Respiratory System, Lecture 3 Flashcards
Tidal Volume (TV) - lung resting volumes
amount of air inhaled (tidal inspiration) or exhaled (tidal expiration) in one breath
Inspiratory Reserve Volume (IRV) - lung resting volumes
amount of air in excess of tidal inspiration that can be inhaled with maximum effort; end of tidal inspiration to maximum inspiration
Expiratory Reserve Volume (ERV) - lung resting volumes
amount of air in excess of tidal expiration that can be exhaled with maximum effort; end of tidal expiration to maximum expiration
◦ have a reserve ability to breath more than what you typically breath at resting
Residual Volume - lung resting volumes
amount of air remaining in lungs after maximum expiration; keeps alveoli inflated between breaths, mixes with fresh air on next inspiration
* there is still volume left in lungs after maximum expiration (can be left in passageways or alveoli)
* prevents all the passageways from collapsing
* it will mix with the volume used during inspiration
Lungs - resting capacities
- capacities are combinations of volumes
- vital capacity (VC; combining IRV + TV + ERV): amount of air that can be exhaled with maximum effort after maximum inspiration; maximum inspiration to maximum expiration
◦ 3 of the volumes (everything but residual)
◦ breath it in to highest volume and breath out to highest amount
◦ critical one because it is diagnostic - use it to understand respiratory problems - total lung capacity (TLC; combining IRV + TV + ERV + RV): maximum amount of air lungs can contain
◦ all 4 volumes added together
Changes - rest to exercise
increased breathing from rest to exercise:
- increased TV (any activity leads to growth as you need more volume)
- decreased reserve volumes (both IRV and ERV) - getting smaller as it is no longer being reserved, the tidial volumes becomes bigger at the expense of these two
- increased TV at the expense of IRV and ERV
- what was reserve is now being used actively as part of tidal volume
- no change in VC or RV - vital capacity is just three added together will still lead to same sum
Vital Capacity - forced
forced vital capacity (FVC): volume of air expired forcefully after maximum inspiration (as fast as you can - take in as deep a breath as you can and breath out as fast as possible)
- forced expiratory volume in 1 seconds (FEV1): volume of air expired forcefully in the 1st second of FVC effort (how much can you get out in the first second)
- FEV1/FVC: percentage of total FVC expired in 1st second
- when lungs are working pretty normal, value is typically around 80% (FEV1)
- when you get into respiratory diseases, percentages can drop significantly
Vital Capacity - forced (obstructive vs. restrictive lung diseases)
- either lung disease can cause substantial change from normal
some differences - diagnostic
obstructive lung diseases - difficulty fully expiring air out of lungs (can breath in fairly normally)
- FEV1 decreases much more than FVC so percentage goes down substantially
- quite a low percentage (around 50%) -> cannot blow out as quickly
restrictive lung diseases
- difficulty fully inspiring air into lungs (opposite of obstructive)
- both FVC and FEV1 decrease, but a similar amount so percentage may actually stay same or increase
- percentage can be higher than normal despite the decrease in both because this has more impact on inspiration
- around 90% (depends on lung size of individual)
*can use FEV test to see how someone’s lungs are functioning
Minute Ventilation and Dead Space
minute ventilation (Ve): total air volume flowing into or out of lungs per unit time (L/min or mL/min)
- tidal volume: volume breathing (mL/breath)
- breath frequency (f): breathing rate (breath/min or bpm)
Ve = Vt x f (can increase either or to increase minute ventilation)
- not all of minute ventilation can reaches gas exchange areas:
- dead space (Vd): volume not reaching gas exchange areas (mL/breath) (that does not make alveolar level)
- not all of the air you inspire makes it to the exchange level (alveoli)
Types of Dead Space
- anatomical dead space - structures like airways (structures where gas exchange does not occur)
- alveolar dead space - damaged of blocked alveoli (alveoli where we should be getting gas exchange but due to some reason we cannot) (can be due to cold, mucus buildup or asthma)
- physiological dead space - anatomical + alveolar (usually only about anatomical in normal healthy lungs)
Alveolar Ventilation and Effective Ventilation
to measure air that does reach gas exchange areas convert minute ventilation to:
- alveolar ventilation (Va): total air volume flowing into or out of alveoli per unit time (L/min or mL/min)
(just what is getting down to exchange level)
- Va = (Vt - Vd) x f
example:
- Vt = 500 mL/breath/f = 12 bpm/ Vd = 150 mL/breath
◦ Ve = 500 x 12 = 6L/min
◦ Va = (500 - 150) x 12 = 4.2 L/min (getting down to exchange level)
- effective ventilation (how much of minute ventilation reaches gas exchange areas of alveoli):
◦ Va/Ve = 4.2 L/min/6 L/min = 70%
never ask specific numbers on test
