Ventilation and Gas Exchange Flashcards
What is minute ventilation?
-the volume of air expired in one minute or per minute
volume of air entering and leaving the lungs
What is the respiratory rate RF?
-the frequency of breathing per minute
What is the alveolar ventilation (Valv)?
- the volume of air reaching the respiratory zone per minute
- (volume of air entering and leaving the alveoli)
What is respiration?
-the process of generating ATP either with an excess of oxygen (aerobic) and a shortfall (anaerobic)
What is the anatomical dead space?
-the capacity of the airways incapable of undertaking gas exchange
What is alveolar dead space?
-the capacity of the airways should be able to undertake gas exchange but cannot (e.g hypoperefused alveoli)
What is the physiological dead space?
-equivalent to the sum of alveolar and anatomical dead space
What is hypoventilation?
-deficient ventilation- unable to meet demands (increased PO2- acidosis)
What is hyperventilation?
-excessive ventilation
reduced PCO2- alkalosis
What is hyperpnoea?
-increased depth of breathing to meet metabolic demand
What is hypopnea?
-decreased depth of breathing
What is apnoea?
- cessation of breathing
- no air movement
What is dyspnoea?
-difficult breathing
What is bradypnoea?
-abnormally slow breathing rate
What is tachypnoea?
-abnormally fast breathing rate
What is orthopnoea?
-positional difficulty in breathing (when lying down)
How is minute ventilation calculated and units?
What is normal?
tidal volume (L) x breathing frequency (breaths/min)
L/min
6 L/min
How is alveolar ventilation calculated and units?
What is normal?
(tidal volume (L) - dead space (L) ) x breathing frequency (breaths/min)
4.2 L/min
What 5 factors affect lung volume and capacities?
- body size
- fitness
- sex
- disease (pulmonary, neurological)
- age
What is the conducting zone?
- 16 generations
- no gas exchange
- typically 150ml in adults at FRC (functional residual capacity)
- equivalent to anatomical dead space
What is equivalent to the anatomical dead space?
-the conducting zone
What is the respiratory zone?
- 7 generations
- gas exchange
- typically 350 ml in adults
- air reaching here is equivalent to alveolar ventilation
What is non-perfused parenchyma?
- alveoli without a blood supply
- no gas exchange
- typically 0ml in adults
- called alveolar dead space
Which area is called the alveolar dead space?
-the non-perfused parenchyma
What is the physiological dead space?
-anatomical + alveolar dead space
How can you decrease the volume of dead space?
- tracheostomy (making hole to place tube)
- cricothyrocotomy
How can you increase the volume of dead space?
- anaesthetic circuit
- snorkelling
What is the chest wall relationship?
- the chest wall has a tendency to spring outwards, and the lung has a tendency to recoil inwards
- these forces are in equilibrium at end-tidal expiration (functional residual capacity FRC), which is the ‘neutral’ position of the intact chest
- inspiration when inspiratory muscle effort + chest recoil > lung recoil
- expiration when expiratory muscle effort + lung recoil > chest recoil
When are the lung-chest forms at equilibrium?
- at FRC
- chest recoil = lung recoil
What is the inner surface of the chest wall covered by?
-the parietal pleural membrane
What is the pleural cavity?
- gap between the pleural membrane (visceral and parietal)
- fixed volume containing protein-rich pleural fluid
What surrounds the lungs?
-visceral pleural membrane
What happens in a haemothorax?
-intrapleural bleeding
What happens in a pneumothorax?
- perforated chest wall
- could be caused by punctured lung
What is type of pressure breathing is normal breathing?
-negative
What are some examples of positive pressure breathing?
- mechanical ventilation
- CPR
- fighter pilots
What is PTT?
-transthoracic pressure
= Ppl - Patm
cmH2O
What is PTP?
-transpulmonary pressure
=Palv - Ppl
cmH2O
What is is PRS?
-transrespiratory system pressure
= Palv - Patm
cmH2O
What is Ppl?
-intrapleural pressure
cmH2O
What will a negative PRS (trans-respiratory system pressure) lead to?
-inspiration
What will a positive PRS (trans-respiratory system pressure) lead to?
-expiration
How is inspired gas modified?
-warmed, humidified, slowed and mixed (as air passes down the respiratory tree)
What is HbA made of?
- 2 alpha
- 2 beta
What is HbA2 made of?
- 2 alpha
- 2 delta
What is HbF made of?
- 2 alpha
- 2 gamma
What type of protein is Hb?
-allosteric
What causes a leftwards shift on the oxygen dissociation curve?
increased affinity (loading)
- decrease in temperature
- alkalosis
- hypocapnia
- decreased 2,3-DPG (in RBC determines the ease with which Hb releases oxygen into the tissues)
What causes a rightwards shift on the oxygen dissociation curve?
- increase in temperature
- acidosis- bohr effect
- hypercapnia (elevated CO2)
- increased 2,3- DPG
What causes an upwards shift on the oxygen dissociation curve?
- polycythaemia
- increased oxygen-carrying capacity
What causes a downwards shift on the oxygen dissociation curve?
- anaemia
- impaired oxygen-carrying capacity
What effect does carbon monoxide have on the oxygen dissociation curve?
- downwards and leftwards shift
- decreased capacity
- increased affinity
- increased HbCO
Contrast the oxygen dissociation curves for myoglobin and HbA and foetal.
-myoglobin has much greater affinity than adult HbA and foetal Hb to extract oxygen from circulating blood and store it.
How is carbon dioxide transported?
-CO2 + H2O -> H2CO3
H2CO3 -> H+ + HCO3-
CO2 into RBC
CO2 + H2O -> H2CO3 via carbonic anhydrase
H2CO3 -> H+ + HCO3-
negative chloride ions enter the RBC to maintain resting membrane potential via AE1 transporter
H2O enters RBC
CO2 + Hb -> HbCO2
What effect will supplemental oxygen therapy have on the oxygen dissociation curve?
- oxygen therapy will increase the partial pressure of oxygen, and increase concentration of dissolved oxygen
- dissolved oxygen doesn’t really affect Hb saturation above 13 kPa
What effect will blood doping have on the oxygen dissociation curve?
- doping involves exogenous or autologous transfusion of RBCs to improve endurance performance
- this would stretch the ODC upwards, but not right
What effect will 30 mins sunbathing in 30 degrees have on the oxygen dissociation curve?
- sunbathing in the heat has the potential to increase body temperature, but unlikely to have an effect
- human are thermoregulatory
What effect will uncontrolled type 1 diabetes have on the oxygen dissociation curve?
-uncontrolled diabetes may lead to diabetic ketoacidosis, and the increased acidity displaces the ODC rightwards
lecture slides
https://d3c33hcgiwev3.cloudfront.net/X-Nfu2GaRfGjX7thmtXx1w_759626291f6740fe98f7685856c7a7ae_Final_SV_CVR_LE05Gas_transport_and_exchange.pdf?Expires=1582588800&Signature=JOGZvqOe9~rFdTr0AL2iO72HoAxguAqb6aW16oM-VE9fTJcbD3VcQjtlFuvV6uHLtGqWVHsGd5lnKq2lrhfXNudRRrQll-Kui4Aa4CN2TBsfG5hkKCFklDNIHtW5F2Y0zN6HndcOTXz~NitdyhMqlcU48fZYaimKo0DdpO9dT7s&Key-Pair-Id=APKAJLTNE6QMUY6HBC5A
