The goal of this observational study is to determine if Intrapulmonary Percussive Ventilation (IPV) improves lung compliance in children receiving conventional invasive mechanical ventilation. The main questions it aims to answer are: 1. Does IPV improve lung compliance 15 minutes after and 3 hours after receiving one treatment in a heterogeneous group of pediatric patients? 2. Does IPV improve lung compliance in patients with Pediatric Acute Respiratory Distress Syndrome (PARDS), and what is the degree of change compared to those without PARDS? 3. What is the effect of IPV on lung compliance according to PARDS severity (mild-moderate disease vs. severe disease). 4. What is the incidence of adverse effects of IPV? Participants will receive IPV because their medical team feels it will help their lung recovery and has already determined them to be safe candidates to receive this therapy, which is a standard airway clearance modality already routinely used in our PICU. Nothing additional will happen to participants as a result of this study. Enrolling in this study simply gives the study team permission to collect specific health information that identifies your child for research purposes, which may include results from medical tests found in their medical record and information from your child's bedside monitor and ventilator. This information will be collected before and after the IPV treatments to evaluate their response to the therapy.