Heated Humidifiers Research Articles

In vivo efficacy of two heated humidifiers used during CPAP-therapy for obstructive sleep apnea under various environmental conditions.

To investigate the humidification performance-defined as the maximum achievable absolute humidity in the CPAP tube-of two heated humidifier systems (HH) offered as CPAP accessories, as a function of ambient air conditions. In 48 patients undergoing CPAP treatment, temperature (T) and relative humidity (RH) in the distal CPAP tube system were measured, with and without either of the two heated humidifiers A (HH-A, n=23), or B (HH-B, n=25), until a steady state was achieved. At the same time, ambient T and RH in the examination room were recorded. T and RH were used to calculate the absolute humidity (AH). University Hospital, Erlangen, Germany. PATICIPANTS: 48 patients with obstructive sleep apnea undergoing CPAP therapy. N/A. Conditions in the examination room during measurement with the HH-A, T = 22.5+2.1 (16.4-26.0) degrees C and AH = 9.3+2.4 (5.3-13.9) g/m3 did not differ significantly from those prevailing during measurements with the HH-B, T = 22.9+1.9 (18.9-26.3) degrees C and AH = 9.9+2.8 (6.2-16.4) g/m3. The mean humidification performance (steady state AH with HH within the CPAP tube) of the HH-A was 23.5+2.9 (19.1-29.9) g/m3, that of the HH-B 26.8+3.9 (21.0-34.4) g/m3. Under the ambient conditions of humidity and temperature, commonly found in European and North American bedrooms, both HH demonstrate a high humidification performance that even falls within the range recommended for intubated patients. The difference between the two HH is small, and probably not clinical relevant. Thus, it would appear that both HH are suitable for the treatment of dry upper airways under CPAP therapy.

Comparison of the Effects of Heat and Moisture Exchangers and Heated Humidifiers on Ventilation and Gas Exchange During Weaning Trials From Mechanical Ventilation

Heat and moisture exchangers (HME) are increasingly used to warm and humidify inspired gases in intubated ventilated patients. But these devices add dead space that may alter the alveolar ventilation. This could impair the efficiency of spontaneous ventilation (SV) during weaning trials from mechanical ventilation. Fifteen patients were tested with an HME (Hygrobac-DAR) and a heated humidifier (HH) (Fischer-Paykel MR 450) in a random order during weaning trials in SV with inspiratory pressure support. Minute ventilation VE, tidal volume), and respiratory rate were recorded and arterial blood was sampled for blood gas analysis with each device. The HME gave a significantly greater VE than the HH (9.3 +/- 0.8 L/min vs 8.1 +/- 0.8 L/min; p < 0.005), because of increased respiratory rate (21 +/- 2/min vs 19 +/- 2/min; p < 0.05). Tidal volume was unchanged for HME and HH (470 +/- 32 mL vs 458 +/- 39 mL). The higher PaCO2 with HME than with HH (44 +/- 2 mm Hg vs 42 +/- 2 mm Hg; p < 0.005) revealed an insufficient alveolar ventilation response to the increase in dead space. Arterial Po2 rose with the HME, but not significantly above the HH values (103 +/- 6 mm Hg vs 97 +/- 6 mm Hg; p = 0.055), possibly because of a positive end-expiratory pressure effect of the HME. The need to increase VE in SV when an HME is used should be taken into account during difficult weaning from mechanical ventilation.

Is reduction of intraoperative heat loss and management of hypothermic patients with anesthetic gas climate control advisable? Heat and humidity exchangers vs. active humidifiers ina functional lung model

Heated humidifiers (HH) as well as heat and moisture exchangers (HME) are commonly used in intubated patients as air-conditioning devices to raise the moisture content of the air, thus preventing mucosal damage and heat loss resulting from ventilation with dry inspired gases. In contrary to HME, HH are able to add heat and moisture to the inspired air in surplus, which is often stressed as an advantage in warming hypothermic patients or reducing major heat losses, e.g., during long operations. The impact of air conditioning on the energy balance of man was calculated comparing HME and HH. The efficiency of a HME (Medisize Hygrovent) and a HH (Fisher & Paykel MR 730) was evaluated in a mechanically ventilated lung model simulating the physiological heat and humidity conditions of the upper airways. The gas flow from the central supply was dry; the model temperature varied between 32 and 40 degrees C. By using a HH in the inspiratory limb, a circle system was simulated with water-saturated inspired air at room temperature. The water content of the ventilated air was determined at the tracheal tube connection using a fast, high-resolution humidity meter and was compared with the moisture return of the HME. The energy balance was calculated according to thermodynamic laws. Both HME and HH were able to create physiological heat and humidity conditions in the airways. With the normothermic patient model, the moisture return of the HME was equal to that of the HH set at 34 degrees C. Increasing the heating temperature resulted only in reduced water loss from the lung; heat and water input in the normothermic model was not possible. This was only effective with almost negligible amounts under hypothermic patient model conditions. The water content in the inspired and expired air is the most important parameter for estimating pulmonary heat loss in mechanically ventilated patients. In adults (minute volume approximately 71/min) the main fraction of pulmonary heat loss results from water evaporation from the airways (approximately 6 kcal/h), whereas the heat loss due to convection is negligible (approximately 1.2 kcal/h). In intubated patients ventilated with dry air, the heat loss increases to approximately 8 kcal/h due to greater water evaporation from the airways. Both HME and HH are able to reduce the pulmonary heat loss to 1-2 kcal/h. In normothermic as well as hypothermic patients, HH do not offer significant advantages in heat balance compared to effective HME. In conclusion, air conditioning in intubated patients is neither a powerful too for maintaining body temperature during long-lasting anaesthesia nor a sufficient method of warming hypothermic patients in intensive care units.

Evaluation du réchauffeur de perfusion Hotline™ chez l'enfant de moins de 10 kg

This randomized study assessed the efficacy of the Hotline™ fluid warner in 42 children under 10 kg, undergoing surgery of more than 1 h of duration. In all a heating mattress and a heating humidifier were also used. The decrease in core temperature was more important in children without warner (1.1 ± 1.4 °C vs 0.1 ± 0.3 °C in those with a warner). Efficiency of this device is demonstrated even at the low perfusion flows requested for surgery in newborns and infants.

Humidification in the Intensive Care Unit: Prospective Study of a New Protocol Utilizing Heated Humidification and a Hygroscopic Condenser Humidifier

Determine the utility of a proposed algorithm in allowing safe, efficient humidification in mechanically ventilated patients using both a hygroscopic condenser humidifier (HCH) and heated humidifier (HH). A prospective study using an algorithm to chose humidification devices based on physical examination and sputum characteristics. All patients admitted to the surgical ICU. One hundred twenty consecutive patients requiring mechanical ventilation (MV) were studied. Patients were examined by the attending respiratory care practitioner and given either an HCH or HH. If patients demonstrated any of the following--thick or tenacious secretions, core temperature < 32 degrees C, or bloody secretions--they were given an HH. All others used an HCH. If any of the above conditions occurred during HCH use, the patient was given an HH. Duration of ventilation, incidence of nosocomial pneumonia, ventilator circuit colonization, and mortality were determined for patients in each group. Cost of humidification devices, number of suctioning procedures per day, and volume of saline solution instilled were also recorded. Initially, 27 percent (32/120) of patients used an HH and 73 percent (88/120) used an HCH. During the study, ten patients required changing to an HH during HCH use. Patients in the HH group were more likely to have preexisting lung disease and had a longer duration of ventilation (83 +/- 21 h) and higher mortality (21 percent). Patients in the HCH group were more likely to be postoperative, had shorter durations of ventilation (38 +/- 14 h), and lower mortality (9 percent). There was no difference in the incidence of nosocomial pneumonia between the two groups (9 percent vs 6 percent) and endotracheal tube occlusion did not occur in either group. Circuit colonization was common in the HH group (64 percent) but rate in the HCH group (5 percent). Cost per day was significantly less for the HCH group ($4 vs $19.80). Patients who required a change from HCH to HH did so at a mean of 5 days. The proposed algorithm resulted in cost-efficient and safe application of humidification devices in patients in the surgical ICU.

Do heated humidifiers and heat and moisture exchangers prevent temperature drop during lower abdominal surgery?

Study Objective: To compare the effects of using a heated humidifier (HH), a heat and moisture exchanger (HME), or no warming device in maintaining body temperature during surgical procedures of 1 to 4 hours' duration. Design: A randomized, controlled study. Setting: Operating room, Thomas Jefferson University Hospital, Philadelphia, PA. Patients: 51 ASA physical status I, II, and III patients, age 16 to 69 years, scheduled, for a variety of lower abdominal procedures under general endotracheal anesthesia anticipated to last 1 to 4 hours. Interventions: We randomly assigned patients to receiving an IIH, an HME, or no warming device during the procedure. We then measured the patient's sublingual temperature every 5 minutes prior to induction, every 15 minutes intraoperatively, and every 15 minutes postoperatively until he or she was discharged from the postanesthesia care unit, (PACU). We also measured the esophageal temperature every 15 minutes intraoperatively. Measurements and Main Results: Sublingual temperature or esophageal temperature probes placed at the site of maximal heart tones indicated that the patients' temperatures dropped significantly from baseline values in all three groups during the first 60 minutes of surgery, then remained constant during the next 120 minutes of surgery. Patients who had no warming device shivered and felt cold significantly more often than patients in the HH group but not more often than patients in the HME group. There was no difference in shivering between the HH and HME groups. The patients who received an HH tended to have a higher temperature (a mean of 0.5°C) throughout the study, but this did not reach statistical significance. Conclusions: Results indicate that these warming devices provide little benefit in preventing a temperature drop during procedures of 1 to 4 hours' duration, although patients with an HH tended to have a higher temperature than those with an HME or no device.

Heat and Moisture Exchanger vs Heated Humidifier during Long-Term Mechanical Ventilation: A Prospective Randomized Study

Adequate humidification of inspired gases with HMEs during long-term MV remains controversial. In this study, a comparison is made between tracheal secretions during long-term MV either with HME or conventional HH. Both the HME and HH groups were similar with respect to age, sex, diagnosis, duration of MV, SAPS and mortality. Temperature of gases in the tracheal tube was lower and the amount of tracheal instillations was greater in the HME group than in the HH group. Tracheal secretions became thicker between day 1 (control) and day 5, in the HME group than in the HH group. Four and two tube occlusions occurred in HME and HH groups, respectively. Tracheal bacterial colonization was similar in the two groups. Given the advantages of HME (reduced nurses' work and financial cost), HME could be routinely used under cautious surveillance and replaced by HH if difficulty in suctioning occurs.

Inexpensive temperature monitor for heated humidifiers

A commercially available indoor/outdoor electronic thermometer has been adapted to monitor both airway gas temperature and operating room temperature when heated humidifiers are used. Heated humidifiers that do not have temperature monitoring capabilities pose a risk of dangerously high inspired gas temperatures.

A Practical Way of Using Heated Humidifiers with Pediatric T-piece Systems

A Practical Way of Using Heated Humidifiers with Pediatric T-piece Systems