Tuyển tập các báo cáo nghiên cứu về y học được đăng trên tạp chí y học 'Respiratory Research cung cấp cho các bạn kiến thức về ngành y đề tài: "Positive End-Expiratory Pressure may alter breathing cardiovascular variability and baroreflex gain in . | Van de Louw et al. Respiratory Research 2010 11 38 http content 11 1 38 RESPIRATORY RESEARCH RESEARCH Open Access Positive End-Expiratory Pressure may alter breathing cardiovascular variability and baroreflex gain in mechanically ventilated patients Andry Van de Louw 1 2 Claire Médigue3 Yves Papelier4 and Francois Cottin1 Abstract Background Baroreflex allows to reduce sudden rises or falls of arterial pressure through parallel RR interval fluctuations induced by autonomic nervous system. During spontaneous breathing the application of positive end-expiratory pressure PEEP may affect the autonomic nervous system as suggested by changes in baroreflex efficiency and RR variability. During mechanical ventilation some patients have stable cardiorespiratory phase difference and high-frequency amplitude of RR variability HF-RR amplitude over time and others do not. Our first hypothesis was that a steady pattern could be associated with reduced baroreflex sensitivity and HF-RR amplitude reflecting a blunted autonomic nervous function. Our second hypothesis was that PEEP widely used in critical care patients could affect their autonomic function promoting both steady pattern and reduced baroreflex sensitivity. Methods We tested the effect of increasing PEEP from 5 to 10 cm H2O on the breathing variability of arterial pressure and RR intervals and on the baroreflex. Invasive arterial pressure ECG and ventilatory flow were recorded in 23 mechanically ventilated patients during 15 minutes for both PEEP levels. HF amplitude of RR and systolic blood pressure SBP time series and HF phase differences between RR SBP and ventilatory signals were continuously computed by complex demodulation. Cross-spectral analysis was used to assess the coherence and gain functions between RR and SBP yielding baroreflex-sensitivity indices. Results At PEEP 10 the 12 patients with a stable pattern had lower baroreflex gain and HF-RR amplitude of variability than the 11 .
