Physiology Flashcards
what is a normal value for the FEV1/FVC ratio?
> 75%
what is the value for FEV1/FVC in asthma and what can change this?
<75%
reversibility response to bronchodilator
what is the value of FEV1/FVC that is diagnostic for COPD?
<70% post bronchodilator
what is considered to be mild COPD on the GOLD classification?
FEV1 >80% predicted
what is considered to be moderate COPD on the GOLD classification?
FEV1 50-79% predicted
what is considered to be severe COPD on the GOLD classification?
FEV1 30-49% predicted
what is considered to be very severe COPD on the GOLD classification?
FEV1 <30% predicted
what effect can obesity have on the functional residual capacity?
decreased
what effect does COPD have on functional residual capacity?
increased
what lung volumes and capacities cannot be measured by spirometry?
residual volume
functional residual capacity
total lung capacity
what is the tidal volume (TV)?
volume of air entering or leaving lungs during a single breath
what is the inspiratory reserve volume (IRV)?
extra volume of air that can be maximally inspired over and above the typical resting tidal volume
what is the expiratory reserve volume (ERV)?
extra volume of air that can be actively expired by maximal contraction beyond the normal volume of air after a resting tidal volume
what is the residual volume (RV)?
the minimum volume of air remaining in the lungs even after a maximal expiration
what is the inspiratory capacity (IC)?
maximum volume of air that can be inspired at the end of a normal quiet expiration
how is inspiratory capacity calculated?
inspiratory reserve volume + tidal volume
what is the functional residual capacity?
volume of at the end of normal passive expiration
how do you calculate the functional residual capacity?
expiratory reserve volume + residual volume
what is the vital capacity?
the minimum volume of air that can be moved out during a single breath following a maximal inspiration
how do you calculate vital capacity?
inspiratory reserve volume + tidal volume + expiratory reserve volume
what is the total lung capacity?
total volume of air the lungs can hold
how do you calculate the total lung capacity?
TLC = VC + RV
what effect does increasing partial pressure have on the rate of gas transfer?
increases rate of transfer
what effect does increasing diffusion coefficient have on the rate of gas transfer?
increases rate of transfer
what effect does increasing surface area of the alveolar membrane have on the rate of gas transfer?
increases rate of transfer
what effect does increasing thickness of the alveolar membrane have on the rate of gas transfer?
decreases rate of transfer
what is pulmonary compliance?
a measure of the effort that has to go into stretching the lungs
the change in lung volume per unit change in the transmural pressure gradient across the lung wall
what does reduced pulmonary compliance mean?
more work needed to inflate the lungs
name some things that can cause decreased pulmonary compliance
pulmonary fibrosis oedema lung collapse pneumonia lack of surfactant
what symptom does a lack of pulmonary compliance cause?
SOB - especially on exertion
what can be seen on spirometry in a patient with decreased pulmonary compliance?
restrictive pattern
what effect can giving excessive oxygen have on COPD patients?
can lead to hypercapnic respiratory failure due to CO2 retention
what is the target SaO2 in patients with COPD?
88-92%
name a condition that can cause abnormal increase of pulmonary compliance
emphysema (COPD)
what effect does increasing age have on compliance?
compliance increases as you become older
what is CaO2?
the oxygen content of arterial blood
how is CaO2 determined and what is the equation for this?
by the Hb concentration and the Hb saturation
CaO2 = 1.34 x [Hb] x SaO2
what three things can impair oxygen delivery to the tissues?
respiratory disease
heart failure
anaemia
