Measurement Of Regional Ventilation Research Articles

537: 129Xe MRI is a repeatable measure of regional ventilation in children with stable CF

537: 129Xe MRI is a repeatable measure of regional ventilation in children with stable CF

What hinders pulmonary gas exchange and changes distribution of ventilation in immobilized white rhinoceroses (Ceratotherium simum) in lateral recumbency?

This study used electrical impedance tomography (EIT) measurements of regional ventilation and perfusion to elucidate the reasons for severe gas exchange impairment reported in rhinoceroses during opioid-induced immobilization. EIT values were compared with standard monitoring parameters to establish a new monitoring tool for conservational immobilization and future treatment options. Six male white rhinoceroses were immobilized using etorphine, and EIT ventilation variables, venous admixture, and dead space were measured 30, 40, and 50 min after becoming recumbent in lateral position. Pulmonary perfusion mapping using impedance-enhanced EIT was performed at the end of the study period. The measured impedance (∆Z) by EIT was compared between pulmonary regions using mixed linear models. Measurements of regional ventilation and perfusion revealed a pronounced disproportional shift of ventilation and perfusion toward the nondependent lung. Overall, the dependent lung was minimally ventilated and perfused, but remained aerated with minimal detectable lung collapse. Perfusion was found primarily around the hilum of the nondependent lung and was minimal in the periphery of the nondependent and the entire dependent lung. These shifts can explain the high amount of venous admixture and physiological dead space found in this study. Breath holding redistributed ventilation toward dependent and ventral lung areas. The findings of this study reveal important pathophysiological insights into the changes in lung ventilation and perfusion during immobilization of white rhinoceroses. These novel insights might induce a search for better therapeutic options and is establishing EIT as a promising monitoring tool for large animals in the field.NEW & NOTEWORTHY Electrical impedance tomography measurements of regional ventilation and perfusion applied to etorphine-immobilized white rhinoceroses in lateral recumbency revealed a pronounced disproportional shift of the measured ventilation and perfusion toward the nondependent lung. The dependent lung was minimally ventilated and perfused, but still aerated. Perfusion was found primarily around the hilum of the nondependent lung. These shifts can explain the gas exchange impairments found in this study. Breath holding can redistribute ventilation.

Quantitative multivolume proton-magnetic resonance imaging in patients with cystic fibrosis lung disease: comparison with clinical indicators.

This cross-sectional study aims to verify the relationship between quantitative multivolume proton-magnetic resonance imaging (1H-MRI) and clinical indicators of ventilatory abnormalities in cystic fibrosis (CF) lung disease.Non-enhanced chest MRI, spirometry and multiple breath washout was performed by 28 patients (10-27 years) with CF lung disease. Images acquired at end-inspiration and end-expiration were registered by optical flow to estimate expiratory-inspiratory proton-density change (Δ1H-MRI) as a measure of regional ventilation. Magnetic resonance images were also evaluated using a CF-specific scoring system.Biomarkers of CF ventilation impairment were defined from the Δ1H-MRI as follows: Δ1H-MRI median, Δ1H-MRI quartile coefficient of variation (QCV) and percentage of low-ventilation volume (%LVV). Imaging biomarkers correlated to all the clinical measures of ventilation abnormality, with the strongest correlation between Δ1H-MRI median and forced expiratory volume in 1 s (r2=0.44, p<0.001), Δ1H-MRI QCV and lung clearance index (LCI) (r2=0.51, p<0.001) and %LVV and LCI (r2=0.66, p<0.001). Correlations were also found between imaging biomarkers of ventilation and morphological scoring.The study showed a significant correlation between quantitative multivolume MRI and clinical indicators of CF lung disease. MRI, as a non-ionising imaging technique, may be particularly attractive in CF care for longitudinal evaluation, providing a new imaging biomarker to detect early ventilatory abnormalities.

Lung aeration and ventilation after percutaneous tracheotomy measured by electrical impedance tomography in non-hypoxemic critically ill patients: a prospective observational study

BackgroundPercutaneous dilatational tracheotomy (PDT) may lead to transient impairment of pulmonary function due to suboptimal ventilation, loss of positive end-expiratory pressure (PEEP) and repetitive suction maneuvers during the procedure. Possible changes in regional lung aeration were investigated using electrical impedance tomography (EIT), an increasingly implied instrument for bedside monitoring of pulmonary aeration.MethodsWith local ethics committee approval, after obtaining written informed consent 29 patients scheduled for elective PDT under bronchoscopic control were studied during mechanical ventilation in supine position. Anesthetized patients were monitored with a 16-electrode EIT monitor for 2 min at four time points: (a) before and (b) after initiation of neuromuscular blockade (NMB), (c) after dilatational tracheostomy (PDT) and (d) after a standardized recruitment maneuver (RM) following surgery, respectively. Possible changes in lung aeration were detected by changes in end-expiratory lung impedance (Δ EELI). Global and regional ventilation was characterized by analysis of tidal impedance variation.ResultsWhile NMB had no detectable effect on EELI, PDT led to significantly reduced EELI in dorsal lung regions as compared to baseline, suggesting reduced regional aeration. This effect could be reversed by a standardized RM. Mean delta EELI from baseline (SE) was: NMB − 47 ± 62; PDT − 490 ± 180; RM − 89 ± 176, values shown as arbitrary units (a.u.). Analysis of regional tidal impedance variation, a robust measure of regional ventilation, did not show significant changes in ventilation distribution.ConclusionThough changes of EELI might suggest temporary loss of aeration in dorsal lung regions, PDT does not lead to significant changes in either regional ventilation distribution or oxygenation.

TU‐A‐12A‐02: Novel Lung Ventilation Imaging with Single Energy CT After Single Inhalation of Xenon: Comparison with SPECT Ventilation Images

Purpose:We propose a novel lung functional imaging method to determine the spatial distribution of xenon (Xe) gas in a single inhalation as a measure of regional ventilation. We compare Xe‐CT ventilation to single‐photon emission CT (SPECT) ventilation, which is the current clinical reference. Regional lung ventilation information may be useful for the diagnosis and monitoring of pulmonary diseases such as COPD, radiotherapy planning, and assessing the progression of toxicity after radiation therapy.Methods:In an IRB‐approved clinical study, Xe‐CT and SPECT ventilation scans were acquired for three patients including one patient with severe emphysema and two lung cancer patients treated with radiotherapy. For Xe‐ CT, we acquired two breath‐hold single energy CT images of the entire lung with inspiration of 100% O2 and a mixture of 70% Xe and 30% O2, respectively. A video biofeedback system was used to achieve reproducible breath‐holds. We used deformable image registration to align the breathhold images with each other to accurately subtract them, producing a map of the distribution of Xe as a surrogate of lung ventilation. We divided each lung into twelve parts and correlated the Hounsfield unit (HU) enhancement at each part with the SPECT ventilation count of the corresponding part of the lung.Results:The mean of the Pearson linear correlation coefficient values between the Xe‐CT and ventilation SPECT count for all three patients were 0.62 (p&lt;0.01). The Xe‐CT image had a higher resolution than SPECT, and did not show central airway deposition artifacts that were present in the SPECT image.Conclusion:We developed a rapid, safe, clinically practical, and potentially widely accessible method for regional lung functional imaging. We demonstrated strong correlations between the Xe‐CT ventilation image and SPECT ventilation image as the clinical reference. This ongoing study will investigate more patients to confirm this finding.

Quantification of ventilation distribution in regional lung injury by electrical impedance tomography and xenon computed tomography

Validation studies of electrical impedance tomography (EIT) based assessment of regional ventilation under pathological conditions are required to prove that EIT can reliably quantify heterogeneous ventilation distribution with sufficient accuracy. The objective of our study was to validate EIT measurements of regional ventilation through a comparison with xenon-multidetector-row computed tomography (XeCT) in an animal model of sub-lobar lung injury. Nine anesthetized mechanically ventilated supine pigs were examined before and after the induction of lung injury in two adjacent sub-lobar segments of the right lung by saline lavage or endotoxin instillation. Regional ventilation was determined in 32 anteroposterior regions of interest in the right and left lungs and the ventilation change quantified by difference images between injury and control. Six animals were included in the final analysis. Measurements of regional ventilation by EIT and XeCT correlated well before (rs = 0.89 right, rs = 0.90 left lung) and after local injury (rs = 0.79 and 0.92, respectively). No bias and narrow limits of agreement were found during both conditions. The ventilation decrease in the right injured lung was correspondingly measured by both modalities (5.5%±1.1% by EIT and 5.4%±1.9% by XeCT, p = 0.94). EIT was inferior to clearly separate the exact anatomical location of the regional injuries. Regional ventilation was overestimated (<2%) in the most ventral and dorsal regions and underestimated (2%) in the middle regions by EIT compared to XeCT. This study shows that EIT is able to reliably discern even small ventilation changes on sub-lobar level.

Regional lung ventilation in humans during hypergravity studied with quantitative SPECT

Recently we challenged the view that arterial desaturation during hypergravity is caused by redistribution of blood flow to dependent lung regions by demonstrating a paradoxical redistribution of blood flow towards non-dependent regions. We have now quantified regional ventilation in 10 healthy supine volunteers at normal and three times normal gravity (1G and 3G). Regional ventilation was measured with Technegas (99mTc) and quantitative single photon emission computed tomography (SPECT). Hypergravity caused arterial desaturation, mean decrease 8%, p<0.05 vs. 1G. The ratio for mean ventilation per voxel for non-dependent and dependent lung regions was 0.81±0.12 during 1G and 1.63±0.35 during 3G (mean±SD), p<0.0001. Thus, regional ventilation was shifted from dependent to non-dependent regions. We suggest that arterial desaturation during hypergravity is caused by quantitatively different redistributions of blood flow and ventilation. To our knowledge, this is the first study presenting high-resolution measurements of regional ventilation in humans breathing normally during hypergravity.

Lung Physiology and Aerosol Deposition Imaged with Positron Emission Tomography

Physiological conditions and pathophysiological changes in the lungs may affect many applications in aerosol medicine and pulmonary drug delivery. In the diseased lung, spatial heterogeneity in function and structure may cause substantial changes in aerosol transport and local deposition among different lung regions. Non-uniform aerosol deposition affects airway or tissue pharmacological dosing, which could reduce the therapeutic effectiveness of inhalation therapy. This review article presents examples of pulmonary imaging using PET and PET-CT in lung physiology with an emphasis on their implications for aerosol medicine. Measurements of regional ventilation, perfusion, and ventilation/perfusion ratio, by imaging local kinetics of intravenously injected Nitrogen-13 in saline solution, and of pulmonary inflammation, by assessing the regional uptake of the radiotracer (18)F-FDG, are presented. These examples demonstrate that it is possible to access both preexisting conditions, such as heterogeneity of ventilation, perfusion, and/or inflammatory stimuli, which may affect inhalation therapy, and the functional effects of inhaled medications or inflammatory agents on lung regional function. The imaging techniques described could be efficient tools to evaluate quantitatively and noninvasively these processes in vivo. Furthermore, it can be expected that imaging of respiratory structure and function will yield sensitive biomarkers of disease, which will help and speed drug discovery, and the evaluation of novel inhalation therapies.

Ventilation heterogeneity: small length scales, big challenges

the distribution of regional ventilation is heterogeneous in normal lung and increases dramatically under pathological conditions. This has been demonstrated both in humans and in animal models using a number of different imaging techniques. General anesthesia and mechanical ventilation can

SU‐C‐217BCD‐01: Breathing Maneuvers Result in Regional Changes in Ventilation as Assessed by 4D‐CT

Purpose: Different breathing maneuvers typically Result in slightly different tidal volumes that can lead to changes in alveolar recruitment. Recently, there has been tremendous interest in utilizing 4D‐CT based measurements of regional ventilation for treatment planning and treatment assessment. In this work, we wanted to demonstrate the effect of different breathing maneuvers on fractional regional ventilation (FRV) extracted using 4D‐CT. Methods: In this work, we evaluate the effect of different breathing maneuvers: a) free‐breathing (FB), b) audio‐visual assistance (AV), and c) active breathing control (ABC), on FRV. We measured these changes using a 4D‐CT based technique that quantifies changes in CT characteristics of the pulmonary parenchyma. Five subjects were imaged using 4D‐CT during a single session under 3 different breathing maneuvers. 4D‐CT images were used to extract fractional regional ventilation by applying a ‘mass correction’ that is estimated using the ratio of the global inhale‐mass and end‐exhale mass. A subtraction of the corrected images is performed by spatially matching the images at each phase of the respiratory cycle using a deformable image registration algorithm in Insight Toolkit. A distribution of the fractional regional ventilation values is used to estimate a ratio of tidal volume to functional residual capacity. Results: Increased fractional regional ventilation is observed in all the subjects when they were breathing using the ABC maneuver. Statistically significant difference (p=0.079) in fractional regional ventilation was observed when we compared the means for the FB and ABC breathing maneuvers. These global differences were also reflected on a regional level when we compared the fractional regional ventilation maps. Conclusions: This is the first study to report that breathing pattern changes can significantly impact the recruitment of alveoli resulting in marked changes in the fractional regional ventilation.

Imaging regional PaO2 and gas exchange

Several methods allow regional gas exchange to be inferred from imaging of regional ventilation and perfusion (V/Q) ratios. Each method measures slightly different aspects of gas exchange and has inherent advantages and drawbacks that are reviewed. Single photon emission computed tomography can provide regional measure of ventilation and perfusion from which regional V/Q ratios can be derived. PET methods using inhaled or intravenously administered nitrogen-13 provide imaging of both regional blood flow, shunt, and ventilation. Electric impedance tomography has recently been refined to allow simultaneous measurements of both regional ventilation and blood flow. MRI methods utilizing hyperpolarized helium-3 or xenon-129 are currently being refined and have been used to estimate local PaO(2) in both humans and animals. Microsphere methods are included in this review as they provide measurements of regional ventilation and perfusion in animals. One of their advantages is their greater spatial resolution than most imaging methods and the ability to use them as gold standards against which new imaging methods can be tested. In general, the reviewed methods differ in characteristics such as spatial resolution, possibility of repeated measurements, radiation exposure, availability, expensiveness, and their current stage of development.

Using MRI to Measure Aerosol Deposition

This article provides a concise review of the use of magnetic resonance imaging (MRI) for measurement of regional aerosol deposition in the lungs. Basic aspects of MRI and its use in lung imaging and measurement of regional ventilation are introduced. Imaging of hydrogen protons (water) and inhaled hyperpolarized gases as the MRI source signals are discussed. The addition of contrast agents to aerosol particles in order to allow measurement of regional aerosol deposition is considered. Existing in vitro human and in vivo animal model measurements of regional aerosol deposition in the respiratory tract demonstrate the capability of MRI in this regard. However, as a tool for human deposition studies, current approaches require contrast agent doses that are too high to be considered competitive with traditional radionuclide aerosol deposition measurement methods. Thus, future use of MRI in human studies of regional aerosol deposition is predicated on improvement over present approaches.

TH‐A‐220‐10: Ventilation Imaging of the Lung: Comparison of 4DCT with Hyperpolarized Helium‐3 MR

Purpose: Radiation induced pulmonary diseases can change the tissue material properties of lung parenchyma and the regional ventilation. 4DCT can be used to measure regional ventilation when combined with non‐linear 3D image registration. The purpose of this study is to analyze the effects of the B‐Spline grid spacing and the weighting of linear elasticity in 4DCT and image registration based measurement of ventilation by comparing the result to hyperpolarized helium‐3 MR (HP He‐3 MR). Methods: 4DCT data set and HP He‐3 MR before RT were acquired from one patient. The regularized tissue volume and vesselness preserving image registration algorithm was applied to register the maximum inhalation image to the maximum exhalation image for the measurement of regional ventilation. The HP He‐3 MR ventilation map was rigidly registered to the maximum exhalation image for direct comparison to the 4DCT derived ventilation map. Relative overlap (RO) was used to quantify the similarity between the two measurements. Ventilation maps derived from different B‐Spline grid spacing and Laplacian weighting in the image registration were compared. Results: The similarity between the two measurements increases as the increase of the B‐Spline grid spacing and Laplacian weighting which result a smoother ventilation map. In this study, the best similarity with the RO value 0.75 is found with Laplacian weighting of 0.5 and B‐Spline grid spacing of 32 mm. The Laplacian weighting of 0.01 with B‐Spline grid spacing of 8 mm shows the lowest OR value of 0.68. Visual inspection indicates the two measurements have similar anterior/posterior and superior/inferior gradients. Conclusions: We have compared the 4DCT based ventilation measurement with the results from hyperpolarized helium‐3 MR. This result will be valuable for improving the lung CT image registration algorithm toward accuracy not only in the measure of landmark error but also the underlying physiological changes.This work is is supported in part by NIH 1R21CA144063.

3D Hyperpolarized 129Xe MRI of Mouse Lung at Low Xenon Concentration using a Continuous Flow-type Hyperpolarizing System: Feasibility for Quantitative Measurement of Regional Ventilation

We investigated the feasibility of 3D hyperpolarized (HP) (129)Xe magnetic resonance (MR) imaging at an extremely low concentration of HP (129)Xe supplied from a continuous flow-type hyperpolarizing (CF-HP) system and established a standard procedure for measuring regional lung ventilation of small animals, such as the mouse, as a baseline for further studies. We performed 3D HP (129)Xe MR imaging of the lungs of 2 healthy and 2 emphysematous mice that were spontaneously breathing diluted HP (129)Xe (<1%). From the three 3D MR images acquired by varying the flip angle of the radiofrequency (RF) pulse, we calculated the time constant of regional recovery, tau'(rep), which represents the time required for HP (129)Xe magnetization to be replenished approximately 63% after destruction of hyperpolarization by RF saturation pulse. After calculating the tau'(rep) maps, we examined the validity of our method. We used diluted xenon from the CF-HP system to acquire 3D HP (129)Xe MR images of the mouse lung that were undiminished under spontaneous respiration. The averaged tau'(rep) values were longer for the emphysematous lungs than for the healthy lungs, which reflected ventilation defects in the emphysematous lung. This procedure permitted us to estimate the regional lung ventilation for any arbitrarily set slice, and it will provide a standard for measuring regional lung ventilation as a baseline for further studies.

Electrical impedance tomography compared with thoracic computed tomography during a slow inflation maneuver in experimental models of lung injury*

To determine the validity of functional electric impedance tomography to monitor regional ventilation distribution in experimental acute lung injury, and to develop a simple electric impedance tomography index detecting alveolar recruitment. Randomized prospective experimental study. Academic research laboratory. Sixteen anesthetized, tracheotomized, and mechanically ventilated pigs. Acute lung injury was induced either by acid aspiration (direct acute lung injury) or by abdominal hypertension plus oleic acid injection (indirect acute lung injury) in ten pigs. Six pigs with normal lungs were studied as a control group and with endotracheal suction-related atelectasis. After 4 hrs of mechanical ventilation, a slow inflation was performed. During slow inflation, simultaneous measurements of regional ventilation by electric impedance tomography and dynamic computed tomography were highly correlated in quadrants of a transversal thoracic plane (r2 = .63-.88, p < .0001, bias <5%) in both direct and indirect acute lung injury. Variability between methods was lower in direct than indirect acute lung injury (11 +/- 2% vs. 18 +/- 3%, respectively, p < .05). Electric impedance tomography indexes to detect alveolar recruitment were determined by mathematical curve analysis of regional impedance time curves. Empirical tests of different methods revealed that regional ventilation delay, that is, time delay of regional impedance time curve to reach a threshold, correlated well with recruited volume as measured by CT (r2 = .63). Correlation coefficients in subgroups were r2 = .71 and r2 = .48 in pigs with normal lungs with and without closed suction related atelectasis and r2 = .79 in pigs subject to indirect acute lung injury, respectively, whereas no significant correlation was found in pigs undergoing direct acute lung injury. Electric impedance tomography allows assessment of regional ventilation distribution and recruitment in experimental models of direct and indirect acute lung injury as well as normal lungs. Except for pigs with direct acute lung injury, regional ventilation delay determined during a slow inflation from impedance time curves appears to be a simple index for clinical monitoring of alveolar recruitment.

Elektrische Impedanztomographie

Electrical impedance tomography (EIT) is a non-invasive, radiation-free functional imaging technique, which offers the possibility of continuous bedside measurement of regional lung ventilation. The principle of EIT is based on the input of alternating current and voltage measurement via surface electrodes placed around the thorax, which measure changes of electrical impedance parallel to changes in aeration within the lungs. This enables the measurement of regional ventilation. Because of the rapid time resolution of this technique, it can be used for the measurement of fast physiological effects. For more than 20 years EIT has been intensively used for research purposes, but has not yet been used for the monitoring of regional lung function in the routine clinical setting. This review describes the status of EIT in the clinical routine, its possibilities and limitations.

Hyperpolarized 3He MRI in Asthma : Measurements of Regional Ventilation Following Allergic Sensitization and Challenge in Mice—Preliminary Results 1

Rationale and Objectives Quantitative regional measurement of physiological parameters of lung may improve both early detection of asthma and its response to treatment by elucidating the characteristics of airway obstruction. Recent emergence of hyperpolarized helium-3 magnetic resonance imaging as a sensitive pulmonary imaging tool has shown great potential in capturing important structural and functional aspects of normal and diseased lungs. The objective of this study was to investigate regional ventilation changes in the mouse lung following allergen sensitization and challenge. Materials and Methods A murine model of allergic airway inflammation was created in mice following allergen challenge using Af and IgE-mediated asthma. The creation of model was verified using pulmonary function test and histology. Regional fractional ventilation was then measured in the animals using hyperpolarized 3He MRI on a pixel-by-pixel basis with a planar resolution of 0.24 mm. The sensitized and healthy animals were then compared statisticall to assess the potential sensitivity of this technique in detection of such pulmonary abnormalities. Results In this work, we have demonstrated for the first time the quantitative measurement of regional ventilation in normal and asthmatic mice. Results of this study show significant changes in regional ventilation in murine model of allergic airway sensitization compared with that in normal control animals. Conclusion Further development of this technique can potentially serve as a quantitative marker to investigate the physiology of allergen-induced airway hyperresponsiveness and to assist in disease treatment and prevention.

Error analysis of combined measurements of regional ventilation and V/Q ratio using positron emission tomography

The authors measured the regional pulmonary ventilation/perfusion ratio with intravenous 13N in saline solution, using positron emission tomography, in eight normal healthy volunteers, 10 patients with asthma and 10 patients with chronic obstructive pulmonary disease. Regional pulmonary ventilation was also measured with 19Ne, and this information was used to (i) correct ventilation/perfusion ratios obtained with 13N in regions with impaired ventilation and (ii) calculate regional perfusion, Q. The authors analyse the errors inherent in these measurements. Dead space ventilation and focal inhomogeneities in ventilation and/or blood flow will affect the transport of both 19Ne and 13N, but in different ways. Combining the two methods, values of blood flow obtained tend to overestimate Q in normal supine subjects by some 6% in the non-dependent part of the lung and to underestimate Q by a similar amount in the dependent part. In patients with air flow obstruction, blood flow is underestimated in regions with low ventilation/perfusion ratios and overestimated in regions with high ventilation/perfusion ratios. In the groups of patients studied, errors may reach a level of 10-20%.

Prediction of Postoperative Loss of Lung Function in Patients with Malignant Lung Mass: Quantitative Regional Ventilation-Perfusion Scanning

The quantitative measurement of regional ventilation and perfusion distribution is simply and reliably accomplished by using routinely available radioactive gas and perfusion lung scanning agents, and a large field-of-view gamma camera with an on-line computer. The preoperative prediction of postsurgical loss in lung function can be made accurately by using the quantitative ventilation-perfusion lung scan technique. Either a regional ventilation study or perfusion study may be used for the prediction, but analysis of regional ventilation distribution appears to be a better parameter than that of perfusion distribution for the prediction of postoperative loss of FEV1. In the rare case of a patient with a marked ventilation-perfusion deficit, quantitative distribution of both ventilation and perfusion may be needed for an accurate assessment of postsurgical lung function.

Pulmonary permeability in never-smokers between 21 and 67 yr of age.

During the last 5-10 years, measurements of pulmonary clearance (PCl) of aerosolized 99mTc-labeled diethylenetriamine pentaacetic acid (99mTC-DTPA) have become increasingly used as an index of pulmonary epithelial injury. The aim of this study was to apply a carefully defined procedure for measurements of PCl in healthy nonsmoking individuals and analyze whether sex, age, and height are clinically relevant confounders contributing to the range of interindividual variation. Measurements of regional ventilation (V) and perfusion (Q) were included to analyze whether these indexes are influenced by the same confounders. We studied 39 males and females between 21 and 67 yr of age. Average PCl of the lungs was 0.85 +/- 0.25%.min-1. There was a significant difference between PCl of the central and peripheral parts of the lungs (P less than 0.01). Regional V and Q were greater in the lower than in the upper halves of the lungs (P less than 0.01). There was no relation between PCl, V, or Q and the sex, age, and height of the individuals. It is concluded that when measuring PCl in adult individuals anthropometric measurements need not be considered.