Effect Of Lung Volume Research Articles

The Repeatability of Pharyngeal Opening Pressure Under Drug-Induced Sleep Endoscopy.

Pharyngeal opening pressure (PhOP) is a measure of upper airway collapsibility that can be obtained during drug-induced sleep endoscopy (DISE) using a continuous positive airway pressure (CPAP) titration. However, the stability of PhOP over the course of sedation during DISE remains unclear. This study aims to compare repeat measures of PhOP over the course of DISE. Single arm prospective study. Single tertiary care institution. Patients had 2 CPAP titrations while undergoing DISE. Collected data included patient demographics, PhOP, patient sedation index (PSI), and duration of and between CPAP titrations. t Tests, test-retest coefficient analysis, and repeated measures correlation were performed. Twenty-five patients completed the study between 2022 and 2023 with 22 patients having sedation depth (PSI) recording. Most were male (76%), obese (average body mass index: 30.24 kg/m2), with severe obstructive sleep apnea (average apnea-hypopnea index: 39.8 events/hr). Test-retest analysis showed good-excellent correlation between PhOP values (intraclass correlation coefficient = 0.892, P < .0001, n = 25). Average time between CPAP titrations was 15 minutes to 6 seconds. Over that time, PhOP increased by an average of 0.72 cmH2O (P = .06, n = 25) and PSI decreased by 9.5 units (P = .01, n = 22). Repeated measures correlation showed a weak negative correlation between PhOP and PSI (r = -.45, P = .03, n = 22). The results showed repeatability of PhOP values over the course of DISE. When adjusted for sedation depth (PSI), deeper sedation was weakly associated with greater PHOP. However, the magnitude of this change was small and we conclude that PhOP remains relatively stable over the course of DISE (Effects of Lung Volume on Upper Airway Patency During DISE [DISE-Pulm], NCT05350332, clinicaltrials.gov).

Effect of lung volume on helical radiotherapy in esophageal cancer: are there predictive factors to achieve acceptable lung doses?

The dose received by the lungs in radiotherapy (RT) is affected by the patient's current lung volume. The presence of predictive factors and cut-off points were investigated to achieve acceptable lung doses in esophageal cancer (EC) treatment. Virtual RT volumes of supracarinal EC were delineated. RT plans were designed with standard criteria in the TomoTherapy planning system (TomoTherapy Inc., Madison, WI, USA). The total dose was 50.4 Gy (1.8 Gy/fraction). ROC (Receiver operating characteristic) analysis and Mann-WhitneyU tests were performed. There was atotal of 65patient plans included. ROC analysis showed that lung/PTV (Planning target volume) volume ratio (AUC [Area under curve]: 0.91, 95% CI: 0.83-0.99, p = 0.000) and bilateral lung volume (AUC: 0.81, 95% CI: 0.70-0.92, p = 0.000) have diagnostic power to predict the suitability of RT plans according to QUANTEC (Quantitative Analyses of Normal Tissue Effects in the Clinic) for lung dose constraints. The cut-off points of 7 and 3500 cc were selected for lung/PTV ratio and bilateral lung volume, respectively. The effect of the cut-off points on the dose data was assessed with the Mann-WhitneyU test. The mean lung and heart doses, lung V5, V15, and V20, as well as heart V5, V20, V30, and V45 values were found to be lower in both groups separated by cut-off points (p < 0.05). The lung/PTV ratio ≥7 and bilateral lung volume ≥3500 cc cut-off points are predictive of whether TomoTherapy plans may meet QUANTEC lung dose limits in patients with supracarinal esophageal cancer. The patients with lung/PTV ratio and lung volume above these cut-off points may be candidates for treatment with TomoTherapy.

Effects of lung volume on the depth of center of gravity, trunk inclination angle, and projected frontal area during front crawl swimming

Effects of lung volume on the depth of center of gravity, trunk inclination angle, and projected frontal area during front crawl swimming

Effects of the Lung Volume on the Electroglottographic Waveform in Trained Female Singers

ObjectivesTo determine if in singing there is an effect of lung volume on the electroglottographic waveform, and if so, how it varies over the voice range. Study designEight trained female singers sang the tune “Frère Jacques” in 18 conditions: three phonetic contexts, three dynamic levels, and high or low lung volume. Conditions were randomized and replicated. MethodsThe audio and EGG signals were recorded in synchrony with signals tracking respiration and vertical larynx position. The first 10 Fourier descriptors of every EGG cycle were computed. These spectral data were clustered statistically, and the clusters were mapped by color into a voice range profile display, thus visualizing the EGG waveform changes under the influence of fo and SPL. The rank correlations and effect sizes of the relationships between relative lung volume and several adduction-related EGG wave shape metrics were similarly rendered on a color scale, in voice range profile-style ʻvoice maps.ʼ ResultsIn most subjects, EGG waveforms varied considerably over the voice range. Within subjects, reproducibility was high, not only across the replications, but also across the phonetic contexts. The EGG waveforms were quite individual, as was the nature of the EGG shape variation across the range. EGG metrics were significantly correlated to changes in lung volume, in parts of the range of the song, and in most subjects. However, the effect sizes of the relative lung volume were generally much smaller than the effects of fo and SPL, and the relationships always varied, even changing polarity from one part of the range to another. ConclusionsMost subjects exhibited small, reproducible effects of the relative lung volume on the EGG waveform. Some hypothesized influences of tracheal pull were seen, mostly at the lowest SPLs. The effects were however highly variable, both across the moderately wide fo-SPL range and across subjects. Different singers may be applying different techniques and compensatory behaviors with changing lung volume. The outcomes emphasize the importance of making observations over a substantial part of the voice range, and not only of phonations sustained at a few fundamental frequencies and sound levels.

Dysanapsis and the resistive work of breathing during exercise in healthy men and women.

We asked if the higher work of breathing (Wb) during exercise in women compared with men is explained by biological sex. We created a statistical model that accounts for both the viscoelastic and the resistive components of the total Wb and independently compares the effects of biological sex. We applied the model to esophageal pressure-derived Wb values obtained during an incremental cycle test to exhaustion. Subjects were healthy men (n = 17) and women (n = 18) with a range of maximal aerobic capacities (V̇o2 max range: men = 40-68 and women = 39-60 ml·kg(-1)·min(-1)). We also calculated the dysanapsis ratio using measures of lung recoil and forced expiratory flow as index of airway caliber. By applying the model we found that the differences in the total Wb during exercise in women are due to a higher resistive Wb rather than viscoelastic Wb. We also found that the higher resistive Wb is independently explained by biological sex. To account for the known effect of lung volumes on the dysanapsis ratio we compared the sexes with an analysis of covariance procedures and found that when vital capacity was accounted for the adjusted mean dysanapsis ratio is statistically lower in women (0.17 vs. 0.25 arbitrary units; P < 0.05). Our collective findings suggest that innate sex-based differences may exist in human airways, which result in significant male-female differences in the Wb during exercise in healthy subjects.

Using the same cut-off for sulfur hexafluoride and nitrogen multiple-breath washout may not be appropriate.

Recent evidence suggests that results from multiple-breath washout (MBW) using nitrogen (N 2 ) as washout gas are different to those obtained by using sulfur hexafluoride (SF 6 ). Explanations were mainly related to different MBW equipment and gas properties. We aim to mention a new aspect, namely using the same cut-off in both techniques to determine lung clearance index (usually 2.5% of initial tracer concentration) irrespective of additional contribution of tissue-nitrogen in N 2 -MBW. In a simple model calculation we subtracted 1% tissue-N 2 from the N 2 -MBW in real washout traces from two children, one with cystic fibrosis (CF) and one healthy. This "SF 6 -washout simulation" decreased LCI differently in the children. In the healthy subject 1/40 th (2.5%) was achieved two breaths earlier compared to the original signal and changed LCI from 6.7 to 5.9 (12%), while in CF 1/40 th was achieved 19 breaths earlier leading to a LCI decrease from 13.7 to 10.0 (27%). It would have been required to wash out SF6 until 1/66 th (1.5%) to be comparable to N 2 washout at 1/40th (2.5%), or to stop N2-MBW already at 3.5% of the starting concentration to make both techniques comparable. We show that a basic physiological-mathematical difference between both techniques additionally accounts for different sensitivities and poor agreement between SF 6 - and N 2 -MBW. The best way of adjusting for the contribution of tissue-N 2 needs to be examined in future studies. Thus, despite increasing use in different disease groups, the books on MBW technology are obviously not closed yet.

Evaluation of ensemble averaging methods in 3D ballistocardiography.

Ballistocardiography (BCG) is a non-invasive technique which measures the acceleration of a body induced by cardiovascular activity, namely the force exerted by the beating heart. Measuring a BCG in a gravity-free environment provides ideal conditions where the subject is completely decoupled from its environment. Furthermore, because gravity constrains the motion in two dimensions, the non-negligible accelerations taking place in the third dimension are lost. In every experimental situation, the measured BCG signal contains artifacts pertaining to different causes. One of them is the undesirable involuntary movements of the subject. Ensemble averaging (EA) tackles the issue of constructing a typical one cardiac cycle BCG signal which best represents a longer recording. The present work compares state-of-the-art EA methods and proposes two novel techniques, one taking into account the ECG sub-intervals and the other one based on Dynamic Time Warping. The effects of lung volume are also assessed.

Effect of Lung Volume on Airway Luminal Area Assessed by Computed Tomography in Chronic Obstructive Pulmonary Disease

BackgroundAlthough airway luminal area (Ai) is affected by lung volume (LV), how is not precisely understood. We hypothesized that the effect of LV on Ai would differ by airway generation, lung lobe, and chronic obstructive pulmonary disease (COPD) severity.MethodsSixty-seven subjects (15 at risk, 18, 20, and 14 for COPD stages 1, 2, and 3) underwent pulmonary function tests and computed tomography scans at full inspiration and expiration (at functional residual capacity). LV and eight selected identical airways were measured in the right lung. Ai was measured at the mid-portion of the 3rd, the segmental bronchus, to 6th generation of the airways, leading to 32 measurements per subject.ResultsThe ratio of expiratory to inspiratory LV (LV E/I ratio) and Ai (Ai E/I ratio) was defined for evaluation of changes. The LV E/I ratio increased as COPD severity progressed. As the LV E/I ratio was smaller, the Ai E/I ratio was smaller at any generation among the subjects. Overall, the Ai E/I ratios were significantly smaller at the 5th (61.5%) and 6th generations (63.4%) and than at the 3rd generation (73.6%, p<0.001 for each), and also significantly lower in the lower lobe than in the upper or middle lobe (p<0.001 for each). And, the Ai E/I ratio decreased as COPD severity progressed only when the ratio was corrected by the LV E/I ratio (at risk v.s.stage3 p<0.001, stage1 v.s.stage3 p<0.05).ConclusionsFrom full inspiration to expiration, the airway luminal area shrinks more at the distal airways compared with the proximal airways and in the lower lobe compared with the other lobes. Generally, the airways shrink more as COPD severity progresses, but this phenomenon becomes apparent only when lung volume change from inspiration to expiration is taken into account.

Effect of Lung Volume and Gravity on the Attenuation and Size of a Pure Ground-Glass Nodule

Detecting potentially malignant changes in a pure ground-glass nodule (GGN) is challenging. The development of a solid component is a known sign, which may help in differentiating benign from malignant GGN. We report the case of a 58-year-old man presenting with a pure GGN in the posterior segment of the right lower lobe. Follow-up computed tomographic scan after 1 year showed marked increase in attenuation (from -319 HU to +27 HU), whereas the average size of the nodule decreased (from 7 to 4.7 mm). On a computed tomographic scan in the prone position the nodule seemed larger (7.8 mm) and appeared as a pure GGN (-406 HU). Such changes were attributed to the reduction of lung volume and gravity.

3D Airway Tree Reconstruction in Healthy Subjects and Emphysema

Several algorithms for the segmentation of the 3D human airway tree from computed tomography (CT) images have recently been proposed, but the effects of lung volume and the presence of emphysema on segmentation accuracy has not been investigated. Two different sets of CT images taken on nine healthy subjects and nine patients with severe emphysema (FEV(1) = 19 ± 4.1 SD % pred) were used to reconstruct the trachea-bronchial tree by a region-growing algorithm at two different lung volumes: total lung capacity (TLC) and residual volume (RV). The sixth generation was reached in 67% of the healthy subjects and 22% of the emphysematous patients at TLC. At RV, fifth generation was reached in 33 and 11% of healthy subjects and emphysematous patients. At TLC, 67 ± 2 and 39 ± 2% of airways belonging to the fourth generation were successfully reconstructed, respectively in healthy and emphysematous subjects. At RV, the percentage of successful reconstruction was 33 ± 2 and 16 ± 2%, respectively. Segmentation was significantly influenced by the presence of disease (P < 0.001) and lung volume (P < 0.001) at which the CT scans were acquired. Airway tree reconstruction performed by means of a region-growing algorithm depends on lung volume and presence of emphysema, both of which have significant effect, even at the level of lobar and segmental bronchi.

Pulmonary Emphysema: Effect of Lung Volume on Objective Quantification at Thin-Section CT

To prospectively investigate the effect of submaximal inspiration on computed tomographic (CT) indexes used to quantify emphysema and to discriminate between effects of lung tissue loss and increase in total lung capacity (TLC) on these indexes. In this ethical committee-approved study, 20 control subjects and 16 patients with chronic obstructive pulmonary disease (COPD) who provided written informed consent were included. Three 1-mm-thick sections were obtained from each participant at 100%, 90%, 80%, 70%, and 50% of vital capacity (VC). At each volume, eight percentiles of attenuation distribution, as well as relative area (RA) of lung occupied by attenuation coefficients lower than nine thresholds, were calculated. A linear regression line between TLC and each CT index was plotted for control subjects. Mean distance from data points measured in patients with COPD to the normal regression line was used to reflect the effect of lung tissue loss, regardless of TLC. The RA of lung occupied by attenuation coefficients lower than -950 HU (RA(950)) at any percentage of VC lower than 100% decreased significantly from that at 100% VC (P ≤ .002) in control subjects and patients with COPD; however, between 100% VC and 90% VC, the average difference in RA(950) was only 3% and 2% in control subjects and patients with COPD, respectively. The 1st percentile at any percentage of VC lower than 100% increased from that at 100% VC (P < .001) in control subjects. This percentile did not significantly differ from 100% VC at 90% VC or 80% VC (P = .176 and P = 0.077, respectively), but it did significantly differ from 100% VC at 70% VC and 50% VC (P ≤ .002 for both) in patients with COPD. Slope and mean distance were different from zero for all RAs and percentiles except for mean distance for RAs between RA(900) and RA(920). Submaximal inspiration induces underestimation of pulmonary emphysema. Both lung tissue loss and TLC influence CT indexes, suggesting the need to establish normal CT values.

The effect of lung volume on efficacy of hands-on defibrillation during each phase of ongoing manual cardiopulmonary resuscitation

The effect of lung volume on efficacy of hands-on defibrillation during each phase of ongoing manual cardiopulmonary resuscitation

The effect of lung volume on efficacy of hands-on defibrillation during each phase of ongoing manual cardiopulmonary resuscitation

Critical Care Medicine: May 2010 - Volume 38 - Issue 5 - p 1392-1393 doi: 10.1097/CCM.0b013e3181d53a1d

Optimizing Performance of Respiratory Airflow Resistance Measurements

In contrast to spirometry, airflow resistance determinations provide an effort independent measure of the airway status and allow measurement in individuals unable or unwilling to provide adequate effort during spirometry. Resistance measurements may be performed using an esophageal balloon, airflow perturbation techniques (including interrupter and oscillatory techniques), or total-body plethysmography. Esophageal balloons are invasive, and airflow perturbation techniques are becoming more widely used. Airflow perturbation methods assess small airway dysfunction using frequency dependence of resistance, a surrogate for frequency dependence of compliance. Body plethysmography remains the "gold standard" for measuring airway resistance and is based on measures of pressure changes and flows with the patient enclosed in a body plethysmograph. While plethysmographic procedures may be completed rapidly, yielding multiple trials within preset repeatability criteria, the equipment is costly and the operator must be highly trained. Plethysmographic specific resistance loops have definite shapes (morphologies) indicative of specific airway disorders, which may be interpreted in a manner analogous to spirometry. Specific resistance and conductance assess the important effects of lung volumes. Reimbursement for resistance measurements varies depending on regional guidelines.

Rebuttal from Dr. Glenny

POINT-COUNTERPOINTRebuttal from Dr. GlennyPublished Online:01 May 2008https://doi.org/10.1152/japplphysiol.01092.2007cMoreSectionsPDF (56 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Drs. Hughes and West (6) argue convincingly that a vertical gradient of perfusion exists in human lungs. We agree completely and have never stated otherwise. The controversy, however, is about whether gravity is the most important determinant of regional pulmonary blood flow. They reason that gravity must be the single most important determinant of regional perfusion because numerous prior studies have observed a gradient vertical. This logic parallels the argument that the sun revolves around the earth because it is repeatedly seen traversing from one horizon to the other. While the observation is consistent with the hypothesis, it is not sufficient proof. When it was discovered that the earth spins about its axis, prior observations were not invalidated but rather reinterpreted. The realization that blood flow within horizontal planes is present, well structured, and stable over time, suggests a reinterpretation of prior studies of pulmonary blood flow distribution.None of the studies cited in their Point (6) can determine if gravity is the most important determinant of regional pulmonary blood flow. To settle this issue, high spatial resolution measurements of perfusion must be obtained under varying conditions of posture or gravity while tracking the same lung regions across conditions. Although this kind of study is not currently possible in humans, the requisite study has been performed in baboons (2). The baboon is a biped that has similar lung anatomy, muscularization of pulmonary vessels, hydrostatic gradients, and pulmonary arterial pressures found in humans and therefore meets the criteria set by Drs. Hughes and West (4, 6). Baboons were studied in the upright, supine, prone, and head-down postures. Blood flow to each lung region was described by its vertical position in the lung and a structural component that remained stable across changes in posture. Vertical gradients of perfusion were observed in all postures, corroborating prior observations in humans (5, 8). Multiple stepwise linear regression was used to estimate the relative importance of the gravitational and structural components of blood flow. As expected, gravity had its largest influence in the upright posture. However, structure was more than twice as important as gravity in determining regional pulmonary blood flow (59 vs. 25%).The perspective that the geometry of the vascular tree is more important than gravity in determining regional blood flow requires that other concepts of the gravitational model be reconsidered. While the zones of the lung must exist due to physical laws, they do not need to be vertically stacked in the lung (3). The fractal model predicts that all three zones can exist within the same horizontal plane. The concept that the shared effects of gravity cause matching of regional ventilation and perfusion, however, cannot explain efficient gas exchange in the face of large heterogeneities of ventilation (1) and perfusion within isogravitational planes or during sustained microgravity (7).REFERENCES1 Altemeier WA, McKinney S, Glenny RW. Fractal nature of regional ventilation distribution. J Appl Physiol 88: 1551–1557, 2000.Link | ISI | Google Scholar2 Glenny RW, Bernard S, Robertson HT, Hlastala MP. Gravity is an important but secondary determinant of regional pulmonary blood flow in upright primates. J Appl Physiol 86: 623–632, 1999.Link | ISI | Google Scholar3 Glenny RW, Robertson HT. Regional differences in the lung. In: Complexity in Structure and Function of the Lung, edited by Hlastala MP and Robertson HT. New York: Marcel Dekker, 1998, p. 461–481.Google Scholar4 Hughes JM. Pulmonary blood flow distribution in exercising and in resting horses. J Appl Physiol 81: 1049–1050, 1996.Link | ISI | Google Scholar5 Hughes JM, Glazier JB, Maloney JE, West JB. Effect of lung volume on the distribution of pulmonary blood flow in man. Respir Physiol 4: 58–72, 1968.Crossref | Google Scholar6 Hughes JM, West JB. Counterpoint: Gravity is not the major factor determining the distribution of blood flow in the healthy human lung. J Appl Physiol; doi:10.1152/japplphysiol.01092.2007a.Link | ISI | Google Scholar7 Prisk GK, Guy HJ, Elliott AR, West JB. Inhomogeneity of pulmonary perfusion during sustained microgravity on SLS-1. J Appl Physiol 76: 1730–1738, 1994.Link | ISI | Google Scholar8 West JB, Dollery CT. Distribution of blood flow and ventilation-perfusion ratio in the lung, measured with radioactive carbon dioxide. J Appl Physiol 15: 405–410, 1960.Link | ISI | Google Scholar Download PDF Previous Back to Top Next FiguresReferencesRelatedInformation Collections More from this issue > Volume 104Issue 5May 2008Pages 1535-1536 Copyright & PermissionsCopyright © 2008 the American Physiological Societyhttps://doi.org/10.1152/japplphysiol.01092.2007cHistory Published online 1 May 2008 Published in print 1 May 2008 Metrics

Rebuttal from Drs. Hughes and West

POINT-COUNTERPOINTRebuttal from Drs. Hughes and WestPublished Online:01 May 2008https://doi.org/10.1152/japplphysiol.01092.2007bMoreSectionsPDF (59 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInEmailWeChat The areas of agreement in this debate are twofold: 1) mean pulmonary blood flow per horizontal slice [per unit volume or, more accurately, per unit density or “alveolus” (1,6)] increases in the gravity direction, independent (for the most part) of postural orientation, 2) there is considerable inhomogeneity of blood flow within a slice of minimal vertical height. Heterogeneity, whether random or ordered, is inevitable as the spatial resolution increases, just as the length of the shoreline increases indefinitely as the sample size gets smaller. Suffice to say that there are two extremes, 1) a well-expanded, vasodilated lung with low PVR and a mean Ppa level below the top of the lung, and 2) a low volume vasoconstricted lung with high PVR and a Ppa level greater than the lung's vertical height. The effects of gravity will be prominent in the former and largely obscured in the latter.The core of the debate is about the mechanisms responsible for pulmonary blood flow heterogeneity. There has been acceptance (for more than 40 yr) that mean pulmonary blood flow per horizontal slice is influenced by the relations between Ppa, Palv, and Pv (zones I, II, and III) (7), provided the lung is well expanded and PVR is normal. But what determines heterogeneity at the same horizontal level? Between acini, or larger domains, the Seattle group maintains that the architecture of the vascular tree (presumably, arterial) determines local vascular resistance and blood flow by, for example, uneven diameters of the two daughter vessels at a bifurcation. Glenny (5) maintains that this is not random, but forms part of the fractal design of the lung (4). Against this hypothesis is 1) the arterial system contributes only 40% to total PVR (2), and 2) the compliance of the arterial tree means diameters are not fixed, but respond to changes of smooth muscle tone or intra- or extravascular pressures (themselves influenced by gravity from distortion of the lung by its own weight and by other intrathoracic structures).Distal to the arterial tree, at the alveolar septal level, recruitment and distension of vessels occurs (3), independent of arteriolar domains (8), as input pressure increases and exceeds critical opening pressure (9); in the lung periphery, input pressures are a function of vertical height and gravity. So, in subtle ways, gravity may interact with compliant vascular structures to influence local PVR within as well as between horizontal lung slices.REFERENCES1 Anthonisen NR, Milic-Emili J. Distribution of pulmonary perfusion in erect man. J Appl Physiol 21: 760–766, 1966.Link | ISI | Google Scholar2 Dawson CA. Dynamics of blood flow and pressure-volume relationship. In: The Lung: Scientific Foundations, edited by Crystal RG, West JB, et al. Philadelphia: Lippincott-Raven, 1997, p. 1503–1522.Google Scholar3 Glazier JB, Hughes JMB, Maloney JE, West JB. Measurements of capillary dimensions and blood volume in rapidly frozen lungs. J Appl Physiol 26: 65–76, 1969.Link | ISI | Google Scholar4 Glenny RW, Robertson HT. Fractal modelling of pulmonary blood flow inhomogeneity. J Appl Physiol 70: 1024–1030, 1991.Link | ISI | Google Scholar5 Glenny RW. Spatial correlation of regional pulmonary perfusion. J Appl Physiol 72: 2378–2386, 1992.Link | ISI | Google Scholar6 Hughes JMB, Glazier JB, Maloney JE, West JB. Effect of lung volume on the distribution of pulmonary blood flow in man. Respir Physiol 4: 58–72, 1968.Crossref | Google Scholar7 West JB, Dollery CT, Naimark A. Distribution of blood flow in isolated lung; relation to vascular and alveolar pressures. J Appl Physiol 19: 713–724, 1964.Link | ISI | Google Scholar8 Warrell DA, Evans JW, Clarke RO, Kingaby JP, West JB. Pattern of filling in the pulmonary vascular bed. J Appl Physiol 32: 346–356, 1972.Link | ISI | Google Scholar9 West JB, Schneider AM, Mitchell MM. Recruitment in networks of pulmonary capillaries. J Appl Physiol 39: 976–984, 1975.Link | ISI | Google Scholar Download PDF Previous Back to Top Next FiguresReferencesRelatedInformation More from this issue > Volume 104Issue 5May 2008Pages 1535-1535 Copyright & PermissionsCopyright © 2008 the American Physiological Societyhttps://doi.org/10.1152/japplphysiol.01092.2007bHistory Published online 1 May 2008 Published in print 1 May 2008 Metrics

The effect of lung volume on the co-ordinated recruitment of scalene and sternomastoid muscles in humans.

The human scalenes are obligatory inspiratory muscles that have a greater mechanical advantage than sternomastoid, an accessory muscle. This study determined scalene and sternomastoid recruitment during voluntary inspiratory tasks, and whether this activity varied with lung volume, when feedback from the lungs and inspiratory muscles would differ. If afferent feedback has a major role in determining the recruitment of the scalenes and sternomastoid, then at each lung volume, activity would be altered. Intramuscular EMG from scalene and sternomastoid muscles, and oesophageal pressure were recorded while subjects (n = 7) performed inspiratory isovolumetric ramps to maximal inspiratory pressure (MIP) and dynamic inspirations from functional residual capacity (FRC) to total lung capacity (TLC). The static inspiratory ramps were repeated at three lung volumes: FRC, FRC + tidal volume, and TLC. To determine the profile of inspiratory activation, i.e. the initial and ongoing recruitment of the muscles, the root mean square of the EMG was measured throughout the tasks. Scalene was recruited early, and EMG increased with pressure, reaching a plateau at 80% MIP. In contrast, sternomastoid activity began later, but then increased with pressure from 20 to 100% MIP. Similar profiles of activation occurred at all three lung volumes (n.s.). The ratio of sternomastoid to scalene EMG was also the same irrespective of the initial lung volume (n.s.). In dynamic inspirations, scalene and sternomastoid activation had similar stereotypical profiles to the static tasks, but scalene EMG was 15-40% greater (P < 0.05). Sternomastoid activation was the same in both tasks (n.s.). These results suggest that in voluntary tasks, scalene and sternomastoid are recruited in the order of their mechanical advantages, and that alterations in feedback related to changes in lung volume failed to alter their activation. Thus, in humans, the mechanism responsible for the differential activation of these two inspiratory muscles has an element that is preset.

The Effect of Lung Volume on Nodule Size on CT

We sought to determine how measures of nodule diameter and volume on computed tomography (CT) vary with changes in inspiratory level. CT scans were performed with inspiration suspended at total lung capacity (TLC) and then at residual volume (RV) in 41 subjects, in whom 75 indeterminate lung nodules were detected. A fully automated contouring program was used to segment the lungs; followed by segmentation of all nodules and the corresponding lobe using semiautomated contouring in both TLC and RV scans. The percent changes in lung and lobar volumes between TLC and RV were correlated with percent changes in nodule diameters and volumes. Both nodule diameter and volume varied nonuniformly from TLC to RV-some nodules decreased in size, while others increased. There was a 16.8% mean change in absolute volume across all nodules. Stratified by size, the mean value of the absolute percent volume changes for nodules > or =5 mm and <5 mm were not significantly different (P = .26). Stratified by maximum attenuation, the mean value of the absolute percent volume changes between the TLC and RV series for noncalcified (17.7%, SD = 13.1) and completely calcified nodules (8.6% SD = 5.7) were significantly different (P < .05). Significant differences in nodule size were measured between TLC and RV scans. This has important implications for standardizing acquisition protocols in any setting where size and, more important, size change are being used for purposes of lung cancer staging, nodule characterization, or treatment response assessment.

Effect of lung volume on counting efficiency: A Monte Carlo investigation

Lung counters are usually calibrated with an anthropometric phantom that has a fixed lung size; however, people have widely varying lung sizes (both volume and dimensions). This work uses a simple Monte Carlo simulation to investigate the effect on the counting efficiency of a lung counter based on a four detector array of 50 mm diameter, 70 mm diameter, or 85 mm diameter as lung size varies. The simulations were carried out at several photon energies (17, 60, 120, and 1,000 keV). Comparing the simulated efficiencies with a reference value close to the lung volume of Reference Man, biases in the range of -21% to 63% were discovered. The values from the Monte Carlo simulation have also been compared with some literature data based on experimental measurements, and the agreement was found to be comparable suggesting that lung volume is indeed a factor that should be considered when trying to make an accurate estimate of a lung burden.

Impact of lung volume on MR signal intensity changes of the lung parenchyma

To test the hypothesis that, in magnetic resonance (MR) imaging of healthy individuals, equal relative changes in lung volume cause equal relative changes in MR signal intensity of the lung parenchyma. In two experimental runs, 10 volunteers underwent spirometrically monitored MR imaging of the lungs, with MR images acquired at 10 incremental lung volumes ranging from total lung capacity to 10% above residual volume. Average signal intensity, signal variability, and signal intensity integrals were calculated for each volunteer and for each lung volume. The effect of lung volume on signal intensity was quantified using linear regression analysis complemented by the runs test. Slopes and intercepts of regression lines were compared with an analysis of covariance. Slopes of the lines of best fit for lung volumes and signal intensities from the two runs were compared to the slope of the line of identity. Comparisons between the two runs were visualized using Bland and Altman plots. The slopes of the 10 individual regression lines yielded no significant differences (F = 1.703, P = 0.101; F = 1.321, P = 0.239). The common slopes were -0.556 +/- 0.027 (P = 0.0001) for the first and -0.597 +/- 0.0031 (P = 0.0001) for the second experimental run. Both slopes displayed no significant nonlinearity (P = 0.419 and P = 0.067). There was a strong association between changes in lung volumes (rs = 0.991, P = 0.0001) and changes in signal intensity (rs = 0.889, P = 0.0001) in the two experimental runs. Lines of best fit for lung volume and signal intensities were not significantly different from the slope of the line of identity (P = 0.321 and P = 0.212, respectively). Equal changes in lung volume cause equal changes in MR signal intensity of the lung parenchyma. This linear and reproducible phenomenon could be helpful in comparing pulmonary MR signal intensity between individuals.