Critical care nurses care for intubated patients undergoing tube feeding who are at very high risk of aspiration and the resulting pneumonia. This author reviews the research to determine factors contributing to aspiration and suggests a clinical protocol to help prevent the problem or decrease the complications if aspiration occurs.
Aspiration of gastric contents can be a serious complication of providing enteral nutrition for patients via various feeding tubes. Frequently referred to in nursing literature, many nursing actions are aimed at preventing this complication. Critical care nurses care for intubated patients receiving tube feeding who are at high risk for aspiration and the resulting pneumonia. In the area of trauma nursing, aspiration prevention has been identified as an important research priority. The research question, "What are the most effective methods for preventing aspiration in trauma patients during the postoperative phase?" was ranked second highest in value for practicing nurses and second highest in having an impact on patient welfare.
This author reviews the research aimed at preventing aspiration, to determine factors contributing to aspiration, and suggests a clinical protocol to help prevent the problem or decrease the complications if aspiration occurs. The researchbased protocol presented in this article guides the nurse in both risk assessment and preventive actions.
Aspiration is the introduction of a foreign substance into the lungs, but the mere instillation of foreign substance into the subglottic airway is not sufficient to produce disease. Damage to the pulmonary tree, which ranges from mild to fatal, depends on the nature, volume and pH of the aspirated contents, and the pathogenicity of the organisms. Physiologic changes resulting from aspiration of acidic fluid or gastric contents include a decline in arterial blood oxygen tension, increased alveolar capillary membrane permeability, and a decrease in intravascular volume. The lungs can become edematous and gas exchange abnormalities are the result. Histologic examination shows tracheal mucosal desquamation, damage to the cells of the alveolar lining and capillary inflammation 24 to 36 hours after aspiration.
Aspiration of nonacidic solutions containing food particles results in a foreign-body reaction of cell inflammation with granuloma formation. Even aspiration of distilled water or normal saline can result in damage to the alveolar capillary membrane as detected by electron microscope.
Gastric acid aspirant results in chemical burns that destroy alveoli, which results in acute onset of respiratory distress secondary to widespread bronchospasm, hypoxemia, and parenchymal infection. The lower the pH (less than or equal to 2.5) the more severe the injury. There is a 30% incidence of subsequent development of adult respiratory distress syndrome (ARDS) after acidic aspiration.
Plasma concentrations of hydrochloric acid administered tracheally to anesthetized dogs reached peak concentrations in two to three minutes. The pulmonary absorption is immediate, which suggests that any attempts to neutralize aspirated material would be futile.
Normally, micro-aspirates are cleared by several mechanisms or lines of defense. The materials are entrapped and removed by filtration, coughing, or by action of the cilia. At the cellular level, the immune system clears by using inactivation, IgA antibodies, or opsonization, and subsequent phagocytosis. Loss of these defense mechanisms results in infection and colonization by pathogenic organisms.
Aspiration pneumonia is diagnosed clinically by noting its manifestations: a predisposition for aspiration; recovery of oropharyngeal, gastric or exogenous secretions from the pulmonary bed; and radiographic evidence of an infiltrative process, usually in a gravity-dependent section of the lung. The clinical manifestations of aspiration pneumonia are acute and cover a spectrum from asymptomatic, also known as silent aspiration, to exhibiting a cough, fever, sputum production, chest pain, increased white blood cell production, acute respiratory distress, tachypnea, tachycardia, wheezing, and transient hypoxemia with cyanosis. Aspiration pneumonia can progress to necrotizing lung infections, abscess formation and empyema. Shaking chills are uncommon in aspiration pneumonia.
Signs of tachypnea, cough, rales, cyanosis, wheezing, fever, leukocytosis and, occasionally, apnea develop, usually, within two hours of the aspiration. In addition, pulmonary infiltrates in dependent lung segments - such as posterior segments of upper lobes, superior segments of lower lobes and basilar segments of lower lobes - are evident on radiographic examination.
Interestingly, the incidence of aspiration pneumonia is variably presented in the literature. Aspiration is the most common route of entry for both community-acquired and hospital-acquired pneumonia. It is difficult to determine the true incidence of aspiration pneumonia because consistency in the definition of aspiration pneumonia across studies does not exist and because the clinical course after aspiration is highly variable. Haleem concludes that it is an uncommon, rarely diagnosed problem that often goes unrecognized. With silent, asymptomatic aspiration, the only evidence is in the pulmonary secretions; overt signs are absent. Studies describing the incidence of aspiration pneumonia fall into two categories: (1) those that aspirate oropharyngeal contents and (2) those that aspirate gastric contents, the former group having the higher incidence. Table 1 shows the incidence of aspiration pneumonia in several studies.
| Hassett, Sunby & Flint (1988); | 53% |
| Cogen, & Weinryb (1989); | 22.9% |
| Cogen, Weinryb, Pomerantz & Fenstemacher (1991); | 15.9% |
| Kingston, Phang & Leathley (1991); | 20.8% |
| Elpern, Jacobs & Bone (1987); | 27% |
| Methany, Eisenberg & Spies (1986); | 5.7% |
| Bernard, Braunstein, & Stevens (1982); | 38% |
| Olivares39, Segovia & Revuelta (1974); | 24% |
Overall prevalence of aspiration pneumonia resulting in death is described by Haleem7. Based on a ten-year prospective analysis of all autopsies in York, England, an overall incidence was 6.5 per 1000 postmortem examinations performed, or 0.65 % mortality. Haleem concludes that aspiration pneumonia is an uncommon condition and it is rarely diagnosed on clinical grounds, but it does cause death occasionally. In fact, mortality in patients who aspirate gastric contents is described as between 30 to 60% and it is directly related to the extent of roentgenographic pulmonary involvement.
Hickling and Howard found a 7.5% mortality related to aspiration. They conducted a retrospective survey of 38 patients with severe aspiration pneumonitis requiring artificial ventilation and intensive care. The mean predicted mortality using APACHE II was 43%. The authors conclude that the retrospective mortality rate was lower due to aggressive medical management of the aspiration pneumonia, including rapid intravascular volume restoration with crystalloid fluids, and early ventilation. Immediate use of steroids or antibiotics was not part of their treatment.
The pathophysiology and research studies help guide critical care nurses to prevent aspiration. The factors suggested by researchers have been added to a protocol to guide nurses in prevention on this problem.
The critical care nurse is often the first to recognize patients who are at risk of aspiration pneumonia. Risk factors associated with aspiration pneumonia are not clearly defined; although certain patient characteristics, such as altered level of consciousness, depressed cough and gag reflexes, gastrointestinal disorders, use of various breathing and feeding tubes, and increased age are associated with increased risk for aspiration pneumonia. Many patients have greater than one risk factor at a time; for instance, the elderly patient can also experience altered level of consciousness (LOC) and have a nasogastric tube (NGT) and decreased gastric motility while on bedrest. Studies addressing patient risk factors are reviewed in this section.
Pneumonias occurring in the context of aspiration have a low attack rate because acquisition depends on the susceptibility of the individual patient. Patients with compromised host-defense systems, especially those with underlying pulmonary disease or immunosuppression, are principal victims. Even Legionnaires' disease is suspected of being associated with a mode of transmission of aspiration rather than aerosolization.
Nurses routinely assess tube-fed patients because they are at risk of aspiration. However, researchers are unclear about how often aspiration pneumonia occurs in patients with feeding tubes. Cogen and Weinryb conducted a retrospective chart review of 109 nursing home patients with gastrostomies and found a 22% incidence of aspiration of gastric contents.
The only significant risk factor was a history of a previous episode of pneumonia (p<0.05). No association was found with age, mental status or continuous versus intermittent method of infusion of feeding formula. The authors reasoned that it was likely that the previous episode of pneumonia also could have been due to aspiration.
Later, in 1991, Cogen, Weinryb, Pomerantz, and Fenstemacher11 studied 44 jejunostomy-fed patients in a skilled nursing facility. Again, using a retrospective chart review, the authors revealed a 15.9% incidence of aspiration pneumonia. A history of pneumonia was the only significant risk factor (p<0.05) for developing aspiration. Again, the authors conclude that patients known to aspirate were not protected by gastrostomy and jejunostomy tubes. Because of potentially missed or inaccurate reporting of information, use of a retrospective chart review was a limitation to the study.
Nurses must assess patients with nasogastric tubes because they are at increased risk for aspiration with both types of tubes. Elpern, Jacobs and Bone state that both smaller-bore feeding tubes and the stiffer, larger-bore NGT cause decreased pharyngeal sensation and compromised upper and lower esophageal sphincter function.
Kirsch and Sanders found that NGT are associated with a depressed cough reflex and pooling of secretions in the hypopharynx resulting in aspiration. Treolar and Stechmiller support the use of Dobbhoff feeding tubes to the small bowel, but Metheny concludes that a small-bore tube is not more effective in decreasing aspiration incidence. This could be due, in part, to a problem often associated with small-bore Dobbhoff feeding tubes (nurses do not often check residuals). Ibanez et al. found that NGT significantly (P = 0.0002) increased the likelihood of gastroesophageal reflux (GER) in 70 patients. Montecalvo et al. found no significant difference in the incidence of pneumonia for 19 gastric-versus 19 jejunostomy-fed patients. Because of the small sample size, it cannot be established that there is any difference in incidence of aspiration between the two methods of feeding.
Nurses interested in minimizing risk for aspiration check the patient history for presence of gastrointestinal problems. Gastrointestinal disorders such as dysphagia, achalasia, and gastroesophageal reflux (GER), have been implicated as major causes of aspiration pneumonia.
Hassett, Sunby and Flint determined that for preoperative gastrostomy patients, a history of GER was associated with postoperative aspiration (predictive value of 0.70). They conclude that no benefit results from placing a feeding gastrostomy in neurologically impaired patients with GER. Their findings were similar to those of Cogen et al. who determined that gastrostomy tube insertion did not prevent aspiration of feeding solutions in nursing home patients. Trulzsch, Penmetsa Karim and Evans described a case of a fatal aspiration of gastrografin in a patient with dysphagia secondary to squamous cell carcinoma of the esophagus. The presence of gastrointestinal disorders should alert the nurse to a potential increased risk for aspiration.
Depressed cough reflex has been suggested as a cause of aspiration in patients by several authors. Sekizawa et al. induced a cough with varying concentrations and amounts of citric acid, and with mechanical irritation. Ten control subjects, who were not suffering from pneumonia, coughed more often than the five aspiration pneumonia patients. Nakawazaw et al. found similar results when they replicated this study. Ten control subjects coughed while only seven of the ten with aspiration pneumonia coughed, even at the highest concentration of citric acid (360 mg/ml).
Nurses need to be aware that the presence of a tracheostomy does not provide protection from aspiration. Patients with tracheostomies are at risk for aspiration because of decreased laryngeal elevation, obstruction by the tracheal cuff, desensitization of the larynx, a loss of protective reflexes due to chronic air diversion through the tube and uncoordinated laryngeal closure due to chronic upper airway bypass. Ironically, it is commonly believed that one of the purposes of a tracheostomy is to protect the patient's airway. In an effort to define the incidence of aspiration in critically ill patients with tracheal intubation, Elpern, Jacobs and Bone determined that inflated tracheal cuffs did not prevent aspiration. Thirty-one patients received Evans blue dye every four to six hours on the posterior area of the tongue. They were suctioned every four to six hours; 907 samples were collected over an average of five days.
Twenty-four (77%) of the 31 patients did aspirate, and 27% of the overall samples (247 out of 907) were positive for blue dye. No difference in incidence of aspiration was related to level of consciousness. The heads of bed were elevated 80% of the time, but still aspiration occurred. Aspiration with NGT occurred significantly (p < 0.05) more often (34%) than without an NGT (24%). Aspiration also occurred significantly (p< 0.05) more often with tracheostomies (40%) than with translaryngeal tubes (25%).
The authors conclude: (a) the majority of patients with artificial airways aspirated; (b) aspiration occurred despite preventive measures, such as head-of-bed elevation, tracheal cuff inflation, and use of small-bore feeding tubes; (c) tracheal cuff inflation at occlusion pressure did not prevent aspiration; and (d) the presence of altered LOC did not change incidence. Aspiration of oropharyngeal or gastrointestinal secretions occurs past inflated tracheal cuffs. Use of occlusion pressure for tracheal tubes increases the risk for aspiration significantly more often than cuffs inflated at less than occlusion pressure, i.e., minimal leak technique (cuff pressure of 25 cm of water). Perhaps, this is caused by the small cuff leaks for patients on positive pressure ventilation allowing for exsufflation of the secretions toward the oropharynx offering some protection against aspiration into the lungs. The authors advise that the potential interactions among variables of cuff inflation status, mechanical ventilation and aspiration need further investigation.
Nurses should take aspiration prevention measures when caring for patients with an altered level of consciousness. Sedated patients or those with an altered level of consciousness, such as those who have had significant alcohol intake or are postanesthesia, or those receiving anxiolytics can be at increased risk for aspiration. Nishino et al. studied 10 subjects and determined that the swallow reflex is depressed during sedation and/or relative analgesia with 50% nitrous oxide in oxygen.
Many studies link aspiration pneumonia to decreased LOC. A decreased LOC can be a reason for a patient to receive a NGT, which, as described above, can further increase the risk for aspiration. Metheny proposes that only alert patients with intact cough and gag reflexes should receive NGTs.
Neurologic disorders can predispose patients to aspiration. Hassett, Sunby, and Flint conclude that use of a gastrostomy tube did not decrease incidence of aspiration pneumonia in 87 neurologically disabled patients. They found an aspiration incidence of 33% before gastrostomy and 32.7% aspirated after gastrostomy.
Haleem determined that one-third of the subjects who aspirated were unconscious during epileptic convulsions, or under the influence of alcohol or drugs. For example, Marik and Ballhausen describe a case in which a 35-year-old male with seizures, ataxia and, confusion aspirated the end of a mercury thermometer. Some studies found opposite conclusions suggesting that LOC is not linked to incidence of aspiration. Elpern and colleagues conclude that LOC does not play a significant role in the incidence of aspiration. The incidence of aspiration pneumonia in (a) awake-alert, (b) awake-lethargic, and (c) unresponsive patients was not significantly different. The authors did not explain these findings. Likewise, Cogen and Weinryb, did not demonstrate that mental status affected the risk of aspiration pneumonia, even though it is an often-cited risk factor. However, theirs was a retrospective chart review, and aspiration of alert patients might have occurred in sleep or during periods of sedation. These are situations that may not be reflected in a chart review.
Advanced age is considered a risk factor often associated with aspiration (Marino, 1991). Achalasia, the failure of the lower esophageal sphincter to relax completely during swallowing, is a common disorder seen in elderly patients that increases the risk for aspiration. No studies linking age and aspiration were identified. However, Hickling and Howard described a mortality rate of 7.5%, in which only one of the subjects who died was under 70 years of age. Hickling and Howard conclude that low mortality in severe aspiration pneumonia is due to aggressive medical management of the problem, particularly in young patients.
A clear understanding of the hazards of aspiration is needed by those caring for the critically ill patient. After identifying those patients at increased risk for aspiration, critical care nurses are ready to take actions intended to reduce the risk of aspiration pneumonia.
Many nursing efforts are aimed at reducing the risk or prevention of aspiration. Efforts, such as elevating head of bed and periodic checking for residual stomach amount, are believed to decrease the risk of aspiration. Research addresses these and other nursing practices aimed at aspiration prevention. In many cases, nursing measures assist in decreasing the incidence of aspiration but they do not eliminate the risk altogether. Following is a summary of these research findings.
Continue to evaluate the merits of continuous or intermittent feedings because it is unclear which method is better. There is debate as to whether continuous or intermittent infusion methods of enteral feeding of formula affect the likelihood of aspiration. Proponents of the continuous infusion method argue that gradual delivery of small amounts prevent distention and, therefore, decrease the occurrence of gastroesophageal reflux.
Proponents of the intermittent administration say that it is a more physiologically normal feeding method and decreases the risk of aspiration by decreasing the amount of time that the enteral formula is in the stomach. Cogen and Weinryb found no significant difference in incidence of aspiration (p>0.8) between intermittent infusions at a mean of 300 ml per feeding and continuous infusions at a mean rate of 82.7 ml per hour in a retrospective chart review of 103 patients.
Intermittent feedings can be associated with higher risk for aspiration. Treolar and Stechmiller state that bolus intermittent feedings increase intragastric pressures and contribute to aspiration. In 30 patients, 6 with Shiley tracheostomy tubes and 24 with endotracheal tubes, continuous feedings were delivered at a rate of 25 to 100 cc per hour over 8 days.
One regurgitation into the oropharynx was observed but no aspiration was observed. This study supported the use of small bore, continuous feedings. Marino stated that only continuous feedings should be used for duodenal or jejunal tubes because the small bowel is not a reservoir for large amounts of solution.
Observe outcome differences between nasointestinal versus nasogastric tubes because research does not clearly describe the risks of each yet. Many clinicians favor the use of nasointestinal tubes (NIT) over NGT in decreasing the risk of GER. Cogen et al., state that although it is believed that small bowel tube feeding decreases the risk of aspiration, this has not been confirmed.
Metheny supports the use of NIT but described one woman who aspirated gastric secretions while being fed through the jejunum. Occasionally, NIT are used to deliver feedings while a NGT is used for suctioning for delayed gastric emptying. Intermittent aspiration of stomach contents with simultaneous administration of small-bowel feedings are performed for patients with a high potential for delayed gastric emptying, thus avoiding gastric pooling of formula in the stomach.
Few studies compare the risks and benefits of gastric versus intestinal tube feeding. Ibanez et al. showed that the presence of NGT was associated with an increased incidence of GER, but they did not address the use of NIT. Montecalvo et al. examined the risks and benefits of gastric versus jejunal tube feedings in 38 intensive care unit patients. For 19 patients in each group (gastric and jejunal) no significant difference in pneumonia incidence was found, but significantly more calories were delivered to patients with jejunal tubes. Pre-albumin levels were also significantly higher in patients with jejunal tubes, due in part to the more frequent interruptions of gastric tube feedings during nursing care. The authors state that greater than 300 patients would be needed to detect a difference in the incidence of pneumonia between the two feeding methods.
Daily x-rays have shown that Dobbhoff feeding tubes migrate frequently from stomach to intestine. The nurse cannot assume once placement has been established, the tube will remain in position. The danger occurs when the Dobbhoff migrates to the esophagus. As Metheny (1993) suggests, if "too much tube" is outside the nose, the nurse should suspect esophageal placement. Other less reliable indicators of esophageal placement include detection of a non-acidic pH of aspirate or an immediate burping by the patient if air is insufflated.
Confirm placement of the feeding tube by reliable methods. Radiographic confirmation of feeding tube placement is the most reliable method of establishing correct positioning of the tube. It is effective in preventing respiratory complication of aspiration pneumonia. Several studies examine alternative confirmation methods, comparing them to x-rays. A popular method for evaluating tube position is to auscultate the left, upper quadrant, while insufflating air through the tube. A gurgling sound in this region is taken as evidence that the tube is in the stomach. However, this can be misleading because sounds emanating from a tube in the lower chest can be transmitted to the left, upper quadrant.
Researchers conclude that auscultation has been found to be ineffective in determining the placement of NGT or NITs. Metheny et al., found that nurses and physicians failed to recognize, in eight out of nine patients, the respiratory placement of the NGT when auscultating for the "gurgle," which was thought to signal gastric placement. The authors were able to tape record the air insufflation sound in two of three respiratory tract-placed feeding tubes. Thus, auscultation for the gurgle is not considered a reliable method for confirming tube placement.
Monitoring for cough if the tube enters the lungs is also not a reliable method of detecting respiratory intubation with NGT, because small-bore feeding tubes may not cause respiratory symptoms if inadvertently inserted into the lungs. Likewise, small-bore tubes do not separate vocal cords enough to interfere with phonation. A decreased LOC and a depressed cough can also blunt the respiratory response to feeding tube placement in the pulmonary bed.
The nurse helps assess if the aspiration is from gastric juices. Several methods for detection of aspiration of gastric contents into the pulmonary bed have been identified. Food coloring is widely used for the early detection of aspiration. Generally, green or blue color added to tube feeding solution provides visual confirmation of aspiration.
Checking pH is another means of detecting aspiration of gastric fluid into the lungs. Methany et al. determined that pulmonary fluid has a pH of approximately 7.6, while gastric pH is less than 4. Potential inaccuracies exist when gastric contents are elevated due to H2 blockers or antacids. Nasogastric tube intubation into the small bowel can also produce an elevated pH, mimicking respiratory intubation.
Relying on pH alone is not recommended. The appearance of the fluid aspirated is also important. The clinician should ask himself or herself, "What color is the aspirate?" and "Is bile present?"
Test aspirate for glucose content to identify gastric fluid. Glucose strips can help identify if fluid aspirated from NGT or NIT is pulmonary or gastrointestinal. Non-bloody pulmonary fluid normally contains no glucose. Kingston, Phang, and Leathley studied 24 ventilated patients with nasogastric tube feedings. Twelve patients aspirated on one to five occasions, but seven had bloody aspirate. Of those that aspirated, 20.8% had non-bloody glucose-positive aspirate. Kingston and colleagues conclude that subclinical aspiration, as detected by non-bloody glucose positive endotracheal aspirate, is associated with the development of nosocomial pneumonia (p<0.001).
Critical care nurses carefully monitor the cuff pressure in airways to prevent aspiration around the cuff. Inflation of the cuff for artificial airways helps but does not eliminate the risk for aspiration of oral secretions into the lower airways.[3] On the contrary, an association between aspiration and use of tracheostomy tube with cuff inflated has been established.[21] Spray, Zuidema and Cameron determined that low-volume, high pressure endotracheal tube cuffs have been associated with a higher incidence (87%) of aspiration than high-volume, low pressure cuffs (15-20%).
Maintaining pressures between 25 to 34 cm H2O in large-diameter, thin-walled cuffs should prevent significant aspiration without compromising capillary mucosal blood flow. Treolar and Stechmiller recommend monitoring for adequate cuff inflation of endotracheal or tracheal tubes. Underinflated cuffs, with pressures less than 25 cm of water, can act as a wick for aspiration of oropharyngeal contents.
Elpern, Jacobs and Bone12 found that use of "no leak" occlusion cuff pressure increased the risk (p<0.05) of aspiration of dye more than when using "minimal leak" cuff pressure.
To avoid incurring risk of aspiration, the critical care nurse puts the patient in an upright position. Many authors believe the head of the bed elevated to an angle between 30 to 45 degrees will help prevent aspiration because the effect of gravity will decrease gastroesophageal reflux and as such, the risk of aspiration. Treolar and Stechmiller found a zero incidence of aspiration when the head of the bed was elevated 30 to 45 degrees. Torres et al. supported the use of the head-up position. For 19 patients randomized to two positions, supine and semirecumbent, radioactive isotopes in gastric contents were aspirated more in the supine position. Length of time in the supine position was also a risk. Longer time spent in the supine position correlated to the more radioactive tracheal aspirates.
Continuous elevation of the head of the bed during clinical research is a difficult variable to control. In her 1986 study, Metheny[14] discovered that five out of six patients who aspirated had the head of the bed lowered at some time near the time of aspiration. Later, Metheny determined that head of bed is difficult to maintain upright, unless one is observing the patient for 24 hours per day.
The use of the head-up position was supported by Torres et al. For 19 patients randomized to two positions, supine and semirecumbent at a 45 degree angle, radioactive isotopes in the gastric contents were aspirated more often when the patient was in the supine position. According to Torres, longer length of time (greater than 300 minutes) spent in the supine position correlated to more radioactive tracheal aspirates (P= 0.036).
Some studies contradict the above findings that elevated head of bed prevents aspiration. Elpern, Jacobs and Bone state that the belief that elevated head of bed prevents aspiration is not supported. Authors used the head-up position 80% of the time in 31 intubated patients. This did not prove beneficial in protecting against aspiration; the aspiration rate was 27%.
Likewise, Ibanez et al. found no significant difference in incidence of gastroesophageal reflux when placing 70 patients in a supine position for two hours and in semirecumbent position for two hours. In the supine position, incidence of reflux was 81% while semirecumbent position reflux was 67%. Ibanez and colleagues conclude that elevated HOB did not prevent gastroesophageal reflux, but it did reduce it.
The contradictory results of the Torres and Ibanez studies is due to some differences between the studies. Both the Torres and the Ibanez studies evaluated supine and semirecumbent positions for intubated, enterally fed patients with nasogastric tubes. However, Torres used a longer time for observation than Ibanez. Torres et al. stopped the feeding 12 hours before the study began so food would not affect the results.
Ibanez et al. delivered nutrition via continuous enteral feeding during the study. The lower incidence of gastric aspirate in the pulmonary bed noted by Torres et al. may have been affected by the discontinuance of feeding solution. Because both studies involved small sample sizes, there is a need for replication before conclusions can be reached regarding position affecting aspiration.
Future studies relating positioning and aspiration are needed. Turning the tube feeding off 30 to 60 minutes prior to placing the patient supine and recumbent is recommended, but no studies were identified to support this recommendation. Reverse Trendelenburg position for patients who cannot bend at the hip has been recommended but not studied. Russin and Adler recommend that patients not be restrained in the supine position, but the optimal position for restraining while preventing aspiration is unclear.
Monitoring gastric residual amounts every four hours to assess adequate gastrointestinal functioning is a measure used to prevent overfeeding and aspiration of stomach contents. Many conditions decrease gastrointestinal motility, such as receiving narcotics or analgesics and experiencing surgery, trauma, burns, shock, and respiratory failure. Decreased gastric motility is associated with increased gastric residual amounts.
The frequency of checking residuals and the amount of fluid that is considered excessive, are unclear. Treolar and Stechmiller recommended checking residuals every four hours. They found a zero percent incidence of aspiration by using this and other aspiration precautions. Silberman recommend checking residuals every three to four hours at first because residuals are higher in the beginning of tube feedings, then checking daily, once full volume and tolerance have been established. Kleibeuker and Boersma-Van Ek arrive at the same conclusion stating that the increased amount or residual was found in the beginning of the tube feeding, thus increasing the risk for aspiration.
Kleibuker and Boersma-Van Ek, conclude that the risk of aspiration from continuous nasogastric feeding is probably greatest during the first few hours. They observe that maximal residual volume was realized at two hours after starting tube feeding. A smaller residual amount was seen at 7 1/2 hours after the initiation of tube feeding. They concur with the practice of delivering a smaller volume at first and gradually increasing the amount.
Nurses should collect data and record the amount of residual so research can investigate this factor for patients who aspirate. Many references say 100 to 200 cc is the amount of residual that would be sufficient to stop tube feedings. McClave, Snider, and Lowen recommend 100 cc or less as the acceptable residual if a gastrostomy tube is used and 200 cc if a nasogastric tube is used. They conclude that a single high residual should not cause the interruption of feeding. The acceptable amount and frequency of checking residuals needs further research.
Dobbhoff tubes are not checked for residuals as frequently as large-bore tubes because there is a popular misconception that the small bore tubes collapse when suction is applied. However, Metheny et al. describe a technique for aspirating fluid from a Dobbhoff tube that yielded a 91.8% percent success rate when testing for pH.
Mortality rates can be affected by unique methods of treatment of aspiration pneumonia. In patients who aspirate gastric contents, mortality rates have been described between 7.5% and 38%. In a retrospective review of 38 aspiration pneumonia patients, 7.5% of deaths were directly due to aspiration pneumonia. When Hickling and Howard compared this to a mean-predicted mortality by Apache II of 43%, the authors attributed their lower mortality rate to a unique method of patient management with rapid volume restoration using crystalloids, early ventilation, and no steroids or immediate antibiotics.
If prevention fails, and the patient has aspirated, the critical care nurse can slow the cascade of complications. First, immediately turn off the tube feeding, complete tracheal suctioning of the patient, and provide supplemental oxygen. The extreme rapidity of acid-induced airway and parenchymal lung damage precludes effective therapy by attempts at neutralization of acid with intratracheal alkaline solutions.
Laryngoscopy and bronchoscopy are useful in patients suspected to have aspirated large particles that may be retrieved from the airway. Mechanical ventilation and/or oxygenation with positive end-expiratory pressure may be warranted in severe cases of hypoxemia. Positive end-expiratory pressure improves outcome by combating the tendency of alveoli and small airways to collapse, thus increasing the functional residual capacity (FRC) so that shunting is reduced and compliance is improved. Use of corticosteroids is controversial. Overhydration of the patient can aggravate pulmonary injury and insertion of a Swan Ganz catheter to monitor fluid administration is sometimes necessary.
Monitor the outcome of antibiotics because their usefulness is uncertain. The use of antibiotics as prophylaxis against subsequent bacterial pneumonia in patients with aspiration has not been shown to affect the incidence of infection or to alter mortality.[4] Therapy for aspiration pneumonia is based upon the adequate drainage of infected material, which can be accomplished by patient cough and chest physical therapy with postural drainage.
Request bronchodilator therapy in patients with evidence of obstructive airway disease. It has been found to be effective in increasing oxygen exchange following aspiration.
Prepare patients for surgery when indicated. The propriety of surgical correction for this debilitating problem depends upon the patient's quality of life and prospects for survival after therapy. More common surgical techniques, such as tracheostomy, gastrostomy, or jejunostomy can be indicated. Some physicians conceive of a tracheotomy as a solution to long- term aspiration, but, in reality, a tracheotomy can increase the incidence of aspiration. Assist patients in deciding on treatment options. In some cases, aspiration prevention can be achieved when laryngotracheal closure procedures or laryngeal diversion or total laryngectomy are performed. However, permanent loss of speech can result and is unacceptable to some patients who choose to refuse this option.
Question treatment orders not based on research. For example, an ineffective treatment used for recurrent aspiration pneumonia is that of complete obstruction of the glottic airway by injecting both vocal cords with Teflon. If this is ordered, request review of the order.
Participate in research studies. Numerous surgical procedures are described for the treatment of aspiration pneumonia, including total laryngectomy, tracheoesophageal diversion, laryngotracheal separation, epiglottic flaps, glottic closures, laryngeal suspension, posterior cricoid resection, and laryngeal stents. The effectiveness of these procedures in decreasing aspiration is yet to be determined. Critical care nurses are likely to care for patients in clinical trials to determine the effectiveness of new techniques.
As specialists, critical care nurses are expected to exercise a highly evolved level of clinical judgement and leadership, often through application of protocols. Advanced clinical judgement is utilized when acquiring clinical skills and knowledge or when nursing practice is interpreted to nurses and non-nurses.
Prevention of complications and maintenance of standards of care are goals of the critical care nurse. Review and update the aspiration prevention policy yearly to include new research findings.
Teaching aspiration prevention information can involve separating fact from fiction or "unteaching" certain traditional nursing practices. Such traditionally held false beliefs are: (a) auscultating for a gurgle sound with air insufflation to detect feeding tube placement (it is not reliable for placement) and (b) tracheostomy tubes are airway protectors (they are not).
Competency-based nursing practice includes teaching elements of the aspiration prevention protocol, proper testing of pH of aspirated secretions, the techniques of successful Dobbhoff tube aspiration, and the necessity of having confirmation of tube placement by radiography prior to initiation of feeding.
When a valuable study is found and is in need of replication, the critical care nurse can contact the original investigator and organize a replication in her or his unit.
Certain patient populations such as those with feeding tubes and artificial airways are identified to be at risk for developing aspiration pneumonia. Critical care nurses have a primary role in decreasing the incidence of aspiration pneumonia as well as its severity and risk. Use of research findings can aid in decreasing the risk of aspiration.
Rose S. Goodwin, RN, MSN, CCRN, is an Adjunct Faculty Member at Columbia Union College, Takoma Park, MD.