The stable microbubble test on tracheal aspirate samples from newborn babies for diagnosis of surfactant deficiency and/or surfactant malfunction

Diagnostic accuracy of lamellar body count as a predictor of fetal lung maturity: A systematic review and meta-analysis

Objective

This study aimed to synthesize evidence from published studies about the diagnostic accuracy of lamellar body count (LBC) as a predictor of fetal lung maturity.

Study design

We searched Medline (via PubMed), EBSCO, Web of Science, Scopus and the Cochrane Library for relevant published studies assessing the accuracy of LBC as a predictor of fetal lung maturity. Studies were classified according to the counting essays, centrifugation protocols, and the reported optimum cut off values. Data of the true positive, true negative, false positive, and false negative were extracted and analyzed to calculate the overall sensitivity and specificity of the LBC.

Results

Thirty-one studies were included in the final analysis. Fourteen studies reported data for centrifuged amniotic fluid (AF) samples, 13 studies reported data for uncentrifuged samples, and four studies did not have enough information about whether centrifugation was done. LBC showed an area under the curve >80% in diagnosing lung immaturity with variable cut off values. Pooled analysis showed that LBC a 100% specificity to exclude respiratory distress syndrome (RDS) at a cut off value of 15,000 and 100% sensitivity to diagnose RDS at a cut off value of 55,000.

Conclusion

Cases with LBC < 15,000 are considered to have lung immaturity while cases with LBC > 45,000 in centrifuged AF samples or >55,000 in uncentrifuged AF samples are likely to have mature lungs. Cases with LBC ranging between these maturity and immaturity limits should be considered for further evaluation by other lung maturity tests.

Surfactant deficiency in full-term newborns with transient tachypnea delivered by elective C-section

INTRODUCTION

Previous studies have suggested that full-term newborns delivered by elective cesarean section who develop transient tachypnea have low gastric microbubble counts. In the present study, microbubble concentrations in oral fluid samples were used to evaluate pulmonary maturity.

OBJECTIVE

To evaluate lung maturity in full-term newborns delivered by elective caesarean section using the stable microbubble test in oral aspirates collected at birth.

METHOD

The study involved newborns with gestational age >37 weeks delivered by elective cesarean section. Oral fluid samples were obtained in the delivery room immediately after birth, and gastric fluid was collected within the first hour of life. Samples were frozen and analyzed by two blinded researchers.

RESULTS

The sample comprised 544 newborns. Twenty-two were diagnosed with transient tachypnea of the newborn by the assisting physician, and required admission to the Neonatal Intensive or Intermediate Care Unit. The median (interquartile range) of the number of microbubbles in the oral samples of these patients was 67.5 (45-150) microbubbles/mm(2) . The remaining 498 newborns without respiratory difficulties had a count of 350 (150-750) microbubbles/mm(2) -P < 0.001. Gastric fluid tests revealed a count of 150 (82.5-700) microbubbles/mm(2) for neonates with respiratory difficulties, and of 600 (216-1125) microbubbles/mm(2) -P < 0.05 for those without respiratory symptoms.

CONCLUSION

The present results suggest that transient tachypnea of the newborn is associated with surfactant dysfunction. Pediatr Pulmonol. 2016;51:596-600. © 2015 Wiley Periodicals, Inc.

Evaluation of specificity and sensitivity of gastric aspirate shake test to predict surfactant deficiency in Iranian premature infants

INTRODUCTION

Respiratory failure secondary to pulmonary surfactant deficiency is an important cause of severe respiratory distress in term and preterm infants. The aim of this study was to evaluate the specificity and sensitivity of gastric aspirate shake test (GAST) to predict surfactant deficiency in newly born premature infants in Arash Hospital (Iran) during 2012-13.

METHODS

In this case-control study, the case group comprised 69 premature infants (gestational age<37 weeks) who were admitted to the neonatal intensive care unit due to respiratory distress. The control group included 50 healthy infants .GAST test was done. The subjects were finally categorized as healthy or surfactant-deficient based on clinical and radiological assessments.

RESULTS

Using statistical methods the sensitivity, specificity, and positive and negative predictive values of GAST were 60%, 75%, 15%, and 52%, respectively. There was a significant difference between respiratory distress syndrome (RDS) scores and receiving surfactant in neonates with gestational age below 34 weeks. Moreover, there were significant differences between GAST results and both radiological findings of RDS and receiving oxygen in premature infants (gestational age<34 weeks). Negative GAST results were more prevalent in neonates who were born to mothers with hypothyroidism, preeclampsia, diabetes mellitus, and premature rupture of membranes. However, this difference was not significant.

CONCLUSION

According to our findings, the application of GAST on gastric aspirate secretions is not a useful method to predict surfactant deficiency. Therefore, decisions for RDS management must be made based on clinical and radiological findings.

Effect of Microbubble Mixtures on the Washing Rate of Surfactant Solutions in a Swirling Flow and an Alternating Flow

Wastewater from laundry cleaning contributes to water pollution, and the amount of detergent used needs to be reduced. In the present study, water, four types of surfactants, and their microbubble mixtures were used, and washing rates were measured in swirling flows and alternating flows. The microbubble/water mixtures (average particle diameter: 25 μm; mixed with air at 1.5 vol % in water) achieved washing rates higher than those of water alone. Furthermore, microbubbles mixed with an aqueous surfactant solution had a washing rate that depended on the ionization of the surfactant: the mixtures with microbubbles and non-ionic and anionic surfactants had a washing rate that was higher than that of aqueous non-ionic and anionic surfactant solutions without microbubbles. The surface tensions of microbubble/water mixtures and mixtures of microbubbles with non-ionic and anionic surfactants were lower than those without microbubbles. These results provide evidence of an enhanced washing effect for microbubble mixtures in laundry cleaning.

The stable microbubble test for determining continuous positive airway pressure (CPAP) success in very preterm infants receiving nasal CPAP from birth

BACKGROUND

Very preterm infants can be treated with nasal continuous positive airway pressure (CPAP) from birth, but some fail. A rapid test, such as the stable microbubble test (SMT) on gastric aspirate, may identify those who can be managed successfully using CPAP.

OBJECTIVE

To determine if SMT can identify soon after birth, very preterm infants who may be successfully managed on CPAP alone.

METHODS

Stable microbubbles (diameter <15 µm) were counted in gastric aspirates taken <1 h of age from infants <30 weeks' gestation, who received CPAP from birth. Infants failed CPAP if intubated at <72 h of age. Clinicians were masked to SMT results. A receiver operating characteristic curve was generated to determine the relationship between number of microbubbles/mm(2) and subsequent intubation.

RESULTS

68 infants of mean (SD) 28.1 (1.4) weeks' gestation received CPAP in the delivery room at a median (interquartile range) pressure 7 (6-8) cmH2O and FiO2 0.25 (0.21-0.3). Gastric aspirates were taken at a median (interquartile range) age of 0.5 (0.3-0.6) hours. The best cut-off point for predicting CPAP success or failure was a SMT count of 8 microbubbles/mm(2). The area under the receiver operating characteristic curve was 0.8 (95% CI 0.7-0.9). A SMT count ≥8 microbubbles/mm(2) had a sensitivity of 53%, a specificity of 100%, a positive predictive value of 100%, and a negative predictive value of 60% for predicting CPAP success.

CONCLUSION

Infants treated with CPAP from birth, who had SMT counts ≥8 microbubbles/mm(2) on their gastric aspirate, did not fail CPAP.

Lamellar body count and stable microbubble test on tracheal aspirates from infants for the diagnosis of respiratory distress syndrome

OBJECTIVES

To evaluate the performance of lamellar body count in tracheal aspirates from intubated preterm babies to predict respiratory distress syndrome.

DESIGN

Case-control study.

SETTING

Three neonatal intensive care units.

PATIENTS

Seventy-two patients not older than 3 days were included in the study, 38 preterm infants with respiratory distress syndrome, 16 preterms without respiratory distress syndrome, and 18 term infants. All required mechanical ventilation.

INTERVENTIONS

Lamellar body count was performed in an automated cell counter. Tracheal samples were diluted in dithiothreitol without centrifugation and kept frozen at -20°C until use. Samples were placed in a dithiothreitol-containing test tube at a ratio of one part tracheal aspirate to six parts dithiothreitol solution, vortexed for 10 secs, and aspirated by the cell counter. Lamellar body count was performed using the platelet channel. All results were multiplied by seven. The stable microbubble test was done for comparison.

MEASUREMENTS

Lamellar body count and stable microbubble test.

MAIN RESULTS

Lamellar body count was significantly lower in the respiratory distress syndrome group compared with the non respiratory distress syndrome preterm group and also with the term group. The median and interquartile range obtained for lamellar body count were 38,500/μL (14,000-112,000) for the respiratory distress syndrome group, 822,500/μL (442,000-962,500) for the non respiratory distress syndrome preterm group, and 633,000/μL (322,000-1,608,000) for the term group (p < .001). The sensitivity and specificity of lamellar body count and stable microbubble test for the diagnosis of respiratory distress syndrome were calculated, taking into consideration the respiratory distress syndrome and the non respiratory distress syndrome preterm groups. Considering a cutoff point of 200,000 lamellar bodies/μL, lamellar body count sensitivity was 92.1% (95% confidence interval 78.6-98.3) and lamellar body count specificity was 93.8% (95% confidence interval 69.8-99.8). The area under the curve was 0.94 (95% confidence interval 0.84-1.00).

CONCLUSIONS

Lamellar body count and stable microbubble test can be rapidly and easily performed on tracheal aspirates and they seem to have very good performance for diagnosing respiratory distress syndrome in intubated patients.

Surfactant deficiency in transient tachypnea of the newborn

OBJECTIVE

To evaluate surfactant production and function in term neonates with transient tachypnea of the newborn (TTN).

STUDY DESIGN

Samples of gastric aspirates collected within 30 minutes of birth from 42 term newborns with gestational age ≥ 37 weeks (21 patients with TTN and 21 control subjects), delivered via elective cesarean delivery, were analyzed with lamellar body count and stable microbubble test.

RESULTS

Results of lamellar body counts and stable microbubble tests were significantly lower in the TTN group than in control subjects (P = .004 and .013, respectively). Lamellar body counts were significantly lower in infants with TTN requiring oxygen for ≥ 24 hours after birth than in infants requiring oxygen for < 24 hours (P = .029). When the cutoff point was 48 hours, the stable microbubble count was significantly lower in the group requiring oxygen for ≥ 48 hours than in the group requiring oxygen for < 48 hours (P = .047).

CONCLUSIONS

Term infants with TTN had low lamellar body counts associated with decreased surfactant function, suggesting that prolonged disease is associated with surfactant abnormalities.

Selective surfactant prophylaxis in preterm infants born at < or =31 weeks' gestation using the stable microbubble test in gastric aspirates

OBJECTIVE

To evaluate the stable microbubble test (SMT) ability to select candidates for surfactant prophylaxis for respiratory distress syndrome (RDS).

STUDY DESIGN

We followed patients treated according to a new routine for surfactant prophylaxis based on the SMT to determine timing of the initial dose of surfactant, proportion of infants using surfactant, and the predictive value of the SMT. Gastric secretions were collected after birth. Newborns with < 25 microbubbles (MB)/mm(2) received prophylactic surfactant. Surfactant was given only after confirmation of RDS (rescue therapy) to newborns with > or =25 MB/mm(2).

RESULTS

Fifty-four (55%) had a low MB count and received prophylactic surfactant. Three out of 44 infants with a high MB count required rescue therapy (negative predictive value 93%; CI:81.3-98.6%). The median interval and interquartile range between surfactant administration and birth in the prophylaxis group was 20 (17-27) minutes. Surfactant was used in 23 of 28 (82%) infants born at < 28 weeks of gestation and in 34 of 70 (49%) infants between 28 and 31 weeks.

CONCLUSIONS

The SMT may be useful to determine surfactant prophylaxis (< 30 min after birth). This approach may reduce costs and the number of unnecessary interventions.

Stable Microbubble Test on Tracheal Aspirate for the Diagnosis of Respiratory Distress Syndrome

BACKGROUND

Exogenous surfactant should be used as early as possible in the presence of respiratory distress syndrome (RDS), but diagnosis may only become clear late in the course of the disease. The stable microbubble test (SMT) in the tracheal aspirates could help in the decision to give early surfactant to preterm babies with respiratory distress.

OBJECTIVES

The objective of this study was to evaluate the accuracy of the SMT on tracheal aspirate for the diagnosis of RDS in newborns requiring mechanical ventilation.

METHODS

The test was performed on specimens obtained from 74 infants requiring mechanical ventilation, through routine suctioning.

RESULTS

Patients with RDS and meconium aspiration syndrome (MAS) had a significantly lower stable microbubble count than non-RDS and non-MAS patients. Preterm infants without RDS had a significantly higher microbubble count than preterm babies with RDS and a similar count to that of term babies. Considering a cutoff point of 120 microbubbles/mm(2) for the diagnosis of RDS, the sensitivity of the microbubble test was 96.3% (95% CI: 79.1-99.8) and the specificity 97.6% (95% CI: 85.9-99.9).

CONCLUSIONS

The SMT on tracheal aspirates is accurate for RDS diagnosis and may be useful to support the decision to give surfactant to newborns on mechanical ventilation.