Influence of Ambient and Ventilator Output Temperatures on Performance of Heated-Wire Humidifiers

Abstract

Although heated humidifiers are considered the most efficient humidification devices for mechanical ventilation, endotracheal tube occlusion caused by dry secretions has been reported with heated-wire humidifiers. We tested the hypothesis that inlet chamber temperature, influenced by ambient air and ventilator output temperatures, may affect humidifier performance, as assessed by hygrometry. Hygrometry was measured with three different humidifiers under several conditions, varying ambient air temperatures (high, 28-30 degrees C; and normal, 22-24 degrees C), ventilators with different gas temperatures, and two VE levels. Clinical measurements were performed to confirm bench measurements. Humidifier performance was strongly correlated with inlet chamber temperature in both the bench (p < 0.0001, r2 = 0.93) and the clinical study. With unfavorable conditions, absolute humidity of inspired gas was much lower than recommended (approximately 20 mg H2O/L). Performance was improved by specific settings or new compensatory algorithms. Hygrometry could be evaluated from condensation on the wall chamber only when ambient air temperature was normal but not with high air temperature. An increase in inlet chamber temperature induced by high ambient temperature markedly reduces the performance of heated-wire humidifiers, leading to a risk of endotracheal tube occlusion. Such systems should be avoided in these conditions unless automatic compensation algorithms are used.

Estudo comparativo entre os sistemas de umidificação aquoso aquecido e trocador de calor e de umidade na via aérea artificial de pacientes em ventilação mecânica invasiva

“…Entretanto, deve-se ressaltar as possíveis alterações na eficiência no aquecimento e umidade do gás administrado ao paciente em ventilação mecânica. Ainda, pode-se destacar vários estudos reportados na literatura que enfocam os efeitos deletérios de altos volumes correntes na redução da efetividade dos umidificadores e por esta razão o VC foi mantido entre 6-10 ml/Kg 13,20,21,22,23,24 .…”

Hygrometric Properties of Inspired Gas and Oral Dryness in Patients With Acute Respiratory Failure During Noninvasive Ventilation

“…11 High ambient temperature and high temperature of the ventilator output also reduce HH performance. 12 Even with HH some patients with acute respiratory failure (ARF) report oral dryness and discomfort during NIV 13 or high-flow oxygen via a oronasal mask. 14 Although manufacturers recommend that the NIV gas temperature be set at 31°C in the HH chamber and 34°C at the Y-piece, 15 there are few available data on HH performance or the optimal humidity of the inspired gas during NIV.…”

Inspired gas temperature in ventilated neonates

“…Placing the heated inspiratory limb in the incubator, and exposing it to a raised ambient temperature, can also lead to inadequate humidification. 12 This study measured the temperature of the gas stream closer to the patient, at the level of connection of the inspiratory and expiratory limbs to the patient manifold and at the airway opening in the endotracheal tube adapter (Fig. 1).…”