The effect of closing pressure and extraction volume on the measurement of nasal volume by manometric rhinometry

A device was designed to provide a “square” pulse of blood flow into the arterial system. Pulses were injected into the carotid artery of the rabbit during transient cardiac arrest. Analysis of pressure response curves generated by the flow provides information as to the state of the arterial tree. With certain assumptions it is possible to estimate from these curves lumped values of peripheral resistance, critical closing pressure, and arterial compliance. In a series of 12 rabbits the mean value of peripheral resistance was found to be 0.21 +/- 0.7 mmHg-ml-1-min and critical closing pressure was estimated to be 23.6 +/- 3.8 mmHg. This method gives two possible values for arterial compliance 0.036 +/- 0.010 and 0.055 +/- 0.010 ml-mm-1 based, respectively, on the rise and decay curves of the pressure response. The theory and limitations of the method are discussed. The use of the method is illustrated in following the response to increased PCO2 and hemorrhage.

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Predicting critical closing pressure in children with obstructive sleep apnea using fluid structure interaction simulations

Journal of Applied Physiology ◽

10.1152/japplphysiol.00694.2020 ◽

2021 ◽

Author(s):

Goutham Mylavarapu ◽

Ephraim Gutmark ◽

Sally Shott ◽

Robert J. Fleck ◽

Mohamed Mahmoud ◽

...

Keyword(s):

Obstructive Sleep Apnea ◽

Sleep Apnea ◽

Upper Airway ◽

Dynamic Mri ◽

Patient Specific ◽

Apnea Hypopnea Index ◽

Structure Interaction ◽

Obstructive Sleep ◽

Mri Scans ◽

Closing Pressure

Surgical treatment of obstructive sleep apnea (OSA) in children requires knowledge of upper airway dynamics, including the closing pressure (Pcrit), a measure of airway collapsibility. We applied a Flow-Structure Interaction (FSI) computational model to estimate Pcrit in patient-specific upper airway models obtained from magnetic resonance imaging (MRI) scans. We sought to examine the agreement between measured and estimated Pcrit from FSI models in children with Down syndrome. We hypothesized that the estimated Pcrit would accurately reflect measured Pcrit during sleep and therefore reflect the severity of OSA as measured by the obstructive apnea hypopnea index (AHI). All participants (n=41) underwent polysomnography and sedated sleep MRI scans. We used Bland Altman Plots to examine the agreement between measured and estimated Pcrit. We determined associations between estimated Pcrit and OSA severity, as measured by AHI, using regression models. The agreement between passive and estimated Pcrit showed a fixed bias of -1.31 (CI=-2.78, 0.15) and a non-significant proportional bias. A weaker agreement with active Pcrit was observed. A model including AHI, gender, an interaction term for AHI and gender and neck circumference explained the largest variation (R2 = 0.61) in the relationship between AHI and estimated Pcrit. (P <0.0001). Overlap between the areas of the airway with lowest stiffness, and areas of collapse on dynamic MRI, was 77.4%±30% for the nasopharyngeal region and 78.6%±33% for the retroglossal region. The agreement between measured and estimated Pcrit and the significant association with AHI supports the validity of Pcrit estimates from the FSI model.

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Reflections on the HIFI Trial

PEDIATRICS ◽

10.1542/peds.87.4.565 ◽

1991 ◽

Vol 87 (4) ◽

pp. 565-567

Author(s):

A. CHARLES BRYAN ◽

ALISON B. FROESE

Keyword(s):

Carbon Dioxide ◽

Mechanical Ventilation ◽

Lung Disease ◽

Prolonged Mechanical Ventilation ◽

Mechanical Ventilators ◽

History Of ◽

Closing Pressure

Mechanical ventilators have only two functions: to provide a flux to eliminate carbon dioxide from those who will not or cannot breathe and to establish an adequate gas-exchanging volume to reduce shunting. The concept of volume recruitment to reduce shunting goes back at least to Mead and Collier in 1959,1 who showed that without periodic inflations there was a progressive fall in compliance during prolonged mechanical ventilation. Much of the subsequent history of mechanical ventilation in acute lung disease has really been the search for better methods of volume recruitment. The lung has to be inflated past the pressure at which atelectatic lung begins to open and be maintained above its closing pressure (that pressure below which alveoli and airways start to close again).

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A neuromuscular mechanism maintaining extrathoracic airway patency

Journal of Applied Physiology ◽

10.1152/jappl.1979.46.4.772 ◽

1979 ◽

Vol 46 (4) ◽

pp. 772-779 ◽

Cited By ~ 248

Author(s):

R. T. Brouillette ◽

B. T. Thach

Keyword(s):

Negative Pressure ◽

Hyoid Bone ◽

Electromyographic Activity ◽

Depth Of Anesthesia ◽

Blood Gas ◽

Nerve Section ◽

Airway Patency ◽

Airway Occlusion ◽

Extrathoracic Airway ◽

Closing Pressure

The ability of the extrathoracic airway (ETA) to remain open when exposed to negative pressure was investigated in rabbits. Postmortem, the ETA collapsed at -6.3 +/- 0.6 cmH2O whereas, during airway occlusion maneuvers in lightly anesthetized animals, it remained patent at pressures as low as -80 cmH2O. This discrepancy suggested that a neuromuscular mechanism maintains ETA patency. Four findings indicated that the genioglossus and geniohyoid muscles, which pull the tongue and hyoid bone anteriorly, help maintain ETA patency: 1) anterior movement of the hyoid bone increased the negative pressure at which the ETA collapsed postmortem, 2) ETA closure during occluded inspirations occurred after 12th nerve section abolished electromyographic activity in these muscles and 3) after deep anesthesia depressed such activity, and 4) closing pressure was linearly related to peak integrated electromyograms of the two muscles. After 12th nerve section, ETA closing pressure became more negative with progressive asphyxia greatly exceeding postmortem closing pressure, which suggests that other muscles also help maintain ETA patency. Blood gas tensions, respiratory system mechanoreceptors, and depth of anesthesia appear to influence genioglossus and geniohyoid activity.

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Static mechanics of the velopharynx of patients with obstructive sleep apnea

Journal of Applied Physiology ◽

10.1152/jappl.1993.75.1.148 ◽

1993 ◽

Vol 75 (1) ◽

pp. 148-154 ◽

Cited By ~ 107

Author(s):

S. Isono ◽

D. L. Morrison ◽

S. H. Launois ◽

T. R. Feroah ◽

W. A. Whitelaw ◽

...

Keyword(s):

Obstructive Sleep Apnea ◽

Sleep Apnea ◽

Atmospheric Pressure ◽

Exponential Relationship ◽

Obstructive Sleep ◽

Pressure Area ◽

Mean Pressure ◽

The Mean ◽

Closing Pressure ◽

Single Exponential

The static mechanics of the hypotonic pharynx were endoscopically evaluated in nine sleeping patients with obstructive sleep apnea, having a primary narrowing only at the velopharynx. The velopharynx closed completely at a mean pressure of 0.18 +/- 1.21 cmH2O, and the mean half-dilation pressure was 1.93 cmH2O above closing pressure. The dependence of area on pressure was distinctly curvilinear, being steep near closing pressure and asymptotically approaching maximum area (mean = 1.32 cm2). The data for each patient were satisfactorily fitted by an exponential function (mean R2 = 0.98), and a single exponential relationship usefully represented the dependence of relative area on pressure above closing pressure for the population (R2 = 0.85). During the test inspiration, flow limitation was consistently observed when mask pressure exceeded closing pressure by 0.5–3.0 cmH2O. In summary, the static mechanics of the hypotonic velopharynx of patients with obstructive sleep apnea can be described by an exponential pressure-area relationship, with a closing pressure near atmospheric pressure and a high compliance in the range of airway pressure 0–3 cmH2O above closing pressure.

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Critical Closing Pressure During a Controlled Increase in Intracranial Pressure

Acta Neurochirurgica Supplement - Intracranial Pressure & Neuromonitoring XVI ◽

10.1007/978-3-319-65798-1_28 ◽

2018 ◽

pp. 133-137

Author(s):

Katarzyna Kaczmarska ◽

Magdalena Kasprowicz ◽

Antoni Grzanka ◽

Wojciech Zabołotny ◽

Peter Smielewski ◽

...

Keyword(s):

Intracranial Pressure ◽

Critical Closing Pressure ◽

Closing Pressure

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Producing Drink like Grafted Milk from Chickpeas and Evaluation of its Qualitative Properties

International Journal of Drug Delivery Technology ◽

10.25258/ijddt.10.3.12 ◽

2020 ◽

Vol 10 (03) ◽

pp. 374-377

Author(s):

Ibtihal Ismail Muhammad Al-Ani

Keyword(s):

Room Temperature ◽

Extraction Efficiency ◽

Ph Value ◽

Bacterial Number ◽

Qualitative Properties ◽

Product Density ◽

Ph Values ◽

Extraction Volume ◽

Refrigerator Temperature ◽

Soda Solution

The present study aimed to study the possibility of producing a drink that looks like grafted milk by using chickpeas and evaluate its physical, chemical, microbial, and sensory properties. The result showed the superiority of F treatment (soaking 100 grams of chickpeas at the refrigerator temperature 4ºC for 12 hours) over the rest seven treatments in extraction efficiency, which was 70%, while, it was 50.5% in H treatment (soaking 100 grams of chickpeas in the heated water at 60ºC for 30 minutes). The highest value of the product density was after water and flavorings addition in the D treatment (soaking 100 grams chickpeas in 0.05 soda solution at 60ºC for 30 minutes), and it was 0.97 g cm-3, compared with the lowest density 0.57 g cm-3 in A treatment (soaking 100 grams chickpeas in 0.05 soda solution at room temperature 25ºC for 12 hours). pH values were highest in A treatment compared with the other treatments, and its value was 7.66 in the 1st and 2nd day, after dissolving in a refrigerator at 4ºC, and then, for 5 minutes at room temperature 30ºC. The lowest value in the D treatment was 6.45 on the 1st day, and 6.87 on the 2nd day in the G treatment. On the 3rd day, the highest pH value was 7.13 in the D treatment, and the lowest value 6.79 was in the E treatment. pH highest value was 6.2 on the 4th day in A treatment. From the last results, it may be concluded that F treatment was the best in extraction efficiency, the final product density, and less total bacterial number, after dissolving for 5 days at refrigerator temperature 4ºC, and then, at room temperature 30ºC for 3 and 48 hours incubation. The best extraction volume and pH were in A treatment.

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Impaired Upper Airway Integrity by Residual Meeting Abstracts

Anesthesiology ◽

10.1097/aln.0b013e31819faa71 ◽

2009 ◽

Vol 110 (6) ◽

pp. 1253-1260 ◽

Cited By ~ 56

Author(s):

Frank Herbstreit ◽

Jürgen Peters ◽

Matthias Eikermann

Keyword(s):

Neuromuscular Blockade ◽

Lung Volume ◽

Upper Airway ◽

Random Order ◽

Compensatory Response ◽

Residual Neuromuscular Blockade ◽

Pharyngeal Pressure ◽

Pressure Threshold ◽

Airway Collapsibility ◽

Closing Pressure

Background Residual neuromuscular blockade increases the risk to develop postoperative complications. The authors hypothesized that minimal neuromuscular blockade (train-of-four [TOF] ratio 0.5-1) increases upper airway collapsibility and impairs upper airway dilator muscle compensatory responses to negative pharyngeal pressure challenges. Methods Epiglottic and nasal mask pressures, genioglossus electromyogram, respiratory timing, and changes in lung volume were measured in awake healthy volunteers (n = 15) before, during (TOF = 0.5 and 0.8 [steady state]), and after recovery of TOF to unity from rocuronium-induced partial neuromuscular blockade. Passive upper airway closing pressure (negative pressure drops, random order, range +2 to -30 cm H2O) and pressure threshold for flow limitation were determined. Results Upper airway closing pressure increased (was less negative) significantly from baseline by 54 +/- 4.4% (means +/- SEM), 37 +/- 4.2%, and 16 +/- 4.1% at TOF ratios of 0.5, 0.8, and 1.0, respectively (P < 0.01 vs. baseline for any level). Phasic genioglossus activity almost quadrupled in response to negative (-20 cm H2O) pharyngeal pressure at baseline, and this increase was significantly impaired by 57 +/- 44% and 32 +/- 6% at TOF ratios of 0.5 and 0.8, respectively (P < 0.01 vs. baseline). End-expiratory lung volume, respiratory rate, and tidal volume did not change. Conclusion Minimal neuromuscular blockade markedly increases upper airway closing pressure, partly by impairing the genioglossus muscle compensatory response. Increased airway collapsibility despite unaffected values for resting ventilation may predispose patients to postoperative respiratory complications, particularly during airway challenges.

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Validation of the Pseudo Imprinted Microspheres for Solid-Phase Extraction of Acyclovir from Swine Tissue

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.393-395.1591 ◽

2011 ◽

Vol 393-395 ◽

pp. 1591-1594

Author(s):

Feng Xia Qiao ◽

Hong Yuan Yan

Keyword(s):

Solid Phase Extraction ◽

Solid Phase ◽

Suspension Polymerization ◽

Aqueous Suspension ◽

Selective Extraction ◽

Phase Extraction ◽

Matrix Interferences ◽

The Matrix ◽

Extraction Volume ◽

Swine Tissue

The novel pseudo imprinted microspheres were synthesized by aqueous suspension polymerization using theophylline as the template and employed as a special sorbent of solid-phase extraction for selective extraction of acyclovir from swine tissue. The pseudo imprinted microspheres revealed high affinity and selectivity to acyclovir, and the matrix interferences could be efficiently eliminated, which make the extract of solid-phase extraction clean enough for HPLC analysis. The parameters that affect the extraction efficiency of solid-phase extraction were investigated, including solvent of extraction, volume of loading sample, washing and elution solvent, etc. Good linearity was obtained in a range of 0.05~15 μg/mL with correlation coefficient (r2) of 0.9991. The recoveries at three spiked levels were ranged from 91.4% to101.0% with RSD less than of 5.0%.

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