Humidification and Alarm Systems
List and describe devices used to provide humidification to patients with a bypassed upper airway Identify ventilator alarms and proper settings relating to ventilator management Identify actions that must be taken in the event of ventilator alarm activation Background Patients who receive mechanical ventilation lose the natural function of their upper airway; therefore, since the upper airway is bypassed the inspired air that a patient receives must be filtered, warmed, and humidified. Humidification should be provided to all patients with an artificial airway to prevent the following: Dehydration – excessive loss of water Inspissation of secretions – secretions that are thick and dehydrated Destruction of airway epithelium – destruction of the thin tissue lining the airways Re-absorption atelectasis – collapse or incomplete inflation of the lung due to obstruction of the airway There are two primary types of humidification systems used during invasive mechanical ventilation: active and passive humidifiers. An active humidification system delivers optimal humidity by conditioning inspired gas to body temperature (37°C) and fully saturates the gas with 44mg/L of water vapor. An active humidifier usually consists of a servo-controlled heater which includes a temperature display and alarms. A temperature probe is placed near the patients airway and alarms are set on the humidifier to warn of high or low temperatures. The high-temperature alarm should be set at around 37°C to 38°C, so the inspired gas does not exceed 37°C and the low-temperature alarm setting should be set no less than 30°C. Active humidifiers humidify the inspired gas by passing the gas over the surface of a water reservoir or by a moist, heated wick. Two examples of an active humidifier are pass-over and wick humidifiers. Passive humidifiers do not have an external energy or water source. Passover humidifiers function as an artificial nose. An artificial nose, also referred to as a heat and moisture exchanger (HME), captures the heat and moisture from the expired air and uses it to heat and humidify the inspired gas during inspiration. Pass-over humidifier HME A ventilator may malfunction during use, therefore, alarms are set to warn of possible dangers related to ventilator systems. To avoid alarms being constantly triggered they should not be set so closely, however, they must be adequate to denote changes in the status of the machine and patient. Below are suggestions for setting common ventilator alarms: Most Commonly Used Ventilator Alarms High Pressure Alarm Detects and limits a volume needing too much force to be delivered. Activated by coughing, increase in secretions, decreased compliance or kinks in ETT or circuit about 10 cmH2O above PIP Low Pressure Alarm Detects leaks in the endotracheal tube or ventilator circuit about 5 – 10 cmH2O below PIP High Respiratory Rate Detects an excessively high respiratory rate about 10 above average rate but not more than 30 breaths/min Apnea Alarm Detects cessation of spontaneous breaths no more than 20 seconds Low Exhaled VT Detects leaks in the endotracheal tube or ventilator circuit about 10% – 15% below set VT Low PEEP Initiates when PEEP level decreases. Activated by leaks in the system about 2 – 5 cmH2O below PEEP level Prompt For this assignment, you will provide detailed responses to the following: Using the AARC Clinical Practice Guidelines, list the indications, contraindications, hazards/complications and limitations for the use of an HME during invasive mechanical ventilation. Be sure to cite your source. What criteria must be met when using any heated humidification device with patients receiving mechanical ventilation? Why? When is the use of heated humidifiers preferred over the use of heat and moisture exchangers (HME)? Submit your answers in at least 500 words on a Word document. You must cite at least three references in IWG format to defend and support your position.