Changes In Partial Pressure Of CO2 Research Articles

Physiological and Anesthetic Considerations of Safe and Optimal Pneumoperitoneal Pressures for Laparoscopic Surgeries in Children.

In the era of minimally invasive surgeries, pediatric laparoscopic surgeries are now becoming the standard of care. In this study, we aim to determine the safe and optimal pneumoperitoneal pressures (PPs) for laparoscopic surgery in children aged 1-5 years, along with the technical ease for the surgeon. Prospective, randomized, single-blinded study was conducted at SGPGI Lucknow. Children aged 1-5 years were randomized into Group I (n = 24): PP = 6-8 mmHg and Group II: (PP) = 9-10 mmHg. Hemodynamic, ventilatory, and blood gas changes were measured before CO2 insufflation (T0), 20 min after insufflation (T1), before desufflation (T2), and 10 min after desufflation (T3). Surgeon's technical ease of surgery, postoperative pain, the requirement of rescue analgesia, time to resume feeding, and complications were recorded and analyzed. Paired t-test, Mann-Whitney test, and Wilcoxon signed-rank test were used for nonparametric/parametric data. Chi-square/Fisher's test was used for nominal data. Partial pressure of CO2 (PaCO2) was significantly higher in Group II at T1, T2, and T3, requiring frequent changes in ventilatory settings. Postoperative pain scores were higher in Group II at 1, 6, and 12 h, requiring rescue analgesia. Surgeon's scores and hemodynamics were similar in both groups. Higher PP in Group II caused significant changes in PaCO2, end-tidal CO2, and postoperative pain requiring rescue analgesia, but blood gas changes were clinically insignificant and there were no significant changes in hemodynamic parameters. Since the surgeon's ease of performing surgery was similar in both groups, we recommend that laparoscopy in children aged 1-5 years can be started with lower PPs of 6-8 mmHg, which can be increased if needed based on the surgeon's comfort and the patient's body habitus.

The effect of changing arterial blood pressure and carbon dioxide on cerebral blood flow

The short article entitled ‘Effect of alterations in the arterial carbon dioxide tension on the blood flow through the cerebral cortex at normal and low arterial blood pressures’, published in...

Measuring cerebrovascular reactivity: the dynamic response to a step hypercapnic stimulus.

We define cerebral vascular reactivity (CVR) as the ratio of the change in blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) signal (S) to an increase in blood partial pressure of CO2 (PCO2): % Δ S/Δ PCO2 mm Hg. Our aim was to further characterize CVR into dynamic and static components and then study 46 healthy subjects collated into a reference atlas and 20 patients with unilateral carotid artery stenosis. We applied an abrupt boxcar change in PCO2 and monitored S. We convolved the PCO2 with a set of first-order exponential functions whose time constant τ was increased in 2-second intervals between 2 and 100 seconds. The τ corresponding to the best fit between S and the convolved PCO2 was used to score the speed of response. Additionally, the slope of the regression between S and the convolved PCO2 represents the steady-state CVR (ssCVR). We found that both prolongations of τ and reductions in ssCVR (compared with the reference atlas) were associated with the reductions in CVR on the side of the lesion. τ and ssCVR are respectively the dynamic and static components of measured CVR.

Regional brain blood flow in man during acute changes in arterial blood gases

Despite the importance of blood flow on brainstem control of respiratory and autonomic function, little is known about regional cerebral blood flow (CBF) during changes in arterial blood gases.We quantified: (1) anterior and posterior CBF and reactivity through a wide range of steady-state changes in the partial pressures of CO2 (PaCO2) and O2 (PaO2) in arterial blood, and (2) determined if the internal carotid artery (ICA) and vertebral artery (VA) change diameter through the same range.We used near-concurrent vascular ultrasound measures of flow through the ICA and VA, and blood velocity in their downstream arteries (the middle (MCA) and posterior (PCA) cerebral arteries). Part A (n =16) examined iso-oxic changes in PaCO2, consisting of three hypocapnic stages (PaCO2 =∼15, ∼20 and ∼30 mmHg) and four hypercapnic stages (PaCO2 =∼50, ∼55, ∼60 and ∼65 mmHg). In Part B (n =10), during isocapnia, PaO2 was decreased to ∼60, ∼44, and ∼35 mmHg and increased to ∼320 mmHg and ∼430 mmHg. Stages lasted ∼15 min. Intra-arterial pressure was measured continuously; arterial blood gases were sampled at the end of each stage. There were three principal findings. (1) Regional reactivity: the VA reactivity to hypocapnia was larger than the ICA, MCA and PCA; hypercapnic reactivity was similar.With profound hypoxia (35 mmHg) the relative increase in VA flow was 50% greater than the other vessels. (2) Neck vessel diameters: changes in diameter (∼25%) of the ICA was positively related to changes in PaCO2 (R2, 0.63±0.26; P<0.05); VA diameter was unaltered in response to changed PaCO2 but yielded a diameter increase of +9% with severe hypoxia. (3) Intra- vs. extra-cerebral measures: MCA and PCA blood velocities yielded smaller reactivities and estimates of flow than VA and ICA flow. The findings respectively indicate: (1) disparate blood flow regulation to the brainstem and cortex; (2) cerebrovascular resistance is not solely modulated at the level of the arteriolar pial vessels; and (3) transcranial Doppler ultrasound may underestimate measurements of CBF during extreme hypoxia and/or hypercapnia.

A randomized controlled study evaluating the effects of the temperature of insufflated CO2 on core body temperature and blood gases (an experimental study)

Heated carbon dioxide (CO2) was used for pneumoperitoneum (Pp) to prevent hypothermia. This study aimed to investigate the relationship between the temperature of the insufflated CO2 and blood gases together with the core body temperature (CBT). A prospective controlled study was performed with 24 pigs weighing approximately 20 kg randomized into four groups of 6 pigs each. A pneumoperitoneum at 12 mmHg of pressure was applied for 60 min with the pig under general anesthesia. The CO2)temperature was 22 degrees C in group 1, 37 degrees C in group 2, and 7 degrees C in group 3. In the "sham" group, pneumoperitoneum was not applied. Arterial blood pH and partial pressure of CO2 (PaCO2) were analyzed before insufflation, every 15 min during the pneumoperitoneum, and 15 min after the desufflation. The CBT was recorded before the insufflation, every 20 min during pneumoperitoneum, and 20 min after the desufflation. Blood gas analyses and CBT records for the "sham" group were performed at the same intervals. Arterial blood pH gradually decreased during pneumoperitoneum. At the 60th minute of pneumoperitoneum, a minimum decrease in arterial blood pH (0.04; p = 0.027) and a minimum increase in PaCO2 (3.67; p = 0.027) were recorded in group 3, whereas a maximum decrease in arterial blood pH (0.18; p = 0.027) and a maximum increase in PaCO2 (17.17; p = 0.027) were recorded in group 2. There was a significant negative correlation between PaCO2 and arterial blood pH in all the groups (r = -0.993; p < 0.01). The mean values of CBT decreases were statistically significant in all the groups: group 1 (p = 0.023), group 2 (p = 0.026), group 3 (p = 0.026), and "sham" group (p = 0.024). The changes in PaCO2 were directly proportional and the changes in pH contrarily proportional to the temperature of the insufflated CO2. Significant differences in CBT decreases were found between the groups receiving heated gas and room temperature gas and the groups receiving heated gas and gas below room temperature.

PCO2, chemical properties, and estimated new production in the equatorial Pacific in January–March 1991

Measurements of the partial pressure of CO2 (PCO2) at the sea surface, dichlorodifluoromethane (F12), salinity, temperature, oxygen, nutrients, wind, and current velocities were made during a cruise (January–March 1991) in the equatorial Pacific from Panama to Nouméa via Tahiti. In the western Pacific (140°W to 165°E) the westward South Equatorial Current is well established. Distributions of tracers show extrema near the equator in the eastern Pacific (from 95°W to 140°W), indicating that the upwelling is especially active in this area. The zonal distribution of chemical tracers is not regular because of intrusions of warmer water from the north associated with equatorial long waves. The temporal changes in PCO2 result from thermodynamic changes, biological activity, and gas exchange with the atmosphere. In order to compare the magnitude of these processes, we assess the variations of PCO2 (dPCO2) between two stations as the sum of thermodynamic changes driven by temperature and salinity changes, air‐sea exchange computed from observed wind and difference of PCO2 between the sea and the atmosphere, and the biological activity estimated from the nitrate decrease and C:N ratio (106:16). The resulting assessed change in PCO2 is in agreement with the observed change for 42 pairs of stations. Each of these pairs of stations is thus considered as representing a simple water mass advected by the measured currents between the two stations so that daily fluxes can be estimated. The contribution of CO2 outgassing to dPCO2 is low, between −0.2 to −0.0 μatm d−1. The thermodynamical dPCO2 averages 0.7±0.2 μatm d−1 in the mixed layer. The biological dPCO2 (‐1.5±0.5 μatm d−1) is the highest in absolute value implying an average value of new production along the equator of 72±25 mmolC m−2 d−1 (0.9±0.3 gC m−2 d−1) for the equatorial Pacific (130°W‐165°E). This value is very high and the overestimation could result from the simplistic description of the advection and mixing of water. An attempt to account for these processes by constraining the net heat flux to 100 W m−2 [Weare et al., 1981] reduces the estimate of new production to 58 mmolC m−2 d−1 (0.7 gC m−2 d−1 ). A mean upwelling velocity of 0.5±0.1 m d−1 east of 140°W is calculated, based on F12 undersaturations.