Inflation Volume Research Articles

Links between the Mechanics of Ventilation and Spine Stability

Spine stability is ensured through isometric coactivation of the torso muscles; however, these same muscles are used cyclically to assist ventilation. Our objective was to investigate this apparent paradoxical role (isometric contraction for stability or rhythmic contraction for ventilation) of some selected torso muscles that are involved in both ventilation and support of the spine. Eight, asymptomatic, male subjects provided data on low back moments, motion, muscle activation, and hand force. These data were input to an anatomically detailed, biologically driven model from which spine load and a lumbar spine stability index was obtained. Results revealed that subjects entrained their torso stabilization muscles to breathe during demanding ventilation tasks. Increases in lung volume and back extensor muscle activation coincided with increases in spine stability, whereas declines in spine stability were observed during periods of low lung inflation volume and simultaneously low levels of torso muscle activation. As a case study, aberrant ventilation motor patterns (poor muscle entrainment), seen in one subject, compromised spine stability. Those interested in rehabilitation of patients with lung compromise and concomitant back troubles would be assisted with knowledge of the mechanical links between ventilation during tasks that impose spine loading.

Acquired tracheoesophageal fistula due to high intracuff pressure

High-compliance endotracheal tube cuffs are used to prevent gas leak and also pulmonary aspiration in mechanically ventilated patients. However, the use of the usual cuff inflation volumes may cause tracheal damage and lead to tracheoesophageal fistula.Tracheostomy tube cuffs seal against the tracheal wall and prevent leakage of air around the tube, assuring that the tidal volume is delivered to the lungs. In the past, high-pressure cuffs were used, but these contributed to tracheal injury and have been replaced by high-volume, low-pressure cuffs. For long-term applications, some newer tubes have low-profile (tight to shaft) cuffs that facilitate the tracheostomy tube changes by eliminating the lip that forms when standard cuffs are deflated.

Expanded Reverse Abdominoplasty for Reconstruction of Burns in the Epigastric Region and the Inframammary Fold in Female Patients

We report the use of expanded reverse abdominoplasty in three female patients with postburn scars involving the entire epigastric region in which the inframammary folds were effaced, resulting in distortion of breast contour. In two of the patients, tissue expanders were used, and subsequently, reverse abdominoplasty was performed, thus re-creating the inframammary fold. The third patient reported to be pregnant after expanders were placed; therefore, smaller volumes of inflation for tissue expansion were necessary. We believe that this procedure is an optimal solution, both aesthetically and functionally, in respect to other reconstructive techniques in female patients with normal skin inferior to epigastric burns. The surgical technique and results are discussed.

Moving toward the petroclival region: a model for quantitative and anatomical analysis of tumor shift

The authors quantitatively assessed the effects of balloon inflation as a model of tumor compression on the brainstem, cranial nerves, and clivus by measuring the working area, angle of attack, and brain shift associated with the retrosigmoid approach. Six silicone-injected cadaveric heads were dissected bilaterally via the retrosigmoid approach. Quantitative data were generated, including key anatomical points on the skull base and brainstem. All parameters were measured before and after inflation of a balloon catheter (inflation volume 4.8 ml, diameter 20 mm) intended to mimic tumor compression. Balloon inflation significantly shifted (p < 0.001) the brainstem and cranial nerve foramina (mean [+/- standard deviation] displacement of upper brainstem, 10.2 +/- 3.7 mm; trigeminal nerve exit, 6.99 +/- 2.38 mm; facial nerve exit, 9.52 +/- 4.13 mm; and lower brainstem, 13.63 +/- 8.45 mm). The area of exposure at the petroclivus was significantly greater with balloon inflation than without (change, 316.26 +/- 166.75 mm2; p < 0.0001). Before and after balloon inflation, there was no significant difference in the angles of attack at the origin of the trigeminal nerve (p > 0.5). This study adds an experimental component to the emerging field of quantitative neurosurgical anatomy. Balloon inflation can be used to model the effects of a mass lesion. The tumor simulation created "natural" retraction and an opening toward the upper clivus. The findings may be helpful in selecting a surgical approach to increase the working space for resection of certain extraaxial tumors.

Moving toward the petroclival region: a model for quantitative and anatomical analysis of tumor shift

Object The authors quantitatively assessed the effects of balloon inflation as a model of tumor compression on the brainstem, cranial nerves, and clivus by measuring the working area, angle of attack, and brain shift associated with the retrosigmoid approach. Methods Six silicone-injected cadaveric heads were dissected bilaterally via the retrosigmoid approach. Quantitative data were generated, including key anatomical points on the skull base and brainstem. All parameters were measured before and after inflation of a balloon catheter (inflation volume 4.8 ml, diameter 20 mm) intended to mimic tumor compression. Results Balloon inflation significantly shifted (p < 0.001) the brainstem and cranial nerve foramina (mean [± standard deviation] displacement of upper brainstem, 10.2 ± 3.7 mm; trigeminal nerve exit, 6.99 ± 2.38 mm; facial nerve exit, 9.52 ± 4.13 mm; and lower brainstem, 13.63 ± 8.45 mm). The area of exposure at the petroclivus was significantly greater with balloon inflation than without (change, 316.26 ± 166.75 mm2; p < 0.0001). Before and after balloon inflation, there was no significant difference in the angles of attack at the origin of the trigeminal nerve (p > 0.5). Conclusions This study adds an experimental component to the emerging field of quantitative neurosurgical anatomy. Balloon inflation can be used to model the effects of a mass lesion. The tumor simulation created “natural” retraction and an opening toward the upper clivus. The findings may be helpful in selecting a surgical approach to increase the working space for resection of certain extraaxial tumors.

Recommended inflation volumes result in lower cuff pressures in paediatric patients with Ambu AuraOnce when compared to LMA-Classic

Genzwuerker, H. V; Sinkowitsch, J.; Hinkelbein, J.; Jandewerth, O.; Hohl, E. Ch. Author Information

Establishment of a canine spinal cord injury model induced by epidural balloon compression

A model that provides reproducible, submaximal yet sufficient spinal cord injury is needed to allow experiments leading to development of therapeutic techniques and prediction of clinical outcome to be conducted. This study describes an experimental model for spinal cord injury that uses three different volumes of balloon inflation and durations of compression to create a controlled gradation outcome in adult dogs. Twenty-seven mongrel dogs were used for this study. A 3-french embolectomy catheter was inserted into the epidural space through a left hemilaminectomy hole at the L4 vertebral arch. Balloons were then inflated with 50, 100, or 150 µl of a contrast agent at the L1 level for 6, 12, or 24 h and spinal canal occlusion (SCO) measured using computed tomography. Olby score was used to evaluate the extent of spinal cord injury and a histopathologic examination was conducted 1 week after surgery. The SCO of the 50, 100, and 150 µl inflations was 22-46%, 51-70%, and 75-89%, respectively (p < 0.05). Olby scores were diminished significantly by a combination of the level of SCO and duration of inflation in all groups. Olby scores in the groups of 150 µl-12 h, 150 µl-24 h, and 100 µl-24 h were 0.5, 0, and 1.7, respectively. Based on these results, a SCO > 50% for 24 h, and > 75% for 12 h induces paraplegia up to a week after spinal cord injury.

Development of a Novel, Remote‐Controlled Artificial Bowel Sphincter Through Microsystems Technology

An artificial sphincter prototype has been developed, specifically designed for comfortable remote control by fecally incontinent patients. The artificial sphincter includes a fluid reservoir, an occlusive cuff, and a micropump based on piezo-technology in a single unit. Continence and implantation management were evaluated around isolated porcine anal canals and in vivo. The design of the prosthesis reduces the occlusion pressure and allows low inflation volumes (6.5-16 mL). Operating pressures between 24 and 58 mm Hg indicate a minor risk of ischemic injury to the bowel. The operation time is estimated at about 7 days with no recharging of the battery. The novel prototype is a highly integrated prosthesis for placement around the anal canal or lower rectum, effecting continence with comfortable control.

Economic variables and stock market returns: evidence from the Athens stock exchange

This research examines the short run dynamic adjustments and the long run equilibrium relationships between selected macroeconomic variables, trading volume and stock returns in the emerging Greek stock market during the period 1990 to 1999. Empirical results show that short run and long run equilibrium relationship exists between inflation, money supply and trading volume and the stock prices in the Athens stock exchange. No short run or long run equilibrium relationship is found between the exchange rates and stock prices. The results of this research are consistent with the theoretical arguments and practical developments that occurred in the Greek stock markets during the sample period. The results also imply that the ASE is informationally inefficient because publicly available information on macroeconomic variables and trading volumes can be potentially used in predicting stock prices.

An Experimental Facility to Measure the Chemorheological Response of Inflated Elastomeric Membranes at High Temperature

An experimental facility for measuring the time-dependent deformation of an inflated elastomer membrane at elevated temperatures is presented. The facility controls the temperature and inflation volume of a membrane specimen and measures the pressure and deformation field. The finite deformation field is determined by comparing the configuration of the inflated membrane to the initially flat reference configuration, determined by photogrammetry of an array of dots printed on the surface of the membrane. The facility provides an effective method to investigate the changes in mechanical properties due to scission and cross-linking in the context of a simple elastomeric structure that has a distribution of multi-axial deformation states.

Effect of ouabain on the afterhyperpolarization of slowly adapting pulmonary stretch receptors in the rat lung

In anesthetized, artificially ventilated rats with one vagus nerve section, the purposes of the present study were to investigate whether release from phasic consecutive hyperinflations (inflation volume = 3 tidal volumes) results in the afterhyperpolarization (AHP) of the slowly adapting pulmonary stretch receptor (SAR) activity and whether the effect of ouabain, a Na +–K + ATPase inhibitor, alters AHP of the SAR activity seen after release from maintained inflations. Release from 10 consecutive phasic hyperinflations did not cause any significant inhibition of SAR activity. Release from maintained inflations (for approximately 10 and 15 cmH 2O) for 5 s produced the induction of disappearance of SAR activity, corresponding with the AHP. Intravenous administration of ouabain (20 and 40 μg/kg) had no significant effects on the responses of SAR activity and SAR adaptation index (AI) to maintained inflations, but ouabain treatment with at 40 μg/kg resulted in a significant increase in the SAR activity after stopping the respirator and significantly attenuated the AHP of the SAR activity. In the immunohistochemical study, we found Na +–K + ATPase α 3-subunit-isoforms-like immunoreactivity in SAR terminals, forming leaflike extensions in the intrapulmonary bronchioles at different diameters, and those terminals were buried in the smooth muscle. In the same sections, the α 1 subunit immunoreactivity of SAR terminals was not found. These results suggest that the mechanism of generating the AHP of SARs is mainly mediated by the activation of Na +–K + ATPase α 3 subunit isoform.

Laypersons may learn basic life support in 24 min using a personal resuscitation manikin

Bystander basic life support (BLS) is an important part of cardiopulmonary resuscitation (CPR) and improves outcome after out-of-hospital cardiac arrest. However, the general population has poor BLS skills. Several training initiatives could be used to improve this situation and the challenge is to find the most efficient one. To compare the efficiency of a 24 min instruction using a DVD-based self-training BLS course combined with a simple, take-home resuscitation manikin to a conventional 6h course for teaching BLS to laypersons. In total, 238 laypersons (age 21-55 years) without previous BLS-training were allocated into two groups: one group received 24 min of instruction using a DVD-based instruction tool on a big screen combined with a BLS self-training device, Laerdal MiniAnne manikin (MAM), before taking home the instruction material for subsequent self-training. The second group attended a conventional 6 h BLS course (6 HR). After 3 months BLS skills were assessed on a Laerdal ResusciAnne manikin using the Laerdal PC Skill reporting System, and a total score was calculated. There was no significant difference between groups in BLS performance using the total score. Assessment of breathing was performed significantly more often in the 6 HR-group (91% versus 72%, P=0.03). In the MAM-group, average inflation volume and chest compression depth were significantly higher (844 mL versus 524 mL, P=0.006, and 45 mm versus 39 mm, P=0.005). When assessed after 3 months, a 24 min DVD-based instruction plus subsequent self-training in BLS appears equally effective compared to a 6h BLS course and hence is more efficient.

Impact of A Pressure-Responsive Flow-Limiting Valve on Bag–valve–mask Ventilation in an Airway Model

Using a simulated airway model, we compared ventilation performance by emergency medical services (EMS) providers using a traditional bag-valve-mask (Easy Grip) resuscitator to their performance when using a new device, the SMART BAG resuscitator, which has a pressure-responsive flow-limiting valve. We recruited EMS providers at an EMS educational forum and performed a randomized, non-blinded, prospective crossover comparison of ventilation with 2 devices on a non-intubated simulated airway model. Subjects were instructed to ventilate a Mini Ventilation Training Analyzer as they would an 85-kg adult patient in respiratory arrest. After being randomized to order of device use, they performed ventilation for 1 minute with each device. Primary outcomes were ventilation rates and peak airway pressures. We also measured average tidal volume, gastric inflation volume, minute ventilation and inspiratory:expiratory (I:E) ratio, and compared our results to the American Heart Association standards (2005 edition). We observed statistically significant differences between the SMART BAG and the traditional bag-valve-mask for respiratory rate (12 v. 14 breaths/min), peak airway pressure (15.6 v. 18.9 cm H(2)O), gastric inflation (239.6 v. 1598.4 mL), minute ventilation (7980 v. 8775 mL), and I:E ratio (1.3 v. 1.1). Average tidal volume was similar with both devices (679.6 v. 672.2 mL). The SMART BAG(R) provided ventilation performance that was more consistent with American Heart Association guidelines and delivered similar tidal volumes when compared with ventilation with a traditional bag-valve-mask resuscitator.

In vivo assessment of coronary artery angioplasty and stent deployment from balloon pressure–volume data

This study assessed the clinical and practical value of angioplasty balloon pressure–volume data, obtained by a computer-controlled balloon inflation device, during standard percutaneous coronary intervention (PCI) procedures. Stent deployment was studied for 57 lesions in 34 patients. Angiographic predilation data were available in 9 patients. Vessel lumen improvement with pre-dilation was determined using the area difference under the pressure–volume curves of two consecutive inflations and compared to the angiographically determined lumen improvement. Stent opening pressure, the inflation volume needed to unfold the stent and the shape of the pressure–volume curve were assessed for differences between stent sizes (diameter, length) and manufacturer types. A Pearson correlation of 0.8 between the pressure–volume area difference and the angiographic lumen improvement was significant (p = 0.01), confirming that pressure–volume curves are useful in assessing lumen improvement after pre-dilation. There was a significant difference in stent opening pressure between stent types but not between different stent sizes (length, diameter). The inflation volume measured during the unfolding process of the stent correlated with the calculated stent lumen when deployed (Pearson correlation: 0.65, p = 0.001). The shape of the pressure–volume curve during stent deployment illustrated differences between different stent sizes (length, diameter) during inflation. Pressure–volume curves obtained from an automatic balloon inflation device have shown their usefulness in providing additional feedback about lumen improvement and the mechanical characteristics and quality of stent deployment.

Cuff filling volumes and pressures in pediatric laryngeal mask airways

Hyperinflation of LMA cuffs carries the risk of airway morbidity by exerting pressure on laryngeal and pharyngeal structures. Cuff hyperinflation in LMAs can result from nitrous oxide diffusion into the LMA cuff and from deliberate manual cuff inflation. In an in vitro set up, maximum recommended cuff filling volumes for size 1, 1.5, 2, 2.5, 3 disposable LMAs from different manufacturers [SoftSeal LMA (Portex); Unique LMA (Intavent); Marshall LAD, LaryngoSeal (Tyco)] and reusable Classic and ProSeal LMAs (Intavent) were inflated into completely emptied LMA-cuffs and into LMA-cuffs at resting volume. Cuff pressures were measured using a cuff manometer. Experiments were performed eight times using two exemplars of each brand/size. Maximum recommended cuff filling volumes for pediatric LMAs resulted in hyperinflation (cuff pressure >60 cmH(2)O) in almost all LMAs, starting with emptied cuff. Starting from resting cuff volume, the maximum recommended inflation volume resulted in cuff pressures of >120 cmH(2)O in all LMAs and sizes except in the ProSeal size 3 (101 +/- 1 cmH(2)O). Since the volume of air which is effectively required depends on several factors and varies between patients, the cuffs should be inflated only with the minimum volume of air required to form an effective seal with the respiratory and gastrointestinal tracts and the cuff pressure should be controlled.

Stretch increases alveolar epithelial permeability to uncharged micromolecules

We measured stretch-induced changes in transepithelial permeability in vitro to uncharged tracers 1.5-5.5 A in radius to identify a critical stretch threshold associated with failure of the alveolar epithelial transport barrier. Cultured alveolar epithelial cells were subjected to a uniform cyclic (0.25 Hz) biaxial 12, 25, or 37% change in surface area (DeltaSA) for 1 h. Additional cells served as unstretched controls. Only 37% DeltaSA (100% total lung capacity) produced a significant increase in transepithelial tracer permeability, with the largest increases for bigger tracers. Using the permeability data, we modeled the epithelial permeability in each group as a population of small pores punctuated by occasional large pores. After 37% DeltaSA, increases in paracellular transport were correlated with increases in the radii of both pore populations. Inhibition of protein kinase C and tyrosine kinase activity during stretch did not affect the permeability of stretched cells. In contrast, chelating intracellular calcium and/or stabilizing F-actin during 37% DeltaSA stretch reduced but did not eliminate the stretch-induced increase in paracellular permeability. These results provide the first in vitro evidence that large magnitudes of stretch increase paracellular transport of micromolecules across the alveolar epithelium, partially mediated by intracellular signaling pathways. Our monolayer data are supported by whole lung permeability results, which also show an increase in alveolar permeability at high inflation volumes (20 ml/kg) at the same rate for both healthy and septic lungs.

Tilt recorded by a portable broadband seismograph: The 2003 eruption of Anatahan Volcano, Mariana Islands

The horizontal components of broadband seismographs are highly sensitive to tilt, suggesting that commonly deployed portable broadband seismic sensors may record important tilt information associated with volcanic eruptions. We report on a tilt episode that coincides with the first historical eruption of Anatahan volcano on May 10, 2003. The tilt was recorded by a Strekheisen STS‐2 seismograph deployed in an underground insulated chamber 7 km west of the active vent. An ultra‐long period signal with a dominant period of several hours was recorded on the E‐W component beginning at 06:20 GMT on May 10, which coincides with the onset of continuous volcano‐tectonic (VT) seismicity and is one hour prior to the eruption time estimated by the Volcanic Ash Advisory Center. The signal is much smaller on the N‐S component and absent on the vertical component, suggesting it results from tilt that is approximately radial with respect to the active vent. An estimate of tilt as a function of time is recovered by deconvolving the record to acceleration and dividing by the acceleration of gravity. The record indicates an initial episode of tilt downward away from the volcanic center from 06:20–09:30 GMT, which we interpret as inflation of the shallow volcanic source. The tilt reverses, recording deflation, from 09:30 until 17:50, after which the tilt signal becomes insignificant. The inflation corresponds to a period of numerous VT events, whereas fewer events were recorded during the deflation episode, and the VT events subsequently resumed after the end of the deflationary tilt. The maximum tilt of 2 microradians can be used to estimate the volume of the source inflation (∼2 million m3), assuming a simple Mogi source model. These calculations are consistent with other estimates of source volume if reasonable source depths are assumed. Examination of broadband records of other eruptions may disclose further previously unrecognized tilt signals.

The inhibitory effect of ouabain on the response of slowly adapting pulmonary stretch receptors to hyperinflation in the rabbit

The combined effects of ouabain (Na +–K + ATPase inhibitor) and hyperinflation (inflation volume = three tidal volumes) on slowly adapting pulmonary stretch receptors (SARs) were studied before and after administration of nifedipine (an L-type Ca 2+ channel blocker) and KB-R7943 (a reverse-mode Na +–Ca 2+ exchanger blocker) in anesthetized, artificially ventilated rabbits after bilateral vagotomy. Before ouabain administration, hyperinflation stimulated SAR activity. After 20 min of ouabain administration (30 μg/kg) the SARs increased discharge rates in normal inflation. Under these conditions, hyperinflation initially stimulated SAR activity but subsequently inhibited the activity at peak inflation. Additional administration of 60 μg/kg ouabain (total dose = 90 μg/kg) caused a further stimulation of SAR activity, but 20 min later both normal inflation and hyperinflation resulted in a greater inhibition of the receptor activity. The hyperinflation-induced SAR inhibition in the presence of ouabain (30 μg/kg) was not significantly altered by administration of either nifedipine (2 and 4 mg/kg) or KB-R7943 (1 and 3 mg/kg). In another series of experiments, we further examined the combined effects of ouabain and hyperinflation in veratridine (a Na + channel opener, 40 μg/kg)-treated animals. After recovery from the veratridine effect on SAR activity, which vigorously stimulated the receptor activity, ouabain treatment (30 μg/kg) that silenced the receptor activity at peak inflation greatly inhibited hyperinflation-induced SAR stimulation. These results suggest that hyperinflation-induced SAR inhibition in the presence of ouabain may be related to a Na + overload, but not to a Ca 2+ influx via activation of L-type Ca 2+ channels, in the SAR endings.

Alkaline hemolysis fragility is dependent on cell shape: Results from a morphology tracker

The morphometric analysis of red blood cells (RBCs) is an important area of study and has been performed previously for fixed samples. We present a novel method for the analysis of morphologic changes of live erythrocytes as a function of time. We use this method to extract information on alkaline hemolysis fragility. Many other toxins lyse cells by membrane poration, which has been studied by averaging over cell populations. However, no quantitative data are available for changes in the morphology of individual cells during membrane poration-driven hemolysis or for the relation between cell shape and fragility. Hydroxide, a porating agent, was generated in a microfluidic enclosure containing RBCs in suspension. Automatic cell recognition, tracking, and morphometric measurements were done by using a custom image analysis program. Cell area and circular shape factor (CSF) were measured over time for individual cells. Implementations were developed in MATLAB and on Kestrel, a parallel computer that affords higher speed that approaches real-time processing. The average CSF went through a first period of fast increase, corresponding to the conversion of discocytes to spherocytes under internal osmotic pressure, followed by another period of slow increase until the fast lysis event. For individual cells, the initial CSF was shown to be inversely correlated to cell lifetime (linear regression factor R=0.44), with discocytes surviving longer than spherocytes. The inflated cell surface area to volume ratio was also inversely correlated to lifetime (R=0.43) but not correlated to the CSF. Lifetime correlated best to the ratio of cell inflation volume (Vfinal-Vinitial) to surface area (R=0.65). RBCs inflate at a rate proportional to their surface area, in agreement with a constant flux model, and lyse after attaining a spherical morphology. Spherical RBCs display increased alkaline hemolysis fragility (shorter lifetimes), providing an explanation for the increased osmotic fragility of RBCs from patients who have spherocytosis.

Does sustained lung inflation at resuscitation reduce lung injury in the preterm infant?

Background: Bronchopulmonary dysplasia (BPD) is a common outcome of preterm birth. Experimental animal work has shown that initial ventilation strategies injure the immature lung and may lead to BPD. Studies...