Enhanced Expiratory Rebreathing Space (EERS)

Enhanced Expiratory Rebreathing Space (EERS) may be a solution for individuals that experience therapy onset central apnea with CPAP or bilevel therapy. The rebreathing space prevents all of the exhaled air from being vented through the CPAP mask. This increases the amount of carbon dioxide that the user breathes in in the next breath. CPAP and Bilevel therapy flush most of the user's expired air out of the mask. For some sensitive individuals this decreases the amount of carbon dioxide which leads to the appearance of central apnea. Many of these individuals find that CPAP/BPAP therapy is uncomfortable due to the central apnea and hypopnea that they experience. EERS can ensure a volume of expired air is available for rebreathing, and this can prevent these therapy onset central apnea.

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. At his time there is no commercial or retail availability of the EERS circuit and they must be custom bilt by the user or a few knowledgeable durable medical providers or doctors. This section describes a simple method of constructing EERS using available Corr-A-Flex CPAP tubing, a mask vent / swivel and an optional antiasphixiation safety valve.

EERS on Resmed N20 Nasal Mask,
EERS on Mirage FX Full Face Mask

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 one-half (0.7) of that volume).

Currently we know of two DMEs that work with Dr. Robert J Thomas (see references) to fabricate the EERS. This information is not provided as an endorsement, and patients may require a prescription to obtain the device. The only DMEs we are aware of that provide the EERS supplies are:

Regional Homecare
125 Tolman Avenue
Leominster MA, 01453
Phone: 978-840-0113

Reliable Respiratory
1504 Boston Providence Turnpike, Suite 11A
Norwood, MA 02062
Phone: 781-551-3335