Acute Respiratory Failure I and II and Chronic Respiratory Failure Flashcards
Hypoexemic Respiratory Failure
– Hypoxemic (“Type 1”)
• PaO2 <60 mmHg
Hypercapnic Respiratory Failure
-Hypercapnic (Ventilatory-”Type 2”)
• PaCO2 >50 mmHg
Hypoxemic Respiratory Failure Causes
- Pneumonia
- Cardiogenic Pulmonary Edema
- Noncardiogenic Pulmonary Edema
– Acute Respiratory Distress Syndrome (ARDS)
• Others
Causes of Hypoxemia
- Ventilation/Perfusion Abnormalities
- Shunt
- Hypoventilation
- Diffusion
- Decreased “FIO2 ” (PIO2)
Hypercapnic Respiratory Failure Causes
- CNS depression
- Neuromuscular Disease
- Chest wall abnormalities
- Upper airway obstruction
- Obstructive lung disease
Status Asthmaticus
- Inability to speak in phrases or full sentences
- Use of accessory muscles
- Pulsus paradoxus >25 mmHg
- Eucapnia or hypercapnia
- “Quiet” chest
- Altered mental status
Variable Extrathoracic Obstruction
Variable Intrathoracic Obstruction
Causes of Pulmonary Edema
- Increased capillary hydrostatic pressure
- Increased capillary permeability
- Reduced lymph drainage
- Decreased interstitial pressure
- Decreased colloid osmotic pressure
- Uncertain etiology
– High altitude
– Neurogenic
– Heroin
Capillary hydrostatic pressure favors movement […] of the capillary.
out
Plasma colloid oncotic pressure favors movement […] the capillary.
in to
Tissue hydrostatic pressure favors movement […] the capillary.
in to
*except in the lung where tissue hydrostatic pressure is probably negative
Tissue colloid pressure favors movement […] the capillary.
out of
Clinical Disorders Associated with the Development of ARDS - Direct Lung Injury
Direct Lung Injury
• Common Causes
– Pneumonia
– Aspiration of gastric contents
• Uncommon Causes
– Pulmonary contusion
– Fat emboli
– Near drowning
– Inhalational injury
Clinical Disorders Associated with the Development of ARDS - Indirect Lung Injury
Indirect Lung Injury
• Common Causes
– Sepsis
– Severe trauma with shock
• Uncommon
– Acute pancreatitis
– Transfusion of blood products (TRALI)
Acute ARDS ( diffuse alveolar damage)
ARDS Fibroproliferative Stage
Hypercapnia - decreased alveolar ventilation
- increased physiologic dead space
- decreased minute ventilation
pulsus paradoxus
Pulsus paradoxus, also paradoxic pulse or paradoxical pulse, is an abnormally large decrease in stroke volume, systolic blood pressure and pulse wave amplitude during inspiration. The normal fall in pressure is less than 10 mmHg. When the drop is more than 10 mmHg, it is referred to as pulsus paradoxus.
stridor
- on inspiration
- extrathoracic
Respiratory Failure
The term respiratory failure is used clinically to denote failure of the respiratory system to deliver oxygen to the blood and to remove carbon dioxide.
Respiratory Failure Diagnosis
- begins wih clo=inical suspicion
- confirmation based on ABG analysis
- cardiogenic
- develops in the context of a history of left ventricular dysfunction or valvular heart disease
- A history of previous cardiac disease, recent symptoms of chest pain, paroxysmal nocturnal dyspnea, and orthopnea suggest cardiogenic pulmonary edema
•noncardiogenic
- ARDS
- typical clinical contexts such as sepsis, trauma, aspiration, pneumonia, pancreatitis, drug toxicity, and multiple transfusions.
Cardinal Symptom of Respiratory Failure
dyspnea
Physical Exam Findings in Respiratory Failure
The signs and symptoms of acute respiratory failure reflect the underlying disease process and the associated hypoxemia or hypercapnia. Localized pulmonary findings reflecting the acute cause of hypoxemia, such as pneumonia, pulmonary edema, asthma, or COPD, may be readily apparent. In patients with ARDS, the manifestations may be remote from the thorax, such as abdominal pain or long-bone fracture.
Lobar Pneumonia Physical Exam Findings
- dullness to percussion
- bronchial breath sounds
- crackles
- egophony.
Status Asthmaticus and Severe Hypercapnic Respiratory Failure
- patients will be unable to speak in full sentences and will use accessory muscles due to difficulty breathing
- pulsus paradoxus >25 mmHg is associated with severe status asthmaticus.
- Neurological manifestations include restlessness, anxiety, confusion, seizures, or coma
Asterixis
- a tremor of the hand when the wrist is extended, sometimes said to resemble a bird flapping its wings
- this motor disorder is characterized by an inability to maintain a position, which is demonstrated by jerking movements of the outstretched hands when bent upward at the wrist
- observed with severe hypercapnia
Myoclonis and Seizures
•may be observed with severe hypoxemia
Tachycardia and Various Arrythmias
•may result from hypoxemia and acidosis
Cyanosis
- a bluish color of skin and mucous membranes, indicates hypoxemia
- visible cyanosis typically is present when the concentration of deoxygenated hemoglobin in the capillaries or tissues is at least 5 g/dL
Polycythemia
- a disease state in which the hematocrit (the volume percentage of red blood cells in the blood) is elevated
- complication of long standing hypoxemia
Pulmonary Hypertension - Cor Pulmonale
- frequently is present in chronic respiratory failure
- Alveolar hypoxia potentiated by hypercapnia causes pulmonary arteriolar constriction. If chronic, this is accompanied by hypertrophy and hyperplasia of the affected smooth muscles and narrowing of the pulmonary arterial bed. The increased pulmonary vascular resistance increases afterload of the right ventricle, which may induce right ventricular failure. This, in turn, causes enlargement of the liver and peripheral edema.
- The entire sequence is known as cor pulmonale. The definition of cor pulmonale includes the requirement that the pulmonary hypertension and right ventricular dysfunction must be due to diseases of the lung.
- Right heart disease due to left heart failure or congenital heart disease is NOT considered cor pulmonale
Acute Respiratory Distress Syndrome
- an acute, diffuse, inflammatory form of lung injury that is associated with a variety of etiologies.
- Clinically, ARDS is acute respiratory failure characterized by the acute onset of bilateral alveolar opacities and hypoxemia.
- Approximately 10 to 15 percent of patients admitted to intensive care units have ARDS.
- Healthy lungs regulate the movement of fluid to maintain a small amount of interstitial fluid and dry alveoli, as described in the Starling equation. The injury to the lung markedly increases the alveolar capillary permeability causing excess fluid in both the interstitium and alveoli. Consequences include impaired gas exchange, decreased compliance, and increased pulmonary arterial pressure
Diagnostic Criteria for ARDS
- Respiratory symptoms must have begun within one week of a known clinical insult,or the patient must have new or worsening symptoms during the past week.
- Bilateral opacities must be present on a chest radiograph or computed tomographic (CT) scan.
- The patient’s respiratory failure must not be explained by cardiac failure or fluid overload.
- A moderate to severe impairment of oxygenation must be present, as defined by the ratio of arterial oxygen tension to fraction of inspired oxygen (PaO2/FiO2). The severity of the hypoxemia defines the severity of the ARDS
