1 Design of the Portable mass spectrometric sensor for vascular and endocrine disease diagnostics

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1 1 Design of the Portable mass spectrometric sensor for vascular and endocrine disease diagnostics Andrei Antonov, Viktor Kogan, Aleksandr Krutikov A.F. Ioffe Physical Technical Institute, Academy of Science, St. Petersburg, Russia

2 2 Abstract Design and testing of the interface systems between the entrance of a portable mass spectrometric sensor and human skin under noninvasive diagnostics of vascular and endocrine diseases with monitoring of transcutaneous (through the skin) gas composition were reported. The description of the interface systems, the operating mode and the factors, making an impact on the efficiency of measurement procedure, were considered. The estimation of transcutaneous gas tensions on the skin surface were realized through mass spectrometry gas flow determination. The results of testing of the mass spectrometric sensor were presented. The efficiency of mass spectrometry method application was discussed.

3 Among the methods of noninvasive diagnostics of human vascular and endocrine diseases the respiration process control is really important Schematic diagram (left) of TB entering an acinus; inspired

3 3 Among the methods of noninvasive diagnostics of human vascular and endocrine diseases the respiration process control is really important Schematic diagram (left) of TB entering an acinus; inspired air reaches TB by bulk flow, but gas exchange between TB and acinus is by molecular diffusion. Blood gas barrier is shown enlarged (right) with O2 molecules traversing alveolo capillary membranes and plasma to combine with Hb..

4 4 A good relationship between transcutaneous oxygen tension (Ptc,O2) and arterial oxygen tension (Pa,O2) was demonstrated in neonates and this led to the use of continuous noninvasive Ptc,O2 monitoring in neonatal intensive care units [Huch R, Huch A, lbani M, et al. Transcutaneous PO2 monitoring in routine management of infants and children with cardiorespiratory problems. Pediatrics 1976; 57: ]. It was initially believed that PtcO2 measurements would not be satisfactory in adults due to their thicker epidermis, but subsequent studies have shown that this technology may work just as well for older children and adults [Hutchison DCS, Rocca G, Honeybourne D. Estimation of arterial oxygen tension in adult subjects using transcutaneous electrode. Thorax 1981; 36: , Hughes JA, Gray BJ, Hutchison DCS. Changes in transcutaneous oxygen tension during exercise in pulmonary emphysema. Thorax 1984; 39: ].

5 5 Electrochemical method

6 6 Example : ТСМ 400

7 The position of an electrochemical sensor at monitoring of transcutaneous gas composition Photo of the sensor attachment on the forearm skin.

7 7 The position of an electrochemical sensor at monitoring of transcutaneous gas composition Photo of the sensor attachment on the forearm skin. The sensor and the thermistor was attached using fixing tape Calibration plot of the wearable oxygen sensor for dissolved oxygen concentration measurements

8 8

9 Mass spectrometry application allows to exclude: the response delay caused by electrochemical detector feature, low measurement accuracy caused by current mode of registration, the impossibility of multicompound analysis Sensors for mass spectrometry analysis: 1. sensor volume vacuumization, direct delivery of transcutaneous gas flow to vacuum chamber of mass spectrometer, disadvantages: damage to skin, high requirement to vacuum, great water vapor flow through the system, hardship of delivery to mass spectrometer, 2. transcutaneous gas accumulation in pure nitrogen at 1 bar, gas delivery from patient to the instrument with assistant gas (pure nitrogen), transcutaneous gas introduction to mass spectrometer through capillary, disadvantages: low sensitivity, complecated 3. pure nitrogen ablution of sensor volume, infill of sensor volume with transcutaneous gas and its following from sensor volume to ion source of MS through capillary. disadvantages: complicated, 4. direct delivery of transcutaneous gas from sensor volume to MS through capillary. disadvantages:?

10 10 Block scheme of system 4 1- ion source, 2- mass analyzer, 3- vacuum pumps, 4- capillary, 5- sensor

11 11 Test system

12 12 The position of MS sensor under monitoring of transcutaneous gas composition

13 13 Sensors and componentry

14 Experimental results calibration test O2

14 14 Experimental results calibration test O2 composition monitoring in air were carried out before and after of measurement cycles. It was necessary for system calibration The response of the wearable oxygen sensor (transition process to transcutaneous O2 partial pressure in sensor)

15 15 Measurement procedure 1- calibration performs by atmospheric air measurement, 2- interface is attached to the skin surface, it turns on stabilized heating, 3- after minutes heating transcutaneous oxygen partial pressure may be determined.

16 Conclusions conditions for determination of transcutaneous oxygen partial pressure using direct delivery gas from sensor volume to MS ion source through capillary: Small interface volume: transient time to steady state hasn t to essentially delay measurement procedure. Flow rate of the gas entering to the mass spectrometer has not to result to difference between pressure in sensor and that of transcutaneous gas. my andrey.s.antonov@gmail.com

Estimation of arterial oxygen tension in adult

Estimation of arterial oxygen tension in adult subjects using a transcutaneous electrode D C S HUTCHISON, G ROCCA, AND D HONEYBOURNE From the Chest Unit, King's College Hospital, London Tharax, 1981, 36,