Oscillatory mechanics at birth for identifying infants requiring surfactant: a prospective, observational trial.

BACKGROUND: Current criteria for surfactant administration assume that hypoxia is a direct marker of lung-volume de-recruitment. We first introduced an early, non-invasive assessment of lung mechanics by the Forced Oscillation Technique (FOT) and evaluated its role in predicting the need for surfactant therapy. OBJECTIVES: To evaluate whether lung reactance (Xrs) assessment by FOT within 2 h of birth identifies infants who would need surfactant within 24 h; to eventually determine Xrs performance and a cut-off value for early detection of infants requiring surfactant. METHODS: We conducted a prospective, observational, non-randomized study in our tertiary NICU in Milan. Eligible infants were born between 27+0 and 34+6 weeks' gestation, presenting respiratory distress after birth. EXCLUSION CRITERIA: endotracheal intubation at birth, major malformations participation in other interventional trials, parental consent denied. We assessed Xrs during nasal CPAP at 5 cmH2O at 10 Hz within 2 h of life, recording flow and pressure tracing through a Fabian Ventilator for off-line analysis. Clinicians were blinded to FOT results. RESULTS: We enrolled 61 infants, with a median [IQR] gestational age of 31.9 [30.3; 32.9] weeks and birth weight 1490 [1230; 1816] g; 2 infants were excluded from the analysis for set-up malfunctioning. 14/59 infants received surfactant within 24 h. Xrs predicted surfactant need with a cut-off - 33.4 cmH2O*s/L and AUC-ROC = 0.86 (0.76-0.96), with sensitivity 0.85 and specificity 0.83. An Xrs cut-off value of - 23.3 cmH2O*s/L identified infants needing surfactant or respiratory support > 28 days with AUC-ROC = 0.89 (0.81-0.97), sensitivity 0.86 and specificity 0.77. Interestingly, 12 infants with Xrs < - 23.3 cmH2O*s/L (i.e. de-recruited lungs) did not receive surfactant and subsequently required prolonged respiratory support. CONCLUSION: Xrs assessed within 2 h of life predicts surfactant need and respiratory support duration in preterm infants. The possible role of Xrs in improving the individualization of respiratory management in preterm infants deserves further investigation.

Accuracy of volume and pressure delivery by mechanical ventilators in use in neonatal intensive care units: A quality control study.

OBJECTIVE: Despite technical specifications of neonatal mechanical ventilators (MVs) guarantee clinically irrelevant discrepancies between the set and the delivered values of ventilation parameters, previous studies reported large deviations. Most studies characterized performances of a given model/brand by studying a single device, disregarding possible intramodel differences, and leaving the accuracy of the ventilation parameters effectively delivered in clinical settings unknown. The aim of this study was to evaluate the real-life accuracy of pressure and volume parameters delivered by neonatal ventilators ready to be used on patients in neonatal intensive care units (NICUs). STUDY DESIGN: In vitro study. SUBJECTS SELECTION: Neonatal ventilators (n = 33 of 8 different models) available in four European NICUs. METHODOLOGY: The MVs were connected to a test lung (resistance = 50 cmH2 O*s/L, compliance = 0.35 mL/cmH2 O) provided with pressure and flow sensors. MVs were tested over two different ventilation modes randomly: (a) pressure controlled (PC) with a peak inspiratory pressure (PIP) of 22 cmH2 O, and (b) PC with volume targeted ventilation (VTV) with a tidal volume (VT ) of 6 mL. In all tests, positive end-expiratory pressure (PEEP) was set to 6 cmH2 O, respiratory rate to 45 breaths/min, inspiratory time to 0.33 seconds, and oxygen fraction to 0.3. RESULTS: During PC the median (min-max) values delivered were: PEEP = 5.84(4.95-6.48) cmH2 O, PIP = 21.63(20.04-22.62) cmH2 O. During VTV, VT was 5.94(4.63-8.01) mL. VT was considerably variable, ranging from -22% to +33% of the set and displayed values. Differences in accuracy among devices of the same model were comparable to those found among different models. CONCLUSIONS: Our findings suggest that loss of accuracy in ventilation variables is likely related to daily use of the devices rather than weakness in the design or manufacturing process, urging the improvement of maintenance and quality control procedures to preserve the performances of neonatal MVs during their entire lifespan.

Accuracy of oscillatory pressure measured by mechanical ventilators during high frequency oscillatory ventilation in newborns.

BACKGROUND: Oscillatory pressure (ΔP) measurement during high frequency oscillatory ventilation (HFOV) is technically challenging and influenced by all the components of the measurement system. OBJECTIVES: To evaluate the differences between the ΔP delivered at the inlet of the endotracheal tube and those displayed by commercial neonatal mechanical ventilators and monitoring devices and to characterize how the ventilator circuit and the flowmeter proximal to the patient affect these differences. METHODS: Six devices were evaluated while ventilating three mechanical analogues representing the newborn respiratory system in different disease states. ΔP measured at different points of the ventilator circuit were compared. RESULTS: ΔP accuracy is highly variable and decreases with increasing oscillation frequency and amplitude, independently of the mean airway pressure. At 15 Hz, a ΔP displayed by ventilators of 40 cmH2 O resulted in a ΔP effectively delivered at the tracheal tube ranging from 22 to 49 cmH2 O, depending on the ventilator model, the ventilator circuit, and the patient condition. At these settings, the errors exclusively due to the ventilator circuit and the presence of the flowmeter ranged from 6 to 9 cmH2 O and from 1 to 6 cmH2 O, respectively. CONCLUSIONS: The ventilator model, the breathing circuit, the flowmeter, and the patient condition severely impacts ΔP measurement accuracy during HFOV, leading to highly variable performances. This prevents the possibility of using the ΔP required to normalize gas exchange as an indicator of patients' condition, complicates comparison of ventilators performances, and adds a significant element of complexity in clinical management of HFOV.