A comparison of endotracheal tube compensation techniques for the measurement of respiratory mechanical impedance at low frequencies

2021 ◽  
Author(s):  
Andrea F. Cruz ◽  
Jacob Herrmann ◽  
Carlos R. R. Carvalho ◽  
David W. Kaczka
Keyword(s):  
Endotracheal Tube ◽  
Mechanical Impedance ◽  
Low Frequencies ◽  
Tube Compensation

Low-frequency respiratory mechanical impedance in the rat

1987 ◽  
Vol 63 (1) ◽  
pp. 36-43 ◽  
Author(s):  
Z. Hantos ◽  
B. Daroczy ◽  
B. Suki ◽  
S. Nagy
Keyword(s):  
Frequency Dependence ◽  
Chest Wall ◽  
Low Frequency ◽  
Mechanical Impedance ◽  
Total Resistance ◽  
Low Frequencies ◽  
Chest Wall Compliance ◽  
Before And After ◽  
Airway Opening ◽  
Wall Compliance

modified forced oscillatory technique was used to determine the respiratory mechanical impedances in anesthetized, paralyzed rats between 0.25 and 10 Hz. From the total respiratory (Zrs) and pulmonary impedance (ZL), measured with pseudorandom oscillations applied at the airway opening before and after thoracotomy, respectively, the chest wall impedance (ZW) was calculated as ZW = Zrs - ZL. The pulmonary (RL) and chest wall resistances were both markedly frequency dependent: between 0.25 and 2 Hz they contributed equally to the total resistance falling from 81.4 +/- 18.3 (SD) at 0.25 Hz to 27.1 +/- 1.7 kPa.l–1 X s at 2 Hz. The pulmonary compliance (CL) decreased mildly, from 2.78 +/- 0.44 at 0.25 Hz to 2.36 +/- 0.39 ml/kPa at 2 Hz, and then increased at higher frequencies, whereas the chest wall compliance declined monotonously from 4.19 +/- 0.88 at 0.25 Hz to 1.93 +/- 0.14 ml/kPa at 10 Hz. Although the frequency dependence of ZW can be interpreted on the basis of parallel inhomogeneities alone, the sharp fall in RL together with the relatively constant CL suggests that at low frequencies significant losses are imposed by the non-Newtonian resistive properties of the lung tissue.

scholarly journals Expiratory automatic endotracheal tube compensation reduces dynamic hyperinflation in a physical lung model

Critical Care ◽  
2009 ◽  
Vol 13 (1) ◽  
pp. R4 ◽  
Author(s):  
Christoph Haberthür ◽  
Annekathrin Mehlig ◽  
John F Stover ◽  
Stefan Schumann ◽  
Knut Möller ◽  
...  
Keyword(s):  
Endotracheal Tube ◽  
Lung Model ◽  
Dynamic Hyperinflation ◽  
Tube Compensation ◽  
Physical Lung Model

Isolation from Vibration with a Mounting Utilizing Low- and High-Damping Rubberlike Materials

1962 ◽  
Vol 35 (3) ◽  
pp. 798-812
Author(s):  
J. C. Snowden
Keyword(s):  
Natural Frequencies ◽  
Mechanical Impedance ◽  
Dynamic Mechanical Properties ◽  
Lumped Mass ◽  
Low Frequencies ◽  
Synthetic Rubber ◽  
Wave Effects ◽  
Linear Manner ◽  
Rubberlike Materials ◽  
Solid Type

Abstract This paper describes a theoretical investigation of the performance of an antivibration mounting utilizing elements of low- and high-damping rubberlike materials in parallel, arranged such that both materials experience the same strain. Knowledge of the dynamic mechanical properties of natural rubber and a high-damping synthetic rubber has enabled the behavior of the so-called parallel mounting to be estimated realistically. General expressions have been derived from which the response ratio of a parallel mounting employed in one- and two-stage mounting systems may be determined, once the variation with frequency of the mechanical impedance Zω of the foundation of the mounting system is known. The mounting systems have been assumed throughout to possess natural frequencies of 5 cps. To compare the response ratios of the mounting systems, a specific nonrigid foundation has been considered, namely, a simply supported beam possessing damping of the solid type. The beam possesses a “springlike” impedance at frequencies below its fundamental resonance, which is assumed to occur/at 50 cps. The ratio of the mechanical impedance of the beam to the value it takes at low frequencies is plotted in Figure 3 of Reference 1, through the frequency range 1–1000 cps. The mounted item is supposed to behave purely as a lumped mass. “Wave effects” that may occur in the rubberlike mount materials are disregarded. These materials are always assumed to behave in a linear manner.

scholarly journals Low-pressure support vs automatic tube compensation during spontaneous breathing trial for weaning

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Claude Guérin ◽  
Nicolas Terzi ◽  
Mehdi Mezidi ◽  
Loredana Baboi ◽  
Nader Chebib ◽  
...  
Keyword(s):  
Endotracheal Tube ◽  
Spontaneous Breathing ◽  
Pressure Support ◽  
Spontaneous Breathing Trial ◽  
Lung Ventilation ◽  
Low Pressure ◽  
Ventilation Distribution ◽  
Data Logger ◽  
Impedance Tomography ◽  
Tube Compensation

Abstract Background During spontaneous breathing trial, low-pressure support is thought to compensate for endotracheal tube resistance, but it actually should provide overassistance. Automatic tube compensation is an option available in the ventilator to compensate for flow-resistance of endotracheal tube. Its effects on patient effort have been poorly investigated. We aimed to compare the effects of low-pressure support and automatic tube compensation during spontaneous breathing trial on breathing power and lung ventilation distribution. Results We performed a randomized crossover study in 20 patients ready to wean. Each patient received both methods for 30 min separated by baseline ventilation: pressure support 0 cmH2O and automatic tube compensation 100% in one period and pressure support 7 cmH2O without automatic tube compensation in the other period, a 4 cmH2O positive end-expiratory pressure being applied in each. Same ventilator brand (Evita XL, Draeger, Germany) was used. Breathing power was assessed from Campbell diagram with esophageal pressure, airway pressure, flow and volume recorded by a data logger. Lung ventilation distribution was assessed by using electrical impedance tomography (Pulmovista, Draeger, Germany). During the last 2 min of low-pressure support and automatic compensation period breathing power and lung ventilation distribution were measured on each breath. Breathing power generated by the patient’s respiratory muscles was 7.2 (4.4–9.6) and 9.7 (5.7–21.9) J/min in low-pressure support and automatic tube compensation periods, respectively (P = 0.011). Lung ventilation distribution was not different between the two methods. Conclusions We found that ATC was associated with higher breathing power than low PS during SBT without altering the distribution of lung ventilation.

The S-SH Confusion Test and the Effects of Frequency Lowering

2019 ◽  
Vol 62 (5) ◽  
pp. 1486-1505
Author(s):  
Joshua M. Alexander
Keyword(s):  
Cognitive Processing ◽  
Hearing Aids ◽  
Response Times ◽  
Nonlinear Frequency ◽  
Low Frequencies ◽  
Frequency Compression ◽  
Negative Side ◽  
Minimal Word ◽  
Low Pass ◽  
Negative Side Effects

PurposeFrequency lowering in hearing aids can cause listeners to perceive [s] as [ʃ]. The S-SH Confusion Test, which consists of 66 minimal word pairs spoken by 6 female talkers, was designed to help clinicians and researchers document these negative side effects. This study's purpose was to use this new test to evaluate the hypothesis that these confusions will increase to the extent that low frequencies are altered.MethodTwenty-one listeners with normal hearing were each tested on 7 conditions. Three were control conditions that were low-pass filtered at 3.3, 5.0, and 9.1 kHz. Four conditions were processed with nonlinear frequency compression (NFC): 2 had a 3.3-kHz maximum audible output frequency (MAOF), with a start frequency (SF) of 1.6 or 2.2 kHz; 2 had a 5.0-kHz MAOF, with an SF of 1.6 or 4.0 kHz. Listeners' responses were analyzed using concepts from signal detection theory. Response times were also collected as a measure of cognitive processing.ResultsOverall, [s] for [ʃ] confusions were minimal. As predicted, [ʃ] for [s] confusions increased for NFC conditions with a lower versus higher MAOF and with a lower versus higher SF. Response times for trials with correct [s] responses were shortest for the 9.1-kHz control and increased for the 5.0- and 3.3-kHz controls. NFC response times were also significantly longer as MAOF and SF decreased. The NFC condition with the highest MAOF and SF had statistically shorter response times than its control condition, indicating that, under some circumstances, NFC may ease cognitive processing.ConclusionsLarge differences in the S-SH Confusion Test across frequency-lowering conditions show that it can be used to document a major negative side effect associated with frequency lowering. Smaller but significant differences in response times for correct [s] trials indicate that NFC can help or hinder cognitive processing, depending on its settings.

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