Rib Cage Expansion Research Articles

Effects of inspiratory muscle training on thoracoabdominal volume regulation in older adults: A randomised controlled trial

ObjectivesWe investigated the effect of inspiratory muscle training (IMT) on inspiratory muscle strength, functional capacity and respiratory muscle kinematics during exercise in healthy older adults. Methods24 adults were randomised into an IMT or SHAM-IMT group. Both groups performed 30 breaths, twice daily, for 8 weeks, at intensities of ∼50 % maximal inspiratory pressure (PImax; IMT) or <15 % PImax (SHAM-IMT). Measurements of PImax, breathing discomfort during a bout of IMT, six-minute walk distance, physical activity levels, and balance were assessed pre- and post-intervention. Respiratory muscle kinematics were assessed via optoelectronic plethysmography (OEP) during constant work rate cycling. ResultsPImax was significantly improved (by 20.0±11.9 cmH2O; p=0.001) in the IMT group only. Breathing discomfort ratings during IMT significantly decreased (from 3.5±0.9–1.7±0.8). Daily sedentary time was decreased (by 28.0±39.8 min; p=0.042), and reactive balance significantly improved (by 1.2±0.8; p<0.001) in the IMT group only. OEP measures showed a significantly greater contribution of the pulmonary and abdominal rib cage compartments to total tidal volume expansion post-IMT. ConclusionsIMT significantly improves inspiratory muscle strength and breathing discomfort in this population. IMT induces greater rib cage expansion and diaphragm descent during exercise, thereby suggesting a less restrictive effect on thoracic expansion and increased diaphragmatic power generation.

맥켄지 운동이 젊은 성인의 호흡 기능과 호흡근에 미치는 즉각적인 효과

Purpose: Habitual abnormal postures, such as forward head posture, rounded shoulders, and decreased lumbar lordosis, can adversely affect respiratory function by limiting thoracic rib cage expansion and lung capacity. This study aimed to investigate the immediate effects of a single session of Mckenzie exercises on respiratory function and respiratory muscle. Methods: Eighteen young adults (mean age, 24.22 ± 2.415), including 4 men and 14 women, participated in the study. Spirometry tests were conducted before and after the single exercise session, which consisted of two types of Mckenzie exercises performed in 20 repetitions each. Forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), FEV1/FVC ratio, and peak expiratory flow (PEF) were measured to evaluate respiratory function, and maximal inspiratory pressure (MIP), maximal expiratory pressure (MEP) were measured to assess respiratory muscle strength. Paired-sample t-tests were employed to analyze the significance of respiratory measurements pre- and post-Mckenzie exercises, with a significance level set at 0.05. Results: A significant increase in MIP was found after Mckenzie exercises (p=.012), indicating improved inspiratory muscle strength. However, no significant changes were observed in FVC, FEV1, FEV1/FVC, PEF, and MEP. Conclusion: Mckenzie exercises, designed to stretch respiratory muscles and correct thoracic rib cage alignment through spinal extension, demonstrated an immediate positive effect on MIP. Therefore, Mckenzie exercises could be considered a valuable chest expansion exercise in respiratory rehabilitation programs. More studies are warranted to explore the potential long-term effects of Mckenzie exercises on respiratory function and respiratory muscle strength.

Real-time changes in rib cage expansion and use of abdominal mechanical stimulation in newborns: a quasi-experimental study.

To assess the rib cage expansion and respiratory rate in newborns using an abdominal stabilization band. The study included 32 newborns of both genders, with gestational age between 35 and 41 weeks. The abdominal stabilization band was used for 15 minutes between the xiphoid process and the anterosuperior iliac crest, with an abdominal contention 0.5cm smaller than the abdominal circumference. The rib cage expansion was evaluated by a breathing transducer (Pneumotrace II™) three minutes before using the band, during the use (15 minutes), and ten minutes after removing the band. The Shapiro-Wilk test verified data normality, and the Wilcoxon test compared the variables considering rib cage expansion and respiratory rate. Significance was set to p<0.05. There was an increase in respiratory rate when comparing before and ten minutes after removing (p=0.008) the abdominal stabilization band, as well as when comparing during its use and ten minutes after its removal (p=0.001). There was also an increase in rib cage expansion when comparing before and during the use of the abdominal stabilization band (p=0.005). The use of the abdominal stabilization band promoted an increase in the rib cage expansion and respiratory rate in the assessed newborns and may be a viable option to improve the respiratory kinematics of this population.

Telerehabilitation, A Viable Option in Patients with Persistent Post-COVID Syndrome: A Systematic Review.

The number of patients with post-COVID-19 syndrome continues to increase considerably, having serious healthcare, social and economic repercussions. The objective of this study is to describe the effectiveness of telerehabilitation to alleviate the symptoms of post-COVID-19 syndrome. A systematic review was conducted using the information available on four databases (PubMed, Medline, Scielo and PEDRo) on these patients until November 2022. The MeSH search terms were: Post-COVID syndrome, Post-COVID-19, Long COVID, Telerehabilitation, Physiotherapy, Rehabilitation, Virtual, Home care. Six articles were included which provided information on 140 patients, detailing their symptomatology, assessment, treatment and monitoring. The variables measured were dyspnea, fatigue, physical performance and quality of life. All studies included aerobic and anaerobic exercises. Most notable among the techniques used were rib cage expansion exercises, respiratory control and thoracic cage stretching, patient education, Mindfulness and virtual reality games to address physical, mental and relaxation aspects. The use of telerehabilitation could be an effective tool for the treatment of persistent symptoms after suffering from COVID-19. It has been shown in these studies that patients improve both their physical performance and their quality of life.

The Effects of Rib Cage Expansion Exercise Applying Taekwondo Makki Motion on Pulmonary Functions

Purpose : In this study, we aimed to investigate the effects of rib cage expansion exercise applying Taekwondo Makki motion on pulmonary functions. Methods : We examined 30 female university students without any dysfunctions of the nervous, muscular, and cardiopulmonary systems. Pulmonary functions were tested using a digital pulmonary function measuring device (Pony FX, COSMED Inc, Italy). The experimental group performed three movements of expanding their rib cage applying Taekwondo Makki motion. The participants performed exercises twice a day, once in the morning and again in the afternoon, for 4 weeks. The control group did not perform any other exercise. Pulmonary functions were measured again after 4weeks. SPSSWIN (ver 25.0) package program was used for statistical analysis. Results : In the experimental group, forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), inspiratory reserve volume (IRV), inspiratory capacity (IC), expiratory reserve volume, vital capacity (VC), and maximal voluntary ventilation (MVV) improved significantly after 4 weeks of exercise; the control group showed no change. The changes in FVC, FEV1, IRV, IC, VC, and MVV in the experimental group were higher than those in the control group. Conclusion : The rib cage expansion exercise applying Taekwondo Makki motion can improve pulmonary functions.

Adaptation of lung, chest wall, and respiratory muscles during pregnancy: preparing for birth.

A plethora of physiological and biochemical changes occur during normal pregnancy. The changes in the respiratory system have not been as well elucidated, in part because radioimaging is usually avoided during pregnancy. We aimed to use several noninvasive methods to characterize the adaptation of the respiratory system during the full course of pregnancy in preparation for childbirth. Eighteen otherwise healthy women (32.3 ± 2.8 yr) were recruited during early pregnancy. Spirometry, optoelectronic plethysmography, and ultrasonography were used to study changes in chest wall geometry, breathing pattern, lung and thoraco-abdominal volume variations, and diaphragmatic thickness in the first, second, and third trimesters. A group of nonpregnant women were used as control subjects. During the course of pregnancy, we observed a reorganization of rib cage geometry, in shape but not in volume. Despite the growing uterus, there was no lung restriction (forced vital capacity: 101 ± 15% predicted), but we did observe reduced rib cage expansion. Breathing frequency and diaphragmatic contribution to tidal volume and inspiratory capacity increased. Diaphragm thickness was maintained (1st trimester: 2.7 ± 0.8 mm, 3rd trimester: 2.5 ± 0.9 mm; P = 0.187), possibly indicating a conditioning effect to compensate for the effects of the growing uterus. We conclude that pregnancy preserved lung volumes, abdominal muscles, and the diaphragm at the expense of rib cage muscles.NEW & NOTEWORTHY Noninvasive analysis of the kinematics of the chest wall and the diaphragm during resting conditions in pregnant women revealed significant changes in the pattern of thoracoabdominal breathing across the trimesters. That is, concomitant with the progressive changes of chest wall shape, the diaphragm increased its contribution to both spontaneous and maximal breathing, maintaining its thickness despite its lengthening due to the growing uterus. These results suggest that during pregnancy the diaphragm is conditioned to optimize its active role provided during parturition.

Influence of posture, sex, and age on breathing pattern and chest wall motion in healthy subjects

ObjectiveWe evaluated the effects of posture, sex, and age on breathing pattern and chest wall motion during quiet breathing in healthy participants. MethodsEighty-three participants aged 42.72 (SD=21.74) years presenting normal pulmonary function were evaluated by optoelectronic plethysmography in the seated, inclined (with 45° of trunk inclination), and supine positions. This method allowed to assess the chest wall in a three dimensional way considering the chest wall as three compartments: pulmonary rib cage, abdominal rib cage and abdomen. ResultsPosture influenced all variables of breathing pattern and chest wall motion, except respiratory rate and duty cycle. Chest wall tidal volume and minute ventilation were reduced (p<0.05) in both sexes from seated to inclined and from seated to supine positions, mainly in males. Moreover, moving from seated to supine position significantly increased the percentage contribution of the abdomen to the tidal volume in both sexes (p<0.0001). Regarding sex, women showed higher contribution of thoracic compartment compared to men (p=0.008). Aging provided reductions on rib cage contributions to tidal volume that were compensated by increases of abdomen contributions (p<0.0001). In addition, increases in end-inspiratory and end-expiratory volumes over the years were observed. ConclusionThe degree of contribution of chest wall compartments is dependent on posture, sex, and age. Therefore, verticalization increases expansion of pulmonary rib cage as well as horizontalization increases abdominal displacement. Women presented higher thoracic contribution to tidal volume than men. Aging reduces rib cage contributions to tidal volume that were compensated by increases of abdomen contributions.

Pilates en pacientes con espondilitis anquilosante: repercusión en la función pulmonar

AimTo evaluate the impact of physiotherapy, based on the Pilates Method, on the lung function of patients with Ankylosing Spondylitis (AS). Material and methodsA randomised clinical trial (RCT) was performed with 49 patients diagnosed with AS according to the modified New York criteria. Two groups were randomly established. Therapeutic Pilates-based exercise was performed by 26 patients for 17 weeks, in 90minute sessions on alternative days, supervised by a physiotherapist. The control group (23 patients) used a conventional exercise program at home. The variables analysed were: rib cage expansion, forced vital capacity (FVC), forced expiratory volume (FEV1), and the FEV1/FVC ratio. ResultsNo significant differences were found in the values of rib cage expansion between control and experimental groups (P=.686), while there were differences before and after intervention in the experimental group (P=.780). The values of spirometry were similar in both control and experimental groups. No-significant increase in FVC was observed in the experimental group (P=.122). ConclusionsThe impact of Pilates-based exercises on spirometry values and rib cage expansion is limited, although there was a tendency to improve FVC after Pilates exercises. These types of exercise protocols should be considered, for their clinical application, in specific respiratory physiotherapy.

Lack of a pulmonary vein causing unilateral interlobular septal thickening

A 24-year-old woman presented with an 8-year history of chest tightness and shortness of breath during intense exercise. Physical examination showed decreased expansion of the right rib cage and respiratory...

Action of the diaphragm on the rib cage.

When the diaphragm contracts, pleural pressure falls, exerting a caudal and inward force on the entire rib cage. However, the diaphragm also exerts forces in the cranial and outward direction on the lower ribs. One of these forces, the "insertional force," is applied by the muscle at its attachments to the lower ribs. The second, the "appositional force," is due to the transmission of abdominal pressure to the lower rib cage in the zone of apposition. In the control condition at functional residual capacity, the effects of these two forces on the lower ribs are nearly equal and outweigh the effect of pleural pressure, whereas for the upper ribs, the effect of pleural pressure is greater. The balance between these effects, however, may be altered. When the abdomen is given a mechanical support, the insertional and appositional forces are increased, so that the muscle produces a larger expansion of the lower rib cage and, with it, a smaller retraction of the upper rib cage. In contrast, at higher lung volumes the zone of apposition is decreased, and pleural pressure is the dominant force on the lower ribs as well. Consequently, although the force exerted by the diaphragm on these ribs remains inspiratory, rib displacement is reversed into a caudal-inward displacement. This mechanism likely explains the inspiratory retraction of the lateral walls of the lower rib cage observed in many subjects with chronic obstructive pulmonary disease (Hoover's sign). These observations support the use of a three-compartment, rather than a two-compartment, model to describe chest wall mechanics.

Mechanism of the increased rib cage expansion produced by the diaphragm with abdominal support.

When the abdomen in quadriplegic subjects is given a passive mechanical support, the expansion of the lower rib cage during inspiration is greater and the inward displacement of the upper rib cage is smaller. These changes have traditionally been attributed to an increase in the appositional force of the diaphragm, but the mechanisms have not been assessed. In this study, the inspiratory intercostal muscles in all interspaces were severed in anesthetized dogs, so that the diaphragm was the only muscle active during inspiration, and the displacements of the ribs 10 and 5 and the changes in pleural and abdominal pressure were measured during unimpeded breathing and during breathing with a plate applied on the ventral abdominal wall. In addition, external forces were applied to the 10th rib pair in the cranial and lateral directions, and the rib trajectories thus obtained were used as the basis for a vector analysis to estimate the relative contributions of the insertional and appositional forces to the rib 10 displacements during breathing. Application of the abdominal plate caused a marked increase in the inspiratory cranial and outward displacement of rib 10 and a decrease in the inspiratory caudal displacement of rib 5. Analysis of the results showed, however, that 1) the insertional and appositional forces contributed nearly equally to the increased inspiratory displacement of rib 10 and 2) the decrease in the expiratory displacement of rib 5 was the result of both the greater displacement of the lower ribs and the decrease in pleural pressure.

The expansion of the pulmonary rib cage during breath stacking is influenced by age in obese women.

ObjectiveTo analyze in obese women the acute effects of the breath stacking technique on thoraco-abdominal expansion.Design and MethodsNineteen obese women (BMI≥30 kg/m2) were evaluated by anthropometry, spirometry and maximal respiratory muscle pressures and successively analyzed by Opto-Electronic Plethysmography and a Wright respirometer during quiet breathing and breath stacking maneuvers and compared with a group of 15 normal-weighted healthy women. The acute effects of the maneuvers were assessed in terms of total and compartmental chest wall volumes at baseline, end of the breath stacking maneuver and after the maneuver. Obese subjects were successively classified into two groups, accordingly to the response during the maneuver, group 1 = prevalent rib cage or group 2 = abdominal expansion.ResultsAge was significantly lower in group 1 than group 2. When considering the two obese groups, FEV1 was lower and minute ventilation was higher only in group 2 compared to controls group. During breath stacking, inspiratory capacity was significant differences in obese subjects with a smaller expansion of the pulmonary rib cage and a greater expansion of the abdomen compared to controls and also between groups 1 and 2. A significant inverse linear relationship was found between age and inspiratory capacity of the pulmonary rib cage but not of the abdomen.ConclusionsIn obese women the maximal expansion of the rib cage and abdomen is influenced by age and breath stacking maneuver could be a possible therapy for preventing respiratory complications.

Paper #21: Serial Measures of Lung and Inspiratory Muscle Function in Children With Early-Onset Scoliosis

change in diaphragm volume less than convex, 1 had concave greater than convex, and 2 had equal volumes. For 3 patients with postoperative scans, concave change in rib cage volume increased 57% (convex, 72%) and change in diaphragm volume increased 128% (convex, 109%). Concave kidney excursion increased 6.3 mm (320%), and convex 5.2 mm (192%). Complications included 2 patients with migration of devices proximally. Conclusions: Quantitative dMRI can measure separate contributions of diaphragm and rib cage to lung expansion during respiration for each hemithorax, enabling accurate assessment of thoracic function for the first time. Vertical Expandable Prosthetic Titanium Rib treatment appears to increase rib cage expansion more on the convex side of the thorax than the concave, and conversely increases diaphragm excursion on the concave side. With treatment, renal excursion increases bilaterally, concave more than convex, probably reducing a blockade effect on the diaphragm. Quantitative dMRI has the potential to increase understanding of the anatomic mechanisms of spine/chest wall deformity that cause restrictive lung disease in NM scoliosis, and may enable the development of new treatments for it.

Acute Effects of Volume-Oriented Incentive Spirometry on Chest Wall Volumes in Patients After a Stroke

The aim of the present study was to assess how volume-oriented incentive spirometry applied to patients after a stroke modifies the total and compartmental chest wall volume variations, including both the right and left hemithoraces, compared with controls. Twenty poststroke patients and 20 age-matched healthy subjects were studied by optoelectronic plethysmography during spontaneous quiet breathing (QB), during incentive spirometry, and during the recovery period after incentive spirometry. Incentive spirometry was associated with an increased chest wall volume measured at the pulmonary rib cage, abdominal rib cage and abdominal compartment (P = .001) and under 3 conditions (P < .001). Compared with healthy control subjects, the tidal volume (VT) of the subjects with stroke was 24.7, 18.0, and 14.7% lower during QB, incentive spirometry, and postincentive spirometry, respectively. Under all 3 conditions, the contribution of the abdominal compartment to VT was greater in the stroke subjects (54.1, 43.2, and 48.9%) than in the control subjects (43.7, 40.8, and 46.1%, P = .039). In the vast majority of subjects (13/20 and 18/20 during QB and incentive spirometry, respectively), abdominal expansion precedes rib cage expansion during inspiration. Greater asymmetry between the right and left hemithoracic expansions occurred in stroke subjects compared with control subjects, but it decreased during QB (62.5%, P = .002), during incentive spirometry (19.7%), and postincentive spirometry (67.6%, P = .14). Incentive spirometry promotes increased expansion in all compartments of the chest wall and reduces asymmetric expansion between the right and left parts of the pulmonary rib cage; therefore, it should be considered as a tool for rehabilitation.

Moving boundary simulation of airflow and micro-particle deposition in the human extra-thoracic airway under steady inspiration. Part I: Airflow

Airflow into the lung is the result of negative alveolar pressure caused by the simultaneous action of diaphragm contraction and rib cage expansion. However, all of the determinate CFD simulations on airflow and particle deposition in the human upper respiratory tract to date have employed a fixed boundary condition, i.e. uniform or axial symmetrical velocity profiles at the mouth inlet and outlet/opening boundary at the end of the airway. In this study, the realistic breathing mechanism, i.e. expansion of the pleural cavity, is mimicked by the fluid–structure interaction employing a junction box routine to assign the motion of the moving wall boundary at the bottom of the extra-thoracic airway model with an extra bell-mouthed tube. The airflow and particle deposition are investigated, particularly for the movable boundary cases, and compared with the fixed cases. In Part I, the flow characteristics which are important factors for particle deposition, i.e. pressure drop, turbulence intensity, secondary intensity and velocity profiles, are illustrated at three flow rates, as well as the detailed recirculation flow in the trachea region. Compared with the fixed boundary cases, several notable differences are found:(i) the velocity profiles at the mouth inlet are not uniform or axially symmetric, but askew with high-speed flow shifted to the upper wall of the mouth inlet tube, and a more evident recirculation zone occurs near the lower wall of the inlet tube; (ii) the pressure drop and turbulence intensity are lower and the secondary intensity is higher than that in the fixed boundary case because of the askew profile in the mouth cavity and modified recirculation flow in the trachea region; (iii) at three flow rates, the secondary intensities exhibit identical characteristics before the larynx where the turbulence fluctuations are very weak, but discrepancies are evident in the trachea region because of the high level of turbulence intensity and different pattern of recirculation zones; (iv) the length of the recirculation zones increase at three flow rates and the minor separation and reattachment occur in the middle portion of the recirculation flow, while the recirculation flow layer is divided into two parts at higher flow rates; (v) the peaks of the secondary flow intensity in the trachea region are located near the flow separation and reattachment points (both the major and minor) and the peaks of turbulence intensity in the trachea seem to correspond to the major separation and reattachment region.

Invited Commentary

Invited Commentary

A Diet and Exercise Program to Improve Clinical Outcomes in Patients with Obstructive Sleep Apnea – A Feasibility Study

To assess the feasibility and efficacy of a novel 16-week exercise and diet program for important clinical outcomes in obstructive sleep apnea (OSA). Cohort study assessing sleep disordered breathing, cardiovascular risk factors, and neurobehavioral function prior to and following completion of the 16-week program. The program used a proprietary very low energy diet (Optifast, Novartis), and subjects participated in a supervised exercise schedule, which included both aerobic and resistance training. Follow-up contact was made at 12 months after program exit. Consecutive patients with newly diagnosed sleep apnea were approached who had an apnea-hypopnea index (AHI) of 10 to 50, a body mass index (BMI) of greater than 30 kg/m2, no significant comorbidities, and able to exercise. All data are presented as mean [SD]. Of 21 patients with OSA who were approached, 12 middle-aged (42.3 [10.4] years old), obese (BMI 36.1 [4.3] kg/m2), and predominantly female (75%) subjects with mild to moderate OSA were enrolled (AHI 24.6 [12.0]). Weight loss was significant (12.3 [9.6] kg, p <0.001), and 5 of the 10 who completed the program were able to independently maintain good weight loss at 12 months. At the 16-week assessment, there was a small nonsignificant fall in the AHI. Six of the 10 subjects had a reduction in sleep disordered breathing, and the AHI was less than 10 in 3 patients. There were significant improvements in neurobehavioral and cardiometabolic outcomes. Snoring improved in most subjects, but the improvement was clinically important (a score of < 2) in only 7. A supportive diet and exercise program may be of benefit to obese patients with mild to moderate sleep apnea. The results of this feasibility study showed significant weight loss and improvement in clinically important neurobehavioral and cardiometabolic outcomes but no significant change in sleep disordered breathing. These promising preliminary results need confirmation with a larger randomized trial.

Mechanism of increased inspiratory rib elevation in ascites

The detrimental effect of ascites on the lung-expanding action of the diaphragm is partly compensated for by an increase in the inspiratory elevation of the ribs, but the mechanism of this increase is uncertain. To identify this mechanism, the effect of ascites on the response of rib 4 to isolated phrenic nerve stimulation was first assessed in four dogs with bilateral pneumothoraces. Stimulation did not produce any axial displacement of the rib (X(r)) in the control condition and caused a cranial rib displacement in the presence of ascites. This displacement, however, was small. In a second experiment, the effects of ascites on the pleural pressure swing (DeltaP(pl)), intercostal activity, and X(r) during spontaneous inspiration were measured in eight animals. As the volume of ascites increased from 0 to 200 ml/kg body wt, X(r) increased from 3.5 +/- 0.5 to 7.5 +/- 0.9 mm (P < 0.001), DeltaP(pl) decreased from -6.4 +/- 0.4 to -3.6 +/- 0.3 cmH(2)0 (P < 0.001), and parasternal intercostal activity increased 61 +/- 19% (P < 0.001). The role of the decrease in DeltaP(pl) in causing the increase in X(r) was then separated from that of the increase in intercostal muscle force using the relation between X(r) and DeltaP(pl) during passive lung inflation. The loss in DeltaP(pl) accounted for two-thirds of the increase in X(r). These observations indicate that 1) the increased inspiratory elevation of the ribs in ascites is not the result of the increase in the rib cage-expanding action of the diaphragm and 2) it is due mostly to the decrease in DeltaP(pl) and partly to the increase in the force exerted by the parasternal intercostals on the ribs. These observations also suggest, however, that the rib cage expansion caused by ascites makes the parasternal intercostals less effective in pulling the ribs cranially.

Dysfunction of the canine respiratory muscle pump in ascites

Ascites, a complicating feature of many diseases of the liver and peritoneum, commonly causes dyspnea. The mechanism of this symptom, however, is uncertain. In the present study, progressively increasing ascites was induced in anesthetized dogs, and the hypothesis was initially tested that ascites increases the impedance on the diaphragm and, so, adversely affects the lung-expanding action of the muscle. Ascites produced a gradual increase in abdominal elastance and an expansion of the lower rib cage. Concomitantly, the caudal displacement of the diaphragm and the fall in airway opening pressure during isolated stimulation of the phrenic nerves decreased markedly; transdiaphragmatic pressure during phrenic stimulation also decreased. To assess the adaptation to ascites of the respiratory system overall, we subsequently measured the changes in lung volume, the arterial blood gases, and the electromyogram of the parasternal intercostal muscles during spontaneous breathing. Tidal volume and minute ventilation decreased progressively as ascites increased, leading to an increase in arterial PCO2 and parasternal intercostal inspiratory activity. It is concluded that 1) ascites, acting through an increase in abdominal elastance and an expansion of the lower rib cage, impairs the lung-expanding action of the diaphragm; 2) this impairment elicits a compensatory increase in neural drive to the inspiratory muscles, but the compensation is not sufficient to maintain ventilation; and 3) dyspnea in this setting results in part from the dissociation between increased neural drive and decreased ventilation.

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.