Abstract
To the Editor:
Since the emergence of the coronavirus disease 2019 (COVID-19) pandemic, several recommendations have been made to improve the safety of health workers and patients. The addition of filters in respiratory circuits has been recommended by the American Association of Anesthesiology [1] and by the Anesthesia Patient Safety Foundation [2]. However, some institutions have decided to remove the Y filters from the anesthetic circuit because they have presented cases of severe hypercapnia in pediatric patients [3]. But is this a correct decision? Is the risk of contagion lower when caring for children? What considerations should be taken into account to use filters in this population?
There is evidence that the air dispersion distance is in direct relation to the volume administered during positive pressure ventilation. Thus, when ventilating a newborn weighing 3 kg with a tidal volume between 15 and 18 mL (5–6 mL/kg), the air dispersion distance is 1.5 to 1.8 cm [4]. However, an 8-mL filter (the smallest size available) has a tidal volume range between 30 and 200 mL, which is very large for neonates and premature infants and increases dead space considerable. These small filters are usually electrostatic with less filtration efficiency compared with mechanical filters. There are no mechanical filters less than 150 mL. This information, plus the absence of reported cases of COVID-19 in premature infants to date, makes it reasonable not to use filters for positive pressure ventilation under mask becaues of the risk of hypercapnia and intraventricular hemorrhage in premature infants and the lower risk of contagion for healthcare personnel. However, for older patients who require a larger tidal volume, the aerosol dispersion distance may be longer and the use of filters provide additional protection. In these cases, the appropriate size filter must be chosen for the patient weight, taking into account the tidal volume range it allows and the dead space it generates. This information is supplied by each manufacturer and is visible on the product label. In any case, the anesthesia machine should always be protected with a large mechanical filter placed on the expiratory path of the respiratory circuit. This location does not generate increased dead space for the patient. Additionally, the gases sampled from the anesthetic circuit must be filtered, otherwise they must not return to the respiratory circuit again and must be directed towards the evacuation system.
In summary, the decision to place filters on the Y of the anesthetic circuit in pediatric patients requires clinical judgment and should not be a standard measure for all cases. The risk and benefit should also be considered, especially in smaller patients.