Quantitative effects of trunk and head position on the apnea hypopnea index in obstructive sleep apnea

Abstract

Study objectives: To test the hypothesis that head position, separately from trunk position, is an additionally important factor for the occurrence of apnea in obstructive sleep apnea (OSA) patients.

Design: Prospective cohort study.

Setting: St. Lucas Andreas Hospital, Amsterdam, the Netherlands.

Patients and participants: Three hundred patients referred to our department because of clinically suspected OSA.

Interventions: N/A.

Measurements and results: Patients underwent overnight polysomnography with 2 position sensors: one on the trunk, and one in the mid-forehead. Of the 300 subjects, 241 were diagnosed with OSA, based on an AHI > 5. Of these patients, 199 could be analyzed for position-dependent OSA based on head and trunk position sensors (AHI in supine position twice as high as AHI in non-supine positions): 41.2% of the cases were not position dependent, 52.3% were supine position dependent based on the trunk sensor, 6.5% were supine position dependent based on the head sensor alone. In 46.2% of the trunk supine position-dependent group, head position was of considerable influence on the AHI (AHI was > 5 higher when the head was also in supine position compared to when the head was turned to the side).

Conclusions: The results of this study confirm our hypothesis that the occurrence of OSA may also be dependent on the position of the head. Therefore in patients with a suspicion of position-dependent OSA, sleep recording with dual position sensors placed on both trunk and head should be considered.

Keywords: OSA; position dependence.

Figures

Figure 1

Flowchart of subjects included in the study.

Figure 2

Overnight hypnogram in a single subject with respiratory events and trunk/head position indicated. Normally, there is only a single position channel displayed. To show the effect of head position, the head position channel recording was inserted into the standard hypnogram report by means of a picture editor program. Notice that in this subject apneas are primarily related to the position of the head, not to the position of the trunk. Hypopneas are more apparent in the remainder of the night.

Figure 3

Mean AHI values determined over the total sleep time (TST) and the different time periods spent in supine position based on the trunk position sensor (tsp) and head position sensor (hsp) in OSA patients (n = 199).

Figure 4

Correlation of the AHI determined over the total sleeping time with the AHI during trunk-supine position for OSA positive subjects (n = 199, using the standard trunk position sensor). The line indicates the unity line (x = y).

Figure 5

Correlation of the AHI over the time period spent in supine position based on the trunk position sensor (x-axis) and head position sensor (y-axis). The line indicates the linear regression line of the correlation between the 2 AHI values in our OSA positive study group (n = 199).

Figure 6

Correlation between the relative time spent in supine position based on the trunk and head sensor in OSA positive subjects (n = 199).

Figure 7

Relative time spent in the different positions of head and trunk for men and women in patients with head position-aggravated trunk supine position-dependent OSA (n = 47).

Figure 8

Mean AHI over the time spent in the different positions of head and trunk in patients with a head position-aggravated trunk supine position-dependent OSA (n = 47).