Anaesthesia for laparoscopic nephrectomy: Does end-tidal carbon dioxide measurement correlate with arterial carbon dioxide measurement?

Monitored arterial and end-tidal carbon dioxide during in-flight mechanical ventilation

Clinical measures of ventilation and the relationship between arterial and end-tidal carbon dioxide tensions were studied during inhalational anaesthesia in 18 patients using a laryngeal mask airway or a facemask. Tidal volumes were similar in both groups but expired minute volume, respiratory rate and physiological deadspace ventilation were significantly increased in the facemask group. Both end-tidal and arterial carbon dioxide tensions were higher in the laryngeal mask group. Mean arterial to end-tidal carbon dioxide tension differences ranged from 0.13 to 4.13 kPa in the facemask group and from 0-1.73 kPa with the laryngeal mask airway. Pooled data analysis revealed a better correlation between arterial and end-tidal carbon dioxide tensions during laryngeal mask ventilation as compared to facemask breathing. With both techniques the arterial to end-tidal carbon dioxide tension difference was related to respiratory rate and physiological deadspace ventilation. Estimation of arterial carbon dioxide partial pressure by monitoring end-tidal carbon dioxide tension is more reliable with the laryngeal mask airway than during facemask breathing, in particular at small tidal volumes.

Background: Patients undergo mechanical ventilation need continuous evaluation of their respiratory condition. Monitoring of end-tidal carbon dioxide (ETCO2) as noninvasive measurement of arterial carbon dioxide (PaCO2) is a good tool for assessment and management of mechanically ventilated patients. Aim of the work: The aim of this work is to correlate expiratory end-tidal carbon dioxide tension with arterial carbon dioxide tension in patients with respiratory failure on mechanical ventilation and its significance. Patients and methods: This study was carried out on 50 patients on invasive mechanical ventilation with acute or acute on top of chronic respiratory failure admitted to respiratory I.C.U. at Bab El- Shaeria University Hospital, Studied patients had obtained two ABG samples one at the onset of mechanical ventilation(M.V.) and the second when the patient was on weaning mode of mechanical ventilation with continuous capnographic monitoring and reading record at the onset of ABG sampling. Results: The study include 31 males (62%),and 19 female (38%),24 patients (48%) had C.O.P.D, 9 patients (18%) had pneumonia, 8 patients (16%) had O.H.S, 7 patients (14%) had I.L.D and2 patients (4%) had acute severe asthma. The study shows no statistical significant difference between PaCO2 and ETCO2 at the onset of mechanical ventilation (74.78 ± 20.19 and67.5 ± 19.23) mmHg and on weaning mode (43.98 ± 8.07 and 42.2±7.2) mmHg. that PaCO2 measurements vary approximately 2-7 mmHg above ETCO2 values which mean good correlation between PaCO2 and ETCO2. Conclusion: - ETCO2 measurement provides an accurate estimation of PaCO2 in ventilation and weaning which may reduce the need for invasive, high coast monitoring and repeated arterial blood gas analyses.

The changes occurring in total respiratory system, lung and chest wall mechanics, lung volume and gas-exchange during abdominal insufflation with carbon dioxide for laparoscopic cholecystectomy were studied. Using the technique of rapid airway occlusion during constant flow inflation together with an oesophageal balloon, we computed compliance and maximum resistance of the respiratory system, subsequently apportioning it into its lung and chest wall components. Maximum resistance of the respiratory system was further divided into airway resistance and the viscoelastic properties of the lung and the chest wall. In 10 patients (group 1), we measured respiratory system, lung and chest wall mechanics (compliance and resistance), functional residual capacity, end-tidal carbon dioxide tension and oxygen saturation. In addition, arterial blood gas analysis and end-tidal carbon dioxide tension were measured in a second group of 10 patients (group 2). Measurements, in both groups, were obtained in the reverse Trendelenburg position, at 15 min after the induction of anaesthesia, 5 min and 45 min after abdominal insufflation and at 15 min after abdominal deflation. Tidal volume, respiratory rate, inspiratory flow and the fraction of inspired oxygen were similar in both groups and maintained constant during the procedure. We found that abdominal carbon dioxide insufflation caused: a reduction in compliance of the respiratory system (both lung and chest wall components) and of functional residual capacity; a marked increase in the maximum resistance of the respiratory system (mainly due to increases in the viscoelastic properties of the lung and chest wall); no change in oxygenation, but an increase in the end-tidal carbon dioxide tension (which was correlated closely with the arterial carbon dioxide tension). These changes were not affected by the duration of anaesthesia.

The relationship between arterial carbon dioxide tension and end-tidal carbon dioxide tension was studied in 25 patients during laparoscopy. Thirteen patients received general anaesthesia and 12 epidural anaesthesia. The overall mean difference between arterial and end-tidal carbon dioxide tensions was 0.44 kPa (95% confidence intervals 0.28-0.60 kPa) which was significantly less than that reported in studies during other procedures. The reasons for this difference are probably associated with the physiological changes induced by CO2 pneumoperitoneum and steep Trendelenburg positioning. The choice of anaesthetic technique did not affect the arterial to end-tidal carbon dioxide tension difference significantly (p greater than 0.9).


 Nowadays, laparoscopic surgeries are being performed under subarachnoid block (SAB) safely.
 Aims: This study was to compare the arterial and end-tidal carbon dioxide (CO2) tension changes during spinal and general anaesthesia (GA) in CO2 pneumoperitoneum for upper abdominal laparoscopic surgeries.
 Settings and Design: This was a prospective randomized comparative clinical study.
 Materials and Methods: Eighty patients posted for upper abdominal laparoscopic surgeries were randomly allocated to two groups either to receive standard GA or lumbar SAB.
 Results: The demographic profiles of both the groups were comparable. The PaCO2 was increased gradually and sustained at its peaks within 20±4.37 minutes in both the groups. The mean±SD revealed to be higher in Group B (41.5500±2.1315) than Group A (40.8460±2.1136), but the difference between the two was not statistically significant (P=0.6142). There was a gradual increase in ETCO2 over the initial 10±2.07 minutes and reached a plateau within 20±5.74 minutes in both the groups and declined faster after deflation of pneumoperitoneum in SAB group. The mean±SD was found to be higher in Group B (33.923±1.642) than Group A (33.408±1.772), but it was also not statistically significant (P=0.4492). The difference of the arterial blood pH between the groups was not statistically significant. Three (7.5%) patients developed transient urinary retention and 2 (5%) patients suffered from post-dural puncture headache in SAB group.
 Conclusions: Arterial and end-tidal CO2 tension changes during upper abdominal laparoscopic surgery under SAB remain within physiological limit and comparable to the CO2 tensions under GA. However, per-operative complications in SAB are greater, while it is lesser in postoperative period in comparison to GA. SAB may be adopted in ASA physical status I patients with proper preoperative counselling.
 J Bangladesh Coll Phys Surg 2019; 37(1): 13-18
 

We investigated alveolar-arterial gas tension differences as a measurement of ventilatory impairment during exercise in patients who had undergone the Fontan operation. The ventilatory response to exercise in 13 operated patients was compared with that of 11 control subjects. The difference between end-tidal and arterial oxygen tension (P(ET-a)DO2) and between arterial and end-tidal carbon dioxide tension (P(a-ET)DCO2) as well as the physiologic dead space-tidal volume ratio were calculated during progressive treadmill exercise testing. In the Fontan group, P(ET-a)DO2 and P(a-ET)DCO2 were significantly higher than in control subjects and increased in parallel during the study period. The physiologic dead space-tidal volume ratio was higher in the Fontan group than in the control group, and the difference in these ratios between the values obtained using end-tidal carbon dioxide tension and those using arterial carbon dioxide tension correlated well with P(a-ET)DCO2 (r = -0.79 to -0.98, p < 0.001). The physiologic dead space-tidal volume ratio during exercise was significantly higher in patients with low exercise capacities than in those with high exercise capacities (p < 0.05). The alveolar-arterial gas tension differences during exercise were greater in Fontan patients than in control subjects. We conclude that the size of the physiologic dead space can be evaluated from measurements of arterial carbon dioxide tension and is correlated with impaired exercise capacity after the Fontan operation.

COMPARISON OF END-TIDAL AND ARTERIAL CARBON DIOXIDE MEASUREMENTS DURING ANAESTHESIA WITH THE LARYNGEAL MASK AIRWAY

Background and Aim:Arterial carbon dioxide tension (PaCO2) is considered the gold standard for scrupulous monitoring in pediatric intensive care unit (PICU), but it is invasive, laborious, expensive, and intermittent. The study aims to explore when we can use end-tidal carbon dioxide tension (PETCO2) as a reliable, continuous, and noninvasive monitor of arterial CO2Materials and Methods:Concurrent PETCO2, fraction of inspired oxygen, PaCO2, and arterial oxygen tension values of clinically stable children on mechanical ventilation were recorded. Children with extra-pulmonary ventriculoatrial shunts were excluded. The PETCO2 and PaCO2 difference and its variability and reproducibility were studied.Results:A total of 624 concurrent readings were obtained from 105 children (mean age [SD] 5.53 [5.43] years) requiring invasive bi-level positive airway pressure ventilation in the PICU. All had continuous PETCO2 monitoring and an arterial line for blood gas measurement. The mean (SD) number of concurrent readings obtained from each child, 4-6 h apart was 6.0 (4.05). The PETCO2 values were higher than PaCO2 in 142 observations (22.7%). The PaCO2–PETCO2 difference was individual admission specific (ANOVA, P < 0.001). The PaCO2–PETCO2 difference correlated positively with the alveolar-arterial oxygen tension [P(A-a)O2] difference (ρ = 0.381 P < 0.0001). There was a fixed bias between the PETCO2 and PaCO2 measuring methods, difference +0.66 KPa (95% confidence interval: +0.57 to +0.76).Conclusions:The PaCO2–PETCO2 difference was individual specific. It was not affected by the primary disorder leading to the ventilation.

IntroductionNew technology using partial carbon dioxide rebreathing has been developed to measure cardiac output. Because rebreathing increases respiratory effort, we investigated whether a newly developed system with 35 s rebreathing causes a lesser increase in respiratory effort under partial ventilatory support than does the conventional system with 50 s rebreathing. We also investigated whether the shorter rebreathing period affects the accuracy of cardiac output measurement.MethodOnce a total of 13 consecutive post-cardiac-surgery patients had recovered spontaneous breathing under pressure support ventilation, we applied a partial carbon dioxide rebreathing technique with rebreathing of 35 s and 50 s in a random order. We measured minute ventilation, and arterial and mixed venous carbon dioxide tension at the end of the normal breathing period and at the end of the rebreathing periods. We then measured cardiac output using the partial carbon dioxide rebreathing technique with the two rebreathing periods and using thermodilution.ResultsWith both rebreathing systems, minute ventilation increased during rebreathing, as did arterial and mixed venous carbon dioxide tensions. The increases in minute ventilation and arterial carbon dioxide tension were less with 35 s rebreathing than with 50 s rebreathing. The cardiac output measures with both systems correlated acceptably with values obtained with thermodilution.ConclusionWhen patients breathe spontaneously the partial carbon dioxide rebreathing technique increases minute ventilation and arterial carbon dioxide tension, but the effect is less with a shorter rebreathing period. The 35 s rebreathing period yielded cardiac output measurements similar in accuracy to those with 50 s rebreathing.

Hyperventilation is a frequently used method for inducing hypercarbia in neurosurgical patients. This practice requires careful carbon dioxide monitoring that might be replaced by a less expensive and less invasive alternative to arterial blood gas monitoring. To determine the accuracy of end-tidal carbon dioxide monitoring in hyperventilated neurosurgical patients. Nineteen adult patients requiring hyperventilation for the reduction of intracranial pressure following head injury or neurosurgery were enrolled from the surgical intensive care unit of a level I trauma center. A correlation design was used to compare arterial carbon dioxide tensions and end-tidal carbon dioxide measurements during specific periods; secondary analysis with bias and precision estimates was performed. Also, changes in arterial carbon dioxide tensions were compared with simultaneous changes in end-tidal carbon dioxide values. End-tidal carbon dioxide values showed a moderately acceptable correlation with arterial blood gas measurements. However, changes in end-tidal carbon dioxide values failed to correlate with simultaneous changes in arterial carbon dioxide tension measures. Bias and precision measures confirmed these findings. In this patient sample, changes in end-tidal carbon dioxide values did not accurately reflect changes in arterial carbon dioxide tension levels in the intensive care setting. Further technological advances in noninvasive carbon dioxide monitoring may lead to a significant cost savings over traditional arterial blood gas analysis.

To determine if end-tidal carbon dioxide tension (PETCO2) is a clinically reliable indicator of arterial carbon dioxide tension (PaCO2) under conditions of heterogeneous tidal volumes and ventilation-perfusion inequality, we examined the expiratory gases of 25 postcardiotomy patients being weaned from ventilator support with intermittent mandatory ventilation. Using a computerized system that automatically sampled airway flow, pressure, and expired carbon dioxide tension, we were able to distinguish spontaneous ventilatory efforts from mechanical ventilatory efforts. The PETCO2 values varied widely from breath to breath, and the arterial to end-tidal carbon dioxide tension gradient was appreciably altered during the course of several hours. About two-thirds of the time, the PETCO2 of spontaneous breaths was greater than that of ventilator breaths during the same 70-second sample period. The most accurate indicator of PaCO2 was the maximal PETCO2 value in each sample period, the correlation coefficient being 0.768 (P less than 0.001) and the arterial to end-tidal gradient being 4.24 +/- 4.42 mm Hg (P less than 0.01 compared with all other measures). When all values from an 8-minute period were averaged, stability was significantly improved without sacrificing accuracy. We conclude that monitoring the maximal PETCO2, independent of breathing pattern, provides a clinically useful indicator of PaCO2 in postcardiotomy patients receiving intermittent mandatory ventilation.

SUMMARY End-tidal carbon dioxide tension (PetCO2) and arterial carbon dioxide tension (PaCO2) were determined and compared in isoflurane-anesthetized spontaneously breathing equine neonates. End-tidal carbon dioxide and PaCO2 values increased with respect to time. Difference between values of PetCO2 and PaCO2 increased over time. End-tidal carbon dioxide tension was useful to predict changes in and was more closely correlated with PaCO2 early in the anesthetic period (T ≤ 60 minutes). The dead space volume to tidal volume (Vd/Vt) ratio increased with respect to time, indicating increase in physiologic dead space in isoflurane-anesthetized foals. The data indicate that the increased difference between widening of the PetCO2 and PaCO2 values over time may have been attributable to hypoventilation and decreased pulmonary capillary perfusion of alveoli.

End-tidal carbon dioxide tension (Pet(CO(2))) is reduced during an orthostatic challenge, during heat stress, and during a combination of these two conditions. The importance of these changes is dependent on Pet(CO(2)) being an accurate surrogate for arterial carbon dioxide tension (Pa(CO(2))), the latter being the physiologically relevant variable. This study tested the hypothesis that Pet(CO(2)) provides an accurate assessment of Pa(CO(2)) during the aforementioned conditions. Comparisons between these measures were made: 1) after two levels of heat stress (N = 11); 2) during combined heat stress and simulated hemorrhage [via lower-body negative pressure (LBNP), N = 8]; and 3) during an end-tidal clamping protocol to attenuate heat stress-induced reductions in Pet(CO(2)) (N = 7). Pet(CO(2)) and Pa(CO(2)) decreased during heat stress (P < 0.001); however, there was no group difference between Pa(CO(2)) and Pet(CO(2)) (P = 0.36) nor was there a significant interaction between thermal condition and measurement technique (P = 0.06). To verify that this nonsignificant trend for the interaction was not due to a type II error, Pet(CO(2)) and Pa(CO(2)) at three distinct thermal conditions were also compared using paired t-tests, revealing no difference between Pa(CO(2)) and Pet(CO(2)) while normothermic (P = 0.14) and following a 1.0 ± 0.2°C (P = 0.21) and 1.4 ± 0.2°C (P = 0.28) increase in internal temperature. During LBNP while heat stressed, measures of Pet(CO(2)) and Pa(CO(2)) were similar (P = 0.61). Likewise, during the end-tidal carbon dioxide clamping protocol, the increases in Pet(CO(2)) (7.5 ± 2.8 mmHg) and Pa(CO(2)) (6.6 ± 3.4 mmHg) were similar (P = 0.31). These data indicate that mean Pet(CO(2)) reflects mean Pa(CO(2)) during the evaluated conditions.

Objective: To evaluate a new method of air tonometry to assess gastro-intestinal intramucosal pH (pHi) and to assess the utility of intramucosal carbon dioxide tension (PrCO2), in isolation or in conjunction with arterial carbon dioxide tension, in order to identify patients with decreased pHi. Design: A prospective study of critically ill intensive care patients. Setting: A 12-bed university hospital intensive care unit. Methods: Patients in whom pulmonary and systemic arterial catheterisation were used for the management of clinical shock were studied. Semi-continuous air tonometry was used. Blood gas analysis and haemodynamic studies were performed as clinically indicated. At the same time PrCO2 and end-tidal carbon dioxide tensions (ETCO2) were obtained. Correlation coefficients for PrCO2, alone or referenced to arterial carbon dioxide (PaCO2) and ETCO2, and pHi were calculated. Correlation coefficients were also calculated between PrCO2, pHi and conventional haemodynamic parameters. Results: Eleven patients were studied. There was a highly significant correlation between PrCO2 and pHi (r=-0.79, p&lt;0.001). The correlation between these variables was significantly better in patients without a significant metabolic acidosis than in those with an existing acidosis (p=0.0045; confidence interval 0.19-0.78). No significant correlation was found between PrCO2 (or pHi) and heart rate, central venous, pulmonary artery wedge or systemic arterial pressures, cardiac index or oxygen delivery. A PrCO2 value in excess of 8 kPa was associated with a sensitivity value of 0.69 and a specificity value of 1 in predicting a pHi &lt;7.35. Conclusion: Semi-continuous air tonometry allows a more accessible view of PrCO2. Intramucosal carbon dioxide tension, without formal calculation of pHi, may allow the recognition of patients at risk from splanchnic ischaemia. As in previous studies no correlation between conventional haemodynamic parameters and pHi was found.