Heart-related parameters monitoring apparatus

Abstract

A non-invasive method, and an apparatus, for determining heart-related parameters in patients. The method and apparatus determine pulse pressure, time constant of the arterial system, systolic and diastolic pressure, peripheral resistance, cardiac output and mean arterial blood pressure.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This ((1/Δt_c))^Y

φ_i =((1/Δt_i))^Y

Δt_c =(Δt'_iφc

Δt_i =Δt'_iφ

where

T_c =T at calibration Δt_c =Δt at calibration Δt'_iφ (see FIG. 4B)

t_c =t at calibration Δt'_iφ_c (see FIG. 4B)

φ_c =(T_c /t_c)=(T/t) at calibration φ_c =(1/Δt)^y at calibration

y=constant

The remainder of the terms in equation 5' are the same as similar terms in equation 5.

Determination of ratio R (FIG. 4b)

From FIG. 4b, the ratio R is

R_i =(ΔV_it /ΔV_i)

where

ΔV_it =change in volume at predetermined time ti

ΔV_i =total volume change during cycle i

t_i =time such that Δt_i =K_T Δt'_iφ

K_T =constant

Estimation of pulse pressure, PP ##EQU10## where PP_i =pulse pressure=p_s -P_d

P_s =systolic blood pressure

P_d =diastolic blood pressure

k=constant

K'_T =constant ≃ K_T

In FIG. 4B

Δ V'_i =ΔV_i -ΔV_it ##EQU11## wherein from the above equation: ##EQU12## multiply numerator and denominator by e^kPP i ##EQU13##

Determination of r

From FIG. 4

r_i = (V_imax /ΔV_i)G(t)

where

V_imax =maximum time rate of volume increase in cycle i

ΔV_i =total volume increase during cycle i

From FIG. 4b

r_i = (V_it ΔV_i)G(t)

r_i =(V_it /V_i)G(t)

V_it =time rate of increase of volume V_i(t) at time t_i

ΔV_i =total volume increase of volume during ΔV_i =total increase of volume during time interval Δt_iφ

Estimation of Mean Blood Pressure

(1) P_mi '=K₁ r_ic^a

K₁ =calibration constant

P_mi '=(P s +P_d)/2-P_o

P_si =systolic blood pressure, in cycle i

P_mi =(P s +P_d)/2

P_di =diastolic blood pressure, in cycle i

a=constant

P_o =constant

(2) e^kp mi=K₂ R_ic^b (2) e^kp mi=K₂ r_ic^b

where

K₂ =constant (calibration)

b=constant ##EQU14## where P_mo =constant at calibration

φ₁i +φ₂i =PP_i =pulse pressure during cycle i

k=constant

j=constant

solve equation by making LHS=RHS by varying φ₁i and φ₂i (φ₂i =PP_i -φ₁i)

then

P_si =P_mo +φ₂i +P₀

P_di =P_mo -φ₁i +P_o

P_mi =(P si +P_di)/2

P₀ =constant

r_i =ratio of exponentials

K₃ =coefficient (variable or constant)

Correction for r_i

r_i (corrected)=r_ic =r_i e^m(φ^_o-φ^_i)

m=constant

φ₀ =PP_i at calibration

φ_i =current value of PP_i.

Equation (9) above is only one form which this particular equation can take. By simple mathematical manipulations, the invention may take two other forms as per (10) and (11) below. What follows is the manipulations as well as the two other forms of the equation:

As above noted

φ₂i +φ₁i =PP_i =P_si -P_di

φ₂i +φ₁i =(P si -P_o)-(P di -P_o)

Let

P'_si =P_si -P_o

p'_di =P_di -P₀

φ₂i +φ₁i =P'_si -P'_di

add and subtract P_mo on RHS above

φ₂i +φ₁i =P'_si -P_mo +P_mo -P'_di (A)

φ₂i and φ₁i can take on any values in satisfying the above equation (A)

Put φ₂i =P'_si -P_mo

and φ₁i =P_mo -P'_di in equation (9)

then ##EQU15## simplifying the denominator ##EQU16##

To solve equation 11:

(1) Set P'_di =P'_si -PP_i and solve for P'_si

P'_mi =(P_si +P_di)/2-P_o

(2) Set P'_si =P'_di -PP_i and solve for P'_di

Although particular embodiments have been illustrated, this was for the purpose of describing, but not limiting, the invention. Various modifications, which will come readily to the mind of one skilled in the art, are within the scope of the invention as defined in the appended claims.

P_mi =(P_si +P_di)/2

Claims

1. Apparatus for determining the magnitude of heart-related parameters in a patient;

comprising;

means for detecting blood volume, and thereby blood volume variation, in said patient, and for providing a signal representative of said blood volume, and thereby said blood volume variation;

said means for detecting being attachable to said patient to thereby detect said blood volume, and thereby said blood volume variation;

said blood volume variation being cyclic in nature whereby said signal comprises a cyclic curve having, in each cycle of variation, a variable slope, a maximum amplitude representative of the maximum amount of blood volume, a minimum amplitude representative of the minimum amount of blood volume, a first time interval between said minimum amplitude and said maximum amplitude, a maximum rate of change of said signal being representative of the maximum rate of increase of blood volume, a second time interval between the minimum amplitude and the time of the maximum rate of change of said signal, a first difference in amplitude between said maximum amplitude and said minimum amplitude, a second difference in amplitude between the maximum amplitude and the amplitude at the time of maximum rate of change of said signal being representative of the difference in volume between the maximum amount of blood volume and the volume at the time of maximum rate of change of said blood volume, and a pulse repetition period;

means for measuring said maximum amplitude, said minimum aplitude, said maximum rate of change of said signal, said first difference, said second different, said first time interval, and said second time interval; and

means for calculating the magnitude of selected ones of said parameters, said means for calculating being connected to both said means for detecting and means for measuring;

wherein means for calculating calculates the magnitude of the pulse pressure parameter in accordance with the following expression; ##EQU17## wherein p_pi =pulse pressure during cycle i

K_pp =constant determined by a first calibration

r₁ =constant

r₂ =constant

R_il =(ΔV_iVm /ΔV_i)

where ΔV_iVm =volume change at time t_iVm during cycle i corresponding to maximum rate of volume change, V_imax

ΔV_i =maximum volume change during cycle i

Δt_iVm =time interval from start of cycle i to time of maximum rate of volume change V_imax.

2. Apparatus for determining the magnitude of heart-related parameters in a patient;

comprising;

means for detecting blood volume, and thereby blood volume variation, in said patient, and for providing a signal representative of said blood volume, and thereby said blood volume variation;

said means for detecting being attachable to said patient to thereby detect said blood volume, and thereby said blood volume variation;

said blood volume variation being cyclic in nature whereby said signal comprises a cyclic curve having, in each cycle of variation, a variable slope, a maximum amplitude representative of the maximum amount of blood volume, a minimum amplitude representative of the minimum amount of blood volume, a first time interval between said minimum amplitude and said maximum amplitude, a maximum rate of change of said signal being representative of the maximum rate of increase of blood volume, a second time interval between the minimum amplitude and the time of the maximum rate of change of said signal, a first difference in amplitude between said maximum amplitude and said minimum amplitude, a second difference in amplitude between the maximum amplitude and the amplitude at the time of maximum rate of change of said signal being representative of the difference in volume between the maximum amount of blood volume and the volume at the time of maximum rate of change of said blood volume, and a pulse repetition period;

means for measuring said maximum amplitude, said minimum aplitude, amplitude, said maximum rate of change of said signal, said first difference, said second different, difference, said first time interval, and said second time interval; and

means for calculating the magnitude of selected ones of said parameters, said means for calculating being connected to both said means for detecting and means for measuring;

wherein means for calculating calculates calculates the magnitude of the mean arterial blood pressure, p_mi parameter in accordance with the following expression: ##EQU18## where K₄ =constant determined for each subject

b₃ =constant

p_mmi =pseudo mean arterial blood pressure during cycle i

Δ_i ΔV_i =maximum volume change during cycle i ##EQU19##

3. Apparatus for determining the magnitude of heart-related parameters in a patient;

comprising;

means for detecting blood volume, and thereby blood volume variation, in said patient, and for providing a signal representative of said blood volume, and thereby said blood volume variation;

said means for detecting being attachable to said patient to thereby detect said blood volume, and thereby said blood volume variation;

said volume variation being cyclic in nature whereby said signal comprises a cyclic curve having, in each cycle of variation, a variable slope, a maximum amplitude representative of the maximum amount of blood volume, a minimum amplitude representative of the minimum amount of blood volume, a first time interval between said minimum amplitude and said maximum amplitude, a maximum rate of change of said signal being representative of the maximum rate of increase of blood volume, a second time interval between the minimum amplitude and the time of the maximum rate of change of said signal, a first difference in amplitude between said maximum amplitude and said minimum amplitude, a second difference in amplitude between the maximum amplitude and the amplitude at the time of maximum rate of change of said signal being representative of the difference in volume between the maximum amount of blood volume and the volume at the time of maximum rate of change of said blood volume, and a pulse repetition period;

means for measuring said maximum amplitude, said minimum aplitude, amplitude, said maximum rate of change of said signal, said first difference, said second different, difference, said first time interval, and said second time interval; and

means for calculating the magnitude of selected ones of said parameters, said means for calculating being connected to both said means for detecting and means for measuring;

wherein means for calculating calculates the magnitude of the systolic pressure (p_si) parameter in accordance with the following expression:

p_si =P_mi +(1-g₀)p _pi

wherein

g₀ =constant.

4. Apparatus for determining the magnitude of heart-related parameters in a patient;

comprising:

means for detecting blood volume, and thereby blood volume variation, in said patient, and for providing a signal representative of said blood volume, and thereby said blood volume variation;

said means for detecting being attachable to said patient to thereby detect said blood volume, and thereby said blood volume variation;

said blood volume variation being cyclic in nature whereby said signal comprises a cyclic curve having, in each cycle of variation, a variable slope, a maximum amplitude representative of the maximum amount of blood volume, a minimum amplitude representative of the minimum amount of blood volume, a first time interval between said minimum amplitude and said maximum amplitude, a maximum rate of change of said signal being representative of the maximum rate of increase of blood volume, a second time interval between the minimum amplitude and the time of the maximum rate of change of said signal, a first difference in amplitude between said maximum amplitude and said minimum amplitude, a second difference in amplitude between the maximum amplitude and the amplitude at the time of maximum rate of change of said signal being representative of the difference in volume between the maximum amount of blood volume and the volume at the time of maximum rate of change of said blood volume, and a pulse repetition period;

means for measuring said maximum amplitude, said minimum aplitude, amplitude, said maximum rate of change of said signal, said first difference, said second different, difference, said first time interval, and said second time interval; and

means for calculating the magnitude of selected ones of said parameters, said means for calculating being connected to both said means for detecting and means for measuring;

wherein means for calculating calculates the magnitude of the systolic pressure (p_si) parameter in accordance with the following expression:

p_si =P_mi +(1-g_i)p _pi

wherein:

g_i =(ΔV_iAV /ΔV_i)

p_pi =pulse pressure during cycle i

ΔV_i =represented by said first difference

ΔV_iAV =represented by the difference between said minimum amplitude and an amplitude equal to the average value of a pulse in a cycle i.

5. Apparatus for determining the magnitude of heart-related parameters in a patient;

comprising;

means for detecting blood volume, and thereby blood volume variation, in said patient, and for providing a signal representative of said blood volume, and thereby said blood volume variation;

said means for detecting being attachable to said patient to thereby detect said blood volume, and thereby said blood volume variation;

said blood volume variation being cycle cyclic in nature whereby said signal comprises a cyclic curve having, in each cycle of variation, a variable slope, a maximum amplitude representative of the maximum amount of blood volume, a minimum amplitude representative of the minimum amount of blood volume, a first time interval between said minimum amplitude and said maximum amplitude, a maximum rate of change of said signal being representative of the maximum rate of increase of blood volume, a second time interval between the minimum amplitude and the time of the maximum rate of change of said signal, a first difference in amplitude between said maximum amplitude and said minimum amplitude, a second difference in amplitude between the maximum amplitude and the amplitude at the time of maximum rate of change of said signal being representative of the difference in volume between the maximum amount of blood volume and the volume at the time of maximum rate of change of said blood volume, and a pulse repetition period;

means for measuring said maximum amplitude, said minimum aplitude, amplitude, said maximum rate of change of said signal, said first difference, said second different, difference, said first time interval, and said second time interval; and

means for calculating the magnitude of selected ones of said parameters, said means for calculating being connected to both said means for detecting and means for measuring;

wherein means for calculating calculates the magnitude of the arterial blood pressure, p_mi parameter in accordance with the following expression: ##EQU20## where K₄ =constant determined for each subject

b₃ =constant

p_mmi =pseudo mean arterial blood pressure during cycle i

ΔV_i =maximum volume change during cycle i ##EQU21## p_o =constant where

G(t)=a function of t.

6. A method for determining the magnitude of heart-related parameters in a patient;

comprising:

detecting blood volume, and thereby blood volume variation, in said patient and providing a signal representative of said blood volume, and thereby said blood volume variation;

said blood volume variation being cyclic in nature whereby said signal comprises a cyclic curve having, in each cycle of variation, a variable slope, a maximum amplitude representative of the maximum amount of blood volume, a minimum amplitude representative of the minimum amount of blood volume, a first time interval between said maximum amplitude and said minimum amplitude, a maximum rate of change of said signal being representative of the maximum rate of change of blood volume, a second time interval between the minimum amplitude and the time of the maximum rate of change of said signal, a first difference in amplitude between said maximum amplitude and said minimum amplitude, a second difference in amplitude between the maximum amplitude and the amplitude at the time of maximum change of rate of said signal being representative of the difference in volume between the maximum amount of blood volume and the volume at the time of maximum rate of change of said blood volume, and a pulse repetition period;

measuring said maximum amplitude, said minimum amplitude, said maximum rate of change of said signal, said first difference, said second difference, said first time interval, and said second time interval; and

calculating the magnitude of the pulse pressure parameter in accordance with the following expression: ##EQU22## wherein p_pi =pulse pressure during cycle i

K_pp =constant determined by a first calibration

r₁ =constant

r₂ =constant

R_il =(ΔV_iVm /ΔV_i)

where

ΔV_iVm =volume change at time t_iVm during cycle i corresponding to maximum rate of volume change, V_imax

ΔV_iVm =volume change at time t_iVm during cycle i corresponding to maximum rate of volume change, V_imax

ΔV_i =maximum volume change during cycle i

Δt_iVm =time interval from start of cycle i to time of maximum rate of volume change V_imax.

7. A method for determining the magnitude of heart-related parameters in a patient;

comprising:

detecting blood volume, and thereby blood volume variation, in said patient and providing a signal representative of said blood volume, and thereby said blood volume variation;

said blood volume variation being cyclic in nature whereby said signal comprises a cyclic curve having, in each cycle of variation, a variable slope, a maximum amplitude representative of the maximum amount of blood volume, a minimum amplitude representative of the minimum amount of blood volume, a first time interval between said maximum amplitude and said minimum amplitude, a maximum rate of change of said signal being representative of the maximum rate of change of blood volume, a second time interval between the minimum amplitude and the time of the maximum rate of change of said signal, a first difference in amplitude between said maximum amplitude and said minimum amplitude, a second difference in amplitude between the maximum amplitude and the amplitude at the time of maximum change of rate of said signal being representative of the difference in volume between the maximum amount of blood volume and the volume at the time of maximum rate of change of said blood volume, and a pulse repetition period;

measuring said maximum amplitude, said minimum amplitude, said maximum rate of change of said signal, said first difference, said second difference, said first time interval, and said second time interval; and

calculating the magnitude of the mean artial arterial pressure p_mi in accordance with the following expression: ##EQU23## where K₄ =constant determined for each subject

b₃ =constant

p_mmi =pseudo mean arterial blood pressure during cycle i

ΔV_i =maximum volume change during cycle i

ΔV_imax =maximum time rate of change of ΔV_i =V_imax ##EQU24##

8. A method for determining the magnitude of heart-related parameters in a patient;

comprising:

detecting blood volume, and thereby blood volume variation, in said patient and providing a signal representative of said blood volume, and thereby said blood volume variation;

said blood volume variation being cyclic in nature whereby said signal comprises a cyclic curve having, in each cycle of variation, a variable slope, a maximum amplitude representative of the maximum amount of blood volume, a minimum amplitude representative of the minimum amount of blood volume, a first time interval between said maximum amplitude and said minimum amplitude, a maximum rate of change of said signal being representative of the maximum rate of change of blood volume, a second time interval between the minimum amplitude and the time of the maximum rate of change of said signal, a first difference in amplitude between said maximum amplitude and said minimum amplitude, a second difference in amplitude between the maximum amplitude and the amplitude at the time of maximum change of rate of said signal being representative of the difference in volume between the maximum amount of blood volume and the volume at the time of maximum rate of change of said blood volume, and a pulse repetition period;

measuring said maximum amplitude, said minimum amplitude, said maximum rate of change of said signal, said first difference, said second difference, said first time interval, and said second time interval; and

calculating the magnitude of the systolic pressure (p_si parameter in accordance with the following expression:

p_si =P_mi +(1-g₀)p _pi

wherein

g₀ =constant.

9. A method for determining the magnitude of heart-related parameters in a patient;

comprising:

detecting blood volume, and thereby blood volume variation, in said patient and providing a signal representive of said blood volume, and thereby said blood volume variation;

said blood volume variation being cyclic in nature whereby said signal comprises a cyclic curve having, in each cycle of variation, a variable slope, a maximum amplitude representative of the maximum amount of blood volume, a minimum amplitude representative of the minimum amount of blood volume, a first time interval between said maximum amplitude and said minimum amplitude, a maximum rate of change of said signal being representative of the maximum rate of change of blood volume, a second time interval between the minimum amplitude and the time of the maximum rate of change of said signal, a first difference in amplitude between said maximum amplitude and said minimum amplitude, a second difference in amplitude between the maximum amplitude and the amplitude at the time of maximum change of rate of said signal being representative of the difference in volume between the maximum amount of blood volume and the volume at the time of maximum rate of change of said blood volume, and a pulse repetition period;

measuring said maximum amplitude, said minimum amplitude, said maximum rate of change of said signal, said first difference, said second difference, said first time interval, and said second time interval; and

calculating the magnitude of the systolic pressure (p_si) parameter in accordance with the following expression:

p_si =P_mi +(1-g_i)p _pi

wherein:

g_i =(ΔV_iAV /ΔV_i)

p_pi =pulse pressure during cycle i

ΔV_i =represented by said first difference

ΔV_iAV =represented by the difference between said minimum amplitude and an amplitude equal to the average value of a pulse in a cycle i.

10. A method for determining the magnitude of heart-related parameters in a patient;

comprising:

detecting blood volume, and thereby blood volume variation, in said patient and providing a signal representative of said blood volume, and thereby said blood volume variation;

said blood volume variation being cyclic in nature whereby said signal comprises a cyclic curve having, in each cycle of variation, a variable slope, a maximum amplitude representative of the maximum amount of blood volume, a minimum amplitude representative of the minimum amount of blood volume, a first time interval between said maximum amplitude and said minimum amplitude, a maximum rate of change of said signal being representative of the maximum rate of change of blood volume, a second time interval between the minimum amplitude and the time of the maximum rate of change of said signal, a first difference in amplitude between said maximum amplitude and said minimum amplitude, a second difference in amplitude between the maximum amplitude and the amplitude at the time of maximum change of rate of said signal being representative of the difference in volume between the maximum amount of blood volume and the volume at the time of maximum rate of change of said blood volume, and a pulse repetition period;

measuring said maximum amplitude, said minimum amplitude, said maximum rate of change of said signal, said first difference, said second difference, said first time interval, and said second time interval; and

calculating the magnitude of the arterial blood pressure, p_mi parameter in accordance with the following expression: ##EQU25## where

K₄ =constant determined for each subject

b₃ =constant

p_mmi =pseudo mean arterial blood pressure during cycle i

ΔV_i =maximum volume change during cycle i

ΔV_imax =maximum time rate of change of V_i =V_imax

p_o =constant

G(t)=a function of t and t.

11. Apparatus for determining the magnitude of heart-related parameters in a patient;

comprising:

means for detecting blood volume, and thereby blood volume variation, in said patient, and for providing a signal representative of said blood volume, and thereby said blood volume variation;

said means for detecting being attachable to said patient to thereby detect said blood volume, and thereby said blood volume variation;

said blood volume variation being cyclic in nature whereby said signal comprises a cyclic curve having, in each cycle of variation, a variable slope, a maximum amplitude representative of the maximum amount of blood volume, a minimum amplitude representative of the minimum amount of blood volume, a first time interval between said minimum amplitude and said maximum amplitude, a maximum rate of change of said signal being representative of the maximum rate of increase of blood volume, a second time interval between the minimum amplitude and the time of the maximum rate of change of said signal, a first difference in amplitude between said maximum amplitude and said minimum amplitude, a second difference in amplitude between the maximum amplitude and the amplitude at the time of maximum rate of change of said signal being representative of the difference in volume between the maximum amount of blood volume and the volume at the time of maximum rate of change of said blood volume, and a pulse repetition period;

means for measuring said maximum amplitude, said minimum aplitude, amplitude, said maximum rate of change of said signal, said first difference, said second different, difference, said first time interval, and said second time interval; and

means for calculating the magnitude of selected ones of said parameters, said means for calculating being connected to both said means for detecting and means for measuring;

wherein means for calculating calculates the magnitude of the pulse pressure parameter in accordance with the following expression: ##EQU26## wherein p_pi =pulse pressure during cycle i

K_pp =constant determined by a first calibration

r₁ =constant

r₂ =constant

R_i1 =ΔV_iVm /ΔV_i

where

ΔV_iVm =volume change at preselected time t_iVm during cycle i

ΔV_i =maximum volume change during cycle i

Δt_iVm =time interval from start of cycle i to preselected time of t_iVm.

12. A method for determining the magnitude of heart-related parameters in a patient;

comprising:

detecting blood volume, and thereby blood volume variation, in said patient and providing a signal representative of said blood volume, and thereby said blood volume variation;

said blood volume variation being cyclic in nature whereby said signal comprises a cyclic curve having, in each cycle of variation, a variable slope, a maximum amplitude representative of the maximum amount of blood volume, a minimum amplitude representative of the minimum amount of blood volume, a first time interval between said maximum amplitude and said minimum amplitude, a maximum rate of change of said signal being representative of the maximum rate of charge change of blood volume, a second time interval between the minimum amplitude and the time of the maximum rate of change of said signal, a first difference in amplitude between said maximum amplitude and said minimum amplitude, a second difference in amplitude between the maximum amplitude and the amplitude at the time of maximum change of rate of said signal being representative of the difference in volume between the maximum amount of blood volume and the volume at the time of maximum rate of change of said blood volume, and a pulse repetition period;

measuring said maximum amplitude, said minimum amplitude, said maximum rate of change of said signal, said first difference, said second difference, said first time interval, and said second time interval; and

calculating the magnitude of the pulse pressure parameter in accordance with the following expression: ##EQU27## wherein p_pi =pulse pressure during cycle i

K_pp =constant determined by a first calibration

r₁ =constant

r₂ =constant

R_i1 =(ΔV_iVm /V_i)

where

ΔV_iVm =volume change at preselected time t_iVm during cycle i

ΔV_i =maximum volume change during cycle i

Δt_iVm =time interval from start of cylcle i to predetermined time of t_iVm.

13. Apparatus for determining the magnitude of heart-related parameters in a patient;

comprising;

means for detecting blood volume, and thereby blood volume variation, in said patient, and for providing a signal representative of said blood volume, and thereby said blood volume variation;

said means for detecting being attachable to said patient to thereby detect said blood volume, and thereby said blood volume variation;

said blood volume variation being cyclic in nature whereby said signal comprises a cyclic curve having, in each cycle of variation, a variable slope, a maximum amplitude representative of the maximum amount of blood volume, a minimum amplitude representative of the minimum amount of blood volume, a first time interval between said minimum amplitude and said maximum amplitude, a maximum rate of change of said signal being representative of the maximum rate of increase of blood volume, a second time interval between the minimum amplitude and the time of the maximum rate of change of said signal, a first difference in amplitude between said maximum amplitude and said minimum amplitude, a second difference in amplitude between the maximum amplitude and the amplitude at the time of maximum rate of change of said signal being representative of the difference in volume between the maximum amount of blood volume and the volume at the time of maximum rate of change of said blood volume, and a pulse repetition period;

means for measuring said maximum amplitude, said minimum amplitude, said maximum rate of change of said signal, said first difference, said second different, said first time interval, and said second time interval; and

means for calculating the magnitude of selected ones of said parameters, said means for calculating being connected to both said means for detecting and means for measuring;

wherein the means for calculating calculates the magnitude of the mean pressure parameter in accordance with the following expression:

(1) p'_mi =K₁ r_ic^a

where

K₁ =calibration constant

p'_mi =(p_s +p_d)/2-p_o

p_si =systolic blood pressure, in cycle i

p_mi =(p_s +p_d)/2

p_di =diastolic blood pressure, in cycle i

a=constant

p_o =constant.

14. A method for determining the magnitude of heart-related parameters in a patient;

comprising:

detecting blood volume, and thereby blood volume variation, in said patient and providing a signal representation representative of said blood volume, and thereby said blood volume variation;

said blood volume variation being cyclic in nature whereby said signal comprises a cyclic curve having, in each cycle of variation, a variable slope, a maximum amplitude representative of the maximum amount of blood volume, a minimum amplitude representative of the minimum amount of blood volume, a first time interval between said maximum amplitude and said minimum amplitude, a maximum rate of change of said signal being representative of the maximum rate of change of blood volume, a second time interval between the minimum amplitude and the time of the maximum rate of change of said signal, a first difference in amplitude between said maximum amplitude and said minimum amplitude, a second difference in amplitude between the maximum amplitude and the amplitude at the time of maximum change of rate of said signal being representative of the difference in volume between the maximum amount of blood volume and the volume at the time of maximum rate of change of said blood volume, and a pulse repetition period;

measuring said maximum amplitude, said minimum amplitude, said maximum rate of change of said signal, said first difference, said second difference, said first time interval, and said second time interval; and

calculating the magnitude of mean pulse pressure in accordance with the following expression:

(1) p_mi =K₁ r_ic^a

(1) p'_mi =K_l r_ic a

where

K₁ =calibration constant

p'_mi =(p_s +p_d)/2-p_o

p'_mi =(p_si +p_di)/2-p_o

p_si =systolic blood pressure, in cycle i

p_mi =(p_s +p_d)/2

p_mi =(p_si +p_di)/2

p_di =diastolic blood pressure, in cycle i

a=constant

p_o =constant.

15. Apparatus for determining the magnitude of heart-related parameters in a patient;

comprising;

means for detecting blood volume, and thereby blood volume variation, in said patient, and for providing a signal representative of said blood volume, and thereby said blood volume variation;

said means for detecting being attachable to said patient to thereby detect said blood volume, and thereby said blood volume variation;

said blood volume variation being cyclic in nature whereby said signal comprises a cyclic curve having, in each cycle of variation, a variable slope, a maximum amplitude representative of the maximum amount of blood volume, a minimum amplitude representative of the minimum amount of blood volume, a first time interval between said minimum amplitude and said maximum amplitude, a maximum rate of change of said signal being representative of the maximum rate of increase of blood volume, a second time interval between the minimum amplitude and the time of the maximum rate of change of said signal, a first difference in amplitude between said maximum amplitude and said minimum amplitude, a second difference in amplitude between the maximum amplitude and the amplitude at the time of maximum rate of change of said signal being representative of the difference in volume between the maximum amount of blood volume and the volume at the time of maximum rate of change of said blood volume, and a pulse repetition period;

means for measuring said maximum amplitude, said minimum amplitude, said maximum rate of change of said signal, said first difference, said second different, difference, said first time interval, and said second time interval; and

means for calculating the magnitude of selected ones of said parameters, said means for calculating being connected to both said means for detecting and means for measuring;

wherein the means for calculating calculates implicitly the magnitude of the mean pulse pressure in accordance with the following expression: ##EQU28## where p_mo =constant at calibration

φ₁i +φ₂i =PP_i =pulse pressure during cycle i

k=constant

j=constant

p_si =P_mo +φ₂i +p_o

p_di =P_mo -φ₁i +p_o

p_mi =(p _{si +pdi)/2}

p_o =constant

r_i =ratio of exponentials

K₃ =coefficient (variable or constant).

16. A method for determining the magnitude of heart-related parameters in a patient;

comprising:

detecting blood volume, and thereby blood volume variation, in said patient and providing a signal representative of said blood volume, and thereby said blood volume variation;

said blood volume variation being cyclic in nature whereby said signal comprises a cyclic curve having, in each cycle of variation, a variable slope, a maximum amplitude representative of the maximum amount of blood volume, a minimum amplitude representative of the minimum amount of blood volume, a first time interval between said maximum amplitude and the said minimum amplitude, a maximum rate of change of said signal being representative of the maximum rate of change of blood volume, a second time interval between the minimum amplitude and the time of the maximum rate of change of said signal, a first difference in amplitude between said maximum amplitude and said minimum amplitude, a second difference in amplitude between the maximum amplitude and the amplitude at the time of maximum change of rate of said signal being representative of the difference in volume between the maximum amount of blood volume and the volume at the time of maximum rate of change of said blood volume, and a pulse repetition period;

measuring said maximum amplitude, said minimum amplitude, said maximum rate of change of said signal, said first difference, said second difference, said first time interval, and said second time interval; and

wherein the means for calculating calculates implicitly the magnitude of mean pulse pressure in accordance with the following expressure expression: ##EQU29## where p_mo =constant at calibration

φ₁i +φ₂i =PP_i =pulse pressure during cycle i

k=constant

j=constant

p₂i =P_mo +φ₂i +p_o

p_si =P_mo +φ₂i +p_o

p_di =P_mo -φ₁i +p_o

p_mi =(p _{si +pdi)/2}

p_o =constant

r_i =ratio of exponentials

K₃ =coefficient (variable or constant).

17. Apparatus for determining the magnitude of heart-related parameters in a patient;

comprising:

means for detecting blood volume, and thereby blood volume variation, in said patient, and for providing a signal representative of said blood volume, and thereby said blood volume variation;

said means for detecting being attachable to said patient to thereby detect said blood volume, and thereby said blood volume variation;

said blood variation being cyclic in nature whereby said signal comprises a cyclic curve having, in each cycle of variation, a variable slope, a maximum amplitude representative of the maximum amount of blood volume, a minimum amplitude representative of the minimum amount of blood volume, a first time interval between said minimum amplitude and said maximum amplitude, a maximum rate of change of said signal being representative of the maximum rate of increase of blood volume, a second time interval between the minimum amplitude and the time of the maximum rate of change of said signal, a first difference in amplitude between said maximum amplitude and said minimum amplitude, a second difference in amplitude between the maximum amplitude and the amplitude at the time of maximum rate of change of said signal being representative of the difference in volume between the maximum amount of blood volume and the volume at the time of maximum rate of change of said blood volume, and a pulse repetition period;

means for measuring said maximum amplitude; said minimum amplitude, said maximum rate of change of said signal, said first difference, said second difference, said first time interval, and said second time interval; and

means for calculating the magnitude of selected ones of said parameters, said means for calculating being connected to both said means for detecting and means for measuring;

wherein means for calculating calculates the magnitude of the pulse pressure parameter in accordance with the following expression; ##EQU30## where PP_i =Pulse pressure-- p_s -p_d

p_s =Systolic blood pressure

p_d =diastolic blood pressure

k=constant

K'=constant.

18. A method for determining the magnitude of heart-related parameters in a patient;

comprising:

detecting blood volume, and thereby blood volume variation, in said patient and providing a signal representative of said blood volume, and thereby said blood volume variation;

said blood volume variation being cyclic in nature whereby said signal comprises a cyclic curve having, in each cycle of variation, a variable slope, a maximum amplitude representative of the maximum amount of blood volume, a minimum amplitude representative of the minimum amount of blood volume, a first time interval between said maximum amplitude and said minimum amplitude, a maximum rate of change of said signal being representative of the maximum rate of change of blood volume, a second time interval between the minimum amplitude and the time of the maximum rate of change of said signal, a first difference in amplitude between said maximum amplitude and said minimum amplitude, a second difference in amplitude between the maximum amplitude and the amplitude at the time of maximum change of rate of said signal being representative of the difference in volume between the maximum amount of blood volume and the volume at the time of maximum rate of change of said blood volume, and a pulse repetition period;

measuring said maximum amplitude, said minimum amplitude, said maximum rate of change of said signal, said first difference, said second difference, said first time interval, and said second time interval; and

calculating the magnitude of the mean arterial pressure p_mi in accordance with the following expression: ##EQU31## where PP_i =Pulse Pressure=P_s -p_d

p_s =Systolic blood pressure

p_d =Diastolic blood pressure

k=constant

K'=constant.