Nibp and oxygen analyser
- 1. NIBP & O2 ANALYSER S. Balasubramanian Moderator- Dr. Aswin
- 2. NIBP • Fundamental in monitoring • ASA recommends Mandatory monitoring every five minutes during anaesthesia • Reduces 93% intra-op mortality rate compared to those where BP monitoring not done
- 3. Definition • Blood pressure is the latersl pressure exerted by the column of blood against the rterial walls • During the cardiac cycle the highest pressure attained is the systolic pressure and the lowest is the diastolic pressure
- 4. Definition • Pulse pressure(PP) =SBP-DBP • Mean arterial pressure (MAP) = average pressure during one cardiac cycle • MAP = DBP + PP/3
- 5. Staging of blood pressure
- 6. History • Riva Rocci 1896- SBP using inflatable cuff and Mercury manometer • Disappearance of Arterial Pulse on cuff inflation • Modified Riva Rocci: Return of flow technique- Return of flow during cuff deftatiom • Korotkoff(1905)- Auscultatory.
- 7. Methods Manual intermittent technique Automated intermittent technique
- 8. Korotkoff • Sphigmomanometer, ,cuff, stethoscope • Measures both SBP and DBP • SBP- Appearance of first Korotkoff sound • DBP- Disappearance of sound or muffling of tone on auscultation • Simple, Almost reliable, low level technology
- 9. Korotkoff • Non correlation with invasive BP, mostly • Erroneous Readings during 1. Decreased peripheral flow states 2. Inappropriate cuff size 3. Rapid cuff deftatiom 4. Large inter observer variation 5. Frequency not possible as like invasive monitoring
- 10. Automated intermittent technique • Marvey (1846)- Principle of Oscillometry. • Oscillations(Arterial pulsations) sensed by monitor during cuff deflation • Peak amplitude – MAP • SBP and DBP- Increasing and decreasing magnitude of oscillations Prefixed by manufacturer
- 11. • Cuff size: • Optimal size- Bladder length of 80% and width of 40% of arm circumference • Large cuffs- underestimates blood pressure • Small cuffs- overestimates blood presure Factors affecting
- 12. Factors affecting • Site: • If arm is not accessible,forearm, wrist, ankles • On more peripheral placement SBP increases and DBP decreases • At the level of heart • For every 10cm above or below heart level: 10cm added or substracted from measured pressure • Cardiac Rhythm: Oscillometry could be erroneous Manual measurement is advisable.
- 13. Standards • Maximum inflatable limit: 300mmhg for adults and 150 mmhg for neonates • Should not remain inflated for longer times • NIBP and IBP correlation is best only in normal healthy individuals and varies largely in extremes of pressures
- 14. Tips • Not to be placed in limbs with continuous infusion • Not to be applied over Bony prominences, superficial nerves or joint • Too tight bruising or nerve injury • Too light Inappropriate reading • If prolonged measurement change to alternative site
- 15. Erroneous readings • Cuff malposition • Incorrect size • Leaking cuff/connector • Motion atrifacts: Shivering, convulsions, external pressure on cuffs
- 16. Complications • Trauma or impaired limb perfusion: excessive frequency for longer times • Bruise • Pain • Erythema • Petechiae • Ecchymosis • Limb edema • Peripheral neuropathy • Compartment syndrome
- 17. Advantages of oscillometry • Compared to Invasive measurement: • Simple, inexpensive • Fewer complications as compared to Invasive measurement Compared to manual measurement: • Regular and reliable • Performers bias reduced(external noise) • Frees clinician to concentrate on patient • Audible alarms and trend view
- 18. Limitations (compared to IBP) • No rapid monitoring • Unreliable during- Extremes of heart rate and BP • Prolonged cycle times : in HTN, poor peripheral circulation, circuit leak, causing discomfort to patients
- 19. Continuous NIBP • Vasotrac, T-Line Tensymeter, Tensys TL-200 • Patented measurement technique • By using radial artery wave forms • Blood pressure updated every 15 Seconds VASOTRAC
- 20. Doppler NIBP • Uses reflected Ultrasound waves from the pulsatile blood flow • Non invasive • Only Systolic pressure is measured • Currently primarily used in animals
- 21. Plethysmographic NIBP • Cuff inflated proximally. • Plethysmography probe attached distally. • Measurement with Pleth wave forms
- 22. Tonometry • External pressure over artery using tonometer • Artery located over a bony prominence • Measured in half compressed artery • Correct positioning of tonometer over artery required • More prone to motion artifacts
- 23. Oxygen Analyser
- 24. Introduction • AAGBI (Association of anaesthetist of Great Britain and Ireland) recommends continuous monitoring of respiratory gas during anaesthesia. Analysers: • Oxygen analyser • CO2 analyser • Vapour analyser ASA(1997) claims that 72% of litigatory claims were due to inappropriate delivery of respiratory gases (High CO2, High inhaled anaesthetics, low oxygen)
- 25. Main stream analyser • Only O2 and CO2 monitoring • Sensor placed directly in main gas stream • For intubated and non- intubated (oral mask, nasal prongs) patients
- 26. Main stream analyser For O2, • Electrochemical technology • If placed in inspiratory limb- measures FiO2 • If placed between patient and breathing system- measures both FiO2 and EtO2
- 27. Main stream analyser Advantages • Fast response time • No sampling tube- no problem of block by water or secretions • No effect due to pressure drop • No pollution Disadvantages • Only for CO2 and O2 • Bulky sensor placed near patient • Leak , Disconnection common • Cross contamination risk.
- 28. Sidestream Analyser • Gas from breathing circuit aspirated by pump • Passed through sampling tube to sensor • Lengthy sampling tube Time delay
- 29. Oxygen analysis 1.Electro chemical O2 Analysis Galvanic Cell, Hersch or Fuel sensor Polarographic (Clark) sensor 2.Paramagnetic analysis
- 30. Paramagnetic Oxygen analysis • Principle: in a magnetic field, some substances locae them into strongest portion of field and are termed as Para-magnetic substances. • Oxygen is Paramagnetic • Gas passed through magnetic field Gases contract and expand • Pressure wave generation Proportional to Partial pressure of oxygen.
- 31. Paramagnetic oxygen sensor Reference gas of known O2 conc. passed. Both gases combines Alternating magnetic field is applied Difference in O2 Conc. Of both gases Pressure wave generated Detected by sensor
- 32. Paramagnetic oxygen sensor • If Reference gas is Air, and N2O is used, N2O gets accumulated in air, O2 conc alters. • Desflurane: Disturbs paramagnetic O2 analyser Falsely high O2 conc. • Environmental Argon interferes
- 33. Electrochemical Analysis • Sensor: Cathode, Anode, surrounding electrolytes • Analyser: Electronic circuit, Display of partial pressure of O2, Alarm • Sensor in inspiratory limb • Mostly used for inspiratory O2 measurement
- 34. Galvanic cell • 1 Anode- Lead (Pb), 2 Cathodes – (Au or Ag) • Surrounded by electrolyes: KOH • Only O2 diffuses through electrochemical membrane and electrolyte • O2 gets reduced current passes • Amount of current <=> Rate of O2 entering cell <=> Partial pressure of O2
- 35. Galvanic cell • No power source required. • Generated current is enough to run the sensor • Temperature dependant sensor • A Thermostat is attached to maintain ideal temperature
- 36. Galvanic cell • Lifespan: Percentage hours • Product of percentage of O2 exposed and hours of usage • Higher O2 conc. Lowerlife span • Disconnect sensor when not in use to increase lifespan
- 37. Polarographic elecrode • Clark sensor • 1anode (Ag), 1 cathode(Au), electrolye(KCl or KBr), gas permeable membrane • Power source required • Passage of Current Hydroxyl ions • Current that flows is proportional to PO2 of sample tube
- 38. Clark sensor • Usage of N2O Reduction of silver anode • N2O usage leads to falsely high o2
- 39. O2 Analyser Advantage: • Ease of use • Low cost • Compact • No effect from Argon Disadvantage: • Maintanence: Frequent replacement needed • Atleast 8th hourly calibration • Not an integral of machine, hence manually be attached • Slow response time
- 40. Thank you all