Percussion

Percussion of the chest can aid in secretion clearance. It is performed by clapping cupped hands over the thorax in a rhythmic fashion or using mechanical devices that mimic the same action. The energy of the force generated by the cupped hands is transmitted through the thorax to dislodge secretions. When used in conjunction with postural drainage, this is an effective method to mobilize secretions from the pulmonary tract. It is a technique often used in the daily management of cystic fibrosis patients³ and those with severe bronchiectasis.

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.^4–6 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.

Manual Hyperinflation

Manual hyperinflation with an inflation bag and using high tidal volumes involves disconnecting the patient from the ventilator. Typically the lungs are inflated slowly to 1.5 to 2 times the tidal volume or to peak airway pressures of 40 cm H₂O (as measured by a manometer) and then at end inspiration with an inspiratory pause to allow for filling of alveoli with slow time constants. This is followed by a quick release to allow for rapid expiration. The goal of manual hyperinflation is to recruit atelectatic lung regions to improve oxygenation and improve clearance of secretions. Similar to recruitment maneuvers described with mechanical ventilators, manual hyperinflation leads to only transient improvements in oxygenation, without any long-term clinically significant improvement in outcomes.^8–12 It also has the disadvantage of requiring a ventilator disconnect, and this method can be mimicked by a mechanical ventilator.¹³

Contraindications to manual hyperinflation include hemodynamic compromise and elevated intracranial pressure. There is also a risk of barotrauma due to preferential inflation of open lung regions that are highly compliant compared to collapsed regions.

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 () 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.^23–25

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.

Continuous Rotation Therapy

Continuous rotational or kinetic therapy extends the practice of regular 2-hourly repositioning of patients from one side to the other by placing the patient on a bed that moves to preprogrammed angles on a more frequent basis or through the use of air mattresses that deflate alternatively from side to side to provide postural position changes. Most studies demonstrate a lower incidence of nosocomial pneumonia or atelectasis.^26–32 Only one small randomized trial found a reduction in duration of mechanical ventilation and length of stay, which was not confirmed in other prior studies.³³

Assisted Coughing

Assisted coughing is often required in spontaneously breathing patients who have an ineffective cough. Techniques include “huffing” in the setting of an open glottis, where in expiration the patient forcibly exhales quickly several times. Other maneuvers include abdominal or thoracic compression on expiration to generate high intrathoracic pressures mimicking a cough.

Positive Expiratory Pressure Therapy

Positive expiratory pressure therapy (PEP) involves use of a facemask or mouthpiece that provides resistance to airflow of 10 to 20 cm H₂O on expiration. After repeating this maneuver a number of times, mucus in the peripheral airways is mobilized and moved toward the larger airways to be coughed or expelled with other techniques. The use of PEP in critically ill patients who are spontaneously breathing is likely limited because of the coordination involved for slow expirations. Other methods to aid in secretion clearance may be easier to perform in this patient population.

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.

Chest Physiotherapy

Chest physiotherapy is a multimodal therapy with the goals of improving pulmonary function (gas exchange, improved lung compliance, and improved pulmonary mucus clearance). Techniques include percussive therapies (manual or mechanical chest percussion), postural drainage, chest vibration, manual hyperinflation, mobilization, suctioning, and rotational therapy. Overall, chest physiotherapy provides transient improvements in oxygenation and lung compliance, likely secondary to airway clearance and recruitment of atelectatic regions. In specific situations, it may improve outcome and clinical course, such as preventing ventilator-associated pneumonia³⁶ or acute lobar atelectasis.³⁷

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.^39–42 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 effective^44,45 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,^46–48 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.^49–51

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.

Mucoactive Agents

In chronic inflammatory lung conditions such as chronic obstructive pulmonary disease (COPD), cystic fibrosis, bronchiectasis, and intubation/tracheostomy, overproduction of mucus and impaired clearance results in complications such as airflow obstruction, atelectasis, and infection. Mucus is primarily composed of water, mucin glycoprotein, cellular debris, neutrophil-derived filamentous actin and DNA, and bacteria.⁵⁵ Mucoactive agents can help improve the clearance of mucus secretions.

Expectorant methods such as simple hydration together with oral expectorant medications (e.g., guaifenesin, bromhexine) that act via the vagal-mediated increase in airway secretion to decrease mucus viscosity have not been shown to be effective methods of clearing secretions.^56,57 Oral iodine preparations (e.g., saturated solution of potassium iodide), although described as mucoactive agents, are similarly ineffective and may be associated with significant side effects such as hypothyroidism or hyperkalemia.⁵⁵

Mucolytic agents reduce the viscosity of mucus by breaking down the mucin glycoprotein network or free DNA strands, thereby improving mucus rheology to improve clearance. Aerosolized N-acetylcysteine (NAC) breaks down the disulfide bonds of the mucin glycoprotein network and is associated with improved mucus clearance. However, because of increased incidence of bronchospasm with its use, therapy with NAC is not frequently initiated but may be used in conjunction with an inhaled bronchodilator.⁵⁵ Free DNA can significantly increase the viscosity of mucus and therefore impede clearance from the airways. Recombinant human DNase (rhDNase, dornase alpha) improves pulmonary function in the chronic management of cystic fibrosis patients but has no significant effect in acute exacerbations of cystic fibrosis.^58,59 In bronchiectasis not due to cystic fibrosis, rhDNase is not effective and may potentially be harmful.⁶⁰