Acute Respiratory Failure

1. Acute Respiratory Failure Yoon Jung Oh,M.D. Departments of Pulmonary and Critical Care Medicin Ajou University School of Medicine

2. Definition • Hypoxemic respiratory failure • PaO2 < 55 mmhg , FiO2 ≥ 0.6 • Acute : develops in min to hr • Chronic : develops over several days or longer • Hypercapnic respiratory failure • PaCO2 > 45 mmHg • Acute : develops in min to hr( pH < 7.3) • Chronic : develops over several days or longer Hypercapnic and hypoxemic respiratory failure coexist.

3. Acute Respiratory Failure PaCO2 < 45 mmHg Type 1 respiratory failure PaCO2 > 45 mmHg Type II ventilatory failure ABGA • Black • acute pulmonary embolism • vascular obstruction • R-L shunt • Black • COPD • Status asthmaticus • Alveolar hypoventilation • Drug overdose • Neuromuscular disease CXR • White • Diffuse • ARDS • Pulmonay edema • Pulmonary fibrosis • Localized • Pneumonia • atelectasis • White • Diffuse • ARDS • Pulmonary edema • Pulmonary fibrosis • Localized • Pneumonia + COPD • Drug overdose

4. Ventilatory demand Ventilatory supply A Ventilatory supply exceeds ventilatory demand. Ventilatory supply Ventilatory demand B Ventilatory supply equals ventilatory demand. Ventilatory supply Ventilatory demand C Ventilatory demand exceeds ventilatory supply.

5. TABLE 165-3 Factors That Increase Ventilatory Demand Factors Clinical Examples Increased VD/VT Increased Vo2 Increased RQ Decreased Pa CO2 Acute asthma, emphysema, late phase of acute respiratory distress syndrome, pulmonary emboli Fever, sepsis, trauma, shivering, increased work of breathing, massive obesity Excessive carbohydrate feeding Hypoxemia, metabolic acidosis, anxiety, sepsis, renal failure, hepatic failure SOURCE: Data from Lanken. 23

6. TABLE 165-2 Factors That Diminish Ventilatory Supply Factors Examples Decreased respiratory muscle strength Muscle fatigue Disuse atrophy Malnutrition Electrolyte abnormalities Arterial blood gas abnormalities Fatty infiltration of diaphragm Unfavorable alteration in diaphragm length-tension relationship Increased muscle energy requirement or decreasedsubstrate supply High elastic work of breathing High resistive work of breathing Reduced diaphragm perfusion Decreased motor neuron function Decreased phrenic nerve output Decreased neuromuscular transmission Abnormal respiratory mechanics Airflow limitation Loss of lung volume Other restrictive defects Recovery from acute respiratory failure, high respiratory rates, increased Pdi/Pdimax,* increased inspiratory time Prolonged mechanical ventilation, following phrenic nerve injury Protein-calorie starvation Low serum phosphate or potassium concentrations Low pH, low PaO2, high PaCO2 Obesity Flattened domes of diaphragm caused by hyperinflation Low lung or chest wall compliance, high respiratory rate Airway obstruction Shock, anemia Polyneuropathy, Guillain-Barré syndrome, phrenic nerve transection or injury, poliomyelitis Myasthenia gravis, use of paralyzing agents Bronchospasm, upper-airway obstruction, excessive airway secretions After lung resection, large pleural effusion Pain-limited inspiration; tense abdominal distention due to ileus peritoneal dialysis fluid, or ascites

7. Pathophysiology(1) Hypoxemic Respiratory Failure

8. Pathophysiology(2) Hypercapnic Respiratory Failure

9. Case 1.1 F/30 Hx : 3년전 bronchial asthma 진단받았으며 3일전 URI 후 악화된 호흡곤란을 주소로 내원. ABGA : pH 7.5 PaO2 50 mmHg, PaCO2 30 mmHg HCO3 22 mmol/L at room air O2 5 L/min  PaO2 65 mmHg P/E : RR 30/min, use of accessory muscle wheezing on whole lung field CXR : hyperinflation

10. Diagnosis 1. Acute hypoxemic respiratory failure due to acute exacerbation of asthma

11. Case 1.2 병동에서 치료중 호흡곤란을 계속 호소함. ABGA : pH 7.4 PaO2 65 mmHg PaCO2 40 mmHg O2 sat 92%

12. Case 1.3 다음날 아침, 밤새 호흡곤란으로 한숨도 자지 못했다하며 지속적인 호흡곤란을 호소함. ABGA : pH 7.35 PaO2 60mmHg PaCO2 50mmHg O2sat 90%

13. Case 2. F/19 남자친구와 다툰 후 수면제 100알을 복용후 응급실로 내원. ABGA : pH 7.25 PaO2 60mmHg PaCO2 70mmHg HCO3 27 mmol/L O2sat 90%

14. Diagnosis 2 Acute hypercapnic respiratory failure due to drug overdose

15. Case 3.1 M/67 50 pack year smoker, 평소 100m 정도 걸으면 심해지는 DOE 있었으며 최근 감기앓은 후 fever,cough,dyspnea 로 내원. P/E : RR 28/min wheezing on whole lung field ABGA : pH 7.4 PaO2 50 mmHg PaCO2 50 mmHg HCO3 28 mmol/L O2sat 85% at room air Nasal O2투여후 O2 sat 92% 로 증가

16. Diagnosis 3.1 • Chronic obstructive pulmonary disease • (Emphysema )

17. Case 3.2 응급실에서 산소를 투여한지 4시간 후 , 환자가 헛소리를 하고 자꾸 자려고만 한다고 보호자가 호소함. ABGA : pH 7.2 PaO2 80 mmHg PCO2 90 mmHg nasal O2 5L/min

18. Diagnosis 3.2 Acute hypercapnic respiratory failure CO2 narcosis

19. Effector Components CNS Efferents Perepheral Nerves Repiratory m. Chest wall Airway Alveoli Afferent Integration In CNS Chemo- receptors PaO2 PaCO2 VA, VE

20. *PaO2 may decrease when pneumonia or atelectasis occurs as a complication #P(A-a)O2 widens when pnumonia or atelectasis occurs as a complication $VE declines when frank respiratory muscle failure occurs.

21. &PaCO2 may increase during an exacerbation

22. Treatment of Acute Respiratory Failure • Correct hypoxemia/respiratory acidosis • Patent upper airway • Adequate ventilation • Supplemental oxygen

23. Treatment of Respiratory Failure • Increase VA • Bronchodilator • Control of infection • Oxygen therapy

24. Ventilatory Failure • To decrease VCO2 • Antipyretics • Cooling blanket • Decrease muscle activity • To increase VA • Prevent airflow obstruction • Respiratory training • Intubation & mechanical ventilation • Cautious administration of sedatives