Automated Oxygen Delivery Method
The present invention advantageously provides a method of automatically delivering oxygen to a patient. A desired concentration of oxygen in a bloodstream of a patient is received from a user. Data, including a measurement of the amount of oxygen in the bloodstream of the patient, as well as status information associated with the measurement, is received from a sensor. The measured data are determined to be valid or invalid based on the measurement value and the status information, and, based on this determination, a delivered fraction of inspired oxygen is delivered to the patient. If the measured data are determined to be valid, then the delivered fraction of inspired oxygen is based on the desired oxygen concentration and the measured data. On the other hand, if the measured data are determined to be invalid, then the delivered fraction of inspired oxygen is set to a predetermined value.
1 . A method of automatically delivering oxygen to a patient, comprising:
receiving, from a user, a desired concentration of oxygen in a bloodstream of a patient;
receiving, from a sensor, data including a measurement of the amount of oxygen in the bloodstream of the patient and status information associated with the measurement;
determining whether the measured data are valid or invalid based on the value of the measured data and the status information;
controlling a delivered fraction of inspired oxygen, FiO 2 , to the patient, including:
if the measured data are valid, controlling the FiO 2 based on the desired oxygen concentration and the measured data, and
if the measured data are not valid, setting the FiO 2 to a predetermined value; and
delivering the FiO 2 to the patient.
2 . The method of claim 1 , wherein the FiO 2 is not less than an FiO 2 threshold.
3 . The method of claim 2 , wherein the FiO 2 is increased if the measured S P O 2 is below a lower S P O 2 threshold, and the FiO 2 is decreased if the measured S P O 2 is above an upper S P O 2 threshold.
4 . The method of claim 1 , wherein the sensor is a pulse oximeter, and the sensor data include a saturation of peripheral oxygen measurement, S P O 2 , a perfusion index and a signal quality index.
5 . The method of claim 1 , wherein the sensor is a transcutaneous gas tension sensor, and the sensor data include an arterial oxygen partial pressure measurement, PtcO 2 , and an arterial carbon dioxide partial pressure measurement, PtcCO 2 .
6 . The method of claim 1 , wherein the sensor is an invasive catheter blood analyzer, and the sensor data include a dissolved oxygen in the blood measurement, pO 2 , a dissolved carbon dioxide in the blood measurement, pCO 2 , a blood acidity pH measurement, and a blood temperature measurement.
7 . A method of automatically delivering oxygen to a patient, comprising:
receiving, from a user, a desired concentration of oxygen in a bloodstream of a patient;
receiving, from a pulse oximeter sensor, data including a measurement of the saturation of peripheral oxygen, S P O 2 , in the bloodstream of the patient, a perfusion index and a signal quality index;
determining whether the S P O 2 is valid or invalid based on the S P O 2 value and at least one of the perfusion index and the signal quality index;
controlling a delivered fraction of inspired oxygen, FiO 2 , to the patient, including:
if the S P O 2 is valid, categorizing the S P O 2 within a hypoxemia range, a normoxemia range or a hyperoxemia range, and controlling the FiO 2 based on the desired oxygen concentration, the S P O 2 and the respective range, and
if the S P O 2 is invalid, setting the FiO 2 to a predetermined value; and
delivering the FiO 2 to the patient.
8 . The method of claim 7 , wherein the FiO 2 is not less than an FiO 2 threshold.
9 . The method of claim 8 , wherein the FiO 2 is increased if the measured S P O 2 is below a lower S P O 2 threshold, and the FiO 2 is decreased if the measured S P O 2 is above an upper S P O 2 threshold.
10 . The method of claim 7 , further comprising identifying measurement artifacts, including optical interference and electrical interference, wherein said determining whether the S P O 2 is valid or invalid is based on at least one of the perfusion index, the signal quality index, and one or more of the measurement artifacts.
11 . The method of claim 7 , wherein the perfusion index is a fractional variation in the optical absorption of the S P O 2 between the systole and diastole periods of an arterial pulse.
12 . The method of claim 7 , wherein the signal quality index provides a confidence metric for the S P O 2 .
13 . The method of claim 12 , wherein the signal quality index is based on variations in the optical absorption of the S P O 2 .
14 . The method of claim 7 , wherein hypoxemia is excessively-low blood oxygen saturation, normoxemia is a clinically-appropriate blood oxygen saturation, and hyperoxemia is excessively-high blood oxygen saturation.
15 . The method of claim 7 , further comprising applying a transformation to the S P O 2 values to normalize frequency distribution, and applying one or more linear filters to the transformed S P O 2 values.
16 . The method of claim 15 , wherein the transformation is an inverse transform of an oxyhemoglobin saturation curve.