Humidifiers.pptx

humidifier

1. HUMIDIFIERS MODERATOR- DR. MOHIT JAGGA PRESENTER- DR. AMIT

2. Humidity: Amount of water vapor in a gas. Absolute humidity: Mass of water vapor present in a volume of gas. (milligram of water per liter of gas) Humidity at saturation: Maximum amount of water vapor that volume of gas can hold. Varies with temperature. Warmer the temp-more the water vapor held by the gas. At body temp 37˚C- 44mg H 2 O/ L

3. Relative humidity (percent saturation) :  Amount of water vapor at particular temperature expressed as percentage of amount that would be held if the gas were saturated.​ Water vapor pressure:  Pressure exerted by water vapor in a gas mixture.​

4. Gas saturated with water vapor Heated Cooled Capacity to hold moisture ↑ (becomes unsaturated) Condense (rain out) water <100% relative humidity Absolute humidity unchanged 100% relative humidity Absolute humidity falls

5. ANAESTHETIC CONSIDERATIONS Upper respiratory tract ( esply nose) functions as principal heat and moisture exchanger. Temp in upper trachea- 30˚C- 33˚C Relative humidity- 98% Water content- 33mg/L Tracheal tubes and supraglottic airway devices bypass the airway when tracheobronchial mucosa takes up this role but its capacity is limited.

6. Water is intentionally removed from medical gases to prevent clogging of regulators and valves, thus gases delivered from  anaesthesia  machine are dry and at room temperature.  ​ When such gas is inspired it gets warmed to body temp and absorbs water by evaporation from surface of resp tract mucosa till it becomes saturated causing drying of the resp mucosa. ​

7. EFFECTS OF DRY GAS INHALATION Damage to resp. tract- Secretions thicken                                             - Ciliary function↓                                             - Surfactant activity impaired                                             - Atelectasis  and airway obstruction                                             - loci for infection                                             - Susceptible to injury Body heat loss Absorbent desiccation Tracheal tube obstruction- due to thickened secretions Excessive humidity causes ciliary degeneration and paralysis, pulmonary edema, decreased hematocrit and serum sodium.

8. SOURCES OF HUMIDITY AND HEART CO2 absorbent- reaction of absorbent with CO2 liberates water and heat (exothermic reaction) Exhaled gases- by rebreathing Rinsing inside of breathing tubes and reservoir bag with water Low fresh gas flow with circle breathing system conserves moisture Coaxial breathing circuits NOTE- Bains circuit though coaxial does not meet optimal humidification requirement due to high fresh gas flows

9. HUMIDIFIERS are devices that add molecules of water to gas. Classified as :- Active humidifiers (presence of external sources of heat and water) Passive humidifiers (utilization of patient’s own temperature and hydration to achieve humidification in successive breaths) HUMIDIFIERS   ​

10. ACTIVE HUMIDIFIERS   Act by allowing air passage inside a heated water reservoir.  Add water to gas by passing the gas over a water chamber, through a saturated wick, bubbling it through water, or mixing it with vaporized water.  Do not filter respiratory gases Two types – Heated Unheated 

11. HEATED HUMIDIFIERS Incorporate a device to warm water in the humidifier, some also heat inspiratory tube. Humidification chamber – contains liquid water, disposable/ reusable, clear (easy to check water level

12. COMPONENTS HUMIDIFICATION CHAMBER- contains water. HEAT SOURCE- heated rods immersed in water or plate at bottom of chamber. INSPIRATORY TUBE- conveys humidified gas to pt. Has a water trap to collect condensed water. Heated wire inside the tube to prevent moisture rainout and for more precise control of temperature. TEMPERATURE MONITOR-  to measure gas temperature at patient end of breathing system THERMOSTAT CONTROLS FOR TEMPERATURE SELECTION ALARMS

13. THERMOSTAT - SERVO CONTROLLED UNIT- automatically regulates power to heating element in response to temperature sensed by probe near patient connection. NON SERVO CONTROLLED UNIT- provides power to heating element according to the setting of a control irrespective of delivered temperature.

14. Controls – most allow temperature selection at end of delivery tube or at humidification chamber outlet  Alarms – to indicate temperature deviation by a fixed amount. displacement of temperature probe. disconnection of heater wire. low water level in humidification chamber. faulty airway temperature probe. lack of gas flow in the circuit

15. ADVANTAGES Provide saturated gas at body temperature or above even with high flow rates Some can be used for spontaneously breathing and tracheostomized patients DISADVANTAGES Bulky, complex High maintenance costs Electrical hazards Increased work Little protection against heat loss during anesthesia

16. Different designs and different techniques for humidification.

17. STANDARD REQUIREMENTS Must be capable of producing output of at least     10 mg H2O/L and 33 mg H2O/L with supraglottic  airway devices. Average temperature at delivery tube outlet not to fluctuate by >2˚C from set temperature. (Alarm activated if not so) Volume of liquid exiting humidifier shall not exceed 1ml/min or 20ml/ hr (neonates) and 5ml/min or 20ml/ hr (others).

18. Gas temperature at outlet shall not exceed 41˚C. Interrupt heating and activate alarm if > 41˚C. Accessible surface temperature of delivery tube not >44˚C with in 25cm of patient connection port. No water spillage into breathing system if humidifier tilted 20˚  from normal position. All calibrated controls and indicators accurate to within 5% of their full scale values (except temp ±2˚C). Direction of flow must be marked on humidifiers with flow direction sensitive components.

19. HOW TO USE IN CIRCLE SYSTEM- Heated humidifier to be placed in inspiratory limb downstream of unidirectional valve and filter should be upstream of humidifier. IN MAPELSON SYSTEM- placed in the fresh gas supply tube. The temperature probe should be between fresh gas supply tube and T-piece or between T-piece and patient.

20. HAZARDS Infection Breathing system problems- sticking valves, leaks, noise, clogged filters and HMEs, fires, overheating etc. Water aspiration Overhydration Thermal injury Increased work of breathing Monitoring intreference with flow and pressure sensors Altered anaesthetic agents Equipement damage or malfunction

21. UNHEATED HUMIDIFIERS Disposable, bubble-through devices used to increase humidity in oxygen supplied to patients via facemask or nasal cannula. Simple containers containing distilled water through which oxygen is passed and it gets humidified. Maximum humidity that can be achieved is 9 mg H2O/L

22. PASSIVE HUMIDIFIERS Simplest designs are Heat & Moisture Exchangers (HMEs). Artificial noses - mimic the action of nasal cavity in gas humidification. Also called as condenser humidifier, Swedish nose, nose humidifier, regenerative humidifier, vapor condenser 

23. HEAT AND MOISTURE EXCHANGERS   (HME) Conserves some exhaled water and heat and returns them to patient in the inspired gas. Placed between ET tube and breathing circuit  Also filter bacteria/ virus (heat and moisture exchanging filter). Pediatric and neonatal low dead space HMEs are also available.

24. OTHER END PATIENT END

25. INDICATIONS ↑ Inspired heat and humidity during both short and long term ventilation. Especially useful when transporting intubated patients on transport ventilators. Supply supplemental oxygen to intubated pt or pt with supraglottic airway.

26. CONTRAINDICATIONS Patients with thick, copious or bloody secretions Pts with a leak that prevents exhaled gas from traversing the passive humidifier ( bronchopleuralcutaneous fistula or leaking or absent tracheal tube cuff) Pts managed with low tidal volume like ARDS Hypothermic pts <32˚C Pts with high minute ventilation volumes (>10L/min)

27. Hygroscopic HME- Wool, foam or paper like material coated with moisture retaining chemical Hydrophobic HME- Pleated hydrophobic membrane with small pores

28. Composite hydrophobic and hygroscopic- A hygroscopic salt (calcium or lithium chloride) is added inside the hydrophobic HME. Composite hygroscopic HMES- Hygroscopic HME with a layer of thin, non woven fiber subjected to electric field which increases its polarity and improves filtration efficiency OTHER TYPES

29. USE Small HMEs used in large pts will be inefficient. Connecting more than 1 HME in series will improve performance. Increase in dead space should not be excessive. Should be accessible and visible- to detect contamination or disconnection. Greatest inspired humidity when placed next to tracheal tube. Sampling line should be on machine side to decrease amount of moisture exposed to it. Can be used with any breathing system, in tracheostomised pts. Can be combined with unheated humidifier. Can be used with nebulizer (to be placed bt pt and HME). Should be replaced if contaminated with secretions.

30. ADVANTAGES Inexpensive, easy to use Small, light weight, Reliable Low resistance when dry No need of water, external source of energy, temperature monitor or alarms No danger of overhydration , hyperthermia, burns or electrical shocks Decreased obstruction of lines and ventilator malfunction Barrier for large particles DISADVANTAGES Limited humidity Not enough contribution to temperature preservation Not effective in retaining body heat, alleviating thick secretions or preventing tracheal tube block Increased dead space with increased tidal volume increases rebreathing Increased work of breathing

31. HAZARDS Excessive resistance Airway obstruction Inefficient filtration Foreign particle aspiration Rebreathing Leaks and disconnections Hypothermia Dry CO2 absorbent

32. HEAT AND MOISTURE EXCHANGING FILTER (HMEF) Operate based on electrostatic or mechanical filtration. classified into : Pleated Electrostatic filters  

33. In certain devices, an active heated water source can be added to HMEs converting them from passive to active, increasing their humidification capacity. If the external source of water runs out, these devices will still work as passive HMEs Several models exist :  Booster Performer Humid heat Hygrovent gold ACTIVE HMES

34. THANK YOU