The main purpose of this study is to investigate effects of SIMV+VG (synchronized intermittent mandatory ventilation+volume guarantee) or PSV+VG (pressure support ventilation+volume guarantee) ventilation on vital signs, patient - mechanical ventilation synchrony, ventilation parameters and inflammatory mediators in neonates.

Term or preterm neonates may need mechanical ventilation due to different etiologies. In all patients aim of mechanical ventilation is to promote pulmonary gas exchange, reduce the respiratory work of patient. Ideal mechanical ventilation must minimize pulmonary trauma with low inspiratory pressures that obtains adequate and constant tidal volumes. Ventilation associated pulmonary injury is an important subject that must be considered during mechanical ventilation. Atelectotrauma, volutrauma, barotrauma and biotrauma must be monitored. Volutrauma, barotrauma and oxygen toxicity cause cytokine increase that results in biotrauma. This parenchymal inflammation is a risk factor for chronic lung disease which is an important morbidity of ventilated neonates.

From past to present neonates were ventilated with different ventilation modes including IMV (Intermittent Mandatory Ventilation), SIMV, A/C (Assist Control Ventilation), PSV,HFV (High Frequency Ventilation). Both PSV and SIMV are patient trigger ventilation modes but SIMV is a time cycled and PSV is a flow cycled mode. In recent years hybrid techniques were developed to combine beneficial features of volume and pressure limited ventilation. In commercial ventilation devices these techniques have different names as volume guaranteed pressure limited ventilation (Drager Babylog 8000), pressure regulated volume controlled ventilation (Siemens servo 3000), volume guaranteed pressure support ventilation (VIP Bird Gold).

Since there is not a standard protocol for mechanical ventilation of neonates different countries and even different NICU's use different ventilation protocols.

Literature supports volume targetted ventilation to reduce barotrauma with low maximum inspiratory pressures and to reduce volutrauma with constant tidal volumes. When A/C+VG and SIMV+VG were compared in a crossover trial, more constant tidal volumes were obtained in A/C mode. Inflammatory cytokines have also been measured in different groups of patients with variable ventilatory management techniques. So far there has not been a randomized study published comparing VG+SIMV with VG+PSV in newborns with regards to tidal volume , peak inspiratory pressure variability,or inflammatory cytokines. Therefore in this study the investigators aimed to compare these two ventilation modes with regards to short term outcome.

Inclusion Criteria:

• neonates with respiratory distress who need mechanical ventilation
• gestational age less than or equal to 37 weeks
• neonates who need mechanical ventilation within first 24 hours

Exclusion Criteria:

• neonates who need mechanical ventilation other than conventional ventilation