Comparing Two Heat and Moisture Exchangers With One Vaporizing Humidifier in Patients With Minute Ventilation Greater Than 10 L/min

doi:10.1378/chest.107.5.1411

Chest

Volume 107, Issue 5, May 1995, Pages 1411-1415

https://doi.org/10.1378/chest.107.5.1411 Get rights and content

Study objective

To evaluate in patients submitted to minute ventilation >10 L/min the ability to preserve patients' heat and humidity of two heat and moisture exchangers (HMEs) and one vaporizing humidifier (VH).

Design

Prospective, randomized, comparative, nonblinded study.

Setting

Intensive care unit of a university hospital.

Patients

Nine tracheally intubated, mechanically ventilated patients, sedated and submitted to mechanical ventilation with minute ventilation >10 L/min.

Interventions

Using the psychrometric method, relative humidity (RH) and absolute humidity (AH) of inspired gas were obtained as well as temperature of inspired gas and tracheal temperatures (maximal and minimal). Following a randomized order, each patient was ventilated for two 24-h periods with a vaporizing humidifier (Bennett Cascade 2, Bennett; France) and one of two HMEs: Pall Ultipor filter BB50 (Pall Biomedical; France) or DAR Hygroster filter (Peters; France). Both were first tested for a 45-min period and then the HME that achieved the best performance in terms of temperature and water preservation was tested for 24 h.

Measurements and results

During the 45-min test period, the Pall Ultipor HME achieved a lower performance than the other two systems for any of the studied parameters (p<0.05 to p<0.0001). The DAR Hygroster HME achieved lower temperature of inspired gas (29.9 vs 32.0°C, p<0.005) and lower absolute humidity (29.3 vs 33.2 mg H₂O/L, p<0.005) than the Bennett Cascade 2. After 24 h of use, lower values of temperature of inspired gas (28.5 vs 32.0°C, p<0.002) and of AH (28.0 vs 33.6 mg H₂O/L, p<0.001) were obtained with the DAR Hygroster HME than with the Bennett Cascade 2. No differences were found between the two systems for the other tested parameters. At that time, no patients had RH lower than 97% and absolute humidity lower than 23 mg H₂O/L with the use of the DAR Hygroster HME.

Conclusions

In patients with minute ventilation > 10 L/min, the DAR Hygroster HME showed a thermic and humidification capability similar to the reference system, the Bennett Cascade 2 VH. In these patients, the Pall Ultipor HME had a significantly lower capability.

Section snippets

Methods

The patients were included in a prospective, randomized, controlled, nonblinded study. With institutional approval and informed consent from the families, we studied tracheally intubated, mechanically ventilated patients sedated with sufentanil and paralyzed with vecuronium bromide. They needed mechanical ventilation for acute respiratory failure following multiple trauma. The ventilatory circuit consisted of inspiratory and expiratory lines connected by a Y-piece (Fig 1). The ventilator used

Results

Nine patients were included in the study: 7 men and 2 women with a mean age of 55 ± 8 years (17 to 71 years) and a mean weight of 67 ± 10 kg (44 to 75 kg). The minute ventilation was 11.9 ± 1.2 L/min (10 to 14 L/min), the tidal volume was 694±143 mL (400 to 840 mL), the respiratory rate was 17.6±1.9 cycles/min (15 to 23 cycles/min), the PEEP was 7.4±3.5 cm H₂O (0 to 13 cm H₂O), and the FI0₂ was 0.55 ±0.12 (0.4 to 0.7). The esophageal temperature was 37.5±1,4°C (36.0 to 39.5°C) at the beginning

Discussion

This prospective randomized controlled study clearly shows large variations in the ability of one VH and two HMEs to preserve heat and water of the ventilatory gases when used in patients with minute ventilation >10 L/min. The VH tested (Bennett Cascade 2) was significantly superior to the other two devices (Pall Ultipor filter and DAR Hygroster). The DAR Hygroster HME was also clearly superior, in terms of temperature and water preservation, to the Pall Ultipor HME. This was observed in each

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This may underline the specific issue of the hygrometric measurements. Given that the performance of some devices may decrease with prolonged use, one limitation of the present study was that the performances of the devices were not assessed after prolonged use.17,49 The impact of prolonged use on HME performance and clinical consequences remains poorly documented and should be assessed, especially if passive humidifiers are used as first-line humidification devices.
Heat and moisture exchangers (HMEs) are increasingly used in the ICU for gas conditioning during mechanical ventilation. Independent assessments of the humidification performance of HMEs are scarce. The aim of the present study was thus to assess the humidification performance of a large number of adult HMEs.
We assessed 48 devices using a bench test apparatus that simulated real-life physiologic ventilation conditions. Thirty-two devices were described by the manufacturers as HMEs, and 16 were described as antibacterial filters. The test apparatus provided expiratory gases with an absolute humidity (AH) of 35 mg H₂O/L. The AH of inspired gases was measured after steady state using the psychrometric method. We performed three hygrometric measurements for each device, measured their resistance, and compared our results with the manufacturer data.
Of the 32 HMEs tested, only 37.5% performed well (≥ 30 mg H₂O/L), while 25% performed poorly (< 25 mg H₂O/L). The mean difference (± SD) between our measurements and the manufacturer data was 3.0 ± 2.7 mg H₂O/L for devices described as HMEs (maximum, 8.9 mg H₂O/L) [p = 0.0001], while the mean difference for 36% of the HMEs was > 4 mg H₂O/L. The mean difference for the antibacterial filters was 0.2 ± 1.4 mg H₂O/L. The mean resistance of all the tested devices was 2.17 ± 0.70 cm H₂O/L/s.
Several HMEs performed poorly and should not be used as HMEs. The values determined by independent assessments may be lower than the manufacturer data. Describing a device as an HME does not guarantee that it provides adequate humidification. The performance of HMEs must be verified by independent assessment.
Performance of heated wire humidifiers: An in vitro study
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The dry probe directly measures the actual gas temperature, whereas the wet probe, which is coated with sterile water–wetted cotton, measures the dryness of the gas. The evaporation of the sterile water is proportional to the dryness of the gas; thus, the difference in temperature levels between the dry and wet probes is related to the dryness of the gas [20]. The temperature levels at the dry and wet probes were measured over 10 consecutive breaths, and the mean value was calculated.
We assessed the performance of heated wire humidifiers (HWHs), which should avoid water condensation in the circuit.
We evaluated the efficiency of 3 HWHs, MR850 (Fisher & Paykel, Auckland, New Zealand), CONCHATHERM IV (Hudson RCI, Temecula, Calif), and DAR HC 2000 (Mallinckrodt DAR, Mirandola, Italy), in comparison with that of the MR730 heated humidifier (HH), which has a standard circuit. We measured gas temperature and absolute humidity (AH) at the Y piece of the ventilatory circuit using a test lung ventilated at 2 minute ventilation volumes (5 and 15 L/min). Temperature levels at the Y piece of the ventilatory circuit of the HHs were set at 35°C, 37°C, and 39°C with different gradients (−2°C, 0°C, and +2°C) between the outlet chamber and the Y piece of the ventilatory circuit.
At the set temperature levels of 35°C, 37°C, and 39°C with a gradient of 0°C, the MR850 and CONCHATHERM IV had lower gas temperature and AH levels as compared with the DAR HC 2000 and MR730 HH. With increasing temperature gradient, gas temperature increased only with the CONCHATHERM IV but AH increased with all the HWHs. The MR850 showed lower gas temperature and AH levels as compared with CONCHATHERM IV. The condensate was abolished inside the inspiratory circuit with the HWHs.
Heated wire humidifiers eliminate water condensation but present significant differences in gas temperature and AH levels that are lower than the expected settings.
Main Techniques for Evaluating the Performances of Humidification Devices Used for Mechanical Ventilation
2023, Humidification in the Intensive Care Unit: The Essentials
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Chest

Clinical Investigations in Critical CareComparing Two Heat and Moisture Exchangers With One Vaporizing Humidifier in Patients With Minute Ventilation Greater Than 10 L/min

Study objective

Design

Setting

Patients

Interventions

Measurements and results

Conclusions

Section snippets

Methods

Results

Discussion

Br J Anaesth

Chest

Br J Anaesth

Effect of dry anesthetic gases on tracheobronchial epithelium

Anesthesiology

Adult body temperature and heated humidification during general anesthesia

Anesth Analg

Effect of dry and humidified gases on the respiratory epithelium in rabbits

J Pediatr Surg

Humidification and mucus flow in the intubated trachea

Br J Anaesth

A study of humidification in tracheostomized dogs

Br J Anaesth

Humidity and the anesthetized patient

Anesthesiology

Contaminated condensate in mechanical ventilator circuits: a risk factor for nosocomial infections

Am Rev Respir Dis

Comparative evaluation of disposable humidifiers

Acta Anaesthesiol Scand

Hydrophobic versus hygroscopic heat-moisture exchangers

Anaesthesia

The Pall Ultipor breathing circuit filters—an efficient heat and moisture exchanger

Anesth Analg

A comparison of five heat and moisture exchangers

Anaesthesia

An evaluation of six disposable heat moisture exchangers

Anaesth Intensive Care

Laboratory investigation of six artificial noses for use during endotracheal anesthesia

Anesth Analg

Clinical Investigations in Critical Care
Comparing Two Heat and Moisture Exchangers With One Vaporizing Humidifier in Patients With Minute Ventilation Greater Than 10 L/min