Reference values for airway resistance in newborns, infants and preschoolers from a Latin American population.

BACKGROUND AND OBJECTIVE: Several studies have determined reference values for airway resistance measured by the interrupter technique (Rint) in paediatric populations, but only one has been done on Latin American children, and no studies have been performed on Mexican children. Moreover, these previous studies mostly included children aged 3 years and older; therefore, information regarding Rint reference values for newborns and infants is scarce. METHODS: Rint measurements were performed on preschool children attending eight kindergartens (Group 1) and also on sedated newborns, infants and preschool children admitted to a tertiary-level paediatric hospital due to non-cardiopulmonary disorders (Group 2). RESULTS: In both groups, Rint values were inversely associated with age, weight and height, but the strongest association was with height. The linear regression equation for Group 1 (n = 209, height 86-129 cm) was Rint = 2.153 - 0.012 × height (cm) (standard deviation of residuals 0.181 kPa/L/s). The linear regression equation for Group 2 (n = 55, height 52-113 cm) was Rint = 4.575 - 0.035 × height (cm) (standard deviation of residuals 0.567 kPa/L/s). Girls tended to have slightly higher Rint values than boys, a difference that diminished with increasing height. CONCLUSIONS: In this study, Rint reference values applicable to Mexican children were determined, and these values are probably also applicable to other paediatric populations with similar Spanish-Amerindian ancestries. There was an inverse relationship between Rint and height, with relatively large between-subject variability.

[Airway resistance and urinary LTE4 in children with bronchopulmonary dysplasia. Preliminary report]. / Resistencia de las vías aéreas y LTE4 urinario en niños con displasia broncopulmonar. Informe preliminar.

OBJECTIVE: To assess airway resistance values and urinary leukotriene E4 (LTE4) concentrations before and after salbutamol inhalation in children with bronchopulmonary dysplasia (BPD). MATERIAL AND METHODS: Children with BPD were cross-sectionally studied to measure airway resistance by the interrupter technique (Rint), before and after inhaling 200 ig salbutamol, and to quantify urinary leukotriene E4 (LTE4) by immunoassay. RESULTS: Thirty one children with BPD (15 females) aged between 3 months and 9 years were studied. Our results showed that LTE4 did not correlate with Rint values (r = 0.12, p = 0.52) even after adjusting by gender, atopy history, steroid use, and gastroesophageal reflux. Likewise, LTE4 did not correlate with the degree of the airway response to salbutamol (r = -0.13, p = 0.50). A strong inverse association between age and Rint (r = -0.58, p < 0.001) was observed. CONCLUSION: We concluded that urinary LTE, did not correlate with airway resistance or with the response to a bronchodilator drug in children with BPD, suggesting that leukotrienes are not involved in airway obstruction in this disease.

Day-night fluctuation of pulse oximetry: an exploratory study in pediatric inpatients.

BACKGROUND: Pulse oximetry is a simple and non-invasive procedure widely used nowadays in the clinical practice. However, it is unclear if SpO2 values are constant throughout the 24 hours of the day or have periodic fluctuations. In the present study we evaluated if progressive day-night variations of SpO, values occur in children. MATERIAL AND METHODS: Pulse oximetry (Nonin 2500) was carried out approximately every 2 hours during a 24-hours period in pediatric patients hospitalized due to different diseases but without acute or chronic respiratory diseases. Measurements were analyzed through the cosinor method (sinusoidal curve fitting). RESULTS: A total of 131 patients (23 days to 16 years old) were studied. A sinusoidal fitting of the SpO2 values was accomplished in 84.7% of children. According to these curves, maximal SpO2 values occurred in the late afternoon [4:53 PM (3:49-5:32 PM), median (quartile 1-quartile 3)], while minimal values appeared in the first hours of the day [3:06 AM (2:12-4:08 AM)]. This pattern was the same in sleeping or awake children. More than half of these sinusoidal curves had a period near to 24 hours (between 20 and 28 hours). An additional finding was that maximal and minimal SpO2 values diminished with age (approximately 0.15 and approximately 0.13% SpO2 per year, respectively). In children less than six years old 5th percentile of SpO2 values were 93.8% in the late afternoon and 89.8% in the early hours of the day, while corresponding figures for older children were 91.0% and 88.5%, respectively. CONCLUSIONS: Our results suggested that, regardless of the sleep influence, in most children the SpO2 follows a progressive fluctuation during a 24-hours cycle, a pattern which is suggestive of a circadian rhythm. A prospective study in healthy children is warranted.

Underestimation of the peak flow variability in asthmatic children: evaluation of a new formula.

Asthma guidelines suggest evaluation of peak expiratory flow (PEF) variability, but timing for the two PEF measurements is not mentioned. Usual formula calculates amplitude as percentage of mean day-night PEF values. Since PEF circadian changes follow a sinusoidal function, we reasoned that variability might be calculated by measuring PEF at 4 pm (PEF(1)) and either at 10 am or 10 pm (PEF(2)) with the formula %variability = 200 . |PEF(1)-PEF(2)|/PEF(2). Children with stable, mild intermittent asthma were recruited from an Asthma Clinic and asked to perform PEF measurements at even hours during a week, until 12 measurements covering a 24-h period were accomplished. From these measurements we calculated PEF variability through several methods. Accuracy of such methods to predict actual PEF variability was assessed through the concordance correlation coefficient (r(c)). Thirty five asthmatic children were recruited. Actual PEF variability, calculated with the usual formula using the highest and lowest PEF obtained at any time of the 24 h cycle had a median of 37.3% (range, 0-88.5%). Variability calculated through other methods was: usual formula with highest and lowest PEF obtained from the sinusoidal curve, 21.4% (r(c) = 0.79); usual formula with PEF measured at 4 pm and 4 am, 17.8% (r(c) = 0.67); proposed formula using PEF measured at 4 pm and either 10 pm, 15.9% (r(c) = 0.68), or 10 am, 17.4% (r(c) = 0.69). Some examples with PEF measured in the morning (8 am or 10 am) and at night (8 pm or 10 pm) yielded median PEF variability from 4.0% (r(c) = 0.18) to 8.7% (r(c) = 0.38). Current methods for calculating PEF variability seemed not to be accurate enough as to be confident, suggesting that an in-deep reevaluation of the usefulness of PEF variability or, conversely, of the methods to assess it, should be done.

Neumonitis por Chlamydia trachomatis en lactantes / Chlamydia trachomatis pneumonitis in infant

La neumonitis por Chlamydia trachomatis es un padecimiento de adquisición en el periodo perinatal que puede manifestarse en la etapa de recién nacido o lactantes menores de 6 meses. Se realizó un estudio retrolectivo de casos, identificándose 8 pacientes con esta entidad. La edad al diagnóstico osciló entre 10 días y 19 meses con una mediana de 3 meses; resaltan dos casos cuya edad al diagnóstico fue de 9 y 19 meses. La mediana de evolución fue de 30 días. Todos los casos presentaron dificultad respiratoria y tos en la mitad de ellos. La imagen radiológica predominante fue de sobredistensión pulmonar o imagen retículo nodular difusa. El diagnóstico bacteriológico se realizó por inmunofluorescencia directa. Todos los pacientes respondieron satisfactoriamente al tratamiento con eritromicina durante 14 días. En nuestro medio la infección por chlamydia trachomatis deberá investigarse en los recién nacidos y lactantes con neumonitis