Physiologic Effects of 3 Different Neonatal Volume-Targeted Ventilation Modes in Surfactant-Deficient Juvenile Rabbits.

BACKGROUND: Different brands of volume-targeted modes may vary the location of tidal volume (VT) monitoring and whether peak inspiratory pressure is adjusted based on inspiratory, expiratory, or leak-compensated VT. These variables may result in different levels of support provided to patients, especially when an endotracheal tube (ETT) leak is present. We hypothesized that there would be no differences in gas exchange, triggering, or work of breathing between volume-targeted modes of 3 different brands of equipment in a surfactant-deficient, spontaneously breathing animal model with and without an ETT leak. METHODS: Twelve rabbits (mean ± SD 1.61 ± 0.20 kg) were sedated, anesthetized, intubated, lavaged with 0.9% saline solution, and randomized in a crossover design so that each animal was supported by 3 different volume-targeted modes at identical settings with and without an ETT leak. After 30 min, arterial blood gas, VT, and esophageal and airway pressure were recorded for each condition, and pressure-rate product and percentage of successfully triggered breaths were calculated. RESULTS: Gas exchange and the pressure-rate product were not different between the ventilators in the absence of an ETT leak. When an ETT leak was introduced, volume-guarantee modes allowed a higher percentage of triggered breaths and peak inspiratory pressure, which resulted in higher minute ventilation, pH, and lower PaCO2 than the pressure-regulated volume control mode (P < .05). CONCLUSIONS: When a moderate ETT leak was present, volume-targeted modes that used proximal VT monitoring and triggering with adaptive leak compensation capabilities appeared more effective in providing ventilation support than did a ventilator that used measurements obtained from the back at the ventilator and does not have leak compensation.

Bronchodilator delivery during simulated pediatric noninvasive ventilation.

BACKGROUND: Noninvasive ventilation (NIV) is usually applied using bi-level positive airway pressure devices, and many of these devices use a single-limb patient circuit with an integrated leak port to purge the circuit of exhaled carbon dioxide. Sometimes bronchodilator therapy is indicated in pediatric patients, but there have been no studies of the optimal nebulizer position, with respect to leak, during pediatric NIV. We hypothesized that there would be no differences in albuterol delivery with a vibrating-mesh nebulizer between 3 different positions/exhalation leak valve combinations in the patient circuit during simulated pediatric NIV. METHODS: A simulated upper airway model was attached to a lung model that simulated spontaneous breathing. A noninvasive ventilator equipped with heated wire circuit and heated humidifier was attached to the lung model via a pediatric oronasal mask. Albuterol (5 mg) was delivered with a vibrating-mesh nebulizer, at 3 different circuit position/leak condition combinations: prior to the humidifier and leak valve; between the humidifier and leak valve; and integrated within the mask and after the leak. Albuterol was captured on a filter and quantified with chromatography. RESULTS: Greater albuterol mass was delivered to the filter with the nebulizer integrated into the mask than at any other testing condition (P < .001). In the conditions where the nebulizer was placed prior to the exhalation leak valve, greater drug delivery was observed when the nebulizer was placed proximal to the mask (position 2) than when placed prior to the humidifier (position 3, P = .002). CONCLUSIONS: Albuterol delivery during simulated pediatric NIV was affected by the position of the nebulizer in relation to the expiratory leak valve and the nebulizer's distance from the filter. A vibrating-mesh nebulizer placed intra-mask may provide a better alternative for medication delivery than those previously used during pediatric NIV.

Use of a lung model to assess mechanical in-exsufflator therapy in infants with tracheostomy.

BACKGROUND: The mechanical in-exsufflator (MIE) is commonly used to augment cough in patients with neuromuscular disease from infancy to adulthood. Little is known about the alveolar pressures, lung volumes, and expiratory flow rates generated by the MIE when used via tracheostomy tube in infants and children. METHODS: A high-fidelity mechanical lung model was programmed to simulate infants with tracheostomy tubes. Generated pressures, volumes, and expiratory flows using the MIE device at variable insufflation/exsufflation pressures and times were recorded. The primary measure of interest was maximal expiratory flow (MEF). RESULTS: Pressure equilibration across the tracheostomy tube did not occur with insufflation time <1 sec. Longer insufflation time significantly increased measured alveolar pressures, lung volume, and MEF until TLC was reached. Longer exsufflation time did not significantly increase MEF. Higher insufflation pressures resulted in greater lung volumes, with >70% vital capacity attained at insufflation pressures as low as 20 cmH2 O. Though higher insufflation pressures resulted in increased expiratory flow rates, more negative exsufflation pressure had a greater absolute impact on MEF. CONCLUSIONS: Using the MIE via tracheostomy tube in an infant lung model, we found that an insufflation time of >1 sec is required for equilibration of insufflation pressure and alveolar pressure. Longer exsufflation time does not significantly alter MEF. Higher insufflation and exsufflation pressures both increased MEF, but greater exsufflation pressure had more substantial impact.

Therapeutic bilateral lung lavage in a child with pulmonary alveolar proteinosis.

OBJECTIVE: Pulmonary alveolar proteinosis is a rare condition that can cause life-threatening respiratory failure attributable to excessive alveolar accumulation of surfactant proteins. The standard treatment for removing these secretions is through therapeutic bilateral lung lavage. Descriptions of procedures for performing therapeutic bilateral lung lavage and methods used to evaluate the overall effectiveness of this invasive procedure in children with pulmonary alveolar proteinosis have not been adequately described in the medical literature. We successfully and safely performed therapeutic bilateral lung lavage and obtained lung mechanics measurements in a child with pulmonary alveolar proteinosis. DESIGN: Case report. SETTING: Operating room within a pediatric hospital. PATIENTS/SUBJECTS: A 13-yr-old boy with pulmonary alveolar proteinosis requiring serial therapeutic bilateral lung lavage for recurrent respiratory distress. INTERVENTIONS: The patient presented to the hospital operating room for therapeutic lung lavage after a recent history of progressive dyspnea, respiratory distress, declining lung function measurements, and worsening radiographic abnormalities. We obtained baseline spirometric and respiratory system compliance measurements before and after therapeutic bilateral lung lavage. The left lung was lavaged on the first day and the right lung was lavaged on the third day using selective endobronchial intubation and selective lung ventilation. RESULTS: The procedure was well-tolerated and resulted in the removal of a significant volume of accumulated secretions. After the lavage, the patient demonstrated improvement in respiratory distress, chest radiograph appearance, lung compliance, and spirometric measurements. CONCLUSIONS: This case report demonstrates that therapeutic bilateral lung lavage can be performed safely and effectively in a pediatric patient with pulmonary alveolar proteinosis by isolating individual lungs using a dual-lumen endotracheal tube. In this patient, therapeutic bilateral lung lavage was found to have a significant impact on lung function and mechanics after this procedure.

The impact of imposed expiratory resistance in neonatal mechanical ventilation: a laboratory evaluation.

BACKGROUND: Small endotracheal tubes (ETTs) and neonatal ventilators can impact gas exchange, work of breathing, and lung-mechanics measurements in infants, by increasing the expiratory resistance (R(E)) to gas flow. METHODS: We tested two each of the Babylog 8000plus, Avea, Carestation, and Servo-i ventilators. In the first phase of the study we evaluated (1) the imposed R(E) of an ETT and ventilator system during simulated passive breathing at various tidal volume (V(T)), positive end-expiratory pressure (PEEP), and frequency settings, and (2) the intrinsic PEEP at various ventilator settings. In the second phase of this study we evaluated the imposed expiratory work of breathing (WOB) of the ETT and ventilator system at various PEEP levels during simulated spontaneous breathing using an infant lung model. Pressure and flow were measured continuously, and we calculated the imposed R(E) of the ETT and each ventilator, and the intrinsic PEEP with various PEEP, V(T), and frequency settings. We measured the imposed expiratory WOB with several PEEP levels during a simulated spontaneous breathing pattern. RESULTS: The ventilator's contribution to the imposed R(E) was greater than that of the ETT with nearly all of the ventilators tested. There were significant differences in ventilator-imposed R(E) between the ventilator brands at various PEEP, V(T), and frequency settings. The Babylog 8000plus consistently had the lowest ventilator-imposed R(E) in the majority of the test conditions. There was no intrinsic PEEP (>1 cm H(2)O) in any of the test conditions with any ventilator brand. There were also no significant differences in the imposed expiratory WOB between ventilator brands during simulated spontaneous breathing. CONCLUSIONS: The major cause of R(E) appears to be the ventilator exhalation valve. Neonatal ventilators that use a set constant flow during inhalation and exhalation appear to have less R(E) than ventilators that use a variable bias flow during exhalation. Clinical studies are needed to determine whether the imposed R(E) of these ventilator designs impacts gas exchange, lung mechanics, or ventilator weaning.

The conversion to metered-dose inhaler with valved holding chamber to administer inhaled albuterol: a pediatric hospital experience.

BACKGROUND: Metered-dose inhalers with valved holding chambers (MDI-VHCs) have been shown to be equivalent to small-volume nebulizers (SVNs) for the delivery of bronchodilators in children. At Seattle Children's Hospital and Regional Medical Center we sought to implement the conversion from SVN to MDI-delivered albuterol in nonintubated patients receiving intermittent treatments. METHODS: There were 4 distinct interventions used to plan and implement this conversion program: (1) literature review, (2) product selection, (3) policy and operational changes, and (4) staff training. Bronchodilator administration guidelines and clinical pathways for asthma and bronchiolitis were revised to recommend MDI-VHC use in lieu of SVNs. Computerized physician order sets were amended to indicate MDI-VHC as the preferred method of delivering inhaled albuterol in children with asthma and bronchiolitis. Data from administrative case mix files and computerized medication delivery systems were used to assess the impact of our program. RESULTS: MDI-VHC utilization increased from 25% to 77% among all non-intensive-care patients receiving albuterol, and from 10% to 79% among patients with asthma (p < 0.001). Duration of stay among patients with asthma was unchanged after conversion to MDI-VHC (p = 0.53). CONCLUSIONS: Our program was very successful at promoting the use of MDI-VHC for the administration of albuterol in our pediatric hospital. Duration of stay among patients with asthma did not change during or since the implementation of this program.

Neonatal and pediatric pulse oximetry.

The pulse oximeter has become a vital instrument in the care of infants and children with cardiopulmonary disease. Recent advances in pulse oximetry technology have improved some aspects of pulse oximeter performance. However, the reliability, accuracy, and clinical utility of pulse oximetry remain problematic in some types of patients under certain conditions. Improved signal processing technology has substantially improved the ability of certain oximeters to work reliably under conditions of poor perfusion and motion artifact. There is a growing body of evidence describing the effect of pulse oximeter utilization on processes and outcomes. This article describes the principles, limitations, current state of oximetry technology, and the impact of oximetry data and alarms on diagnosis and clinical decision-making.

A survey of albuterol administration practices in intubated patients in the neonatal intensive care unit.

INTRODUCTION: Aerosolized albuterol is commonly used in the treatment of neonatal respiratory illnesses. Clinical and in vitro studies have identified numerous factors that affect aerosol drug delivery during neonatal mechanical ventilation, including the choice of metered-dose inhaler (MDI) or nebulizer, the use of a holding chamber, time between actuations, the volume of nebulized solution, and the position and placement of the nebulizer or MDI. Because there is no consensus on the optimal method of administration, there is probably substantial variability among institutions in how aerosolized albuterol is administered to mechanically ventilated infants in the neonatal intensive care unit (NICU). OBJECTIVE: Survey academic medical centers in the United States regarding their practices of administering aerosolized albuterol to intubated newborns in the NICU. METHODS: A survey instrument was developed that queried 18 aspects of albuterol administration in mechanically ventilated infants, including the frequency of MDI and nebulizer use, the average and maximum dose, the time between MDI actuations and following the final actuation, the use of a holding chamber, and the placement location of the holding chamber or nebulizer. Respiratory therapists and respiratory therapy managers having direct knowledge of neonatal clinical practices in their neonatal fellowship program NICUs were surveyed via telephone. Those who did not respond via telephone were surveyed via fax. RESULTS: Eighty institutions were surveyed and there were 68 respondents (85% response rate). Responders averaged 35 +/- 13 NICU beds and 11 +/- 5 ventilators/d. Nineteen percent of the respondents reported administering albuterol via MDI 100% of the time; 22% use MDIs 75-99% of the time; 9% use MDIs 50-74% of the time; 4% use MDIs 25-49% of the time; and 43% never use MDIs to deliver albuterol. The average dose via MDI was: 1 puff: 30%; 2 puffs: 65%; and 4 puffs: 5%. The maximum dose via MDI was: 2 puffs: 30%; 3 puffs: 14%; 4 puffs: 36%; 6 puffs: 11%; and 8 puffs: 6%. Thirty-one percent of the respondents place the holding chamber in-line with the ventilator circuit, 56% administer the aerosol via manual ventilation, and 13% use both methods. Fifty-six percent place the in-line holding chamber between the endotracheal tube and ventilator circuit, and the other 44% place the in-line holding chamber in the inspiratory limb. The time between MDI actuations depended on whether the holding chamber was placed in-line or the aerosol was administered via manual ventilation (MV): < or = 0.5 min: 18% in-line and 28% MV; 1 min: 47% in-line and 43% MV; 2 min: 6% in-line and 4% MV; 3 min: 6% in-line and 0% MV. Eighty-three percent of respondents indicated that dead space introduced by a holding chamber/spacer was not a concern. Forty-three percent use nebulizers exclusively to administer albuterol to mechanically ventilated patients. Seventy-four percent of centers that nebulize albuterol use a dose of 1.25-2.5 mg. Eighty-eight percent of the surveyed institutions place nebulizers in-line with the ventilator circuit, and the other 12% use manual ventilation to administer the nebulized aerosol. Of those that use in-line nebulization, 95% place the nebulizer in the inspiratory limb of the circuit, and the other 5% place the nebulizer between the endotracheal tube and circuit Y-piece. Among centers that place the nebulizer in the inspiratory limb, 52% place it adjacent to the circuit Y-piece, 36% place it midway upstream in the inspiratory limb, and 12% place it near the humidifier. CONCLUSION: There is substantial variability among NICUs in albuterol administration to mechanically ventilated infants, with the majority of institutions now administering albuterol via MDI.