Resp Failure Flashcards
What are the 2 types of respiratory failure & their definitions?
Hypercapneic PaCO2 >50
Hypoxemic: PaO2 < 60mmHg
What are the major causes of alvolar hypoventilation?
Decreased resp drive/effort (drugs, sleep, breath holding)
Neuromuscular incompetence
Muscle fatigue due to increased load (abnormal mechanics i.e. obseity, scoliosis OR increased dead space)
**all are decreased ventilatory capacity EXCEPT increased dead space, which is increased ventilatory demand
What are the clinical consequences of hypercapnea?
CNS effects: anxiety, confusion, coma, death
Cardiovascular effects: hypertension, hypotension, ventricular irritability
Can be acute or chronic
What is the difference between acute and chronic hypercapnia?
Chronic can be mediated by the kidney, which makes more bicarbonate; pH near 7.40
Acute: renal compensation limited, pH < 7.3
What are the clinical consequences of hypoxemia?
Tissue hypoxia –> CNS effects, cardiovascular effects (arrhythmias, shock), other organ systems fail
Why is SpO2 not the best measure for hypoxemia?
Whats a better measure?
Because the Hb holds on to O2 even at low PaO2
If PaO2=60, O2 saturation is 90!
A better measure is PaO2
What are the signs and symptoms of hypoxemic respiratory failure?
Acute: dyspnea, tachypnea, cyanosis,somnolence (sleepy state), asterixis (tremor of hand), seizures, tachycardia
Chronic: polycythemia (more RBC/volume whole blood), cor pulmonale
How can you tell whether hypoxemic respiratory failure is acute or chronic?
Can’t tell from ABG
Polycythemia & cor pulmonale (pulm htn) are signs of chronicity
What doesn’t respond well to increased O2 supplementation?
Every condition does except a shunt from alveolar filling!!
It’s diagonstic of a shunt: if they don’t respond to supplemental O2
What are the indications for intubation & mechanical ventilation?
Progressive hypercapnea with fatigue
Refractory hypoxemia
Inability to protect the airway
Severe respiratory acidosis – pH<7.2
Increased metabolic demand
Pulmonary toilet
What does a + pressure mechanical ventilator do?
Pushes gas into lungs
You set the:
Flow rate
Respiratory rate
FiO2
Tidal Volume
Pressure generated is based on compliance of the pt’s airways, lungs, chest wall
What is PEEP and why do we use it?
Minimum pressure is maintained in the ventilator circuit at all times
Keeps alveoli from collapsing
What are the problems with positive pressure ventilation?
Not good for your heart: messes with the pressures –> reduced venous return, hypotension & reduced CO
Damage to lungs: high volume & high FiO2, pneumothorax, gas trapping
Trapped gas: if ventilator pushes air before it can all escape
