Langhan ML, Shabanova V, Li FY, et al. A randomized controlled trial of capnography during sedation in a pediatric emergency setting. Am J Emerg Med. 2015 Jan;33(1):25-30.

OBJECTIVE: Data suggest that capnography is a more sensitive measure of ventilation than standard modalities and detects respiratory depression before hypoxemia occurs. We sought to determine if adding capnography to standard monitoring during sedation of children increased the frequency of interventions for hypoventilation, and whether these interventions would decrease the frequency of oxygen desaturations.

METHODS: We enrolled 154 children receiving procedural sedation in a pediatric emergency department. All subjects received standard monitoring and capnography, but were randomized to whether staff could view the capnography monitor (intervention) or were blinded to it (controls). Primary outcome were the rate of interventions provided by staff for hypoventilation and the rate of oxygen desaturation less than 95%.

RESULTS: Seventy-seven children were randomized to each group. Forty-five percent had at least 1 episode of hypoventilation. The rate of hypoventilation per minute was significantly higher among controls (7.1% vs 1.0%, P = .008). There were significantly fewer interventions in the intervention group than in the control group (odds ratio, 0.25; 95% confidence interval [CI], 0.13-0.50). Interventions were more likely to occur contemporaneously with hypoventilation in the intervention group (2.26; 95% CI, 1.34-3.81). Interventions not in time with hypoventilation were associated with higher odds of oxygen desaturation less than 95% (odds ratio, 5.31; 95% CI, 2.76-10.22).

CONCLUSION: Hypoventilation is common during sedation of pediatric emergency department patients. This can be difficult to detect by current monitoring methods other than capnography. Providers with access to capnography provided fewer but more timely interventions for hypoventilation. This led to fewer episodes of hypoventilation and of oxygen desaturation.

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Commentary: 

Continuous monitoring is an integral component of procedural sedation. In addition to the physical exam, modalities such pulse oximetry and capnography are also used and required per American Academy of Pediatrics guidelines, especially for deep sedation. However, end tidal capnography is a sensitive marker of ventilation status, which can detect hypoventilation before hypoxemia occurs.

In the randomized controlled trial presented in Am J Emerg Med by Langhan et al looked at the overall effects of capnography on detecting hypoventilation. The authors hypothesized that the addition of end-tidal capnography during procedural sedation in the emergency setting would improve recognition of hypoventilation by the sedation providers. This improved recognition would then both 1) increase the rate of interventions to address hypoventilation and 2) reduce the rate of oxygen desaturations due to timely interventions. A total of 154 patients were enrolled in the study. There were 77 patients into each of two separate groups: a control group in which the sedation team was blinded to the capnography screen, and an intervention group in which the capnography screen was viewable by all of the sedation team members. The primary outcomes were the rate of hypoventilation (capnography less than 30mm Hg or greater than 50mm Hg) and the rate of desaturations (oxygen saturation less than 95%). Eligible children were less than 20 years old who received IV medications for procedural sedation during the study period. Most were ASA class I-II. Excluded children were those that were intubated, had a baseline oxygen requirement, major trauma, conditions associated with baseline abnormal ETC02, patients who could not tolerate the cannula or patients who cried for greater for 20% of the sedation.

The results showed that all episodes of hypoventilation were due to hypopnea (ETC02 which was less than 30mm Hg without hyperventilation). The overall rate of hypoventilation within a minute of sedation increased over time in both groups but was significantly greater in the control group (7.1% vs 1%; OR 1.06; 95% CI: 1.02-1.11). Additionally, the rate of either persistent hypoventilation, or of 2 consecutive abnormal values was also greater among the controls (7.5% vs 1.0%; OR 1.01; 95% CI: 1.01-1.12). The most common intervention was verbal or physical stimulation, which was noted to be slightly lower in the intervention group (OR 1.02 per minute increase; 95% CI: 1.005-1.03). The authors concluded that access to capnography provided fewer but more timely interventions for hypoventilation, resulting in fewer episodes of hypoventilation and oxygen desaturation.

The main limitation of this study is that it is a convenience sample of patients. The research team collected the data, leading to possible observer bias. Additionally, the sedation team may have behaved differently while being observed (Hawthorne effect). Further, only Ketamine was offered as a sedation option. However, the study was well-designed where the interventions were randomized in a 1:1 fashion. The cohort of patients was not huge but was appropriately powered.

So, does this change your medical practice? Your thoughts on what should be standard monitoring during routine sedations?

A key point here that the authors make is that most of the episodes of hypoventilation in this study were due to hypopnea, not apnea. Hypopnea appears to be difficult to detect by standard monitors and physical examination. Capnography appears superior at detecting all forms of hypoventilation. While capnography is considered standard in the anesthesia literature, it is not yet routinely used by all pediatric sedation providers, despite its reference in the AAP guidelines for deep sedation by Cote, et al. Further, while there are fewer interventions in the intervention group, the interventions were simple and non-invasive. This makes the point that hypoventilation can be easily corrected when recognized early, resulting in fewer episodes of oxygen desaturation. In a previous study Langhan et al (Arch Pediatr Adolesc Med. 2012 Nov; 166(11):990-8) examined 114, 855 subjects using data from the Pediatric Sedation Research Consortium (PSRC). This data showed that a large degree of variability exists in the physiologic monitoring modalities for procedural sedation. Guidelines published by the American Academy of Pediatrics (AAP), the American College of Emergency Physicians (ACEP), and the American Society of Anesthesiologists (ASA) for non-anesthesiologists and were adhered to for 52% of subjects.

Reviewed by: 

Carmen D. Sulton, MD

Assistant Professor of Pediatrics and Emergency Medicine

Emory University School of Medicine

Sedation Services, Children’s Healthcare of Atlanta at Egleston

Atlanta, GA