hypoxic respiratory failure

1. Sub Title
Hypoxemic
Respiratory Failure
Curtis N. Sessler, MD, FCCP, FCCM, ATSF
Orhan Muren Professor of Medicine
Virginia Commonwealth University Health System
Director, Center for Adult Critical Care
Associate Chair, Faculty Development
Medical College of Virginia Hospitals
Curtis.sessler@vcuhealth.org

2. Sub Title
Hypoxemic
Respiratory Failure
Curtis N. Sessler, MD, FCCP, FCCM, ATSF
No potential conflicts of interest to disclose

3. At the conclusion of this presentation, you will be
able to understand key concepts:
1. Mechanisms and causes of hypoxemic respiratory failure
2. Pathophysiology, diagnostic criteria, clinical features and
epidemiology of ARDS
3. Management strategies for hypoxemic respiratory failure and ARDS
including ventilatory management, medical management, and
rescue therapy for refractory hypoxemia
Learning Objectives

4. At the conclusion of this presentation, you
will be able to understand key concepts:
1. Mechanisms and causes of hypoxemic respiratory
failure
2. Pathophysiology, diagnostic criteria, clinical features
and epidemiology of ARDS
Part 1. Basics of Hypoxemic
Respiratory Failure and ARDS

5. Gas Exchange
• Efficiency dependent upon
§ Alveolar ventilation (V)
§ Pulmonary blood flow (Q)
§ Matching of V and Q
• Impairment results in
hypoxemia or hypercapnia
• Measure pO2 and pCO2 by
arterial blood gas analysis
Frank
Netter

6. Blood Gas Alterations in
Various Causes of Hypoxemia
Mechanism PaO2 PaCO2 PA-aO2
on RA
PA-aO2 on
100%O2
High altitude ¯ ¯ N N
Alveolar hypoventilation ¯ h N N
Decreased ventilation vs
perfusion
¯ ¯ , N,
or h
h corrects
Diffusion block ¯ N or ¯ h corrects
Right-to-left shunt ¯ N or ¯ h h

7. • ARDS
• Pulmonary edema
• Diffuse alveolar
hemorrhage
• Pulmonary embolism
• Interstitial lung disease
• Pulmonary infection
• Pneumonitis
• Neoplasm
• Pulmonary
contusion
• Atelectasis
• Emphysema
• Asthma
• Chronic bronchitis
• Bronchiolitis
Common Causes of Hypoxemic
Respiratory Failure

8. ARDS: Berlin Definition
Category Criterion
Timing Within 1 week of clinical insult or new/worsening
respiratory sx
Chest Imaging Bilateral opacities – not fully explained by effusions,
lobar/lung collapse, or nodules
Origin of edema Not fully explained by cardiac failure or fluid overload.
Objective measure to r/o hydrostatic edema
Oxygenation: Mild 200 mm Hg < PaO2/FIO2 < 300 mm Hg*
Oxygenation: Moderate 100 mm Hg < PaO2/FIO2 < 200 mm Hg**
Oxygenation: Severe PaO2/FIO2 < 100 mm Hg**
* PEEP or CPAP > 5 cm H2O; ** PEEP > 5 cm H2O
JAMA
2012;307:2526-33

9. Chest Radiographic Features of ARDS
• Diffuse bilateral infiltrates
§ Patchy, confluent
§ Alveolar, ground-glass
• In contrast to CHF, no
prominence of..
§ Cardiomegaly
§ Pleural effusion
§ Widened vascular pedicle

10. Chest CT Demonstrates Dependent
Densities in ARDS

11. • Pulmonary infection
• Aspiration injury
• Inhalation injury
• Lung contusion
• Re-expansion injury
• Embolic
• Sepsis
• Shock
• Non-pulmonary trauma
• Transfusion-related lung injury
• Cardiopulmonary bypass
• Anaphylaxis
• Medication
• Acute pancreatitis
Direct Causes Indirect Causes
Common Causes of ARDS

12. ARDS: Acute Respiratory
Distress Syndrome
ARDS is an acute diffuse,
inflammatory lung injury,
leading to increased pulmonary
vascular permeability,
increased lung weight, and loss
of aerated lung tissue with
hypoxemia and bilateral
radiographic opacities,
associated with reduced lung
compliance.

13. Ware
&
Matthay.
N
Engl
J
Med
2000;
342:1334-49

14. Ware
&
Matthay.
N
Engl
J
Med
2000;
342:1334-49

15. Epidemiology, Patterns of Care, and
Mortality for 3022 Patients with
ARDS in ICUs in 50 Countries
• ARDS accounted for 10% of all ICU admissions
• 25% of mechanically ventilated patients
• 40% of patients with ARDS died in the hospital
• Clinical recognition of ARDS
§ 51.3% of mild ARDS
§ 78.5% of severe ARDS
• Lack of recognition of ARDS associated with…
§ Use of lung destructive ventilation (excessive tidal
volumes, low PEEP)
Bellani et al. JAMA 2016;315:788

16. Management of ARDS
• Treat underlying condition
• Support oxygenation and ventilation
§ Mechanical ventilation; avoid / minimize
barotrauma and oxygen toxicity
§ Use lung protective ventilation / low tidal volumes
§ Pressure or volume? Recruitment? Higher PEEP?
• Supportive (non-ventilatory) therapy
§ Conservative fluid management
• Management of severe hypoxemia