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The weaning process may be taxing for some patients. Ensure that the patient does not become exhausted or develop signs of respiratory compromise. If at any time the patient exhibits signs or symptoms that suggest intolerance to the process, discontinue weaning and place him or her back on ventilator support.
Assess the patient’s level of sedation before weaning. Sedation impedes the weaning process and increases the length of time spent receiving mechanical ventilation.
Weaning is defined as a progressive decline in the amount of ventilatory support that a patient receives from a ventilator. The weaning process includes decreasing ventilator support, assessing the patient’s response, and possibly extubating the patient. The purpose of the weaning process is to liberate patients from mechanical ventilation. Removing the artificial airway is a desirable outcome of the weaning process but is not essential for liberation from ventilatory support. Knowledge and skills related to the care of patients on mechanical ventilation (e.g., airway management, suctioning, mechanical ventilator modes, blood gas analysis interpretation) are necessary for implementing the weaning process.
Weaning is successful when the patient’s pulmonary system has the ability and capacity to perform the necessary work of spontaneous breathing. Both respiratory and nonrespiratory factors contribute to weaning success. The patient’s oxygenation status before and during weaning is a strong indicator of success or failure. Cardiovascular function and psychological factors should be optimized for successful weaning from ventilatory support.
Weaning readiness is determined by assessment of the patient’s stability, resolution of the reason for mechanical ventilation, and achievement of selected weaning criteria goals (e.g., weaning indices) (Box 1) (Box 2). Attention to other clinical factors is also important before initiating weaning trials.1,2 Clinical tools and checklists ensure systematic attention to these factors and may help ensure good outcomes (Box 3). In addition, prophylaxis regimens are recommended to prevent complications in patients who are being mechanically ventilated. Complications include ventilator-associated pneumonia (VAP), deep vein thrombosis, gastrointestinal bleeding, and sinusitis.1
The respiratory therapist (RT) remains with the patient, especially at the beginning of the trial; makes assessments frequently during the trial; coaches the patient; reinforces the goals and desired outcomes; and reminds the patient that successful weaning and extubation facilitate talking, eating, self-care activities, and mobilization.
Weaning indices have proven to be limited predictors of a patient’s ability to wean.1 Most predictors focus on pulmonary-specific factors. In general, the indices are poor positive predictors (they do not indicate that the patient will wean), but they are good negative predictors (they indicate that the patient will not wean). Thus, use of the indices is not widespread. The various weaning indices are best used to evaluate the components from which they are designed (breathing pattern, respiratory muscle strength, etc.). These indices, if measured, are generally measured by the RT.
The patient’s overall status should be optimized before weaning of the ventilatory support is attempted. In addition to respiratory condition, assessment of weaning readiness should include acid-base status, electrolyte balance, status of other organ systems, nutritional status, and psychological state.
During weaning, the patient should be continuously monitored for respiratory distress. No single symptom defines failure. Patients should be monitored for:
Protocol-directed spontaneous breathing trials (SBTs) can reduce ventilator duration. When combined with aggressive sedation management, they may also reduce intensive care unit length of stay, hospital length of stay, and mortality. Protocol-directed multidisciplinary weaning using weaning screens and short-duration SBTs are superior to individualized weaning processes,2 although acceptance of and adherence to protocols may be low. The use of the protocols decreases practice variation, which may be the major reason for their effectiveness. Key to a protocol’s success is the use of the weaning screen, which requires that a minimum of clinical factor thresholds (e.g., hemodynamic stability, fraction of inspired oxygen [FIO2], and positive end-expiratory pressure [PEEP] level) are met. Screening ensures early and aggressive testing of the patient’s readiness. Once the screen is passed, the patient is placed on an SBT for a short duration before extubation. If signs of intolerance emerge, the patient is returned to ventilatory support and a trial is reattempted at a later time as predetermined by the protocol.
SBTs appear to be the best method;1,2 most of these methods employ breathing through a T-piece or on the ventilator (with or without the addition of continuous positive airway pressure [CPAP], low respiratory rates on synchronized intermittent mechanical ventilation [SIMV], or other flow mechanisms, such as automatic tube compensation). Other modes, such as pressure-support ventilation (PSV), may be equally as effective.
During the weaning process, prevention of respiratory muscle fatigue must be considered. All muscles may fatigue if work exceeds energy stores. Signs and symptoms of impending fatigue include dyspnea, tachypnea, chest-abdominal asynchrony, and increasing arterial partial pressure of carbon dioxide (PaCO2), which is a late sign. Generally, avoiding premature or excessively long or difficult weaning trials can prevent fatigue.
The concepts of work, rest, and conditioning are useful to consider when selecting weaning modes and methods. A higher respiratory workload is similar to strength training, and low-pressure, high-volume work is similar to endurance conditioning. These two methods of muscle conditioning apply to the respiratory muscles as well as other muscle groups within the body:
With both types of conditioning, the goal is to progress through the trials without inducing fatigue. To that end, rest is that level of ventilatory support that unloads the respiratory muscles. The level of support needed may differ with each patient; however, two basic concepts may be useful:
A plan for weaning is determined by the multidisciplinary team and is applied and monitored carefully. The plan, whether it employs a protocol or consists of a more individualized plan, should be available to all health care professionals involved in the weaning process. Assessment of weaning potential may include checklists of factors important to weaning, such as the Burns Weaning Assessment Program (Box 3). In addition, prophylaxis for VAP and other potential complications associated with mechanical ventilation must be considered.
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Rationale: Premature weaning attempts may be harmful and frustrating for all involved. A multidisciplinary team approach ensures active attention to the diverse factors that affect weaning readiness (
Box 1) (
Box 2) (
Rationale: Heated aerosol replaces water, which normally is added by the upper airway when it is not bypassed by an endotracheal or a tracheostomy tube.
Rationale: Signs and symptoms of tolerance must be heeded to prevent respiratory muscle fatigue.
Closely tend to the patient because the T-piece and tracheostomy collar have no alarms for apnea or hypoventilation.
Do not exceed the predetermined duration of the weaning trial.
Rationale: Adequate rest between trials and at night offsets fatigue and encourages effective respiratory muscle conditioning. The patient is placed back on the ventilator to rest until all data regarding weaning response can be assessed.
Rationale: An advantage of CPAP over T-piece trials is that V
T and respiratory rate are monitored easily throughout the trial by the ventilator. The RT can set alarms with a CPAP trial.
Rationale: As with the T-piece, this method employs high-pressure, low-volume work. Prompt return to the ventilator is necessary to prevent excessive work and fatigue.
Rationale: Adequate rest between trials and at night offsets fatigue and encourages effective respiratory muscle conditioning. The patient is placed back on the ventilator to rest until all data regarding the weaning response can be assessed.
Rationale: This method of weaning provides a gradual reduction of ventilator support. The preset breaths are progressively decreased as the patient assumes a greater proportion of the minute volume with spontaneous breathing.
Some IMV and SIMV demand valves offer high resistance to spontaneous breathing. Work of breathing may be greatly increased and cause fatigue, especially at low IMV rates. To avoid this, add PSV.
Lower levels of IMV, when not used with PSV, are similar to strength-conditioning trials. Ensure adequate rest times between trials and at night.
Rationale: PSV max is the level that attains the absence of increased work of breathing and allows for suitable V
T according to the patient’s demand. Higher respiratory rates and smaller V
T values are generally acceptable during trials. Full support should be ensured at night and for rest, especially early in the weaning process.
Be cautious when using high levels of PSV with patients who have obstructive lung conditions because the higher levels may promote overdistention and air trapping.
Rationale: PSV, despite requiring spontaneous effort, reduces the work of breathing associated with circuits, endotracheal tubes, and high breathing rates. However, fatigue is possible if the level is not appropriately set. Alternately, PSV can provide relief and rest to the respiratory muscles.
Hemodynamic instability should result in a return to ventilatory support until the patient is stable.
Azeredo, L.M. and others. (2016). The integrative weaning index in elderly ICU subjects. Respiratory Care, respcare.04524. Epub ahead of print. doi:10.4187/respcare.04524
Holets, S.R., Marini, J.J. (2016). Is automated weaning superior to manual spontaneous breathing trials? Respiratory Care, 61(6), 749-760. doi:10.4187/respcare.04329
Lu, Z. and others. (2016). Diaphragmatic dysfunction is characterized by increased duration of mechanical ventilation in subjects with prolonged weaning. Respiratory Care, 61(10), 1316-1322. doi:10.4187/respcare.04746
Sklar, M.C. and others. (2016). Effort to breathe with various spontaneous breathing trial techniques. A physiological meta-analysis. American Journal of Respiratory and Critical Care Medicine, Oct 21. Epub ahead of print.
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