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

Thoracoabdominal asynchrony in a virtual preterm infant: computational modeling and analysis

Thoracoabdominal asynchrony (TAA), the asynchronous volume changes between the rib cage and abdomen during breathing, is associated with respiratory distress, progressive lung volume loss, and chronic lung disease in the newborn infant. Preterm infants are prone to TAA risk factors such as weak intercostal muscles, surfactant deficiency, and a flaccid chest wall. The causes of TAA in this fragile population are not fully understood and, to date, the assessment of TAA has not included a mechanistic modeling framework to explore the role these risk factors play in breathing dynamics and how TAA can be resolved. We present a dynamic compartmental model of pulmonary mechanics that simulates TAA in the preterm infant under various adverse clinical conditions, including high chest wall compliance, applied inspiratory resistive loads, bronchopulmonary dysplasia, anesthesia-induced intercostal muscle deactivation, weakened costal diaphragm, impaired lung compliance, and upper airway obstruction. Sensitivity analyses performed to screen and rank model parameter influence on model TAA and respiratory volume outputs show that risk factors are additive so that maximal TAA occurs in a virtual preterm infant with multiple adverse conditions, and addressing risk factors individually causes incremental changes in TAA. An abruptly obstructed upper airway caused immediate nearly paradoxical breathing and tidal volume reduction despite greater effort. In most simulations, increased TAA occurred together with decreased tidal volume. Simulated indices of TAA are consistent with published experimental studies and clinically observed pathophysiology, motivating further investigation into the use of computational modeling for assessing and managing TAA.NEW & NOTEWORTHY A novel model of thoracoabdominal asynchrony incorporates literature-derived mechanics and simulates the impact of risk factors on a virtual preterm infant. Sensitivity analyses were performed to determine the influence of model parameters on TAA and respiratory volume. Predicted phase angles are consistent with prior experimental and clinical results, and influential parameters are associated with clinical scenarios that significantly alter phase angle, motivating further investigation into the use of computational modeling for assessing and managing thoracoabdominal asynchrony.

Mid‐Arm Point in PAEDiatrics (MAPPAED): An effective procedural aid for safe pleural decompression in trauma

OBJECTIVE

Life-threatening thoracic trauma requires emergency pleural decompression and thoracostomy and chest drain insertion are core trauma procedures. Reliably determining a safe site for pleural decompression in children can be challenging. We assessed whether the Mid-Arm Point (MAP) technique, a procedural aid proposed for use with injured adults, would also identify a safe site for pleural decompression in children.

METHODS

Children (0-18 years) attending four EDs were prospectively recruited. The MAP technique was performed, and chest wall skin marked bilaterally at the level of the MAP; no pleural decompression was performed. Radio-opaque markers were placed over the MAP-determined skin marks and corresponding intercostal space (ICS) reported using chest X-ray.

RESULTS

A total of 392 children participated, and 712 markers sited using the MAP technique were analysed. Eighty-three percentage of markers were sited within the 'safe zone' for pleural decompression (4th to 6th ICSs). When sited outside the 'safe zone', MAP-determined markers were typically too caudal. However, if the site for pleural decompression was transposed one ICS cranially in children ≥4 years, the MAP technique performance improved significantly with 91% within the 'safe zone'.

CONCLUSIONS

The MAP technique reliably determines a safe site for pleural decompression in children, albeit with an age-based adjustment, the Mid-Arm Point in PAEDiatrics (MAPPAED) rule: 'in children aged ≥4 years, use the MAP and go up one ICS to hit the safe zone. In children <4 years, use the MAP.' When together with this rule, the MAP technique will identify a site within the 'safe zone' in 9 out of 10 children.

Low-cost structured light imaging of regional volume changes for use in assessing mechanical ventilation

BACKGROUND

Optimal setting of mechanical ventilators is critical for improving outcomes. Accurate, predictive lung mechanics models are effective in optimizing MV settings, but only at a global level as they cannot estimate regional lung volume ventilation to assess the potential of local distension or under-ventilation. This study presents a low-cost structured light system for non-contact high resolution chest motion measurement to estimate regional lung volume changes.

METHODS

The system consists of a structured light projector and two cameras. A new pattern is designed to extract motion from sub-regions of the chest surface, and an efficient feature is proposed to provide a fast and accurate correspondence matching between two views. Reconstruction of 3D surface points is based on the matched points and stereo method. Asymmetric distribution of tidal volume into left and right lungs is estimated based on reconstructed regional chest expansion. A proof-of-concept experiment using a dummy model and two test lungs connected to a ventilator to provide differential chest expansion is conducted under tidal volumes of 400 ml, 500 ml and 600 ml, with results compared to the widely-used SURF and ORB methods.

RESULTS

Compared to the SURF and ORB methods, the proposed method is more computationally efficient with ∼40% less computational time cost, and higher accuracy for dense point correspondence. Finally, the proposed method estimated the region lung volumes with the maximum error of 8 ml under 600 ml tidal volume, indicating a good accuracy.

CONCLUSIONS

Surface reconstruction results in a proof-of-concept experiment with differential chest expansion show good performance for the proposed pattern and method in extracting the key information for regional chest expansion. The proposed method is generalizable, with potential for use in other applications.

Thorax Dynamic Modeling and Biomechanical Analysis of Chest Breathing in Supine Lying Position

During respiration, the expansion and contraction of the chest and abdomen are coupled with each other, presenting a complex torso movement pattern. A finite element (FE) model of chest breathing based on the HUMOS2 human body model was developed. One-dimensional muscle units with active contraction functions were incorporated into the model based on Hill's active muscle model so as to generate muscle contraction forces that can change over time. The model was validated by comparing it to the surface displacement of the chest and abdomen during respiration. Then, the mechanism of the coupled motion of the chest and abdomen was analyzed. The analyses revealed that since the abdominal wall muscles are connected to the lower edge of the rib cage through tendons, the movement of the rib cage may cause the abdominal wall muscles to be stretched in both horizontal and vertical in a supine position. The anteroposterior and the right-left diameters of the chest will increase at inspiration, while the right-left diameter of the abdomen will decrease even though the anteroposterior diameter of the abdomen increases. The external intercostal muscles at different regions had different effects on the motion of the ribs during respiration. In particular, the external intercostal muscles at the lateral region had a larger effect on pump handle movement than bucket handle movement, and the external intercostal muscles at the dorsal region had a greater influence on bucket handle movement than pump handle movement.

Quantitative Analysis by 3D Graphics of Thoraco-Abdominal Surface Shape and Breathing Motion

Chest wall motion can provide information on respiratory muscles' action and on critical vital signs, like respiration and cardiac activity. The chest wall is a structure with three compartments that are independent to each other and can move paradoxically according to the pathophysiology of the disease. Opto-electronic plethysmography (OEP) allows for non-invasively 3D tracking of body movements. We aimed to extend the characteristics of OEP analysis to local analyses of thoraco-abdominal surface geometry and kinematics during respiration. Starting from the OEP output file, the 3D markers’ coordinates were combined with a triangulation matrix. A smoothing procedure (an automatic and iterative interpolation process to increase the number of vertices from 93 to 548) was applied to allow for precise local analysis of the thoraco-abdominal surface. A series of measurements can be performed to characterize the geometry of the trunk and its three compartments, in terms of volumes, height, diameters, perimeters, and area. Some shape factors, such as surface-to-volume ratio or height-to-perimeter ratio, can be also computed. It was also possible to build the vector field associated with the breathing motion of all the vertices, in terms of magnitude and motion direction. The vector field data were analyzed and displayed through two graphic tools: a 3D heatmap, in which the magnitude of motion was associated to different colors, and a 3D arrow plot, that allowed us to visualize both the magnitude and the direction of motion with color-coded arrows. The methods were applied to 10 healthy subjects (5 females) and also applied to two cases: a pregnant woman at each trimester of gestation and a patient before and after a demolition thoracic surgery. The results proved to be coherent with the physiology of healthy subjects and the physiopathology of the cases. We developed a new non-invasive method for respiratory analysis that allowed for the creation of realistic 3D models of the local and global trunk surface during respiration. The proposed representation constituted a very intuitive method to visualize and compare thoraco-abdominal surface movements within and between subjects, therefore enforcing the potential clinical translational value of the method.

Breathing patterns recognition: A functional data analysis approach

BACKGROUND AND OBJECTIVE

The ongoing pandemic proved fundamental is to assess a subject's respiratory functionality and breathing pattern measurement during quiet breathing is feasible in almost all patients, even those uncooperative. Breathing pattern consists of tidal volume and respiratory rate in an individual assessed by data tracks of lung or chest wall volume over time. State-of-art analysis of these data requires operator-dependent choices such as individuation of local minima in the track, elimination of anomalous breaths and individuation of breath clusters corresponding to different breathing patterns.

METHODS

A semi-automatic, robust and reproducible procedure was proposed to pre-process and analyse respiratory tracks, based on Functional Data Analysis (FDA) techniques, to identify representative breath curve and the corresponding breathing patterns. This was achieved through three steps: 1) breath separation through precise localization of the minima of the volume trace; 2) functional outlier breaths detection according to time-duration, magnitude and shape; 3) breath clustering to identify different pattern of interest, through K-medoids with Alignment. The method was firstly validated on simulated tracks and then applied to real data in conditions of clinical interest: operational volume change, exercise, mechanical ventilation, paradoxical breathing and age.

RESULTS

The total error in the accuracy of minima detection and in was less than 5%; with the artificial outliers being almost completely removed with an accuracy of 99%. During incremental exercise and independently on the bike resistance level, five clusters were identified (quiet breathing; recovery phase; onset of exercise; maximal and intermediate levels of exercise). During mechanical ventilation, the procedure was able to separate the non-ventilated from the ventilatory-supported breathing and to identify the worsening of paradoxical breathing due to the disease progression and the breathing pattern changes in healthy subjects due to age.

CONCLUSIONS

We proposed a robust validated automatic breathing patterns identification algorithm that extracted representative curves that could be implemented in clinical practice for objective comparison of the breathing patterns within and between subjects. In all case studies the identified patterns proved to be coherent with the clinical conditions and the physiopathology of the subjects, therefore enforcing the potential clinical translational value of the method.

Measurement of chest wall motion using a motion capture system with the one-pitch phase analysis method

Spirometry is a standard method for assessing lung function. However, its use is challenging in some patients, and it has limitations such as risk of infection and inability to assess regional chest wall motion. A three-dimensional motion capture system using the one-pitch phase analysis (MCO) method can facilitate high precision measurement of moving objects in real-time in a non-contacting manner. In this study, the MCO method was applied to examine thoraco-abdominal (TA) wall motion for assessing pulmonary function. We recruited 48 male participants, and all underwent spirometry and chest wall motion measurement with the MCO method. A significant positive correlation was observed between the vital capacity (Spearman’s ρ = 0.68, p < 0.0001), forced vital capacity (Spearman’s ρ = 0.62, p < 0.0001), and tidal volume (Spearman’s ρ = 0.61, p < 0.0001) of spirometry and the counterpart parameters of MCO method. Moreover, the MCO method could detect regional rib cage and abdomen compartment contributions and could assess TA asynchrony, indicating almost complete synchronous movement (phase angle for each compartment: − 5.05° to 3.86°). These findings suggest that this technique could examine chest wall motion, and may be effective in analyzing chest wall volume changes and pulmonary function.

Partitioning the work of breathing during running and cycling using optoelectronic plethysmography

Work of breathing ([Formula: see text]) derived from a single lung volume and pleural pressure is limited and does not fully characterize the mechanical work done by the respiratory musculature. It has long been known that abdominal activation increases with increasing exercise intensity, yet the mechanical work done by these muscles is not reflected in [Formula: see text]. Using optoelectronic plethysmography (OEP), we sought to show first that the volumes obtained from OEP (V_CW) were comparable to volumes obtained from flow integration (V_t) during cycling and running, and second, to show that partitioned volume from OEP could be utilized to quantify the mechanical work done by the rib cage ([Formula: see text]_RC) and abdomen ([Formula: see text]_AB) during exercise. We fit 11 subjects (6 males/5 females) with reflective markers and balloon catheters. Subjects completed an incremental ramp cycling test to exhaustion and a series of submaximal running trials. We found good agreement between V_CW versus V_t during cycling (bias = 0.002; P > 0.05) and running (bias = 0.016; P > 0.05). From rest to maximal exercise,[Formula: see text]_AB increased by 84% (range: 30%-99%; [Formula: see text]_AB: 1 ± 1 J/min to 61 ± 52 J/min). The relative contribution of the abdomen increased from 17 ± 9% at rest to 26 ± 16% during maximal exercise. Our study highlights and provides a quantitative measure of the role of the abdominal muscles during exercise. Incorporating the work done by the abdomen allows for a greater understanding of the mechanical tasks required by the respiratory muscles and could provide further insight into how the respiratory system functions during disease and injury.NEW & NOTEWORTHY We demonstrated that optoelectronic plethysmography (OEP) is a reliable tool to determine ventilatory volume changes during cycling and running, without restricting natural upper arm movements. Second, using OEP volumes coupled with pressure-derived measures, we calculated the work done by the rib cage and abdomen, respectively, during exercise. Collectively, our findings indicate that pulmonary mechanics can be accurately quantified using OEP, and abdominal work performed during ventilation contributes substantially to the overall work of the respiratory musculature.

Randomized trial of lung hyperinflation therapy in children with congenital muscular dystrophy

OBJECTIVE

Respiratory compromise in congenital muscular dystrophy (CMD) occurs, in part, from chest wall contractures. Passive stretch with hyperinsufflation therapy could reduce related costo-vertebral joint contractures. We sought to examine the impact of hyperinsufflation use on lung function and quality of life in children with CMD.

STUDY DESIGN

We conducted a randomized controlled trial on hyperinsufflation therapy in children with CMD at two centers. An individualized hyperinsufflation regimen of 15 minutes twice daily using a cough assist device over a 12 months period was prescribed. We measured lung function, quality of life, and adherence. To demonstrate reproducibility, pulmonary function was measured twice on the same day. A mixed-effects regression model adjusting for confounders was used to assess the effects of hyperinsufflation.

RESULTS

We enrolled 34 participants in the study; 31 completed the trial (n = 17 treatment group and n = 14 controls). Participants in the treatment group demonstrated a relative gain in lung volume measured at 4 and 8 months, but not at 12 months. The control group required increases in the maximum insufflation pressures to achieve maximum lung volumes while the treatment group did not. Adherence was best early in the study, peaking at the first visit and decreasing at subsequent visits. Caregiver-reported quality of life was higher in the treatment group.

CONCLUSION

Hyperinsufflation therapy is effective in increasing and sustaining lung volume over time. Adherence, however, was inconsistent and difficult to maintain. Further research should determine if improved adherence leads to sustained benefits of hyperinsufflation.

RESPIRATORY AND SYMPTOMATIC IMPACT OF ASCITES RELIEF BY PARACENTESIS IN PATIENTS WITH HEPATIC CIRRHOSIS

BACKGROUND

Liver cirrhosis is a highly prevalent disease that, at an advanced stage, usually causes ascites and associated respiratory changes. However, there are few studies evaluating and quantifying the impact of ascites and its relief through paracentesis on lung function and symptoms such as fatigue and dyspnea in cirrhotic patients.

OBJECTIVE

To assess and quantify the impact of acute reduction of ascitic volume on respiratory parameters, fatigue and dyspnea symptoms in patients with hepatic cirrhosis, as well as to investigate possible correlations between these parameters.

METHODS

Thirty patients with hepatic cirrhosis and ascites who underwent the following pre and post paracentesis evaluations: vital signs, respiratory pattern, thoracoabdominal mobility (cirtometry), pulmonary function (ventilometry), degree of dyspnea (numerical scale) and fatigue level (visual analog scale).

RESULTS

There was a higher prevalence of patients classified as CHILD B and the mean MELD score was 14.73±5.75. The comparison of pre and post paracentesis parameters evidenced after paracentesis: increase of predominantly abdominal breathing pattern, improvement of ventilatory variables, increase of the differences obtained in axillary and abdominal cirtometry, reduction of dyspnea and fatigue level, blood pressure reduction and increased peripheral oxygen saturation. Positive correlations found: xiphoid with axillary cirtometry, degree of dyspnea with fatigue level, tidal volume with minute volume, Child "C" with higher MELD score, volume drained in paracentesis with higher MELD score and with Child "C". We also observed a negative correlation between tidal volume and respiratory rate.

CONCLUSION

Since ascites drainage in patients with liver cirrhosis improves pulmonary volumes and thoracic expansion as well as reduces symptoms such as fatigue and dyspnea, we can conclude that ascites have a negative respiratory and symptomatological impact in these patients.

Association between lung function, thoracoabdominal mobility and posture in cystic fibrosis: pilot study

Abstract Introduction: Deterioration of lung function is the main cause of mortality in cystic fibrosis (CF), so it is essential to study different related factors. Objective: To assess the association of pulmonary function with thoracoabdominal mobility and postural alignment in individuals with CF. Method: A cross-sectional study was performed in individuals with CF (8-17 years). Pulmonary function was assessed by spirometry. Thoracoabdominal mobility and postural alignment were evaluated by photogrammetry using the Postural Assessment Software (PAS/Sapo). Pearson correlation coefficient analysis was performed, and p < 0.05 was considered significant. Results: The following spirometric variables showed a decrease compared to predicted values: FEV1, FEV1/FVC, PEF and FEF25-75%. Postural assessment showed alterations in head horizontal alignment (HHA; 2.71 ± 2.23o), acromion horizontal alignment (AHA; 1.33 ± 1.35o), anterior superior iliac spine (ASIS) horizontal alignment (ASISHA; 1.11 ± 0.89o), angle between acromia and ASIS (AAASIS; 0.89 ± 0.39o), scapula horizontal asymmetry - T3 (SHAT3; 16.95 ± 12.03%), and asymmetry of the projection of the center of gravity within the base of support in the frontal (11.45 ± 8.10%) and sagittal (48.98 ± 18.55%) planes. A strong positive correlation was found between pulmonary function and thoracoabdominal mobility in the variables anteroposterior mobility of the upper chest (APMUC) and FVC (r = 0.818, p = 0.024), APMUC and FEV1 (r = 0.874, p = 0.010), and APMUC and FEF25-75% (r = 0.797, p = 0.032). A strong negative correlation was detected between FEV1/FVC and AHA (r = -0.761, p = 0.047). Conclusion: Our study showed in CF a reduction in pulmonary function, strong positive correlation between APMUC and pulmonary function, high prevalence of kyphoscoliosis and strong negative correlation between AHA and pulmonary function.

Chest wall volume and asynchrony in stroke and Parkinson's disease subjects: A case-control study

Background

The expansion of the rib cage and abdomen occurs in a synchronic way during a coordinated contraction of the diaphragm and the abdominal and intercostal muscles under normal conditions and healthy. The presence of restrictive respiratory disease may lead to uncoordinated action of the respiratory muscles which affects breathing pattern and chest wall volumes. The aim of this study was to evaluate chest wall volumes, chest wall asynchrony and inspiratory paradoxical movement of breathing, as well as the influence of the time of disease diagnosis in subjects with Parkinson’s disease and post-Stroke in comparison to healthy individuals.

Methods

Total and compartmental chest wall volumes, chest wall asynchrony and paradoxical movement were measured at rest in a seated position by Optoelectronic Plethysmography in 76 individuals (29 healthy individuals, 20 post-Stroke and 27 Parkinson’s disease subjects). Post-stroke and Parkinson’s disease subjects were also grouped according to the length of diagnosis.

Results

In both groups with restrictive respiratory disease we observed that pulmonary rib cage compartment (V_RCp) volume is reduced when compared to healthy subjects (p <0.05). This same pattern was observed when analyzing post-stroke subjects with more than three years of diagnosis and Parkinson’s subjects with less than three years of diagnosis (p<0.05). Furthermore, post-stroke subjects with inspiratory paradoxical movement showed decreased total and compartmental chest wall volumes (p<0.05), while individuals with Parkinson’s disease with inspiratory paradoxical movement only presented a decrease in pulmonary rib cage compartment volume (p<0.05).

Conclusion

Our study presents new findings for better understanding of chest wall volumes and chest wall asynchrony in post-stroke and Parkinson’s disease individuals. Half of the subjects with post-Stroke and Parkinson’s disease presented inspiratory paradox movement, but changes in breathing pattern was especially observed in post-stroke subjects with more than three years of diagnosis.

Thoracoabdominal asynchrony and paradoxical motion in middle stage amyotrophic lateral sclerosis

AIM

To assess thoracoabdominal asynchrony (TAA) and the presence of paradoxical motion in middle stage amyotrophic lateral sclerosis (ALS) and its relationships with chest wall tidal volume (V_T,CW), breathing pattern and cough peak flow (CPF).

METHODS

Phase angle (θ) between upper (RCp) and lower ribcage (RCa) and abdomen (AB), as well as percentage of inspiratory time for the lower ribcage (IP_RCa) and abdomen (IP_AB) moving in opposite directions were quantified using optoelectronic plethysmography in 12 ALS patients during quiet breathing and coughing. Paradoxical motion of the compartments was based on threshold values of θ and IP, obtained in twelve age and sex matched healthy persons.

RESULTS

During quiet breathing, significantly higher RCa and AB θ (p < .05), IP_RCa (p = 0.001) and IP_AB (p < 0.05) were observed in ALS patients as compared to controls. In ALS patients, correlations between RCa and AB θ with forced vital capacity (FVC) (r=-0.773, p < 0.01), vital capacity (r=-0.663, p < 0.05) and inspiratory capacity (IC) (r=-0.754, p < 0.01), as well as between RCp and RCa θ with FVC (r=-0.608, p < 0.05) and CPF (r=-0.601, p < 0.05) were found. During coughing, correlations between RCp and AB θ with CPF (r=-0.590, p < 0.05), IC (r=-0.748, p < 0.01) and V_T,CW (r=-0.608, p < 0.05), as well as between RCa and AB θ with CPF (r=-0.670, p < 0.05), IC (r=-0.713, p < 0.05) and peak expiratory flow (r=-0.727, p < 0.05) were also observed in ALS patients. ALS patients with paradoxical motion presented lower vital capacity and FVC_%pred (p < 0.05) compared to those without paradoxical motion.

CONCLUSIONS

Middle stage ALS patients exhibit TAA and paradoxical motion during quiet spontaneous breathing and coughing. In addition, diaphragmatic weakness (i.e. decrease in excursion of the RCa and AB compartments) was observed earlier in the lower ribcage rather than the abdominal compartment in this population.

Thoracoabdominal Asynchrony Contributes to Exercise Limitation in Mild Asthmatic Subjects

This study aimed to better understand how subjects with stable asthma and without exercise-induced bronchoconstriction respond to mild exercise. Breathing pattern, chest wall compartmental and operational volumes, and thoracoabdominal asynchrony were assessed in 11 stable asthmatic subjects and 10 healthy subjects at rest and during exercise in a cycle-ergometer through optoelectronic plethysmography. Dyspnea and sensation of leg effort were assessed through Borg scale. During exercise, with similar minute ventilation, a significant lower chest wall tidal volume (p = 0.003) as well as a higher respiratory rate (p < 0.05) and rapid shallow breathing (p < 0.05) were observed in asthmatic when compared to healthy subjects. Asthmatic subjects exhibited a significantly lower inspiratory (p < 0.05) and expiratory times (p < 0.05). Intergroup analysis found a significant higher end-expiratory chest wall volume in asthmatic subjects, mainly due to a significant increase in volume of the pulmonary ribcage (RCp; 170 ml, p = 0.002), indicating dynamic hyperinflation (DH). Dyspnea and sensation of leg effort were both significantly greater (p < 0.0001) in asthmatic when compared to healthy subjects. In addition to a higher thoracoabdominal asynchrony found between RCp and abdominal (AB) (p < 0.005) compartments in asthmatic subjects, post-inspiratory action of the inspiratory ribcage and diaphragm muscles were observed through the higher expiratory paradox time of both RCp (p < 0.0001) and AB (p = 0.0002), respectively. Our data suggest that a different breathing pattern is adopted by asthmatic subjects without exercise-induced bronchoconstriction during mild exercise and that this feature, associated with DH and thoracoabdominal asynchrony, contributes significantly to exercise limitation.

3D analysis of sexual dimorphism in size, shape and breathing kinematics of human lungs

Sexual dimorphism in the human respiratory system has been previously reported at the skeletal (cranial and thoracic) level, but also at the pulmonary level. Regarding lungs, foregoing studies have yielded sex-related differences in pulmonary size as well as lung shape details, but different methodological approaches have led to discrepant results on differences in respiratory patterns between males and females. The purpose of this study is to analyse sexual dimorphism in human lungs during forced respiration using 3D geometric morphometrics. Eighty computed tomographies (19 males and 21 females) were taken in maximal forced inspiration (FI) and expiration (FE), and 415 (semi)landmarks were digitized on 80 virtual lung models for the 3D quantification of pulmonary size, shape and kinematic differences. We found that males showed larger lungs than females (P < 0.05), and significantly greater size and shape differences between FI and FE. Morphologically, males have pyramidal lung geometry, with greater lower lung width when comparing with the apices, in contrast to the prismatic lung shape and similar widths at upper and lower lungs of females. Multivariate regression analyses confirmed the effect of sex on lung size (36.26%; P < 0.05) and on lung shape (7.23%; P < 0.05), and yielded two kinematic vectors with a small but statistically significant angle between them (13.22°; P < 0.05) that confirms sex-related differences in the respiratory patterns. Our 3D approach shows sexual dimorphism in human lungs likely due to a greater diaphragmatic action in males and a predominant intercostal muscle action in females during breathing. These size and shape differences would lead to different respiratory patterns between sexes, whose physiological implications need to be studied in future research.

Thoracoabdominal asynchrony: Two methods in healthy, COPD, and interstitial lung disease patients

Background

Thoracoabdominal asynchrony is the nonparallel motion of the ribcage and abdomen. It is estimated by using respiratory inductive plethysmography and, recently, using optoelectronic plethysmography; however the agreement of measurements between these 2 techniques is unknown. Therefore, the present study compared respiratory inductive plethysmography with optoelectronic plethysmography for measuring thoracoabdominal asynchrony to see if the measurements were similar or different.

Methods

27 individuals (9 healthy subjects, 9 patients with interstitial lung disease, and 9 with chronic obstructive pulmonary disease performed 2 cycle ergometer tests with respiratory inductive plethysmography or optoelectronic plethysmography in a random order. Thoracoabdominal asynchrony was evaluated at rest, and at 50% and 75% of maximal workload between the superior ribcage and abdomen using a phase angle.

Results

Thoracoabdominal asynchrony values were very similar in both approaches not only at rest but also with exercise, with no statistical difference. There was a good correlation between the methods and the Phase angle values were within the limits of agreement in the Bland-Altman analysis.

Conclusion

Thoracoabdominal asynchrony measured by optoelectronic plethysmography and respiratory inductive plethysmography results in similar values and has a satisfactory agreement at rest and even for different exercise intensities in these groups.

Comparison between the phase angle and phase shift parameters to assess thoracoabdominal asynchrony in COPD patients

Determining the presence of thoracoabdominal asynchrony in chronic obstructive pulmonary disease (COPD) patients is clinically relevant, but there is no consensus on the optimal parameters for performing this analysis. We assessed 22 COPD patients (FEV1 40 ± 10% predicted) and 13 healthy controls during rest and exercise with optoelectronic plethysmography (70% maximum workload) on a cycle ergometer. Thoracoabdominal asynchrony was calculated by using phase angle and phase shift parameters following a three-compartment model involving the upper and lower rib cages and abdomen. Patients were classified as having thoracoabdominal asynchrony (TAA+) or not (TAA−) based on control values (mean ± 2 SDs). The chest wall volume and compartmental contribution were also measured. Thoracoabdominal asynchrony was observed in the lower rib cage. The phase angle detected more TAA+ patients at rest (15 vs. 7 patients) and during exercise (14 vs. 8 patients) compared with the phase shift. TAA+ patients also presented a lower chest wall volume, lower rib cage contribution, and higher abdominal contribution to chest wall volume compared with the control and TAA− patients. Thoracoabdominal asynchrony was more detectable during rest and exercise using the phase angle parameter, and it was observed in the lower rib cage compartment, reducing the chest wall volume during exercise in patients with COPD.

NEW & NOTEWORTHY This study contributes to advance the knowledge over the previous lack of consensus on the assessment of thoracoabdominal asynchrony. We rigorously evaluated the related features that interfere in the measurement of the asynchrony (measurement tool, chest wall model and calculation parameter). Our results suggest that phase angle detects more suitably thoracoabdominal asynchrony that occurs on the lower ribcage and leads to a reduction in the chest wall volume during exercise in COPD patients.

Effects of posture on chest-wall configuration and motion during tidal breathing in normal men

[Purpose] The purpose of this study was to clarify the impact of postural changes during tidal breathing on the configuration and motion of chest-wall in order to further breathing motion evaluation. [Subjects and Methods] Chest-wall configuration and motion in the supine, right lateral, and sitting positions were measured using optoelectronic plethysmography in 15 healthy adult men. [Results] The anteroposterior diameters of the chest wall were significantly lower in the supine position for the pulmonary and abdominal rib cages, whereas the mediolateral diameters in the lateral position were lowest for the abdominal rib cage. Regarding chest-wall motion, both craniocaudal and anteroposterior motions of the anterior surface of the pulmonary and abdominal rib cages were significantly greater in the sitting position. Regarding motion of the left lateral abdominal rib cage, lateral motion was greatest in the lateral position. [Conclusion] Chest-wall configuration and motion changed according to posture in healthy men, particularly in the pulmonary and abdominal rib cages.

In Vivo 3D Analysis of Thoracic Kinematics: Changes in Size and Shape During Breathing and Their Implications for Respiratory Function in Recent Humans and Fossil Hominins

The human ribcage expands and contracts during respiration as a result of the interaction between the morphology of the ribs, the costo-vertebral articulations and respiratory muscles. Variations in these factors are said to produce differences in the kinematics of the upper thorax and the lower thorax, but the extent and nature of any such differences and their functional implications have not yet been quantified. Applying geometric morphometrics we measured 402 three-dimensional (3D) landmarks and semilandmarks of 3D models built from computed tomographic scans of thoraces of 20 healthy adult subjects in maximal forced inspiration (FI) and expiration (FE). We addressed the hypothesis that upper and lower parts of the ribcage differ in kinematics and compared different models of functional compartmentalization. During inspiration the thorax superior to the level of the sixth ribs undergoes antero-posterior expansion that differs significantly from the medio-lateral expansion characteristic of the thorax below this level. This supports previous suggestions for dividing the thorax into a pulmonary and diaphragmatic part. While both compartments differed significantly in mean size and shape during FE and FI the size changes in the lower compartment were significantly larger. Additionally, for the same degree of kinematic shape change, the pulmonary thorax changes less in size than the diaphragmatic thorax. Therefore, variations in the form and function of the diaphragmatic thorax will have a strong impact on respiratory function. This has important implications for interpreting differences in thorax shape in terms of respiratory functional differences within and among recent humans and fossil hominins. Anat Rec, 300:255-264, 2017. © 2016 Wiley Periodicals, Inc.

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.

Effects of a multidisciplinary body weight reduction program on static and dynamic thoraco-abdominal volumes in obese adolescents

The objective of this study was to characterize static and dynamic thoraco-abdominal volumes in obese adolescents and to test the effects of a 3-week multidisciplinary body weight reduction program (MBWRP), entailing an energy-restricted diet, psychological and nutritional counseling, aerobic physical activity, and respiratory muscle endurance training (RMET), on these parameters. Total chest wall (VCW), pulmonary rib cage (VRC,p), abdominal rib cage (VRC,a), and abdominal (VAB) volumes were measured on 11 male adolescents (Tanner stage: 3-5; BMI standard deviation score: >2; age: 15.9 ± 1.3 years; percent body fat: 38.4%) during rest, inspiratory capacity (IC) maneuver, and incremental exercise on a cycle ergometer at baseline and after 3 weeks of MBWRP. At baseline, the progressive increase in tidal volume was achieved by an increase in end-inspiratory VCW (p < 0.05) due to increases in VRC,p and VRC,a with constant VAB. End-expiratory VCW decreased with late increasing VRC,p, dynamically hyperinflating VRC,a (p < 0.05), and progressively decreasing VAB (p < 0.05). After MBWRP, weight loss was concentrated in the abdomen and total IC decreased. During exercise, abdominal rib cage hyperinflation was delayed and associated with 15% increased performance and reduced dyspnea at high workloads (p < 0.05) without ventilatory and metabolic changes. We conclude that otherwise healthy obese adolescents adopt a thoraco-abdominal operational pattern characterized by abdominal rib cage hyperinflation as a form of lung recruitment during incremental cycle exercise. Additionally, a short period of MBWRP including RMET is associated with improved exercise performance, lung and chest wall volume recruitment, unloading of respiratory muscles, and reduced dyspnea.

Influence of posture on the ventilatory pattern and the thoraco-abdominal kinematics of patients with chronic obstructive pulmonary disease (COPD)

OBJECTIVE

Evaluate the influence of posture on ventilatory pattern, compartmental distribution of volume of chest wall and thoraco-abdominal kinematics of patients with severe chronic obstructive pulmonary disease (COPD).

DESIGN

Cross-sectional study.

METHODS

Twelve, male patients with severe COPD (Forced Expiratory Volume in the first second (FEV1) = 24.35 ± 4.52%, Forced Vital Capacity% (FVC%) = 60 ± 13.39% and relationship FEV1/FVC = 53.42 ± 14.47). The distribution of the volume of the ribcage [pulmonary rib cage (Rcp), abdominal ribcage (Rca) and abdomen (Ab)] during quiet breathing in a sitting position without back support (SWB), sitting with backrest (SB) and supine position (SUP) was determined using an opto-electronic plethysmograph.

RESULTS

The following differences were observed: a greater tidal volume in the SWB position when compared to the SB position (p = 0.01); greater expiratory time in the SUP position in relation to the SWB (p = 0.03) and SB (p = 0.01); and increased abdominal contribution to the tidal volume in the SUP position in relation to the SWB (p < 0.01) and SB (p < 0.001). No difference was found in the thoraco-abdominal synchrony among the positions.

CONCLUSION

Sitting position without back support enhances the activation of respiratory muscles by increasing the tidal volume and supine position seems to favor lung deflation by increasing the expiratory time. It seems appropriate to adopt these positions to optimize the ventilation/perfusion relationship and physiotherapeutic intervention in different clinical conditions.

Differential growth and development of the upper and lower human thorax

The difficulties in quantifying the 3D form and spatial relationships of the skeletal components of the ribcage present a barrier to studies of the growth of the thoracic skeleton. Thus, most studies to date have relied on traditional measurements such as distances and indices from single or few ribs. It is currently known that adult-like thoracic shape is achieved early, by the end of the second postnatal year, with the circular cross-section of the newborn thorax transforming into the ovoid shape of adults; and that the ribs become inclined such that their anterior borders come to lie inferior to their posterior. Here we present a study that revisits growth changes using geometric morphometrics applied to extensive landmark data taken from the ribcage. We digitized 402 (semi) landmarks on 3D reconstructions to assess growth changes in 27 computed tomography-scanned modern humans representing newborns to adults of both sexes. Our analyses show a curved ontogenetic trajectory, resulting from different ontogenetic growth allometries of upper and lower thoracic units. Adult thoracic morphology is achieved later than predicted, by diverse modifications in different anatomical regions during different ontogenetic stages. Besides a marked increase in antero-posterior dimensions, there is an increase in medio-lateral dimensions of the upper thorax, relative to the lower thorax. This transforms the pyramidal infant thorax into the barrel-shaped one of adults. Rib descent is produced by complex changes in 3D curvature. Developmental differences between upper and lower thoracic regions relate to differential timings and rates of maturation of the respiratory and digestive systems, the spine and the locomotor system. Our findings are relevant to understanding how changes in the relative rates of growth of these systems and structures impacted on the development and evolution of modern human body shape.

The effect of posture on asynchronous chest wall movement in COPD

Chronic obstructive pulmonary disease (COPD) patients often show asynchronous movement of the lower rib cage during spontaneous quiet breathing and exercise. We speculated that varying body position from seated to supine would influence rib cage asynchrony by changing the configuration of the respiratory muscles. Twenty-three severe COPD patients (forced expiratory volume in 1 s = 32.5 ± 7.0% predicted) and 12 healthy age-matched controls were studied. Measurements of the phase shift between upper and lower rib cage and between upper rib cage and abdomen were performed with opto-electronic plethysmography during quiet breathing in the seated and supine position. Changes in diaphragm zone of apposition were measured by ultrasounds. Control subjects showed no compartmental asynchronous movement, whether seated or supine. In 13 COPD patients, rib cage asynchrony was noticed in the seated posture. This asynchrony disappeared in the supine posture. In COPD, upper rib cage and abdomen were synchronous when seated, but a strong asynchrony was found in supine. The relationships between changes in diaphragm zone of apposition and volume variations of chest wall compartments supported these findings. Rib cage paradox was noticed in approximately one-half of the COPD patients while seated, but was not related to impaired diaphragm motion. In the supine posture, the rib cage paradox disappeared, suggesting that, in this posture, diaphragm mechanics improves. In conclusion, changing body position induces important differences in the chest wall behavior in COPD patients.

Dynamics of chest wall volume regulation during constant work rate exercise in patients with chronic obstructive pulmonary disease

This study evaluated the dynamic behavior of total and compartmental chest wall volumes [(V CW) = rib cage (V RC) + abdomen (V AB)] as measured breath-by-breath by optoelectronic plethysmography during constant-load exercise in patients with stable chronic obstructive pulmonary disease. Thirty males (GOLD stages II-III) underwent a cardiopulmonary exercise test to the limit of tolerance (Tlim) at 75% of peak work rate on an electronically braked cycle ergometer. Exercise-induced dynamic hyperinflation was considered to be present when end-expiratory (EE) V CW increased in relation to resting values. There was a noticeable heterogeneity in the patterns of V CW regulation as EEV CW increased non-linearly in 17/30 "hyperinflators" and decreased in 13/30 "non-hyperinflators" (P < 0.05). EEV AB decreased slightly in 8 of the "hyperinflators", thereby reducing and slowing the rate of increase in end-inspiratory (EI) V CW (P < 0.05). In contrast, decreases in EEV CW in the "non-hyperinflators" were due to the combination of stable EEV RC with marked reductions in EEV AB. These patients showed lower EIV CW and end-exercise dyspnea scores but longer Tlim than their counterparts (P < 0.05). Dyspnea increased and Tlim decreased non-linearly with a faster rate of increase in EIV CW regardless of the presence or absence of dynamic hyperinflation (P < 0.001). However, no significant between-group differences were observed in metabolic, pulmonary gas exchange and cardiovascular responses to exercise. Chest wall volumes are continuously regulated during exercise in order to postpone (or even avoid) their migration to higher operating volumes in patients with COPD, a dynamic process that is strongly dependent on the behavior of the abdominal compartment.

Effects of the Nuss procedure on chest wall kinematics in adolescents with pectus excavatum

No data are available on the effects of the Nuss procedure on volumes of chest wall compartments (the upper rib cage, lower rib cage and abdomen) in adolescents with pectus excavatum. We used optoelectronic plethysmography to provide a quantitative description of chest wall kinematics before and 6 months after the Nuss procedure at rest and during maximal voluntary ventilation in 13 subjects with pectus excavatum. An average 11% increase in chest wall volume was accommodated within the upper rib cage (p=0.0001) and to a lesser extent within the abdomen and lower rib cage. Tidal volumes did not significantly change during the study. The repair effect on chest wall kinematics did not correlate with the Haller index of deformity at baseline. Six months of the Nuss procedure do increase chest wall volume without affecting chest wall displacement and rib cage configuration.

Rib stress fractures among rowers: definition, epidemiology, mechanisms, risk factors and effectiveness of injury prevention strategies

Rib stress fractures (RSFs) can have serious effects on rowing training and performance and accordingly represent an important topic for sports medicine practitioners. Therefore, the aim of this review is to outline the definition, epidemiology, mechanisms, intrinsic and extrinsic risk factors, injury management and injury prevention strategies for RSF in rowers. To this end, nine relevant books, 140 journal articles, the proceedings of five conferences and two unpublished presentations were reviewed after searches of electronic databases using the keywords 'rowing', 'rib', 'stress fracture', 'injury', 'mechanics' and 'kinetics'. The review showed that RSF is an incomplete fracture occurring from an imbalance between the rate of bone resorption and the rate of bone formation. RSF occurs in 8.1-16.4% of elite rowers, 2% of university rowers and 1% of junior elite rowers. Approximately 86% of rowing RSF cases with known locations occur in ribs four to eight, mostly along the anterolateral/lateral rib cage. Elite rowers are more likely to experience RSF than nonelite rowers. Injury occurrence is equal among sweep rowers and scullers, but the regional location of the injury differs. The mechanism of injury is multifactorial with numerous intrinsic and extrinsic risk factors contributing. Posterior-directed resultant forces arising from the forward directed force vector through the arms to the oar handle in combination with the force vector induced by the scapula retractors during mid-drive, or repetitive stress from the external obliques and rectus abdominis in the 'finish' position, may be responsible for RSF. Joint hypomobility, vertebral malalignment or low bone mineral density may be associated with RSF. Case studies have shown increased risk associated with amenorrhoea, low bone density or poor technique, in combination with increases in training volume. Training volume alone may have less effect on injury than other factors. Large differences in seat and handle velocity, sequential movement patterns, higher elbow-flexion to knee-extension strength ratios, higher seat-to-handle velocity during the initial drive, or higher shoulder angle excursion may result in RSF. Gearing may indirectly affect rib loading. Increased risk may be due to low calcium, low vitamin D, eating disorders, low testosterone or use of depot medroxyprogesterone injections. Injury management involves 1-2 weeks cessation of rowing with analgesic modalities followed by a slow return to rowing with low-impact intensity and modified pain-free training. Some evidence shows injury prevention strategies should focus on strengthening the serratus anterior, strengthening leg extensors, stretching the lumbar spine, increasing hip joint flexibility, reducing excessive protraction, training with ergometers on slides or floating-head ergometers, and calcium and vitamin D supplementation. Future research should focus on the epidemiology of RSF over 4-year Olympic cycles in elite rowers, the aetiology of the condition, and the effectiveness of RSF prevention strategies for injury incidence and performance in rowing.

Chest wall kinematics in young subjects with Pectus excavatum

Quantifying chest wall kinematics and rib cage distortion during ventilatory effort in subjects with Pectus excavatum (PE) has yet to be defined. We studied 24 patients: 19 during maximal voluntary ventilation (MVV) and 5 during MVV and cycling exercise (CE). By optoelectronic plethysmography (OEP) we assessed operational volumes in upper rib cage, lower rib cage and abdomen. Ten age-matched healthy subjects served as controls. Patients exhibited mild restrictive lung defect. During MVV end-inspiratory and end-expiratory volumes of chest wall compartments increased progressively in controls, whereas most patients avoided dynamic hyperinflation by setting operational volumes at values lower than controls. Mild rib cage distortion was found in three patients at rest, but neither in patients nor in controls did MVV or CE consistently affect coordinated motion of the rib cage. Rib cage displacement was not correlated with a CT-scan severity index. Conclusions, mild rib cage distortion rarely occurs in PE patients with mild restrictive defect. OEP contributes to clinical evaluation of PE patients.

Effect of helium breathing on intercostal and quadriceps muscle blood flow during exercise in COPD patients

Emerging evidence indicates that, besides dyspnea relief, an improvement in locomotor muscle oxygen delivery may also contribute to enhanced exercise tolerance following normoxic heliox (replacement of inspired nitrogen by helium) administration in patients with chronic obstructive pulmonary disease (COPD). Whether blood flow redistribution from intercostal to locomotor muscles contributes to this improvement currently remains unknown. Accordingly, the objective of this study was to investigate whether such redistribution plays a role in improving locomotor muscle oxygen delivery while breathing heliox at near-maximal [75% peak work rate (WR(peak))], maximal (100%WR(peak)), and supramaximal (115%WR(peak)) exercise in COPD. Intercostal and vastus lateralis muscle perfusion was measured in 10 COPD patients (FEV(1) = 50.5 ± 5.5% predicted) by near-infrared spectroscopy using indocyanine green dye. Patients undertook exercise tests at 75 and 100%WR(peak) breathing either air or heliox and at 115%WR(peak) breathing heliox only. Patients did not exhibit exercise-induced hyperinflation. Normoxic heliox reduced respiratory muscle work and relieved dyspnea across all exercise intensities. During near-maximal exercise, quadriceps and intercostal muscle blood flows were greater, while breathing normoxic heliox compared with air (35.8 ± 7.0 vs. 29.0 ± 6.5 and 6.0 ± 1.3 vs. 4.9 ± 1.2 ml·min(-1)·100 g(-1), respectively; P < 0.05; mean ± SE). In addition, compared with air, normoxic heliox administration increased arterial oxygen content, as well as oxygen delivery to quadriceps and intercostal muscles (from 47 ± 9 to 60 ± 12, and from 8 ± 1 to 13 ± 3 mlO(2)·min(-1)·100 g(-1), respectively; P < 0.05). In contrast, normoxic heliox had neither an effect on systemic nor an effect on quadriceps or intercostal muscle blood flow and oxygen delivery during maximal or supramaximal exercise. Since intercostal muscle blood flow did not decrease by normoxic heliox administration, blood flow redistribution from intercostal to locomotor muscles does not represent a likely mechanism of improvement in locomotor muscle oxygen delivery. Our findings might not be applicable to patients who hyperinflate during exercise.

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.

The evolutionary origin of the mammalian diaphragm

The comparatively low compliance of the mammalian lung results in an evolutionary dilemma: the origin and evolution of this bronchoalveolar lung into a high-performance gas-exchange organ results in a high work of breathing that cannot be achieved without the coupled evolution of a muscular diaphragm. However, despite over 400 years of research into respiratory biology, the origin of this exclusively mammalian structure remains elusive. Here we examine the basic structure of the body wall muscles in vertebrates and discuss the mechanics of costal breathing and functional significance of accessory breathing muscles in non-mammalian amniotes. We then critically examine the mammalian diaphragm and compare hypotheses on its ontogenetic and phylogenetic origin. A closer look at the structure and function across various mammalian groups reveals the evolutionary significance of collateral functions of the diaphragm as a visceral organizer and its role in producing high intra-abdominal pressure.

Optoelectronic Plethysmography has Improved our Knowledge of Respiratory Physiology and Pathophysiology

It is well known that the methods actually used to track thoraco-abdominal volume displacement have several limitations. This review evaluates the clinical usefulness of measuring chest wall kinematics by optoelectronic plethysmography [OEP]. OEP provides direct measurements (both absolute and its variations) of the volume of the chest wall and its compartments, according to the model of Ward and Macklem, without requiring calibration or subject cooperation. The system is non invasive and does not require a mouthpiece or nose-clip which may modify the pattern of breathing, making the subject aware of his breathing. Also, the precise assessment of compartmental changes in chest wall volumes, combined with pressure measurements, provides a detailed description of the action and control of the different respiratory muscle groups and assessment of chest wall dynamics in a number of physiological and clinical experimental conditions.

Effect of effort pain after upper abdominal surgery on two independent measures of respiratory function

STUDY OBJECTIVE

To determine how effort pain interacts with changing pulmonary function after upper abdominal incisions.

DESIGN

Prospective, case-controlled study.

SETTING

Academic teaching hospital.

PATIENTS

34 ASA physical status I, II, and III patients recovering from elective, major incisional, upper abdominal surgery.

MEASUREMENTS

Manometry (maximal inspiratory and expiratory pressure) and spirometry (forced vital capacity, forced expiratory volume during the first second, peak expiratory flow) for three postoperative days. Pain scores (Visual Analog Pain Scale; VAS) at rest and after the manometric or spirometric efforts.

MAIN RESULTS

Effort pain during either manometry or spirometry was greater than pain at rest on the first postoperative day. Maximal respiratory pressure concomitantly recovered with pain during daily efforts (slopes: -0.429 and -0.278% max/mm VAS; P < 0.05). Spirometric measurements showed minimal improvement.

CONCLUSION

The direct relationship between resolution of pain with effort and direct measures of respiratory muscle effort using manometry, but not those obtained less directly by spirometry, suggests that assessing interactions between pain and effort requires a direct, quantifiable measure of effort.

Chest wall kinematics during cough in healthy subjects

AIM

The study of kinematics of the chest wall (CW) could allow us to define the relative deflationary contribution of its compartments during fits of coughing. We hypothesized that if forces applied to the lung apposed rib cage are not commensurate with those applied to the abdomen-apposed rib cage, cough could result in rib cage distortion.

METHODS

In 12 (five women) healthy subjects we evaluated the volumes of CW (Vcw) and its compartments: the lung apposed rib cage, the abdomen apposed rib cage and the abdomen, by optoelectronic plethysmography. The loop of volume of the lung apposed rib cage/volume of the abdomen apposed rib cage allowed the calculation of mean rib cage distortion, resulting in a dimensionless number which, when multiplied by 100, gives percentage distortion. Each subject performed voluntary single and prolonged coughing efforts at functional residual capacity (FRC) and after maximal inspiration (max). The normal level of mean distortion was set at <0.5%.

RESULTS

The three compartments contributed to reducing end-expiratory Vcw during cough at FRC and prolonged maximum cough, with the latter resulting in the greatest CW deflation. Mean rib cage distortion did not differ between men and women (P > 0.1), but tended to significantly increase from single to prolonged Cough Max (1.3% +/- 1.0 vs. 2.3% +/- 1.6, respectively; P = 0.06).

CONCLUSION

Rib cage distortion may ensue during coughing, probably as a result of uneven distribution of forces applied to the rib cage.

An Alternative Approach to the Monitoring of Respiration by Dynamic Air-Pressure Sensor

Monitoring and assessing of patient respiratory function during conscious sedation are important because many drugs used for conscious sedation produce respiratory depression and subsequent hypoventilation. The purpose of this study is to assess the value of a dynamic air-pressure sensor for respiratory monitoring of clothed patients. Eight clothed adult volunteers were reclined on a dental chair positioned horizontally. The air bag for measuring air-pressure signals corresponding to respiration was placed on the seat back of the dental chair in the central lumbar area of the subject. The subject breathed through a face mask with a respirometer attached for measuring expiratory tidal volume. The air-pressure signals corresponding to respiration were obtained and the time integration values for air pressure during each expiration (integral P(exp)) were calculated. The expiratory tidal volume (TV(exp)) was measured simultaneously by respirometer. The relationship between TV(exp) and integral P(exp) for each subject was assessed by a Pearson correlation coefficient. A strong correlation between TV(exp) and integral P(exp) was observed in all subjects. Measuring integral P(exp) by dynamic air-pressure sensor makes it possible to estimate respiratory volume breath by breath, and the respiratory pressure-time integral waveform was useful in visually monitoring the respiration pattern. We believe that in the future this device will be used to monitor respiratory physiology in clothed patients, contributing to safer sedative procedures.

Chest wall motion after thixotropy conditioning of inspiratory muscles in healthy humans

Inspiratory muscle conditioning at a lower or higher lung volume based on the principles of muscle thixotropy causes acute changes in end-expiratory chest wall and lung volumes. The present study aimed to demonstrate the time course of effects of this conditioning on both end-expiratory chest wall volume and thoracoabdominal synchrony. We measured chest wall motion with respiratory induction plethysmography at 0.5, 1, 2, 3, and 6 min after conditioning at three different lung volumes in 15 healthy men. After conditioning at total lung capacity - 20% inspiratory capacity, increases in end-expiratory chest wall volume were significant at 0.5, 1, and 2 min (P < 0.05), being most obvious at 0.5 min (Delta 0.24 +/- 0.20 liter). After conditioning at residual volume, reductions in end-expiratory chest wall volume were significant at any time point (P < 0.05), being most obvious at 0.5 min (Delta 0.16 +/- 0.08 liter). Conditioning at functional residual capacity had little effect on the volume. Spirometric inspiratory capacity at 6 min after conditioning at residual volume (2.68 +/- 0.35 liter) was higher than the baseline value (2.53 +/- 0.31 liter, P < 0.05). Reductions in the phase angle, quantified by the Konno-Mead diagram, occurred after conditioning at residual volume at any time point (P < 0.05), being most obvious at 2 min (Delta 3.47 +/- 3.02 degrees). In conclusion, there is a 6-min time course of changes in end-expiratory chest wall volume after conditioning. More synchronous motion between the rib cage and abdomen occurs after conditioning at residual volume.

Chest wall mechanics during pressure support ventilation

Introduction

During pressure support ventilation (PSV) a part of the breathing pattern is controlled by the patient, and synchronization of respiratory muscle action and the resulting chest wall kinematics is a valid indicator of the patient's adaptation to the ventilator. The aim of the present study was to analyze the effects of different PSV settings on ventilatory pattern, total and compartmental chest wall kinematics and dynamics, muscle pressures and work of breathing in patients with acute lung injury.

Method

In nine patients four different levels of PSV (5, 10, 15 and 25 cmH₂O) were randomly applied with the same level of positive end-expiratory pressure (10 cmH₂O). Flow, airway opening, and oesophageal and gastric pressures were measured, and volume variations for the entire chest wall, the ribcage and abdominal compartments were recorded by opto-electronic plethysmography. The pressure and the work generated by the diaphragm, rib cage and abdominal muscles were determined using dynamic pressure-volume loops in the various phases of each respiratory cycle: pre-triggering, post-triggering with the patient's effort combining with the action of the ventilator, pressurization and expiration. The complete breathing pattern was measured and correlated with chest wall kinematics and dynamics.

Results

At the various levels of pressure support applied, minute ventilation was constant, with large variations in breathing frequency/ tidal volume ratio. At pressure support levels below 15 cmH₂O the following increased: the pressure developed by the inspiratory muscles, the contribution of the rib cage compartment to the total tidal volume, the phase shift between rib cage and abdominal compartments, the post-inspiratory action of the inspiratory rib cage muscles, and the expiratory muscle activity.

Conclusion

During PSV, the ventilatory pattern is very different at different levels of pressure support; in patients with acute lung injury pressure support greater than 10 cmH₂O permits homogeneous recruitment of respiratory muscles, with resulting synchronous thoraco-abdominal expansion.

Noninvasive monitoring of chest wall movement in infants using laser

Traditionally, non-invasive monitoring of tidal volume in infants has been performed using impedance plethysmography analyzed using a one or two compartment model. We developed a new laser system for use in infants, which measures antero-posterior movement of the chest wall during quiet sleep. In 24 unsedated or sedated infants (11 healthy, 13 with respiratory disease), we examined whether the analysis of thoracoabdominal movement based on a three compartment model could more accurately estimate tidal volume in comparison to V(T) measured at the mouth. Using five laser signals, chest wall movements were measured at the right and left, upper and lower ribcage and the abdomen. Within the tidal volume range from 4.6 to 135.7 ml, a three compartment model showed good short term repeatability and the best agreement with tidal volume measured at mouth (r(2) = 0.86) compared to that of a single compartment model (r(2) = 0.62, P < 0.0001) and a two compartment model (r(2) = 0.82, P < 0.01), particularly in the presence of respiratory disease. Three compartment modeling of a 5 laser thoracoabdominal monitoring permits more accurate estimates of tidal volume in infants and potentially of regional differences of chest wall displacement in future studies.