Sex differences in thoracic adaptation to pulmonary hyperinflation in cystic fibrosis.

Sex differences in thoracic adaptation have been reported in patients with cystic fibrosis (CF). The interplay between the pattern of thoracic adaptation and the function of the respiratory muscles in male and female CF patients with pulmonary hyperinflation was investigated. Thoracic dimensions and diaphragm length were measured at residual volume, functional residual capacity and total lung capacity using chest radiography in 23 CF (12 males) and 18 normal (11 males) subjects. Respiratory muscle recruitment during resting breathing was assessed by recording intrathoracic and intra-abdominal pressures. In female CF patients, ribcage expansion was predominant, tending to preserve diaphragm length. In male CF patients, thoracic configuration was normal and diaphragm shortening consequently greater. Ribcage cross-sectional area for a given rib inclination was greater in CF patients, indicating a structural expansion of the ribcage 2.5 times greater in females than males. The contribution of inspiratory ribcage muscles to inspiratory pressure was also greater relative to the diaphragm in the CF group. In conclusion, a structural expansion of the ribcage occurs in cystic fibrosis patients with lung hyperinflation that is greater in females than males. This is associated with an apparent greater contribution of inspiratory ribcage muscles to inspiratory pressure.     

Sternum length and rib cage dimensions compared with bodily proportions in adults with cystic fibrosis

BACKGROUND:

A greater structural expansion of the rib cage in females compared with males has been described in cystic fibrosis (CF) patients; however, conflicting data exist as to whether an elongation of the bony ribs and sternum contributes to this expansion.

OBJECTIVES:

To compare height-adjusted anthropometric measures and sternum length between a group of normal subjects and a group of CF patients of both sexes.

METHODS:

Anthropometric measurements including body weight, height, upper and lower limb lengths, biacromial distance and pelvic width were measured in the standing position in 30 CF patients (13 males) and 28 normal subjects (14 males). Body surface measurements of anterior-posterior and lateral diameters of the rib cage at functional residual capacity, and sternum length were also obtained.

RESULTS:

Compared with normal subjects, CF patients had lower body weight, shorter standing height and shorter height-adjusted upper and lower limb lengths. Rib cage diameters were greater in CF patients than in normal subjects of either sex, but height-adjusted sternum length was not different.

CONCLUSION:

Significant differences in bodily proportions were found between normal subjects and CF patients, suggesting a differential growth pattern for the trunk and limbs. However, increased rib cage dimensions with lung hyperinflation and airway obstruction was not associated with an elongation of the sternum.     

Thoracic dimensions at maximum lung inflation in normal subjects and in patients with obstructive and restrictive lung diseases

OBJECTIVES: To compare the distribution of lung volume at total lung capacity (TLC) among adult men and women known to have normal lung function or chronic obstructive disease or restrictive lung disease (RLD). DESIGN: Five-year retrospective study. SETTING: Review of available clinical pulmonary function testing (PFT) reports and chest radiographs. PATIENTS: Sixty-four patients presenting with normal PFT and chest radiograph findings (normal subjects), 26 patients with severe COPD and increased TLC (COPD group), 29 patients with cystic fibrosis (CF) and increased TLC (CF group), and 19 patients with RLD with a clinical diagnosis of pulmonary fibrosis and a reduced TLC (RLD group). MEASUREMENTS: Average posteroanterior rib cage diameter (PAave), average lateral rib cage diameter (LAave), and average vertical height of the diaphragm (HDIave) were measured using radiography. Normal prediction equations were generated based on stature, body mass index (BMI), age, and sex as independent variables and then used in between-group comparisons. RESULTS: PAave correlated positively with BMI and age but not with height, whereas LAave correlated positively with BMI and height but not with age. HDIave correlated positively with height and age but negatively with BMI. PAave and LAave were smaller and HDIave was greater in women than men having the same stature. In the COPD group and in male CF group patients, BMI was low and only HDIave was greater than in sex-, age-, and height-matched normal subjects, but in female CF group patients, only the rib cage diameters were greater than normal. In the RLD group, PAave and HDIave were smaller than predicted and inversely related to each other, but LAave was normal. CONCLUSION: Variations in maximum lung volume caused by gender, growth, or by lung diseases are nonisotropic and entail substantial changes in chest wall shape.     

Influence of lung volume and rib cage configuration on transdiaphragmatic pressure during phrenic nerve stimulation in man

Transdiaphragmatic pressure was recorded during bilateral supramaximal percutaneous phrenic nerve stimulation at 1 Hz (twitch Pdi) to investigate the effect of lung volume and rib cage configuration on diaphragm contractility in man. Stimulations were performed in 5 normal supine subjects at resting end expiration (FRC) and at lung volumes above and below FRC, during relaxation against a closed airway and during isovolume manoeuvres. Twitch Pdi at FRC was 24.4 cm H2O. At lung volumes above FRC, twitch Pdi decreased by 7.04 +/- 3.2 cm H2O per litre of volume change. At lung volumes below FRC, twitch Pdi increased by 12.4 +/- 8.6 cm H2O per litre of volume change. When the diaphragm was lengthened during an isovolume manoeuvre at FRC, twitch Pdi increased. A similar relationship between lung volume and twitch Pdi was obtained during stimulations performed with abdominal binding. These results demonstrate that the pressure developed by the diaphragm during phrenic nerve stimulation is significantly affected both by increases and decreases in lung volume and by the rib cage configuration at which stimulation is performed.     

Chest wall mechanics in obstructive lung disease

The effects of overinflation of the lung in obstructive lung disease on the function of chest wall (rib cage, diaphragm) were studied. Concerning the function of the rib cage, the lateral motion of the lower lateral rib cage was evaluated using several experimental models. The results showed that the lower lateral rib cage was moved by many factors, including the force of the diaphragm, rib cage, compliance of abdominal wall, zone of apposition and angle of the diaphragm at the part of its insertion into the rib cage with respect to the transverse section of the trunk. The inward motion of the lower lateral rib cage due to overinflation of the lung occurred by participation of these factors. Concerning the function of the diaphragm, the diaphragm at high lung volume in healthy subjects and patients with pulmonary emphysema was evaluated by the three-dimensional stereoscopic method. The radius of the portion of the dome in the diaphragm decreased at higher lung volume, and changes in lung volume at that lung volume were caused by changes in the shape in the posterior of the diaphragm.     

A dynamic analysis of chest wall motions with MRI in healthy young subjects

OBJECTIVE: The objective of this study was to analyse respiratory-related motion of the chest wall with non-invasive method. METHODOLOGY: Using magnetic resonance image (MRI), 30 sequential images (scanning time, 0.4 s per image) on sagittal, axial and coronal planes were obtained in nine healthy young subjects during quiet breathing (QB) and maximal deep breathing (MDB). The coronal planes were obtained in five of nine subjects during MDB. Ventilation was simultaneously measured with pneumotachometer. RESULTS: There was a linear correlation between instantaneous lung volume and lung cross-sectional area. Motion of the diaphragm and rib cage was also linearly related to instantaneous lung volume. The exception was lower anteroposterior (AP) diameter of the rib cage. The contribution of individual part of the chest wall motion to a unit lung volume change was assessed by slope (S) of the linear regression line. The S at the anterior diaphragm was significantly smaller than those at middle and posterior parts during MDB. The S of middle and posterior diaphragmatic motion was approximately five times that of AP motion of upper rib cage. The S of AP motion of upper rib cage was twice that of transverse motion during either QB or MDB. CONCLUSION: We concluded that dynamic MRI study with concurrent ventilation measurement is a simple and reliable method for evaluation of local chest wall motion, and that neither diaphragm nor rib cage works as a single functional unit during active ventilation.     

Respiratory mechanics in acute quadriplegia. Lung and chest wall compliance and dimensional changes during respiratory maneuvers

We measured lung and chest wall compliance as well as rib cage and abdominal dimensions in the supine position in five acute C4-7 quadriplegics. Studies were performed serially from 1 to 12 months after injury. Results were compared with those of control groups of chronic (greater than 1 yr after injury) quadriplegics and normal volunteers. We found that lung compliance was lower in acute and chronic quadriplegics (0.129 +/- 0.023 and 0.176 +/- 0.043 L/mm Hg, respectively) than in normal subjects (0.278 +/- 0.086 L/mm Hg) and that these changes apparently occurred within 1 month of injury. Specific lung compliance appeared to be reduced to a lesser degree, suggesting that the changes in lung compliance were partly due to reduced lung volumes and partly to altered mechanical properties of the lung. During respiratory maneuvers, abdomen and rib cage dimensional changes demonstrated rib cage distortion. This distortion was less severe in chronic than in acute quadriplegics. The improvement in chest wall stability was likely due to increased strength of cervical accessory muscles of respiration and improved coupling of the various rib cage elements in chronic quadriplegics.     

A mathematical and graphical analysis of inspiratory muscle action

In this paper a mathematical and graphical analysis is presented for the action of the diaphragm and the intercostal/accessory muscles of inspiration, in terms of the pressure developed, the volumes displaced and the work performed by each set of muscles. An analogous model is described which behaves according to the analysis. The critical variable by which the action of the diaphragm and intercostal/accessory muscles can be measured is the change in abdominal pressure Pab. When delta Pab = 0 it is assumed that the diaphragm has contracted isometrically and is acting as a fixator preventing an expiratory displacement of the abdomen. When delta Pab greater than 0 the diaphragm shortens and acts as an agonist. When delta Pab less than 0 the diaphragm lengthens as it contracts, performs negative work and the abdomen is displaced in an expiratory direction. For a given change in lung volume, as delta Pab diminishes, there is progressive recruitment of intercostal/accessory muscles and a progressive increase in the work of breathing over and above that required to produce the same change in lung volume by contraction of the diaphragm alone. For values of delta Pab greater than 0 the sum of diaphragm and intercostal/accessory muscle work is less than the total work, because of an increase in the elastic energy stored in the rib cage. For Pab less than 0 there is a decrease in the elastic energy stored in the rib cage leading to a marked increase in work performed and pressures developed by the intercostal/accessory muscles.     

Pleural pressure from abdominal to pulmonary rib cage: sweep of the lung border

Pleural pressure was measured by a capsule placed in the superior part of right 8th or 9th intercostal space of dogs in left lateral posture. Transit of lung border was observed through endothoracic fascia at sides of the capsule. During inspiration the capsule membrane faced sequentially: diaphragm, lung border, lung; vice versa during expiration. Pressure on the diaphragm at end expiration was -5.3 +/- 0.5 cm H2O, reflecting outward recoil of the rib cage. At transit of lung border during inspiration (bor. I) a marked negative pressure spike occurred; a smaller spike occurred at expiratory transit (bor. E). These spikes should reflect pleural liquid pressure at lung border. At bor. I lung volume and radial displacement of rib 9 or 10 were greater during active than passive ventilation, whereas at bor. E they were similar under both conditions. Hence, during spontaneous inspiration displacement of lung border lags behind lung and rib expansion. Speed of lung border (assessed from duration of negative spike) ranged from 0.8 to 2.3 cm/sec during spontaneous breathing. On average it was similar at bor. I and bor. E, while air flow was greater at bor. I.     

Chest wall configuration assessed at total lung capacity during acute asthma and after recovery

During acute asthma reversible increase in lung compliance and total lung capacity (TLC) have been observed. The magnitude of the increase in TLC, however, was found to be relatively small when TLC was measured radiographically. We wondered if structural distortion of the respiratory bellows develops during acute asthma attacks, accounting for the limited increase in TLC. We analyzed the chest wall dimensions using chest roentgenograms obtained in 32 patients who had previously participated in the study of radiographic evaluation of TLC. We found that the dimensional changes accompanying the small increase in TLC during acute asthma were nonuniform, consisting of mainly an increase in lung height (0.45 ± 0.15 cm) with limited coordinated expansion of other dimensions and a small but significant distortional contraction of lung width at the lowest portion of the rib cage (–0.25 ± 0.12 cm). These findings were interpreted to mean that in response to the decrease in elastic lung recoil (internal load) occurring during acute asthma, the diaphragm makes limited but effective further caudad descent without provoking serious structural distortion and that rib cage muscles, working at mechanical disadvantage at high lung volume, act largely as fixators. Offprint requests to: S. S. Park     

Rib cage mechanics in simulated diaphragmatic paralysis

To determine the action of the parasternal intercostals on the human rib cage, we studied the pattern of rib cage motion in relation to the pattern of respiratory muscle contraction in 4 normal subjects during attempts to perform tidal volume breathing with the parasternal intercostals alone. The dimensions of the chest wall, including the anteroposterior (AP) diameters of the lower rib cage and the abdomen, the transverse diameter of the lower rib cage, and the xiphipubic distance, were measured with linearized magnetometers. The electromyogram (EMG) of the diaphragm was obtained with an esophageal lead, while the EMGs of the intercostal, neck, and abdominal muscles were recorded using concentric needle electrodes. Minimizing diaphragmatic use during inspiration (transdiaphragmatic pressure = 0.08 to 1.54 cm H2O) was accompanied by a recruitment of the parasternals that was substantially greater than that of the scalenes; in 2 of the subjects, the activation of the scalenes at the beginning of inspiration was even delayed relative to the parasternals. The lateral intercostals showed variable changes during the maneuver, but the sternocleidomastoids, pectoralis major, rectus abdominis, and abdominal external oblique muscles were always silent. This pattern of EMG activity was associated with profound deformations of the rib cage. In all 4 subjects, the rib cage expanded considerably more along its transverse than its AP dimension relative to its relaxed configuration, and in 3 subjects, the xiphi-pubic distance decreased rather than increased in early inspiration.(ABSTRACT TRUNCATED AT 250 WORDS)     

Lung and thorax development during adolescence: relationship with pubertal status.

The aim of the present study was to define reference values for lung volumes and the lung transfer factor for carbon monoxide (TL,CO) for an adolescent population using thoracic volume index (TVI) and an index of pubertal stage in order to account for the variation in growth pattern between adolescents. TVI, pubertal stage by Tanner scale (PST), time since menarche, functional residual capacity measured using the helium-dilution technique, vital capacity, total lung capacity and TL,CO measured using a steady-state method were determined in 51 males (aged 13-20 yrs; PST T3-T5) and 52 females (aged 13-18 yrs; PST T2-T4; all but three had already undergone menarche). In male adolescents, height, weight, TVI, lung volumes and TL,CO increased with age. This was not the case in female adolescents. In males, the TVI was the independent variable that best correlated with pulmonary volumes. In females, height was the independent variable that best correlated with pulmonary volumes. In both sexes, the variable that best correlated with TL,CO was PST, associated with height in males. This cross-sectional study provides prediction equations for lung volumes and the lung transfer factor for carbon monoxide taking into account thoracic volume index and pubertal stage. It shows that, in adolescent males, lung and thoracic development occurs during and until the end of puberty. Conversely, in adolescent females, lung development is almost finished following menarche.     

Role of the mediastinum as a part of the chest wall: analyzed by computed tomography

Using computed tomography (CT), geometrical changes in pulmonary structures in 4 human volunteers were analyzed. A series of parallel transaxial CT scans of the lung were obtained for each volunteer while he held his breath at maximal inspiration and maximal expiration. Changes in pulmonary structures were evaluated by comparing the maximal inspiration scans for each slice position. The longitudinal displacement of the lung volume was categorized as either a rib cage displacement or a diaphragm-abdominal displacement. The ratio of diaphragm-abdominal contribution to vital capacity was 0.49-0.65 for the volunteers. The thoracic volume displacement was categorized as either a mediastinal displacement or a rib cage displacement. The former was considerably larger than the latter. Since the rostral end of the mediastinum is fixed to the thoracic cage and the caudal end is fixed to the diaphragm, we conclude that the mediastinum-diaphragm boundary converts the axial force generated by the diaphragmatic excursion into radial force.     

Effect of thoracoabdominal configuration on the diaphragmatic contribution to rib cage motion

Owing to the diaphragm-rib cage interaction the diaphragm can reduce the load on the intercostal muscles. The extent of this load reduction was evaluated by analyzing the EMG activity of intercostal muscles as an index of the pressure generated by the intercostal muscles. Three trained subjects shifted their breathing configuration while the rib cage volume and flow were kept constant. Analysis of data thus obtained indicated that the diaphragmatic contribution to the rib cage motion improved with a thoracic shift of breathing. The significance of this effect was further evaluated by performing respiratory maneuvers at constant tidal volume and flow at normal and elevated functional residual capacity. At both lung volumes, a substantial saving of diaphragmatic activity attained by the thoracic shift of breathing was associated with a moderate increase or even a decrease in the intercostal EMG activity, suggesting an overall mechanical advantage of inspiratory muscles during thoracic breathing. Support by National Institute of Health Grant HL 25230 Preliminary results have been reported at the 66th annual FASEB meeting in New Orleans, 1982     

Absence of a hemidiaphragm: Mechanical implications

Respiratory system mechanics were evaluated in a 22-year-old asymptomatic man with absence of the left hemidiaphragm. We described changes in esophageal pressure (Pes), gastric pressure (Pga), chest wall configuration, and mediastinal motion during tidal breathing, breaths to total lung capacity (TLC), and Mueller maneuvers in the upright and supine position. We predicted that contraction of the single hemidiaphragm would drive the abdominal contents caudal on the side with the intact hemidiaphragm and displace the abdominal contents cephalad on the other side. This would drive the mediastinum toward the side with the intact diaphragm, thereby reducing its effectiveness in expanding the lung on that side. When upright, this effect would be minimized to the extent that the rib cage muscles lower pleural pressure in the thorax without the diaphragm. We found that (vital capacity) VC and TLC were greater upright than supine and that Pga deflections were almost as strongly negative as Pes deflections during upright quiet breathing and breaths to TLC. Thus the rib cage muscles enhanced the inspiratory action of the right hemidiaphragm in the upright position. In the supine position, Pes became negative without change of Pga during breaths to TLC and quiet inspirations. Here, contraction of the hemidiaphragm was the dominant mechanism generating the inspiratory pressure. During maximal Mueller efforts, the mediastinum shifted toward the side with the intact diaphragm in both positions and the maximum inspiratory pressures were low. These pressures were likely to have been limited by both the finite impedance to rotation of the thoracoabdominal contents or mediastinum and a mechanical disadvantage of the remaining hemidiaphragm. We conclude that the effectiveness of the single hemidiaphragm as an inspiratory pump requires passive impedance of the abdominal viscera and mediastinum and is enhanced in the upright position by the action of the rib cage muscles.     

Absence of a hemidiaphragm: mechanical implications

Respiratory system mechanics were evaluated in a 22-year-old asymptomatic man with absence of the left hemidiaphragm. We described changes in esophageal pressure (Pes), gastric pressure (Pga), chest wall configuration, and mediastinal motion during tidal breathing, breaths to total lung capacity (TLC), and Mueller maneuvers in the upright and supine position. We predicted that contraction of the single hemidiaphragm would drive the abdominal contents caudal on the side with the intact hemidiaphragm and displace the abdominal contents cephalad on the other side. This would drive the mediastinum toward the side with the intact diaphragm, thereby reducing its effectiveness in expanding the lung on that side. When upright, this effect would be minimized to the extent that the rib cage muscles lower pleural pressure in the thorax without the diaphragm. We found that (vital capacity) VC and TLC were greater upright than supine and that Pga deflections were almost as strongly negative as Pes deflections during upright quiet breathing and breaths to TLC. Thus the rib cage muscles enhanced the inspiratory action of the right hemidiaphragm in the upright position. In the supine position, Pes became negative without change of Pga during breaths to TLC and quiet inspirations. Here, contraction of the hemidiaphragm was the dominant mechanism generating the inspiratory pressure. During maximal Mueller efforts, the mediastinum shifted toward the side with the intact diaphragm in both positions and the maximum inspiratory pressures were low. These pressures were likely to have been limited by both the finite impedance to rotation of the thoracoabdominal contents or mediastinum and a mechanical disadvantage of the remaining hemidiaphragm. We conclude that the effectiveness of the single hemidiaphragm as an inspiratory pump requires passive impedance of the abdominal viscera and mediastinum and is enhanced in the upright position by the action of the rib cage muscles.     

Effect of lung volume reduction surgery on diaphragm length in severe chronic obstructive pulmonary disease

Lung volume reduction surgery (LVRS) has been suggested as improving respiratory mechanics in patients with severe chronic obstructive pulmonary disease (COPD). We hypothesized that LVRS might lengthen the diaphragm, increase its area of apposition with the chest wall, and thereby improve its mechanical function. To determine the effect of bilateral LVRS on diaphragm length, we measured diaphragm length at TLC, using plain chest roentgenograms (CXRs), in 25 patients (11 males and 14 females) before LVRS and 3 to 6 mo after LVRS. A subgroup of seven patients (reference data) also had diaphragm length measurements made with CXRs, using films made within a year before their presurgical evaluation. Right hemidiaphragm silhouette length (PADL) and the length of the most vertically oriented portion of the right hemidiaphragm muscle (VDML) were measured. Diaphragm dome height was determined from the: (1) distance between the dome and transverse diameter at the manubrium; and (2) highest point of the dome referenced horizontally to the vertebral column. Patients also underwent spirometry, measurements of lung volumes and diffusion capacity, an incremental symptom-limited maximum exercise test, and measurements of 6 min walk distance (6MWD) and transdiaphragmatic pressures during maximum static inspiratory efforts (Pdimax sniff) and bilateral supramaximal electrophrenic twitch stimulation (Pditwitch) both before and 3 mo after LVRS. Patients were 58 +/- 8 yr of age, with severe COPD and hyperinflation (FEV1 = 0.68 +/- 0.23 L, FVC = 2.56 +/- 7.3 L, and TLC = 143 +/- 22% predicted). Following LVRS, PADL increased by 4% (from 13.9 +/- 1.9 cm to 14.5 +/- 1.7 cm; p = 0.02), VDML increased by 44% (from 2.08 +/- 1.5 cm to 3.00 +/- 1.6 cm, p = 0.01), and diaphragm dome height increased by more than 10%. In contrast, diaphragm lengths were similar in subjects with CXRs made before LVRS and within 1 yr before evaluation. The increase in diaphragm length correlated directly with postoperative reductions in TLC and RV, and also with increases in transdiaphragmatic pressure with maximal sniff (Pdimax sniff), maximal oxygen consumption (V O2max), maximal minute ventilation (V Emax), and maximum voluntary ventilation following LVRS. We conclude that LVRS leads to a significant increase in diaphragm length, especially in the area of apposition of the diaphragm with the rib cage. Diaphragm lengthening after LVRS is most likely the result of a reduction in lung volume. Increases in diaphragm length after LVRS correlate with postoperative improvements in diaphragm strength, exercise capacity, and maximum voluntary ventilation.     

Stiffness of the rib cage in a subset of rheumatoid patients

In a previous investigation of lung function in patients with rheumatoid arthritis (RA), we observed that some patients had significant dysfunction of their chest wall mechanics without pleural disease that could contribute to their respiratory symptoms. To investigate further the chest wall functions of patients with RA, we selected 10 female lifetime nonsmoking patients with RA and compared them to 10 paid normal volunteers in detailed functional evaluations of lung and chest wall. Patients with significant airflow limitation were excluded from this study. We found a significant 7% reduction in total lung capacity in the RA patients without significant change in lung compliance. However, we found a significant reduction in rib cage compliance in patients with RA (0.044 +/- 0.006 L/cmH2O vs. 0.064 +/- 0.012 in controls), which was associated with a significant 38% reduction in expansion of the rib cage volume during various breathing maneuvers. These changes occurred in the absence of lung or pleural disease. This study documents that patients with RA have limited expansion of rib cage relative to abdomen, thus rib cage restriction and stiffness, which may contribute to reduced lung volume. The shift of thoracoabdominal breathing configuration observed in patients with RA will likely reduce the effectiveness of breathing muscles and thus could contribute to the dyspnea sensation experienced by patients with RA.     

Effects of emphysema and lung volume reduction surgery on transdiaphragmatic pressure and diaphragm length

STUDY OBJECTIVES: To determine the effect of emphysema and lung volume reduction surgery (LVRS) on diaphragm length (Ldi) and its capacity to generate transdiaphragmatic pressure (Pdi). DESIGN: Prospective clinical trial with a parallel group design. SETTING: Laboratory investigations in normal volunteers recruited by advertisement and in emphysema outpatients being evaluated for elective LVRS. STUDY POPULATION: Thirteen normal subjects and 13 emphysema patients matched for age and sex. Six emphysema patients underwent LVRS. MEASUREMENTS: Ldi and maximal Pdi during static inspiratory efforts (PdiMax) were measured at three different lung volumes (LVs). Pdi during maximal bilateral phrenic nerve twitch stimulation (PdiTw) was measured at functional residual capacity (FRC). All measurements were repeated at 3, 6, and 12 months postoperatively. RESULTS: Ldi, PdiMax, and PdiTw were lower in emphysema patients than in normal subjects at their respective LVs. PdiMax and PdiTw at FRC returned within the normal range after LVRS in emphysema patients. The relationships between PdiMax and LV or Ldi were shifted respectively to higher LV and shorter Ldi in emphysema patients relative to normal subjects, both before and after LVRS. LVRS effected craniad displacement of the diaphragm but no change in rib cage dimensions. Improvements in dyspnea and quality of life after LVRS correlated with changes in LV and Ldi but not with changes in airway caliber. CONCLUSION: Adaptive mechanisms, consistent with sarcomere deletion, tend to restore diaphragm strength in emphysema patients at FRC, which are fully expressed after LVRS. Lung remodeling by LVRS may alter pleural surface pressure distribution, causing a sustained change in chest wall shape.     

Chest wall hyperinflation during acute bronchoconstriction in asthma.

The mechanics of the chest wall was studied in seven asthmatic patients before and during histamine-induced bronchoconstriction (B). The volume of the chest wall (VCW) was calculated by three-dimensional tracking of 89 chest wall markers. Pleural (Ppl) and gastric (Pga) pressures were simultaneously recorded. VCW was modeled as the sum of the volumes of the pulmonary-apposed rib cage (VRC,p), diaphragm-apposed rib cage (VRC,a), and abdomen (VAB). During B, hyperinflation was due to the increase in end-expiratory volume of the rib cage (0.63 +/- 0.09 L, p < 0.01), whereas change in VAB was inconsistent (0.09 +/- 0.07 L, NS) because of phasic recruitment of abdominal muscles during expiration. Changes in end-expiratory VRC,p and VRC,a were along the rib cage relaxation configuration, indicating that both compartments shared proportionally the hyperinflation. VRC,p-Ppl plot during B was displaced leftward of the relaxation curve, suggesting persistent activity of rib cage inspiratory muscles throughout expiration. Changes in end-expiratory VCW during B did not relate to changes in FEV(1) or time and volume components of the breathing cycle. We concluded that during B in asthmatic patients: (1) rib cage accounts largely for the volume of hyperinflation, whereas abdominal muscle recruitment during expiration limits the increase in VAB; (2) hyperinflation is influenced by sustained postinspiratory activity of the inspiratory muscles; (3) this pattern of respiratory muscle recruitment seems to minimize volume distortion of the rib cage at end-expiration and to preserve diaphragm length despite hyperinflation.