Estimation of inspiratory pressure drop in neonatal and pediatric endotracheal tubes

Jarreau, Pierre‐Henri; Louis, Bruno; Dassieu, Gilles; Desfrère, Luc; Blanchard, Pierre‐Yves; Moriette, G; Isabey, Daniel; Harf, Alain

doi:10.1152/jappl.1999.87.1.36

Cited by 61 publications

(44 citation statements)

References 23 publications

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“…Apart from the inertance component, it thus is similar to their method of calculating the pressure fall in the adult setting (3). Jarreau et al (4) presented another approach to indirect measurement by dividing the total pressure drop into a fraction owing to loss of kinetic energy at entry and exit of tube, and a fraction owing to viscous pressure drop. The kinetic energy loss may be approximated by various equations (5), but its actual value is best estimated in the actual setting by subtracting the viscous pressure from the total pressure drop.…”

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confidence: 99%

Direct Measurement of Intratracheal Pressure in Pediatric Respiratory Monitoring

et al. 2002

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We describe a method based on a Fabry-Perot interferometer at the tip of an optic fiber with a diameter of 0.25 mm for direct measurement of tracheal pressure in pediatric respiratory monitoring. The response time of the pressure transducer and its influence on the resistance of pediatric endotracheal tubes (internal diameter, 2.5 to 5 mm) during constant and dynamic flow at different ventilator settings in a lung model were measured. The transducer was positioned at Ϫ1.5 (inside), 0, and ϩ1.5 cm (outside) relative to the tip of the endotracheal tube and compared with a reference pressure inside the trachea. The clinical application of the transducer was tested in five pediatric patients. The response time of the transducer was 1.3 ms. The influence of the fiberoptic transducer on tube resistance was negligible during constant flow in inspiratory and expiratory directions for all endotracheal tubes tested. There was no difference in pressure measurements with the transducer positioned at or 1.5 cm below or above the tip of the endotracheal tube during dynamic measurements. During clinical circumstances insertion of the fiberoptic transducer was easy, recordings were stable, and the safety of the patient was not jeopardized. The fiberoptic transducer provided a reliable and promising way of monitoring tracheal pressure in intubated pediatric patients. The presence of the probe did not interfere with either pressure-flow relationship or patient care and safety. The technique is proposed for monitoring of respiratory mechanics and calculation of changes in tube resistance caused by kinking and secretions. Respiratory monitoring in pediatric intensive care is currently represented by proximal P/V loops obtained in ventilator software or intensive care monitors using flowmeters placed near the connection between the ventilator system and ETT. This is obviously insufficient as information gained from such P/V loops mainly stems from ETT resistance and performance of ventilator valves. We have previously demonstrated that monitoring respiratory mechanics by direct measurement of tracheal pressure offers considerable advantages compared with monitoring based on either measurements obtained proximal to the tube or tracheal pressures calculated by subtracting pressure needed to overcome flow-dependent tube resistance. In the adult setting tracheal pressure measurement is accomplished by introducing an air-or liquid-filled catheter into the ETT and connecting it to a conventional pressure transducer (1). In the pediatric setting it has generally been held to be impossible to use endotracheal catheters for continuous pressure measurement owing to the encroachment on cross-sectional area of the narrow pediatric tubes (2). Instead hydrodynamic models of varying complexity have been proposed for the calculation of tracheal pressure, i.e. the pressure fall across the ETT because of its resistance, based on measurements above the tube. Guttmann et al. (2)

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confidence: 99%

Direct Measurement of Intratracheal Pressure in Pediatric Respiratory Monitoring

et al. 2002

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“…Jarreau et al 30 reported that the mean range of ETT curvature diameters from magnetic resonance imaging scans were 8-18 cm with a ,16% variation in pressure between these extremes. Both of the studied curves present in the ETT, which can be seen in Figure 2, 31 were within these parameters.…”

Section: Airflow Analysismentioning

confidence: 99%

“…32 To better evaluate the computational model, the critical Reynold's number was calculated according to the following formula proposed in Jarreau et al, where D is the diameter of the tube and R c is the radius of curvature. 30 The critical Reynolds number is 5668. The approximations for the fluid model also assumed quasistatic flow in the ETT.…”

Section: Airflow Analysismentioning

confidence: 99%

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Decreased Staphylococcus aureus biofilm formation on nanomodified endotracheal tubes: a dynamic airway model

Machado

Tarquinio²,

Webster

2012

IJN

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Ventilator-associated pneumonia (VAP) is a serious and costly clinical problem. Specifically, receiving mechanical ventilation for over 24 hours increases the risk of VAP and is associated with high morbidity, mortality, and medical costs. Cost-effective endotracheal tubes (ETTs) that are resistant to bacterial infections could help prevent this problem. The objective of this study was to determine differences in the growth of Staphylococcus aureus on nanomodified and unmodified polyvinyl chloride (PVC) ETTs under dynamic airway conditions simulating a ventilated patient. PVC ETTs were modified to have nanometer surface features by soaking them in Rhizopus arrhisus, a fungal lipase. Twenty-four-hour experiments (supported by computational models) showed that airflow conditions within the ETT influenced both the location and the concentration of bacterial growth on the ETTs, especially within areas of tube curvature. More importantly, experiments revealed a 1.5 log reduction in the total number of S. aureus on the novel nanomodified ETTs compared with the conventional ETTs after 24 hours of airflow. This dynamic study showed that lipase etching can create nanorough surface features on PVC ETTs that suppress S. aureus growth, and thus may provide clinicians with an effective and inexpensive tool to combat VAP.

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“…Critical Reynolds numbers (i.e. Reynolds numbers for which flow pattern change) are known for small ETT in natural curvature and without entry flow (Jarreau et al, 1999). These critical Reynolds numbers are unknown for adult ETT, under both laboratory and clinical conditions.…”

Section: Introductionmentioning

confidence: 99%

Effects of helium–oxygen mixtures on endotracheal tubes: an in vitro study

Gerbeaux

Gainnier

Arnal

et al. 2005

Journal of Biomechanics

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Estimation of inspiratory pressure drop in neonatal and pediatric endotracheal tubes

Cited by 61 publications

References 23 publications

Direct Measurement of Intratracheal Pressure in Pediatric Respiratory Monitoring

Direct Measurement of Intratracheal Pressure in Pediatric Respiratory Monitoring

Decreased Staphylococcus aureus biofilm formation on nanomodified endotracheal tubes: a dynamic airway model

Effects of helium–oxygen mixtures on endotracheal tubes: an in vitro study

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