Snoring, EDS, and obesity have been identified as historical risk factors for sleep apnea.¹ Studies of inspiratory loading in the awake subject show that inspiratory loading results in increased repiratory effort.² We measured changes in respiratory effort during inspiratory muscle loading in awake subjects, and found the transcutaneous diaphragmatic EMG, (respiratory effort), signals were significantly different in OSA subjects than in non-OSA subjects.

METHOD

Five subjects with RDI’s > 30 (OSA) and five patients with RDI’s <5 (normals) were monitored while awake, for changes in transcutaneous diaphragmatic EMG (tcDEMG) signal during changes in inspiratory muscle loading. Each subject was monitored for tcDEMG while breathing with an inspiratory muscle training device set at -7.0, -14.0, & -21.0 cm of H2O pressure.³ The inspiratory muscle training device provides a constant inspiratory pressure load by having the subject breathe through a mouthpiece attached to a device containing a spring-loaded valve.

RESULTS

A greater increase in tcDEMG signal (respiratory effort) with inspiratory muscle loading was noted in awake subjects who subsequently demonstrated OSA, than was noted in normal subjects.

T-tests of tcDEMG signals at each of the inspiratory loaded pressures for OSA subjects vs. non-OSA subjects showed that the means were different at the P< .05 level for each of the inspiratory loaded pressures, but not for the baseline signals.

Baseline -.22

@7.0cm HO 2.77

@14.0cm H2O 4.56

@ 21.0cmH2O 4.23

CONCLUSION

In subjects with RDI’s of >30, the average area of respiratory effort as measured by tcDEMG during loads, significantly exceeded that of non-OSA subjects.

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1 Guileminault, C. Sleep and Waking Disorders,Indications and Techniques, Menlo Park, CA, Addison-Wesley 1982, p.161

2 Gugger M., Molloy J, Gould G, Whyte K, Raab G, Shapiro C, Douglas N, Ventilatory and Arousal Responses to Added Respiratory Resistance during Sleep, Amer. Review of Respiratory Diseases;1989, Nov. pp.1301-1307

3 Larson J, Kim M, Sharp J, Larson O, Inspiratory Muscle Training with a Pressure Threshold Device in Patients with Chronic Obstructive Pulmonary Disease; Amer. Review of Pulmonary Disease 1988; p.690