RESP-breathing in special circumstances Flashcards
what happens to the respiratory system in old age?
- Decreased elastic recoil of lung tissues and chest wall compliance
- Decreased strength in the respiratory muscles
- Increased residual volume, decreased vital capacity and decreased FEV 1
what happens to the respiratory system in obesity?
- Upper airway restriction and lung volume reduction = decreased functional residual capacity (volume in lungs after normal exhalation)
- Increases risk of atelectasis (collapsed alveoli = example of shunting)
- Alveoli have little volume - V/Q mismatching (shunt - alveoli stops gas exchange)
what are the respiratory changes seen in fear?
- The hypothalamus sends signals once stress is perceived
- Sympathetic NS stimulates adrenal medulla to secrete adrenaline/noradrenaline – increases alertness, blood flow to muscles, respiration rate and cardiac output
- Stimulation of corticotrophs (by CRH) causes release of ACTH which stimulates release of cortisol from the adrenal cortex – increasing glucose metabolism and suppressing the immune system
what are the 3 ways breathing is initiated in infancy?
- mechanical
- chemical
- sensory
describe how breathing is initiated mechanically
The compression from the vaginal canal forces any remaining fluid out of the neonate’s lungs
describe how breathing is initiated chemically
-Cutting of the umbilical cord results in asphyxia (CO2 increase, O2 decrease, pH decreases = acidosis). This acidotic state is detected by chemoreceptors and respiratory centres in the medulla initiate breathing
describe how breathing is initiated sensorily
Decrease in temperature, stimulation of nerve endings in the skin, experiencing light and sound in the extrauterine environment all stimulate breathing
how does the position of the diaphragm change during birth?
moves up by 4cm
increase vol
how does the position of ribs change during birth?
ribs flare out-A=P dimension
increase vol
how does tidal volume change during birth and what does this cause?
increase by 200ml
- > results in 5% increase in VC
- > and 20% in residual vol
how does the respiratory rate change during birth?
it doesn’t
what is the end result for ventilation during birth?
- > increase in ventilation
- > decrease in PaCO2
- > PaO2 essentially unchanged
what is the normal range for arterial blood gas pH?
pH= 7.35-7.45
what is the normal range for arterial blood gas pCO2?
pCO2= 35-45mmHg
what is the normal range for arterial blood gas HCO3-?
HCO3-= 22-26EQ/L
how would you describe the overall state of pregnancy in accordance to arterial blood gases?
compensated respiratory alkalosis
describe the change in blood gases seen during pregnancy
- > decrease in PaCO2=more bicarb=alkalosis
- > to compensate for change=decrease in HCO3- ions
- > allows pH to remain unchanged during pregnancy (hence compensated)
how do the partial pressures of air change with increasing altitude?
-all decrease (at same rate)
what is the effect of falling PaO2 at higher altitude?
- reduces partial pressure gradient
- driving O2 uptake
- caused hypoxia
- causing sensory and cognitive functions to decline
what can the body’s responses to increased altitude be?
- acute
- adaptive
- acclimation
describe the acute response during altitude change
- Hypoxia sensed by peripheral chemoreceptors (in aortic arch) and the respiratory centre responds by increasing ventilatory drive which increases oxygen uptake and carbon dioxide emission
- Respiratory centre also suppresses the cardioinhibitory centre – increasing heart rate/cardiac output and hence increasing oxygen uptake by pulmonary perfusion
how long does the acute response during altitude change take to occur?
within minutes
how long does the adaptive response during altitude change take to occur?
days-weeks
describe the adaptive response during altitude change
- The central chemoreceptors adapt slowly allowing ventilation rates to climb to address altitude-induced hypoxia
- This decreases PaCO 2 causing respiratory alkalosis
- Kidneys compensate by decreasing acid secretion and blood pH renormalizes
- Alkalosis also stimulates 2,3-DPG production
what is the effect of 2,3-DPG on Hb’s O2 affinity?
-2,3-DPG decreases Hb’s O₂ affinity, causing O₂ Hb dissociation curve to shift to the right and this enhances O₂ unloading to tissues
how long does the acclimation response during altitude change take to occur?
months to years
describe the acclimation response during altitude change
- Hypoxia will stimulate erythropoietin to be released from kidneys ->increase amount of Hb → increases blood’s O2 carrying capacity by 50%
- Hypoxia stimulates angiogenesis → capillary density and perfusion will increase
how does pressure with increased water depth?
pressure rises quickly
water is denser than air
how does increased water depth affect the alveoli?
compresses gas within alveoli = increase partial pressure of gases but decreases alveolar volume
what are the 2 issues with diving and the pressure involved?
1-At sea level, only O2 and CO2 can dissolve in blood to any significant extent. Depth increases the partial pressures of all gases – so other gases will now be able to dissolve leading to potentially lethal effects
2-Pressurising a gas decreases its volume – when a diver resurfaces this can cause severe damage to the tissues that contain the gas
describe what nitrogen narcosis is
At a depth of ≥40m, Pa(N2) rises so that it is able to dissolve in cell membranes → this disrupts ion channel function. (worsens with depth and causes loss of function below 80m)
describe what oxygen poisoning is
Oxygen is inherently toxic due to its tendency to form free radicals. Usually, Hb acts as a buffer as it closely regulates the amount of O2 delivered to the tissues. High Pa(O2) will eventually exceed the buffering capacity of Hb
which gases is air principally made up of?
N2 (78%) and O2 (21%)
what is the problem with inhaling N2 and O2 under pressure?
both are toxic when inhaled under pressure
what substance do divers who work at depth breathe and why?
-helium/oxygen (heliox) mix
-Helium replaces N2 because it dissolves in the body tissues less readily
Inhaling Heliox reduces airway resistance and decreases the work of breathing.
outline how decompression sickness arises
- As the diver ascends, Pa(N2) decreases and comes out of solution.
- It forms pure bubbles of N2 that enter the blood stream and eventually, form a mass in major vessels that cause ischaemia.
- The dependent tissues experience pain. If serious, will result in death.
how can decompression sickness be avoided?
Managed by slowing the rate of ascent to give more time for the gas to diffuse out of tissues and into the lungs.
how can decompression sickness be treated?
If ascent occurs too quickly, there are specialised decompression chambers for divers to help them acclimate.
(hyperbaric chambers)
With regards to the initiation of breathing; cutting the umbilical cord will result in what?
A-Acidotic state
B-alkalosis
C-increased cardiac output
D-decreased cardiac output
A
Which of the following is Not a change that occurs for respiration at birth?
A-tidal volume increases by 200ml
B-20% increase in residual volume
C-diaphragm moves up by 4cm
D-decrease in PaCO2
B
Decrease in PaCO2
In the adaptive response to altitude change, the alkalosis state of the body will stimulate the production of what?
A-erythropoetin
B-blood vessels (angiogenesis)
C-2,3-DPG
C
outline the acid/ base equation
CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO-
which receptors in the medulla detect changes in H+ in the CSF?
Central chemoreceptors
what does hyperventilation cause?
decrease in CO2
how is hyperventilation compensated?
kidneys excrete bicarbonate
what does hypoventilation cause?
increase in CO2=acidosis
what do the kidneys do in response to hypoventilation?
resorb bicarbonate
where are the 2 types of peripheral chemoreceptors found?
- > carotid chemoreceptors found at bifurcation of common carotid artery
- > aortic arch chemoreceptors
what do carotid chemoreceptors detect?
Detect change in: PCO2, PO2 and pH
what do aortic arch chemoreceptors detect?
detect changes in PCO2 and PO2
the change in which molecule is the most important?
CO2 is the most important; it drastically changes H+ in CSF
O2 is only relevant when very/chronically low
how can you tell if the blood gas abnormality is respiratory or metabolic?
Is the imbalance being caused by the lungs or the kidneys
HCO3-=kidney (metabolic)
CO2=lungs (respiratory)
how can you tell if the blood gas abnormality is compensated or uncompensated?
Has the body worked to bing the imbalance back to normal
what do these blood gas results show?
pH: 7.25
pCO2: 85
HCO3-: 25
uncompensated respiratory alkalosis
what do these blood gas results show?
pH: 7.25
pCO2: 55
HCO3-: 20
uncompensated mixed acidosis
what do these blood gas results show?
pH: 7.41
pCO2: 27
HCO3-: 23
23
why are vaccines important?
- This is the only type of medical intervention that is able to eradicate a disease.
- It is also one of the most cost-effective public health interventions
name the 5 types of vaccines
- active
- passive
- polysaccharide (PS)
- conjugate-PS
- adjuvant
describe active vaccination
Administration of an antigen (either a modified infectious agent or a toxin of it) resulting in active adaptive immunity (long term)
describe passive vaccination
Administration of an antibody-containing serum (short term)
describe passive vaccination
- Immune response is induced by polysaccharide antigens which are T-Cell independent (polysaccharides cannot bind to MHC complexes to be presented to T-Cells).
- They activate B-Cells directly, but without the T-Cell activation, no memory B-Cells can be made.
describe conjugate-PS vaccination
- In a conjugate-PS vaccine, there is a carrier protein attached to the PS. Polysaccharides alone cannot be loaded onto the MHC of an APC alone, since MHCs can only bind to proteins.
- However, in a conjugate-PS, there is now a carrier protein which can bind and activate MHCs on APCs such as T-Cells.
- This results in T and B Cell activation 🡪 memory cells are produced, and long-term immunity is achieved.
what is adjuvant?
- a chemical added to any vaccine in order to help the vaccine work better.
- The adjuvant acts to activate immune cells (e.g. dendritic cells) by binding to toll-like receptors (TLRs), which results in a stronger immune response
