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Biomedical subjects

Jay S Greenspan

Publications and source records attributed to Jay S Greenspan.

13 recordsLinked to original sources
PubMed2006

Physiologic implications of helium as a carrier gas for inhaled nitric oxide in a neonatal model of Bethanecol-induced bronchoconstriction.

OBJECTIVE: To compare heliox to nitrogen-oxygen (nitrox) as a carrier gas for inducible nitric oxide (iNO) in the presence of pharmacologically inhaled bronchoconstriction. We hypothesized that respiratory resistance and gas exchange would improve when iNO is delivered with heliox. DESIGN: Interventional laboratory study. SETTING: An academic medical research facility in the northeastern United States. SUBJECTS: Sedated, ventilated newborn piglets. INTERVENTIONS: Newborn piglets (n = 16; 2.3 +/- 0.1 kg) were placed on a flow-controlled ventilator and given intravenous Bethanecol (2 x 1 mg/kg followed by 1 mg/kg/hr) to induce bronchoconstriction. Piglets were randomized to heliox or nitrox (Fio2 = 0.3) and given 80 ppm iNO. MEASUREMENTS AND MAIN RESULTS: Hemodynamics, blood chemistry, and pulmonary mechanics were recorded at 30-min intervals for 2 hrs. Bethanecol dosing increased inspiratory respiratory resistance (cm H2O/L/min; p < .01) and decreased respiratory compliance (mL/cm H2O/kg; p < .01). Following carrier gas assignment, hemodynamics and respiratory compliance were similar between groups and respiratory resistance decreased (p < .01) in the heliox group. Over 2 hrs with iNO therapy, Paco2 increased (p < .01) whereas blood pH decreased (p < .01) in the heliox group. Respiratory resistance trended downward, oxygenation index improved (p < .01), and blood methemoglobin levels trended higher for nitrox compared with heliox. CONCLUSIONS: The INOvent was effective for controlling heliox delivery of iNO. Despite marked reduction in respiratory resistance with heliox gas ventilation in a neonatal model of pharmacologic bronchoconstriction, nitrox might perform better as a delivery vehicle for iNO.

Animals↗
PubMed2005

Heliox attenuates lung inflammation and structural alterations in acute lung injury.

Low-density gas mixtures, such as heliox, were shown to reduce the work of breathing and facilitate the distribution of inspired gas. Since supplemental ventilatory and oxygen requirements may lead to pulmonary inflammation and structural alterations, we hypothesized that by reducing these requirements, heliox breathing may attenuate the acute inflammatory and structural changes associated with acute lung injury. Spontaneously breathing neonatal pigs were anesthetized, instrumented, supported with continuous positive airway pressure (CPAP), injured with oleic acid, and randomized to nitrox (n = 6) or heliox (n = 5).F(I)O(2) was titrated for pulse oximetry (SpO(2)) 95 +/- 2% for 4 hr. Gas exchange and pulmonary mechanics were measured. Lungs were analyzed for myeloperoxidase (MPO), interleukin-8 (IL-8), and histomorphometery. Relationships between physiologic indices and cumulative lung structure and inflammatory indices were evaluated. With heliox, compliance was significantly greater, while tidal volume, frequency, minute ventilation, F(I)O(2), arterial carbon dioxide tension (PaCO(2)), MPO, and IL-8 were significantly lower compared to nitrox. The expansion index and number of exchange units were significantly greater with heliox, while the exchange unit area (EUA) was smaller. MPO was significantly and positively correlated with F(I)O(2) (r = 0.76) and EUA (r = 0.63), and negatively correlated with number of open exchange units/field (r = -0.73). Compared to breathing nitrox, these data indicate that heliox improved the distribution of inspired gas, thereby recruiting more gas exchange units, improving gas exchange efficiency, reducing ventilatory and oxygen requirements, and attenuating lung inflammation. These data suggest that heliox breathing may have the combined therapeutic benefits of attenuating lung inflammation by reducing mechanical and oxidative stress in the clinical management of acute lung injury.

Animals↗
PubMed2005

Tracheal gas insufflation as a lung-protective strategy: physiologic, histologic, and biochemical markers.

OBJECTIVE: Conventional mechanical ventilation in acute lung failure potentiates lung injury, which can be assessed by physiologic, histologic, and biochemical markers. Thus, new ventilation strategies are directed at reducing lung injury. Tracheal gas insufflation has been shown to reduce endotracheal tube prosthetic deadspace and peak inspiratory pressure during conventional mechanical ventilation. Our objective was to use physiologic, histologic, and biochemical markers to test the hypothesis that tracheal gas insufflation in acute lung injury is lung protective. DESIGN: Animal experiment. SETTING: University setting. SUBJECTS: Juvenile rabbits (n = 12; 1.95 +/- 0.1 SE kg). INTERVENTIONS: Rabbits were anesthetized, instrumented, paralyzed, and ventilated with Fio(2) = 1.0. Lung injury was induced with repeated saline lavage (10 mL/kg per lavage until Pao(2) </=150 mm Hg and compliance </=0.50 mL/cm H(2)O/kg for 30 mins). Animals were randomized to conventional mechanical ventilation with and without 0.5 lpm of continuous tracheal gas insufflation (Vygon endotracheal tube) for 4 hrs to maintain Paco(2) at 45-55 mm Hg by adjusting the peak inspiratory pressure; other conventional mechanical ventilation settings remained constant. MEASUREMENTS AND MAIN RESULTS: Gas exchange and pulmonary mechanics were measured every 30 mins; plasma and pulmonary tissue were taken for cytokine and histologic evaluation after 4 hrs. Peak inspiratory pressure, tidal volume, and physiologic deadspace were significantly less (p < .05) in the tracheal gas insufflation animals when compared with conventional mechanical ventilation animals. Pao(2), positive end-expiratory pressure, mean airway pressure, vital signs, Paco(2), and respiratory resistance and compliance were not statistically different between the two groups. There was a difference (p < .05) in interleukin-8 tissue (pg/mug protein; dependent = 52.4 +/- 7.6 vs. nondependent = 32.8 +/- 4.2) and plasma levels (pg/mL; preinjury = 7.2 +/- 2.3 vs. postinjury = 118 +/- 58). Histology showed a trend toward protection of alveolar structures for tracheal gas insufflation. CONCLUSIONS: Tracheal gas insufflation resulted in lower ventilatory requirements (peak inspiratory pressure, tidal volume, and deadspace) and a more favorable histologic trend than conventional mechanical ventilation. Tracheal gas insufflation offers potential as a lung-protective strategy for acute lung injury in the developing rabbit lung and may be a useful clinical adjunct to neonatal respiratory management.

Animals↗
PubMed2002

Intensive care management of the term neonate: are there regional differences in outcome?

The objective of this study was to evaluate the patterns of hospitalization of term infants in 3 major metropolitan areas. We hypothesized that regional practice variation occurred in the care of term infants and that these differences would be reflected in the hospitalization patterns of infants. All infants cared for in an Intensive Care Nursery (ICN) after maternal discharge in 1 of 3 major metropolitan areas followed up by the same neonatal management company were compared (n=4,487). Term infants were grouped into 1 of 2 categories based on illness severity: Group 1 (G1) infants-those who required supplemental oxygen or ventilation for 24 hours or more (n=611); and Group 2 (G2) infants-those infants without an oxygen or ventilation requirement (n=1,549). Excluded were infants in the following categories: birth weight <2,500 grams, major congenital anomalies, surgical patients, extracorporeal membrane oxygenation (ECMO) support, or babies who died before discharge. The number of infants in each of these categories was compared as a percentage of the total number of infants cared for in that region. The average length of stay (ALOS) and percentage of patient days attributed to infants in each category were compared across regions using multiple comparison tests (Tukey). The total ALOS was greatest in City A, as was the ALOS for sick term infants. Patient days for sick term infants were lowest in City C, and healthier term infants comprised the lowest percentage of patient days in City A. This difference resulted in the lowest percentage of patient days for all term admissions in City A. These data demonstrated that significant variation existed in the delivery of care to term neonates among major metropolitan regions. Cities that admitted fewer term infants for observation periods (G2) tended to have sicker term neonates with higher acuity hospitalizations (GI) and longer lengths of stay (LOS). These findings suggested that a conservative admission policy for this population can decrease overall LOS.

Catchment Area, Health↗
PubMed2002

Managing our first breaths: a reflection on the past several decades of neonatal pulmonary therapy.

Lung disease has been a leading cause of significant morbidity and mortality since neonates first drew breath. Over the past few decades, many treatment options have evolved to aid us in our ability to support neonatal breathing. The history of neonatal pulmonary care, both its successes and controversies, can teach us a great deal about the future of this dynamic field. As new developments occur, we constantly modify the therapies we offer to preterm and term infants. Understanding traditional therapeutic options and knowing what may be on the horizon can help caregivers to better match treatment plans with individual infants. This article reviews advances in mechanical ventilation, adjuvant therapies, and respiratory drugs through the past few decades and speculates on future directions in this field.

Humans↗
PubMedDate not supplied

The impact of cobedding on sleep patterns in preterm twins.

Interest in cobedding multiple-gestation infants has grown as focus has increased on the developmental approach to the care of the neonate. Little data, however, exist on the infants' response to cobedding. It is important to evaluate the safety, efficacy, and physiologic impact of this practice. Cobedding was offered to parents of twin infants < 37 weeks gestation, without arterial lines or ventilator requirements, by the health care team according to standard practice in our nursery. After parental informed consent, infants were placed on an event-recording cardiorespiratory monitor for 12 hours before cobedding and for the first 12 hours of cobedding. Recordings were evaluated by an investigator blinded to the bedding status of the infant. Apnea (a pause of respiration > 10 seconds, central apnea), bradycardia (a decline in heart rate to < 80 beats per minute), periodic breathing (a respiratory pattern in which there are > or = 3 pauses in respiration of > or = 3 seconds with < 20 seconds of breathing between pauses), adverse events (changes in medication, changes in oxygen requirements, temperature instability, the need for sepsis evaluation, or death) were evaluated. Other physiologic parameters were obtained through the use of standard bedside monitoring. Eleven sets of preterm infants, n = 22, with a mean gestation of 31.8+/-2.9 weeks and a mean birth weight of 1,698.7+/-552.0 grams were studied. Infants were evaluated at a corrected gestational age of 33.5+/-1.9 weeks and a mean weight of 1,713.2+/-484.0 grams. The number of events of central apnea before cobedding (57) was greater than those recorded during cobedding (18), p<0.05. There was no difference found in any of the other parameters compared. The numbers of events recorded before and during cobedding were compared by Student's t-test and significance was determined by p < 0.05. No adverse events (AE) were noted, and all infants remained cobedded throughout the study. This preliminary study suggests that cobedding of healthy preterm twins showed no increase in adverse events. Of the physiologic parameters studied, only the occurrence of central apnea changed with cobedding. This decrease in central apnea may reflect a change in sleep pattern due to more frequent arousal by the twin. Alternatively, a more regular breathing pattern may reflect a positive physiological response to contact between twins.

Beds↗
PubMedDate not supplied

Physiologic effects of CPAP: application and monitoring.

Although a wide array of respiratory care modalities has been employed to manage neonatal respiratory distress syndrome (RDS), the recent focus has emphasized strategies that correct lung pathophysiology while protecting the lung from further insult. Continuous positive airway pressure (CPAP) has remained a viable option for NICU infants since its introduction in 1971. Current methods of monitoring allow clinicians to troubleshoot and better understand the physiologic and clinical impact of administering CPAP to neonates with RDS. This article highlights the renewed interest in CPAP therapy and current methods of monitoring.

Continuous Positive Airway Pressure↗
PubMedDate not supplied

Inhaled nitric oxide therapy in the near-term or term neonate with hypoxic respiratory failure.

Inhaled nitric oxide (iNO) has altered the management strategy for treating near-term and term infants with hypoxic respiratory failure (HRF). There is a strong relationship between HRF and persistent pulmonary hypertension of the newborn (PPHN). PPHN is characterized by elevated pulmonary resistance, pulmonary vasoconstriction, and altered vascular reactivity. The resulting high pulmonary pressure may lead to HRF, which is defined as a relative deficiency of oxygen in arterial blood and insufficient minute ventilation. iNO improves oxygenation and decreases the need for extracorporeal membrane oxygenation. Although iNO therapy is effective, its efficacy can depend on the fine points of its use and on other care the infant is receiving. Even in NICUs that do not have iNO available, those who care for term infants with HRF must be familiar with its use and know when and how to transfer these infants and how to help families through this difficult period. Because iNO therapy will probably be used more frequently in nurseries over the next few years, more information on the safety and efficacy of its use in the broader neonatal population needs to be available.

Administration, Inhalation↗
PubMedDate not supplied

The neonatal respiratory pump: a developmental challenge with physiologic limitations.

Newborn lungs are particularly susceptible to pathophysiology. Respiratory distress commonly brings infants to the intensive care nursery. Premature birth compromises the infant's ability to respond to early lung dysfunction because of the reduced functional reserve available at younger gestational ages. The respiratory pump consists of respiratory musculature and the chest wall. The respiratory pump is the physiologic "machine" that responds to lung pathology. From gestation onward, components of the pump undergo developmental changes that influence its compensatory ability in the neonate. Careful observation of the synchrony of the chest wall and abdomen during spontaneous breathing efforts assists the caretaker in detecting respiratory compromise and impending respiratory failure. Noninvasive monitoring of respiratory patterns is a valuable tool for the neonatal caregiver, who must understand the developmental changes in the respiratory pump and be able to identify an infant's ineffective responses to lung pathophysiology.

Child Development↗
PubMedDate not supplied

Ventilator-induced airway injury: a critical consideration during mechanical ventilation of the infant.

The clinical management of respiratory failure in the newborn often focuses on lung parenchymal stiffness due to immaturity, surfactant deficiency, infiltrates, and other causes. However, health care personnel should also consider the airway, which plays an important role in gas exchange and lung mechanics. The airway can be easily injured, and an injured airway can significantly alter both the acute and chronic course of lung disease in infants. Further, there are developmental changes that affect the susceptibility of the neonatal airway to injury. Recognizing and preventing causes of airway injury can help to ensure optimal outcomes for the critically ill neonate.

Humans↗
PubMedDate not supplied

Optimizing the neonatal thermal environment.

Devices used to maintain thermal stability in preterm infants have advanced over time from the first incubator reported by Jean-Louis-Paul Denuce in 1857 to the latest Versalet Incuwarmer and Giraffe Omnibed devices today. Optimizing the thermal environment has proven significant for improving the chances of survival for small infants. Understanding the basic physiologic principles and current methodology of thermoregulation is important in the clinical care of these tiny infants. This article highlights principles of thermoregulation and the technologic advances that provide thermal support to our vulnerable

Air Movements↗
PubMedDate not supplied

A prototype infant incubator for heliox therapy.

Heliox (Hx) gas has been shown to improve pulmonary function in infants, but methods for its delivery are invasive and problematic. To this end, we modified an Isolette (Hill-Rom Air-Shields) infant incubator (Hxl) to deliver Hx respiratory gas mixtures noninvasively while providing thermal stability for neonatal care in the Neonatal Intensive Care Unit (NICU). In vitro tests and in vivo animal studies were performed to compare the original design specifications and established baseline performance criteria for the Hxl design. The experimental environments at 50% and 80% relative humidity (RH) consisted of helium (He) with 21% and 50% O2 and control (C) of 21% and 50% O2 with the balance nitrogen (N). Elapsed times to steady state (SS) and recovery time back to SS (OCDss) due to opening and closing the door were recorded for each variable. All rabbits survived and appeared comfortable during all experimental conditions. These data show that the newly designed Isolette provides similar thermal, O2, CO2, and RH responses as the control incubator. Based on these positive safety/efficacy studies, study of the therapeutic impact of Hxl care on neonatal growth and development is in progress.

Administration, Inhalation↗