RESUMO
Open-loop computer control of inspired oxygen concentration was evaluated in 16 newborn infants requiring mechanical ventilation. FIO2 and oxygen saturation were compared for 2-hour periods of computer versus routine manual FIO2 adjustment. During computer-assisted FIO2 adjustment, patients spent more time at the target SaO2 and less time with SaO2 < 90%.
Assuntos
Consumo de Oxigênio , Respiração Artificial , Terapia Assistida por Computador , Humanos , Recém-Nascido , OximetriaRESUMO
OBJECTIVE: To examine the role of endogenous nitric oxide (NO) and endothelin-1 (ET-1) in the pathogenesis of persistent pulmonary hypertension of the newborn (PPHN) and to determine whether inhaled NO, currently under investigation as a new therapy for PPHN, affects plasma concentrations of these vasoactive mediators. METHODS: Circulating ET-1 and cyclic guanosine monophosphate (cGMP) concentrations were measured by radioimmunoassay in 15 healthy term newborn infants and 46 newborn infants with PPHN enrolled in a randomized, controlled trial of inhaled NO. These concentrations were followed up longitudinally and compared between the NO and the conventionally treated group. RESULTS: Concentrations of ET-1 were significantly higher and cGMP concentrations significantly lower in infants with PPHN compared with healthy newborn infants (median ET-1, 28 vs 11 pmol/L; p = 0.0001; median cGMP, 35 vs 61 pmol/ml; p = 0.0001, respectively). ET-1 concentrations showed an upward trend at 1 and 24 hours of treatment and a subsequent decline at recovery in both subgroups of patients, with the most pronounced decrease in the NO group. cGMP concentrations increased significantly only in the NO group, with a peak at 1 hour of treatment (median, 61 pmol/ml). As the dose of NO decreased, cGMP concentrations declined. In contrast, conventionally treated infants manifested no change in cGMP concentrations from baseline until recovery, when a significant decrease was noted (median decrease of 13 pmol/ml; p = 0.002). We did not find a significant difference between ET-1 and cGMP concentrations in infants who required extracorporeal membrane oxygenation compared with those who did not. CONCLUSIONS: PPHN is associated with increased ET-1 and decreased cGMP plasma concentrations, which may contribute to the pathogenesis of the disease. Inhaled NO appears to modulate these mediators during the disease process, suggesting an interaction between ET-1 and NO in vivo.
Assuntos
GMP Cíclico/sangue , Endotelina-1/sangue , Óxido Nítrico/administração & dosagem , Síndrome da Persistência do Padrão de Circulação Fetal/tratamento farmacológico , Administração por Inalação , Feminino , Humanos , Recém-Nascido , Masculino , Óxido Nítrico/fisiologia , Síndrome da Persistência do Padrão de Circulação Fetal/sangueRESUMO
Axial movement of the right hemidiaphragm during tidal breathing was recorded using real-time ultrasonography in 46 healthy term infants. Displacement was 2.6 +/- 0.1, 3.6 +/- 0.2, and 4.5 +/- 0.2 mm (mean +/- SEM) for the anterior, middle, and posterior thirds, respectively. Diaphragmatic movement was significantly greater in the middle and posterior segments than in the anterior segment (P less than 0.0001). Excursion of the diaphragm was similar in sleeping and awake infants, and during quiet and active sleep, as identified by behavioral criteria. Diaphragmatic movement was also assessed in nine infants who required mechanical ventilation and pharmacologic paralysis because of respiratory disease. In these infants, axial movement of the right hemidiaphragm was less in the middle and posterior thirds (P less than 0.05 and P less than 0.01, respectively) than in spontaneously breathing infants, and posterior movement was not predominant. Normative data for axial diaphragmatic movement may be of clinical value in the assessment of defects of the diaphragm, rib cage, or abdomen in newborn infants and may allow further understanding of the direct effects of therapeutic interventions on the respiratory system in infancy.
Assuntos
Diafragma/fisiologia , Doença da Membrana Hialina/fisiopatologia , Recém-Nascido/fisiologia , Síndrome de Aspiração de Mecônio/fisiopatologia , Diafragma/efeitos dos fármacos , Diafragma/fisiopatologia , Humanos , Pancurônio/farmacologia , Respiração Artificial , UltrassonografiaRESUMO
We evaluated the effect of muscle paralysis on gas exchange and incidence of pneumothorax in 35 severely ill infants on mechanical ventilation. Pancuronium (0.1 mg/kg) was given repeatedly until spontaneous respirations ceased in infants with inadequate gas exchange with FIO2 greater than 0.60, or peak inspiratory pressure greater than 30 cm H2O, or who were breathing out of phase with the respirator. Of 27 infants who had an alveolar-arterial oxygen gradient greater than 300 torr before paralysis, AaDO2 improved by greater than 100 torr within one hour of paralysis in only two infants; it worsened in two infants within the same period. By six hours postparalysis, 12 of 27 infants had improved, five of whom had had a worsening AaDO2 before administration of pancuronium. Changes in oxygenation were unrelated to changes in arterial carbon dioxide tension in most infants. Peak transpulmonary pressures after paralysis were lower than during spontaneous breathing, and may explain the low incidence of pneumothorax (3 of 35) during paralysis. Since those who improved could not be distinguished by birth weight, gestational age, or diagnosis, pancuronium might be worthy of trial in a mechanically ventilated infant with severe lung disease who is at risk for pneumothorax.
Assuntos
Contração Muscular , Relaxamento Muscular , Oxigênio/sangue , Pancurônio/farmacologia , Respiração Artificial , Dióxido de Carbono/sangue , Humanos , Recém-Nascido , Doenças do Recém-Nascido/sangue , Doenças do Recém-Nascido/terapia , Pneumopatias/sangue , Pneumopatias/terapia , Pancurônio/uso terapêutico , Pneumotórax/etiologia , Pneumotórax/prevenção & controle , Respiração Artificial/efeitos adversosRESUMO
Forty-three apneic episodes were observed in eight preterm infants, four of whom had a history of spells. Measurements of expiratory airflow and respiratory effort indicated that 36 of 43 spells were mixed, consisting of central apnea preceded or followed by airway obstruction. The episodes occurred more frequently during periods of spontaneous neck flexion. This association can be related to previous studies indicating that neck flexion interferes with neuromuscular regulation of pharyngeal patency and can produce intermittent airway obstruction. Our observations suggest that airway obstruction may be an important factor in the pathogenesis of apnea in certain preterm infants.