Endotracheal Tube Leak Research Articles

Accuracy of Abbreviated Indirect Calorimetry Protocols for Energy Expenditure Measurement in Critically Ill Children

Accurate measurement of resting energy expenditure (REE) using indirect calorimetry (IC) facilitates optimal energy prescription. Steady-state (SS) REE obtained using a 5-minute protocol (SS5) has been used as a surrogate for 24-hour REE measurement. However, SS5 conditions are difficult to achieve in critically ill children on mechanical ventilatory support. The authors prospectively examined factors associated with successful IC testing using the standard SS5 protocol in mechanically ventilated children. They examined the agreement of REE between SS5 and 2 abbreviated SS protocols: 4-minute (SS4) and 3-minute (SS3) protocols as well as the Schofield prediction equation, using Bland-Altman analysis. IC testing (n = 45) was completed in 34 children. SS was achieved during 25 (56%), 31 (69%), and 42 (93%) tests, using the SS5, SS4, and SS3 protocols, respectively. Intratest variability in respiratory rate, endotracheal tube leak, and inspiratory time was associated with failed IC by the SS5 protocol. The mean bias (limits of agreement) for REE was 2.8 (-47 to 65), 5.8 (-71 to 72), and -127 (-418 to 1176) kcal/d using SS4, SS3, and Schofield, respectively. A stronger agreement was observed when means of all abbreviated SS REE values during a 30-minute test were used. In mechanically ventilated children, 4-minute and 3-minute SS protocols allowed REE measurements to be obtained in most patients with reasonable accuracy. Abbreviated protocols may decrease the need to rely on inaccurate equations when assessing energy expenditure in children who fail IC testing by standard SS criteria.

Heat and Moisture Exchangers and Humidification Efficacy in Pediatrics: Effects of Ventilator Settings and ETT Leakage

Heat and moisture exchangers (HMEs) have been increasingly used for humidification during mechanical ventilation in pediatric patients [1]. However, efficacy of HMEs in the pediatric population has not yet been fully evaluated and there is limited information in the literature regarding the effects of ventilator settings and endotracheal tube (ETT) leakage on the humidification performance of HMEs. Chikata et al. [2] tested ten pediatric HMEs in a model lung, measuring performance under different respiratory rates, tidal volumes TVs (achieved with different pressure control levels), and leakage conditions. They found that eight of the ten HMEs maintained absolute humidity (AH) at more than 30 mg/L, the minimum level recommended by the American Association for Respiratory Care (AARC). With a small leak, AH decreased below 30 mg/L (26.6 to 29.5 mg/L), decreasing further (19.7 to 27.3 mg/L) with a larger leak. Pressure control (tidal volume) level did not statistically significantly affect AH values, although there was a trend to decreased AH at higher tidal volumes. In three of the HMEs, increased respiratory rate resulted in a significantly higher AH. In six of the other seven HMEs, there was a nonstatistically significant trend to higher AH with increased respiratory rate, with one HME showing a nonsignificant trend to lower AH. We think this is a well-designed and conducted study and provides valuable information regarding the use of HMEs in pediatric patients under different conditions. The effect of ETT leakage on AH is nicely demonstrated and is consistent with previously published data on mechanically ventilated adults. However, we had some questions regarding the study's other findings and their possible explanation as follows the study found that 8 out of 10 pediatric HMEs maintained AH at more than 30 mg/L, while they quote the Luchetti et al. [3] study they reference as showing “AH of less than 28 mg/L in all HMEs used with pediatric patients” despite using similar one-way valve methodology in their circuit to prevent mixing of inspired and expired gases? This finding is even more puzzling given that one of the two HMEs used in the Luchetti study, the Hygroboy (Covidien [formerly Tyco Healthcare], Mirandola, Italy), in the present study was found to produce the highest AH (32.4 mg/L) of the ten HMEs tested. How is this difference in findings between the 2 studies of the same HME explained? the finding that increased respiratory rates resulted in a trend to higher AH that reached significance in 3 of the tested humidifiers is interesting. Previous studies of HMEs in adults and children have found lower AH associated with higher tidal volumes [4, 5] and minute volumes (MVs) [1, 6, 7]. It would seem more logical that an increasing respiratory rate presumably would result in a higher MV, with resultant lower AH, but Chikata et al. found the opposite. The authors did not comment on this in their paper, and we wonder if they have a plausible explanation for this; finally, the authors speculate that the finding of a linear relationship between increasing dead space and increasing AH might possibly be related to improved humidification in those HMEs with larger internal volume and dead space. Since it is generally recommended to minimize dead space with HMEs, in particular in pediatric use, would the authors care to comment on striking a balance between maximizing humidification capacity and minimizing dead space?

Respiratory mechanics during high-frequency oscillatory ventilation: a physical model and preterm infant study

Accurate mechanics measurements during high-frequency oscillatory ventilation (HFOV) facilitate optimizing ventilator support settings. Yet, these are influenced substantially by endotracheal tube (ETT) contributions, which may dominate when leaks around uncuffed ETT are present. We hypothesized that 1) the effective removal of ETT leaks may be confirmed via direct comparison of measured vs. model-predicted mean intratracheal pressure [mPtr (meas) vs. mPtr (pred)], and 2) reproducible respiratory system resistance (Rrs) and compliance (Crs) may be derived from no-leak oscillatory Ptr and proximal flow. With the use of ETT test-lung models, proximal airway opening (Pao) and distal (Ptr) pressures and flows were measured during slow-cuff inflations until leaks are removed. These were repeated for combinations of HFOV settings [frequency, mean airway pressure (Paw), oscillation amplitudes (ΔP), and inspiratory time (%t(I))] and varying test-lung Crs. Results showed that leaks around the ETT will 1) systematically reduce the effective distending pressures and lung-delivered oscillatory volumes, and 2) derived mechanical properties are increasingly nonphysiologic as leaks worsen. Mean pressures were systematically reduced along the ventilator circuit and ETT (Paw > Pao > Ptr), even for no-leak conditions. ETT size-specific regression models were then derived for predicting mPtr based on mean Pao (mPao), ΔP, %t(I), and frequency. Next, in 10 of 11 studied preterm infants (0.77 ± 0.24 kg), no-to-minimal leak was confirmed based on excellent agreement between mPtr (meas) and mPtr (pred), and consequently, their oscillatory respiratory mechanics were evaluated. Infant resistance at the proximal ETT (R(ETT); resistance airway opening = R(ETT) + Rrs; P < 0.001) and ETT inertance (P = 0.014) increased significantly with increasing ΔP (50%, 100%, and 150% baseline), whereas Rrs showed a modest, nonsignificant increase (P = 0.14), and Crs was essentially unchanged (P = 0.39). We conclude that verifying no-leak conditions is feasible by comparison of model-derived vs. distending mPtr (meas). This facilitated the reliable and accurate assessment of physiologic respiratory mechanical properties that can objectively guide ventilatory management of HFOV-treated preterm infants.

Mechanical Ventilation of the Premature Neonate

Although the trend in the neonatal intensive care unit is to use noninvasive ventilation whenever possible, invasive ventilation is still often necessary for supporting pre-term neonates with lung disease. Many different ventilation modes and ventilation strategies are available to assist with the optimization of mechanical ventilation and prevention of ventilator-induced lung injury. Patient-triggered ventilation is favored over machine-triggered forms of invasive ventilation for improving gas exchange and patient-ventilator interaction. However, no studies have shown that patient-triggered ventilation improves mortality or morbidity in premature neonates. A promising new form of patient-triggered ventilation, neurally adjusted ventilatory assist (NAVA), was recently FDA approved for invasive and noninvasive ventilation. Clinical trials are underway to evaluate outcomes in neonates who receive NAVA. New evidence suggests that volume-targeted ventilation modes (ie, volume control or pressure control with adaptive targeting) may provide better lung protection than traditional pressure control modes. Several volume-targeted modes that provide accurate tidal volume delivery in the face of a large endotracheal tube leak were recently introduced to the clinical setting. There is ongoing debate about whether neonates should be managed invasively with high-frequency ventilation or conventional ventilation at birth. The majority of clinical trials performed to date have compared high-frequency ventilation to pressure control modes. Future trials with premature neonates should compare high-frequency ventilation to conventional ventilation with volume-targeted modes. Over the last decade many new promising approaches to lung-protective ventilation have evolved. The key to protecting the neonatal lung during mechanical ventilation is optimizing lung volume and limiting excessive lung expansion, by applying appropriate PEEP and using shorter inspiratory time, smaller tidal volume (4-6 mL/kg), and permissive hypercapnia. This paper reviews new and established neonatal ventilation modes and strategies and evaluates their impact on neonatal outcomes.

A practical guide to neonatal volume guarantee ventilation

A recent systematic review and meta-analysis shows that volume-targeted ventilation (VTV) compared with pressure-limited ventilation (PLV) reduce death and bronchopulmonary dysplasia, pneumothorax, hypocarbia and severe cranial ultrasound abnormalities. In this paper, we present published research and our experience with volume guarantee (VG) ventilation, a VTV mode available on the Dräger Babylog 8000plus and VN500 ventilators. The VG algorithm measures the expired tidal volume (V(T)) for each inflation and adjusts the peak inflating pressure for the next inflation to deliver a V(T) set by the clinician. The advantage of controlling expired V(T) is that this is less influenced by endotracheal tube leak than inspired V(T). VG ventilation can be used with an endotracheal tube leak up to ∼50%. Initial set V(T) for infants with respiratory distress syndrome should be 4.0 to 5.0 ml kg(-1). The set V(T) should be adjusted to maintain normocapnoea. Setting the peak inflating pressure limit well above the working pressure is important to enable the ventilator to deliver the set V(T), and to avoid frequent alarms. This paper provides a practical guide on how to use VG ventilation.

Recurrent endotracheal tube leak: ask and take a look

Recurrent endotracheal tube leak: ask and take a look

Extent and incidence of endotracheal tube leakage in ventilated neonates

Extent and incidence of endotracheal tube leakage in ventilated neonates

Relationship between endotracheal tube leakage and under‐reading of tidal volume in neonatal ventilators

Protective ventilation in neonates requires careful volume monitoring to prevent ventilator-induced lung injury caused by baro/volutrauma and hence chronic lung disease. This study investigated the effect of endotracheal tube (ET) leakage on the displayed tidal volume using an in vitro model. A neonatal lung model was ventilated via a 3 mm ET using three ventilators [Babylog 8000 (BL), Leoni (LE) and Stephanie (ST)]. Tidal volume was measured by each ventilator at the Y-piece and by a pneumotach (CO(2)SMO(+)) in the model. ET leaks were simulated by open tubes of different lengths. PIP (20 cmH(2)O) and PEEP (5 cmH(2)O) were kept constant, and the respiratory rate (RR) was varied between 20/min and 70/min (Ti:Te = 1:1). Tidal volume displayed by a ventilator decreased independently of RR with increasing leakage up to 21% (BL), 30% (LE) and 33% (ST). However, the volume delivered to the lung was nearly constant. The displayed leakage varied between 0 and 78% and was dependent on RR and leakage resistance. There were distinct differences between the three ventilators in the relationship between displayed leakage and volume error. Accepting a volume error <10% for RR between 20 and 70/min, ET leakage of up to 20% for BL, 12% for LE, but only <5% for ST, was acceptable. Tidal volume underestimation arising from ET leakage depends on ventilator pressures, timing parameters and ventilator-specific algorithms for signal processing. Therefore, neonatologists should be aware of these issues to prevent lung over-inflation when adjusting target volume in the presence of ET leakage.

Effect of endotracheal air leakages on the monitoring of ventilation and respiratory mechanics in ventilated newborns

The prevention of lung over-distension and ventilator induced lung injury (VILI) requires a lung protective mechanical ventilation with careful monitoring of ventilation and lung mechanics. However, this will be impaired by endotracheal tube (ET) leakages. The aim of this study was to investigate the effect of ET leakages on the monitoring of tidal volume (VT) and respiratory mechanics using an in-vitro model. Methods: A neonatal lung model was ventilated via a 3mm ET using 3 ventilators: Babylog 8000 (BL), Leoni (LE), Stephanie (SE). VT and lung mechanics were measured by the pneumotach of the ventilator at the Y-piece. Additionally, VT delivered to the lung model was measured by a second pneumotach (CO2SMO+). ET leakages were simulated by open silicone tubes of different lengths. PIP (20cmH2O) and PEEP (5cmH2O) were kept constant, respiratory rate (RR) was changed from 20 to 70/min (I: E=1: 1). Results: The displayed leakage varied between 0 and 78% and was dependent on RR. VT measured by the ventilator decreased with increasing leakage up to 21%(BL), 30%(LE) and 33%(ST) independent of RR,. whereas VT delivered to the lung was nearly constant. With increasing ET leakage for BL and ST the displayed compliance was overestimated, while for LE the compliance was underestimated. The displayed resistance increased with increasing ET leakage for all ventilators, however, in different way: distinctly for BL and ST, minimally for LE. Conclusion: The effect of ET leakage on the displayed ventilatory and lung mechanic parameters are ventilator dependent which impairs the between ventilators comparability. General recommendations what level of ET leakage can be tolerated are not possible.

Evaluation of the M-COVX metabolic monitor in mechanically ventilated adult patients

Summary Background & aims: Indirect calorimetry is commonly used for energy expenditure studies. However, older metabolic carts can be cumbersome and difficult to use. This study was aimed at validating the new M-COVX indirect calorimeter. Methods: This prospective study was performed in all ventilated critically ill adults, with a Fractional Inspired Oxygen <60%, respiratory rate below 35 breaths-per-minute and endotracheal tube leak <10%. Patients were studied in steady-state only. Repeated, sequential measurements were performed comparing Deltatrac II NMN-200 to the new M-COVX. For each instrument, 5 consecutive, 1 min measurements of volume of oxygen and carbon dioxide, respiratory quotient and energy expenditure were recorded. Results: Of the 20 patients enrolled in the study, the data of 11 patients was used for analysis. Bland Altman plots indicated clinically significant differences between the 2 indirect calorimeters for volume of oxygen (19.2%) and carbon dioxide (17.6%) and energy expenditure (15.3%). Conclusion: The results show that the M-COVX metabolic monitor might not provide measurement within a clinically accepted range in certain ventilation modes and in non-sedated patients. Further research has to be performed to confirm our findings. a 2008 European Society for Clinical Nutrition and Metabolism. Published by Elsevier Ltd. All rights reserved.

Limitation of measurements of expiratory tidal volume and expiratory compliance under conditions of endotracheal tube leaks

Endotracheal tube leaks (ETTLs) occur in neonates ventilated with uncuffed tubes. Assuming that the influence of ETTLs might be neglected during expiration, only expiratory tidal volume is measured for calculation of expiratory compliance in cases of large ETTLs. However, expiratory ETTL might be substantial. Therefore, we evaluated the effect of ETTL size on expiratory tidal volume and compliance. Prospective laboratory study and retrospective clinical study. University research laboratory and neonatal intensive care unit. Sixty ventilated neonates (weight 640-2160 g, gestational age 25-33 wks) were investigated. The impact of increasing ETTLs on inspiratory and expiratory measured tidal volume (Vm), corrected tidal volume (Vc), and leak volume (Vl) was investigated in a ventilated neonatal lung model. The range of ETTLs (1% to 95%) was subdivided into five groups of 12 infants each. Furthermore, the relationships between standard ETTL size and inspiratory and expiratory ETTLs were evaluated using nonlinear regression. Standard ETTL size was defined as the difference between measured inspiratory and expiratory tidal volume (Vm) related to inspiratory Vm. The size of a standard ETTL was 40% when expiratory ETTL reached 10% and was 12% when the inspiratory ETTL reached 10%. In infants, the differences between Vm and Vc were statistically significant during inspiration in the group beginning at a standard ETTL of 41% and during expiration in the group beginning at a standard ETTL of 69% (p < .05). Results of nonlinear regression showed that the standard ETTL was 33% (95% confidence interval, 28% to 36%) when expiratory ETTL reached 10% and was 13% (95% confidence interval, 12% to 15%) when inspiratory ETTL reached 10%. Expiratory Vl has a relevant impact if a certain ETTL size is reached.

Commentary: Morrow B, Futter M, Argent A. (2006). Effect of endotracheal suction on lung dynamics in mechanically‐ventilated paediatric patients

AbstractEndotracheal suctioning is performed regularly in ventilated infants and children to remove obstructive secretions. The effect of suctioning on respiratory mechanics is not known. This study aimed to determine the immediate effect of endotracheal suctioning on dynamic lung compliance, tidal volume and airway resistance in mechanically ventilated paediatric patients by means of a prospective observational clinical study. Lung mechanics were recorded for 5 min before and 5 min after a standardized suctioning procedure in 78 patients intubated with endotracheal tubes of ≤4·0 mm internal diameter. Twenty‐four patients with endotracheal tube leaks ≥20% were excluded from analysis. There was a significant overall decrease in dynamic compliance (p &lt; 0·001) and mechanical expired tidal volume (p = 0·03) following suctioning with no change in the percentage of endotracheal tube leak (p = 0·41). The change in dynamic compliance was directly related to both endotracheal tube and catheter sizes. There was no significant change in expiratory or inspiratory airway resistance following suctioning (p &gt; 0·05). Although most of the patients (68·5%) experienced a drop in dynamic compliance following suctioning, dynamic compliance increased in 31·5% of patients after the procedure. This study demonstrates that endotracheal suctioning frequently causes an immediate drop in dynamic compliance and expired tidal volume in ventilated children with variable lung pathology, intubated with small endotracheal tubes, probably indicating loss of lung volume caused by the suctioning procedure. There is no evidence that suctioning reduces airway resistance. Abstract reprinted from the Australian Journal of Physiotherapy volume 52, Morrow B et al., ‘Effect of endotracheal suction on lung dynamics in mechanically‐ventilated paediatric patients’, pages 121–126. © 2006, reproduced with permission from the Australian Physiotherapy Association.

More about Telescoping for Nasotracheal Intubation in Children

We thank the authors of both letters for their thought-provoking comments. In the first letter, Dr. Mahajan et al . refer to the incidence of nasopharyngeal bleeding after native tubes in our study1(56%) and the incidence after warmed tubes and a vasoconstrictor in the study by Elwood et al .2(29%). Although these were both “control” groups, the two treatments have no common basis for comparison. Considering the incidence of bleeding associated with warmed tubes in the two studies,1,2Dr. Mahajan et al . posit that the 0.5-mm-larger tube diameter in our study contributed to the greater incidence of bleeding. This is a possibility that we did not test. Whether the larger tube diameters in our study contributed to the incidence of bleeding with native and warm tubes is a moot point because the incidence of bleeding with a larger diameter tube telescoped into a soft rubber catheter seems to be trivial (5%).1Further direct comparisons between the results of the two studies should be limited because we did not test the effect of oxymetazoline in our study. Although the larger-diameter uncuffed tubes may have contributed to the incidence of bleeding in our study, this was a compromise rooted in our other concern to minimize the magnitude of the endotracheal tube leak. The authors correctly point out that we did not report complications from nasotracheal intubation that occurred in the postanesthesia care unit and thereafter. We can state categorically, though, that whereas surrogate markers for complications may have occurred, neither ear, nose, and throat consultation nor admission to or delayed discharge from the hospital occurred as a result of nasopharyngeal bleeding.Dr. Wu also questions the sizes of the tubes that we used and the magnitude of the endotracheal tube leak. We did not change any of the tubes because the tracheal leak was too large. This is not to suggest that such a situation cannot occur. However, during dental surgery, we minimize the clinical impact of a small endotracheal tube leak by maintaining spontaneous ventilation and by packing the throat with gauze. There is no evidence that the size of the larynx in children in the United States varies geographically. Dr. Wu describes a modification to the proximal end of a cuffed straight nasal tube to facilitate its use in dental surgery, which is analogous to using the old-fashioned metal “nasal” connectors. However, we urge caution when considering the use of “homemade” modifications to airway devices that have not been tested under rigorous conditions to identify the risks of failure and disconnect during anesthesia.*Women and Children’s Hospital of Buffalo, State University of New York at Buffalo, Buffalo, New York. jerroldlerman@gmail.com

Calculation of intratracheal airway pressure in ventilated neonatal piglets with endotracheal tube leaks

In ventilated neonates, only the applied pressure of the ventilator is adjusted and monitored. When an endotracheal tube leaks, intratracheal pressure decreases depending on the size of the endotracheal tube and of the leak. Furthermore, an increase in resistance and/or compliance might delay the increase of intratracheal pressure during inspiration and its decline during expiration. Short inspiratory time can cause insufficient ventilation, because intratracheal pressure peak might not be reached. Short expiratory time may lead to air trapping, because intratracheal pressure could not return to baseline. The aim of this study was to develop a mathematical algorithm to calculate intratracheal pressure continuously during ventilation and to evaluate the accuracy of this method. Prospective, animal study. University research laboratory. To verify the mathematical algorithm, eight neonatal piglets (1600-2600 g) were studied under different endotracheal tube leak conditions (45% to 98%). The median compliance and resistance were 1.06 mL/cm H2O/kg and 123 cm H2O/L/sec, respectively. Pressure decreases caused by the different endotracheal tubes were measured in a model while air flow was increased stepwise. Based on these results, a mathematical method was developed to calculate intratracheal pressure under leak conditions continuously in relation to the flow through the endotracheal tube as well as to calculate the values of resistance, compliance, and applied pressure of the ventilator. The intratracheal pressure calculated was compared with the measured intratracheal pressure over time. The differences between measured and calculated intratracheal pressure related to peak applied pressure of the ventilator did not exceed 10%. The medians of absolute amounts of differences between measured and calculated intratracheal pressure were <1 cm H2O. The accuracy of the calculation of intratracheal pressure ensures adequate monitoring of artificial ventilation, even in the presence of endotracheal tube leaks. This might decrease the risk of barotrauma and improve the effectiveness of ventilation.

Correction of compliance and resistance altered by endotracheal tube leaks and non-linear pressure/volume-relationships

Measurements of lung compliance (C) and resistance (R) are influenced by endotracheal tube leaks (ETTL) as well as non-linear pressure/volume relationships (P/V relationship). To keep C and R reliable, we developed an algorithm to mathematically correct inspiratory and expiratory volume (V) and flow. In this study, a ventilated lung model for non-linear P/V relationship with adjustment of an increasing ETTL was studied. In addition, the recordings (airway pressure, flow, and volume) of 21 infants (median weight: 1,220 g, range: 640-2,160 g, with a median leak size of 32%, range: 24-56%) were investigated. C and R were calculated continuously from the recordings of flow, volume, and airway pressure over time according to the changing volume. A method especially developed for the analysis of non-linear pressure-volume-relationship (APVNL) was employed. C and R affected by leaks were corrected applying the newly developed mathematical algorithm and compared with measurements without leakage. C could be corrected up to a leak of 80% and R up to 55% leak at half tidal V for the model with non-linear P/V-R. C and R without leak and after leak correction did not differ significantly in all infants where the APVNL method was applied (P > 0.05).

Volume-targeted ventilation

Recognition that volume, not pressure, is the key factor in ventilator-induced lung injury and the association of hypocarbia and brain injury dictate the need to better control delivered tidal volume. Volume-controlled ventilation, though much improved, still suffers from loss of volume due to endotracheal tube leak and gas compression in the circuit. Recent microprocessor-based modifications of pressure-limited, time-cycled ventilators combine advantages of pressure-limited ventilation with the ability to deliver a more consistent tidal volume. Each of the modes has advantages and disadvantages, with limited data available to judge their effectiveness. The Volume Guarantee mode, studied most thoroughly, provides automatic weaning of peak pressure in response to improving lung compliance and respiratory effort. More consistent tidal volume, fewer excessively large breaths, lower peak pressure, less hypocarbia and lower levels of inflammatory cytokines have been documented. It remains to be seen if these short-term benefits translate into shorter duration of ventilation or reduced incidence of chronic lung disease.

Prone positioning can be safely performed in critically ill infants and children*

To describe the effects of prone positioning on airway management, mechanical ventilation, enteral nutrition, pain and sedation management, and staff utilization in infants and children with acute lung injury. Secondary analysis of data collected in a multiple-center, randomized, controlled clinical trial of supine vs. prone positioning. Seven pediatric intensive care units located in the United States. One hundred and two pediatric patients (51 prone and 51 supine) with acute lung injury. Patients randomized to the supine group remained supine. Patients randomized to the prone group were positioned prone per protocol during the acute phase of their illness for a maximum of 7 days. Both groups were managed using ventilator and sedation protocols and nutrition and skin care guidelines. Airway management and mechanical ventilatory variables before and after repositioning, enteral nutrition management, pain and sedation management, staff utilization, and adverse event data were collected for up to 28 days after enrollment. There were a total of 202 supine-prone-supine cycles. There were no differences in the incidence of endotracheal tube leak between the two groups (p = .30). Per protocol, 95% of patients remained connected to the ventilator during repositioning. The inadvertent extubation rate was 0.85 for the prone group and 1.03 for the supine group per 100 ventilator days (p = 1.00). There were no significant differences in the initiation of trophic (p = .24), advancing (p = .82), or full enteral feeds (p = .80) between the prone and supine groups; in the average pain (p = .81) and sedation (p = .18) scores during the acute phase; and in the amount of comfort medications received between the two groups (p = .91). There were no critical events during a turn procedure. While prone, two patients experienced an obstructed endotracheal tube. One patient, supported on high-frequency oscillatory ventilation, experienced persistent hypercapnea when prone and was withdrawn from the study. The occurrence of pressure ulcers was similar between the two groups (p = .71). Compared with the supine group, more staff (p </= .001) and more time were necessary to reposition patients in the prone group. Our data show that prone positioning can be safely performed in critically ill pediatric patients and that these patients can be safely managed while in the prone position for prolonged periods of time.

Effect of endotracheal suction on lung dynamics in mechanically-ventilated paediatric patients

Endotracheal suctioning is performed regularly in ventilated infants and children to remove obstructive secretions. The effect of suctioning on respiratory mechanics is not known. This study aimed to determine the immediate effect of endotracheal suctioning on dynamic lung compliance, tidal volume, and airway resistance in mechanically-ventilated paediatric patients by means of a prospective observational clinical study. Lung mechanics were recorded for five minutes before and five minutes after a standardised suctioning procedure in 78 patients intubated with endotracheal tubes < or = 4.0 mm internal diameter. Twenty-four patients with endotracheal tube leaks > or = 20% were excluded from analysis. There was a significant overall decrease in dynamic compliance (p < 0.001) and mechanical expired tidal volume (p = 0.03) following suctioning with no change in the percentage endotracheal tube leak (p = 0.41). The change in dynamic compliance was directly related to both endotracheal tube and catheter sizes. There was no significant change in expiratory or inspiratory airway resistance following suctioning (p > 0.05). Although the majority of patients (68.5%) experienced a drop in dynamic compliance following suctioning, dynamic compliance increased in 31.5% of patients after the procedure. This study demonstrates that endotracheal suctioning frequently causes an immediate drop in dynamic compliance and expired tidal volume in ventilated children with variable lung pathology, intubated with small endotracheal tubes, probably indicating loss of lung volume caused by the suctioning procedure. There is no evidence that suctioning reduces airway resistance.

Effect of lung compliance and endotracheal tube leakage on measurement of tidal volume

IntroductionThe objective of this laboratory study was to measure the effect of decreased lung compliance and endotracheal tube (ETT) leakage on measured exhaled tidal volume at the airway and at the ventilator, in a research study with a test lung.MethodsThe subjects were infant, adult and pediatric test lungs. In the test lung model, lung compliances were set to normal and to levels seen in acute respiratory distress syndrome. Set tidal volume was 6 ml/kg across a range of simulated weights and ETT sizes. Data were recorded from both the ventilator light-emitting diode display and the CO2SMO Plus monitor display by a single observer. Effective tidal volume was calculated from a standard equation.ResultsIn all test lung models, exhaled tidal volume measured at the airway decreased markedly with decreasing lung compliance, but measurement at the ventilator showed minimal change. In the absence of a simulated ETT leak, calculation of the effective tidal volume led to measurements very similar to exhaled tidal volume measured at the ETT. With a simulated ETT tube leak, the effective tidal volume markedly overestimated tidal volume measured at the airway.ConclusionPrevious investigators have emphasized the need to measure tidal volume at the ETT for all children. When ETT leakage is minimal, it seems from our simulated lung models that calculation of effective tidal volume would give similar readings to tidal volume measured at the airway, even in small patients. Future studies of tidal volume measurement accuracy in mechanically ventilated children should control for the degree of ETT leakage.

Measuring energy expenditure in preterm and unstable infants

Measuring energy expenditure in preterm and unstable infants