Improvement In Pulmonary Mechanics Research Articles

Evaluation of the influence of individualized protective ventilation on the lung mechanical properties

The work is devoted to the study of the influence of individualized protective ventilation support on pulmonary mecha-nics. The study included 47 patients who underwent open abdominal surgery under general anesthesia. All patients had a moderate to high risk of developing postoperative pulmonary complications by the ARISCAT scale. Intraoperatively, the impact of individualized protective ventilation on respiratory mechanics, namely Ppeak, Pplat, Pdrive, dynamic pulmonary compliance was assessed. Individualized protective respiratory support was ventilation with a tidal volume of 7 ml/kg of ideal body weight, with the selection of the optimal level of positive pressure at the end of exhalation (PEEP), focusing on dynamic pulmonary compliance and performing recruiting maneuver, and then in the case of a decrease in dynamic pulmonary compliance by more than 20 %, followed by re-selection of PEEP. The studied parameters were recorded before and after the recruiting maneuver, as well as on the 30th, 60th, 90th, 120th, 150th, 180th minutes after the recruiting maneuver, depending on the duration of the operation. The use of alveolar straightening techniques led to an improvement in pulmonary mechanics, namely, an increase in dynamic pulmonary compliance by 16 % and a decrease in Pdrive by 17 %. The intraoperative level of PEEP averaged 4 [4; 5] cm of water. No cases of hypoxemia or recurrence of recruiting maneuver were reported. The obtained results indicate that chosen technique of recruiting maneuver is effective and safe, and its use allows reducing the negative impact of mechanical ventilation. The study did not find a statistically significant correlation between the level of PEEP and the value of dynamic pulmonary compliance. Such data prove the need for individual selection of ventilation parameters according to the characteristics of the mechanical properties of each patient.

Lidocaine for postoperative pain after cardiac surgery: a systematic review

ObjectiveLidocaine is one of the most widely used local anesthetics with well-known pharmacological properties. The purpose of this systematic review is to investigate the effects of lidocaine on postoperative pain scores and recovery after cardiac surgery.MethodsA comprehensive database search was conducted by a reference librarian for randomized clinical trials (RCT) from January 1, 1980 to September 1, 2019. Eligible study designs included randomized controlled trials of lidocaine for postoperative pain management in adults undergoing cardiac surgery. After removal of duplicates, 947 records were screened for eligibility and 3 RCTs met inclusion criteria.ResultsSources of bias were identified in 2 of 3 RCTs. Lidocaine was administered intravenously, topically, and intrapleurally. Key findings included [1] 2% lidocaine placed topically on chest tube prior to intraoperative insertion was associated with significantly lower pain scores and lower cumulative doses of fentanyl; and [2] 2% lidocaine administered intrapleurally was associated with significantly lower pain scores and significant improvements in pulmonary mechanics. Lidocaine infusions were not associated with significant changes in pain scores or measures of recovery. No significant associations were observed between lidocaine and overall mortality, hospital length of stay or ICU length of stay. No data were reported for postoperative nausea and vomiting or arrhythmias.ConclusionsDue to the favorable risk profile of topical lidocaine and the need for further advancements in the postoperative care of adults after cardiac surgery, topically administered lidocaine could be considered for incorporation into established postoperative recovery protocols.

Caffeine is associated with improved alveolarization and angiogenesis in male mice following hyperoxia induced lung injury

BackgroundCaffeine therapy for apnea of prematurity reduces the incidence of bronchopulmonary dysplasia (BPD) in premature neonates. Several mechanisms, including improvement in pulmonary mechanics underly beneficial effects of caffeine in BPD. As vascular development promotes alveologenesis, we hypothesized that caffeine might enhance angiogenesis in the lung, promoting lung growth, thereby attenuating BPD.MethodsC57Bl/6 mice litters were randomized within 12 h of birth to room air (RA) or 95%O2 to receive caffeine (20 mg/kg/day) or placebo for 4 days and recovered in RA for 12wks. The lung mRNA and protein expression for hypoxia-inducible factors (HIF) and angiogenic genes performed on day 5. Lung morphometry and vascular remodeling assessed on inflation fixed lungs at 12wks.ResultsCaffeine and hyperoxia in itself upregulate HIF-2α and vascular endothelial growth factor gene expression. Protein expression of HIF-2α and VEGFR1 were higher in hyperoxia/caffeine and angiopoietin-1 lower in hyperoxia. An increase in radial alveolar count, secondary septal count, and septal length with a decrease in mean linear intercept indicate an amelioration of hyperoxic lung injury by caffeine. An increase in vessel surface area and a significant reduction in smooth muscle thickness of the pulmonary arterioles may suggest a beneficial effect of caffeine on vascular remodeling in hyperoxia, especially in male mice.ConclusionsPostnatal caffeine by modulating angiogenic gene expression early in lung development may restore the pulmonary microvasculature and alveolarization in adult lung.

Effects of positive end-expiratory pressure and 30% inspired oxygen on pulmonary mechanics and atelectasis in cats undergoing non-bronchoscopic bronchoalveolar lavage.

Objectives The objective of this study was to determine if modification of inspired oxygen concentration or positive end-expiratory pressure (PEEP) would alter bronchoalveolar lavage (BAL)-induced changes in pulmonary mechanics or atelectasis, as measured using ventilator-acquired pulmonary mechanics and thoracic CT. Methods Six experimentally asthmatic cats underwent anesthesia and non-bronchoscopic BAL, each under four randomized treatment conditions: 100% oxygen, zero PEEP; 30% oxygen, zero PEEP; 100% oxygen, PEEP 2 cmH2O; and 30% oxygen, PEEP 2 cmH2O. Pulse oximetry was used to estimate oxygen saturation (SpO2). Ventilator-acquired pulmonary mechanics and thoracic CT scans were collected prior to BAL and at 1, 5 and 15 mins post-BAL. Results While receiving 100% oxygen, no cat had SpO2 <91%. Some cats receiving 30% oxygen had decreased saturation immediately post-BAL (mean ± SD 70.8 ± 31%), but 6/8 of these had SpO2 >90% by 1 min later. There was a significant increase in airway resistance and a decrease in lung compliance following BAL, but there was no significant difference between treatment groups. Cats receiving no PEEP and 30% oxygen conserved better aeration of the lung parenchyma in BAL-sampled areas than those receiving no PEEP and 100% oxygen. Conclusions and relevance Alterations in pulmonary mechanics or atelectasis may not be reflected by SpO2 following BAL. The use of 30% inspired oxygen concentration failed to show any significant improvement in pulmonary mechanics but did diminish atelectasis. In some cats, it was also associated with desaturation of hemoglobin. The use of PEEP in this study did not show any effect on our outcome parameters. Further studies using higher PEEP (5-10 cmH2O) and intermediate inspired oxygen concentration (40-60%) are warranted to determine if they would confer clinical benefit in cats undergoing diagnostic BAL.

Effects of Exercise Training on Pulmonary Mechanics and Functional Status in Patients With Prolonged Mechanical Ventilation

The functional status and outcomes in patients with prolonged mechanical ventilation (PMV) are often limited by poor endurance and pulmonary mechanics, which result from the primary diseases or prolonged time bedridden. We evaluate the impact of exercise training on pulmonary mechanics, physical functional status, and hospitalization outcomes in PMV patients. Twenty-seven subjects with PMV in our respiratory care center (RCC) were divided randomly into an exercise training group (n = 12) and a control group (n = 15). The exercise program comprised 10 sessions of exercise training. The measurement of pulmonary mechanics and physical functional status (Functional Independence Measurement and Barthel index) were performed pre-study and post-study. The hospitalization outcomes included: days of mechanical ventilation, hospitalization days, and weaning and mortality rates during RCC stay. The training group had significant improvement in tidal volume (143.6 mL vs 192.5 mL, P = .02) and rapid shallow breathing index after training (162.2 vs 110.6, P = .009). No significant change was found in the control group except respiratory rate. Both groups had significant improvement in functional status during the study. However, the training group had greater changes in FIM score than the control group (44.6 vs 34.2, P = .024). The training group also had shorter RCC stay and higher weaning and survival rates than the control group, although no statistical difference was found. Subjects with PMV in our RCC demonstrated significant improvement in pulmonary mechanics and functional status after exercise training. The application of exercise training may be helpful for PMV patients to improve hospitalization outcomes.

Patent Ductus Arteriosus Ligation Alters Pulmonary Gene Expression in Preterm Baboons

Ibuprofen-induced ductus closure improves pulmonary mechanics and increases alveolar surface area in premature baboons compared with baboons with a persistent patent ductus arteriosus (PDA). Ibuprofen-treatment has no effect on the expression of genes that regulate pulmonary inflammation but does increase the expression of alpha-ENaC (the transepithelial sodium channel that is critical for alveolar water clearance). Although ligation eliminates the PDA, it does not improve pulmonary mechanics or increase alveolar surface area. We used preterm baboons (delivered at 67% of term gestation and ventilated for 14 d) to study whether the lack of beneficial effects, after PDA ligation, might be due to alterations in pulmonary gene expression. We found no differences in ventilation or oxygenation indices between animals that were ligated (n = 7) on day of life 6 and those that had a persistent PDA (n = 12) during the entire 14 d study. In contrast with no intervention, PDA ligation produced a significant increase in the expression of genes involved with pulmonary inflammation (COX-2, TNF-α, and CD14) and a significant decrease in alpha-ENaC sodium channel expression. We speculate that these changes may decrease the rate of alveolar fluid clearance and contribute to the lack of improvement in pulmonary mechanics after PDA ligation.

Bronchioalveolar lavage with perfluorochemical liquid during conventional ventilation

Therapeutic approaches with bronchioalveolar lavage are currently used in infants with severe alveolar space-occupying material. In many circumstances, bronchioalveolar lavage has been performed in conjunction with extracorporeal membrane oxygenation. A 2-month-old boy with severe respiratory failure requiring assisted ventilation did not respond to any conventional treatments, including surfactant. An open-lung biopsy showed intra-alveolar accumulation of proteinaceous material and foamy macrophages but was not diagnostically conclusive. Therapeutic trials with bronchioalveolar lavage using normal saline were unsuccessful, causing episodes of severe hypoxemia. Then, bronchioalveolar lavage during conventional mechanical ventilation was performed with the use of a medical-grade perfluorochemical liquid (perfluordecalin). After instillation of liquid (10 mL/kg), the lungs were refilled three times during the first 24 hrs and repeated 48 hrs later. During perfluorochemical liquid treatment, the infant's condition remained stable, with small improvements in pulmonary mechanics. Suction from the endotracheal cannula yielded only small amounts of gelatinous material. Considering the progression of the disease and just minimal pulmonary improvements by this intervention, further treatment was considered futile. Support was, thus, minimized, and the infant died a few days later. An autopsy revealed the diagnosis to be consistent with Niemann-Pick C2 disease. This study demonstrated that bronchioalveolar lavage with perfluorochemical liquid could be performed safely during conventional mechanical ventilation without the additional support of extracorporeal membrane oxygenation in infants with severe alveolar space-occupying material.

HFOV in premature neonates: effects on pulmonary mechanics and epithelial lining fluid cytokines. A randomized controlled trial

Ventilation strategies for preterm neonates may influence the severity of pulmonary dysfunction and later development of chronic lung disease. The objective of this report is to compare the effects of high-frequency oscillatory ventilation (HFOV) versus synchronized intermittent mandatory ventilation (sIMV) from the points of views of biochemical and functional variables. Randomized controlled trial. Third level NICU. Forty preterm neonates with a gestational age of 24-29 weeks were randomly assigned to one of the two above-mentioned ventilation strategies within 30 min from birth. At 1, 3, 5, and 7 days, the babies were monitored by means of ventilator indices, pulmonary function, and eight pro-inflammatory or anti-inflammatory cytokines measured in bronchoalveolar lavage fluid. The neonates assigned to the HFOV procedure benefited from early and sustained improvement in pulmonary mechanics and gas exchange-significantly higher dynamic respiratory compliance values, significantly lower expiratory airway resistance and oxygenation index values-with earlier extubation as compared to the neonates assigned to sIMV treatment, and showed significantly lower transforming growth factor-beta1 concentrations in bronchoalveolar lavage fluid. The results of this randomized clinical trial support the hypothesis that early and exclusive use of HFOV, combined with optimum volume strategy, has a beneficial effect during the acute phase of lung injury.

Pulmonary function after surfactant lung lavage followed by surfactant administration in infants with severe meconium aspiration syndrome

Objective: The effect of surfactant lung lavage (SLL) on pulmonary function was examined in neonates with severe form of meconium aspiration syndrome (MAS) (mean ± standard deviation: birth weight, 3178.1 ± 237.6 g; gestational age, 37.7 ± 1.8 weeks). Methods: The infants were on mechanical ventilation and were subjected to SLL with Survanta®. Dynamic compliance (Cdyn), airway resistance (Raw) and mean airway pressure (MAP) were obtained with use of the pneumotachometric method. Measurements of Cdyn, Raw, MAP and time constant (Tc) were compared in the study and control groups and between the groups before SLL and 24 and 48 h after SLL. Results: A significant increase in Cdyn (from 1.06 ± 0.23 to 2.12 ± 0.99 (ml/cmH2O)/kg) (p < 0.05) and a drop in both Raw (from 264.7 ± 41.5 to 146.6 ± 39.4 (cmH2O/l)/s) and MAP (from 12.4 ± 3.6 to 5.4 ± 2.1 cmH2O) were observed 48 hours after SLL. Conclusions: These data suggest that SLL is associated with a rapid and significant improvement in pulmonary mechanics, together with an improvement in oxygenation, in newborns with severe MAS. We found that the beneficial effects of SLL on pulmonary mechanics persisted for at least 48 h after introduction of the procedure.

Can Exogenously Administered Hyaluronan Improve Respiratory Function in Patients With Pulmonary Emphysema?

While most attempts at developing a treatment for pulmonary emphysema have focused on the use of elastase inhibitors to reduce elastic fiber damage and the loss of alveoli, this laboratory has developed a method of preventing such injury by the intratracheal administration of hyaluronan (HA). Animals treated with HA prior to the induction of experimental emphysema develop significantly less disease than untreated controls. The protective effect of HA may be related to its ability to bind to lung elastic fibers, thereby preventing their breakdown by elastases. Although clinical trials involving nebulized HA are not expected to yield a measurable treatment effect for at least several years, it is proposed that the special ability of this polysaccharide to retain water may increase the elasticity of lung elastic fibers, producing a relatively rapid improvement in pulmonary mechanics. Such an outcome might speed the development of this potential treatment for pulmonary emphysema.

Effects of inhalation of perfluorocarbon aerosol on oxygenation and pulmonary function compared to PGI2 inhalation in a sheep model of oleic acid-induced lung injury.

To evaluate the effects of PFC aerosol compared to PGI2 aerosol and NaCl aerosol on gas exchange and lung mechanics in oleic acid-induced acute lung injury. A prospective, controlled, randomised, in vivo animal laboratory study. Research laboratory at an university hospital. Twenty one (n = 21) adult sheep of either gender weighing 26.8+/-6.4 kg. The animals were randomised to three groups: PFC aerosol (perfluorooctane), PFC group; prostacyclin aerosol (Flolan), PGI2 group; and NaCl aerosol (0.9% sodium chloride solution), control group. After induction of anaesthesia and placement of vascular catheters, lung injury was induced with 0.12 ml x kg(-1) oleic acid. Aerosols were continuously administered for 2 h using a jet nebuliser. Gas exchange, pulmonary mechanic, and haemodynamic parameters were obtained at regular intervals. PFC aerosol increased oxygenation (PaO2) 15 min after the initiation of treatment up to 120 min (P < 0.05). Transpulmonary shunt improved in the PFC group (P < 0.05) while it did not change in the two other groups. PFC aerosol reduced maximum airway pressure (Pmax) (median) significantly from (median) 38 mbar to 32 mbar (P < 0.05). Static compliance improved significantly in the PFC group (P < 0.05). The inhalation of a PFC aerosol led to a significant improvement in pulmonary mechanics and gas exchange, which was not observed in the other two groups. These data suggest that a small dose of perfluorocarbon will have beneficial effects on gas exchange and respiratory mechanics. Therefore, the non-invasive aerosol application technique seems to be a reasonable alternative to administer perfluorocarbons in severe lung injury.

Changes in dead space/tidal volume ratio and pulmonary mechanics after surfactant replacement therapy in respiratory distress syndrome of the newborn infants.

This study was performed to elucidate the mechanism of improved oxygenation after surfactant replacement therapy in respiratory distress syndrome (RDS) of the newborn infants. In 26 newborns with RDS, end tidal-CO2 tension (PetCO2), arterial blood gas analysis and pulmonary function tests were measured at baseline, 30 min, 2 hr and 6 hr after surfactant administration. The changes in dead space/tidal volume ratio (VD/VT ratio=(PaCO2-PetCO2)/PaCO2), oxygenation index and arterial-alveolar partial pressure difference for oxygen ((A-a)DO2) were elucidated and correlated with pulmonary mechanics. Oxygenation index and (A-a)DO2 improved, and VD/VT ratio decreased progressively after surfactant administration, becoming significantly different from the baseline at 30 min and thereafter with administration of surfactant. Pulmonary mechanics did not change significantly during the observation period. VD/VT ratio showed close correlation with OI and (A-a)DO2, but not with pulmonary mechanics. These results suggest that decreased physiologic dead space resulting from the recruitment of atelectatic alveoli rather than improvement in pulmonary mechanics is primarily responsible for the improved oxygenation after surfactant therapy in the RDS of newborn.

High-frequency Oscillatory Ventilation

Acute lung injury models demonstrate that high-frequency oscillatory ventilation (HFOV) improves lung function, mechanics, and histopathology with reduced inflammatory mediators. Neither human HFOV trials nor premature animal studies have adequately evaluated these factors during prolonged HFOV. The objective of this study was to compare the effect of prolonged HFOV with low tidal volume (VT) positive pressure ventilation (LV-PPV) in an immature baboon model for neonatal chronic lung disease (CLD). After administration of prenatal steroids, 18 baboons were delivered by cesarean section at 125 d (term = 185 d), treated with exogenous surfactant, then randomized to either HFOV or LV-PPV by 5 min age. Animals were maintained on oxygen on an "as needed" basis and on nutritional support for 1 to 2 mo. Serial pulmonary function testing (PFT) was performed. Tracheal aspirates were analyzed for interleukin-6 (IL-6), IL-8, tumor necrosis factor-alpha (TNF-alpha), IL-1beta, and IL-10. Lungs were inflation fixed for morphometric analyses. From 12 h through 10 d age, HFOV animals had consistently lower fraction of inspired oxygen (FI(O(2))) and higher a/ A ratio. Pulmonary mechanics were significantly improved in HFOV animals at nearly every time point analyzed from 12 h to 28 d. There were no consistent differences in tracheal IL-6, TNF-alpha, IL-1beta, or IL-10 after 24 h age. Higher tracheal IL-8 values and macrophage/monocyte numbers were found in LV-PPV animals after 1 wk and 3 to 4 wk ventilation. Both groups exhibited pulmonary pathologic lesions found in extremely immature humans, including alveolar hypoplasia, variable saccular wall fibrosis, and minimal airway disease. HFOV animals had significantly better lung inflation patterns by panel of standards analysis. Early, prolonged HFOV significantly improved early lung function with sustained improvement in pulmonary mechanics out to 28 d. Immature baboons managed with HFOV had less pulmonary inflammation in the hyaline membrane disease (HMD) recovery phase. Though enhanced alveolization was not observed, HFOV for 1 to 2 mo resulted in consistently more uniform lung inflation than LV-PPV.

Weight Gain After Lung Volume Reduction Surgery Is Not Correlated With Improvement in Pulmonary Mechanics

Malnutrition and low body weight are common in patients with emphysema. Previous work has demonstrated correlation between severity of airflow obstruction and body weight. Lung volume reduction surgery (LVRS) is a recent advance in the treatment of patients with severe emphysema that results in improved pulmonary function. We formed the hypothesis that improved lung mechanics after LVRS would result in body weight gain. Retrospective chart review. All patients who underwent bilateral LVRS for severe emphysema at the University of Michigan between January 1995 and April 1996 were eligible for the study. Pulmonary function and body weight were measured preoperatively and at 3, 6, and 12 months postoperatively for patients who underwent bilateral LVRS between January 1995 and April 1996. The average weight gain in 38 patients returning for 12 months of follow-up was 3.8 +/- 0.9 kg, or 6.2% of the preoperative weight. Women gained significantly more weight than men (9.2 vs 2.2%, respectively) at 1 year. Interestingly, there was no correlation between change in weight and postoperative change in FEV(1), FVC, residual volume (RV), total lung capacity (TLC), or RV/TLC at 12 months. However, there was a statistically significant correlation between weight gained and improvement in diffusion of carbon monoxide measured 12 months postoperatively. This study shows that patients with severe emphysema gain weight after LVRS. These changes were independent of changes in pulmonary mechanics but may be a result of improved gas exchange. These findings provide further information about benefits of LVRS in patients with advance emphysema that are beyond simple changes in pulmonary function.

Causes of allograft dysfunction after single lung transplantation for emphysema: extrinsic restriction versus intrinsic obstruction

Background: A subset of patients with emphysema who have undergone single lung transplantation (SLT) may subsequently present with dyspnea, worsening airways obstruction, hypoxemia, and progressive chronic native lung hyperinflation. The leading cause of late allograft dysfunction is bronchiolitis obliterans syndrome (BOS). However, extrinsic restriction manifests with a similar clinical presentation and is an additional mechanism to consider. We describe the use of the inspiratory lung resistance (R Li) to distinguish a decline in respiratory status due predominantly to either extrinsic restriction or BOS. Methods We studied five patients who underwent SLT for emphysema between 1992 and 1995, in whom the diagnoses of BOS and extrinsic restriction were subsequently entertained. Forced expiratory volume in 1 second (FEV 1), R Li, static lung compliance, elastic recoil pressure at total lung capacity (TLC), and the slope of the maximum flow static recoil (MFSR) plot were measured. Results All patients had severe airflow obstruction, with mean FEV 1 0.98 ± 0.24 liter (26 ± 5% predicted), elevated static lung compliance, reduced elastic recoil pressure at TLC, and reduced slope of the MFSR plot. Three patients had “low” R Li (9.3–12.8 cm H 2O/L/sec). Obstruction was attributed predominantly to extrinsic restriction. These patients underwent lung volume reduction surgery (LVRS) on the native lung; improvements in pulmonary mechanics were observed at 6 months. In contrast, two patients had markedly elevated R Li (17.3 and 17.4 cm H 2O/L/sec). Obstruction was attributed predominantly to intrinsic airway disease from BOS that was subsequently documented at autopsy. Conclusions The R Li appears to be a useful adjunct to the clinical history in distinguishing a decline in respiratory status due predominantly to either BOS or extrinsic restriction in patients who have undergone SLT for emphysema. Determination of the mechanism of allograft dysfunction may allow the selection of an appropriate subset of patients who would benefit from LVRS.

LUNG VOLUME REDUCTION IS OF QUESTIONABLE BENEFIT IN A TRANSPLANT POPULATION

985 PURPOSE: To determine the benefit of lung volume reduction surgery (LVRS) in those patients awaiting lung transplant (LTx). METHODS: The records of 13 patients who were listed for LTx and had undergone LVRS were reviewed and compared to 10 non listed patients (NLP) who had undergone LVRS with respect to pulmonary mechanics, exercise capacity, and functional status. As well, the pulmonary architecture was evaluated with CT scanning and grading. RESULTS: Bilateral procedures were done in 12/13 patients. A gradient was present in 7/13 patients but was less pronounced than the NSP group where a significant gradient was observed. The table below shows functional data of the LTx group compared to the NLP. Results for pulmonary mechanics are reported as a percentage ± SD based on indexed BSA.Table*Currently 2 listed patients feel "too well" for transplant, 3 patients have been transplanted, and 8 patients are awaiting transplant. CONCLUSIONS: LVRS for LTx patients does not appear to offer significant improvement or durable relief from emphysema when compared to a cohort of carefully selected patients with a significant gradient on CT scanning. Although participation in pulmonary rehabilitation did improve exercise capability significantly in both groups, this did not appear to be due to a significant improvement in pulmonary mechanics in the LTx group. The use of LVRS as a bridge to transplant may be of benefit in only carefully selected patients.

Improved pulmonary function after surgical reduction of congenital diaphragmatic hernia in lambs

Background/Purpose: Modern trends are toward delayed surgical reduction of congenital diaphragmatic hernia. This study was conducted to verify the hypothesis that the “ease” of ventilation found in the authors' postoperative experience in infants with congenital diaphragmatic hernia (CDH) is associated with postsurgical improvement in pulmonary mechanics. Methods: Very severe CDH was surgically induced in utero at 90 days' gestation in 31 lambs. At birth pulmonary mechanics (PeDS-Lab) was measured in these preterm lambs with (n = 24) and without (n = 7) early surgical reduction, and in eight non-CDH controls over the same period; functional residual capacity (FRC) also was obtained from 14 of the 31 CDH lambs (seven reduced animals and seven unreduced ones). Management excluded aspiration from the thorax and insertion of chest drains. Results: After 30 minutes of life CDH animals with early surgical reduction demonstrated significantly greater improvement in lung volume, pulmonary mechanics, and oxygenation than those without reduction: FRC, 235% versus 19%; compliance, 57% versus 14%; minute ventilation, 71% versus 30%; and P o 2, 143% versus −15%. Over the same period, in preterm controls without CDH, only the compliance varied significantly, demonstrating a 32% increase. Conclusion: Based on the mechanics of breathing in these lambs, the authors speculate that neonates with CDH could benefit from early surgical repair because of improvement in pulmonary function, provided extra care is taken to prevent pulmonary overdistension.

Respiratory drive and pulmonary mechanics during haemodialysis with ultrafiltration in ventilated patients.

The improvements of respiratory drive and pulmonary mechanics which follow haemodialysis with ultrafiltration in mechanically ventilated renal failure patients seem predictable but have not been studied before. In this study, 14 renal failure patients with stable haemodynamics mechanically ventilated with pressure support ventilation (PSV) were enrolled. Respiratory drive (represented as P0.1), pulmonary mechanics, breathing pattern, arterial blood gas and haemodynamics were measured according to the time schedule: pre-dialysis (Time 0), and at 60, 120, 180, 240 minutes thereafter. Following the removal of excess lung water during haemodialysis, auto-PEEP and patient's work of breathing (WOBp) decreased gradually. P0.1 lessened progressively along with the improvement in pulmonary mechanics. The changes in auto-PEEP and WOBp correlated closely to the pre- and post-dialysis decline of P0.1 (delta P0.1). There was a negative, moderately significant correlation between the amount of fluid ultrafiltrated during dialysis (delta UF) and the delta P0.1 (R = -0.54). The breathing pattern remained stable during dialysis. No hypoventilation or hypoxaemia occurred despite the development of metabolic alkalosis induced by bicarbonate dialysate. We have shown that respiratory drive decreases gradually during bicarbonate haemodialysis. The improvements of pulmonary mechanics, rather than the rapid alkalization of body fluids, responds to the decrease of P0.1 in renal failure patients ventilated with PSV.

Pulmonary Effect of Inhaled Furosemide in Ventilated Infants With Severe Bronchopulmonary Dysplasia

To the Editor. We read with interest the article by Kugelman et al in the January 1997 issue of Pediatrics entitled “Pulmonary effect of inhaled furosemide in ventilated infants with severe bronchopulmonary dysplasia.”1In the article the authors conclude that a single dose of 1 mg/kg inhaled furosemide does not improve the pulmonary mechanics in ventilator-dependent infants with bronchopulmonary dysplasia (BPD).When a drug is administered by nebulization, only a fraction of the dose administered reaches terminal bronchioles and alveoli. Because the exact mode and site of action of nebulized furosemide on lung mechanics is not known, it may be important for the drug to reach the distal part of the tracheobronchial tree for it to have any effect on pulmonary mechanics. Hence, the lack of pulmonary response in this study may be due to furosemide not reaching the distal bronchial tree.We have previously shown that 1 mg/kg body weight of furosemide administered by nebulization significantly improved pulmonary compliance and tidal volume compared with a single identical dose of furosemide administered intravenously.23 The pulmonary beneficial effects of furosemide were independent of its diuretic action. We nebulized furosemide with a side flow of 2 liters per minute. With a side flow of 5 to 6 liters per minute as used by the authors in this study, in infants who are on low ventilatory settings, it would take less than 2 minutes to nebulize 2 mL of furosemide solution. Therefore, it is possible that much of the drug has gone into the expiratory limb without reaching the lung. Administering the drug over a longer period with lower side flow may enhance the proportion of the drug reaching the distal airway.Also, the infants studied by Kugelman et al are comparatively older (mean age: 47 ± 6 days) than the infants studied by us (mean age: 27 ± 13 days). It is possible that the nebulized furosemide improves pulmonary mechanics when used well before the chronic lung disease of prematurity is fully established.In Reply. We appreciate the comments of Drs Prabhu and Dhanireddy, who reported recently on a positive response to inhaled furosemide in infants with bronchopulmonary dysplasia (BPD).1-1 They reported increased pulmonary compliance in 15 preterm infants after nebulized furosemide (1 mg/kg) as compared with intravenous furosemide; neither nebulized nor intravenous furosemide had any significant effect on airway resistance.1-1Furosemide, a loop diuretic, has been shown to improve pulmonary mechanics when administered parenterally to infants with BPD.1-21-3 Specific improvement in clinical status, airway resistance, and dynamic pulmonary compliance has been observed.1-21-3 Furthermore, Rastogi et al1-4 have shown in a preliminary study that inhaled furosemide improved respiratory compliance and resistance in preterm infants with BPD. Our preliminary study1-5 and a report of Raval et al,1-6 both randomized, double-blind, controlled studies, failed to show improvement in pulmonary mechanics in ventilated infants with severe BPD with a single dose of 1 mg/kg of inhaled furosemide. Negative results using aerosolized furosemide have also been reported in another double-blind study involving wheezing infants at 2 to 18 months of age.1-7 It is possible that the latter studies1-5-1-7 highlight the need for placebo-controlled studies of new therapies (ie, inhaled furosemide) when assessing efficacy in diseases with a high degree of variability such as BPD.The lack of response to inhaled furosemide in intubated infants could be attributed to technical and physiological factors as discussed in our article.1-5 We agree with Drs Prabhu and Dhanireddy that furosemide may not affect pulmonary mechanics because of poor delivery to the distal part of the tracheobronchial tree, and that the mode of delivery of presently available systems1-5-1-7 has to be improved or perhaps a higher dose should be used. Using a lower side flow as a method to improve delivery is a speculation that has to be studied further. However, attention should be given to keeping the same ventilator pressures and to the increased dead space at the time of furosemide delivery when it is prolonged.Our patients were older (mean age, 47 ± 6 days) compared with those in the report of Prabhu et al (27 ± 13 days), and had lower baseline respiratory compliance when compared with the report of Rastogi et al.1-4 Thus, different results could be explained by different severity of lung disease.In summary, further study is required to resolve whether there is a role for inhaled furosemide in the treatment of infants with BPD, and to define the dose, mode of delivery, and the target population.

Lung reduction surgery for emphysema.

Lung reduction surgery, a procedure that entails removal of portions of the most diseased lung tissue in patients with diffuse emphysema, has been resurrected based on advances in surgical technique, radiographic imaging, and pulmonary physiologic assessment. We outline potential mechanisms for improvement in pulmonary mechanics, gas exchange, pulmonary vascular function, and exercise tolerance following surgery. Available literature is reviewed, and patterns that are beginning to emerge with respect to optimal surgical approach and patient selection criteria are presented. Early results suggest that this procedure offers real hope to our patients; however, long-term follow-up studies will be necessary to define its ultimate utility.