Albuterol delivery in a neonatal ventilated lung model: Nebulization versus chlorofluorocarbon- and hydrofluoroalkane-pressurized metered dose inhalers.

The aim of this study was to compare albuterol delivery in a neonatal ventilated lung model, using three delivery methods: 1) jet nebulizer; 2) chlorofluorocarbon-pressurized metered dose inhaler (CFC-MDI) actuated into an ACE(R) spacer; and 3) hydrofluoroalkane-pressurized MDI (HFA-MDI) actuated into an ACE(R) spacer. The bench model consisted of a mechanically ventilated infant test lung with ventilator settings to simulate a very low birth weight neonate with moderate lung disease. Albuterol solution (0.5%) was nebulized at the humidifier and temperature port, 125 cm and 30 cm from the Y-piece, respectively. Albuterol metered dose inhalers (MDIs) were actuated into an ACE(R) spacer that was tested in two positions: 1) inline between the endotracheal (ET) tube and the Y-piece; and 2) attached to the ET tube and administered by manual ventilation. Albuterol was collected on a filter at the distal end of the ET tube and was quantitatively analyzed by high performance liquid chromatography. Albuterol delivery by CFC-MDI (position 1, 4.8 +/- 1.0%, vs. position 2, 3.8 +/- 1.6%, P > 0.05) and HFA-MDI (position 1, 5.7 +/- 1.6%, vs. position 2, 5.5 +/- 2.4%, P > 0.05) were significantly greater than delivery by nebulization at 30 cm (0.16 +/- 0.07%) and 125 cm (0.15 +/- 0.03%) from the Y-piece (P < 0.001). A single actuation of albuterol MDI delivered the equivalent of nebulizing 2.5-3.7 mg of albuterol solution. We conclude that albuterol administered by MDI and ACE(R) spacer resulted in more efficient delivery than by nebulization in this mechanically ventilated neonatal lung model. There was no significant difference in drug delivery between CFC-MDI and HFA-MDI; nor did the placement of the spacer significantly affect drug delivery.

Accumulation of CO(2) in reservoir devices during simulated neonatal mechanical ventilation.

Aerosolized albuterol is frequently administered to mechanically ventilated neonates by metered dose inhaler (MDI) and a reservoir device. These reservoirs are often placed between the Y-piece and endotracheal tube, thereby creating mechanical dead space and increasing the risk of rebreathing carbon dioxide (CO(2)). The objectives of this study were: 1) to quantify CO(2) accumulation in two commonly used reservoirs (ACE(R), Aerochamber(R)-MV) and a bidirectional nonreservoir actuator (Airlife(R) Minispacer) during mechanical ventilation of a neonatal lung model; and 2) to determine the effect of tidal volume (V(T)) on CO(2) accumulation. We hypothesized that the accumulation of CO(2) in these devices is clinically insignificant at the small tidal volumes used in mechanically ventilated premature neonates. The model was constructed to simulate CO(2) exhalation by a ventilated neonate and consisted of a neonatal ventilator circuit (rate = 40/min; peak inspiratory pressure (PIP) = 20 cm H(2)0) attached to a reservoir/actuator and neonatal test lung. The ventilator delivered inspiratory gas (room air) to the test lung, which was vented into the atmosphere by a small adjustable leak. Expiration was simulated by manually ventilating 7.1% CO(2) (partial pressure of CO(2) (PCO(2)) = 48 mm Hg) back through the model. Accumulation of CO(2) within the reservoir/actuator was measured using an end-tidal CO(2) monitor. Each 4-min experiment was conducted at three V(T) (7.5 mL, 15 mL, and 25 mL), and the median PCO(2) was calculated in 0.5-min increments. For V(T) = 7.5 mL, CO(2) accumulated slowly in the ACE(R) and Minispacer(R) and reached a maximum at 4.0 min (PCO(2) = 2.3 mm Hg and 7.3 mm Hg, respectively). In contrast, the Aerochamber(R)-MV rapidly reached a PCO(2) of 9.5-10.0 mm Hg by 1-1. 5 min. A similar trend occurred with V(T) = 15 mL; however, higher partial pressures (approximately 10-12 mm Hg) were achieved with all devices. At V(T) = 25 mL, PCO(2) rose rapidly with the ACE(R), Aerochamber(R)-MV, and Minispacer(R), reaching peaks of 17.2, 12.3, and 20.3 mm Hg, respectively (P < 0.05). In conclusion, accumulation of CO(2) in reservoir/actuator depends on V(T) as well as the chamber design and internal volume. Due to the short duration of use when administering drugs via MDI, accumulation of CO(2) in these devices is not likely to be clinically relevant for the majority of ventilated newborns.

Albuterol in acute bronchiolitis--continued therapy despite poor response?

To determine whether clinicians continue to treat acute bronchiolitis with nebulized albuterol despite lack of clinical improvement after such treatment, we reviewed the medical records of 90 randomly selected infants and children with the primary diagnosis of that disorder who were treated in this 232-bed tertiary care children's hospital. Clinical improvement and no clinical improvement were defined as improvement and lack of improvement, respectively, in air movement, wheezing, retractions, oxygen saturation, work of breathing, and respiratory rate after administration of nebulized albuterol. Response to nebulized albuterol was determined from explicit written documentation in the medical records. Of 68 children who received nebulized albuterol in the emergency department, 52% had written documentation indicating no clinical improvement; however, 94% had admission orders to continue the therapy. Within 12 hours after admission, 61% were again noted to have no clinical improvement with nebulized albuterol. Eighty-seven percent of nonresponders continued to receive albuterol throughout hospitalization, and 54% continued to receive it after discharge. Continuing therapy despite lack of response resulted in unnecessary medical expenses.

Outcomes of pediatric mechanical ventilation.

Mechanical ventilation is one of the most commonly used life-support technologies in the PICU, is an absolute indicator of the need for PICU care, and adds considerably to the cost of intensive care. Patients with chronic disease account for a large proportion of admissions to the PICU and of patients undergoing cardiovascular surgery and neurosurgery. Although the average length of use of mechanical ventilation in the PICU is about 5 days, there is tremendous variability in the length of ventilation (SD approximately 9 days). Survival among ventilated patients varies greatly and depends mostly on the nature and severity of the underlying disease.

Pediatric mechanical ventilation technology.

An in-depth examination of ventilators currently marketed for the pediatric population and the technology associated with each is provided with this article. Also included is a discussion of an "ideal pediatric ventilator" and its application to the pediatric intensive care patient. Triggering, cycling, and limiting variability, costs, and special features currently available are detailed.

High-frequency jet ventilation in the pediatric intensive care unit.

Scientific data and anecdote on the utility of HFJV in children remain divergent. There seems to be some evidence that ventilation and oxygenation in critically ill patients can sometimes be achieved at lower peak airway pressures and tidal volumes. There is also growing consensus that HFJV may be a superior ventilatory technique for patients with air leak syndrome. However, conclusive evidence of the effect of this technology on overall survival, length of ventilation, or even resource consumption remains illusive. Until such time, a general recommendation for the use of HFJV in pediatric patients is not possible.

Evaluation of a prototype expiratory-phase aerosol controller during simulated pediatric volume-controlled ventilation.

BACKGROUND: Some methods of administering aerosolized medications during volume-controlled ventilation require adjustment of ventilator settings to avoid inadvertent increases in tidal volume (VT). Our bench evaluation of an expiratory-phase aerosol controller (EXPAC) sought to determine the differences (1) in aerosol delivery between continuous and EXPAC nebulization in pediatric and neonatal ventilator circuits and (2) in delivered VT with a 30-cm vs a 213-cm nebulizer supply line. DESCRIPTION OF DEVICE: An electrically powered EXPAC linked to the VIP Bird ventilator by a fiberoptic cable and driven by flow from an integral blender was developed to our performance specifications. EVALUATION METHODS: In Phase 1, VT was measured at the patient connection under 3 conditions: (1) no nebulizer in-line, (2) a dry in-line nebulizer driven by EXPAC with a 30-cm supply line, and (3) Condition 2 with a 213-cm supply line. In Phase 2, we measured the aerosol delivered to a filter placed between the patient connector and the test lung. Aerosol delivery = filter wet weight-filter dry weight. RESULTS: (1) When EXPAC was operated according to manufacturer's recommendations, no significant differences were found between VTS measured with EXPAC plus the 30-cm line and with no nebulizer in-line. VT increased significantly (p = 0.0001, 1-way ANOVA) in both circuits with the 213-cm supply line. (2) Mean (SD) aerosol delivery at the patient connection of the pediatric circuit was 1.5 (0.002)% with EXPAC and 1.7 (0.003)% with continuous nebulization (p = 0.23, t test) and of the neonatal circuit 1.6 (0.002)% with EXPAC and 1.5 (0.002)% with continuous nebulization (p = 0.45, t test). CONCLUSIONS: EXPAC eliminated need for adjustment of ventilator settings and according to our data was as effective as continuous nebulization for delivering aerosol to the patient connection.

Patterns of practice in neonatal and pediatric respiratory care.

UNLABELLED: Because little information has been available regarding common respiratory care practices in neonatology and pediatrics, it has been difficult to develop departmental standards of care. We therefore conducted a national survey of current practices, hoping to establish whether any de facto standards exist in the U.S. METHODS: A 47-item multiple-choice survey instrument was mailed in 1988 to 689 U.S. hospitals that included all neonatal and perinatal high-risk centers. RESULTS: Response was received from 323 hospitals, for a 47% response rate. Some de facto standards do seem to exist, notably (1) q 2 h ventilator checks, (2) continuous measurement of oxygen concentration in oxygen hoods and ventilator circuits, (3) staffing ratio of four ventilator patients to one respiratory care practitioner, and (4) changing of ventilator circuits q 48 h. CONCLUSION: While we do not claim that such de facto standards have a scientific basis, we suggest that respiratory care services whose practices vary from the de facto standards should investigate why their own practices differ and whether they can be justified.

Pulse oximetry: application in the pediatric and neonatal critical care unit.

The use of pulse oximetry in the pediatric and neonatal intensive care units has grown tremendously in recent years. Opinions about this growth are divergent. Arriving at a generalized statement about the accuracy of pulse oximeters is difficult, but it has generally been found to be acceptably accurate in most patient populations under most conditions. However, there are limitations to its application. Pulse oximetry accuracy can be adversely affected by elevated levels of certain abnormal hemoglobin varieties as well as motion artifact and low peripheral perfusion. Some authors suggest a caveat against the use of pulse oximetry to prevent hyperoxemia in the neonatal population, whereas others suggest it is an important advancement. The affect of the use of pulse oximetry on respiratory morbidity and mortality has not been established, and suggestions that all mechanically ventilated patients should be continuously monitored are unsubstantiated.