Term
|
Definition
| amount of air inspired with each normal breath V(t) |
|
|
Term
|
Definition
amount of air inspired each minute V(m)
V(m) = V(t) x f
= 500 x 12 |
|
|
Term
|
Definition
amount of gas exhaled each minute V(e)
V(m) > V(e) because CO2 production is slightly less than O2 consumption (Respiratory quotient) |
|
|
Term
|
Definition
V(d) The air that remains in the conducting airways with each breath. 500 mL is the normal tidal volume. Of that, 150 mL remains in the conducting airways and does not take part in gas exchange.
Approx. = to the body weight in pounds |
|
|
Term
|
Definition
| 1. Alveolar dead space - any alveoli that are not perfused are considered dead space. Fresh gas will enter these alveoli, but cannot diffuse into the blood stream |
|
|
Term
|
Definition
| anatomic dead space + alveolar dead space. Ventilating physiologic dead space requires increased energy demands in order to maintain adequate oxygenation and ventilation. Can lead to respiratory insufficiency or failure |
|
|
Term
| How can we measure dead space? |
|
Definition
Bohr Equation
By using the concentration of carbon dioxide in expired gas and in the arterial blood.
(Vd/Vt) = (PaCO2-PeCO2)/PaCO2 |
|
|
Term
| How do anatomic and physiologic dead space compare in healthy individuals vs. sick? |
|
Definition
| In healthy people, anatomic dead space = physiologic dead space. In diseased individuals, physiologic dead space can greatly increase |
|
|
Term
| If alveolar ventilation increases, what happens to P(A)CO2? e.g. if V(A) doubles from 4.2 L/min to 8.4 L/min, what happens to P(A)CO2? |
|
Definition
| It decreases. P(A)CO2 would halve from 40 to 20. |
|
|
Term
| What is hyperventilation? How is it diagnosed? |
|
Definition
| An increase in alveolar ventilation greater than that required by the rate of CO2 production. It is diagnosed when PaCO2 is less than 35 mmHg (normal is 35-45). |
|
|
Term
| What are causes of hyperventilation? (6) |
|
Definition
Hypoxemia
Metabolic Acidosis
Anxiety
Pain
Hypotension
Fever or sepsis |
|
|
Term
| What is hypoventilation? How is it diagnosed? |
|
Definition
| It is a decrease in alveolar ventilation below the level required by the rate of CO2 production. Diagnosis is PaCO2 above 45 mmHg |
|
|
Term
| What happens to the blood in hypoventilation? |
|
Definition
| CO2 is retained and can lead to respiratory acidosis. |
|
|
Term
| What are the causes of hypoventilation? |
|
Definition
Airway obstruction
Restriction of the chest wall or lung parenchyma
Respiratory depression by drugs, alcohol, or neurological disease
Neuromuscular diseases producing weakness of th respiratory muscles
Spinal cord injury resulting in paralysis of the respiratory muscles |
|
|
Term
| Can hypoventilation cause alveolar hypoxia? |
|
Definition
Yes - it causes and increased P(A)CO2 which will dilute the amount of O2 within the alveoli, leading to a reduced level of alveolar oxygen
As P(A)CO2 goes up, P(A)O2 goes down |
|
|
