Where Must Bacterial/Viral Filters Be Positioned In The Ventilator Circuit?

 

Heat and moisture exchangers became obtainable with HME Filter Dealers in the 1950s after the induction of tracheostomy for easing mechanical ventilation of the lungs. Ventilators may require ‘external’ sieves (biological, HME, and fan, as well as air intake sieves for turbine or compressor ventilators) and internal sieves (oxygen inlet sieves). Filters may be located at the air consumption, inspiratory limb, patient Wye, expiratory limb, and/or finish port, though, assignment at each of these places does not deliver an equivalent function. Preferably a two-filter setup must be used (Anesthesia Patient Security Foundation):  

Inspiratory/Patient sieve: the first sieve must be positioned between the circuit Wye connector and the patient and attains two things: 1) defends the ventilator and the room from respired gases from an ill patient, 2) defends a non-infected patient from a probably dirtied ventilator. If using an active warmth and humidification system, then this must be a microbial viral filter (not an HME bought from the HME Filter Dealers). If not consuming vigorous warmth and humidification, then this must be an HMEF or a microbial viral sieve in series with an HME (HME must be between the endotracheal tube and B/V sieve). In a dual-limb ICU ventilator, the inspiratory bacterial viral sieve may be positioned on the inspiratory limb at the takeoff from the ventilator.

Expiratory filter: A second bacterial viral sieve is suggested on the exhalation limb before the inhalation valve, to defend the room setting and healthcare staff from stray atoms (and to defend the machine in a dual limb circuit setup).    

The location of sieves between the circuit Wye and the patient’s endotracheal tube can add noteworthy dead space to the circuit, particularly for pediatric patients. Bacterial–viral air filters are medical machines used in respiratory ventilators or breathing circuits to defend patients, equipment, and/or the setting from worms and bacteria. They may be either electrostatic or machine-driven, founded on their working principle: electrostatic sieves use an encouraged electrostatic charge to seize atoms, while mechanical sieves use a frilled porous membrane. Mechanical sieves can reach higher filtration efficacy than electrostatic filters, but they levy higher airflow resistance. Air filters are grouped upon their efficacy: efficacy particulate air (EPA), high-efficiency particulate air (HEPA), and ultra-low diffusion air sieves hold a minimum of 99.95%, 99.97%, and 99.999% of 0.3 µm particles, correspondingly. Heat moisture and exchangers supplied by HME Filter Dealers (HMEs) recall warmth and humidity from exhaled air and return them to the patient during the following inspiration. HMEs also deliver a percolation function that can be either electrostatic or mechanical, and they can be grouped as either EPA or HEPA founded on their filtration efficacy. HMEs are inert humidifiers and, as such, they should be positioned at the inlet of the airway interface. HMEs must not be used with moistened gasses because the moisture reserved by the hygroscopic membrane may surge airflow resistance. 

Linking a bacterial–viral sieve to the breathing circuit adapts its mechanical characteristics: (1) it surges the obedience of the circuit; (2) it surges dead space if positioned at the airway interface; (3) it adds a resistance that reasons a pressure drop between the inlet (P1) and the outlet (P2) of the sieve.