Impact of endotracheal tube shortening on work of breathing in neonatal and pediatric in vitro lung models

Preoperative Rehearsal in the Removal of an Airway Foreign Body in a Preterm Septic Neonate

We report a case of a septic, 21 day old, former 26-week neonate who had clinical and x-ray concern for an airway foreign body. 3D CT remodeling was used to identify the foreign body as the tip of a suction catheter. Preoperative planning to confirm optimal bronchoscopic instrumentation was done, and the foreign body was successfully removed in a single attempt. This case highlights the importance of preoperative radiographic evaluation and instrument rehearsal in high-risk airway foreign body cases.

Insertion of cuff inflation line into pediatric tracheal tubes related to oral and nasal tracheal intubation depth

BACKGROUND

In clinical practice, the cuff inflation line of cuffed pediatric tracheal tubes often interferes with securing tracheal tubes.

METHODS

The insertion site of the cuff inflation lines and the lengths of four different brands and nine sizes of commonly used cuffed pediatric tracheal tubes were measured and compared in vitro with oral and nasotracheal intubation depths as calculated by different formulas for pediatric patients aged from birth to 16 years. Motoyama's recommendation was used for age-related size selection of cuffed pediatric tracheal tubes.

RESULTS

The proportion of the distance from the tracheal tube tip to the insertion site of the cuff inflation line varied considerably between the tracheal tubes (Microcuff: 48.5-60.7%; Parker: 48.7-73.2%; Ruesch: 59.1-77.8%; and Shiley: 46.0-60.3%). Using different formulas for oral or nasotracheal intubation depth, the insertion site of the cuff inflation line was placed within the oral or nasal cavity or within an area 1 cm beyond the teeth or the nostrils in almost all tracheal tubes tested. Positioning the insertion site 2 cm from the proximal end of the tracheal tubes resulted in a cuff line-free tube area of ≥1 cm in all orally and almost in all nasally inserted tracheal tubes, considering maximum recommended tracheal intubation depths.

CONCLUSION

The cuff inflation line in almost all commonly used cuffed pediatric tracheal tubes interferes with securing the tracheal tube due to its insertion site into the tracheal tube. This potentially carries the risk of kinking, obstruction, or damage to the cuff inflation line with ensuing failure to deflate or inflate the cuff. The proposed position of the insertion of the cuff inflation line 2 cm from the proximal end of the tracheal tube would ensure a 1-cm-wide cuff line-free circular area beyond the oral or nasal cavity in nearly all assessed tracheal tube sizes.

Spontaneous Breathing and Imposed Work During Pediatric Mechanical Ventilation: A Bench Study

OBJECTIVES

To calculate imposed work of breathing during simulated spontaneous breathing at a given tidal volume across the range of normal length or shortened pediatric endotracheal tube sizes and endotracheal tubes with an intraluminal catheter in situ.

DESIGN

In vitro study.

SETTING

Research laboratory.

INTERVENTIONS

A bench model (normal compliance, no airway resistance) simulating sinusoid flow spontaneous breathing used to calculate imposed work of breathing for various endotracheal tube sizes (3.0-7.5 mm). Imposed work of breathing was calculated by integrating inspiratory tidal volume over the end-expiratory difference between the positive end-expiratory pressure and the tracheal pressure. Measurements were taken at different combinations of set spontaneous tidal volume (2.5, 5.0, 7.5, and 10 mL/kg), age-appropriate inspiratory times, length of endotracheal tube, and presence of intraluminal catheter.

MEASUREMENTS AND MAIN RESULTS

Overall median imposed work of breathing (Joules/L) was not significantly different between the four age groups: 0.047 Joules/L (interquartile range, 0.020-0.074 Joules/L) for newborns, 0.077 Joules/L (interquartile range, 0.032-0.127 Joules/L) for infants, 0.109 Joules/L (interquartile range, 0.0399-0.193 Joules/L) for small children, and 0.077 Joules/L (interquartile range, 0.032-0.132 Joules/L) for adolescents. Shortening the endotracheal tubes resulted in a significant difference in reduction in overall imposed work of breathing, but the absolute reduction was most notable in small children (0.030 Joules/L) and the least effect in neonates (0.016 Joules/L). Overall imposed work of breathing increased in each age group when an intraluminal catheter was in situ: 91.09% increase in imposed work of breathing in neonates to 0.168 Joules/L, 84.98% in infants to 0.142 Joules/L, 81.98% in small children to 0.219 Joules/L, and 55.45% in adolescents to 0.140 Joules/L.

CONCLUSIONS

Calculated imposed work of breathing were not different across the range of endotracheal tube sizes. The low imposed work of breathing values found in this study might be appreciated as clinically irrelevant. Our findings add to the change in reasoning that it is appropriate to perform spontaneous breathing trials without pressure support. Nonetheless, our findings on the measured imposed work of breathing values need to be confirmed in a clinical study.

Changes in peak inspiratory flow rate and peak airway pressure with endotracheal tube size during chest compression

BACKGROUND

Adequate airway management plays an important role in high-quality cardiopulmonary resuscitation (CPR). Airway management is usually performed using an endotracheal tube (ETT) during CPR. However, no study has assessed the effect of ETT size on the flow rate and airway pressure during CPR.

METHODS

We measured changes in peak inspiratory flow rate (PIFR), peak airway pressure (P_peak), and mean airway pressure (P_mean) according to changes in ETT size (internal diameter 6.0, 7.0, and 8.0 mm) and with or without CPR. A tidal volume of 500 mL was supplied at a rate of 10 times per minute using a mechanical ventilator. Chest compressions were maintained at a constant compression depth and speed using a mechanical chest compression device (LUCAS2, mode: active continuous, chest compression rate: 102±2/minute, chest compression depth 2-2.5 inches).

RESULTS

The median of several respiratory physiological parameters during CPR was significantly different according to the diameter of each ETT (6.0 vs. 8.0 mm): PIFR (32.1 L/min [30.5-35.3] vs. 28.9 L/min [27.5-30.8], P<0.001), P_peak (48.84 cmH₂O [27.46-52.11] vs. 27.45 cmH₂O [22.53-52.57], P<0.001), and P_mean (18.34 cmH₂O [14.61-21.66] vs.13.66 cmH₂O [8.41-19.24], P<0.001).

CONCLUSION

The changes in PIFR, P_peak, and P_mean were related to the internal diameter of ETT, and these values tended to decrease with an increase in ETT size. Higher airway pressures were measured in the CPR group than in the no CPR group.

Work of breathing for cuffed and uncuffed pediatric endotracheal tubes in an in vitro lung model setting

BACKGROUND

Over the last decade, cuffed endotracheal tubes are increasingly used in pediatric anesthesia and also in pediatric intensive care. However, the smaller inner diameter of cuffed endotracheal tubes and, implicitly, the increased endotracheal tube resistance is still a matter of debate.

AIMS

This in vitro study investigated work of breathing and inspiratory airway pressures in cuffed and uncuffed endotracheal tubes and the impact of pressure support ventilation and automatic tube compensation.

METHODS

In 5 simulated neonatal and pediatric lung models, the Active Servo Lung 5000 and an intensive care ventilator were used to quantify the differences in work of breathing under spontaneous breathing (with and without pressure support ventilation and automatic tube compensation) between cuffed and uncuffed endotracheal tubes. Additionally, differences in inspiratory airway pressures, measured either proximal or distal of the endotracheal tube, between cuffed and uncuffed endotracheal tubes under mechanical ventilation were investigated.

RESULTS

Work of breathing was overall 10.27% [95% confidence interval 9.01-11.94] higher with cuffed than with uncuffed endotracheal tubes and was dramatically reduced by 34.19% [95% confidence interval 31.61-35.25] with the application of pressure support. Automatic tube compensation almost diminished work of breathing differences between the 2 endotracheal tube types in nearly all pediatric lung models. Peak inspiratory and mean airway pressures measured at the proximal endotracheal tube end revealed significantly higher values in cuffed than in uncuffed endotracheal tubes. However, these differences measured at the distal end of the endotracheal tube became minimal.

CONCLUSION

This in vitro study confirmed significant differences in work of breathing and inspiratory pressures between cuffed and uncuffed endotracheal tubes. Work of breathing, however, is almost neutralized by pressure support ventilation with automatic tube compensation and distal inspiratory airway pressures that, from a clinical perspective, are not significantly increased.

An in vitro evaluation of the influence of neonatal endotracheal tube diameter and length on the work of breathing

BACKGROUND

Neonates, particularly premature babies, are often managed with endotracheal intubation and subsequent mechanical ventilation to maintain adequate pulmonary gas exchange. There is no consensus on the standard length of endotracheal tube. Although a short tube reduces resistance and respiratory dead space, it is believed to increase the risk of accidental extubation. There are not entirely coherent data regarding the effect of endotracheal tube length on work of breathing in infants.

AIM

The aim of this study was to evaluate the impact of neonatal endotracheal tube diameter and length on the work of breathing using an infant in vitro lung model.

METHOD

We assessed the work of breathing index and mechanical ventilation settings with various endotracheal tube diameters and lengths using the JTR100 in vitro infant lung model. The basic parameters of the model were breathing frequency of 20 per minutes, inspiratory-expiratory ratio of 1:3, and positive end-expiratory pressure of 5 cmH₂ O. In addition, the diaphragm driving pressure to maintain the set tidal volume was measured as the work of breathing index. The JTR100 was connected to the Babylog 8000plus through the endotracheal tube. Finally, we monitored the peak inspiratory pressure generated during assist-control volume guarantee mode with a targeted tidal volume of 10-30 mL.

RESULTS

The diaphragm driving pressure using a 2.0-mm inner diameter tube was twice as high as that using a 4.0-mm inner diameter tube. To maintain the targeted tidal volume, a shorter tube reduced both the diaphragm driving pressure and ventilator-generated peak inspiratory pressure. The difference in the generated peak inspiratory pressure between the shortest and longest tubes was 5 cmH₂ O.

CONCLUSION

In our infant lung model, a shorter tube resulted in a lower work of breathing and lower ventilator-generated peak inspiratory pressure.