Approximately 1.5% of total child deaths are caused by neonatal infections and complications. According to the Centers for Disease Control and Prevention1 the prevalence of respiratory distress syndrome (RDS) in a US study population is 3.9 in every 1000 infants, which poses a great threat to the survival rate of preterm neonates.1 RDS is caused by insufficient production of surfactant in the lungs, which results in the respiratory organs being unable to develop and operate fully.2 Clinical symptomatic presentations include central cyanosis, tachypnoea and nasal flaring, and a pulmonary radiograph showing the lungs to have a ground-glass appearance is generally regarded as a confirmatory diagnostic test for RDS.3 Acute RDS may cause the lungs to collapse, resulting in death,4 but antenatal administration of corticosteroids, postnatal surfactant replacement therapy5 and ventilation support with continuous positive airway pressure (CPAP) may be used as therapeutic options for RDS.6–8
Most of the public medical centres in developing countries cannot cope with the requirements of all patients and, as a result, maternal health and neonatal care is often compromised. Consequently, a large number of neonates who are born with, or develop, serious difficulties and complications may not survive and the mortality rate for infants is increasing. Additionally, preterm neonates are at a greater risk of developing postpartum disorders, including RDS. Only a small number of studies in Pakistan have addressed the frequency of various prenatal and postnatal diseases. Bhutta et al.9 and Ghafoor et al.10 comprehensively discuss the prevalence of RDS in a Karachi and Rawalpindi population, respectively. However, to the best of our knowledge, no study in a Lahore population has been reported.
In view of this, the present study offers an assessment of RDS prevalence in preterm neonates residing in Lahore. The relationship between the presence of RDS and either gestational age or weight at the time of birth is also examined. Both of these parameters, along with other considerations, may serve as useful predictive markers of RDS in preterm neonates.
Materials and methods
Patients from the neonatal ward of the Children's Hospital in Lahore, Pakistan, were included in the study after approval from the hospital's ethical committee. This descriptive study was conducted over a period of 6 months (September 2011–February 2012). There were 180 non-probability based and purposive preterm neonates who were included in the study, with a confidence interval of 95%.
Preterm neonates who were born between 26 and 34 weeks' gestation were selected for the study and gestational age was calculated using the Ballard scoring system. The subjects with clinical presentation of respiratory distress, tachypnoea, cyanosis and radiological findings of a ground-glass appearance in the lungs were categorized as having RDS.
Preterm neonates suffering from congenital defects such as cleft palate, Pierre Robin syndrome, Down syndrome, Turner syndrome, hydrocephalus and cyanotic heart disease were not included in the study. Infants whose mothers suffered from chronic diseases such as diabetes mellitus, renal failure and congenital pneumonia were also excluded from the study.
Informed consent was requested from the parents of the participants and participant age, sex and weight were recorded and all the information was collected on a specifically designed questionnaire. A physical examination provided information regarding nasal flaring, tachypnoea (with subcostal and intercostal recession) and cyanosis, whereas chest radiography was carried out to assess the appearance of the lungs. A combination of nasal flaring, tachypnoea, cyanosis and a ground-glass appearance of the lungs on chest radiography confirmed the diagnosis of RDS.
The collected data were entered into SPSS (SPSS v.17, SPSS Inc., Chicago, IL, USA) for analysis. Qualitative data such as sex (male or female) and RDS (present or absent) were presented as frequency distributions and percentages. The association of RDS with gestational age and birthweight was evaluated using Pearson's correlation coefficients with a 95% confidence interval.
General characteristics of observed neonates
A total of 180 neonates with a mean gestational age of 30 ± 0.91 weeks (range 26–34 weeks) were studied. The relative proportions of male and female neonates were 62.8% (n = 113) and 37.2% (n = 67) respectively, giving a male to female ratio of 1.68:1.
Gestational age varied: 14 neonates (7.8%) were born during week 26 of gestation, 26 (14.4%) in week 27, 15 (8.3%) in week 28, 19 (10.6%) in week 29, 27 (15%) in week 30, 16 (8.9%) in week 31, 20 (11.1%) in week 33, 26 (14.4%) in week 33 and 17 (9.4%) in week 34. Thus, the greatest number of neonates were born in week 30 (n = 27). The variable presentation provided the opportunity to compare respiratory outcome at different gestational ages.
Among the 180 neonates observed in this study, 42 (23.3%) had a birthweight of < 1000 g, 39 (21.7%) of 1001–1500 g, 44 (24.4%) of 1501–2000 g, 32 (17.8%) of 2001–2500 g and 23 (12.8%) of > 2500 g.
Symptoms associated with pulmonary infections were considered but exclusion criteria were strictly applied. Nasal flaring was seen in 89 neonates (49.4%), tachypnoea in 78 (43.3%) and central cyanosis in 63 (35%) (Figure 1). In view of these clinical presentations, radiography was performed in all participants and a ground-glass appearance in the lungs clearly indicated the presence of RDS in a subset of the neonates.
Frequency of respiratory distress syndrome
Respiratory distress syndrome was present in 50 participants (27.8%) and not present in 130 (72.2%), as confirmed by radiological examination (Figure 1). These values indicated a high frequency of RDS in this population.
Gestational age at birth versus frequency of respiratory distress syndrome
Among the 50 neonates diagnosed with RDS, 14 (28%) were born at 26 weeks' gestation, seven (14%) at 27 weeks, five (10%) at 28 weeks, seven (14%) at 29 weeks, five (10%) at 30 weeks, six (12%) at 31 weeks, three (6%) at 32 weeks, two (4%) at 33 weeks and one (2%) at 34 weeks. The number of patients with RDS showed a negative correlation with gestational age. The association of RDS with gestational age was statistically significant (P < 0.005) with a correlation co-efficient (r) of −0.86 (Figure 2).
Birthweight and respiratory distress syndrome
Among the infants with RDS, birthweight was < 1000 g in 11 (22%), 1001–1500 g in 15 (30%), 1501–2000 g in 12 (24%), 2001–2500 g in nine (18%) and > 2500 3g in three (6%). Increasing birthweight was found to be inversely correlated with RDS frequency, indicating a higher risk for RDS in early preterm infants. The correlation was statistically significant (P <0.05; r = − 0.98) (Figure 2).
Neonatal morbidity is an issue of prime importance in the underdeveloped and developing countries. Many infant deaths may be attributed to pulmonary diseases such as pneumonia and asphyxia, or other congenital anomalies.11 A few studies in Pakistani populations9,10 have reported the high incidence of RDS, but it is necessary to look to studies conducted in other populations for a guide to the management of this disorder.12
The present study attempted to quantify the recent RDS frequency in preterm neonates presenting at a local hospital with access to basic paediatric intensive care facilities. A total of 180 preterm neonates were assessed with a mean birth age of 30 ± 0.91 weeks' gestation, birthweight ranging from 500 to 3000 g and clinical presentation of nasal flaring, tachypnoea, cyanosis and a ground-glass appearance of the lungs after radiological examination.
Sex-based differences in the frequency of preterm neonates were observed. Almost twice as many boys (n = 113) as girls were affected (n = 67) and the male to female ratio was 1.68:1. Previous studies have observed a tendency for more males to be born prematurely, which may be due to various sex-specific biochemical processes during the later trimesters.13,14
The gestational age of our neonates ranged from 26 to 34 weeks; most were born in week 27, 30 or 33 (14.4%, 15% and 14.4%, respectively). The lowest number were born at 26 weeks' gestation. The study group included neonates with a range of birthweights and with those weighing 1501–2000 g forming the largest group (24.4%).
Infants in the study group presented symptoms of pulmonary discomfort. Some of the notable presentations included nasal flaring (49.4%), tachypnoea (43.3%) and central cyanosis (35%). In 50 infants (27.8%), RDS was confirmed by a groundglass appearance of the lungs on radiography and a bell-shaped chest due to decreased lung volume. The remaining 130 patients (72.2%) also had signs of respiratory distress but chest radiographs were notably different and indicated absence of RDS. The incidence of RDS was therefore found to be 27.8% over a period of 6 months. It is very important to address this alarming number of affected infants as this high incidence of RDS in preterm neonates may contribute dramatically to decreased neonatal survival rate. RDS serves as an additional threat to neonates born at an early gestational age as they have a compromised state of health. However, this number of neonates with RDS could be an overestimate because of the small sample size in this study, which could be evaluated by further studies over a longer time period.
The prevalence of RDS among preterm newborns in our study decreased with increasing gestational age, a correlation that that was found to be statistically significant (r = −0.86, P < 0.005). The risk of preterm neonates developing RDS can be predicted from the gestational age, as reported in previous studies.15 This may be useful for risk assessment of RDS in preterm neonates, which may enable physicians to prepare for treatment. In addition, the frequency of RDS was found to increase with decreasing birthweight, highlighting the importance of birthweight for risk assessment of RDS in both preterm and full-term neonates.
The observations of the study were limited because of its limited scope and small sample size. A larger number of neonates with a larger variety of gestational ages and a more precise diagnosis of RDS is required to derive more accurate conclusions. A larger-scale study may be useful in devising a numeric score for the health of a fetus to estimate the chance of preterm parturition and, ultimately, the probability of developing RDS. Additionally, as indicated by some studies,16,17 the health status of the mother should also be utilized as an indicator for the subsequent risk of neonatal RDS. An account of the survival and mortality rates of the affected neonates may also be helpful for postnatal management of the infants.
Our observations highlight the significance of gestational age and birthweight in prediction of the incidence of RDS. Infants born prematurely should receive particular attention and an appropriate intensive care and therapeutic protocol should be instituted. The appearance of any of the symptoms of pulmonary discomfort should assist the physician in making the correct diagnosis. If the symptoms are not noted, or the wrong diagnosis is given, the life of the neonate may not be secured.