Capnography-An Essential Monitor, Everywhere: A Narrative Review

Capnography is now recognized as an indispensable patient safety monitor. Evidence suggests that its use improves outcomes in operating rooms, intensive care units, and emergency departments, as well as in sedation suites, in postanesthesia recovery units, and on general postsurgical wards. Capnography can accurately and rapidly detect respiratory, circulatory, and metabolic derangements. In addition to being useful for diagnosing and managing esophageal intubation, capnography provides crucial information when used for monitoring airway patency and hypoventilation in patients without instrumented airways. Despite its ubiquitous use in high-income-country operating rooms, deaths from esophageal intubations continue to occur in these contexts due to incorrect use or interpretation of capnography. National and international society guidelines on airway management mandate capnography's use during intubations across all hospital areas, and recommend it when ventilation may be impaired, such as during procedural sedation. Nevertheless, capnography's use across high-income-country intensive care units, emergency departments, and postanesthesia recovery units remains inconsistent. While capnography is universally used in high-income-country operating rooms, it remains largely unavailable to anesthesia providers in low- and middle-income countries. This lack of access to capnography likely contributes to more frequent and serious airway events and higher rates of perioperative mortality in low- and middle-income countries. New capnography equipment, which overcomes cost and context barriers, has recently been developed. Increasing access to capnography in low- and middle-income countries must occur to improve patient outcomes and expand universal health care. It is time to extend capnography's safety benefits to all patients, everywhere.

Integrated Pulmonary Index during nurse-administered procedural sedation: Study protocol for a cluster-randomized trial

AIM

To determine if smart alarm-guided treatment of respiratory depression using the Integrated Pulmonary Index is an effective way to implement capnography during nurse-administered sedation.

DESIGN

Parallel cluster-randomized trial.

METHODS

Nurses will be randomized to use capnography with or without the Integrated Pulmonary Index enabled. Capnography alarm performance will be compared between nurses using capnography alone or with the Integrated Pulmonary Index enabled. The target sample size is 400 adult patients scheduled for elective procedures with nurse-administered sedation. The primary outcome is the number of seconds in an alert condition state without an intervention being applied. Secondary outcomes are alarm burden, number of appropriate alarms, number of inappropriate alarms, total duration of alert conditions, choice of alarm settings and adverse sedation events. This study has been funded since April 2021.

DISCUSSION

Implementing capnography into practice for respiratory monitoring during nurse-administered sedation is considered a high priority. The Integrated Pulmonary Index shows promise as a strategy to optimize the implementation of capnography for respiratory monitoring during nurse-administered sedation. If it is found in this study that using the Integrated Pulmonary Index improves the nursing management of physiologically abnormal states during nurse-administered sedation, it would provide the high-level evidence needed to support broader use of this 'smart alarm' strategy for respiratory monitoring in practice.

IMPACT

With advances in medical technology continuing to expand the indications for minimally invasive surgical techniques, the use of nurse-administered sedation during medical procedures is likely to expand in the future. The findings may be applied to other populations receiving nurse-administered sedation during medical procedures. Results from this study will help translate the usage of smart alarm-guided treatment of respiratory depression during procedural sedation.

TRIAL REGISTRATION

NCT05068700.

Recommendations for standards of monitoring during anaesthesia and recovery 2021: Guideline from the Association of Anaesthetists

This guideline updates and replaces the 5th edition of the Standards of Monitoring published in 2015. The aim of this document is to provide guidance on the minimum standards for monitoring of any patient undergoing anaesthesia or sedation under the care of an anaesthetist. The recommendations are primarily aimed at anaesthetists practising in the UK and Ireland, but it is recognised that these guidelines may also be of use in other areas of the world. Minimum standards for monitoring patients during anaesthesia and in the recovery phase are included. There is also guidance on monitoring patients undergoing sedation and during transfer. There are new sections specifically discussing capnography, sedation and regional anaesthesia. In addition, the indications for processed electroencephalogram and neuromuscular monitoring have been updated.

Computer-Generated Three-Dimensional Airway Models as a Decision-Support Tool for Preoperative Evaluation and Procedure-Planning in Pediatric Anesthesiology

Technology improvements have rapidly advanced medicine over the last few decades. New approaches are constantly being developed and utilized. Anesthesiology strongly relies on technology for resuscitation, life-support, monitoring, safety, clinical care, and education. This manuscript describes a reverse engineering process to confirm the fit of a medical device in a pediatric patient. The method uses virtual reality and three-dimensional printing technologies to evaluate the feasibility of a complex procedure requiring one-lung isolation and one-lung ventilation. Based on the results of the device fit analysis, the anesthesiology team confidently proceeded with the operation. The approach used and described serves as an example of the advantages available when coupling new technologies to visualize patient anatomy during the procedural planning process.

Impact of capnography on patient safety in high- and low-income settings: a scoping review

BACKGROUND

Capnography is universally accepted as an essential patient safety monitor in high-income countries (HICs) yet is often unavailable in low and middle-income countries (LMICs). Increasing capnography availability has been proposed as one of many potential approaches to improving perioperative outcomes in LMICs. This scoping review summarises the existing literature on the effect of capnography on patient outcomes to help prioritise interventions and guide expansion of capnography in LMICs.

METHODS

We searched MEDLINE and EMBASE databases for articles published between 1980 and March 2019. Studies that assessed the impact of capnography on morbidity, mortality, or the use of airway interventions both inside and outside the operating room were included.

RESULTS

The search resulted in 7445 unique papers, and 31 were included for analysis. Retrospective and non-randomised data suggest capnography use may improve outcomes in the operating room, ICU, and emergency department, and during resuscitation. Prospective data on capnography use for procedural sedation suggest earlier detection of hypoventilation and a reduction in haemoglobin desaturation events. No randomised studies exist that assess the impact of capnography on patient outcomes.

CONCLUSION

Despite widespread endorsement of capnography as a mandatory perioperative monitor, rigorous data demonstrating its impact on patient outcomes are limited, especially in LMICs. The association between capnography use and a reduction in serious airway complications suggests that closing the capnography gap in LMICs may represent a significant opportunity to improve patient safety. Additional data are needed to quantify the global capnography gap and better understand the barriers to capnography scale-up in LMICs.

Prospective Observational Investigation of Capnography and Pulse Oximetry Monitoring After Cesarean Delivery With Intrathecal Morphine

BACKGROUND

Intrathecal morphine provides excellent analgesia after cesarean delivery; however, respiratory events such as apnea, bradypnea, and hypoxemia have been reported. The primary study aim was to estimate the number of apneas per subject, termed "apnea alert events" (AAEs) defined by no breath for 30-120 seconds, using continuous capnography in women who underwent cesarean delivery.

METHODS

We performed a prospective, observational study with institutional review board approval of women who underwent cesarean delivery with spinal anesthesia containing 150-µg intrathecal morphine. A STOP-Bang obstructive sleep apnea assessment was administered to all women. Women were requested to use continuous capnography and pulse oximetry for 24 hours after cesarean delivery. Nasal sampling cannula measured end-tidal carbon dioxide (EtCO2) and respiratory rate (RR), and oxygen saturation (SpO2) as measured by pulse oximetry. Capnography data were defined as "valid" when EtCO2 >10 mm Hg, RR >5 breaths per minute (bpm), SpO2 >70%, or during apnea (AAE) defined as "no breath" (EtCO2, <5 mm Hg) for 30-120 seconds. Individual respiratory variable alerts were 10-second means of EtCO2 <10 mm Hg, RR <8 bpm, and SpO2 <94%. Nurse observations of RR (hourly and blinded to capnography) are reported.

RESULTS

We recruited 80 women, mean (standard deviation [SD]) 35 (5) years, 47% body mass index >30 kg/m2/weight >90 kg, and 11% with suspected obstructive sleep apnea (known or STOP-Bang score >3). The duration of normal capnography and pulse oximetry data was mean (SD) (range) 8:28 (7:51) (0:00-22:32) and 15:08 (6:42) (1:31-23:07) hours:minutes, respectively; 6 women did not use the capnography. There were 198 AAEs, mean (SD) duration 57 (27) seconds experienced by 39/74 (53%) women, median (95% confidence interval for median) (range) 1 (0-1) (0-29) per subject. Observation of RR by nurses was ≥14 bpm at all time-points for all women, r = 0.05 between capnography and nurse RR (95% confidence interval, -0.04 to 0.14). There were no clinically relevant adverse events for any woman. Sixty-five women (82%) had complaints with the capnography device, including itchy nose, nausea, interference with nursing baby, and overall inconvenience.

CONCLUSIONS

We report 198 AAEs detected by capnography among women who underwent cesarean delivery after receiving intrathecal morphine. These apneas were not confirmed by the intermittent hourly nursing observations. Absence of observer verification precludes distinction between real, albeit nonclinically significant alerts with capnography versus false apneas. Discomfort with the nasal sampling cannula and frequent alerts may impact capnography application after cesarean delivery. No clinically relevant adverse events occurred.

Investigating Capnography Innovation for Better Patient Monitoring in the Resource Limited Surgical Setting

BACKGROUND

Access to basic anesthetic monitoring in the developing world is lacking, which contributes to the 100 times greater anesthesia-related mortality in low- and middle-income countries. We hypothesize that an environmental sensor with a lower sampling rate could provide some clinical utility by providing CO₂ levels, respiratory rate, and support in detection of clinical abnormalities.

MATERIALS AND METHODS

A bench-top lung simulation was created to replicate CO₂ waveforms, and an environmental sensor was compared with industry-available technology. Sensor response time and respiratory rates were compared between devices. Additionally, an in silico model was created to replicate capnography pathology as waveforms would appear using the environmental sensor.

RESULTS AND CONCLUSION

Breath simulations using the bench-top lung simulation produced similar results to industry standards with a degree of variability. Respiratory rates did not differ between the environmental sensor and all other devices tested. Finally, pathological waveforms created in silico carried a certain level of detail regarding ventilatory pathology, which could provide some clinical insight to an anesthesiologist. We believe our prototype is the first step toward making low-cost and portable capnography available in the resource-limited setting, and future efforts should focus on bridging the gap to safer anesthesia and surgery globally.

Patient safety during procedural sedation using capnography monitoring: a systematic review and meta-analysis

OBJECTIVE

To evaluate the effect of capnography monitoring on sedation-related adverse events during procedural sedation and analgesia (PSA) administered for ambulatory surgery relative to visual assessment and pulse oximetry alone.

DESIGN AND SETTING

Systematic literature review and random effects meta-analysis of randomised controlled trials (RCTs) reporting sedation-related adverse event incidence when adding capnography to visual assessment and pulse oximetry in patients undergoing PSA during ambulatory surgery in the hospital setting. Searches for eligible studies published between 1 January 1995 and 31 December 2016 (inclusive) were conducted in PubMed, the Cochrane Library and EMBASE without any language constraints. Searches were conducted in January 2017, screening and data extraction were conducted by two independent reviewers, and study quality was assessed using a modified Jadad scale.

INTERVENTIONS

Capnography monitoring relative to visual assessment and pulse oximetry alone.

PRIMARY AND SECONDARY OUTCOME MEASURES

Predefined endpoints of interest were desaturation/hypoxaemia (the primary endpoint), apnoea, aspiration, bradycardia, hypotension, premature procedure termination, respiratory failure, use of assisted/bag-mask ventilation and death during PSA.

RESULTS

The literature search identified 1006 unique articles, of which 13 were ultimately included in the meta-analysis. Addition of capnography to visual assessment and pulse oximetry was associated with a significant reduction in mild (risk ratio (RR) 0.77, 95% CI 0.67 to 0.89) and severe (RR 0.59, 95% CI 0.43 to 0.81) desaturation, as well as in the use of assisted ventilation (OR 0.47, 95% CI 0.23 to 0.95). No significant differences in other endpoints were identified.

CONCLUSIONS

Meta-analysis of 13 RCTs published between 2006 and 2016 showed a reduction in respiratory compromise (from respiratory insufficiency to failure) during PSA with the inclusion of capnography monitoring. In particular, use of capnography was associated with less mild and severe oxygen desaturation, which may have helped to avoid the need for assisted ventilation.