Sympathetic neuronal activity is primarily responsible for the neurogenic control of cerebral autoregulation. The stimulation of sympathetic nerves causes both large arterial constriction and small vessel dilation in experimental animals. However, the role of the sympathetic nervous system in the control of cerebral hemodynamics has yet to be clarified in humans. In order to assess the effect of sympathetic activation on human cerebral hemodynamics, we performed a simultaneous transcranial Doppler (TCD) monitoring of bilateral middle cerebral arterial flow velocity in 16 healthy male volunteers (mean age 26) during well-known sympathetic activation measures such as isometric hand-grip exercise (IHE) and cold pressor test (CPT). Blood pressure was checked manually before and at each minute during tests. The mean arterial pressure (MAP) was calculated as (systolic pressure + 2 X diastolic pressure)/3. There was a significant increase in MCA flow velocities during both sympathetic activation tests. The percent increase of diastolic velocity (36% with IHE and 24% with CPT) was significantly higher than systolic velocity (21% with IHE and 9% with CPT). The pulsatility index was significantly decreased during the tests (from 0.75 to 0.58 with IHE and from 0.81 to 0.63 with CPT). These results suggest that sympathetic activation increases MCA flow velocities, related with a reduction in small vessel resistance and/or a constriction of large arteries.
Adult ; Blood Flow Velocity ; Carbon Dioxide/blood ; Cerebral Arteries/physiology* ; Cerebrovascular Circulation* ; Hemodynamics ; Human ; Male ; Sympathetic Nervous System/physiology*

To have a thorough understanding of the CPR quality based on patients' various physiological states, the doctors must do something to simulate the chest compression physiological feedback parameters (CCPFP). The CCPFP simulation plays an important role in raising efficiency of CPR training and improving chest compression quality. In this study, the CCPFP, including cardiac output (CO), coronary perfusion pressure (CPP), partial pressure of End-tidal CO2 (PETCO2) and mean arterial relaxation pressure (MARP), was simulated using Charles F. Babbs' Model. Simulation results showed that the effect of compression depth upon CCPFP was important in the range of 2-6 cm, whereas compression rate had little effect on the CCPFP higher than 100/min; the thoracic factor is inversely proportional to the CCPFP with fixed compression depth and compression rate. The CCPFP simulation can be implemented at the various physiological statuses, and verified well with the animal experimental results and the clinical results.
Blood Pressure ; physiology ; Carbon Dioxide ; blood ; Cardiac Output ; physiology ; Chest Wall Oscillation ; Computer Simulation ; Feedback, Physiological ; physiology ; Humans ; Models, Biological ; Partial Pressure

OBJECTIVETo observe oxygen uptake efficiency plateau (OUEP, i.e.highest V˙O2/V˙E) and carbon dioxide output efficiency (lowest V˙E/V˙CO2) parameter changes during exercise in normal subjects.

METHODSFive healthy volunteers performed the symptom limited maximal cardiopulmonary exercise test (CPET) at Harbor-UCLA Medical Center. V˙O2/V˙E and V˙E/V˙CO2 were determined by both arterial and central venous catheters. After blood gas analysis of arterial and venous sampling at the last 30 seconds of every exercise stage and every minute of incremental loading, the continuous parameter changes of hemodynamics, pulmonary ventilation were monitored and oxygen uptake ventilatory efficiency (V˙O2/V˙E and V˙E/V˙CO2) was calculated.

RESULTSDuring CPET, as the loading gradually increased, cardiac output, heart rate, mixed venous oxygen saturation, arteriovenous oxygen difference, minute ventilation, minute alveolar ventilation, tidal volume, alveolar ventilation and pulmonary ventilation perfusion ratio increased near-linearly (P < 0.05-0.01, vs.resting); arterial oxygen concentration maintained at a high level without significant change (P > 0.05); stroke volume, respiratory rate, arterial partial pressure of carbon dioxide, arterial blood hydrogen ion concentration and dead space ventilation ratio significantly changed none-linearly (compare resting state P < 0.05-0.01).OUE during exercise increased from 30.9 ± 3.3 at resting state to the highest plateau 46.0 ± 4.7 (P < 0.05 vs.resting state), then, declined gradually after anaerobic threshold (P < 0.05-0.01, vs.OUEP) and reached 36.6 ± 4.4 at peak exercise. The V˙E/V˙CO2 during exercise decreased from the resting state (39.2 ± 6.5) to the minimum value (24.2 ± 2.4) after AT for a few minutes (P > 0.05 vs.earlier stage), then gradually increased after the ventilatory compensation point (P < 0.05 vs.earlier stage) and reached to 25.9 ± 2.7 at peak exercise.

CONCLUSIONSCardiac and lung function as well as metabolism change during CPET is synchronous.In the absence of pulmonary limit, appearing before and after anaerobic threshold, OUEP and lowest V˙E/V˙CO2 could be used as reliable parameters representing the circulatory function.

Arteries ; Blood Gas Analysis ; Blood Pressure ; Carbon Dioxide ; metabolism ; Cardiac Output ; Exercise ; physiology ; Exercise Test ; Heart ; Heart Rate ; Hemodynamics ; Humans ; Lung ; Oxygen ; metabolism ; Oxygen Consumption

The changes of arterial carbon dioxide partial pressure considerably influence cerebral blood flow and different anesthetic agents have different effects on cerebrovascular physiology. However the importance of these differences in neuroanesthetic practice are unclear. Transcranial Doppler ultrasonography allows the noninvasive direct measurements of cerebral blood flow velocity and direction in the basal brain arteries. The authors performed transcranial Doppler ultrasonography to measure the blood flow velocity of middle cerebral artery in 12 patients who were anesthetized with 10 mcg/kg of fentanyl and 66 % nitrous oxide in oxygen(fentanyl group) and 12 patients with 1.0 vo1% isoflurane and 66 % nitrous oxide in oxygen(isoflurane group) during normocapnia(P(ET)CO(2)=38 mmHg) and hypocapnia(P(ET)CO(2)=28 mmHg)state. The carbon dioxide reactivity was expressed as the changes in mean blood flow velocity per unit changes in endtidal carbon dioxide partial pressure(P(ET)CO(2)). Mean blood flow velocity of middle cerebral artery decreased from 46.6+/-8.9 cm/s to 30.0+/-5.3 cm/s in the fentanyl group and 42.7+/-5.6 cm/s to 32.5+/-4.6 cm/s in the isoflurane group as the P(ET)CO(2) decreased from 38 mmHg to 28 mmHg. There was a significant difference between the CO2 reactivity of fentanyl group(1.7+/-0.7 cm/s/mmHg) and isoflurane group(1,0+/-0,2 cm/s/mmHg) (p<0.05). It is concluded that hyperventilation is more likely to affect cerebral blood flow during fentanyl-nitrous oxide anesthesia than during isoflurane-nitrous oxide anesthesia.
Anesthesia ; Anesthetics ; Arteries ; Blood Flow Velocity ; Brain ; Carbon Dioxide ; Fentanyl* ; Humans ; Hyperventilation ; Isoflurane* ; Middle Cerebral Artery ; Nitrous Oxide ; Partial Pressure ; Physiology ; Ultrasonography, Doppler, Transcranial

PURPOSE: Removal of CO₂ is much efficient during high-frequency oscillatory ventilation (HFOV) for preterm infants. However, an optimal carbon dioxide diffusion coefficient (DCO₂) and tidal volume (VT) have not yet been established due to much individual variance. This study aimed to analyze DCO₂ values, VT, and minute volume in very-low-birth-weight (VLBW) infants using HFOV and correlates with plasma CO₂ (pCO₂). MATERIALS AND METHODS: Daily respiratory mechanics and ventilator settings from twenty VLBW infants and their two hundred seventeen results of blood gas analysis were collected. Patients were treated with the Dräger Babylog VN500 ventilator (Drägerwerk Ag & Co.) in HFOV mode. The normocapnia was indicated as pCO₂ ranging from 45 mm Hg to 55 mm Hg. RESULTS: The measured VT was 1.7 mL/kg, minute volume was 0.7 mL/kg, and DCO₂ was 43.5 mL²/s. Mean results of the blood gas test were as follows: pH, 7.31; pCO₂, 52.6 mm Hg; and SpO₂, 90.5%. In normocapnic state, the mean VT was significantly higher than in hypercapnic state (2.1±0.5 mL/kg vs. 1.6±0.3 mL/kg), and the mean DCO₂ showed significant difference (68.4±32.7 mL²/s vs. 32.4±15.7 mL²/s). The DCO₂ was significantly correlated with the pCO₂ (p=0.024). In the receiver operating curve analysis, the estimated optimal cut-off point to predict the remaining normocapnic status was a VT of 1.75 mL/kg (sensitivity 73%, specificity 80%). CONCLUSION: In VLBW infants treated with HFOV, VT of 1.75 mL/kg is recommended for maintaining proper ventilation.
Blood Gas Analysis ; Carbon Dioxide/analysis ; Female ; High-Frequency Ventilation ; Humans ; Hypercapnia/physiopathology ; Incidence ; Infant ; Infant, Newborn ; Infant, Very Low Birth Weight/physiology ; Male ; ROC Curve ; Tidal Volume

BACKGROUNDAfter cardiac surgery, central venous oxygen saturation (ScvO 2 ) and serum lactate concentration are often used to guide resuscitation; however, neither are completely reliable indicators of global tissue hypoxia. This observational study aimed to establish whether the ratio between the veno-arterial carbon dioxide and the arterial-venous oxygen differences (P(v-a)CO 2 /C(a-v)O 2 ) could predict whether patients would respond to resuscitation by increasing oxygen delivery (DO 2 ).

METHODSWe selected 72 patients from a cohort of 290 who had undergone cardiac surgery in our institution between January 2012 and August 2014. The selected patients were managed postoperatively on the Intensive Care Unit, had a normal ScvO 2 , elevated serum lactate concentration, and responded to resuscitation by increasing DO 2 by >10%. As a consequence, 48 patients responded with an increase in oxygen consumption (VO 2 ) while VO 2 was static or fell in 24.

RESULTSAt baseline and before resuscitative intervention in postoperative cardiac surgery patients, a P(v-a)CO 2 /C(a-v)O 2 ratio ≥1.6 mmHg/ml predicted a positive VO 2 response to an increase in DO 2 of >10% with a sensitivity of 68.8% and a specificity of 87.5%.

CONCLUSIONSP(v-a)CO 2 /C(a-v)O 2 ratio appears to be a reliable marker of global anaerobic metabolism and predicts response to DO 2 challenge. Thus, patients likely to benefit from resuscitation can be identified promptly, the P(v-a)CO 2 /C(a-v)O 2 ratio may, therefore, be a useful resuscitation target.

Adult ; Aged ; Blood Gas Analysis ; Carbon Dioxide ; blood ; Cardiac Surgical Procedures ; Female ; Humans ; Hyperlactatemia ; blood ; therapy ; Intensive Care Units ; statistics & numerical data ; Lactic Acid ; blood ; Male ; Middle Aged ; Oxygen Consumption ; physiology ; Prospective Studies ; Resuscitation

A reduction in diaphragm mobility has been identified in patients with chronic obstructive pulmonary disease (COPD) and has been associated with a decline in pulmonary function parameters. However, little information exists regarding the potential role of diaphragm mobility on hypercapnia in COPD. A new method of assessing the mobility of the diaphragm, using ultrasound, has recently been validated. The purpose of the present study was to investigate the relationship between diaphragm mobility and pulmonary function parameters, as well as that between arterial blood gas values and diaphragm mobility, in COPD patients. Thirty seven COPD patients were recruited for pulmonary function test, arterial blood gas analysis and diaphragm mobility using ultrasound to measure the craniocaudal displacement of the left branch of the portal vein. There were significant negative correlations between diaphragmatic mobility and PaCO2 (r = -0.373, P = 0.030). Diaphragmatic mobility correlated with airway obstruction (FEV1, r = 0.415, P = 0.011) and with ventilatory capacity (FVC, r = 0.302, P = 0.029; MVV, r = 0.481, P = 0.003). Diaphragmatic mobility also correlated significantly with pulmonary hyperinflation. No relationship was observed between diaphragm mobility and PaO2 (r = -0.028, P = 0.873). These findings support a possibility that the reduction in diaphragm mobility relates to hypercapnia in COPD patients.
Aged ; Airway Resistance/physiology ; Carbon Dioxide/blood/physiology ; Diaphragm/physiopathology/*ultrasonography ; Female ; Humans ; Hypercapnia/complications/*physiopathology ; Male ; Middle Aged ; Portal Vein ; Pulmonary Disease, Chronic Obstructive/complications/*physiopathology/ultrasonography ; Pulmonary Gas Exchange ; Respiratory Muscles/physiopathology

To compare the effects of ketamine and tiletaminezolazepam (TZ) drugs widely used for the chemical restraint and immobilization of primates, on various physiological parameters and blood gas values in cynomolgus monkeys (Macaca facicularis). Rectal temperature, heart rate, respiration rate and blood gas analysis were measured before treatment and at 1, 10, 20, 30, 40, 50 and 60 min after administration. Additionally, in both groups, induction and maintenance times were compared. Heart rate, respiration rate, rectal temperature, pH and pCO2 were not significant different in the two groups. However, pO2 in the ketamine-treated group was significantly lower at 30 and 40 min than in the TZ-treated group. The induction time was short in both groups, and the maintenance time was longer in the TZ-treated group (67.8+/-6.5 min) than in the ketamine-treated group (42.3+/-6.7 min). However, decreased rectal temperatures must be watched and prevented following TZ administration to cynomolgus monkeys. It was considered that ketamine may be useful for short duration anesthesia including handling, physical examination, blood sampling and TZ may be useful for prolonged anesthesia including minor surgery and other surgical procedure.
Animals ; Body Temperature/drug effects ; Carbon Dioxide/blood ; Excitatory Amino Acid Antagonists/*pharmacology ; Female ; Heart Rate/drug effects ; Hydrogen-Ion Concentration ; Immobilization/*physiology ; Ketamine/*pharmacology ; Macaca fascicularis ; Male ; Partial Pressure ; Respiratory Mechanics ; Restraint, Physical/*methods ; Tiletamine/*pharmacology ; Time Factors

OBJECTIVETo study the effects of mild hypothermia on cerebral oxygen partial pressure, carbon dioxide partial pressure, pH and body temperature (PbrO2, PbrCO2, pHbr and BT) in patients with acute severe head injury.

METHODSThirty-eight patients with acute severe head injury were treated with mild hypothermia, meantime PbrO2, PbrCO2, pHbr and BT were monitored in order to study the changes of PbrO2, PbrCO2, pHbr and BT.

RESULTSIn patients with acute head injury, mild hypothermia obviously increased PbrO2, decreased PbrCO2 and CO2 accumulation and acidosis in brain tissue. BT was 1-1.5 deg. higher than rectal temperature (RT) after injury. The BT and RT were decreased when the patients were treated with mild hypothermia, but at the same time the difference between BT and RT was increased.

CONCLUSIONSIn patients with acute severe head injury the direct monitoring of PbrO2, PbrCO2, pHbr and BT was safe and reliable, and is helpful in estimating prognosis and mild hypothermia therapy.

Acute Disease ; Adolescent ; Adult ; Biomarkers ; blood ; Body Temperature ; physiology ; Brain Injuries ; diagnosis ; mortality ; therapy ; Carbon Dioxide ; blood ; Female ; Follow-Up Studies ; Glasgow Coma Scale ; Humans ; Hydrogen-Ion Concentration ; Hypothermia, Induced ; Injury Severity Score ; Male ; Middle Aged ; Monitoring, Physiologic ; methods ; Oxygen ; blood ; Probability ; Risk Assessment ; Survival Rate ; Treatment Outcome

The aim of this study was to determine the effect of partial liquid ventilation (PLV) using a perfluorocarbon (PFC) on gas exchange and lung inflammatory response in a canine acute lung injury model. After inducing severe lung injury by oleic acid infusion, beagle dogs were randomized to receive either gas ventilation only (control group, n = 6) or PLV (PLV group, n = 7) by sequential instillation of 10 mL/kg of perfluorodecalin (PFC) at 30 min intervals till functional residual capacity was attained. Measurements were made every 30 min till 210 min. Then the lungs were removed and bronchoalveolar lavage (BAL) (35 mL/kg) was performed on the right lung and the left lung was submitted for histologic analysis. There was significant improvement in PaO2 and PaCO2 in the PLV group compared to the control group (p < 0.05) which was associated with a significant decrease in shunt (p < 0.05). There was no significant difference in parameters of lung mechanics and hemodynamics. There was a significant decrease in cell count and neutrophil percentage in BAL fluid and significantly less inflammation and exudate scores in histology in the PLV group (p < 0.05). We conclude that PLV with perfluorodecalin improves gas exchange and decreases inflammatory response in the acutely-injured lung.
Animal ; Blood Cell Count ; Bronchoalveolar Lavage Fluid ; Carbon Dioxide/analysis ; Disease Models, Animal ; Dogs ; Female ; Fluorocarbons/pharmacology* ; Hemodynamics ; Histocytochemistry ; Inflammation/prevention & control ; Lung Diseases/physiopathology* ; Lung Diseases/chemically induced ; Male ; Oleic Acid ; Oxygen/analysis ; Pulmonary Gas Exchange/drug effects* ; Pulmonary Ventilation/physiology* ; Respiratory Function Tests ; Ventilators, Mechanical