Effects of gravity and blood volume shifts on cardiogenic oscillations in respired gas

Montmerle, Stéphanie; Linnarsson, Dag

doi:10.1152/japplphysiol.00252.2005

Cited by 7 publications

(2 citation statements)

References 81 publications

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“…The volume of the adult trachea is typically between 25 ml and 35 ml , whereas the literature indicates that the volume of cardiogenic oscillations is typically 6–40 ml . Taylor dispersion causes longitudinal spreading of a plug gas flowing in a pipe , and this will mix gas longitudinally in the trachea in analogous fashion to the longitudinal mixing demonstrated by van der Kooij and Luijendijk in the bronchi .…”

Section: Discussionmentioning

confidence: 99%

A physiological study to determine the mechanism of carbon dioxide clearance during apnoea when using transnasal humidified rapid insufflation ventilatory exchange (THRIVE)

et al. 2019

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Summary Clinical observations suggest that compared with standard apnoeic oxygenation, transnasal humidified rapid‐insufflation ventilatory exchange using high‐flow nasal oxygenation reduces the rate of carbon dioxide accumulation in patients who are anaesthetised and apnoeic. This suggests that active gas exchange takes place, but the mechanisms by which it may occur have not been described. We used three laboratory airway models to investigate mechanisms of carbon dioxide clearance in apnoeic patients. We determined flow patterns using particle image velocimetry in a two‐dimensional model using particle‐seeded fluorescent solution; visualised gas clearance in a three‐dimensional printed trachea model in air; and measured intra‐tracheal turbulence levels and carbon dioxide clearance rates using a three‐dimensional printed model in air mounted on a lung simulator. Cardiogenic oscillations were simulated in all experiments. The visualisation experiments indicated that gaseous mixing was occurring in the trachea. With no cardiogenic oscillations applied, mean (SD) carbon dioxide clearance increased from 0.29 (0.04) ml.min−1 to 1.34 (0.14) ml.min−1 as the transnasal humidified rapid‐insufflation ventilatory exchange flow rate was increased from 20 l.min−1 to 70 l.min−1 (p = 0.0001). With a cardiogenic oscillation of 20 ml.beat−1 applied, carbon dioxide clearance increased from 11.9 (0.50) ml.min−1 to 17.4 (1.2) ml.min−1 as the transnasal humidified rapid‐insufflation ventilatory exchange flow rate was increased from 20 l.min−1 to 70 l.min−1 (p = 0.0014). These findings suggest that enhanced carbon dioxide clearance observed under apnoeic conditions with transnasal humidified rapid‐insufflation ventilatory exchange, as compared with classical apnoeic oxygenation, may be explained by an interaction between entrained and highly turbulent supraglottic flow vortices created by high‐flow nasal oxygen and cardiogenic oscillations.

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Section: Discussionmentioning

confidence: 99%

A physiological study to determine the mechanism of carbon dioxide clearance during apnoea when using transnasal humidified rapid insufflation ventilatory exchange (THRIVE)

et al. 2019

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“…Therefore, the inspiratory and expiratory times are from actual patients undergoing anaesthesia. We included data on a range of cardiogenic stroke volumes (5–40 ml) as reported clinically . We did not report results from models with different airway geometries in our publication, although preliminary data indicated detectable enhancement of carbon dioxide clearance in stenotic airways using transnasal humidified rapid insufflation ventilatory exchange (THRIVE), consistent with clinical data; we intend to publish these data shortly.…”

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confidence: 99%

Carbon dioxide clearance during apnoea. A reply

et al. 2019

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We thank Dr. Lyons for his observations on our paper [1], and offer the following thoughts in response.Firstly, the mouth was modelled as being open. As stated in the paper, we used the flow profile measured by Tusman et al. [2]. Therefore, the inspiratory and expiratory times are from actual patients undergoing anaesthesia. We included data on a range of cardiogenic stroke volumes (5-40 ml) as reported clinically [2][3][4]. We did not report results from models with different airway geometries in our publication, although preliminary data indicated detectable enhancement of carbon dioxide clearance in stenotic airways using transnasal humidified rapid insufflation ventilatory exchange (THRIVE), consistent with clinical data;we intend to publish these data shortly. Indeed, the clinical observation that THRIVE is efficacious in patients with stenoses [5, 6] suggests a driving pressure high enough to generate tracheal gas flow, which would be consistent with the driving pressure arising from cardiogenic oscillations.The effect of cardiogenic oscillations operating on the small airways is included in the model, not through replication of small airways per se but through the computer-controlled 'diaphragm' that acts on the model plenum. As Dr. Lyons notes, there is inter-patient variation in the rate of carbon dioxide clearance in patients treated with THRIVE [5, 7]. However, this does not imply that oxygenation and clearance of carbon dioxide are not occurring simultaneously. Furthermore, different efficacies of oxygenation and carbon dioxide clearance do not speak to the validity of the model. Indeed, one would not expect accurate symmetry due to the inherent fluid characteristics and physiological non-linearities of the gases. Naturally there is also less variation in oxygenation success when measured using S p O 2 , and drawing conclusions about the symmetry of carbon dioxide clearance and oxygenation from clinical measures is complex.We would suggest caution in comparing clinical data from children [8] and adults [5,7]. There are obvious physiological and anatomical differences. Our model is of an adult airway and it was not our intention to imply that these mechanisms are applicable to the neonatal airway.Indeed, preliminary data from neonatal versions of our models, which we intend to publish in the future, show significant differences in the fluid flow compared with the adult model that was the subject of our publication. The preliminary laboratory results in the neonatal version of our model are consistent with the clinically observed lower rates of carbon dioxide clearance in children, which provides further validation of our model.We agree that there are differences in end-tidal and arterial blood gas measures and noted this in our paper.Finally, we note that the mechanisms we have proposed have been corroborated by further work [9]. That said, there is undoubtedly more to understand and further clinical and modelling work will be beneficial in augmenting our current understanding of THRIVE in clinical pr...

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Pulmonary artery pulsatility is the main cause of cardiogenic oscillations

Suárez-Sipmann

Santos

Peces-Barba³

et al. 2012

J Clin Monit Comput

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The genesis of cardiogenic oscillations, i.e. the small waves in airway pressure (COS(paw)) and flow (COS(flow)) signals recorded at the airway opening is under debate. We hypothesized that these waves are originated from cyclic changes in pulmonary artery (PA) pressure and flow but not from the physical transmission of heartbeats onto the lungs. The aim of this study was to test this hypothesis. In 10 anesthetized pigs, COS were evaluated during expiratory breath-holds at baseline with intact chest and during open chest conditions at: (1) close contact between heart and lungs; (2) no heart-lungs contact by lifting the heart apex outside the thoracic cavity; (3) PA clamping at the main trunk during 10 s; and (4) during manual massage after cardiac arrest maintaining the heart apex outside the thorax, with and without PA clamping. Baseline COS(paw) and COS(flow) amplitude were 0.70 ± 0.08 cmH(2)O and 0.51 ± 0.06 L/min, respectively. Both COS amplitude decreased during open chest conditions in step 1 and 2 (p < 0.05). However, COS(paw) and COS(flow) amplitude did not depend on whether the heart was in contact or isolated from the surrounding lung parenchyma. COS(paw) and COS(flow) disappeared when pulmonary blood flow was stopped after clamping PA in all animals. Manual heart massages reproduced COS but they disappeared when PA was clamped during this maneuver. The transmission of PA pulsatilty across the lungs generates COS(paw) and COS(flow) measured at the airway opening. This information has potential applications for respiratory monitoring.

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Effects of gravity and blood volume shifts on cardiogenic oscillations in respired gas

Cited by 7 publications

References 81 publications

A physiological study to determine the mechanism of carbon dioxide clearance during apnoea when using transnasal humidified rapid insufflation ventilatory exchange (THRIVE)

A physiological study to determine the mechanism of carbon dioxide clearance during apnoea when using transnasal humidified rapid insufflation ventilatory exchange (THRIVE)

Carbon dioxide clearance during apnoea. A reply

Pulmonary artery pulsatility is the main cause of cardiogenic oscillations

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