Tidal Volume Delivery during the Anesthetic Management of Neonates Is Variable

Ventilation in pediatric anesthesia: A French multicenter prospective observational study (PEDIAVENT)

INTRODUCTION

Protective ventilation is now a standard of care in adults. However, management of ventilation is heterogeneous in children and little is known regarding the mechanical ventilation parameters actually used during pediatric anesthesia.

AIM

The aim of the study was to assess current ventilatory practices during pediatric anesthesia in France and to compare them with pediatric experts' statements, with a specific focus on tidal volume.

PATIENTS AND METHODS

We conducted a prospective multicenter observational study, regarding the ventilatory management and the mechanical ventilation parameters, over two days (21 and 22 June 2017) in 29 pediatric centers in France. All children undergoing general anesthesia during these 2 days were eligible; those who required extracorporeal circulation or one-lung ventilation were excluded.

RESULTS

A total of 701 children were included; median [IQR] age was 60 [24-120] months. Among the patients in whom controlled ventilation was used, 254/515 (49.3%) had an expired tidal volume >8 mL/kg and 44 children (8.8%) an expired tidal volume ≥10 mL/kg. Lower weight and use of a supraglottic airway device were significantly associated with provision of a tidal volume ≥10 mL/kg (odds ratio 0.94, 95% confidence interval [0.92; 0.97], P < .001 and 2.28 [1.20; 4.31], P = .012, respectively). The positive end-expiratory pressure was set at a median [IQR] of 4 [3-5] cmH₂ O; it was <3 cmH₂ O in 15.7% of children and not used in 56/499 (9.3%). Among intubated children, 57 (18.3%) received a tidal volume < 10 mL/kg with a positive end-expiratory pressure ≥3 cmH₂ O in association with recruitment maneuvers.

CONCLUSIONS

Ventilatory practices in children were heterogenous, and a large proportion of children were not ventilated as it is currently recommended by some experts.

Volume-targeted ventilation with a Fabian ventilator: maintenance of tidal volumes and blood CO2

OBJECTIVE

To analyse the performance of the Fabian +NCPAP evolution ventilator during volume guarantee (VG) ventilation in neonates at maintaining the target tidal volume and what tidal and minute volumes are required to maintain normocapnia.

METHODS

Clinical and ventilator data were collected and analysed from 83 infants receiving VG ventilation during interhospital transfer. Sedation was used in 26 cases. Ventilator data were downloaded with a sampling rate of 0.5 Hz. Data were analysed using the Python computer language and its data analysis packages.

RESULTS

~107 hours of ventilator data were analysed, consisting of ~194 000 data points. The median absolute difference between the actual expiratory tidal volume (VTe) of the ventilator inflations and the target tidal volume (VTset) was 0.29 mL/kg (IQR: 0.11-0.79 mL/kg). Overall, VTe was within 1 mL/kg of VTset in 80% of inflations. VTe decreased progressively below the target when the endotracheal tube leak exceeded 50%. When leak was below 50%, VTe was below VTset by >1 mL/kg in less than 12% of inflations even in babies weighing less than 1000 g. Both VTe (r=-0.34, p=0.0022) and minute volume (r=-0.22, p=0.0567) showed a weak inverse correlation with capillary partial pressure of carbon dioxide (Pco₂) values. Only 50% of normocapnic blood gases were associated with tidal volumes between 4 and 6 mL/kg.

CONCLUSIONS

The Fabian ventilator delivers volume-targeted ventilation with high accuracy if endotracheal tube leakage is not excessive and the maximum allowed inflating pressure does not limit inflations. There is only weak inverse correlation between tidal or minute volumes and Pco₂.

A dedicated respiratory function monitor to improve tidal volume delivery during neonatal anesthesia

BACKGROUND

Tight control of tidal volume using accurate monitoring may improve neonatal outcomes. However, respiratory function monitors incorporated in current anesthetic workstations are generally inaccurate at tidal volumes used for infants.

AIMS

To determine if a specific respiratory function monitor for neonatal infants improved expired tidal volume delivery during anesthesia.

METHOD

Infants <3 months old requiring intubation for surgery in the operating theater were studied. After intubation a Phillips NM3, Acutronic Florian, or Novametrix Ventcheck Respiratory Function Monitor was integrated into the circuit, and clinicians given access to the display for the duration of anesthesia. Breath-to-breath expired tidal volume delivery, leak, and delivered pressure were recorded, with cardiorespiratory parameters. These were compared with a matched control group with clinicians blinded to respiratory function monitor display.

RESULTS

A total of 10 055 and 2569 inflations were measured in the respiratory function monitor visible (n = 32) and masked (n = 33) groups, respectively, with mean (standard deviation) delivered expired tidal volume 7.5 (2.4) mL/kg and 7.7 (3.0) mL/kg, respectively; mean difference (95% confidence interval) -0.2 (-1.1, 0.8) mL/kg (Welch's t test). In the visible group, 55.6% of expired tidal volumes were between 4 and 8 mL/kg compared to 51.7% in the masked group; relative benefit (95% confidence interval), 1.08 (1.03, 1.12). Expired tidal volume was less likely to be <4 mL/kg in the visible group compared to masked group; 6.4% vs 9.8%, 1.53 (1.33, 1.76). The use of a respiratory function monitor also reduced the number of inflations >10 mL/kg; 13.0% vs 22.0%, 1.11 (1.09, 1.14).

CONCLUSION

Tidal volumes <4 mL/kg and >10 mL/kg are frequently delivered during neonatal anesthesia. The inclusion of an accurate respiratory function monitor may reduce the risk of exposure to potentially harmful tidal volumes.

Paramedics' Newborn Life Support Knowledge and Skills Before and After a Targeted Simulation-Based Educational Intervention

Objective: Resuscitation of neonates after birth in the out-of-hospital setting is challenging. Thus, we aimed to assess paramedics' newborn life support knowledge and skills before and after targeted simulation-based training. Methods: Voluntary paramedics were recruited from a single Red Cross division. During a 1-day simulation-based educational intervention, essential aspects of neonatal resuscitation were taught and practiced. Before and after simulation-based training, we assessed (1) knowledge of current European Resuscitation Council (ERC) guidelines using a 20-item-questionnaire and (2) the quality of simulated bag-valve-mask ventilation by measuring face mask leakage, using a respiratory function monitor (Standardized Measurement of Airway Resuscitation Training [SMART], GM Instruments Ltd., United Kingdom). Results: Forty-one paramedics participated in the initial survey and 12 took part in the simulation-based educational intervention. There was a significant increase in the number of correctly answered questions: median 62.1% (IQR 37.5-77.4%) vs. 91.7% (IQR 83.3-100%; p = 0.001). A total of 1,332 inflations were analyzed. The incidence of substantial mask leakage >75% decreased significantly after training (15.8 vs. 6.1%; p < 0.001), while median mask leakage was similar (17.0% [IQR 0.0-55.0%] vs. 18.0% [IQR 6.0-34.0%]; p = 0.414). Conclusions: Among paramedics, theoretical knowledge of current ERC guidelines was moderate in this study. Participation in a targeted simulation-based educational intervention was associated with a significant increase in theoretical knowledge. The initially high incidence of substantial mask leakage >75% was decreased after simulation-based training using respiratory function monitoring.

Accuracy of near-patient vs. inbuilt spirometry for monitoring tidal volumes in an in-vitro paediatric lung model

Spirometric monitoring provides precise measurement and delivery of tidal volumes within a narrow range, which is essential for lung-protective strategies that aim to reduce morbidity and mortality in mechanically-ventilated patients. Conventional anaesthesia ventilators include inbuilt spirometry to monitor inspiratory and expiratory tidal volumes. The GE Aisys CS² anaesthesia ventilator allows additional near-patient spirometry via a sensor interposed between the proximal end of the tracheal tube and the respiratory tubing. Near-patient and inbuilt spirometry of two different GE Aisys CS² anaesthesia ventilators were compared in an in-vitro study. Assessments were made of accuracy and variability in inspiratory and expiratory tidal volume measurements during ventilation of six simulated paediatric lung models using the ASL 5000 test lung. A total of 9240 breaths were recorded and analysed. Differences between inspiratory tidal volumes measured with near-patient and inbuilt spirometry were most significant in the newborn setting (p < 0.001), and became less significant with increasing age and weight. During expiration, tidal volume measurements with near-patient spirometry were consistently more accurate than with inbuilt spirometry for all lung models (p < 0.001). Overall, the variability in measured tidal volumes decreased with increasing tidal volumes, and was smaller with near-patient than with inbuilt spirometry. The variability in measured tidal volumes was higher during expiration, especially with inbuilt spirometry. In conclusion, the present in-vitro study shows that measurements with near-patient spirometry are more accurate and less variable than with inbuilt spirometry. Differences between measurement methods were most significant in the smallest patients. We therefore recommend near-patient spirometry, especially for neonatal and paediatric patients.