Change In ETCO Research Articles

Effect of short-term ketogenic diet on end-tidal carbon dioxide.

Previous studies have shown that end-tidal carbon dioxide (EtCO2) is lower with the presence of supraphysiological ketones as in the case of chronic ketogenic diet (KD) and diabetic ketoacidosis (DKA). This study aimed to determine changes in EtCO2 upon short term KD. Healthy subjects were screened not to have conditions that exerts abnormal EtCO2 nor contraindicated for KD. Subjects underwent seven days of KD while the EtCO2 and blood ketone (beta-hydroxybutyrate; β-OHB) parameters were sampled at day zero (t0) and seven (t7) of ketosis respectively. Statistically, the t-test and Pearson's coefficient were conducted to determine the changes and correlation of both parameters. 12 subjects completed the study. The mean score±standard deviation (SD) for EtCO2 were 35.08±3.53 and 35.67±3.31mm Hg for t0 and t7 respectively. The mean score ±SD for β-OHB were 0.07±0.08 and 0.87±0.84mmol/L for t0 and t7 respectively. There was no significant difference of EtCO2 between the period of study (p>0.05) but the β-OHB increased during t7 (p<0.05). There was also no correlation between the parameters. These findings suggest that EtCO2 may not be utilized to determine short term nutritional ketosis.

Intravenous Sodium Bicarbonate Verifies Intravenous Position of Catheters in Ventilated Children

Vascular access in children carries a significant risk of accidental extravasation of IV fluids and medications with the potential for tissue injury. In this prospective controlled study we assessed the diagnostic utility of using IV diluted sodium bicarbonate to confirm placement of IV catheters in ventilated children. Diluted sodium bicarbonate was created using undiluted standard 8.4% (1 mEq/mL) sodium bicarbonate mixed in a 1:3 and 1:5 ratio with sterile water to achieve a final diluted concentration of 2.1% (0. 25 mEq/mL) and 1.05% (0.125 mEq/mL) sodium bicarbonate, respectively. In 18 ASA I-II mechanically ventilated children ages 1 to 8 years, the effects of 1 mL/kg of dilute 2.1%, 1.05% sodium bicarbonate, or 0.9% normal saline, injected in a randomized order, were analyzed. All children had oxygen saturation, arterial blood pressure, electrocardiograph, and end-tidal carbon dioxide (ETCO(2)) monitoring. In addition, venous blood samples were taken before injection and 10 minutes after the final injection for analysis of venous blood pH and electrolytes. In children, IV diluted 2.1% sodium bicarbonate resulted in significantly increased etco(2) (mean of 32.8 ± 3.4 mm Hg to 39.0 ± 3.5 mm Hg, P < 0.001), a mean increase of 6.2 mm Hg (95% prediction interval: 4.3 to 8.1 mm Hg) within 3 breaths. Intravenous diluted 1.05% sodium bicarbonate caused a less pronounced but still significant increase in etco(2) (33.4 ± 3.8 mm Hg to 36.3 ± 3.4 mm Hg, P < 0.001), a mean increase of 2.9 mm Hg (95% prediction interval: 1.8 to 4.1 mm Hg) within 3 breaths. Normal saline did not result in any significant changes, with a mean increase of 0.06 mm Hg (95% prediction interval: -1.3 to 1.4 mm Hg). Both concentrations of sodium bicarbonate were easily differentiated from normal saline injection by blinded anesthesiologists observing the change in etco(2) values immediately after injection. Analysis of pre- and postinjection venous pH, bicarbonate, and sodium levels could not detect clinically significant changes. A small but statistically significant increase in venous bicarbonate was noted. The injection of 2.1% sodium bicarbonate in mechanically ventilated ASA I-II children identified intravascular placement and patency of an IV catheter by an increase in the exhaled CO(2) concentration. The injections did not have any clinically significant effects on blood pH, bicarbonate, or sodium concentration.

End‐tidal carbon dioxide monitoring in very low birth weight infants: Correlation and agreement with arterial carbon dioxide

We aimed to determine the correlation and the agreement between end-tidal carbon dioxide (ETCO(2)) and partial pressure of arterial carbon dioxide (PaCO(2) ) in very low birth weight infants (VLBWI); furthermore, we assessed factors that could affect the ETCO(2)-PaCO(2) relationship. Simultaneous end-tidal and arterial CO(2) pairs were obtained from ventilated VLBWI who were monitored by mainstream capnography and had umbilical arterial catheter. Correlation and agreement between ETCO(2) and PaCO(2) were evaluated by using Spearman test and Bland-Altman method, respectively. A total of 143 simultaneous ETCO(2)-PaCO(2) pairs were analyzed from 45 ventilated VLBWI. There was a significant correlation (r = 0.69; P < 0.0001) between ETCO(2) and PaCO(2) values. The ETCO(2) value was lower than the corresponding PaCO(2) value in 94% pairs, with a mean bias of 13.5 ± 8.4 mmHg (95% agreement levels, -3.0 to 29.9 mmHg). Mean PaCO(2)-ETCO(2) bias was similar between ELBWI (13.1 ± 7.7 mmHg; 95% agreement levels, -1.9 and 28.2 mmHg) and infants with birth weight 1,001-1,500 g (14.8 ± 9.7 mmHg; 95% agreement levels -4.3 and 33.8 mmHg). The bias between ETCO(2) and PaCO(2) was significantly increased with increasing FiO(2), mean airway pressure and oxygenation index. Within each patient, there was a positive correlation (r = 0.78, P < 0.0001) between the changes in PaCO(2) and the simultaneous changes in ETCO(2). In ventilated VLBWI, the correlation between mainstream ETCO(2) and PaCO(2) is good, but the agreement is poor and negatively influenced by the severity of pulmonary disease. Capnography is feasible in ELBWI. ETCO(2) should not replace PaCO(2) measurements in ventilated VLBWI, but may have a role to detect trends of PaCO(2).

Utility of endtidal carbon dioxide monitoring in detection of hypoxia during sedation for brain magnetic resonance imaging in children with developmental disabilities

We have shown previously that children with developmental disabilities have three times higher incidence of sedation-related hypoxia when compared with normal children. Our objectives were to describe the changes in endtidal carbon dioxide (ETCO(2)) values and the utility of ETCO(2) monitoring in earlier identification of hypoxia during sedation for brain magnetic resonance imaging (MRI) in children with developmental disabilities. We conducted a prospective observational study of a convenience sample of 150 children with developmental disabilities aged 1-10 years who received intravenous sedation for brain MRI. Children were sedated and monitored according to the institution's sedation protocol. We recorded ETCO(2) levels, hypoxia, and adverse events during sedation. Hypoxia was defined as SpO(2) < 93%. A change in ETCO(2) level ≥ 10 mm Hg from presedation baseline, an intra-sedation ≥ 50 mm Hg, and loss of capnographic waveform were considered as significant ETCO(2) abnormalities. Of the children, 80.7% (121/150) were sedated with a combination of pentobarbital and fentanyl. ETCO(2) abnormalities were noted in 42.6% (64/150) of sedation encounters. Hypoxia occurred in 18% (27/150) of subjects. ETCO(2) abnormalities were documented in 19(70%) patients with hypoxia before changes in pulse oximetry were noted. ETCO(2) changes were noted a mean of 4.38 ± 1.89 min prior to occurrence of hypoxia. ETCO(2) abnormalities and hypoxia occur commonly during sedation in children with developmental disabilities. ETCO(2) monitoring is useful in early recognition of impending hypoxia during sedation in children with developmental disabilities.

Randomized Clinical Trial of Propofol Versus Ketamine for Procedural Sedation in the Emergency Department

The objective was to compare the occurrence of respiratory depression, adverse events, and recovery duration of propofol versus ketamine for use in procedural sedation in the emergency department (ED). This was a randomized nonblinded prospective clinical trial of adult patients undergoing procedural sedation for painful procedures in the ED. Patients with pain before the procedure were treated with intravenous (IV) morphine sulfate until their pain was adequately treated at least 20 minutes before starting the procedure. Patients were randomized to receive either propofol 1 mg/kg IV followed by 0.5 mg/kg every 3 minutes as needed or ketamine 1.0 mg/kg IV followed by 0.5 mg/kg every 3 minutes as needed. Doses, vital signs, nasal end-tidal CO(2) (ETCO(2)), and pulse oximetry were recorded. Subclinical respiratory depression was defined as a change in ETCO(2) of >10 mm Hg, an oxygen saturation of <92% at any time, or an absent ETCO(2) waveform at any time. Clinical interventions related to respiratory depression were noted during the procedure, including the addition of or increase in the flow rate of supplemental oxygen, the use of a bag-valve mask apparatus, airway repositioning, or stimulation to induce breathing. After the procedure, patients were asked if they experienced pain during the procedure and had recall of the procedure. Physicians were asked to describe any adverse events or the occurrence of recovery agitation. One-hundred patients were enrolled; 97 underwent sedation and were included in the analysis. Fifty patients received propofol and 47 received ketamine. Subclinical respiratory depression was seen in 20 of 50 patients in the propofol group and 30 of 47 patients in the ketamine group (p = 0.019, effect size 22.8%; 95% CI = 4.0% to 43.6%). Clinical interventions related to respiratory depression were used in 26 of 50 propofol patients and 19 of 47 ketamine patients (p = 0.253, effect size = -13.7%; 95% CI = -33.8% to 6.4%). The median times of the procedures were 11 minutes (range = 4 to 33 minutes) for the ketamine group versus 10 minutes (range = 5 to 33 minutes) for the propofol group (p = 0.256). The median time to return to baseline mental status after the procedure was completed was 14 minutes (range = 2 to 47 minutes) for the ketamine group and 5 minutes (range = 1 to 32 minutes) for the propofol group (p < 0.001). Pain during the procedure was reported by 3 of 50 patients in the propofol group and 1 of 47 patients in the ketamine group (effect size = -3.9%, 95% confidence interval [CI] = -11.9 to 4.1). Recall of some part of the procedure was reported by 4 of 50 patients in the propofol group and 6 of 47 patients in the ketamine group (effect size = 4.8%, 95% CI = -7.6% to 17.1%). Forty-eight of 50 procedures were successful in the propofol group and 43 of 47 in the ketamine group (p = 0.357, effect size = 0.3%; 95% CI = -7.8% to 8.4%). Recovery agitation was reported in 4 of 50 in the propofol group and 17 of 47 in the ketamine group (effect size = 28.2%, 95% CI = 12.4% to 43.9%). This study detected a higher rate of subclinical respiratory depression in patients in the ketamine group than the propofol group. There was no difference in the rate of clinical interventions related to respiratory depression, pain, or recall of the procedure between the groups. Recovery agitation was seen more frequently in patients receiving ketamine than in those receiving propofol. The time to regain baseline mental status was longer in the ketamine group than the propofol group. This study suggests that the use of either ketamine or propofol is safe and effective for procedural sedation in the ED.

Automatic electrical stimulation of abdominal wall muscles increases tidal volume and cough peak flow in tetraplegia

Paralysis of the respiratory muscles in people with tetraplegia affects their ability to breathe and contributes to respiratory complications. Surface functional electrical stimulation (FES) of abdominal wall muscles can be used to increase tidal volume (V_{T}) and improve cough peak flow (CPF) in tetraplegic subjects who are able to breathe spontaneously. This study aims to evaluate the feasibility and effectiveness of a novel abdominal FES system which generates stimulation automatically, synchronised with the subjects' voluntary breathing activity. Four subjects with complete tetraplegia (C4-C6), breathing spontaneously, were recruited. The automatic stimulation system ensured that consistent stimulation was achieved. We compared spirometry during unassisted and FES-assisted quiet breathing and coughing, and measured the effect of stimulation on end-tidal CO_2 (EtCO_2) during quiet breathing. The system dependably recognised spontaneous respiratory effort, stimulating appropriately, and was well tolerated by patients. Significant increases in V_T during quiet breathing (range 0.05-0.23 L) and in CPF (range 0.04-0.49 L/s) were observed. Respiratory rate during quiet breathing decreased in all subjects when stimulated, whereas minute ventilation increased by 1.05-2.07 L/min. The changes in EtCO_2 were inconclusive. The automatic stimulation system augmented spontaneous breathing and coughing in tetraplegic patients and may provide a potential means of respiratory support for tetraplegic patients with reduced respiratory capacity.

Effect of Patient Weight and Anesthetic Technique on CO2 Excretion During Thoracoscopy in Children Assessed by End-Tidal CO2

The aim of this study was to review the changes in CO(2) excretion and anesthetic management during thoracoscopy in children. We analyzed end-tidal carbon dioxide concentration (EtCO(2); kPa) during CO(2) pneumothorax. EtCO(2) was measured on a continuous basis by using a positive sampling system and recorded every 10 minutes. Baseline and highest EtCO(2) were used to derive the maximum change in the intraoperative period. EtCO(2) was also analyzed in three time periods: (1) preinsufflation, (2) during insufflation of CO(2) into the chest, and (3) after desufflation. Core temperature was also recorded as an index of thermoregulation. Data are presented as the mean +/- standard error of the mean. Differences within time periods were compared by using paired t tests or repeated measures analysis of variance. Correlation between changes in EtCO(2) and patient demographics was performed by using linear regression. The pattern of change was compared to children undergoing laparoscopy. Median age was 1.9 years (range, 1 day to 15 years). EtCO(2) increased significantly from preinsufflation 5.1 +/- 0.2 to 6.4 +/- 0.3 during insufflation (P < 0.01); values were still significantly elevated after desufflation 6.4 +/- 0.4 (P < 0.01). Single-lung ventilation was associated with higher EtCO(2) levels during insufflation than with two-lung ventilation (P = 0.02). Maximum change in the EtCO(2) in the group undergoing one-lung ventilation negatively correlated to patient weight (r(2) = 0.25, P = 0.02); this correlation was not present with two-lung ventilation (r(2) = 0.02, P = 0.84). Laparoscopy increased EtCO(2) from 4.7 +/- 0.2 preinsufflation to 5.3 +/- 0.2 (P < 0.001) during and decreased to 4.8 +/- 0.2 postdesufflation (P = 0.60). There was a significant increase in core temperature from 35.9 +/- 0.3 to 36.9 +/- 0.2 postoperatively (P = 0.007). There is a significant increase in EtCO(2) in children undergoing thoracoscopy, which is higher than during laparoscopy. Changes in EtCO(2) are larger in smaller children undergoing single-lung ventilation. Thoracoscopy may preserve intraoperative thermoregulation.

Effect of Small Bowel Perforation During Laparoscopy on End-Tidal Carbon Dioxide: Observation in a Small Animal Model

There are currently no reports in the literature regarding changes in end-tidal carbon dioxide (ETCO(2)) when the small bowel is deliberately or inadvertently perforated during laparoscopic surgery. The aim of this study was to assess the influence of small bowel perforation during laparoscopy on ETCO(2) in a rat model. Two groups of Wistar rats (n = 8/group) were anesthetized, tracheostomized, and mechanically ventilated at a fixed tidal volume and respiratory rate. After a stabilization phase of 30 min, CO(2) pneumoperitoneum was established to 5 mmHg in one group and 12 mmHg in the other group, and maintained for 30 min. A small bowel perforation was then created and pneumoperitoneum was reestablished for another 30 min. Blood pressure, heart rate, peak ventilatory pressure, and ETCO(2) were recorded throughout the experiment. No significant changes in blood pressure throughout the experiment were noted in either group. The ventilatory pressure increased in both groups after the induction of pneumoperitoneum. In the 5 mmHg group, there was a modest increase in ETCO(2) following the induction of pneumoperitoneum (from 39.4 +/- 1.9 to 41.1 +/- 1.4, P = 0.014), and a further increase following the small bowel perforation (from 41.1 +/- 1.4 to 42 +/- 0.8, P = 0.007). In the 12 mmHg group, there was no change in ETCO(2) after the induction of pneumoperitoneum; however, there was a substantial increase in ETCO(2) following bowel perforation (35.0 +/- 2.0 to 49.8 +/- 7.1, P = 0.002). ETCO(2) increases when the small bowel is perforated during CO(2) pneumoperitoneum. This increase seems more substantial under higher pneumoperitoneal pressures. Small bowel injury may enable the diffusion of CO(2) through the bowel mucosa, causing ETCO(2) elevation. Therefore, an abrupt increase in ETCO(2) observed during laparoscopy may indicate small bowel injury.

The Effect of the Assignment of a Pre-Sedation Target Level on Procedural Sedation Using Propofol

The goal of this study was to determine if there is a difference in the achieved depth of sedation, the rate of respiratory depression, procedural difficulty, or patient perceived pain or recall between patients randomized to a pre-procedural target sedation level of moderate or deep procedural sedation using propofol during the reduction of fractures and dislocations in the Emergency Department (ED). This was a randomized, prospective study of adults undergoing procedural sedation (PS) with propofol for fracture or dislocation reduction in the ED between July 2003 and March 2004. Patients were randomized to a target sedation level of moderate or deep, using American Society of Anesthesiologists’ definitions. Doses, vital signs, nasal end tidal CO 2 (ETCO 2), pulse oximetry, and bispectral EEG analysis (BIS) scores were recorded. Respiratory depression was defined as a change in ETCO 2 >10, an oxygen saturation of <90% at any time, or an absent ETCO 2 waveform at any time. After the procedure, patients were asked if they perceived any pain or had any recall of the procedure. Physicians were asked to rate the difficulty of completing the reduction using a 100-mm visual analog scale (VAS). Respiratory depression rates were compared with chi-square tests, BIS and VAS scores were compared with t tests. Seventy-five patients were enrolled, 39 randomized to the target of moderate PS and 36 to the target of deep PS. No significant complications were noted. There were 25/36 (69%) of the patients assigned to the deep sedation target group who actually achieved a deep level of sedation and 21/39 (54%) of the patients assigned to the moderate sedation target group who actually achieved a moderate level of sedation ( p = 0.40). Respiratory depression was seen in 19/39 (49%) patients with the moderate PS target and 18/36 (50%) with the deep PS target ( p = 0.91). The mean minimum recorded BIS score was 67.7 (95% confidence interval [CI] 62.2–73.3) for the moderate PS target group and 59.2 (95% CI 55.1–64.2) for the deep PS target group ( p = 0.03). There were 12/39 (31%) in the moderate PS target group and 4/36 (11%) in the deep PS target group who reported pain with or recall of the procedure ( p = 0.04). The mean physician VAS for procedural difficulty was 34.0 (95% CI 23.7–44.3) for the moderate PS group and 28.8 (95% CI 18.4–39.2) for the deep PS group ( p = 0.46). In this study, the assignment of a pre-procedural target sedation level of moderate or deep PS did not influence the level of sedation achieved, the rate of respiratory depression, the occurrence of complications, the time to return of baseline mental status, or the success of the procedure. It does not seem that the assignment of a pre-procedural target sedation level is an effective means of changing the outcome of ED PS.

Changes in vagal tone with posture in asthma are related to changes in ventilatory pattern

Posturally induced changes in minute ventilation in patients may be autonomically driven. This study aimed to test whether changes in autonomic tone with posture differed between normal and asthmatic subjects and whether this related to changes in indices of ventilation. Ten patients with type 1 brittle asthma (BA), 10 with non-brittle, severe asthma (SA), 10 with mild asthma (MA) and 10 normal individuals were studied lying flat, at 60 degrees head up tilt and flat again each for 30min, assessing end-tidal CO(2) (ETCO(2)), respiratory rate and autonomic tone by heart rate variability. Parasympathetic tone (as high-frequency [HF] power) fell on tilt in all four groups, all showing increases in LF (low frequency)/HF ratio (sympatho-vagal balance) on tilt (BA, 2.03-4.9; SA, 3.3-8.2; MA, 1.5-4.9; normals, 2.3-6.6). ETCO(2) on tilt fell significantly in all 3 asthma groups (BA, DeltaETCO(2) -0.4, 95% CIs -0.18 to -0.75, P=0.005; SA, -0.7, 95% CIs -0.27 to -1.16, P=0.004; MA, -0.5, 95% CIs -0.14 to -0.78, P=0.01) but not in normals (-0.1, 95% CIs +0.23 to -0.49). The fall in ETCO(2) on tilt correlated with the fall in HF power in all three asthma groups but not in normal subjects. Changes in vagal tone posture are seen on tilt in both normal and asthmatic subjects which relate to changes in ETCO(2) only in asthmatic subjects. This provides support for the hypothesis that hyper-ventilatory response to postural change in asthma is autonomically influenced.

The Utility of the Bispectral Index in Procedural Sedation with Propofol in the Emergency Department

The bispectral index (BIS) may be a useful monitor to predict the level of awareness in patients undergoing procedural sedation in the emergency department (ED). The authors hypothesized that using the BIS during procedural sedation in the ED would increase the recognition of adequately sedated patients, thus reducing oversedation and the corresponding increased rate of respiratory depression (RD). As a result, the occurrence of RD would be reduced. This was a prospective randomized study of ED procedural sedation with propofol. Sedations were randomized to have the treating physician either blinded or not blinded to information from the BIS monitor. Vital signs, pulse oximetry, end-tidal carbon dioxide (ETCO(2)), propofol dosage, and the BIS score were recorded. RD was defined as a change in ETCO(2) greater than 10 mm Hg, an oxygen saturation of less than 90% at any time, or an absent ETCO(2) waveform. The RD rates were compared with chi-square tests. One hundred five patients were enrolled in the study; five were excluded due to study protocol violations. No serious adverse events were reported. RD was seen in 29 of 100 (29%) patients; 18 of 48 in the BIS-blinded group and 11 of 52 in the BIS-unblinded group had RD (p = 0.06). For patients requiring only a single dose of propofol, three of 15 in the BIS-blinded group and four of 18 in the BIS-unblinded group met the criteria for RD (p = 0.87). For patients requiring multiple doses of propofol, 15 of 33 patients in the BIS-blinded group and seven of 34 patients in the BIS-unblinded group met criteria for RD (p = 0.02). The mean BIS nadir for BIS-blinded patients was 60.9 (95% CI = 56.9 to 65.0) and that for BIS-unblinded patients was 63.2 (95% CI = 57.7 to 65.3) (p = 0.22). There was a lower rate of RD when physicians had access to the BIS during procedural sedations. This difference was greater in sedations requiring multiple doses of propofol. There was no difference in the rate of RD when only a single dose was given.