Noninvasive system and method for enhanced arterial oxygen saturation determination and arterial blood pressure monitoring

A monitoring system for enhanced noninvasive monitoring of a patient's arterial oxygen saturation level, said system comprising:

• light means for periodically directing a first light beam and a second light beam into both capillary and arterial blood vessels contained in a patient's body part;
• pressure means for imposing a pressure on the patient's body part to increase the absorption of at least one of the light beams by blood in the arterial blood vessels in relation to blood in the nonarterial blood vessels, the light means being connected to the pressure means such that the first and second light beans are directed into the body part upon which the pressure is imposed by the pressure means;
• detection means for detecting relative amounts of each said light beam absorbed by arterial blood within the body part;
• processor means, electronically coupled to the pressure means and the detection means, for (a) controlling the pressure means so as to cause the pressure to be imposed on the body part for at least a portion of the time that the light beams are passing into the body part, and for (b) deriving from the detected relative amounts of each said light beam an arterial oxygen saturation level;
• and
• display means, electronically coupled to the processor means, for outputting a visually perceptible indication of the arterial oxygen saturation level.

A monitoring system for enhanced noninvasive monitoring of a patient's arterial oxygen saturation level, the system comprising:

• pressure means for imposing a pressure on a patient's body part, the pressure means steadily imposing a pressure which is less than completely occlusive to both arterial and capillary blood vessels contained in the body part and which is great enough to substantially increase the volume changes of the pulsing arterial vessels;
• first light means and second light means for periodically directing first and second light beams in the visible red and infrared light spectra, respectively, into arterial and capillary blood vessels contained in the body part;
• transducer means for detecting relative amount of the first and second light beams absorbed by the blood after being directed into the capillary and arterial blood vessels, the transducer means connected to the pressure means such that the transducer means only receives the first and second light beams which have passed through the body part which is intermittently imposed upon by the pressure means;
• processor means, electronically coupled to the pressure means for (a) controlling the pressure means so as to cause the pressure to be intermittently imposed on the body part as the first and second light beams are passing into the body part, whereby absorption of said light beams by arterial blood is increased relative to absorption by non-arterial blood, and for (b) deriving from the detected relative amount of the first and second light beams absorbed by the arterial blood an arterial oxygen saturation level;
• and
• display means, electronically coupled to the processor means, for outputting a visually perceptible indication of the arterial oxygen saturation level.

A noninvasive monitoring system for providing an indication of both a patient's arterial blood pressures and arterial oxygen saturation level, the system comprising:

• light means for passing first and second light beams into a body part of the patient containing both arterial and nonarterial blood vessels, the first and second light beams having wavelengths in the visible and infrared portions of the spectrum, respectively;
• pressure means, for periodically imposing an increased pressure on the body part, said pressure means being associated with said light means and normally nonocclusive in relation to the blood vessels;
• light detection means for detecting relative amounts of the first and second light beams reflected by and transmitted through arterial blood vessels and for outputting first and second electric signals proportional to the detected amounts of the first and second light beams respectively, at least one of the signals being proportional to relative volume of said arterial blood vessels;
• pressure detection means for detecting the pressure imposed on the body part by the pressure means and for outputting a third electric signal proportional to the increased pressure;
• processor means for receiving the first, second and third electric signals, the processor means comprising means for deriving arterial pressures and for deriving an oxygen saturation level from said electric signals;
• and
• display means, electronically coupled to the processor means, for outputting visually perceptible indications of the patient's arterial pressure waveform and oxygen saturation level.

A noninvasive, monitoring method for determining the arterial oxygen blood saturation level in a patient's body part containing both arterial and nonarterial blood vessels, the method comprising the steps of:

• (a) directing a first and a second light beam in the body part, the first and second light beams having different wavelengths;
• (b) imposing an enhancement pressure on the body part, said enhancement pressure being less than a completely occlusive pressure and great enough so as to substantially increase the compliance of the arterial vessels contained in the body part thereby increasing arterial pulses;
• (c) detecting the relative amounts of the first and second light beams absorbed by the blood contained in the arterial vessels;
• (d) determining the arterial oxygen saturation level in the body part by the detected amounts of the first and second light beams;
• and
• (e) displaying a value representing the determined arterial oxygen saturation level.

A noninvasive method for monitoring a patient's arterial oxygen saturation level, the method comprising the steps of:

• (a) establishing a calibration interval comprised of the following steps:
• (1) directing a first light beam and a second light beam into a body part of the patient containing at least one arterial and at least one nonarterial blood vessel, the first light beam having a first wavelength and the second light beam having a different, second wavelength;
• (2) imposing a first pressure to the body part such that the arterial blood vessel located therein is at least partially unloaded;
• (3) detecting the amount of light from the first light beam and from the second light beam which is absorbed by said body part;
• (4) determining from said detected amount of the first and second light beams the arterial oxygen saturation level in the body part;
• (5) releasing the first pressure from the body part;
• (6) detecting the amount of light from the first light beam and from the second light beam which is absorbed by the body part after the first pressure is released;
• (7) determining a calibration factor derived from the differences in the amount of the first and second light beams which were detected when the first pressure was applied to, and released from, the body part, the calibration factor representing the contribution of non-arterial blood oxygen saturation to the amount of light detected;
• (b) establishing a monitoring interval by continuing to detect the amount of the first and second light beams which are absorbed by the body part after the calibration factor is determined;
• (c) calculating during the monitoring interval the oxygen saturation level of the arterial blood using the calibration factor;
• and
• (d) displaying the oxygen saturation level on a visual display.

A method for noninvasively determining a patient's arterial oxygen saturation level, the method comprising the steps of:

• (a) imposing an enhancement pressure on a body part containing both arterial and nonarterial blood vessels so as to significantly increase the pulsation by the arterial blood vessels in the body part;
• (b) directing a first and a second light beam into the body part, the first and second light beams having different wavelengths;
• (c) detecting the amounts of the first and second light beams absorbed by the arterial blood;
• (d) determining the arterial oxygen saturation level in the body part from the detected amounts of the first and second light beams;
• (e) displaying the arterial oxygen saturation level;
• (f) releasing the enhancement pressure from the body part;
• (g) detecting the relative amounts of the first and second light beams absorbed by the arterial and nonarterial blood in the body part;
• (h) determining the relative contribution to said absorption attributable to the arterial blood with respect to the total of the amount of the first and second light beams which are detected;
• and
• (i) displaying an oxygen saturation level corresponding to substantially only the contribution of the arterial blood to the detected amounts of the first and second light beams when the enhancement pressure is removed.

A noninvasive method for continuously monitoring a patient's arterial oxygen saturation and arterial blood pressure waveform, the method comprising:

• imposing an occlusive pressure on a patient's body part containing both arterial and nonarterial blood vessels;
• directing at least a first light beam into the body part;
• gradually releasing the occlusive pressure;
• detecting when a pulsatile signal first modulates the first light beam;
• measuring the occlusive pressure imposed on the body part when the pulsatile signal first modulates the first light beam and storing the value of the pressure as the systolic pressure;
• releasing the occlusive pressure;
• imposing an enhancement pressure on the body part such that the modulation of the first light beam is substantially maximized to determine a measured mean arterial pressure;
• estimating an arterial diastolic pressure;
• calculating a mean arterial pressure using the estimated diastolic pressure, the measured systolic pressure, the detected amounts of the first light beam, and a formula which relates arterial pressure to arterial volume;
• comparing the calculated mean arterial pressure to the measured mean arterial pressure and displaying at least the diastolic pressure if the measured mean arterial pressure and the calculated arterial pressure agree within predetermined limits;
• directing a second light beam into the body part while the enhancement pressure is imposed on the first and second light beams having different wavelengths;
• detecting the relative amounts of the first and second light beams absorbed by the arterial blood contained in the body part;
• deriving an arterial oxygen saturation level from the detected amounts of the first and second light beams;
• releasing the enhancement pressure from the body part;
• calculating at least a new systolic and diastolic arterial blood pressure based upon the changes in the detected amount of the first light beam representing volume changes in the arteries contained in the body part while all pressure is released from the body part;
• detecting the relative amounts of the first and second light beams absorbed by the arterial and nonarterial blood vessels contained in the body part while all pressure is removed;
• determining the contribution of the arterial blood vessels to the detected amount of the first and second light beam so that the arterial oxygen saturation level may be determined;
• and
• displaying the arterial oxygen saturation level and the systolic and diastolic arterial blood pressure of the body part on a visually perceptible display.