Acute Resp Failure Cyndy Kin

1. Acute Respiratory FailureAcute Respiratory Failure
Cindy Kin
Trauma Conference
6 August 2007
Stanford Surgery

2. Acute Respiratory FailureAcute Respiratory Failure
•Failure in one or both gas exchange functions:
oxygenation and carbon dioxide elimination
•In practice:
PaO2<60mmHg or PaCO2>46mmHg
•Derangements in ABGs and acid-base status

3. Acute Respiratory FailureAcute Respiratory Failure
•Hypercapnic v Hypoxemic respiratory failure
•ARDS and ALI

4. Hypercapnic Respiratory FailureHypercapnic Respiratory Failure
(PAO2 - PaO2)
Alveolar
Hypoventilation
V/Q abnormality
¯ PI max
increased
normal
Nl VCO2
PaCO2 >46mmHg
Not compensation for metabolic alkalosis
Central
Hypoventilation
Neuromuscular
Problem
­ VCO2
V/Q
Abnormality
Hypermetabolism
Overfeeding

5. The Case of Patient RVThe Case of Patient RV
71M s/p L AKA revision.
PMH: CAD s/p CABG, COPD on home O2 and CPAP, DM,
CVA, atrial fibrillation
PACU: L pleural effusion, hypotension, altered mental status.
Sent to ICU for monitoring.
POD#1: ­RR overnight, intermittently hypoxic.
BiPAP 40%: 7.34/65/63/35/+10
Preintubation: 7.28/91/81/43

6. Hypercapnic Respiratory FailureHypercapnic Respiratory Failure
(PAO2 - PaO2)
Alveolar
Hypoventilation
V/Q abnormality
¯ PI max
increased
normal
Nl VCO2
PaCO2 >46mmHg
Not compensation for metabolic alkalosis
Central
Hypoventilation
Neuromuscular
Problem
­ VCO2
V/Q
Abnormality
Hypermetabolism
Overfeeding

7. Hypercapnic Respiratory FailureHypercapnic Respiratory Failure
Alveolar
Hypoventilation
Brainstem respiratory depression
Drugs (opiates)
Obesity-hypoventilation syndrome
¯ PI max
Central
Hypoventilation
Neuromuscular
Disorder
nl PI max
Critical illness polyneuropathy
Critical illness myopathy
Hypophosphatemia
Magnesium depletion
Myasthenia gravis
Guillain-Barre syndrome

8. Hypercapnic Respiratory FailureHypercapnic Respiratory Failure
(PAO2 - PaO2)
Alveolar
Hypoventilation
V/Q abnormality
¯ PI max
increased
normal
Nl VCO2
PaCO2 >46mmHg
Not compensation for metabolic alkalosis
Central
Hypoventilation
Neuromuscular
Disorder
­ VCO2
V/Q
Abnormality
Hypermetabolism
Overfeeding

9. Hypercapnic Respiratory FailureHypercapnic Respiratory Failure
V/Q abnormality
Increased Aa gradient
Nl VCO2
­ VCO2
V/Q
Abnormality
Hypermetabolism
Overfeeding

10. Hypercapnic Respiratory FailureHypercapnic Respiratory Failure
V/Q abnormality
Increased Aa gradient
Nl VCO2
­ VCO2
V/Q
Abnormality
Hypermetabolism
Overfeeding
• Increased dead space ventilation
• advanced emphysema
• ­PaCO2 when Vd/Vt >0.5
• Late feature of shunt-type
• edema, infiltrates

11. Hypercapnic Respiratory FailureHypercapnic Respiratory Failure
V/Q abnormality
Increased Aa gradient
Nl VCO2
­ VCO2
V/Q
Abnormality
Hypermetabolism
Overfeeding
• VCO2 only an issue in pts with ltd
ability to eliminate CO2
• Overfeeding with carbohydrates
generates more CO2

12. Hypoxemic Respiratory FailureHypoxemic Respiratory Failure
Is PaCO2 increased?
Hypoventilation ­(PAO2 - PaO2)?
Hypoventilation
alone
¯Respiratory drive
Neuromuscular dz
Hypovent plus
another
mechanism
Shunt
¯Inspired PO2
High altitude
¯FIO2
­(PAO2 - PaO2) No
NoYes
Is low PO2
correctable
with O2?
V/Q mismatch
No
Yes
Yes

13. The Case of Patient ESThe Case of Patient ES
77F s/p MVC.
Injuries include multiple L rib fxs, L hemopneumothorax
s/p chest tube placement, L iliac wing fx.
PMH: atrial arrhythmia, on coumadin. INR>2
HD#1
RR 30s and shallow. Pain a/w breathing deeply.
Placed on BiPAP overnight
PID#1
BiPAP 80%:7.45/48/66/32/+10

14. Hypoxemic Respiratory FailureHypoxemic Respiratory Failure
Is PaCO2 increased?
Hypoventilation ­(PAO2 - PaO2)?
Hypoventilation
alone
¯Respiratory drive
Neuromuscular dz
Hypovent plus
another
mechanism
Shunt
¯Inspired PO2
High altitude
¯FIO2
­(PAO2 - PaO2) No
NoYes
Is low PO2
correctable
with O2?
V/Q mismatch
No
Yes
Yes

15. Hypoxemic Respiratory FailureHypoxemic Respiratory Failure
V/Q mismatch
V/Q mismatch
DO2/VO2
Imbalance
PvO2>40mmHg PvO2<40mmH
g
¯DO2: anemia, low CO
­VO2: hypermetabolism

16. Hypoxemic Respiratory FailureHypoxemic Respiratory Failure
V/Q mismatch
SHUNT
V/Q = 0
DEAD SPACE
V/Q = ∞
Atelectasis
Intraalveolar filling
Pneumonia
Pulmonary edema
Pulmonary embolus
Pulmonary vascular dz
Airway dz
(COPD, asthma)
Intracardiac shunt
Vascular shunt in lungs
ARDS
Interstitial lung dz
Pulmonary contusion

17. Hypoxemic Respiratory FailureHypoxemic Respiratory Failure
V/Q mismatch
SHUNT
V/Q = 0
DEAD SPACE
V/Q = ∞
Atelectasis
Intraalveolar filling
Pneumonia
Pulmonary edema
Pulmonary embolus
Pulmonary vascular dz
Airway dz
(COPD, asthma)
Intracardiac shunt
Vascular shunt in lungs
ARDS
Interstitial lung dz
Pulmonary contusion

18. Hypoxemic Respiratory FailureHypoxemic Respiratory Failure
Acute Respiratory Distress Syndrome
•Severe ALI
•B/L radiographic
infiltrates
•PaO2/FiO2 <200mmHg
(ALI 201-300mmHg)
•No e/o ­L Atrial P;
PCWP<18

19. Hypoxemic Respiratory FailureHypoxemic Respiratory Failure
Acute Respiratory Distress Syndrome
•Develops ~4-48h
•Persists days-wks
•Diagnosis:
–Distinguish from
cardiogenic edema
–History and risk
factors

21. Inflammatory
Alveolar Injury

22. Inflammatory
Alveolar Injury
Pro-inflmm cytokines
(TNF, IL1,6,8)

23. Inflammatory
Alveolar Injury
Pro-inflmm cytokines
(TNF, IL1,6,8)
Neutrophils - ROIs
and proteases
damage capillary
endothelium and
alveolar epithelium

24. Inflammatory
Alveolar Injury
Fluid in interstitium
and alveoli
Pro-inflmm cytokines
(TNF, IL1,6,8)
Neutrophils - ROIs
and proteases
damage capillary
endothelium and
alveolar epithelium

25. Inflammatory
Alveolar Injury
Fluid in interstitium
and alveoli
•Impaired gas exchange
"¯ Compliance
"­ PAP
Pro-inflmm cytokines
(TNF, IL1,6,8)
Neutrophils - ROIs
and proteases
damage capillary
endothelium and
alveolar epithelium

26. Hypoxemic Respiratory FailureHypoxemic Respiratory Failure
Acute Respiratory Distress Syndrome
Exudative phase Fibrotic phaseProliferative phase
Diffuse alveolar damage

27. Hypoxemic Respiratory FailureHypoxemic Respiratory Failure
Acute Respiratory Distress Syndrome
Direct Lung Injury
•Infectious pneumonia
•Aspiration, chemical pneumonitis
•Pulmonary contusion, penetrating lung injury
•Fat emboli
•Near-drowning
•Inhalation injury
•Reperfusion pulmonary edema s/p lung transplant

28. Hypoxemic Respiratory FailureHypoxemic Respiratory Failure
Acute Respiratory Distress Syndrome
Indirect Lung Injury
•Sepsis
•Severe trauma with shock/hypoperfusion
•Burns
•Massive blood transfusion
•Drug overdose: ASA, cocaine, opioids,
phenothiazines, TCAs.
•Cardiopulmonary bypass
•Acute pancreatitis

29. Hypoxemic Respiratory FailureHypoxemic Respiratory Failure
Acute Respiratory Distress Syndrome
Complications
•Barotrauma
•Nosocomial pneumonia
•Sedation and paralysis ® persistent MS
depression and neuromuscular weakness

30. Hypoxemic Respiratory FailureHypoxemic Respiratory Failure
Acute Respiratory Distress Syndrome
•861 patients, 10 centers
•Randomized
•Tidal Vol 12mL/kg PDW,
PlatP<50cmH2O
•Tidal Vol 6mL/kg PDW,
PlatP<30cmH2O
•NNT 12
•31% mortality v 39.8%
•65.7% breathing without assistance by day 28 v 55%
•Significantly more ventilator-free days
•Significantly more days without failure of nonpulmonary
organs/systems