Sedation Physiology - Respiratory Flashcards
What muscle(s) are used when quiet breathing?
Diaphragm
What muscle(s) are used during more forceful breathing?
Intercostal and accessory muscles
Describe Intrapulmonary pressure in relation to atmospheric pressure during inspiration.
Intrapulmonary pressure is less than atmospheric pressure during inspiration
Describe Intrapulmonary Ipressure in relation to atmospheric pressure during expiration.
Intrapulmonary pressure greater than atmospheric pressure during expiration
Describe the change in Intrapleural pressure during inspiration.
Intrapleural pressure falls during inspiration = brings air into the lungs
Describe the change in Intrapleural pressure during expiration.
Intrapleural pressure raises during expiration = takes air out of the lungs
Describe lung tidal volume
represents air moving in and out during quiet breathing
Describe inspiratory reserve volume.
when you force inspiration to its maximum
Describe expiratory reserve volume.
when you force expiration to its maximum
Describe residual volume
the volume left even after maximum expiration
Describe how we calculate lung vital capacity.
add all of the IRV, TV and ERV volumes
Describe how we calculate total lung capacity
Add vital capacity and residual volume
What causes a person to have restricted vital capacity? (5)
- Obesity
- Pneumonia
- Fibrosis
- Tb
- Pneumoniosis
Describe restricted vital capacity in relation to FEV1.
VC value is close to the FEV1 that means small volumes are exchanged but they occur at a similar rate to a normal patient
What causes a person to have an obstructive vital capacity? (3)
• Emphysema
• Asthma
• Bronchitis
What occurs in the conducting zone?
No gas exchange = anatomical dead space
What anatomy is present in the conducting zone? (3)
• trachea
• broncho
• bronchi terminals
What is the volume of dead space in the conducting zones?
150ml
What volume of new air is inhaled during breathing and why?
What is the tidal volume?
when we inhale air - only 300ml will be new/fresh air
150ml already present as dead space
Tidal volume = 450ml
What occurs in the respiratory zone?
Gas exchange
What anatomy is present? (3)
• respiratory bronchioles
• alveolar duct
• alveolar sack
What is diffusion of gases determined by?
partial pressure gradients
(equivalent to concentration gradients)
Describe diffusion barriers during respiration. (4)
Gases have to travel through a barrier of:
• Thin and flat type 1 pneumocytes on the alveolar wall
• Endothelial cells of capillaries
• Basement membrane between the 2 cells (0.5 – 2 micrometers)
• Type 2 pneumocytes covering the alveolar wall
What is the role of type 2 pneumocytes?
have a role producing surfactants
What is ventilation?
The amount of gases passing through the lungs
What is perfusion?
The amount of gases travelling through the pulmonary circulation
Describe the gas levels of oxygen and CO2 in arterial blood and venous blood. (2)
Arterial blood had higher oxygen levels and lower carbon dioxide levels
compared to venous blood which has lower oxygen and higher carbon dioxide levels.
What cells have an important role in the transport of blood and CO2?
Erythrocytes
What protein is important In oxygen transport?
Haemoglobin
How is nitrous oxide transported in the blood?
As a simple solution
Describe the structure and composition of haemoglobin. (4)
- Globular protein
- 2 alpha protein chains
- 2 beta protein chains
- 4 haem groups with a porphyrin ring and an iron atom inside the ring
How is oxygen transported? (2)
• Mostly transported attached to haemoglobin = 97%
• Small amounts dissolved in plasma
Describe what occurs to oxygen saturation of haemoglobin and the plasma when an individual inhales pure oxygen.
Haemoglobin is already saturated so when more oxygen is provided (via breathing pure oxygen or hyperbaric oxygen) the amount of oxygen bound to haemoglobin only increases slightly whereas the oxygen in the plasma increases much more.
Describe what happens to oxygen saturation when an individual has hypothermia or alkalosis. (2)
Increases haemoglobins affinity to oxygen
- easier to harvest oxygen in the lungs but harder to move oxygen into the tissues
Describe what happens to oxygen saturation when an individual has increased temperatures, acidosis or increased 2,3 diphosphoglycerate . (2)
- Decreases haemoglobins affinity to oxygen
- Facilitates haemoglobins ability to release oxygen when dissolved in the tissues
What occurs during carbon monoxide poisoning?
CO binds to haemoglobin and prevents haemoglobin from carrying oxygen to tissues
How is Carbon dioxide transported - give %’s? (3)
- 70% transported as bicarbonate ions
- 20% transported combined to a protein or in carbamino compounds
- 10% transported as dissolved CO2
What effect does providing an oxygen and nitrous oxide mixture have on perfusion?
no effect on perfusion as it saturates the haemoglobin molecule and any excess will be dissolved
Describe what occurs if we suddenly stop providing oxygen and nitrous oxide to a patient at the same time?
If we remove all of the mixture and let patient breathe air only = sudden drop in ventilated oxygen whilst the nitrous oxide is diffused out slowly = more nitrous oxide present than oxygen
What type of process is breathing - describe how it occurs physiologically?
an automatic process
a rhythm is generated by respiratory centres in the brainstem and can be modified by various sensory receptor
What sensory receptors modify the breathing rhythm in the brainstem - describe how? (5)
Modified by the conscious cerebral cortex
Peripheral arterial receptors sense a drop in partial pressure oxygen and increase in ppcarbon dioxide and modify the rhythm
Central chemoreceptors can sense the increase in partial pressure of carbon dioxide in the cerebrospinal fluid and reduction in pH and modify the rhythm
Increase in physical activity the joint and muscle receptors recognise movement and stimulate an increase in rhythm
If a conscious increase in breathing is carried out lung stretch receptors can recognise inflation and reduce the rhythm
List the 4 types of hypoxia.
• Hypoxic hypoxia
• Anaemic hypoxia
• Stagnant
• Cytotoxic hypoxia
Describe hypoxic hypoxia
occurs when there is a reduction of oxygen is reaching the alveoli or when there is a reduction in oxygen that is diffusing into the blood
Describe anaemic hypoxia
reduction of oxygen transport in blood from low haemoglobin or reduction in haemoglobin’s ability to function as a carrier
i.e. carbon monoxide poisoning
Describe stagnant hypoxia
(ischaemic)
reduction of oxygen transport in blood from low blood flow
Describe cytotoxic hypoxia
reduce oxygen utilisation by cells
what causes anaemic hypoxia to occur?
carbon monoxide poisoning
What signs indicate cyanosis?
Blue colour of skin and mucous membranes
What causes cyanosis?
Occurs when there is > 5gm of de-oxygenated haemoglobin per dl of blood
(an increase of deoxygenated blood)
Name the 2 types of cyanosis
Central
peripheral
What hypoxia commonly causes central cyanosis?
Hypoxic hypoxia - decrease in oxygen deliverey to the blood
What causes central cyanosis? (6)
Caused by a decrease in oxygen deliverey to the blood (hypoxic hypoxia)
Low atmospheric oxygen conc
reduced airflow in airways (obstruction)
reduced oxygen diffusion into blood
reduced pulmonary blood flow
shunting – where venous blood enters the arteries (from anatomical anomaly)
What hypoxia commonly causes peripheral cyanosis?
stagnant hypoxia - decrease in blood flow to tissues
e.g. peripheral vascular disease such as atherosclerosis
Describe how a pulseoximeter works.
Uses the variations in the wavelengths between oxygenated and deoxygenated haemoglobin to calculate the saturation of oxygen in pulsating arterial blood.
