Share this article on:

Continuous Pulse Oximetry and Capnography Monitoring for Postoperative Respiratory Depression and Adverse Events: A Systematic Review and Meta-analysis

Lam, Thach MD*; Nagappa, Mahesh MD; Wong, Jean MD*; Singh, Mandeep MD, MSc*; Wong, David MD*; Chung, Frances MBBS*

doi: 10.1213/ANE.0000000000002557
Respiration and Sleep Medicine: Systematic Review Article
Continuing Medical Education

BACKGROUND: Death and anoxic brain injury from unrecognized postoperative respiratory depression (PORD) is a serious concern for patient safety. The American Patient Safety Foundation has called for continuous electronic monitoring for all patients receiving opioids in the postoperative period. These recommendations are based largely on consensus opinion with currently limited evidence. The objective of this study is to review the current state of knowledge on the effectiveness of continuous pulse oximetry (CPOX) versus routine nursing care and the effectiveness of continuous capnography monitoring with or without pulse oximetry for detecting PORD and preventing postoperative adverse events in the surgical ward.

METHODS: We performed a systematic search of the literature databases published between 1946 and May 2017. We selected the studies that included the following: (1) adult surgical patients (>18 years old); (2) prescribed opioids during the postoperative period; (3) monitored with CPOX and/or capnography; (4) primary outcome measures were oxygen desaturation, bradypnea, hypercarbia, rescue team activation, intensive care unit (ICU) admission, or mortality; and (5) studies published in the English language. Meta-analysis was performed using Cochrane Review Manager 5.3.

RESULTS: In total, 9 studies (4 examining CPOX and 5 examining continuous capnography) were included in this systematic review. In the literature on CPOX, 1 randomized controlled trial showed no difference in ICU transfers (6.7% vs 8.5%; P = .33) or mortality (2.3% vs 2.2%). A prospective historical controlled trial demonstrated a significant reduction in ICU transfers (5.6–1.2 per 1000 patient days; P = .01) and rescue team activation (3.4–1.2 per 1000 patient days; P = .02) when CPOX was used. Overall, comparing the CPOX group versus the standard monitoring group, there was 34% risk reduction in ICU transfer (P = .06) and odds of recognizing desaturation (oxygen saturation [SpO2] <90% >1 hour) was 15 times higher (P < .00001). Pooled data from 3 capnography studies showed that continuous capnography group identified 8.6% more PORD events versus pulse oximetry monitoring group (CO2 group versus SpO2 group: 11.5% vs 2.8%; P < .00001). The odds of recognizing PORD was almost 6 times higher in the capnography versus the pulse oximetry group (odds ratio: 5.83, 95% confidence interval, 3.54–9.63; P < .00001). No studies examined the impact of continuous capnography on reducing rescue team activation, ICU transfers, or mortality.

CONCLUSIONS: The use of CPOX on the surgical ward is associated with significant improvement in the detection of oxygen desaturation versus intermittent nursing spot-checks. There is a trend toward less ICU transfers with CPOX versus standard monitoring. The evidence on whether the detection of oxygen desaturation leads to less rescue team activation and mortality is inconclusive. Capnography provides an early warning of PORD before oxygen desaturation, especially when supplemental oxygen is administered. Improved education regarding monitoring and further research with high-quality randomized controlled trials is needed.

Supplemental Digital Content is available in the text.

From the *Department of Anesthesiology and Pain Medicine, University of Toronto, Toronto, Ontario, Canada; and Department of Anesthesia & Perioperative Medicine, London Health Sciences Centre and St. Joseph Health Care, Western University, London, ON, Canada.

Accepted for publication August 16, 2017.

Funding: Supported by the Department of Anesthesiology, Toronto Western Hospital, University Health Network, University of Toronto.

Conflicts of Interest: See Disclosures at the end of the article.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s website.

Reprints will not be available from the authors.

Address correspondence to Frances Chung, MBBS, Department of Anesthesiology and Pain Medicine, Toronto Western Hospital, University Health Network, University of Toronto, 399 Bathurst St, MCL 2–405, Toronto, ON M5T 2S8, Canada. Address e-mail to Frances.chung@uhn.ca.

This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal.

Opioids are widely prescribed for treatment of moderate to severe pain after surgery. While opioids are generally safe for most patients, they may lead to acute respiratory depression in unmonitored settings such as a surgical ward. The incidence of postoperative opioid overdose has doubled from 0.6 to 1.1 per 1000 operative cases from 2002 to 2011 and patients with postoperative opioid overdose have a 4-fold higher mortality rate.1 Of the opioid-related adverse drug events in the Joint Commission’s Sentinel Event database between 2004 and 2011, 47% were wrong-dose medication errors, 29% were related to improper monitoring of the patient, and 11% were related to excessive dosing, medication interactions, and adverse drug reactions.2 In a review of 92 closed claims related to opioid-induced respiratory depression, 97% of claims could have been prevented with (1) improvements in assessment of sedation level; (2) monitoring of oxygenation and ventilation; and (3) early response and intervention, particularly within the first 24 hours postoperatively.3

For these reasons, the Anesthesia Patient Safety Foundation,4 the Joint Commission,2 and the American Society for Pain Management Nursing5 have called for continuous electronic monitoring for all patients receiving opioids in the postoperative period. Due to the rarity of respiratory depression, the recommendations are based mainly on consensus opinion because there are limited studies on the efficacy of postoperative monitoring. There is a need to review and summarize the existing available data and evidence on pulse oximetry and capnography.

Pulse oximetry is a noninvasive method for measuring heart rate and oxygen saturation in the blood. The value in pulse oximetry monitoring lies in its ability to provide an estimation of the degree of hypoxemia in arterial blood. Capnography is a noninvasive method for estimating the partial pressure of carbon dioxide in the arterial blood. Capnography is composed of end-tidal capnography that measures partial pressure of carbon dioxide in exhaled gases and transcutaneous capnography that measures partial pressure of carbon dioxide via a heated electrochemical sensor applied to the skin. The benefits of capnography lie in the ability to monitor ventilatory status through changes in end-tidal or transcutaneous CO2 from baseline, respiratory rate, and the occurrence of breathing pauses (hypopnea and apnea) that may occur as a result of opioid use. In the operating room, the use of pulse oximetry and capnography have significantly improved patient safety and have been accepted as the standard of practice.6,7 At present, these monitors have not been accepted as the standard of postoperative care in the surgical ward.

In this systematic review, we summarize the current state of knowledge on the effectiveness of continuous pulse oximetry (CPOX) versus routine nursing care and the effectiveness of continuous capnography with and without pulse oximetry for the detection of postoperative respiratory depression (PORD) and prevention of postoperative adverse events.

Back to Top | Article Outline

METHODS

Search Strategy and Study Selection

We screened published articles evaluating the effectiveness of CPOX and/or capnography monitoring for detection of PORD and prevention of postoperative adverse events. The literature search and review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines, and the search strategy was implemented with the help of an expert librarian familiar with the literature search. We searched the literature databases PubMed-MEDLINE (1946 to May 2017), MEDLINE in-process, and other nonindexed citations (to May 2017), Embase and Embase Classic (1947 to May 2017), Cochrane Central Register of Controlled Trials (to May 2017), Cochrane database of systematic reviews (to May 2017), and PubMed (to May 2017).

The search used the Medical Subject Heading keywords “monitoring,” “oximetry,” “capnography,” “clinical alarms,” “opioid analgesics,” “patient-controlled analgesia,” “respiratory insufficiency,” “pulmonary ventilation,” “anoxia,” “apnea,” “dyspnea,” “hypoventilation,” “work of breathing,” “respiratory rate,” “vital signs,” “oxygen saturation,” “adverse events,” “rescue,” “intensive care unit,” “perioperative care,” “postoperative care,” “sudden cardiac death,” “cardiopulmonary arrest,” “heart arrest,” “respiratory arrest,” and “death.”

The criteria to include studies in our review were as follows: (1) adult surgical patients (>18 years old); (2) prescribed opioids during the postoperative period; (3) monitored with CPOX and/or capnography; (4) available reports on oxygen desaturation, bradypnea, hypercarbia, rescue team activation, adverse events, intensive care unit (ICU) transfers, or mortality; and (5) published studies in the English language. The exclusion criteria were as follows: (1) case reports and (2) studies not meeting the inclusion criteria.

Studies were selected independently by 2 reviewers (T.L., M.N.), who screened the titles and abstracts to determine whether the studies met the eligibility criteria. Full text copies of articles deemed to be potentially relevant were retrieved. Duplicate publications were excluded. A citation search by manual review of references from primary or review articles was performed.

Back to Top | Article Outline

Data Extraction

Data extraction was performed independently by 2 reviewers (T.L., M.N.). Any disagreements were resolved by consensus or by consulting another author (F.C.). The following information was collected from each study: author, year of publication, type of study design, sample size of the monitored group, and type of monitoring.

Back to Top | Article Outline

Study Quality Assessment

All included studies were graded for strength of evidence according to the Oxford Centre for Evidence-Based Medicine Levels of Evidence 2011.8 The classification was as follows: level I: systematic review of randomized trials; level II: randomized trial or observational study with dramatic effect; level III: nonrandomized controlled cohort; level IV: case-series, case–control studies, or historically controlled studies; and level V: mechanism-based reasoning.

Back to Top | Article Outline

Statistical Analysis

Summary Measures.

The measure of detection for PORD was the weighted odds ratio (OR) with 95% confidence interval (CI) and the weighted risk ratio (RR) with 95% CI for the ICU transfer. The Mantel-Haenszel (M-H) method was used to combine dichotomous events. By extracting the crude data, the OR and RR for the individual studies was recalculated and then pooled across studies using random-effects modeling. The results were displayed as forest plots using Review manager (RevMan, version 5.3., Copenhagen, Denmark). P < .05 was considered statistically significant. Heterogeneity across studies was investigated for each adverse event by calculating I 2.

Back to Top | Article Outline

Outcome Definitions

Our primary outcome measure was PORD and adverse events. Respiratory depression was defined as an episode of oxygen desaturation, bradypnea, or hypercarbia. Adverse events were defined as any rescue team activation, ICU transfer, or death. Postoperative period was defined as the time from admission to a surgical unit after discharge from the postanesthesia care unit. Continuous monitoring was defined as the uninterrupted application of pulse oximetry and/or capnography with collection of serial oxygen saturation and end-tidal/transcutaneous CO2 and respiratory rate measurements, respectively. Routine nursing care was defined as nurses obtaining vital signs, typically at 4- to 6-hour intervals.

Back to Top | Article Outline

RESULTS

The review was conducted according to the PRISMA guidelines. Our search strategy is listed in Figure 1. Our initial electronic search identified 11,583 citations. After screening titles and abstracts, 11,527 studies were excluded for not meeting the predetermined eligibility criteria. Of the remaining 56 studies, 47 were excluded and the reasons are listed in Figure 1. Articles were most often excluded because they did not study the monitoring intervention of interest. In total, 9 studies (2 randomized controlled trials [RCTs], 1 prospective historical controlled trial, 5 prospective observational studies, and 1 retrospective observational study) were included in this systematic review. According to the Oxford Centre for Evidence-Based Medicine Levels of Evidence 2011,8 the strength of the evidence in the 9 studies was low to moderate.

Figure 1

Figure 1

Table 1

Table 1

Table 2

Table 2

Out of the 9 included studies, 4 examined the effectiveness of CPOX monitoring versus routine nursing care9–12 and 5 examined the effectiveness of continuous capnography with or without pulse oximetry13–17 for the detection of PORD or prevention of adverse events. The characteristics and main findings of the 9 studies are shown in Tables 1 and 2 (sorted according to mode of monitoring, methodological quality, and sample size). Of the 4 studies examining the impact of CPOX, 1 was a prospective RCT,9 1 was a prospective, historical controlled trial,10 and 2 were observational studies.11,12 Of the 5 studies examining the impact of continuous capnography and CPOX, 1 was a prospective RCT,14 3 were prospective observational studies,13,16,17 and 1 was a retrospective observational study.15

Back to Top | Article Outline

Use of Pulse Oximetry Monitoring

Of the 4 studies examining the performance of CPOX monitoring versus routine nursing checks, 2 evaluated the impact on rescue team activation, ICU admission, or mortality,9,10 and 2 evaluated the impact for detection of oxygen desaturation versus intermittent nursing checks.11,12

The strongest evidence examining the use of CPOX is derived from a nonblinded RCT study of 1218 patients from a 33-bed postcardiothoracic surgery care floor.9 Ochroch et al9 found that CPOX monitoring did not reduce transfer to ICU (CPOX versus control: 6.7% vs 8.4%; RR: 0.81; 95% CI, 0.54–1.2; P = .29) or mortality (CPOX versus control: 2.3% vs 2.2%) versus standard nursing care (Table 3). However, the use of CPOX monitoring significantly reduced the number of patients transferred to the ICU for pulmonary reasons (CPOX versus control: 1.3% vs 4.2%; RR: 0.32; 95% CI, 0.15–0.69; P = .004). Of those transferred to ICU, the CPOX group had significantly shorter ICU stays and overall costs.9

Table 3

Table 3

In a prospective, historical controlled trial, Taenzer et al10 implemented a patient surveillance system using CPOX monitoring with nursing notifications via pager when physiologic limits were violated. This patient surveillance system was implemented in a 36-bed orthopedic unit for 10 months and data were compared to the 11 months before implementation of the system and concurrent data on 2 other postoperative units.10 The use of CPOX monitoring was associated with a significant reduction in rescue events from 3.4 to 1.2 per 1000 patient discharges and ICU transfers from 5.6 to 2.9 per 1000 patient days, whereas the comparison units had no change.10 This correlated with a reduced need for rescue team activation by 65% and ICU transfers by 48% (Table 3).

Overall, comparing the CPOX group versus the standard monitoring group, there was a trend toward reduced ICU transfers in the CPOX group (RR 0.66, CI, 0.42–1.01; P = .06; Table 3).

Two observational studies compared the use of CPOX to routine nursing care (spot-check vitals every 4–6 hours) for detection of oxygen desaturation.11,12 In 833 patients after noncardiac surgery, Sun et al11 determined that oxygen desaturation was common (21% had >10 min/h with oxygen saturation [SpO2] <90%) and prolonged (37% had at least 1 episode of SpO2 <90% for an hour or more). Nurses missed 90% of hypoxemic episodes in which saturation was <90% for at least 1 hour.11 The odds of recognizing desaturation (SpO2 <90%) was 15 times higher in the CPOX group when compared to the standard monitoring group (OR, 15.7; 95% CI, 10.6–23.2; P < .00001; Table 3). In 16 patients considered to be at high risk for deterioration, Taenzer et al12 showed that manual charted oxygen saturations every 4 hours were on average 6.5% higher than those recorded with CPOX.

Back to Top | Article Outline

Use of Capnography Monitoring

Of the 5 studies evaluating the use of continuous capnography, 1 RCT examined the effectiveness of continuous capnography without pulse oximetry versus routine nursing care and 4 studies evaluated the effectiveness of continuous capnography with CPOX for detecting PORD. Pooled data from 3 capnography studies13,14,16 showed that continuous capnography versus CPOX monitoring identified 8.6% more PORD events (bradypnea versus desaturation <90% >1 hour) (CO2 group versus SpO2 group: 11.5% vs 2.8%; P < .00001). The odds of recognizing PORD was 5.8 times higher in the capnography versus the CPOX group (OR: 5.83, 95% CI, 3.54–9.63; P < .00001, I 2 0%) (Figure 2).

Figure 2

Figure 2

In a RCT of opioid-naive postoperative orthopedic patients, 54 patients were randomized in the postanesthesia care unit to either postoperative monitoring with continuous capnography group (n = 29) or control group (spot-check pulse oximetry and respiration rate assessment by observation or auscultation every 4 hours) (n = 25).14 PORD was defined as a respiratory rate <6 per minute, apnea >20 seconds, end-tidal CO2 greater than 60 mm Hg, or SpO2 <88%. The capnography group and the control group had no significant differences in opioid use on the day of surgery or on the first postoperative day. PORD was detected at a higher rate in the capnography group versus the control group (140 vs 6 respiratory depression events; P = .03).14 The majority of PORD events in Hutchison’s study was detected by capnography when patients breathed at 6 or less per minute or had repeated apneas longer than 20 seconds.14 The other 2 indicators of PORD (an end-tidal CO2 level >60 mm Hg and oxygen saturation <88%) did not contribute to the outcomes measured, suggesting that they may be less-sensitive indicators of changes in respiratory function when supplemental oxygen is in use.14

Four observational studies support the combined use of continuous capnography and CPOX for the detection of PORD.13,15–17 McCarter et al16 showed that in patients receiving intravenous (IV) patient-controlled analgesia (PCA) opioids, continuous capnography identified a 1.4% (9 of 634) incidence of PORD (defined as respiratory rate <6 per minute, apnea >20 seconds or end-tidal CO2 >50 mm Hg). Of the 9 patients with PORD, all were receiving supplemental oxygen therapy, and all of the PORD events were detected by continuous capnography, and none was detected by CPOX. In 44% (4 of 9) cases of PORD, naloxone was given and the rescue team was activated.16

Overdyk et al13 found that in 178 postsurgical patients receiving IV PCA opioids, continuous capnography identified a 41% incidence of bradypnea (defined as RR <10 × 3 minutes) and CPOX detected a 12% incidence of desaturation (defined as SpO2 < 90%). Of the 15 patients in this study receiving supplemental oxygen, 11 patients had significantly prolonged (3 or more minutes) episodes of bradypnea, while only 4 patients had coincident desaturation events (P = .01).

Similarly, Kopka et al17 demonstrated that in patients receiving IV PCA morphine and supplemental oxygen, transcutaneous CO2 monitoring identified significantly prolonged (average 6.6 hours) hypercarbia (defined as CO2 >45 mm Hg) despite normal oxygen saturation readings.

Finally, Maddox et al15 showed that in a 33-month period, an IV safety system that combined PCA pump and a continuous capnography/pulse oximetry module with preset alarms (HR <50 beats per min or >120 beats per min; SpO2 <90%, RR <10 breaths per min, EtCO2 >60 mm Hg, or apnea >30 seconds) was able to identify 16 patients who required intervention by a respiratory therapist.

Back to Top | Article Outline

DISCUSSION

This systematic review and meta-analysis summarizes the evidence concerning the use of CPOX versus routine nursing care and continuous capnography combined with or without CPOX monitoring for the detection of PORD and/or adverse events. Comparing the CPOX group versus the standard monitoring group, the odds of recognizing desaturation (SpO2<90% >1 hour) with CPOX was 15 times higher (P < .00001) and there was a trend toward less ICU transfer (RR, 0.66; P = .06). The effect of CPOX on rescue team activation and mortality is inconclusive. Pooled data from 3 capnography studies showed that the continuous capnography group identified 8.8% more PORD events versus the pulse oximetry group (CO2 group versus SpO2 group: 11.5% vs 2.8%; P < .00001). The odds of recognizing PORD was almost 6 times higher in the capnography versus the pulse oximetry group (OR: 5.83, 95% CI, 3.54–9.63; P < .00001). No studies examined the impact of continuous capnography on reducing rescue team activation, ICU transfers, or mortality.

Back to Top | Article Outline

CPOX Monitoring

The advantages of CPOX lie in its ability to accurately detect hypoxemia versus routine nursing care, low cost, ease of use, and ease of interpretation. Two observational studies illustrated that periodic spot-checks of vitals every 4–6 hours grossly underestimates postoperative hypoxemia.11,12 Given that acute hypoxemia (and not hypercarbia) is the most serious threat to human life, and that the most important factor for the success of rescue teams is the timely detection of patient deterioration,18 it is important that SpO2 measurements reflect true patient physiology. Early warning scores depend on an accurate assessment of SpO2 to determine whether a rescue team should be activated.19 By providing an accurate SpO2 measurement, CPOX may allow for advance recognition of patient deterioration and prompt activation of rescue teams in surgical ward; however, this hypothesis needs further testing. More evidence from RCTs is important and needed, but may not be necessary for acceptance as a safety practice.20 Pulse oximetry was adopted in the operating room without good evidence that it reduced adverse outcomes but is currently standard of practice because it has compelling benefit without harm.

CPOX has its limitations. First, the evidence is inconclusive on whether CPOX has an impact on clinically relevant outcomes. Ochroch et al9 found that CPOX monitoring per se did not reduce ICU transfer or mortality. Similarly, a Cochrane systematic review examining the use of pulse oximetry during and after surgery found that CPOX is superior at detecting hypoxemia but did not reduce the risk of complications or dying after anesthesia.21 In a closed claims analysis, Lee et al3 found that in one-third of the claims on PORD, CPOX monitoring was in use at the time of the PORD event.

It may be possible that pulse oximetry monitoring without nursing notification is insufficient to detect postoperative cardiopulmonary complications. Electronic patient surveillance systems may provide a qualitatively superior method of continuous monitoring by delivering alert pages to nurses to notify desaturation. Taenzer et al12,22 demonstrated that CPOX monitoring with a centralized alarm warning system reduced rescue events and ICU transfers. Monitoring oxygen saturation with alerts may need to be transmitted in real time to a centralized nurse’s station or to the nurse’s handheld device/pager to proactively alert staff of patient deterioration. The differences in the study results with respect to ICU transfers may also be dependent on the effort of the rescue team to remedy a clinical problem on the floor versus transfer all patients to the ICU immediately. ICU transfer results may be dependent on hospital policy.

Second, oxygen desaturation lags behind hypoventilation and is a late sign of postoperative opioid-induced respiratory depression when supplemental oxygen is administered.23–25 When arterial PCO2 rises secondary to hypoventilation, so does alveolar PCO2, resulting in a fall in alveolar PO2, as per the alveolar gas equation. When patients are breathing room air, oxygen desaturations will occur early and pulse oximetry is a sensitive indicator for hypoventilation. On the contrary, when supplemental oxygen is used, the alveolar PO2 is higher and alveolar PCO2 needs to rise further before hypoxemia and desaturation occurs.26 A mathematical model demonstrates that with a fraction of inspired oxygen (FIO2) of 0.21, by the time alveolar PCO2 has increased to 65 mm Hg, alveolar PO2 will decrease to 60 mm Hg. In contrast, with a FIO2of 0.3, alveolar PO2 is maintained at 100 mm Hg when PaCO2 is 90 mm Hg.23 Oxygen saturation level in the presence of supplemental oxygen imparts late information on the adequacy of ventilation. It provides a false sense of security27 and may delay appropriate respiratory care.28

Back to Top | Article Outline

Continuous Capnography Monitoring

It is important to recognize that oxygenation and ventilation are 2 distinct physiologic processes. SpO2 reflects oxygenation while EtCO2 and RR reflect ventilation; 1 parameter may be normal while the other is abnormal.15 Measuring oxygenation or ventilation alone may not provide a complete picture of respiratory status.

In our systematic review, we found that when continuous capnography monitoring was used in conjunction with CPOX, capnography provided additional information on ventilation that helped herald respiratory depression before oxygen desaturation when supplemental oxygen was administered.13–16 These findings mirror a RCT examining the use of capnography in emergency department procedural sedation.29 Capnography was able to identify respiratory depression before clinical examination and before oxygen desaturation and decreases the rate of sedation-associated hypoxia.7,29 In the pediatric postanesthesia care unit, patients with capnography monitoring had significantly fewer hypopnea and apnea episodes versus routine monitoring with CPOX.30 Together, these studies suggest that continuous capnography should be used in conjunction with pulse oximetry particularly in the presence of supplemental oxygen.25,31 Integrating oxygenation (SpO2, HR) and ventilation (RR, EtCO2) parameters in the form of an index may help identify clinically significant respiratory changes earlier and more reliably.32

In addition to alerting clinicians of patients with impending respiratory failure, respiratory rate had the added benefit of helping nurses individualize pain management regimens.15 Patients with low respiratory rate received less opioids and patients in severe pain with adequate respiratory rate received more. Continuous capnography allowed for better titration of narcotics and improved pain management.15

Table 4

Table 4

Capnography has its limitations. No studies have been published on the effectiveness of capnography on clinically important outcomes (rescue team activation, ICU transfers, or mortality). EtCO2 may not accurately reflect the PaCO2 in nonintubated patients in the setting of low-tidal volume breathing or mouth breathing. End-tidal CO2 reading has been shown to correlate with PaCO2 only on a full vital capacity breath.33 Thus, the EtCO2 value may lie in trend analysis. Transcutaneous capnography, on the other hand, has the advantages of providing an accurate reflection PaCO2.34–36 Capnography may require extra training of staff members before implementation.14 The nasal cannula may impede activities of daily living and may hinder postoperative ambulation.14 In patients with OSA, it is unclear whether accurate readings of end-tidal CO2 can be obtained when a continuous positive airway pressure device is used at the same time.14 Transcutaneous CO2 monitors may need to be resited regularly, erythema can occur, and monitors may require repeated calibration and time to calibrate.37 Implementing continuous monitoring comes with obstacles, and similar to any new technology, monitoring with continuous capnography ± pulse oximetry requires careful risk–benefit analysis (Table 4).

Back to Top | Article Outline

Strengths and Limitations of the Systematic Review

This is the first systematic review to summarize the evidence of the effectiveness of CPOX versus routine nursing care and the effectiveness of continuous capnography with CPOX for detecting PORD and preventing adverse events. The limitations of this review included the variable methodological quality of the studies with low to modest level of evidence. In the CPOX studies, it is not possible to directly attribute oxygen desaturation to respiratory depression. Other than hypoventilation, oxygen desaturation can be caused by decreased FIO2, ventilation-perfusion mismatch, shunt, diffusion defects, and increased O2 consumption. Due to the paucity of evidence, it is difficult to make any strong recommendations regarding best practice with respect to type of monitoring for PORD.

Back to Top | Article Outline

Future Directions

Recognizing the patient at risk for PORD would allow for better triaging of monitoring resources. Multiple patient,1,40–53 surgical,1,3,44,47,48,54,55 and anesthetic3,45,47,55–58 risk factors for respiratory depression have been identified (Supplemental Digital Content, Table 1, http://links.lww.com/AA/C69). Improved education on respiratory depression and monitoring is needed. Predicting patients at risk is challenging and may be inaccurate. At the same time, significant costs are involved with a nation-wide shift to mandatory continuous monitoring for all postoperative patients and even greater costs in installing surveillance systems based on continuous monitoring data. There is a need for further research on whether all patients or only high-risk patients should be monitored, the cost–benefit ratio of monitoring every patient versus high-risk patients, how can we better define high risk, and comparative effectiveness research of monitoring technology on clinically relevant outcomes (rescue team activation, ICU transfer, mortality).

The Joint Commission issued a 2013 sentinel event alert implicating alarm fatigue in 98 adverse events, including 80 deaths.59 To indicate a serious adverse event, alarm criterion based on a single variable is simpler, but may be a less-sensitive alternative.60 Alarm thresholds may have to be customized for specific clinical units, group of patients, or individual patients.61–63 Further research examining which physiologic (or a combination) parameters to monitor and their appropriate alarm limits are needed to find the best balance between sensitivity and specificity, while controlling false alarms.61,64

Patient monitors with smart technology (ie, acoustic respiratory rate monitors,65 noninvasive respiratory volume monitors,66,67 single plate sensing units placed under the mattress to detect a patient’s heart rate, respiratory rate and motion,68,69 alarm management technology that incorporate several physiologic parameters and reduces clinically insignificant respiratory alarms)38,39,69,70 are available or on the horizon. A balance may be needed to find the best technology that is able to detect PORD and other common causes of deterioration postoperatively that require escalation of care.

Back to Top | Article Outline

CONCLUSIONS

Comparing the CPOX group versus the standard monitoring group, the odds of recognizing desaturation (SpO2 <90% >1h) was 15 times higher and there was a trend towards less ICU transfers. The evidence on whether CPOX leads to less rescue team activation and mortality is inconclusive. The odds of recognizing PORD was almost 6 times higher in the capnography versus the pulse oximetry group. No studies examined the impact of continuous capnography on reducing rescue team activation, ICU transfers, or mortality. There is preliminary evidence to support the use of CPOX and capnography in postoperative monitoring to prevent respiratory depression and adverse events. Further research with well-designed, adequately powered RCTs is needed to address the effectiveness of CPOX and capnography monitoring on patient outcomes.

Back to Top | Article Outline

ACKNOWLEDGMENTS

The authors thank Marina Englesakis, BA (Hons), MLIS, Information Specialist, Surgical Divisions, Neuroscience & Medical Education, Health Sciences Library, University Health Network, Toronto, ON, Canada, for her assistance with the literature search.

Back to Top | Article Outline

DISCLOSURES

Name: Thach Lam, MD.

Contribution: This author helped design the study, conduct the study, analyze the data, and write the manuscript.

Conflicts of Interest: None.

Name: Mahesh Nagappa, MD.

Contribution: This author helped design the study, conduct the study, analyze the data, and write the manuscript.

Conflicts of Interest: None.

Name: Jean Wong, MD.

Contribution: This author helped write the manuscript.

Conflicts of Interest: J. Wong received research grants from Ontario Ministry of Health and Long-Term Care Innovation Fund, Anesthesia Patient Safety Foundation, and Acacia Pharma.

Name: Mandeep Singh, MD, MSc.

Contribution: This author helped write the manuscript.

Conflicts of Interest: None.

Name: David Wong, MD.

Contribution: This author helped write the manuscript.

Conflicts of Interest: None.

Name: Frances Chung, MBBS.

Contribution: This author helped design the study, conduct the study, analyze the data, and write the manuscript.

Conflicts of Interest: F. Chung received research grants from Ontario Ministry of Health and Long-Term Care Innovation Fund, University Health Network Foundation, ResMed Foundation, Acacia Pharma, Medtronic; STOP Bang tool: proprietary to University Health Network; Royalties from Up-To-Date.

This manuscript was handled by: David Hillman, MD.

Back to Top | Article Outline

REFERENCES

1. Cauley CE, Anderson G, Haynes AB, Menendez M, Bateman BT, Ladha KPredictors of in-hospital postoperative opioid overdose after major elective operations: a nationally representative cohort study. Ann Surg. 2017;265:702–708.
2. Joint Commission Sentinel Event Alert. Issue Safe use of opioids in hospitals. 2012.49;
3. Lee LA, Caplan RA, Stephens LS, et alPostoperative opioid-induced respiratory depression: a closed claims analysis. Anesthesiology. 2015;122:659–665.
4. Weinger MB, Lee LA“No patient shall be harmed by opioid-induced respiratory depression.” [Proceedings of “essential monitoring strategies to detect clinically significant drug-induced respiratory depression in the postoperative period” Conference]. Anesthesia Patient Safety Foundation Newsletter. 2011;26:21–28.
5. Jarzyna D, Jungquist CR, Pasero C, et alAmerican Society for Pain Management Nursing guidelines on monitoring for opioid-induced sedation and respiratory depression. Pain Manag Nurs. 2011;12:118–145.e10.
6. Whitaker DK, Benson JPCapnography standards for outside the operating room. Curr Opin Anaesthesiol. 2016;29:485–492.
7. Kodali BSCapnography outside the operating rooms. Anesthesiology. 2013;118:192–201.
8. Oxford Center for Evidence-Based Medicine 2011 Levels of Evidence. Available at: http://www.cebm.net/wp-content/uploads/2014/06/CEBM-Levels-of-Evidence-2.1.pdf. Accessed September 12, 2016.
9. Ochroch EA, Russell MW, Hanson WC 3rd, et alThe impact of continuous pulse oximetry monitoring on intensive care unit admissions from a postsurgical care floor. Anesth Analg. 2006;102:868–875.
10. Taenzer AH, Pyke JB, McGrath SP, Blike GTImpact of pulse oximetry surveillance on rescue events and intensive care unit transfers: a before-and-after concurrence study. Anesthesiology. 2010;112:282–287.
11. Sun Z, Sessler DI, Dalton JE, et alPostoperative hypoxemia is common and persistent: a prospective blinded observational study. Anesth Analg. 2015;121:709–715.
12. Taenzer AH, Pyke J, Herrick MD, Dodds TM, McGrath SPA comparison of oxygen saturation data in inpatients with low oxygen saturation using automated continuous monitoring and intermittent manual data charting. Anesth Analg. 2014;118:326–331.
13. Overdyk FJ, Carter R, Maddox RR, Callura J, Herrin AE, Henriquez CContinuous oximetry/capnometry monitoring reveals frequent desaturation and bradypnea during patient-controlled analgesia. Anesth Analg. 2007;105:412–418.
14. Hutchison R, Rodriguez LCapnography and respiratory depression. Am J Nurs. 2008;108:35–39.
15. Maddox RR, Oglesby H, Williams CK, Fields M, Danello SHenriksen K, Battles JB, Keyes MA, Grady MLContinuous respiratory monitoring and a “Smart” infusion system improve safety of patient-controlled analgesia in the postoperative period. Advances in Patient Safety: New Directions and Alternative Approaches Vol 4: Technology and Medication Safety. 2008.Rockville, MD: Agency for Healthcare Research and Quality (US).
16. McCarter T, Shaik Z, Scarfo K, Thompson LJCapnography monitoring enhances safety of postoperative patient-controlled analgesia. Am Health Drug Benefits. 2008;1:28–35.
17. Kopka A, Wallace E, Reilly G, Binning AObservational study of perioperative PtcCO2 and SpO2 in non-ventilated patients receiving epidural infusion or patient-controlled analgesia using a single earlobe monitor (TOSCA). Br J Anaesth. 2007;99:567–571.
18. Calzavacca P, Licari E, Tee A, et alA prospective study of factors influencing the outcome of patients after a Medical Emergency Team review. Intensive Care Med. 2008;34:2112–2116.
19. National Early Warning Score (NEWS) Standardising the assessment of acute-illness severity in the NHS. 2012. Available at: https://www.rcplondon.ac.uk/projects/outputs/national-early-warning-score-news. Accessed August 31, 2016.
20. Stoelting RKContinuous postoperative electronic monitoring and the will to require it. Anesth Analg. 2015;121:579–581.
21. Pedersen T, Nicholson A, Hovhannisyan K, Moller AM, Smith AF, Lewis SRPulse oximetry for perioperative monitoring. Cochrane Database Syst Rev. 2014:CD002013.
22. Taenzer AH, Blike GTPostoperative monitoring—The Dartmouth experience. Anesthesia Patient Safety Foundation Newsletter. 2012;27:1–28.
23. Fu ES, Downs JB, Schweiger JW, Miguel RV, Smith RASupplemental oxygen impairs detection of hypoventilation by pulse oximetry. Chest. 2004;126:1552–1558.
24. Niesters M, Mahajan RP, Aarts L, Dahan AHigh-inspired oxygen concentration further impairs opioid-induced respiratory depression. Br J Anaesth. 2013;110:837–841.
25. Liao P, Wong J, Singh M, et alPostoperative oxygen therapy in patients with OSA: a randomized controlled trial. Chest. 2017;151:597–611.
26. Hutton P, Clutton-Brock TThe benefits and pitfalls of pulse oximetry. BMJ. 1993;307:457–458.
27. Davidson JA, Hosie HELimitations of pulse oximetry: respiratory insufficiency–a failure of detection. BMJ. 1993;307:372–373.
28. Downs JBHas oxygen administration delayed appropriate respiratory care? Fallacies regarding oxygen therapy. Respir Care. 2003;48:611–620.
29. Deitch K, Miner J, Chudnofsky CR, Dominici P, Latta DDoes end tidal CO2 monitoring during emergency department procedural sedation and analgesia with propofol decrease the incidence of hypoxic events? A randomized, controlled trial. Ann Emerg Med. 2010;55:258–264.
30. Langhan ML, Li FY, Lichtor JLThe impact of capnography monitoring among children and adolescents in the postanesthesia care unit: a randomized controlled trial. Paediatr Anaesth. 2017;27:385–393.
31. Aarrestad S, Tollefsen E, Kleiven AL, Qvarfort M, Janssens JP, Skjønsberg OHValidity of transcutaneous PCO2 in monitoring chronic hypoventilation treated with non-invasive ventilation. Respir Med. 2016;112:112–118.
32. Ronen M, Weissbrod R, Overdyk FJ, Ajizian SSmart respiratory monitoring: clinical development and validation of the IPI™ (Integrated Pulmonary Index) algorithm. J Clin Monit Comput. 2017;31:435–442.
33. Takano Y, Sakamoto O, Kiyofuji C, Ito KA comparison of the end-tidal CO2 measured by portable capnometer and the arterial PCO2 in spontaneously breathing patients. Respir Med. 2003;97:476–481.
34. Tobias JD, Meyer DJNoninvasive monitoring of carbon dioxide during respiratory failure in toddlers and infants: end-tidal versus transcutaneous carbon dioxide. Anesth Analg. 1997;85:55–58.
35. Nicolini A, Ferrari MBEvaluation of a transcutaneous carbon dioxide monitor in patients with acute respiratory failure. Ann Thorac Med. 2011;6:217–220.
36. Bendjelid K, Schütz N, Stotz M, Gerard I, Suter PM, Romand JATranscutaneous PCO2 monitoring in critically ill adults: clinical evaluation of a new sensor. Crit Care Med. 2005;33:2203–2206.
37. Eberhard PThe design, use, and results of transcutaneous carbon dioxide analysis: current and future directions. Anesth Analg. 2007;105:S48–S52.
38. Maddox RR, Williams CKClinical experience with capnography monitoring for PCA patients. Anesthesia Patient Safety Foundation Newsletter. 2012;26:47–50.
39. Voepel-Lewis T, Parker ML, Burke CN, et alPulse oximetry desaturation alarms on a general postoperative adult unit: a prospective observational study of nurse response time. Int J Nurs Stud. 2013;50:1351–1358.
40. Chung F, Liao P, Yegneswaran B, Shapiro CM, Kang WPostoperative changes in sleep-disordered breathing and sleep architecture in patients with obstructive sleep apnea. Anesthesiology. 2014;120:287–298.
41. Chung F, Liao P, Yang Y, et alPostoperative sleep-disordered breathing in patients without preoperative sleep apnea. Anesth Analg. 2015;120:1214–1224.
42. Opperer M, Cozowicz C, Bugada D, et alDoes obstructive sleep apnea influence perioperative outcome? A qualitative systematic review for the Society of Anesthesia and Sleep Medicine Task Force on Preoperative Preparation of Patients with Sleep-Disordered Breathing. Anesth Analg. 2016;122:1321–1334.
43. Chung F, Memtsoudis SG, Ramachandran SK, et alSociety of Anesthesia and Sleep Medicine Guidelines on Preoperative Screening and Assessment of Adult Patients With Obstructive Sleep Apnea. Anesth Analg. 2016;123:452–473.
44. Taylor S, Kirton OC, Staff I, Kozol RAPostoperative day one: a high risk period for respiratory events. Am J Surg. 2005;190:752–756.
45. Etches RCRespiratory depression associated with patient-controlled analgesia: a review of eight cases. Can J Anaesth. 1994;41:125–132.
46. Khelemsky Y, Kothari R, Campbell N, Farnad SIncidence and demographics of post-operative naloxone administration: a 13-year experience at a major tertiary teaching institution. Pain Physician. 2015;18:E827–E829.
47. Gordon DB, Pellino TAIncidence and characteristics of naloxone use in postoperative pain management: a critical examination of naloxone use as a potential quality measure. Pain Manag Nurs. 2005;6:30–36.
48. Ramachandran SK, Haider N, Saran KA, et alLife-threatening critical respiratory events: a retrospective study of postoperative patients found unresponsive during analgesic therapy. J Clin Anesth. 2011;23:207–213.
49. Niesters M, Overdyk F, Smith T, Aarts L, Dahan AOpioid-induced respiratory depression in paediatrics: a review of case reports. Br J Anaesth. 2013;110:175–182.
50. Dean MOpioids in renal failure and dialysis patients. J Pain Symptom Manage. 2004;28:497–504.
51. Overdyk F, Dahan A, Roozekrans M, van der Schrier R, Aarts L, Niesters MOpioid-induced respiratory depression in the acute care setting: a compendium of case reports. Pain Manag. 2014;4:317–325.
52. Gasche Y, Daali Y, Fathi M, et alCodeine intoxication associated with ultrarapid CYP2D6 metabolism. N Engl J Med. 2004;351:2827–2831.
53. Niesters M, Dahan A, Kest B, et alDo sex differences exist in opioid analgesia? A systematic review and meta-analysis of human experimental and clinical studies. Pain. 2010;151:61–68.
54. Weingarten TN, Warner LL, Sprung JTiming of postoperative respiratory emergencies: when do they really occur? Curr Opin Anaesthesiol. 2017;30:156–162.
55. Rosenfeld DM, Betcher JA, Shah RA, et alFindings of a naloxone database and its utilization to improve safety and education in a tertiary care medical center. Pain Pract. 2016;16:327–333.
56. Weingarten TN, Herasevich V, McGlinch MC, et alPredictors of delayed postoperative respiratory depression assessed from naloxone administration. Anesth Analg. 2015;121:422–429.
57. Weingarten TN, Jacob AK, Njathi CW, Wilson GA, Sprung JMultimodal analgesic protocol and postanesthesia respiratory depression during phase I recovery after total joint arthroplasty. Reg Anesth Pain Med. 2015;40:330–336.
58. Correa D, Farney RJ, Chung F, Prasad A, Lam D, Wong JChronic opioid use and central sleep apnea: a review of the prevalence, mechanisms, and perioperative considerations. Anesth Analg. 2015;120:1273–1285.
59. Medical device alarm safety in hospitals. Joint Commission Sentinel Event Alert. 2013:1–3.
60. Bein B, Seewald S, Gräsner JTHow to avoid catastrophic events on the ward. Best Pract Res Clin Anaesthesiol. 2016;30:237–245.
61. Curry JP, Lynn LLThreshold monitoring, alarm fatigue, and the patterns of unexpected hospital death. Anesthesia Patient Safety Foundation Newsletter. 2011;26:32–35.
62. Graham KC, Cvach MMonitor alarm fatigue: standardizing use of physiological monitors and decreasing nuisance alarms. Am J Crit Care. 2010;19:28–34.
63. Curry JP, Jungquist CRA critical assessment of monitoring practices, patient deterioration, and alarm fatigue on inpatient wards: a review. Patient Saf Surg. 2014;8:29.
64. Taenzer AH, Pyke JB, McGrath SPA review of current and emerging approaches to address failure-to-rescue. Anesthesiology. 2011;115:421–431.
65. McGrath SP, Pyke J, Taenzer AHAssessment of continuous acoustic respiratory rate monitoring as an addition to a pulse oximetry-based patient surveillance system. J Clin Monit Comput. 2017;31:561–569.
66. Williams GW 2nd, George CA, Harvey BC, Freeman JEA comparison of measurements of change in respiratory status in spontaneously breathing volunteers by the ExSpiron noninvasive respiratory volume monitor versus the Capnostream capnometer. Anesth Analg. 2017;124:120–126.
67. Galvagno SM Jr, Duke PG, Eversole DS, George EEEvaluation of respiratory volume monitoring (RVM) to detect respiratory compromise in advance of pulse oximetry and help minimize false desaturation alarms. J Trauma Acute Care Surg. 2016;81(5 Suppl 2 Proceedings of the 2015 Military Health System Research Symposium):S162–S170.
68. Slight SP, Franz C, Olugbile M, Brown HV, Bates DW, Zimlichman EThe return on investment of implementing a continuous monitoring system in general medical-surgical units. Crit Care Med. 2014;42:1862–1868.
69. Brown H, Terrence J, Vasquez P, Bates DW, Zimlichman EContinuous monitoring in an inpatient medical-surgical unit: a controlled clinical trial. Am J Med. 2014;127:226–232.
70. Chung F, Liao P, Elsaid H, Shapiro CM, Kang WFactors associated with postoperative exacerbation of sleep-disordered breathing. Anesthesiology. 2014;120:299–311.

Supplemental Digital Content

Back to Top | Article Outline
© 2017 International Anesthesia Research Society