TY - JOUR. T1 - Effects of hypercapnia and hypocapnia on [Ca2+]i mobilization in human pulmonary artery endothelial cells. AU - Nishio, Kazumi. AU - Suzuki, Yukio. AU - Takeshita, Kei. AU - Aoki, Takuya. AU - Kudo, Hiroyasu. AU - Sato, Nagato. AU - Naoki, Katsuhiko. AU - Miyao, Naoki. AU - Ishii, Makoto. AU - Yamaguchi, Kazuhiro. PY - 2001/6. Y1 - 2001/6. N2 - The hydrogen ion is an important factor in the alteration of vascular tone in pulmonary circulation. Endothelial cells modulate vascular tone by producing vasoactive substances such as prostacyclin (PGI2) through a process depending on intracellular Ca2+ concentration ([Ca2+]i). We studied the influence of CO2-related pH changes on [Ca2+]i and PGI2 production in human pulmonary artery endothelial cells (HPAECs). Hypercapnic acidosis appreciably increased [Ca2+]i from 112 ± 24 to 157 ± 38 nmol/l. Intracellular acidification at a normal extracellular pH increased [Ca2+]i comparable to that observed during hypercapnic acidosis. The ...
CONCLUSION: This animal model revealed reduced cerebral blood flow and brain tissue oxygenation during hypocapnia without detectable changes in regional oxygen saturation as measured by NIRS. Changes occurred as early as during moderate hypocapnia. This article is protected by copyright. All rights reserved. PMID: 31472089 [PubMed - as supplied by publisher]...
Hypercapnia has been shown in animal experiments to induce pulmonary hypertension. This study measured the sensitivity and time course of the human pulmonary vascular response to sustained (4 h) hypercapnia and hypocapnia. Twelve volunteers undertook three protocols: 1) 4-h euoxic (end-tidal Po(2) = 100 Torr) hypercapnia (end-tidal Pco(2) was 10 Torr above normal), followed by 2 h of recovery with euoxic eucapnia; 2) 4-h euoxic hypocapnia (end-tidal Pco(2) was 10 Torr below normal) followed by 2 h of recovery; and 3) 6-h air breathing (control). Pulmonary vascular resistance was assessed at 0.5- to 1-h intervals by using Doppler echocardiography via the maximum tricuspid pressure gradient during systole. Results show progressive changes in pressure gradient over 1-2 h after the onset or offset of the stimuli, and sensitivities of 0.6 to 1 Torr change in pressure gradient per Torr change in end-tidal Pco(2). The human pulmonary circulatory response to changes in Pco(2) has a slower time course and
Twenty-four male Wistar rats weighing 250 to 350 g were randomly assigned to 4 groups: chronic cerebral hypoperfusion with hypocapnia (group 1; n=6); chronic cerebral hypoperfusion with normocapnia (group 2; n=6); sham operation with hypocapnia (group 3; n=7); and sham operation with normocapnia (group 4; n=5). The procedures for the chronic cerebral hypoperfusion were approved by the animal research committee of Kansai Medical University.. The rats were anesthetized with 3% halothane in 50% N2O and 50% O2 and were left to respirate spontaneously. The bilateral common carotid arteries were exposed through a midline cervical incision and double ligated with silk sutures. Sham-operated animals underwent the same surgical procedure but without bilateral carotid ligation. The rectal temperature was monitored and maintained between 36.5°C and 37.5°C with the use of a warm water mattress and a heating lamp during the surgical procedure. After the operation, the rats were kept under controlled ...
TY - JOUR. T1 - Oxygen transfer during exercise-induced hypocapnia. AU - Robertshaw, D.. AU - Rawson, R.. AU - Entin, P.. AU - Cole, F.. AU - Wilson, D.. PY - 1997/12/1. Y1 - 1997/12/1. N2 - A panting animal, the sheep, develops hyperthermia (40-41°C) , hypocapnia (10-20 Torr), and lactacidosis (3-5 mM) during exercise at 50% of maximum oxygen consumption. Experiments were performed to determine if the lactacidosis was caused by impaired oxygen transfer caused by a hypocapnic increase in oxygen affinity of hemoglobin. A flow probe (Transonic Systems, Inc., Ithaca, NY) was placed on the external iliac artery and blood samples were taken from the carotid artery and iliac vein. Net oxygen and lactate flux were calculated for one hindlimb during exercise. Oxygen delivery to the limb increased due to a rise in both hemoglobin concentration (7 to 11 g/dl) and blood flow (0.5 to 2.5 1/min). Oxygen extraction remained constant during exercise and the arteriovenous difference in lactate was zero. It was ...
Diluted ammonia and acetic acid served as conditional odor cues (CSs) in a differential associative learning paradigm. Hyperventilation-induced hypocapnia (unconditional stimulus [US]) was used to induce lightheadedness. In a training phase, participants (n = 28) performed three hypocapnic and three normocapnic overbreathing trials of 60 seconds each. One odor was consistently paired with the hypocapnic overbreathing (CS+); the other (control) odor was paired with normocapnic overbreathing (CS-). In the test phase, each odor was presented once during spontaneous breathing and once during normocapnic overventilation. Lightheadedness was assessed online during each breathing trial, which was followed by an extensive hyperventilation symptom checklist. Fractional end-tidal CO2, breathing frequency, and inspiratory volume were measured throughout the experiment ...
The effects of systemic human recombinant interleukin 2 (rIL-2) infusion upon both the vasoconstrictor effect of hypocapnia and the endothelium-dependent vasodilator effect of acetylcholine (Ach) were examined in anesthetized rats equipped with cranial windows. Prior to the functional studies, each of six animals received an i.v. infusion of rIL-2 (6 × 105 IU/kg) every 8 h for 3 days. At the same time, six control animals received infusions of equivalent volumes of sterile water. Eight h after the final infusion, each animal was anesthetized and equipped with a cranial window for the observation of pial arterioles overlying the left frontoparietal cortex. Pial arteriolar diameters were measured before and after the topical application of Ach which in normal cerebral arterioles elicits the release of endothelium-dependent relaxing factor, causing vasodilation. When arteriolar diameters returned to base line, they were measured again both before and during hyperventilation-induced hypocapnia. ...
During ventilatory acclimatization to hypoxia (VAH), the relationship between ventilation (VE) and end-tidal PCO2 (PETCO2) changes. This study was designed to determine 1) whether these changes can be seen early in VAH and 2) if these changes are present, whether the responses differ between isocapnic and poikilocapnic exposures. Ten healthy volunteers were studied by using three 8-h exposures: 1) isocapnic hypoxia (IH), end-tidal PO2 (PETO2) = 55 Torr and PETCO2 held at the subjects normal prehypoxic value; 2) poikilocapnic hypoxia (PH), PETO2 = 55 Torr; and 3) control (C), air breathing. The VE-PETCO2 relationship was determined in hyperoxia (PETO2 = 200 Torr) before and after the exposures. We found a significant increase in the slopes of VE-PETCO2 relationship after both hypoxic exposures compared with control (IH vs. C, P | 0.01; PH vs. C, P | 0.001; analysis of covariance with pairwise comparisons). This increase was not significantly different between protocols IH and PH. No significant changes
In this study, we prospectively identified adult patients after cardiac arrest and determined the prevalence of hypocapnia exposure and hypercapnia exposure during the first 24 hours after ROSC. Our objective was to test whether post-ROSC exposure to hypocapnia and hypercapnia was associated with poor neurological function at hospital discharge. We found that 36% of patients had any hypocapnia exposure, and 42% had any hypercapnia exposure. By the use of multivariable logistic regression, including multiple sensitivity analyses, we found that both hypocapnia exposure and hypercapnia exposure after ROSC were independent predictors of poor neurological function at hospital discharge. These findings suggest that both hypocapnia and hypercapnia are common during the initial post-ROSC period and are independently associated with poor neurological outcome.. The 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care recommend that ventilation ...
The authors seek to find new connections between recent results of biology and older theories. This paper aims to assemble the jigsaw puzzle. The theoretical background of the hypothesis was described in the previous issue of the journal (Sikter et al. 2017a). Human stress response often coexists with persistent hypocapnia or hypercapnia - developing via psychosomatic pathomechanism - which can lead to mental and psychosomatic illnesses. Chronic hypocapnia mainly generates hyperarousal disorders which may be reversible for an extended time, however, vicious cycles may start when hypoxia and/or severe somatic diseases are simultaneously present (commonly in the elderly), which conditions often end with death without medical help ...
TY - JOUR. T1 - Asphyxiated neonates who received active therapeutic hypothermia during transport had higher rates of hypocapnia than controls. AU - Szakmar, Eniko. AU - Kovacs, Kata. AU - Meder, Unoke. AU - Bokodi, Geza. AU - Szell, Andras. AU - Somogyvari, Zsolt. AU - Szabo, Attila J.. AU - Szabó, M.. AU - Jermendy, Agnes. PY - 2018/1/1. Y1 - 2018/1/1. N2 - Aim: We investigated the association between active hypothermia and hypocapnia in neonates with moderate-to-severe hypoxic-ischaemic encephalopathy (HIE) transported after birth. Methods: This was a retrospective cohort study of neonates with HIE born between 2007 and 2011 and transported to Semmelweis University, Hungary, for hypothermia treatment before and after we introduced active cooling during transport in 2009. Of these, 71 received intensive care plus controlled active hypothermia during transport, while the 46 controls just received standard intensive care. Incident hypocapnia was defined as a partial pressure of carbon-dioxide ...
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Quick, deep breathing can cause hyperventilation, which can cause health problems. Find out what causes hyperventilation, what the symptoms are, and how to treat it at home.
不同的醫學資料對於呼吸相關的名詞,也有不同的定義。 有些來源認為呼吸急促就是指呼吸率較高的情形。过度换气(Hyperventilation)是指肺泡通氣量增加(可能因為呼吸加快或是深呼吸而造成,也有可能二者都是),而代謝產生二氧代碳量的增加幅度比呼吸率的增加要少。呼吸深快(英语:Hyperpnea)則是呼吸的速度及呼吸深度都比靜息時的呼吸要高[2]。 也有些來源有不同的定義:呼吸急促就是指呼吸率較高,过度换气是指靜息時的呼吸率較高,呼吸深快是指呼吸率的增加大致和體內代謝率的增加成正比[3], ...
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We induced abrupt hypovolemia in an awake, spontaneously breathing or noninvasively ventilated subject. The combination of hypovolemia and PPV was associated with a 15% reduction in ICA‐BF, whereas MAP was stable during compensated central hypovolemia. CI and ETCO2 contributed significantly to these changes. Our results suggest that CBF is vulnerable to hypovolemia and mild hypocapnia despite circulatory reflex adaptations and absence of hypotension.. On the induction of hypovolemia, MAP decreased transiently, being restored after 20 sec despite the large persisting reduction in SV and CI. Baroreceptor unloading and SNS activation probably mediated MAP restoration and HR increase. Despite the restored MAP, the reduction in CI was a significant predictor of ICA‐BF drop in our model, analogous to previously reported results (Ogoh et al. 2005; Meng et al. 2015). In a recent review, the integrated effect of the various CBF‐regulatory mechanisms, including CO, on the cerebrovascular resistance ...
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All of these hyperventilation symptoms are typical in people who routinely overbreathe. So, why is chronic Hyperventilation Syndrome so seldom diagnosed and talked about? Especially since medical studies have estimated that up to 10% of the otherwise healthy population suffer from chronic hyperventilation to some degree. People with asthma and COPD are also prone to overbreathing. Thats a lot of people wandering around out there, breathing more than they need to be. Many of them are also wondering why they feel so bad as their doctors have found nothing wrong or told them they are suffering anxiety. Certainly the symptoms of Hyerperventilation Syndrome alone are enough to make one anxious, but in most cases the overbreathing precedes the panic and worry. Dr Claude Lum, a British chest physician who wrote extensively about chronic hyperventilation said that one of the diagnostic clues to this disorder was fat folder syndrome - anyone with a fat case file and no obvious organic disease but ...
EDITOR, - Kjell Larsson and colleagues described the high prevalence of asthma and increased bronchial responsiveness in cross country skiers in Sweden.1 They attributed their findings to the skiers breathing large volumes of cold air during strenuous exercise. They should, in addition, consider other factors causing bronchoconstriction such as humidity, hypocapnia, and hypoxia.. Absolute humidity is depressed at reduced … ...
Cardiovascular health; cerebral blood flow regulation; cerebrovascular function Dr. Philip Ainslies research is focused on the integrated mechanisms that regulate human cerebral blood flow in health and disease, the influence of environmental stress, and the effects of exercise training on cerebrovascular function.. Dr. Philip Ainslie is a Professor in the School of Health and Exercise Sciences at UBC Okanagan, the Co-Director of the Centre for Heart, Lung & Vascular Health, and an ICORD Investigator. His Ph.D. (in exercise physiology & metabolism) was a collaborative project between the Liverpool John Moores University, University of Manchester and University of Oxford. Following completion of a post-doctoral research fellowship at the University of Calgary he began a faculty position in 2005, as Lecturer and Principal Investigator in the Department of Physiology at the University of Otago, New Zealand. Here, he established his independent research program, focusing on the integrative ...
Eucapnic hyperventilation (eucapnic voluntary hyperpnoea) is a provocative indirect stimulus test used to diagnose exercise-induced asthma or exercise-induced bronchospasm. Exercise-induced asthma (EIA) is defined in a patient with preexisting asthma who has an exacerbation of the asthma with exercise.
Eucapnic hyperventilation (eucapnic voluntary hyperpnoea) is a provocative indirect stimulus test used to diagnose exercise-induced asthma or exercise-induced bronchospasm. Exercise-induced asthma (EIA) is defined in a patient with preexisting asthma who has an exacerbation of the asthma with exercise.
Effects of acute systemic hypoxia on the cardiovascular system (CYS) and respiration of spontaneously breathing cats were studied in two conditions. 1): Hypoxic air (6-8% 02 in N2) was given to the animal to induce systemic hypoxia for 20 minutes. Hyperventilation at this condition lowered arterial C02 tension (PaC02 hypocapnia). ...
In this largely self-selected cohort of asthma sufferers with high medication use, those randomised to BBT lowered their minute volume, reduced beta2-agonist use, and demonstrated a trend towards lower inhaled steroid doses and greater improvement in quality of life than did those randomised to a control breathing program. No change in lung function was noted.. To minimise the effect of environmental influences and to maintain blinding, BBT and control group classes ran simultaneously. This posed logistic problems not often encountered in asthma intervention studies, where subjects are usually enrolled sequentially over a substantial period of time, giving an opportunity to adjust treatment. The need to complete randomisation for all subjects before the interventions precluded comprehensive pre-study medication optimisation.. Conventional teaching argues that hyperventilation and hypocapnia are the result rather than the cause of airway narrowing in asthma. Thus, increases in ventilation are ...
Promotes Healthy Cardiovascular Function* Promotes Healthy Cerebrovascular Function* Enhances Cognition* Promotes Healthy Sexual Function* Antioxidant* Enhances Utilization of Oxygen and Glucose* PHARMACEUTICAL GRADE Registered Product and Sells Under Prescription in Germany Clinically Tested in Over 10,000 Patients INGREDIENT AMOUNT Ginkgo biloba extract 90 mg Standardized to contain: Minimum 24% Ginkgoflavonglucosides (HPLC) Minimum 6% Terpene Lactones (GLC)
About two months ago I experienced a hyperventilation attack which has turned into what I think is a type of chronic hyperventilation. Because I have practiced yoga and learned to control my panic atta...
Hyperventilation means breathing faster than normal. It feels like one cant get enough air. This makes the carbon dioxide level in your blood and brain tissue fall. Usually caused by psychic and/or social stress.
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UNLABELLED: Using transcranial Doppler ultrasonography, we investigated the moving correlation between slow waves in arterial blood pressure (ABP) and blood flow velocity (FV) at different levels of cerebrovascular vasodilation provoked by changing PETCO2. Fourteen healthy volunteers were examined. The FV in middle cerebral arteries, PETCO2, and ABP were recorded during normocapnia, hypercapnia, and hypocapnia. The moving correlation coefficients between ABP and mean FV (FVm) or systolic FV (FVs) during spontaneous fluctuations in ABP were calculated for 3-min epochs and averaged for each investigation, thus yielding the mean index (Mx) and systolic index (Sx). As a reference method, Aaslids cuff tests were performed to obtain the rate of regulation (RoR). RoR, Mx, and Sx significantly depended on PETCO2 (analysis of variance, P | 0.00001). At high PETCO2, cerebrovascular reactivity was disturbed as reflected in RoR values of | 0.17/s for all volunteers and increased values of Mx (| 0.4 in 86% of
Hyperventilation occurs when the rate and quantity of alveolar ventilation of carbon dioxide exceed the bodys production of carbon dioxide. Hyperventilation can be voluntary or involuntary.. When breathing is excessive, more carbon dioxide will be removed from the bloodstream than the body can produce. This causes the concentration of carbon dioxide in the bloodstream to fall and produces a state known as hypocapnia. The body normally attempts to compensate for this metabolically.. If excess ventilation cannot be compensated metabolically, it will lead to a rise in blood PH. This rise in blood pH is known as respiratory alkalosis. When hyperventilation leads to respiratory alkalosis, it may cause a number of physical symptoms: dizziness, tingling in the lips, agitation, confusion, feeling they cannot breathe, headache, weakness, fainting and seizures. In extreme cases, it can cause spasms flapping and contraction of the hands and feet and is sometimes referred to as claw hands.. Swimmers ...
Type 2 diabetes exerts complex effects on cerebral microvasculature that may alter cerebral blood flow regulation. We found a decrease of mean BFV and an increase of CVR in type 2 diabetic patients during baseline, hypocapnia, and hypercapnia. Baseline mean BFV was negatively associated with periventricular WMH grade and volume on T2-weighted images and with A1C and inflammation markers. WMHs were also linked with uncontrolled diabetes, elevated CVR, and impaired CO2 reactivity. The relationship between WMH, uncontrolled diabetes and reduced BFV is of clinical relevance as a potential mechanism for cerebrovascular disease in elderly with type 2 diabetes.. Aging is associated with brain atrophy, changes in frontal subcortical white matter, and executive cognitive dysfunction (9). The CO2 reactivity diminishes with age, uncontrolled diabetes, and risk factors for atherosclerosis (22). In community-living elderly people, blood flow in the WMHs was lower compared with normal-appearing white matter ...
Hyperventilation occurs when the rate and quantity of alveolar ventilation of carbon dioxide exceed the bodys production of carbon dioxide. Hyperventilation can be voluntary or involuntary.When breat
In clinical practice, seizures independent of hypoglycemia are observed in patients with type 1 diabetes mellitus (T1DM) more frequently than expected by chance, suggesting a link. However, seizures during management of diabetic ketoacidosis (DKA) have generally been considered a bad prognostic factor, and usually associated with well-known biochemical or neurological complications. We present the case of a 17-year-old girl with known T1DM managed for severe DKA complicated by hypocapnic seizure. We review the literature on this rare occurrence as well as outline other possible differentials to consider when faced with the alarming combination of DKA and seizure. ...
Narimanbekov I.O.; Rozycki H.J., 1992: Hyperoxic hyperventilation induced lung damage manifested within eight hours in a rabbit model
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Question - Doing sudarshankriya. Any side effects?. Ask a Doctor about diagnosis, treatment and medication for Hyperventilation, Ask an Internal Medicine Specialist
Our findings are in sharp contrast to current textbook concepts and the observations previously reported from smaller patient groups. The clinical reports with voluntary HV have been followed by a large number of experimental studies in which severe hyper- or hypocapnic conditions are created to evaluate their effects on seizures (8,9). Findings from these different types of studies have been merged to formulate the premise that HV-induced hypocapnia is invariably epileptogenic and constitutes the mechanism of action whereby HV provokes epileptic seizures (8).. Several reasons may have existed for the discrepancy between our findings and the earlier clinical studies. Small numbers and selection of patients in previous investigations may have biased the results. Because of the absence of a positive confirmation of epilepsy in the era before long-term EEG-video monitoring, it is probable that at least some previous studies included subjects with nonepileptic seizures. It also is possible that the ...
Your doctor or nurse will determine the cause of your hyperventilation. Rapid breathing may be a medical emergency -- unless you have have had this before and have been reassured by your health care provider that it can be self treated.. Often, panic and hyperventilation become a vicious cycle. Panic leads to rapid breathing, and breathing rapidly can make you feel panicked.. If you frequently overbreathe, you may have hyperventilation syndrome that is triggered by emotions of stress, anxiety, depression, or anger. Occasional hyperventilation from panic is generally related to a specific fear or phobia, such as a fear of heights, dying, or closed-in spaces (claustrophobia).. If you have hyperventilation syndrome, you might not be aware you are breathing fast. However, you will be aware of having many of the other symptoms, including:. ...
The absolute best way to treat this problem is to treat the anxiety itself and its subsequent panic attacks as these are the heart of the reason why p
Advice on lifestyle changes (diet, red wine and physical activity) does not affect internal carotid and middle cerebral artery blood flow velocity in patients with carotid arteriosclerosis in a randomized controlled trial ...
Advice on lifestyle changes (diet, red wine and physical activity) does not affect internal carotid and middle cerebral artery blood flow velocity in patients with carotid arteriosclerosis in a randomized controlled trial ...
Advice on lifestyle changes (diet, red wine and physical activity) does not affect internal carotid and middle cerebral artery blood flow velocity in patients with carotid arteriosclerosis in a randomized controlled trial ...
Apnea and Hyperventilation Children with Pitt-Hopkins can have periods of very unusual breathing patterns, which has been reported by some parents may be due to anxiety issues. Treatment of anxiety could help reduce apnea and hyperventilation.
List of causes of Chest symptoms and Hyperventilation and Palpitations, alternative diagnoses, rare causes, misdiagnoses, patient stories, and much more.
CO 2 Reactivity With hypercarbia - Hypoventilation, CO 2 ↑ ∆  Vasodilatation  CBF ↑ With hypocarbia - Hyperventilation, CO 2 ↓  Vasoconstriction  CBF ↓
End-tidal carbon dioxide (EtCO2) can be measured by colorimetry and capnography. Colorimetric devices provide continuous, semi-quantitative EtCO2 monitoring. A typical device has the following three color ranges: Purple-EtCO2 is less than 0.5% Tan-EtCO2 is 0.5-2% Yellow-EtCO2 is greater than 2% Tip .... Read More » ...
We investigated the effect of acute hypoxia (AH) on dynamic cerebral autoregulation (CA) using two independent assessment techniques to clarify previous, conflicting reports. Twelve healthy volunteers (6 men, 6 women) performed six classic leg cuff tests, three breathing normoxic (Fi(O2) = 0.21) and three breathing hypoxic (Fi(O2) = 0.12) gas, using a single blinded, Latin squares design with 5-min washout between trials. Continuous measurements of middle cerebral artery blood flow velocity (CBFv; DWL MultiDop X2) and radial artery blood pressure (ABP; Colin 7000) were recorded in the supine position during a single experimental session. Autoregulation index (ARI) scores were calculated using the model of Tiecks et al. (Tiecks FP, Lam AM, Aaslid R, Newell DW. Stroke 26: 1014-1019, 1995) from ABP and CBFv changes following rapid cuff deflation (cuff ARI) and from ABP to CBFv transfer function, impulse, and step responses (TFA ARI) obtained during a 4-min period prior to cuff inflation. A new ...
Parameters describing dynamic cerebral autoregulation (DCA) have limited reproducibility. 59 In an international, multi-centre study, we evaluated the influence of multiple analytical 60 methods on the reproducibility of DCA. Fourteen participating centers analyzed repeated 61 measurements from 75 healthy subjects, consisting of five minutes of spontaneous 62 fluctuations in blood pressure (BP) and cerebral blood flow velocity (CBFv) signals, based on 63 their usual methods of analysis. DCA- methods were grouped into three broad categories, 64 depending on output types: 1. Transfer function analysis (TFA); 2. Autoregulation index 65 (ARI); and 3. correlation coefficient. Only TFA gain in the low frequency (LF) band showed 66 good reproducibility in approximately half of the estimates of gain, defined as an intraclass 67 correlation coefficient (ICC) of , 0.6. None of the other DCA metrics had good 68 reproducibility. For TFA-like and ARI-like methods, ICCs were lower than values obtained 69 with ...
Although dipyridamole produces coronary vasodilation, most reports on dipyridamole effects in animals have failed to show a change in CBF after intravenous infusion of dipyridamole.16 17 18 19 To our knowledge, this is the first study to quantitatively estimate the change in CBF in response to intravenous dipyridamole in humans. We found CBF values for the dipyridamole stress to be lower than those at rest (Table 2⇑ and Figure 2⇑). Dipyridamole stress also caused a significant reduction in Paco2 (Table 1⇑), and the vascular response to Paco2 change caused by the dipyridamole infusion closely followed the response due to hypocapnia (Table 2⇑ and Figure 1⇑). Thus, the decrease in CBF during dipyridamole stress can be explained by the decrease in Paco2 rather than the direct action of dipyridamole on CBF. The decrease in Paco2 during dipyridamole stress is most likely due to the hyperventilation side effect of adenosine.29 It has been reported that large doses of intravenous adenosine and ...