• Pradip Kamat, Children’s Healthcare of Atlanta/Emory University School of Medicine
  • Rahul Damania, Cleveland Clinic Children’s Hospital

Case Introduction:

  • 6-year-old patient admitted to PICU with severe pneumonia complicated by pediatric Acute Respiratory Distress Syndrome (pARDS).
  • Presented with respiratory distress, hypoxemia, and significant respiratory acidosis.
  • Required intubation and mechanical ventilation.
  • Despite initial interventions, condition remained precarious with persistent hypercapnia.

Physiology Concept: Dead Space

  • Defined as the volume of air that does not participate in gas exchange.
  • Consists of anatomic dead space (large airways) and physiologic dead space (alveoli).
  • Physiologic dead space reflects ventilation-perfusion mismatch.

Pathological Dead Space:

  • Occurs due to conditions disrupting pulmonary blood flow or ventilation.
  • Common in conditions like pulmonary embolism, severe pneumonia, or ARDS.

Clinical Implications:

  • Increased dead space fraction (DSF) in PARDS is a prognostic factor linked to severity and mortality.
  • Elevated DSF indicates worse lung injury and inefficient gas exchange.
  • DSF can be calculated using the formula: DSF = (PaCO2 – PetCO2) / PaCO2.

Practical Management:

  • Optimize Mechanical Ventilation
  • Enhance Perfusion
  • Consider Positioning (e.g., prone positioning)

Summary of Physiology Concepts:

  • Bohr equation for physiologic dead space.
  • Importance of lung-protective ventilation strategies.
  • Monitoring and trending dead space fraction.
  • Strategies to improve airway patency and mucociliary clearance.

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  • Yehya N, Bhalla AK, Thomas NJ, Khemani RG. Alveolar Dead Space Fraction Discriminates Mortality in Pediatric Acute Respiratory Distress Syndrome. Pediatr Crit Care Med. 2016 Feb;17(2):101-9. doi: 10.1097/PCC.0000000000000613. PMID: 26669646; PMCID: PMC4740261.