Improving portable inhalation therapy through real-time assessment of patient pulmonary state.

Metered-dose inhalation therapy is the method of choice for a number of respiratory conditions including asthma and bronchitis. Correct use of the metered-dose inhaler (MDI) has been the subject of much research. Devices have been developed to assist with training in their proper use and to enhance the effectiveness of MDI therapy. However, all lack patient pulmonary state assessment. We have approached the development of an improved portable MDI device by focusing on the total system elements that contribute to a smart inhalation therapy device. Components of such a system should include assessment of the patient's therapeutic state, tracking of drug usage, and also include physician-modified alarm thresholds. Therapeutic state is best assessed with end-expiratory CO2 measurements augmented by inspiratory and expiratory flow efforts. Drug usage monitoring needs to include the time history of drug administration. Physician-modified alarms should allow configuration of the smart inhaler to account for patient condition so that appropriate alarm limits can be established; for example, raising the CO2 alarm threshold for patients with chronic lung disease.

A device for urologic post-surgical monitoring.

This article reports on the preliminary development of an instrument that is intended to monitor catheterized, post-TURP patients specifically to assist care-providers in the reduction of clot retention. The primary objective of the instrument is to detect conditions that indicate an alarm condition for which the probability of clot retention is considered to be high. In response to an alarm, intervention by means of increased irrigation flow rate or other action is expected. The density of outflow consisting of the mixture of irrigation fluid, urine, and blood from the prostate, is monitored optically. Multiple transducer sites along the catheter improve the monitoring by minimizing the effects of bubbles and particulates in the stream. Development of algorithms for processing the data have concentrated on the use of fuzzy logic in keeping with the linguistic descriptors used by medical experts. This allows the formulation of decision rules that mimic the knowledge base and syntax used by care providers who judge the conditions of the outflow and make decisions about the patient's condition and the optimum flow rate for irrigation fluid. A laboratory prototype has been completed and tested in vitro; a second-generation prototype has been designed in preparation for a clinical study.

VXIbus: a modern alternative for instrumentation.

VMEbus extensions for instrumentation (VXIbus) is currently in its fourth revision (1.4) and being adopted as an IEEE standard. VXIbus instruments are now available from a variety of manufacturers and are following the pattern established by the familiar IEEE 488.1/.2 interface standard. The difference is that "instruments on a card" with a wide range of performance are available within a common standard. Users can choose from low cost A- and B-size cards, moderate price and performance C-size cards, up to high performance, high cost D-size cards. Instruments can be relatively simple, register-based cards or more complex, message-based cards with local intelligence. The fundamental basis for VXIbus is the VMEbus standard. VXIbus adds additional power supplies, local buses, triggers, and other features to support collections of instruments organized in a 13-slot backplane. This paper briefly introduces VXIbus, highlighting some of its major architectural features. Other papers in this session illustrate a number of considerations that range from application-oriented to instrument development concepts.

An oximeter for measuring hemoglobin concentration and oxygen content.

We have developed an oximeter that measures both the total hemoglobin concentration in whole blood and the percentage of the hemoglobin saturated with oxygen. The oximeter uses red and infrared light-emitting diodes to illuminate a capillary tube filled with a sample of whole blood. Light scattered by the blood travels a short distance down the length of the capillary tube and reaches a photodetector, the output of which is amplified, digitized, and fed into a microprocessor. The microprocessor computes the total hemoglobin concentration as a nonlinear function of the infrared light intensity. Oxyhemoglobin saturation is computed from the ratio of the logarithms of the intensities of red and infrared light. Our instrument has the following advantages over existing oximeters: 1) it provides a measurement of total hemoglobin concentration, 2) it is immune to the calibration shifts that fluctuations in total hemoglobin concentration cause in other oximeters, 3) it is accurate over a wide range of oxygen saturation, and 4) the blood samples are not diluted and can thus be preserved for further analysis. A detailed parts list and circuit diagram are presented, and sources of error are discussed.

An optical hemoglobinometer for whole blood.

To overcome the disadvantages of the presently available hemoglobinometers, we have developed an optical instrument that measures the total hemoglobin (Hb) concentration in whole, undiluted blood. The device uses an infrared light-emitting diode to illuminate a capillary tube filled with a sample of whole blood. Light scattered in the blood travels a short distance down the length of the capillary tube, passes through a second light path, and reaches a photodetector, the output of which is amplified, digitized, and fed into a microprocessor. The microprocessor computes the Hb concentration as a nonlinear function of the light intensity. The optical device yielded Hb content measurements that correlated well with standard methods (r = 0.99, slope = 0.94, mean absolute difference = 0.75 g Hb/dl). Thus the accuracy appears to be less than 1 g Hb/dl. The advantages of the present device are as follows: 1) no chemical reaction is required (hence neither accurate dilutions nor toxic reagents are necessary); 2) it reads Hb concentration within a few seconds; 3) it can be operated by unskilled personnel; 4) it could be made portable and thus could be operated in the field, in rural settings, or at accident sites; 5) sample size is small (25-70 microliters); and 6) the same capillary tube can be centrifuged if a measure of hematocrit is also desired. A detailed parts list and circuit diagram are presented, and sources of error are discussed.