A new two-breath technique for extracting the  cerebrovascular response to arterial carbon dioxide

Cerebrovascular autoregulation is evaluated from spontaneous fluctuations in mean flow velocity (MFV) by transcranial Doppler ultrasound of the middle cerebral artery (MCA) with respect to changes in arterial blood pressure (BPMCA), but the effects of spontaneous fluctuations in arterial Pco 2 on MFV have been largely ignored. Autoregressive moving average analysis (ARMA), a closed-loop system identification technique, was applied to data from nine healthy subjects during spontaneous breathing, during inspiration of 10% CO2 for two breaths once per minute for 4 min, and during sustained breathing of 7% CO2. Cerebrovascular resistance index (CVRi) was calculated (CVRi = BPMCA/MFV). Reliable estimates of gain for BPMCA → MFV were obtained for spontaneous breathing and the two-breath method. In contrast, reliable gain estimates for Pco 2 → MFV or Pco 2 → CVRi were achieved only under the two-breath method. Pco 2 → MFV gain was smaller with the two-breath method than during sustained 7% CO2 ( P < 0.05). BPMCA was elevated by 7% CO2 but not by the two-breath method. The closed-loop model provides insight into interactions between BPMCA and Pco 2 on cerebrovascular control, but reliable solutions for Pco 2effects with ARMA analysis require perturbation by the two-breath method.

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System identification of closed-loop cardiovascular control: effects of posture and autonomic blockade

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1997.272.1.h448 ◽

1997 ◽

Vol 272 (1) ◽

pp. H448-H461 ◽

Cited By ~ 38

Author(s):

T. J. Mullen ◽

M. L. Appel ◽

R. Mukkamala ◽

J. M. Mathias ◽

R. J. Cohen

Keyword(s):

Blood Pressure ◽

Heart Rate ◽

System Identification ◽

Closed Loop ◽

Cardiac Contraction ◽

Loop Model ◽

Physiological Mechanisms ◽

Arterial Blood ◽

Autonomic Blockade ◽

Coupling Mechanisms

We applied system identification to the analysis of fluctuations in heart rate (HR), arterial blood pressure (ABP), and instantaneous lung volume (ILV) to characterize quantitatively the physiological mechanisms responsible for the couplings between these variables. We characterized two autonomically mediated coupling mechanisms [the heart rate baroreflex (HR baroreflex) and respiratory sinus arrhythmia (ILV-HR)] and two mechanically mediated coupling mechanisms [the blood pressure wavelet generated with each cardiac contraction (circulatory mechanics) and the direct mechanical effects of respiration on blood pressure (ILV⇢ABP)]. We evaluated the method in humans studied in the supine and standing postures under control conditions and under conditions of beta-sympathetic and parasympathetic pharmacological blockades. Combined beta-sympathetic and parasympathetic blockade abolished the autonomically mediated couplings while preserving the mechanically mediated coupling. Selective autonomic blockade and postural changes also altered the couplings in a manner consistent with known physiological mechanisms. System identification is an “inverse-modeling” technique that provides a means for creating a closed-loop model of cardiovascular regulation for an individual subject without altering the underlying physiological control mechanisms.

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Two-breath CO2 test detects altered dynamic cerebrovascular autoregulation and CO2 responsiveness with changes in arterial Pco2

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00384.2003 ◽

2004 ◽

Vol 287 (3) ◽

pp. R627-R632 ◽

Cited By ~ 17

Author(s):

Michael R. Edwards ◽

Deanna L. Devitt ◽

Richard L. Hughson

Keyword(s):

Dynamic Response ◽

Response Time ◽

Middle Cerebral Artery ◽

Cerebral Artery ◽

Moving Average ◽

Mean Flow ◽

Average Analysis ◽

Identification Technique ◽

Breath Co2 ◽

End Tidal

The new two-breath CO2 method was employed to test the hypotheses that small alterations in arterial Pco2 had an impact on the magnitude and dynamic response time of the CO2 effect on cerebrovascular resistance (CVRi) and the dynamic autoregulatory response to fluctuations in arterial pressure. During a 10-min protocol, eight subjects inspired two breaths from a bag with elevated Pco2, four different times, while end-tidal Pco2 was maintained at three levels: hypocapnia (LoCO2, 8 mmHg below resting values), normocapnia, and hypercapnia (HiCO2, 8 mmHg above resting values). Continuous measurements were made of mean blood pressure corrected to the level of the middle cerebral artery (BPMCA), Pco2 (estimated from expired CO2), and mean flow velocity (MFV, of the middle cerebral artery by Doppler ultrasound), with CVRi = BPMCA/MFV. Data were processed by a system identification technique (autoregressive moving average analysis) with gain and dynamic response time of adaptation estimated from the theoretical step responses. Consistent with our hypotheses, the magnitude of the Pco2-CVRi response was reduced from LoCO2 to HiCO2 [from −0.04 (SD 0.02) to −0.01 (SD 0.01) (mmHg·cm−1·s)·mmHg Pco2−1] and the time to reach 95% of the step plateau increased from 12.0 ± 4.9 to 20.5 ± 10.6 s. Dynamic autoregulation was impaired with elevated Pco2, as indicated by a reduction in gain from LoCO2 to HiCO2 [from 0.021 ± 0.012 to 0.007 ± 0.004 (mmHg·cm−1·s)·mmHg BPMCA−1], and time to reach 95% increased from 3.7 ± 2.8 to 20.0 ± 9.6 s. The two-breath technique detected dependence of the cerebrovascular CO2 response on Pco2 and changes in dynamic autoregulation with only small deviations in estimated arterial Pco2.

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Baroreflex gain: characterization using autoregressive moving average analysis

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1996.270.4.h1240 ◽

1996 ◽

Vol 270 (4) ◽

pp. H1240-H1249 ◽

Cited By ~ 13

Author(s):

D. J. Patton ◽

J. K. Triedman ◽

M. H. Perrott ◽

A. A. Vidian ◽

J. P. Saul

Keyword(s):

Impulse Response ◽

Moving Average ◽

Step Response ◽

Autoregressive Moving Average ◽

Response Curves ◽

Sharp Maximum ◽

Additional Information ◽

Arterial Blood ◽

Average Analysis ◽

The One

To study heart rate baroreflex gain, autoregressive moving average (ARMA) analysis, a multivariate method that allows evaluation of the dynamic ("beat-to-beat") interactions between changes in biological signals, was used to evaluate the relationships between R-R interval and arterial blood pressure (BP) during random-interval breathing. Parameters obtained by ARMA analysis of spontaneous fluctuations in BP and R-R interval in 17 volunteers were used to model the response of R-R interval to a transient 1-mmHg increase in BP; the resulting impulse-response and step-response curves were compared with baroreflex gain measured using bolus injections of phenylephrine (PE) and sodium nitroprusside (SNP). Impulse-response curves for the systolic BP-R-R relationship showed an early (0-1 s) sharp maximum of 5.5 +/- 4.2 ms/mmHg, which was smaller in magnitude but linearly correlated with baroreflex gain derived from SNP (14.5 +/- 9.7 ms/mmHg; r = 0.80, P < 0.002) and PE (31.6 +/- 26.7 ms/mmHg; r = 0.53, P < 0.05) injections. A similar relationship was also found between the one-beat ARMA step response and SNP injection (r = 0.70, P = 0.01). The integrated step response of the BP-R-R relationship over 6 s was 6.4 +/- 4.1 ms/mmHg, with no correlation to baroreflex gain determined by SNP (r = 0.33, P = 0.20) or PE (r = -0.15, P = 0.57). In conclusion, quantification of baroreflex gain consistent with other techniques may be achieved by ARMA analysis without perturbing mean BP. Correlation of baroreflex gain obtained by bolus injection to early measures of baroreflex gain obtained from the ARMA maximum impulse and early step responses, but not the late step response, suggests that the ARMA method may provide additional information regarding the frequency dependent effects of BP on R-R-interval.

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Multivariate modeling of cognitive-motor stimulation on neurovascular coupling: transcranial Doppler used to characterize myogenic and metabolic influences

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00161.2012 ◽

2012 ◽

Vol 303 (4) ◽

pp. R395-R407 ◽

Cited By ~ 31

Author(s):

Ronney B. Panerai ◽

Michelle Eyre ◽

John F. Potter

Keyword(s):

Transcranial Doppler ◽

Cerebral Blood Flow Velocity ◽

Moving Average ◽

Neurovascular Coupling ◽

Transcranial Doppler Ultrasound ◽

Diagnostic Value ◽

Cognitive Stimulation ◽

Neural Activation ◽

Arterial Blood ◽

End Tidal

Neural activation induces changes in cerebral blood flow velocity (CBFV) with separate contributions from resistance-area product (VRAP) and critical closing pressure (VCrCP). We modeled the dependence of VRAP and VCrCP on arterial blood pressure (ABP), end-tidal CO2 (EtCO2), and cognitive stimulation to test the hypothesis that VRAP reflects myogenic activity while VCrCP reflects metabolic pathways. In 14 healthy subjects, CBFV was measured with transcranial Doppler ultrasound, ABP with the Finapres device and EtCO2 with infrared capnography. Two different paradigms (word or puzzle) were repeated 10 times (30 s on-off), and the corresponding square-wave signal was used, together with ABP and EtCO2, as inputs to autoregressive-moving average (ARMA) models, which allowed identification of the separate contributions of the three inputs to either VRAP or VCrCP. For both paradigms, the contribution of ABP was mainly manifested through VRAP ( P < 0.005 for word; P < 0.004 for puzzle), while stimulation mainly contributed to VCrCP ( P < 0.002 for word; P < 0.033, for puzzle). The contribution of EtCO2 was relatively small (<10%) with greater contribution to VCrCP ( P < 0.01 for puzzle; not significant for word). Separate step responses were also obtained for each of the three inputs. ARMA modeling of VRAP and VCrCP allows the separation of the effects of cerebral autoregulation and CO2 reactivity from the main effects of cognitive-motor stimulation and have the potential to improve the diagnostic value of neurovascular coupling testing in physiological and clinical studies.

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Prior head-down tilt does not impair the cerebrovascular response to head-up tilt

Journal of Applied Physiology ◽

10.1152/japplphysiol.00871.2014 ◽

2015 ◽

Vol 118 (11) ◽

pp. 1356-1363 ◽

Cited By ~ 4

Author(s):

Changbin Yang ◽

Yuan Gao ◽

Danielle K. Greaves ◽

Rodrigo Villar ◽

Thomas Beltrame ◽

...

Keyword(s):

Blood Pressure ◽

Cardiac Output ◽

Peripheral Resistance ◽

Resistance Index ◽

Cardiovascular Responses ◽

Mean Flow ◽

Cerebrovascular Autoregulation ◽

Arterial Blood ◽

Head Up Tilt ◽

S Period

The hypothesis that cerebrovascular autoregulation was not impaired during head-up tilt (HUT) that followed brief exposures to varying degrees of prior head-down tilt (HDT) was tested in 10 healthy young men and women. Cerebral mean flow velocity (MFV) and cardiovascular responses were measured in transitions to a 60-s period of 75° HUT that followed supine rest (control) or 15 s HDT at −10°, −25°, and −55°. During HDT, heart rate (HR) was reduced for −25° and −55°, and cardiac output was lower at −55° HDT. MFV increased during −10° HDT, but not in the other conditions even though blood pressure at the middle cerebral artery (BPMCA) increased. On the transition to HUT, HR increased only for −55° condition, but stroke volume and cardiac output transiently increased for −25° and −55°. Total peripheral resistance index decreased in proportion to the magnitude of HDT and recovered over the first 20 s of HUT. MFV was significantly less in all HDT conditions compared with the control in the first 5-s period of HUT, but it recovered quickly. An autoregulation correction index derived from MFV recovery relative to BPMCA decline revealed a delay in the first 5 s for prior HDT compared with control but then a rapid increase to briefly exceed control after −55° HDT. This study showed that cerebrovascular autoregulation is modified by but not impaired by brief HDT prior to HUT and that cerebral MFV recovered quickly and more rapidly than arterial blood pressure to protect against cerebral hypoperfusion and potential syncope.

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Continuous estimates of dynamic cerebral autoregulation during transient hypocapnia and hypercapnia

Journal of Applied Physiology ◽

10.1152/japplphysiol.01157.2009 ◽

2010 ◽

Vol 108 (3) ◽

pp. 604-613 ◽

Cited By ~ 56

Author(s):

N. E. Dineen ◽

F G. Brodie ◽

T. G. Robinson ◽

R. B. Panerai

Keyword(s):

Blood Pressure ◽

Cerebral Autoregulation ◽

Moving Average ◽

Cerebral Arteries ◽

Transcranial Doppler Ultrasound ◽

Breath Hold ◽

New Approach ◽

Arterial Blood ◽

The Right ◽

Dynamic Cerebral Autoregulation

Dynamic cerebral autoregulation (CA) is the transient response of cerebral blood flow (CBF) to rapid blood pressure changes: it improves in hypocapnia and becomes impaired during hypercapnia. Batch-processing techniques have mostly been used to measure CA, providing a single estimate for an entire recording. A new approach to increase the temporal resolution of dynamic CA parameters was applied to transient hypercapnia and hypocapnia to describe the time-varying properties of dynamic CA during these conditions. Thirty healthy subjects (mean ± SD: 25 ± 6 yr, 9 men) were recruited. CBF velocity was recorded in both middle cerebral arteries (MCAs) with transcranial Doppler ultrasound. Arterial blood pressure (Finapres), end-tidal CO2 (ETCO2; infrared capnograph), and a three-lead ECG were also measured at rest and during repeated breath hold and hyperventilation. A moving window autoregressive moving average model provided continuous values of the dynamic CA index [autoregulation index (ARI)] and unconstrained gain. Breath hold led to significant increase in ETCO2 (+5.4 ± 6.1 mmHg), with concomitant increase in CBF velocity in both MCAs. Continuous dynamic CA parameters showed highly significant changes ( P < 0.001), with a temporal pattern reflecting a delayed dynamic response of CA to changes in arterial Pco2 and a maximal reduction in ARI of −5.1 ± 2.4 and −5.1 ± 2.3 for the right and left MCA, respectively. Hyperventilation led to a marked decrease in ETCO2 (−7.2 ± 4.1 mmHg, P < 0.001). Unexpectedly, CA efficiency dropped significantly with the inception of the metronome-controlled hyperventilation, but, after ∼30 s, the ARI increased gradually to show a maximum change of 5.7 ± 2.9 and 5.3 ± 3.0 for the right and left MCA, respectively ( P < 0.001). These results confirm the potential of continuous estimates of dynamic CA to improve our understanding of human cerebrovascular physiology and represent a promising new approach to improve the sensitivity of clinical applications of dynamic CA modeling.

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Determination of baroreflex gain using auto-regressive moving-average analysis during spontaneous breathing

Clinical Physiology ◽

10.1046/j.1365-2281.1999.00190.x ◽

1999 ◽

Vol 19 (5) ◽

pp. 369-377 ◽

Cited By ~ 13

Author(s):

O’Leary ◽

Lin ◽

Hughson

Keyword(s):

Spontaneous Breathing ◽

Moving Average ◽

Average Analysis ◽

Auto Regressive

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Spontaneous fluctuations in cerebral blood flow regulation: contribution of PaCO2

Journal of Applied Physiology ◽

10.1152/japplphysiol.00857.2010 ◽

2010 ◽

Vol 109 (6) ◽

pp. 1860-1868 ◽

Cited By ~ 39

Author(s):

R. B. Panerai ◽

N. E. Dineen ◽

F. G. Brodie ◽

T. G. Robinson

Keyword(s):

Blood Pressure ◽

Blood Flow ◽

Cerebral Blood Flow ◽

Temporal Resolution ◽

Cerebral Blood Flow Velocity ◽

Moving Average ◽

Breath Hold ◽

New Approach ◽

Arterial Blood ◽

Spontaneous Fluctuations

To investigate the temporal variability of dynamic cerebral autoregulation (CA), the transient response of cerebral blood flow to rapid changes in arterial blood pressure, a new approach was introduced to improve the temporal resolution of dynamic CA assessment. Continuous bilateral recordings of cerebral blood flow velocity (transcranial Doppler, middle cerebral artery), end-tidal Pco2 (PetCO2, infrared capnograph), and blood pressure (Finapres) were obtained at rest and during breath hold in 30 young subjects (25 ± 6 yr old) and 30 older subjects (64 ± 4 yr old). Time-varying estimates of the autoregulation index [ARI( t)] were obtained with an autoregressive-moving average model with coefficients expanded by orthogonal decomposition. The temporal pattern of ARI( t) varied inversely with PetCO2, decreasing with hypercapnia. At rest, ARI( t) showed spontaneous fluctuations that were significantly different from noise and significantly correlated with spontaneous fluctuations in PetCO2 in the majority of recordings (young: 72% and old: 65%). No significant differences were found in ARI( t) due to aging. This new approach to improve the temporal resolution of dynamic CA parameters allows the identification of physiologically meaningful fluctuations in dynamic CA efficiency at rest and in response to changes in arterial CO2.

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Physiologic and hemodynamic changes in patients undergoing open abdominal cytoreductive surgery with hyperthermic intraperitoneal chemotherapy

Journal of International Medical Research ◽

10.1177/0300060520983263 ◽

2021 ◽

Vol 49 (1) ◽

pp. 030006052098326

Author(s):

Myoung Hwa Kim ◽

Young Chul Yoo ◽

Sun Joon Bai ◽

Kang-Young Lee ◽

Nayeon Kim ◽

...

Keyword(s):

Body Temperature ◽

Systemic Vascular Resistance ◽

Vascular Resistance ◽

Intraperitoneal Chemotherapy ◽

Cytoreductive Surgery ◽

Hyperthermic Intraperitoneal Chemotherapy ◽

Resistance Index ◽

Volume Index ◽

Hemodynamic Changes ◽

Arterial Blood

Objective We aimed to determine the physiological and hemodynamic changes in patients who were undergoing hyperthermic intraperitoneal chemotherapy (HIPEC) cytoreductive surgeries. Methods This prospective, observational study enrolled 21 patients who were undergoing elective cytoreductive surgery with HIPEC at our hospital over 2 years. We collected vital signs, hemodynamic parameters including global end-diastolic volume index (GEVI) and extravascular lung water index (ELWI) using the VolumeView™ system, and arterial blood gas analysis from all patients. Data were recorded before skin incision (T1); 30 minutes before HIPEC initiation (T2); 30 (T3), 60 (T4), and 90 (T5) minutes after HIPEC initiation; 30 minutes after HIPEC completion (T6); and 10 minutes before surgery completion (T7). Results Patients showed an increase in body temperature and cardiac index and a decrease in the systemic vascular resistance index. GEDI was 715.4 (T1) to 809.7 (T6), and ELWI was 6.9 (T1) to 7.3 (T5). Conclusions HIPEC increased patients’ body temperature and cardiac output and decreased systemic vascular resistance. Although parameters that were extracted from the VolumeView™ system were within their normal ranges, transpulmonary thermodilution approach is helpful in intraoperative hemodynamic management during open abdominal cytoreductive surgery with HIPEC. Trial registry name: ClinicalTrials.gov Trial registration number: NCT02325648 URL: https://clinicaltrials.gov/ct2/results?cond=NCT02325648&term

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