18

Question 1

what’s the fick principle

Answer 1

The volume of gas per unit time which diffuses across a membrane surface (eg the alveolar membrane) is ​

1. proportional to the area of the surface, ​
2. inversely proportional to the thickness​
3. Proportional to the difference in partial pressure of the gas on the two sides​
4. Dependant upon the permeability coefficient for that gas in the membrane (related to the solubility)​

Question 2

what key aspects of lungs make it good for gas transport

Answer 2

Large exchange area
think diffusion membrane
high partial pressure difference
high permeability coefficient

Question 3

when is gas transfer from alveoli to capillaries reduced

Answer 3

Reduced membrane surface area, (lobectomy or reduced effective membrane area with pneumonia​)
​
Decreased diffusion across membrane with pulmonary fibrosis, and acute lung injury​
​
Decreased partial pressure of oxygen as in high altitude​
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Collapse of alveoli during expiration due to lack of surfactant​
​
Poor pulmonary perfusion of alveolar membrane

Question 4

pathophysiology of pneumonia

Answer 4

alveoli become filled with bacteria which make toxins. inflammation. so alveolar sac becomes packed w fluid and cant take in oxygen

Question 5

why does radiating therapy result in upper respiratory tract infections

Answer 5

bc kills of macrophages on alveoli periphery

Question 6

pathophysiology of pulmonary fibrosis

Answer 6

fibroblast proliferate in the lungs (lung ‘scarring’) and reduce alveolar size and numbers​

Question 7

main obstructive lung disease

Answer 7

COPD asthma

Question 8

main restrictive lung disease

Answer 8

fibrosis

Question 9

what effect does altitude have on partial pressure

Answer 9

Oxygen fraction stays constant but total pressure decreases with height; therefore oxygen partial pressure decreases with height; lower partial pressure of inspired air – lower partial pressure of alveolar air – less saturation of haemoglobin in lungs. Can get altitude sickness if respiration rate not increased​

Question 10

what happens to your body when you’re altitude

Answer 10

receptors in carotid bodies sense low oxygen so start to make you breath more but then your drop in Co2 means CSF is more alkaline than it should be and bc its dominant you stop breathing fast.

Question 11

which cells make surfactant

Answer 11

type II pneumocystis

Question 12

what are the different forms of surfactant

Answer 12

​
There are different forms of surfactant (with different proportions of lipoproteins type A,B,C, D) which make with different properties:​
​
Surfactant containing lipoproteins B &C is used to reduce surface tension and ensure proper lung function. ​
​
Surfactants containing lipoproteins A & D coat bacteria and viruses and help the immune system deal with them. (surfactant D deficiency is a particular risk factor for pulmonary tuberculosis)​

Question 13

‘Infant Respiratory Distress Syndrome’

Answer 13

fetal lung alveoli are shut closed by surface tension and NO surfactant.
surfactant made in weeks 24.28

Question 14

surfactant deficiency in adults cause

Answer 14

​

Bacterial or viral disease can affect type 2 pneumocyte function and thus surfactant release

Question 15

how come sometimes people with COPD can have a small or no change in airway compliance

Answer 15

bc of an increase in compliance in the upper zones combined w a decrease in lung airway compliance at the bases of the lungs
This reduces V/Q still further at the bases and decreases oxygen uptake in the zone where the blood flow is high.​

Question 16

what is the PACO2 and PAO2 of blood leaving the base of the lung

Answer 16

low PAO2 and high PACO2

bc less good gas exchange but greater blood flow in the base

Question 17

Persistent fetal circulation cause

Answer 17

caused by a failure in the systemic circulation and pulmonary circulation to convert from the antenatal circulation pattern to the “normal” pattern at birth.​

Question 18

what other condition is Persistent fetal circulation associated with

Answer 18

pulmonary hypertension

Question 19

how to reduce or eliminate PPHN

Answer 19

by the addition of the vasodilator nitric oxide to the inspired gas in the infant ventilator.

Question 20

why does NO work as vasodilator

Answer 20

increases cGAMP which sequesters Ca in smooth muscle and makes it relax

Question 21

why use spirometry

Answer 21

​Assess the prognosis of respiratory disease in a patient.​

Assess whether lung disease is present at an early stage, i.e. prior to overt clinical disease.

Assist in quantifying the severity of airway disease.​

Assess the effect of therapy, such as corticosteroids, bronchodilators​

Delineate risk factors, e.g. the odds of developing future respiratory disease, or operative risks.​

Monitor whether the pattern of lung growth or aging is normal.

Question 22

lung function test measurement

Answer 22

spirometry

Question 23

Total lung capacity

Answer 23

inclues forced vital capacity plus residual volume plus physiological dead space.

TLC, the total volume of the lungs, cannot be measured directly by spirometry. ​
It is measured by inspiration of a fixed volume of a gas mixture which includes helium, followed by rebreathing the mixture until the helium is evenly distributed in the lung gases. Helium does not get absorbed into the blood, so if we sample the rebreathed gas it will contain a lower concentration of helium than the original inspired gas as it has penetrated the residual volume. Let C1 be concentration of helium in inspired gas & V1 volume of inspired gas. Similarly let C2 be concentration in rebreathed gas and V2 the volume (ie V2 = TLC) ​

Question 24

Peak flow measurement​

Answer 24

measures FEV1
The peak flow rate assess airway resistance​
​
The test is useful in patients with obstructive lung disease (e.g. asthma and COPD)​
​
It is measured by the patient taking a full inspiration and then giving a short sharp blow into the peak flow meter​
​
The average of three attempts is usually taken​
​
The peak flow rate in normal adults vary with age and height​
​

Question 25

which is done more easily and commonly peak flow or total vital capacity

Answer 25

peak flow

Question 26

what test would you do to test for COPD

Answer 26

peak flow

Question 27

peak flow for man

Answer 27

660 l/min

Question 28

peak flow for woman

Answer 28

320 l/min

Question 29

Lung Function testing ​

4) Tests of ventilation/perfusion (V/Q) matching​

Answer 29

if there is poor saturation of arterial haemoglobin (hypoxaemia), V/Q ratio can be measured​
​
V/Q ratios can be analysed using isotope scanning​
​
Whole lung reduced ventilation with normal perfusion (reduced V/Q ratio) in pneumonia causes hypoxaemia​
​
Decreased perfusion with normal ventilation (too high V/Q ratio) in pulmonary emboli also causes hypoxaemia​
​
in COPD Regional V/Q mismatch due to regional emphysema reduces the efficiency of gas transfer and thus hypoxaemia​

Question 30

5) Measurement of gas transfer

Answer 30

The efficiency of oxygen transport across the alveolar membrane can be measured by comparing alveolar oxygen levels (PAO2) with arterial levels (PaO2) ​
​
Alveolar oxygen partial pressure can be obtained by analysis with an oxygen meter of the ‘end tidal ‘ expired gas, ie the last portion of expired gas, which will have the same composition as alveolar gas.​
​
Arterial oxygen partial pressure can be measured with a pulse oximeter which measures the saturation of the haemoglobin with oxygen. The haemoglobin oxygen saturation is related to the oxygen partial pressure by the oxygen-haemoglobin saturation curve​

Question 31

exercice training

Answer 31

How far can the patient walk, is it enough to carry out essential tasks ?​
​
Physiotherapy and OT assessment ​
​
Assess breathlessness on exercise with visual analogue score ​
​
Treadmill or bicycle exercise tests show ventilation as a function of work and anaerobic threshold, which correlates with cardiopulmonary capacity and operative risk​

Question 32

Main Tests used to assess lung function

Answer 32

Tests of lung volumes (spirometer)​
Tests of total lung capacity using helium​
Tests of airflow (peak flow meter/vitalograph)​
Tests of V/Q mismatch using isotopes​
Tests of gas transfer (compare PO2 at different sites)​
Tests of challenge by exercise