Capnography sensor use is associated with reduction of adverse outcomes during gastrointestinal endoscopic procedures with sedation administration

Gastrointestinal endoscopic procedures (GEP) such as esophagogastroduodenoscopy (EGD), endoscopic retrograde cholangiopancreatography (ERCP), and colonoscopy are standard procedures for the diagnosis and therapy of gastrointestinal disorders, but can be associated with patient discomfort. To improve patient comfort, the use of sedation in these procedures is common. However, the use of sedative agents can result in drug-induced airway obstruction, respiratory depression with hypoventilation, and hypoxemia [1‐6]. Cardiopulmonary adverse events remain a leading cause of morbidity and mortality during GEP with procedural sedation [3‐6].

Given these concerns and potential sequelae, patient monitoring guidelines for procedural sedation have typically recommended continuous pulse oximetry combined with visual assessment of a patient’s breathing pattern [7, 8]. Despite the value of these assessments, monitoring of arterial oxygen saturation (SaO₂) via pulse oximetry does not necessarily provide a satisfactory assessment of the adequacy of ventilation. Importantly, significant alveolar hypoventilation can occur in the presence of normal SaO₂ as shown by pulse oximetry (SpO₂) and inadequate ventilation can precede hypoxemia by several minutes [1, 9, 10]. The risks of procedural sedation are further compounded by the fact that GEP with sedation administration are often conducted without an anesthesia provider present and the delivery of care is performed in a remote hospital location rather than within the primary operating room suite [11].

Given these potential limitations of pulse oximetry and the recognized need for improved patient monitoring during GEP with sedation administration, the use of capnography to monitor end-tidal carbon dioxide (ETCO₂) is increasingly common [1, 12‐14]. Sidestream and mainstream capnography, by continuously monitoring ETCO₂ levels, respiratory rate, and waveform pattern, allow for the near real-time assessment of ventilation in spontaneously breathing patients and provide a more complete assessment of the adequacy of ventilation than either SpO₂ or visual inspection of breathing [9, 15‐17]. As such, capnography has been clinically demonstrated to provide an earlier indicator of respiratory distress than SpO₂ alone [9, 13]. Several studies have shown that the addition of capnography monitoring during GEP with procedural sedation results in a significant reduction in the incidence of hypoxemia [1, 12‐14].

While published evidence to date suggests that capnography monitoring during GEP reduces the incidence of hypoxemia, the association of capnography monitoring with incidence of adverse outcomes when these procedures are performed with sedation has been insufficiently studied. Thus, the aims of this analysis were to estimate the incidence of pharmacological rescue events and death as assessed upon discharge from an inpatient or outpatient hospitalization during which GEP was performed with sedation, separately, for matched patients with and without capnography monitoring using an administrative database.

The results of this large database analysis indicate that the use of capnography was associated with a 47% estimated reduction in the odds of death for the matched inpatient population and a 61% estimated reduction in the odds of pharmacological rescue event for the matched outpatient population. For the matched inpatient population, the use of capnography was associated with a reduction in both mortality and pharmacologic rescue rates, though reduction in pharmacologic rescue rates was not statistically significant. The reason for close rates of pharmacologic rescue in the inpatient setting may be explained by several factors. First, patients with more monitors may be more closely watched by attending clinicians, who may check both alarms and patients. Second, in the inpatient setting, resuscitation may proceed immediately to mask bag ventilation or endotracheal intubation instead of reliance on pharmacologic reversal agents, whereas in the outpatient setting where anesthesia personnel may be limited, pharmacologic reversal may be preferred to primary airway control. Lastly, the fact that the outpatient group demonstrated a reduction in pharmacologic rescue but not death rates may be related to patient flow in the outpatient setting. If a patient’s condition declines significantly, they are likely to be admitted to hospital well before death occurs; thus, it is not surprising that mortality is rarely seen in the outpatient setting. However, inpatient admissions from the outpatient setting are not reliably retrievable from this retrospective database, so this analysis is not presented here. Regardless, to our knowledge, these data provide the first evidence that capnography use during GEP with procedural sedation is associated with a reduction in the odds of these adverse outcomes.

Procedural sedation can result in loss of protective pharyngeal airway reflexes, upper airway obstruction, central respiratory depression, alveolar hypoventilation, atelectasis, hypercapnia and hypoxemia [21]. Cardiopulmonary adverse events remain a leading cause of morbidity and mortality with GEP [3‐6]. In a study of 21,011 procedures using midazolam and/or diazepam, Arrowsmith et al. reported serious cardiopulmonary complications in 5.4 per 1000 procedures [4]. Similarly, in a database analysis of over 300,000 endoscopic procedures with sedation, Sharma et al. reported an incidence of 9.3 cardiopulmonary adverse events per 1000 procedures [6]. These authors also noted that the presence of the endoscope across the upper airway along with a depressed respiratory drive due to the sedative medications in combination with the inability to accurately assess ventilation using pulse oximetry can result in undetected hypoventilation and a higher incidence of cardiopulmonary adverse events [6]. Importantly, the risks of GEP adverse events exceed those typically reported for general anesthesia procedures performed outside the operating room [11].

Given these risks of procedural sedation and the fact that sedation levels during GEP often approach those of general anesthesia, [2] adequate patient monitoring is critical, especially with these types of procedures often conducted by non-anesthesiologists outside of the operating room, where personnel and equipment availability can limit effective response to acute deterioration. In fact, in an analysis of 63,000 patients undergoing diagnostic or therapeutic procedures under sedation or anesthesia, over 40% of patients were sedated by non-anesthesia providers and 12.4% of the anesthesiology cases were performed outside of the operating room [22].

Historically, patient monitoring during GEP has focused on pulse oximetry in combination with vital sign monitoring and visual inspection of ventilation [7, 8]. Unfortunately, as noted above, monitoring arterial oxygen saturation via pulse oximetry, especially in patients receiving supplemental oxygen therapy, is inadequate for effectively detecting the onset of hypoventilation [1, 9, 10, 23]. Importantly, several closed claims analyses have indicated that the application of better monitoring, including capnography, could have prevented nearly half of claims associated with oversedation [11, 24]. To date, a number of studies have indicated that the addition of capnography to standard monitoring provides superior detection of respiratory depression during procedural sedation [10, 12, 13, 25‐27]. These data and others have led to the recent recognition of capnography as a critical component of adequate patient monitoring during moderate or deep sedation by the American Society of Anesthesiologists (ASA) [28]. In addition, several recent cost-benefit analyses support the use of capnography [29, 30]. Despite the apparent clinical and economic benefits of capnography and support by the ASA and other governing bodies, the use of capnography in these types of procedures remains relatively low.

The results of our analysis indicate that the use of capnography during GEP with procedural sedation is associated with significant reductions in the risk of pharmacological rescue events in outpatients and death in inpatients. Despite the limitations of this retrospective data-based study, we believe the use of capnography during GEP performed with sedation should be recommended.