Exam 4 - Calculations for Respiratory
Why does some air that enters the respiratory system not reach the alveoli?
Part of each breath remains in the conducting airways (trachea, bronchi).
Given an atmosphere with a pressure of 720mmHg, calculate the partial pressures of all gases if the air is made up of 4% argon.
Partial Pressure of Argon = 0.04 x 720mmHg = 28.8 mmHg
Given an atmosphere with a pressure of 720mmHg, calculate the partial pressures of all gases if the air is made up of 1% carbon dioxide.
Partial Pressure of CO2 = 0.01 x 720mmHg = 7.2 mmHg
Given an atmosphere with a pressure of 720mmHg, calculate the partial pressures of all gases if the air is made up of 80% nitrogen.
Partial Pressure of N2 = 0.80 x 720mmHg = 576 mmHg.
Given an atmosphere with a pressure of 720mmHg, calculate the partial pressures of all gases if the air is made up of 15% oxygen.
Partial Pressure of O2 = 0.15 x 720mmHg = 108 mmHg
What is the air was also humid? How does this change the partial pressures of the above gases if the air has 100% humidity at a partial pressure of 40 mmHg?
720 mmHg - 40 mmHg = 680 mmHg "Dry Air" N2 = 0.8 x 680 mmHg = 544 mmHg O2 = 0.15 x 680 mmHg = 102 mmHg Argon = 0.04 x 680 mmHg = 27.2 mmHg CO2 = 0.01 x 680 mmHg = 6.8 mmHg Under a lower atmospheric pressure, O2 may be harder to get enough of than under normal atmospheric conditions. You would still have a higher PO2 (102 mmHg) than inside the lungs (100 mmHg) so inhaling would be okay. You would still have a lower PCO2 in the atmosphere (6.8 mmHg) than in the lungs (46 mmHg), so you could exhale okay.
Calculation/Definition for Minute Ventilation?
Breaths/min x Tidal Volume (mL/breath). Total volume of air entering and leaving the respiratory system each minute.
Does vital capacity increase or decrease with age? Why?
Decreases; because the muscles weaken and the lungs become less elastic.
Calculation/Definition for Tidal Volume?
End of Normal Inspiration MINUS end of normal expiration. Avg: 500mL The volume of air that moves during a single inspiration or expiration. "Breath quietly" normal breathing.
Calculation for Functional Residual Capacity (FRC)?
Expiratory Reserve Volume (ERV) + Reserve Volume (RV).
Calculation/Definition for Expiratory Reserve Volume (ERV)?
From the end of normal expiration to the lowest dipped curve. The amount of air forcefully exhaled after the end of normal expiration (avg = 1100mL).
Calculation/Definition of Residual Volume (RV)?
From the lowest part of the dipped curve to the bottom of the scale; How much air is left in the lungs, trachea, and bronchi upon blowing all the air out/the volume of air in the respiratory system after maximum exhalation. Cannot be directly measured. Avg: 1200mL (depends on sizeof person)
Calculation/Definition for Inspiratory Reserve Volume (IRV)?
From the top of the peak (highest point) to top of tidal volume curve (or end of normal inspiration). The additional volume you inspire above the tidal volume (6 fold increase over Vt). "At the end of quiet inspiration, take in as much additional air as you possibly can." Avg = 3000mL in a 70kg man.
How do we measure vital capacity? What does this also allow measurement of? When is this decreased?
The person takes in as much air as possible, then blows it all out as fast as possible; This also allows measurement of forced expiratory volume in 1 sec or FEV1 (how fast air leaves the airways in the 1st second of expiration) - this is decreased in certain lung diseases like asthma and with increased age.
What is a lung capacity?
The sum of 2 or more lung volumes.
Calculation for Total Lung Capacity (TLC)?
Tidal Volume (Vt) + Inspiratory Reserve Volume (IRV) + Expiratory Reserve Volume (ERV) + Reserve Volume (RV).
Calculation for Vital Capacity?
Tidal Volume (Vt) + Inspiratory Reserve Volume (IRV) + Expiratory Reserve Volume (ERV). Represents the maximum amount of air that can be voluntarily moved into or out of the respiratory system with one breath.
Calculation/Definition for Inspiratory Capacity?
Tidal Volume (Vt) + Inspiratory Reserve Volume (IRV). Definition: How much you can breathe in.
How do we measure the volume of fresh air entering the alveoli?
Tidal Volume - Dead Space Volume
Calculation/Definition for dead space?
Tidal Volume - Trachea Volume; The volume of air which is inhaled but does not take part in the gas exchange (it either remains in the conducting airways, or reaches alveoli that are not or are poorly perfused).
Calculation/Definition for minute alveolar ventilation with the above numbers?
Ventilation Rate x Tidal Volume - Dead Space 5 breaths/min x 500mL/breath - 150mL = 5 breaths/min x 350mL = 1750mL/min
Would you be able to breath in the above environment? Would it be harder or easier?
You would be able to inhale and intake oxygen because the PO2 is higher than inside the lungs (108mmHg vs 100mmHg). Exhalation should also be okay because the PCO2 is lower in the atmosphere than in the lungs (46 mmHg returning versus 7.2 mmHg outside). However getting enough O2 may be harder than under normal atmospheric conditions. HIGH TO LOW PRESSURE GRADIENTS.
What is the normal respiration rate?
12-20 breaths per minute.
Given respiration rate of 5 breaths/minute, tidal volume of 500mL, and dead space volume of 150mL - what is the minute ventilation? What is the normal minute ventilation for these numbers?
5 breaths/min x 500mL/breath = 2500mL/min. Minute Ventilation: 500mL x 5 breaths/minute = 2500mL/min
