Expiratory muscle contribution to tidal volume in head-up dogs

A change from the supine to the head-up posture in anesthetized dogs elicits increased phasic expiratory activation of the rib cage and abdominal expiratory muscles. However, when this postural change is produced over a 4- to 5-s period, there is an initial apnea during which all the muscles are silent. In the present studies, we have taken advantage of this initial silence to determine functional residual capacity (FRC) and measure the subsequent change in end-expiratory lung volume. Eight animals were studied, and in all of them end-expiratory lung volume in the head-up posture decreased relative to FRC [329 +/- 70 (SE) ml]. Because this decrease also represents the increase in lung volume as a result of expiratory muscle relaxation at the end of the expiratory pause, it can be used to determine the expiratory muscle contribution to tidal volume (VT). The average contribution was 62 +/- 6% VT. After denervation of the rib cage expiratory muscles, the reduction in end-expiratory lung volume still amounted to 273 +/- 84 ml (49 +/- 10% VT). Thus, in head-up dogs, about two-thirds of VT result from the action of the expiratory muscles, and most of it (83%) is due to the action of the abdominal rather than the rib cage expiratory muscles.     

Role of rib cage elastance in the coupling between the abdominal muscles and the lung.

The abdominal muscles expand the rib cage when they contract alone. This expansion opposes the deflation of the lung and may be viewed as pressure dissipation. The hypothesis was raised, therefore, that alterations in rib cage elastance should affect the lung deflating action of these muscles. To test this hypothesis and evaluate the quantitative importance of this effect, we measured the changes in airway opening pressure (Pao), abdominal pressure (Pab), and rib cage transverse diameter during isolated stimulation of the transversus abdominis muscle in anesthetized dogs, first with the rib cage intact and then after rib cage elastance was increased by clamping the ribs and the sternum. Stimulation produced increases in Pao, Pab, and rib cage diameter in both conditions. With the ribs and sternum clamped, however, the change in Pab was unchanged but the change in Pao was increased by 77% (P < 0.001). In a second experiment, the transversus abdominis was stimulated before and after rib cage elastance was reduced by removing the bony ribs 3-8. Although the change in Pab after removal of the the ribs was still unchanged, the change in Pao was reduced by 62% (P < 0.001). These observations, supported by a model analysis, indicate that rib cage elastance is a major determinant of the mechanical coupling between the abdominal muscles and the lung. In fact, in the dog, the effects of rib cage elastance and Pab on the lung-deflating action of the abdominal muscles are of the same order of magnitude.     

Action of neck accessory muscles on rib cage in dogs

To investigate the action of the neck accessory muscles on the rib cage, we stimulated the sternocleidomastoid and the scalenus muscles separately in supine anesthetized dogs. Hooks screwed into the sternum and ribs were used to measure their axial displacements and the changes in anteroposterior (AP) and transverse (T) diameters of the rib cage. We found that the sternocleidomastoid and scalenus muscles, when they contract alone, cause a large axial displacement of the sternum and the ribs in a cephalad direction and expand the rib cage along both its AP and T diameters. Opening the abdomen increased the cephalad displacement of the ribs and the expansion of the lower rib cage, particularly along its T diameter, but reduced the increase in lung volume. These experiments indicate 1) that the action of the sternocleidomastoid and scalenus muscles on the rib cage is essentially the consequence of a rotation of the ribs' neck axes, resulting from the cephalad displacement of the ribs, and 2) that the fall in abdominal pressure, almost certainly by acting through the zone of apposition of the diaphragm to the rib cage, has a deflationary action on the lower rib cage, more markedly so on its lateral than its anterior wall. The experiments also suggest that the fall in abdominal pressure prevents the diaphragm from moving cephalad and aids the neck accessory muscles in inflating the lungs.     

Gas exchange during separate diaphragm and intercostal muscle breathing.

In patients with diaphragm paralysis, ventilation to the basal lung zones is reduced, whereas in patients with paralysis of the rib cage muscles, ventilation to the upper lung zones in reduced. Inspiration produced by either rib cage muscle or diaphragm contraction alone, therefore, may result in mismatching of ventilation and perfusion and in gas-exchange impairment. To test this hypothesis, we assessed gas exchange in 11 anesthetized dogs during ventilation produced by either diaphragm or intercostal muscle contraction alone. Diaphragm activation was achieved by phrenic nerve stimulation. Intercostal muscle activation was accomplished by electrical stimulation by using electrodes positioned epidurally at the T(2) spinal cord level. Stimulation parameters were adjusted to provide a constant tidal volume and inspiratory flow rate. During diaphragm (D) and intercostal muscle breathing (IC), mean arterial Po(2) was 97.1 +/- 2.1 and 88.1 +/- 2.7 Torr, respectively (P < 0.01). Arterial Pco(2) was lower during D than during IC (32.6 +/- 1.4 and 36.6 +/- 1.8 Torr, respectively; P < 0.05). During IC, oxygen consumption was also higher than that during D (0.13 +/- 0.01 and 0.09 +/- 0.01 l/min, respectively; P < 0.05). The alveolar-arterial oxygen difference was 11.3 +/- 1.9 and 7.7 +/- 1.0 Torr (P < 0.01) during IC and D, respectively. These results indicate that diaphragm breathing is significantly more efficient than intercostal muscle breathing. However, despite marked differences in the pattern of inspiratory muscle contraction, the distribution of ventilation remains well matched to pulmonary perfusion resulting in preservation of normal gas exchange.     

Transdiaphragmatic pressure and rib motion in area of apposition during paralysis

Changes in pleural surface pressure in area of apposition of diaphragm to rib cage (delta Ppl,ap), changes in abdominal pressure (delta Pab), and redial displacement of the 11th rib have been recorded in anesthetized, paralyzed dogs during lung inflation or deflation. Above functional residual capacity (FRC) changes in transdiaphragmatic pressure in area of apposition (delta Pdi,ap) were essentially nil in intact (INT) dogs either in lateral or supine posture, and in partially eviscerated (EVS) dogs in lateral posture, either in the 10th or 11th intercostal space. Below FRC delta Pdi,ap could be positive (INT lateral and EVS), nil (EVS), or negative (INT supine and EVS); it could be different in the 10th and 11th intercostal spaces. Hence, with stretched (like with contracted) diaphragm, delta Ppl,ap measured at one site often differs from delta Pab and is not representative of average pressure acting on area of apposition. With volume increase above FRC, the 11th rib moved slightly in and then out in EVS and linearly out in INT. With volume decrease below FRC it moved out progressively in EVS, and it moved in and eventually reversed in INT. In paralyzed dogs in lateral posture the factor having the greatest influence on displacement of the abdominal rib cage is Pab. Mechanical linkage with pulmonary rib cage becomes relevant at large volume, whereas insertional traction of diaphragm becomes relevant at low volume.     

Action of the diaphragm on the rib cage inferred from a force-balance analysis

Displacements of the rib cage are determined by the intrinsic passive properties of the rib cage, rib cage musculature, pleural and abdominal pressures, and the diaphragm. The diaphragm's mechanical actions on the rib cage are inferred from a force-balance analysis in which the diaphragm is seen to cause expansion of the rib cage by pulling cephalad at its insertions on the lower ribs (insertional component) and by raising intra-abdominal pressure, which pushes outward on the diaphragm's zone of apposition to the rib cage (appositional component). Goldman and Mead suggested that the diaphragm, acting alone, could drive both the rib cage and abdomen on their passive characteristics. The force-balance analysis shows that the diaphragm's inspiratory action on the rib cage is less than predicted by Goldman and Mead, but that in the special circumstances of their experiment (low lung volumes), the appositional component is large and the rib cage can be driven close to its passive characteristics. The force-balance analysis is consistent with recent observations by other investigations and is incompatible with the model proposed by Macklem and colleagues and with the Goldman-Mead hypothesis. Experiments on three subjects produced data consistent with the force-balance analysis, showing that the inspiratory action of the diaphragm on the rib cage is greatest at low lung volumes.     

Respiratory mechanical effects of abdominal distension

We develop a theory to predict the partitioning of a change in volume of the abdominal contents into the end-expiratory volume changes of the lung, rib cage, and anterior abdominal wall. First, we calculate the distribution of such a volume change using the relative compliances of the three compartments. We then consider the inspiratory influence of abdominal pressure on the rib cage and its effect on the distribution of this volume. We test our theory by inducing gastric distension in three experienced laboratory personnel. We instilled and subsequently withdrew 1 liter of water from a gastric balloon and examined the effects of this change in gastric volume on the relaxation characteristics of the respiratory system. The distribution of the volume change that would be expected from the observed relative compliances of the three compartments would be approximately 66% into change in lung volume, 25% into change in rib cage volume, and 9% into change in abdominal volume. Instead, in line with our predictions for acute gastric distension, approximately 33% went into decrease in lung volume, 40% into increase in rib cage volume, and 26% into increase in abdominal volume. These results suggest that the interactions among the rib cage, abdomen, and diaphragm are such as to defend against large changes in end-expiratory lung volume in the face of abdominal distension.     

Respiratory changes in parasternal intercostal length

In an attempt to understand the role of the parasternal intercostals in respiration, we measured the changes in length of these muscles during a variety of static and dynamic respiratory maneuvers. Studies were performed on 39 intercostal spaces from 10 anesthetized dogs, and changes in parasternal intercostal length were assessed with pairs of piezoelectric crystals (sonomicrometry). During static maneuvers (passive inflation-deflation, isovolume maneuvers, changes in body position), the parasternal intercostals shortened whenever the rib cage inflated, and they lengthened whenever the rib cage contracted. The changes in parasternal intercostal length, however, were much smaller than the changes in diaphragmatic length, averaging 9.2% of the resting length during inflation from residual volume to total lung capacity and 1.3% during tilting from supine to upright. During quiet breathing the parasternal intercostals always shortened during inspiration and lengthened during expiration. In the intact animals the inspiratory parasternal shortening was close to that seen for the same increase in lung volume during passive inflation and averaged 3.5%. After bilateral phrenicotomy, however, the parasternal intercostal shortening during inspiration markedly increased, whereas tidal volume diminished. These results indicate that 1) the parasternal intercostals in the dog are real agonists (as opposed to fixators) and actively contribute to expand the rib cage and the lung during quiet inspiration, 2) the relationship between lung volume and parasternal length is not unique but depends on the relative contribution of the various inspiratory muscles to tidal volume, and 3) the physiological range of operating length of the parasternal intercostals is considerably smaller than that of the diaphragm.(ABSTRACT TRUNCATED AT 250 WORDS)     

Chest wall motion during epidural anesthesia in dogs

To determine the relative contribution of rib cage and abdominal muscles to expiratory muscle activity during quiet breathing, we used lumbar epidural anesthesia in six pentobarbital sodium-anesthetized dogs lying supine to paralyze the abdominal muscles while leaving rib cage muscle motor function substantially intact. A high-speed X-ray scanner (Dynamic Spatial Reconstructor) provided three-dimensional images of the thorax. The contribution of expiratory muscle activity to tidal breathing was assessed by a comparison of chest wall configuration during relaxed apnea with that at end expiration. We found that expiratory muscle activity was responsible for approximately half of the changes in thoracic volume during inspiration. Paralysis of the abdominal muscles had little effect on the pattern of breathing, including the contribution of expiratory muscle activity to tidal breathing, in most dogs. We conclude that, although there is consistent phasic expiratory electrical activity in both the rib cage and the abdominal muscles of pentobarbital-anesthetized dogs lying supine, the muscles of the rib cage are mechanically the most important expiratory muscles during quiet breathing.     

Ventilatory effectiveness of high-frequency oscillation applied to the body surface

To determine the ventilatory effectiveness of high-frequency oscillation (HFO) at different sites on the body surface, we applied HFO separately to the abdomen, the rib cage, or the whole body in eight anesthetized and paralyzed dogs. Test frequencies were 5, 7, 9, and 11 Hz with tidal volume kept constant at 2.5 ml/kg. During HFO application to the abdomen, we observed significantly higher arterial O2 partial pressure (P less than 0.05) at 5, 7, and 9 Hz and lower arterial CO2 partial pressure (P less than 0.05) at 7, 9, and 11 Hz than with rib cage or whole-body HFO. There was no significant difference in blood gases between rib cage and whole-body HFO. Thus, using blood gases as an index of ventilatory effectiveness, the present study showed that HFO applied at the abdomen was the most effective of the three kinds of body surface HFO. In comparison to rib cage or whole-body application, abdominal HFO was accompanied by substantial paradoxical movement of the diaphragm and rib cage. The associated lung distortion may result in pendelluft, which in turn may be the mechanism for increased ventilatory effectiveness with abdominal application of HFO.     

N-acetylcysteine counteracts oxidative stress and protects alveolar epithelial cells from lung contusion-induced apoptosis in rats with blunt chest trauma

The aim of this study was to investigate the protective effects of N-acetylcysteine (NAC) on peroxidative and apoptotic changes in the contused lungs of rats following blunt chest trauma. The rats were randomly divided into three groups: control, contusion, and contusion + NAC. All the rats, apart from those in the control group, performed moderate lung contusion. A daily intramuscular NAC injection (150 mg/kg) was given immediately following the blunt chest trauma and was continued for two additional days following cessation of the trauma. Samples of lung tissue were taken in order to evaluate the tissue malondialdehyde (MDA) level, histopathology, and epithelial cell apoptosis using terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay and active caspase-3 immunostaining. In addition, we immunohistochemically evaluated the expression of surfactant protein D (SP-D) in the lung tissue. The blunt chest trauma-induced lung contusion resulted in severe histopathological injury, as well as an increase in the MDA level and in the number of cells identified on TUNEL assay together with active caspase-3 positive epithelial cells, but a decrease in the number of SP-D positive alveolar type 2 (AT-2) cells. NAC treatment effectively attenuated histopathologic, peroxidative, and apoptotic changes, as well as reducing alterations in SP-D expression in the lung tissue. These findings indicate that the beneficial effects of NAC administrated following blunt chest trauma is related to the regulation of oxidative stress and apoptosis.     

Airway closure in humans does not result in overestimation of plethysmographic lung volume

Exercise Physiol. 52: 638-641, 1982) have shown in dogs that airway closure may induce rib cage deformation and nonhomogeneous alveolar pressure swings, and they have suggested that this could lead to thoracic gas volume (TGV) overestimation by body plethysmography. However, in humans the rib cage is less easy to distort than in dogs. In four healthy volunteers we measured TGV by plethysmography before (B) and during (D) the occlusion of the middle and lower right lobes by a balloon (attached to a double-lumen catheter) positioned in the intermediate right bronchus. Subjects were trained to perform panting maneuvers preferentially with intercostals and accessory muscles or the diaphragm. Five to eleven TGV measurements were made in each subject with each panting pattern B and D occlusion. Balloon inflation resulted in no change in TGV whether low [13.3 +/- 3.4 (SD) cmH2O] or high (46.8 +/- 8.4 cmH2O) transdiaphragmatic pressures (Pdi) were used: TGV 4.0 +/- 0.4 (B) vs. 4.0 +/- 0.4 liters (D) and 4.3 +/- 0.4 (B) vs. 4.3 +/- 0.4 liters (D) for low and high Pdi, respectively. Thus, in trained subjects performing maneuvers aimed to distort the rib cage, no pressure difference was observed between the occluded and the nonoccluded lung during panting against the closed shutter. We conclude that it is unlikely that the mechanism proposed by Brown et al. might explain errors in lung volume measurements by body plethysmography in humans.     

Action of intercostal muscles on the lung in dogs

The action on the lung of interosseous intercostal muscles located in the third and the seventh interspaces was studied in 15 anesthetized-curarized supine dogs. Changes in pleural pressure, airflow rate, and lung volume produced by maximal stimulation of both intercostal muscle layers were measured at and above functional residual capacity (FRC). In five animals measurements were also obtained during isolated stimulation of the internal layer. At FRC, intercostal stimulation in the upper interspaces had invariably an inspiratory effect on the lung but no effect was detectable in the lower interspaces. Qualitatively similar results were obtained during isolated stimulation of the internal layer. Increasing lung volume reduced the inspiratory action of the upper intercostals and conferred an expiratory action to the lower intercostals. These results indicate the following: 1) when contracting in a single interspace, the external and internal intercostals have a qualitatively similar action on the lung; and 2) this action, however, depends critically on their location along the cephalocaudal axis of the rib cage: in the upper portion of the rib cage, both muscle layers have an inspiratory effect at and above FRC; in the lower portion of the rib cage, they have no respiratory action at FRC and act in the expiratory direction at higher lung volumes.     

Shape of the chest wall in the prone and supine anesthetized dog

The shape of the passive chest wall of six anesthetized dogs was determined at total lung capacity (TLC) and functional residual capacity (FRC) in the prone and supine body positions by use of volumetric-computed tomographic images. The transverse cross-sectional areas of the rib cage, mediastinum, and diaphragm were calculated every 1.6 mm along the length of the thorax. The changes in the volume and the axial distribution of transverse area of the three chest wall components with lung volume and body position were evaluated. The decrease of the transverse area within the rib cage between TLC and FRC, as a fraction of the area at TLC, was uniform from the apex of the thorax to the base. The volume of the mediastinum increased slightly between TLC and FRC (14% of its TLC volume supine and 20% prone), squeezing the lung between it and the rib cage. In the transverse plane, the heart was positioned in the midthorax and moved little between TLC and FRC. The shape, position, and displacement of the diaphragm were described by contour plots. In both postures, the diaphragm was flatter at FRC than at TLC, because of larger displacements in the dorsal than in the ventral region of the diaphragm. Rotation from the prone to supine body position produced a lever motion of the diaphragm, displacing the dorsal portion of the diaphragm cephalad and the ventral portion caudad. In five of the six dogs, bilateral isovolume pneumothorax was induced in the supine body position while intrathoracic gas volume was held constant.(ABSTRACT TRUNCATED AT 250 WORDS)     

Action of human respiratory muscles inferred from finite element analysis of rib cage.

The actions of several human respiratory muscles have been inferred from finite element analysis of the rib cage. The human model is based on anatomic and mechanical measurements in dogs and human cadavers. As in an earlier canine model, the external and internal (interosseous) intercostal muscles were found to cause, respectively, inspiratory and expiratory displacements of the rib cage, in agreement with the two-dimensional geometric analysis of Hamberger. When extended to three dimensions, Hamberger's analysis helps explain why muscles at the side of the rib cage produce changes in the anteroposterior diameter, whereas muscles at the front and back of the rib cage cause changes in the transverse diameter.     

Effect of lung volume on the respiratory action of the canine pectoral muscles.

Lung volume influences the mechanical action of the primary inspiratory and expiratory muscles by affecting their precontraction length, alignment with the rib cage, and mechanical coupling to agonistic and antagonistic muscles. We have previously shown that the canine pectoral muscles exert an expiratory action on the rib cage when the forelimbs are at the torso's side and an inspiratory action when the forelimbs are held elevated. To determine the effect of lung volume on intrathoracic pressure changes produced by the canine pectoral muscles, we performed isolated bilateral supramaximal electrical stimulation of the deep pectoral and superficial pectoralis (descending and transverse heads) muscles in 15 adult supine anesthetized dogs during hyperventilation-induced apnea. Lung volume was altered by application of a negative or positive pressure (+/- 30 cmH2O) to the airway. In all animals, selective electrical stimulation of the descending, transverse, and deep pectoral muscles with the forelimbs held elevated produced negative intrathoracic pressure changes (i.e., an inspiratory action). Moreover, with the forelimbs elevated, increasing lung volume decreased both pectoral muscle fiber precontraction length and the negative intrathoracic pressure changes generated by contraction of each of these muscles. Conversely, with the forelimbs along the torso, increasing lung volume lengthened pectoral muscle precontraction length and augmented the positive intrathoracic pressure changes produced by muscle contraction (i.e., an expiratory action). These results indicate that lung volume significantly affects the length of the canine pectoral muscles and their mechanical actions on the rib cage.     

Blunt Liver Injury with Intact Ribs under Impacts on the Abdomen: A Biomechanical Investigation

Abdominal trauma accounts for nearly 20% of all severe traffic injuries and can often result from intentional physical violence, from which blunt liver injury is regarded as the most common result and is associated with a high mortality rate. Liver injury may be caused by a direct impact with a certain velocity and energy on the abdomen, which may result in a lacerated liver by penetration of fractured ribs. However, liver ruptures without rib cage fractures were found in autopsies in a series of cases. All the victims sustained punches on the abdomen by fist. Many studies have been dedicated to determining the mechanism underlying hepatic injury following abdominal trauma, but most have been empirical. The actual process and biomechanism of liver injury induced by blunt impact on the abdomen, especially with intact ribs remained, are still inexhaustive. In order to investigate this, finite element methods and numerical simulation technology were used. A finite element human torso model was developed from high resolution CT data. The model consists of geometrically-detailed liver and rib cage models and simplified models of soft tissues, thoracic and abdominal organs. Then, the torso model was used in simulations in which the right hypochondrium was punched by a fist from the frontal, lateral, and rear directions, and in each direction with several impact velocities. Overall, the results showed that liver rupture was primarily caused by a direct strike of the ribs induced by blunt impact to the abdomen. Among three impact directions, a lateral impact was most likely to cause liver injury with a minimum punch speed of 5 m/s (the momentum was about 2.447 kg.m/s). Liver injuries could occur in isolation and were not accompanied by rib fractures due to different material characteristics and injury tolerance.     

Analysis of human chest wall motion using a two-compartment rib cage model.

We present a model of chest wall mechanics that extends the model described previously by Macklem et al. (J. Appl. Physiol. 55: 547-557, 1983) and incorporates a two-compartment rib cage. We divide the rib cage into that apposed to the lung (RCpul) and that apposed to the diaphragm (RCab). We apply this model to determine rib cage distortability, the mechanical coupling between RCpul and RCab, the contribution of the rib cage muscles to the pressure change during spontaneous inspiration (Prcm), and the insertional component of transdiaphragmatic pressure in humans. We define distortability as the relationship between distortion and transdiaphragmatic pressure (Pdi) and mechanical coupling as the relationship between rib cage distortion and the pressure acting to restore the rib cage to its relaxed configuration (Plink), as assessed during bilateral transcutaneous phrenic nerve stimulation. Prcm was calculated at end inspiration as the component of the pressure displacing RCpul not accounted for by Plink or pleural pressure. Prcm and Plink were approximately equal during quiet breathing, contributing 3.7 and 3.3 cmH2O on average during breaths associated with a change in Pdi of 3.9 cmH2O. The insertional component of Pdi was measured as the pressure acting on RCab not accounted for by the change in abdominal pressure during an inspiration without rib cage distortion and was 40 +/- 12% (SD) of total Pdi. We conclude that there is substantial resistance of the human rib cage to distortion, that, along with rib cage muscles, contributes importantly to the fall in pleural pressure over the costal surface of the lung.     

Relationship between parasternal intercostal length and rib cage displacement in dogs

The relationship between parasternal intercostal length and rib cage cross-sectional area was examined in nine supine dogs during passive inflation and during quiet breathing before and after phrenicotomy. Parasternal intercostal length (PSL) was measured with a sonomicrometry technique, and rib cage cross-sectional area (Arc) was measured with a Respitrace coil placed around the middle rib cage. During active inspiration as well as during passive inflation, PSL decreased as Arc increased. However, the relationship between PSL and Arc during active inspiration, whether in the intact or phrenicotomized animal, was almost invariably different from that during passive inflation, so that the same increase in Arc was associated with a greater decrease in PSL in the former than in the latter instance. This difference between passive inflation and active inspiration is probably due to the active contraction of the parasternals during inspiration and the consequent caudal displacement of the sternum. In upright humans, the sternum moves cephalad and not caudad during inspiration, so the relationship between PSL and Arc during active breathing might be similar to that during passive inflation.     

Computed Tomography Measurement of Rib Cage Morphometry in Emphysema

Background

Factors determining the shape of the human rib cage are not completely understood. We aimed to quantify the contribution of anthropometric and COPD-related changes to rib cage variability in adult cigarette smokers.

Methods

Rib cage diameters and areas (calculated from the inner surface of the rib cage) in 816 smokers with or without COPD, were evaluated at three anatomical levels using computed tomography (CT). CTs were analyzed with software, which allows quantification of total emphysema (emphysema%). The relationship between rib cage measurements and anthropometric factors, lung function indices, and %emphysema were tested using linear regression models.

Results

A model that included gender, age, BMI, emphysema%, forced expiratory volume in one second (FEV₁)%, and forced vital capacity (FVC)% fit best with the rib cage measurements (R² = 64% for the rib cage area variation at the lower anatomical level). Gender had the biggest impact on rib cage diameter and area (105.3 cm²; 95% CI: 111.7 to 98.8 for male lower area). Emphysema% was responsible for an increase in size of upper and middle CT areas (up to 5.4 cm²; 95% CI: 3.0 to 7.8 for an emphysema increase of 5%). Lower rib cage areas decreased as FVC% decreased (5.1 cm²; 95% CI: 2.5 to 7.6 for 10 percentage points of FVC variation).

Conclusions

This study demonstrates that simple CT measurements can predict rib cage morphometric variability and also highlight relationships between rib cage morphometry and emphysema.