Chest wall motion during epidural anesthesia in dogs

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

Chest wall motion during tidal breathing

De Groote, A., M. Wantier, G. Cheron, M. Estenne, and M. Paiva. Chest wall motion during tidal breathing. J. Appl. Physiol. 83(5): 1531-1537, 1997.We have used an automaticmotion analyzer, the ELITE system, to study changes inchest wall configuration during resting breathing in five normal,seated subjects. Two television cameras were used to record thex-y-z displacements of 36 markers positioned circumferentiallyat the level of the third (S₁) and fifth(S₂) costal cartilage, corresponding to the lung-apposedrib cage; midway between the xyphoid process and thecostal margin (S₃), corresponding to the abdomen-apposedrib cage; and at the level of the umbilicus (S₄).Recordings of different subsets of markers were made by submitting thesubject to five successive rotations of 45-90°. Each recordinglasted 30 s, and three-dimensional displacements of markers wereanalyzed with the Matlab software. At spontaneous end expiration,sections S_1-3 were elliptical but S₄ wasmore circular. Tidal changes in chest wall dimensions were consistentamong subjects. For S_1-2, changes during inspirationoccurred primarily in the cranial and ventral directions and averaged3-5 mm; displacements in the lateral direction were smaller(1-2 mm). On the other hand, changes at the level ofS₄ occurred almost exclusively in the ventral direction. Inaddition, both compartments showed a ventral displacement of theirdorsal aspect that was not accounted for by flexion of the spine. Weconclude that, in normal subjects breathing at rest in the seatedposture, displacements of the rib cage during inspiration are in thecranial, lateral outward, and ventral directions but that expansion ofthe abdomen is confined to the ventral direction.

     

Chest wall motion during spontaneous breathing and mechanical ventilation in dogs

We measured the volume change of the thoracic cavity (delta Vth) and the volumes displaced by the diaphragm (delta Vdi) and rib cage (delta Vrc) in six pentobarbital-anesthetized dogs lying supine. A high-speed X-ray scanner (dynamic spatial reconstructor) provided three-dimensional images of the thorax during spontaneous breathing and during mechanical ventilation with paralysis. Tidal volume (VT) was measured by integrating gas flow. Changes in thoracic liquid volume (delta Vliq, presumably caused by changes in thoracic blood volume) were calculated as delta Vth - VT. Absolute volume displaced by the rib cage was not significantly different during the two modes of ventilation. During spontaneous breathing, thoracic blood volume increased during inspiration; delta Vliq was 12.3 +/- 4.1% of delta Vth. During mechanical ventilation, delta Vliq was nearly zero. Configuration of the relaxed chest wall was similar during muscular relaxation induced by either pharmacological paralysis or hyperventilation. Expiratory muscle activity produced 50 +/- 11% of the delta Vth during spontaneous breathing. We conclude that at constant VT the volume displaced by the rib cage is remarkably similar during the transition from spontaneous breathing to mechanical ventilation, while both diaphragmatic volume displacement and changes in intrathoracic blood volume decrease by a similar amount.     

Chest wall motion and expiratory muscle use during phonation in normal humans

The pattern of rib cage (RC) and abdomen (AB) motion and the electromyograms of the triangularis sterni (TS) and abdominal external oblique (EO) muscles were studied during speech and reading in six normal uninformed subjects in the sitting posture. Most phrases were started from within the tidal breathing range and extended below RC and AB spontaneous end-expiratory volumes. On the average, 75% of the change in chest wall volume occurred below the resting end-expiratory level. The expired volume resulted from a large predominance of RC displacement, and this was accompanied by marked recruitment of the TS. The EO was also generally activated, but the pattern of activation was less consistent. We conclude that 1) speech occurs primarily below the spontaneous end-expiratory level; 2) most of the volume change is caused by active emptying of the RC produced, at least in part, by contraction of the TS; 3) concomitant activation of the abdominal muscles serves to optimize the inspiratory function of the diaphragm, which has to contract rapidly between phrases to refill the respiratory system.     

Chest wall distortion during resistive inspiratory loading

We studied six (1 naive and 5 experienced) subjects breathing with added inspiratory resistive loads while we recorded chest wall motion (anteroposterior rib cage, anteroposterior abdomen, and lateral rib cage) and tidal volumes. In the five experienced subjects, transdiaphragmatic and pleural pressures, and electromyographs of the sternocleidomastoid and abdominal muscles were also measured. Subjects inspired against the resistor spontaneously and then with specific instructions to reach a target pleural or transdiaphragmatic pressure or to maximize selected electromyographic activities. Depending on the instructions, a wide variety of patterns of inspiratory motion resulted. Although the forces leading to a more elliptical or circular configuration of the chest wall can be identified, it is difficult to analyze or predict the configurational results based on insertional and pressure-related contributions of a few individual respiratory muscles. Although overall chest wall respiratory motion cannot be readily inferred from the electromyographic and pressure data we recorded, it is clear that responses to loading can vary substantially within and between individuals. Undoubtedly, the underlying mechanism for the distortional changes with loading are complex and perhaps many are behavioral rather than automatic and/or compensatory.     

Chest wall mechanics during artificial ventilation.

Chest wall mechanics were studied in six healthy volunteers before and during anesthesia prior to surgery. The intratracheal, esophageal, and intragastric pressures were measured concurrently. Gas flow was measured by pneumotachography and gas volume was obtained from it by electrical integration. Rib cage and abdomen movements were registered with magnetometers, these being calibrated by "isovolume" maneuvers. During spontaneous breathing in the conscious state, rib cage volume displacement corresponded to 40% of the tidal volume. During anesthesia and artificial ventilation, this rose to 72% of the tidal volume. The relative contributions of rib cage and abdomen displacements were not influenced by a change in tidal volume. Compliance was higher with a larger tidal volume, a finding which could be due to a curved pressure-volume relationship of the overall chest wall.     

Chest wall and lung volume estimation by optical reflectance motion analysis

Cala, S. J., C. M. Kenyon, G. Ferrigno, P. Carnevali, A. Aliverti, A. Pedotti, P. T. Macklem, and D. F. Rochester. Chest wall and lung volume estimation by optical reflectance motion analysis.J. Appl. Physiol. 81(6):2680-2689, 1996.Estimation of chest wall motion by surfacemeasurements only allows one-dimensional measurements of the chestwall. We have assessed an optical reflectance system (OR), which tracksreflective markers in three dimensions (3-D) for respiratory use. Weused 86 (6-mm-diameter) hemispherical reflective markers arrangedcircumferentially on the chest wall in seven rows between the sternalnotch and the anterior superior iliac crest in two normal standingsubjects. We calculated the volume of the entire chest wall andcompared inspired and expired volumes with volumesobtained by spirometry. Marker positions were recorded by four TVcameras; two were 4 m in front of and two were 4 m behind the subject.The TV signals were sampled at 100 Hz and combined with gridcalibration parameters on a personal computer to obtain the 3-Dcoordinates of the markers. Chest wall surfaces were reconstructed bytriangulation through the point data, and chest wall volume wascalculated. During tidal breathing and vital capacity maneuvers andduring CO₂-stimulated hyperpnea, there was a very close correlation of the lung volumes(VL) estimated by spirometry[VL(SP)] and OR[VL(OR)]. Regressionequations of VL(OR)(y) vs.VL(SP)(x,BTPS in liters) for the two subjects were given by y = 1.01x  0.01 (r = 0.996) andy = 0.96x + 0.03 (r = 0.997), and byy = 1.04x + 0.25 (r = 0.97) andy = 0.98x + 0.14 (r = 0.95) for the two maneuvers,respectively. We conclude spirometric volumes can be estimated veryaccurately and directly from chest wall surface markers, and wespeculate that OR may be usefully applied to calculations of chest wallshape, regional volumes, and motion analysis.

     

Chest wall and trunk muscle activity during inspiratory loading.

We measured the electromyographic (EMG) activity in four chest wall and trunk (CWT) muscles, the erector spinae, latissimus dorsi, pectoralis major, and trapezius, together with the parasternal, in four normal subjects during graded inspiratory efforts against an occlusion in both upright and seated postures. We also measured CWT EMGs in six seated subjects during inspiratory resistive loading at high and low tidal volumes [1,280 +/- 80 (SE) and 920 +/- 60 ml, respectively]. With one exception, CWT EMG increased as a function of inspiratory pressure generated (Pmus) at all lung volumes in both postures, with no systematic difference in recruitment between CWT and parasternal muscles as a function of Pmus. At any given lung volume there was no consistent difference in CWT EMG at a given Pmus between the two postures (P > 0.09). However, at a given Pmus during both graded inspiratory efforts and inspiratory resistive loading, EMGs of all muscles increased with lung volume, with greater volume dependence in the upright posture (P < 0.02). The results suggest that during inspiratory efforts, CWT muscles contribute to the generation of inspiratory pressure. The CWT muscles may act as fixators opposing deflationary forces transmitted to the vertebral column by rib cage articulations, a function that may be less effective at high lung volumes if the direction of the muscular insertions is altered disadvantageously.     

两种椎管内麻醉剖宫产术后PCEA镇痛效果比较

目的比较两种不同麻醉方式剖宫产术后应用PCEA的影响。方法选择拟行剖宫产产妇80例,ASAⅠ～Ⅱ级,随机分为腰麻组40例,硬膜外麻醉组40例,两组均输入羟乙基淀粉130/0.4氯化钠溶液10ml/kg(共同负荷),分别采用腰麻、硬膜外麻醉两种麻醉方式行剖宫产,两组产妇术后均连接相同配方PCEA,并观察术后镇痛效果,恶心呕吐、瘙痒、腰痛等不良反应;观察下肢运动神经阻滞情况、下床时间、肠排气时间、开始泌乳时间等术后恢复情况。观察时间点为术后2、4、8、12、24、48、72h。结果两组术后应用PCEA比较,腰麻组静息VAS疼痛评分T1时点腰麻组高于硬膜外麻醉组(P<0.05),T2、T3时点腰麻组低于硬膜外麻醉组(P<0.05);活动VAS评分T1时点腰麻组高于硬膜外麻醉组,T2、T3、T4时点腰麻组低于硬膜外麻醉组(P<0.05);腰麻组较硬膜外麻醉组产妇的肠排气时间和泌乳时间短(P<0.05),瘙痒发生率高(P<0.05),腰痛发生率低。结论在剖宫产手术中,相对硬膜外麻醉而言,腰麻能使PCEA产生更好的镇痛效果,术后产妇运动功能恢复快,无其它严重不良反应,且利于肠蠕动功能恢复和泌乳。     

Chest wall mechanics in sustained microgravity

We assessed theeffects of sustained weightlessness on chest wall mechanics in fiveastronauts who were studied before, during, and after the 10-daySpacelab D-2 mission (n = 3)and the 180-day Euromir-95 mission (n = 2). We measured flow and pressure at the mouth and rib cage andabdominal volumes during resting breathing and during a relaxationmaneuver from midinspiratory capacity to functional residual capacity.Microgravity produced marked and consistent changes () in thecontribution of the abdomen to tidal volume [Vab/(Vab + Vrc), where Vab is abdominal volume and Vrc is rib cagevolume], which increased from 30.7 ± 3.5 (SE)% at1 G head-to-foot acceleration to 58.3 ± 5.7% at 0 G head-to-foot acceleration (P < 0.005). Values ofVab/(Vab + Vrc) did not change significantly during the 180 days of the Euromir mission, but in the two subjects Vab/(Vab + Vrc) was greater on postflight day1 than on subsequent postflight days or preflight. Inthe two subjects who produced satisfactory relaxation maneuvers, the slope of the Konno-Mead plot decreased in microgravity; this decrease was entirely accounted for by an increase in abdominal compliance because rib cage compliance did not change. These alterations aresimilar to those previously reported during short periods ofweightlessness inside aircrafts flying parabolic trajectories. They arealso qualitatively similar to those observed on going from upright tosupine posture; however, in contrast to microgravity, such posturalchange reduces rib cage compliance.

     

Association of chest wall motion and tidal volume responses during CO2 rebreathing

Yan, Sheng, Pawel Sliwinski, and Peter T. Macklem.Association of chest wall motion and tidal volume responses during CO₂ rebreathing.J. Appl. Physiol. 81(4):1528-1534, 1996.The purpose of this study is to investigate theeffect of chest wall configuration at end expiration on tidal volume(VT) response duringCO₂ rebreathing. In a group of 11 healthy male subjects, the changes in end-expiratory andend-inspiratory volume of the rib cage (Vrc,E andVrc,I, respectively) and abdomen (Vab,E and Vab,I, respectively) measured by linearizedmagnetometers were expressed as a function of end-tidalPCO₂(PET_CO2). The changes inend-expiratory and end-inspiratory volumes of the chest wall(Vcw,E and Vcw,I,respectively) were calculated as the sum of the respectiverib cage and abdominal volumes. The magnetometer coils were placed atthe level of the nipples and 1-2 cm above the umbilicus andcalibrated during quiet breathing against theVT measured from apneumotachograph. TheVrc,E/PET_CO2 slope was quite variable among subjects. It was significantly positive (P < 0.05) in fivesubjects, significantly negative in four subjects(P < 0.05), and not different fromzero in the remaining two subjects. TheVab,E/PET_CO2slope was significantly negative in all subjects(P < 0.05) with a much smallerintersubject variation, probably suggesting a relatively more uniformrecruitment of abdominal expiratory muscles and a variable recruitmentof rib cage muscles during CO₂rebreathing in different subjects. As a group, the meanVrc,E/PET_CO2,Vab,E/PET_CO2, andVcw,E/PET_CO2slopes were 0.010 ± 0.034, 0.030 ± 0.007, and0.020 ± 0.032 l / Torr, respectively;only theVab,E/PET_CO2 slope was significantly different from zero. More interestingly, theindividualVT/PET_CO2slope was negatively associated with theVrc,E/PET_CO2(r = 0.68,P = 0.021) and Vcw,E/PET_CO2slopes (r = 0.63,P = 0.037) but was not associated withtheVab,E/PET_CO2slope (r = 0.40, P = 0.223). There was no correlation oftheVrc,E/PET_CO2 andVcw,E/PET_CO2slopes with age, body size, forced expiratory volume in 1 s, orexpiratory time. The groupVab,I/PET_CO2 slope (0.004 ± 0.014 l / Torr) was not significantlydifferent from zero despite theVT nearly being tripled at theend of CO₂ rebreathing. Inconclusion, the individual VTresponse to CO₂, althoughindependent of Vab,E, is a function ofVrc,E to the extent that as theVrc,E/PET_CO2slope increases (more positive) among subjects, theVT response toCO₂ decreases. These results maybe explained on the basis of the respiratory muscle actions andinteractions on the rib cage.

     

Chest wall mesenchymal hamartoma: a case report

Chest wall mesenchymal hamartoma is an extremely rare benign tumor. Approximately 80 cases have been reported in the literature. Most tumors are manifested at birth with a painless palpable mass of the chest wall, usually unilateral. Respiratory symptoms result from extrinsic compression of the pulmonary parenchyma, and the severity of the symptoms will depend on the size and location of the lesion. Imaging features are characteristic, but definitive diagnosis is histological. Herein, a case is described of a four month old infant with diagnosis of chest wall mesenchymal hamartoma, manifested at birth. Different treatment options are described, including expectations from tumor management, the possibility of spontaneous regression, and the morbidity associated with the surgical option.