Microfluidic chest cavities reveal that transmural pressure controls the rate of lung development.

Mechanical forces are increasingly recognized to regulate morphogenesis, but how this is accomplished in the context of the multiple tissue types present within a developing organ remains unclear. Here, we use bioengineered 'microfluidic chest cavities' to precisely control the mechanical environment of the fetal lung. We show that transmural pressure controls airway branching morphogenesis, the frequency of airway smooth muscle contraction, and the rate of developmental maturation of the lungs, as assessed by transcriptional analyses. Time-lapse imaging reveals that branching events are synchronized across distant locations within the lung, and are preceded by long-duration waves of airway smooth muscle contraction. Higher transmural pressure decreases the interval between systemic smooth muscle contractions and increases the rate of morphogenesis of the airway epithelium. These data reveal that the mechanical properties of the microenvironment instruct crosstalk between different tissues to control the development of the embryonic lung.

Abdominal insufflation for laparoscopy increases intracranial and intrathoracic pressure in human subjects.

BACKGROUND: Laparoscopy has emerged as an alternative to laparotomy in select trauma patients. In animal models, increasing abdominal pressure is associated with an increase in intrathoracic and intracranial pressures. We conducted a prospective trial of human subjects who underwent laparoscopic-assisted ventriculoperitoneal shunt placement (lap VPS) with intraoperative measurement of intrathoracic, intracranial and cerebral perfusion pressures. METHODS: Ten patients undergoing lap VPS were recruited. Abdominal insufflation was performed using CO2 to 0, 8, 10, 12 and 15 mmHg. ICP was measured through the ventricular catheter simultaneously with insufflation and with desufflation using a manometer. Peak inspiratory pressures (PIP) were measured through the endotracheal tube. Blood pressure was measured using a noninvasive blood pressure cuff. End-tidal CO2 (ETCO2) was measured for each set of abdominal pressure level. Pressure measurements from all points of insufflation were compared using a two-way ANOVA with a post hoc Bonferroni test. Mean changes in pressures were compared using t test. RESULTS: ICP and PIP increased significantly with increasing abdominal pressure (both p < 0.01), whereas cerebral perfusion pressure (CPP) and mean arterial pressure did not significantly change with increasing abdominal pressure over the range tested. Higher abdominal pressure values were associated with decreased ETCO2 values. CONCLUSION: Increased ICP and PIP appear to be a direct result of increasing abdominal pressure, since ETCO2 did not increase. Though CPP did not change over the range tested, the ICP in some patients with 15 mmHg abdominal insufflation reached values as high as 32 cmH2O, which is considered above tolerance, regardless of the CPP. Laparoscopy should be used cautiously, in patients who present with baseline elevated ICP or head trauma as abdominal insufflation affects intracranial pressure.

Subperitoneal extension of disease processes between the chest, abdomen, and the pelvis.

The subserous space is a large, anatomically continuous potential space that interconnects the chest, abdomen, and pelvis. The subserous space is formed from areolar and adipose tissue, and contains branches of the vascular, lymphatic, and nervous systems. As such, it provides one large continuous space in which many disease processes can spread between the chest, abdomen, and the pelvis.

Effect of changes in intrathoracic pressure on cardiac function at rest and during moderate exercise in health and heart failure.

This study investigated the effect of changes in inspiratory intrathoracic pressure on stroke volume at rest and during moderate exercise in patients with heart failure and reduced ejection fraction (HFREF) as well as healthy individuals. Stroke volume was obtained by echocardiography during 2 min of spontaneous breathing (S), two progressive levels of inspiratory unloading (UL1 and UL2) using a ventilator, and two progressive levels of inspiratory loading using resistors in 11 patients with HFREF (61 ± 9 years old; ejection fraction 32 ± 4%; NYHA class I-II) and 11 age-matched healthy individuals at rest and during exercise at 60% of maximal aerobic capacity on a semi-recumbent cycle ergometer. At rest, inspiratory unloading progressively decreased stroke volume index (SVI; S, 35.2 ± 5.4 ml m(-2); UL1, 33.3 ± 5.1 ml m(-2); and UL2, 32.2 ± 4.4 ml m(-2)) in healthy individuals, while it increased SVI (S, 31.4 ± 4.6 ml m(-2); UL1, 32.0 ± 5.9 ml m(-2); and UL2, 34.0 ± 7.2 ml m(-2)) in patients with HFREF (P = 0.04). During moderate exercise, inspiratory unloading decreased SVI in a similar manner (S, 43.9 ± 7.1 ml m(-2); UL1, 40.7 ± 4.7 ml m(-2); and UL2, 39.9 ± 3.7 ml m(-1)) in healthy individuals, while it increased SVI (S, 40.8 ± 6.5 ml m(-2); UL1, 42.8 ± 6.9 ml m(-2); and UL2, 44.1 ± 4. ml m(-2)) in patients with HFREF (P = 0.02). Inspiratory loading did not significantly change SVI at rest or during moderate exercise in both groups. It is concluded that inspiratory unloading improved SVI at rest and during moderate exercise in patients with HFREF, possibly due to a reduction in left ventricular afterload.

Pulse transit time for quantifying inspiratory effort in patients with obstructive sleep apnea.

OBJECTIVES: To investigate the feasibility of pulse transit time (PTT) as a quantitative measure of inspiratory effort in patients with obstructive sleep apnea (OSA). METHODS: Nineteen moderate to severe OSA patients were included to undergo overnight polysomnography simultaneously with esophageal pressure (P(es)) and PTT. The quantitative relationships between the size of P(es) variations (ΔP(es)) and PTT variations (ΔPTT) on a breath-by-breath basis in obstructive apneas were assessed. RESULTS: A total of 19,833 breaths from 6,087 obstructive apneas were analyzed. There were good correlations with r = 0.779 ± 0.095 (mean ± SD) between ΔP(es) and ΔPTT based on overnight sleep. The correlation coefficients for supine and lateral position were of the approximated magnitude (r = 0.783 ± 0.060 and 0.757 ± 0.106, respectively), whereas they were lower in rapid eye movement (REM) sleep (r = 0.564 ± 0.140) compared with non-rapid eye movement (NREM) sleep (r = 0.787 ± 0.071). In NREM sleep, the regression lines of ΔPTT against ΔP(es) were plotted with intercepts (5.1 ± 2.1 ms) and slopes (0.35 ± 0.08 ms·cm H(2)O(-1)). CONCLUSIONS: PTT showed good ability in detecting changes of inspiratory effort in overnight sleep and was proved to be a clinically useful method in quantifying increases in inspiratory effort in NREM sleep. Hence, PTT has prospects to become an alternative to P(es) in respiratory sleep studies.

Measuring thoracic excursion: reliability of the cloth tape measure technique.

OBJECTIVE: To assess the reliability of using a cloth tape measure to determine thoracic respiratory excursion as a measurement of chest expansion or mobility. METHODS: Physicians and residents experienced in osteopathic manipulative treatment measured thoracic excursion with a cloth tape measure held around the circumference of healthy male subjects' chests at two levels. Upper thoracic excursion measurements were taken at the level of the fifth thoracic spinous process and the third intercostal space at the midclavicular line. Lower thoracic excursion measurements were taken at the level of the 10th thoracic spinous process and the xiphoid process. At peak inhalation and exhalation, three examiners measured thoracic excursion at both levels. In the first session (n=5), examiners measured the same subject inhalation and exhalation. In the second session (n=4), examiners measured separate respiratory cycles. For each session, interexaminer intraclass correlation coefficients (ICCs) were calculated for thoracic excursion, inhalation, and exhalation in the upper and lower positions using a two-way random-effects analysis of variance model. RESULTS: Intraclass correlation coefficients for thoracic excursion ranged from 0.81 to 0.91 (95% confidence interval, 0.69-0.99) at both measurement levels in both sessions. When inhalation and exhalation were considered separately, interexaminer ICCs were 0.99 and greater. Standard deviations for measurements of each subject's thoracic excursion at both levels ranged from 0.5 cm to 0.8 cm with a mean of 0.6 cm. CONCLUSION: The method of using a tape measure to assess thoracic excursion was highly reliable in men, resulting in ICCs of substantial reliability. The SDs at each level of measurement indicate that this method may be most useful in measuring changes in thoracic excursion that are expected to be 0.6 cm or greater.

TFC (thoracic fluid content): a new parameter for assessment of changes in chest fluid volume.

Clinical assessment of cardiac status can be difficult and incomplete without an assessment of fluid volume status, especially of the lungs. Now, a new parameter is available, thoracic fluid content (TFC). It is an indicator of total fluid volume, both intracellular and extracellular. Because it is measured noninvasively using impedance cardiography (ICG), it could be a welcome addition to the physician's assessment. An evaluation of TFC was performed beginning with 1) an examination of chest impedance (Z) as an accurate means of following fluid changes, 2) the relationship of TFC to Z using both loop and spot electrodes, and 3) clinical applications of TFC. In 1) 12 dogs, Z was superior (r = 0.935, P < 0.006) to 10 traditional hemodynamic and gas transfer parameters in trending a lactated Ringer's infusion; 2) a plastic model, changes in TFC values derived from Z measurements using both loop and spot electrodes were virtually identical and paralleled infused saline (r = 0.999, P < 0.001); 3) the clinical setting, TFC trended fluid changes well. From these results, we conclude that TFC is a reliable measurement of chest fluid status and of changes in that fluid. Along with cardiac index (CI), also provided by the ICG monitor, TFC can be very helpful to the clinician.

The effects of Valsalva manoeuvre on Ocular Response Analyzer measurements.

BACKGROUND: The aim was to evaluate the effects of the Valsalva manoeuvre on Ocular Response Analyzer (ORA) measurements. METHODS: A total of 152 eyes of 76 healthy individuals were included. The biomechanical properties of cornea, including corneal hysteresis (CH), corneal resistance factor (CRF) and intraocular pressure (IOP) parameters, namely, cornea compensated IOP (IOPcc) and Goldmann correlated IOP (IOPg) as measured with ORA were obtained before and during the Valsalva manoeuvre. Wilcoxon test for group analysis, Mann-Whitney test for intergroup analysis, Generalized Estimating Equation, and Spearman's test for correlation analysis were used. RESULTS: The mean age of the 76 subjects (52 female) was 34.18 ± 10.20 years (range, 21 to 58 years). The mean IOPcc was 14.50 ± 0.30 mmHg before and 19.80 ± 0.60 mmHg during the Valsalva manoeuvre (p < 0.001). The mean IOPg before the Valsalva manoeuvre was 15.02 ± 0.33 mmHg and during was 20.18 ± 0.63 mmHg (p < 0.001). The mean corneal hysteresis was 11.40 ± 0.15 mmHg before Valsalva manoeuvre, and 10.60 ± 0.16 mmHg during Valsalva manoeuvre (p < 0.001). Pre-Valsalva manoeuvre mean corneal resistance factor was 11.97 ± 0.16 mmHg, whereas during the Valsalva manoeuvre, the mean corneal resistance factor was 12.06 ± 0.20 mmHg (p < 0.001). There was no correlation between age and either pre- or during-Valsalva manoeuvre measurements. The change in IOPcc and corneal hysteresis before and during Valsalva manoeuvre showed no intersexual difference; however, IOPg and corneal resistance factor change before and during Valsalva manoeuvre were significantly higher in male subjects. A negative correlation between pre-Valsalva manoeuvre corneal hysteresis and pre- and during-corneal resistance factor difference (r = -0.167) was detected. CONCLUSIONS: Valsalva manoeuvre causes a statistically significant increment in IOPcc, IOPg and corneal resistance factor and statistically significant decrement in corneal hysteresis. For this reason, to obtain reliable results, ORA measurements should be performed in suitable positions and with clothes that do not increase thoracic or abdominal pressure.

Efficiency of a gas diffuser and influence of suction in carbon dioxide deairing of a cardiothoracic wound cavity model.

OBJECTIVE: In cardiac surgery, insufflation of carbon dioxide is used for deairing of the heart and great vessels. The aim of this study was to assess a new insufflation device for efficient deairing and to study the influence of suction. METHODS: We measured the content of remaining air at two positions in the cardiothoracic wound model. A new insufflation device, a gas diffuser, was compared with a conventional 0.25-inch tube. Carbon dioxide flow (5 and 10 L/min) and suction (0, 1.5, 10, and 25 L/min) were varied. Suction was studied in combination with the gas diffuser. RESULTS: With the tube the median air content in the wound model was 19.5% to 51.7% at the studied carbon dioxide flows, whereas with the gas diffuser the median air content was no greater than 1.2% at 5 L/min and no greater than 0.31% at 10 L/min (P <.001). When suction of 1.5 L/min was applied, the median air content in the model remained low (

Intraabdominal pressure after full abdominoplasty in obese multiparous patients.

This study measured intraabdominal pressure in morbidly obese and multiparous patients who underwent abdominoplasty with musculoaponeurotic plication. The purpose of this study was to evaluate any potential adverse effect on pulmonary function by virtue of pulmonary function tests and measurement of peak airway pressure. The study included 43 multiparous, morbidly obese women (mean body mass index, 35.8 kg/m2) with a mean age (+/- SD) of 38.6 +/- 7 years. All had full abdominoplasty and repair of the musculoaponeurotic system during the period from June of 1999 to May of 2002. Forty-three morbidly obese multiparous patients were seen over a period of 24 months. Their intraabdominal pressure was estimated by measuring the intravesical pressure before and after repair of severe diastases (divarication) of the rectus abdominis muscles with severely flaccid myofascial component before using a hydrometer connected to a Foley catheter both before and after repair. All patients had pulmonary function checked before and 2 months after the repair. The study confirmed that there are minimal changes on the intraabdominal pressure parameters compared with measurement before and after full abdominoplasty with plication of the rectus muscles, with minimal to negligible changes in the intrathoracic pressure. These changes are clinically and statistically significant (p < 0.0001). The study also recommended the safety of full abdominoplasty and repair of the musculoaponeurotic system in multiparous and morbidly obese patients. Furthermore, no statistically significant difference was found in pulmonary function parameters before and after surgery in patients with a history of bronchial asthma.

Effect of one-lung ventilation on oxygen delivery in anesthetized dogs with an open thoracic cavity.

OBJECTIVE: To evaluate effects of one-lung ventilation on oxygen delivery in anesthetized dogs with an open thoracic cavity. ANIMALS: 8 clinically normal adult Walker Hound dogs. PROCEDURE: Each dog was anesthetized and subjected to one-lung ventilation during a period when it had an open thoracic cavity. A Swan-Ganz catheter was used to measure hemodynamic variables and obtain mixed-venous blood samples. A catheter was inserted in the dorsal pedal artery to measure arterial pressure and obtain arterial blood samples. Oxygen delivery index was calculated and used to assess effects of one-lung ventilation on cardiopulmonary function. Effects on hemodynamic and pulmonary variables were analyzed. RESULTS: One-lung ventilation caused significant decreases in PaO2, arterial oxygen saturation (SaO2), mixed-venous oxygen saturation, and arterial oxygen content (CaO2). One-lung ventilation caused significant increases in PaCO2, physiologic dead space, and alveolar-arterial oxygen difference. Changes in SaO2, CaO2, and PaCO2, although significantly different, were not considered to be of clinical importance. One-lung ventilation induced a significant increase in pulmonary arterial wedge pressure, mean pulmonary artery pressure, and shunt fraction. One-lung ventilation did not have a significant effect on cardiac index, systemic vascular resistance index, pulmonary vascular resistance index, and oxygen delivery index. CONCLUSIONS AND CLINICAL RELEVANCE: One-lung ventilation affected gas exchange and hemodynamic function, although oxygen delivery in clinically normal dogs was not affected during a period with an open thoracic cavity. One-lung ventilation can be used safely in healthy dogs with an open thoracic cavity during surgery.

Comparing thoracic and intra-nasal pressure transients to monitor active odor sampling during odor-guided decision making in the mouse.

BACKGROUND: Recording of physiological parameters in behaving mice has seen an immense increase over recent years driven by, for example, increased miniaturization of recording devices. One parameter particularly important for odorant-driven behaviors is the breathing frequency, since the latter dictates the rate of odorant delivery to the nasal cavity and the olfactory receptor neurons located therein. NEW METHOD: Typically, breathing patterns are monitored by either measuring the breathing-induced temperature or pressure changes in the nasal cavity. Both require the implantation of a nasal cannula and tethering of the mouse to either a cable or tubing. To avoid these limitations we used an implanted pressure sensor which reads the thoracic pressure and transmits the data telemetrically, thus making it suitable for experiments which require a freely moving animal. RESULTS: Mice performed a Go/NoGo odorant-driven behavioral task with the implanted pressure sensor, which proved to work reliably to allow recording of breathing signals over several weeks from a given animal. COMPARISON TO EXISTING METHOD(S): We simultaneously recorded the thoracic and nasal pressure changes and found that measuring the thoracic pressure change yielded similar results compared to measurements of nasal pressure changes. CONCLUSION: Telemetrically recorded breathing signals are a feasible method to monitor odorant-guided behavioral changes in breathing rates. Its advantages are most significant when recording from a freely moving animal over several weeks. The advantages and disadvantages of different methods to record breathing patterns are discussed.

Sternal wall pressure comparable to leaning during CPR impacts intrathoracic pressure and haemodynamics in anaesthetized children during cardiac catheterization.

AIM: Force due to leaning during cardiopulmonary resuscitation (CPR) negatively affects haemodynamics and intrathoracic airway pressures (ITP) in animal models and adults, but has not been studied in children. We sought to characterize the effects of sternal force (SF) comparable to leaning force on haemodynamics and ITP in anaesthetized children. METHODS: Children (6 months to 8yrs) presenting for routine haemodynamic cardiac catheterization with anaesthesia and mechanical ventilation >6 months after cardiac transplant were studied. Haemodynamics and ITP were measured before and during incremental increases in SF of 10% and 20% body weight. RESULTS: 20 subjects (5.4±1.7yrs of age and 18.3±3.3kg) were studied. Mean right atrial pressure (6.5±2.6 at baseline vs. 7.7±2.6 at 10% SF vs. 8.6±2.7mmHg at 20% SF), mean pulmonary capillary wedge pressure (10.2±2.9 at baseline vs. 11±3.3 at 10% SF vs. 11.8±3.4mmHg at 20% SF) and ITP (16.3±3.2 at baseline vs. 17.9±3.9 at 10% SF vs. 19.5±4cm H2O) all increased significantly with incremental SF (p<0.001 for all). Aortic systolic pressure (85±10mmHg at baseline vs. 83±10mmHg at 10% SF vs. 82±10mmHg at 20% SF, p=0.014) and coronary perfusion pressure (42±7mmHg at baseline vs. 39±7mmHg at 10% SF vs. 38±7mmHg at 20% SF, p<0.001) both decreased significantly with incremental SF. CONCLUSIONS: In asymptomatic, anaesthetized children after cardiac transplantation, sternal forces comparable to leaning previously reported to occur during CPR elevate ITP and right atrial pressure and decrease coronary perfusion pressure. These haemodynamic effects may be clinically important during CPR and warrant further study.

Unexpected effect of recruitment procedure on lung volume measured by respiratory inductive plethysmography (RIP) during high frequency oscillatory ventilation (HFOV) in preterm neonates with respiratory distress syndrome (RDS).

BACKGROUND: In clinical practice, one of the major problems in optimizing recruitment or lung volume during HFOV in preterm infants is the inability to accurately measure direct changes in lung volume at bedside. OBJECTIVE: To evaluate changes in lung volume during the recruitment phase of elective HFOV in preterm infants with RDS using respiratory inductive plethysmography. MATERIAL AND METHODS: The preliminary results of an observational prospective study were reported. Newborns with GA ≤ 27 weeks requiring elective HFOV for a diagnosis of RDS were studied within the first 6 hours of life using RIP technology, before surfactant instillation. HFOV was performed with Draeger Babylog 8000 plus ventilator with "optimum lung volume strategy "(continuous distending pressure (CDP) increased step-by-step until FiO(2) ≤ 0.25 was reached). Data on ventilator settings, gas exchange and RIP volume were collected and analyzed. The analysis package used in this study visualizes measured data from the Bicore-II device (CareFusion), Pulse Oximeter Masimo, AX300 FiO(2) monitor device and TCM4 shuttle (TCM4, Radiometer, Copenaghen, Denmark). RESULTS: Four preterm infants (two females) with mean ± SD gestational age of 26.5 ± 1.0 weeks and mean ± SD birth weight of 978 ± 188 grams were studied. Relative FRC slightly increased during the first steps of the recruitment phase, while deeply decreased at higher CDP values (≥ 15 cm H(2)O). Notwithstanding FiO(2) decreased until 0.25 in all the newborns except one. CONCLUSIONS: Because RIP cannot differentiate between changes in lung fluid or intrathoracic gas, we hypothesized that as CDP increases and total lung capacity is approached, pulmonary vascular resistance increases as a consequence of the compression of intra-alveolar vessels. This increases right ventricular afterload which, combined with re-establishment of right-to left shunting, results in decreased pulmonary blood flow and then decreased lung volume. Caution should then be used when using high CDP values during the recruitment procedure.

The effect of increased physical load during an active straight leg raise in pain free subjects.

PURPOSE: It has been proposed that pelvic girdle pain (PGP) subjects adopt a high load motor control strategy during the low load task of the active straight leg raise (ASLR). This study investigated this premise by observing the motor control patterns adopted by pain free subjects during a loaded ASLR (ASLR+PL). METHOD: Trunk muscle activation, intra-abdominal pressure, intra-thoracic pressure, pelvic floor motion, downward pressure of the non-lifted leg and respiratory rate were compared between resting supine, ASLR and ASLR+PL. Additionally, side-to-side comparisons were performed for ASLR+PL. RESULTS: Incremental increases in muscle activation were observed from resting supine to ASLR to ASLR+PL. During the ASLR+PL there was a simultaneous increase in intra-abdominal pressure with a decrease in intra-thoracic pressure, while respiratory fluctuation of these variables were maintained. The ASLR+PL also resulted in increased pelvic floor descent and greater downward pressure of the non-lifted leg. Trunk muscle activation was comparable between sides during ASLR+PL in all muscles except lower obliquus internus abdominis, which was more active on the leg lift side. CONCLUSION: Pain free subjects respond to an ASLR+PL by a general increase in anterior trunk muscle activation, but preserve the pattern of greater activation on the side of the leg lift observed during an unloaded ASLR. This contrasts to findings in PGP subjects who, despite having a high load strategy for performing an ASLR on the symptomatic side of the body, display equal bilateral activation of the anterior abdominal wall during the ASLR. This differentiates PGP subjects from pain free subjects, supporting the notion that PGP subjects have aberrant motor control patterns during an ASLR.

Combination of a model-deformation method and a positional MRI to quantify the effects of posture on the anatomical structures of the trunk.

Understanding the postural effects on organs and skeleton could be crucial for several applications. This paper reports on a methodology to quantify the three-dimensional effects of postures on deformable anatomical structures. A positional MRI scanner was used to image the full trunk in four postures: supine, standing, seated and forward-flexed. The MRI stacks were processed with a custom toolbox, implemented using open source software. The semi-automated segmentation was based on the deformation of generic models of the pelvis, sternum, femoral heads, spine, liver, kidneys, spleen, skin, thoracic and abdominal cavities. The toolbox was designed to be easily extended by additional image filters, deformation schemes, or new generic models. Results obtained on one subject demonstrate that the method can be used to quantify the effects of postures on skeleton and organs. The spinal curvature, the pelvic parameters and the volume of the thoracic cavity were affected by the four postures. The volumes of the kidneys, spleen, liver and abdominal object were mostly unaffected. The movement of organs was coherent with the effect of gravity. The deformation of organs between postures was expressed using geometrical transformations. Investigations should be pursued on a larger population to confirm the patterns observed on the first subject.

Lung size and thoracic morphology in shallow- and deep-diving cetaceans.

Shallow-diving, coastal bottlenose dolphins (Tursiops truncatus) and deep-diving, pelagic pygmy and dwarf sperm whales (Kogia breviceps and K. sima) will experience vastly different ambient pressures at depth, which will influence the volume of air within their lungs and potentially the degree of thoracic collapse they experience. This study tested the hypotheses that lung size will be reduced and/or thoracic mobility will be enhanced in deeper divers. Lung mass (T. truncatus, n = 106; kogiids, n = 18) and lung volume (T. truncatus, n = 5; kogiids, n = 4), relative to total body mass, were compared. One T. truncatus and one K. sima were cross-sectioned to calculate lung, thoracic vasculature, and other organ volumes. Excised thoraxes (T. truncatus, n = 3; kogiids, n = 4) were mechanically manipulated to compare changes in thoracic cavity shape and volume. Kogiid lungs were half the mass and one-fifth the volume of those of similarly sized T. truncatus. The lungs occupied only 15% of the total thoracic cavity volume in K. sima and 37% in T. truncatus. The kogiid and dolphin thoraxes underwent similar changes in shape and volume, although the width of the thoracic inlet was relatively constrained in kogiids. A broader phylogenetic comparison demonstrated that the ratio of lung mass to total body mass in kogiids, physeterids, and ziphiids was similar to that of terrestrial mammals, while delphinids and phocoenids possessed relatively large lungs. Thus, small lung size in deep-diving odontocetes may be a plesiomorphic character. The relatively large lung size of delphinids and phocoenids appears to be a derived condition that may permit the lung to function as a site of respiratory gas exchange throughout a dive in these rapid breathing, short-duration, shallow divers.

Measurement of thoracic fluid content in heart failure: the role of impedance cardiography.

Current guidelines for assessing the fluid status of patients with heart failure include subjective physical findings, which often occur late in decompensation, and objective pulmonary artery catheter measurements, whose use is controversial in patients with heart failure. Impedance cardiography, which assesses cardiac function by measuring the opposition to an alternating electric current in the thorax, indicates the amount of fluid in the thorax. It is used externally by employing electrodes on the thorax but can also be used internally by electrodes within a cardiac pacemaker. Recent studies have suggested that one of its direct measurements, thoracic impedance, may identify patients at risk for decompensation of heart failure, but because these measurements inconsistently correlate with pulmonary artery catheter measurements and study sample sizes are small, further research is required before its use can be recommended.

Factors of thoracic cage deformity that affect pulmonary function in adolescent idiopathic thoracic scoliosis.

STUDY DESIGN: This clinical study examined the association between pulmonary function and thoracic cage deformities in scoliosis. OBJECTIVE: To determine the factors in spinal and thoracic cage deformities that affect pulmonary function in scoliosis. SUMMARY OF BACKGROUND DATA: Pulmonary function in scoliosis has generally been evaluated in terms of lateral spinal curvature. No previous report has evaluated changes in pulmonary function taking into consideration measurements reflecting not only spinal curvature but also thoracic cage deformities, although scoliosis is a three-dimensional deformity. METHODS: A total of 109 patients (mean age, 14.2 years) with adolescent idiopathic right thoracic scoliosis (mean lateral spinal curvature, 37.7 degrees) had full assessment of pulmonary function and a radiographic evaluation from radiographs of the whole spine, Moiré topography, and thoracic computed tomography. RESULTS: Multiple regression analysis (stepwise method) was performed at each vertebral level from T3-T12 to identify the factor that most strongly affects %VC. The correlation coefficient was highest at T9 and next highest at T8, with values of 0.641 (r2 = 0.411, P < 0.0001) and 0.625 (r2 = 0.390, P < 0.0001), respectively. At T9, multiple regression analysis showed that the sagittal diameter of the thoracic cage and the total lung area were identified as factors that most strongly affect %VC. Similarly, the sagittal diameter of the thoracic cage and the rotation angle to the sagittal plane were identified at T8. CONCLUSIONS: The factors that reduced %VC were the sagittal diameter of the thoracic cage, total lung area and vertebral rotation at the T8 and T9 levels.