The simultaneous use of a heat and moisture exchanger and a heated humidifier causes critical airway occlusion in less than 24 hours

Heat and Moisture Exchanger Occlusion Leading to Sudden Increased Airway Pressure: A Case Report Using ChatGPT as a Personal Writing Assistant

Heat and moisture exchangers (HMEs) are commonly used during general anesthesia to provide appropriate humidification and warming of inspired gases. While they play a critical role in mechanical ventilation, they can also lead to acute difficult ventilation if not correctly monitored and drained. We present a case of a 56-year-old female patient who underwent lower extremity vascular bypass surgery under general anesthesia and experienced sudden increased airway pressures due to occlusion of the HME caused by excessive moisture accumulation. Proper monitoring and management of the airway circuit and HMEs can help prevent complications and ensure proper ventilation during surgery. When acute difficult ventilation is encountered during general anesthesia, a systematic approach should be taken to differentiate between patient and external factors. Other differential diagnoses for acute difficult ventilation include bronchospasm, aspiration, endotracheal tube misplacement, pulmonary embolism, and tension pneumothorax. HME occlusion should be considered as part of the differential diagnosis for intraoperative hypoxia. Proactive replacement of HMEs in long cases can prevent occlusion and ensure proper ventilation.

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.

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

PURPOSE

The 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 METHODS

In 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.

RESULTS

Only 30% (6/20) recognised and undertook corrective measures.

CONCLUSIONS

Despite 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.