The work of breathing

what sort of compliance should lungs have

high compliance to easily expand and accomodate air

two types of forces opposing ventilation

restrictive and obstructive

restrictive (what and causes)

reduced lung capacity due to reduced compliance

what causes surface tension and how does it affect lung compliance

water molecules bond to create surface tension which restricts expansion of the thin-walled alveoli therefore reducing lung compliance

how does surfactant affect surface tension?

surfactant molecules interrupt interactions between water molecules decreasing surface tension and therefore increasing lung compliance

obstructive (what and causes)

resistance to airflow from walls of bronchioles

restrictive conditions

pulmonary fibrosis (pneumocytes replaced with inflexible fibrotic/scar tissue), insufficient surfactant secretion

obstructive conditions

asthma, chronic bronchitis

spinometry trace volumes

tidal, inspiratory/expiratory reserve, residual, minimal

spinometry trace capacities

vital, total lung, inspiratory, functional residual

Tidal volume

volume of air moved in and out during normal quiet breath

Inspiratory reserve volume (IRV)

Extra volume of air brought in with maximal inhalation

Expiratory reserve volume (ERV)

extra volume of air pushed out with maximal effort

Residual volume

Volume remaining in lungs after maximal exhalation

minimal volume

volume remaining in lungs if they collapsed

vital capacity (definition and calculation)

Volume of air shifted in and out of lungs with maximal inhalation and exhalation
expiratory reserve + tidal volume + inspiratory reserve

total lung capacity (definition and calculation)

volume in lungs when filled to max
residual volume + vital capacity

inspiratory capacity (definition and calculation)

total volume inspired from rest
tidal + inspiratory

functional residual capacity (definition and calculation)

volume remaining in lungs after normal exhalation
residual + expiratory

advantages of spirometry

easy, non-invasive
can indicate type of condition

what does spirometry measure

FEV1 forced expiratory volume in one second/how quickly we can breathe out air

FEV1/VC ratio defintion

percentage of total vital capacity breathed out in one second

what can FEV1/VC ratio tell us about condition?

below 70%, likely to be obstructive (restricted airflow, easy accomodation)
above 70% likely to be restrictive (easy airflow, stiff accomodation)