00:00:00] Once our patient is on a spontaneous breathing trial for 30 minutes to 2 hours, it's time to monitor weaning parameters that will help guide the decision of extubation. Now, before moving forward, according to evidence-based practice, we should always note that the single most important criterion to consider, when evaluating for extubation, is whether there has been significant alleviation or reversal of the primary cause for mechanical ventilation. Okay. So, success with extubation is related to
[00:00:30] assessing four key areas. The assessment of the respiratory, cardiovascular, neurologic, and psychologic status of the patient. Each of these areas can be assessed using a variety of indices but the challenge is sometimes knowing which indices to use for each key area. For example, to evaluate the respiratory status during a spontaneous breathing trial, you can use the p / f ratio, A-a gradient, MIP, vital capacity,
[00:01:00] minute ventilation, MVV, RSBI, the airway occlusion pressure P0.1, and on and on and on. In fact, a comprehensive evidence-based review identified a possible role for 66 specific measurements, as predictors of weaning success. Yikes, that's a lot of predictors and unfortunately, there are enormous discrepancies in the literature regarding their accuracy with regard to the prediction of successful extubation.
[00:01:30] So, let's see if we can bring some simplicity to at least give us a general overview of how to assess for extubation. First, the respiratory status. The clinician should evaluate the ventilatory work of breathing and the oxygenation status during the spontaneous breathing trial. The ventilation status can be assessed using two generally good observations. The first, is the RSBI or the rapid shallow breathing index. This is assessed during one-minute of unsupported
[00:02:00] spontaneous breathing, with no pressure support. And it is calculated using the patient's respiratory rate, divided by the spontaneous tidal volume. An RSBI of less than 105 may indicate successful extubation. An RSBI less than 80 is associated with an almost 95% probability of successful discontinuation. Now, another good observation is the absence of dyspnea and the respiratory rate less than 35 breaths per minute.
[00:02:30] If the patient has an increased respiratory rate greater than 35 breaths per minute for more than five minutes, the patient most likely will have a low probability of successful extubation. Now, in assessing the oxygenation status, the patient should tolerate an FiO2 less than 40% and a PEEP of 5 to 8 or less. Additionally, if performing an ABG to assess the oxygenation status, the clinician can calculate the p / f ratio. Generally, a p / f ratio of greater than 150
[00:03:00] on 40% of oxygen or less is acceptable. Next, is evaluating the cardiovascular status during weaning. The cardiovascular status usually is a hemodynamic assessment ensuring that the patient is stable, with minimum or no pressors. Now, this varies from institution to institution and from case to case. Next, is the evaluation of the neurologic status. Generally, the patient should be awake and alert,
[00:03:30] free of seizures, and able to follow instructions. And lastly, evaluating the psychological status. Fear, anxiety, and stress should all be minimized, since these non-respiratory contributing factors may actually lead to prolonged ventilator dependence. So, with these four key areas in mind, hopefully, you'll be better equipped to monitor patients during weaning and ensure the best probability for successful extubation.