In this special episode of *PICU Doc on Call*, hosts Dr. Monica Gray and Dr. Rahul Damania welcome new pediatric critical care fellows across the U.S. with practical advice for day one of fellowship. Joined by third-year PICU fellow Dr. Alexandra Bryant, the episode covers three key areas: navigating PICU logistics, protecting mental health, and managing the overwhelming volume of critical care knowledge. Dr. Bryant shares candid insights from her own training journey, offering actionable strategies for success. The hosts remind listeners that fellowship is a learning process and that new fellows can make a meaningful impact.

Show Highlights

• Introduction to pediatric critical care fellowship for new fellows and learners
• Key insights and advice for first-year fellows in pediatric intensive care
• Importance of understanding logistics in the PICU environment
• Strategies for effective communication and collaboration within the PICU team
• Managing mental health and self-care during fellowship
• Techniques for absorbing and retaining vast knowledge in pediatric critical care
• Recommendations for organizing study materials and resources
• Emphasis on lifelong learning and accessing information effectively
• Practical tips for time management and responsibility organization
• Suggested resources for mindfulness and emotional support in medical training

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PICU Doc on Call Episode 31

In this episode of *PICU Doc on Call Shorts*, pediatric ICU physicians Dr. Pradip Kamat and Dr. Rahul Damania discuss respiratory time constants and their clinical relevance in pediatric critical care. Using a case of a six-year-old with near-fatal status asthmaticus on mechanical ventilation, they explain how prolonged time constants from high airway resistance cause air trapping, dynamic hyperinflation, and intrinsic PEEP. They emphasize recognizing these issues through ventilator waveforms and highlight that increasing respiratory rate can worsen hypercapnia in obstructive disease. Key management strategies include reducing respiratory rate, extending expiratory time, and accepting permissive hypercapnia to ensure hemodynamic stability.

Show Highlights

• Respiratory time constants and their clinical significance in pediatric patients
• Case study of a six-year-old boy with near-fatal status asthmaticus
• Management of severe obstructive respiratory failure in pediatric patients
• Understanding airway resistance and lung compliance in relation to time constants
• Impact of ventilator settings on patient outcomes, including air trapping and intrinsic PEEP
• Importance of adequate expiratory time to prevent dynamic hyperinflation
• Recognizing signs of inadequate expiratory time in mechanically ventilated patients
• Strategies for managing hypercapnia and optimizing ventilator settings
• Differences in time constants related to various pediatric respiratory conditions
• Key takeaways for pediatric critical care practice and ventilator management

1. Depta F, Kallet RH, Gentile MA, Kassis EN. Expiratory time constants in mechanically ventilated patients: rethinking the old concept — a narrative review. Intensive Care Medicine Experimental. 2025;13:40. The review summarizes the definition of expiratory time constant, the relationship to resistance and compliance, the 63/86/95/98/99% rule, and clinical applications in obstructive and acute lung injury states.
2. Depta F, et al. Six methods to determine expiratory time constants in mechanically ventilated patients: a prospective observational physiology study. Intensive Care Medicine Experimental. 2024. This study describes expiratory time constant as a parameter that can guide respiratory rate and I:E adjustment to support complete exhalation.
3. Alibrahim O, Rehder KJ, Miller AG, Rotta AT. Mechanical Ventilation and Respiratory Support in the Pediatric Intensive Care Unit. Pediatric Clinics of North America. 2022;69(3):587–605. This pediatric review specifically discusses passive exhalation, the expiratory time constant, and why asthma and bronchiolitis require longer expiratory times to avoid gas trapping.
4. Arnal JM. Monitoring respiratory mechanics in mechanically ventilated patients. Hamilton Medical Knowledge Base. This source provides a practical bedside description of time constants, waveform-based respiratory mechanics, and typical RCexp ranges, while emphasizing dependence on resistance and compliance.
5. Emeriaud G, López-Fernández YM, Iyer NP, et al.; PALICC-2 Group; PALISI Network. Executive summary of the second international guidelines for the diagnosis and management of pediatric ARDS. Pediatric Critical Care Medicine. 2023;24(2):143–168. The PALICC-2 guideline framework supports lung-protective ventilation in PARDS, including attention to tidal volume, PEEP, plateau pressure, and driving pressure.