Home About us Contact
|
Home About us Contact | ||
|
|
||
Functional Residual Capacity (functional + residual_capacity)
Selected AbstractsLung Function Tests in Neonates and Infants with Chronic Lung Disease of Infancy: Functional Residual CapacityPEDIATRIC PULMONOLOGY, Issue 1 2006Georg Hülskamp MD Abstract This is the second paper in a review series that will summarize available data and discuss the potential role of lung function testing in infants and young children with acute neonatal respiratory disorders and chronic lung disease of infancy. The current paper addresses the expansive subject of measurements of lung volume using plethysmography and gas dilution/washout techniques. Following orientation of the reader to the subject area, we focus our comments on areas of inquiry proposed in the introductory paper to this series. The quality of the published literature is reviewed critically, and recommendations are provided to guide future investigation in this field. Measurements of lung volume are important both for assessing growth and development of lungs in health and disease, and for interpreting volume-dependent lung function parameters such as respiratory compliance, resistance, forced expiratory flows, and indices of gas-mixing efficiency. Acute neonatal lung disease is characterized by severely reduced functional residual capacity (FRC), with treatments aimed at securing optimal lung recruitment. While FRC may remain reduced in established chronic lung disease of infancy, more commonly it becomes normalized or even elevated due to hyperinflation, with or without gas-trapping, secondary to airway obstruction. Ideally, accurate and reliable bedside measurements of FRC would be feasible from birth, throughout all phases of postnatal care (including assisted ventilation), and during subsequent long-term follow-up. Although lung volume measurements in extremely preterm infants were described in a research environment, resolution of several issues is required before such investigations can be translated into routine clinical monitoring. Pediatr Pulmonol. © 2005 Wiley-Liss, Inc. [source] Reproducibility of multiple breath washout indices in the unsedated preterm neonate,PEDIATRIC PULMONOLOGY, Issue 1 2010Sanjay Sinhal FRACP Abstract Multiple breath inert gas washout (MBW) is gaining popularity for measurements of resting lung volume and ventilation inhomogeneity. Test reproducibility is an important determinant of the clinical applicability of diagnostic tests. The between-test reproducibility of variables derived from MBW tests in newborn infants is unknown. We aimed to determine the within-test repeatability and short-term between-test reproducibility of MBW variables in unsedated preterm infants. We hypothesized that measurements obtained within a 3-day interval in clinically stable preterm infants would be reproducible and suitable for use as an objective clinical outcome measurement. In this cross-sectional observational study, clinically stable hospitalized preterm infants whose parents had given informed consent for MBW studies were tested twice within 72,hr during quiet, unsedated sleep. Functional residual capacity (FRC), lung clearance index (LCI), and the first and second to zeroeth moment ratios (M1:M0; M2:M0) were computed from MBW traces obtained using a mainstream ultrasonic flowmeter and 4% sulphur hexafluoride (MBWSF6). Within-test repeatability and between-test reproducibility were determined. Within-test repeatability (expressed as a coefficient of variability (Cv)) for differences between two and four replicate measurements on the same test occasion, were 9.3% (FRC), 9.0% (LCI), 7.6% (M1:M0), and 15.6% (M2:M0), respectively. The within-test Cv's were not statistically different to the between-tests Cv's, which were 7.7% (FRC), 10.3% (LCI), 6.1% (M1:M0), and 13.0% (M2:M0), respectively. Among unsedated preterm infants, between-test reproducibility over a 3-day interval was similar to within-test repeatability. The wide limits of agreement may limit the application of these measures to detect a clinically significant change in condition in small preterm infants. Pediatr Pulmonol. 2010; 45:62,70. © 2009 Wiley-Liss, Inc. [source] Effects of Lung Volume on Parasternal Pressure-Generating Capacity in DogsEXPERIMENTAL PHYSIOLOGY, Issue 3 2000Anthony F. DiMarco Previous studies have suggested that the optimum length for force generation of the parasternal intercostal (PS) muscles is well above functional residual capacity (FRC). We further explored this issue by examining the pressure-generating capacity of the PS muscles as a function of lung volume in anaesthetized dogs. Upper thoracic spinal cord stimulation (SCS) was used to electrically activate the PS muscles. Changes in airway pressure and parasternal resting length (LR) during airway occlusion were monitored over a wide range of lung volumes during SCS. To assess the effects of parasternal contraction alone, SCS was performed following phrenicotomy and section of the external intercostal, levator costae and triangularis sterni muscles. With increasing lung volume, there were progressive decrements in the capacity of the PS muscles to produce changes in airway pressure. The relationship between PS pressure generation and lung volume was similar to a previous comparable assessment of the external intercostal muscles. The PS muscles shortened during passive inflation and also shortened further (by > 20% of LR) during SCS. Total shortening (passive plus active) increased progressively with increasing lung volume. Our results indicate that the capacity of the PS muscles to produce changes in airway pressure (a) falls progressively with increasing lung volume and (b) is similar to that of the external intercostal muscles. We speculate that the fall in PS pressure-generating capacity is related, in part, to progressive reductions in end-inspiratory length. [source] Electrical impedence tomography and heterogeneity of pulmonary perfusion and ventilation in porcine acute lung injuryACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 10 2009A. FAGERBERG Background: The heterogeneity of pulmonary ventilation (V), perfusion (Q) and V/Q matching impairs gas exchange in an acute lung injury (ALI). This study investigated the feasibility of electrical impedance tomography (EIT) to assess the V/Q distribution and matching during an endotoxinaemic ALI in pigs. Methods: Mechanically ventilated, anaesthetised pigs (n=11, weight 30,36 kg) were studied during an infusion of endotoxin for 150 min. Impedance changes related to ventilation (ZV) and perfusion (ZQ) were monitored globally and bilaterally in four regions of interest (ROIs) of the EIT image. The distribution and ratio of ZV and ZQ were assessed. The alveolar,arterial oxygen difference, venous admixture, fractional alveolar dead space and functional residual capacity (FRC) were recorded, together with global and regional lung compliances and haemodynamic parameters. Values are mean±standard deviation (SD) and regression coefficients. Results: Endotoxinaemia increased the heterogeneity of ZQ but not ZV. Lung compliance progressively decreased with a ventral redistribution of ZV. A concomitant dorsal redistribution of ZQ resulted in mismatch of global (from ZV/ZQ 1.1±0.1 to 0.83±0.3) and notably dorsal (from ZV/ZQ 0.86±0.4 to 0.51±0.3) V and Q. Changes in global ZV/ZQ correlated with changes in the alveolar,arterial oxygen difference (r2=0.65, P<0.05), venous admixture (r2=0.66, P<0.05) and fractional alveolar dead space (r2=0.61, P<0.05). Decreased end-expiratory ZV correlated with decreased FRC (r2=0.74, P<0.05). Conclusions: EIT can be used to assess the heterogeneity of regional pulmonary ventilation and perfusion and V/Q matching during endotoxinaemic ALI, identifying pivotal pathophysiological changes. [source] Measurements of functional residual capacity during intensive care treatment: the technical aspects and its possible clinical applicationsACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 9 2009H. HEINZE Direct measurement of lung volume, i.e. functional residual capacity (FRC) has been recommended for monitoring during mechanical ventilation. Mostly due to technical reasons, FRC measurements have not become a routine monitoring tool, but promising techniques have been presented. We performed a literature search of studies with the key words ,functional residual capacity' or ,end expiratory lung volume' and summarize the physiology and patho-physiology of FRC measurements in ventilated patients, describe the existing techniques for bedside measurement, and provide an overview of the clinical questions that can be addressed using an FRC assessment. The wash-in or wash-out of a tracer gas in a multiple breath maneuver seems to be best applicable at bedside, and promising techniques for nitrogen or oxygen wash-in/wash-out with reasonable accuracy and repeatability have been presented. Studies in ventilated patients demonstrate that FRC can easily be measured at bedside during various clinical settings, including positive end-expiratory pressure optimization, endotracheal suctioning, prone position, and the weaning from mechanical ventilation. Alveolar derecruitment can easily be monitored and improvements of FRC without changes of the ventilatory setting could indicate alveolar recruitment. FRC seems to be insensitive to over-inflation of already inflated alveoli. Growing evidence suggests that FRC measurements, in combination with other parameters such as arterial oxygenation and respiratory compliance, could provide important information on the pulmonary situation in critically ill patients. Further studies are needed to define the exact role of FRC in monitoring and perhaps guiding mechanical ventilation. [source] Hyperpolarized 3He apparent diffusion coefficient MRI of the lung: Reproducibility and volume dependency in healthy volunteers and patients with emphysemaJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 4 2008Sandra Diaz MD Abstract Purpose To measure the apparent diffusion coefficient (ADC) of hyperpolarized (HP) 3He gas using diffusion weighted MRI in healthy volunteers and patients with emphysema and examine the reproducibility and volume dependency. Materials and Methods A total of eight healthy volunteers and 16 patients with emphysema were examined after inhalation of HP 3He gas mixed with nitrogen (N2) during breathhold starting from functional residual capacity (FRC) in supine position. Coronal diffusion-sensitized MR images were acquired. Each subject was imaged on three separate days over a seven-day period and received two different volumes (6% and 15% of total lung capacity [TLC]) of HP 3He each day. ADC maps and histograms were calculated. The mean and standard deviation (SD) of the ADC at different days and volumes were compared. Results The reproducibility of the mean ADC and SD over several days was good in both healthy volunteers and patients (SD range of 0.003,0.013 cm2/second and 0.001,0.009 cm2/second at 6% and 15% of TLC for healthy volunteers, and a SD range of 0.001,0.041 cm2/second and 0.001,0.011 cm2/second, respectively, for patients). A minor but significant increase in mean ADC with increased inhaled gas volume was observed in both groups. Conclusion Mean ADC and SD of HP 3He MRI is reproducible and discriminates well between healthy controls and patients with emphysema at the higher gas volume. This method is robust and may be useful to gain new insights into the pathophysiology and course of emphysema. J. Magn. Reson. Imaging 2008. © 2008 Wiley-Liss, Inc. [source] Positive end-expiratory pressure optimization using electric impedance tomography in morbidly obese patients during laparoscopic gastric bypass surgeryACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 7 2006K. Erlandsson Background:, Morbidly obese patients have an increased risk for peri-operative lung complications and develop a decrease in functional residual capacity (FRC). Electric impedance tomography (EIT) can be used for continuous, fast-response measurement of lung volume changes. This method was used to optimize positive end-expiratory pressure (PEEP) to maintain FRC. Methods:, Fifteen patients with a body mass index of 49 ± 8 kg/m2 were studied during anaesthesia for laparoscopic gastric bypass surgery. Before induction, 16 electrodes were placed around the thorax to monitor ventilation-induced impedance changes. Calibration of the electric impedance tomograph against lung volume changes was made by increasing the tidal volume in steps of 200 ml. PEEP was titrated stepwise to maintain a horizontal baseline of the EIT curve, corresponding to a stable FRC. Absolute FRC was measured with a nitrogen wash-out/wash-in technique. Cardiac output was measured with an oesophageal Doppler method. Volume expanders, 1 ± 0.5 l, were given to prevent PEEP-induced haemodynamic impairment. Results:, Impedance changes closely followed tidal volume changes (R2 > 0.95). The optimal PEEP level was 15 ± 1 cmH2O, and FRC at this PEEP level was 1706 ± 447 ml before and 2210 ± 540 ml after surgery (P < 0.01). The cardiac index increased significantly from 2.6 ± 0.5 before to 3.1 ± 0.8 l/min/m2 after surgery, and the alveolar dead space decreased. PaO2/FiO2, shunt and compliance remained unchanged. Conclusion:, EIT enables rapid assessment of lung volume changes in morbidly obese patients, and optimization of PEEP. High PEEP levels need to be used to maintain a normal FRC and to minimize shunt. Volume loading prevents circulatory depression in spite of a high PEEP level. [source] Association of lower airway inflammation with physiologic findings in young children with cystic fibrosis,PEDIATRIC PULMONOLOGY, Issue 5 2009Stacey L. Peterson-Carmichael MD Abstract Background The relationship between lower airway markers of inflammation and infection with physiologic findings is poorly understood in young children with cystic fibrosis (CF). The goal of this study was to evaluate the association of bronchoalveolar lavage fluid (BALF) markers of infection and inflammation, including mediators linked to airway remodeling, to infant lung function values in young children with CF undergoing clinically indicated bronchoscopy. Methods Plethysmography and the raised volume rapid thoracoabdominal compression (RVRTC) technique were performed in 16 sedated infants and young children with CF prior to bronchoscopy. BALF was collected and analyzed for pathogen density, cell count, % neutrophils, transforming growth factor beta 1 (TGF-,1), matrix metalloproteinases (MMP), and interleukin-8 (IL-8). Results There was a significant direct correlation between functional residual capacity (FRC), the ratio of residual volume to total lung capacity (RV/TLC) and FRC/TLC with % neutrophils (P,<,0.05). Forced expiratory flows were inversely correlated to % neutrophils (P,<,0.01). Lung function parameters did not differentiate those with and without lower airway infection; however, pathogen density directly correlated with FRC and inversely correlated with flows (P,<,0.05). In a subset of the population, MMP-2 directly correlated with RV/TLC and inversely correlated with flows (P,<,0.05) and TGF-,1 directly correlated with FRC (P,<,0.05). Conclusions Results from this study suggest that lower airway inflammation as well as mediators linked to airway remodeling play an active role in pulmonary deterioration in CF infants and young children undergoing clinically indicated bronchoscopy. Pediatr Pulmonol. 2009; 44:503,511. © 2009 Wiley-Liss, Inc. [source] Chest radiograph thoracic areas and lung volumes in infants developing bronchopulmonary dysplasiaPEDIATRIC PULMONOLOGY, Issue 1 2009Caroline May MRCPCH Abstract Objectives To determine whether chest radiograph (CXR) thoracic areas and lung volumes differed between infants who did and did not develop BPD and according to the severity of BPD developed. Working Hypothesis Infants developing BPD, particularly if moderate or severe, would have low CXR thoracic areas and lung volumes in the perinatal period. Study Design Prospective study. Patient-Subject Selection 53 infants with a median gestational age of 28 (range 24,32) weeks. Methodology CXR thoracic areas were calculated using a Picture Archiving and Communicating System (PACS) and lung volume assessed by measurement of functional residual capacity (FRC) in the first 72 hr after birth. BPD was diagnosed if the infants were oxygen dependent beyond 28 days, mild BPD in infants no longer oxygen dependent at 36 weeks post-menstrual age (PMA) and moderate/severe BPD in infants who required supplementary oxygen with or without respiratory support at 36 weeks PMA. Results Thirty two infants developed BPD, 21 had moderate/severe BPD. The median CXR thoracic areas were higher (P,<,0.0001) and FRCs were lower (P,<,0.0001) in the BPD compared to no BPD infants. The median CXR thoracic areas of the moderate/severe group (P,<,0.001) and the mild group (P,<,0.05) were greater than that of the no BPD group and the median FRC of the moderate/severe BPD group was lower than the no BPD group (<0.001) and the mild BPD group (P,<,0.05). Conclusion These results highlight that in the perinatal period infants developing BPD, particularly if moderate/severe, have low functional lung volumes and may have gas trapping, which likely reflects ventilation inhomogeneity. Pediatr Pulmonol. 2009; 44:80,85. © 2008 Wiley-Liss, Inc. [source] Lung function and exhaled nitric oxide levels in infants developing chronic lung diseasePEDIATRIC PULMONOLOGY, Issue 2 2007Olivia Williams MRCPCH Abstract Chronic lung disease (CLD) is a common outcome of neonatal intensive care. To determine whether the results of serial exhaled nitric oxide (eNO) measurements during the perinatal period differed between infants who did and did not develop CLD. In addition, we wished to assess whether eNO results were more predictive of CLD development than lung function test results or readily available clinical data (gestational age and birthweight). The patients were 24 infants with a median gestational age of 27 (range 25,31) weeks. Measurements of eNO levels, functional residual capacity (FRC), and compliance of the respiratory system (CRS) were attempted on postnatal days 1, 3, 5, 7, 14, and 28 days. The 12 infants who developed CLD were of significantly lower birthweight and gestational age than the rest of the cohort; in addition, they had lower median FRC (P,<,0.02) and CRS (P,<,0.02) results, but not higher eNO levels, in the first week after birth. Construction of receiver operator characteristic (ROC) curves demonstrated that the CRS and FRC results on Day 3 were the best predictors of CLD development; the areas under the ROC curves were 0.94 and 0.91, respectively. Early lung function test results, but not eNO levels, are useful in predicting CLD development, but are not significantly better than birthweight. Pediatr Pulmonol. 2007; 42:107,113. © 2006 Wiley-Liss, Inc. [source] Physiologic, bronchoscopic, and bronchoalveolar lavage fluid findings in young children with recurrent wheeze and cough,PEDIATRIC PULMONOLOGY, Issue 8 2006John Saito MD Abstract Assessing airway disease in young children with wheeze and/or cough is challenging. We conducted a prospective, descriptive study of lung function in children <3 years old with recurrent wheeze and/or cough, who had failed empiric antiasthma and/or antireflux therapy and subsequently underwent flexible bronchoscopy. Our goals were to describe radiographic, anatomical, microbiological, and physiological findings in these children, and generate hypotheses about their respiratory physiology. Plethysmography and raised-volume rapid thoracoabdominal compression (RVRTC) techniques were performed prior to bronchoscopy. Mean Z-scores (n,=,19) were ,1.34 for forced expiratory volume at 0.5 sec (FEV0.5), ,2.28 for forced expiratory flows at 75% of forced vital capacity (FVC) (FEF75), ,2.25 for forced expiratory flows between 25,75% of FVC (FEF25,75), 2.53 for functional residual capacity (FRC), and 2.23 for residual volume divided by total lung capacity (RV/TLC). Younger, shorter children had markedly depressed FEF75 and FEF25,75 Z-scores (P,=,0.002 and P,=,<0.001, respectively). As expected, lower airway anatomical abnormalities, infection, and inflammation were common. Elevated FRC was associated with anatomical lower airway abnormalities (P,=,0.03). FVC was higher in subjects with neutrophilic inflammation (P,=,0.03). There was no association between other physiologic variables and bronchoscopic/bronchoalveolar lavage fluid findings. Half of those with elevated RV/TLC ratios (Z-score >2) had no evidence of chest radiograph hyperinflation. We conclude that in this population, plethysmography and RVRTC techniques are useful in identifying severity of hyperinflation and airflow obstruction, and we hypothesize that younger children may have relatively small airways caliber, significantly limiting airflow, and thus impairing secretion clearance and predisposing to lower airway infection. Pediatr Pulmonol. 2006; 41: 709,719. © 2006 Wiley-Liss, Inc. [source] Lung Function Tests in Neonates and Infants with Chronic Lung Disease: Forced Expiratory ManeuversPEDIATRIC PULMONOLOGY, Issue 3 2006Sooky Lum PhD Abstract This fourth paper in a review series on the role of lung function testing in infants and young children with acute neonatal disorders and chronic lung disease of infancy (CLDI) addresses measurements of forced expiration using rapid thoraco-abdominal compression (RTC) techniques and the forced deflation technique. Following orientation of the reader to the subject area, we focus our comments on the areas of inquiry proposed in the introductory paper to this series. The quality of the published literature is reviewed critically, and recommendations are provided to guide future investigation in this field. All studies on infants and young children with CLDI using forced expiratory or deflation maneuvers demonstrated that forced flows at low lung volume remain persistently low through the first 3 years of life. Measurement of maximal flow at functional residual capacity (V,maxFRC) is the most commonly used method for assessing airway function in infants, but is highly dependent on lung volume and airway tone. Recent studies suggested that the raised volume RTC technique, which assesses lung function over an extended volume range as in older children, may be a more sensitive means of discriminating changes in airway function in infants with respiratory disease. The forced deflation technique allows investigation of pulmonary function during the early development of CLDI in intubated subjects, but its invasive nature precludes its use in the routine setting. For all techniques, there is an urgent need to establish suitable reference data and evaluate within- and between-occasion repeatability, prior to establishing the clinical usefulness of these techniques in assessing baseline airway function and/or response to interventions in subjects with CLDI. Pediatr Pulmonol. © 2005 Wiley-Liss, Inc. [source] Lung Function Tests in Neonates and Infants with Chronic Lung Disease of Infancy: Functional Residual CapacityPEDIATRIC PULMONOLOGY, Issue 1 2006Georg Hülskamp MD Abstract This is the second paper in a review series that will summarize available data and discuss the potential role of lung function testing in infants and young children with acute neonatal respiratory disorders and chronic lung disease of infancy. The current paper addresses the expansive subject of measurements of lung volume using plethysmography and gas dilution/washout techniques. Following orientation of the reader to the subject area, we focus our comments on areas of inquiry proposed in the introductory paper to this series. The quality of the published literature is reviewed critically, and recommendations are provided to guide future investigation in this field. Measurements of lung volume are important both for assessing growth and development of lungs in health and disease, and for interpreting volume-dependent lung function parameters such as respiratory compliance, resistance, forced expiratory flows, and indices of gas-mixing efficiency. Acute neonatal lung disease is characterized by severely reduced functional residual capacity (FRC), with treatments aimed at securing optimal lung recruitment. While FRC may remain reduced in established chronic lung disease of infancy, more commonly it becomes normalized or even elevated due to hyperinflation, with or without gas-trapping, secondary to airway obstruction. Ideally, accurate and reliable bedside measurements of FRC would be feasible from birth, throughout all phases of postnatal care (including assisted ventilation), and during subsequent long-term follow-up. Although lung volume measurements in extremely preterm infants were described in a research environment, resolution of several issues is required before such investigations can be translated into routine clinical monitoring. Pediatr Pulmonol. © 2005 Wiley-Liss, Inc. [source] Lung volumes in healthy Afro-Caribbean children aged 4,17 yearsPEDIATRIC PULMONOLOGY, Issue 2 2005Karl P. Sylvester BSc Abstract Lung volumes in healthy children differ according to their ethnic origin. We wished to determine if any differences in the lung volumes of Afro-Caribbean (AC) children from those predicted by Caucasian reference values disappeared if the results were related to sitting height or to 90% or 77% of lung volumes predicted for height from Caucasian reference values based on standing height. We took, as our working hypothesis, that it is inappropriate to use Caucasian reference values to interpret data from Afro-Caribbean children, and that ethnic-specific reference values are required. This was a prospective, observational study. Subjects included 80 AC children with a median age of 9 (range, 4.3,17.8) years. Standing and sitting height were measured. Lung volumes were measured by body plethysmography (total lung capacity, TLCpleth; functional residual capacity, FRCpleth; and vital capacity, VCpleth), helium gas dilution (functional residual capacity, (FRCHe), spirometry (forced expiratory volume in 1 sec, FEV1), and forced vital capacity (FVC). The lung volumes of AC children correlated significantly with standing height, but differed significantly from values predicted from Caucasian reference values based on standing height (P,<,0.05). Significant differences remained for TLCpleth, FRCpleth, FRCHe, RVpleth, VCpleth, FEV1, and FVC when the results were related to sitting height or 90% or 77% of values predicted from Caucasian reference values based on height (P,<,0.05). Lung volumes in Afro-Caribbean children should be compared to ethnic-specific reference values. Pediatr Pulmonol. 2005; 40:109,112. © 2005 Wiley-Liss, Inc. [source] Association of tobacco smoke exposure and respiratory syncitial virus infection with airways reactivity in early childhoodPEDIATRIC PULMONOLOGY, Issue 6 2001Alan Adler MD Abstract Exposure to infectious agents and environmental tobacco smoke are thought to induce bronchial hyperresponsiveness (BHR). This study was undertaken to determine the effects of passive exposure to tobacco smoke and respiratory syncitial virus (RSV) lower respiratory infection (LRI) during infancy on the occurrence of BHR in the first 2 years of life. Eighty-six cases of documented RSV (mean age, 188 days) and 78 controls (mean age, 162 days) were enrolled from the clinic and in-patient service of a single hospital. None had a history of prior LRI. Subjects were studied at 6-month intervals up to 19 months of age with a standardized respiratory illness and parental smoking questionnaire, partial expiratory flow-volume curves by the "hug" (rapid thoracic compression) technique, and methacholine challenge. Exposure to maternal and paternal cigarette smoking, maternal history of asthma, and mold exposure were associated with decreased levels of length-corrected maximal flow at functional residual capacity (V,maxFRC). RSV-LRI was not related to V,maxFRC. After adjustment of V,maxFRC for these factors, V,maxFRC was a significantly and positively correlated with a methacholine concentration provoking a 40% fall in V,maxFRC (PC40) and negatively correlated with dose-response slope. After adjustment for V,maxFRC, there were no independent effects of tobacco smoke exposure or RSV-LRI on methacholine responses. These data do not support a role for RSV as a risk factor for airways reactivity in childhood and indicate that exposure to tobacco smoke affects airways reactivity through its effects on airways. Pediatr Pulmonol. 2001; 32:418,427. © 2001 Wiley-Liss, Inc. [source] Which pulmonary volume should be used in physiotherapy to obtain higher maximal inspiratory pressure in COPD patients?PHYSIOTHERAPY RESEARCH INTERNATIONAL, Issue 4 2005Patricia EM Marinho Abstract Background and Purpose Patients with chronic obstructive pulmonary disease (COPD) present pulmonary hyperinflation as the main cause of mechanical disadvantage in respiratory muscles. Measurement of the force generated by those muscles is converted into pressure changes. The aim of the present study was to evaluate the maximal inspiratory pressure (MIP) from the residual volume (RV) and from the functional residual capacity (FRC), in patients with COPD, and to determine which pulmonary volume should be used in physiotherapy so as to obtain higher MIP results. Method An investigation of 18 male patients with stable COPD. Patients were examined using a manual vacuometer to measur the MIP of 20 daily manoeuvres. Ten measurements were taken from the RV and 10 from the FRC, taken alternately with an interval of 1 minute between each measurement, for five consecutive days. Results Increases in MIP were obtained from the RV measurements (mean ± SE) from 59.7 (±5.2) to 66.6 (±5.3) cm H2O (F (4,64) = 3.34; p < 0.015) and from the FRC measurements, from 55.4 (±4.9) to 64.4 (±4,8) cm H2O (F (4,64) = 6.72; p < 0.001). Post hoc analysis showed an increase, over consecutive days, in both RV and FRC. For FRC, an increase was revealed on the second and third days, a fall was found on the fourth day and a new increase was found on the last day. MIP reached different levels, between RV and FRC, on the first (t = 2.888; p = 0.010) and fourth ( t = 2.165; p = 0.045) days. Conclusion In the present study, MIP reached higher levels at FRC during the five days of evaluation, and a learning effect occurred in the patients. Motor units from the respiratory muscles may have been recruited in order to performe the manoeuvres during the days of evaluation. The study suggests that there is good evidence for the use of the FRC as a parameter to find the major MIP value. Copyright © 2005 John Wiley & Sons, Ltd. [source] IMAGING LUNG AERATION AND LUNG LIQUID CLEARANCE AT BIRTH USING PHASE CONTRAST X-RAY IMAGINGCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 1 2009Stuart B Hooper SUMMARY 1The transition to extra-uterine life at birth is critically dependent on airway liquid clearance to allow the entry of air and the onset of gaseous ventilation. We have used phase contrast X-ray imaging to identify factors that regulate lung aeration at birth in spontaneously breathing term and mechanically ventilated preterm rabbit pups. 2Phase contrast X-ray imaging exploits the difference in refractive index between air and water to enhance image contrast, enabling the smallest air-filled structures of the lung (alveoli; < 100 µm) to be resolved. Using this technique, the lungs become visible as they aerate, allowing the air,liquid interface to be observed as it moves distally during lung aeration. 3Spontaneously breathing term rabbit pups rapidly aerate their lungs, with most fully recruiting their functional residual capacity (FRC) within the first few breaths. The increase in FRC occurs mainly during individual breaths, demonstrating that airway liquid clearance and lung aeration is closely associated with inspiration. We suggest that transpulmonary pressures generated by inspiration provide a hydrostatic pressure gradient for the movement of water out of the airways and into the surrounding lung tissue after birth. 4In mechanically ventilated preterm pups, lung aeration is closely associated with lung inflation and a positive end-expiratory pressure is required to generate and maintain FRC after birth. 5In summary, phase contrast X-ray imaging can image the air-filled lung with high temporal and spatial resolution and is ideal for identifying factors that regulate lung aeration at birth in both spontaneously breathing term and mechanically ventilated preterm neonates. [source] Measurements of functional residual capacity during intensive care treatment: the technical aspects and its possible clinical applicationsACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 9 2009H. HEINZE Direct measurement of lung volume, i.e. functional residual capacity (FRC) has been recommended for monitoring during mechanical ventilation. Mostly due to technical reasons, FRC measurements have not become a routine monitoring tool, but promising techniques have been presented. We performed a literature search of studies with the key words ,functional residual capacity' or ,end expiratory lung volume' and summarize the physiology and patho-physiology of FRC measurements in ventilated patients, describe the existing techniques for bedside measurement, and provide an overview of the clinical questions that can be addressed using an FRC assessment. The wash-in or wash-out of a tracer gas in a multiple breath maneuver seems to be best applicable at bedside, and promising techniques for nitrogen or oxygen wash-in/wash-out with reasonable accuracy and repeatability have been presented. Studies in ventilated patients demonstrate that FRC can easily be measured at bedside during various clinical settings, including positive end-expiratory pressure optimization, endotracheal suctioning, prone position, and the weaning from mechanical ventilation. Alveolar derecruitment can easily be monitored and improvements of FRC without changes of the ventilatory setting could indicate alveolar recruitment. FRC seems to be insensitive to over-inflation of already inflated alveoli. Growing evidence suggests that FRC measurements, in combination with other parameters such as arterial oxygenation and respiratory compliance, could provide important information on the pulmonary situation in critically ill patients. Further studies are needed to define the exact role of FRC in monitoring and perhaps guiding mechanical ventilation. [source] | ||||||||||