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Cardiogenic oscillations extracted from spontaneous breathing airway pressure and flow signal are related to chest wall motility and continuous positive airway pressure
Critical Carevolume 13, Article number: P7 (2009)
During mechanical ventilation, signal pulses within pressure and flow curves can be observed that are related to the activity of the beating heart. From a signal-processing view, these cardiogenic oscillations (COS) can be understood as repeated pulses that are transferred via the lungs and airways to the airway opening. It was demonstrated earlier that COS, achieved during breath-holding maneuvers, were influenced by changes in mechanical properties of the thorax . We hypothesized that these COS can be extracted from the airway pressure and flow signal during spontaneous breathing. Furthermore, we hypothesized that these isolated signals contain information about the mechanical properties of the respiratory system.
Fifteen healthy volunteers breathed spontaneously against continuous positive airway pressure (CPAP) of 0 to 9 cmH2O at normal thorax or at thorax bending, limiting motility to 90% of the normal circumference. Airway pressure and flow as well as an electrocardiogram were recorded at a sample frequency of 200 Hz. To isolate the signals that are related to the activity of the heart, pressure and flow data were aligned in time to the R-wave of the QRS complex and averaged.
Highly characteristic pressure and flow oscillations could be extracted from the spontaneous breathing signals. Both signals were closely related (r2 = 0.97 ± 0.02, each P < 0.0001). The pressure amplitude of the COS was influenced by CPAP (P = 0.049) and thorax motility (P < 0.001); in contrast, the flow amplitude was influenced only by thorax motility (P < 0.001).
COS can be extracted from the airway pressure and flow signal during spontaneous breathing. They contain information about the mechanical properties of the respiratory system. After further investigations, our new method potentially allows an estimation of compliance of the respiratory system during spontaneous breathing.
Bijaoui E, Baconnier PF, Bates JH: Mechanical output impedance of the lung determined from cardiogenic oscillations. J Appl Physiol 2001, 91: 859-865.