Acute Respiratory Insufficiency NURCAN KIZILCIK Learning objectives Definition

Acute Respiratory Insufficiency NURCAN KIZILCIK

Learning objectives Definition of acute respiratory insufficiency Diagnosis of acute respiratory insufficiency Causes of acute respiratory insufficiency Clinical and laboratory findings of acute respiratory insufficiency • Treatment of acute respiratory insufficiency • •

one or both of its gas exchange functions: oxygenation and carbon dioxide elimination Results from inadequate gas exchange § Insufficient O 2 transferred to the blood • Hypoxemia § Inadequate CO 2 removal • Hypercapnia

Not a disease but a condition Result of one or more diseases involving the lungs or other body systems

Respiratory tract Lungs Pump System Gas exchange Oxygen and carbon dioxide cross the alveolarcapillary wall by diffusion. Oxygen is transported from the lungs to the cells and carbon dioxide is transported from the cells to the lungs. Roussos et al, Eur Respir J 2003; 22; suppl 47: 3 s-14 s Laghi and Tobin, AJRCCM 2003; 168: 10 Ventilation

Inability to sustain • arterial partial oxygen pressure (Pa. O 2) • and carbon dioxide (Pa. CO 2) pressure at physiological range

Clinical findings Tachypnea Dyspnea Stridor Wheezing The use of auxiliary respiratory muscles

Intercostal retractions Sweating Hypertension Mental status changes Tachycardia / bradycardia

HYPOXIA EVALUATION OF CLINICAL FINDINGS MILD-MODERATE HYPOXIA SEVERE HYPOXIA RESPIRATORY FINDINGS Tachypnea Dyspnea + Cyanosis CARDIOVASCULAR FINDINGS Tachycardia Slight HT Peripheral VK Bradycardia Arrhythmia Hypotension Inaction Disoriantation Headache Fatigue Decreased ability of decision making Confusion, Somnolence Blurred vision Loss of coordination Reduced deceleration time of reaction NEUROLOGICAL FINDINGS

EVALUATION OF CLINICAL FINDINGS HYPERCAPNIA MILD-MODERATE HYPOXIA SEVERE HYPOXIA RESPIRATORY FINDINGS Tachypnea Dyspnea Bradipnea Apnea NEUROLOGICAL FINDINGS Headache Trend sleep Seizure Sweating Hallucination Hypomania Coma Skin rashes OTHER FINDINGS

Traditionally, respiratory failure is divided into: type 1 and type 2 but these are not practical terms and it is better to think instead of: ü Failure to ventilate ü Failure to oxygenate ü Failure to both ventilate and oxygenate

Respiratory Failure Lung Failure Gas exchange Problem Hypoxemia Pump Failure Decrease in ventilation Hypercapnia Roussos et al, Eur Respir J 2003; 22; suppl 47: 3 s-14 s

Laboratory • Hypoxia: p. O 2 < 60 mm. Hg • Hypercarbia: p. CO 2 > 45 mm. Hg

Most important lab indicator of adequate ventilation is arterial partial carbon dioxide level (Pa. CO 2). The normal value is 35 to 45 mm. Hg.

Partial arterial oxygen (Pa. O 2) is an indicator of adequate of tissue oxygenation. Normal Pa. O 2: 80 -100 mm. Hg at room air. When decreased below this level, tissue hypoxia may occur.

Respiratory physiology The act of respiration engages 3 processes: 1 -Transfer of oxygen across the alveolus 2 -Transport of oxygen to the tissues 3 -Removal of carbon dioxide from blood into the alveolus and then into the environment Respiratory failure may occur from malfunctioning of any of these processes.

Respiration primarily occurs at the alveolar capillary units of the lungs Fig. 66 -

• After diffusing into the blood, the oxygen molecules reversibly bind to the hemoglobin. • 1 g of hemoglobin combines with a maximum of 1. 36 m. L of oxygen.

The carbon dioxide is transported in 3 main forms: 1 - in simple solution 2 - as bicarbonate 3 -combined with protein of hemoglobin as a carbamino compound.

ETIOLOGY Pulmonary % 52 – Pneumonia % 23. 7 – Atelectasis % 15. 4 – Chronic obstructive pulmonary disease % 13. 7 – Pulmonary edema - cardiogenic %9. 2 – Aspiration % 5. 7 – Pulmonary edema –non-cardiogenic % 4. 9

Non- Pulmonary % 47. 9 – Abdominal % 18. 4 – Central nervous system % 17. 2 – Sepsis % 12. 3

Hypoxemic respiratory failure The pathophysiologic mechanisms 1 -V/Q mismatch: common cause of hypoxemia 2 -Shunt: persistence of hypoxemia despite 100% oxygen inhalation

Common causes of type I (hypoxemic) respiratory failure include the following: • • COPD Pneumonia Pulmonary edema Pulmonary fibrosis Asthma Pneumothorax Pulmonary embolism Pulmonary arterial hypertension • Pneumoconiosis • Granulomatous lung diseases • Cyanotic congenital heart disease • Bronchiectasis • Acute respiratory distress syndrome (ARDS) • Fat embolism syndrome • Kyphoscoliosis • Obesity

Diffusion Limitation Fig. 68 -5

NORMAL RESPIRATORY FAILURE Respiratory workload Neuromuscular capacity Laghi and Tobin, AJRCCM 2003; 168: 10

Increased respiratory workload : • % 30 -50 Inspiratory resistance Elastic recoil • %100 • % 100 -200 i. PEEP -Bronchoconstriction -Bronchial edema -Pulmonary inflammation

Decreased neuromuscular capacity : • Hyperinflation • Critical illness polyneuropathy • Myopathy – – • • Critical illness myopathy Sepsis Ventilator-related muscle damage Drugs Metabolic abnormalities Reduction in the transport of oxygen Drugs Muscle fatigue

Patient Evaluation • Adequacy of oxygenation is evaluated with – Pulse oximetry (Sp. O 2) – Arterial blood gas • Adequacy of Ventilation – End-tidal CO 2 – Arterial blood gas CO 2 • Chest x-ray

Cardiopulmonary Tests • Vital signs and organ perfusion – Blood pressure – Skin symptoms – Consciousness / cooperation • Pneumonia • Congestive Heart Failure • Asthma /COPD

Objectives of clinical evaluation • Detection and correction of life-threatening blood gas abnormalities • Determination of ventilation requirements – Noninvasive Positive Pressure Ventilation – Invasive Mechanical Ventilation • Clarify the cause of respiratory failure • Additional diagnostic tests 2003; 21: 239 Sigillito et al, Emerg Med Clin N Am

TREATMENT • Adequate tissue oxygenation must be ensured Provision airway Adequate ventilation should be started Oxygen therapy Blood transfusion Respiratory depression, muscle and nerve function discontinued medications that may affect • • The primary cause should be treated Symptomatic treatment

Oxygen Therapy • • • Nasal cannula Simple oxygen mask partial nonrebreathing mask Non-rebreathing maske Large volume nebulizer mask

When Mechanical Ventilation is needed? • • • Pa. O 2 < 60 mm. Hg ± Pa. CO 2 > 45 mm. Hg Respiratory rate > 30 -35 /minute Abdominal breathing Rapid shallow breathing Supporting the use of inspiratory respiratory muscles

Objectives of Mechanical Ventilation • • • ↑ Pa. O 2 ↓ Pa. CO 2 ↓ Acidosis Unloading of respiratory muscles Reduce breathlessness

Mechanical Ventilation Treatment Options • Endotracheal intubation + invasive mechanical ventilation • Noninvasive mechanical ventilation

Indications for Intubation • • Respiratory arrest Hemodynamic instability Confusion Acute progressive respiratory acidosis When NIPPV is contraindicated No response to NIPPV Hypoxemic patients unresponsive to oxygen therapy

Differential Diagnosis • Pulmonary Diseases • Cardiovascular Diseases • Systemic Diseases