Regional distribution of chest wall displacements in infants during high-frequency ventilation.

The distribution of ventilation during high-frequency ventilation (HFV) is asynchronous, nonhomogeneous, and frequency dependent. We hypothesized that differences in the regional distribution of ventilation at different oscillatory frequencies may affect gas exchange efficiency. We studied 15 newborn infants with a median gestational age of 28.9 (26.4-30.3) wk and body weight of 1.0 (0.8-1.4) kg. Five ventilation frequencies (5, 8, 10, 12, and 15 Hz) were tested, keeping carbon dioxide diffusion coefficient constant. The displacements of 24 passive markers placed on the infant's chest wall were measured by optoelectronic plethysmography. We evaluated the amplitude and phase shift of displacements of single markers placed along the midline and the regional displacements of the chest wall surface. Blood gases were unaffected by frequency. Chest wall volume changes decreased from 1.6 (0.4) ml/kg at 5 Hz to 0.7 ml/kg at 15 Hz. At all frequencies, the abdomen (AB) oscillated more markedly than the ribcage (RC). The mean (SD) AB/RC ratio was 1. 95 (0.7) at 5 Hz, increased to 2.1 (1.3) at 10 Hz, and then decreased to 1.1 (0.5) at 15 Hz ( P < 0.05 vs. 10 Hz). Volume changes in the AB lagged the RC and this phase shift increased with frequency. The AB oscillated more than the RC at all frequencies. Regional oscillations were highly inhomogeneous up to 10 Hz, and they became progressively more asynchronous with increasing frequency. When the carbon dioxide diffusion coefficient is held constant, such differences in regional chest wall expansion do not affect gas exchange. NEW & NOTEWORTHY We characterized the regional distribution of chest wall displacements in infants receiving high-frequency oscillatory ventilation at different frequencies. When carbon dioxide diffusion coefficient is held constant, there is no combination of frequency and tidal volume that optimizes gas exchange. The relative displacement between different chest wall compartments is not affected by frequency. However, at high frequencies, chest wall displacements are lower, with the potential to reduce total and regional overdistension without affecting gas exchange.

Effect of continuous positive airway pressure on breathing variability in early preterm lung disease.

OBJECTIVES: In preterm infants, the application of nasal Continuous Positive Airway Pressure (nCPAP) improves lung function through several mechanisms and may interact with the control of breathing. Our aim was to evaluate the effect of increasing/decreasing nCPAP on gas exchange, breathing pattern, and its variability in preterm infants. METHODS: Fifeteen infants with mild to moderate respiratory distress syndrome (RDS) were studied on the first day of life. Infants had a mean (SD) gestational age of 30 + 4 (3 + 4) weeks + day and body weight of 1405 (606) g. nCPAP was increased every 10 min stepwise (0-4-8-10 cmH2 O) and then decreased every 20 min (8-6-4-2 cmH2 O). At each step, vital parameters, oxygenation, and chest wall volume changes (optoelectronic plethysmography) were evaluated. Tidal volume (VT ), inter-breath interval (IBI), end-expiratory lung volume (EELV) changes, and other breathing pattern parameters were computed breath-by-breath. The correlation properties of VT , IBI, and EELV were quantified by detrended fluctuation analysis, computing the scaling exponent α. RESULTS: During nCPAP, oxygenation improved and VT decreased significantly compared with no nCPAP. No significant changes in breathing pattern were observed between nCPAP levels. α of EELV was significantly higher off nCPAP than during nCPAP, suggesting that nCPAP helps stabilize EELV control mechanisms. CONCLUSIONS: In our population of preterm infants with mild to moderate RDS, in the first day of life, nCPAP improved gas exchange, VT , and EELV stability independent of nCPAP level.

Effect of frequency on pressure cost of ventilation and gas exchange in newborns receiving high-frequency oscillatory ventilation.

BackgroundWe hypothesized that ventilating at the resonant frequency of the respiratory system optimizes gas exchange while limiting the mechanical stress to the lung in newborns receiving high-frequency oscillatory ventilation (HFOV). We characterized the frequency dependence of oscillatory mechanics, gas exchange, and pressure transmission during HFOV.MethodsWe studied 13 newborn infants with a median (interquartile range) gestational age of 29.3 (26.4-30.4) weeks and body weight of 1.00 (0.84-1.43) kg. Different frequencies (5, 8, 10, 12, and 15 Hz) were tested, keeping carbon dioxide diffusion coefficient (DCO2) constant. Oscillatory mechanics and transcutaneous blood gas were measured at each frequency. The attenuation of pressure swings (ΔP) from the airways opening to the distal end of the tracheal tube (TT) and to the alveolar compartment was mathematically estimated.ResultsBlood gases were unaffected by frequency. The mean (SD) resonant frequency was 16.6 (3.5) Hz. Damping of ΔP increased with frequency and with lung compliance. ΔP at the distal end of the TT was insensitive to frequency, whereas ΔP at the peripheral level decreased with frequency.ConclusionThere is no optimal frequency for gas exchange when DCO2 is held constant. Greater attenuation of oscillatory pressure at higher frequencies offers more protection from barotrauma, especially in patients with poor compliance.

Enteral nutrition for preterm infants: by bolus or continuous? An update.

Optimization of nutritional management of preterm infants is crucial for achievement of their long-term health. Enteral nutrition is preferred to total parenteral nutrition (TPN) because the former avoids complications related to vascular catheterization, sepsis, adverse effects of TPN, and fasting. Due to the lack of ability of preterm infants to coordinate suckling, swallowing, and breathing, tube feeding is necessary for most infants less than 1500 g to ensure sufficient feeding tolerance, to support optimal growth and to reduce the risk of aspiration. Therefore, feeding by orogastric or nasogastric tube using either continuous or intermittent bolus delivery of formula or human milk is common practice for these infants. Theoretical risks and benefits of both continuous nasogastric milk feeding and intermittent bolus milk feeding have been proposed. According to the literature, continuous nutrition could be preferred in smaller infants (as those with a birthweight below 1250 g) or hemodynamically impaired infants; in stable growing infants nutrition can be administered intermittently as in healthy term infants.

Enteral feeding of intrauterine growth restriction preterm infants: theoretical risks and practical implications.

Intrauterine growth restriction (IUGR) infants are thought to have impaired gut function after birth secondary to intrauterine redistribution of the blood flow, due to placental insufficiency, with a consequent reduction of gut perfusion. For this reason, infants complicated by IUGR have been considered at higher risk of feeding intolerance. Postnatal evaluation of splanchnic perfusion, through Doppler of the superior mesenteric artery, and of splanchnic oxygenation, through near infrared spectroscopy measurements, may be useful in evaluating the persistence (or not) of the redistribution of blood flow occurred in utero.

Nutritional approach to preterm infants on noninvasive ventilation: An update.

Nutrition and pulmonary function in very-low-birth-weight infants (VLBWIs) are strictly related. Preterm infants on noninvasive ventilation may have respiratory instability that can interfere with feeding tolerance. Moreover, feeding may impair pulmonary function. These infants have nutritional requirements different from nonventilated infants. The main challenge of the nutritional support in such patients is to guarantee adequate caloric intake while avoiding episodes of feeding intolerance. The aim of this study was to review the issues and strategies of enteral feeding of preterm infants on noninvasive ventilation.

Relationship between Mean Airways Pressure, Lung Mechanics, and Right Ventricular Output during High-Frequency Oscillatory Ventilation in Infants.

OBJECTIVE: To characterize changes in lung mechanics and right ventricular output (RVO) during incremental/decremental continuous distending pressure (CDP) maneuvers in newborn infants receiving high-frequency oscillatory ventilation, with the aim of evaluating when open lung maneuvers are needed and whether they are beneficial. STUDY DESIGN: Thirteen infants on high-frequency oscillatory ventilation were studied with a median (IQR) gestational age of 261 (253-291) weeks and median (IQR) body weight of 810 (600-1020) g. CDP was increased stepwise from 8 cmH2O to a maximum pressure and subsequently decreased until oxygenation deteriorated or a CDP of 8 cmH2O was reached. The lowest CDP that maintained good oxygenation was considered the clinically optimal CDP. At each CDP, the following variables were evaluated: oxygenation, respiratory system reactance (Xrs), and RVO by Doppler echocardiography. RESULTS: At maximal CDP reached during the trial, 19 [1] cmH2O (mean [SEM]), oxygenation markedly improved, and Xrs and RVO decreased. During deflation, oxygenation remained stable over a wide range of CDP settings, Xrs returned to the baseline values, and RVO increased but the baseline values were not readily restored in all patients. CONCLUSION: These results suggest that Xrs and RVO are more sensitive than oxygenation to overdistension and they may be useful in clinical practice to guide open lung maneuvers.

Impact of Continuous vs Bolus Feeding on Splanchnic Perfusion in Very Low Birth Weight Infants: A Randomized Trial.

OBJECTIVE: To detect changes in splanchnic perfusion and oxygenation induced by 2 different feeding regimens in infants with intrauterine growth restriction (IUGR) and those without IUGR. STUDY DESIGN: This was a randomized trial in 40 very low birth weight infants. When an enteral intake of 100 mL/kg/day was achieved, patients with IUGR and those without IUGR were randomized into 2 groups. Group A (n = 20) received a feed by bolus (in 10 minutes), then, after at least 3 hours, received the same amount of formula by continuous nutrition over 3 hours. Group B (n = 20) received a feed administered continuously over 3 hours, followed by a bolus administration (in 10 minutes) of the same amount of formula after at least 3 hours. On the day of randomization, intestinal and cerebral regional oximetry was measured via near-infrared spectroscopy and Doppler ultrasound (US) of the superior mesenteric artery was performed. Examinations were performed before the feed and at 30 minutes after the feed by bolus and before the feed, at 30 minutes after the start of the feed, and at 30 minutes after the end of the feed for the 3-hour continuous feed. RESULTS: Superior mesenteric artery Doppler US showed significantly higher perfusion values after the bolus feeds than after the continuous feeds. Near-infrared spectroscopy values remained stable before and after feeds. Infants with IUGR and those without IUGR showed the same perfusion and oxygenation patterns. CONCLUSION: According to our Doppler US results, bolus feeding is more effective than continuous feeding in increasing splanchnic perfusion. TRIAL REGISTRATION: ClinicalTrials.gov: NCT01341236.

Cerebral and somatic NIRS-determined oxygenation in IUGR preterm infants during transition.

BACKGROUND: Fetal growth restriction (intra-uterine growth restriction [IUGR]) has a considerable impact on perinatal morbidity. Preterm IUGR infants are prone to impaired intestine function. Near-infrared spectroscopy (NIRS) has been used to monitor oxygenation status of the brain and of the intestine. PATIENTS AND METHODS: We conducted a prospective case-control study at our NICU in 20 preterm infants of whom 10 infants complicated by compared with 10 non-IUGR preterm infants. Splanchnic and cerebral regional oximetry values were measured with NIRS. Three hours of consecutive recordings were performed in the first 24 h of life, T0, and during the transitional period, T1. The cerebral/splanchnic oxygenation ratio, CSOR, (cerebral regional saturations [rScO2]/splanchnic regional saturations [rSsO2]) was also calculated. RESULTS: Both in the IUGR and the non-IUGR infants, at T0 and T1 monitoring time-points, the rSO2 values were higher in the cerebral district when compared to those of the splanchnic area. Comparison of the NIRS parameters between the IUGR and non-IUGR infants at T0 showed no difference in rScO2, while rSsO2 was significantly lower in the IUGR group. At T1, rScO2 was significantly lower and rSsO2 higher in the IUGR group. CONCLUSIONS: Cerebral/splanchnic vascular adaptation of IUGR infants to the extra-uterine environment is characterized by a postnatal persistence of the brain sparing effect with reperfusion in the transitional period.

Impact of a dedicated enteral feeding system in an Italian NICU.

The inadvertent connection between an enteral feeding system and a nonenteral system such as a vascular line may occur. Intravenous administration of an enteral admixture may lead to severe, sometimes lethal, complications. We report our experience with a new set of enteral devices that may prevent any risk of misconnection.

Monitoring Doppler patterns and clinical parameters may predict feeding tolerance in intrauterine growth-restricted infants.

AIM: To detect predictors of feeding tolerance in intrauterine growth restriction (IUGR) infants with or without brain-sparing effect (BS). METHODS: We conducted a case-control study in 70 IUGR infants (35 IUGR with BS, matched for gestational age with 35 IUGR infants with no BS). BS was classified as pulsatility index (PI) ratio [umbilical artery (UAPI) to middle cerebral artery (MCAPI) (U/C ratio)] > 1. Clinical parameters of feeding tolerance - days to achieve full enteral feeding (FEF) - were compared between the IUGR with BS and IUGR without BS infants. Age at the start of minimal enteral feeding (MEF) was analysed. RESULTS: Achievement of FEF was significantly shorter in IUGR infants without BS than in IUGR with BS. IUGR with BS started MEF later than IUGR without BS infants. Significant correlation of MEF and FEF with UA PI, U/C ratio and CRIB score was found. Multiple linear regression analysis showed significant correlations with CRIB score and caffeine administration (MEF only), and sepsis (FEF only) and U/C ratio (for both). CONCLUSION: Impaired gut function can be early detected by monitoring Doppler patterns and clinical parameters.

Survey on retinopathy of prematurity (ROP) in Italy.

BACKGROUND: This study aims to investigate the incidence and the relative risk factors of retinopathy of prematurity (ROP) and posterior-ROP (P-ROP): ROP in Zone I and posterior Zone II, as well as to analyze the occurrence of surgical treatment of ROP and to evaluate the short term outcome of the disease in Italy. METHODS: It is a prospective multicenter observational study; all infants with a birth weight (BW) ≤ 750 g and/or a gestational age (GA) ≤27 weeks born between January 1st 2008 and December 31st 2009 in 25 III level Italian neonatal intensive care units were eligible for the study. RESULTS: 421 infants were examined: 265 (62.9%) developed ROP and 102 (24.2%) P-ROP. CONCLUSIONS: P-ROP is the most aggressive type of ROP. It associates with lower GA and sepsis. Obstetricians and Neonatologists must focus on the reduction of severe preterm births and on the prevention of neonatal early and late onset sepsis in order to reduce the incidence of P-ROP.

Feeding issues in IUGR preterm infants.

Intra-uterine growth restriction (IUGR) is a severe and quite common problem in obstetrics. A condition of placental dysfunction can lead to a cardiovascular adaptation in the fetus characterized by a redistribution of cardiac output to maintain oxygen supply to the heart, adrenal glands and brain - the so-called brain sparing effect - at the expense of visceral organs (such as the gastrointestinal system). This condition may predispose IUGR infants to impaired gut function after birth. A higher incidence of necrotizing enterocolitis (NEC) is documented in IUGR preterm infants. Therefore, a common practice in neonatal intensive care units is to delay feeds to reduce the risk of feeding intolerance. Recent trials, however, have shown that early enteral feeding in IUGR infants is safe and it would appear, on the basis of the few available data, that breast milk could offer protection against NEC. This mini-review offers an update on feeding in IUGR infants. Future perspectives on the usefulness of Doppler and regional splanchnic and cerebral saturation monitoring for deciding when to start feeding are also provided.

Feeding tolerance of preterm infants appropriate for gestational age (AGA) as compared to those small for gestational age (SGA).

Preterm infants are often considered too unstable to be fed enterally so they are exposed to complications related to a prolonged enteral fasting. Our study aims to compare feeding tolerance of adequate for gestational age (AGA) versus small for gestational age (SGA) infants and to evaluate which perinatal factors affect feeding tolerance (measured as time to achieve full enteral feeding, FEF). Inborn infants with a gestational age (GA) less than 32 weeks, born from January 2006 to December 2010, were eligible for this study. We enrolled 310 infants. The time to FEF was longer for SGA infants than for AGA, while a longer GA was associated to a reduced time to FEF. A beneficial effect was observed for antenatal steroids, while Apgar score below 7, the administration of inotrops or caffeine, the occurrence of sepsis or NEC and the presence of PDA were associated to a longer time to FEF. When evaluated jointly with a multivariate analysis, GA (p < 0.0001), antenatal steroids prophylaxis (p = 0.002), SGA (p < 0.0001) and occurrence of NEC (p = 0.0002) proved to have independent prognostic impact on the time to FEF. Feeding tolerance is better as GA increases, and worsen in SGA infants. Antenatal betamethasone is effective in reducing the time to FEF in both AGA and SGA.

Evaluation of splanchnic oximetry, Doppler flow velocimetry in the superior mesenteric artery and feeding tolerance in very low birth weight IUGR and non-IUGR infants receiving bolus versus continuous enteral nutrition.

BACKGROUND: IUGR infants are thought to have impaired gut function after birth, which may result in intestinal disturbances, ranging from temporary intolerance to the enteral feeding to full-blown NEC.In literature there is no consensus regarding the impact of enteral feeding on intestinal blood flow and hence regarding the best regimen and the best rate of delivering the enteral nutrition. METHODS/DESIGN: This is a randomized, non-pharmacological, single-center, cross-over study including 20 VLBW infants. Inclusion criteria * Weight at birth ranging: 700-1501 grams * Gestational age up to 25 weeks and 6 days * Written informed consent from parents or guardians Exclusion criteria * Major congenital abnormality * Patients enrolled in other trials * Significant multi-organ failure prior to trial entry * Pre-existing cutaneous disease not allowing the placement of the NIRS' probe. In the first 24 hours of life, between the 48th and 72nd hours of life, and during Minimal Enteral Feeding, all infants' intestinal perfusion will be evaluated with NIRS and a Doppler of the superior mesenteric artery will be executed.At the achievement of an enteral intake of 100 mL/Kg/day the patients (IUGR and NON IUGR separately) will be randomized in 2 groups: Group A (n=10) will receive a feed by bolus (in 10 minutes); then, after at least 3 hours, they will receive the same amount of formula administered in 3 hours. Group B (n=10) will receive a feed administered in 3 hours followed by a bolus administration of the same amount of formula (in 10 minutes) after at least 3 hours. On the randomization day intestinal and cerebral regional oximetry will be measured via NIRS. Intestinal and celebral oximetry will be measured before the feed and 30 minutes after the feed by bolus during the 3 hours nutrition the measurements will be performed before the feed, 30 minutes from the start of the nutrition and 30 minutes after the end of the gavage. An evaluation of blood flow velocity of the superior mesenteric artery will be performed meanwhile. The infants of the Group A will be fed with continuous nutrition until the achievement of full enteral feeding. The infants of the Group B will be fed by bolus until the achievement of full enteral feeding. DISCUSSION: Evaluations of intestinal oximetry and superior mesenteric artery blood flow after the feed may help in differentiating how the feeding regimen alters the splanchnic blood flow and oxygenation and if the changes induced by feeding are different in IUGR versus NON IUGR infants. TRIAL REGISTRATION NUMBER: NCT01341236.