Intermittent hypoxia and respiratory patterns during sleep of preterm infants aged 3 to 18 months residing at high altitude.

STUDY OBJECTIVES: The aim of this study was to determine the impact of apneas on oxygen saturation and the presence of intermittent hypoxia, during sleep of preterm infants (PTIs) born at high altitudes and compare with full-term infants (FTIs) at the same altitude. METHODS: PTIs and FTIs from 3 to 18 months were included. They were divided into three age groups: 3-4 months (Group 1); 6-7 months (Group 2), and 10-18 months (Group 3). Polysomnography parameters and oxygenation indices were evaluated. Intermittent hypoxia was defined as brief, repetitive cycles of decreased oxygen saturation. Kruskal-Wallis test for multiple comparisons, t-test or Mann-Whitney U-test were used. RESULTS: 127 PTI and 175 FTI were included. Total apnea-hypopnea index (AHI) was higher in PTI that FTI in all age groups (Group 1: 33.5/h vs. 12.8/h, p = 0.042; Group 2: 27.0/h vs. 7.4/h, p < 0.001; and Group 3: 11.6/h vs. 3.1/h, p < 0.001). In Group 3, central-AHI (8.0/h vs. 2.3/h, p < 0.001) and obstructive-AHI (1.8/h vs. 0.6/h, p < 0.008) were higher in PTI than FTI. T90 (7.0% vs. 0.5, p < 0.001), oxygen desaturation index (39.8/h vs. 11.3, p < 0.001) were higher in PTI than FTI, nadir SpO2 (70.0% vs. 80.0, p<0.001) was lower in PTI. CONCLUSION: At high altitude, compared to FTI, PTI have a higher rate of respiratory events, greater desaturation, and a delayed resolution of these conditions, suggesting the persistence of intermittent hypoxia during the first 18 months of life. This indicates the need for follow-up of these infants for timely diagnosis and treatment of respiratory disturbances during sleep.

Nav1.5 cardiac sodium channels, regulation and clinical implications / Canales de sodio Nav1.5 cardíacos, regulación e implicaciones clínicas

Voltage-gated sodium channels constitute a group of membrane proteins widely distributed thought the body. In the heart, there are at least six different isoforms, being the Nav1.5 the most abundant. The channel is composed of an α subunit that is formed by four domains of six segments each, and four much smaller β subunits that provide stability and integrate other channels into the α subunit. The function of the Nav1.5 channel is modulated by intracellular cytoskeleton proteins, extracellular proteins, calcium concentration, free radicals, and medications, among other things. The study of the channel and its alterations has grown thanks to its association with pathogenic conditions such as Long QT syndrome, Brugada syndrome, atrial fibrillation, arrhythmogenic ventricular dysplasia and complications during ischemic processes.

Los canales de Sodio dependientes de voltaje constituyen un grupo de proteínas de membrana ampliamente distribuidas en el cuerpo humano. En el corazón se dispone de al menos seis diferentes isoformas de estos canales: los Nav1.5 son los más abundantes. El canal está constituido por una subunidad α, formada por cuatro dominios, cada uno de estos con seis segmentos y cuatro subunidades β mucho más pequeñas que estabilizan la estructura e integran la subunidad α de otros canales. La función del canal Nav1.5 se ve modulada por proteínas del citoesqueleto, proteínas extracelulares, concentraciones de calcio, radicales libres, medicamentos, entre otros. El estudio del canal y sus alteraciones se ha incrementado gracias a la asociación de este con condiciones patológicas como el síndrome de QT largo, el síndrome de Brugada, la fibrilación auricular, la displasia ventricular arritmogénica y por las complicaciones de en procesos isquémicos.