Variety of expiratory resistance between different continuous positive airway pressure devices for preterm infants.

Continuous positive airway pressure (CPAP) systems for preterm infants work with conventional ventilators or use a jet ventilation system. It is assumed that the most important advantage of jet-CPAP systems is a lower expiratory resistance (R(E) ). We investigated the R(E) of seven different CPAP systems. We studied two primary-care CPAP systems, three jet-CPAP generators, and two conventional CPAP devices. All devices were adjusted at 6 mbar and connected with a test lung simulating a standardized expiration volume. Maximum pressure increase during expiration was measured and maximum R(E) was calculated. In primary-care CPAP devices, the maximum R(E) of the Benveniste valve was 9.7 mbar/L/s (SD 1.2) while that of the Neopuff was 102.8 mbar/L/s (SD 7.9) (P < 0.01). In jet-CPAP devices, the R(E) of the Infant Flow was 6.8 mbar/L/s (SD 1.7), the one of the Medijet REF 1000 was 43.5 mbar/L/s (SD 1.5), and that of the Medijet REF 1010 was 36.7 mbar/L/s (SD 0.3) (P < 0.01). In conventional CPAP systems, the R(E) of the Baby Flow was 29.7 mbar/L/s (SD 1.1) and that of the Bubble CPAP was 37.1 mbar/L/s (SD 4.3) (P < 0.01). All CPAP devices created an R(E). Jet-CPAP devices did not produce lower R(E) than conventional CPAP devices.

Danger of low pressure alarm failure in preterm infants on continuous positive airway pressure.

In certain settings of conventional continuous positive airway pressure (CPAP) application, the ventilator may not be able to detect dislodgement of the prongs. This occurs especially in settings with high flow and small prongs. We investigated the relation between ventilator flows, size of the nasal prongs, and pressure generated within the ventilator circuit due to the flow resistance of the prongs. We studied a Baby-flow CPAP connected to a Babylog 8000plus ventilator. Five prongs of increasing size (x-small, small, medium, large, x-large) and one nose mask were connected to the CPAP in turn. Starting at 30 lpm, the flow was reduced in 2 lpm steps. The dynamic pressure caused by the flow resistance of the prongs within the ventilator circuit was recorded. For all devices, we observed a correlation between the reduction of the flow and the reduction in pressure within the ventilator circuit. However, the flow resistance of the x-small prongs generated the highest dynamic pressure (30 mbar at 22 lpm) within the ventilator circuit while the mask gave rise to the lowest pressure (9 mbar at 30 lpm). The pressure value generated with x-small prongs at low flow rate was observed at high flow rate with x-large prongs or with a mask. We conclude that in settings with high flow rates, low CPAP levels, and small prongs, the resistance of the prongs will create enough dynamic pressure within the ventilator circuit to permit the ventilator to compensate a large leakage flow by closing the expiratory valve. Thus, in case of dislodgement of the prongs, the pressure within the ventilator circuit will not decrease below the alarm level, and the machine will not be able to generate an alarm.

Must screening examinations for retinopathy of prematurity necessarily be painful?

PURPOSE: This study investigates the impact of the length of the examination, the insertion of eyelid specula, and the indentation of the globe on the pain and stress sensation of premature infants. METHODS: Ninety-two premature infants in three neonatal wards were included. In two wards, the patients were examined using eyelid specula and scleral indentation as recommended in the official guidelines. In the third ward, the investigation time was minimized and ophthalmoscopy was performed without eyelid specula and scleral indentation. Physical and mental disturbance of the patients was assessed by the Neonatal Infant Pain Score and by monitoring the heart rate. The results were divided into two groups: in the one, eyelid specula and scleral indentation were used, whereas in the other one, they were not used. An independent-samples t-test was performed, which allowed us to calculate the correlation between the way the examination was executed and the condition of the patients. RESULTS: Demographic data and baseline values of heart rate and pain score did not differ between the two groups. Heart rate and pain score during and after the investigation were significantly higher and increased significantly with the duration of the examination for the patients who were investigated using lid specula and scleral indentation. CONCLUSION: Our study shows that indirect ophthalmoscopy without specula causes significantly less stress to infants than screening with lid specula and scleral indentation.

Long hospitalization is the most important risk factor for early weaning from breast milk in premature babies.

AIM: To identify certain variables related to the infants' course that might have an impact on the mothers' decision to breastfeed. PATIENTS AND METHOD: Retrospective survey including all patients <1500 g birth weight (BW) treated between January 1, 2000 and December 31, 2005 at the Neonatal Intensive Care Unit of the Medical University of Vienna who were not transferred to another hospital. Multiple regression analysis of the following variables was carried out: gestational age (GA), BW, length of stay (LOS), parity, singleton or multiple gestation, sex and severe morbidity. RESULTS: Of the 239 patients included, 142 (60%) were fed breast milk at the time of final discharge, 97 (40%) were fed formula. LOS was significantly correlated with the probability of being breastfed: the shorter it was, the higher was the probability of being breastfed at the time of final discharge (p = 0.0064 for singletons, p = 0.001 for multiples). Lower GA also increased the probability of being breastfed, but this was only statistically significant for multiples (p = 0.001). CONCLUSION: This study shows clearly that the most important influencing factor on the mothers' decision to continue breastfeeding is the LOS. Thus more emphasis should be put on encouraging mothers to continue lactation throughout their babies' hospital stay.

A new modified Seldinger technique for 2- and 3-French peripherally inserted central venous catheters.

This study describes a modified Seldinger technique for 2- and 3-French peripherally inserted central venous catheters: A device similar to that used in heart catherisation with a standard micro-introducer serving as sheath and an arterial catheter serving as inner dilator was pushed forward over a wire guide that had before been inserted via a peripheral venous catheter. With this method 2-and 3-French catheters could be safely inserted into peripheral veins of 14 paediatric patients. In conclusion successful insertion of a small peripheral venous catheter offers in most cases a possibility for the placement of a central venous line.

Effect of the Y-piece of the ventilation circuit on ventilation requirements in extremely low birth weight infants.

OBJECTIVE: Volutrauma caused by high tidal volumes contributes considerably to the development of bronchopulmonary dysplasia. Yet high tidal volumes are required to overcome dead space. In an experimental arrangement we tested whether reduction of dead space might reduce ventilation requirements and thus reduce volutrauma in preterm infants. MATERIALS AND METHODS: The time required to eliminate CO2 by standardized mechanical ventilation from a preterm infant's test lung flooded with CO2 was measured. Four different Y-pieces and flow sensor combinations were tested with and without a device for closed suction: Y-piece without flow sensor; integrated flow sensor; small dead-space flow sensor; and a new dead-space free-flow sensor for preterm infants. CO2 concentrations were measured by a capnograph. Mean CO2 elimination times (+/-SD) were compared. RESULTS: Mean CO2 elimination time was 37.5 s (+/-1.18 s) with and 37.4 s (+/-0.97 s) without closed suction device for the Y-piece without flow sensor, 47.7 s (+/-0.82 s) and 45.5 s (+/-1.18 s) for the integrated flow sensor, 42.5 s (+/-1.27 s) and 41.1 s (+/-0.99 s) for the small dead-space flow sensor and 38.3 s (+/-1.16 s) and 36.8 s (+/-0.79 s) for the dead-space free-flow sensor. CONCLUSION: CO2 elimination time with and without closed suction device was nearly identical for the Y-piece without flow sensor and for the dead-space free-flow sensor. With both systems, ventilation requirements were significantly lower than for the integrated flow sensor and for the small dead-space flow sensor (integrated flow sensor vs dead-space free-flow sensor 23.6 and 24.5%, respectively, small dead-space flow sensor vs dead-space free flow sensor 11.7 and 10.9%, respectively); thus, we think that introduction of the innovative dead-space free-flow sensor into clinical practice might reduce incidence and severity of bronchopulmonary dysplasia by reduction of volutrauma.

Dead-space washout by split-flow ventilation. A new method to reduce ventilation needs in premature infants.

OBJECTIVE: Chronic lung disease caused by volutrauma is one of the most important consequences of preterm delivery. In this pilot study a new method is presented that consists of flushing part of the dead space with fresh gas in order to reduce high tidal volumes, the chief cause of volutrauma. The aim of the study was to evaluate if the new method could reduce ventilatory effort in preterm infants by diminishing dead space. DESIGN AND SETTING: In split-flow ventilation, gas required for dead-space washout is split off from the regular ventilation circuit. The split flow bypasses the apparatus dead space and fills it retrogradely with fresh breathing gas, mainly in the pause between exhalation and inspiration. The mean per-minute ventilation and ventilation index after 12 h of conventional ventilation were compared with corresponding mean values after 12 h of split-flow ventilation in 17 preterm infants weighing <2,000 g. Statistical analysis was performed using the T -test for matched pairs. RESULTS: After switching from conventional ventilation to split-flow ventilation, the mean per-minute ventilation per kilogram of body weight decreased significantly from a mean value of 0.314+/-0.097 l/kg/min to 0.190+/-0.043 l/kg/min ( p <0.001), while the ventilation index decreased significantly from 28.47+/-7.48 to 16.10+/-4.13 ( p <0.001). CONCLUSION: Split-flow ventilation significantly reduces apparatus dead space during ventilation in preterm infants. This leads to reduced ventilatory effort.

In vitro comparison of noise levels produced by different CPAP generators.

INTRODUCTION: Minimization of noise exposure is an important aim of modern neonatal intensive care medicine. Binasal continuous positive airway pressure (CPAP) generators are among the most important sources of continuous noise in neonatal wards. The aim of this study was to find out which CPAP generator creates the least noise. METHOD: In an experimental setup, two jet CPAP generators (Infant Flow® generator and MediJet®) and two conventional CPAP generators (Bubble CPAP® and Baby Flow®) were compared. Noise production was measured in decibels in an A-weighted scale [dB(A)] in a closed incubator at 2 mm lateral distance from the end of the nasal prongs. Reproduction of constant airway pressure and air leak was achieved by closure of the nasal prongs with a type of adhesive tape that is semipermeable to air. RESULTS: The noise levels produced by the four generators were significantly different (p < 0.001). Values measured at a continuous constant flow rate of 8 l/min averaged 83 dB(A) for the Infant Flow® generator with or without sound absorber, 72 dB(A) for the MediJet®, 62 dB(A) for the Bubble CPAP® and 55 dB(A) for the Baby Flow®. CONCLUSION: Conventional CPAP generators work more quietly than the currently available jet CPAP generators.

A flow sensor suitable for use with split-flow ventilation--first preclinical data.

Volutrauma caused by artificial ventilation represents a major morbidity risk for premature infants. Our working group has recently developed an innovative "split-flow ventilation" system aiming at the reduction of tidal volumes (TVs). The main problem for the practical use of this system is the fact that conventional measurements of commercially available flow sensors are distorted by the split flow. In this study, we present the first preclinical data from testing an adapted flow sensor combination recognizing the split flow. A preterm infant test lung was conventionally ventilated, modified by insertion of a split-flow line. In addition to the customary flow sensor (FS-1), a second flow sensor (FS-2) was integrated into the split-flow line, and a third (FS-3) was placed at the exit of the test lung for reference measurements. The signals of all three flow sensors were read and processed by a computer. The program was set to graphically add up flow curves 1, 2, and 3 during one ventilation loop. After 10 runs, a mean curve of FS-1+2 was calculated and compared to the mean curve of FS-3. Furthermore, the mean TV of 10 runs measured by FS-1+2 was calculated and compared with the mean TV calculated by FS-3. The summation curve FS-1+2 proved identical to the reference curve FS-3. FS-1+2 yielded a TV of 6.6 +/- 0.01 mL (inspiratory) and 6.7 +/- 0.02 mL (expiratory). The corresponding values of FS-3 were 6.5 +/- 0.20 mL and 6.6 +/- 0.09 mL, respectively. According to our results, the presented flow sensor constellation allows exact flow measurements in the experimental setting and appears suitable for usage in a split-flow ventilation circuit under clinical conditions.