Rib Cage Motion Research Articles

Chest Wall Kinematics during Speech Breathing in Tracheoesophageal Speakers

The purpose of the present study was to determine how tracheoesophageal (TE) speakers manipulate the chest wall (rib cage and abdomen) to speak and how respiratory compromise (chronic obstructive pulmonary disease; COPD) and task variables influence those behaviors. The chest wall movements of 11 male TE speakers (5 with COPD and 6 without COPD) were measured during tidal breathing, spontaneous speech, and reading. Repeated-measures multivariate analyses were used to compare breathing behaviors across speech tasks and by respiratory health. Additional repeated-measures multivariate analyses and 1-way analyses of variance were conducted on temporal, aerodynamic, and linguistic measures. There was a significant main effect of task and a significant interaction effect of COPD and task on chest wall movements. Rib cage movements varied by task, whereas abdominal movements were as predicted. There was a significant difference in utterance length by task. There were no main effects of COPD on the chest wall and no significant group differences in utterance length, aerodynamic measures, or intelligibility. The TE speakers were generally accurate in inspiring at appropriate linguistic boundaries. The results suggest that there is robust control for speech breathing following laryngectomy, but that there is also increased effort within the chest wall. Implications for future research considerations are discussed.

Distribution of electrical activation to the external intercostal muscles during high frequency spinal cord stimulation in dogs

In contrast to previous methods of electrical stimulation of the inspiratory muscles, high frequency spinal cord stimulation (HF-SCS) results in more physiological activation of these muscles. The spatial distribution of activation to the external intercostal muscles by this method is unknown. In anaesthetized dogs, multiunit and single motor unit (SMU) EMG activity was monitored in the dorsal portion of the 3rd, 5th and 7th interspaces and ventral portion of the 3rd interspace during spontaneous breathing and HF-SCS following C2 spinal section. Stimulus amplitude during HF-SCS was adjusted such that inspired volumes matched spontaneous breathing (Protocol 1). During HF-SCS, mean peak SMU firing frequency was highest in the 3rd interspace (dorsal) (18.8 ± 0.3 Hz) and significantly lower in the 3rd interspace (ventral) (12.2 ± 0.2 Hz) and 5th interspace (dorsal) (15.3 ± 0.3 Hz) (P <0.05 for each comparison). Similar rostrocaudal and dorsoventral gradients of activity were observed during spontaneous breathing prior to C2 section. No significant activity was observed in the 7th interspace during either spontaneous breathing or HF-SCS. Since peak discharge frequencies of the SMUs were higher and rib cage movement greater during HF-SCS compared to spontaneous breathing, stimulus amplitude during HF-SCS was adjusted such that rib cage movement matched (Protocol 2). Under these conditions, mean peak SMU frequencies and rostrocaudal and dorsoventral gradients of activity during HF-SCS were not significantly different compared to spontaneous breathing. These results indicate that (a) the topographic pattern of electrical activation of the external intercostal muscles during HF-SCS is similar to that occurring during spontaneous breathing and (b) differential descending synaptic input from supraspinal centres is not a required component of the differential spatial distribution of external intercostal muscle activation. HF-SCS may provide a more physiological method of inspiratory muscle pacing.

Padrão respiratório e movimento toracoabdominal em indivíduos saudáveis: influência da idade e do sexo

to describe the breathing pattern and thoracoabdominal motion of healthy individuals, taking age and sex into consideration. the study included 104 individuals aged 20 to 39, 40 to 59, and 60 to 80 years (41 males and 63 females), with normal body mass index and spirometric values. Participants were evaluated at rest in the supine position, by means of respiratory inductive plethysmography. The following variables were measured: tidal volume (Vt), respiratory frequency (f), minute ventilation (VE), inspiratory duty cycle (Ti/Ttot), mean inspiratory flow (Vt/Ti), rib cage motion (%RC), inspiratory phase relation (PhRIB), expiratory phase relation (PhREB), and phase angle (PhaseAng). Comparisons between the age groups were performed using one-way ANOVA or Kruskal-Wallis H, while comparisons between the sexes were performed using Student's t test or the Mann-Whitney U test, depending on the data distribution; p<0.05 was taken to be significant. comparison between the sexes showed that, in the age groups 20 to 39 and 60 to 80 years, women presented significantly lower values for Vt, VE, and Ti/Ttot than men, and there was no significant difference in the age group 40 to 59 years. Comparisons between the age groups showed that participants aged 60 to 80 presented significantly greater PhRIB and PhaseAng than participants aged 20 to 39 years, without significant differences in the breathing pattern. the data suggest that breathing pattern is influenced by sex whereas thoracoabdominal motion is influenced by age.

Validity in measuring breathing movements with the Respiratory Movement Measuring Instrument, RMMI

The respiratory movement measuring instrument (RMMI) is a method for examining the differences in anteroposterior diameter of the body during breathing. The aim of this study was to investigate the known group validity of the RMMI by comparing different body positions and breathing behaviours in healthy persons. The respiratory motion of the rib cage and the abdomen was measured by the RMMI in 40 healthy subjects. The measurements were undertaken in the supine and sitting positions and during normal, abdominal and thoracic breathing. The proportion of rib cage motion was 36% in the supine and 52% in the sitting position (P<0·001). The proportion of rib cage motion in the supine position was 21% during abdominal breathing and 57% during thoracic breathing, both significantly different (P<0·001) in comparison to normal breathing. The RMMI showed a high degree of validity concerning distribution of motion between the rib cage and abdomen.

Inspiratory flow rate, not type of incentive spirometry device, influences chest wall motion in healthy individuals

This study investigated the effect of flow rates and spirometer type on chest wall motion in healthy individuals. Twenty-one healthy volunteers completed breathing trials to either two times tidal volume (2xVT) or inspiratory capacity (IC) at high, low, or natural flow rates, using a volume- or flow-oriented spirometer. The proportions of rib cage movement to tidal volume (%RC/VT), chest wall diameters, and perceived level of exertion (RPE) were compared. Low and natural flow rates resulted in significantly lower %RC/VT compared to high flow rate trials (p=0.001) at 2xVT. Low flow trials also resulted in significantly less chest wall motion in the upper anteroposterior direction than high and natural flow rates (p<0.001). At IC, significantly greater movement occurred in the abdominal lateral direction during low flow compared to high and natural flow trials (both p<0.003). RPE was lower for the low flow trials compared to high flow trials at IC and 2xVT (p<0.01). In healthy individuals, inspiratory flow (not device type) during incentive spirometry determines the resultant breathing pattern. High flow rates result in greater chest wall motion than low flow rates.

A Simple Dynamic Model of Respiratory Pump

To study the interaction of forces that produce chest wall motion, we propose a model based on the lever system of Hillman and Finucane (J Appl Physiol 63(3):951-961, 1987) and introduce some dynamic properties of the respiratory system. The passive elements (rib cage and abdomen) are considered as elastic compartments linked to the open air via a resistive tube, an image of airways. The respiratory muscles (active) force is applied to both compartments. Parameters of the model are identified in using experimental data of airflow signal measured by pneumotachography and rib cage and abdomen signals measured by respiratory inductive plethysmography on eleven healthy volunteers in five conditions: at rest and with four level of added loads. A breath by breath analysis showed, whatever the individual and the condition are, that there are several breaths on which the airflow simulated by our model is well fitted to the airflow measured by pneumotachography as estimated by a determination coefficient R(2) > or = 0.70. This very simple model may well represent the behaviour of the chest wall and thus may be useful to interpret the relative motion of rib cage and abdomen during quiet breathing.

Effects of breathing exercises on breathing pattern and thoracoabdominal motion after gastroplasty

To evaluate breathing pattern and thoracoabdominal motion during breathing exercises. Twenty-four patients with class II or III obesity (18 women; 6 men) were studied on the second postoperative day after gastroplasty. The mean age was 37 +/- 11 years, and the mean BMI was 44 +/- 3 kg/m(2). Diaphragmatic breathing, incentive spirometry with a flow-oriented device and incentive spirometry with a volume-oriented device were performed in random order. Respiratory inductive plethysmography was used in order to measure respiratory variables and thoracoabdominal motion. Comparisons among the three exercises showed significant differences: tidal volume was higher during incentive spirometry (with the flow-oriented device or with the volume-oriented device) than during diaphragmatic breathing; the respiratory rate was lower during incentive spirometry with the volume-oriented device than during incentive spirometry with the flow-oriented device; and minute ventilation was higher during incentive spirometry (with the flow-oriented device or with the volume-oriented device) than during diaphragmatic breathing. Rib cage motion did not vary during breathing exercises, although there was an increase in thoracoabdominal asynchrony, especially during incentive spirometry with the flow-oriented device. Among the breathing exercises evaluated, incentive spirometry with the volume-oriented device provided the best results, because it allowed slower, deeper inhalation.

Computational model of rib movement and its application in studying the effects of age-related thoracic cage calcification on respiratory system

A 3D finite element model of rib cage movement is developed and used to study the role of age-related costal cartilage and sternocostal joint calcification, as well as respiratory muscle weakness on the ‘bucket-handle’ movement of human rib. The volume displacement of the rib cage is related to changes in its circumference using an empirical equation presented by Agostoni et al. (1965, J Appl Physiol, 20:1179–1186). A systematic study is carried out to quantify the role of costal cartilage, sternocostal joint calcification and muscle weakness on the volume displacement of the rib cage. The results provide insight into some of the mechanisms underlying age-related changes in the respiratory system.

Microgravity alters respiratory abdominal and rib cage motion during sleep.

The abdominal and rib cage contributions to tidal breathing differ between rapid-eye-movement (REM) and non-NREM sleep. We hypothesized that abdominal relative contribution during NREM and REM sleep would be altered in different directions when comparing sleep on Earth with sleep in sustained microgravity (microG), due to conformational changes and differences in coupling between the rib cage and the abdominal compartment induced by weightlessness. We studied respiration during sleep in five astronauts before, during, and after two Space Shuttle missions. A total of 77 full-night (8 h) polysomnographic studies were performed; abdominal and rib cage respiratory movements were recorded using respiratory inductive plethysmography. Breath-by-breath analysis of respiration was performed for each class: awake, light sleep, deep sleep, and REM sleep. Abdominal contribution to tidal breathing increased in microG, with the first measure in space being significantly higher than preflight values, followed by a return toward preflight values. This was observed for all classes. Preflight, rib cage, and abdominal movements were found to be in phase for all but REM sleep, for which an abdominal lead was observed. The abdominal leading role during REM sleep increased while deep sleep showed the opposite behavior, the rib cage taking a leading role in-flight. In microG, the percentage of inspiratory time in the overall breath, the duty cycle (T(I)/T(Tot)), decreased for all classes considered when compared with preflight, while normalized inspiratory flow, taking the awake values as reference, increased in-flight for light sleep, deep sleep, and REM. Changes in abdominal-rib cage displacements probably result from a less efficient operating point for the diaphragm and a less efficient coupling between the abdomen and the apposed portion of the rib cage in microG. However, the preservation of total ventilation suggests that short-term adaptive mechanisms of ventilatory control compensate for these mechanical changes.

Effects of the Aging Process on Respiratory Function

Background: The identification of breathing patterns in healthy elderly individuals and changes in the respiratory system related to the normal aging process is important to detect and prevent respiratory dysfunction. Objectives: To assess and compare respiratory function between adults and elderly individuals according to baseline conditions. Methods: Nineteen adults aged 20–59 years (group 1), 12 elderly aged 60–69 years (group 2) and 12 elderly above 69 years of age (group 3) who were all nonsmokers, untrained and with normal pulmonary function tests were studied using calibrated respiratory inductive plethysmography to assess tidal volume (Vt), respiratory frequency (f), minute ventilation, mean inspiratory flow [Vt/inspiratory time (Ti)], inspiratory duty cycle (Ti/total cycle time), labored breathing index (an asynchrony index measurement), percentage of rib cage motion and abdominal motion. Measurements of the maximal inspiratory pressure (MIP), maximal expiratory pressure and transcutaneous oxygen saturationwere also obtained. Results: The MIP was statistically significantly lower in group 2 (54.58 ± 32.37 cm H₂O) and group 3 (54.58 ± 33.61 cm H₂O) compared to group 1 (92.11 ± 43.22 cm H₂O; p = 0.037). There were no significant differences between the groups regarding breathing patterns, respiratory variables and thoracoabdominal motion. No statistically significant differences between groups 2 and 3 were found for any of the investigated variables. Conclusion: These findings suggest that the aging process of the respiratory system reduces the inspiratory muscle strength but does not have a significant impact on breathing pattern variables.

Human respiratory mechanics demonstration model

Respiratory mechanics is a difficult topic for instructors and students alike. Existing respiratory mechanics models are limited in their abilities to demonstrate any effects of rib cage movement on alveolar and intrapleural pressures. We developed a model that can be used in both large and small classroom settings. This model contains digital pressure displays and computer integration for real-time demonstration of pressure changes that correspond to the different phases of breathing. Moving the simulated diaphragm and rib cage causes a volume change that results in pressure changes visible on the digital sensors and computer display. Device testing confirmed the model's ability to accurately demonstrate pressure changes in proportion to physiological values. Classroom testing in 427 surveyed students showed improved understanding of respiratory concepts (P < 0.05). We conclude that our respiratory mechanics model is a valuable instructional tool and provide detailed instructions for those who would like to create their own.

Design and Testing of a Simulation Framework for Dosimetric Motion Studies Integrating an Anthropomorphic Computational Phantom into Four-dimensional Monte Carlo

We have designed a simulation framework for motion studies in radiation therapy by integrating the anthropomorphic NCAT phantom into a 4D Monte Carlo dose calculation engine based on DPM. Representing an artifact-free environment, the system can be used to identify class solutions as a function of geometric and dosimetric parameters. A pilot dynamic conformal study for three lesions ( approximately 2.0 cm) in the right lung was performed (70 Gy prescription dose). Tumor motion changed as a function of tumor location, according to the anthropomorphic deformable motion model. Conformal plans were simulated with 0 to 2 cm margin for the aperture, with additional 0.5 cm for beam penumbra. The dosimetric effects of intensity modulated radiotherapy (IMRT) vs. conformal treatments were compared in a static case. Results show that the Monte Carlo simulation framework can model tumor tracking in deformable anatomy with high accuracy, providing absolute doses for IMRT and conformal radiation therapy. A target underdosage of up to 3.67 Gy (lower lung) was highlighted in the composite dose distribution mapped at exhale. Such effects depend on tumor location and treatment margin and are affected by lung deformation and ribcage motion. In summary, the complexity in the irradiation of moving targets has been reduced to a controlled simulation environment, where several treatment options can be accurately modeled and quantified The implemented tools will be utilized for extensive motion study in lung/liver irradiation.

Breathing pattern and thoracoabdominal motion during exercise in chronic obstructive pulmonary disease

Subjects with chronic obstructive pulmonary disease (COPD) present breathing pattern and thoracoabdominal motion abnormalities that may contribute to exercise limitation. Twenty-two men with stable COPD (FEV1 = 42.6 +/- 13.5% predicted; age 68 +/- 8 years; mean +/- SD) on usual medication and with at least 5 years of diagnosis were evaluated at rest and during an incremental cycle exercise test (10 watts/2 min). Changes in respiratory frequency, tidal volume, rib cage and abdominal motion contribution to tidal volume and the phase angle that measures the asynchrony were analyzed by inductive respiratory plethysmography at rest and during three levels of exercise (30-50, 70-80, and 100% maximal work load). Repeated measures ANOVA followed by pre-planned contrasts and Bonferroni corrections were used for analyses. As expected, the greater the exercise intensity the higher the tidal volume and respiratory frequency. Abdominal motion contributed to the tidal volume increase (rest: 49.82 +/- 11.19% vs exercise: 64.15 +/- 9.7%, 63.41 +/- 10%, and 65.56 +/- 10.2%, respectively, P < 0.001) as well as the asynchrony [phase angle: 11.95 +/- 7.24 degrees at rest vs 22.2 +/- 15 degrees (P = 0.002), 22.6 +/- 9 degrees (P < 0.001), and 22.7 +/- 8 degrees (P < 0.001), respectively, at the three levels of exercise]. In conclusion, the increase in ventilation during exercise in COPD patients was associated with the major motion of the abdominal compartment and with an increase in the asynchrony independent of exercise intensity. It suggests that cycling exercise is an effective way of enhancing ventilation in COPD patients.

Respiratory Movement Patterns During Vocalizations at 7 and 11 Months of Age

The present investigation was designed to study the modulation of abdomen and rib cage movements during vocalization over a period of development associated with rapid decreases in the compliance of the chest wall. Rib cage and abdominal kinematics were recorded during spontaneous vocalizations in 7- and 11-month old infants. Principal component analysis was used to represent each infant's abdomen and rib cage traces as the weighted sum of a small number of principal component (PC) waveforms. The fundamental periods of infants' PC waveforms in the 11-month group were significantly shorter than those in the 7-month group. In addition, the variance contributed by PCs describing unidirectional patterns of respiratory movement decreased in the 11-month group, whereas the variances contributed by PCs describing modulated patterns of movement increased. Lastly, the extent to which abdomen and rib cage movements predicted the duration of corresponding vocalizations also increased significantly in the 11-month group compared with the 7-month group. The findings of the present study were consistent with the hypothesis that decreases in the compliance of the chest wall result in more rapid modulation of chest wall movements and greater control of those movements by the developing neuromuscular system.

Paradoxical Respiration: An indication for Adenotonsillectomy?

Paradoxical breathing or inward rib cage movements without frank sleep apnea is a clinical de- scription of the upper airway resistance syndrome. Upper airway resistance syndrome is thought to be a distinct entity and not just a part of the continuum of obstructive sleep apnea; paradoxical breathing in children appears to be a separate entity from the classic patient with marked adenotonsillar hypertrophy causing obstructive apnea. The treatment also dif- fers. We present a case of paradoxical breathing in a child who resolved spontaneously over a two year period.

Exhaled NO and iNOS expression in sputum cells of healthy, obese and OSA subjects

Obstructive sleep apnoea (OSA) is associated with airways inflammation; a key role in this regard seems to be played by nitric oxide (NO). The aim of this study was to measure exhaled NO and expression of its enzyme, the inducible nitric oxide synthase (iNOS) in cells of induced sputum in OSA patients and in obese subjects without sleep apnoea and to correlate these inflammatory markers with severity of OSA. We enrolled 18 obese patients with OSA (10 men, age 48.2 +/- 8.4 years), 15 obese patients without OSA (eight men, age 52.8 +/- 11 years) and 10 healthy subjects (five men, age 42 +/- 4 years). Exhaled NO was measured using a chemiluminescence analyser; iNOS expression was measured in the sputum cells by immunocytochemistry. Exhaled NO resulted significantly increased in OSA and in obese patients (23.1 +/- 2.1 and 17.9 +/- 2.1 p.p.b.) than in healthy subjects (7.2 +/- 0.6 p.p.b.; P < 0.001). OSA and obese patients showed a higher percentage of neutrophils and a lower percentage of macrophages in the induced sputum compared to healthy subjects. In addition, OSA and obese patients showed higher iNOS expression in neutrophils and in macrophages with respect to healthy subjects. A positive correlation between exhaled NO, iNOS expression and AHI was observed. These data confirm the presence of airway inflammation in OSA and in obese patients, and suggest the possible role for NO and iNOS expression in neutrophils of the induced sputum as noninvasive markers to identify and monitor the airway inflammation in these subjects.

Plethysmographic Comparison of Breathing Pattern in Heaves (Recurrent Airway Obstruction) Versus Experimental Bronchoconstriction or Hyperpnea in Horses

Horses with recurrent airway obstruction (heaves) are described as exhibiting "increased abdominal effort," but it is unknown whether this translates to an effective contribution to ventilation. We hypothesized that heaves is characterized by asynchrony between rib cage and abdominal motions, and that the abdominal component is the major contributor to ventilation. The rib cage versus abdominal motion in naturally occurring heaves (n = 15) was compared to controls at rest (n = 7) and during hyperpnea because of lobeline treatment, and the effects of histamine-induced bronchoconstriction in controls (n = 10). Flow patterns, phase angle (theta) between the rib and abdominal compartments, abdominal (Vabd) contribution to tidal volume (VT), and lung mechanics were measured. Findings unique to the heaves group included the loss of biphasic expiratory flow, severely increased theta with the abdomen consistently lagging behind the rib cage, and a reduced contribution of the abdomen to ventilation. A subgroup of heaves (n = 5) with abdominal paradox showed a significant (P < .05) reduction in tidal volume, and increased respiratory rate. Bronchodilation reduced theta in heaves (P = .06), but theta remained significantly higher after bronchodilation than found in controls. We conclude that breathing pattern in horses with heaves is characterized by severe rib cage/abdominal asynchrony, with the rib cage motion in synchrony with flow, therefore dominating ventilation. In a subset of heaves, the abdominal compartment (diaphragm, abdominal muscles) was completely out of synchrony with flow ("abdominal paradox") despite the clinical appearance of "increased abdominal effort."

Plethysmographic Comparison of Breathing Pattern in Heaves (Recurrent Airway Obstruction) Versus Experimental Bronchoconstriction or Hyperpnea in Horses

Background: Horses with recurrent airway obstruction (heaves) are described as exhibiting “increased abdominal effort,” but it is unknown whether this translates to an effective contribution to ventilation.Hypothesis: We hypothesized that heaves is characterized by asynchrony between rib cage and abdominal motions, and that the abdominal component is the major contributor to ventilation.Animals: The rib cage versus abdominal motion in naturally occurring heaves (n = 15) was compared to controls at rest (n = 7) and during hyperpnea because of lobeline treatment, and the effects of histamine‐induced bronchoconstriction in controls (n = 10).Methods: Flow patterns, phase angle (9) between the rib and abdominal compartments, abdominal (Vabd) contribution to tidal volume (VT), and lung mechanics were measured.Results: Findings unique to the heaves group included the loss of biphasic expiratory flow, severely increased 9 with the abdomen consistently lagging behind the rib cage, and a reduced contribution of the abdomen to ventilation. A subgroup of heaves (n = 5) with abdominal paradox showed a significant (P&lt; .05) reduction in tidal volume, and increased respiratory rate. Bronchodilation reduced 9 in heaves (P= .06), but 9 remained significantly higher after bronchodilation than found in controls.Conclusions and Clinical Importance: We conclude that breathing pattern in horses with heaves is characterized by severe rib cage/abdominal asynchrony, with the rib cage motion in synchrony with flow, therefore dominating ventilation. In a subset of heaves, the abdominal compartment (diaphragm, abdominal muscles) was completely out of synchrony with flow (“abdominal paradox”) despite the clinical appearance of “increased abdominal effort.”

Frequency of Hoover's sign in stable patients with chronic obstructive pulmonary disease

Hoover's sign (the inward motion of the lower lateral rib cage with inspiration) is conventionally considered to be a sign of severe disease in chronic obstructive pulmonary disease (COPD). However, no studies have been done regarding the frequency of Hoover's sign in patients with stable COPD. We aim to establish the frequency of Hoover's sign in a large series of stable patients with COPD and to analyse the characteristics associated with its presence. One hundred and fifty-seven consecutive patients with COPD, 150 of whom were men (95%), with a mean (standard deviation) age of 68 (8) years were included. Seventy-one patients had Hoover's sign (45%) on clinical examination. Hoover's sign was not detected in mild COPD patients, and it was present in 36% of moderate, 43% of severe and 76% of very severe COPD patients. In the multivariate analysis, dyspnea, body mass index (BMI), number of exacerbations and number of prescribed drugs were independently associated with the presence of Hoover's sign in COPD. Hoover's sign is a frequent finding in COPD, and the frequency increases with severity. Its presence is independently related to higher values of dyspnea, BMI, number of exacerbations and number of prescribed drugs.

Acute effects of thixotropy conditioning of inspiratory muscles on end-expiratory chest wall and lung volumes in normal humans

Thixotropy conditioning of inspiratory muscles consisting of maximal inspiratory effort performed at an inflated lung volume is followed by an increase in end-expiratory position of the rib cage in normal human subjects. When performed at a deflated lung volume, conditioning is followed by a reduction in end-expiratory position. The present study was performed to determine whether changes in end-expiratory chest wall and lung volumes occur after thixotropy conditioning. We first examined the acute effects of conditioning on chest wall volume during subsequent five-breath cycles using respiratory inductive plethysmography (n = 8). End-expiratory chest wall volume increased after conditioning at an inflated lung volume (P < 0.05), which was attained mainly by rib cage movements. Conditioning at a deflated lung volume was followed by reductions in end-expiratory chest wall volume, which was explained by rib cage and abdominal volume changes (P < 0.05). End-expiratory esophageal pressure decreased and increased after conditioning at inflated and deflated lung volumes, respectively (n = 3). These changes in end-expiratory volumes and esophageal pressure were greatest for the first breath after conditioning. We also found that an increase in spirometrically determined inspiratory capacity (n = 13) was maintained for 3 min after conditioning at a deflated lung volume, and a decrease for 1 min after conditioning at an inflated lung volume. Helium-dilution end-expiratory lung volume increased and decreased after conditioning at inflated and deflated lung volumes, respectively (both P < 0.05; n = 11). These results suggest that thixotropy conditioning changes end-expiratory volume of the chest wall and lung in normal human subjects.