Aspiration Pneumonia is Defined as Pneumonitis/Pneumonia Resulting from the Entry of Oropharyngeal/Gastric Fluids or Material into the Lower Airways and/or Lung

• Aspiration Pneumonia Exists on a Continuum Which Also Includes Community-Acquired Pneumonia (CAP) and Hospital-Acquired Pneumonia (see Community-Acquired Pneumonia and Hospital-Acquired Pneumonia and Ventilator-Associated Pneumonia)
  • Aspiration Pneumonia Accounted for Approximately 15% of All Community-Acquired Pneumonias (NEJM, 2001) [MEDLINE]
  • Similar Data for Hospital-Acquired Pneumonias are Not Available

Incidence

• Study of Aspiration Pneumonia According to the Site of Acquisition (J Am Geriatr Soc, 2006) [MEDLINE]: n = 1,946 adults admitted with pneumonia (from 6 Alberta, Canada hospitals)
  • Aspiration Pneumonia Accounted for 10% of Community-Acquired Pneumonia Cases
    • Most Aspiration Pneumonia Cases were Associated with Altered Mental Status Due to Alcohol, Drugs, and/or Liver Disease
  • Aspiration Pneumonia Accounted for 30% of Continuing Care Facility-Acquired Pneumonia Cases
    • Approximately 72% of Aspiration Pneumonia Cases were Due to Neurologic Disease Associated with Dysphagia

General Comments

• Multiple Risk Factors May Be Present and Engender Additive/Multiplicative Risk of Aspiration Pneumonia
  • In a Meta-Analysis in Frail Elderly Patients, Dysphagia Increased the Odds Ratio for Aspiration Pneumonia by a Factor of 9.4 (J Dent Res, 2011) [MEDLINE]
    • When Cerebrovascular Disease was Added, the Odds Ratio Increased to 12.9

Airway Procedures

• Bronchoscopy (see Bronchoscopy)
  • Physiology
    • Due to Pharyngeal Anesthesia
• Endotracheal Intubation (of Any Duration) (see Endotracheal Intubation)
  • Epidemiology
    • Aspiration of Oropharyngeal Secretions is Common with Endotracheal Tubes and Tracheostomy Tubes
    • Presence of Gag Reflex Does Not Confer Protection Against Aspiration with Endotracheal Intubation or Tracheostomy (Crit Care Med, 1990) [MEDLINE]
    • Polyurethane Endotracheal Tube Cuffs Decrease the Amount of Leakage Around the Cuff, as Compared to Polyvinyl Chloride Cuff Endotracheal Tubes (Crit Care Med, 2008) [MEDLINE]
    • In Patients Extubated Following Acute Respiratory Failure, Dysphagia/Aspiration atre Observed in 20% of Cases (Chest, 2014) [MEDLINE]
      • The Frequency of Swallowing Dysfunction Decreases Over Time from Extubation, But Up to 35% of Patients with Swallowing Dysfunction at the Time of Extubation Continue to Manifest Swallowing Dysfunction at the Time of Discharge
    • No Clinical Factors Reliably Predict if a Patient Will Aspirate
  • Physiology
    • Aspiration Pneumonia Can Occur as an Immediate Adverse Effect/Complication of Endotracheal Intubation (Manifest During or Immediately Following Intubation) Due to Emesis with Aspiration at the Time of Intubation
    • Aspiration Pneumonia Can Occur as an Early Adverse Effect/Complication (Manifest Within Hours-Weeks After Intubation) Due to Pooling of Pharyngeal Pooling of Oropharyngeal Secretions Above the Endotracheal Tube Cuff with Subsequent Aspiration, as Well as Delayed Triggering of the Swallowing Response (Crit Care Med, 1990) [MEDLINE]
• Tracheostomy (see Tracheostomy)
  • Epidemiology
    • Aspiration of Oropharyngeal Secretions is Common with Endotracheal Tubes and Tracheostomy Tubes
    • Presence of Gag Reflex Does Not Confer Protection Against Aspiration with Endotracheal Intubation or Tracheostomy (Crit Care Med, 1990) [MEDLINE]
  • Physiology
    • Due to Pooling of Pharyngeal Pooling of Oropharyngeal Secretions Above the Endotracheal Tube Cuff with Subsequent Aspiration (Crit Care Med, 1990) [MEDLINE] (Br J Anaesth, 2012) [MEDLINE]
    • Due to Delayed Triggering of the Swallowing Response (Crit Care Med, 1990) [MEDLINE] (Br J Anaesth, 2012) [MEDLINE]
      • Swallowing Dysfunction (Particularly Disorder of the Pharyngeal Phase) and Aspiration are Common with Tracheostomy (Chest, 1994) [MEDLINE]: increasing age increases the risk of aspiration and aspiration is frequently silent

Altered Mental Status with Inability to Protect Airway

• Antipsychotic Medications
  • Epidemiology
    • In a Large Study Involving 146,552 Hospitalized Patients, Antipsychotic Medications were Found to Increase the risk of Aspiration Pneumonia by 1.5-Fold (J Am Geriatr Soc, 2017) [MEDLINE]
  • Physiology
    • May Be Related to Alteration in Mental Status and/or Dysphagia/Swallowing Dysfunction (Expert Rev Clin Pharmacol, 2019) [MEDLINE]
• Cardiac Arrest (see Cardiac Arrest)
  • Epidemiology
    • Early-Onset Post-Cardiac Arrest (Aspiration) Pneumonia Developed within 3 Days Post-Cardiac Arrest in 65% of the Patients and the Risk was Found to Be Associated with the Use of Therapeutic Hypothermia (Am J Respir Crit Care Med, 2011) [MEDLINE]
    • A Target Temperature of 36°C May Be Associated with a Lower Risk of Pneumonia (Chest 2018) [MEDLINE]
  • Physiology
    • Multiple Factors May Contribute to Cardiac Arrest-Associated Aspiration Pneumonia
      • Altered Mental Status
      • Emergent Intubation
      • Use of Bag-Valve-Mask (BVM) Ventilation
• Hepatic Encephalopathy (see Hepatic Encephalopathy)
  • Epidemiology
    • Liver Disease was Present in 11.3% of Aspiration Pneumonia Cases (as Compared to 3.7% of Community-Acquired Pneumonia Cases) (Am J Med, 2013) [MEDLINE]
• Intoxication
  • Alcohol Intoxication (see Ethanol)
  • Any Other Sedative Intoxication Resulting in Altered Mental Status with Inability to Protect Airway
• Intracerebral Hemorrhage (see Intracerebral Hemorrhage)
• Ischemic Cerebrovascular Accident (CVA) (see Ischemic Cerebrovascular Accident)
• Sedation (see Sedation)
  • Barbiturates (see Barbiturates)
  • Benzodiazepines (see Benzodiazepines)
    • In a Study Examining Aspiration Risk Factors on the Risk of Community-Onset Pneumonia, Dementia Had an Odds Ratio of 5.2, Poor Performance Status Had an Odds Ratio of 3.31, and the Use of Sleeping Pills Had an Odds Ratio of 2.08 (Clin Interv Aging, 2017) [MEDLINE]
      • Patients with ≥2 Risk Factors Had an Increased Incidence of Recurrent Pneumonia and Increased 30-Day and 6-Month Mortality Rates with Rates Increasing in Association with the Number of Risk Factors
  • Etomidate (Amidate) (see Etomidate)
  • General Anesthesia (see General Anesthesia)
  • Opiates (see Opiates)
  • Propofol (Diprivan) (see Propofol)
• Seizure (see Seizures)
• Subarachnoid Hemorrhage (SAH) (see Subarachnoid Hemorrhage)
• Subdural Hematoma (SDH) (see Subdural Hematoma)
• Traumatic Brain Injury (TBI) (see Traumatic Brain Injury)
• Withdrawal
  • Any Drug Withdrawal Resulting in Altered Mental Status with Inability to Protect Airway

Dysphagia Due to Esophagogastric Disease (see Dysphagia)

• Emesis (see Nausea and Vomiting)
• Esophagogastroduodenoscopy (EGD) (see Esophagogastroduodenoscopy)
• Esophageal Cancer (see Esopohageal Cancer)
• Esophageal Motility Disorder
  • Esophageal Achalasia (see Esophageal Achalasia)
    • Epidemiology
      • Associated with Scleroderma (see Scleroderma)
• Esophageal Stricture (see Esopohageal Stricture)
• Gastric Outlet Obstruction (see Gastric Outlet Obstruction)
• Gastroesophageal Reflux Disease (GERD) (see Gastroesophageal Reflux Disease)
  • Physiology
    • Increased Risk of Gastric Contents Entering the Lung
• Gastroparesis (see Gastroparesis)
• Ileus (see Ileus)
• Incompetent Lower Esophageal Sphincter
  • Nasogastric/Orogastric Enteral Feeding Tube (see Nasogastric-Orogastric Tube)
    • Nasogastric/Orogastric Tubes Impair the Function of the Lower Esophageal Sphincter, Increasing the Risk of Gastroesophageal Reflux
    • Enteral feeding Can Result in High-Volume Aspiration (Especially When Associated with Gastric Dysmotility, Poor Cough Reflex, and Altered Mental Status
    • However, In 3 Studies of Enteral Feeding Following Stroke (Total of >5000 Patients), Early Enteral Tube Feeding Improved Survival, as Compared to No Feeding, and in the First 2-3 weeks Following Stroke, Nasogastric Tube Feeding was Associated with Improved Survival and Functional Outcomes, as Compared to Percutaneous Enteral Tube Feeding (Health Technol Assess, 2006) [MEDLINE]
    • Enteral Feedings Tubes are Not Currently Recommended for Patients with Dementia (J Am Geriatr Soc, 2014) [MEDLINE]
• Mixed Connective Tissue Disease (MCTD) (see Mixed Connective Tissue Disease)
• Tracheoesophageal Fistula (see Tracheoesophageal Fistula)
  • Epidemiology
    • Aspiration May Be Recurrent
• Zenker’s Diverticulum (see Zencker’s Diverticulum)

Oropharyngeal Dysphagia (Due to Disease of the Pharynx/Upper Esophagus or Upper Esophageal Sphincter Dysfunction) (see Dysphagia)

General Comments

• In Aspiration Pneumonia Cases Which Occur in Patients in Continuing Care Facilities, Neurologic Disease with Associated Dysphagia was a Risk Factor in 72% of Cases (J Am Geriatr Soc, 2006) [MEDLINE]
• In a Group of Older Patients (>70 y/o) Admitted for Pneumonia, Oropharyngeal Dysphagia was Present in 55% of Cases (Age Ageing, 2010) [MEDLINE]
• In a Case-Control Study of Elderly Patients, Oropharyngeal Dysphagia Increased the Risk of Community-Acquired Pneumonia (Odds Ratio: 11.9) and ws Present in 92% of the Patients with Pneumonia (Eur Respir J, 2013) [MEDLINE]
  • By Videofluoroscopic Evaluation, Only 16.7% of the Patients with Pneumonia were Able to Swallow Safely, as Compared to 80% of the Control Patients

Neurologic Disease

• Amyotrophic Lateral Sclerosis (ALS) (see Amotrophic Lateral Sclerosis)
• Ankylosing Spondylitis (see Ankylosing Spondylitis)
  • Physiology
    • Due to Dysphagia (Dysphagia, 2021) [MEDLINE]
• Antipsychotic Medications
  • Epidemiology
    • In a Large Study Involving 146,552 Hospitalized Patients, Antipsychotic Medications were Found to Increase the risk of Aspiration Pneumonia by 1.5-Fold (J Am Geriatr Soc, 2017) [MEDLINE]
  • Physiology
    • May Be Related to Alteration in Mental Status and/or Dysphagia/Swallowing Dysfunction (Expert Rev Clin Pharmacol, 2019) [MEDLINE]
• Brainstem Tumor
• Cerebral Palsy (CP) (see Cerebral Palsy)
• Chronic Obstructive Pulmonary Disease (COPD) (see Chronic Obstructive Pulmonary Disease)
  • Physiology
    • Due to Dysphagia (J Bras Pneumol, 2011) [MEDLINE]
    • Due to Gastroesophageal Reflux (Int J Chron Obstruct Pulmon Dis, 2015) [MEDLINE]
• Dementia (see Dementia)
  • Epidemiology
    • In a Study Examining Aspiration Risk Factors on the Risk of Community-Onset Pneumonia, Dementia Had an Odds Ratio of 5.2, Poor Performance Status Had an Odds Ratio of 3.31 and the Use of Sleeping Pills Had an Odds Ratio of 2.08 (Clin Interv Aging, 2017) [MEDLINE]
      • Patients with ≥2 Risk Factors Had an Increased Incidence of Recurrent Pneumonia and Increased 30-Day and 6-Month Mortality Rates with Rates Increasing in Association with the Number of Risk Factors
• Guillain-Barre Syndrome (GBS) (see Guillain-Barre Syndrome)
• Huntington Disease (see Huntington Disease)
• Intracerebral Hemorrhage (Hemorrhagic Cerebrovascular Accident) (see Intracerebral Hemorrhage)
• Ischemic Cerebrovascular Accident (CVA) (see Ischemic Cerebrovascular Accident)
  • Epidemiology
    • Stroke was Present in 26.9% of Aspiration Pneumonia Cases (as Compared to 9.5% of Community-Acquired Pneumonia Cases) (Am J Med, 2013) [MEDLINE]
    • The Frequency of CVA-Associated Pneumonia is Related to the Severity of Neurologic Injury and its Associated Immune Impairment (Cerebrovasc Dis, 2013 [MEDLINE]
      • Higher Rates of CVA-Associated Pneumonia Occur in Patients Requiring Intensive Care, as Compared to Patients Admitted to a General Stroke Unit
• Multiple Sclerosis (see Multiple Sclerosis)
• Myasthenia Gravis (MG) (see Myasthenia Gravis)
• Older Age
  • Epidemiology
    • Age 74 y/o (Interquartile Range: 60-84 y/o) (Am J Med, 2013) [MEDLINE]
    • Older Age is Associated with Higher Prevalence of Comorbidities Which Predispose to Aspiration Pneumonia (Stroke, Degenerative Neurologic Disease, Institutionalization in Long-Term Care, etc) (Am J Med, 1998) [MEDLINE] (J Crit Care, 2015) [MEDLINE] (J Hosp Med, 2019) [MEDLINE]
• Parkinson’s Disease (see Parkinson’s Disease)
• Polydermatomyositis (see Polydermatomyositis)
• Progressive Supranuclear Palsy (PSP) (see Progressive Supranuclear Palsy)
• Pseudobulbar Palsy (see Pseudobulbar Palsy)
• Respiratory Tardive Dyskinesia (see Tardive Dyskinesia)
• Subarachnoid Hemorrhage (SAH) (see Subarachnoid Hemorrhage)
• Traumatic Brain Injury (TBI) (see Traumatic Brain Injury)

Structural Disease

• Bilateral Vocal Fold Immobility (BVFI) (of Any Etiology) (see Bilateral Vocal Fold Immobility)
  • Examples
    • Vocal Cord Paralysis
      • Glottic Insufficiency
• Cervical Osteophyte
• Cervical Web
• Cricopharyngeal Bar
• Head and Neck Cancer (see Head and Neck Cancer)
• Poor Dental Hygiene
  • Physiology
    • Aspiration Results in a Larger Bacterial Inoculum from the Oropharynx and Prevalence of More Pathogenic Bacteria (Am J Respir Crit Care Med, 2003) [MEDLINE]
• Post-Head and Neck Surgery/Cervical Spine Surgery
• Xerostomia (see Xerostomia)

Infectious Disease

• Botulism (see Botulism)
• Diphtheria (see Diphtheria)
• Lyme Disease (see Lyme Disease)
• Mucositis (Herpes, Cytomegalovirus, Candida, etc) (see Mucositis)
• Syphilis (see Syphilis)

Metabolic Disease

• Amyloidosis (see Amyloidosis)
• Cushing’s Syndrome (see Cushing’s Syndrome)
• Thyrotoxicosis (see Hyperthyroidism)
• Wilson’s Disease (see Wilson’s Disease)

Myopathic Disease

• Myotonic Dystrophy (see Myotonic Dystrophy)
• Oculopharyngeal Dystrophy
• Paraneoplastic Syndrome
• Polydermatomyositis (see Polydermatomyositis)
• Sarcoidosis (see Sarcoidosis)

Other Disease

• Corrosive Injury (Pill Injury, Intentional)
• Radiation Therapy (see Radiation Therapy)

Other

• Congestive Heart Failure (CHF) (see Congestive Heart Failure)
  • Epidemiology
    • Congestive Heart Failure was Present in 28% of Aspiration Pneumonia Cases (as Compared to 17.1% of Community-Acquired Pneumonia Cases) (Am J Med, 2013) [MEDLINE]
• Near Drowning (see Near Drowning)
  • Physiology
    • Aspiration of Fresh/Salt Water
• Recumbent Body Position
  • Physiology
    • Recumbency Increases the Risk of Reflux of Gastric Contents into the Oropharynx, Resulting in Aspiration

Spectrum of Aspiration

• Aspiration of Small Amounts of Oropharyngeal Secretions is Normal in Healthy Persons During Sleep (Chest, 1997) [MEDLINE]
• In Addition, Microaspiration is Predominant Pathogenetic Mechanism of Most Pneumonias
• Large-Volume Aspiration (Macroaspiration) of Colonized Oropharyngeal or Upper Gastrointestinal Contents Defines True Aspiration Pneumonia
• Aspiration Syndromes May Involve the Airways or Pulmonary Parenchyma, Resulting in a Variety of Distinct Clinical Presentations (J Crit Care, 2015) [MEDLINE]

Aspirated Fluids or Material May Consist of Any of the Following

• Food Particles
• Gastric Acid
• Hydrocarbons (see Hydrocarbons)
• Oropharyngeal Bacteria
• Water (Fresh or Salt Water)

Aspiration Pneumonia vs Aspiration (Chemical) Pneumonitis

• Aspiration Pneumonia is a Pulmonary Parenchymal Infection Caused by Specific Microorganisms
• Chemical Pneumonitis is a Pulmonary Inflammatory Response to Irritative Gastric Contents

Bacterial Colonization of Human Oropharynx and Upper Airway

• Bacteria Colonize the Oral Cavity (Including the Gingiva, Dental Plaque, and Tongue) (J Clin Microbiol, 2005) [MEDLINE] (J Bacteriol, 2010) [MEDLINE]
• Pathogenic Bacteria (Gram-Negative Bacteria Which are Not Found in the Normal Host), May Emerge in the Elderly, Nursing Home Residents, Hospitalized Patients, and in Patients with Nasogastric Tubes (Isr Med Assoc J, 2003) [MEDLINE] (Chest, 2004) [MEDLINE] (J Gerontol A Biol Sci Med Sci, 2018) [MEDLINE]

Microbiology

General Comments

• In the 1970’s, Anaerobes (with or without Aerobes) were the Predominant Microbial Pathogens Associated with Aspiration Pneumonia (Am J Med, 1974) [MEDLINE] (Ann Intern Med, 1974) [MEDLINE] (Arch Intern Med, 1975) [MEDLINE] (Infect Dis Clin North Am, 2013) [MEDLINE]
• More Recently, There Has Been a Shift to Bacteria Usually Associated with Community-Acquired Pneumonia and Hospital-Acquired Pneumonia (Infect Dis Clin North Am, 2013) [MEDLINE]
  • Anaerobes are Now Recovered Less Frequently
• Prospective Study of Microbiology in Aspiration Pneumonia and Ventilator-Associated Pneumonia (Chest, 1999) [MEDLINE]
  • In Aspiration Pneumonia Associated with Gastrointestinal Disorders, Enteric Gram-Negative Organisms were Predominant
  • In Community-Acquired Aspiration Events, Streptococcus Pneumoniae and Haemophilus Influenzae were Predominant
  • Only One Anaerobic Organism Non-Pathogenic) was Isolated in Their Patients

Assessment of Swallowing Function

• Bedside Swallowing Evaluation
  • Relatively Insensitive for Evidence of Aspiration in Patients with Tracheostomy, Since up to 77% of Aspiration was Silent (Chest, 1994) [MEDLINE] (Chest, 1996) [MEDLINE]
• Gag Reflex
  • Does Not Predict Adequacy of Swallowing Function (as the Gag Reflex Uses Different Muscles than Swallowing and Many Patients without Gag Can Swallow Normally)
• Modified Barium Swallow (see Videofluoroscopic Modified Barium Swallow)
  • Considered the Best Test

Chest X-Ray (CXR)/Chest Computed Tomography (Chest CT) Patterns (see Chest X-Ray and Chest Computed Tomography)

• Findings
  • Alveolar Infiltrate: often located in dependent lung region (particularly in the superior segment of the right lower low)
  • Bibasilar Fibrosis: may be seen in cases of chronic aspiration

General Comments

• Aspiration of Tube Feedings/Blood
  • Aspiration of Tube Feedings/Blood Generally Does Not Cause Either a Bacterial Pneumonia or Chemical Pneumonitis, Since the Aspirate is Higher pH and Uncontaminated by Bacteria (NEJM, 2019) [MEDLINE]
• Unwitnessed Aspiration
  • In These Cases, it is Generally Difficult to Distinguish Between Chemical Pneumonitis, Aspiration Pneumonia, and/or Aspiration of Bland Material

Aspiration-Related Airway Manifestations

• Clinical
  • Bronchospasm (see Bronchospasm)
  • Cough (Acute and/or Chronic) (see Cough)
  • Exacerbation of Asthma (see Asthma)

Acute Respiratory Distress Syndrome (ARDS) (see Acute Respiratory Distress Syndrome)

• Epidemiology
  • Associated with Aspiration (Chemical) Pneumonitis (See Below) or Large-Volume Aspiration

Cryptogenic Organizing Pneumonia (COP) (see Cryptogenic Organizing Pneumonia)

• Epidemiology
  • French Retrospective Study of Gastroesophageal Reflux Disease as a Risk Factor for Organizing Pneumonia (Respiration, 2015) [MEDLINE]
    • Organizing Pneumonia Associated with Gastroesophageal Reflux Disease is More Severe and Results in More Frequent Relapses
    • Microinhalation of Gastric Secretions Might Induce Lung Inflammation Resulting in Organizing Pneumonia and Relapse

Airway Foreign Body Obstruction (see Airway Foreign Body)

• Epidemiology
  • In a Study of Older Patients (>65 y/o) with Foreign Body Aspiration, the Event was Clinically Recognized in Only 29% of Cases, Leading to a DIagnostic Delay of 1-3 mos (Clin Interv Aging, 2014) [MEDLINE]
    • Food Material (Bone Fragments, Plants, etc) Accounted for >80% of the Episodes
    • Chest Radiographic Findings were Localized to the Right Lung in 65% of the Cases
    • Flexible Bronchoscopy Removed the Foreign Body Successfully in All Cases (Predominantly in the Right Lower Lobe Bronchus)
• Physiology
  • Aspiration of Foreign Body

Interstitial Pulmonary Fibrosis (see Interstitial Lung Disease)

• Epidemiology
  • Typically Associated with Chronic Aspiration (Microaspiration)
• Physiology
  • Smaller Volumes of Acid Aspiration (Perhaps Over a Long Period of Time) Likely Result in Less Severe Aspiration/Chemical Pneumonitis, Recurrent Aspiration/Chemical Pneumonitis, and/or Pulmonary Fibrosis (Chest, 1976) [MEDLINE] (Chest, 1988) [MEDLINE]

Lung Abscess (see Lung Abscess)

• Physiology
  • Bacterial Superinfection

Necrotizing Pneumonia/Pulmonary Gangrene (Necrotizing Pneumonia and Pulmonary Gangrene)

• Epidemiology
  • Bacterial Superinfection

Parapneumonic Pleural Effusion (see Pleural Effusion-Parapneumonic)

• Epidemiology
  • Bacterial Superinfection

Bacterial Aspiration Pneumonia (see Pneumonia)

Epidemiology

• Approximately 13-26% of Patients with Observed Aspiration Develop Pulmonary Superinfection During Their Clinical Course (Am Rev Respir Dis, 1976) [MEDLINE]

Diagnosis

• Chest X-Ray (CXR)/Chest CT (see Chest X-Ray and Chest Computed Tomography)
  • Chest X-Ray May Be Negative Early in the Course
  • Chest X-Ray is Less Sensitive than Chest CT for the Detection of Pulmonary Infiltrates in Pneumonia (Including Aspiration Pneumonia)
    • In a Study of 208 Patients with Pneumonia (Aspiration Pneumonia Accounted for 6o% of the Cases), the Chest X-Ray was Negative in 28% of Cases (with Pneumonia Detected by Chest CT Scan) (J Infect Chemother 2015) [MEDLINE]
  • Infiltrates are Most Commonly Posterior and Dependent in Location (Accounting for the Fact that Most Patients Aspiration in the Recumbent Position) and May Appear as Bronchopneumonia (Diffuse Pattern)
    • In a Study of 53 Patients with Fluoroscopically Documented Dysphagia and Pneumonia, More Patients Had Bronchopneumonia than Lobar Pneumonia (68% vs 15%) (Geriatr Gerontol Int, 2013) [MEDLINE]
      • 92% of Patients in This Study Had Posterior Infiltrates
      • A Decreased Performance Status was Significantly Associated with a Diffuse Distribution of Infiltrates
• Serum Procalcitonin (see Serum Procalcitonin)
  • In a Study of 65 Intubated Patients with Risk Factors for Aspiration and a New Pulmonary Infiltrate, Using Quantitative Bronchoalveolar Lavage Cultures, Serum Procalcitonin Measurement on Days 1 and 3 Did Not Distinguish the 32 Patients with Culture-Positive Aspiration Pneumonia from the 33 with Culture-Negative Pneumonitis (Crit Care Med, 2011) [MEDLINE]
• In Mechanically Ventilated Patients, Airway Secretion α-Amylase Levels (from Salivary and Pancreatic Sources) are Elevated (Reflecting the Number of Risk Factors for Aspiration), But Have an Unclear Role in the Diagnosis of Ventilator-Associated Aspiration Pneumonia (Crit Care Med, 2013) [MEDLINE] (Crit Care Med, 2018) [MEDLINE]

Clinical

• General Comments
  • Time of Onset
    • Onset of Parenchymal Aspiration Pneumonia is Typically within Hours-Few Days After the Aspiration Event
      • However, Anaerobic Aspiration May Be Subacute Due to Less Virulent Bacteria
  • Severity of Illness
    • In a Study of Patients >80 y/o with Pneumonia, Aspiration Pneumonia Had a Higher Mortality Rate, Higher Serum Sodium Level, and Worse Renal Function, as Compared to Patients with Non-Aspiration Pneumonia (Rev Esp Quimioter, 2015) [MEDLINE]
• Cough (see Cough)
• Dyspnea (see Dyspnea)
• Fever (see Fever)

Aspiration (Chemical) Pneumonitis (Mendelson Syndrome)

• Epidemiology
  • In 1946, Mendelson Described Gastric Acid Aspiration with Aspiration/Chemical Pneumonitis (and Acute Respiratory Distress Syndrome within 2 hrs) in a Series of Young Obstetric Patients Undergoing Ether Anesthesia (Am J Obstet Gynecol, 1946) [MEDLINE]
    • All Patients Recovered within 24-36 hrs with Radiogrpahic Resolution within 4-7 Days without the Use of Antibiotics
  • Aspiration/Chemical Pneumonitis May Occur During Laryngoscopic Intubation for General Anesthesia, During Extubation, etc
    • Chemical Pneumonitis is Uncommon with Modern Anesthesia Technique (as Low as 1 Case Per 3,216 Procedures) (Anesthesiology, 1993) [MEDLINE]
      • Higher Risk Occurs During Emergency Surgery
      • Lower Risk Occurs During Elective Surgery
  • While the Use of Acid-Suppressing Medication (Proton-Pump Inhibitors, Histamine H2 Blockers, etc) is Associated with an Increased Risk of Community-Acquired Pneumonia/Hospital-Acquired Pneumonia (Both of Which are Related to Gastric Overgrowth by Gram-Negative Rod Bacteria), the Neutralization of Gastric pH by These Agents Decreases the Risk of Chemical Pneumonitis (PLoS One, 2015) [MEDLINE] (Anaesth Intensive Care, 2015) [MEDLINE]
• Physiology
  • Macroaspiration of Gastric Contents May Result in Chemical Pneumonitis, But Only with Large-Volume, Low pH (Usually <2.5) Aspiration (NEJM, 2019) [MEDLINE]
    • In Animal Models of Aspiration, Chemical Pneumonitis Develops Only After Exposure to at Least 120 ml of Low pH (pH = 1) Gastric Contents (NEJM, 2019) [MEDLINE]
    • In Other Animal Studies, a Large Volume (Around 70 mL in an Adult Human) Inoculum with pH of ≤2.5 was required Cause Chemical Pneumonitis (Surgery, 1972) [MEDLINE]
      • Smaller Volumes of Acid Aspiration (Perhaps Over a Long Period of Time) Likely Result in Less Severe Aspiration/Chemical Pneumonitis, Recurrent Aspiration/Chemical Pneumonitis, and/or Pulmonary Fibrosis (Chest, 1976) [MEDLINE] (Chest, 1988) [MEDLINE]
  • Aspiration Gastric Acid, Resulting in an Inflammatory Reaction in the Lower Airways (Independent of Bacterial Infection of the Airways and/or Lungs)
    • Involves Pro-Inflammatory Tumor Necrosis Factor-α and Interleukin-8 (Crit Care Med, 2011) [MEDLINE]
    • Neutrophil Recruitment (Crit Care Med, 2011) [MEDLINE]
  • Pulmonary Surfactant Dysfunction
  • Reflex Airway Closure
  • Hyaline Membrane Formation
  • Alveolar Hemorrhage
  • Noncardiogenic Pulmonary Edema
  • Aspiration of Bile Acids May Also Elicit an Inflammatory Response (Chest, 2009) [MEDLINE]
• Diagnosis
  • Chest X-Ray (CXR)/Chest Computed Tomography (Chest CT) (see Chest X-Ray and Chest Computed Tomography)
    • Rapid (within 2 hrs) Developent of Pulmonary Infiltrates (Typically in Dependent Portions of the Lung or in Superior or Posterior Segments of the Lower Lobes, if Aspiration Occurred in the Recumbent Position)
    • Diffuse Pulmonary Infiltrates (in Patients with the Development of Acute Respiratory Distress Syndrome) (see Acute Respiratory Distress Syndrome)
    • In Up to 64% of Patients with Aspiration During General Anesthesia, Radiographic Abnormalities Do Not Develop (Crit Care Med, 2011) [MEDLINE]
  • Bronchoscopy (see Bronchoscopy): not usually necessary
• Clinical
  • General Comments
    • In Up to 64% of Patients with Aspiration During General Anesthesia, Clinical Manifestations Do Not Occur (Crit Care Med, 2011) [MEDLINE]
    • Approximately 13-26% of Patients with Observed Aspiration Develop Pulmonary Superinfection During Their Clinical Course (Am Rev Respir Dis, 1976) [MEDLINE]
  • Abrupt Onset of Symptoms/Signs
    • Dyspnea (see Dyspnea)
    • Hypoxemia (see Hypoxemia)
    • Cough (see Cough)
    • Tachycardia (see Sinus Tachycardia)
  • Low-Grade Fever (see Fever)
  • Diffuse Crackles/Wheezing on Physical Examination
  • Acute Respiratory Distress Syndrome (ARDS) (Am J Respir Crit Care Med, 1995) [MEDLINE]
    • Acute Respiratory Distress Syndrome Occurs in Approximately 16.5% of Cases (Am J Respir Crit Care Med, 2011) [MEDLINE]
    • Frequency of Acute Respiratory Distress Syndrome is Higher in Patients with Concomitant Shock, Trauma, or Pancreatitis (Am J Respir Crit Care Med, 2011) [MEDLINE]

Perioperative Measures To Decrease the Risk of Aspiration

• No Food for at Least 8 hrs and No Clear Liquids for at Least 2 hrs Prior to Elective Surgery Involving General Anesthesia
• Avoid Medications Which Promote Aspiration and Interfere with Swallowing (Sedatives, Antipsychotic Agents, Antihistamines, etc) (J Am Geriatr Soc, 2017) [MEDLINE]

Measures to Decrease Risk of Aspiration in Patient with Chronic Dysphagia

Dietary/Feeding Modifications

• Speech Therapy-Guided Modification of Patient’s Diet is Recommended
  • Examples
    • Mechanical Soft Diet with Thickened Liquids (Rather than Pureed Food and Thin Liquids)
• “Nutritional Rehabilitation” (Swallowing Exercises and Early Mobilization, etc) May Assist Patients with Dysphagia and Prevent Aspiration Pneumonia (J Gen Fam Med, 2017) [MEDLINE]
• Useful Measures In Patients with Oropharyngeal Dysphagia (Chest, 2014) [MEDLINE]
  • Patient’s Chin Can Be Positioned Down with the Head Turned to One Side During Feeding
  • Swallow Small Volumes
  • Multiple Swallows
  • Coughing After Each Swallow

Oral Hygiene

• Oral Hygiene Has an Inconsistent Clinical Effect on the Risk of Aspiration Pneumonia, Possibly Due to Various Study Design Issues (J Am Geriatr Soc, 2018) [MEDLINE]
  • Chlorhexidine Oral Care Has Been Demonstrated to Be Associated with Increased Mortality in Ventilated Patients (Possibly Due to Toxic Effects of Aspirated Chlorhexidine) (JAMA Intern Med 2014)
  • In Non-Ventilated Patients at Risk for Aspiration Pneumonia, a Meta-Analysis Demonstrated that Chlorhexidine Oral Care or Mechanical Oral Cleaning were Effective in Preventing Pneumonia (Odds Ratio: 0.4-0.6) (Infect Control Hosp Epidemiol, 2015)
  • In a Cluster-Randomized Trial of Nursing Home Patients (n = 834 Patients, Mean Observation Time of >1 Year), There was No Benefit of a Comprehensive Oral Care Program (Manual Tooth and Gum Brushing, Chlorhexidine Oral Washes, and Upright Positioning During Feeding) (Clin Infect Dis, 2015) [MEDLINE]
    • There was Radiographic Evidence of Pneumonia in 25% of the Patients
  • In a Randomized Trial (n = 252 Patients), Supplemental Nutrition Plus Daily Oral Cleaning Decreased the Frequency of Pneumonia (7.8%, vs 17.7% with Usual Care; p = 0.06) (Ann Nutr Metab 2017)
  • In a Case–Control Study (n = 539 Patients) Undergoing Surgery for Esophageal Cancer, Postoperative Pneumonia Developed in 19.1% of the Patients (Medicine-Baltimore, 2017)
    • Lack of Preoperative Oral Care (Tooth Scaling, Mechanical Cleaning, and Tooth Extraction if Necessary) was an Important Risk Factor

Elimination of Oral Intake

• While Difficult, This May Be Required to Decrease the Risk of Aspiration in Patients with Chronic Dysphagia

Nasogastric Tube Feeding

• This May Be Required to Decrease the Risk of Aspiration in Patients with Chronic Dysphagia
• Feeding Should Be Administered in a Semirecumbent Position (Rather than Supine Position) to Minimize the Risk of Aspiration
• Role of Nasogastric Tubes in Preventing Aspiration Pneumonia is Unclear
  • In a Study (n = 1260 Patients), Patients with a Nasogastric Tube in Place Did Not Have More Aspiration Events During Endoscopic Observation of Swallowing than Patients without a Nasogastric Tube (Arch Phys Med Rehabil, 2008) [MEDLINE]
  • Post-Pyloric Feeding is Not Superior to Gastric Feeding and the Monitoring of Post-Feeding Gastric Residual Volume May Not Decrease the Risk of Aspiration (Nutr Clin Pract, 2015) [MEDLINE]

Gastrostomy Tube Placement (see Gastrostomy Tube)

• This May Be Required to Decrease the Risk of Aspiration in Patients with Chronic Dysphagia

Cuffed Tracheostomy

• This May Be Required to Decrease the Risk of Aspiration in Patients with Chronic Dysphagia

Laryngeal-Tracheal Separation/Laryngectomy

• Considered a Last Resort Treatment to Decrease the Risk of Aspiration in Patients with Chronic Dysphagia
  • Allows Oral Intake, But Speaking is Not Possible
  • Proven Effective and Beneficial to Improve Mood and Clinical Outcome

Measures to Decrease Risk of Aspiration in the Stroke Patient (see Ischemic Cerebrovascular Accident)

• Angiotensin-Converting Enzyme Inhibitors (see Angiotensin-Converting Enzyme Inhibitors)
  • For Stroke Patients (Especially Asian Patients), the Use of ACE Inhibitors to Control Blood Pressure Can Decrease the Risk of Aspiration Pneumonia (Possibly by Elevating Substance P Levels, Which Promotes Cough and Improves the Swallowing Reflex) (Am J Respir Crit Care Med, 2004) [MEDLINE] (Adv Ther, 2012) [MEDLINE]
• Cilostazol (see Cilostazol)
  • The Antiplatelet Agent, Cilostazol, Has Been Demonstrated to Increase Substance P Levels, Decreasing the Risk of Post-Stroke Aspiration Pneumonia (Cerebrovasc Dis, 2013) [MEDLINE]

Measures to Decrease Risk of Aspiration in the Comatose Patient

• Maintain Semirecumbent Body Position
  • In Comatose Patients, the Risk of Aspiration Pneumonia was Decreased by Maintaining the Patient in Either the Prone or Semirecumbent Body Position (Crit Care Med, 1999) [MEDLINE]

Preemptive Antibiotics in the Setting of Cardiac Arrest/Comatose Patient Requiring Emergent Intubation

General Comments

• Preemptive Antibiotics May Be Utilized in Selected Patients with Coma or Post-Cardiac Arrest Encephalopathy to Decrease the Risk of Developing Aspiration Pneumonia

Clinical Efficacy-Cardiac Arrest

• French Study of Early Antibiotic Administration in Patients Undergoing Therapeutic Hypothermia After Out-of-Hospital Cardiac Arrest (Targeted Temperature Management) (NEJM, 2019) [MEDLINE]
  • A 2-Day Amoxicillin-Clavulanate Course in Patients Underoing Therapeutic Hypothermia (32-34 Degrees C) After Cardiac Arrest with an Initial Shockable Rhythm Resulted in a Lower Incidence of Early Ventilator-Associated Pneumonia, as Compared to Placebo
  • There was No Significant Difference in Ventilator-Free Days or 28-Day Mortality Rate

Clinical Efficacy-Emergency Intubation of Comatose Patient

• Cefuroxime Administered Post-Intubation of Patients Comatose Due to Head Injury or Stroke was Found to Be an Effective Prophylactic Strategy to Decrease the Incidence of Ventilator-Associated Pneumonia (Am J Respir Crit Care Med, 1997) [MEDLINE]
• In Comatose Patients (Glasgow Coma Score ≤ 8), A Single Dose of Antibiotic Prophylaxis at the Time Intubation Might Decrease the Incidence of Early-Onset Ventilator-Associated Pneumonia, But Not Late-Onset Pneumonia (Chest, 2013) [MEDLINE]

Supportive Care

• Measures to Decrease Further Aspiration
  • Oropharyngeal Suctioning
  • Turn Patient to Side/Positon Patient Upright
• Supplemental Oxygen (If Required) (see Oxygen)
• Mechanical Ventilation (If Required) (see Mechanical Ventilation-General)
• Bronchoscopy (see Bronchoscopy)
  • Bronchoscopy May Be Considered in Selected Cases to Clear a Suspected Foreign Body from the Airway and/or to Obtain Bronchoalveolar Lavage (BAL) Samples for Culture

Antibiotics

Need for Antibiotic Treatment of Aspiration Pneumonia

• Since it is Diffciult to Exclude Bacterial Infection as a Contributing Factor in the Setting of Aspiration, Antibiotics are Commonly Prescribed Despite a Lack of Clear Clinical Benefit
  • In a Study of Comatose, Mechanically-Ventilated Patients with Aspiration, 46.7% of Patients Had Bacterial Aspiration Pneumonia Based on Bronchoscopic Brush Samples (Crit Care Med, 2017) [MEDLINE]
    • Authors Suggested that Routine Antibiotic Therapy Should Be Initiated Only if Bacterial Infection is Suspected, But May be Discontinued if Bronchoscopic Cultures are Negative
  • Retrospective Cohort Study of Adult Patients with Acute Aspiration Pneumonitis (Defined by Macroaspiration Event with Witnessed Vomiting/Choking on Food with New Radiographic Pulmonary Infiltrate in Non-Ventilated Patient) (Clin Infect Dis, 2018) [MEDLINE]: n = 200 patients with acute aspiration pneumonitis
    • Antimicrobial Prophylaxis Did Not Impact the 30-Day Mortalty Rate or Need for Critical Care
• Antibiotics are Generally Recommended Only for Patients with Persistent/Progressive Hypoxemia and/or Signs of Inflammation
• Recommendations (American Thoracic Society-ATS and Infectious Diseases Society of America-IDSA Community-Acquired Pneumonia Practice Guidelines, 2019) (Am J Respir Crit Care Med, 2019) [MEDLINE]
  • Routine Addition of Anaerobic Antibiotic Coverage for Suspected Aspiration Pneumonia is Not Recommended, Unless Lung Abscess or Empyema is Suspected (Conditional Recommendation, Very Low Quality of Evidence)

Antibiotic Selection in the Treatment of Aspiration Pneumonia

• Antibiotic Selection Depends on the Site of Acquisition (Community, Hospital, or a Long-Term Care Facility) and Risk Factors for Multidrug-Resistant Organisms (MDRO’s)
  • Risk Factors Include Treatment with Broad-Spectrum Antibiotics in the Past 90 days and Hospitalization for at Least 5 Days
• If Antibiotics are Initially Started, Reevaluation of the Need (After 24-48 hrs) for Continued Antibiotic Therapy is Recommended
• With Mixed (Aerobic and Anaerobic) Infections, Elimination of Aerobic Organisms Usually Alters the Local Redox Potential, Eliminating the Anaerobes (NEJM, 2019) [MEDLINE]

Agents

• Ampicillin–Sulbactam (Unasyn) (see Ampicillin–Sulbactam): 1.5–3 g q6 hrs IV
• Amoxicillin–Clavulanic Acid (Augmentin) (see Amoxicillin–Clavulanic Acid): 875 mg BID PO
• Piperacillin-Tazobactam (Zosyn) (see Piperacillin-Tazobactam): 4.5 g q8 hrs or 3.375 g q6 hrs IV
• Ceftriaxone (Rocephin) (see Ceftriaxone): 1–2 g qday IV
• Cefepime (Maxipime) (see Cefepime): 2g q8-12 hrs IV
• Ertapenem (Invanz) (see Ertapenem): 1 g qday IV
• Imipenem (Primaxin) (see Imipenem): 500 mg q6 hrs IV or 1 g q8 hrs IV
• Meropenem (Merrem) (see Meropenem): 1 g q8 hrs IV
• Levofloxacin (Levaquin) (see Levofloxacin): 750 mg qday PO/IV
• Moxifloxacin (Avelox, Avalox, Avelon) (see Moxifloxacin): 400 mg qday IV or PO
• Clindamycin (Cleocin, Clinacin, Dalacin) (see Clindamycin): 450 mg TID-QID PO or 600 mg q8hrs IV
• Gentamicin (Cidomycin, Septopal, Genticyn, Garamycin) or Tobramycin (Tobrex, Tobi) (see Gentamicin and Tobramycin): 5–7 mg/kg qday IV
  • Dose Should Be Adjusted to Trough Level of <1 mg/L with Renal Function Taken into Consideration
• Amikacin (Amikin, Amiglyde-V, Arikayce) (see Amikacin): 15 mg/kg qday IV
  • Dose Should Be Adjusted to Trough Level of <4 mg/L with Renal Function Taken into Consideration
• Colistin (Polymyxin E, Colistimethate Sodium) (see Colistin): loading dose of 6-9 million IU IV, then 9 million IU qday in 2-3 divided doses IV
• Vancomycin (Vancocin) (see Vancomycin): 15 mg/kg q12hrs IV
  • Dose Should Be Adjusted to Trough Level of 10-15 μg/mL with Renal Function Taken into Consideration
• Linezolid (Zyvox) (see Linezolid): 600 mg q12 hrs IV or PO

Corticosteroids (see Corticosteroids)

• Corticosteroids Have No Clinical Benefit in the Setting of Aspiration Pneumonia or Aspiration/Chemical Pneumonitis (Am J Med, 1977) [MEDLINE]

Mortality Rate

• Patients at Risk for Aspiration Pneumonia Have a 30-Day Mortality Rate of 17.2%, as Compared to Other Patients (7.7%) (Am J Med, 2013) [MEDLINE]
  • However, After Adjusting for Greater Severity of Illness and Comorbidities, the Difference was Not Significant (Odd Ratio: 1.05; 95% Confidence Interval: 0.63-1.76; p = 0.8)
• Patients at Risk for Aspiration Pneumonia were at Greater Risk for Poor Long-Term Outcome and Increased 1-Year Mortality Rate After Multivariate Assessment (Hazard Ratio: 1.73; 95% CI: 1.15-2.58) (Am J Med, 2013) [MEDLINE]
• Aspiration Pneumonia is Associated with a Higher Mortality Rate than Other Types of Community-Acquired Pneumonia (29.4% vs 11.6%) (Ann Am Thorac Soc, 2018) [MEDLINE]
  • In This Study Which Included Data from 4,200 Hospitals, Aspiration was Found to Be Documented in 4-26% of Pneumonia Episodes
  • Consequently, the Risk-Adjusted Mortality (Used as a Quality Metric) is Lower for Hospitals Reporting a High Frequency of Aspiration than for Hospitals Reporting a Low Frequency of Aspiration