Treatment of hypotension in pigs with an inspiratory impedance threshold device: A feasibility study

Lurie, Keith G.; Zielinski, Todd; McKnite, Scott; Idris, Ahamed H.; Yannopoulos, Demetris; Raedler, Claus; Sigurðsson, Garðar; Benditt, David G.; Voelckel, Wolfgang G.

doi:10.1097/01.ccm.0000131207.29081.a2

Cited by 49 publications

(40 citation statements)

References 15 publications

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“…During ITD breathing there are three key effects associated with central hemodynamics; a decrease in intrathoracic pressure (26), an increase in arterial pressure oscillations (Table 2), and the protection of Q (8,9). At the cerebral level, there are similar decreases in ICP (40), and we have now presented evidence in this investigation to indicate increases in CBFV oscillations (Table 2).…”

Section: Discussionsupporting

confidence: 59%

“…The ITD is a small, light-weight, disposable plastic valve that was recently developed for treatment of a number of different clinical conditions associated with significant life-threatening hypotension (24,26,32,33,38). The ITD includes a specially designed valve that closes when the pressure within the thorax is less than atmospheric pressure and a second valve (termed the safety check valve) that opens at a preset negative intrathoracic pressure.…”

Section: Methodsmentioning

confidence: 99%

“…This vacuum promotes an increase in venous return, thereby increasing ventricular preload and subsequent cardiac output (Q) and arterial blood pressure (9,26). Breathing on the ITD also increases cerebral blood flow velocity (CBFV) in resting, supine humans (12) and in the hemorrhaging porcine model, application of negative intrathoracic pressure reduces intracranial pressure (ICP) and subsequently elevates cerebral perfusion pressure (40,41).…”

mentioning

confidence: 99%

“…The ITD was designed to create a greater reduction in intrathoracic pressure during inspiration, enhancing the natural vacuum within the chest (26,37). This vacuum promotes an increase in venous return, thereby increasing ventricular preload and subsequent cardiac output (Q) and arterial blood pressure (9,26).…”

mentioning

confidence: 99%

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Inspiratory resistance delays the reporting of symptoms with central hypovolemia: association with cerebral blood flow

Rickards

Ryan

Cooke

et al. 2007

American Journal of Physiology-Regulatory, Integrative and Comp

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Rickards CA, Ryan KL, Cooke WH, Lurie KG, Convertino VA. Inspiratory resistance delays the reporting of symptoms with central hypovolemia: association with cerebral blood flow. Am J Physiol Regul Integr Comp Physiol 293: R243-R250, 2007. First published May 16, 2007; doi:10.1152/ajpregu.00087.2007.-We tested the hypothesis that breathing through an inspiratory threshold device (ITD) during progressive central hypovolemia would protect cerebral perfusion and attenuate the reporting of presyncopal symptoms. Eight human subjects were exposed to lower-body negative pressure (LBNP) until the presence of symptoms while breathing through either an active ITD (Ϫ7 cmH2O impedance) or a sham ITD (0 cmH2O). Cerebral blood flow velocity (CBFV) was measured continuously via transcranial Doppler and analyzed in both time and frequency domains. Subjects were asked to report any subjective presyncopal symptoms (e.g., dizziness, nausea) at the conclusion of each LBNP exposure. Symptoms were coincident with physiological evidence of cardiovascular collapse (e.g., hypotension, bradycardia). Breathing on the active ITD increased LBNP tolerance time (mean Ϯ SE) from 2,014 Ϯ 106 s to 2,259 Ϯ 138 s (P ϭ 0.006). We compared CBFV responses at the time of symptoms during the sham ITD trial with those at the same absolute time during the active ITD trial (when there were no symptoms). While there was no difference in mean CBFV at these time points (sham, 44 Ϯ 4 cm/s vs. active, 47 Ϯ 4; P ϭ 0.587), total oscillations (sum of high-and low-frequency spectral power) of CBFV were higher (P ϭ 0.004) with the active ITD (45.6 Ϯ 10.2 cm/s 2 ) than the sham ITD (22.1 Ϯ 5.4 cm/s 2 ). We conclude that greater oscillations around the same absolute level of mean CBFV are induced by inspiratory resistance and may contribute to the delay in symptoms and cardiovascular collapse that accompany progressive central hypovolemia.inspiratory threshold device; cerebral blood flow regulation; lowerbody negative pressure THE PRESERVATION OF CEREBRAL blood flow during hypotensive stress is integral in delaying the onset of presyncopal symptoms and maintaining consciousness. Recent data reported from several investigations have demonstrated the benefits of an inspiratory impedance threshold device (ITD) in elevating cerebral perfusion pressure in animals (39, 40) and reducing the reporting of presyncopal symptoms in humans (8, 27) with reductions in central blood volume.The ITD was designed to create a greater reduction in intrathoracic pressure during inspiration, enhancing the natural vacuum within the chest (26, 37). This vacuum promotes an increase in venous return, thereby increasing ventricular preload and subsequent cardiac output (Q) and arterial blood pressure (9, 26). Breathing on the ITD also increases cerebral blood flow velocity (CBFV) in resting, supine humans (12) and in the hemorrhaging porcine model, application of negative intrathoracic pressure reduces intracranial pressure (ICP) and subsequently elevates cerebral perfusion pressure (40, 41). Th...

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Section: Discussionsupporting

confidence: 59%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Inspiratory resistance delays the reporting of symptoms with central hypovolemia: association with cerebral blood flow

Rickards

Ryan

Cooke

et al. 2007

American Journal of Physiology-Regulatory, Integrative and Comp

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“…13 Animal studies had previously demonstrated that an ITD increased mean arterial pressure in heat stroke, 23 and blood pressure, 24 cardiac output, 25 and survival time 26 after hypotension induced by severe blood loss. To determine if there were similar effects in humans, healthy subjects were exposed to progressive lower-body negative pressure.…”

Section: Patient Tolerance and Response To Acute Central Hypovolemia mentioning

confidence: 99%

Optimizing the Respiratory Pump: Harnessing Inspiratory Resistance to Treat Systemic Hypotension

et al. 2011

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We review the physiology and affects of inspiration through a low level of added resistance for the treatment of hypotension. Recent animal and clinical studies demonstrated that one of the body's natural response mechanisms to hypotension is to harness the respiratory pump to increase circulation. That finding is consistent with observations, in the 1960s, about the effect of lowering intrathoracic pressure on key physiological and hemodynamic variables. We describe studies that focused on the fundamental relationship between the generation of negative intrathoracic pressure during inspiration through a low level of resistance created by an impedance threshold device and the physiologic sequelae of a respiratory pump. A decrease in intrathoracic pressure during inspiration through a fixed resistance resulting in a pressure difference of 7 cm H 2 O has multiple physiological benefits, including: enhanced venous return and cardiac stroke volume, lower intracranial pressure, resetting of the cardiac baroreflex, elevated cerebral blood flow oscillations, increased tissue blood flow/pressure gradient, and maintenance of the integrity of the baroreflexmediated coherence between arterial pressure and sympathetic nerve activity. While breathing has traditionally been thought primarily to provide gas exchange, studies of the mechanisms involved in animals and humans provide the physiological underpinnings for "the other side of breathing": to increase circulation to the heart and brain, especially in the setting of physiological stress. The existing results support the use of the intrathoracic pump to treat clinical conditions associated with hypotension, including orthostatic hypotension, hypotension during and after hemodialysis, hemorrhagic shock, heat stroke, septic shock, and cardiac arrest. Harnessing these fundamental mechanisms that control cardiopulmonary physiology provides new opportunities for respiratory therapists and others who have traditionally focused on ventilation to also help treat serious and often life-threatening circulatory disorders.

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Intrathoracic Pressure Regulation for the Treatment of Hypotension

Cinel

Metzger

Dellinger

2009

Intensive Care Medicine

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Treatment of hypotension in pigs with an inspiratory impedance threshold device: A feasibility study

Cited by 49 publications

References 15 publications

Inspiratory resistance delays the reporting of symptoms with central hypovolemia: association with cerebral blood flow

Inspiratory resistance delays the reporting of symptoms with central hypovolemia: association with cerebral blood flow

Optimizing the Respiratory Pump: Harnessing Inspiratory Resistance to Treat Systemic Hypotension

Intrathoracic Pressure Regulation for the Treatment of Hypotension

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