Detecting Post-Operative Respiratory Depression in Children

Study Site: Children will be enrolled in the post-anesthesia care unit (PACU) at Yale-New Haven Children's Hospital, where capnography is not currently utilized. The pediatric PACU is a 12-bed monitored unit and a 4-bed perioperative area where patients receive one-on-one nursing care. Generally, between 20-30 patients are cared for in the PACU each day with a typical length of stay of approximately 2 hours.

Specific Aim 1b: To determine whether the addition of capnography will lead to a decrease in the frequency of oxygen desaturations as measured by pulse oximetry and respiratory depression in children recovering from general anesthesia.

Study Design and Setting: The investigators will conduct a randomized controlled trial in the Yale-New Haven Children's PACU.

The identical population, inclusion and exclusion criteria and recruitment procedures will apply. A random number list will again be generated to guide recruitment. Investigators will be blinded to group designation prior to consent and enrollment.

Study Intervention and Data Collection: Prior to the onset of this study, PACU nursing staff will receive focused training on the application and interpretation of capnography. Proper positioning of the nasal-oral cannula will be demonstrated. Capnography waveforms will be reviewed including normal respiratory patterns and end-tidal CO2 (ETCO2) levels that would indicate hypoventilation, apnea or obstruction. Staff will be instructed that they can provide interventions when ETCO2 values greater than 50mmHg or less than 30mmHg are obtained without a concomitant increase in respiratory rate. Simple noninvasive interventions may include reposition of the head, instructing the patient to take several deep breaths, physical stimulation, or placing a shoulder roll under the patient. Invasive interventions may include administration of reversal medications, bag-valve mask assisted ventilation, the insertion of an oral or nasal airway and endotracheal intubation. Patients who develop oxygen saturations less than 93% may receive an increased amount of supplemental oxygen at the discretion of the treating staff.

Patients will undergo routine care and monitoring while in the PACU. As part of this study, a duo-port nasal-oral cannula for ETCO2 monitoring will be placed in the nostrils and over the lip of the patient prior to transfer from the operating room to the PACU (Filterline Smart CapnoLine Plus) and attached to the portable capnography monitor (Capnostream 20 Bedside Capnography Monitor by Oridion). Subjects will be randomized into 2 groups: those in whom the responsible nurse and physician are blinded to the capnography monitor (controls), and those in whom the capnography monitor is viewed by treating staff during the recovery period (cases). The investigators control group represents the current standard of care for PACU monitoring. Stratified block randomization will take place. Patients will be stratified by type of surgery: otolaryngology (ENT) or non-ENT. The randomization sequence will be placed in sequentially numbered opaque envelopes for each stratum. Although each patient and his/her family will consent to the study prior to surgery, they will not be officially enrolled until the patient demonstrates that he/she can tolerate the nasal-oral cannula upon arrival to the PACU. Thus, when an enrolled subject arrives to the PACU and is successfully tolerating the nasal-oral cannula the study envelope containing their group designation will be opened by the research assistant (RA) or principal investigator (PI) for this study and data collection will commence. All staff will be blinded to group designation until this time.

For the case subjects, alarm settings will be programmed on the monitor to alert the provider to ETCO2 levels below 30mmHg and above 50mmHg. The monitor will be positioned where it can be easily viewed by both the treating staff and the RA/PI for this study. For control subjects, the portable capnography monitor will be positioned by the PI or RA and out of the line of sight of other treating staff. The alarm function will be turned off so as not to alert staff to abnormal readings on the monitor. Since the investigators are not mandating that staff intervene for abnormal ETCO2 values, the RA or PI will be the only participant to view the capnography monitor in the control group and will not inform the treating staff of any abnormal values under 2 minutes in length. The Yale Human Investigations committee was consulted regarding the ethics of withholding information from the control arm of this study and approves this decision. Instances where the PI or RA had to notify staff of events will be recorded on the data form.

Methodology: For the purposes of this randomized controlled trial, heart rate, respiratory rate, and oxygen saturation will be routinely monitored and recorded on a data sheet every 30 seconds while the patient is in the PACU by the PI or RA who will not otherwise be involved in patient care. ETCO2 values are recorded by the capnography monitor every 30 seconds and waveforms are continuously captured. These data will be downloaded from the capnography monitor at the time of discharge for each patient. Adverse respiratory events as well as nurse and physician interventions related to airway and ventilatory management will be documented by the PI/RA. These were described previously. Additional pain or sedative medications may be administered by nursing staff and will be recorded during this study. Patient disposition and total length of stay in the PACU will be recorded.

The investigators primary outcome will be frequency of The investigators previously defined respiratory events that occur with and without the use of capnography.

Sample size calculations: While the investigators will refine their sample size based on event rates found in the first cohort of this proposal, the investigators plan to enroll at least 200 children in this pilot study in order to detect a 30% reduction in adverse event rates.

Statistical Analysis: Variable distributions will first be examined with descriptive statistics, including box-plots and histograms. Any missing data due to artifact or equipment malfunction will be explored for each group. The investigators will describe the two groups of patients, those with blinded capnography readings vs. those without, in terms of their age, gender, ethnicity, type of condition for which sedation was required, and physician performing procedure. The investigators will use Student's t-test for continuous variables and chi-square/Fisher's exact test for categorical variables. Statistically significant (p < 0.05) or clinically meaningful differences (10%) between two randomized groups will be added to the multivariate analysis of the primary outcome. Groups will then be analyzed by strata - patients receiving ENT procedures and those receiving other non-ENT procedures.

The primary outcomes, airway or respiratory adverse events, will be summarized by group in terms of the number and percent of patients in each group who experience these outcomes. Generalized estimating equation (GEE) approach will be used to model the probability of an outcome (two separate models for each outcome of interest) with the randomization group (blinded vs. not to capnography readings) as the main independent predictor. The investigators will adjust the model with other important predictors, especially the ones that were different between the two groups. Odds ratios (OR) and surrounding confidence intervals will be reported for each predictor. The investigators can use the adjusted OR for the group variable to calculate relative risk (RR).37 Significance will be established with a two-tailed alpha=0.05. The investigators will use this data to obtain funding for a larger, randomized trial which will also include cost-effectiveness analyses.