Ventilation Efficiency Index Research Articles

High flow nasal heliox improves work of breathing and attenuates lung injury in a newborn porcine lung injury model.

High flow nasal cannula (HFNC) has been shown to improve ventilation and oxygenation and reduce work of breathing in newborns with respiratory distress. Heliox, decreases resistance to airflow, reduces the work of breathing, facilitates the distribution of inspired gas, and has been shown to attenuate lung inflammation during the treatment of acute lung injury. Heliox delivered by HFNC will decrease resistive load, decrease work of breathing, improve ventilation and attenuate lung inflammation during spontaneous breathing following acute lung injury in the newborn pig. Spontaneously breathing neonatal pigs received Nitrox or Heliox by HFNC and studied over 4 hrs following oleic acid injury. Gas exchange, pulmonary mechanics and systemic inflammation were measured serially. Lung inflammation biomarkers were assessed at termination. Heliox breathing animals demonstrated lower work of breathing reflected by lower tracheal pressure, phase angle and phase relationship. Ventilation efficiency index was greater compared to Nitrox. Heliox group showed less lung inflammation reflected by lower tissue interleukin-6 and 8. High flow nasal Heliox decreased respiratory load, reduced resistive work of breathing indices and attenuated lung inflammatory profile while ventilation was supported at less pressure effort in the presence of acute lung injury.

Tracheal suctioning improves gas exchange but not hemodynamics in asphyxiated lambs with meconium aspiration.

BackgroundCurrent neonatal resuscitation guidelines recommend tracheal suctioning of non-vigorous neonates born through meconium stained amniotic fluid.MethodsWe evaluated the effect of tracheal suctioning at birth in 29 lambs with asphyxia induced by cord occlusion and meconium aspiration during gasping.ResultsTracheal suctioning at birth (n=15) decreased amount of meconium in distal airways (53±29 particles/mm2 lung area) compared to no-suction (499±109 particles/mm2, n=14, p<0.001). Three lambs in the suction group had cardiac arrest during suctioning requiring chest compressions and epinephrine. Onset of ventilation was delayed in the suction group (146±11 vs. 47±3 sec in no-suction group, p=0.005). There was no difference in pulmonary blood flow, carotid blood flow, pulmonary or systemic blood pressure between the two groups. Left atrial pressure was significantly higher in the suction group. Tracheal suctioning resulted in higher PaO2/FiO2 levels (122±21 vs. 78±10 mmHg) and ventilator efficiency index (0.3±0.05 vs.0.16±0.03). Two lambs in the no-suction group required inhaled NO. Lung 3-nitrotyrosine levels were higher in the suction group (0.65±0.03 ng/μg protein) compared to the no-suction group (0.47 ± 0.06).ConclusionTracheal suctioning improves oxygenation and ventilation. Suctioning does not improve pulmonary/systemic hemodynamics or oxidative stress in an ovine model of acute meconium aspiration with asphyxia.

The lowest VE/VCO2 ratio best identifies chronic thromboembolic pulmonary hypertension

IntroductionThe natural history of acute pulmonary embolism (PE) under treatment is about a gradual resolution of the thrombi, and uncommonly, the development of chronic thromboembolic pulmonary hypertension (CTEPH). We hypothesized that ventilatory efficiency parameters during cardiopulmonary exercise testing (CPET) may be able to monitor the process and predict CTEPH. Methods15 patients rehabilitated from acute PE (total resolution of thrombi), 44 patients with chronic PE (with residual thrombi), 66 patients with CTEPH, and 36 sedentary healthy controls performed incremental CPET. ResultsThe lowest VE/VCO2 was higher in CTEPH patients than that in chronic PE and rehabilitated patients (43.4L/min vs 29.9L/min vs 27.1L/min, p<0.005). The VE/VCO2 slope (48.4L/min/L/min vs 29.9L/min/L/min vs 28.0L/min/L/min, p<0.005) and oxygen uptake efficiency plateau (OUEP) (37.1L/min vs 27.0L/min vs 25.2L/min, p<0.005) had the similar changes. In logistic regression analysis, the lowest VE/VCO2≥34.35L/min was the best predictor of CTEPH (OR 159.0, 95% CI 36.0-702.3, p<0.001). The lowest VE/VCO2 was higher in chronic PE patients compared with the controls (29.9L/min vs 26.5L/min, p<0.05), but there was no difference between the rehabilitated patients and the controls. In multiple linear regression analysis, the percentage of vascular obstruction by ventilation-perfusion lung scanning (PVO) was the most significant independent predictor for indices of ventilatory efficiency in chronic PE and rehabilitated patients. ConclusionsCTEPH is associated with weakened ventilatory efficiency. The lowest VE/VCO2 ratio has the best capability to predict CTEPH. Ventilatory inefficiency improves along with recovery of acute PE.

Ventilator „Chirana Aura V“ In Two Models Of Neonatal Acute Lung Injury - A Pilot Study

Abstract In severe respiratory insufficiency, neonatal and pediatric patients should be ventilated artificially by a ventilator. Aim of this experimental study was to evaluate whether the newly developed ventilator Chirana Aura V may effectively ventilate the lungs of animals with two different models of acute lung injury: acute respiratory distress syndrome (ARDS) induced by repetitive saline lavage and meconium aspiration syndrome (MAS) induced by intratracheal instillation of neonatal meconium. The experiments were performed on 10 adult rabbits (New Zealand white). In ARDS group (n=5), the lungs were repetitively lavaged with saline (30 ml/kg) until partial pressure of oxygen (PaO2) in arterial blood was under 26.7 kPa at inspiratory fraction of oxygen FiO2=1.0. In MAS group (n=5), animals were instilled 4 ml/kg of suspension of human meconium (25 mg/ml). When the model of acute lung injury was developed, animals were ventilated for additional 2 hours with pressure control ventilation (PCV) regime by ventilator Chirana Aura V. Ventilatory parameters, blood gases, acid-base balance, end-tidal CO2, O2 saturation of hemoglobin, oxygenation indexes, ventilation efficiency index, dynamic lung compliance, and right-to-left pulmonary shunts were measured and calculated in regular time intervals. In both experimental groups, used ventilatory settings provided acceptable gas exchange within the period of observation. Thus, the results indicate that ventilator Chirana Aura V might be suitable for ventilation of animal models of acute lung injury. However, further pre-clinical investigation is needed before its use may be recommended in neonatal and/or pediatric patients with acute lung injury.

Respiratory function parameters in ventilated newborn infants undergoing whole body hypothermia

Whole body hypothermia (WBH) exerts proven neuroprotective effects in infants with hypoxic-ischaemic encephalopathy (HIE). Our aim was to describe how WBH could impact on respiratory function in mechanically ventilated newborn infants, by recording primary and composite indices of oxygenation and ventilation before, during and after WBH. The medical notes of 31 mechanically ventilated full-term newborn infants who underwent WBH for HIE were retrospectively reviewed. Fraction of inspired oxygen (FiO2), tidal volume (TV), mean airway Pressure (MAP), minute ventilation (MV), static compliance of the respiratory system (C(statRS)), ventilation efficiency index (VEI), alveolar-arterial gradient (A-a gradient) and oxygenation index (OI) were documented before and during hypothermic treatment, as well as during and after rewarming. Fraction of inspired oxygen, MAP, OI and A-a gradient decreased during induction of hypothermia and tended to increase during rewarming. C(statRS), VEI and TV increased during induction of hypothermia and tended to decrease during rewarming. None of the changes achieved statistical significance. These results suggest that WBH might affect respiratory function in mechanically ventilated infants with HIE. Oxygenation might be enhanced by hypothermia, probably as a result of decreased metabolism, while ventilation might also be facilitated as a result of the effect of hypothermia on lung mechanics.

New surfactant with SP-B and C analogs gives survival benefit after inactivation in preterm lambs.

BackgroundRespiratory distress syndrome in preterm babies is caused by a pulmonary surfactant deficiency, but also by its inactivation due to various conditions, including plasma protein leakage. Surfactant replacement therapy is well established, but clinical observations and in vitro experiments suggested that its efficacy may be impaired by inactivation. A new synthetic surfactant (CHF 5633), containing synthetic surfactant protein B and C analogs, has shown comparable effects on oxygenation in ventilated preterm rabbits versus Poractant alfa, but superior resistance against inactivation in vitro. We hypothesized that CHF 5633 is also resistant to inactivation by serum albumin in vivo.Methodology/Principal FindingsNineteen preterm lambs of 127 days gestational age (term = 150 days) received CHF 5633 or Poractant alfa and were ventilated for 48 hours. Ninety minutes after birth, the animals received albumin with CHF 5633 or Poractant alfa. Animals received additional surfactant if PaO2 dropped below 100 mmHg. A pressure volume curve was done post mortem and markers of pulmonary inflammation, surfactant content and biophysiology, and lung histology were assessed. CHF 5633 treatment resulted in improved arterial pH, oxygenation and ventilation efficiency index. The survival rate was significantly higher after CHF 5633 treatment (5/7) than after Poractant alfa (1/8) after 48 hours of ventilation. Biophysical examination of the surfactant recovered from bronchoalveolar lavages revealed that films formed by CHF 5633-treated animals reached low surface tensions in a wider range of compression rates than films from Poractant alfa-treated animals.ConclusionsFor the first time a synthetic surfactant containing both surfactant protein B and C analogs showed significant benefit over animal derived surfactant in an in vivo model of surfactant inactivation in premature lambs.

Effects of High-Intensity Training on Indices of Ventilatory Efficiency in Chronic Heart Failure

Measures of ventilatory inefficiency, such as the slope of the relation between ventilation and carbon dioxide production ((Equation is included in full-text article.)slope) and the oxygen uptake efficiency slope (OUES) have recently been shown to be strong prognostic markers in patients with heart failure. Little is known regarding the effects of exercise training on these indices. Fifty heart failure patients (mean age = 55 ± 6 years, ejection fraction = 33 ± 6%) referred to a residential cardiac rehabilitation program were randomized to a 2-month high-intensity training program (n = 24) or to a control group (n = 26). Before and after the study period, maximal cardiopulmonary exercise testing was performed, and markers of ventilatory inefficiency were determined. Training increased peak oxygen uptake ((Equation is included in full-text article.); 23%), exercise time (29%), and peak workload (28%), whereas no changes were observed in controls (all P < .05 between groups). No differences were observed in the (Equation is included in full-text article.)slope in either group. However, the ventilatory equivalent for oxygen ((Equation is included in full-text article.)ratio) was reduced at matched work rates throughout exercise (P < .01). The OUES increased by 12% in the exercise groups (P = .003) and 4% in controls. At baseline, trained patients had an OUES that was 69% of the age-predicted value and this improved to 78% after training (P = .004). The change in OUES was significantly related to the change in peak (Equation is included in full-text article.)with training (r = 0.63, P = .001). High-intensity training resulted in marked improvements in exercise capacity in patients with heart failure. Training improved the OUES and reduced the (Equation is included in full-text article.)ratio, but the (Equation is included in full-text article.)slope was unchanged. Among measures of ventilatory inefficiency, the OUES may be more sensitive to training than the (Equation is included in full-text article.)slope.

Variable ventilation improves ventilation and lung compliance in preterm lambs

In adult animals, ventilation with variable tidal volume and rate improves lung mechanics, arterial oxygenation and ventilation compared to a monotonously controlled ventilation pattern. We assessed the physiological consequences of variable ventilation in the immature lung. Lambs delivered at 129 days (term = 150 days) were euthanised (n = 9) or anaesthetised, tracheostomised and suctioned prior to prophylactic intra-tracheal surfactant instillation (Curosurf(®), 100 mg/kg) and commencement of controlled ventilation (50 breaths/min, tidal volume 7.7 ± 0.8 mL/kg). Volume history was standardised at 20 min with two sustained (3 s) inflations to 30 cmH(2)O followed immediately by measurement of baseline dynamic lung mechanics (FlexiVent, Scireq, Canada). Ventilation was continued according to prior randomisation (variable or conventional ventilation). For variable ventilation (n = 9), breath-to-breath tidal volume and respiratory rate varied but intra-breath minute volume (MV) and average tidal volume were equivalent to the conventional ventilation group with fixed tidal volume and rate (n = 7). Lung mechanics and gas exchange were measured at intervals. Lambs were euthanised at 2 h. Inflammatory cell counts and protein from bronchoalveolar lavage fluid and lung tissue cytokine mRNA were quantified. At study completion, PaCO(2) (p = 0.026) and mean airway pressure (p = 0.002) were lower and pH (p = 0.047), ventilation efficiency index (p = 0.021) and dynamic compliance were higher (p = 0.003) in lambs on variable rather than conventional ventilation. However, oxygenation indices and post-mortem static compliances were not different between groups. Variable ventilation improves ventilation efficiency and in vivo lung compliance in the preterm lung, but unlike adult models, had no effect on arterial oxygenation.

Ventilator Gas Flow Rates Affect Inspiratory Time and Ventilator Efficiency Index in Term Lambs

Background: Despite increasing survival in the smallest preterm infants, the incidence of chronic lung disease has not decreased. Research into ventilatory strategies has concentrated on minimising barotrauma, volutrauma and atelectotrauma, but little attention has been paid to the role of bias gas flow rates and the potential for rheotrauma or shear stress injury. Ventilated preterm infants frequently receive relatively high gas flow rates. Objectives: We hypothesised that altering bias gas flow rates would change the efficiency of ventilation and thereby affect ventilatory parameters. Methods: We tested this hypothesis using an artificial lung followed by ventilation of 8 term lambs. Results: Between flows of 2 and 15 l/min, inflation time (Ti) in the artificial lung was inversely related to the bias gas flow rate. In the ventilated lambs, Ti was inversely related to flow rates up to 10 l/min, with no statistically significant effect at flow rates >10 l/min. There were no adverse effects on gas exchange or cardiovascular parameters until a flow rate of 3 l/min was used, when inadequate gas exchange occurred. Conclusions: Ti is inversely associated with the bias gas flow rate. Flow rates much lower than those used in many neonatal units seem to provide adequate ventilation. We suggest that the role of ventilator gas flow rates, which may potentially influence shear stress in ventilator-induced lung injury, merits further investigation.

Recombinant Human Clara Cell Secretory Protein Treatment Increases Lung mRNA Expression of Surfactant Proteins and Vascular Endothelial Growth Factor in a Premature Lamb Model of Respiratory Distress Syndrome

Infant respiratory distress syndrome (IRDS) can lead to impaired alveolarization and dysmorphic vascularization of bronchopulmonary dysplasia. Clara cell secretory protein (CC10) has anti-inflammatory properties but is deficient in the premature infant. Because surfactant and vascular endothelial growth factor (VEGF) profiles are impaired by inflammation and CC10 inhibits lung inflammation, we hypothesized that CC10 may up-regulate surfactant protein (SP) and VEGF expression. Preterm lambs ( N = 24; 126 +/- 3 days [standard error] gestation) with IRDS were randomized to receive 100 mg/kg surfactant, 100 mg/kg surfactant followed by intratracheal 0.5, 1.5, or 5 mg/kg rhCC10 and studied for 4 hours. Gas exchange and lung mechanics were monitored; surfactant protein and VEGF mRNA profiles in lung were assessed. There was a significant rhCC10 dose-dependent increase in respiratory compliance and ventilation efficiency index; both parameters were significantly greater in animals treated with 5 mg/kg rhCC10 than those treated with surfactant alone. Similarly, there was a significant rhCC10 dose and protein-dependent increase in surfactant protein (SP-B > SP-C > SP-A) and dose- and isoform-dependent increase in VEGF (VEGF189 > VEGF165 > VEGF121). These data demonstrate that early intervention with rhCC10 up-regulates surfactant protein and VEGF expression, supporting the role of CC10 to protect against hyperoxia and mechanical ventilation in the immature lung.

Surfactant replacement and open lung concept – Comparison of two treatment strategies in an experimental model of neonatal ARDS

BackgroundSeveral concepts of treatment in neonatal ARDS have been proposed in the last years. The present study compared the effects of open lung concept positive pressure ventilation (PPVOLC) with a conventional ventilation strategy combined with administration of two different surfactant preparations on lung function and surfactant homoeostasis.MethodsAfter repeated whole-lung saline lavage, 16 newborn piglets were assigned to either PPVOLC (n = 5) or surfactant treatment under conventional PPV using a natural bovine (n = 5) or a monomeric protein B based surfactant (n = 6).ResultsComprehensive monitoring showed each treatment strategy to improve gas exchange and lung function, although the effect on PaO2 and pulmonary compliance declined over the study period in the surfactant groups. The overall improvement of the ventilation efficiency index (VEI) was significantly greater in the PPVOLC group. Phospholipid and protein analyses of the bronchoalveolar lavage fluid showed significant alterations to surfactant homoeostasis in the PPVOLC group, whereas IL-10 and SP-C mRNA expression was tendentially increased in the surfactant groups.ConclusionThe different treatment strategies applied could be shown to improve gas exchange and lung function in neonatal ARDS. To which extent differences in maintenance of lung function and surfactant homeostasis may lead to long-term consequences needs to be studied further.

Multicenter Comparative Study of Conventional Mechanical Gas Ventilation to Tidal Liquid Ventilation in Oleic Acid Injured Sheep

We performed a multicenter study to test the hypothesis that tidal liquid ventilation (TLV) would improve cardiopulmonary, lung histomorphological, and inflammatory profiles compared with conventional mechanical gas ventilation (CMV). Sheep were studied using the same volume-controlled, pressure-limited ventilator systems, protocols, and treatment strategies in three independent laboratories. Following baseline measurements, oleic acid lung injury was induced and animals were randomized to 4 hours of CMV or TLV targeted to "best PaO2" and PaCO2 35 to 60 mm Hg. The following were significantly higher (p < 0.01) during TLV than CMV: PaO2, venous oxygen saturation, respiratory compliance, cardiac output, stroke volume, oxygen delivery, ventilatory efficiency index; alveolar area, lung % gas exchange space, and expansion index. The following were lower (p < 0.01) during TLV compared with CMV: inspiratory and expiratory pause pressures, mean airway pressure, minute ventilation, physiologic shunt, plasma lactate, lung interleukin-6, interleukin-8, myeloperoxidase, and composite total injury score. No significant laboratories by treatment group interactions were found. In summary, TLV resulted in improved cardiopulmonary physiology at lower ventilatory requirements with more favorable histological and inflammatory profiles than CMV. As such, TLV offers a feasible ventilatory alternative as a lung protective strategy in this model of acute lung injury.

CASE STUDIES OF EFFECTIVE VENTILATED VOLUME BASED ON CFD SIMULATIONS

It is very important to keep indoor air quality good in order to avoid health problems such as Sick House Syndrome occurred in Japan. It is also very important to ventilate indoor spaces efficiently to reduce energy consumption and CO2 emission. Ventilation efficiency indexes have been proposed as means to evaluate the efficiency of ventilation systems and these indexes have been taken into account in ventilation design. The previous paper proposed the effective ventilated volume, hereafter EVV, as a ventilation efficiency index and showed a definition of EVV based on the volume integral with a weighting function. The meaning of EVV depends on the selected weighting function, therefore three types of weighting function were examined. In this paper, several case studies on the EVV based on computation fluid dynamics (CFD) are demonstrated. In the cases of office models and factory models, mixing ventilation and displacement ventilation are compared with EVV results. In the house kitchen models, the ventilation efficiency is examined with various positions of supply opening of outdoor air. In the house models, two conditions are studied. EVV is evaluated when 24 hour ventilation system is operated and when the kitchen exhaust system is operated. In the clean room models, the position of exhaust openings is examined. When the exhaust openings are installed at ceiling, calculated EVV is much higher than that in the case of wall exhaust openings.

Surfactant “fortification” by topical inhibition of nuclear factor-κB activity in a newborn piglet lavage model*

In acute respiratory distress syndrome of term newborn infants, surfactant replacement may be effective because endogenous surfactant is decreased and structurally changed. Inflammation is central to acute respiratory distress syndrome, and hence, attenuation of proinflammatory transcription factor nuclear factor (NF)-[kappa]B activation in the lung might prevent secondary loss of surfactant function. In this study, we tested the hypothesis that the topical use of a NF-[kappa]B inhibitor (I[kappa]B kinase-NF-[kappa]B essential modulator binding domain [IKK-NBD] peptide), together with surfactant as a carrier substance, improves surfactant function by attenuation of pulmonary inflammation during 24 hrs of mechanical ventilation in a neonatal piglet model of acute respiratory distress syndrome by repeated airway lavage. Prospective, randomized, controlled study. Research laboratory of a university children's hospital. A total of 24 anesthetized, mechanically ventilated newborn piglets. After 20 +/- 6 (mean +/- sd) lavages to induce lung failure and inflammation, a porcine surfactant (100 mg/kg) with (S+IKK) or without (S) 1.25 mg of IKK-NBD peptide, or an air bolus (control) was administered into the airways. Lung function was monitored throughout 24 hrs of mechanical ventilation and completed by ex vivo analyses. Pao2 (S+IKK, 125 +/- 16 mm Hg; S, 105 +/- 33; control, 61 +/- 20), ventilation efficiency index, functional residual capacity, compliance of the respiratory system, and extravascular lung water (S+IKK, 24 +/- 2 mL/kg; S, 30 +/- 7; control, 34 +/- 8) were all significantly improved in S+IKK piglets after 24 hrs. Decreased leukocyte concentrations in bronchoalveolar lavage (S+IKK, 152 +/- 94 cells/microL; S, 202 +/- 100; control, 276 +/- 57) were observed together with reduced acid sphingomyelinase activity, lowered ceramide concentrations, improved surfactant function (minimum surface tension: S+IKK, 10.8 +/- 6.1 mN/m; S, 13.2 +/- 3.9; control, 20.9 +/- 8.5), and decreased NF-[kappa]B activation in lung tissue. Supplementation of exogenous surfactant with a NF-[kappa]B inhibitor to create a "fortified" surfactant improves gas exchange, lung function, and pulmonary edema during 24 hrs of mechanical ventilation, without a secondary functional relapse. Inhibition of NF-[kappa]B suppressed acid sphingomyelinase activity and ceramide generation, indicating a novel proinflammatory link of NF-[kappa]B.

Cardiac Output and Cardiopulmonary Responses to Exercise in Heart Failure: Application of a New Bio-Reactance Device

Background Cardiopulmonary exercise testing (CPX) is widely used to evaluate heart failure (HF) patients, but lacks information about ventricular performance. There is a need for a noninvasive cardiac output (CO) measurement. Methods and Results Twenty-three HF patients and 13 normals underwent CPX and CO measurements with a new, noninvasive, bioreactance technology based on assessment of relative phase shifts (dΦ/dt) of electric currents injected across the thorax, heart rate, and ventricular ejection time. CO and oxygen uptake (VO 2) closely paralleled each another during exercise, and peak CO was strongly correlated with peak VO 2 ( r = 0.73, P < .001). The relationships between peak VO 2 and peak cardiac index (CI) were similar for directly measured CI ( r = 0.61) and noninvasive CI ( r = 0.61). The CO-VO 2 relationship was also similar between the current study and previous studies from the literature, as evidenced by a similar line of best fit and 95% confidence limits. Maximal CO was significantly related to indices of ventilatory efficiency, including the VE/VCO 2 slope ( r = −0.47, P < .01), and the oxygen uptake efficiency slope ( r = 0.67, P < .01). Conclusion Noninvasive measurement of CO during exercise using a novel bioreactance-based device has potentially important applications as a simple, inexpensive tool to supplement the clinical evaluation of patients with HF.

Retinoids Increase Lung Elastin Expression But Fail to Alter Morphology or Angiogenesis Genes in Premature Ventilated Baboons

Retinoids regulate elastin synthesis by alveolar myofibroblasts and affect angiogenesis pathways, both of which are processes critical for alveolar development. Retinoids accelerate alveolarization in rodents and are now used therapeutically in premature infants at risk of bronchopulmonary dysplasia (BPD). This study examined the effects of retinoid supplementation on alveolar elastin expression and deposition and angiogenesis-related signaling in a primate model of BPD. Premature baboons delivered at 125 d of gestation after maternal steroid treatment were given surfactant and ventilated with minimal supplemental oxygen for 14 d with (n = 5) and without (n = 5) supplemental vitamin A (5000 U/kg/d) and compared with 140-d unventilated controls. Ventilatory efficiency index (VEI) and oxygenation index (OI) were not statistically different between ventilated treatment groups. Expression of vascular endothelial growth factor A (VEGF-A), fms-related tyrosine kinase 1 (Flt-1), and tyrosine kinase with immunoglobulin-like and EGF-like domains 1 (TIE-1) was repressed by premature delivery and mechanical ventilation and was not altered by retinoid supplementation. Retinoid supplementation did not enhance alveolar angiogenesis. Elastin expression was repressed by premature delivery and extended ventilation, and retinoid supplementation increased elastin expression specifically in alveolar myofibroblasts within alveolar walls. These results suggest that the small decrease in mortality among premature infants receiving retinoid supplementation may not be mediated through enhanced alveolar development.

Lung function measurements in a preterm animal model of respiratory failure: Comparison of two different neonatal ventilators

A variety of ventilators are used in the NICU. Ventilator and lung function measures are often applied in weaning protocols or as outcome variables. The effect of different ventilators on these measures has not been well studied. Our objective was to compare ventilator and lung function measurements in a chronic preterm animal model managed with two different neonatal ventilators. Timed baboon pregnancies exposed to antenatal steroids were delivered by C/S at 125 days (term = 185 days). Infants were immediately intubated, given surfactant, and ventilated with low tidal volumes (4-6 ml/kg) for 6-14 days using well-defined protocols. One group was ventilated via InfantStar (IS) and the other by VIP-Bird (VIP). Physiologic and pulmonary function data were serially recorded with the VitalTrends plethysmography system. Between ventilator comparisons were made. InfantStar (IS) was used on 22 infants in 2002-03, VIP was used on 29 infants in 2004-05. No differences were found for gestation, birth weight, gender, paO(2), paCO(2), FiO(2), arterial/alveolar ratio, dynamic compliance, inspiratory resistance, or tidal volumes. From 24 to 336 h, peak and mean airway pressure, ventilator rate, and ventilatory efficiency index (VEI: PIP x R x CO(2)/1,000) were significantly greater in the VIP group at multiple time points. VIP use was associated with a significant increase in expiratory airway resistance (Rexp - cmH(2)O/L/s) at all but one-time points studied. Compared to the IS, use of the VIP-Bird ventilator in surfactant treated immature baboons with RDS was associated with increased expiratory airway resistance and indices of impaired ventilation, but not oxygenation. Ventilator management in the NICU, especially weaning, may be affected by the specific ventilator in use.

Prenatal Glucocorticoids and Exogenous Surfactant Therapy Improve Respiratory Function in Lambs with Severe Diaphragmatic Hernia Following Fetal Tracheal Occlusion

Fetal tracheal occlusion (TO) accelerates lung growth and can reverse severe lung hypoplasia associated with diaphragmatic hernia (DH), however, lung compliance (Cl) and respiratory gas exchange remain abnormal. We determined the individual and combined effects of prenatal glucocorticoids (GC) and exogenous surfactant therapy (S) on postnatal pulmonary function in lambs with DH that underwent prolonged TO. DH was created in 22 fetal sheep at 65 d of gestation and TO performed at 110 d. Eleven DH/TO animals received prenatal GC (betamethasone, 0.5 mg/kg) 48 h before delivery; six GC-treated and five non-GC lambs were administered surfactant (Infasurf, 3 mg/kg) at birth. Six sham-operated lambs served as controls. Lambs were delivered at 139 d gestation and ventilated for 2 h. GC or surfactant therapy alone significantly improved respiratory gas exchange, Cl, and ventilatory efficiency index. Total lung capacity was normalized only in DH/TO lambs that received both GC and S.

Test–retest reliability for two indices of ventilatory efficiency measured during cardiopulmonary exercise testing in healthy men and women

The level of ventilation (VE)) at a given carbon dioxide output (CO2) determines ventilatory efficiency. During cardiopulmonary exercise testing (CPET), ventilatory efficiency can be measured as the slope of the (VE) versus VCO2 relationship or the lowest VE/VCO2. We evaluated the test-retest reliability of these two ventilatory efficiency indices in 29 healthy subjects (14 males). Each subject performed duplicate cycle ergometer tests on different days. Ventilation and the gas fractions for oxygen and CO2 were measured with a Vacumed metabolic cart. Linear regression analysis of the VE versus VCO2 slope for the duplicate tests in the males, females, and both sexes combined yielded correlation coefficients of 0.822, 0.942, and 0.910, respectively. The corresponding correlation coefficients for the lowest VE/VCO2 were 0.745, 0.929, and 0.884. A comparison of the test-retest correlation coefficients between the two ventilatory efficiency measures for the men, women, and both sexes combined revealed that they were not significantly different and, for a given index, there were no sex differences. The bias (mean of difference scores between tests) and 95% limits of agreement for the VE versus VCO2 slope in the males, females, and both sexes combined were -0.05 +/- 2.41, -0.57 +/- 1.92, and -0.32 +/- 2.20, respectively. The bias and 95% limits of agreement for the lowest VE/VCO2 were very similar with values of 0.06 +/- 2.45, -0.22 +/- 2.03, and -0.10 +/- 2.27. We conclude that the test-retest reliability for the VE versus VCO2 slope and the lowest VE/VCO2 is the same and that there is no sex difference in reliability for either index of ventilatory efficiency.

Exercise test mode dependency for ventilatory efficiency in women but not men

Ventilatory efficiency is commonly defined as the level of ventilation V(E) at a given carbon dioxide output (V(CO(2) )). The slope of the V(E) versus V(CO(2) ) relationship and the lowest V(E)/V(CO(2) ) are two ventilatory efficiency indices that can be measured during cardiopulmonary exercise testing (CPET). A possible CPET mode dependency for these indices was evaluated in healthy men and women. Also evaluated was the relationship between these two indices as, in theory, V(E)/V(CO(2) ) falls hyperbolically towards an asymptote that numerically equals the V(E) versus V(CO(2) ) slope at exercise levels below the ones that cause respiratory compensation for metabolic acidosis. Twenty-eight healthy subjects (14 men) underwent treadmill and cycle ergometer CPET on different days. Ventilation and the gas fractions for oxygen and CO(2) were measured with a vacumed metabolic cart. In men, paired t-test analysis failed to find a mode difference for either ventilatory efficiency index but the opposite was true in the women as each woman had higher values for both indices on the treadmill. For men, the lowest V(E)/V(CO(2) ) was larger than the V(E) versus V(CO(2) ) slope by 1.3 on the treadmill and 0.8 on the cycle ergometer. The corresponding values for women were 1.7 and 1.4. We conclude that in healthy subjects, women, but not men, demonstrate a mode dependency for the two ventilatory efficiency indices investigated in this study. Furthermore, our results are consistent with the theoretical expectation that the lowest V(E)/V(CO(2) ) has a numerical value just above the asymptote of the V(E)/V(CO(2) ) versus V(CO(2) ) relationship.