Characteristics and outcomes of interventions for pediatric laryngomalacia: A systematic review with meta-analysis.

OBJECTIVES: To analyze characteristics of children treated for laryngomalacia to determine predictive factors and provide an updated meta-analysis on outcomes. METHODS: A systematic review was conducted according to PRISMA guidelines from inception to May 2, 2023, using CINAHL, PubMed, and Scopus databases. Study screening, data extraction, quality rating, and risk of bias assessment were performed by 2 independent reviewers. Data were meta-analyzed using fixed-/random-effects model to derive continuous measures (mean), proportions (%), and mean difference (Δ) with 95% confidence interval (CI). RESULTS: 100 articles were identified with information on outcomes of pediatric patients with laryngomalacia (N = 18,317). The mean age was 10.6 months (range: 0 to 252, 95%CI: 9.6 to 11.6, p = 0.00) with a 1.4:1 male to female ratio. Many patients presented with stridor (87.9%, 95% CI: 69.8 to 98.4), and the most common comorbidity at time of diagnosis was gastroesophageal reflux disease (48.8%, 95%CI: 40.9 to 56.8). Based on the patient population included in our analysis, 86.1% received supraglottoplasty (95% CI: 78.7 to 92.1). A total of 73.6% (95% CI: 65.5 to 81.0) had reported complete resolution of symptoms. For patients with a concurrent diagnosis of sleep disordered breathing receiving supraglottoplasty, the apnea-hypopnea index improved with a mean difference of -10.0 (95%CI: 15.6 to -4.5) events per hour post-treatment. CONCLUSIONS: Laryngomalacia continues to be a common problem in the pediatric population. Supraglottoplasty remains an effective treatment option leading to symptomatic improvement in many cases. For those with concurrent sleep disordered breathing, supraglottoplasty lowers the apnea-hypopnea index.

Adult Laryngomalacia: A Scoping Review.

OBJECTIVE: This review sought to determine the characteristics of adults diagnosed with new onset laryngomalacia including airway symptoms, laryngoscopic findings, treatments, and outcomes. Moreover, we wanted to highlight suspected limitations in the literature. DATA SOURCES: Studies were identified through CINAHL, Cochrane Review, PubMed, and Scopus published between 1966 and 2023. REVIEW METHODS: The search was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analysis Extension for Scoping Reviews checklist by 2 independent investigators. A meta-analysis of proportions and continuous measures was conducted. RESULTS: Of the 1121 abstracts identified, 33 articles pertaining to laryngomalacia in the adult population were included. The most common presenting symptoms were stridor at rest (78.3%, 65.1-88.3) and dyspnea with exertion (83.8%, 64.8-96.3). The most suspected etiology was exercise-induced (86.0%, 69.4-95.5), and the most common description of laryngomalacia on visualization was collapse of supraglottic structures during exercise (93.3%, 79.0-99.1). Nonsurgical options were attempted in 87.0% (54.0-99.1), which included oral appliances, respiratory retraining, breathing techniques, and working with a speech pathologist. Surgical options were ultimately performed in 84.2% (75.0-91.0). Complete resolution of symptoms following therapy was seen in 61.9% (48.0-74.6). CONCLUSION: Adult onset laryngomalacia is difficult to characterize. It typically presents in patients during exercise, with neurological injury, or idiopathically. Surgical management can lead to improvement or complete resolution of symptoms. The need for a universal nomenclature is highlighted in this review, as it is inconsistently classified.

Placebo effect in randomized controlled trials for Meniere's disease: A meta-analysis.

PURPOSE: Meniere's Disease is a condition known for its recurrent vertigo, fluctuating sensorineural hearing loss, aural fullness, and tinnitus. Previous studies have demonstrated significant influence of placebo treatments. Our objective was to quantify the magnitude of the placebo effect in randomized controlled trials for Meniere's Disease. MATERIALS AND METHODS: A systematic review was performed by searching PubMed, SCOPUS, CINAHL, and Cochrane databases from inception through September 27, 2022. Data extraction, quality rating, and risk of bias assessment were performed by two independent reviewers. A meta-analysis of mean differences with 95 % confidence interval, weighted summary proportions, and proportion differences were calculated using random and fixed effects models. RESULTS: A total of 15 studies (N = 892) were included in the review. Significant improvement was seen in the functional level scores of the pooled placebo groups, with a mean difference of -0.6 points, (95%CI: -1.2 to -0.1). There was no difference in pure tone audiometry, speech discrimination score, or vertigo frequency at 1 and 3 months for the placebo group. Patient-reported vertigo episodes were improved in 52.5 % (95%CI: 39.2 to 65.5) of the placebo group and was significantly less than the pooled experimental group (90.1 %, 95%CI: 39.2 to 65.5, p < 0.001). CONCLUSIONS: The placebo effect in Meniere's Disease trials is associated with some symptomatic improvement in subjective outcomes, such as patient reported vertigo episodes. However, the clinical significance is questionable across other outcomes measures, especially when analyzing objective data. The extent and strength of the placebo effect continues to be a hurdle in the search for better treatment options.

Editorial: Special Issue on the Epidemiology of Human Papilloma Virus-Associated Oropharyngeal Squamous Cell Carcinoma.

In this Special Issue of Cancers, the role of oncogenic human papilloma virus (HPV) with oropharyngeal squamous cell carcinoma is explored […].

Time to Lung Volume Stability After Pressure Change During High-Frequency Oscillatory Ventilation.

Clinicians have little guidance on the time needed before assessing the effect of a mean airway pressure change during high-frequency oscillatory ventilation. We aimed to determine: 1) time to stable lung volume after a mean airway pressure change during high-frequency oscillatory ventilation and 2) the relationship between time to volume stability and the volume state of the lung. DESIGN: Prospective observational study. SETTING: Regional quaternary teaching hospital neonatal ICU. PATIENTS: Thirteen term or near-term infants receiving high-frequency oscillatory ventilation and muscle relaxants. INTERVENTIONS: One to two cm H2O mean airway pressure changes every 10 minutes as part of an open lung strategy based on oxygen response. MEASUREMENTS AND MAIN RESULTS: Continuous lung volume measurements (respiratory inductive plethysmography) were made during the mean airway pressure changes. Volume signals were analyzed with a biexponential model to calculate the time to stable lung volume if the model R 2 was greater than 0.6. If volume stability did not occur within 10 minutes, the model was extrapolated to maximum 3,600 s. One-hundred ninety-six mean airway pressure changes were made, with no volume change in 33 occurrences (17%). One-hundred twenty-five volume signals met modeling criteria for inclusion; median (interquartile range) R 2, 0.96 (0.91-0.98). The time to stable lung volume was 1,131 seconds (718-1,959 s) (mean airway pressure increases) and 647 seconds (439-1,309 s) (mean airway pressure decreases), with only 17 (14%) occurring within 10 minutes and time to stability being longer when the lung was atelectatic. CONCLUSIONS: During high-frequency oscillatory ventilation, the time to stable lung volume after a mean airway pressure change is variable, often requires more than 10 minutes, and is dependent on the preceding volume state.

Metabolic Analysis of Drosophila melanogaster Larval and Adult Brains.

This protocol describes a method for measuring the metabolism in Drosophila melanogaster larval and adult brains. Quantifying metabolism in whole organs provides a tissue-level understanding of energy utilization that cannot be captured when analyzing primary cells and cell lines. While this analysis is ex vivo, it allows for the measurement from a number of specialized cells working together to perform a function in one tissue and more closely models the in vivo organ. Metabolic reprogramming has been observed in many neurological diseases, including neoplasia, and neurodegenerative diseases. This protocol was developed to assist the D. melanogaster community's investigation of metabolism in neurological disease models using a commercially available metabolic analyzer. Measuring metabolism of whole brains in the metabolic analyzer is challenging due to the geometry of the brain. This analyzer requires samples to remain at the bottom of a 96-well plate. Cell samples and tissue punches can adhere to the surface of the cell plate or utilize spheroid plates, respectively. However, the spherical, three-dimensional shape of D. melanogaster brains prevents the tissue from adhering to the plate. This protocol requires a specially designed and manufactured micro-tissue restraint that circumvents this problem by preventing any movement of the brain while still allowing metabolic measurements from the analyzer's two solid-state sensor probes. Oxygen consumption and extracellular acidification rates are reproducible and sensitive to a treatment with metabolic inhibitors. With a minor optimization, this protocol can be adapted for use with any whole tissue and/or model system, provided that the sample size does not exceed the chamber generated by the restraint. While basal metabolic measurements and an analysis after a treatment with mitochondrial inhibitors are described within this protocol, countless experimental conditions, such as energy source preference and rearing environment, could be interrogated.

A novel ex vivo method for measuring whole brain metabolism in model systems.

BACKGROUND: Many neuronal and glial diseases have been associated with changes in metabolism. Therefore, metabolic reprogramming has become an important area of research to better understand disease at the cellular level, as well as to identify targets for treatment. Model systems are ideal for interrogating metabolic questions in a tissue dependent context. However, while new tools have been developed to study metabolism in cultured cells there has been less progress towards studies in vivo and ex vivo. NEW METHOD: We have developed a method using newly designed tissue restraints to adapt the Agilent XFe96 metabolic analyzer for whole brain analysis. These restraints create a chamber for Drosophila brains and other small model system tissues to reside undisrupted, while still remaining in the zone for measurements by sensor probes. RESULTS: This method generates reproducible oxygen consumption and extracellular acidification rate data for Drosophila larval and adult brains. Single brains are effectively treated with inhibitors and expected metabolic readings are observed. Measuring metabolic changes, such as glycolytic rate, in transgenic larval brains demonstrates the potential for studying how genotype affects metabolism. COMPARISON WITH EXISTING METHODS AND CONCLUSIONS: Current methodology either utilizes whole animal chambers to measure respiration, not allowing for targeted tissue analysis, or uses technically challenging MRI technology for in vivo analysis that is not suitable for smaller model systems. This new method allows for novel metabolic investigation of intact brains and other tissues ex vivo in a quick, and simplistic way with the potential for large-scale studies.

Are All Oscillators Created Equal? In vitro Performance Characteristics of Eight High-Frequency Oscillatory Ventilators.

BACKGROUND: The mode of waveform generation and circuit characteristics differ between high-frequency oscillators. It is unknown if this influences performance. OBJECTIVES: To describe the relationships between set and delivered pressure amplitude (x0394;P), and the interaction with frequency and endotracheal tube (ETT) diameter, in eight high-frequency oscillators. METHODS: Oscillators were evaluated using a 70-ml test lung at 1.0 and 2.0 ml/cm H2O compliance, with mean airway pressures (PAW) of 10 and 20 cm H2O, frequencies of 5, 10 and 15 Hz, and an ETT diameter of 2.5 and 3.5 mm. At each permutation of PAW, frequency and ETT, the set x0394;P was sequentially increased from 15 to 50 cm H2O, or from 20 to 100% maximum amplitude (10% increments) depending on the oscillator design. The x0394;P at the ventilator (x0394;PVENT), airway opening (x0394;PAO) and within the test lung (x0394;PTRACH), and tidal volume (V(T)) at the airway opening were determined at each set x0394;P. RESULTS: In two oscillators the relationships between set and delivered x0394;P were non-linear, with a plateau in x0394;P thresholds noted at all frequencies (Dräger Babylog 8000) or ≥10 Hz (Dräger VN500). In all other devices there was a linear relationship between x0394;PVENT, x0394;PAO and x0394;PTRACH (all r2 >0.93), with differing attenuation of the pressure wave. Delivered V(T) at the different settings tested varied between devices, with some unable to deliver V(T) >3 ml at 15 Hz, and others generating V(T)>20 ml at 5 Hz and a 1:1 inspiratory-to-expiratory time ratio. CONCLUSIONS: Clinicians should be aware that modern high-frequency oscillators exhibit important differences in the delivered x0394;P and V(T).

Indicators of optimal lung volume during high-frequency oscillatory ventilation in infants.

OBJECTIVES: During high-frequency oscillatory ventilation, an understanding of the relationship between lung volume and lung mechanics may help clinicians better apply ventilation. The objectives of this study were: 1) to describe the relationship between lung volume and lung function parameters during mapping of the deflation limb of the pressure-volume relationship in infants receiving high-frequency oscillatory ventilation, and 2) to determine whether these parameters might be useful in targeting an optimal volume to apply ventilation. DESIGN: Observational physiological study. SETTING: Tertiary neonatal intensive care unit in a pediatric hospital. PATIENTS: Fifteen infants receiving high-frequency oscillatory ventilation and muscle relaxants. INTERVENTIONS: The deflation limb of the pressure-volume relationship was mapped in each infant, after recruitment to total lung capacity, using stepwise airway pressure decrements. Total lung capacity and closing volume were defined by oxygenation response. MEASUREMENTS AND MAIN RESULTS: Lung volume (respiratory inductive plethysmography), oxygen saturation, transcutaneous carbon dioxide, and indicators of lung mechanics were recorded at each pressure. A distinct bell-shaped relationship between lung volume and carbon dioxide, minute ventilation, and tidal volume (both at airway opening and by inductive plethysmography) could be identified on the deflation limb, with an improvement of 21.6 mm Hg (CO2), 168 mL/sec (minute ventilation), 0.25 mL/kg (airway opening tidal volume), and 13.7% (plethysmography tidal volume) compared with total lung capacity levels. The mean (SD) optimal volumes and pressures for these parameters were significantly lower than total lung capacity, occurring at volumes between 38.6 (39.8)% and 62.8 (31.1)% of total lung capacity, and 28 (36.3)% and 41.3 (38.7)% of pressure at total lung capacity (p < 0.05; Bonferroni post-test). These coincided with the lowest pressure and volumes that maintained the oxygenation benefit of recruitment. CONCLUSIONS: Transcutaneous carbon dioxide, tidal volume, and minute ventilation may assist in refining strategies to identify optimal lung volume.

Fluid recovery during lung lavage in meconium aspiration syndrome.

UNLABELLED: Lung lavage using two aliquots of 15 mL/kg of dilute surfactant was performed in 30 ventilated infants with severe meconium aspiration syndrome (MAS). Mean recovery of instilled lavage fluid was 46%, with greater fluid return associated with lower mean airway pressure at 24 h and a shorter duration of respiratory support. CONCLUSION: Recovery of instilled lavage fluid is paramount in effective lung lavage in MAS and must be afforded priority in the lavage technique.

Randomized controlled trial of lung lavage with dilute surfactant for meconium aspiration syndrome.

OBJECTIVE: To evaluate whether lung lavage with surfactant changes the duration of mechanical respiratory support or other outcomes in meconium aspiration syndrome (MAS). STUDY DESIGN: We conducted a randomized controlled trial that enrolled ventilated infants with MAS. Infants randomized to lavage received two 15-mL/kg aliquots of dilute bovine surfactant instilled into, and recovered from, the lung. Control subjects received standard care, which in both groups included high frequency ventilation, nitric oxide, and, where available, extracorporeal membrane oxygenation (ECMO). RESULTS: Sixty-six infants were randomized, with one ineligible infant excluded from analysis. Median duration of respiratory support was similar in infants who underwent lavage and control subjects (5.5 versus 6.0 days, P = .77). Requirement for high frequency ventilation and nitric oxide did not differ between the groups. Fewer infants who underwent lavage died or required ECMO: 10% (3/30) compared with 31% (11/35) in the control group (odds ratio, 0.24; 95% confidence interval, 0.060-0.97). Lavage transiently reduced oxygen saturation without substantial heart rate or blood pressure alterations. Mean airway pressure was more rapidly weaned in the lavage group after randomization. CONCLUSION: Lung lavage with dilute surfactant does not alter duration of respiratory support, but may reduce mortality, especially in units not offering ECMO.

Volume not guaranteed: closed endotracheal suction compromises ventilation in volume-targeted mode.

BACKGROUND: Closed endotracheal suction interferes with mechanical ventilation received by infants, but the change to ventilation may be different when ventilator modes that target expired tidal volume (VT(e)) are used. OBJECTIVE: To measure airway pressure and tidal volume distal to the endotracheal tube (ETT) during and after closed suction in a volume-targeted ventilation mode with the Dräger Babylog 8000+, and to determine the time until VT(e) returns to the baseline level. METHODS: In this benchtop study, closed suction was performed on 2.5- to 4.0-mm ETTs connected to a test lung. 5-8 French suction catheters were used at suction pressures of 80-200 mm Hg during tidal-volume-targeted ventilation. RESULTS: During catheter insertion and suction, circuit inflating pressure increased and tidal volume was maintained, except when a large catheter relative to the ETT was used, in which case tidal volume decreased. End-expiratory pressure distal to the ETT was reduced during suction by up to 75 cm H(2)O while circuit end-expiratory pressure was unchanged. Reduction in end-expiratory pressure distal to the ETT was greatest with large catheters and high suction pressures. Following suction, circuit and tracheal inflating pressures increased and tidal volume increased before returning to baseline in 8-12 s. CONCLUSIONS: Closed endotracheal suction interferes with ventilator function in volume-targeted mode, with substantially negative intratracheal pressure during suction, and the potential for high airway pressures and tidal volumes following the procedure. These effects should be considered and pressure limits set appropriately whenever using volume-targeted ventilation.

Cardiac output measurement in newborn infants using the ultrasonic cardiac output monitor: an assessment of agreement with conventional echocardiography, repeatability and new user experience.

OBJECTIVE: To assess (1) agreement between the ultrasonic cardiac output monitor (USCOM) 1A device for measurement of cardiac output in newborn infants and conventional echocardiography (ECHO), (2) repeatability of USCOM measurements and (3) agreement between novice and expert users of the USCOM. DESIGN: A prospective observational study. SETTING: The Neonatal Unit at the Royal Children's Hospital, Melbourne, Australia. PATIENTS: 56 term and near-term infants, with no evidence of structural or functional cardiovascular disease, or haemodynamic shunts. MEASUREMENTS: Agreement between ECHO and USCOM was assessed by paired measurements of ventricular outputs by a single experienced user. Repeatability was assessed using five repeated measurements in 10 infants. Agreement between five novices and one expert user was assessed by paired USCOM measurements over 30 training measurements. RESULTS: Agreement between USCOM and ECHO for left ventricular output (LVO) was (bias, ±limits of agreement, mean % error): 14, ±108 ml/kg/min, 43%, and for right ventricular output (RVO): -59, ±160, ml/kg/min, 57%. Intra-observer repeatability was 6.7% for USCOM LVO and 3.6% for ECHO LVO. After five training measurements, the mean difference between USCOM measures of LVO by novice and expert users was less than 50 ml/kg/min, but with variability. CONCLUSIONS: Repeatability of USCOM measures is high in newborn infants. New users can be trained quickly, but with high inter-user variability. Agreement between USCOM and conventional ECHO is broad, and worse for RVO and LVO. Further studies are required to assess the ability of the device to detect clinically significant changes in infant cardiac output.

Comparison of four methods of lung volume recruitment during high frequency oscillatory ventilation.

PURPOSE: To compare four methods of volume recruitment upon initiation of high frequency oscillatory ventilation (HFOV). METHODS: Anesthetized intubated neonatal piglets (n = 10) underwent repeated saline lavage, followed by conventional mechanical ventilation (CMV). After transition to HFOV at a mean airway pressure 8 cmH2O above CMV (P(basal)), four methods of lung volume recruitment were tested in each animal in random order: Escalating--step-wise pressure increments over 6 min to a peak mean airway pressure 12 cmH2O above P(basal); Sustained dynamic inflation (DI)--a 20 s inflation to the same peak pressure; DI repeated six times for 1 s; Standard--mean airway pressure set directly at P(basal). After each recruitment method, HFOV continued at P(basal) for 15 min. Thoracic gas volume and distribution of aeration were determined by single slice computed tomography, and oxygenation by arterial blood gas sampling. RESULTS: Escalating recruitment resulted in the greatest thoracic gas volume 15 min post recruitment [77 +/- 3.3% of total lung capacity vs. 70 +/- 4.2% (Sustained DI), 65 +/- 3.5% (Repeated DI),63 +/- 5.1% (Standard); mean +/- SEM; P = 0.042, ANOVA]. All methods resulted in a reduction in non-aerated lung, with the greatest redistribution to normally aerated lung being with Escalating recruitment. Oxygenation 15 min post recruitment was better with the Escalating method than with Repeated DI or Standard recruitment (pO2 307 +/- 41 vs. 159 +/- 36 vs. 134 +/- 39 mmHg, respectively; P = 0.016, ANOVA). CONCLUSIONS: Escalating recruitment produced the greatest increase in lung volume and resolution of atelectasis, and is recommended for lung volume recruitment upon initiation of HFOV.

The effects of closed endotracheal suction on ventilation during conventional and high-frequency oscillatory ventilation.

In newborn infants, closed endotracheal tube (ETT) suction may reduce associated adverse effects, but it is not clear whether ventilation is maintained during the procedure. We aimed to determine the effect of ETT size, catheter size, and suction pressure on ventilation parameters measured distal to the ETT. Suction was performed on a test lung, ventilated with conventional (CMV) and high-frequency oscillatory ventilation (HFOV) using ETT sizes 2.5-4.0 mm, catheter sizes 5-8 French gauge (Fr), and suction pressures 80-200 mm Hg. Tracheal and circuit peak inspiratory pressure, positive end-expiratory pressure, and tracheal tidal volume (VT) were recorded for each suction episode. During both CMV and HFOV, tracheal pressures and VT were considerably reduced by suctioning; this reduction was dependent on the combination of ETT, catheter, and suction pressure. Loss of VT, inflation pressure (CMV), and pressure amplitude (HFOV) occurred primarily with insertion of the catheter, and loss of end-expiratory pressure (CMV) and mean tracheal pressure (HFOV) occurred with the application of suction. Circuit pressures were reduced to lesser degree. We conclude that airway pressures and VT are not maintained during closed endotracheal suction with either CMV or HFOV, and choice of equipment and settings will affect the degree of interruption to ventilation.

The effect of suction method, catheter size, and suction pressure on lung volume changes during endotracheal suction in piglets.

We aimed to identify the effect of suction pressure and catheter size on change in lung volume during open and closed endotracheal suction. Anesthetized piglets (n = 12) were intubated with a 4.0-mm endotracheal tube. Lung injury was induced with saline lavage. Three suction methods (open, closed in-line, and closed with a side-port adaptor) were performed in random order using 6, 7, and 8 French gauge (FG) catheters, at vacuum pressures of 80, 140, and 200 mm Hg. Lung volume change was measured with respiratory inductive plethysmography. Overall, open suction resulted in greater lung volume loss during and at 60-s postsuction than either closed method (p < 0.001). When open and closed methods were analyzed separately, volume change was independent of catheter size and suction pressure with open suction. With closed suction, volume loss increased with larger catheter sizes and higher suction pressures (p < 0.001). With an 8-FG catheter and suction pressure of 140 or 200 mm Hg, volume loss was equivalent with open and closed suction. Lung volume changes are influenced by catheter size and suction pressure, as well as suction method. With commonly used suction pressures and catheter sizes, closed suction has no advantage in preventing loss of volume in this animal model.

Assessment of right ventricular function using tissue Doppler imaging in infants with pulmonary hypertension.

BACKGROUND: In infants with pulmonary hypertension (PHT), right ventricular (RV) function may be altered and contribute to disease severity. Tissue Doppler imaging (TDI) is a new echocardiographic modality which directly measures myocardial velocities and may allow quantitative assessment of systolic and diastolic ventricular function in infants. OBJECTIVE: To measure and compare RV myocardial velocities in infants with PHT and in normal control infants, using TDI. METHODS: This was a prospective case-control study. Twenty-eight control infants and 15 infants with PHT, of whom 11 had congenital diaphragmatic hernia (CDH), were recruited. TDI was used to obtain systolic and diastolic myocardial velocities in the RV and interventricular septum in all infants. RESULTS: There were significant reductions in systolic isovolumic contraction velocity (IVV; 5.3 vs. 6.6 cm/s) and systolic ejection velocity (S; 6.6 vs. 9.2 cm/s) in the PHT group compared to the control group. Early diastolic myocardial velocity, E', was also significantly reduced in the RV in the PHT infants compared to controls (-4.3 vs. 8.6 cm/s). The same significant reductions in systolic and early diastolic TDI velocities were observed in the subgroup of CDH infants alone. CONCLUSIONS: TDI permits non-invasive assessment of RV myocardial velocities in infants. Reduced systolic and diastolic velocities in PHT may represent impaired systolic contraction and early diastolic relaxation. Therapies which target inotropic and lusitropic function may be appropriate in infants with PHT and RV dysfunction. The load-dependency of TDI measures in infants and the effects of specific therapies on RV function in PHT require further investigation.

Use of the myocardial performance index to assess right ventricular function in infants with pulmonary hypertension.

BACKGROUND: This study aimed to measure and compare right ventricular (RV) function in normal infants and those with pulmonary hypertension (PHT) using the myocardial performance index (RVMPI) and to investigate the relationship between RV function and pulmonary artery pressure. METHODS: A case-control study measured RVMPI in 16 infants with PHT (9 of whom had congenital diaphragmatic hernia) and 28 normal control infants. For the PHT infants, 43 paired measures of RVMPI and pulmonary artery pressure (estimated from tricuspid regurgitation jet velocity) were taken to allow investigation of the relationship between RVMPI and pulmonary artery pressure. RESULTS: The mean RVMPI for the control infants was 0.24+/-0.09. The RVMPI was significantly elevated in the PHT group (0.55+/-0.17; p<0.0001), including a subgroup of infants with PHT secondary to congenital diaphragmatic hernia (0.58+/-0.18; p<0.0001). The correlation between RVMPI and pulmonary artery pressure in the infants with PHT (R2=0.05; p=0.17) was poor. CONCLUSIONS: In infants, RVMPI allows quantification of right ventricular function and detection of RV dysfunction in PHT. No linear relationship exists between RVMPI pulmonary artery pressure. Use of RVMPI in the clinical setting must take into account the global and load-dependent nature of this measure.

Refining the method of therapeutic lung lavage in meconium aspiration syndrome.

BACKGROUND: Therapeutic lung lavage is an emerging treatment for meconium aspiration syndrome (MAS), but the ideal fluid volume and lavage technique remain unclear. OBJECTIVE: To evaluate the impact of suction technique, chest squeeze and aliquot volume on the efficacy of lung lavage in MAS. METHODS: MAS was induced in ventilated 2-week-old piglets using 4 ml/kg of 20% human meconium. Lung lavage with either two 8 ml/kg saline aliquots (n = 5) or a single 15 ml/kg aliquot (n = 6) was performed soon after meconium instillation. Lavage fluid was recovered by three methods performed in sequence: closed suction via a suction adaptor; open suction with the ventilator disconnected, and open suction with manual vibratory chest squeezing. Return fluid was collected separately with each method. Recovery of meconium and lavage fluid was determined and expressed as a proportion of the amount instilled. RESULTS: Closed suction resulted in poor meconium and fluid returns, with recovery of meconium being only 5.2 +/- (SD) 2.5% with 2 x 8 ml/kg lavage and 19 +/- 11% with a single 15 ml/kg aliquot. Chest squeeze during suction increased recovery of both meconium and lavage fluid. Overall recovery of instilled meconium was greater with 15 ml/kg lavage (45 +/- 17%) than with two 8 ml/kg aliquots (24 +/- 4.5%, p = 0.028, repeated-measures ANOVA); the corresponding values for return of lavage fluid were 73 +/- 10 and 49 +/- 13%, respectively (p < 0.01). CONCLUSIONS: Open suction, vibratory chest squeezing and an aliquot volume of 15 ml/kg each improve the efficacy of lung lavage in MAS, and merit inclusion in the lavage technique in clinical trials of this therapy.

Negative tracheal pressure during neonatal endotracheal suction.

Endotracheal tube (ETT) suction is the most frequently performed invasive procedure in ventilated newborn infants and is associated with adverse effects related to negative tracheal pressure. We aimed to measure suction catheter gas flow and intratracheal pressure during ETT suction of a test lung and develop a mathematical model to predict tracheal pressure from catheter and ETT dimensions and applied pressure. Tracheal pressure and catheter flow were recorded during suction of ETT sizes 2.5-4.0 mm connected to a test lung with catheters 5-8 French Gauge and applied pressures of 80-200 mm Hg. The fraction of applied pressure transmitted to the trachea was calculated for each combination, and data fitted to three nonlinear models for analysis. Tracheal pressure was directly proportional to applied pressure (r = 0.82-0.99), and catheter flow fitted a turbulent flow model (R = 0.85-0.96). With each ETT, increasing catheter size resulted in greater catheter flow (p < 0.0001) and thus lower intratracheal pressure (p < 0.0001). The fraction of applied pressure transmitted to the trachea was accurately modeled using ETT and catheter dimensions (R = 0.98-0.99). Negative tracheal pressure during in vitro ETT suction is directly proportional to applied pressure. This relationship is determined by ETT and catheter dimensions.