Enhanced Expiratory Rebreathing Space (EERS)

Enhanced Expiratory Rebreathing Space (EERS) is a potentially useful therapy for positive pressure CPAP and BPAP) associated respiratory instability and CPAP treatment failures. Individuals that experience therapy onset central apnea seem to be particularly likely to benefit from EERS. Some patients experience hypocapnea,a state of reduced carbon dioxide in the blood. The theory is that the use of positive air pressure, especially with pressure support (PS) or exhale pressure relief (EPR) can result in a drop in carbon dioxide in the blood, which through various respiratory feedback mechanisms can result in the emergence of central apnea (CA). By adding dead-spece or a larger volume of re-breathed air, the normal carbon dioxide balance can be restored, and thereby prevent the side effect of central apnea in these individuals.

EERS is accomplished by blocking the mask exhaust vents, and adding a length of tubing to the mask that terminates in a mask exhaust vent. For safety purposes an antiasphyxiation/saftey valve is included in EERS for full-face mask setups to ensure continued airflow in the patient circuit in the event of CPAP failure. This safety valve can be omitted in nasal therapy. EERS creates a larger dead-space by moving the mask vent to a position further down the tubing toward the xPAP machine.

Fabrication of EERS

EERS can be added to nasal or full face mask interfaces.

Without adding the Corr-a-Flex segment, the nasal mask tube (16-inches x 15 mm) provides about 70 mL of dead space. Standard Corr-a-Flex is in 6-inch (15.24 cm) segments which has about 58 mL of dead space. (The volume of the tubing is V = Pi * r squared * length and 22 mm diameter tubing has about 3.8 mL/cm with 15 mm diameter tubing being about half (1.7) of that).

Donate to Apnea Board