Ventilated Newborns Research Articles

Assessment of exhaled gases in ventilated preterm infants

Hydrogen peroxide (H2O2) production in exhaled air was measured in ventilated preterm newborns at 5, 24 and 48 hours after delivery, using originally designed method of exhaled breath condensate (EBC) collection. H2O2 production in expired gas was 812+/-34 pmol/20 min during the first measurement and then declined to 389+/-21 at 24 hours and 259+/-26 pmol/20 min at 48 hours.

Clinical Score Validation for Detecting Cardiac Output Variations in Ventilated Newborns

Introduction: Measuring cardiac output (CO) is an important clinical feature in the neonatal intensive care unit (NICU). Although different clinical methods have been used to evaluate CO clinically, there are no studies validating those results regarding any instrumental method to measure CO. In this prospective study we analyzed the relationship between estimation of CO through clinical methods and Doppler ultrasonography. Material and Methods: 26 patients admitted consecutively in the NICU at Hospital de Pediatría “Prof. J.P.Garrahan” were studied. Inclusion criteria were patients receiving mechanical ventilation with admission longer than 4 hrs. Patient with structural congenital heart disease and those who required reanimation maneuver during the preceding 6 hrs were excluded. CO was classified into normal and low, using a score including physical examination, blood gas, arterial tension and urinary output during the preceding 4 hrs. Ultrasonography measurements were performed 30 min after clinical examination and were the average of 4 examinations, blinded to the clinical method. Sensibility (S), specificity (SP), positive predictive value (PPV), negative predictive value (NPV), and p value were estimated for the clinical method. Results: CO was normal in 20 patients and low in 6 patients. Clinical CO had a S=75%, SP= 88%, PPV=75%, NPV=88%, and p= 0.003. Two patients had normal clinical CO and low CO in ultrasonography evaluation. Two patients had low clinical CO and normal CO in ultrasonographic evaluation, both with ductal shunting. Conclusions: Low CO prevalence in our study sample was not significant. CO measuring in NICU through clinical methods was satisfactory and would be useful to complement CO evaluation in ventilated newborns without structural congenital heart disease.

Interleukin-16 in tracheal aspirate fluids of newborn infants.

It is currently unknown if interleukin (IL)-16 exists in the lungs of ventilated infants, and because the predominant cells in the airways of infants with CLD are CD4+ macrophages, we hypothesized that IL-16 plays a role as a pro-inflammatory mediator in lung inflammation. To examine if IL-16, a chemoattractant for CD4+ cells, is detectable in airway secretions of ventilated newborns. Its presence may be associated with lung inflammatory responses. Cohort cross-sectional study. Thirty-four mechanically ventilated newborn infants. Tracheal fluid (TF) specimens collected during the first month of life were examined for cell differentials determined from cytospin slides and supernatant was analyzed by ELISA for IL-16. Eighty-three cross-sectional tracheal fluid (TF) specimens were analyzed. Eleven of the 27 preterm but none of the 7 term infants developed chronic lung disease (CLD). IL-16, ranging from 203 to 42,073 pg/ml, was detected in 16 of the 46 specimens obtained from CLD infants, 1 of the 30 specimens from 16 non-CLD preterm and 2 of the 7 specimens from 7 term infants (p<0.001). Leukocyte counts (median 16.6 vs. 2.0 x 10(-9)/l, p<0.0001) and percentage neutrophils (median 93% vs. 73%, p<0.001) were higher in IL-16 positive specimens. IL-16 is detectable within the airway secretions of ventilated newborn infants and its presence is associated with a neutrophilic infiltration. Further studies are required to investigate its role in chronic inflammation in CLD.

Results of mechanical ventilation in premature infants with respiratory distress syndrome

This paper reveals the results of synchronized intermittent mandatory ventilation in premature babies over a period of 8 years. Out of 1532 mechanical ventilated newborns 438 were prematures with severe hyaline membrane disease. The incidence of barotraumatic complications (Pneumothorax 1.2%, pulmonary interstitial emphysema 3% and bronchopulmonary dysplasia 3.4%) was relatively low. We discuss this as an effect of using low respirator frequencies guaranteering sufficient emptying time of the lungs.

Permissive hypercapnia for the prevention of morbidity and mortality in mechanically ventilated newborn infants.

Experimental animal data and uncontrolled, observational studies in human infants have suggested that hyperventilation and hypocapnia may be associated with increased pulmonary and neurodevelopmental morbidity. Protective ventilatory strategies allowing higher levels of arterial CO2 (permissive hypercapnia) are now widely used in adult critical care. The aggressive pursuit of normocapnia in ventilated newborn infants may contribute to the already present burden of lung disease. However, the safe or ideal range for PCO2 in this vulnerable population has not been established. To assess whether, in mechanically ventilated neonates, a strategy of permissive hypercapnia improves short and long term outcomes (esp. mortality, duration of respiratory support, incidence of chronic lung disease and neurodevelopmental outcome). Standard strategies of the Cochrane Neonatal Review Group were used. Searches were made of the Oxford Database of Perinatal Trials, MEDLINE, CINAHL, and Current Contents. Searches were also made of previous reviews including cross-referencing, abstracts, and conference and symposia proceedings published in Pediatric Research. All randomised controlled trials in which a strategy of permissive hypercapnia was compared with conventional strategies aimed at achieving normocapnia (or lower levels of hypercapnia) in newborn infants who are mechanically ventilated were eligible. Standard methods of the Cochrane Neonatal Review Group were used. Trials identified by the search strategy were independently reviewed by each author and assessed for eligibility and trial quality. Data were extracted separately. Differences were compared and resolved. Additional information was requested from trial authors. Only published data were available for review. Results are expressed as relative risk and risk difference for dichotomous outcomes, and weighted mean difference for continuous variables. Two trials involving 269 newborn infants were included. Meta-analysis of combined data was possible for three outcomes. There was no evidence that permissive hypercapnia reduced the incidence of death or chronic lung disease at 36 weeks (RR 0.94, 95% CI 0.78, 1.15), intraventricular haemorrhage grade 3 or 4 (RR 0.84, 95% CI 0.54, 1.31) or periventricular leukomalacia (RR 1.02, 95% CI 0.49, 2.12). There were no differences in any other reported outcomes when the strategy of permissive hypercapnia/minimal ventilation was compared to routine ventilation in newborn infants. Long term neurodevelopmental outcomes were not reported. One trial reported that permissive hypercapnia reduced the incidence of chronic lung disease in the 501 to 750 gram subgroup. This review does not demonstrate any significant overall benefit of a permissive hypercapnia/minimal ventilation strategy compared to a routine ventilation strategy. At present, therefore, these ventilation strategies cannot be recommended to reduce mortality, or pulmonary and neurodevelopmental morbidity. Ventilatory strategies which target high levels of PCO2 (> 55 mmHg) should only be undertaken in the context of well-designed controlled clinical trials. These trials should aim to establish the safe, or ideal, range for CO2 in ventilated newborns, and examine the role of protective ventilatory techniques in achieving this target.

What Is on the Horizon for Neonatal Resuscitation?

After completing this article, readers should be able to: 1. Define the indeterminate class of recommendations for neonatal resuscitation. 2. Describe the two areas of current investigation within the indeterminate class recommendations. 3. Describe the application of two techniques from other settings within the indeterminate class recommendations. 4. Describe the indeterminate class recommendation for which conflicting evidence is emerging. With the shift to evidence-based guidelines, the process of revising the scientific framework for neonatal resuscitation and the derivative educational efforts will become more predictable and accessible. Beginning with the International Guidelines 2000, an Indeterminate Class of recommendations appeared. These focused on areas of intense scientific research that may lead to clinically important therapies; technological developments widely adopted for use in other age groups that may find a role in neonatal resuscitation; or emerging evidence that conflicts substantially with previous data, resulting in a revision of recommendations to withdraw support of a particular therapeutic approach. The advent of changes in evidence-based guidelines carries the obligation to monitor the impact of such changes. Finally, entirely new questions and proposed guideline recommendations will be submitted to evidence evaluation in the future. Five Indeterminate Class recommendations appeared in the neonatal resuscitation portion of the International Guidelines 2000 (Table⇓ ). Cerebral hypothermia following hypoxic-ischemic insult and positive-pressure ventilation with room air represent proposals in the translational research phase, moving from animal and molecular models into clinical trials. The recommendations relating to adjunctive airway techniques, laryngeal mask airway and exhaled carbon dioxide detection, recognize the importance of these techniques in the older pediatric and adult populations, but acknowledge the significant limitations in their application to neonates. The statement regarding high-dose epinephrine reinforces the conflicting nature of evidence relating to this therapy, yet it acknowledges that available evidence is extrapolated largely from older age groups and falls short of supporting …

Accuracy of deadspace free ventilatory measurements for lung function testing in ventilated newborns: a simulation study.

A deadspace free method based on simultaneous ventilatory measurements in the inspiratory and expiratory limb of the ventilator circuit was compared to the conventional endotracheal method where the flow is measured between ETT and Y-Piece. The aim of our study was to find out how the arrangement of this setup affects the measuring accuracy of 1) the ventilatory and 2) the lung mechanical parameters by means of a computer simulation. The system consisting of ventilator tubes and lung was described in state space and the flow signals of endotracheal method, of deadspace free method and the pressure at the Y-piece were simulated in the time domain. To investigate the influence of the position of the pneumotachographs (PNTs) in the ventilator circuit on measuring accuracy, the distance d0 of the PNT from the Y-piece was varied between 0 and 900 mm. The respiratory compliance C, resistance R and inertance I were calculated by least square method using the simulated flow and pressure signals of both methods. Compared to the endotracheal method, with increasing d0, the tidal volume measured with the deadspace free method rose linearly, depending on the ratio between the compliance of the ventilator tubes to the respiratory compliance. The differences of C and R for both methods were acceptable (< 10%) if the distance between each PNT and the y-piece didn't exceed 200 mm and the shorter do the higher the measuring accuracy. The inertance could not be measured by this method with satisfactory accuracy if d0 was higher than 100 mm. The dead space free method can be used for accurate ventilatory measurements during mechanical ventilation. However, for lung mechanic measurements in very low birth weight infants the position of the PNTs must be as short as possible.

Advances in Neonatal Neurology 1950-2000

There have been innumerable advances in medicine and its specialties in the last half century. Neonatal intensive care did not really begin until the 1960's, when adequate mechanical ventilation for newborns became generally available. With the increased survival of very small prematures, even with a smaller individual morbidity, a larger total number of survivors is graduating these units. Will they be able to function in this increasingly more complicated world? Organizational, Diagnostic, and Therapeutic advances in Neonatology and Neonatal Neurology are reviewed. Then, advances in some of those neonatal entities that threaten the CNS are briefly reviewed. Congenital anomalies, metabolic disease, infection, intraventricular hemorrhage, hydrocephalus, periventricular leukomalacia, are touched upon. Finally, the entity of hypoxi-ischemic encephalopathy is reviewed, emphasizing that its morbidity has changed little through the years, and describing a new hypothermic approach to its management currently under way in a global cooperative study.

Accumulation of CO(2) in reservoir devices during simulated neonatal mechanical ventilation.

Aerosolized albuterol is frequently administered to mechanically ventilated neonates by metered dose inhaler (MDI) and a reservoir device. These reservoirs are often placed between the Y-piece and endotracheal tube, thereby creating mechanical dead space and increasing the risk of rebreathing carbon dioxide (CO(2)). The objectives of this study were: 1) to quantify CO(2) accumulation in two commonly used reservoirs (ACE(R), Aerochamber(R)-MV) and a bidirectional nonreservoir actuator (Airlife(R) Minispacer) during mechanical ventilation of a neonatal lung model; and 2) to determine the effect of tidal volume (V(T)) on CO(2) accumulation. We hypothesized that the accumulation of CO(2) in these devices is clinically insignificant at the small tidal volumes used in mechanically ventilated premature neonates. The model was constructed to simulate CO(2) exhalation by a ventilated neonate and consisted of a neonatal ventilator circuit (rate = 40/min; peak inspiratory pressure (PIP) = 20 cm H(2)0) attached to a reservoir/actuator and neonatal test lung. The ventilator delivered inspiratory gas (room air) to the test lung, which was vented into the atmosphere by a small adjustable leak. Expiration was simulated by manually ventilating 7.1% CO(2) (partial pressure of CO(2) (PCO(2)) = 48 mm Hg) back through the model. Accumulation of CO(2) within the reservoir/actuator was measured using an end-tidal CO(2) monitor. Each 4-min experiment was conducted at three V(T) (7.5 mL, 15 mL, and 25 mL), and the median PCO(2) was calculated in 0.5-min increments. For V(T) = 7.5 mL, CO(2) accumulated slowly in the ACE(R) and Minispacer(R) and reached a maximum at 4.0 min (PCO(2) = 2.3 mm Hg and 7.3 mm Hg, respectively). In contrast, the Aerochamber(R)-MV rapidly reached a PCO(2) of 9.5-10.0 mm Hg by 1-1. 5 min. A similar trend occurred with V(T) = 15 mL; however, higher partial pressures (approximately 10-12 mm Hg) were achieved with all devices. At V(T) = 25 mL, PCO(2) rose rapidly with the ACE(R), Aerochamber(R)-MV, and Minispacer(R), reaching peaks of 17.2, 12.3, and 20.3 mm Hg, respectively (P < 0.05). In conclusion, accumulation of CO(2) in reservoir/actuator depends on V(T) as well as the chamber design and internal volume. Due to the short duration of use when administering drugs via MDI, accumulation of CO(2) in these devices is not likely to be clinically relevant for the majority of ventilated newborns.

Volume Targetted Mechanical Ventilation of Newborns Maintains More Stable Tidal Volume but Does Not Prevent Hypocarbia in the First 24 Hours of Life

Volume Targetted Mechanical Ventilation of Newborns Maintains More Stable Tidal Volume but Does Not Prevent Hypocarbia in the First 24 Hours of Life

Early prediction of chronic lung disease by tracheal aspirate cytology in ventilated newborns.

We assessed the specificity of squamous metaplasia in tracheal aspirates of 69 ventilated newborns (gestational age 25-41 weeks) between days 3 and 7 of life for prediction of chronic lung disease (CLD). CLD was diagnosed when the patient was still requiring ventilation or supplementary oxygen at the postconceptional age of 36 weeks (or postnatal age of 28 days for babies born after 32 weeks gestation) and showed X-ray changes compatible with CLD. In the total population the presence of squamous metaplasia had a sensitivity of 59% and a specificity of 74% for the early diagnosis of CLD. The combination of squamous metaplasia and very low birth weight (VLBW) had a much higher specificity (94%), but a lower sensitivity (45%). Our results show that the presence of squamous metaplasia in VLBW babies during the 1st week of life predicts development of CLD with a specificity of 94% and may be helpful for entering patients into early treatment protocols or trials when a high risk population needs to be identified. As sensitivity of this approach is only 45%, further studies are needed to evaluate the predictive value of the combination of cytology with other markers in tracheal aspirate specimens. The presence of squamous metaplasia in tracheal aspirates of VLBW babies between days 3 and 7 of life is significantly associated with the development of chronic lung disease. Simple microscopic evaluation of fresh tracheal aspirates enables us to identify patients at high risk of CLD at a very early stage.

Cardiovascular Responses During Transition from Fetal to Neonatal Life in Intact and Vagotomized Lambs † 1664

Evidence suggests that pulmonary vagal innervation contributes more significantly to the alveolar ventilation in newborns than in older animals. To investigate whether vagal efferents play a role in the control of pulmonary blood flow during transition from fetal to neonatal life, we studied 12 unanesthetized, spontaneously breathing, chronically instrumented newborn lambs at 143-147 d gestation (Term=147±2d) after unassisted vaginal delivery. Surgery was performed between 130-134 d gestation to implant jugular venous and carotid arterial catheters, diaphragmatic electrode and left pulmonary artery blood flow probe (Transonic Inc). Six of 12 fetuses underwent intrathoracic vagotomy (VAG), whereas the remainder six were sham-operated(SHAM). Breathing frequency (breaths per minute) remained higher in the SHAM animals as compared with the VAG group, during the entire postnatal period(92-104 vrs 30-40, respectively; p=0.001). Inspiratory and expiratory times were significantly longer in the VAG group; p<0.01). Furthermore, similar to our previous studies, vagotomized animals were unable to establish adequate alveolar ventilation and remained hypothermic despite attempts to rewarm. Left pulmonary arterial (LPA) blood flow (ml/min/kg) increased from pre-birth values of 2.67±2.45 and 0.2±0.2 to 48±7 and 57±17 at five minutes after birth, in sham-operated and vagotomized animals, respectively (p<0.05). LPA continued to increase gradually reaching the maximum value of 101±10 and 126±19 ml/kg/min at 12 minutes of age in both SHAM and VAG groups, respectively. LPA blood flow pleatued at 85±8 and 84±6 ml/kg/min by 40 minute of age. Heart rate(beats/min) increased from 128±11(pre-birth) to 180±18 and 260±7(p<0.05),and from 134±15 (pre-birth), to 167±25 and 227±9 (p<0.05) at 10 and 30 minutes of age in SHAM and VAG groups, respectively. Heart rate was significantly higher in the SHAM group as compared with the VAG group at 30 minutes of age (p=0.02) whereas no significant changes were observed in systolic, diastolic or mean blood pressure between the two groups. We conclude that vagal innervation does not play significant role in cardiovascular adaptation at birth and inadequate pulmonary gas exchange in vagotomized animals is not due to lack of an increase in pulmonary blood flow. In addition, our study provides the first evidence of sequential changes in pulmonary blood flow during the first hour after birth in unanesthetized, spontaneously breathing newborn animals.

Epidemiology of Gram Negative Bacilli (GNB) Airway Colonization in an NICU 1203

GNB airway colonization occurs in one-third of newborns who are mechanically ventilated for longer than 2 weeks. This colonization is associated with significant morbidity and mortality. To ascertain their origin and potential modes of transmission, 52 GNB isolates from 14 ventilated newborns were analyzed by pulsed-field gel electrophoresis (PFGE). These isolates were from 41 serial tracheal cultures obtained (July-October 1997) at the NICU where pts. were located in four contiguous rooms. Routine bacteriology showed that five neonates were colonized with two different GNB and one was colonized with three. PFGE analysis revealed that one pt. acquired two strains and one subtype of Klebsiella (A1,E, E1), and another harbored multiple subtypes of Klebsiella(A,A1,A2,A3). For the remaining pts., colonizations were due to unrelated strains. Table

Accuracy of volume measurements in mechanically ventilated newborns: a comparative study of commercial devices.

Ventilatory measurements in ventilated newborns are increasingly used to monitor and to optimize mechanical ventilation. The aim of this study was to compare the accuracy of volume measurements by different instruments using standardized laboratory conditions. The accuracy of displayed volume values of different commercial devices (Bicore CP-100, Ventrak 1500, Ventrak 1550, Babylog 8000, PEDS IV and SensorMedics 2600) was investigated using adjustable calibration syringes (volume range 2-60 ml, breathing rates 30/min-60/min) and humidified (>95%), heated (35 degrees C) breathing gas with adjustable FIO2 (0.21-1.0). The pneumotach and also the tubes were placed within an incubator (37 degrees C). The relative volume error of all devices was in conformity with clinically allowed tolerances (Bicore CP-100 6.4+/-0.5% (mean +/- SD), Ventrak 1500 3.6+/-4.2%, Ventrak 1550 6.5+/-2.7%, Babylog 8000 -5.5+/-1.5%, PEDS IV -4.0+/-1.4%, SensorMedics 2600 3.5+/-1.75%) for the measuring range studied (10 ml < V < 60 ml, rate 30-60/min, FIO2 = 0.21). Unacceptable errors were obtained for volumes lower than 10 ml with Bicore CP-100 (-28.5+/-26%) and PEDS IV (-10.3+/-3.4%). Changes in FIO2 had an important influence on volume measurements and only the SensorMedics 2600 and the PEDS IV corrected properly for FIO2 changes. Most of the currently available neonatal spirometry devices allow sufficiently accurate volume measurements in the range of 10-60 ml and at frequencies between 30-60/min provided that an increased FIO2 is taken into account.

PROTEIN BALANCE IN PARENTERALLY-FED, VENTILATED NEWBORNS IN THE FIRST DAYS OF LIFE: FACTORS CONTRIBUTING TO AN ANABOLIC STATE. † 1435

To determine which nutrient intakes and demographic factors contribute to achieving a positive protein balance in parenterally fed neonates during the first week of life, 19 ventilated newborns had protein kinetic studies performed after a minimum of 24 hours on a clinically determined hyperalimentation intake. Using 1-13C leucine methodology and indirect calorimetry, protein synthesis, protein catabolism and net protein balance(i.e. synthesis-catabolism) were determined. Based on net protein balance measurements, infants were considered anabolic (ana) if this value was>0.25 g/kg/d, in zero balance (z bal) if ≤0.25 to ≥-0.25 g/kg/d, and catabolic (cat) if <-0.25 g/kg/d. Table Using linear regression analysis, the best predictor of protein balance was protein intake(p<0.0001), followed by non-protein energy intake (p<0.005) and lipid intake (p<0.05). Protein balance was not correlated with glucose intake, birth weight or gestational age. Only one of the 9 infants who weighed<1250 g was catabolic. These data demonstrate that the majority of ventilated newborns can achieve an anabolic state in the first days of life, and that extremely low birth weight infants do not exhibit protein intolerance compared to more mature infants.

Simultaneous measurements of end-expiratory and transcutaneous carbon dioxide partial pressure in ventilated premature and newborn infants

The aim of the present trial was to study the relationship between end-tidal pCO2 (p(et)CO2) and transcutaneous pCO2 (ptcCO2) after in-vivo calibration in ventilated newborns. 61 end-tidal and transcutaneous pCO2 measurements were simultaneously performed in 30 ventilated preterm and term newborn infants (weight at birth 1862.6 +/- 981.9 g). End-tidal pCO2 was measured in mainstream mode at the end of the endotracheal tubus (Novametrix 7000 Medical Systems Inc., USA, dead volume of the chamber 0.6 ml). Transcutaneous pCO2 was measured by means of a Servomed (SMK 365 Hellige, FRG) analyser. The statistical analysis demonstrated a good correlation (r = 0.72, p < 0.001) between ptcCO2 (mean +/- SD, 44.3 +/- 11.2 mmHg) and p(et)CO2 (32.4 +/- 10.4 mmHg). A considerable difference between transcutaneous and end-tidal pCO2 values was observed (p(tc-et)CO2 = +11.9 +/- 8.7 mmHg). This phenomenon was probably caused by ventilation-perfusion disturbances in the studied critically ill neonates. The statistical analysis revealed that the absolute magnitude of the P(tc-et)CO2 difference was independent from disease, episodes of spontaneous respiration or of respiratory frequency. Capnographic determination of P(et)CO2 provides informations about alveolar ventilation-perfusion-disturbances. Capnography enables the on-line control of end-tidal pCO2 in neonates with respiratory failure. It cannot replace transcutaneous pCO2 measurements or blood gas analysis but it can reduce its frequency in clinically stable patients. The analysis of the capnogram can be used to optimise artificial ventilation. A quantitative evaluation of the capnogram by calculation of Murányi's-CO2-Index was possible only in 28% of the ventilated newborns which limits its value in such patients.

Hemodynamic effects of intravenous morphine infusion in ventilated preterm babies.

the importance of sedation and analgesia of newborn babies in intensive care is only now receiving recognition in many neonatal units. to evaluate the hemodynamic effects of morphine on Cerebral Blood Flow velocities (CBFv), Cardiac Output (CO), Stroke Volume (SV), Mean Arterial Blood Pressure (MABP) and Heart Rate (HR) in ventilated preterm infants, before and during the infusion of a loading dose. prospective, open, non-randomized, before-after intervention study with hemodynamic measurements made by Doppler ultrasound. neonatal Intensive Care Unit, Tertiary Care Center. sequential sample of 30 ventilated preterm newborns (gestational age (GA) 29 +/- 2 wks, range 27-31, birth weight (BW) 1240 +/- 440 g, range 800-1680). each subject received an intravenous loading dose of morphine (100 mcg/Kg/h) for 2 h, followed by a continuous infusion of 25 mcg/kg/h. the following Doppler parameters of the anterior cerebral artery were estimated: Peak systolic flow velocity (Vs), end-diastolic flow velocity (Vd), mean flow velocity (Vm) and Pourcelot' Resistance Index (RI). Measurements of CBFv, CO and SV (by Doppler ultrasound), MABP and HR were made 30 min before (baseline values) and at 15 (M15), 30 (M30), 60 (M60) and 120 min (M120), during the morphine loading infusion. Statistical evaluation analysis of variance, significance was calculated by Student-Newman-Kenfeld test. there were no statistically significant changes in the cerebral and cardiac Doppler parameters before or during the 120 min of morphine loading infusion. There was a non-significant fall in MABP (MABP: Baseline value = 44 +/- 6 mmHg, M120 = 42 +/- 4 mmHg; reduction = 4%) and HR (HR = Baseline value = 148 +/- 12 beats/min., M120 = 140 +/- 16 beats/min.; reduction = 5%). a loading dose of morphine over 2 h did not have any significant effect on MABP or cerebral and cardiac hemodynamics. No adverse effects were noted that could be attributed to morphine therapy.

Changes in TcPCO2 regarding pulmonary mechanics due to pneumotachometer dead space in ventilated newborns.

The aim of this study was to analyze the effect of added dead space on PaCO2 after application of a pneumotachometer during the measurement of pulmonary mechanics. The study was based on 24 observations of TcPCO2 changes during the measurement of pulmonary function in 9 newborns subjected to mechanical ventilation. All newborns remained stable during the 23 minutes of the test. The introduction of a low dead space pneumotachometer (1.7 mL) for 10 minutes led to an increase in TcPCO2 of 5.40 +/- 2.66 mm Hg, from 39.76 +/- 8.69 to 45.17 +/- 9.22. Pulmonary mechanics indexes that correlated with the percentage of CO2 increase were peak inspiratory flow and expiratory time/time constant. When the pneumotachometer was removed, TcPCO2 fell but remained 0.99 +/- 2.13 mm Hg above basal TcPCO2. Final TcPCO2 tended to relate negatively with the minute volume. We conclude that this transient increase in PaCO2 should be born in mind in neonates with a high basal level and can be prevented by maintaining a long expiratory time and a high minute volume.

Inspiratory work of breathing in ventilated preterm infants.

In ventilated newborns, part of the inspiratory work of breathing (WOB) may be due to the inspiratory efforts preceding inspiratory ventilator flow. This study was designed to quantify the contribution of these efforts to WOB. WOB was evaluated in six intubated preterm infants ventilated by the Dräger Babylog 8000. The ventilatory modes studied were intermittent mandatory ventilation (IMV), continuous positive airway pressure (CPAP), and assist-control ventilation at 10 (ACV10) and 15 (ACV15) cmH2O peak pressure. Mouth flow (V) and esophageal pressure (Pe) were recorded, and WOB was estimate from the area delineated by the esophageal pressure-volume curve, where volume is the time integral of V. Calculation of WOB started either at the onset of the infant's inspiratory flow (WOBi), or at the beginning of the infant's inspiratory muscle efforts, detected on Pe and confirmed on the V tracing (WOBm). WOBm was found to be significantly higher than WOBi under all ventilatory conditions studied. The difference in work of breathing (delta W) between WOBm and WOBi did not depend on the type of ventilatory mode. When delta W was related to WOBm, it amounted to about 30% of WOBm in IMV and CPAP, and 60% in ACV (P < 0.05, ACV15 vs. IMV). These results suggest that, in preterm infants connected to a ventilator, inspiratory efforts preceding flow inspiration might account for a large fraction of the inspiratory work of breathing.

Nellcor Stat Cap differentiates oesophageal from tracheal intubation.

A trial of the Nellcor Stat Cap, which detects exhaled carbon dioxide, as an aid to determining whether endotracheal tubes are placed in the oesophagus or the trachea, was carried out in the neonatal unit of this hospital. Twenty five neonates, with a mean (range) gestational age of 33 (24-42) weeks and a mean (range) birthweight of 2.17 (0.54-4.1) kg were studied over two months. These babies underwent a total of 58 intubations and 20 suspected self-extubations. The Nellcor Stat Cap was easy to use. It confirmed clinical findings on 20/20 occasions when the endotracheal tube was in the oesophagus and on 57/58 (98%) occasions when it was in the trachea. On 14/78 (19%) occasions the machine provided helpful additional information in reaching a decision on the adequacy of tube placement. Failure to detect rapidly accidental oesophageal intubation or unintentional tracheal extubation can result in rapid deterioration of the condition of ventilated newborns. The machine is a valuable aid to intubation and rapid diagnosis of self-extubation.