Heated Humidifiers Research Articles

Mist nebulizer versus heated humidifier on endotracheal tube patency in spontaneously breathing intubated patients: A prospective, randomized controlled trial.

Using a humidifier in intubated patients is now a standard of care as the humidifying effect of the upper airway is lost. We conducted this study to compare the efficacy of a heated humidifier (HH) with the more commonly used conventional mist nebulizer on overnight intubated and spontaneously breathing post-operative patients. This prospective, randomized control trial included 60 post-operative overnight intubated and spontaneously breathing patients, of which 30 patients were allocated to the HH group and 30 to the mist nebulizer group. The reduction of endotracheal tube (ETT) patency was measured quantitatively by the difference between the pre-intubation and immediate post-extubation ETT volume and compared between the two groups. Also, the characteristics of secretion, the temperature of inspired gas at the Y-piece, and the frequency of refilling the humidifier chamber were recorded and compared. The reduction of ETT volume was significantly more in the mist nebulizer group compared to the HH group (P-value 0.00026). The mean temperature of the inspired gas (°C) was higher in the HH group (P-value < 0.0001). More patients in the mist nebulizer group had thicker (P-value 0.057) and drier secretions (P-value 0.005) compared to the HH group. None of the patients in the HH group required refilling of the humidifier chamber while the mean frequency of the refilling was 3.5 times per patient in the mist nebulizer group. HH may be preferred over mist nebulizer as the latter requires more frequent refilling which may not be practically possible in a busy recovery room rendering the patient at the risk of inhaling dry gas and consequent thick and dry secretions with decreased ETT patency.

Effect of active airway warming with a heated-humidified breathing circuit on core body temperature in patients under general anesthesia: a systematic review and meta-analysis with trial sequential analysis.

The application of a heated-humidified breathing circuit (HHBC) may reduce respiratory heat loss during mechanical ventilation, but its effect in preventing intraoperative hypothermia is controversial. This study aimed to investigate the effectiveness of HHBC in maintaining the core temperature of patients receiving mechanical ventilation under general anesthesia. We searched MEDLINE, Embase, Cochrane library (CENTRAL), and Google Scholar to identify all randomized controlled trials (RCTs) up to February 2022 that compared the intraoperative core temperature in patients with heated humidifier (HH) and other circuit devices. The primary outcome was the intraoperative core temperature at the end of surgery. The weighted mean differences (WMDs) between the groups and their 95% CIs were calculated for each outcome. We performed a trial sequential analysis of the primary outcomes to assess whether our results were conclusive. Eighteen RCTs with 993 patients were included in the analysis. A significantly higher core temperature was observed at the end of surgery in patients with HH than those with no device (WMD = 0.734, 95% CI [0.443, 1.025]) or heat and moisture exchanger (WMD = 0.368, 95% CI [0.118, 0.618]), but with substantial heterogeneity. Although HHBC did not absolutely prevent hypothermia, this meta-analysis suggests that it can be used as an effective supplemental device to maintain the intraoperative core temperature under general anesthesia. However, considering the substantial heterogeneity and limitations of this study, further well-designed studies are needed to clarify the effectiveness of HHBC.

REDUCING VENTILATOR ALARMS THROUGH DECREASED RAINOUT IN VENTILATOR CIRCUITS: A BENCH STUDY

Alarm fatigue is a significant problem in healthcare, particularly in high acuity settings such as intensive care, surgery, and emergency departments. Alarms are triggered by various devices such as anesthesia machines, ventilators, patient monitors or humidifiers. Heated humidifiers (HH) used with mechanical ventilators, while necessary to prevent other complications associated with mechanical ventilators, may cause condensation in the ventilator circuit, prompting occlusion alarms indicating a risk for the patient. Technological advances in HH circuits may reduce rainout in the circuits and therefore occlusion alarms. Bench experiments measured alarms and rainout of two commercially available humidifiers (AirLife DuoTherm™ and Fisher &amp; Paykel MR850) and four different pediatric and adult patient breathing circuits. The tests examined condensation accumulation in the circuits after 24 hours of low-, nominal-, or high-flow rates of gas at low-, nominal-, and high-ambient temperature settings. Dual-limb designs of adult- and neonate-sized circuits underwent evaluation. Data on alarms was collected for each system. Low temperature and occlusion alarms were less common in DuoTherm vs. MR850 HH circuits (6 vs. 68 alarms, respectively). DuoTherm products accumulated significantly less rainout for both circuit sizes at all ambient temperatures. In general, the set flow rate did not dramatically affect the amount of rainout for adult and infant circuits, but low versus high ambient temperatures yielded increased rainout for all circuit types (p &lt; 0.02). The DuoTherm HH device and patient circuits developed significantly less alarms due to rainout and low temperatures compared to those from MR850 under all the conditions tested. Such reduction in patient alarms should help reduce alarm fatigue among healthcare workers in critical care settings.

Gas conditioning during helmet noninvasive ventilation: effect on comfort, gas exchange, inspiratory effort, transpulmonary pressure and patient\u2013ventilator interaction

BackgroundThere is growing interest towards the use of helmet noninvasive ventilation (NIV) for the management of acute hypoxemic respiratory failure. Gas conditioning through heat and moisture exchangers (HME) or heated humidifiers (HHs) is needed during facemask NIV to provide a minimum level of humidity in the inspired gas (15 mg H2O/L). The optimal gas conditioning strategy during helmet NIV remains to be established.MethodsTwenty patients with acute hypoxemic respiratory failure (PaO2/FiO2 < 300 mmHg) underwent consecutive 1-h periods of helmet NIV (PEEP 12 cmH2O, pressure support 12 cmH2O) with four humidification settings, applied in a random order: double-tube circuit with HHs and temperature set at 34 °C (HH34) and 37 °C (HH37); Y-piece circuit with HME; double-tube circuit with no humidification (NoH). Temperature and humidity of inhaled gas were measured through a capacitive hygrometer. Arterial blood gases, discomfort and dyspnea through visual analog scales (VAS), esophageal pressure swings (ΔPES) and simplified pressure–time product (PTPES), dynamic transpulmonary driving pressure (ΔPL) and asynchrony index were measured in each step.ResultsMedian [IqR] absolute humidity, temperature and VAS discomfort were significantly lower during NoH vs. HME, HH34 and HH37: absolute humidity (mgH2O/L) 16 [12–19] vs. 28 [23–31] vs. 28 [24–31] vs. 33 [29–38], p < 0.001; temperature (°C) 29 [28–30] vs. 30 [29–31] vs. 31 [29–32] vs 32. [31–33], p < 0.001; VAS discomfort 4 [2–6] vs. 6 [2–7] vs. 7 [4–8] vs. 8 [4–10], p = 0.03. VAS discomfort increased with higher absolute humidity (p < 0.01) and temperature (p = 0.007). Higher VAS discomfort was associated with increased VAS dyspnea (p = 0.001). Arterial blood gases, respiratory rate, ΔPES, PTPES and ΔPL were similar in all conditions. Overall asynchrony index was similar in all steps, but autotriggering rate was lower during NoH and HME (p = 0.03).ConclusionsDuring 1-h sessions of helmet NIV in patients with hypoxemic respiratory failure, a double-tube circuit with no humidification allowed adequate conditioning of inspired gas, optimized comfort and improved patient–ventilator interaction. Use of HHs or HME in this setting resulted in increased discomfort due to excessive heat and humidity in the interface, which was associated with more intense dyspnea.Trail Registration Registered on clinicaltrials.gov (NCT02875379) on August 23rd, 2016.

Effect of using Heated Humidifier versus Heat Moister Exchangers on Tracheobronchial Secretion and Body Temperature among Mechanically Ventilated Patients

Effect of using Heated Humidifier versus Heat Moister Exchangers on Tracheobronchial Secretion and Body Temperature among Mechanically Ventilated Patients

Impact of Airway Humidification Strategy in Mechanically Ventilated COVID-19 Patients.

Humidification of inspiratory gases is mandatory in all mechanically ventilated patients in ICUs, either with heated humidifiers (HHs) or with heat and moisture exchangers (HMEs). In patients with COVID-19, the choice of the humidification device may have relevant impact on patients' management as demonstrated in recent studies. We reported data from 2 ICUs using either HME or HH. Data from patients with COVID-19 requiring invasive mechanical ventilation during the first wave in 2 ICUs in Québec City were reviewed. In one ICU, HMEs were used, whereas heated-wire HHs were used in the other ICU. We compared ventilator settings and arterial blood gases at day one after adjustment of ventilator settings. Episodes of endotracheal tube occlusions (ETOs) or subocclusions and a strategy to limit the risk of under-humidification were reported. On a bench test, we measured humidity with psychrometry with HH at different ambient temperature and evaluated the relation with heater plate temperature. We reported data from 20 subjects positive for SARS-Cov-2, including 6 in the ICU using HME and 14 in the ICU using HH. In the HME group, PaCO2 was higher (48 vs 42 mm Hg) despite higher minute ventilation (171 vs 145 mL/kg/min predicted body weight [PBW]). We also reported 3 ETOs occurring in the ICU using HH. The hygrometric bench study reported a strong correlation between heater plate temperatures of the HH and humidity delivered. After implementation of measures to avoid under-humidification, including heater plate temperature monitoring, no more ETOs occurred. The choice of the humidification device used in subjects with COVID-19 had a relevant impact on ventilation efficiency (increased CO2 removal with lower dead space) and on complications related to low humidity, including ETOs that may be present with heated-wire HHs when used with high ambient temperatures.

Knowledge and current practices of ICU nurses regarding aerosol therapy for patients treated with invasive mechanical ventilation: A nationwide cross-sectional study.

This study aimed to determine the knowledge and current practices of ICU nurses regarding aerosol therapy for patients with invasive mechanical ventilation in China. Aerosol therapy is a routine operation for intensive care unit (ICU) nurses; however, evidence of the knowledge and current practices of ICU nurses regarding aerosol therapy for patients with invasive mechanical ventilation is insufficient in China. A total of 433 hospitals in 92 cities (including 31 capital cities) in 31 provinces in China participated in the study. A questionnaire was used to investigate the knowledge and current practices of ICU nurses regarding aerosol therapy for patients treated with invasive mechanical ventilation, including 42 questions covering five aspects: sociodemographic information, aerosolisation devices, atomised drugs, atomisation operation and atomisation-related knowledge. Descriptive analyses of the distribution of the sample are reported as percentages and medians. Univariate and multivariate analysis was used to detect the factors of the interviewee's atomisation knowledge and practices scores. A STROBE checklist was used to guide the reporting of the research. Of the 1995 questionnaires that were returned, 1978 were analysed. Bronchodilators and glucocorticoids were the most frequently administered drugs. Seventy-four per cent of the total respondents reported placing a filter on the expiratory limb during aerosol therapy, and 47% of these reported that the filter was changed once a day. Only 13% of the respondents reported always turning the heating humidifier off during aerosol therapy, and 48% never did. Knowledge about the optimal droplet size or atomisation yield was poor. Work experience in the ICU and frequency of atomisation training were the independent influencing factors for atomisation knowledge and practice scores (F=279.653,p<.001;F=120.556,p<.001, respectively). The knowledge of ICU nurses about the optimal implementation of aerosol therapy is poor, and the current scientific knowledge about optimal implementation seemed to be applied infrequently. Atomisation-related training should be strengthened, especially for nurses with junior titles and with less work experience. Improving the level of ICU nurses' atomisation practice ability is helpful to ensure patient safety. In clinical work, atomisation expert consensus can be used to carry out relevant training and standardise atomisation operation.

Removal of a catheter mount and heat-and-moisture exchanger improves hypercapnia in patients with acute respiratory distress syndrome: A retrospective observational study.

To avoid ventilator-associated lung injury in acute respiratory distress syndrome (ARDS) treatment, respiratory management should be performed at a low tidal volume of 6 to 8 mL/kg and plateau pressure of ≤30 cmH2O. However, such lung-protective ventilation often results in hypercapnia, which is a risk factor for poor outcomes. The purpose of this study was to retrospectively evaluate the effectiveness and safety of the removal of a catheter mount (CM) and using heated humidifiers (HH) instead of a heat-and-moisture exchanger (HME) for reducing the mechanical dead space created by the CM and HME, which may improve hypercapnia in patients with ARDS.This retrospective observational study included adult patients with ARDS, who developed hypercapnia (PaCO2 > 45 mm Hg) during mechanical ventilation, with target tidal volumes between 6 and 8 mL/kg and a plateau pressure of ≤30 cmH2O, and underwent stepwise removal of CM and HME (replaced with HH). The PaCO2 values were measured at 3 points: ventilator circuit with CM and HME (CM + HME) use, with HME (HME), and with HH (HH), and the overall number of accidental extubations was evaluated. Ventilator values (tidal volume, respiratory rate, minutes volume) were evaluated at the same points.A total of 21 patients with mild-to-moderate ARDS who were treated under deep sedation were included. The values of PaCO2 at HME (52.7 ± 7.4 mm Hg, P < .0001) and HH (46.3 ± 6.8 mm Hg, P < .0001) were significantly lower than those at CM + HME (55.9 ± 7.9 mm Hg). Measured ventilator values were similar at CM + HME, HME, and HH. There were no cases of reintubation due to accidental extubation after the removal of CM.The removal of CM and HME reduced PaCO2 values without changing the ventilator settings in deeply sedated patients with mild-to-moderate ARDS on lung-protective ventilation. Caution should be exercised, as the removal of a CM may result in circuit disconnection or accidental extubation. Nevertheless, this intervention may improve hypercapnia and promote lung-protective ventilation.

Heated Humidifiers for Noninvasive Respiratory Support and the Risk of Burns in Neonates: A Bench Evaluation.

User errors in managing heated humidifiers (HHs) have been suggested to be a source of nasal burns in newborns treated with nasal CPAP. This study evaluated the risk of burns by reproducing 3 typical errors concerning the use of HHs. Six HHs were tested on a bench in a traditional nasal CPAP setup: PMH5000, Aircon (Wilamed); MR730, MR850, MR950 (Fisher & Paykel); and H900 (Hamilton). Temperature was measured at the end of the inspiratory tubing limb. Errors tested were (1) misconnection of the HH thermal probes (NoProbe), (2) absence of gas flow while the HH is on (NoFlow), and (3) unsuitable repeated acknowledgment of the HH alarm (NoAlarm). These errors were combined in 3 standardized scenarios: (1) NoProbe + NoFlow + NoAlarm; (2) NoProbe + NoAlarm, and (3) NoFlow + NoAlarm. The NoProbe + NoFlow + NoAlarm and NoProbe + NoAlarm scenarios were not tested in the H900 and MR950 because the proprietary circuits of these HHs are equipped with embedded probes. For each HH, the highest inspiratory gas temperature (HIGT) and the rating on a self-designed risk-of-burn scale (ie, no risk, moderate risk, or severe risk) were reported. In the NoProbe + NoFlow + NoAlarm scenario, the risk was severe for the MR730, PMH5000, MR850, and Aircon, with HIGTs of > 65°C, 58°C, 56°C, and > 65°C, respectively. In the NoProbe + NoAlarm scenario, the risk was also severe for the same 4 HHs, with HIGTs of 56°C, 47°C, 56°C, and 48°C, respectively. In the NoFlow + NoAlarm scenario, the risk was severe for the PMH5000, Aircon, and H900, with HIGTs of 52°C, > 65°C, and 49°C, respectively, and moderate for the MR730, MR850, and MR950, with HIGTs of 45°C, 47°C, and 44°C, respectively). In case of misuse, 5 of the 6 tested devices presented a severe risk of inducing skin burns, whereas the MR950 presented a moderate risk.

Humidicare – an implementation study of a novel HME safety device designed to prevent ventilator circuit occlusion due to inadvertent dual humidification

Mechanical ventilation bypasses the protective mechanisms of the upper respiratory tract which are designed to heat and humidify inspired air to 37 °C and 44 mg H2O/L respectively. Artificial humidification systems are therefore incorporated into ventilation circuits to condition cold and dry medical gases before they reach the lower respiratory tract and cause patient harm. Commonly either a heat and moisture exchanger (HME) or a heated humidifier (HH) are utilised for this purpose, however the inadvertent simultaneous use of both devices within the same circuit can cause critical airway occlusion within 24 h. The Humidicare HME (Medovate, Cambridge, UK) is a safety engineered temperature-dependent warning system designed to activate when inadvertently placed into a warm circuit containing a HH. This study aimed to determine the efficacy of the Humidicare HME warning system in simulated clinical conditions. The threshold temperature for activation of the device was determined in a digital incubator, and the device was tested for efficacy with a HH present or absent from the breathing circuit. The device performed reliably and activated rapidly when required across all simulations. The Humidicare HME warning system is a simple and unobtrusive device which can effectively alert the operator to the error of dual humidification.

A comparative evaluation of three common airway humidification methods for patients with severe traumatic brain injury

Airway humidification methods are commonly used in clinical practice, but no clear consensus exists on which particular method is best suited for specific clinical conditions. In this retrospective study, we carried out a quantitative evaluation of three methods commonly used for patients with severe traumatic brain injury (STBI). We recruited 150 patients who received airway humidification after tracheotomy. Subjects were divided into three groups according to the humidification method they received which included oxygen atomizer (OA) group, heat and moisture exchangers (HMEs) group, and heated humidifiers (HHs) group. Variables including phlegm viscosity, humidification effects, phlegm formation rates, daily sputum inhalation times, airway spasm, secondary lung infections, daily nursing load, and evaluation of nurse job satisfaction levels were documented. Results indicated that the OA tended to cause either insufficient or excessive humidification, whereas phlegm scab formation was significantly reduced in HHs. HMEs and HHs displayed equal humidification effects, and a similar daily sputum induction and consequent nursing load. Airway spasm was a frequent occurrence in OA. The severity, but not the infection ratio, of secondary infection decreased significantly in HHs by the 30th day. The OA significantly reduced nursing load, but demonstrated the worst humidification effects. Overall results suggested that the HHs is more suitable for airway nursing of STBI patients who are bedridden for extended periods.

Performance of Different Active Humidification Systems in High-Flow Oxygen Therapy.

We sought to evaluate the performance in terms of absolute humidity (AH), relative humidity (RH), and temperature of different heated humidifiers (HH) and circuits that are commonly used to deliver high-flow oxygen therapy in conventional ranges (30-60 L/min) and unconventional ranges (70-100 L/min). In this prospective, observational study, an electronic thermohygrometer was used to obtain the required measurements. A mechanical ventilator was used as a source for high-flow nasal cannula oxygen therapy. For active humidification, the following equipment was used: a HH with standard disposable water trap circuit, 3 servo-controlled HH, and 7 circuits with a heated wire. Data on environmental conditions (ie, temperature, RH, AH) were collected from the laboratory during each measurement; the temperature, RH, and AH resulting from the application of 8 flows (30-100 L/min) were also recorded. Variables were compared with analysis of variance for repeated measurements with Tukey post hoc tests. A value of P < .05 was assumed to be significant. During the study, a statistically significant difference was found in the average AH for each flow for the different devices (P < .005). The highest AH values were recorded with the Fisher & Paykel MR850 and the Medtronic-DAR circuit (AH = 40.8 mg/L with flow of 50 L/min, P < .005), and the lowest AH values were recorded with the Flexicare FL9000 HH and the Flexicare circuit (AH = 11.4 mg/L with 100 L/min flow, P < .005). For flows > 50 L/min, the best performance for all flows in terms of AH was found with the Fisher & Paykel MR850 HH, regardless of the circuit used. During oxygen therapy with very high gas flows, HH devices behave differently and in many cases are inefficient in delivering adequate humidification, even at conventional flows. Caution is therefore recommended when selecting the device and flow settings for the implementation of high-flow nasal cannula oxygen therapy.

Active humidification in mechanical ventilation is not associated to an increase in respiratory infectious complications in a quasi-experimental pre–post intervention study

ObjectiveThere is controversy regarding the influence of humidification systems upon the incidence of respiratory infections associated to invasive mechanical ventilation (IMV). An evaluation was made of the differences in the incidence of pneumonia and tracheobronchitis associated to mechanical ventilation (VAP and VAT, respectively) with passive and active humidification. DesignA retrospective pre–post quasi-experimental study was carried out. SettingA polyvalent ICU with 14 beds. PatientsAll patients connected to IMV for >48h during 2014 and 2016 were included. InterventionsDuring 2014, passive humidification with an hygroscopic heat and moisture exchanger (HME) was used, while during 2016 active humidification with a heated humidifier (HH) and an inspiratory heated wire was used. Identical measures for the prevention of VAP were established (Zero Pneumonia Project). Main outcome measuresThe incidence of VAP and VAT was estimated for 1000 days of IMV in both groups, and statistically significant differences were assessed using Poisson regression analysis. ResultsA total of 287 patients were included (116 with HME and 171 with HH). The incidence density of VAP per 1000 days of IMV was 5.68 in the HME group and 5.80 in the HH group (p=ns). The incidence density of VAT was 3.41 and 3.26 cases per 1000 days of VMI with HME and HH respectively (p=ns). The duration of IMV was identified as a risk factor for VAP. ConclusionsIn our population, active humidification in patients ventilated for >48h was not associated to an increase in respiratory infectious complications.

Tidal Volume Lowering by Instrumental Dead Space Reduction in Brain-Injured ARDS Patients: Effects on Respiratory Mechanics, Gas Exchange, and Cerebral Hemodynamics.

BackgroundLimiting tidal volume (VT), plateau pressure, and driving pressure is essential during the acute respiratory distress syndrome (ARDS), but may be challenging when brain injury coexists due to the risk of hypercapnia. Because lowering dead space enhances CO2 clearance, we conducted a study to determine whether and to what extent replacing heat and moisture exchangers (HME) with heated humidifiers (HH) facilitate safe VT lowering in brain-injured patients with ARDS.MethodsBrain-injured patients (head trauma or spontaneous cerebral hemorrhage with Glasgow Coma Scale at admission < 9) with mild and moderate ARDS received three ventilatory strategies in a sequential order during continuous paralysis: (1) HME with VT to obtain a PaCO2 within 30–35 mmHg (HME1); (2) HH with VT titrated to obtain the same PaCO2 (HH); and (3) HME1 settings resumed (HME2). Arterial blood gases, static and quasi-static respiratory mechanics, alveolar recruitment by multiple pressure–volume curves, intracranial pressure, cerebral perfusion pressure, mean arterial pressure, and mean flow velocity in the middle cerebral artery by transcranial Doppler were recorded. Dead space was measured and partitioned by volumetric capnography.ResultsEighteen brain-injured patients were studied: 7 (39%) had mild and 11 (61%) had moderate ARDS. At inclusion, median [interquartile range] PaO2/FiO2 was 173 [146–213] and median PEEP was 8 cmH2O [5–9]. HH allowed to reduce VT by 120 ml [95% CI: 98–144], VT/kg predicted body weight by 1.8 ml/kg [95% CI: 1.5–2.1], plateau pressure and driving pressure by 3.7 cmH2O [2.9–4.3], without affecting PaCO2, alveolar recruitment, and oxygenation. This was permitted by lower airway (− 84 ml [95% CI: − 79 to − 89]) and total dead space (− 86 ml [95% CI: − 73 to − 98]). Sixteen patients (89%) showed driving pressure equal or lower than 14 cmH2O while on HH, as compared to 7 (39%) and 8 (44%) during HME1 and HME2 (p < 0.001). No changes in mean arterial pressure, cerebral perfusion pressure, intracranial pressure, and middle cerebral artery mean flow velocity were documented during HH.ConclusionThe dead space reduction provided by HH allows to safely reduce VT without modifying PaCO2 nor cerebral perfusion. This permits to provide a wider proportion of brain-injured ARDS patients with less injurious ventilation.

Heated Humidifier versus Heat-and-Moisture Exchanger During Positive Pressure Ventilation With a T-Piece Resuscitator in Rabbits.

There are many proven benefits of the use of conditioned gases in mechanically ventilated patients. In spite of this, its use in the delivery room is limited, perhaps because of known difficulties with heated humidifiers (HH); moreover, there is no evidence regarding the use of heat-and-moisture exchangers (HME) in a delivery room setting. We sought to asess the airway's absolute humidity level using three diferents strategies: HH, HME and unconditioned gases. We conducted an experimental study in 12 intubated rabbits ventilated with a T-piece resuscitator. Absolute humidity levels in inspired gases were measured at baseline and at 5, 10, 15, and 20 min while using HH, HME, or no conditioning method (ie, unconditioned). The animals were initially randomized to one of the 3 interventions, and each animal underwent the other methods with at least 24 h between each test. There were no differences in vital signs at baseline or at the end of the procedures. Mean absolute humidity at the end of the tests was 38.2 ± 1.7 g/m3 for HH, 28.9 ± 4.7 g/m3 for HME, and 13.9 ± 5.1 g/m3 for unconditioned gas (P = .003). During ventilation with a T-piece resuscitator, the absolute humidity was the highest with HH. The absolute humidity with HME was lower, but it was still significantly more than that with unconditioned gas. Therefore, the use of a T-piece resuscitator with HME could be a good alternative to HH given that positive-pressure ventilation is used ideally for short periods of time in the delivery room.

Effects on Humidification and Ventilatory Parameters of Three Single-limb Heated-wired Circuits for Non-invasive Ventilation: A Bench Study

BackgroundThe objective of this study was to evaluate the effects of three single-limb heated wired circuits (SLHWC) for NIV, on ventilatory parameters and humidification performance in a simulation lung model. MethodsThree SLHWC compatible with the MR-850 Heated Humidifier (HH) (Fisher & Paykel, Auckland, New Zealand) were tested: RT-319 (FP) (Fisher & Paykel, Auckland, New Zealand), Respironics 1045770 (RP) (DEAS, Castel Bolognese, Italy) and Intersurgical B/SYS 5809001 (IT) (Intersurgical, Wokingham, UK). A Bipap Vision ventilator (Philips Respironics, Murrysville, PA, USA) in pressure control ventilation (PCV) connected to a test lung was used for simulation. Each SHWC performance was evaluated in four ventilatory conditions: IPAP of 15cmH2O with FiO2 0.3 and 1, respectively; and, IPAP of 25cmH2O with FiO2 0.3 and 1, respectively. EPAP was set at 5cmH2O. Hygrometric and ventilatory measurements including: relative humidity (RH), temperature (T), Pplat, PIP, PEEP, peak inspiratory flow (PIF), and tidal volume (Vt) were measured. ResultsIn each FiO2 group absolute humidity (AH) was similar with FP regardless of the IPAP level employed compared to IT and RP (P<.001). Except for RP at FiO2 0.3, AH increased significantly in IT and RP groups as IPAP increased (P<.001). PIP, Pplat, PEEP, PIF, and Vt values were significantly higher with FP and RP in each FiO2 group compared to IT (P<.001). ConclusionsHumidification performance varied significantly among the three circuits, being FP the only one able to maintain stable AH values during the study with no influence on ventilatory parameters.

Effects on Humidification and Ventilatory Parameters of Three Single-limb Heated-wired Circuits for Non-invasive Ventilation: A Bench Study

BackgroundThe objective of this study was to evaluate the effects of three single-limb heated wired circuits (SLHWC) for NIV, on ventilatory parameters and humidification performance in a simulation lung model. MethodsThree SLHWC compatible with the MR-850 Heated Humidifier (HH) (Fisher & Paykel, Auckland, New Zealand) were tested: RT-319 (FP) (Fisher & Paykel, Auckland, New Zealand), Respironics 1045770 (RP) (DEAS, Castel Bolognese, Italy) and Intersurgical B/SYS 5809001 (IT) (Intersurgical, Wokingham, UK). A Bipap Vision ventilator (Philips Respironics, Murrysville, PA, USA) in pressure control ventilation (PCV) connected to a test lung was used for simulation. Each SHWC performance was evaluated in four ventilatory conditions: IPAP of 15cmH2O with FiO2 0.3 and 1, respectively; and, IPAP of 25cmH2O with FiO2 0.3 and 1, respectively. EPAP was set at 5cmH2O. Hygrometric and ventilatory measurements including: relative humidity (RH), temperature (T), Pplat, PIP, PEEP, peak inspiratory flow (PIF), and tidal volume (Vt) were measured. ResultsIn each FiO2 group absolute humidity (AH) was similar with FP regardless of the IPAP level employed compared to IT and RP (P<.001). Except for RP at FiO2 0.3, AH increased significantly in IT and RP groups as IPAP increased (P<.001). PIP, Pplat, PEEP, PIF, and Vt values were significantly higher with FP and RP in each FiO2 group compared to IT (P<.001). ConclusionsHumidification performance varied significantly among the three circuits, being FP the only one able to maintain stable AH values during the study with no influence on ventilatory parameters.

Humidification in Very-High-Flow Nasal-Cannula Therapy in an Adult Lung Model.

High-flow nasal cannula (HFNC) therapy is used for patients with respiratory failure. Recently, HFNC therapy with very high gas flows (ie, gas flows of 60-100 L/min) was reported to generate higher positive airway pressure and an associated decrease in breathing frequency. However, the humidification of HFNC therapy with very high gas flow remains to be clarified. We evaluated 3 heated humidifier systems: a single MR850, the Hummax2, and parallel MR850s. The MR850 is a pass-over humidifier system, and the Hummax2 works with a porous hollow polyethylene fiber membrane. The parallel MR850 system included 2 MR850s connected in parallel to the lung with a 22 mm Y-piece. Gas flow was set at 40-90 L/min in increments of 10 L/min, and FIO2 was set at 0.21. Heated humidifiers in the MR850 systems were set in invasive mode (40°C/-3), and with the Hummax2 the vapor temperature was set at 39°C. The simulated external nares were connected to a test lung via a standard ventilator circuit. One-way valves prevented mixing of inspired and expired gases. Compliance of the test lung was 0.05 L/cm H2O and resistance 5 cm H2O/L/s. Simulated tidal volumes (VT) were 300, 500, and 700 mL, with a breathing frequency of 10 or 20 breaths/min and an inspiratory time of 1.0 s. Temperature, relative humidity, and absolute humidity (AH) of inspired gas downstream of the external nares were measured using a hygrometer for 1 min, and results for the last 3 breaths were extracted. With the single MR850, when gas flow was > 80 L/min, AH decreased as gas flow increased (P < .001). With the Hummax2, as gas flow increased, AH decreased (P < .001). With the parallel MR850s, regardless of gas flow, AH was constant. As breathing frequency increased, AH increased in all systems. During HFNC therapy with very high gas flows in this bench study, conventional heated humidifiers did not provide adequate humidification. Caution is advised when using HFNC therapy with very high gas flows with conventional heated humidifiers.

Application of Venturi combined with MR850 in ventilator offline patients with tracheotomy

To investigate the effect of oxygen therapy with Venturi combined with MR850 heating humidifier on patients without mechanical ventilation after tracheotomy. Eighty patients (≥ 18 years old) who had undergone tracheotomy and without mechanical ventilation admitted to Fenyang Hospital of Shanxi Province from June 2016 to December 2017 were enrolled, and they were divided into control group and observation group according to random number table method, with 40 patients in each group. The observation group was given Venturi (removed the mask) combined with MR850 device active warm and humid oxygen therapy; the control group was given one-off ordinary flow device and warm and humid exchanger (artificial nose, HME) passive humid oxygen therapy. Body temperature increased by 1 centigrade above basal body temperature, white blood cell count (WBC) increased 2×109/L than the base value, oxygenation index (PaO2/FiO2) < 300 mmHg (1 mmHg = 0.133 kPa), airway mucosal hemorrhage, pulmonary infection and sputum viscosity were observed in the two groups for 5 days after oxygen therapy. Among the 80 patients, there were 46 males and 34 females, with an average age of (67.7±12.2) years. Compared with the control group, the incidence of increased body temperature (5.0% vs. 20.0%), the incidence of increased WBC (7.5% vs. 35.0%), the incidence of low PaO2/FiO2 (2.5% vs. 7.5%), the incidence of airway mucosal bleeding (5.0 % vs. 15.0%) and the incidence of pulmonary infection (2.5% vs. 10.0%) were significantly decreased in the observation group (all P < 0.01), and the proportion of sputum viscosity I degree of patients was significantly increased (57.5% vs. 12.5%, P < 0.01). Venturi combined with MR850 device can effectively control airway temperature and humidity, promote sputum dilution and conducive to drainage, reduce pulmonary infection in adults patients without mechanical ventilation after tracheotomy, thereby reducing postoperative complications of tracheotomy.

Accidental dual humidification in intensive care units: Repeated alerts and system changes are not enough

PurposeThe inadvertent, simultaneous use of heat and moisture exchangers (HMEs) and heated humidifiers (HHs) can result in waterlogging of the filter and sudden ventilation tube occlusion, with potentially fatal consequences. Following an NHS England Safety Alert, a near miss and educational reminders in our institution, we introduced new guidelines to solely use HHs in the intensive care unit and HMEs only for patient transfers. No further incidents have occurred, however this solution is potentially fallible. Two years later, we sought to assess staff knowledge and likelihood of recognising this error should it occur. Materials and methodsIn a simulation study, a tracheally intubated and ventilated mannequin had a breathing circuit containing both a HME and a HH. Participants were asked to assess the circuit, identify errors and undertake corrective measures. ResultsOnly 30% (6/20) recognised and undertook corrective measures. ConclusionsDespite educational efforts and system changes, recognition of this error remained poor. System changes may reduce the likelihood of the error occurring, but when it does, recognition may not occur. Substantial reductions or elimination of this error may be achieved through a safety-engineered fail-safe within the equipment, which alerts staff to improve recognition and prevent the mistake.