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Reducing Aspiration Pneumonia Risk
Pneumonia development is relatively common among older long-term care residents. Aspiration pneumonia (AP) is defined as inflammation of lung tissue, caused by bacterial infection resulting from the entrance of foreign materials into the bronchial tree and lungs, usually from oral or gastric contents (including food, saliva, and/or nasal secretions). Negative consequences related to pneumonia include respiratory distress, respiratory failure, sepsis, death, increased hospital recidivism, and increased cost of care. Given the many sequelae of pneumonia, it is important to recognize and reduce the risk factors for pneumonia development. This review article explores the literature on AP and provides information on the risk factors for the condition and multidisciplinary interventions that can reduce the risk of AP development, including medication modification, high-quality suctioning, judicious use of feeding tubes, oral hygeine and oral care, diet modification, free-water protocols, and therapeutic rehabilitation services.
Key words: pulmonary aspiration, aspiration pneumonia, skilled nursing facility, feeding tube
Pulmonary aspiration is defined as the entry of material (eg, saliva, food, liquids, stomach contents) from the oropharynx or gastrointestinal tract into the larynx and lower respiratory tract. This occurrence may provoke a physiological response, such as coughing or throat clearing. Alternatively, it may occur silently with no overt signs of aspiration. Aspiration is estimated to occur in 45% of healthy normal people during sleep, 70% of individuals with impaired consciousness, up to 40% of individuals fed via nasogastric (NG) or percutaneous endoscopic gastrostomy (PEG) tube (also known as enteral feeding), and 50–75% of individuals with tracheostomy tubes.1
Pulmonary aspiration can be an innocuous event, and it may not lead to medical complications. Alternatively, aspiration may lead to aspirational pneumonia (AP). AP is described as inflammation of lung tissue that is believed to occur when foreign materials (eg, food, saliva, nasal secretions) are introduced into the bronchial tree and lungs from the pharynx in a sufficient inoculum to overcome the body’s defenses. Local host defense mechanisms usually clear the lung of the aspirate without serious clinical effect, but this is often not the case for frail individuals with compromised immune system response, mobility, and/or airway clearance. Additionally, defenses can be overwhelmed by smaller inocula in the case of more virulent organisms. Negative consequences related to pneumonia include respiratory distress, respiratory failure, sepsis, death, increased hospital recidivism, and increased cost of care.2,3
This review article is focused on risk factors for AP development and multidisciplinary interventions to reduce the risk for AP.
Literature Review
Literature searches were conducted using MEDLINE, PubMed Central, and the Cochrane Central Register of Controlled Trials databases using the following key words: dysphagia, enteral feeding, aspiration, pneumonia, and nursing homes. Original research articles, randomized controlled trials, and expert opinion articles were are included in the search, because there are few systematic reviews or meta-analyses directly related to the topic of reducing the risk of aspiration pneumonia. The bibliographies of several of the randomized controlled trials and review articles identified several additional articles for consideration.
Approximately 45 articles identified in this search were reviewed. The literature review was conducted in December 2014, and all citations included in this review article were published between 1998 and 2014. The premise of the review article was based on two randomized controlled trials with large sample sizes. The primary findings of those articles were noted, and subsequent studies and general discussion articles were reviewed looking for confirmation of findings or contradictory findings.
Predictors of Aspiration Pneumonia
Whether AP develops from one or more episodes of aspiration depends on the volume of aspirated material, aspirate characteristics (eg, bacterial load, liquid versus particulate matter, pH level), aspiration frequency, and integrity of the individual’s immune system.4 According to the Agency for Healthcare Research and Policy, individuals with dysphagia who aspirate have a ~50% greater risk of developing AP than individuals with dysphagia who do not aspirate on videofluoroscopy examinations.
The Agency cautioned that aspiration should not be considered a definitive marker for patient outcome of pneumonia, because other patient characteristics may have an equal or even greater role in the development of pneumonia.5 Other causative mechanisms of pneumonia include chronic diseases such as asthma, chronic obstructive pulmonary disease, and heart disease; immune system compromise related to HIV/AIDS, organ transplant antirejection therapy, chemotherapy, or long-term corticosteroid use; smoking; and atelectasis from prolonged bed rest. Some organisms that cause nursing home–acquired pneumonia include Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. The occurrence of microaspiration of oropharyngeal contents with pathogen contamination results in a high prevalence of Gram-negative pneumonias in this population.6 From a clinical perspective, the diagnosis of “aspiration” is usually based on risk factors with a plausible direct relationship to aspiration. The exact mechanism of a pneumonia episode is seldom determined unless an acute aspiration event is witnessed.
In their 1998 prospective outcomes study, Langmore and colleagues7 recruited 189 patients from outpatient clinics, inpatient acute care medical wards, and a nursing home, and compared the predictors of AP across these various settings. Patients were followed for up to 4 years after comprehensive data collection, including clinical and instrumented swallow analyses, dental examination, saliva and throat cultures, medical diagnoses, and functional status. Of the 189 patients overall, 41 (22%) developed pneumonia, with a significantly higher percentage noted in the skilled-nursing facility setting (44%) than in the inpatient (19%) or the outpatient setting (9%). The authors identified several predictors associated with AP (Table 1).7
Another key finding from this study was that the development of AP could not be predicted by videofluoroscopy or fiberoptic endoscopic evaluation of swallowing studies. Additionally, the authors reported that aspiration of food is much more likely than aspiration of liquid to lead to pneumonia. As only 38% of those who aspirated developed pneumonia, the study demonstrated that dysphagia by itself does not appear to cause AP.7
In a subsequent 2002 study, Langmore and colleagues8 analyzed Minimum Data Sets (MDS) data from three nursing homes (N=102,842) for residents with AP diagnoses. Logistic regression models indicated 18 significant predictors of AP in this nursing home population (Table 2).8 The study demonstrates the “fragile state” of susceptible nursing home residents because of their ability to clear their airways and lungs and fight off infections.
Aspiration of contaminated oral or gastric contents is not prevented by the placement of a feeding tube. In fact, NG and PEG tubes, while commonly used to address dysphagia, are associated with increased risk of AP more so than dysphagia itself,8 because a feeding tube may increase the introduction of gastric contents into the airway.
Many of the risk factors identified increase bacterial colonization in the oropharynx, thereby increasing the likelihood of developing AP. Given these realities, it is important in the SNF setting to explore and implement multidisciplinary strategies to address dysphagia, reduce feeding tube use, and thereby reduce the risk of AP development in high-risk individuals.8
Interventions to Reduce the Risk of Aspiration Pneumonia
Multidisciplinary approaches to decrease the risk of AP may include medication modification, high-quality suctioning, careful use of feeding tubes, proper oral care, diet modification, free-water protocols, and therapeutic rehabilitation services.
Medication Modification
For patients at risk for AP, healthcare providers should conduct a review of patient medications and taper down or discontinue those that have any of the following side effects: decrease in salivation (and thus slow bacterial clearance), impairment in swallowing, facilitation of reflux by relaxing the lower esophageal sphincter and slowing gastric emptying, promotion of gastric colonization, limitation of mobility, and impairment in the strength of the cough; all of which may increase the relative risk of AP. Modifications should be considered especially for diuretics, anticholinergics, anxiolytics, antipsychotics, and levodopa, all of which reduce salivary flow and increase bacterial flora in the oral cavity. Antipsychotics and anxiolytics may also lead to impaired swallowing function, due to their effects on the central nervous system, and can increase the risk of AP. A low pH environment is needed to kill the organisms that colonize the gastrointestinal tract. Histamine H2 blockers and proton pump inhibitors increase the pH of the stomach, supporting the growth of bacteria.9
High-Quality Suctioning
As noted in Table 2, individuals who require suctioning are at greatest risk for developing AP.8 High-quality and frequent suctioning reduce this risk in these patients. Suctioning using proper techniques should be performed whenever the patient feels or hears mucus rattling in the airway or tracheostomy tube, after awakening in the morning, when an increased respiratory rate is noted, before meals, before going outdoors, and before going to sleep. It is a best practice to use separate catheters for oral and tracheal clearance when suctioning.10,11
Judicious Use of Feeding Tubes
As pointed out earlier, NG and PEG tubes, while commonly used to address dysphagia, increase the risk of AP more so than dysphagia itself. In a 1994 12-month clinical outcome study, 40 nursing home residents underwent videofluoroscopic swallowing evaluation. Twenty-two of the patients demonstrated aspiration, and 15 subsequently received feeding tubes. Those with aspiration had a higher rate of re-hospitalization (P<.05) and among those who aspirated, the patients with feeding tubes had a higher rate of pneumonia (P<.05) and pneumonia death (P<.05). Researchers also reported that patients with NG tubes had a higher death rate than those with gastrostomy tubes (P≤.05).12
In a more recent retrospective review of 536 acute stroke patients, Brogan and associates13 reported that dysphagia was not a significant predictor of AP in the study population, as respiratory infections developed in only 17% of those with dysphagia. Being nil by mouth and insertion of an NG tube, however, were significantly associated with AP as a consequence of refluxed gastric contents being aspirated or aspiration of bacteria-laden saliva or nasal secretions.13
Cintra and associates14 specifically examined the risks associated with tube feeding in patients with advanced dementia and dysphagia in their 2014 observational study of 36 orally fed and 31 alternatively fed individuals (28 of whom were fed using an NG tube). Significantly more patients in the alternative feeding group (n=18; 58.1%) had an AP diagnosis compared with the oral feeding group (n=9; 25%; P=.006). Furthermore, the study results indicate that enteral feeding is associated with an increased risk of death compared with oral feeding (at 3 months: 41.9% vs 11.1%, respectively; at 6 months: 58.1% vs 27.8%, respectively).14 Similarly, Finucane et al.15 noted that enteral tube feeding has not been shown to reduce the risks of death, AP, pressure ulcers, other infections, or poor functional outcome in institutionalized people with dementia. Based on these studies, it can be concluded that oral feeding may be safer than enteral feeding in individuals with advanced dementia.
Aspiration in the presence of an NG or PEG tube occurs via one, or both, of the following two mechanisms: anterograde aspiration and/or retrograde aspiration. Anterograde aspiration occurs during oral alimentation due to oropharyngeal dysphagia. Retrograde aspiration results from the entry of refluxed material from the gastroesophageal tract into the lungs. Suspected causes of AP from NG tubes include a loss of anatomical integrity of the upper and lower esophageal sphincters, increased relaxation of the lower esophageal sphincter, and decreased sensitivity of the pharyngoglottal adduction reflex, all due to the presence of the tube. The stomach contains bacteria that cause AP. NG tubes appear to create pathways for these bacteria to move into the pharynx via reflux and/or esophageal migration. Once in the pharynx, the bacteria may colonize and contaminate aspirated secretions.
It is not suggested that NG or PEG tubes never be used, but it is important to carefully consider the clinical indications and implications of NG and PEG tube use. In general, they should be used only in the absence of pharyngeal swallow/upper esophageal opening. While the tube is in place, work on restoring swallow function, with a goal of discontinuing tube feedings as soon as possible (ie, ideally within 30 days) to avoid adverse events such as AP, unintended catheter removal, poorer nutrition, and weight loss. Langmore et al.8 noted that, “Weight gain must be facilitated by offering tasty and attractive meals and holding off on tube feedings as long as it is safe.” Even for those patients who are have a nil per os order (nothing per mouth), high-quality, aggressive, and frequent oral care should be performed to remove bacteria from the oral cavity to reduce the risk of migration into the airway.
Oral Hygiene and Oral Care
There is a strong correlation between the presence of oropharyngeal bacteria and the development of pneumonia. Caregivers should carefully examine a patient’s mouth once or twice per day to assess the presence of food particles, poor oral hygiene, dry mouth, and signs of bacterial infection. According to 2007 guidelines from the American Association of Critical-Care Nurses, good oral care includes all of the following:16 brushing all areas of the oral cavity with a soft toothbrush, including the tongue, palate, cheeks, and sulci; care must be taken when brushing the posterior palate to avoid the induction of gagging or vomiting; avoiding the use of gauze, foam swabs, and lemon glycerin swabs for oral care; using toothpaste that contains additives (such as sodium bicarbonate) to assist in the breakdown of mucus and biofilm in the mouth; using a non-alcohol-based antiseptic mouth rinse; referral to a dentist (when needed) and periodic teeth cleaning by a dental hygienist; adequate hydration; and regularly moisturizing lips and gums using water-soluble moisturizer.
Diet Modification
It is not uncommon for people who experience swallowing difficulty to be placed on mechanically altered diets and/or thickened liquids. For those who aspirate liquids, increasing viscosity appears to decrease the immediate risk of aspiration with each swallow, but some complications with these diet modifications are noted by researchers. For example, very thick liquids and solid food require greater tongue and pharyngeal muscle strength, which is often a problem for weakened individuals. Thicker liquids increase swallow duration and pharyngeal transit times. Both of these issues present a risk of residue remaining in the oropharynx post-swallow and increase the risk of aspirating this residual material.17 Additionally, thickened liquids are generally disliked by patients and may lead to dehydration and one or more of the following complications: orthostatic hypotension, urinary tract infections, slowed healing from infections and wounds, constipation, confusion and lethargy, suffering, increased dependency, and less saliva, which leads to increased bacterial concentrations and therefore greater AP risk.18
In their 2008 study, Robbins and Hind19 reported that honey-thick liquids, nectar-thick liquids, and chin tucks reduced immediate aspiration in patients with Parkinson’s disease and/or dementia. When these strategies were employed, the incidence of AP was reduced in only one-half of patients in the trial. However, those who drank honey-thick liquids had higher incidences of urinary tract infections and dehydration as well as pneumonia-caused hospital stays that were three times longer than those admitted for pneumonia who consumed nectar-thick liquids and performed chin tucks. Honey-thick liquids were therefore found to be both less preferred by patients and to cause more complications when compared with nectar-thick and chin tucks. Furthermore, none of the three strategies were effective in one-half of the patients. The researchers point out that the effectiveness of each strategy should be assessed for each individual patient, as the results varied from patient to patient.19
Free-Water Protocols
Some long-term care providers choose to implement free-water protocols to minimize the negative consequences of thickened liquids in patients with dysphagia. These protocols allow individuals to ingest water freely per a multidisciplinary protocol. In well-controlled clinical trials and operational practices in which patients have strict criteria regarding when and how much water they can “freely” consume, it has been demonstrated that patients with thin liquid dysphagia have been able to ingest water without complications due to the fact that water has a neutral pH level and is generally biocompatible with the lungs. Lung tissue contains aquaporin channels that act like a sieve to drain water and allow it to be absorbed by the blood vessels and carried out to the bloodstream very rapidly.20 In a study by Carlaw and colleagues,18 protocol implementation for eligible participants was deemed “not overly onerous” and resulted in increased water intake in all patients. Exclusion criteria included absent pharyngeal swallow and/or upper esophageal sphincter opening, active pneumonia, an acute or unstable medical condition, uncontrollable oral infection, and/or excessive or uncomfortable coughing after water intake. There were no adverse events reported by the patients, including no cases of pneumonia, and there was a trend toward increased quality of life.18 Although free-water intake protocols are not without controversy for those with dysphagia,21 water intake in controlled conditions appears to be a safe option for maintaining hydration for certain patient populations with dysphagia.
Therapeutic Rehabilitation Services
The most likely physiologic causes of aspiration are delayed initiation of swallow and weak swallow,8 and oropharyngeal dysphagia is often related to muscle weakness. Speech therapy services offer rehabilitative potential to improve swallow function and reduce the risk of AP. Therapeutic exercise is recommended to reduce aspiration and the risk of AP by combatting weakness of oropharyngeal muscles that may result in delayed swallow onset and decreased laryngeal opening and closure.4 Exercises to improve tongue strength in patients using thickened liquids may be helpful.19 Evidence-based preventive strategies include an “individualized plan of exercises to strengthen and improve swallowing muscles.”22-26 Furthermore, a growing body of literature suggests that the therapeutic use of surface electromyography to augment oropharyngeal strengthening exercises can help to improve swallow function.27 In addition to implementing rehabilitative techniques, restorative therapies such as the inclusion of compensatory strategies during swallow therapy may further lower the risk of AP development. Specifically, the chin-down position may decrease the risk of immediate aspiration and the development of AP.19,28 Regardless of whether the goals of therapy are rehabilitative or compensatory, good quality oral care should precede every swallowing therapy session.
Lastly, general full-body exercise and mobility are critical to promote respiration and lung function. Exercise can improve immune function, autonomic nervous system activity, adenosine triphosphate production, and mental health, and may be especially beneficial for patients who have compromised pulmonary function due to congestive heart failure, chronic obstructive pulmonary disease, or similar comorbidities. For individuals who have limited mobility and/or pulmonary compromise, referrals to physical and/or occupational therapy should be considered to support strength training treatment efforts. These include breathing strategies/exercise, chest therapies, functional mobility training, and neuromuscular electrical stimulation to key trunk and/or extremity muscle groups, all of which can promote muscle strength and aerobic capacity.
Conclusion
When pulmonary aspiration occurs, local host defense mechanisms usually clear the lung of the aspirate without serious clinical effect; however, this is often not the case for frail individuals with compromised immune system response, mobility, and/or airway clearance. In these patients, pulmonary aspiration can lead to AP. Some risk factors for AP include suctioning, chronic obstructive pulmonary disease, and feeding tubes. As feeding tubes appear to inadequately protect patients from aspiration and pneumonia, other avenues to reduce the risk of AP must be explored. Multidisciplinary approaches to decrease the risk of AP may include medication modification, high-quality suctioning, careful use of feeding tubes, proper oral care, diet modification, free-water protocols, and therapeutic rehabilitation services.
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