Class 3 (01|25|22) Pulmonary alterations: Acute respiratory failure and Acute respiratory distress syndrome Flashcards
What is respiratory failure?
Respiratory failure is a state in which one or both gas exchange functions are inadequate. Either the amount of oxygen travelling in the blood is insufficient or the amount of carbon dioxide being exhaled from the lungs are inadequate.
When there is inadequate carbon dioxide being eliminated, it results in elevated C02 levels in the body. This leads to HYPERCAPNIA (also called hypercarbia).
What are the two causes of resp failure?
Hypoxemic: There is an issue with oxygenation.
Hypercapnic: Often referred to as ventilatory failure. There is an imbalance between supply and demand.
Describe Hypoxemic respiratory failure.
Hypoxemic: There is an issue with oxygenation.
The primary problem is an inadequate transfer of oxygen between the alveoli and pulmonary capillary bed.
The lungs may be receiving enough oxygen, but the main issue is the inability to transfer the oxygen into the blood.
Usually a result of a combination of reasons
What are the 4 primary reasons for hypoxemic respiratory failure
Ventilation-Perfusion Mismatch
Shunting
Diffusion Limitations/dead space
Alveolar Hypoventilation
Describe Ventilation-Perfusion Mismatch in Hypoxemic resp failure.
What can cause it (3)?
What is the primary intervention/treatment?
There are alterations in the body that can result in a mismatch of this ratio of blood perfusing the lungs and the amount of fresh gas that reaches the alveoli. (normal ratio 1:1)
pneumonia: the alveoli are often collapsed and filled with pus and fluid. So, the amount of blood attempting to perfuse the lungs is going to be greater than the amount of fresh gas that can reach the alveoli.
COPD
Atelectasis or pain: If a patient is post-op and is not breathing deeply due to pain, then hypoventilation can actually cause atelectasis.
Primary intervention/treatment: administration of oxygen/determine the cause of the mismatch
Describe shunting in Hypoxemic resp failure
What can cause it? (2)
Shunting: This is when the blood exits the heart without having participated in gas exchange.
Can be caused by:
Anatomical shunt: hole in between the atria or ventricles of the heart
Intrapulmonary shunt: The blood flows through the capillaries in the lungs but gas exchange is not taking place. Commonly the alveoli being filled with fluid. Examples could be pneumonia, pulmonary edema, acute respiratory distress syndrome.
Describe Diffusion Limitations/dead space Hypoxemic resp failure.
What can cause it? (2)
decrease in gas exchange which takes place on the alveolar capillary membrane, typically happens due to the damage or thickening of the membrane.
Can be caused by
pulmonary fibrosis: condition in which the lungs become scarred over time
emphysema: linings of the tiny air sacs in your lungs become damaged
Describe Alveolar Hypoventilation in Hypoxemic resp failure
What can cause it? (3)
Alveolar Hypoventilation: decrease in the respiratory rate or in the depth of breathing. This causes an increase in carbon dioxide retention and a decrease in Pa02.
Can be caused by:
CNS dysfunction - i.e. CNS depressants, head injury.
chest wall dysfunction, such as having fractured ribs.
neuromuscular disease
Alterations that affect the respiratory system causing hypoxemic respiratory failure. (5)
Acute respiratory distress syndrome
Pneumonia
Toxic inhalation (smoke)
Hepatopulmonary syndrome: low-resistance flow state, ventilation-perfusion mismatch
Massive pulmonary embolism (thrombus emboli, fat emboli)
Alterations that affect the cardiac system casuing hypoxemic respiratory failure.
(3)
Anatomical shunt
Cardiogenic pulmonary edema
Shock (decreased blood flow through pulmonary vasculature)
Describe Hypercapnic respiratory failure.
Hypercapnic: Often referred to as ventilatory failure. There is an imbalance between supply and demand.
The ventilatory supply: is the max ventilation. This is what a patient can do without their respiratory muscles becoming fatigued.
The ventilatory demand: is the amount of ventilation that an individual needs in order to keep the carbon dioxide level within normal range.
In most cases, the supply exceeds the demand. Our bodies are able to adapt to that.
What are the four primary reasons for hypercapnic resp failure? (4)
Dysfunction of the Airway or Alveoli
CNS Depression
Abnormalities of the Chest Wall:
Neuromuscular Conditions:
Describe CNS depression in Hypercapnic respiratory failure.
What can cause it? (4)
CNS Depression: not breathing deeply or quickly enough, then it can suppress the respiratory drive. As a result, that carbon dioxide level is going to increase.
Can be caused by High spinal cord injury Brainstem infarction Sever head injury Overdoes
Describe Abnormalities of the Chest Wall in Hypercapnic respiratory failure.
What can cause it? (2)
Abnormalities of the Chest Wall: Conditions that limit the amount of lung expansion
Can be caused by:
Flail chest: Flail chest is a life-threatening medical condition that occurs when a segment of the rib cage breaks due to trauma and becomes detached from the rest of the chest wall.
Change in spinal cord alterations: scoliosis which effect the lungs ability to take full breaths
Describe Neuromuscular Conditions Hypercapnic respiratory failure.
What can cause it? (3)
Neuromuscular Conditions: muscle dysfunction/paralysis/weakness inhibiting breathing
- Can be caused by:
Multiple sclerosis: common demyelinating disease, in which the insulating covers of nerve cells in the brain and spinal cord are damaged.
Muscular dystrophy: progressive weakness and breakdown of skeletal muscles over time.
Guillain-Barre syndrome: rapid-onset muscle weakness caused by the immune system damaging the peripheral nervous system.
Describe Dysfunction of the Airway or Alveoli Hypercapnic respiratory failure.
What can cause it? (3)
Dysfunction of the Airway or Alveoli: air trapping or any obstruction to air flow.
Can be caused by:
Cystic fibrosis: Long-term issues include difficulty breathing and coughing up mucus as a result of frequent lung infections
Asthma
Emphysema: linings of the tiny air sacs in your lungs become damaged
Alterations that affect the CNS causing hypercapnic respiratory failure. (4)
Brainstem infarction
sedative and opioid overdose
Spinal Cord injury
severe head injury
Alterations that affect the chest wall causing hypercapnic respiratory failure. (4)
Thoracic trauma (eg; flail chest)
Kyphoscoliosis
Pain
Morbid obesity
Alterations that affect the Neuro-muscular system causing hypercapnic respiratory failure. (9)
Myasthenia gravis Critical illness polyneuropathy acute myopathy toxic ingestion amyotrophic lateral sclerosis phrenic nerve injury Guillain-Barré syndrome poliomyelitis muscular dystrophy multiple sclerosis
Alterations that affect the respiratory system causing hypercapnic respiratory failure. (3)
Asthma
COPD
Cystic fibrosis
What is Kyphoscoliosis?
Kyphoscoliosis is an abnormal curve of the spine on two planes: the coronal plane, or side to side, and the sagittal plane, or back to front. It’s a combined spinal abnormality of two other conditions: kyphosis and scoliosis.
What is Myasthenia gravis?
Myasthenia gravis (MG) is a chronic autoimmune disorder in which antibodies destroy the communication between nerves and muscle, resulting in weakness of the skeletal muscles.
What are the early signs of resp failure
change in mental status: restlessness, agitation, confusion, combative
Tachycardia; tachypnea; as body realized no enough O2 or too much CO2 — use of accessory muscles
Mild hypertension in the
patient position - laying flat and sings of resp distress and more comfortable sitting up
dyspnea
respiratory alkalosis: tachy
What are the late signs of resp failure?
Paradoxical breathing - abdomen and chest are moving in the opposite manner (maximal use of accessory)
Bradypnea: For patients who have tachypnea, we might see bradypnea now. This is because they are so tired because of breathing so fast.
respiratory acidosis: Bradypnea causing an accumulation CO2
Dyspnea — worsening — speaking 1-2 words
Cyanosis — unreliable (LATER)
Worsening mental status — unresponsive (LATER)