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List and describe the physiological effects, complications and weaning procedure of PEEP

Learning Objectives Covered

1. List and describe the physiological effects, complications and weaning procedure of PEEP

2. Describe techniques such as: weaning approaches, oxygenation titration, closed-loop control, and evidence-based weaning

3. Explain assessment techniques used to determine successful ventilator discontinuance

Background

In week one we discussed extrapulmonary effects of mechanical ventilation. Equally important however is understanding the pulmonary effects, the actual impacts of positive pressure ventilation on the lungs and other respiratory structures.

Competent respiratory therapists know how to ventilate patients in a way that achieves appropriate oxygenation levels and appropriate carbon dioxide levels, but in a way that also minimizes adverse effects on the pulmonary system. The concepts of barotrauma and volutrauma are especially important. The NBRC is very interested in assessing your knowledge in this area. The national board wants to credential therapists who know how to protect patient’s lungs while effectively ventilating them. Another key topic this week involves weaning your patient from the mechanical ventilator. No patient wants to stay on a ventilator for life. We want to “liberate” the patient from the ventilator as soon as feasible, but it is so important to do that safely. We need to make sure that the problem that put the patient on the ventilator has been corrected, and we need to make certain that key parameters have reached safe levels before we give the patient a “spontaneous breathing trial” away from the ventilator. You will learn this week about essential monitoring to make sure that the patient is succeeding with that spontaneous breathing trial. Let us now take a closer look at weaning.

Weaning from Mechanical Ventilation

Ventilator management should be aimed at getting the patient off ventilator support as quickly and safely as possible after stabilization. Weaning (also known today as liberation) should be considered as soon as the underlying disease process that led to mechanical ventilation is under control. For example, if the patient was intubated and ventilated due to pulmonary edema, then weaning can commence as soon as the excess pulmonary fluid has been removed and the patient’s gas exchange improves. This will also be evident on chest x-ray as the disappearance of the butterfly fluid pattern. If the patient was ventilated due to pneumonia, clearing of the chest x-ray infiltrates and improvement of sputum clearance would indicate that we could begin the weaning process.

Definitions Relating to Weaning from Mechanical Ventilation

First, sharing a few definitions to help us classify weaning:

·  Simple weaning: the ventilator is discontinued after the first weaning assessment

·  Difficult weaning: the ventilator is discontinued within one week after the first weaning assessment

·  Prolonged weaning: the ventilator is discontinued more than one week after the first weaning assessment

·  Weaning failure: this is failure to pass a spontaneous breathing trial (SBT) or the need for reintubation within 48 hours following extubation

Avoiding Reintubation 

Obviously, we do not want to extubate our patient and then have to reintubate them. So predicting weaning success is very important for reducing the rate of reintubation. Careful attention to the criteria for weaning, and optimal patient management to increase weaning success can both help to avoid reintubation. Reintubation is a very bad prognosticator for the patient, but smart RRT’s can keep reintubation rates very low. Consider the following:

· Reintubation is associated with a 7-10 fold increase in hospital mortality

· Reintubation rates of 10 to 15% are typical for most well run Respiratory Therapy weaning programs

· A reintubation rate of 0% is not realistic, and it would mean that we are not being aggressive enough with our weaning efforts