Humidification

1. Humidification Dr. S. Parthasarathy MD., DA., DNB, MD (Acu), Dip. Diab. DCA, Dip. Software statistics PhD (physio) Mahatma Gandhi medical college and research institute , puducherry – India

2. Definition • Humidity is a measure of the amount of water vapourin a gas. • Absolute humidity is defined as actual mass of water vapourpresent in a known volume of gas. • 34 mg / lto 45 mg / l • Upper airway to alveolus

3. Relative humidity • Relative humidity is defined as the ratio of • the mass of water vapour in a given volume of gas to the maximum amount of water vapour that the same gas can hold at the same temperature. • Relative humidity is expressed as a percentage.

4. Yes - humidification • humidification maintains mucosal integrity, ciliary activity, prevents the drying of secretions and helps in easy expulsion of respiratory secretions when coughing. • (e.g. ventilating a patient with dry gas through a tracheal or tracheostomy tube) can result in cracking of mucosa, drying of secretions, keratinisation of the tracheo-bronchial tree, reduction in ciliary activity, atelectasis and infection No

5. Clinical signs • Dry nonproductive cough • Dyspnoea • Substernal pain • Thick secretions

6. Over-humidification It can result in water intoxication, especially in neonates and infants in intensive care, water clogging and airway burns

7. Normal airway humidification • While nose breathing at rest, inspired gases become heated to 36°C and are about 80% to 90% saturated with water vapour. • Mouth breathing reduces this to 60% to 70%

9. Aims of humidity therapy • Gas at nose/mouth • 50% RH with 10 mg/litre --- 22 deg. • Gas at hypopharynx • 95 % RH with 34 mg/l --- 29 degree • Mid trachea • 100 % with 40 mg/l. 31 – 35 deg.

10. Sources • CO2 absorbent • Exhaled gases • Rinsing the tubes

11. Measure humidity • Hair hygrometer This is based on the principle that the length of hair increases with increasing humidity It is fairly accurate between 30 and 90%. • Wet and dry bulb hygrometer Two mercury thermometers, one in ambient temperature and the other in contact with water through a wick are used. Rate of evaporation prop. Humidity

12. Measure humidity • Regnault’s hygrometer • Mass spectrometer • principle of reduction in the ultraviolet light transmitted through the medium containing water vapour

13. Types of humidifiers • Low flow • Less than the inspiratory needs • Bubble • Simple diffuser • High flow Inspiratory needs are met HME , wick type

14. Bubble humidifier

15. Bubble diffuser humidifiers

16. Picture of bubble- diffuser

17. Function • Gas comes from DISS • Capillary tube • Exits as small bubbles • Pick up water vapour and come out • Diffuser – smaller bubbles, greater surface area and better humidification

18. Factors • Flow of gas • Water level • Ambient temperature • 5 l/ min- AH is 10 - 20 mg/l, RH is 40 % at 37 deg.

19. Disadvantages • Transport water borne microbes • High gas flows an aerosol is created and microbes can be transferred • High flows --- delivery tube kinked – high pressure develops – PRV( pressure relief valve) – alarm at 2 PSI can be set.

20. High flow humidifiers • HME • Heat moisture exchangers • Disposable devices that trap some exhaled water and heat, and deliver them to patient on subsequent inhalation (minimize water and heat loss) • combined with a filter for bacteria and viruses  Heat and Moisture Exchanging Filter (HMEF)

21. Swedish nose First – aluminium

24. Most modern HMEs are of 2 types: a. Hydrophobic (not much used) b. Hygroscopic

25. Hydrophobic HMEs – • Hydrophobic membrane with small pores, pleated to increase surface area • Allow passage of water vapor but not liquid water at usual ventilatory pressures • Efficient bacterial and viral filters • Performance may be impaired by high ambient temperatures

26. Hygroscopic HMEs– • Wool, foam or paper like material coated with moisture-retaining chemicals • Medium may be impregnated with a bactericide • When wet – performance is poor

27. Minimum standard • Its not 20 – 20 cricket • Its 30 – 30 cricket • Minimum 30 mg/ litre at 30 deg. c

28. Advantages • Inexpensive • Easy to use • Small, lightweight, simple in design • Silent in operation • Do not require water/ external energy source/ temperature monitor/ alarms • No danger of overhydration/ hyperthermia/ burns/ electrical shock

29. Disadvantages • Can deliver only limited humidity • Insignificant contribution to temperature preservation • Less effective than active humidifiers, specially after intubation lasting for several days • Increased dead space  may necessitate increase in tidal volume  increased work of breathing

30. If you are in continuous search of an ideal one ???

32. Can We use HME here ?? • Preexisting pulmonary disease with copious secretions • Bloody secretions • Expired tidal volume is less than 70 % of the delivered tidal volume ( if there is no other problem) • Be cautious

33. Heated humidifier

34. HEATED HUMIDIFIERS • Incorporate a device to warm water in the humidifier, some also heat inspiratory tube • Humidification chamber • Heat source • Temperature monitor • Thermostat • Controls • Alarms

37. Use • In circle system, heated humidifier is placed in the inspiratory limb downstream of unidirectional valve by using an accessory breathing tube • Must not be placed in the expiratory limb • Filter, if used, must be placed upstream of humidifier to prevent it from becoming clogged • In Mapleson systems, humidifier is usually placed in fresh gas supply tube

39. Clinical tips • Humidifier must be lower than patient • Condensate must be drained periodically • Delivery tube should not rest on other surfaces or be covered with sheets • Beware alarms are set for temperature – not for humidity

40. Advantages • Capable of delivering saturated gas at body temperature or above, even with high flow rates • More effective humidification than an HME

41. Disadvantages • Water spillage into the breathing circuit and even into tracheobronchial tree. A water trap will help reduce this problem. • Airway burns due to thermostat failure and overheating. • Colonization of water with harmful bacteria can occur. This may be reduced by heating the water to 60°C.

42. How was the progress • Hot water bath –(upto 50 deg)-- water condensate because there was difference in temperature between the humidifier and the patient end. • Then a heated wire was introduced in the inspiratory system – then also in the expiratory tubes. • The flow transducers in the ventilators confused with water vapour to confuse readings and hence at the expiration there was a heating element to get the gas to 37. deg

43. Types of humidifiers • Low flow • Less than the inspiratory needs • Bubble • Simple diffuser • High flow Inspiratory needs are met HME , vapor phase , wick type

44. One more classification • Passive • HME • Active -they do not filter respiratory gases • Heated and unheated • Nebulizers

45. Wick on the sides of the bottle WICK

46. Aerosol therapy – different topic

48. MUCOLYTICS • Agents capable of dissolving, digesting or liquefying mucus • N-acetylcysteine (NAC) • Mesna • Sodium bicarbonate • Dornase alpha (Pulmozyme)

49. Act by • Weakening of intermolecular forces binding adjacent glycoprotein chains • Disruption of Disulfide Bonds (NAC, Mesna) • Alteration of pH to weaken sugar side chains of glycoproteins (Soda bicarb.) • Destruction of protein (Proteolysis) contained in the glycoprotein core • Breaking down of DNA in mucus (Dornase alpha

50. N-acetylcysteine (NAC) • Sulfhydryl - containing tripeptide • Better known as the antidote for acetaminophen overdose • Primarily a mucolytic agent that acts by disrupting the disulfide bridges between mucoprotein strands in sputum