None listed
Conditions
Brief summary
Laparoscopy is the preferred surgical approach in several abdominal procedures as it provides several advantages compared to open surgery, including: minimal incision, shorter hospital stay, less pain after the operation, and early mobilization . However, gas insufflation into the abdomen increases abdominal pressure with consequent changes in respiratory mechanics and lung volume de-recruitment. During an operation an anaesthetist will typically use what are called recruitment manoeuvres, e.g. sustained inflation or multiple manual breaths, to re-open collapsed lung areas. Patients undergoing laparoscopic surgery are normally anaesthetised, muscle paralysed, receive a breathing tube and will need to be on a ventilator. The ventilator must generate (positive) pressure to blow oxygen into the lung and inflate them. Prolonged positive pressure ventilation, particularly requiring higher pressures, is damaging to the delicate lining of the lung. The continual opening and closing and/or over-distention of the alveoli caused by the ventilator seem to be the most important trigger for damage. The younger and smaller the children the more susceptible the airway, but also the lower safety margin with the pressures that are safe to use. The forced oscillation technique (FOT) is a non-invasive method for the assessment of lung mechanics, which has been successfully applied in patients with breathing tubes in. Briefly, it applies small pressure waves down into the airway and detects the reflected/returning waves allowing assessment of the airway. While intermittent assessments have been performed in the past, our study proposes a novel continuous technique not previously used in the anaesthetic setting. he aim of this study is therefore to assess the feasibility of this novel continuous assessment of respiratory mechanics in theatre and to track their changes, as measured by FOT, in children undergoing laparoscopic appendectomy. If this study demonstrates the feasibility of this new technique of tracking lung function during laparoscopic surgery, it will allow paediatric anaesthetists to use real time data to continually optimise the ventilator settings required for a child. It could then allow formulation of new evidence-based ventilation guidelines and policies to optimize and personalize the ventilation strategy in children undergoing laparoscopic surgery.
Interventions
The aim of this study is to track changes in oscillatory mechanics (Rrs and Xrs), measured by Forced oscillation technique (FOT), in mechanically ventilated children undergoing laparoscopic appendectomy
Following the induction of anaesthesia, the child will be intubated, and ventilation will be started. Standard monitoring will be established, including non-invasive arterial pressure, electrocardiography, pulse oximetry (SpO2), and end-tidal carbon dioxide (etCO2). Ventilation will be managed a
The aim of this study is to track changes in oscillatory mechanics (Rrs and Xrs), measured by Forced oscillation technique (FOT), in mechanically ventilated children undergoing laparoscopic appendectomy Following the induction of anaesthesia, the child will be intubated, and ventilation will be started. Standard monitoring will be established, including non-invasive arterial pressure, electrocardiography, pulse oximetry (SpO2), and end-tidal carbon dioxide (etCO2). Ventilation will be managed as deemed appropriate by the attending anaesthetist; however, to minimise the confounding effect of different ventilation approaches on lung mechanics, the following guidelines will be applied: Pressure control mode; FiO2: 0.30 – 0.45 to maintain SpO2 above 95%; PEEP: 5 cmH2O; Peak Inspiratory Pressure and (PIP): 10 - 25 cmH2O above PEEP to reach tidal volumes of 6-8 ml/kg; Respiratory rate (RR): dependent on the child’s age; adjusted to maintain etCO2 between 35 - 45 mmHg. The forced oscillation technique (FOT) equipment will be connected to the inspiratory line of the ventilator circuit and FOT data will be collected for the duration of ventilation. The following data will be recorded at relevant protocol steps: FOT Ventilation settings (PEEP, PIP, FiO2, RR) SpO2 etCO2 Abdominal insufflation pressure Train of Four (depth of muscle paralysis) After intubation (before the beginning of the surgical procedure) and after the completion of surgery, lung volume recruitment manoeuvres will be performed manually ventilating the lungs with a peak airway pressure of 40 cm H2O and a PEEP of 15 cm H2O for 10 breaths to standardize lung volume history. We will record timing and dosing of all muscle relaxants used. Pressure and flow will be continuously recorded allowing calculation of Rrs and Xrs throughout the period of general anaesthesia. In order to synthetize results, we will select 30-second data segments or epochs at the event points indicated below. Data will be reported as separate Rrs and Xrs values, every 15 minutes during surgery, (after induction, after recruitment, after insufflation, before and after deflation, before and after first and second recruitment manouevre) as a function of time. Any other event considered relevant to lung mechanics (e.g. changes in insufflation pressure) will be recorded Lung mechanics will be assessed using FOT. Measurements will be carried out following the international guidelines and recommendations set by the American Thoracic Society and the European Respiratory Society. The equipment that will be used to apply FOT during positive pressure ventilation had been developed at Politecnico di Milano University based on previously described methodology. Politecnico di Milano University owns patents on the assessment of lung volume recruitment by FOT. However, the results of this study will only partially link to that patent. The outcomes of the COMET study will primarily contribute to changing anaesthetic practice and will be openly published in an international peer reviewed journal. The equipment consists of a small flow sensor placed close to the airway device with the other equipment inserted further away from the patient within the anaesthetic circuit. This ensures that the deadspace and extra weight on the airway device is minimal (11g). Flow will be measured using a compact commercial sensor (Florian, Acutronic Medical Systems, Hirzel, Switzerland), which has been already characterized and used for measuring FOT parameters in clinical studies and it is regularly used in commercial mechanical ventilators (e.g. Fabian, Vyaire) in both NICU and PICU. This flow sensor has 4 mL dead space and weighs about 11 g, so it will not have a significant impact on the overall equipment. This hot-wire flowmeter is not critically affected by humidity and can be placed close to the HME filter. The device produces small amplitude pressure oscillations (e.g. 2 cmH2O peak-to-peak), which does not cause discomfort and does not affect ventilation as the associated volume changes are very small (e.g. 1 mL). Single use anti-bacterial filters will be used to isolate the patient from the equipment and eliminate the risk of cross-contamination. Low amplitude sinusoidal pressure oscillations (2 cmH2O peak-to-peak) at 5 Hz are generated by a loudspeaker connected to the inspiratory line of the mechanical ventilator and applied at the inlet of the tracheal tube. The rear of the loudspeaker is enclosed in a chamber and connected to the inspiratory outlet of the ventilator to equilibrate the positive pressures on both sides of the loudspeaker membrane. Pressure and flow are measured at the airway opening using a pressure transducer and a mesh-type heated pneumotachograph connected with a differential pressure transducer. Signals are sampled at 200 Hz and exported on a personal computer for offline analysis.
Sponsors
Perth Children's Hospital
Study design
Allocation
Non-randomised trial
Intervention model
Single group
Primary purpose
Diagnosis
Masking
Open (masking not used)
Eligibility
Sex/Gender
All
Age
2 Years to 16 Years
Healthy volunteers
No
Inclusion criteria
Children of any sex Aged 2 to 16 years of age Undergoing laparoscopic appendectomy under general anaesthesia
Exclusion criteria
Children with a thoracic malformation Children with a known major lung and/or cardiopulmonary disease: Uncorrected congenital heart disease Primary/secondary pulmonary hypertension Cardiac/thoracic malformations/tumours Structural lung changes Uncontrolled asthma Cystic Fibrosis Doctor diagnosed bronchiectasis The above list is a non-exhaustive list. Any other less common cardiopulmonary conditions will be assessed by the anaesthetist in charge and accounted for in the exclusion criteria list.
Outcome results
None listed