Effect of a nonrebreathing exhalation valve on long-term nasal ventilation using a bilevel device.
OBJECTIVE
To determine whether an exhalation valve designed to minimize rebreathing improves daytime or nocturnal gas exchange or improves symptoms compared with a traditional valve during nocturnal nasal ventilation delivered using a bilevel pressure ventilation device.


METHODS
Prospective direct comparison trial with each patient sequentially using both valves, during a 2-week run-in period with a traditional valve, a 2-week trial with the nonrebreathing valve, and a 2-week washout period with the traditional valve.


METHODS
Outpatient pulmonary function laboratory and home nocturnal monitoring.


METHODS
Seven patients who received long-term (> 1 year) nocturnal nasal bilevel pressure ventilation with an expiratory pressure of <or= 4 cm H(2)O.


METHODS
Symptoms, pulmonary function, and arterial blood gas levels were assessed at each of three daytime sessions after the sequential 2-week periods using the different valves. Nocturnal studies used a multichannel recorder that measured heart rate, chest wall impedance, nasal airflow, and oximetry. End-tidal PCO(2) (PetCO(2)) from the mask and transcutaneous PCO(2) (PtcCO(2)) were also monitored nocturnally.


RESULTS
Seven patients with a variety of neuromuscular, chest wall, and obstructive defects were enrolled. No mean differences in daytime arterial blood gas levels, pulmonary functions, nocturnal vital signs or oximetry, or PtcCO(2) were apparent regardless of the exhalation valve used. The multichannel recording was indicative of an air leak at least one third of the time, and the PetCO(2) tracing detected a blunted signal or no signal from the mask during the majority of the recording time.


CONCLUSIONS
The use of an exhalation valve designed to minimize rebreathing did not improve daytime or nocturnal gas exchange or symptoms in patients receiving long-term nasal bilevel pressure ventilation in comparison with a traditional exhalation valve, most likely because of air leakage and escape of CO(2) via other routes.
Rhode Island Hospital and Brown University School of Medicine, Providence, RI, USA.
Nicholas S
NS
Hill
Carol
C
Carlisle
Naomi R
NR
Kramer
D000368:Aged; D001784:Blood Gas Analysis; D004867:Equipment Design; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009136:Muscular Dystrophies / Q000628:therapy*; D029424:Pulmonary Disease, Chronic Obstructive / Q000628:therapy*; D011659:Pulmonary Gas Exchange; D012119:Respiration; D012121:Respiration, Artificial / Q000295:instrumentation / Q000379:methods*; D012129:Respiratory Function Tests; D020181:Sleep Apnea, Obstructive / Q000628:therapy*