Volume status monitor: peripheral venous pressure, hypervolemia and coherence analysis
Systems and methods are provided for monitoring changes in blood volume using waveforms in the peripheral vasculature. In particular, the systems and methods relate to detecting ventilation-induced variation (VIV) of waveforms in the peripheral vasculature. Advantageously, the systems and methods may relate to analyzing VIV in peripheral venous pressure (PVP). Thus, the VIV of PVP may be measured, wherein decreased VIV is indicative of decreased blood volume In exemplary embodiments, such as involving spontaneous breathing, it may be necessary to account for changes in respiratory signal strength. Thus systems and methods are also provided for assessing coherence between ventilation and VIV for a flow or pressure waveform. Specifically, coherence is evaluated by comparing the waveform to a detected respiratory signal. Finally, systems and method are provided for distinguishing the impact of respiration on the PG signal during hypervolemia as compared to hypovolemia. Such systems and methods may advantageously be utilized to monitor fluid status during fluid replacement.
1. A method for compensating a cardiovascular waveform having ventilation-induced variation for pulmonary effort using a processor, the method comprising:
generating a cardiovascular waveform representing physiological characteristics of a subject;
generating a respiratory signal for the subject; and
using a processor to calculate the total power spectral intensity due to respiration, wherein the calculating the total power spectral intensity due to respiration includes:
compensating the cardiovascular waveform for pulmonary effort by multiplying the power spectrum of the cardiovascular waveform by the power spectrum of the respiratory signal; and
detecting a change in amplitude of ventilation-induced variation (VIV) in the compensated cardiovascular waveform by integrating the resulting compensated waveform over a range of respiratory frequencies, wherein the change in amplitude is reflective of a physiological change in the subject.
2. The method of claim 1 , wherein the generated cardiovascular waveform is a peripheral venous pressure (PVP) waveform.
3. The method of claim 2 , wherein the PVP waveform is generated from an intravenous site.
4. The method of claim 2 , further comprising calculating an index comparing the amplitude of the VIV in the PVP waveform to one of: (i) an amplitude of the VIV in arterial blood pressure, and (ii) an amplitude of the VIV in a plethysmographic (PG) signal.
5. The method of claim 4 , further comprising detecting hypovolemia based on the index, wherein an index value less than one (1) is indicative of hypovolemia.
6. The method of claim 4 , further comprising detecting arterial vasoconstriction based on the index.
7. The method of claim 1 , wherein the detecting the change in amplitude of VIV in the PVP waveform further comprises determining a relative amplitude of the VIV of the PVP compared to mean PVP.
8. The method of claim 1 , further comprising monitoring fluid responsiveness based on the change in amplitude of the VIV in the compensated cardiovascular waveform.
9. The method of claim 1 , further comprising detecting hypovolemia based on the change in amplitude of the VIV in the compensated cardiovascular waveform.
10. The method of claim 1 , wherein the physiological change in the subject is a change in blood volume of the subject.
11. The method of claim 2 , wherein a decrease in the amplitude of the VIV in the compensated cardiovascular waveform is indicative of a decrease in blood volume.
12. The method of claim 1 , wherein the respiratory power spectrum is normalized prior to multiplication.
13. The method of claim 12 wherein the normalized respiratory power spectrum R n (ω) is equal to one of:
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14. The method of claim 1 , wherein the cardiovascular waveform power spectrum is normalized prior to multiplication.
15. A system for compensating a cardiovascular waveform having ventilation-induced variation for pulmonary effort, the system comprising:
means for generating a cardiovascular waveform representing physiological characteristics of a subject;
means for generating a respiratory signal for the subject; and
means for calculating the total power spectral intensity due to respiration,
wherein the calculating the total power spectral intensity due to respiration includes:
compensating the cardiovascular waveform for pulmonary effort by multiplying the power spectrum of the cardiovascular waveform by the power spectrum of the respiratory signal; and
detecting a change in amplitude of ventilation-induced variation (VIV) in the compensated cardiovascular waveform by integrating the resulting compensated waveform over a range of respiratory frequencies, wherein the change in amplitude is reflective of a physiological change in the subject.
16. The system of claim 15 , wherein the generated cardiovascular waveform is a peripheral venous pressure (PVP) waveform.
17. The system of claim 15 , wherein the respiratory power spectrum is normalized prior to multiplication.
18. The system of claim 17 wherein the normalized respiratory power spectrum R n (ω) is equal to one of:
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19. The system of claim 15 , wherein the cardiovascular waveform power spectrum is normalized prior to multiplication.
20. The system of claim 15 , wherein the generated cardiovascular waveform is a peripheral venous pressure (PVP) waveform.
21. The system of claim 20 , further comprising means for calculating an index comparing the amplitude of the VIV in the PVP waveform to one of: (i) an amplitude of the VIV in arterial blood pressure, and (ii) an amplitude of the VIV in a plethysmographic (PG) signal.
22. The system of claim 20 , wherein the detecting the change in amplitude of (VIV) in the PVP waveform further comprises determining a relative amplitude of the VIV of the PVP compared to mean PVP.