![]() ![]() provided evidence of improvement in ventilation in a randomized crossover trial in adult patients with obesity hypoventilation syndrome. Patient SelectionĪlthough AVAPS debuted in 2003, a study published in 2006 by Storre et al. Recommendations for pediatric settings are lacking. The use of modem enabled devices help monitor pressures, air leaks and objective adherence to patient's healthcare provider. ![]() The rise time is adjusted for patient comfort. The AVAPS rate of change determines the rate of change of IPAP and is kept shorter (range 1–5 cmH 2O) for more unstable patients. The set rate is generally 2 to 3 breaths below resting respiratory rate. The minimum IPAP is set at EPAP +4 cmH 2O, generally no <8 cmH 2O. The maximum IPAP is 25 cmH 2O and depending on the patient pathology can be set to a lower level. The manufacturer provides pre-calculated ideal weights for a range of adult heights 1. The use of ideal body weight is to ensure optimal calculation of tidal volume for obese patients. In adults, a target tidal volume of 8 ml/kg of ideal body weight is recommended. The suggested settings are based on the information provided by the manufacturer and early adult studies 1 ( 12, 13). EPAP is fixed similar to conventional BPAP, although there is an AVAPS auto-titrating EPAP (AVAPS AE) feature to regulate the EPAP as well in some devices ( 11). Tidal volume varies with each breath and it may take several breaths for AVAPS to attain the targeted tidal volume ( 10). Several additional parameters such as AVAPS rate of change ensure that patient-machine desynchronization is minimized and the IPAP pressure changes swiftly and efficiently to ensure patient comfort and optimal ventilation 1. For the minimum IPAP delivery, the machine makes a selection from three pre-set algorithms (IPAP min VT 60 ml/cmH 2O + EPAP or 8 cmH 2O + EPAP), choosing the highest value ( 9). The IPAP maximum also serves as a safety parameter to prevent barotrauma from excessive pressure. The ventilator uses an inbuilt algorithm to either increase or decrease the inspiratory pressure from breath to breath to ensure delivery of the pre-set tidal volume 1. Pressure support is no longer fixed and changes within the set parameters. Rather than having a fixed IPAP setting, AVAPS has the capability to set a range of values for IPAP, a maximum and a minimum IPAP, to target delivery of a set tidal volume. Despite its advantages, data on its use in children are sparse and recommendations on initiation and settings are extrapolated from adult experience. ![]() It intuitively varies the inspiratory pressure, using higher pressure during REM sleep compared to NREM sleep resulting in a more stable ventilation and potentially improving adherence ( 5, 8). It offers several advantages over fixed pressure NIV support such as its ability to compensate for the changes in tidal volume which occur with changes in lung compliance and sleep stages. AVAPS enables the machine to deliver a pre-set tidal volume by automatically adjusting the inspiratory pressure support within a set range. Although conventional fixed pressure NIV has been the mainstay therapy for children with neuromuscular and hypoventilation syndromes requiring respiratory support, several pediatric centres are reporting favorable outcomes with the use of average volume assured pressure support (AVAPS) for home ventilation ( 4– 7). When NIV is initiated, parameters are generally determined based on clinical assessment followed by an in-laboratory polysomnographic titration study where parameters are adjusted throughout the recording to determine optimal ventilatory settings for adequate gas exchange andupper airway patency ( 3). The use of home non-invasive ventilation (NIV) has increased substantially in children over the last few decades, at least in part due to enhanced survival of children with chronic medical conditions along with improvements in home ventilator technology and provision of suitably sized pediatric masks ( 1, 2). ![]()
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