The Application Of High Frequency Oscillatory Ventilation In Neonatal Respiratory Distress Syndrome

BackgroundWith the establishment and improvement of neonatal intensive care unit (NICU), neonatal survival and quality of life is significantly improved, but in critically ill neonates, especially the successful rescue of the premature children is still serious challenge for the newborn workers at home and abroad. Reported in the literature, neonatal respiratory distress syndrome (NRDS) is about1%of all newborns and accounts for7.8%of all preterm children. An average of every three cases of gestational age <34weeks premature children cases the RDS. We should take a series of interventions for prevention of the RDS before birth. Some signs of preterm usually occure, we are ripe to take intrauterine referral interventions if time and conditions permits. However, surfactant increases in the delivery process and it is not recommended for elective cesarean section on gestational age less than39weeks of low-risk pregnancy, because this can lead to the occurrence of RDS or other respiratory diseases. If they can be given birth in hospital neonatal with NICU for gestational age less than27weeks premature children and decrease one years’ mortality rate by half.NRDS also known as hyaline membrane disease (HMD) is one of the main causes of neonatal respiratory failure and one of the main reasons of neonatal deaths. NRDS is due to the lack of pulmonary surfactant (PS) and end-expiratory alveolar atrophy shortly after birth that results in progressive respiratory distress and respiratory failure, mainly seen in preterm infants. The smaller gestational age and the lower body weight are higher. Greater than30weeks gestational age incidence is60%to80%,30to32weeks15%to30%and greater than37weeks is5percent. In addition, for children of diabetic mothers, cesarean section, the second child of pairs and baby boy, the RDS’s incidence is higher. After birth in6-12hours of onset (in severe cases, immediately after birth) performance that shortness of breath (greater than60beats/min), cyanosis, moaning, nose fan, inspiratory three depressions and breath moaning. Shortness of breath respiratory distress is progressively increasing in the characteristics of this disease. The condition begins to improve for2to4days after birth. The pathology is that the alveolar wall hyaline, membrane hyaline membrane into the ring and adherent. A typical chest X-ray is ground glass change, air bronchogram or white lung that can be confirmed.The prevention goal of neonatal respiratory distress syndrome is to maximize survival and minimize the potential adverse effects. This helps to improve the quality of life. Therefore, timely and effective treatment is necessary. Ventilator support for treatment and the use of surfactants are important measure in neonatal respiratory therapy. The preventive or therapeutic use of PS can reduce the pneumothorax (lung air leak) and neonatal death for the children who have occurred or may occure NRDS. All risk of RDS infants should be treated as soon as possible, and the need of surfactant therapy in children can be by "INSURE" technology (tracheal intubation, surfactant and extubation to use CPAP) to avoid mechanical ventilation. Randomized trial has confirmed that it can reduce the time of the use of mechanical ventilation and the incidence of bronchopulmonary dysplasia (BPD).But still part of the children with the use of PS because of respire failure need ventilator support treatment. The conventional mechanical ventilation is main way of breathing support for the NRDS. Its pressure limits the time cycle and change the size of tidal volume through the pressure control. The conventional ventilator due to the lack of monitoring of tidal volume so inspiratory time is blind. The adjustment arising from the consequences of excessive pressure and long inspiratory time caused by the transpulmonary pressure and mean airway pressure increase which result in lung injury or treatment failure and pulmonary air leak, necrotizing tracheal bronchitis, chronic lung disease (CLD) and retinopathy of prematurity(ROP). So how to reduce ventilator-induced complications is an important issue. It has cause attaches great importance for clinicians. There has been more research through a variety of ways and means to reduce its occurrence, including use of lower pressure and low tidal volume, proper breath positive end-expiratory pressure, permissive hypercapnia, lung surfactant and high frequency ventilation. The HFOV has been developed in the1980s as a new ventilation mode have significant clinical efficacy in the treatment of NRDS. With the establishment and improvement of the NICU at home and abroad, the application occurs more and more.With high frequency of low ventilation pressure, low tidal volume, low inspired oxygen concentration, the formation of two-way wave form airway pressure inspiratory and expiratory and an active process and can improve oxygenation without increasing barotraumas and improve the hypoxic state to improve the cure rate and quality of life. So it is safe and effective.To date, whether the HFOV caused the risk of intraventricular hemorrhage and periventricular leukomalacia is still more controversial. Most of the reports denied but some reported that almost constant mean airway pressure of the HFOV limit intracranial venous reflux and cause intracranial pressure. It also is passed in the intracranial children with intracranial pressure fluctuations that lead to an increase of intracranial hemorrhage dangerous. The treatment of early over briefing with HFOV cause low CO2acidosis and reduction in cerebral blood flow can cause ischemic brain injury. These studies mainly are related to neonates especially premature children because of their central nervous immature. It may be related to the severity and timing of treatment, health care workers on the ventilator proficiency and other factors. These may result in restricting the use of HFOV. There are domestic units about the treatment of HFOV in neonatal respirator distress syndrome, but it is exile for randomized controlled clinical trial with larger sample size. ObjectWe assess the efficacy and safety of HFOV through conventional mechanical ventilation and high-frequency oscillatory ventilation in the treatment of neonatal respiratory distress syndrome and promote it for the clinical application.SubjectFrom June2009to June2011in the hospital neonatology RDS children treated a total of64cases were included and the time of admission was1h to15h. The standard refers to the practical neonatologist, X-ray is II-IV NRDS of signs. Based on fetal age, weight, age, use of PS and other serious complications were randomly divided into the HFOV group (n=34) and the CMV group (n=30). The HFOV group includes15males and19females. Fetal age31.12±1.89weeks (27～34weeks), birth weight1.47±0.41Kg(0.85～2.25Kg), the use of PS treatment of18cases accounts for52.94%of the HFOV group. The CMV group includes13males and17females. Fetal age31.33±1.63weeks (28to34weeks), birth weight1.52±0.41Kg (0.90～2.35Kg). The use of PS treatment of17cases accounts for56.67%of the CMV group. Between the difference of two groups with fetal age, birth weight, gender, and the use of PS is statistically comparable (P>0.05).Method1. HFOV treatment methodsUsing high frequency oscillatory ventilation with Stephanie and Sensor Medics3100A’s high-frequency oscillation ventilator. Initial parameters:frequency(F):10to15Hz, pressure amplitude(ΔP):25to40cmH2O, bias airflow (the Bias Flow)6～8L/min, the average airway pressure (Paw):15～20cmH2O, fraction of inspiratory oxygen Fi (O2):60%to100%, absorption/expiratory ratio (I/E):33%or to see or touch the thorax. Adjusting parameters according to blood gas analysis and clinical symptoms. Improving Pa (O2), the following methods can be used (adjust one or two parameters in chronological order):Increasing Fi (O2)5%to10%or Paw0.10～0.20kPa (1～2cm H2O). Lowering Pa (CO2) by improving (ΔP)0.49～0.98kPa (5～10cmH20) or reducing Paw0.10～0.20kPa (1～2cmH2O).2. CMV treatment methodsUsing of the conventional mechanical ventilation with Stephanie and Drager ventilator, the initial parameters:Fi (O2)60%to100%, frequency:20～60times/min, and inspiratory time:0.3-0.6second, peak inspiratory pressure (PIP):20～30cmH2O and end-expiratory positive airway pressure (PEEP):4-7cmH2O.Adjusting parameters according to blood gas analysis and clinical manifestations. Improving Pa (O2), the following methods may be used (adjustment one or two parameters in chronological order):Increasing FiO25%～10%, improving PIP0.10～0.20Pa. For lower Pa (CO2), can improve PIP0.10～0.20kPa (1～2cmH2O), PEEPO.10-0.20kPa (1～2cmH2O) or increase respiratory rate.3. The general treatmentThe children were monitored of vital signs and were treated, including warmth, support nutrition, prevention of infection, bleeding, maintaining water, electrolyte and acid-base balance and the protection of organs. The Fi(O2), pH, Pa(O2) and Pa (CO2) were recorded in the time before of mechanical ventilation,8to12h,24to48h, after48h and calculated the oxygenation index (OI) OI=Fi (O2)×Paw×100÷Pa (O2).We recorded the treatment of complications and disease outcome.Statistical analysisApplicate SPSS13.0. Mean±standard deviation(x±s). Statistical methods include factorial analysis of variance, independent samples t-test, single factor analysis of variance and and the test Pearson χ2.P<0.05means the difference is statistically significant.ResultIn different mechanical ventilation treatment and different time, Fi(O2), pH, Pa(O2), Pa(CO2) and OI exist an interaction effect (F=11.031,3.534,5.970,4.862,17.177,P<0.05).The above indicators of two groups at several time points within48hours increase(F=122.088,58.792,111.492,38.692,205.073P<0.01). The efficacy of different treatment methods produced significant(F=92.554,33.813,68.303,27.290,127.962.P<0.01). There is significant in difference same time and different approaches for pair wise comparisons (P<0.05).The difference of the blood gas analysis was not statistically significant before treatment (P>0.05). The pH and the Pa (O2) increased significantly in the HFOV group in the treatment at the time of8～12h,24～48h and after48h. Pa (CO2) and OI decreased significantly than the CMV (P<0.05). Pulmonary air leak and chronic lung disease in the HFOV group were lower than the CMV group(P<0.05). But other complications showed no significant difference (P>0.05). The cure rate in the two groups was no significant difference(P>0.05).ConclusionThis study showed that Pa (CO2) and fraction of inspiratory oxygen decreased. The pH and Pa (O2) significantly improved and it quickly relieved the symptoms of hypoxia and aerobic concentration decreased significantly after treatment by HFOV. This suggested that HFOV improved pulmonary ventilation function and can quickly and effectively improve pulmonary function. The lower oxygen concentration and airway pressure of HFOV for gas exchange can reduce the incendence of pulmonary air leak and CLD. HFOV has a better pulmonary oxygenation and lower pulmonary air leak and than the CMV. It is effective and safe. It does not increase the incidence of intracranial hemorrhage, pulmonary hemorrhage or other complications.