A simple device for measuring static compliance of lung-thorax combine

Explaining the concept of lung compliance remains a challenge to the physiology teacher because it cannot be demonstrated easily in human subjects and all attempts until now have used only simulation models. A simple device is described in the present article to measure the compliance of the "lung-thorax" combine in human subjects with the caveat that what is recorded is not "lung" compliance and the data generated are of little clinical use. The device comprises a spirometer, a manometer, a mouthpiece, and interconnecting tubes guarded with stopcocks.

Age-related decline in chest wall mobility: a cross-sectional study among community-dwelling elderly women

CONTEXT

Chest wall mobility is strongly related to respiratory function; however, the effect of aging on chest wall mobility-and the level at which this mobility is most affected-remains unclear.

OBJECTIVE

To investigate age-related differences in chest wall mobility and respiratory function among elderly women in different age groups.

METHODS

This cross-sectional observational study was performed in Himeji City in Hyogo Prefecture and Ayabe City in Kyoto Prefecture in Japan. Inclusion criteria were female sex, age 65 years or older, community resident, and ability to ambulate independently, with or without an assistive device. Thoracic excursion at the axillary and xiphoid levels and at the level of the tenth rib was measured with measuring tape. Respiratory function, including forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1), was assessed by spirometry, and FVC percent predicted (%FVC), FEV1 percent predicted (%FEV1), and FEV1/FVC were calculated. Chest wall mobility and respiratory function were compared among 4 age groups.

RESULTS

Of 251 potential participants, 132 met the inclusion criteria. Participants were divided into 4 age groups: group 1, 65 to 69 years; group 2, 70 to 74 years; group 3, 75 to 79 years; and group 4, 80 years or older. Statistically significant differences were found in thoracic excursion at the axillary level between groups 1 and 4 and between groups 2 and 4 when adjusted for height and weight (F4.52, P=.01). In addition, statistically significant differences were found in the FVC and FEV1 values between groups 1 and 3 and between groups 2 and 3 (FVC: F4.97, P=.01; FEV1: F6.17, P=.01).

CONCLUSION

Chest wall mobility at the axillary level and respiratory function decreased with age in community-dwelling women aged 65 years or older. Further longitudinal studies are required to clarify the effects of aging on chest wall mobility and respiratory function.

Prenatal prediction of pulmonary arterial hypertension in congenital diaphragmatic hernia

OBJECTIVE

To evaluate the role of prenatal prognostic markers obtained routinely by ultrasound examination and magnetic resonance imaging (MRI) in the prediction of development of postnatal pulmonary arterial hypertension (PAH) in isolated congenital diaphragmatic hernia (CDH).

METHODS

One hundred and ten cases of isolated CDH were referred to our fetal medicine unit between January 2004 and April 2013. Mortality and morbidity rates were reviewed for those presenting with postnatal PAH. The following prenatal markers were evaluated as potential predictive factors of PAH: liver position, side of the CDH defect, lung area to head circumference ratio (LHR) and observed/expected LHR (o/e-LHR), which were measured by ultrasound, and observed/expected total fetal lung volume (o/e-TFLV), which was measured by MRI. Univariable logistic regression was used to assess associations.

RESULTS

PAH was significantly associated with perinatal mortality and morbidity (P < 0.001). The occurrence of PAH decreased significantly with an increasing LHR, o/e-LHR and o/e-TFLV and was significantly increased for cases with an intrathoracic liver, but not for those with right-sided defects. Univariable regression revealed that o/e-TFLV (odds ratio (OR), 0.9 (95% CI, 0.86-0.95); P < 0.05 for percentage unit change in o/e), LHR (OR, 0.19 (95% CI, 0.09-0.40); P < 0.05 for unit change), o/e-LHR (OR, 0.95 (95% CI, 0.93-0.98); P < 0.05 for percentage unit change in o/e) and liver position (OR, 2.82 (95% CI, 1.13-7.00); P < 0.05 for intrathoracic liver) were significant predictors of subsequent PAH. No differences were found after adjusting for gestational age at delivery. The areas under the receiver-operating characteristics curve were 0.80 and 0.75 for o/e-TFLV and o/e-LHR, respectively.

CONCLUSION

In cases of CDH, PAH is associated with high rates of mortality and morbidity. Routinely obtained prenatal markers, usually used for the assessment of pulmonary hypoplasia, are also relevant for the postnatal prediction of PAH.

Longitudinal assessment of lung area measurements by two-dimensional ultrasound in fetuses with isolated left-sided congenital diaphragmatic hernia

OBJECTIVE

To evaluate lung growth in healthy fetuses and those with congenital diaphragmatic hernia (CDH) using two-dimensional (2D) ultrasound.

METHODS

Fetal right lung measurements obtained by 2D ultrasound between 19 and 37 weeks' gestation were evaluated longitudinally in 66 healthy fetuses and 52 fetuses with isolated left-sided CDH. Right lung areas were determined by the 'tracing' and 'longest-diameters' methods and, subsequently, lung area-to-head circumference ratios (LHRs) were calculated. Functions fitted to these size parameters with respect to gestational age were evaluated for three sets of group-wise comparisons: (1) healthy vs CDH fetuses; (2) different degrees of severity of CDH; and (3) CDH fetuses that survived vs those that died by 6 months postpartum.

RESULTS

There was a significantly slower increase in right lung areas and LHRs with advancing gestational age in CDH fetuses than in healthy individuals (P < 0.05). Compared to those with milder forms of CDH, lung areas and LHRs of fetuses with more severe forms displayed a smaller increase (P < 0.05) and LHRs of fetuses with severe CDH did not increase during pregnancy (P > 0.05). Individuals who died postpartum did not show any increase in LHR (P > 0.05) throughout gestation.

CONCLUSIONS

The right lung area and LHR, calculated using either the longest-diameters or tracing method, display reduced growth rates during gestation in cases of isolated left-sided CDH as compared with healthy fetuses. The growth curve characteristics of fetal lung areas and LHRs may be useful for predicting neonatal mortality.

Feasibility of Lung Volume Recruitment in Early Neuromuscular Weakness: A Comparison Between Amyotrophic Lateral Sclerosis, Myotonic Dystrophy, and Postpolio Syndrome

BACKGROUND

Lung volume recruitment (LVR) is a cough assistance technique used in persons with neuromuscular disorders (NMDs), most typically in those requiring noninvasive ventilation (NIV). Whether it may be useful in persons with NMDs who have milder respiratory impairment is unknown.

OBJECTIVE

To assess the feasibility, impact on quality of life (QOL), and preliminary physiological effects of daily LVR in different categories of persons with NMDs who have an early stage of respiratory impairment.

DESIGN

Feasibility study.

SETTING

Academic tertiary care center.

PARTICIPANTS

Outpatients diagnosed with amyotrophic lateral sclerosis (n = 8), postpolio syndrome (n = 10), and myotonic dystrophy (n = 6) who had restrictive respiratory defects but were not yet using NIV.

METHODS

Participants were asked to perform LVR up to 4 times daily and log their LVR use in a diary. Physiological measurements and questionnaires were completed at baseline and after 3 months.

MAIN OUTCOME MEASUREMENTS

Compliance with LVR use was assessed, along with QOL and willingness to continue the treatment. Physiological measurements included forced vital capacity (FVC), lung insufflation capacity (LIC), and the LIC minus FVC difference.

RESULTS

Of the 24 recruited subjects, 7 with amyotrophic lateral sclerosis, 7 with postpolio syndrome, and 5 with myotonic dystrophy completed the study (n = 19). At baseline, mean values for FVC and spontaneous peak cough flow were 59.9% predicted and 373.1 L/min, respectively. For subjects completing the study, 74% were willing to continue long-term LVR use, and QOL scores were not adversely affected by LVR in any NMD subgroup. The LIC-FVC difference increased from baseline to follow-up by a mean of 0.243 L (P = .006) in all subjects (n = 19), suggesting a possible improvement in respiratory system mechanics.

CONCLUSIONS

In patients with NMDs who have early restrictive respiratory defects but do not yet require NIV, regular use of LVR is feasible with no negative impact on QOL over a 3-month period and may have physiological benefits. Further work is needed to determine whether early institution of LVR can improve respiratory system mechanics and help delay ventilatory failure in persons with NMDs.

Correlated variability in the breathing pattern and end-expiratory lung volumes in conscious humans

In order to characterize the variability and correlation properties of spontaneous breathing in humans, the breathing pattern of 16 seated healthy subjects was studied during 40 min of quiet breathing using opto-electronic plethysmography, a contactless technology that measures total and compartmental chest wall volumes without interfering with the subjects breathing. From these signals, tidal volume (V_T), respiratory time (T_TOT) and the other breathing pattern parameters were computed breath-by-breath together with the end-expiratory total and compartmental (pulmonary rib cage and abdomen) chest wall volume changes. The correlation properties of these variables were quantified by detrended fluctuation analysis, computing the scaling exponentα. V_T, T_TOT and the other breathing pattern variables showed α values between 0.60 (for minute ventilation) to 0.71 (for respiratory rate), all significantly lower than the ones obtained for end-expiratory volumes, that ranged between 1.05 (for rib cage) and 1.13 (for abdomen) with no significant differences between compartments. The much stronger long-range correlations of the end expiratory volumes were interpreted by a neuromechanical network model consisting of five neuron groups in the brain respiratory center coupled with the mechanical properties of the respiratory system modeled as a simple Kelvin body. The model-based α for V_T is 0.57, similar to the experimental data. While the α for T_TOT was slightly lower than the experimental values, the model correctly predicted α for end-expiratory lung volumes (1.045). In conclusion, we propose that the correlations in the timing and amplitude of the physiological variables originate from the brain with the exception of end-expiratory lung volume, which shows the strongest correlations largely due to the contribution of the viscoelastic properties of the tissues. This cycle-by-cycle variability may have a significant impact on the functioning of adherent cells in the respiratory system.

Lung ventilation volumetry with same-breath acquisition of hyperpolarized gas and proton MRI

The purpose of this work was to assess the reproducibility of percentage of ventilated lung volume (PV) measured from hyperpolarized (HP) (3)He and (1)H anatomical images acquired in the same breath-hold when compared with PV measured from (3)He and (1)H images from separate breath-holds. Volumetric (3)He ventilation and (1)H anatomical images of the same resolution were acquired during the same breath-hold. To assess reproducibility, this procedure was performed twice with a short gap between acquisitions. In addition, (1)H images were also acquired in a separate breath for comparison. PV ((3)He ventilated volume divided by (1)H total lung volume) was calculated using the single-breath-hold images (PV(single)) and the separate-breath-hold images (PV(separate)). Short-term reproducibility of PV measurement was assessed for both single- and separate-breath acquisitions. Dice similarity coefficients (DSCs) were calculated to quantify spatial overlap between (3)He and (1)H segmentations for the single- and separate-breath-hold acquisitions. The efficacy of using the separate-breath method combined with image registration was also assessed. The mean magnitude difference between the two sets of PV values (±standard deviation) was 1.49 ± 1.32% for PV(single) and 4.19 ± 4.10% for PV(separate), with a significant difference (p < 0.01). The mean magnitude difference between the two PV values for the registered separate-breath technique (PV(sep-registered)) was 2.27 ± 2.23%. Bland-Altman analysis showed that PV measured with single-breath acquisitions was more repeatable than PV measured with separate-breath acquisitions, regardless of image registration. DSC values were significantly greater (p < 0.01) for single-breath acquisition than for separate-breath acquisition. Acquisition of HP gas ventilation and (1)H anatomical images in a single breath-hold provides a more reproducible means of percentage lung ventilation volume measurement than the previously used separate-breath-hold scan approach, and reduces errors.

Fetal lung volume and quantification of liver herniation by magnetic resonance imaging in isolated congenital diaphragmatic hernia

OBJECTIVE

To determine associations between fetal lung and liver herniation volumes measured by magnetic resonance imaging (MRI) and mortality/need for extracorporeal membrane oxygenation (ECMO) in cases of isolated congenital diaphragmatic hernia (CDH). A secondary objective was to compare prenatal MRI parameters with two-dimensional ultrasound lung measurements.

METHODS

A retrospective review of medical records of all fetuses with isolated CDH evaluated between January 2004 and July 2012 was performed. The following MRI parameters were measured at 20-32 weeks: observed/expected total fetal lung volume (o/e-TLV), predicted pulmonary volume (PPV), percentage of liver herniated into the fetal thorax (%LH) and the liver/thoracic volume ratio (LiTR). These were compared with the ultrasound-determined lung-to-head ratio (LHR) and the observed/expected LHR (o/e-LHR) in the same cohort. The predictive value of MRI and ultrasound parameters for mortality and the need for ECMO was evaluated by univariate, multivariate and factor analysis and by receiver-operating characteristics curves.

RESULTS

Eighty fetuses with isolated CDH were evaluated. Overall mortality was 18/80 (22.5%). Two newborns died a few hours after birth. ECMO was performed in 29/78 (37.2%) newborns, with a survival rate of 48.3% (14/29). The side of the diaphragmatic defect was not associated with mortality (P = 0.99) or the need for ECMO (P = 0.48). Good correlation was observed among o/e-TLV, PPV, LHR and o/e-LHR as well as between %LH and LiTR (r = 0.89; P < 0.01); however, fetal lung measurements and measures of liver herniation were not correlated (all P > 0.05). All parameters were statistically associated with mortality or the need for ECMO. The best combination of measurements to predict mortality was o/e-TLV and %LH, with 83% accuracy.

CONCLUSION

Mortality and the need for ECMO in neonates with isolated CDH can be best predicted using a combination of MRI o/e-TLV and %LH.

Quantitative assessment of emphysematous parenchyma using multidetector-row computed tomography in patients scheduled for endobronchial treatment with one-way valves†

OBJECTIVES

To investigate the role of volume quantitative assessment using multidetector-row computed tomography to select patients scheduled for endobronchial one-way valves treatment.

METHODS

Twenty-five consecutive patients (15 with heterogeneous emphysema and 10 with giant emphysematous bulla) undergoing endobronchial valves treatment were enrolled. All patients were studied pre- and postoperatively with standard pulmonary functional tests and quantitative volume assessment of target lobe and entire lung. Emphysematous parenchyma was obtained applying density thresholds of -1.024/-950 Hounsfield units. Among different subtype of patients, we evaluated: (i) the differences between preoperative versus postoperative data; (ii) the correlation between functional and volumetric quantification changes and (iii) the critical threshold value of volumetric quantification of the target lobe in close association with clinical effects.

RESULTS

Among heterogeneous emphysematous and giant emphysematous bulla patients, a significant improvement of flow-expiratory volume in 1 s (from 36.9 ± 15.3 to 43.9 ± 10.4; P = 0.01; and from 35.8 ± 6.0 to 47.5 ± 7.9; P < 0.0001, respectively); and of forced vital capacity (from 41.9 ± 5.9 to 47.3 ± 9.3; P = 0.0009 and from 40.7 ± 5.9 to 48.8 ± 4.9; P = 0.0002, respectively); and a significant reduction of residual volume (from 185 ± 14 to 157 ± 14.7; P = 0.005; and from 196 ± 13.5 to 137 ± 21; P < 0.0001, respectively) and of total lung volume (from 166.7 ± 13 to 137 ± 18 ; P = 0.0003, and from 169 ± 15 to 134 ± 18; P < 0.0001, respectively) were seen after treatment. The volumetric measurements showed a reduction of volume of the treated lobe among heterogeneous emphysematous patients (from 1448 ± 204 to 1076 ± 364; P = 0.0008); and in those with giant emphysematous bulla (from 1668 ± 140 to 864 ± 199; P < 0.0001). The entire lung and target lobe volume changes were inversely correlated with change in forced expiratory volume in 1 s in patients with heterogeneous emphysematous (r = -0.7; P = 0.0006; and r = -0.7; P = 0.0009, respectively) and giant emphysematous bulla (r = -0.8; P = 0.001; and r = -0.7; P = 0.009, respectively). Among patients with heterogenous emphysematous and giant emphysematous bulla, the value of sensitivity and specificity were 66.6 and 83%, respectively (for a volumetric qunatification >1.5239), and of 60 and 100%, respectively (for a volumetric qunatification >1.762).

CONCLUSIONS

Our study showed that the volumetric quantification adds further informations to the routine evaluation for optimizing the selection of patients scheduled for endobronchial valve treatment.

Automated lung volumetry from routine thoracic CT scans: how reliable is the result?

RATIONALE AND OBJECTIVES

Today, lung volumes can be easily calculated from chest computed tomography (CT) scans. Modern postprocessing workstations allow automated volume measurement of data sets acquired. However, there are challenges in the use of lung volume as an indicator of pulmonary disease when it is obtained from routine CT. Intra-individual variation and methodologic aspects have to be considered. Our goal was to assess the reliability of volumetric measurements in routine CT lung scans.

MATERIALS AND METHODS

Forty adult cancer patients whose lungs were unaffected by the disease underwent routine chest CT scans in 3-month intervals, resulting in a total number of 302 chest CT scans. Lung volume was calculated by automatic volumetry software. On average of 7.2 CT scans were successfully evaluable per patient (range 2-15). Intra-individual changes were assessed.

RESULTS

In the set of patients investigated, lung volume was approximately normally distributed, with a mean of 5283 cm(3) (standard deviation = 947 cm(3), skewness = -0.34, and curtosis = 0.16). Between different scans in one and the same patient the median intra-individual standard deviation in lung volume was 853 cm(3) (16% of the mean lung volume).

CONCLUSIONS

Automatic lung segmentation of routine chest CT scans allows a technically stable estimation of lung volume. However, substantial intra-individual variations have to be considered. A median intra-individual deviation of 16% in lung volume between different routine scans was found.

Application of a photogrammetric kinematic model for prediction of lung volumes in adolescents: a pilot study

BACKGROUND

There are several ways to measure the respiratory system, among them inductance plethysmography and three-dimensional kinematic analysis, methods of high cost and difficult transportability. The objective of this study was to correlate respiratory volumes obtained by spirometry standard equipment with a biomechanical model photogrammetric analysis of adolescents.

METHODS

We evaluated 50 subjects of both genders, aged between 14 and 17 years old, excluding those with respiratory obstruction or restriction. Stickers with markers, there was a five-point mapping for anatomical modeling and photogrammetry, with each evaluated in supine position, was sought to test the Forced Vital Capacity (FVC). The test was filmed and repeated three times. Images of the films were extracted for the moment of maximum exhalation and inhalation of proof with better breathing. With the use of a commercial software, defined the respiratory volumes to the thorax and abdomen.

RESULTS

The photogrammetric analysis has found values strongly correlated with the spirometric measurements of FVC (0.812), forced expiratory volume in one second (FEV1 - 0.708), Peak Expiratory Flow (PEF - 0.762) in addition to post test performed Inspiration (IP- 0.816). There was a higher ventilatory mobility for boys than girls for Lower Chest and Lower and Upper Abdomen. It was possible to reach a regression R2 = 0.866 for proof of FVC and R2 = 0.776 for IP with the use of photogrammetry, presenting a standard error of 0.353 and 0.451, respectively.

CONCLUSIONS

Photogrammetry can be used to study thoracoabdominal movements by applying analytical two-dimensional and three-dimensional images acquired using a video camera being, applicable and reproducible.

Augmenting breath regulation using a mobile driven virtual reality therapy framework

This paper presents a conceptual framework of a virtual reality therapy to assist individuals, especially lung cancer patients or those with breathing disorders to regulate their breath through real-time analysis of respiration movements using a smartphone. Virtual reality technology is an attractive means for medical simulations and treatment, particularly for patients with cancer. The theories, methodologies and approaches, and real-world dynamic contents for all the components of this virtual reality therapy (VRT) via a conceptual framework using the smartphone will be discussed. The architecture and technical aspects of the offshore platform of the virtual environment will also be presented.

[The value of nitrogen washout/washin method in assessing alveolar recruitment volume in acute lung injury patients]

OBJECTIVE

To evaluate the precision and feasibility of nitrogen washout/washin method in assessing lung recruitment of acute lung injury (ALI) patients.

METHODS

Fifteen ALI patients underwent mechanical ventilation were involved. Two positive end-expiratory pressure (PEEP) levels (high and low) were adjusted according to ARDSnet recommendations or measurement of transpulmonary pressure, each for 30 minutes. Tidal volume (Vt), plateau of airway pressure (Pplat), other respiratory mechanics, gas-exchange and hemodynamics were measured. End expiration lung volume (EELV) was measured at different PEEP levels through nitrogen washout/washin method, and formula (EELVhighPEEP-EELVlowPEEP)-VtlowPEEP/(PplatlowPEEP-PEEPlowPEEP)×(PEEPhigh-PEEPlow) was used as recruitment (Rec-N2). Alveolar recruitment was measured using pressure-volume (P-V) curves (Rec-mes). Correlation and consistency of Rec-N2 and Rec-mes were compared by correlation analysis and Bland-Altman technique.

RESULTS

PEEP titrated by ARDSnet recommendations or transpulmonary pressure were (7 ± 2) cm H2O (1 cm H2O = 0.098 kPa) vs (14 ± 5) cm H2O (P = 0.008); and there were significant differences in peak pressure (23 ± 5) cm H2O vs (28 ± 6) cm H2O, plateau of airway pressure (17 ± 4)cm H2O vs (22 ± 6) cm H2O, esophageal pressure, transpulmonary pressure and other respiratory mechanics between the two PEEP levels (P < 0.05). The P-V curve technique gave Rec-mes a value of 100 (-25 ∼ 185)ml. The nitrogen washout/washin technique gave Rec-N2 a value of 180 (-19 ∼ 255) ml, which showed a good correlation with a bias of 46 (8 ∼ 80) ml (R(2) = 0.755, P < 0.0001).

CONCLUSION

Nitrogen washout/washin technique can be used to determine lung recruitment volume of ALI patients.

Three-dimensional ultrasonographic assessment of fetal total lung volume as a prognostic factor in primary pleural effusion

OBJECTIVES

The purpose of this study was to predict perinatal outcomes using fetal total lung volumes assessed by 3-dimensional ultrasonography (3DUS) in primary pleural effusion.

METHODS

Between July 2005 and July 2010, total lung volumes were prospectively estimated in fetuses with primary pleural effusion by 3DUS using virtual organ computer-aided analysis software. The first and last US examinations were considered in the analysis. The observed/expected total lung volumes were calculated. Main outcomes were perinatal death (up to 28 days of life) and respiratory morbidity (orotracheal intubation with mechanical respiratory support >48 hours).

RESULTS

Twelve of 19 fetuses (63.2%) survived. Among the survivors, 7 (58.3%) had severe respiratory morbidity. The observed/expected total lung volume at the last US examination before birth was significantly associated with perinatal death (P < .01) and respiratory morbidity (P < .01) as well as fetal hydrops (P < .01) and bilateral effusion (P = .01).

CONCLUSIONS

Fetal total lung volumes may be useful for the prediction of perinatal outcomes in primary pleural effusion.

Quantification of lung fibrosis and emphysema in mice using automated micro-computed tomography

Background

In vivo high-resolution micro-computed tomography allows for longitudinal image-based measurements in animal models of lung disease. The combination of repetitive high resolution imaging with fully automated quantitative image analysis in mouse models of lung fibrosis lung benefits preclinical research. This study aimed to develop and validate such an automated micro-computed tomography analysis algorithm for quantification of aerated lung volume in mice; an indicator of pulmonary fibrosis and emphysema severity.

Methodology

Mice received an intratracheal instillation of bleomycin (n = 8), elastase (0.25U elastase n = 9, 0.5U elastase n = 8) or saline control (n = 6 for fibrosis, n = 5 for emphysema). A subset of mice was scanned without intervention, to evaluate potential radiation-induced toxicity (n = 4). Some bleomycin-instilled mice were treated with imatinib for proof of concept (n = 8). Mice were scanned weekly, until four weeks after induction, when they underwent pulmonary function testing, lung histology and collagen quantification. Aerated lung volumes were calculated with our automated algorithm.

Principal Findings

Our automated image-based aerated lung volume quantification method is reproducible with low intra-subject variability. Bleomycin-treated mice had significantly lower scan-derived aerated lung volumes, compared to controls. Aerated lung volume correlated with the histopathological fibrosis score and total lung collagen content. Inversely, a dose-dependent increase in lung volume was observed in elastase-treated mice. Serial scanning of individual mice is feasible and visualized dynamic disease progression. No radiation-induced toxicity was observed. Three-dimensional images provided critical topographical information.

Conclusions

We report on a high resolution in vivo micro-computed tomography image analysis algorithm that runs fully automated and allows quantification of aerated lung volume in mice. This method is reproducible with low inherent measurement variability. We show that it is a reliable quantitative tool to investigate experimental lung fibrosis and emphysema in mice. Its non-invasive nature has the unique benefit to allow dynamic 4D evaluation of disease processes and therapeutic interventions.

Morphometric changes in the human pulmonary acinus during inflation

Despite decades of research into the mechanisms of lung inflation and deflation, there is little consensus about whether lung inflation occurs due to the recruitment of new alveoli or by changes in the size and/or shape of alveoli and alveolar ducts. In this study we use in vivo (3)He lung morphometry via MRI to measure the average alveolar depth and alveolar duct radius at three levels of inspiration in five healthy human subjects and calculate the average alveolar volume, surface area, and the total number of alveoli at each level of inflation. Our results indicate that during a 143 ± 18% increase in lung gas volume, the average alveolar depth decreases 21 ±5%, the average alveolar duct radius increases 7 ± 3%, and the total number of alveoli increases by 96 ± 9% (results are means ± SD between subjects; P < 0.001, P < 0.01, and P < 0.00001, respectively, via paired t-tests). Thus our results indicate that in healthy human subjects the lung inflates primarily by alveolar recruitment and, to a lesser extent, by anisotropic expansion of alveolar ducts.

Surfactant and mechanical ventilation

Even if non invasive respiratory support is widespread used in the management of respiratory failure, nevertheless mechanical ventilation and surfactant replacement are standard care for many preterm infants with respiratory distress syndrome (RDS). The interaction between exogenous surfactant and different modalities of ventilatory support are very important and can influence respiratory outcome. The optimization of surfactant replacement during respiratory support is crucial for the successful of this therapy. In course of mechanical ventilation lung recruitment manoeuvres before and after tracheal instillation of surfactant seem to facilitate its distribution and allow to obtain a more homogeneous lung volume. (www.actabiomedica.it).

Measuring end expiratory lung volume after cardiac surgery

BACKGROUND

The aim of this study was to evaluate the interest of end expiratory volume (EELV) measurement after cardiac surgery.

METHODS

After stabilization, four EELV measurements were performed at one hour intervals during three hours using the nitrogen washout technique. EELV was compared to the predicted functional residual capacity (FRC) volume. The relationships between EELV and static compliance of the respiratory system, the PaO2/FiO2 ratio and the body mass index were studied. In addition, a recruitment maneuver was performed using a fixed 45 cm H2O pressure control ventilation during 2 minutes between the second and third EELV measurement in half of the patients. Forty one patients were enrolled and 21 of them received the recruitment maneuver (RM).

RESULTS

Measured EELV corresponded to 52% of the predicted value. It remained stable during the whole study period. EELV correlated well with the PaO2/FiO2 ratio (r2 = 0.40, p <0.0001) and with compliance of the respiratory system (r2 = 0.525, p < 0.0001). EELV was inversely correlated to the body mass index (r2 = 0.165, p = 0.008). RM did not significantly improve EELV.

CONCLUSIONS

EELV is profoundly reduced after cardiac surgery. Measuring EELV is a new tool that is now available during mechanical ventilation. It seems to bring some new robust and possibly useful information. Recruitment maneuvers using sighs does not modify this volume.

In vitro models of the fetal lung: comparison of lung volume measurements with 3-dimensional sonography and magnetic resonance imaging

OBJECTIVES

Three-dimensional (3D) sonography is an established volumetric method in gynecology and obstetrics. The aim of this study was to investigate the variability of 3D sonographic measurements and their accuracy in comparison with magnetic resonance imaging (MRI) for assessing fetal lung volume using in vitro lung models.

METHODS

Twenty-three in vitro lung models with randomly defined volumes ranging from 1 to 60 mL were made from gelatin with plastic sheaths, manually molded into the shape of fetal lungs. The models were measured using 3D sonography and MRI. The 3D sonographic volumes were calculated using the rotational technique with angles of 6° and 30°. Multiplanar T2-weighted sequences were used for the MRI measurements. The percentage error and absolute percentage error were calculated for each method, and intraobserver and interobserver variability in 3D sonographic measurements was assessed with intraclass correlation coefficients (ICCs). Agreement between calculated and real volumes using the limits of agreement method was also evaluated.

RESULTS

The ICCs for the rotation angles indicated very good intraobserver and interobserver variability (6°, 0.995 and 0.996; 30°, 0.997 and 0.985). No systematic errors were observed in the mean percentage errors for 3D sonographic measurements or MRI volumetry. The lowest median absolute percentage error (1.76) was obtained with MRI volumetry, significantly lower than the values for sonography (6°, 5.00; P < .001; 30°, 5.49; P < .001). There were no significant differences in absolute percentage errors between the rotation angles (P = .82) and no significant differences in limits of agreement between 3D sonography and MRI (6°, P = .76; 30°, P = .39).

CONCLUSIONS

Three-dimensional sonographic volumetry was almost as accurate as MRI in this in vitro model and can be regarded as a good alternative method. Further research is needed to confirm these findings in vivo and to assess the prognostic value in fetuses with lung hypoplasia (eg, congenital diaphragmatic hernias).

Influence of different rotation angles in assessment of lung volumes by 3-dimensional sonography in comparison to magnetic resonance imaging in healthy fetuses

OBJECTIVES

Three-dimensional (3D) sonographic volumetry is established in gynecology and obstetrics. Assessment of the fetal lung volume by magnetic resonance imaging (MRI) in congenital diaphragmatic hernias has become a routine examination. In vitro studies have shown a good correlation between 3D sonographic measurements and MRI. The aim of this study was to compare the lung volumes of healthy fetuses assessed by 3D sonography to MRI measurements and to investigate the impact of different rotation angles.

METHODS

A total of 126 fetuses between 20 and 40 weeks' gestation were measured by 3D sonography, and 27 of them were also assessed by MRI. The sonographic volumes were calculated by the rotational technique (virtual organ computer-aided analysis) with rotation angles of 6° and 30°. To evaluate the accuracy of 3D sonographic volumetry, percentage error and absolute percentage error values were calculated using MRI volumes as reference points. Formulas to calculate total, right, and left fetal lung volumes according to gestational age and biometric parameters were derived by stepwise regression analysis.

RESULTS

Three-dimensional sonographic volumetry showed a high correlation compared to MRI (6° angle, R(2) = 0.971; 30° angle, R(2) = 0.917) with no systematic error for the 6° angle. Moreover, using the 6° rotation angle, the median absolute percentage error was significantly lower compared to the 30° angle (P < .001). The new formulas to calculate total lung volume in healthy fetuses only included gestational age and no biometric parameters (R(2) = 0.853).

CONCLUSIONS

Three-dimensional sonographic volumetry of lung volumes in healthy fetuses showed a good correlation with MRI. We recommend using an angle of 6° because it assessed the lung volume more accurately. The specifically designed equations help estimate lung volumes in healthy fetuses.

Lung volume measured during sequential swallowing in healthy young adults

PURPOSE

Outcomes from studying the coordinative relationship between respiratory and swallow subsystems are inconsistent for sequential swallows, and the lung volume at the initiation of sequential swallowing remains undefined. The first goal of this study was to quantify the lung volume at initiation of sequential swallowing ingestion cycles and to identify the respiratory pattern(s) surrounding each sequential swallow ingestion cycle. The second goal was to compare these results with existing data for single swallows.

METHOD

Twenty healthy young adults served as participants, 9 males and 11 females, between 19 and 28 years of age (M = 22 years of age). Participants completed 2 trials each of 100 mL of water self-delivered by cup and by straw. Calibrated respiratory inductance plethysmography, surface electromyography, and a contact throat microphone were used to detect respiratory parameters, identify swallow-related muscle contraction, and identify swallowing sounds, respectively.

RESULTS

Significantly higher lung volume initiation for trials delivered by straw and more variable respiratory patterns surrounding cup and straw sequential swallowing ingestion cycles existed compared with single swallows.

CONCLUSIONS

Results show that as the physiologic demands of swallowing deviate from single, small bolus swallows, the integration of the swallowing and respiratory systems change. This may reflect obligate differences in airway protection strategy and prolonged competition for respiratory resources.

A convenient pulmonary volume and flow detection system

The pulmonary function test (PFT) is a widely used test in patients or for those who are at risk of respiratory dysfunction. In this study, we aimed to develop a more convenient system, namely, the impedance pulmonary function measurement system (IPFS), for overcoming the restrictions posed by the prevalent spirometric PFT. IPFS employs tetra polar electrodes that can measure pulmonary function using the subjects' hands alone. The impedance measured by IPFS extracts AC values of pulmonary impedance from DC values of body impedance in respiration. This system yields changes in the impedance of volume and flow. In order to verify IPFS, we compared the continuous waveforms obtained from the PFT module and developed IPFS using Pearson linear correlation coefficients (p < 0.01) for volume and flow. Further, we evaluated the potential application of IPFS for detecting pulmonary functions such as volume (FEV(1)/FVC Ratio) and flow (PEF), and compared the measured parameters between IPFS and spirometric PFT. Our results demonstrate that the measurements obtained using IPFS reflect pulmonary function parameters.