Table 1.
Main characteristics of the randomized controlled trials included in the meta-analysis (HME vs HH with heated and non-heated wire)
| First Author/year | Study design | Population | Age | Exclusion criteria | Number of patients (HME/HH) | Severity of illness | Characteristic of passive humidifier/frequency of change | Active humidifier (HH) | TV/MV | Frequency of change of ventilator circuit | Diagnosis of VAP |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Oğuz 2013 [83] | SC/RCT | General ICU with intubation <24 hours | 47.9 vs 44.5 | Patients with intubation >24 hours, pneumonia | 18 vs 17 | n.a. | HME replaced daily | HH | n.a. | n.a. | CXR infiltration |
| Boots 2006 [82] | SC/RCT | General ICU with MV >48 hours | 59 vs 60 | Patients presenting history (airway hemorrhage, asthma, or airway burns) suggested a need for HH | 190 vs 191 | APACHE II 20 vs 20 | Hygroscopic HME with a bacterial viral filter/24 hours | Hot-water humidification with a heated wire in both inspiratory and expiratory circuit limbs (DHW) or the inspiratory limb only (SHW) | n.a. | Every new patients | CPIS ≥6 Tracheal suction |
| Lorente 2006 [81] | SC/RCT | ICU with patients expected to require mechanical ventilation for >5 days | 56 vs 55 | Age <18 years, HIV, WBC <1000 cells/mm3 solid or hematological tumor and immunosuppressive therapy | 53 vs 51 | APACHE II 18.11/18.72 | HME: Edith Flex (Datex-Ohmeda) changed at 48-hour interval | MR 850 ® (Fisher & Paykel Health Care Ltd, Auckland, New Zealand) and the Aerodyne 2000®servo-controlled humidifiers with wire-heated circuits without water traps and with an autofeed chamber to refill the chamber with water | n.a. | No routine change of ventilator circuit | Tracheal aspirate |
| Lacherade 2005 [80] | MC/RCT | 5 ICUs located in two French university-affiliated teaching hospitals Medical, Surgical, Neurosurgical requiring MV >48 hours | 55.2 vs 54.7 | Contraindications to the use of an HMEF or of an HH, patients admitted after cardiac arrest, patients already enrolled in a clinical trial, and patients with early decision of treatment withdrawal were not included | 185 vs 184 | SAPS II 45.4 vs 49.3 | DAR Hygrobac filter device (Tyco Healthcare/Nellcor, Pleasanton, CA, USA (changed at 48 hours interval) | The MR730 device (Fisher & Paykel Healthcare Ltd, Auckland, New Zealand). Heated wire | n.a. | Changed for every new patient | Invasive respiratory secretion samplings cultured quantitatively, using a protected telescoping catheter or BAL |
| Diaz 2002 [79] | SC/RCT | Intubated patients | 61 vs 66 | Previous pulmonary disease, hypothermia, pulmonary secretion or low expiratory volume | 23 vs 20 | n.a. | HME | HH | n.a. | n.a | n.a. |
| Memish 2001 [78] | SC/RCT | MV for 48 hours in adult ICUs, Medical surgical unit | 47.7 vs 46 | Ventilated <48 hours | 123 vs120 | APACHE II 20.8 vs 20.6 | HME Hudson RCI, Temecula, CA, USA)/n.a. | HH | n.a. | n.a. | Tracheal aspirate |
| Kollef 1998 [76] | SC/RCT | 17 years and required mechanical ventilation while in the ICU setting. | 57.8 vs 59 | Transferred from other hospitals and had already received mechanical ventilation, if they had heart or lung transplantation, or if they had massive hemoptysis | 163 vs 147 | APACHE II 17 vs 18.2 | Nellcor Puritan-Bennett; Eden Prairie, Minn)/every week | HH with heated wire circuit | The number of patients requiring a minute ventilation >10 L/min (38% vs 34%) | Changed for every new patient | Tracheal aspirate |
| Lucchetti 1998 [77] | SC/RCT | Critically ill patients with mechanical ventilation | 57 vs 56.3 | n.a. | 15 vs 30 | n.a. | Hygrobac DAR | Bennett Cascade II, MR600 Fysher and Paykel set at 37 °C | TV 563 vs 594.2 | n.a. | Airway secretion score |
| Boots 1997 [73] | SC/RCT | General/patients requiring MV > 48 hours | 51 | Patients with asthma, airway burns, or pulmonary hemorrhage | 42 (2 days), 33 (4 days) vs HH 41 (2 days) | APACHE II 19 vs18 | Bacterial-viral filter (Humid-Vent Filter Light, Gibeck Respiration, Vasby, Sweden)/2 days or 4 days circuit change (2 groups) | MR730, Fisher and Paykel Health Care Pty Ltd, Auckland, New Zealand/HH circuit with 2 days circuit change | n.a. | Every 48 hours | Tracheal aspirate |
| Hurni 1997 [74] | SC/RCT | Medical ICU/patients who required >48 hours of MV | 52.6 vs 59.5 | Hypothermic (central or rectal temperature <36 °C), or who had been intubated for 12 hours before ICU admission were excluded | 59 vs 56 | SAPS II 12.9 vs 12.8 | Hygroster; DAR; Mirandola, Italy/every 24 hours | Fisher Paykel; Auckland, New Zealand, or Puritan-Bennett set at 37 °C | n.a. | 48 Hours in HH group and weekly in HME | Tracheal aspirate |
| Kirton 1997 [75] | SC/RCT | 20-Bed trauma ICU >15 years who required MV | 47/46 vs 48 | Yes: requirement for high minute volume | 280 | Injury severity score (ISS) 22 vs 20 | Pall BB-100; Pall Corporation; East Hills, NY, USA (hydrophobic) 24 hours | Heated wire humidifier (H-wH) (Marquest Medical Products Inc., Englewood, CO, USA) | n.a. | Every 7 days | Tracheal aspirate |
| Branson 1996 [71] | SC/RCT | Surgical-medical ICU patients requiring mechanical ventilation deemed suitable for HME | 44 vs 41 | Patients deemed unsuitable for HME such as presence of thick or bloody secretions | 49 vs 54 | SAPS II 9 vs 8 | HME hygroscopic Baxter/24 hours | Heated wire humidifier MR730 (Fisher & Paykel) set at 36 °C | n.a. | Every 7 days | Tracheal aspirate |
| Villafane 1996 [72] | SC/RCT | Intubated and mechanically ventilated patients | 67 vs 59 | Patients with hemorrhagic disorder, intubated >24 hours, expected for intubation for short time, drugs overdose | 16 vs. 7 | SAPS 17 vs 17 | HME hygroscopic BB-2215, Pall. HME Hygroscopic 352/5411 DAR | MR310 Fysher and Paykel set at 32 °C | MV 11.3 vs 10.2 L/min | n.a. | n.a. |
| Dreyfuss 1995 [70] | SC/RCT | Medical patients who required >48 hours of MV | 58 vs 62 | No | 61 vs 70 | SAPS II 16.0 vs 16.4 | HME hygroscopic DAR-Hygrobac II (DAR SpA, Mirandola, Italy) device three-layer water-repellent membranes with electrostatic and mechanical filtering power and of one hygroscopic membrane/change on daily basis | Puritan-Bennett Respiratory Products, Santa Monica, CA) or Fischer-Paykel MR 450 or MR 460 devices | n.a. | Every new patient | Quantitative cultures of protected specimen brush |
| Roustan 1992 [69] | SC/RCT | General/patients requiring MV (France) | 52.7 (18.5) vs 49.3 (18.7) | Weight less than 35 kg and patients requiring high-frequency jet ventilation | 55 vs 61 | SAPS II 11.5 vs 11.5 | Pall Filter BB 2215 HME (hygrophobic)/every 24 hrs | Draegger Aquaport, temperature was set 31 and 32 at the Y piece. | TV 665 vs 460 ml | n.a. | None |
| Misset 1991 [68] | SC/RCT | Medical-surgical/patients requiring MV >5 days (France) | 53(14) vs 49 (13) | No | 30 vs 26 | SAPS II 14 vs 13 | HME hydrophobic (every 24 hours) | Bennett cascade II or Fisher Paykel MR 450 set at 32 °C or 34 °C | No difference in tracheal thickness and characteristic between MV >10 L and <10 L 11.9 (2.5) vs 11.2 (2.9) | Every 48 hours | Tracheal aspirate |
| Martin 1990 [67] | SC/RCT | All patients to receive mechanical ventilation for more than 24 hours | 61 vs 54 | No | 31 vs 42 | n.a. | Pall Ultipor (hydrophobic) breathing circuit filter (PUBCF) replaced at least daily | HH: set at 31 °C | 11 (2.5) vs 10.11 (3) | 3 Times weekly | Tracheal aspirates |
| Kirkegaard 1987 [66] | SC/RCT | Neurosurgical patients | 15 vs 15 | No | 52 vs 36 | n.a. | HME hygroscopic Engstrom Edith, Gambro | HH Hygrotherm | n.a | 24 Hours | None |
HME heat and moisture exchanger, HH heated humidifier, MV mechanical ventilation, VAP, ventilator-associated pneumonia, RCT randomized controlled trial, WBC white blood cells, APACHE acute physiology and chronic health evaluation, SAPS simplified acute physiology score