Inspired gas humidity during mechanical ventilation: Effects of humidification chamber, airway temperature probe position and environmental conditions

Todd, David A; Boyd, J; Lloyd, Jane; John, Elizabeth

doi:10.1046/j.1440-1754.2001.00750.x

Cited by 23 publications

(26 citation statements)

References 26 publications

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“…In neonates, it has been shown that over 30-60% of the time humidity at the patient manifold is below British standards. 13,14 This study has shown that airway temperature, as measured by a probe placed at the distal end of the ETT, was an accurate measure of inspired gas temperature however this was primarily due to conductive heating as the gas passed through the model lung not due to primary heating by the airway heater.…”

Section: Discussionmentioning

confidence: 99%

An experimental model for the measurement of inspired gas temperatures in ventilated neonates

Jardine

Dunster

Davies

2007

Pediatric Pulmonology

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Summary. ObjectiveTo determine the inspired gas temperature at points from the endo-tracheal tube (ETT) circuit manifold to the tip of the ETT in a model neonatal lung. Design A model lung attached to standard ventilator circuit, autofeed chamber and humidifier was ventilated using typical pressure-limited, time cycled settings. Temperatures were measured at various distances along the ETT using a K-type thermocouple temperature probe. Results The inspired gas temperature dropped from the circuit temperature probe site (408C) to the proximal end of the ETT (378C). The temperature dropped further as it passed through the exposed part of the ETT (348C) but then warmed again on entering the lung model so that the inspired gas at the distal end of the ETT was 378C. Statistically significant differences were found with a one-way ANOVA P-value of <0.0001. The differences between each pair of mean temperatures were statistically significant (all P < 0.001) except when comparing the proximal end of the ETT with midway down the ETT (Bonferroni's Multiple Comparison Test, P > 0.05). Conclusions Inspired gas temperature drops as it passes through the circuit temperature probe site, the proximal end of the ETT and the exposed part of the ETT. The inspired gas rewarms on entering the model lung and exits the ETT at the desired temperature. The effect of measuring temperature closer to the patient, setting the circuit temperature higher and/or increasing the ambient temperature through which the circuit passes, need to be evaluated.

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Section: Discussionmentioning

confidence: 99%

An experimental model for the measurement of inspired gas temperatures in ventilated neonates

Jardine

Dunster

Davies

2007

Pediatric Pulmonology

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“…During routine use on an intubated patient, a HH should be set to deliver an inspired gas temperature of Ն 34°C, 8 but Ͻ 41°C at the circuit Y-piece 7,9 and should provide a minimum of 33 mg/L of water vapor. 11 The ISO considers that an inaccuracy of Ͻ 2°C of the displayed measured gas temperature does not compromise the clinical condition or the safety of the patient.…”

Section: Hmv 100 Monitoringmentioning

confidence: 99%

“…8 HMEs operate passively by storing heat and moisture from the patient's exhaled gas and releasing it to the inhaled gas. 9 The upper airway provides 75% of the heat and moisture supplied to the alveoli.…”

mentioning

confidence: 99%

Humidification During Invasive and Noninvasive Mechanical Ventilation: 2012

2012

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When the upper airway is bypassed during invasive mechanical ventilation, humidification is necessary to prevent hypothermia, disruption of the airway epithelium, bronchospasm, atelectasis, and airway obstruction. In severe cases, inspissation of airway secretions may cause occlusion of the endotracheal tube. 1 While there is not clear consensus on whether or not additional heat and humidity are always necessary when the upper airway is not bypassed, such as in noninvasive mechanical ventilation (NIV), active humidification is highly suggested to improve comfort. [2][3][4][5][6][7] Two systems, active humidification through a heated humidifier (HH) and passive humidification through a heat and moisture exchanger (HME), are available for warming and humidifying gases delivered to mechanically ventilated patients. There are 3 types of HME or artificial nose: hydrophobic, hygroscopic, and a filtered HME.Heated humidifiers operate actively to increase the heat and water vapor content of inspired gas. 8 HMEs operate passively by storing heat and moisture from the patient's exhaled gas and releasing it to the inhaled gas. 9 The upper airway provides 75% of the heat and moisture supplied to the alveoli. When bypassed, the humidifier needs to supply this missing heat and moisture. Since The authors have disclosed a relationship with Teleflex Medical, which manufactures humidification devices.

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“…In the neonatal population, Todd et al discovered that a higher gas humidity was delivered when the airway temperature probe was positioned outside the incubator. 47 The study also demonstrated improved inspired humidity with insulating the inspiratory limb in bubble wrap. A commercially available circuit that incorporates this "bubble wrap" concept could prove beneficial.…”

Section: Airway Maintenance Humidificationmentioning

confidence: 79%

Pediatric Airway Maintenance and Clearance in the Acute Care Setting: How To Stay Out of Trouble

2011

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1424RESPIRATORY CARE • SEPTEMBER 2011 VOL 56 NO 9Traditional airway maintenance and clearance therapy and principles of application are similar for neonates, children, and adults. Yet there are distinct differences in physiology and pathology between children and adults that limit the routine application of adult-derived airway-clearance techniques in children. This paper focuses on airway-clearance techniques and airway maintenance in the pediatric patient with acute respiratory disease, specifically, those used in the hospital environment, prevailing lung characteristics that may arise during exacerbations, and the differences in physiologic processes unique to infants and children. One of the staples of respiratory care has been chest physiotherapy and postural drainage. Many new airway clearance and maintenance techniques have evolved, but few have demonstrated true efficacy in the pediatric patient population. Much of this is probably due to the limited ability to assess outcome and/or choose a proper disease-specific or age-specific modality. Airway-clearance techniques consume a substantial amount of time and equipment. Available disease-specific evidence of airway-clearance techniques and airway maintenance will be discussed whenever possible. Unfortunately, more questions than answers remain.

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Inspired gas humidity during mechanical ventilation: Effects of humidification chamber, airway temperature probe position and environmental conditions

Cited by 23 publications

References 26 publications

An experimental model for the measurement of inspired gas temperatures in ventilated neonates

An experimental model for the measurement of inspired gas temperatures in ventilated neonates

Humidification During Invasive and Noninvasive Mechanical Ventilation: 2012

Pediatric Airway Maintenance and Clearance in the Acute Care Setting: How To Stay Out of Trouble

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