Chronological analysis of physiological T2* signal change in the cerebrum during breath holding

The purpose of this study was to examine which physiological factors affect cerebral T2* signal intensity (SI) during breath holding (BH) (apnea after inspiration and breathing after expiration) in normal volunteers. We examined SI changes caused by anoxic gas inhalation, by respiratory movements, and by BH. High-speed echo planar images (EPI) showed changes in SI that could be divided into five phases. Reports indicate that SI changes induced by BH are due to the effects on the magnetic susceptibility of deoxygenated hemoglobin (deoxyhemoglobin (dHb)) and to hypercapnia, but these reports could not fully explain the observed five phases. In addition to deoxyhemoglobin susceptibility and hypercapnia, we found that respiratory movements play a third critical role in modifying SI by affecting blood flow into the region of interest (ROI), as judged from right carotid artery flow. Consequently, we propose that the physiological SI changes induced by BH are derived from blood oxygenation, hypercapnia, and respiratory movements.     

Subtraction image for dynamic liver MRI using free breath-hold at functional residual capacity: a clinical trial

PURPOSE: Dynamic liver MRI images have been obtained under expiration breath holding (BH). However, problems with obtaining reproducible liver positions often observed. This study investigated ways to improve the reproducibility of liver position on dynamic liver MRI. MATERIALS AND METHODS: After giving informed consent, 60 patients (32 males and 28 females, ages 33-85, median age 69) were examined by liver dynamic MRI under two types of BH. The BH phases were voluntary expiration (VE) phase without any explanations and functional residual capacity (FRC) phase after careful explanation was provided. Plain images, arterial phase images, portal phase images and parenchymal phase images were obtained. For statistical evaluation of reproducibility, the area of the 2nd or 3rd images from top of the liver was measured in each phase using a threshold value of half maximum. Misregistration areas were calculated by finding the remainder of the liver area in the plain-arterial (Pl-A) phase, arterial-portal (A-Po) phase, plain-parenchymal (Pl-Pa) phase. Contingency table analysis was done due to the misregistration was occurred or not. RESULTS: Misregistration of liver image on the VE and the FRC of three phase types were statistical significant on the Pl-A (p < 0.01), on the A-Po (p < 0.01) and on the Pl-Pa (p < 0.05), respectively. CONCLUSION: The FRC phase following careful explanation of the BH provided significantly improved reproducibility of liver position on dynamic liver MRI. Therefore, precise subtraction images could be obtained for routine clinical examinations without slice matching.     

Physiologic change in flow velocity and direction of dural venous sinuses with respiration: MR venography and flow analysis

BACKGROUND AND PURPOSE: Blood flow of the internal jugular vein and intracranial venous sinuses is affected by respiratory state. The purpose of this study was to clarify the changes in flow velocity and direction and signal intensities of sigmoid sinuses on phase-contrast (PC) MR images obtained with regular breathing and with deep inspiratory breath holding. METHODS: One hundred seven subjects without venous sinus abnormality were studied. Coronal 2D PC MR venography and axial 2D PC images with peripheral pulse gating were acquired with a 1.5-T MR unit, during regular breathing and deep inspiratory breath holding. The signal intensity changes of bilateral sigmoid sinuses on MR venograms and the changes of flow velocity and direction on the axial 2D PC images were analyzed. RESULTS: Breath holding decreased signal intensities of the right and left sigmoid sinuses on MR venograms in 57 (53.3%) and 36 (33.6%) subjects, respectively. Increased signal intensity was observed in 12 (11.2%) and 33 (30.8%) subjects, respectively. In the flow analysis, retrograde flow was detected at the left sigmoid sinus in four subjects (3.7%) during regular breathing, which was normalized by breath holding. Flow velocities of the right and left sigmoid sinuses decreased during breath holding in 92 (86.0%) and 70 (65.4%) subjects, and increased in 15 (14.0%) and 37 (34.6%) subjects, respectively. CONCLUSION: The signal intensities of sigmoid sinuses were affected by breath holding in about 2/3 of the subjects. Breath-holding maneuver can be used to increase blood flow and signal intensities of dural venous sinuses on PC MR venograms.     

Blood oxygenation level-dependent MRI of cerebral gliomas during breath holding

PURPOSE: To assess the cerebrovascular responses to short breath holding of cerebral gliomas using blood oxygenation level-dependent (BOLD) magnetic resonance imaging (MRI). MATERIALS AND METHODS: Six patients with a low-grade glioma and one patient with a high-grade glioma were studied using T2*-weighted echo planar imaging (EPI) during repeated periods of 15-second or 20-second breath-holding. Tumor vascularity was evaluated using dynamic susceptibility contrast perfusion MRI. RESULTS: Increases in BOLD signal intensity during repeated breath-holding were consistently identified in patients' normal appearing gray matter, comparable with those in healthy adults. Absence of significant BOLD signal enhancement was noted both in low-grade and high-grade gliomas, which is either due to overwhelming hypoxia in a tumor, inadequacy or absence of hypercapnia-induced vasodilatation of tumor vessels, or both. Breath-hold regulated decreases in BOLD signals occurred only in the high-grade glioma, which is most likely due to the hypercapnia-induced steal effect that redistributes blood flow from tumor regions with unresponsive neovasculature to surrounding normal tissue. CONCLUSION: BOLD MRI during short breath holding can disclose differential cerebrovascular response between normal tissue and cerebral glioma.     

Oxygen pulse is not predictive of stroke volume in heart failure

AIM: Stroke volume (SV) is the major cardiovascular discriminator between those that are exercise trained versus untrained individuals and healthy individuals versus those with pathologic left ventricular dysfunction. Furthermore, since the increase in oxygen pulse (O(2)P) (O(2)P=VO(2)/HR?oxygen uptake/heart rate) that occurs with exercise is a function of SV and the arterial-venous oxygen difference (a-vO(2)), O(2)P has been demonstrated a reliable indicator of SV for healthy individuals. Although commonly used as a physiological and clinical marker of SV, the validity of O(2)P as an indicator of SV in patients with heart failure has not been investigated. METHODS: Thirty-one (23 men, 8 women) patients (age: 64+/-7.9; ejection fraction: 24+/-7.8) with chronic heart failure had cardiac output measured during steady-state workloads (25 watts and 75% VO(2peak)) upon entry and again at completion of 12 weeks of exercise training. Four patients were excluded due to clinical complications and 3 because of non-compliance; therefore, 24 patients completed the study. RESULTS: The relationships between SV and O2P are: 1) baseline: SV=11.1+4(O2P), SEE=11.8; r(2)=0.39 and 2) study completion: SV=25.1+2.3(O2P), SEE=12.7; r(2)=0.21. While SV did not increase after 25 watts, O2P continued to increase by 17%, respectively. In addition, there were no training effects on SV or O(2)P. As SV increased, O(2)P underpredicted measured SV. CONCLUSIONS: In patients with heart failure and poor left ventricular function, O(2)P is not recommended as a marker of the SV during exercise.     

Breathing and propelling in crawl as a function of skill and swim velocity

This study analyzes apnea (A), exhalation (E), and inhalation (I) duration with respect to stroke organization in front crawl as a function of inhalation side, swim velocity and performance level. Thirty-six male subjects comprised two groups based on performance level: more expert (ME) and less expert (LE) swimmers. All swam with one inhalation per cycle to the preferred side at speeds corresponding to two specific race paces: 100-m (V100) and 800-m (V800) velocities. The breathing arm (BA) is located on the inhalation side, and the non-breathing arm (NBA) on the opposite side. The sound of air passing in and out of the swimmers' mouths was captured by a microphone and synchronized with video frames. Stroke phases and arm coordination were identified by video analyses. Arm coordination was quantified using two indices of coordination (IdC) corresponding to the lag time between the beginning of the BA (IdC-BA) or NBA (IdC-NBA) propulsive action and the end of that of the other arm. As velocity increases, the ME are observed to reduce I during BA recovery (-19.4 +/- 31.6 %, p < 0.05) while the LE increase A (+ 34.8 +/- 25.2 %, p < 0.05) during BA entry, catch and recovery and NBA pull and push. These variations are related to a lengthening of the pull for both arms at the expense of BA non-propulsive phases. At V100, the ME have greater E (p < 0.05) during BA entry and catch (+ 21.1 +/- 38.2 %) and NBA push (+ 26.3 +/- 39.5 %) compared to the LE. This increase, at the expense of A, corresponds to a shorter BA push and NBA recovery. At V800, the ME exhibit a longer A (p < 0.05) during BA recovery (+ 19.9 +/- 33.2 %) and NBA pull (+ 24.2 +/- 31.5 %), and decreased I during NBA push and pull. These differences are related to a shortening of BA recovery and pull and a longer push for both arms. These breath and stroke adaptations correspond to an increase in stroke rate and IdC-BA with the velocity and performance level. This study points out the breathing-propelling aspects of coordination that indicate technical skill in swimming.     

Assessment of flow in the right human coronary artery by magnetic resonance phase contrast velocity measurement: Effects of cardiac and respiratory motion

Flow in the human right coronary artery was determined using magnetic resonance phase contrast velocity quantification. Two methods were applied to reduce respiratory motion: imaging during breath holding, which is fast, and retrospective respiratory gating, which has a high temporal resolution (32 ms) in the cardiac cycle. Vessel cross-sectional area, through-plane velocity, and volume flow were determined in six healthy subjects. In-plane vessel displacement during the cardiac cycle, caused by cardiac contraction, was about 2–4 mm within a time frame of 32 ms in systole and early diastole. The motion resulted in blurring of images obtained during breath holding caused by the large acquisition time window (126 ms) within the cardiac cycle. Therefore, only with a high temporal resolution correct velocity images over the entire cardiac cycle could be obtained. The time- and cross-sectionally averaged velocity was 7 ± 2 cm/s, and the volume flow was 30 ± 10 ml/min.     

声速匹配技术在原发性甲亢诊断中的应用

目的通过声速匹配技术测定原发性甲亢（Graves病）患者的声速值（soundvelocity,SV）,探讨声速匹配技术对原发性甲亢诊断的应用价值及其测定过程中的影响因素。方法二维彩超常规观察甲状腺,启动声速匹配技术,测量呼吸前、后的声速匹配值（zonespeedindex,ZSI）,分别计算呼吸前、后的组内相关系数（ICC）,并计算呼吸后ZSI的平均值,该区域的SV为（1540＋ZSI）m／s。并分析甲状腺被膜距体表厚度和甲状腺前方脂肪层厚度与ZSI的关系。结果原发性甲亢患者二维彩超表现以侧叶增厚为主,血流丰富,原发性甲亢组的ZSI值低于正常组,差异有统计学意义（P〈0．05）。声速匹配技术具有很好的稳定性（ICC=0．90）,但受呼吸影响大。原发性甲亢患者的ZSI值与甲状腺距体表厚度和甲状腺前方脂肪层厚度无相关性。结论声速匹配技术可以准确测定原发性甲亢患者的声速值,吸气后稳定性良好;能为临床诊断原发性甲亢提供客观参考依据。     

“神舟”7号飞行前后呼吸和应激测试中航天员血流动力学反应(英文)

目的本研究旨在探明3 d航天飞行是否会导致航天员的心脏-压力反射功能及血流动力学参数发生变化。方法在飞行前14 d及返回后第2天,采用SEVE系统以非介入式的逐搏测量技术连续监测航天员做呼吸动作及应激测试时的心电、血压和呼吸信号。通过分析这些生理信号,对航天员自发性压力反射敏感性(SBRs)、心输出量(CO)、每搏量(SV)及总外周血管阻力(TPR)变化进行评价。结果飞行后,航天员的立位耐力评分轻微下降;在基础状态下,飞行导致SBRs和TPR下降,SV和CO升高。在做呼吸动作及应激测试中发现,航天飞行导致收缩压、舒张压、心率(HR)、SV及CO对应激的反应能力下降,而SBRs对应激的反应能力却没有受到影响。结论短期航天飞行导致了基础状态下航天员的SBRs和TPR下降,SV和CO升高,抑制了应激状态下心血管系统的调节功能。     

No association between ACE I/D polymorphism and cardiovascular hemodynamics during exercise in young women

The ACE I/D polymorphism has been shown to interact with habitual physical activity levels in postmenopausal women to associate with submaximal and with maximal exercise hemodynamics. This investigation was designed to assess the potential relationships between ACE genotype and oxygen consumption (VO2), cardiac output (Q), stroke volume (SV), heart rate (HR), blood pressure (BP), total peripheral resistance (TPR), and arteriovenous oxygen difference ([a-v]O2 diff) during submaximal and maximal exercise in young sedentary and endurance-trained women. Seventy-seven 18-35-yr-old women underwent a maximal exercise test and a number of cardiac output tests on a treadmill using the acetylene rebreathing technique. ACE genotype was not significantly associated with VO2max (II 41.4+/-1.2, ID 39.8+/-0.9, DD 39.8+/-1.1 ml/kg/min, p=ns) or maximal HR (II 191+/-2, ID 191+/-1, DD 193+/-2 bpm, p=ns). In addition, systolic and diastolic BP, (a-v)O2 diff, TPR, SV, and Q during maximal exercise were not significantly associated with ACE genotype. During submaximal exercise, SBP, Q, SV, HR, TPR, and (a-v)O2 diff were not significantly associated with ACE genotype. However, the association between diastolic BP during submaximal exercise and ACE genotype approached significance (p=0.08). In addition, there were no statistically significant interactions between ACE genotype and habitual physical activity (PA) levels for any of the submaximal or the maximal exercise hemodynamic variables. We conclude that the ACE I/D polymorphism was not associated, independently or interacting with habitual PA levels, submaximal, or maximal cardiovascular hemodynamics in young women.     

Cardiorespiratory and metabolic responses to a simulated synchronized swimming routine in senior (>18 years) and comen (13-15 years) national level athletes

AIM: This study examined the ventilatory responses and blood lactate concentration after a simulated synchronized swimming routine of athletes of two different age categories. METHODS: Sixteen trained female synchronized swimmers, 8 competing at the comen category (age: 13.8+/-0.2 years) and 8 competing at the senior category (age: 22.6+/-0.9 years), performed a maximal 400 m swimming test and a simulated synchronized swimming routine. Oxygen uptake (VO(2)) of the tests was obtained by backward extrapolation of a monoexponential curve fitted to the postexercise oxygen uptake data. RESULTS: There were no differences in VO(2) at the end of the routine (37.4+/-2.7 vs 40.5+/-2 mL . kg(-1) . min(-1), or 81.8+/-3.1% and 85.8+/-2.7% of VO(2peak)) and blood lactate (5.7+/-0.9 vs 4.5+/-0.4 mmol.L(-1)) between senior and comen synchronized swimmers. There was no difference in the half-time of V.O(2) decay (T(1/2)) between the athletes of the two categories, but T(1/2) was significantly higher after the routine compared with the V.O(2peak) test for both categories (senior: 45.2+/-5.9 vs 33.1+/-2.1 s, P<0.05, comen: 38.2+/-6 vs 27.4+/-8.2 s, P<0.05). The mean end-tidal pressure of CO(2) during the second half of the recovery was higher after the routine than after the VO(2peak) test (37.2+/-1.4 vs 34.5+/-1.5 mmHg, P<0.05), possibly due to the prolonged periods of breath holding (55+/-4% of routine time). Breathing frequency was also high (30+/-2.2 breaths . min(-1)) at the later part of recovery after the routine. CONCLUSION: Cardiorespiratory and metabolic responses to a simulated synchronized swimming routine were similar in senior and comen athletes. The slower recovery of V.O(2)after the routine could be related to the elevated cost of ventilation, especially during the later stages of recovery, possibly as a result of the prolonged apnea.     

电影相位对比与屏气二维相位对比MRI对肝硬化门静脉血流的对照研究

目的探讨MRI电影法相位对比（Cine PC）与屏气二维相位对比（2D PC）在肝硬化患者和正常志愿者门静脉血流测量中的诊断价值。资料与方法对照组为82名志愿者,男45名,女37名,平均年龄26.65岁;肝硬化组24例,男14例,女10例,平均年龄42.00岁。空腹状态下采用CinePC技术对门静脉血流定量测量,同期采用2DPC技术3种不同屏气状态（正常吸气屏气,呼气屏气,平静呼吸屏气）与其进行比较。结果肝硬化患者门静脉血流速度较对照组略减低,除2D PC平静呼吸法,余方法两组差异均无统计学意义,肝硬化组门静脉血流量与对照组比较明显增大（P〈0.01）,但2DPC吸气屏气技术两者差异无统计学意义。采用相关性分析对屏气2DPC（不同呼吸状态）与Cine PC MRI方法定量门静脉血流速度、血流量,显示两种技术相关性很好（r〉0.8;P〈0.01）,但在对照组行相关性分析,仅呼气后屏气2D PC与Cine PC显示中度相关（r〉0.5;P〈0.01）,吸气后屏气与CinePC相关性较差（r〈0.4）。结论MRI Cine PC在正常呼吸情况下对门静脉血流行定量测量,接近人体生理状态,适合门静脉血流测量;正常呼吸状态屏气对肝硬化患者门静脉血流影响较正常人小,在肝硬化血流测量中,MRI Cine PC与屏气2DPCMRI法显示很好相关性。屏气2DPCMRI技术提供了一种简便、实用、相对准确的肝硬化门静脉血流测量方法。     

创伤合并ARDS患者适应性支持通气加肺复张策略的疗效分析

目的 探讨适应性支持通气(adaptive support ventilation,ASV)模式加肺复张策略(lung recruitment maneuvers,LRM)与间歇正压通气(intermittent positive pressure ventilation,IPPV)模式对创伤合并ARDS患者的疗效。 ...     

Differential fMRI-BOLD signal response to apnea in humans and anesthetized rats.

Blood oxygenation level dependent (BOLD) signal intensity (SI) and regional cerebral blood flow (CBF) during a 20-s apnea stimulus in awake humans and pentobarbital-anesthetized rats were measured to assess the usefulness of apnea in estimating cerebral vasodilatory capacity for functional MRI (fMRI) experiments. Rats were ventilated with either room air or 100% O(2.) While breathing room air, apnea for 20 s increased the BOLD SI in humans but decreased it in rats. However, in rats ventilated with 100% O(2), BOLD SI increased upon apnea for 20 s. CBF measurements in rats using laser Doppler flowmetry (LDF) showed a 45% +/- 8% increase during apnea with room air ventilation, and a 10% +/- 3% increase with 100% O(2). Arterial blood oxygen saturation fell from 96% +/- 1% to 29% +/- 5%, and cerebral tissue PO(2) decreased from 15 +/- 3 mmHg to 6 +/- 2 mmHg by the end of 20-s apnea in rats breathing room air. However, with 100% O(2) respiration, apnea produced no change in the arterial blood oxygen saturation, which remained at 99%, but increased tissue PO(2) from 35 +/- 9 mmHg to 39 +/- 10 mmHg. From the results obtained in rats ventilated with room air, it is concluded that apnea induces hypoxia that results in a decrease in fMRI-BOLD signal. The signal decrease occurred despite an increase in P(a)CO(2) and CBF. This BOLD response is the opposite of that observed in humans, who presumably do not develop hypoxia within the applied apnea period. These studies highlight the importance of the choice of ventilating gas mixture on the outcome of BOLD experiments during systemic perturbations.     

磁共振导航回波技术在胆道水成像中的应用

目的:探讨磁共振导航回波技术在胆道水成像中的应用价值。方法:对23例在胆道水成像检查中不能配合吸气屏气的患者,使用磁共振导航回波技术进行扫描,扫描中只要求患者保持平静下自由呼吸,采用厚层快速自旋回波T2WI序列及薄层半傅立叶T2WI序列,扫描完成后,对薄层半傅立叶T2WI序列进行3D重建,以显示胆道全景。结果:19例患者的检查均能达到较理想的效果,可以清晰的显示胆道及病变,4例患者呼吸不稳定导致图像中出现伪影,但不影响最终的诊断。结论:磁共振导航回波技术的应用,可以使配合不好的患者的胆道水成像检查得到较理想的结果,扩大了检查适应症的范围,有助于临床的治疗。     

Acute responses of breathing techniques in maximal inspiratory pressure

Purpose

The purpose of the present study was to examine the effect of three breathing techniques [normal breath (NB), breath holding (BH) and intermittent breath holding (IBH)] on finswimmers’ heart rate (HR), arterial oxygen saturation (SpO₂) and maximum inspiratory pressure (PI_max).

Methods

Ten young finswimmers (15.8 ± 0.5 years) performed 8 × 25 m freestyle leg kick trials under the three different breathing occasions (NB, BH and IBH). HR, SpO₂ and PI_max were recorded immediately after the end of each test.

Results

The results showed lower SpO₂ values immediately after the end of IBH technique in correlation with the other breathing techniques (IBH: 88 ± 0.9%; BH: 93.3 ± 0.7%; NB: 98.3 ± 0.3%; p < 0.001). Additionally, HR was higher after IBH compared to the other breathing techniques (IBH: 177 ± 4.2 bpm^?1; BH: 165.7 ± 7.9 bpm^?1; NB: 158.3 ± 2.2 bpm^?1, p < 0.001) and PI_max was also higher after the IBH compared to the other two techniques (IBH: 168.3 ± 5.3 cmH₂O; BH: 166 ± 11 cmH₂O; NB: 161.7 ± 11.4 cmH₂O; p < 0.05).

Conclusion

The data from the present study support that BH and even more so IBH training acutely increase the inspiratory muscles strength. This is an important training tool to improve the inspiratory muscle performance in athletes.

     

Left ventricular quantification in heart failure by cardiovascular MR using prospective respiratory navigator gating: comparison with breath-hold acquisition

Cardiovascular magnetic resonance (CMR) is the reference standard for the assessment of cardiac function. Faster sequences, such as breath-hold (BH) fast low-angle shot, have made CMR more clinically acceptable and cost effective. In a significantly large patient group, however, holding their breath is difficult, resulting in poor-quality images. We compared prospective navigator-echo respiratory gating (NE), which allows image acquisition during free breathing, and BH imaging in 14 patients with heart failure and 10 normal volunteers. There was good agreement between both NE and BH volumes, mass, and ejection fraction. The image quality of both NE basal and apical slices was significantly better than the corresponding BH slices in both the heart failure (P < 0.01) and normal groups (P < 0.05). The NE image acquisition was more time efficient than the BH acquisition in the heart failure group (P < 0. 01), with no difference in the normal group (P = 0.2). Thus, prospective navigator-echo gating, previously only described in coronary artery imaging, can be used in the assessment of cardiac function. It is particularly useful in patients who find it difficult to hold their breath in whom NE provides good-quality, time-efficient images.     

High spatial and temporal resolution cardiac cine MRI from retrospective reconstruction of data acquired in real time using motion correction and resorting

Cine MRI is used for assessing cardiac function and flow and is typically based on a breath‐held, segmented data acquisition. Breath holding is particularly difficult for patients with congestive heart failure or in pediatric cases. Real‐time imaging may be used without breath holding or ECG triggering. However, despite the use of rapid imaging sequences and accelerated parallel imaging, real‐time imaging typically has compromised spatial and temporal resolution compared with gated, segmented breath‐held studies. A new method is proposed that produces a cardiac cine across the full cycle, with both high spatial and temporal resolution from a retrospective reconstruction of data acquired over multiple heartbeats during free breathing. The proposed method was compared with conventional cine images in 10 subjects. The resultant image quality for the proposed method (4.2 ± 0.4) without breath holding or gating was comparable to the conventional cine (4.4 ± 0.5) on a five‐point scale (P = n.s.). Motion‐corrected averaging of real‐time acquired cardiac images provides a means of attaining high‐quality cine images with many of the benefits of real‐time imaging, such as free‐breathing acquisition and tolerance to arrhythmias. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

Cerebral perfusion during anesthesia with fentanyl, isoflurane, or pentobarbital in normal rats studied by arterial spin-labeled MRI.

The influence of anesthetic agents on cerebral blood flow (CBF) was tested in normal rats. CBF is quantified with arterial spin-labeled MRI in rats anesthetized with either an opiate (fentanyl), a potent inhalation anesthetic agent (isoflurane), or a barbiturate (pentobarbital) using doses commonly employed in experimental paradigms. CBF values were found to be about 2.5-3 times lower in most regions analyzed during anesthesia with either fentanyl (with N(2)O/O(2)) or pentobarbital vs. isoflurane (with N(2)O/O(2)), in agreement with findings utilizing invasive measurement techniques. CBF was heterogeneous in rats anesthetized with isoflurane (with N(2)O/O(2)), but relatively homogeneous in rats anesthetized with either fentanyl (with N(2)O/O(2)) or pentobarbital, also in agreement with studies using other techniques. Magn Reson Med 46:202-206, 2001.     

Real-time MR imaging of aortic flow: influence of breathing on left ventricular stroke volume in chronic obstructive pulmonary disease

PURPOSE: To assess real-time changes of left ventricular stroke volume (SV) in relation to the breathing pattern in healthy subjects and in patients with chronic obstructive pulmonary disease (COPD). MATERIALS AND METHODS: Real-time magnetic resonance (MR) imaging flow measurements were performed in the ascending aorta of 10 healthy volunteers and nine patients with severe COPD. Breathing maneuvers were registered with an abdominal pressure belt, which was synchronized to the electrocardiographic signal and the flow measurement. Healthy subjects performed normal breathing, deep breathing, and the Valsalva maneuver. Patients with COPD performed spontaneous breathing. Paired two-tailed Student t tests were used in healthy volunteers to assess significant SV differences between normal breathing and deep breathing or the Valsalva maneuver. The results of measurements in the patients with COPD were compared with the results during normal breathing in healthy subjects with the unpaired two-tailed Student t test. RESULTS: In healthy subjects, SV decreased during inspiration and increased during expiration (r2 = 0.78, P <.05). When compared with the SV during normal breathing, mean SV did not change during deep breathing but declined during the Valsalva maneuver (P <.05). The difference between minimal and maximal SVs (ie, SV range) increased because of deep breathing or the Valsalva maneuver (P <.05). In normal and deep breathing, velocity of SV elevation and velocity of SV decrease were equal (which resulted in a ratio of 1), whereas during the Valsalva maneuver, this value increased (P <.05). Spontaneous breathing in COPD resulted in SV changes (P <.05) similar to those observed in healthy subjects who performed the Valsalva maneuver. CONCLUSION: Real-time MR imaging of aortic flow reveals physiologic flow alterations, which are dependent on variations in the breathing pattern.