Coupling Between Posture and Respiration Among the Postural Chain: Toward a Screening Tool for Respiratory-Related Balance Disorders.

Alteration of posturo-respiratory coupling (PRC) may precede postural imbalance in patients with chronic respiratory disease. PRC assessment would be appropriate for early detection of respiratory-related postural dysfunction. PRC may be evaluated by respiratory emergence (REm), the proportion of postural oscillations attributed to breathing activity; assessed by motion analysis) as measured from the displacement of the center of pressure (CoP) (measured with a force platform). To propose a simplified method of PRC assessment (using motion capture only), we hypothesized that the REm can appropriately be measured derived from single body segment the postural oscillations of a single body segment rather than whole body postural oscillations. An optoelectronic system recorded the breathing pattern and the postural oscillations of six body segments in 50 healthy participants (22 women), 34 years [26; 48]. The CoP displacements were assessed using a force platform. One-minute recordings were made in standing position in four conditions by varying vision (eyes opened/closed) and jaw position (rest position/dental contact). The Sway Path and Mean Velocity of the CoP and of the representative point of each body segment were recorded. The REm was measured along the major and the minor axis of the 95% confidence ellipse of the CoP position (REm_MajorAxisCoP; REm_MinorAxisCoP) and of that of each body segment. SwayPathCoP and MVCoP varied widely across the four conditions (par< 0.000001). These changes were related to the visual condition ( [Formula: see text]) while the jaw position had no effect. The REm_MajorAxisCoP and the REm_MinorAxisCoP changed across conditions ( [Formula: see text]); this was related to vision while jaw induced changes only for the REm_MinorAxisCoP. The SwayPath, the Mean Velocity and the REm of all body segments were significantly correlated to the CoP, but the highest correlations were observed for the thorax, the pelvis and the shoulder. PRC may be assessed from the postural oscillations of thorax, pelvis and shoulder. This should simplify the evaluation of respiratory-related postural interactions in the clinical environment, by using a single device to simultaneously assess postural oscillations on body segments, and breathing pattern. In addition, this study provides reference data for PRC and its sensory-related modulations on body segments along the postural chain.

Cervical Spine Hyperextension and Altered Posturo-Respiratory Coupling in Patients With Obstructive Sleep Apnea Syndrome.

Obstructive sleep apnea syndrome (OSAS) is associated with postural dysfunction characterized by abnormal spinal curvature and disturbance of balance and walking, whose pathophysiology is poorly understood. We hypothesized that it may be the result of a pathological interaction between postural and ventilatory functions. Twelve patients with OSAS (4 women, age 53 years [51-63] (median [quartiles]), apnea hypopnea index 31/h [24-41]) were compared with 12 healthy matched controls. Low dose biplanar X-rays (EOS® system) were acquired and personalized three-dimensional models of the spine and pelvis were reconstructed. We also estimated posturo-respiratory coupling by measurement of respiratory emergence, obtaining synchronized center of pressure data from a stabilometric platform and ventilation data recorded by an optico-electronic system of movement analysis. Compared with controls, OSAS patients, had cervical hyperextension with anterior projection of the head (angle OD-C7 12° [8; 14] vs. 5° [4; 8]; p = 0.002), and thoracic hyperkyphosis (angle T1-T12 65° [51; 71] vs. 49° [42; 59]; p = 0.039). Along the mediolateral axis: (1) center of pressure displacement was greater in OSAS patients, whose balance was poorer (19.2 mm [14.2; 31.5] vs. 8.5 [1.4; 17.8]; p = 0.008); (2) respiratory emergence was greater in OSAS patients, who showed increased postural disturbance of respiratory origin (19.2% [9.9; 24.0] vs. 8.1% [6.4; 10.4]; p = 0.028). These results are evidence for the centrally-mediated and primarily respiratory origin of the postural dysfunction in OSAS. It is characterized by an hyperextension of the cervical spine with a compensatory hyperkyphosis, and an alteration in posturo-respiratory coupling, apparently secondary to upper airway instability.