Adjunctive Respiratory Therapy

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54 Adjunctive Respiratory Therapy

Many critically ill patients are unable to effectively clear secretions that accumulate in the central and peripheral airways. This can be due to factors such as increased secretion production, impaired cough reflex, weakness, and pain. The presence of an endotracheal tube prevents closure of the glottis to generate the high expiratory pressures necessary for an effective cough, thereby promoting the retention of secretions. In addition, in critically ill patients, cilia in the pulmonary tree are impaired in function and reduced in number.1,2 This leads to an increased risk of aspiration, atelectasis, and pneumonia, which are all detrimental in the critically ill patient.

Adjunctive respiratory therapy is able to prevent and treat respiratory complications that are encountered in the critically ill patient. As highlighted in Table 54-1, measures available range from those that are simple to institute, such as proper body positioning and suctioning, to more complex interventions such as chest physiotherapy, bronchoscopy, and use of aerosolized/inhaled medications that act directly on the pulmonary system.

TABLE 54-1 Adjunctive Respiratory Therapies

Methods to Improve Pulmonary Mucociliary Clearance
Methods to Improve Lung Expansion
Methods to Improve Oxygenation and Ventilation

image Methods to Improve Pulmonary Mucociliary Clearance

High-Frequency Chest Compression

High-frequency chest compression (HFCC) relies on rapid pressure changes to the respiratory system during expiration to enhance movement of mucus from the peripheral airways to the central airways for clearance. This method employs an automated vest device worn by the patient. The vest is attached to an air-pulse generator, and small volumes of gas are introduced into it at a rapid rate ranging from 5 to 25 Hz, producing pressures up to 50 cm H2O. This technique, mainly used in cystic fibrosis patients, is equivalent to conventional chest physiotherapy techniques of percussion and postural drainage.46 One study examined the use of HFCC in nine long-term mechanically ventilated patients.7 In this small observational study, HFCC was compared to percussion and postural drainage. No difference was seen in the amount of sputum production, oxygen saturation, or patient comfort between the two methods, but HFCC was determined to be safe and felt to save staff time. It is difficult to apply this technique to most critically ill patients because of the size of the vest; covering the thorax may prevent adequate monitoring.

Positioning and Mobilization

Mobilization of patients in the intensive care unit (ICU) either through active or passive limb exercises may improve overall patient well being and, in the long term, may lead to better patient outcomes. In a recent randomized controlled trial of ventilated patients, the addition of early physiotherapy and occupational therapy to daily interruption of sedation resulted in slightly more ventilator-free days and improved functional capacity.14

Positioning also plays an important role in improving physiology and outcome in critically ill patients. Position of the patient with the head of the bed elevated at least 30 degrees significantly reduces the risk of aspiration and ventilator-associated pneumonia.15 Upright positioning of patients in whom there is no contraindication improves lung volumes and therefore gas exchange and work of breathing, especially in those where the supine or semirecumbent position leads to increased work of breathing. In some individuals with unilateral lung disease, positioning with the affected side up can lead to improved ventilation/perfusion (image) matching by increasing perfusion to the dependent “good” side.16,17 If atelectasis secondary to retained secretions is the cause, having the affected side up leads to improved postural drainage.

Postural drainage involves positioning the body to allow gravity to assist in the movement of secretions and is indicated in patients with sputum production of more than 25 to 30 mL/day who have difficulty clearing their secretions.18 In cystic fibrosis, postural drainage with percussion is an effective method to clear pulmonary secretions and is associated with improved lung function.19,20

Tracheal Suction

Used in conjunction with other techniques to mobilize secretions from the peripheral to the central airways, suctioning is an effective way of removing secretions to improve bronchial hygiene. It can be performed using open methods where the patient is disconnected from the ventilator and a disposable suction catheter is placed. The closed system involves a suction catheter placed in a protective sheath and directly connected to the ventilator circuit. No disconnect is required, and the risk of environmental cross-contamination is reduced. Routine changes of in-line suction catheters are not required and are cost-effective.21,22 Overall, the risk of nosocomial pneumonia between the two systems is not different.2325

Because of the anatomic arrangement of the large central airways, most often a suction catheter enters the right main bronchus over the left side. Specially designed curved-tipped “left sided” suction catheters increase the likelihood of suctioning from the left mainstem bronchus.

Nasotracheal suctioning has fallen out of favor over direct tracheal suctioning and should only be considered in patients who are able to protect their airway and in conjunction with assisted coughs and other forms of chest physiotherapy.

Complications with suctioning include hypoxemia, especially in the setting of a ventilator disconnect, increased intracranial pressure with vigorous stimulation of the airways, mechanical trauma to the trachea, bronchospasm, and bacterial contamination of the airways. All patients should be preoxygenated with 100% oxygen for 1 or 2 minutes prior to suctioning. To reduce the risk of agitation, the patient should be informed before tracheal suctioning is performed. The suctioning should be limited to 15 to 20 seconds, and the suction port on the catheter should be opened and closed intermittently but not closed for more than 5 seconds at a time.

Bronchoscopy

Fiberoptic bronchoscopy has the advantage of providing direct visualization of the airways and permits suctioning of specific segments where secretions may be retained, causing problems such as atelectasis. The role of bronchoscopy in the ICU is reviewed elsewhere, but it can be considered an adjunctive therapy for the treatment of atelectasis or removal of secretions. As a recent review highlighted,29,34 bronchoscopy is a moderately effective technique for the treatment of atelectasis in the critically ill patient, with success rates ranging from 19% to 89% depending on the extent of atelectasis (lobar atelectasis responds better than subsegmental atelectasis). When compared with aggressive multimodal chest physiotherapy in the only randomized trial, no difference in the rate of resolution was seen between the two methods.35 Because bronchoscopy is an invasive procedure, it is not without associated risks and complications: sedation required for the procedure, transient increases in intracranial pressure, hypoxemia, and hemodynamic consequences/arrhythmias. Therefore bronchoscopy cannot be recommended as first-line therapy except in situations such as extensive unilateral atelectasis leading to significant difficulties in oxygenating or ventilating that have not resolved with other methods such as suctioning.

image Aerosol Therapies

Aerosolization

Aerosolization of medications is an effective method for drug delivery directly to lungs. The theoretical advantage of this form of therapy includes direct delivery and activity at the site of pathology and the ability to deliver high concentrations with minimal systemic absorption and toxicity. The most common aerosolized therapy is administration of bronchodilators. Other medications that can be administered directly to the lungs include corticosteroids, antibiotics, antifungal agents, surfactant, mucolytic agents, and saline.

The two most common methods of delivery by aerosolization are via nebulization or metered-dose inhalers. Nebulization is the process of using a high flow of gas (usually 6–8 L/min) to produce small particles of the liquid medium with the medication of interest. The most common nebulizer uses a pneumatic jet. In the spontaneously breathing patient, approximately 50% of the nebulized liquid is in the respirable range, with a mass median aerodynamic diameter (MMAD) of 1 to 5 µm; approximately 10% reaches the lower respiratory tract/small airways. In mechanically ventilated patients, 1% to 15% of the nebulized liquid and medication is delivered to the lower respiratory tract. Ultrasonic nebulization uses high-frequency ultrasonic waves on the surface of the liquid medium to generate respirable particles. Its use is limited by the expense of the equipment involved.

Metered-dose inhalers (MDI) are pressurized canisters with the drug suspended as a mix of propellants, preservatives, and surfactants. On activation, particles ranging in size from 1 to 2 µm are produced. An MDI used in conjunction with a chamber/spacer device significantly increases drug delivery in both spontaneously breathing patients and when attached to the ventilator circuit—either directly to the endotracheal tube or as part of an in-line device in the inspiratory limb of the Y-piece.

Factors that influence the efficacy of aerosol delivery in the mechanically ventilated patient include38:

Bronchodilators

Bronchodilators are the most frequently administered aerosolized therapy in critically ill patients. Inhaled β2-agonists, such as albuterol or fenoterol, are generally well tolerated in the critically ill patient and are known to improve lung mechanics in patients with and without airflow obstruction. In acute lung injury, β2-agonists may improve lung edema clearance and have additional antiinflammatory properties, although the clinical significance of such therapy has yet to be established.3942 Adverse effects (e.g., arrhythmias, hypokalemia) can occur in patients receiving excessive doses where significant systemic absorption is likely. Other bronchodilators including ipratropium bromide can also be effective in patients with increased airway reactivity, especially when used in conjunction with a β2-agonist. Bronchodilators administered via MDI are equally as effective as a nebulizer in spontaneously breathing patients.38 In mechanically ventilated patients, the use of nebulization is either equally as good as43 or less effective44,45 than an MDI with a spacer. MDI administration has the advantage of easier use without the risk of bacterial contamination and need for adjustment of flow rates.38

Antibiotics

Aerosolization of antibiotics as a form of topical treatment for pulmonary infections has been studied for over 20 years. Theoretical advantages of aerosolized antibiotics include direct therapy to the site of infection at higher concentrations, with a lower risk of systemic absorption and side effects. In chronic pulmonary infective states such as cystic fibrosis and severe bronchiectasis,4648 aerosolized antibiotics have a role in reducing bacterial concentrations in the sputum, but they have only be shown to provide clinical long-term benefit in cystic fibrosis.48 In the acute infective state, aerosolized antibiotics have no additional benefit compared to parenteral antibiotics.4951

In the intubated or tracheostomized patient, the risk of colonization of the airway is high, with a significant increase in the risk for nosocomial pneumonia. In an observational study of six chronically ventilated patients, aerosolized aminoglycosides (tobramycin or amikacin) eradicated the colonizing bacteria 67% of the time and significantly reduced the levels of inflammatory markers in the sputum.52 As a preventive measure, a recent meta-analysis of prospective clinical trials of aerosolized aminoglycosides suggested a significant reduction in the development of ventilator-associated pneumonia but no difference in overall mortality.53 As an adjuvant for treatment of ventilator-associated pneumonia, a meta-analysis of five randomized controlled trials suggested a significant improvement in the clinical resolution of pneumonia.54 Despite the findings, limitations of these analyses must be considered, given the heterogeneity of the trials. In addition, concerns of bacterial resistance must also be considered. Side effects reported in spontaneously breathing patients treated with inhaled tobramycin include increased cough, dyspnea, and chest pain.46

The role for aerosolized or instilled (via the endotracheal tube) antibiotics as adjuvants for prevention or treatment of pulmonary infections in the ICU remains to be defined with adequately powered future clinical studies.

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