10 - resp failure

Question 1

respiratory failure definition

Answer 1

potentially life-threatening deterioration in gas exchange function of resp. system –> impairment of oxygenation, inadequacy of CO2 excretion or a mixture of both

Question 2

oxygen/CO2 cascade

Answer 2

ventilation, altitude and FIO2 determine PAO2 (alveolar). V/Q matching and the shunt help determine PaO2 (arteriolar). SaO2 and Hb conc determine CaO2 –> O2 delivery –> tissue oxygenation

Question 3

diagnosis of respiratory failure

Answer 3

suspected on basis of history and physical exam: but arterial blood gas required to confirm diagnosis

Question 4

clinical features of resp failure are ____, and are related to ____?

Answer 4

nonspecific: often related to underlying cause of failure (and not resp failure itself), or due to end organ dysfunction

Question 5

clinical features of resp. failure

Answer 5

dyspnea, fatigue, headache, anxiety, confusion, tachypnea or bradypnea, altered mental status, cyanosis, accessory muscle use, indrawing, paradoxical abdominal breathing

Question 6

normal ABG values

Answer 6

PaO2 > 60 mmHg. PaCO2 = 40 mmHg. [H+] 20nM/L –> pH 7.4. [HCO3-] 24 mmol/L

Question 7

classification of respiratory failures

Answer 7

type 1 = impaired oxygenation. 2 = hypoventilation. 3 = mixed.

Question 8

what happens to VA, PAO2, PaCO2, PaO2 during hyperventilation

Answer 8

increased alveolar ventilation: as a result, alveolar oxygen increases, and so arteriolar oxygen increases too. arteriolar CO2 decreases

Question 9

what happens to VA, PAO2, PaCO2, PaO2 during hypoventilation

Answer 9

decreased ventilation: decreased PAO2, PaO2 and increased PaCO2

Question 10

what happens to VA, PAO2, PaCO2, PaO2 oxygen impairment

Answer 10

abnormal AaDO2: so decreased PaO2 (also decreased PaCO2). as a result, VA increases, and so does PAO2

Question 11

definition of hypoxemia

Answer 11

PaO2 < 60 mmHg and/or SaO2 < 90%

Question 12

mechanisms of hypoxemia: categorized into normal and abnormal lungs

Answer 12

normal: decreased FiO2 or barometric pressure, hypoventilation. abnormal: shunt, diffusion impairment, ventilation-perfusion mismatch

Question 13

hypercapnia definition and causes

Answer 13

PaCo2 > 40 mmHg with or without acidosis –> caused by increased CO2 production, increased deadspace ventilation, decreased minute ventilation

Question 14

CO2 production is increased by? only leads to hypercapnia when?

Answer 14

fever, sepsis, seizures, exercise, excessive carb loads in diet. only when there is co-existing cardiopulm. dysfunction

Question 15

deadspace ventilation occurs when? examples?

Answer 15

when areas of lung tissue are ventilated by not perfused: COPD, asthma, cystic fibrosis, pulmonary fibrosis, thoracic cage abnormalities, etc.

Question 16

minute ventilation refers to? what if it is inadequate?

Answer 16

volume of air entering and leaving the lungs per unit time (L/min). hypercapnic failure results if MV is inadequate to excrete the CO2 produced by the body

Question 17

reasons for decreased minute ventilation

Answer 17

CNS/resp center depression. spinal cord lesions. peripheral nerve dysfunction. disorders neuromuscular junction. resp muscle weakness. structural abnormalities of the chest/thoracic spine. upper airway, lung or pleural disease.