How can a cough assist machine be simulated?

Manual Simulation of Cough Assist Machine

A cough assist machine can be simulated manually by combining inspiratory assistance (through air stacking, glossopharyngeal breathing, or bag-mask ventilation) followed immediately by forceful expiratory augmentation (via abdominal/chest thrust synchronized with the patient's cough effort). 1

Core Technique: Two-Phase Manual Approach

The manual simulation replicates the mechanical insufflator-exsufflator's positive-then-negative pressure cycle through human-powered methods 1:

Phase 1: Inspiratory Assistance (Simulating Insufflation)

Air Stacking is the most practical home-based technique 2:

• Patient takes consecutive tidal breaths without exhaling between them, progressively filling lungs to maximum capacity 1, 2
• Improves maximum insufflation capacity and increases lung/chest wall range of motion 1
• Requires intact glottic function to hold air with closed glottis 2

Glossopharyngeal Breathing (GPB) uses oral/pharyngeal muscles 2:

• Patient "gulps" air using mouth and throat muscles to force air into lungs 1, 2
• Each gulp delivers approximately 40-200 mL; 6+ consecutive gulps produce full tidal volume 2
• Requires training and intact oropharyngeal/laryngeal muscle strength 2

Bag-Mask Ventilation provides mechanical positive pressure 1:

• Apply positive pressure with self-inflating bag and mask, IPPB device, or mechanical ventilator 1
• Interfaces include facemask, mouthpiece, or direct tracheostomy tube attachment 1

Phase 2: Expiratory Augmentation (Simulating Exsufflation)

Manually Assisted Cough augments forced exhalation 1:

• Apply firm pressure with both hands to upper abdomen and/or lower chest wall 1
• Time thrust precisely to synchronize with patient's own cough effort following inspiratory assistance 1
• Improves peak cough expiratory flow by 14-100% in neuromuscular weakness 1

When Manual Simulation Is Indicated

Use these techniques when peak cough flow is <270 L/min and/or maximal expiratory pressure is <60 cm H₂O 1, 2:

• Peak cough flows <160 L/min indicate ineffective airway clearance requiring intervention 1
• Respiratory muscle function deteriorates further during respiratory infections, making these techniques critical during illness 1, 2
• Particularly important in neuromuscular disease, spinal cord injury, and expiratory muscle weakness 1

Critical Contraindications and Pitfalls

Do NOT use manually assisted cough in COPD or obstructive airway disease 1, 3:

• Manual assistance decreases peak expiratory flow by 144 L/min (95% CI: 25-259) in COPD patients 1
• Detrimental effect occurs with manual assistance alone or combined with mechanical insufflation 1

Avoid in patients with 1:

• Severe scoliosis or stiff chest walls (technique becomes ineffective) 1
• Osteoporosis (risk of rib fractures) 1
• Recent abdominal surgery or intraabdominal catheters 1
• Acute respiratory distress without medical supervision 2

When Manual Techniques Fail

Transition to mechanical insufflation-exsufflation when 1, 2:

• Peak cough flows remain <160 L/min despite manual techniques 2, 3
• Scoliosis prevents optimal manual cough assistance 1
• Manual techniques fail to prevent hospitalization or maintain adequate airway clearance 1, 2

Mechanical insufflation-exsufflation generates superior peak cough flows compared to breath stacking or manual assistance alone 1, and the American Thoracic Society strongly supports its use in neuromuscular disease when manual simulation proves insufficient 1.

Practical Implementation Algorithm

1. Assess baseline cough effectiveness: Measure peak cough flow and maximal expiratory pressure 1
2. If <270 L/min or MEP <60 cm H₂O: Initiate manual simulation techniques 1, 2
3. Choose inspiratory method: Air stacking (first-line for home use) > GPB (requires training) > bag-mask (requires equipment/caregiver) 2
4. Add expiratory augmentation: Coordinate abdominal/chest thrust with patient's cough 1
5. Monitor effectiveness: Use pulse oximetry during respiratory illnesses to guide therapy intensification 1
6. Escalate to mechanical device: If peak flows remain <160 L/min or hospitalization occurs 1, 2, 3