Background and objective: The purpose of this study was to test the hypothesis that the risk of silent aspiration is increased in non-invasive positive pressure ventilation. Methods: We analysed the coordination between respiration and swallowing, in 12 young volunteers and 10 elder volunteers, by simultaneously monitoring respiratory flow, laryngeal movement and swallowing sound in three different conditions: control, continuous positive airway pressure (CPAP), and bi-level positive airway pressure (BiPAP). A step-wise multiple regression analysis was performed with the occurrence rate of inspiration after swallows as the dependent variable and various correlated variables as the independent variables. Results: In both subject groups, the occurrence rate of inspiration after swallow was greater with BiPAP compared with control and CPAP conditions. Repetitive saliva swallowing test count and swallow non-inspiratory flow occurrence rate were extracted as predictor variables for risk of inspiration after swallows during BiPAP treatment. Conclusion: We found that the occurrence rate of inspiration after swallow is increased with BiPAP use irrespective of age. The results suggest that swallow non-inspiratory flow may trigger inspiratory support in the BiPAP mode, resulting in a risk of aspiration.

Purpose As shown in our previous study, inspiration after swallowing (SW-I) increases during the bi-level positive airway pressure ventilation (BiPAP) in healthy subjects because swallowing-associated non-inspiratory flow (SNIF) triggers inspiratory support, while SW-I during continuous positive pressure ventilation (CPAP) is rare. In the present study, we evaluated the coordination between breathing and swallowing during spontaneous breathing, BiPAP, and CPAP in patients with chronic obstructive pulmonary disease (COPD). Patients and methods This study is a prospective intervention study at the Hoshigaoka Medical Center (November 01, 2015–April 30, 2018). We simultaneously recorded the respiratory flow, laryngeal motion, and swallowing sounds during saliva swallowing in patients with COPD. We estimated the respiratory phase after swallowing, frequency of SNIF, the duration of the respiratory pause during swallowing, and timing of swallowing in the respiratory cycle and compared these parameters among control, CPAP, and BiPAP conditions. Results The expiration after swallowing (SW-E) frequency was associated with the occurrence of SNIF ( p <0.01), pause duration ≤0.8 s ( p <0.01), and timing of swallowing at the intermediate respiratory phase (50–80% of the respiratory cycle from the onset of inspiration) ( p <0.01). In particular, the occurrence of SNIF most substantially affected the SW-E frequency. The SW-I frequencies under the control, CPAP, and BiPAP conditions were 35.0%, 3.0%, and 37.7%, respectively. The pause durations were shorter during CPAP and BiPAP than under the control condition ( p <0.01). During CPAP, the occurrence rates of SW-E. Residual denotes the percentage difference between observed and expected values (residual =10.8: p <0.01) and SNIF (residual =9.1: p <0.01) were significantly increased, and timing of swallowing shifted toward the intermediate respiratory phase (residual=3.5: p <0.01). Conclusion CPAP decreases the SW-I frequency, increases the SNIF occurrence, and normalizes the timing of swallowing, all of which suggest that CPAP alleviates the risk of aspiration in patients with COPD.

[Purpose] The purpose of this study was to examine, using a plethysmogram of the fingertips, autonomic responses at motor intensities of 30% or 50% of maximum voluntary contraction (MVC) during isometric handgrip exercise (IHG). [Participants and Methods] The participants of this study were 15 healthy persons. The finger volume pulse wave of each participant was measured continuously, using a BACS Advance equipment (TAOS Co.), for a total of 17 minutes: 5 minutes before IHG (Pre), 2 minutes during IHG (IHG), the first 5 minutes after IHG (Post 5), and then the second 5 minutes after IHG (Post 10). To evaluate autonomic nervous system activity, we used the Detrended fluctuation analysis (DFA) and Approximate Entropy (ApEn). [Results] During IHG, the pulse rate was significantly higher and the ApEn value was significantly lower than during the other periods of measurement. Compared to other analyzed parameters, ApEn decreased during IHG, but returned to its initial Pre period level during the Post 5 period. The α 1 value derived from the DFA analysis remained at a value of 1 during each measurement time point, indicating the absence of malfunctions in autonomic response. [Conclusion] Isometric handgrip exercise with 30% MVC seemed to be useful for the assessment of autonomic nervous system response.