Respiratory Calculations Flashcards

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Questions and Answers

What is the calculation/definition for Tidal Volume?

End of normal inspiration minus end of normal expiration. Avg: 500mL.

What is the calculation/definition for Inspiratory Reserve Volume (IRV)?

From the top of the peak to the top of tidal volume curve. Avg: 3000mL in a 70kg man.

What is the calculation/definition for Expiratory Reserve Volume (ERV)?

The amount of air forcefully exhaled after the end of normal expiration. Avg: 1100mL.

What is the calculation/definition of Residual Volume (RV)?

How much air is left in the lungs, trachea, and bronchi upon blowing all the air out. Avg: 1200mL. Signup and view all the answers

What is the calculation/definition for Inspiratory Capacity?

Tidal Volume (Vt) + Inspiratory Reserve Volume (IRV). Signup and view all the answers

What is the calculation for Vital Capacity?

Tidal Volume (Vt) + Inspiratory Reserve Volume (IRV) + Expiratory Reserve Volume (ERV). Signup and view all the answers

What is the calculation for Functional Residual Capacity (FRC)?

Expiratory Reserve Volume (ERV) + Residual Volume (RV). Signup and view all the answers

What is the calculation for Total Lung Capacity (TLC)?

Tidal Volume (Vt) + Inspiratory Reserve Volume (IRV) + Expiratory Reserve Volume (ERV) + Residual Volume (RV). Signup and view all the answers

What is the calculation/definition for Minute Ventilation?

Breaths/min x Tidal Volume (mL/breath). Total volume of air entering and leaving the respiratory system each minute. Signup and view all the answers

Given respiration rate of 5 breaths/minute and tidal volume of 500mL, what is the minute ventilation?

2500mL/min. Signup and view all the answers

What is the calculation for minute alveolar ventilation with the above numbers?

1750mL/min. Signup and view all the answers

What is a lung capacity?

The sum of 2 or more lung volumes. Signup and view all the answers

Does vital capacity increase or decrease with age?

Decreases. Signup and view all the answers

How do we measure vital capacity?

The person takes in as much air as possible and then blows it all out as fast as possible. Signup and view all the answers

What is the normal respiration rate?

12-20 breaths per minute. Signup and view all the answers

How do we measure the volume of fresh air entering the alveoli?

Tidal Volume - Dead Space Volume. Signup and view all the answers

Why does some air that enters the respiratory system not reach the alveoli?

Part of each breath remains in the conducting airways. Signup and view all the answers

What is the calculation/definition for dead space?

The volume of air which is inhaled but does not take part in gas exchange. Signup and view all the answers

Given an atmosphere with a pressure of 720mmHg, calculate the partial pressure of nitrogen if the air is made up of 80% nitrogen.

576 mmHg. Signup and view all the answers

Given an atmosphere with a pressure of 720mmHg, calculate the partial pressure of oxygen if the air is made up of 15% oxygen.

108 mmHg. Signup and view all the answers

Given an atmosphere with a pressure of 720mmHg, calculate the partial pressure of argon if the air is made up of 4% argon.

28.8 mmHg. Signup and view all the answers

Given an atmosphere with a pressure of 720mmHg, calculate the partial pressure of carbon dioxide if the air is made up of 1% carbon dioxide.

7.2 mmHg. Signup and view all the answers

Would you be able to breathe in the above environment with a pressure of 720mmHg and 15% oxygen?

Yes, but it may be harder. Signup and view all the answers

What happens to partial pressures of gases when the air is humid at a partial pressure of 40 mmHg?

O2 may be harder to get enough of than under normal conditions. Signup and view all the answers

Study Notes

Tidal Volume

Definition: Volume of air during a single breath, average of 500mL.
Calculated as: End of normal inspiration minus end of normal expiration.

Inspiratory Reserve Volume (IRV)

Definition: Additional air inspired beyond tidal volume, allowing for up to 3000mL in a 70kg man.
Calculated from the peak of inspiration to tidal volume curve.

Expiratory Reserve Volume (ERV)

Definition: Air exhaled forcefully after normal expiration, with an average of 1100mL.
Measurement is taken from the end of normal expiration to the lowest point on the curve.

Residual Volume (RV)

Definition: Volume of air remaining after maximum exhalation, average 1200mL.
Cannot be directly measured; varies based on individual size.

Inspiratory Capacity

Definition: Total air capacity for inhaling, calculated as tidal volume (Vt) + IRV.

Vital Capacity

Definition: Represents maximum air movement in one breath, calculated as Vt + IRV + ERV.

Functional Residual Capacity (FRC)

Definition: Total volume of air remaining in the lungs after normal expiration, calculated as ERV + RV.

Total Lung Capacity (TLC)

Definition: Total volume of air in the lungs after maximum inhalation, calculated as Vt + IRV + ERV + RV.

Minute Ventilation

Definition: Total air volume entering and exiting the respiratory system per minute, calculated as breaths per minute x tidal volume (mL/breath).
Example: At 5 breaths/min and 500mL/tidal volume, minute ventilation = 2500mL/min.

Minute Alveolar Ventilation

Definition: Volume of air reaching the alveoli per minute, calculated as (ventilation rate x tidal volume) - dead space.
Example: With 5 breaths/min and a dead space of 150mL, alveolar ventilation = 1750mL/min.

Lung Capacity

Definition: Sum of two or more lung volumes.

Age and Vital Capacity

Decreases with age due to weakening muscles and reduced lung elasticity.

Measuring Vital Capacity

Method: Deep inhale followed by rapid exhalation.
Allows for measurement of forced expiratory volume in 1 second (FEV1), which can decrease in conditions like asthma.

Normal Respiration Rate

Ranges from 12 to 20 breaths per minute.

Measuring Fresh Air Volume

Calculated as tidal volume - dead space volume.

Dead Space

Definition: Volume of inhaled air not participating in gas exchange, calculated as tidal volume - trachea volume.

Partial Pressures of Gases

For an atmosphere at 720mmHg:
- Nitrogen (N2): 576 mmHg (80% of air)
- Oxygen (O2): 108 mmHg (15% of air)
- Argon: 28.8 mmHg (4% of air)
- Carbon Dioxide (CO2): 7.2 mmHg (1% of air)

Breathing in Lower Atmospheric Conditions

Possible to inhale due to higher PO2 (108mmHg vs 100mmHg).
Exhalation is facilitated by lower PCO2 (7.2 mmHg vs 46 mmHg).
However, obtaining sufficient O2 might be more challenging.

Humid Air Considerations

In humid conditions with a partial pressure of 40 mmHg, effective pressure of dry air drops to 680 mmHg.
Calculated partial pressures for gases become:
- N2: 544 mmHg
- O2: 102 mmHg
- Argon: 27.2 mmHg
- CO2: 6.8 mmHg
In this scenario, inhalation remains possible, but lower availability of O2 compared to normal conditions may complicate respiration.

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Description

Test your knowledge of respiratory calculations with these flashcards. This quiz covers key concepts such as Tidal Volume and Inspiratory Reserve Volume, providing definitions and calculations critical for understanding respiratory physiology.