CO2 Tension Research Articles

Effects of Pneumoperitoneum and the Steep Trendelenburg Position on Heart Rate Variability and Cerebral Oxygenation during Robotic Sacrocolpopexy

Study ObjectiveThe aim of this study was to investigate how steep Trendelenburg positioning with pneumoperitoneum modifies brain oxygenation and autonomic nervous system modulation of heart rate variability during robotic sacrocolpopexy. DesignProspective study (Canadian Task Force classification III). SettingRambam Health Care Campus. PatientsEighteen women who underwent robotic sacrocolpopexy for treatment of uterovaginal or vaginal apical prolapse. InterventionsRobotic sacrocolpopexy. Measurements and Main ResultsA 5-minute computerized electrocardiogram, cerebral O2 saturation (cSO2), systemic O2 saturation, heart rate (HR), diastolic blood pressure (BP), systolic BP, and end-tidal CO2 tension were recorded immediately after anesthesia induction (baseline phase) and after alterations in positioning and in intra-abdominal pressure. HR variability was assessed in time and frequency domains. Cerebral oxygenation was measured by the technology of near-infrared spectrometry. cSO2 at baseline was 73% ± 9%, with minor and insignificant elevation during the operation. Mean HR decreased significantly when the steep Trendelenburg position was implemented (66 ± 10 vs 55 ± 9 bpm, p < .05) and returned gradually to baseline with advancement of the operation and the decrease in intra-abdominal pressure. Concomitant with this decrease, the power of both arms of the autonomic nervous system increased significantly (2.8 ± .8 vs 3.3 ± .9 ms2/Hz and 2.5 ± 1.2 vs 3.2 ± .9 ms2/Hz, respectively, p < .05). All these effects occurred without any significant shifts in systolic or diastolic BP or in systemic or cerebral oxygenation. ConclusionThis study supports the safety of robotic sacrocolpopexy performed with steep Trendelenburg positioning with pneumoperitoneum. Only minor alterations were observed in cerebral oxygenation and autonomic perturbations, which did not cause clinically significant alterations in HR rate and HR variability.

Production of Trichophyton rubrum microspores in large quantities and its application to evaluate amorolfine/azole compound interactions in vitro.

Trichophyton rubrum is the most frequently isolated dermatophyte species in European countries. The lack or poor sporulation of T.rubrum has always been a major complication and a limiting factor when performing antifungal susceptibility testing. Therefore, we describe an in vitro method aiming to enhance sporulation of various T.rubrum isolates in order to perform antifungigrams. A combination of high CO2 tensions and incubation on PDA growth medium revealed to be optimal for sporulation of all tested T.rubrum isolates. This method was further used to examine in vitro the combined effects of amorolfine and azole derivatives against fungal growth using adapted checkerboard microdilution assays and an isobolographic approach of the data, adapted disc diffusion and Etest assays. Non-antagonistic and synergistic effects were observed in these settings with amorolfine combined to each of the tested azole compounds. The optimised culture method appeared to be suitable for T.rubrum isolates for which antifungigrams were especially difficult to obtain because of the lack of sporulation.

Physiologic Effects of High-Flow Nasal Cannula in Acute Hypoxemic Respiratory Failure.

High-flow nasal cannula (HFNC) improves the clinical outcomes of nonintubated patients with acute hypoxemic respiratory failure (AHRF). To assess the effects of HFNC on gas exchange, inspiratory effort, minute ventilation, end-expiratory lung volume, dynamic compliance, and ventilation homogeneity in patients with AHRF. This was a prospective randomized crossover study in nonintubated patients with AHRF with PaO2/setFiO2 less than or equal to 300 mm Hg admitted to the intensive care unit. We randomly applied HFNC set at 40 L/min compared with a standard nonocclusive facial mask at the same clinically set FiO2 (20 min/step). Toward the end of each phase, we measured arterial blood gases, inspiratory effort, and work of breathing by esophageal pressure swings (ΔPes) and pressure time product, and we estimated changes in lung volumes and ventilation homogeneity by electrical impedance tomography. We enrolled 15 patients aged 60 ± 14 years old with PaO2/setFiO2 130 ± 35 mm Hg. Seven (47%) had bilateral lung infiltrates. Compared with the facial mask, HFNC significantly improved oxygenation (P < 0.001) and lowered respiratory rate (P < 0.01), ΔPes (P < 0.01), and pressure time product (P < 0.001). During HFNC, minute ventilation was reduced (P < 0.001) at constant arterial CO2 tension and pH (P = 0.27 and P = 0.23, respectively); end-expiratory lung volume increased (P < 0.001), and tidal volume did not change (P = 0.44); the ratio of tidal volume to ΔPes (an estimate of dynamic lung compliance) increased (P < 0.05); finally, ventilation distribution was more homogeneous (P < 0.01). In patients with AHRF, HFNC exerts multiple physiologic effects including less inspiratory effort and improved lung volume and compliance. These benefits might underlie the clinical efficacy of HFNC.

The Intraoperative Effect of Methadone on Somatosensory Evoked Potentials.

Evoked potentials (EP), both somatosensory evoked potentials (SSEP) and transcranial motor evoked potentials (TcMEP), are often used during complex spine surgery to monitor the integrity of spinal pathways during operations in or around the spine. Changes in these monitored EP signals (increased latency and decreased amplitude) may result from ischemia, direct surgical injury, changes in blood pressure, hypoxia, changes in CO2 tension, and anesthetic agents. Typically, a clinically significant change for SSEPs is defined as an increase in latency >10% or a decrease of amplitude >50%. A clinically significant change for TcMEPs is much more complex but is also described in terms of large signal loss or decrease. Opioids have been shown to both increase latency and decrease the amplitude of SSEPs, although this change is usually not clinically significant. There has been a renewed interest in methadone for use in spine and other complex surgeries. However, the effect of methadone on intraoperative monitoring of SSEPs and TcMEPs is unknown. We present the first study to directly look at the effects of methadone on SSEP and TcMEP monitoring during complex spine surgery. The goal of this study was to observe the effect of methadone on an unrandomized set of patients. The primary endpoint was methadone's effect on SSEPs, and the secondary endpoint was methadone's effect on TcMEPs. Adult patients undergoing spine surgery requiring intraoperative neuromonitoring were induced with general anesthesia and had a baseline set of SSEPs and TcMEPs recorded. Next, methadone dosed 0.2 mg/kg/lean body weight was given. Repeat SSEPs and TcMEPs were recorded at 5, 10, and 15 minutes, with the timing based on distribution half-life of methadone between 6 and 8 minutes. Postoperatively, adverse events from methadone administration were collected. There was a statistically significant difference found in SSEPs for N20 latency (95% confidence interval [CI], 0.17-0.53; P=0.028), P37 latency (95% CI, 0.65-1.25; P=0.001), and N20 amplitude (95% CI, 0.09-0.32; P=<0.001), but not for P37 amplitude (95% CI, -0.19 to 0.00; P=0.634). There was no significant effect found for TcMEPs, the secondary endpoint of the study, and there were minimal adverse events recorded postoperatively. The data demonstrate that a single intravenous dose of methadone has a statistically significant difference on the amplitude and latency of SSEPs. However, this statistical difference does not translate into a clinical significance.

Forced vital capacity and not central chemoreflex predicts maximal hyperoxic breath-hold duration in elite apneists

The determining mechanisms of a maximal hyperoxic apnea duration in elite apneists have remained unexplored. We tested the hypothesis that maximal hyperoxic apnea duration in elite apneists is related to forced vital capacity (FVC) but not the central chemoreflex (for CO2). Eleven elite apneists performed a maximal dry static-apnea with prior hyperoxic (100% oxygen) pre-breathing, and a central chemoreflex test via a hyperoxic re-breathing technique (hyperoxic-hypercapnic ventilatory response: HCVR); expressed as the increase in ventilation (pneumotachometry) per increase in arterial CO2 tension (PaCO2; radial artery). FVC was assessed using standard spirometry. Maximal apnea duration ranged from 807 to 1262s (mean=1034s). Average HCVR was 2.0±1.2Lmin−1mmHg−1 PaCO2. The hyperoxic apnea duration was related to the FVC (r2=0.45, p<0.05), but not the HCVR (r2<0.01, p>0.05). These findings were interpreted to suggest that during a hyperoxic apnea, a larger initial lung volume prolongs the time before reaching intolerable discomfort associated with pending lung squeeze, while CO2 sensitivity has little impact.

Interfacial tension of CO2 + brine systems: Experiments and predictive modelling

In this study the interfacial tension (IFT) between CO2 and brines, in the context of geological storage of CO2, was investigated. Investigations covered both experimental and theoretical aspects of this property over a broad range of conditions, including those found in subsurface formations. Measurements for CO2+NaCl(aq) systems, of salt molalities 0.98 and 1.98mol.kg-1, were performed for temperatures and pressures up to 423K and 69.51MPa, respectively. Results clearly showed an increase from CO2+H2O IFT upon the addition of the salt, helping to resolve some discrepancies observed in literature data. Furthermore, a predictive method, based on the Density Gradient Theory, was extended to CO2+brine systems, with modelled IFT values yielding a good agreement with experiments from this work and literature for brines of single and mixed salts, including NaCl, KCl and CaCl2, and ionic strength up to 2.7mol.kg−1.

Anesthetic considerations for patients with esophageal achalasia undergoing peroral endoscopic myotomy: a retrospective case series review.

Peroral endoscopic myotomy (POEM) is a novel technique for treating esophageal achalasia. During POEM, carbon dioxide (CO2) is insufflated to aid surgical dissection, but it may inadvertently track into surrounding tissues, causing systemic CO2 uptake and tension capnoperitoneum. This in turn may affect cardiorespiratory function. This study quantified these cardiorespiratory effects and treatment by hyperventilation and percutaneous abdominal needle decompression (PND). One hundred and seventy-three consecutive patients who underwent POEM were included in this four-year retrospective study. Procedure-related changes in peak inspiratory pressure (pmax), end-tidal CO2 levels (etCO2), minute ventilation (MV), mean arterial pressure (MAP), and heart rate (HR) were analyzed. We also quantified the impact of PND on these cardiorespiratory parameters. During the endoscopic procedure, cardiorespiratory parameters increased from baseline: pmax 15.1 (4.5) vs 19.8 (4.7) cm H2O; etCO2 4.5 (0.4) vs 5.5 (0.9) kPa [34.0 (2.9) vs 41.6 (6.9) mmHg]; MAP73.9 (9.7) vs 99.3 (15.2) mmHg; HR 67.6 (12.4) vs 85.3 (16.4) min-1 (P < 0.001 for each). Hyperventilation [MV 5.9 (1.2) vs 9.0 (1.8) L·min-1, P < 0.001] was applied to counteract iatrogenic hypercapnia. Individuals with tension capnoperitoneum treated with PND (n = 55) had higher peak pmax values [22.8 (5.7) vs 18.4 (3.3) cm H2O, P < 0.001] than patients who did not require PND. After PND, pmax [22.8 (5.7) vs 19.9 (4.3) cm H2O, P = 0.045] and MAP [98.2 (16.3) vs 88.6 (11.8) mmHg, P = 0.013] decreased. Adverse events included pneumothorax (n = 1), transient myocardial ischemia (n = 1), and subcutaneous emphysema (n = 49). The latter precluded immediate extubation in eight cases. Postanesthesia care unit (PACU) stay was longer in individuals with subcutaneous emphysema than in those without [74.9 min (34.5) vs 61.5 (26.8 min), P = 0.007]. Carbon dioxide insufflation during POEM produces systemic CO2 uptake and increased intra-abdominal pressure. Changes in cardiorespiratory parameters include increased pmax, etCO2, MAP, and HR. Hyperventilation and PND help mitigate some of these changes. Subcutaneous emphysema is common and may delay extubation and prolong PACU stay.

Peripheral neuropathy in stable chronic obstructive pulmonary disease: Is the phrenic nerve more affected compared with other peripheral nerves?

Background Chronic obstructive pulmonary disease (COPD) is a multicomponent disease with extrapulmonary manifestation. Peripheral nerve affection may be one of the results or mechanism of COPD. Objective The aim of this study was to evaluate peripheral neuropathy in patients with stable COPD and whether these changes are more or less marked in the phrenic nerve when compared with other peripheral nerves. Patients and methods Eighty patients with COPD and 60 healthy individuals as a control group were included. All were subjected to the following: (i) full history taking; (ii) clinical and neurological examination; (iii) chest radiography; (iv) high-resol ution computed tomography scanning of the chest; (v) arterial blood gases analysis at room air; and (vi) spirometric tests. Results There was a statistically significant increase in smoking packs/year, respiratory rate, hemoglobin, and white blood cells in the COPD group. There was a significant decrease in oxygen saturation, pH, arterial oxygen tension, forced expiratory volume in 1 s, forced expiratory volume in 1 s/forced vital capacity, and forced vital capacity% in the study group when compared with the control group, whereas there was a significant increase in CO2 tension in the COPD group. There was a significant increase in the distal latency of all nerves and a significant decrease in the amplitude and conduction velocity of all nerves, except the amplitude of the phrenic nerve in the COPD group. The difference for phrenic nerve amplitude was statistically nonsignificant. In the COPD group, abnormal motor activity in the median, ulnar, common peroneal, and phrenic nerves of 30, 22.5, 35, and 22.5%, respectively, was reported, whereas abnormal sensory activity in the median, ulnar, and sural nerves of 30.0, 27.5, and 42.5%, respectively, was reported. Finally, we found a statistically significant increase in nerve abnormalities with increased severity of the disease. Conclusion COPD had a significant affection on peripheral nerves, either motor or sensory. In addition, COPD had a significant affection on the phrenic nerve and muscle of the diaphragm. However, this affection of the phrenic nerve was confined to grades III and IV and was the least affection of studied nerves.

Effect of variation in the COPD breathing flow pattern on end-tidal CO2 tension: An in vitro study

Effect of variation in the COPD breathing flow pattern on end-tidal CO2 tension: An in vitro study

Characterization of Na+ transport to gain insight into the mechanism of acid-base and ion regulation in white sturgeon (Acipenser transmontanus)

Freshwater fish actively take up ions via specific transporters to counter diffusive losses to their hypotonic environment. While much is known about the specific mechanisms employed by teleosts, almost nothing is known about the basal fishes, such as white sturgeon (Acipenser transmontanus) which may offer insight into the evolution of osmo- and ionoregulation in fishes. We investigated Na+ uptake in juvenile white sturgeon in the presence and absence of transporter inhibitors. We found that sturgeon acclimated to 100μmoll−1 Na+ have Na+ uptake kinetics typical of teleosts and that a Na+/H+ exchanger (NHE) is the predominant transporter for Na+ uptake. White sturgeon are tolerant to hypercarbia-induced respiratory acidoses and recover blood pH (pHe) at 1.5kPa PCO2 but not at higher PCO2 (6kPa PCO2) where they preferentially regulate intracellular pH (pHi). It was hypothesized that during exposure to hypercarbia Na+ uptake would increase at CO2 tensions at which fish were capable of pHe regulation but decrease at higher tensions when they were preferentially regulating pHi. We found that Na+ uptake did not increase at 1.5kPa PCO2, but at 6kPa PCO2 Na+ uptake was reduced by 95% while low water pH equivalent to 6kPa PCO2 reduced Na+ uptake by 71%. Lastly, we measured net acid flux during hypercarbia, which indicates that net acid flux is not associated with Na+ uptake. These findings indicate Na+ uptake in sturgeon is not different from freshwater teleosts but is sensitive to hypercarbia and is not associated with pHe compensation during hypercarbia.

The effect of habitual waterpipe tobacco smoking on pulmonary function and exercise capacity in young healthy males: A pilot study

BackgroundEvidence regarding the health effects of habitual waterpipe smoking is limited, particularly in young smokers. Respiratory health and cardiopulmonary exercise tests were compared in young male habitual waterpipe smokers (WPS) versus non-smokers. Methods69 WPS (≥3 times/week for three years) and 69 non-smokers were studied. Respiratory health was assessed through the American Thoracic Society and the Division of Lung Diseases (ATS-DLD-78) adult questionnaire. Pulmonary function and cardiopulmonary exercise tests were performed. Self-reported respiratory symptoms, forced expiratory volume in first second (FEV1), forced vital capacity (FVC), FEV1/FVC ratio, forced expiratory flow between 25 and 75% of FVC (FEF25–75%), peak expiratory flow (PEF), exercise time, peak end-tidal CO2 tension (PetCO2), subject-reported leg fatigue and dyspnea; peak O2 uptake (VO2 max), and end-expiratory lung volume (EELV) change from baseline (at peak exercise) were measured. ResultsWPS were more likely than non-smokers to report respiratory symptoms. WPS also demonstrated: shorter exercise time; lower peak VO2; higher perceived dyspnea at mid-exercise; lower values of the following: FEV1, FVC, PEF, and EELV change. ConclusionHabitual waterpipe tobacco smoking in young seemingly healthy individuals is associated with a greater burden of respiratory symptoms and impaired exercise capacity.

Coupling between arterial and venous cerebral blood flow during postural change.

In supine humans the main drainage from the brain is through the internal jugular vein (IJV), but the vertebral veins (VV) become important during orthostatic stress because the IJV is partially collapsed. To identify the effect of this shift in venous drainage from the brain on the cerebral circulation, this study addressed both arterial and venous flow responses in the "anterior" and "posterior" parts of the brain when nine healthy subjects (5 men) were seated and flow was manipulated by hyperventilation and inhalation of 6% carbon dioxide (CO2). From a supine to a seated position, both internal carotid artery (ICA) and IJV blood flow decreased (P = 0.004 and P = 0.002), while vertebral artery (VA) flow did not change (P = 0.348) and VV flow increased (P = 0.024). In both supine and seated positions the ICA response to manipulation of end-tidal CO2 tension was reflected in IJV (r = 0.645 and r = 0.790, P < 0.001) and VV blood flow (r = 0.771 and r = 0.828, P < 0.001). When seated, the decrease in ICA blood flow did not affect venous outflow, but the decrease in IJV blood flow was associated with the increase in VV blood flow (r = 0.479, P = 0.044). In addition, the increase in VV blood flow when seated was reflected in VA blood flow (r = 0.649, P = 0.004), and the two flows were coupled during manipulation of the end-tidal CO2 tension (supine, r = 0.551, P = 0.004; seated, r = 0.612, P < 0001). These results support that VV compensates for the reduction in IJV blood flow when seated and that VV may influence VA blood flow.

Prognostic value of on admission arterial PCO2 in hospitalized patients with community-acquired pneumonia.

There is little data about the correlation between the outcome of community acquired pneumonia (CAP) and the hypercapnic type respiratory failure. In this study we prospectively investigated the prognostic significance of first arterial CO2 tension in patients hospitalized with CAP. In this prospective study patients with CAP, admitted to a general hospital were included. PaCO2 was measured for each subject in an arterial blood sample drawn in the first 2 hours and its correlations with three major outcomes were evaluated: intensive care unit (ICU) admission, duration of admission and mortality in 30 days. A total of 114 patients (mean age: 60.9±18.3; male: 51.8%) diagnosed with CAP were included. Significant relationship was not found between PaCO2 and mortality (P=0.544) or ICU admission (P=0.863). However advanced age, associated CHF, high BUN levels, high CURB-65 scores, associated pleural effusion in chest X-ray and being admitted to the ICU (P=0.012, 0.004, 0.003, <0.001, 0.045 and <0.001 respectively) were all significant prognostic factors of higher mortality risks. Prognostic factors for ICU admission were a history of malignancy (P=0.004), higher CURB-65 (P<0.001) scores and concomitant pleural effusion (P=0.028) in chest X-ray. Hypercapnic patients hospitalized for longer duration compared with normocapnic subjects. Furthermore, patients with lower pH (P=0.041) and pleural effusions (P=0.002) were hospitalized longer than the others. There was less prominent prognostic value regarding on-admission PaCO2 in comparison to other factors such as CURB-65. Considering the inconsistent results of surveys conducted on prognostic value of PaCO2 for CAP outcomes, further investigations are required to reach a consensus on this matter.

Effects of voluntary exercise on structure and function of cortical microvasculature

Aerobic activity has been shown highly beneficial to brain health, yet much uncertainty still surrounds the effects of exercise on the functioning of cerebral microvasculature. This study used two-photon fluorescence microscopy to examine cerebral hemodynamic alterations as well as accompanying geometric changes in the cortical microvascular network following five weeks of voluntary exercise in transgenic mice endogenously expressing tdTomato in vascular endothelial cells to allow visualization of microvessels irrespective of their perfusion levels. We found a diminished microvascular response to a hypercapnic challenge (10% FiCO2) in running mice when compared to that in nonrunning controls despite commensurate increases in transcutaneous CO2 tension. The flow increase to hypercapnia in runners was 70% lower than that in nonrunners (p = 0.0070) and the runners’ arteriolar red blood cell speed changed by only half the amount seen in nonrunners (p = 0.0085). No changes were seen in resting hemodynamics or in the systemic physiological parameters measured. Although a few unperfused new vessels were observed on visual inspection, running did not produce significant morphological differences in the microvascular morphometric parameters, quantified following semiautomated tracking of the microvascular networks. We propose that voluntary running led to increased cortical microvascular efficiency and desensitization to CO2 elevation.

Effect of Fetal Calf Serum and Mid Estrus Cow Serum on In Vitro Maturation and Fertilization of Oocytes from Crossbred Cattle in the Tropics

The objective of the study was to examine the effect of fetal calf serum (FCS) and mid estrus cow serum (ECS) in culture media on in vitro maturation (IVM) and in vitro fertilization (IVF) of oocytes from crossbred cattle in the tropics. Oocytes from abattoir ovaries were cultured in three different maturation media at 39oC temperature, 5% CO2 tension with maximum humidity for 24 h. TCM-199 containing 25mM HEPES, 1mM glutamine L, 2.2mg/mL sodium bicarbonate, antibiotics, 22 µg/mL pyruvate, 1µg/mL estradiol-17β, 0.5µg/mL FSH and 0.06 IU hCG without serum supplement used as treatment-1 and the above media were further supplemented with 10% FCS as treatment-2. In treatment-3, instead of 10% FCS, 20% heat inactivated ECS (serum collected in mid estrum) was used as serum supplement. Oocytes with maximum degree of cumulus expansion were selected as matured and used for further IVF studies using frozen semen. The IVF medium consisted of Fert-TALP medium supplemented with 1µM epinephrine, 10µM hypotaurine, 20µM pencillamine and 0.56µg/ml heparin. Culture conditions set for IVF were 39oC temperature, 5% CO2 tension with maximum humidity. Oocytes showing sperm penetration evidence like presence of enlarged sperm head, male pronuclei with its accompanying sperm tail in the cytoplasm, oocytes with two pronuclei and a clear second polar body but without a sperm tail were considered as fertilized. Significantly higher result of cumulus expansion percentage (p&lt; 0.05) was observed when oocytes matured in media supplemented with FCS as compared to other two treatments. There was no influence of source of serum in maturation media on further IVF of matured oocytes in this study. Int J Appl Sci Biotechnol, Vol 4(3): 308-310

Isocapnic hyperventilation shortens washout time for sevoflurane - an experimental in vivo study.

Isocapnic hyperventilation (IHV) is a method that fastens weaning from inhalation anaesthesia by increasing airway concentration of carbon dioxide (CO2 ) during hyperventilation (HV). In an animal model, we evaluated a technique of adding CO2 directly to the breathing circuit of a standard anaesthesia apparatus. Eight anaesthetised pigs weighing 28 ± 2 kg were intubated and mechanically ventilated. From a baseline ventilation of 5 l/min, HV was achieved by doubling minute volume and fresh gas flow. Respiratory rate was increased from 15 to 22/min. The CO2 absorber was disconnected and CO2 was delivered (DCO2 ) to the inspiratory limb of a standard breathing circuit via a mixing box. Time required to decrease end-tidal sevoflurane concentration from 2.7% to 0.2% was defined as washout time. Respiration and haemodynamics were monitored by blood gas analysis, spirometry, electric impedance tomography and pulse contour analysis. A DCO2 of 261 ± 19 ml/min was necessary to achieve isocapnia during HV. The corresponding FICO2 -level remained stable at 3.1 ± 0.3%. During IHV, washout of sevoflurane was three times faster, 433 ± 135 s vs. 1387 ± 204 s (P < 0.001). Arterial CO2 tension and end-tidal CO2 , was 5.2 ± 0.4 kPa and 5.6 ± 0.4%, respectively, before IHV and 5.1 ± 0.3 kPa and 5.7 ± 0.3%, respectively, during IHV. In this experimental in vivo model of isocapnic hyperventilation, the washout time of sevoflurane anaesthesia was one-third compared to normal ventilation. The method for isocapnic hyperventilation described can potentially be transferred to a clinical setting with the intention to decrease emergence time from inhalation anaesthesia.

Cerebral oxidative metabolism is decreased with extreme apnoea in humans; impact of hypercapnia.

The present study describes the cerebral oxidative and non-oxidative metabolism in man during a prolonged apnoea (ranging from 3min36s to 7min26s) that generates extremely low levels of blood oxygen and high levels of carbon dioxide. The cerebral oxidative metabolism, measured from the product of cerebral blood flow and the radial artery-jugular venous oxygen content difference, was reduced by ∼29% at the termination of apnoea, although there was no change in the non-oxidative metabolism. A subset study with mild and severe hypercapnic breathing at the same level of hypoxia suggests that hypercapnia can partly explain the cerebral metabolic reduction near the apnoea breakpoint. A hypercapnia-induced oxygen-conserving response may protect the brain against severe oxygen deprivation associated with prolonged apnoea. Prolonged apnoea in humans is reflected in progressive hypoxaemia and hypercapnia. In the present study, we explore the cerebral metabolic responses under extreme hypoxia and hypercapnia associated with prolonged apnoea. We hypothesized that the cerebral metabolic rate for oxygen (CMRO2 ) will be reduced near the termination of apnoea, attributed in part to the hypercapnia. Fourteen elite apnoea-divers performed a maximal apnoea (range 3min 36s to 7min 26s) under dry laboratory conditions. In a subset study with the same divers, the impact of hypercapnia on cerebral metabolism was determined using varying levels of hypercapnic breathing, against the background of similar hypoxia. In both studies, the CMRO2 was calculated from the product of cerebral blood flow (ultrasound) and the radial artery-internal jugular venous oxygen content difference. Non-oxidative cerebral metabolism was calculated from the ratio of oxygen and carbohydrate (lactate and glucose) metabolism. The CMRO2 was reduced by ∼29% (P<0.01, Cohen's d=1.18) near the termination of apnoea compared to baseline, although non-oxidative metabolism remained unaltered. In the subset study, in similar backgrounds of hypoxia (arterial O2 tension: ∼38.4mmHg), severe hypercapnia (arterial CO2 tension: ∼58.7mmHg), but not mild-hypercapnia (arterial CO2 tension: ∼46.3mmHg), depressed the CMRO2 (∼17%, P=0.04, Cohen's d=0.87). Similarly to the apnoea, there was no change in the non-oxidative metabolism. These data indicate that hypercapnia can partly explain the reduction in CMRO2 near the apnoea breakpoint. This hypercapnic-induced oxygen conservation may protect the brain against severe hypoxaemia associated with prolonged apnoea.

In Vitro Fertilizability of Oocytes Using Fresh, Frozen and Epididymal Spermatozoa from Crossbred Bulls in the Tropics

The objective of the study was to examine the fertilizability of bovine follicular oocytes from abattoir ovaries using fresh, frozen and epididymal spermatozoa from crossbred bulls in the tropics. Oocytes were cultured in maturation media TCM-199 containing 25mM HEPES, 1mM glutamine L, 2.2mg/mL sodium bicarbonate, antibiotics, 22 µg/mL pyruvate, 1µg/mL estradiol-17β, 0.5µg/mL FSH and 0.06 IU hCG and supplemented with 20% heat inactivated estrus cow serum (serum collected in early estrum) at 39oC temperature, 5% CO2 tension with maximum humidity for 24 hours. Oocytes with maximum cumulus expansion were used for in vitro fertilization. Fresh, frozen and epididymal semen from crossbred bulls was used for in vitro fertilization as treatment 1(n =1690), treatment 2(n = 1620) and treatment 3(n = 1710) respectively. Control group of oocytes (1680) were treated in the same protocol along with each treatment group of oocytes in separate in vitro fertilization drop without sperm injection. The in vitro fertilization medium consisted of Fert-TALP medium supplemented with 1µM epinephrine, 10µM hypotaurine, 20µM pencillamine and 0.56µg/ml heparin. Culture conditions set for IVF were 39oC temperature, 5% CO2 tension with maximum humidity. Oocytes showing sperm penetration evidence like presence of enlarged sperm head, male pronuclei with its accompanying sperm tail in the cytoplasm, oocytes with two pronuclei and a clear second polar body but without a sperm tail were considered as fertilized. None of the oocytes in control group showed cleavage due to parthenogenetic activation. Significantly higher results of fertilization rate (p&lt;0.05) were observed when oocytes inseminated with epididymal spermatozoa than fresh ejaculated semen followed by frozen semen.Int J Appl Sci Biotechnol, Vol 4(2): 166-171

Conidial germination in Scedosporium apiospermum, S. aurantiacum, S. minutisporum and Lomentospora prolificans: influence of growth conditions and antifungal susceptibility profiles.

In the present study, we have investigated some growth conditions capable of inducing the conidial germination in Scedosporium apiospermum, S. aurantiacum, S. minutisporum and Lomentospora prolificans. Germination in Sabouraud medium (pH 7.0, 37ºC, 5% CO2) showed to be a typically time-dependent event, reaching ~75% in S. minutisporum and > 90% in S. apiospermum, S. aurantiacum and L. prolificans after 4 h. Similar germination rate was observed when conidia were incubated under different media and pHs. Contrarily, temperature and CO2 tension modulated the germination. The isotropic conidial growth (swelling) and germ tube-like projection were evidenced by microscopy and cytometry. Morphometric parameters augmented in a time-dependent fashion, evidencing changes in size and granularity of fungal cells compared with dormant 0 h conidia. In parallel, a clear increase in the mitochondrial activity was measured during the transformation of conidia-into-germinated conidia. Susceptibility profiles to itraconazole, fluconazole, voriconazole, amphotericin B and caspofungin varied regarding each morphotype and each fungal species. Overall, the minimal inhibitory concentrations for hyphae were higher than conidia and germinated conidia, except for caspofungin. Collectively, our study add new data about the conidia-into-hyphae transformation in Scedosporium and Lomentospora species, which is a relevant biological process of these molds directly connected to their antifungal resistance and pathogenicity mechanisms.

Effects of vagotomy on hypoglossal and phrenic responses to hypercapnia in the decerebrate rat

Hypercapnia characterizes a variety of physiological and pathological states and must be compensated effectively by the respiratory, cardiovascular, renal, and intra- and extracellular pH buffering systems to maintain homeostasis. Several studies have examined the respiratory response to hypercapnia, but contemporaneous changes in respiratory frequency and tidal volume prevent investigating the pure influence on respiratory amplitude. Therefore, we sought to test the effect of hypercapnia on hypoglossal (XII) and phrenic nerve (PN) inspiratory (Insp) and XII pre-inspiratory (pre-I) activities in vagus-intact and vagus-denervated animals. Experiments were performed on six artificially-ventilated unanesthetized pre-collicular decerebrate Sprague-Dawley adult male rats. Vagotomy under normocapnic conditions effected the consistent appearance of significant XII pre-I and a greater increase in XII than PN Insp amplitude. In the vagus-intact state, administration of a hypercapnic (5% CO2, 95% O2) gas mixture resulted in a greater increase in XII than PN Insp activity. In the vagotomized state, hypercapnia caused a drastic increase in XII pre-I and significant non-differential increases in both XII and PN Insp activity. The increase in XII pre-I was significantly greater than hypercapnia-induced increases in XII and PN Insp discharges. Following vagotomy, duration and amplitude of XII pre-I are potently modulated by CO2 tension. Based on our results, we conclude that vagal afferents exert differential inhibition of PN Insp and XII pre-I/Insp motor outputs. The role of vagal control in orchestration and optimization of respiratory response to hypercapnia is discussed.