What are the preventive measures and treatment options for microaspiration in patients with dysphagia or neurological disorders, particularly those who are critically ill or on mechanical ventilation?

Microaspiration: Prevention and Management

Primary Prevention Strategy

Elevate the head of the bed to 30-45 degrees for all patients at risk for microaspiration, particularly those on mechanical ventilation or receiving enteral feeding—this is the single most critical intervention supported by the highest quality evidence. 1

Risk Stratification and Screening

Immediate Dysphagia Assessment

• Keep all patients NPO until dysphagia screening is completed within 4-24 hours by trained nursing staff, as dysphagia occurs in 40-78% of stroke patients and is the critical gateway to aspiration pneumonia 1
• Perform assessment before any oral intake, including medications 2
• If screening is failed, immediately consult speech-language pathology for formal instrumental evaluation (videofluoroscopic swallowing study) to identify aspiration presence and guide treatment 2

High-Risk Populations Requiring Intensive Monitoring

• Neurological disorders: 50% of stroke patients, 60% of traumatic brain injury patients, essentially all ALS patients, >50% of myasthenia gravis patients develop dysphagia 2
• Mechanically ventilated patients: 70-80% develop significant swallowing impairment after prolonged ventilation, with 6-21 times higher pneumonia risk than non-ventilated patients 2
• Specific risk factors for aspiration despite interventions: vocal fold paralysis, impaired laryngeal sensation, poor performance status, and previous aspiration pneumonia 2

Mechanical Ventilation-Specific Interventions

Airway Management

• Use orotracheal rather than nasotracheal intubation whenever possible, as nasotracheal tubes increase nasopharyngeal colonization and aspiration risk 1
• Consider endotracheal tubes with subglottic secretion drainage capability for continuous or intermittent suctioning of secretions accumulating above the cuff 1
• Maintain continuous cuff pressure monitoring and control—at least one well-designed trial demonstrated this decreases VAP risk 3
• Ensure cuff inflation is adequate; any cuff design fails if insufficiently inflated 3

Ventilator Settings

• Maintain minimum positive end-expiratory pressure (PEEP) of at least 5 cmH₂O, which reduces microaspiration risk both in vitro and in vivo, with one RCT demonstrating reduced VAP in patients ventilated with PEEP 5-8 cmH₂O 3
• Use non-invasive positive-pressure ventilation when feasible instead of endotracheal intubation for patients in respiratory failure not requiring immediate intubation 1
• Avoid repeat endotracheal intubation whenever possible, as reintubation substantially increases aspiration risk 1

Dysphagia-Specific Compensatory Strategies

Liquid Modification

• Recommend thickened liquids at the lowest viscosity level possible without penetration-aspiration based on videofluoroscopic assessment 2
• Honey-thick liquids are most effective at preventing aspiration in Parkinson's disease patients (277 patients studied), followed by nectar-thick liquids; chin-down posture with thin liquids was least effective 2
• Critical caveat: 39% of PD patients and 50% of PD with dementia patients aspirated on all three interventions (chin-down, nectar-thick, honey-thick), indicating thickened fluids are not universally protective 2
• Pudding-thick liquids result in significantly lower penetration-aspiration scores despite higher oral transit time in PD patients 2

Exercise-Based Interventions

• Expiratory muscle strength training (EMST) for 4 weeks improves penetration/aspiration scores and hypolaryngeal complex function in PD patients, demonstrated in both pretreatment comparison and placebo-controlled groups 2
• Oral motor exercise programs supervised by speech-language therapists (5 weeks duration) increase strength and range of motion of mouth, larynx, and pharynx, improving bolus control and airway protection 2

Enteral Feeding Management

Timing and Route Selection

• Initiate enteral feedings within 7 days after stroke for patients who cannot safely swallow 2
• Use nasogastric tube feeding for short-term (2-3 weeks) nutritional support 2
• Place percutaneous gastrostomy tubes in patients with chronic inability to swallow safely, as it is associated with fewer treatment failures, higher feed delivery, and improved albumin concentration after 2-3 weeks 2
• For recurrent aspiration despite other measures, consider post-pyloric feeding (percutaneous gastrojejunostomy) 4

Feeding Protocol

• Maintain head-of-bed elevation at 30-45 degrees during and for 1-2 hours after feeding 4
• Do NOT routinely monitor gastric residual volumes in mechanically ventilated patients receiving enteral nutrition—this practice is not recommended 3
• Withhold enteral feeding if residual volume in stomach is large or bowel sounds are absent on auscultation 2

Pharmacological Interventions

Primary Agent for Gastric Emptying

• Metoclopramide is the primary medication to reduce aspiration risk by promoting gastric emptying in PEG tube patients and reducing gastric volume perioperatively (Category A1 evidence from American Society of Anesthesiologists) 5, 4

Acid Suppression

• H2-receptor antagonists combined with metoclopramide effectively reduce both gastric volume and acidity (Category A2 evidence) 5
• Proton pump inhibitors or H2-receptor antagonists can reduce acidity of gastric contents, potentially decreasing severity of aspiration pneumonitis if aspiration occurs 5, 4
• Critical limitation: Evidence is insufficient to demonstrate that reduced gastric acidity decreases morbidity or mortality in patients who aspirate 5

Medications NOT Recommended

• Do NOT use anticholinergics to decrease aspiration risk 5
• Antacids have equivocal effects on gastric volume and should not be routinely used 5
• Do NOT routinely administer preoperative antiemetics for aspiration prevention 5

Oral Hygiene Protocols

• Implement intensive oral hygiene protocols, which may reduce stroke-associated pneumonia from 28% to 7% 1
• Use oral chlorhexidine gluconate (0.12%) rinse specifically for adult patients undergoing cardiac surgery during the perioperative period 1
• Develop and implement comprehensive oral hygiene programs for high-risk patients 1

Sedation and Mobility Management

• Limit dose and duration of sedatives and analgesics using sedation/pain/agitation scales and/or daily interruptions 1
• Promote early mobilization and good pulmonary toiletry to reduce pneumonia risk 1

Selective Digestive Decontamination

• Consider selective digestive decontamination (SDD) only in environments with low prevalence of multidrug-resistant bacteria, where it has shown significant decreases in mortality, length of mechanical ventilation, and hospital-acquired pneumonia incidence 1
• Current evidence does NOT justify routine use of SDD for prevention of nosocomial pneumonia in ICU patients due to equivocal mortality effects, high cost (need to treat 6 patients to prevent one pneumonia case, 23 patients to prevent one death), and concerns about antimicrobial resistance 2

Interventions of Uncertain Benefit

The following are NOT currently recommended due to insufficient evidence: drug therapy for dysphagia, neuromuscular electrical stimulation, pharyngeal electrical stimulation, physical stimulation, transcranial direct current stimulation, and transcranial magnetic stimulation 2