RESUMO
We tested the hypothesis that an open lung strategy with recruitment maneuvers will improve oxygenation and decrease lung injury in comparison with a permissive hypercapnia strategy in preterm lambs. Preterm lambs born by operative delivery at 131 ± 1 days of gestational age (term = 150 days) were randomized to an open lung group (OLG, n = 5) or a permissive hypercapnia group (PHG, n = 4). In the OLG, ramp recruitment maneuvers were performed by increasing and then decreasing peak inspiratory pressure and positive end-expiratory pressure (adjusting for expiratory tidal volume [V(T)] 6 to 8 mL/kg). In the PHG, lambs received ventilation with V(T) of 6 to 8 mL/kg, adapting pressures and respiratory rate according to arterial blood gases results. Fraction of inspired oxygen was adjusted for oxygen saturation 88 to 93%. Lambs were ventilated for 6 hours. Lung pathology was assessed by masked examiners. There were no significant differences for arterial to alveolar oxygen tension ratio, partial pressure of arterial carbon dioxide, blood pressure, compliance, resistance, and other variables between groups. Gas leaks were noted in four of five lambs in the OLG and one of four in the PHG (relative risk 3.2; 95% confidence interval 0.5 to 18). By histological examination, lung areas were overdistended (49% in the OLG, 37% in the PHG). Open lung ventilation following ramp recruitment maneuvers did not offer advantages and might increase lung injury compared with a permissive hypercapnia strategy in preterm lambs with lung immaturity.
Assuntos
Hipercapnia/fisiopatologia , Respiração com Pressão Positiva/efeitos adversos , Alvéolos Pulmonares/fisiopatologia , Síndrome do Desconforto Respiratório do Recém-Nascido/fisiopatologia , Síndrome do Desconforto Respiratório do Recém-Nascido/terapia , Lesão Pulmonar Induzida por Ventilação Mecânica/etiologia , Animais , Humanos , Recém-Nascido , Troca Gasosa Pulmonar , Ovinos , Volume de Ventilação Pulmonar , Lesão Pulmonar Induzida por Ventilação Mecânica/patologiaRESUMO
OBJECTIVE: To determine the pre- and post-ductal oxygen saturation (SpO2) levels during the first minutes after birth in healthy term infants. STUDY DESIGN: In a prospective cohort study, sensors were placed on the right hand and on 1 foot of the neonate. Pre- and post-ductal SpO2 levels were recorded during the first 15 minutes after birth. Exclusion criteria were gestational age <37 weeks, presence of risk factors for asphyxia, emergency cesarean delivery (C/D), congenital anomalies, and multiple pregnancies. Infants who were treated with O2 or positive pressure ventilation were also excluded from the study. RESULTS: The mean (SD) gestational age of the 110 infants was 39 weeks (1.1), and the mean birth weight was 3340 grams (359). At 5 minutes, the mean pre-ductal SpO2 level was 89% (7), and the mean post-ductal SpO2 level was 81% (10). Pre- and post-ductal SpO2 levels were significantly different during the first 15 minutes after birth. The SpO2 level was lower in babies delivered by C/D in comparison to babies born by vaginal delivery. CONCLUSIONS: In healthy newly born infants, oxygen saturation rises slowly and does not usually reach 90% in the first 5 minutes of life. A gradient between pre- and post-ductal SpO2 levels remains significant for the first 15 minutes of life.