Erin Cooke

Usability and performance characteristics of the pediatric air-Q® intubating laryngeal airway

PurposeThe air-Q® intubating laryngeal airway (ILA) is a supraglottic device (SGD) designed specifically to function as both a primary airway and a bridging device and conduit for fibreoptic intubation in difficult airway scenarios. This observational study evaluated the usability and performance characteristics of pediatric air-Q ILA sizes 1.0, 1.5, 2.0, and 2.5 when used as a primary airway.MethodsOne hundred ten children, American Society of Anesthesiologists physical status I-III and undergoing elective surgery, received a weight-appropriate air-Q ILA following induction of anesthesia. The evaluation criteria included ease of insertion, quality of ventilation, presence of gastric insufflation, oropharyngeal leak pressures (OLPs) and maximum tidal volumes (VT max) in five different head positions, and fibreoptic view of the glottis.ResultsFor sizes 1.0, 1.5, 2.0, and 2.5, the median [P25,P75] neutral OLPs (cm H2O) were 23.0 [20.0,30.0], 16.5 [15.0,20.8], 14.0 [10.0,17.8], and 14.0 [11.3,16.8], respectively. The median [P25,P75] neutral VT max values (mL·kg−1) were 17.4 [14.3,19.7], 20.3 [16.8,25.5], 17.8 [14.5,22.1], and 14.0 [11.6,16.0], respectively. Median [P25,P75] ease of insertion scores (0-10; 0 = easiest ever, 10 = most difficult ever) were 1 [1,2], 2 [2,3], 2 [1,2.8], and 2 [2,3] respectively. Ventilation was adequate in 108/110 cases, and a fibreoptic view of the vocal cords was obtained in 102/110 cases.ConclusionsThe air-Q ILA functions acceptably as a primary SGD in infants and children. The OLPs are lower than published values for the ProSeal laryngeal mask airway (LMA ProSeal™), the current pediatric SGD of choice, but adequate tidal volumes are readily achievable. The fibreoptic views of the glottis portend well for fibreoptic intubation through the device. (This trial was registered at clinicaltrials.gov number, NCT00885911).RésuméObjectifLe masque laryngé d’intubation air-Q® est un dispositif supraglottique (DSG) conçu spécialement pour fonctionner aussi bien seul comme instrument de gestion des voies aériennes que comme pont et guide d’intubation fibroscopique en cas de voies aériennes difficiles. Cette étude observationnelle a évalué les caractéristiques de convivialité et de performance du masque laryngé air-Q de tailles 1,0, 1,5, 2,0 et 2,5 utilisé seul.MéthodeAprès l’induction de l’anesthésie, on a inséré un masque laryngé d’intubation air-Q adapté au poids chez 110 enfants de statut physique I-III selon la classification de l’American Society of Anesthesiologists devant subir une chirurgie non urgente. Les critères d’évaluation comprenaient la facilité d’insertion, la qualité de la ventilation, la présence d’insufflation gastrique, les pressions de fuite oropharyngée (OLP) et les volumes courants maximaux (VT max) dans cinq positions différentes de la tête, ainsi que la vue fibroscopique de la glotte.RésultatsPour les tailles 1,0, 1,5, 2,0, et 2,5, les OLP neutres médianes [P25,P75] (cm H2O) étaient de 23,0 [20,0,30,0], 16,5 [15,0,20,8], 14,0 [10,0,17,8], et 14,0 [11,3,16,8], respectivement. Les valeurs VT maximales neutres médianes [P25,P75] (mL·kg−1) étaient de 17,4 [14,3,19,7], 20,3 [16,8,25,7], 17,8 [14,5,22,1], et 14,0 [11,6,16,0], respectivement. Les scores médians [P25,P75] de facilité d’insertion (0-10; 0 = le plus facile, 10 = le plus difficile) étaient de 1 [1,2], 2 [2,3], 2 [1,2.8], et 2 [2,3] respectivement. La ventilation était adéquate dans 108/110 cas, et une vue fibroscopique des cordes vocales a été obtenue dans 102/110 cas.ConclusionLe fonctionnement du masque laryngé d’intubation air-Q est acceptable utilisé seul chez les nourrissons et les enfants. Les OLP sont plus basses que les valeurs publiées pour le masque laryngé ProSeal (LMA ProSeal™), le DSG actuellement privilégié en pédiatrie, mais on peut facilement atteindre des volumes courants adéquats. Les vues fibroscopiques de la glotte laissent présager une bonne intubation fibroscopique via le dispositif. (Cette étude a été enregistrée au numéro ClinicalTrials.gov NCT00885911).

Changes in cardiac index and blood pressure on positioning children prone for scoliosis surgery

In this prospective observational study we investigated the changes in cardiac index and mean arterial pressure in children when positioned prone for scoliosis correction surgery. Thirty children (ASA 1–2, aged 13–18 years) undergoing primary, idiopathic scoliosis repair were recruited. The cardiac index and mean arterial blood pressure (median (IQR [range])) were 2.7 (2.3–3.1 [1.4–3.7]) l.min−1.m−2 and 73 (66–80 [54–91]) mmHg, respectively, at baseline; 2.9 (2.5–3.2 [1.7–4.4]) l.min−1.m−2 and 73 (63–81 [51–96]) mmHg following a 5‐ml.kg−1 fluid bolus; and 2.5 (2.2–2.7 [1.4–4.8]) l.min−1.m−2 and 69 (62–73 [46–85]) mmHg immediately after turning prone. Turning prone resulted in a median reduction in cardiac index of 0.5 l.min−1.m−2 (95% CI 0.3–0.7 l.min−1.m−2, p = 0.001), or 18.5%, with a large degree of inter‐subject variability (+ 10.3% to − 40.9%). The changes in mean arterial blood pressure were not significant. Strategies to predict, prevent and treat decreases in cardiac index need to be developed.

Respiratory rate estimation using respiratory sinus arrhythmia from photoplethysmography

Respiratory rate (RR) is an important measurement for ambulatory care and there is high interest in its detection using unobtrusive mobile devices. For this study, we investigated the estimation of RR from a photoplethysmography (PPG) signal that originated from a pulse oximeter sensor and had a sub-optimal sampling rate. We explored the possibility of estimating RR by extracting respiratory sinus arrhythmia (RSA) from the PPG-derived heart rate variability (HRV) measurement using real-time algorithms. Data from 29 children and 13 adults undergoing general anesthesia were analyzed. We compared the RSA power derived from electrocardiography (ECG) with PPG at the reference RR derived from capnography. The power of the PPG was significantly higher than that of the ECG (182.42 ± 36.75 dB vs. 162.30 ± 43.66 dB). Further, the mean RR error for PPG was lower than ECG. Both PPG and ECG RR estimation techniques were more powerful and reliable in cases of spontaneous ventilation than when pressure controlled ventilation was used. The analysis of cases containing artifacts in the PPG revealed a significant increase in RR error, a trend that was less pronounced for controlled ventilation. These results indicate that the estimation of RR from the sub-optimally sampled PPG signal is possible and more reliable than from the ECG.

Wavelet transform cardiorespiratory coherence detects patient movement during general anesthesia

Heart rate variability (HRV) may provide anesthesiologists with a noninvasive tool for monitoring nociception during general anesthesia. A novel wavelet transform cardiores-piratory coherence (WTCRC) algorithm has been developed to calculate estimates of the linear coupling between heart rate and respiration. WTCRC values range from 1 (high coherence, no nociception) to 0 (low coherence, strong nociception). We have assessed the algorithms ability to detect movement events (indicative of patient response to nociception) in 39 pediatric patients receiving general anesthesia. Sixty movement events were recorded during the 39 surgical procedures. Minimum and average WTCRC were calculated in a 30 second window surrounding each movement event. We used a 95% significance level as the threshold for detecting nociception during patient movement. The 95% significance level was calculated relative to a red noise background, using Monte Carlo simulations. It was calculated to be 0.7. Values below this threshold were treated as successful detection. The algorithm was found to detect movement with sensitivity ranging from 95% (minimum WTCRC) to 65% (average WTCRC). The WTCRC algorithm thus shows promise for noninvasively monitoring nociception during general anesthesia, using only heart rate and respiration.

Oral morphine dosing predictions based on single dose in healthy children undergoing surgery

Oral morphine has been proposed as an effective and safe alternative to codeine for after‐discharge pain in children following surgery but there are few data guiding an optimum safe oral dose.

Real-time cardiorespiratory coherence detects antinociception during general anesthesia

Heart rate variability (HRV) may provide anesthesiologists with a noninvasive tool for monitoring nociception during general anesthesia. A novel real-time cardiorespiratory coherence (CRC) algorithm has been developed to analyze the strength of linear coupling between heart rate (HR) and respiration. CRC values range from 0 (low coherence, strong nociception) to 1 (high coherence, no nociception). The algorithm uses specially designed filters to operate in real-time, minimizing computational complexity and time delay. In the standard HRV high frequency band of 0.15 - 0.4 Hz, the real-time delay is only 5.25 - 3.25 s. We have assessed the algorithms response to 60 anesthetic bolus events (a large dose of anesthetics given over a short time; strongly antinociceptive) recorded in 47 pediatric patients receiving general anesthesia. Real-time CRC responded strongly to bolus events, changing by an average of 30%. For comparison, three traditional measures of HRV (LF/HF ratio, SDNN, and RMSSD) responded on average by only 3.8%, 14%, and 3.9%, respectively. Finally, two traditional clinical measures of nociception (HR and blood pressure) responded on average by only 3.9% and 0.91%, respectively. CRC may thus be used as a real-time nociception monitor during general anesthesia.

Measuring Adequacy of Analgesia with Cardiorespiratory Coherence

8 Measuring adeQuacy of analgesia with cardiorespiratory coherence Chris Brouse, Walter Karlen, Guy Dumont, Dorothy Myers, Erin Cooke, Jonathan Stinson, Joanne Lim, J. Mark Ansermino The University of British Columbia, Vancouver, Canada Introduction: An automated nociception monitor would be very useful in general anesthesia, providing anesthesiologists with real-time feedback about the adequacy of analgesia. We have developed an algorithm to measure nociception using respiratory sinus arrhythmia (RSA) in heart rate variability (HRV). We have previously shown that this algorithm can detect patient movement (strongly nociceptive events) during general anesthesia 1. We will now attempt to determine if the algorithm responds to boluses of anesthetic drugs (strongly anti-nociceptive events). Method: Algorithm: The algorithm estimates cardiorespiratory coherence, which is the strength of linear coupling between HR and respiration (one measure of RSA). It measures and combines the spectral power in both signals using wavelet analysis. Coherence is dimensionless, and ranges from 0 (no coherence, strong nociception) to 1 (perfect coherence, no nociception). Data Analysis: Following ethics approval and informed consent, 60 drug bolus events (excluding induction of anesthesia) were recorded in 47 pediatric patients receiving general anesthesia during dental surgery. In post hoc analysis, coherence was averaged over the 60s immediately preceding the bolus dose of drug (nociceptive period). The bolus was given 30s to take effect, after which the coherence was averaged over the following 60s (anti-nociceptive period). The change in average coherence between the two periods was calculated. The change in average HR was also calculated, for comparison. Results: Coherence increased by an average of 0.14 (32%) in response to the bolus dose of anesthetic drug. HR decreased by an average of 4.1 beats/min (3.9%). Discussion: Cardiorespiratory coherence responded much more strongly to the anesthetic boluses than did HR alone. This result, combined with previous work showing that coherence is low during periods of nociception [1], demonstrates that cardiorespiratory coherence can be used to measure the adequacy of analgesia during general anesthesia. We are currently adapting the algorithm so that it can be used in real-time.

Real-time cardiorespiratory coherence is blind to changes in respiration during general anesthesia

Purpose. A novel real-time cardiorespiratory coherence (CRC) algorithm has been developed to monitor nociception during general anesthesia. CRC uses custom designed filters to track and analyze the respiratory sinus arrhythmia (RSA) as it moves in time and frequency. CRC is a form of sensor fusion between heart rate and respiration, estimating the strength of linear coupling between the two signals. The aim of this study was to estimate the effect of changes in respiration rate (RR) and peak airway pressure (PPaw) on CRC. The response of CRC was compared to a prior offline wavelet-based algorithm (WTCRC) as well as traditional univariate heart rate variability (HRV) measures. A nociception index was created for each algorithm, ranging from 0 (no nociception) to 100 (strong nociception).