Am. J. Respir. Crit. Care Med., Vol 152, No. 2, Aug 1995, 775-779.
Diagnosis of obstructive sleep apnea using a portable transducer catheter
M Tvinnereim, S Mateika, P Cole, J Haight and V Hoffstein
Department of Otolaryngology, St. Michael's Hospital, University of Toronto, Canada.
As an initial step in simplifying the diagnosis of sleep apnea with a view
toward using portable equipment in the home setting, we examined the
efficacy of a portable transducer catheter that measures intrathoracic
pressure. This catheter, connected to a miniature data- logger, can be
introduced nasally into the airway, and the data so collected can be
acquired, stored, and analyzed off-line. We tested this catheter against
standard nocturnal polysomnography in 10 patients suffering from
obstructive sleep apnea. We found that by using a combination of the raw
pressure signal and an envelope pressure signal, we accurately identified
apneas and hypopneas, and classified them as obstructive, central, and
mixed. For the 10 subjects studied, the polysomnographic apnea/hypopnea
index was 34 + 30, versus 32 + 28 obtained by analysis of the pressure
tracings. Analysis of 200 respiratory events identified one-by-one from
polysomnograms and pressure tracings revealed close correspondence between
the two methods. The average duration of apneas was 22.1 + 6.7 s as
measured by polysomnography, versus 21.9 + 6.6 s as measured from pressure
tracings. Furthermore, there was excellent agreement between the two
methods (kappa = 0.89, 95% confidence limits = 0.84 to 0.94). We conclude
that our technique for identifying apnea based on measurements of
intrathoracic pressure using a thin, portable transducer catheter is a
promising method for simplifying the diagnosis of this disorder.
