Aspiration pneumonia is the inflammation of the lungs caused by breathing in foreign material. This infection is caused by accidentally inhaling secretions of the mouth or contents from the stomach like acid/semi digested food. These materials then damage the lungs and cause blockages in the air passages leading to the lungs. The condition could then lead to abscess or a collection of pus and cause the lungs to be filled with fluid. Aspiration pneumonia could occur due to a person’s inability to swallow either because of a stroke, seizure or loss of consciousness.
In healthy individuals, foreign particles entering the mouth or the saliva that drips into the throat is cleared by the natural defenses of the body like coughing or sneezing before they can enter the lungs and cause any harm. In the event that these particles are not cleared due to an impaired defense mechanism, they can cause aspirated pneumonia.
The elderly or persons under the influence of alcohol or those under the effect of anesthesia or under a coma are at increased risk of aspirated pneumonia. Persons with decreased levels of consciousness or those with a central nervous system disorder often have impaired upper and lower airway reflexes. They could also be at risk of suffering from aspiration pneumonia.
Aspiration of foreign particles can also result from disorders of the esophagus, an absent gag reflex or even dental problems. The extent of injury to the lungs depends on the texture and quantity of the aspirated substance. Generally, greater the acidity of the substance greater is the degree of damage. The injured lung could then get infected with bacteria or by the formation of pus.
Symptoms of aspirated begin only after a day or two. Following are some of the symptoms of aspirated pneumonia.
The doctor will diagnose aspiration pneumonia by using a stethoscope to listen to your heart and lungs. Blood tests and chest X rays may also be needed to determine the infection. You may also be asked to undergo special barium swallowing tests to ascertain the condition of the throat and your ability to swallow. The doctor may even recommend an endoscopy to have a look at your throat, esophagus and stomach.
In case aspiration pneumonia is diagnosed, you may need to get admitted to the hospital and would be put on a course of antibiotics. The procedures will vary depending on the severity of the disease. Oxygen could to be administered or the patient may even be provided with artificial respiration using a machine. Bronchoscopy could be conducted to remove any solid material that may have been aspirated. Care givers may put the patient on a special therapy to help treat swallowing problems and decrease the chances of swallowing something into the lungs again.
Aspiration pneumonia could be a serious life threatening disease causing respiratory failure. The lung infection could spread into the blood stream or even to other parts of the body. The disease can be dangerous for people over 50 years of age or those with compromised immune systems. Recovery from aspiration pneumonia can take a long time. It is better to begin treatment as promptly as possible to ensure a fast and problem free recuperation.
Aspiration pneumonia mostly occurs due to a defect of protective upper and lower airway reflexes in patients who have a low level of consciousness or central nervous system disease.
Aspiration pneumonia is usually caused due to a faulty swallowing mechanism that occurs in some cases of neurological disease (eg strokes) or in case of intoxication. It could also occur as an iatrogenic cause during surgery, under the influence of general anesthesia. Therefore patients are advised not to eat (NPO) atleast 4 hours prior to surgery.
It is still a matter of speculation and controversy as to whether aspiration pneumonia is a bacterial infection or a chemical inflammatory condition. Both causes show similar symptoms.
Disorders of the oesophagus, (gastroesophageal reflux, esophageal stricture), or a low or absent gag reflex in unconscious or semi conscious persons could induce the aspiration of foreign material (often stomach contents) into the lungs. Other factors contributing to this risk include old age, dental problems, use of sedatives, coma and excessive consumption of alcohol. The extent of injury to the lungs depends on the type and quantity of the inhaled substance. The greater the acidity of the substance, the greater is the extent of damage to the lung, although this may not actually lead to pneumonia.
The injured lungs could get infected with species of anaerobic and aerobic bacteria. This could lead to the collection of pus or abscess in the lung around which a protective membrane may form.
Sometimes, it may take some time to for symptoms of aspiration pneumonia to show up. The signs and symptoms of aspiration pneumonia can quickly get worsen, if it is not properly diagnosed and treated. The signs and symptoms may vary depending on what material and the quantity you may have inhaled. Given below are the common signs and symptoms of aspiration pneumonia:
For it to be diagnosed correctly, one should have a close watch on the symptoms of aspiration pneumonia. Proper diagnosis ensures timely intervention by the doctor so that prompt treatment is initiated. Although, symptoms of aspiration pneumonia take several days to appear, do not neglect them.
Inhaling of foreign particles into the lungs causes aspiration pneumonia. The diagnosis is usually based on the indication of pulmonary infiltrates in gravity-dependent lung regions, hypoxemia, fever and leukocytosis after an observed or suspected episode of vomiting or regurgitation in a patient at risk of aspiration pneumonia. Most patients who are infected are febrile and tachypneic. Two thirds of patients have shown rales and one third of the patients have cough, wheezing, or cyanosis.
Most patients with aspiration pneumonia follow a treatment even though there is an absence of a specific microbiologic diagnosis. The two reasons responsible for making diagnosis tricky are the obtaining the specimen of deep respiratory tract secretions without contaminating the normal oral flora and the limited laboratory capacity for isolation of anaerobic microorganisms. Expectorated sputum is considered as a non valid specimen for anaerobic culture because it is contaminated with normal oral flora. However, the sputum specimen should be examined by Gram staining procedure and culture for aerobic pathogens.
A Gram Stain of the sputum showing numerous neutrophils and mixed microflora that contain gram-positive bacilli and cocci and gram-negative rods. This suggests that the person is suffering from polymicrobial infection that is typically seen in aspiration pneumonia and is an important in the diagnosis of aspiration pneumonia. The main aim of carrying out the sputum culture test is to identify serious pathogens (eg, gram-negative enteric bacilli). The information about the antimicrobial susceptibility of the pathogen can be used to adjust treatment. Specimen of blood, transthoracic needle aspirates, and bronchoscopic-protected specimen brush samples, pleural fluid are suitable for anaerobic as well aerobic culture test.
The initial treatment for aspiration pneumonia greatly depends on its early diagnosis and includes treatment of acute hypoxemia and bronchospasm. The patient would most certainly need to be hospitalized. Nasogastric tube feeding would be discontinued and suctioning of the upper airway would be carried out to eliminate all traces of foreign material or secretions still present in the oropharynx. Suctioning should be performed carefully to avoid inducing gagging.
While the initial assessments are being made, supplementary oxygen by a mask or nasal cannula may be administered. A ‘venturi mask’ ensuring a consistent, high concentration oxygen is recommended.In severe cases, intubation and mechanical ventilator support may be required. Aspiration causes almost immediate lung injury and bronchoscopy can only help to remove particles or foreign body accidentally inhaled.
Most episodes of nosocomial pneumonia do not need antibiotic therapy. Prophylactic antibiotic treatment may not prevent subsequent infectious pneumonia and is therefore not recommended. However doctors often prefer starting the treatment with broad spectrum antibiotics as many patients who aspirate are either debilitated or immunocompromised and are at greater risk of developing infectious pneumonia.
In most cases, patients suffering from aspirated pneumonia are initially treated empirically. The patient risk factors, coverage of pathogens, the intensity of the infection and expert opinion will determine the course of antibiotic regimen. Only a few controlled clinical trials that compare treatment regimens for aspiration have been performed. A rational approach based on local pathogens, the physician’s knowledge of the medical history of the patient, and anti microbial resistance patterns works better than the use of a particular regimen or course of treatment. Adjunctive corticosteroids may actually be toxic and have therefore no proven value in the treatment of aspiration pneumonia.
The antibiotic regimens recommended for community acquired aspiration pneumonia are clindamycin (Cleocin), beta-lactam and beta-lactamase inhibitor combinations such as ampicillin sodium and sulbactam sodium (Unasyn), or penicillin plus metronidazole (Flagyl). Despite being effective in vitro activity against most anaerobes, monotherapy with metronidazole has been associated with a high clinical failure rate and should not be used to treat aspiration pneumonia. The newer fluoroquinolones], gatifloxacin [Tequin], (eg, levofloxacin [Levaquin } and moxifloxacin hydrochloride [Avelox]) have reasonable anaerobic activity and achieve high concentrations in lung tissue and endobronchial secretions. Aaztreonam (Azactam), and aminoglycosides and trimethoprim-sulfamethoxazole (Bactrim, Cotrim, Septra)have little or no activity against anaerobes.
In case of nosocomial aspiration pneumonia, antimicrobial coverage for gram-negative bacilli and staphylococci must be considered. For patients in intensive care units and for those in whom pneumonia develops after a hospitalization of 5 or more days, the risk of aggressive pathogens such as Pseudomonas aeruginosa and Acinetobacter species, is highest. Patients with head trauma, coma, end stage renal disease, diabetes mellitus and those diagnosed to be colonized by S aureus are at high risk for staphylococcal pneumonia.
For patients with hospital acquired pneumonia, the recommended course of treatment could be ceftazidime plus clindamycin or metronidazole cefepime hydrochloride (Maxipime) or; a beta-lactamase and beta-lactam inhibitor combination such as sulbactam ampicillin and ticarcillin and clavulanate potassium (Timentin) , piperacillin sodium and tazobactam sodium (Zosyn); or a newer fluoroquinolone. For those patients allergic to penicillin, the phycisian may consider either a combination of clindamycin plus aztreonam or may recommend a newer fluoroquinolone. For patients diagnosed with nasopharyngeal colonization with staphylococci and for patients with other staphylococcal infections, an antistaphylococcal coverage may be recommended. Also, a sample of sputum gram stain would be reviewed for the presence gram-positive cocci in clusters. In hospitals where methicillin resistant S aureus is a concern, vancomycin (Vancocin, Vancoled) should be used initially for antistaphylococcal coverage. The American Thoracic Society has prescribed procedures on treatment of hospital- acquired pneumonia in adults which would prove as a useful tool for phycisians to select appropriate initial antibiotic regimens.
Once the physician decides to begin with an antibiotic course of treatment, the patient’s progress would be closely monitored. If the response over the next 1 to 2 days shows rapid clearing of pulmonary infiltrates, then this indicates chemical pneumonitis rather than bacterial pneumonia and hence antibiotic therapy should be stopped immediately. A review of culture resulta after 2 to 3 days could be used to narrow antimicrobial coverage.
In one study conducted, the evaluation of fever in patients diagnosed with aspiration pneumonia was similar to that in patients with pneumococcal pneumonia. In about one half of the patients with aspiration pneumonia, defervescence occurred within 2 days after being started on antibiotic therapy and 80% became afebrile within 5 days. Fever tends to be prolonged in patients with lung abscess or with infections caused by aggressive pathogens such as P aeruginosa.
The duration of antiobiotic therapy for aspiration pneumonia has not been determined by any specific studies undertaken. A treatment lasting between 5 to 7 days appears to be sufficient for patients who respond promptly. In case highly resistant pathogens such as acinetobacter species or P aeruginosa are isolated, the treatment would be extended up to to 14 to 21 days. A long term treatment of 4 to 8 weeks or more amy be needed for patients with cavitary pneumonia or lung abscess.
Some complications of aspiration pneumonia include empyema, lung abscess and bronchopleural fistula. Most lung abscesses respond well to prolonged antibiotic treatment. In patients with empyema, adequate pleural drainage is required.