Comparison of dynamic and passive measurements of respiratory mechanics in ventilated newborn infants

Pulmonary mechanics may differ in intubated and ventilated infants depending on whether they are measured by a dynamic or passive method. The objective of this study was to compare respiratory mechanics measured by a dynamic technique with those obtained by a single-breath occlusion technique in ventilated newborn infants. Thirty-one preterm and 15 term infants (mean ± SD: gestational age, 29.3 ± 2.3 and 39.5 ± 1.4 weeks; birth weight, 1.2 ± 0.5 and 3.4 ± 0.4 kg; postnatal age, 12 ± 13 and 5 ± 4 days, respectively) were studied. Flows were measured through a pneumotachometer placed between the endotracheal tube and the ventilator circuit: tidal volume by integration of flow, and airway pressure directly with a pressure transducer. Airway occlusion was performed with a Neonatal Occlusion Valve (Bicore pulmonary monitor) at the end of inspiration, and the following relaxed exhalation was analyzed to give passive respiratory system compliance (C_rs) and resistance (R_rs). These values were compared with dynamic respiratory system compliance (C_dyn) and dynamic expiratory resistance (R_e) obtained with the PEDS system (P) within 1 hour, without an esophageal balloon and on the same ventilator settings. Dynamic respiratory system compliance and resistance measured with the PEDS and the Bicore systems did not differ significantly and were well correlated. Mean C_dyn(P) values in preterm and term infants were 77% and 77% of C_rs the equation of the regression line was c_dyn = 0.75 c_rs + 0.02 and C_dyn = 0.78 c_dyn ? 0.02; and standard error of the estimate (SEE) was 0.2 and 0.3 mL/cmH₂O with a correlation coefficient (r) of 0.89 and 0.89 (P < 0.0001), respectively. The mean R_e (P) values in preterm and term infants were 68% and 64% of R_rs and the equation of the regression line was R_e = 0.3 R_rs + 63 and R_e = 0.5 R_rs + 20, with SEE of 25 and 20 cmH₂O/Lsec, and r of 0.65 and 0.69 (P < 0.0001, P < 0.005). respectively. The two methods are non-invasive and were well tolerated. We conclude that passive and dynamic respiratory compliance and resistance measured in intubated infants are highly correlated, although the values measured by the passive technique are higher than those obtained by the dynamic technique. Pediatr Pulmonol. 1995; 20:258–264 . © 1995 Wiley-Liss, Inc.     

Predictive value of measurements of respiratory mechanics in preterm infants with HMD

Conventional methods for measuring respiratory mechanics model the respiratory system as a single compartment. The interrupter technique allows the respiratory system to be considered as a two compartment model with “flow resistance” of the conducting airways (Pinit), calculated from the initial pressure drop (Pinit), considered separately from Pdiff, as a measure of the viscoelastic properties of the lung and chest wall and any pendelluft present. The pulmonary mechanics of 50 intubated and mechanically ventilated preterm infants (≤1500 g) were studied during the first week of life using conventional methods and the interrupter technique to determine whether it was possible to predict which infants would develop bronchopulmonary dysplasia (BPD). Pulmonary mechanics of preterm infants intubated and ventilated for apnea of prematurity were also studied. The dynamic compliance of the respiratory system (C_rsdyn) was significantly lower on day 1 (P<0.001) and during the first week of life in the infants with HMD who developed BPD (ANOVA, P<0.0001). There was no significant difference in the respiratory system resistance (R_rs), Rinit, or Pdiff between BPD and no-BPD groups. However, Pdiff was significantly higher in infants with HMD, regardless of the outcome, when compared to the infants ventilated for apnea of prematurity. This suggests that the pathology of HMD is distal to the conducting airways and significantly alters the viscoelastic properties of the lung on day 1. Using stepwise logistic regression, C_rsdum on day 1 and birth weight or gestational age were significant independent predictors of the development of BPD, correctly classifying 92% of infants. Due to the correlation between birth weight and gestational age (r = 0.72, P<0.0001). only one of these variables was necessary in the prediction model. In conclusion, C_rsdyn is a better independent predictor of the development of BPD in preterm infants with HMD than gestational age or birth weight. Pediatr Pulmonol. 1993; 16:116–123. © 1993 Wiley-Liss, Inc.     

Respiratory oscillation mechanics in infants with bronchiolitis during mechanical ventilation

The aim of the study was to describe the pattern of respiratory oscillation mechanics and responses to positive end-expiratory pressure (PEEP) in bronchiolitis. Six infants were studied during the course of mechanical ventilation. A 20 Hz sinusoidal pressure variation was applied at the endotracheal tube where flow was measured with a pneumotachograph. Resistance and reactance obtained from the complex pressure-flow ratio were separated during inspiration (R_rs,i; X_rs,i) and expiration (R_rs,e; X_rs,e), and the differences between R_rs,i and R_rs,e (ΔR_rs) and X_rs,i and X_rs,e (ΔX_rs) were calculated. The data were corrected for the mechanical characteristics of the endotracheal tube. The measurements were repeated while PEEP was varied between 0 and 8 hPa. Two infants were found to have normal R_rs and near-zero X_rs and both parameters exhibited little change within the respiratory cycle or with varying PEEP. Four infants had high R_rs at zero PEEP. In two, R_rs,i was markedly elevated (108.5 and 85.2 hPa · s/L, respectively), and X_rs,i was markedly negative (−25.0 and −22.5 hPa · s/L, respectively) at zero PEEP, while ΔR_rs and ΔX_rs were small. R_rs,i and the absolute value of X_rs,i decreased with increasing PEEP. This pattern of oscillation mechanics was consistent with low lung volumes and atelectasis, being reversed by increasing PEEP. In the remaining two subjects, R_rs,i was moderately elevated (57.8 and 53.6 hPa · s/L, respectively) and X_rs,i moderately negative (−12.5 and −7.7 hPa · s/L, respectively) at zero PEEP. ΔR_rs (−59.8 and −56.5 hPa · s/L, respectively) and Δ_rs (28.1 and 48.7 hPa · s/L, respectively) were large, but were dramatically reduced by increasing PEEP. These patterns were consistent with expiratory airflow limitation. Measurements of respiratory impedance are, therefore, informative in regard to the pathophysiological mechanisms occurring in bronchiolitis during mechanical ventilation, and they may be helpful in setting the level and assessing the effect of PEEP. Pediatr. Pulmonol. 1998; 25:18–31. © 1998 Wiley-Liss, Inc.     

Assessment of passive respiratory mechanics in infants: double versus single occlusion?

The single breath or occlusion technique (SOT) is widely used to assess passive respiratory mechanics in infants, but depends on various underlying assumptions. Recently, it has been proposed that such measurements could be internally validated by performing two brief airway occlusions during the same expiration. The aim of this study was to evaluate the use of the double occlusion technique (DOT) using a new commercially available program (Jaeger MasterScreen BabyBody Erich Jaeger GmbH, Würzburg, Germany). Paired measurements of respiratory system compliance (Crs) and resistance (Rrs) using both SOT and DOT were obtained in 18 healthy sedated infants (age range 4-41 weeks, weight 2.7-9.9 kg). There was close agreement between both methods of assessing Crs in all infants, the mean within-subject difference (95% confidence interval (CI)) for DOT-SOT being -0.06 (-0.55- +0.42) mL x kPa(-1) x kg(-1). By contrast, estimates of Rrs,DO were on average 20% lower than those for Rrs,SO, (mean within-subject difference (95% CI) being -0.67 (-1.04- -0.31) kPa x L(-1) x s; p<0.01). The relatively lower values obtained for Rrs,DO may reflect the higher mean lung volume at which it was calculated. Further work is required to investigate the clinical and epidemiological relevance of this new approach, and whether there are any advantages of using both techniques when assessing passive mechanics in infants.     

Pulmonary mechanics following albuterol therapy in mechanically ventilated infants with bronchiolitis

Background and aims. Bronchiolitis is a common cause of critical illness in infants. Inhaled β(2)-agonist bronchodilators are frequently used as part of treatment, despite unproven effectiveness. The purpose of this study was to describe the physiologic response to these medications in infants intubated and mechanically ventilated for bronchiolitis. Materials and methods. We conducted a prospective trial of albuterol treatment in infants intubated and mechanically ventilated for bronchiolitis. Before and for 30 minutes following inhaled albuterol treatment, sequential assessments of pulmonary mechanics were determined using the interrupter technique on repeated consecutive breaths. Results: Fifty-four infants were enrolled. The median age was 44 days (25-75%; interquartile range (IQR) 29-74 days), mean hospital length of stay (LOS) was 18.3 ± 13.3 days, mean ICU LOS was 11.3 ± 6.4 days, and mean duration of mechanical ventilation was 8.5 ± 3.5 days. Fifty percent (n = 27) of the infants were male, 81% (n = 44) had public insurance, 80% (n = 41) were Caucasian, and 39% (n = 21) were Hispanic. Fourteen of the 54 (26%) had reduction in respiratory system resistance (Rrs) that was more than 30% below baseline, and were defined as responders to albuterol. Response to albuterol was not associated with demographic factors or hospitalization outcomes such as LOS or duration of mechanical ventilation. However, increased Rrs, prematurity, and non-Hispanic ethnicity were associated with increased LOS. Conclusions. In this population of mechanically ventilated infants with bronchiolitis, relatively few had a reduction in pulmonary resistance in response to inhaled albuterol therapy. This response was not associated with improvements in outcomes.     

Effect of maternal smoking during pregnancy on passive respiratory mechanics in early infancy

We studied the effect of prenatal maternal cigarette smoking on passive expiratory mechanics in 53 healthy infants tested early in infancy (mean ± SD, 5.1 ± 1.5 weeks). Maternal smoking was measured by: 1) questionnaire reports of the number of cigarettes smoked per day; and 2) urine cotinine concentrations (corrected for creatinine) at each visit. Respiratory system mechanics were assessed by the single-breath occlusion-passive-flow-volume maneuver. In ten infants born to smoking mothers the time constant of the respiratory system was 23% reduced [0.34 vs. 0.44 s; 95% confidence interval (CI), ?45% + 1%; P = 0.06]. This was related to an estimated 13% decrease in respiratory system compliance (4.86 vs. 5.62 Ml/cmH₂O; 95%Cl, ?33% + 6%; P = 0.18) and a 10% reduction in respiratory system resistance (0.073 vs. 0.081 cmH H₂O/mL/s; 95%Cl, ?42% + 22%; P = 0.56). Functional residual capacity (FRC), measured by helium-dilution, was also decreased by 13% (78 vs. 90 mL; 95%Cl, ?27% + 0.3%; P = 0.06) in smoke-exposed infants. Forced expiratory flow rates at FRC obtained by thoraco-abdominal compression were reduced by 28% in infants of smoking mothers (VFRc, 99 vs. 138 rnlis; 95%Cl, ?54% + 2%; P = 0.04), as reported previously in a larger sample from this population. This study was limited by small numbers of infants exposed to smoking during pregnancy and by ethnic imbalance among the smoking-exposed and unexposed groups. Nevertheless, it suggests that the diminished forced expiratory flows observed in infants exposed in utero to maternal tobacco smoking (UTS) are not attributable to increases in lung compliance, resistance, or a delay in passive lung emptying. Rather, the data support the hypothesis that UTS exposure may cause a reduction in airway size as well as alterations in the growth and/or maturation of passive mechanical properties of the respiratory system in healthy newborns. © 1995 Wiley-Liss, Inc.     

Recombinant human deoxyribonuclease in infants with respiratory syncytial virus bronchiolitis

BACKGROUND: Treatment of hospitalized infants with respiratory syncytial virus (RSV) bronchiolitis is mainly supportive. Bronchodilators and systemic steroids are often used but do not reduce the length of hospital stay. Because hypoxia and airways obstruction develop secondary to viscous mucus in infants with RSV bronchiolitis, and because free DNA is present in RSV mucus, we tested the efficacy of the mucolytic drug recombinant human deoxyribonuclease (rhDNase). METHODS: In a multicenter, randomized, double-blind, controlled clinical trial, 225 oxygen-dependent infants admitted to the hospital for RSV bronchiolitis were randomly assigned to receive 2.5 mg bid of nebulized rhDNase or placebo until discharge. The primary end point was length of hospital stay. Secondary end points were duration of supplemental oxygen, improvement in symptom score, and number of intensive care admissions. RESULTS: There were no significant differences between the groups with regard to the length of hospital stay (p = 0.19) or the duration of supplemental oxygen (p = 0.07). The ratio (rhDNase/placebo) of geometric means of length of stay was 1.12 (95% confidence interval, 0.96 to 1.33); for the duration of supplemental oxygen, the ratio was 1.28 (95% confidence interval, 0.97 to 1.68). There were no significant differences in the rate of improvement of the symptom score or in the number of intensive care admissions. CONCLUSIONS: Administration of rhDNase did not reduce the length of hospital stay or the duration of supplemental oxygen in oxygen-dependent infants with RSV bronchiolitis.     

A new application of an old method for respiratory mechanics measurements: The passive inflation method in newborn infants during pressure-controlled ventilation

We have previously described a passive inflation method during constant inspiratory flow for measuring total respiratory elastance and resistance during mechanical ventilation in newborns. The simple method for measuring respiratory mechanics had been assessed during decelerating inspiratory flow obtained with pressure controlled ventilation (PCV). We report an application of this method to preterm and full-term mechanically ventilated newborn infants and a comparison with the occlusion method. Twenty-one newborn infants (birth weight 1,060 to 3,650 g; gestational age 26 to 41 weeks), between 1 to 55 days of postnatal age, were enrolled in the study. They were ventilated with a “Servo ventilator 900C,” first set in the pressure-controlled mode and then in the volume-controlled mode without changing the tidal volume (V_T, inspiratory time or ventilator rate. Flow was measured through a pneumotachograph inserted between the endotracheal tube (ETT) and the breathing circuit; V_T, was obtained by integration of flow and airway pressure measured directly at the airway opening. Flow, volume, and pressure were plotted on analog XIY tables to obtain pressure-volume (P/V) and flow-volume (V/V) loops, as well as pressure-time curves. Occlusion was performed by using the end-inspiratory and the end-expiratory pause buttons of the ventilator. The passive inflation method during PCV was based on the analysis of P/V and V/V loops and provided compliance (C_rs(PC)infl.), resistance R_rs(PC)infl.) of the respiratory system, and intrinsic positive end-expiratory pressure (PEEP_(PC)i,infl.). These values were compared with (1) compliance (C_rs(PC)occl.) and intrinsic positive end-expiratory pressure (PEEP_(pc)i,occl.) measured by the occlusion method during PCV; (2) static (C_rs(vc).occl.) and dynamic (C_rs(VC),dyn.) compliance, airway (R_aw(vc),), tissue (R_rs(vc),visc.) and total resistance (R_(VC),occl.), and intrinsic positive end-expiratory pressure (PEEP_(VC)i.occl.) measured by the occlusion method during volume-controlled ventilation. C_rs(PC).infl. correlated will with C_rs(PC).occl., C_rs(VC).occl., and C_(VC)rs.dyn. Furthermore, C_rs(PC).infl. and C_rs(VC).dyn. did not differ significantly. R_rs(PC),infl. correlated well and did not differ significantly from total inspiratory resistance, i.e., the sum of Raw_aw(VC) and R_rs(VC).vis PEEP _PC.i.infl. correlated well and did not differ significantly from PEEP(PC)i.occl. and from PEEP_(VC),I,occl. The passive inflation method can be used during PCV with a decelerating flow waveform. It provides dynamic compliance, inspiratory resistance of the respiratory system, and intrinsic PEEP from the analysis of V/V and P/V loops recorded at the airway opening. This technique is simple to use and well tolerated by preterm and full-term ventilated newborn infants. It can be a good alternative to occlusion methods. Pediatr Pulmonol. 1994;18:244–254 . ©1994 Wiley-Liss, Inc.     

Bronchial reactivity in infants in acute respiratory failure with viral bronchiolitis

Airway reactivity and the effects of bronchodilators in infants are controversial. We studied the response to bronchodilator treatment in 14 mechanically ventilated infants (mean age, 2.74 months; range, 0.6-5.9) in respiratory failure caused by respiratory syncytial virus (RSV)-associated bronchiolitis. Sixteen infants without lung disease, undergoing elective surgery, provided normal values. Maximum expiratory deflation flow-volume (DFV) curves were produced by manual inflation of the lungs with an anesthesia bag to a predetermined static airway pressure followed by rapid deflation with a negative airway pressure before and after administration of bronchodilator. At baseline, the bronchiolitis group had a forced vital capacity (FVC) of 34.5 +/- 3.6 ml/kg compared with 41.8 +/- 1.5 ml/kg in the normal group; maximum expiratory flow rate at 25% of FVC (MEF25) was 10.2 +/- 2.0 ml/kg/s compared with 27.3 +/- 2.0 ml/kg/s in the normal group. The clinical and radiologic impression was severe lower airway obstruction and air trapping. After administration of bronchodilator, FVC did not increase significantly, but MEF25isov increased by over 30% in 13 of 14 infants. Mean MEF25 increased by 148 +/- 43.2% to 21.7 +/- 3.9 ml/kg/s (P less than 0.02). These findings indicate that during the acute phase of severe RSV-positive bronchiolitis most infants have airway reactivity that responds positively to bronchodilator treatment.     

Whole blood gene expression in infants with respiratory syncytial virus bronchiolitis

Background  

Respiratory syncytial virus (RSV) is a major cause of viral bronchiolitis in infants worldwide, and environmental, viral and host factors are all of importance for disease susceptibility and severity. To study the systemic host response to this disease we used the microarray technology to measure mRNA gene expression levels in whole blood of five male infants hospitalised with acute RSV, subtype B, bronchiolitis versus five one year old male controls exposed to RSV during infancy without bronchiolitis. The gene expression levels were further evaluated in a new experiment using quantitative real-time polymerase chain reaction (QRT-PCR) both in the five infants selected for microarray and in 13 other infants hospitalised with the same disease.     

Birthweight, early passive respiratory system mechanics, and ventilator requirements as predictors of outcome in premature infants with respiratory failure.

Early respiratory mechanics have been reported to predict outcome in newborns with respiratory failure. However, it remains unknown whether measurements of pulmonary function add significantly to the predictive value of more readily available variables The present study was designed to answer this question. Passive respiratory system mechanics were measured by an airway occlusion technique in 104 ventilator-dependent premature infants between 6 and 48 hours of life and corrected for infant size. A ventilation index [FiO2 x mean airway pressure (MAP)] was calculated at the time of pulmonary function testing. Poor outcome was defined as death from respiratory failure or need for supplemental oxygen at 28 days. Stepwise logistic function regression examined whether ventilation index and respiratory mechanics added predictive power over and above birthweight. Five infants died, and 45 patients required supplemental oxygen at 28 days. Birthweight was a strong predictor and would have entered the logistic model first in any case. Ventilation index added significantly to the predictive model (P = 0.038). Respiratory system conductance (P = 0.15) and compliance (P = 0.93) entered on the third and last step, respectively. We conclude that in premature infants with respiratory failure, birthweight is a strong predictor of outcome. Early ventilator requirements but not respiratory system mechanics, add significantly to this predictive model.     

Reproducibility of forced expiratory flow and volume measurements in infants with bronchiolitis

The end-tidal rapid thoracoabdominal compression (ETRTC) technique is an established method for lung function testing in infancy. Previous work in healthy infants, however, has shown that measurements with the newly developed raised volume rapid thoracoabdominal compression (RVRTC) technique are more reproducible than those with the ETRTC technique. So far, reproducibility of the two techniques has not been compared in infants with acute airway disease. Twenty-three infants with acute viral bronchiolitis underwent lung function assessment with both the ETRTC and the RVRTC technique. A series of 8-10 measurements with each technique was done in randomized order. Forced expired volumes at 0.5, 0.75, and 1 sec after chest compression (FEV(0.5), FEV(0.75), and FEV(1.0)) were measured with the RVRTC technique; maximum expiratory flow at functional residual capacity (V'(maxFRC)) was measured with the ETRTC technique. Group mean intrasubject coefficients of variation (CV) were 4.84% for FEV(0.5), 5.01% for FEV(0.75), 5.43% for FEV(1. 0), and 13.79% for V'(maxFRC), respectively. Differences between FEV parameters were statistically insignificant, whereas the difference between each FEV parameter and V'(maxFRC) was highly significant (P < 0.001). In infants with acute viral bronchiolitis, RVRTC measurements have significantly less intraindividual variability than flow rates assessed with the conventional ETRTC technique. This finding provides the basis for assessing disease course and effects of therapeutic interventions on an individual basis.     

阻塞性睡眠呼吸暂停低通气综合征患者睡眠过程中呼吸力学的变化

目的 研究阻塞性睡眠呼吸暂停低通气综合征(OSAHS)患者在睡眠过程中的呼吸力学变化特点.方法 60例疑似OSAHS患者及21例无OSAHS临床表现的志愿者入选本研究,其中男70例,女11例,平均年龄(44±13)岁.所有受试者均接受整夜多导睡眠图监测,并同时采用面罩旁气流技术动态描记整个睡眠过程中的呼吸力学指标和潮气量流速容量环(TBFVL).根据呼吸暂停低通气指数(AHI)将入选者分为OSAHS组(AHI≥15次/h)54例和对照组(AHI＜15次/h)27例.采用重复测量方差分析比较OSAHS组各期潮气吸气容积(VTI)/潮气呼气容积(VTE)及对照组各期呼吸力学指标变化;自身比较采用配对t检验;组间比较采用x2检验.结果 清醒状态下呼吸周期的VTI/VTE为0.99±0.04,说明吸气和呼气潮气量大致相等.OSAHS组发生睡眠呼吸暂停后第1个呼吸周期VTI/VTE(1.37±0.18)明显升高,在睡眠呼吸暂停前5次内和最后一次呼吸周期VTI/VTE均值(0.86±0.08和0.72±0.19)明显降低,说明呼吸暂停前一段时间内呼气量明显多于吸气量,而呼吸暂停后吸气量多于呼气量.OSAHS组无呼吸事件浅睡眠期VTI[(463±122)ml]、VTE[(466±127)ml]和分钟通气量[(6.4±1.6)L/min]比睡前[(554±134)ml、(565±147)ml和(8.3±1.9)L/min]明显减少.TBFVL结果显示,OSAHS组吸气阻力升高者占100%(54/54),呼气阻力升高者和两种阻力同时升高者均占96.3%(52/54).结论 在发生睡眠呼吸暂停前OSAHS患者呼气量明显多于吸气量,直至呼吸停止,这使患者发生睡眠呼吸暂停前的功能残气量明显减少,从而上气道更加狭窄,此病理生理过程在OSAHS整个发病过程中占有重要地位.OSAHS患者浅睡眠期的潮气量和通气量较睡前降低,睡眠过程中以上气道吸气相阻力升高为主的同时普遍存在呼气相阻力升高.     

Cord blood gene expression in infants hospitalized with respiratory syncytial virus bronchiolitis

BACKGROUND: Only a few infants develop acute bronchiolitis when exposed to respiratory syncytial virus (RSV), and host, environmental, and viral properties are probably all of importance in determining the severity of infection. METHODS: Microarray analysis was used to identify differentially expressed single genes and gene sets in cord blood from 5 infants hospitalized with RSV bronchiolitis versus cord blood from 5 control infants exposed to RSV without bronchiolitis during infancy. Quantitative real-time polymerase chain reaction (QRT-PCR) was performed on single genes in both the 5 infants selected for microarray analysis and 13 more infants hospitalized with the same disease. Gene set enrichment analysis (GSEA) was performed to identify differentially expressed gene sets within the microarray experiments. RESULTS: Microarray analysis identified 15 single genes to be significantly differentially expressed between case and control infants. Eleven of these genes were evaluated with QRT-PCR, and the genes FAM102A, TNFRSF25, and STMN3 were down-regulated in all but 1 of the 18 infants. A pathway involved in regulation of the actin cytoskeleton was found to be clearly down-regulated when analyzed with GSEA. CONCLUSIONS: FAM102A, TNFRSF25, and STMN3 and a pathway involved in regulation of the actin cytoskeleton are down-regulated in cord blood from infants hospitalized with RSV bronchiolitis.     

Benefits of thickened feeds in previously healthy infants with respiratory syncytial viral bronchiolitis

Infants with respiratory syncytial virus (RSV) bronchiolitis have an increased risk of aspiration. The optimal feeding strategy for these patients has not been described. Fifteen previously healthy and clinically stable infants with RSV bronchiolitis underwent video-fluoroscopy studies to assess swallowing using thin barium. Those with abnormal studies underwent a repeat study, using barium that was thickened with rice cereal. Nine of 15 infants had abnormal studies with thin barium. Laryngeal or tracheal penetration with thin barium was seen in 3 and 2 infants, respectively, but not with thickened barium. Aspiration of thin barium was seen in 4 infants, but it corrected in 3 of these 4 infants with thickened barium. Thickened feeds provide a simple, safe, and cost-effective intervention to improve swallowing dysfunction and prevent aspiration in infants with RSV bronchiolitis.