***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: OBJECTIVE To investigate whether changes in cardiac function and cerebral blood flow ( CBF ) precede the occurrence of peri/intraventricular hemorrhage ( P/IVH ) in extremely preterm infants . STUDY DESIGN In this prospect i ve observational study , 22 preterm infants ( gestational age 25.9 ± 1.2 weeks ; range 23 - 27 weeks ) were monitored between 4 and 76 hours after birth .  Cardiac function and changes in CBF and P/IVH were assessed by ultrasound every 12 hours . Changes in CBF were also followed by continuous monitoring of cerebral regional oxygen saturation ( rSO2 )  and by  calculating cerebral fractional oxygen extraction .  RESULTS Five patients developed P/IVH  ( 1 patient grade II and 4 patients grade IV ) . Whereas measures of cardiac function and CBF remained unchanged in neonates without P/IVH , patients with P/IVH tended to have lower left ventricular output and had lower left ventricle stroke volume and cerebral rSO2 and higher cerebral fractional oxygen extraction during the first 12 hours of the study . By 28 hours , these variables were similar in the 2 groups and myocardial performance index was lower and middle cerebral artery mean flow velocity higher in the P/IVH group . P/IVH was detected after these changes occurred . CONCLUSIONS Cardiac function and CBF remain stable in very preterm neonates who do not develop P/IVH during the first 3 postnatal days . In very preterm neonates developing P/IVH during this period , lower systemic perfusion and CBF followed by an increase in these variables precede the development of P/IVH . Monitoring cardiac function and cerebral rSO2 may identify infants at higher risk for developing P/IVH before the bleeding occurs Background : Changes in head posture influence brain hemodynamics . Optimal positioning has been recommended as 1 of 10 potentially better practice s to reduce the incidence of brain injury in preterm newborns . Objectives : The aim of this study was to evaluate by near-infrared spectroscopy ( NIRS ) the effect of different head and body positions and the influence of gestational age ( GA ) and nasal continuous positive airway pressure on brain hemodynamics in very preterm newborns . Methods : 24 stable preterm newborns were studied by NIRS in 6 different postures including head rotation and head inclination in both supine and prone positions . Changes in normalized tissue hemoglobin index ( nTHI ) and tissue oxygenation index ( TOI ) were measured after posture variations . Results : No statistically significant changes in nTHI and in TOI were found in the 6 postures . nTHI variations , expression of cerebral blood volume variations , were influenced by GA . A reduction in nTHI , with a stable TOI , in the less mature infants ( with GA ≤26 weeks ) , occurred on head rotation ; nTHI increased again when the head was derotated . Conclusions : Hemodynamic changes after posture variations depend on GA . Head rotation in newborns with GA ≤26 weeks produced a reduction in nTHI with stable TOI . Possible physiopathological mechanisms are discussed OBJECTIVE To compare breathing patterns and lung function in the supine , lateral , and prone positions in oxygen-dependent preterm infants . STUDY DESIGN Respiratory function in preterm infants receiving nasal continous positive airway pressure therapy for mild respiratory failure was evaluated by respiratory inductive plethysmography . Infants were r and omized to supine , left lateral , and prone positions for 3 hours . A nest provided a semiflexed posture for the infants placed in the left lateral position , similar to the in utero position . Tidal volume ( Vt ) , phase angle between abdominal and thoracic movements , rib cage contribution to Vt , and dynamic elevation of end-expiratory lung volume were measured . RESULTS Fraction of inspired O2 was similar in the 3 positions for 19 infants ( mean gestational age , 27±2 weeks ; mean birth weight , 950±150 g ; mean postnatal age , 17±5 days ) . However , arterial O2 saturation and Vt were higher in the left lateral and prone positions than in the supine position ( P<.05 ) . The phase angle between abdominal and thoracic movements was lower and rib cage contribution to Vt was higher in the left lateral and prone positions than in the supine position ( P<.05 ) . Dynamic elevation of end-expiratory lung volume was greater in the supine position than in the left lateral and prone positions ( P<.05 ) . CONCLUSION In oxygen-dependent preterm infants , both the left lateral and prone positions improve lung function by optimizing breathing strategy . In the neonatal intensive care unit , the left lateral position can be used as an alternative to the prone position for mild respiratory failure OBJECTIVE To test the hypothesis that near-infrared spectroscopy (NIRS)-determined patterns of regional cerebral oxygen saturation ( rScO2 ) , cerebral fractional tissue oxygen extraction ( cFTOE ) , and autoregulatory ability can identify neonates at risk for developing peri-intraventricular hemorrhage ( PIVH ) . STUDY DESIGN This case-control study is a sub analysis of 30 neonates who developed PIVH > 12 hours after admission as part of a lager prospect i ve observational cohort study comprising 650 preterm neonates born at ≤32 weeks ' gestational age . PIVH was diagnosed by cranial ultrasound , performed at least once daily . Mean arterial blood pressure ( MABP ) , NIRS-determined rScO2 , cFTOE , and MABP-rScO2 correlation were monitored from birth to 72 hours of age . RESULTS Infants with PIVH received more inotropic drugs before being diagnosed with PIVH . Significantly more infants with severe PIVH needed treatment for patent ductus arteriosus . The MABP-rScO2 correlation was > 0.5 significantly more often before mild/moderate PIVH and after severe PIVH compared with controls . rScO2 was higher and cFTOE lower in infants before severe PIVH . CONCLUSION NIRS-monitored rScO2 and cFTOE suggest cerebral hyperperfusion in infants with severe PIVH . Moreover , MABP-rScO2 correlation indicates more blood pressure-passive brain perfusion in infants with PIVH . Continuous assessment of patterns of cerebral oxygenation and arterial blood pressure may identify those preterm infants at risk for severe PIVH and prompt consideration of preventive measures Background : To minimize secondary lung injury , ventilated preterm infants are extubated as soon as possible . To maximize extubation success , they are often placed in prone position . The effect of extubation and subsequent prone positioning on lung volumes is currently unknown . Methods : Changes in end-expiratory lung volume ( ΔEELV ) , tidal volume ( VT ) , and ventilation distribution were monitored during transition from endotracheal to nasal continuous positive airway pressure and following prone positioning using electrical impedance tomography . In addition , the continuous distending pressure ( CDP ) and oxygen need ( FiO2 ) were recorded . Results : Twenty preterm infants ( GA 28.7 ± 1.7 wk ) were included . Following extubation , the CDP decreased from 7.9 ± 0.5 to 6.0 ± 0.2 cmH2O , while the FiO2 remained stable . Both ΔEELV and VT increased significantly ( P < 0.05 ) after extubation , without changing ventilation distribution . Prone positioning result ed in a further increase in ΔEELV ( P < 0.01 ) and a decrease in respiratory rate . VT remained stable but its distribution clearly shifted toward the ventral lung regions . Conclusion : Infants who are transitioned from invasive to noninvasive respiratory support are able to maintain their EELV and increase their VT . Prone positioning increases EELV and shifts tidal ventilation to the ventral lung regions . The latter suggests that infants should preferably be placed in prone position after extubation 
    Output:
    
Their results suggest that cerebral oxygenation is not significantly affected by changes in head positioning .
Conclusions : There is insufficient evidence regarding the effect of head positioning and tilting on the incidence of GMH-IVH and cerebral hemodynamics and oxygenation in preterm infants .