You are here: RCJournal.com » Clinical Practice Guidelines

Reprinted from the August 1992 issue of RESPIRATORY CARE [Respir Care 1992(8);37:887–890]

AARC Clinical Practice Guideline

Humidification during Mechanical Ventilation

HMV 1.0 PROCEDURE:

The addition of heat and moisture to inspired gases delivered to the patient during mechanical ventilatory support via an artificial airway

HMV 2.0 DESCRIPTION/DEFINITION:

When the upper airway is bypassed, humidification during mechanical ventilation is necessary to prevent hypothermia, inspissation of airway secretions, destruction of airway epithelium, and atelectasis.(1-7) This may be accomplished using either a heated humidifier or a heat and moisture exchanger (HME). (HMEs are also known as hygroscopic condenser humidifiers, or artificial noses). The chosen device should provide a minimum of 30 mg H2O/L of delivered gas at 30°C.(8,29) Heated humidifiers operate actively to increase the heat and water vapor content of inspired gas.(11-14) HMEs operate passively by storing heat and moisture from the patient's exhaled gas and releasing it to the inhaled gas.(I5-25)

HMV 3.0 SETTINGS:

3.1 Critical care
3.2 Acute care inpatient
3.3 Extended care and skilled nursing facility
3.4 Home care
3.5 Prolonged transport

HMV 4.0 INDICATIONS:

Humidification of inspired gas during mechanical ventilation is mandatory when an endotracheal or tracheostomy tube is present.(1-7)

HMV 5.0 CONTRAINDICATIONS:

There are no contraindications to providing physiologic conditioning of inspired gas during mechanical ventilation. An HME is contraindicated under some circumstances.
5.1 Use of an HME is contraindicated for patients with thick, copious, or bloody secretions.(8,26-28)
5.2 Use of an HME is contraindicated for patients with an expired tidal volume less than 70% of the delivered tidal volume (eg, those with large bronchopleurocutaneous fistulas or incompetent or absent endotracheal tube cuffs).(15-25)
5.3 Use of an HME is contraindicated for patients with body temperatures less than 32°C.(8,29)
5.4 Use of an HME may be contraindicated for patients with high spontaneous minute volumes (> 10L/min).(8,26,29)
5.5 An HME must be removed from the patient circuit during aerosol treatments when the nebulizer is placed in the patient circuit.(8-29)

HMV 6.0 HAZARDS/COMPLICATIONS:

Hazards and complications associated with the use of humidification devices include
6.1 potential for electrical shock--heated humidifiers;(11-14)
6.2 hypothermia--HME or heated humidifiers; hyperthermia--heated humidifiers;(11-14)
6.3 thermal injury to the airway from heated humidifiers;(30) burns to the patient and tubing meltdown if heated-wire circuits are covered or circuits and humidifiers are incompatible;
6.4 underhydration and impaction of mucus secretions--HME or heated humidifiers;(1-7)
6.5 hypoventilation and/or alveolar gas trapping due to mucus plugging of airways--HME or heated humidifier;(1-7)
6.6 possible increased resistive work of breathing due to mucus plugging of airways--HME or heated humidifiers;(1-7)
6.7 possible increased resistive work of breathing through the humidifier--HME or heated humidifiers;(31-34)
6.8 possible hypoventilation due to increased dead space--HME;(8,15-25,26-30)
6.9 inadvertent overfilling resulting in unintentional tracheal lavage--heated reservoir humidifiers;(35)
6.10 the tact that when disconnected trom the patient, some ventilators generate a high flow through the patient circuit that may aerosolize contaminated condensate, putting both the patient and clinician at risk for nosocomial infection--heated humidifiers;(35)
6.11 potential for burns to caregivers from hot metal--heated humidifiers;
6.12 inadvertent tracheal lavage from pooled condensate in patient circuit--heated humidifiers;(35)
6.13 elevated airway pressures due to pooled condensation--heated humidifiers;
6.14 patient-ventilator dysynchrony and improper ventilator performance due to pooled condensation in the circuit--heated humidifiers;
6.15 ineffective low-pressure alarm during disconnection due to resistance through HME.(36)

HMV 7.0 LIMITATIONS OF METHODS:

7.1 Insufficient heat and humidification can occur with some HME devices, resulting in complications noted in HMV 6.0.(8,15-28)
7.2 Insufficient heat and humidification can occur with heated humidifiers and result in complications noted in HMV 6.0 when
7.2.1 improper temperature settings are selected.
7.2.2 water level in the humidifier falls below manufacturer's suggested level.(37)
7.3 The HME selected should be appropriate to the patient's size and tidal volume.

HMV 8.0 ASSESSMENT OF NEED:

Humidification is needed by all patients requiring mechanical ventilation via an artificial airway. Conditioning of inspired gases should be instituted using either an HME or a heated humidifier.
8.1 HMEs are better suited for short-term use (< or = 96 hours) and during transport.(8,29)
8.2 Heated humidifiers should be used for patients requiring longterm mechanical ventilation (> 96 hours) or for patients who exhibit contraindications for HME use.(8,29)

HMV 9.0 ASSESSMENT OF OUTCOME:

Humidification is assumed to be appropriate if, on regular careful inspection, the patient exhibits none of the hazards or complications listed in HMV 6.0.

HMV 10.0 RESOURCES:

10.1 Equipment: Appropriate equipment should be available to provide for adequate humidification of the inspired gas. Such equipment may include but is not limited to
10.1.1 humidification device;
10.1.2 a system to monitor inspired gas temperature and to alarm when the temperature falls outside a preset range (for heated humidifier);
10.1.3 sterile water for heated humidifiers;
10.1.4 equipment necessary to comply with Universal Precautions.
10.2 Humidifier performance specifications should be checked to assure adequate heating and humidification during expected peak inspiratory flowrate and minute ventilation delivered by the mechanical ventilator. Heated humidifiers selected for use should meet specifications of the American National Standards Institute.(9)
10.3 Personnel:
10.3.1 Level-I personnel should possess
10.3.1.1 a complete understanding of the operation, maintenance, and troubleshooting of the ventilator, circuit, and humidifying device;
10.3.1.2 knowledge of and ability to implement Universal Precautions.
10.3.2 Level-II personnel should possess the abilities described in 10.3.1.1 and 10.3.1.2 and should also have
10.3.2.1 the ability to assess patient response to humidification;
10.3.2.2 the ability to recognize an adverse response to humidification;
10.3.2.3 the ability to appropriately respond to adverse events;
10.3.2.4 the ability to recommend modifications in humidification techniques as

HMV 11.0 MONITORING:

The humidification device should be inspected visually during the patient-ventilator system check and condensate should be removed from the patient circuit as necessary. HMEs should be inspected and replaced if secretions have contaminated the insert or filter. The following variables should be recorded during equipment inspection:
11.1 Humidifier setting (temperature setting or numeric dial setting or both). During routine use on an intubated patient, a heated humidifier should be set to deliver an inspired gas temperature of 33 ± 2°C and should provide a minimum of 30 mg/L of water vapor.(8-10)
11.2 Inspired gas temperature. Temperature should be monitored as near the patient's airway opening as possible, if a heated humidifier is used.
11.2.1 Specific temperatures may vary with patient condition, but the inspiratory gas should not exceed 37°C at the airway threshold.
11.2.2 When a heated-wire patient circuit is used (to prevent condensation) on an infant, the temperature probe should be located outside of the incubator or away from the direct heat of the radiant warmer.(l2)
11.3 Alarm settings (if applicable). High temperature alarm should be set no higher than 37°C, and the low temperature alarm should be set no lower than 30°C.(8,10)
11.4 Water level and function of automatic feed system (if applicable).
11.5 Quantity and consistency of secretions. Characteristics should be noted and recorded. When using an HME, if secretions become copious or appear increasingly tenacious, a heated humidifier should replace the HME.

HMV 12.0 FREQUENCY:

All patients with an artificial airway requiring mechanical ventilation should receive continuous humidification of inspired gases.

HMV 13.0 INFECTION CONTROL:

13.1 Reusable heated humidifiers should be subjected to high-level disinfection between patients.(35) Clean technique should be observed when manually filling the water reservoir. Sterile water should be used.
13.2 When using a closed, automatic feed system, the unused portion of water in the water feed reservoir remains sterile and need not be discarded when the patient circuit is changed. However, the water feed system should be designated for single patient use only.
13.3 Condensation from the patient circuit should be considered infectious waste and disposed of according to hospital policy using strict Universal Precautions.(35,38,39)
13.4 Because condensate is infectious waste, it should never be drained back into the humidifier reservoir.(35,38,39)
Mechanical Verltilatior Guidelines Committee:

Richard D Branson RRT, Chairman, Cincinnati OH
Robert S Campbell RRT, Cincinnati OH
Robert L Chatburn RRT, Cleveland OH
Jack Covington RRT, San Francisco CA

REFERENCES

  1. Mercke U. The influence of varying air humidity on mucociliary activity. Acta Otolaryngol 1975;79: 133-139.
  2. Marfatia S. Donahue PK, Henren WH. Effect of dry and humidified gases on the respiratory epithelium in rabbits. J Pediatr Surg 1975;40:583-585.
  3. Chalon J. Loew DAY, Malebranche J. Effect of dry anaesthetic gases on the tracheobronchial epithelium. Anaesthesiology 1972;37:338.
  4. Proctor D. Physiology of the upper airway. In: Vischer MB, Hastings AB, Pappenhiemer JR, Rahn H. eds. Handbook of physiology-- respiration 1. Baltimore: Williams & Wilkins, 1985:323-325.
  5. Moritz AR, Weisiger JR. Effects of cold air on the air passages and lungs. Arch Intern Med 1945;75:233-240.
  6. Burton JDK. Effects of dry anaesthetic gases on the respiratory mucus membrane. Lancet 1962;1:235.
  7. Dahlby RW, Hogg JC. Etfect of breathing dry air on structure and function of airways. J Appl Physiol 1980; 61(1):312-317.
  8. Branson RD. Humidification of inspired gases during mechanical ventilation. 1991; 3: 55-66.
  9. American National Standards Institute. Standard tor humidifiers and nebulizers for medical use. ANSI Z79;9, 1979.
  10. Chatburn RL, Primiano FP Jr. A rational basis for humidity therapy. Respir Care 1987;32:249-253.
  11. Chamney AR. Humidification requirements and techniques. Anaesthesia 1969;24:602.
  12. Chatburn RL. Physiologic and methodologic issues regarding humidity therapy. J Pediatr 1989; 114:416-42().
  13. Department of Health and Social Security. Evaluation of heated humidifiers. Health Equipment Information 1987; 177.
  14. Emergency Care Research Institute. Heated humidifiers. Health Devices 1987;16(7):223.
  15. Branson RD, Hurst JM. Laboratory evaluation of moisture output of seven airway heat and moisture exchangers. Respir Care 1987;32:741-747.
  16. Shelly MP, Bethune DW, Latimer RD. A comparison of five heat and moisture exchangers. Anaesthesia 1986; 41 :527-532.
  17. Revenas B. Lindholm CE. The foam nose--new disposable heat and moisture exchanger: a comparison with other similar devices. Acta Anaesthesiol Scand 1979;23:34-39.
  18. Ogino M, Kopotic R. Mannino FL. Moisture-conserving etficiency of condenser humidifiers. Anaesthesia 1985; 40:990-995.
  19. Leigh JM, White MG. A new condenser humidifier (letter). Anaesthesia 1984;39:492-493.
  20. Mebius CL. A comparative evaluation of disposable humidifiers. Acta Anaesthesiol Scand 1983;27:403-409.
  21. Gedeon A, Mebius C. The hygroscopic condenser humidifier: a new device for general use in anaesthesia and intensive care. Anaesthesia 1979;34: 1043-1047.
  22. Chalon J. Markham JP, Ali MM, Ramanathan S. Turndorf H. The Pall Ultipor breathing circuit filter: an efficient heat and moisture exchanger. Anaesth Analg 1984;63:566-570.
  23. Weeks DB, Ramsey FM. Laboratory investigation of six artificial noses for use during endotracheal anaesthesia. Anesth Analg 1983;62:758-763.
  24. Walker AK, Bethune DW. A comparative study of condenser humidifers. Anaesthesia 1976;31: 1086-1093.
  25. Turtle MJ, Ilsley AH, Rutten AJ, Runciman WB. An evaluation of six disposable heat and moisture exchangers. Anaesth Intensive Care 1987;15:317-322.
  26. Cohen IL, Weinberg PF, Fein IA, Rowiniski GS. Endotracheal tube occlusion associated with the use of heat moisture exchangers in the intensive care unit. Crit Care Med 1988; 16:277-279.
  27. Perch SA, Realey AM. Effectiveness of the Servo SH150 artificial nose humidifier: a case report. Respir Care 1984;29: 1009-1012.
  28. Martin C, Perrin G. Gevaudan MJ, Saux P. Gouin F. Heat and moisture exchangers and vaporizing humidifiers in the intensive care unit. Chest 1990;97:144-149.
  29. Shelly MP, Lloyd GM, Park GR. A review of the mechanisms and methods of humidification of inspired gas. Intensive Care Med 1988; 14:1-9.
  30. Klein EF Jr, Graves SA. "Hot pot" tracheitis. Chest 1974;65:225226.
  31. Ploysongsang Y. Branson RD, Rashkin MC, Hurst JM. Pressure flow characteristics of commonly used heatmoisture exchangers. Am Rev Respir Dis 1988;138: 675-678.
  32. Ploysongsang Y. Branson Rd. Rashkin MC, Hurst JM. Eftect of flow rate and duration of use on the pressure drop across six artificial noses. Respir Care 1989;34: 902-907.
  33. Nishimura M, Nishijima MK, Okada T. Taenaka Nt Yoshiya 1. Comparison of flow-resistive workload due to humidifying devices. Chest 1990;97:600-604.
  34. Marini JJ. Strategies to minimize breathing eftort during mechanical ventilation. Crit Care Clin 1990;6:635-661.
  35. Craven DE, Steger KA. Pathogenesis and prevention of nosocomial pneumonia in the mechanically ventilated patient. RespirCare 1989;34:85-97.
  36. Slee TA. Paulin EG. Failure of low pressure alarm associated with the use of a humidifier. Anesthesiology 1988;69:791-793.
  37. O'Hagan M, Reid E, Tarnow-Mordi WO. ls neonatal hlspired gas humidity accurately controlled by humidifier temperature? Crit Care Med 1991;19:1370-1373.
  38. Centers tor Disease Control. Update: Universal Precautions for prevention of transmission of human immunodeficiency virus, hepatitis B virus, and other blood-borne pathogens in health care settings. MMWR 1988;37:377-388.
  39. Boyce JM, White RL, Spruill EY, Wall M. Costeffective application of the Centers for Disease Control guidelines for prevention of nosocomial pneumonia. Am J Infect Control 1985;13:228-232.

 

Interested persons may copy these Guidelines for noncommercial purposes of scientific or educational advancement. Please credit AARC and Respiratory Care Journal.

Reprinted from the August 1992 issue of RESPIRATORY CARE [Respir Care 1992(8);37:887–890]

You are here: RCJournal.com » Clinical Practice Guidelines