The Modified Bohr Equation

Feb 11, 2024

Discussion on the management of a six-year-old patient with severe pneumonia and pediatric ARDS, understanding and assessing dead space in arterial blood gas measurements, significance of dead space ratio in evaluating gas exchange, implications and management of dead space in obstructive lung disease, and the concept of dead space fraction in pediatric ARDS.

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Introduction

00:00 • 3min

Understanding Dead Space in Arterial Blood Gas Measurements

02:57 • 5min

Understanding Dead Space Ratio and its Implications for Pediatric ICU Patients

08:03 • 2min

Implications of Dead Space in Obstructive Lung Disease and Management Strategies

10:12 • 2min

Understanding Dead Space Fraction in Pediatric ARDS

12:41 • 5min

Hosts:

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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Hosted by Dr. Pradip Kamat and Dr. Rahul Damania.

Reference:

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.