What is hypoxemia?
insufficient O2 transferred to the blood
What is hypercapnia?
inadequate CO2 removal
Are hypoxemic and hypercapnic states exclusive or can they occur at the same time?
they can occur at the same time
What is the alveolar capillary membrane?
the space between the pulmonary capillary and the alveolus in which O2 and CO2 are exchanged
Is acute respiratory failure a disease or condition?
a condition that may result from a specific disease or system problem
What parameters constitute oxygenation failure?
PaO2 < 60mmHg on 60% oxygen
What parameters constitute ventilatory failure?
PCO2 > 45mmHg and pH < 7.35
Why is there a gap between the lowest value of the normal range of PaO2 and what classifies oxygenation failure?
compensation efforts are accounted for (consider the COPD patient)
What are the three types of causes of hypoxemic respiratory failure?
ventilation-perfusion (V/Q) mismatch, shunt, diffusion limitation
Name five examples of V/Q mismatch.
COPD, pneumonia, asthma, atelectasis, pulmonary embolus
How would you treat a hypoxemic V/Q mismatch?
treat the cause and administer O2
How would you treat the V/Q mismatch of COPD?
inhaled corticosteriods and O2
How would you treat the V/Q mismatch of pneumonia?
antibiotics and O2
How would you treat the V/Q mismatch of asthma
short or long acting bronchodilators or epinephrine and O2
How would you respond to a V/Q mismatch caused by a PE?
d-dimer lab test with great specificity for a negative value, heparin, and O2
What is a shunt?
the passage of blood through the cardiorespiratory system without participating in gas exchange
What is an anatomical shunt?
the passage of blood through an anatomic channel in the heart and therefore does not pass through the lungs (i.e., ventricular septal defect)
What is a intrapulmonary shunt?
the passage of blood through the pulmonary capillaries without participating in gas exchange; caused by non-cardiogenic pulmonary edema from conditions such as ARDS
A severe V/Q mismatch may be classified as this type of hypoxemic respiratory failure.
Do you give O2 to a patient with an intrapulmonary shunt?
no; consider the patient with ARDS, he or she will likely need to be intubated
Define diffusion limitation.
gas exchange across the alveolar capillary membrane is compromised by a process that thickens or destroys the membrane
Name four examples of diffusion limitation.
severe emphysema, recurrent pulmonary emboli, pulmonary fibrosis, hypoxemia present during exercise
How can you that hypoxemic is a result of diffusion limitation?
hypoxemia is present during exercise but not at rest; During exercise, blood moves more rapidly through the lungs. Because transit time is increased, red blood cells are in the lungs for a shorter time, decreasing the time for diffusion of O2 across the alveolar capillary membrane.
What are the four types of hypercapnic respiratory failure?
airways and alveoli, central nervous system, neuromuscular conditions, chest wall
Define hypercapnic respiratory failure.
imbalance between ventilatory supply and demand; supply is the maximum ventilation the patient can sustain without muscle fatigue; demand is the amount of ventilation needed to keep PaCO2 within normal limits
Name four examples of airways and alveoli hypercapnic respiratory failure.
asthma, emphysema, cystic fibrosis, chronic bronchitis
Name three examples of central nervous system hypercapnic respiratory failure.
drug overdose, brainstem infarction (cerebellum injury decreases respiratory drive to breathe), spinal chord injuries (C5 or higher)
Name two examples of neuromuscular hypercapnic respiratory failure.
muscular dystrophy and multiple sclerosis
Name four examples of chest wall hypercapnic respiratory failure.
flail chest, fractures, mechanical restriction, muscle spasm
What is a flail chest?
asymmetric chest expansion
In a very general sense, when does respiratory failure occur?
when compensatory mechanisms fail
In general, what types of signs may be evident with respiratory failure?
specific (classic respiratory systems) or nonspecific
What might you suspect if your patient tells you that he has been waking up with a severe morning headache?
hypercapnia related to slowed breathes secondary to COPD or sleep apnea
Would cyanosis be considered an early sign of respiratory failure? Why or why not?
no; cyanosis doesn't occur until PaO2 is less than 45mmHg
Would tachycardia and mild hypertension be considered an early sign of respiratory failure? What about hypotension?
yes; hypotension is a late sign indicating that the sympathetic nervous system can't compensate
List six clinical manifestations of hypoxemia and hypoxia.
dyspnea; retractions; rapid, shallow breathing pattern; decreased cardiac output; impaired renal function; metabolic acidosis and cell death
Lactic acid is accumulating in your patient and he is being acidotic. You are giving a change of shift report and your fellow nurse asks about the patient's prognosis. What do you say?
Why might your hypoxemic/hypoxic patient experience tachycardia and HTN secondary to increased cardiac output then angina, dysrhythmias, and a decreased cardiac output?
The heart tries to compensate for the decreased O2 level in the blood by increasing the heart rate and cardiac output. A cardiovascular hyperdynamic state may also occur due to catecholamine release that is associated with physiologic stress response. As the PaO2 decreases and acidosis increases, the heart muscle may become dysfunction and cardiac output may decrease. In addition, angina and dysrhythmias may occur. All of these consequences result in a further decrease in oxygen delivery.
Who is the best source of physical and history information?
Why might a chest x-ray of someone with pulmonary edema be misleading?
pulmonary edema is not seen until 30% of the lungs is full
When would you be considered that a patient's Hgb was too low and therefore effecting their O2 carrying capacity?
A patient with abnormal electrolytes might present with this serious secondary condition.
What is the number one cause of respiratory failure?
sepsis (consider the infections origin in urine or sputum)
An elderly patient presents to your unit. You suspect that he has a UTI but you have not received the results of his urine culture. What action should you take?
give a broad spectrum antibiotic to prevent sepsis and subsequent respiratory failure
Why might a pulmonary artery catheter be placed in a patient experiencing respiratory failure?
it measures pressures in the heart; determines if black flow is occurring from the lungs to the heart
What integumentary signs would you see with acute respiratory failure?
cool to touch, cyanotic, clamy, edematous (fluid retention)
What respiratory signs would you see with acute respiratory failure?
retractions, use of accessory muscles, pursed lip breathing, tripod positioning, paradoxic breathing
What cardiac sign would you see with acute respiratory failure?
extra heart sounds (S3) with pulmonary edema
What GI signs would you see with acute respiratory failure?
hard or distended abdomen, ascites
What neurologic sign would you see with acute respiratory failure?
What are your four goals for the patient with acute respiratory failure?
baseline ABGs, baseline breath sounds, baseline breathing patterns (i.e., no dyspnea), effective cough and ability to clear secretions
What is the best way to prevent acute respiratory failure?
thorough history and physical assessment to catch early signs of distress
When administering oxygen we should use the minimum or maximum amount tolerated by the patient?
In a patient with respiratory failure the PaO2 should be maintained at which of the following levels? 45-55mmHg, 55-60mmHg, >80mmHg
True or False. In a patient with acute respiratory failure the SaO2 level should be kept at 90% or more at the lowest O2 concentration possible.
What is PPV?
positive pressure ventilation
What are two examples of noninvasive PPV?
BiPAP and CPAP
Name five ways to mobilize secretions for a patient with acute respiratory failure.
hydration and humidification, chest PT, airway suctioning, effective coughing, effective positioning (supine to prone)
What might you use to reduce airway inflammation causing acute respiratory failure?
If you use corticosteroids to reduce airway inflammation, what secondary condition might you suspect with long term use?
What two medication classes might you use to reduce pulmonary congestion causing acute respiratory failure?
diuretics and nitrates (if heart failure is present)
What two medication classes might you use to reduce severe anxiety, pain, and agitation causing acute respiratory failure?
benzodiazepines and narcotics
Why might you be concerned if your patient with acute respiratory distress is experiencing malnourishment?
they are more likely to use up their energy and protein stores and are less likely to fight an infection such as sepsis