A drop in gas temperature in the external part of the endotracheal tube is problematic during neonatal respiratory support

Abstract

During neonatal respiratory support, maintaining optimal humidity minimizes the risk of airway occlusion and chronic lung disease. With neonatal respiratory support using a heated humidifier,condensation following decreases in temperature within the unheated part of the inspiratory circuit represents a serious problem, due to the resulting drop in absolute humidity. Several reports describing the temperature/humidity gradient in the unheated inspiratory limb have excluded the endotracheal tube (ETT). The present study investigated the extent to which the temperature gradient in the ETT affects breathing gas conditioning in premature infants, who display tiny minute volumes. By measuring temperature/dew point at various sites along the inspiratory circuit, including inside the ETT, we evaluated the effects of temperature change in the ETT using an in vitro model of a micropremie on mechanical respirator care in an incubator. We confirmed significant moisture loss (absolute humidity loss; 7.5-10.1 mg/L) with decreasing gas temperature in the ETT external to the body, with subsequent drying of the gas (relative humidity drop, 10.7-22.3%) as temperature increased in the ETT inside the body. The present results suggest that temperature decreases in the ETT represent an important issue in the respiratory care of very premature infants.

A case of pulmonary artery sling where onset Was induced by therapeutic hypothermia

“…Neonates might be particularly at risk because of their relatively small tidal volume. Even a small change in gas temperature inside the endotracheal tube can induce condensation of distilled water and rapidly trigger mucosal edema of the respiratory tract . Furthermore, even a mild stimulus, such as cold stimulation to facial skin, induces constriction of the bronchus, although its extent is milder than direct cooling …”

The temperature change in an endotracheal tube during high frequency ventilation using an artificial neonatal lung model with Babylog® 8000 plus

“…In IPPV, the temperature drop in the external ETT is dependent on minute volumes; however, there have been no reports measuring the temperature drop in HFV. In the current study, we observed that the temperature in the ETT also decreased during HFV when the oscillatory volume (VThf) decreased.…”

“…In the current study, we observed that the temperature in the ETT also decreased during HFV when the oscillatory volume (VThf) decreased. In IPPV, the temperature decrease in the unheated ETT is lower when the minute volume (MV) is high than when the MV is low . In cases with a very low MV, the time required for inspired gas to reach the patient threshold is sufficiently long to allow the gas to approach environmental temperature.…”

“…Previous reports have demonstrated that during IPPV, the temperature drop in the external ETT is dependent on minute volume. We hypothesized that during HFV using Babylog® 8000 plus, temperature changes in the external ETT would be associated with the oscillatory frequency and oscillatory volume (VThf) because the VThf in HFV, which is similar to the tidal volume (TV) in IPPV, would be regulated by the oscillatory frequency of the Babylog® 8000 plus.…”

“…ETT temperature drops are particularly problematic for very low‐birth weight infants due to the low minute ventilation volume. Yamada et al suggested that, for tiny infants with low minute ventilation, the temperature drop and moisture loss that occurs in the external portion of the ETT is a problem because the relative humidity subsequently drops when the temperature increases in the ETT within the trachea. The temperature decrease in the external ETT represents a problem during respiratory care for very premature infants who are being treated with intermittent positive pressure ventilation (IPPV).…”