Physio lec 2 respiratory mechanics Flashcards
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Intra-alveolar pressure/intrapulmonary pressure:
pressure in the alveoli
Intrapleural presure/intrathoracic pressure:
pressure within pleural sac
Rate of airflow:
affected by autonomus nervous system
airflow is inversly proportional to air resistance
-sympahtetic system causes bronchodialation= dec resistance or more airflow
-parasympathetic system causes bronchoconstriction= inc resistrance or less airflow
transmural pressure gradient:
difference between intra-alveolar and intrapleural pressure (4mm Hg)
opposite of inhale
Sequence of events during expiration:
3 sec
-inspiratory muscles relax
-Decrease in pulmonary volume
-increase in pressure (+1mm Hg)
-process continues until intrapulmonary pressure = 0
2 sec
sequence of events in inspiration:
-contraction
-increase
-gas in
-contraction of inspiratory muscles
-increase in pulmonary volume and decrease in pulmonary pressure
(-1mmHg)
-atmospheric pressure higher (0) so gas moves in
Force that stretches the lungs:
Transmural pressure gradient
lung compliance
measure of lung expansability and distensibility
Low compliance:
(low expansability and distensibility)
-lung become stiffer and less elastic
-higher elastic recoil
-less air inhaled
-fibrosis (stiffness)
-gas exchange impaired
High compliance:
(high expansibility and distensibnility)
-lower elastic recoil
-easily distended
-reduces passive ability of lungs to deflate during expiriation
simply put, lungs appear manfookh
Compliance affected by:
-elastin and collagen fibres
-chest wall flexibility (fat or fit)
-surface tension
forces keeping alveoli open:
-transmural pressure
-pulmonary surfactant (opposes surface tension)
Inspiratory reserve volume (IRV):
extra volume of air that can be inspired OVER the tidal volume= 3000ml
Tidal volume
Aka normal breathing volume
volume of air entering or leaving the lungs duirng a single breath (500ml)
Forces collapsing alveoli:
-elasticity from elastin
-alveolar surface tension
Inspiratory capacity (IC):
(TV+IRV)
500ml+3000ml=3500ml
expiratory reserve volume (ERV):
Extra amount of volume that can be actively expired (1000ml)
Residual volume (RV):
minimum vol of air remaining even after maximum expiration (1200ml)
Vital capacity (VC):
max expiration
max vol of air that can be moved out during maximum expiriation
(VC=IRV+ERV+TV)——- 4500ml
Functional residual capacity (FCR):
Vol of air in lungs after normal expiration
FCR=ERV+RV
1200+1000=2200ml
normal % for FEV1/FVC*100:
80%
(FEV1< 80%)
total lung capacity (TLC):
max vol of air lungs can hold
VC+RV
Forced vital capacity in Un/healthy individual:
forced exhale test
Actual FVC> predicted FVC = healthy
Actual FVC< predicted FVC= pulmonary disease
If FVC < predicted
CONSTRICTIVE pulmonary disease
alveolar SA decreases
Scare tissue from pneumonia and tuberculosis
Dead space:
Exists anatomically in: trachea, bronchial tree… 150 ml of air that doesnt particiapate in gas exchange
Alveolar dead space: space in alveoli where 150 ml of air doesnt participate in gas exchange—- less efficient gas exchange
FEV1<80%
Obstructive pulmonary disease
-emphysema, asthma,asthma, bronchitis, decreased left heart output,pulm edema
Pulmonary rate=
how many breaths?
TV* respiratory rate per min
12-18 breaths
12*500 = 6000ml
Alveolar ventilation:
(TV-dead space volume)*respiratory rate
(500-150)*12= 4200ml
