ABSTRACT
OBJECTIVE: To assess the changes in (regional) lung volume and gas exchange during minimally invasive surfactant therapy (MIST) in preterm infants with respiratory distress syndrome. STUDY DESIGN: In this prospective observational study, infants requiring a fraction of inspired oxygen (FiO2) ≥ 0.30 during nasal continuous positive airway pressure of 6 cmH2O were eligible for MIST. Surfactant (160-240 mg/kg) was administered in supine position in 1-3 minutes via an umbilical catheter placed 2 cm below the vocal cords. Changes in end-expiratory lung volume (EELV), tidal volume, and its distribution were recorded continuously with electrical impedance tomography before and up to 60 minutes after MIST. Changes in transcutaneous oxygen saturation (SpO2) and partial carbon dioxide pressure, FiO2, respiratory rate, and minute ventilation were recorded. RESULTS: A total of 16 preterm infants were included. One patient did not finish study protocol because of severe apnea 10 minutes after MIST. In the remaining infants (gestational age 29.8 ± 2.8 weeks, body weight 1545 ± 481 g) EELV showed a rapid and sustained increase, starting in the dependent lung regions, followed by the nondependent regions approximately 5 minutes later. Oxygenation, expressed as the SpO2/FiO2 ratio, increased from 233 (IQR 206-257) to 418 (IQR 356-446) after 60 minutes (P < .001). This change was significantly correlated with the change in EELV (ρ = 0.70, P < .01). Tidal volume and minute volume decreased significantly after MIST, but transcutaneous partial carbon dioxide pressure was comparable with pre-MIST values. Ventilation distribution remained unchanged. CONCLUSIONS: MIST results in a rapid and homogeneous increase in EELV, which is associated with an improvement in oxygenation.
Subject(s)
Lung/physiopathology , Pulmonary Surfactants/therapeutic use , Respiratory Distress Syndrome, Newborn/therapy , Tidal Volume/physiology , Blood Gas Analysis , Continuous Positive Airway Pressure/methods , Electric Impedance , Female , Humans , Infant, Newborn , Infant, Premature , Lung Volume Measurements , Male , Prospective Studies , Pulmonary Surfactants/administration & dosage , Respiratory Distress Syndrome, Newborn/physiopathology , TomographyABSTRACT
OBJECTIVE: To monitor regional changes in end-expiratory lung volume (EELV), tidal volumes, and their ventilation distribution during different levels of nasal continuous positive airway pressure (nCPAP) and nasal biphasic positive airway pressure (BiPAP) in stable preterm infants. STUDY DESIGN: By using electrical impedance tomography and respiratory inductive plethysmography, we measured changes in EELV and tidal volumes in 22 preterm infants (gestational age 29.7 ± 1.5 weeks) during 3 nCPAP levels (2, 4, and 6 cmH2O) and unsynchronized BiPAP (nCPAP = 6 cmH2O; pressure amplitude = 3 cmH2O; frequency = 50/min; inspiration time = 0.5 seconds) at 10-minute intervals. We assessed the distribution of these volumes in ventral and dorsal chest regions by using electrical impedance tomography. RESULTS: EELV increased with increasing nCPAP with no difference between the ventral and dorsal lung regions. Tidal volume also increased, and a decrease in phase angle and respiratory rate was noted by respiratory induction plethysmography. At the regional level, electrical impedance tomography data showed a more dorsally oriented ventilation distribution. BiPAP resulted in a small increase in EELV but without changes in tidal volume or its regional distribution. CONCLUSION: Increasing nCPAP in the range of 2 to 6 cmH2O results in a homogeneous increase in EELV and an increase in tidal volume in preterm infants with a more physiologic ventilation distribution. Unsynchronized BiPAP does not improve tidal volume compared with nCPAP.
Subject(s)
Continuous Positive Airway Pressure/methods , Lung/pathology , Positive-Pressure Respiration/methods , Calibration , Electric Impedance , Electrocardiography/methods , Female , Humans , Infant, Newborn , Infant, Premature , Lung/physiology , Male , Plethysmography/methods , Pressure , Tidal Volume/physiology , Tomography/methods , VentilationABSTRACT
OBJECTIVES: To assess global and regional changes in lung volume and ventilation during lung recruitment in preterm infants with respiratory distress syndrome. STUDY DESIGN: Using electrical impedance tomography, changes in lung volume and ventilation were measured in 15 high-frequency oscillatory ventilated preterm infants during oxygenation-guided recruitment maneuvers. The inflation and deflation limbs were mapped, and the lower and upper inflection points were calculated using both oxygenation and impedance data. The impedance data were also used to determine recruitment-related changes in oscillation volume and distribution. RESULTS: During inflation, lower and upper inflection points were identified in the majority of infants. The deflation limb showed clear lung hysteresis in all infants. The upper inflection point was significantly lower when comparing the pressure/oxygenation and pressure/impedance curves. Lung volume changes differed between the ventral and dorsal regions, but did not show a consistent pattern. Optimal recruitment increased the oscillation volume, but the distribution of ventilation was relatively homogeneous along the ventral-dorsal axis. CONCLUSIONS: Lung hysteresis is present in preterm infants with respiratory distress syndrome. Regional differences in lung volume changes and ventilation during high-frequency oscillatory ventilation with lung recruitment are relatively modest and do not follow a gravity-dependent distribution.