Elucidation of obstructive sleep apnoea related blood pressure surge using a novel continuous beat-to-beat blood pressure monitoring system

Abstract

Background: Obstructive sleep apnoea (OSA) episode related blood pressure (BP) surge may mediate the association of OSA with cardiovascular disease. However, BP is not measured during a clinical sleep study.

Method: We tested the feasibility of incorporating the Caretaker physiological monitor, which utilizes a novel continuous beat-to-beat (b-b) BP monitoring technology, into polysomnography (PSG) and aimed to characterize BP surges related to obstructive respiratory events. B-b BP was concurrently collected and merged with PSG data on a posthoc basis. We compared BP surge between mean respiratory (apnoea, hypopnea and desaturation-alone events) and nonrespiratory events (spontaneous or leg movement-related arousals). We examined the association of the degree of oxygen desaturation with BP surge in a given respiratory event combining all events. A total of 17 consecutive patients (12 men, mean 52 years old, nine diagnostic and eight split-night PSGs) undergoing clinically indicated PSG were included after excluding one patient with poor signal quality due to excessive movement.

Results: Caretaker was well tolerated. Mean respiratory BP surge ranged from 5 to 19 mmHg [Median (IQR) = 13.9 (9.5--16.2)]. Mean BP surge between the respiratory and nonrespiratory events was similar [13.8 (4.5) vs. 14.9 (5.3) mmHg, P = 0.13]. Accounting for the count distribution of desaturation/BP surge data pair events, there was a linear correlation between the degree of oxygen desaturation and BP surge (R = 0.57, P < 0.001). In eight patients undergoing split-night sleep studies, the number of BP surge events (≥10 mmHg/h) decreased during continuous positive airway pressure in all but one patient.

Conclusion: We demonstrated highly variable OSA-related BP surge patterns using the Caretaker's b-b BP monitoring technology that has the potential to be integrated into sleep studies.

Figure 1.

Illustration of Caretaker BP device.

Figure 2.

Examples of BP change in response to obstructive respiratory events. Obstructive events are labeled by the horizontal rectangles on the airflow tracings. BP response is trivial in one patient (dashed arrow in the upper panel) vs. marked in another patient (solid arrow in the lower panel).

Figure 3.

3-D histogram of respiratory-related systolic BP surge (Y axis) (CT systole change) in relation to O₂ desaturation (X axis). CT, caretaker device; Desat, desaturation

Figure 4.

3D depiction of the quantitative analysis examining the correlation of the degree of O₂ desaturation and BP surge. The 3D scatter graph (dark gray data points) represents the count [Z] of each column (O₂ desaturation [X]-BP surge [Y] pairs) as a function of the respective desaturation and BP surge values extracted from the 3D histogram in Figure 3. The results of a 3D linear fit of the 3D data (i.e., accounting for the count of X-Y pair) are presented as a thick black line (3D fit R = 0.57, p<0.001). To facilitate viewing the 3D graph, the projections of the 3D fit onto the YZ (dashed light gray line), XZ plane (light dashed line) and XY (solid light gray line) are presented. Also presented is the projection of the 3D data plot onto the XY plane (light gray data points) without considering the Z axis. The angles of, respectively, the YZ, XZ and XY plane projections of the 3D fit are 24°, 25° and 44°, measured in each case from the first axis in the plane label, i.e. from the X axis for the XY label. The linear fit between the O₂ desaturation and the minimum BP surge is depicted in the figure by the thin black line in the XY plane. (2D fit R = 0.86, p<0.001). The corresponding 3D fit (R = 0.69, p<0.001) of that data set is not displayed as it would obscure the displayed information.

Figure 5.

Change in apnea hypopnea index (a) and in the number of significant BP surge events (b) and (before vs. during CPAP use) in a subset of patients who underwent a split night sleep study (N=8).

Figure 5.

Change in apnea hypopnea index (a) and in the number of significant BP surge events (b) and (before vs. during CPAP use) in a subset of patients who underwent a split night sleep study (N=8).