Effect of Lung Volume on Lung Resistance and Elastance in Awake Subjects Measured during Sinusoidal Forcing

Barnas, G. M.; Sprung, J.; Craft, Tim; Williams, John E.; Ryder, Ian; Yun, Jihwan; Mackenzie, Colin F.

doi:10.1097/00000542-199306000-00010

Cited by 30 publications

(9 citation statements)

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“…PEEP might also reduce nonlinear mechanical phenomena such as pop-on and -off of closed airways, and formations of menisci and atelectasis, all of which act as unpredictable resistive and elastic elements in the respiratory tissue [8,[11][12][13]. Our results are consistent with the result of Barnas et al [7] suggesting that a moderate amount of PEEP would decrease lung resistance and elastance around the physiological FRC level.…”

Section: Discussionsupporting

confidence: 89%

“…The reduction in ZRs by PEEP might be due to lung volume expansion above FRC level and bimodal, i.e., the decreases in both airway and tissue impedances. In the anesthetized supine position, in which FRC is lower than other postures [9,10], airway derecruitment and atelectasis are characteristic features as well as the reduction of airway caliber [7,8,11]. PEEP may decrease airway resistance by increasing the airway caliber.…”

Section: Discussionmentioning

confidence: 98%

“…Minimal phase differences suggest that pendelluft is not appreciable in the simulation ume below functional residual capacity (FRC) and the other due to the presence of a floppy chest wall segment. Barnas et al [7] demonstrated that in awake sitting humans both lung resistance and elastance increased with decreasing lung volume below FRC. By contrast, Dechman et al [8] reported that in open-chest supine dogs, lung elastance increased with decreasing lung volume whereas lung resistance did not show a consistent change unless FRC was extremely low.…”

Section: Discussionmentioning

confidence: 99%

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Pendelluft is not the major contributor to respiratory insufficiency in dogs with flail chest: a mathematical analysis

et al. 1995

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"Pendelluft", or out-of-phase movement of the airway gas between the intact and flait-chest-side lungs has long been believed to be the major contributor to respiratory dysfunction in patients with flail chest. However, conflicting findings have also been reported mainly from animal studies. The aim of this study was to provide a mathematical projection on this classical problem. We measured respiratory impedance (ZRS) of dogs with flail chest using a pseudorandom forced oscillation method. A mathematical model implementing flail chest was fitted toZRS. The fitted results were used in simulating the mechanical behavior of a respiratory system with flail chest during spontaneous breathing. Our results suggest that the paradoxical movement of breathing between the flail segment and the intact chest wall does not create substantial pendelluft and that alveolar hypoventilation is created by the wasting movement of the flail segment which interferes with effective thoracic expansion.

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Section: Discussionsupporting

confidence: 89%

Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

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Pendelluft is not the major contributor to respiratory insufficiency in dogs with flail chest: a mathematical analysis

et al. 1995

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“…Previous forced oscillation studies have relied on the manual adjustment of small bias flows into the breathing circuit to compensate for leaks and to maintain specified lung volumes during oscillatory excitations. 2,13,15 While several investigators have developed closed-loop systems to maintain mean airway pressure during forced oscillations, 3,5,7,28,29 they must rely on separate servo-controlled systems operating in parallel to an oscillatory pressure or flow generator.…”

Section: Introductionmentioning

confidence: 99%

Servo-Controlled Pneumatic Pressure Oscillator for Respiratory Impedance Measurements and High-Frequency Ventilation

Kaczka¹,

Lutchen²

2004

Annals of Biomedical Engineering

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Abstract-The ability to provide forced oscillatory excitation of the respiratory system can be useful in mechanical impedance measurements as well as high frequency ventilation (HFV). Experimental systems currently used for generating forced oscillations are limited in their ability to provide high amplitude flows or maintain the respiratory system at a constant mean pressure during excitation. This paper presents the design and implementation of a pneumatic pressure oscillator based on a proportional solenoid valve. The device is capable of providing forced oscillatory excitations to the respiratory system over a bandwidth suitable for mechanical impedance measurements and HVF. It delivers high amplitude flows (>1.4 l/s) and utilizes a servo-control mechanism to maintain a load at a fixed mean pressure during simultaneous oscillation. Under open-loop conditions, the device exhibited a static hysteresis of approximately 7%, while its dynamic magnitude and phase responses were flat out to 10 Hz. Broad-band measurement of total harmonic distortion was approximately 19%. Under closed-loop conditions, the oscillator was able to maintain a mechanical test load at both positive and negative mean pressures during oscillatory excitations from 0.1 to 10.0 Hz. Impedance of the test load agreed closely with theoretical predictions. We conclude that this servo-controlled oscillator can be a useful tool for respiratory impedance measurements as well as HFV.

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“…Indeed, CNAP application induces signi®cant decreases in EELV [12], and consequently in gas compliance. Furthermore, these decreases in EELV have already been reported to result in reduced lung compliance under CNAP, due to the sigmoid shape of the lung volume/transpulmonary pressure relationship [26]. Besides, decreases in respiratory reactance have previously been observed during resistive or elastic loading, and attributed to an increase in tissue elastance resulting from increased respiratory muscle activity [27].…”

Section: Respiratory Response To Decreasing Continuous Negative Airwamentioning

confidence: 85%

Respiratory impedance response to continuous negative airway pressure in awake controls and OSAS

et al. 2001

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The aim of the study was to determine whether the response of respiratory impedance (Zrs) to decreasing levels of continuous negative airway pressure (CNAP) during wakefulness, differs in controls and subjects with obstructive sleep apnoea syndrome (OSAS).Zrs was measured by the forced oscillation technique (4±32 Hz) in 15 controls and 21 patients with OSAS (apnoea/hypopnoea index >20 per sleep hour) with normal lung function, in the basal state and with application of decreasing CNAP of -5, -10, and -15 hPa. Respiratory resistance was extrapolated to 0 Hz (R0) and estimated at 16 Hz (R16) by linear regression analysis of respiratory resistive impedance versus frequency. Respiratory elastance (Ers) and inertance (Irs) were estimated by multilinear regression analysis of respiratory reactance versus frequency, and resonance frequency (RF) was determined as RF=(1/2p)(Ers/Irs) 0.5 . In both groups, R0, R16, Ers and RF signi®cantly increased as the CNAP level decreased (pv0.0001 for all). R0, Ers, and RF increased signi®cantly more in OSAS than in controls (pv0.01, 0.001, and 0.0001, respectively), independently of the severity of obesity. Receiver operator characteristic curves showed that the parameter which best detected OSAS was RF, with a sensitivity of 81% and 93% speci®city for the 13.6 Hz cut-off point.The results of the present study suggest that the response of respiratory impedance to decreasing continuous negative airway pressure levels, might allow detection of obstructive sleep apnoea syndrome in subjects with normal lung function. Obstructive sleep apnoea/hypopnoea syndrome (OSAS) is characterized by the occurrence of repetitive upper airway (UA) narrowing and/or closure during sleep. Obstructive respiratory events are generally explained by the inef®ciency of the dilating muscles in counterbalancing the tendency of the pharyngeal airway to collapse, due to the inspiratory decrease in UA transmural pressure [1]. The main factors predisposing subjects to OSAS appear to be: 1) a reduction of UA calibre [2]; 2) an increase in UA resistance, as well as in pulmonary and respiratory resistances [3±5]; 3) an increase in UA compliance [4,6,7]; and 4) dysfunction of the UA dilating muscles [8].The application of continuous negative airway pressure (CNAP) at the airway opening generates a subatmospheric intraluminal UA pressure that simulates the conditions promoting the occurrence of obstructive respiratory events. The effect of CNAP on pharyngeal cross-sectional area and resistance have been widely investigated in control and OSAS subjects [4, 8±11], but, to the authors9 knowledge, CNAPinduced changes in the respiratory mechanical parameters remain poorly documented [12]. The aim of the present study was, therefore, to investigate whether the response of respiratory mechanics to decreasing CNAP levels differs between control and OSAS subjects, and might provide a predictive index of OSAS. To this end, the forced oscillation technique (FOT) was used, which allows easy measurement of respiratory imped...

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Effect of Lung Volume on Lung Resistance and Elastance in Awake Subjects Measured during Sinusoidal Forcing

Cited by 30 publications

References 0 publications

Pendelluft is not the major contributor to respiratory insufficiency in dogs with flail chest: a mathematical analysis

Pendelluft is not the major contributor to respiratory insufficiency in dogs with flail chest: a mathematical analysis

Servo-Controlled Pneumatic Pressure Oscillator for Respiratory Impedance Measurements and High-Frequency Ventilation

Respiratory impedance response to continuous negative airway pressure in awake controls and OSAS

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