Reducing Ventilator Alarms Through Decreased Rainout in Ventilator Circuits: A Bench Study

Background: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 ventilator, may cause condensation in the ventilator circuit, prompting occlusion alarms indicating a risk for the patient. Technological advances in heated humidifier (HH) circuits may reduce rainout and therefore occlusion alarms. Methods:Bench experiments measured alarms and rainout of two commercially available humidifiers (AirLife DuoTherm™ and Fisher & Paykel MR850) and four different pediatric and adult patient’s breathing. The tests examined condensation accumulation 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.Results:Low temperature and occlusion alarms were statistically significantly lower in DuoTherm vs. MR850 HH circuits (6 vs. 68 alarms, respectively; p<nn). DuoTherm products accumulated significantly less rainout for all three 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 < 0.02). Conclusions: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.

Reducing Ventilator Alarms Through Decreased Rainout in Ventilator Circuits: A Bench Study

Background: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 ventilator, may cause condensation in the ventilator circuit, prompting occlusion alarms indicating a risk for the patient. Technological advances in heated humidifier (HH) circuits may reduce rainout and therefore occlusion alarms. Methods:Bench experiments measured alarms and rainout of two commercially available humidifiers (AirLife DuoTherm™ and Fisher & Paykel MR850) and four different pediatric and adult patient’s breathing. The tests examined condensation accumulation 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.Results:Low temperature and occlusion alarms were statistically significantly lower in DuoTherm vs. MR850 HH circuits (6 vs. 68 alarms, respectively; p<nn). DuoTherm products accumulated significantly less rainout for all three 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 < 0.02). Conclusions: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.

Longitudinal changes in compliance, oxygenation and ventilatory ratio in COVID-19 versus non-COVID-19 pulmonary acute respiratory distress syndrome

Background Differences in physiology of ARDS have been described between COVID-19 and non-COVID-19 patients. This study aimed to compare initial values and longitudinal changes in respiratory system compliance (CRS), oxygenation parameters and ventilatory ratio (VR) in patients with COVID-19 and non-COVID-19 pulmonary ARDS matched on oxygenation. Methods 135 patients with COVID-19 ARDS from two centers were included in a physiological study; 767 non-COVID-19 ARDS from a clinical trial were used for the purpose of at least 1:2 matching. A propensity-matching was based on age, severity score, oxygenation, positive end-expiratory pressure (PEEP) and pulmonary cause of ARDS and allowed to include 112 COVID-19 and 198 non-COVID pulmonary ARDS. Results The two groups were similar on initial oxygenation. COVID-19 patients had a higher body mass index, higher CRS at day 1 (median [IQR], 35 [28–44] vs 32 [26–38] ml cmH2O−1, p = 0.037). At day 1, CRS was correlated with oxygenation only in non-COVID-19 patients; 61.6% and 68.2% of COVID-19 and non-COVID-19 pulmonary ARDS were still ventilated at day 7 (p = 0.241). Oxygenation became lower in COVID-19 than in non-COVID-19 patients at days 3 and 7, while CRS became similar. VR was lower at day 1 in COVID-19 than in non-COVID-19 patients but increased from day 1 to 7 only in COVID-19 patients. VR was higher at days 1, 3 and 7 in the COVID-19 patients ventilated using heat and moisture exchangers compared to heated humidifiers. After adjustment on PaO2/FiO2, PEEP and humidification device, CRS and VR were found not different between COVID-19 and non-COVID-19 patients at day 7. Day-28 mortality did not differ between COVID-19 and non-COVID-19 patients (25.9% and 23.7%, respectively, p = 0.666). Conclusions For a similar initial oxygenation, COVID-19 ARDS initially differs from classical ARDS by a higher CRS, dissociated from oxygenation. CRS become similar for patients remaining on mechanical ventilation during the first week of evolution, but oxygenation becomes lower in COVID-19 patients. Trial registration: clinicaltrials.gov NCT04385004

Humidification, Nebulization, and Gas Filtering

‘Humidification, Nebulization, and Gas Filtering’ describes the therapies, which, while not essential to ventilation, are frequently applied together with it. This chapter provides a comprehensive discussion of these devices, including the clinical needs for them and their operating principles, options, and common complications. It describes the composition and operating principle of active heated humidifiers. Artificial humidification brings with it the additional issue of circuit rainout, which may require that heated wires be added to the breathing circuit. The chapter includes a table for troubleshooting issues related to active humidification. Heat and moisture exchangers or HMEs, an alternative to humidifiers, are also discussed. Finally, the chapter turns to the use of in-line nebulizers or aerosol therapy. The chapter ends with a discussion of respiratory gas filtering, which, for all the benefit a bacteria filter brings, also introduce the risk of occlusion.