Optimising continuous positive airway pressure in preterm infants

© 2015 Dr. Risha BhatiaBackground: Respiratory distress syndrome (RDS) and bronchopulmonary dysplasia (BPD) remain common complications of prematurity. Respiratory support may injure the lung and contribute to BPD. Non-invasive methods of respiratory support such as continuous positive airway pressure (CPAP) have the potential to reduce the risk of lung injury but randomised controlled trials comparing early CPAP with mechanical ventilation show no difference in the rates of BPD. In intubated infants, lung recruitment manoeuvres that allow for an ‘open lung’ improve oxygenation and ventilation but there is a paucity of data regarding CPAP strategies and how they impact upon lung behaviour. The series of studies described in this report aim to add to the knowledge regarding lung behaviour and potential complications in very preterm infants receiving CPAP. Method: Five studies of very preterm infants receiving CPAP were designed. These included three studies using respiratory inductive plethysmography and electrical impedance tomography; 1) a physiological study to determine if stepwise increases and decreases in CPAP level would demonstrate hysteresis and thus describe the changes in end-expiratory thoracic volume (∆EEV) and the distribution of ventilation (∆VT) in very preterm infants receiving CPAP from birth; 2) an observational study to describe ∆EEV and ∆VT during extubation to CPAP; and 3) a randomised pilot study comparing ∆EEV and ∆VT in infants extubated to currently used CPAP protocols versus a ‘CPAP recruitment’ manoeuvre. In addition, 4) a laboratory based study to determine whether the stable microbubble test could be used to determine within the first hour of life, which infants would successfully manage CPAP from birth and 5) a case-control study to determine risk factors for the development of pneumothoraces in very preterm infants were conducted. Results: These studies found that 1) it was possible to demonstrate hysteresis in many, but not all, very preterm infants exposed to stepwise increases and decreases in CPAP levels and that ∆EEV and ∆VT were often improved following this manoeuvre; 2) lung behaviour during extubation to CPAP was variable and unpredictable between and within infants; 3) after extubation, there were no differences in ∆EEV following a CPAP recruitment manoeuvre although ∆VT appeared to be more homogeneous when compared with a control group; 4) infants with a stable microbubble count ≥ 8 microbubbles/mm2 in gastric aspirate did not fail CPAP and 5) it may be possible to identify infants at highest risk of pneumothorax on the basis of their inspired fraction of oxygen in the first 12 hours of life. Conclusions: Lung behaviour at different stages of lung disease in very preterm infants receiving CPAP is complex, variable and unpredictable. It is possible to demonstrate hysteresis using CPAP, but optimising CPAP in very preterm infants at the bedside is difficult without tools that provide feedback regarding ∆EEV and ∆VT to clinicians. CPAP protocols that aid an ‘open lung’ require further investigation. Tests of endogenous surfactant status may be used to determine which infants may benefit from CPAP alone and which infants need escalation of respiratory support

Oxygen saturation levels and retinopathy of prematurity in extremely preterm infants - a case control study

Abstract Purpose To investigate the association of risk factors, including oxygen exposure, for developing retinopathy of prematurity (ROP) in preterm infants at increased risk of ROP. Methods A case-control study was conducted where each infant born at  21% showed that were was no difference in SpO2 between the two groups when the infants were receiving oxygen support. Conditional logistic regressions showed neonatal surgery significantly increased the risk of ROP (OR = 1.4347, p = 0.010), while the influence of birthweight (odds ratio of 0.9965, p = 0.001) and oxygen exposure (OR = 0.9983, p = 0.012) on ROP outcome was found to be negligible as their odds ratios indicated no influence. Conclusions At times when infants were receiving respiratory support (FiO2 > 21%) the SpO2 data indicated no difference in SpO2 between the ROP and non-ROP groups. Analysis of clinical variables found that neonatal surgery increased the odds of developing ROP

Effect of Minimally Invasive Surfactant Therapy vs Sham Treatment on Death or Bronchopulmonary Dysplasia in Preterm Infants With Respiratory Distress Syndrome The OPTIMIST-A Randomized Clinical Trial

IMPORTANCE The benefits of surfactant administration via a thin catheter (minimally invasive surfactant therapy [MIST]) in preterm infants with respiratory distress syndrome are uncertain. OBJECTIVE To examine the effect of selective application of MIST at a low fraction of inspired oxygen threshold on survival without bronchopulmonary dysplasia (BPD). DESIGN, SETTING, AND PARTICIPANTS Randomized clinical trial including 485 preterm infants with a gestational age of 25 to 28 weeks who were supported with continuous positive airway pressure (CPAP) and required a fraction of inspired oxygen of 0.30 or greater within 6 hours of birth. The trial was conducted at 33 tertiary-level neonatal intensive care units around the world, with blinding of the clinicians and outcome assessors. Enrollment took place between December 16, 2011, and March 26, 2020; follow-up was completed on December 2, 2020. INTERVENTIONS Infants were randomized to the MIST group (n = 241) and received exogenous surfactant (200 mg/kg of poractant alfa) via a thin catheter or to the control group (n = 244) and received a sham (control) treatment; CPAP was continued thereafter in both groups unless specified intubation criteria were met. MAIN OUTCOMES AND MEASURES The primary outcome was the composite of death or physiological BPD assessed at 36 weeks' postmenstrual age. The components of the primary outcome (death prior to 36 weeks' postmenstrual age and BPD at 36 weeks' postmenstrual age) also were considered separately. RESULTS Among the 485 infants randomized (median gestational age, 27.3 weeks; 241 [49.7%] female), all completed follow-up. Death or BPD occurred in 105 infants (43.6%) in the MIST group and 121 (49.6%) in the control group (risk difference [RD], -63% [95% CI, -14.2% to 1.6%); relative risk [RR], 0.87 [95% CI, 0.74 to 1.03]; P = .10). Incidence of death before 36 weeks' postmenstrual age did not differ significantly between groups (24 [10.0%) in MIST vs 19 [7.8%) in control; RD, 2.1% [95% CI, -3.6% to 7.8%); RR, 1.27 [95% CI, 0.63 to 2.57]; P = .51), but incidence of BPD in survivors to 36 weeks' postmenstrual age was lower in the MIST group (81/217 [37.3%] vs 102/225 [45.3%) in the control group; RD, -7.8% [95% CI, -14.9% to -0.7%); RR. 0.83 [95% CI, 0.70 to 0.98]; P = .03). Serious adverse events occurred in 10.3% of infants in the MIST group and 11.1% in the control group. CONCLUSIONS AND RELEVANCE Among preterm infants with respiratory distress syndrome supported with CPAP, minimally invasive surfactant therapy compared with sham (control) treatment did not significantly reduce the incidence of the composite outcome of death or bronchopulmonary dysplasia at 36 weeks' postmenstrual age. However, given the statistical uncertainty reflected in the 95% CI, a clinically important effect cannot be excluded. (C) 2021 American Medical Association. All rights reserved

Optimal mean airway pressure during high-frequency oscillatory ventilation determined by measurement of respiratory system reactance.

The aims of the present study were (i) to characterize the relationship between mean airway pressure (PAW) and reactance measured at 5 Hz (reactance of the respiratory system (X RS), forced oscillation technique) and (ii) to compare optimal PAW (P opt) defined by X RS, oxygenation, lung volume (VL), and tidal volume (VT) in preterm lambs receiving high-frequency oscillatory ventilation (HFOV).Nine 132-d gestation lambs were commenced on HFOV at PAW of 14 cmH2O (P start). PAW was increased stepwise to a maximum pressure (P max) and subsequently sequentially decreased to the closing pressure (Pcl, oxygenation deteriorated) or a minimum of 6 cmH2O, using an oxygenation-based recruitment maneuver. X RS, regional V L (electrical impedance tomography), and V T were measured immediately after (t 0 min) and 2 min after (t 2 min) each PAW decrement. P opt defined by oxygenation, X RS, V L, and V T were determined.The PAW-X RS and PAW-VT relationships were dome shaped with a maximum at Pcl+6 cmH2O, the same point as P opt defined by VL. Below Pcl+6 cmH2O, X RS became unstable between t 0 min and t 2 min and was associated with derecruitment in the dependent lung. P opt, as defined by oxygenation, was lower than the P opt defined by X RS, V L, or V T.X RS has the potential as a bedside tool for optimizing PAW during HFOV