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Terms in this set (36)
what diffuses more rapidly across the alveolar-capillary bed, oxygen or CO2?
dead space and hunt
what two factors interfere with matching ventilation to perfusion to create effective pulmonary gas exchange?
areas in the respiratory system that do not participate in gas exchange
alveolar dead space
When an area of the lung is ventilated but NOT perfused, what is it is called? high ventilation-perfusion ratio, occurs when ventilation exceeds perfusion; this is seen in PE, pulmonary infarction, cardiogenic shock, and mechanical ventilation associated with high tidal volumes
this refers to blood that bypasses (or shunts) alveoli without picking up oxygen
when blood moves from the right side of the heart to the left side of the heart without passing through the lungs (septal defects in the heart)
when perfusion exceeds ventilation, there is low ventilation-perfusion ratio, and a shunt is present. this is seen in pneumonia, atelectasis, tumor, or mucus plug
when both ventilation and perfusion are decreased; seen with pneumothorax and severe ARDS
dissolved and attached to hgb
in what two forms is oxygen carried throughout the body?
the partial pressure of oxygen in arterial blood (PaO2)
this represents the level of dissolved oxygen in plasma; less than 3% of all oxygen is carried in this form
saturation of oxygen in arterial blood (SaO2)
this represents the percentage of hgb molecules that are bound with oxygen (this is where most of oxygen is bound)
refers to the capacity of hemoglobin to combine with oxygen
true or false: we want affinity to be in the middle, not high or low
hgb binds readily with oxygen at alveolar-capillary membrane but does not readily release oxygen to the tissues
what happens when affinity is high?
hgb releases oxygen more readily at the tissue level
what happens when affinity is low?
oxyhemoglobin dissociation curve
depicts the relationship between oxyhemoglobin saturation (SaO2) and the arterial oxygen tension (PaO2)
Shift to the _____, this indicates alkalosis, decreased PaCO2, decreased temp, high O2 sat, increased affinity of hgb for oxygen, and a decreased release of oxygen to the tissues
Shift to the ______ indicates acidosis, increased PaCO2, and increased temp. There is lower O2 sat, decreased affinity of hgb for oxygen, and increased release of oxygen to the tissues
dissolved (10%), attached to hgb (30%), and bicarbonate (60%)
what 3 forms is carbon dioxide carried in in the blood?
Acute Respiratory Failure
sudden and life-threatening deterioration in pulmonary gas exchange, resulting in CO2 retention and inadequate oxygenation; occurs when insufficient oxygen is transported to the blood or inadequate CO2 is removed from the lungs and the pts compensatory mechanisms fail
PaO2 60 mmHg or less
PaCO2 >45 mmHg
what is the PaO2, PaCO2 and pH in ARF?
- Type 1: Acute hypoxemic resp failure
- Type 2: Acute hypercapnic resp failure
what are the types of Acute Respiratory Failure?
what is the most common cause of hypoxemia?
right-to-left shunt and alveolar hypoventilation
what are the most clinically significant causes of type 1 Respiratory failure?
1. inhalation of hypoxic gas mixtures/severe reduction of barometric pressure (high altitudes)
2. Alveolar hypoventilation
3. Impairment of diffusion (usually small effect, high FiO2 helps, present in ephysema and diffuse lung injury)
4. Ventilation-perfusion mismatching (most common cause of oxygen desaturation)
5. Right to Left Shunt
6. Reduced oxygen in mixed venous blood - may occur from abnormal pulm gas exchange, too high or too low CO or high metabolic rates (fever)
what are some potential causes of type 1 respiratory failure: hypoxemia?
Right to Left Shunt
the result of continuous perfusion of lung regions where gas exchange cannot occur; indicates closure of air passages, especially the distal airways and alveoli; changes in FiO2 have little effect on PaO2 when the true shunt fraction exceeds 30%
dyspnea, cyanosis (lips, skin, nail beds - suggest PaO2 less than 60), restlessness, confusion, anxiety, delirium, tachypnea, tachycardia, HTN, cardiac dysrhythmias, tremors
what are the s/s of ARF type 1?
Type 2 hypercapnic respiratory failure
type of resp failure; result of inadequate alveolar ventilation, characterized by marked elevation of CO2 with relative preservation of oxygenation; caused by alveolar hypoventilation and ventilation-perfusion mismatching when there is no compensation by increased ventilation of well-perfused regions; respiratory acidosis
1. decreased ventilatory drive (caused by meds, brainstem lesions, hypothyroidism, morbid obesity, sleep apnea)
2. Respiratory muscle failure or fatigue (neuromuscular dysfunction, ALS, GBS, MG, etc.)
3. increased work of breathing (COPD, asthma, pneumothorax, etc.)
what 3 factors contribute to acute hypercapnic/ventilatory resp failure?
1. Neuromuscular disorders: MG, GBS, poliomyelitis, spinal cord injuries
2. Airway disease: COPD, asthma
3. CNS dysfunction: stroke, increased ICP, meningitis
4. Chemical depression: opioids, sedatives, anesthetics, sleep apnea, morbid obesity, etc.
5. Ventilation-perfusion mismatch: PE, pneumothorax, ARDS, pulm edema, etc.
what are some common causes of ventilatory/hypercapnic resp failure?
dyspnea, headache, peripheral and conjunctival hyperemia, HTN, tachycardia, tachypnea, impaired consciousness, use of accessory muscles to breathe
what are the s/s of hypercapnia?
combined hypoxemic and hypercapnic respiratory failure
develops as a consequence of a combined inadequate alveolar ventilation and abnormal gas transport; commonly seen in asthmatic exacerbation, emphysema complicated by lower resp tract infection, severe pneumonia, pulm edema, and PE; any type 1 (hypoxemic) failure may lead to this if increased work of breathing and hypercapnia are involved
- increased pulmonary vascular resistance
- cor pulmonale
- right-sided HF
- impaired LV function
- Reduced CO
- Cardiogenic pulmonary edema
- Diaphragmatic fatigue from increased workload of resp muscles
what are some possible complications of hypoxemia and hypercapnia?
- ABGs to determine exact level of PaO2, PaCOs, and pH
- other tests to determine the etiology: CXR, sputum culture, PFTs, CT, CBC, Electrolytes, UA, ECG, echo, etc.
what are the diagnostic tests for acute combined respiratory failure?
to determine whether intubation and positive-pressure ventilation are required and do not delay this!
what is the most critical assessment objective in pts with suspected acute combine respiratory failure?
1. Correct the cause and alleviate the hypoxia and hypercapnia
2. Endotracheal intubation and mechanical ventilation should be performed rapidly to minimize comps associated with prolonged hypoxemia (cardiac dysrhythmias, anoxic encephalopathy)
3. Pts with hyopxemic failure should received rapidly increased FiO2 and continuous pulse ox until SaO2 of 90% or higher is obtained
4. Pts with hypercapnic resp failure should be immediately assessed for impaired central resp drive associated with sedative or narcotic and give reversal agents
5. Also assess for underlying bronchospasm r/t astham exacerbation or COPD and give inhaled bronchodilators and systemic steroids
what are some interventions for managing acute respiratory failure?
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