Respiratory alkalosis - causes, symptoms, diagnosis, treatment, pathology
Summary
TLDRRespiratory alkalosis occurs when the lungs expel too much carbon dioxide, raising blood pH above 7.45. Normally, the respiratory system balances pH by managing CO2 levels. In alkalosis, increased breathing can result from hypoxia, anxiety, or medical interventions. This causes a drop in CO2 levels and a rise in pH. The body responds initially by releasing hydrogen ions, and over time, the kidneys reduce bicarbonate reabsorption to restore pH balance. The condition has acute and chronic phases, depending on whether the kidneys have begun compensating for the pH imbalance.
Takeaways
- 🌬️ Respiratory alkalosis refers to a condition where the lungs remove too much carbon dioxide, causing a rise in blood pH above 7.45.
- 🫁 Normally, the lungs balance pH by pulling in oxygen and releasing carbon dioxide, which regulates carbonic acid and hydrogen ions in the blood.
- 🧠 Chemoreceptors in the carotid arteries and aortic arch detect CO2 levels and signal the brainstem to adjust the breathing rate.
- ⬇️ When CO2 levels drop, the pH rises, and respiratory centers decrease the breathing rate to restore balance.
- 💨 In respiratory alkalosis, the breathing rate increases excessively, leading to a loss of too much CO2 and an increase in blood pH.
- ⛰️ Increased ventilation can occur due to hypoxia from conditions like pneumonia, pulmonary embolism, or even high altitudes.
- 😨 Abnormal increases in ventilation can result from anxiety, panic attacks, sepsis, or salicylate overdose, and sometimes due to brainstem disorders.
- 🩺 Ventilator settings can also cause respiratory alkalosis if not properly adjusted, leading to CO2 depletion.
- ⏳ In the acute phase, cellular mechanisms release hydrogen ions to bind with bicarbonate, but this is usually insufficient to significantly lower the pH.
- 🗓️ Over 3-5 days, the kidneys help by excreting more bicarbonate, lowering its concentration, and bringing the pH closer to normal in the chronic phase.
Q & A
What is respiratory alkalosis?
-Respiratory alkalosis is a condition where the lungs remove too much carbon dioxide from the body, causing the blood's pH to rise above 7.45.
What is the role of carbon dioxide in maintaining pH balance in the body?
-Carbon dioxide binds with water in the blood to form carbonic acid, which dissociates into hydrogen and bicarbonate ions. This process helps maintain pH balance by regulating the concentration of hydrogen ions in the blood.
How do the lungs normally maintain pH balance?
-The lungs regulate pH balance by adjusting the ventilation rate to match the body’s carbon dioxide production. If too much carbon dioxide is removed, pH rises, and if too little is removed, pH falls.
What triggers an increase in ventilation during respiratory alkalosis?
-Increased ventilation during respiratory alkalosis can be triggered by low oxygen levels (hypoxia), anxiety, panic attacks, sepsis, or brain stem disorders. It can also occur due to medical interventions, like improper ventilator settings.
How do chemoreceptors respond to changes in pH and carbon dioxide levels?
-Peripheral chemoreceptors in the carotid arteries and aortic arch detect changes in pH and carbon dioxide. When carbon dioxide levels drop and pH rises, they fire less, signaling the brainstem to reduce the respiratory rate.
What are the body's initial compensatory mechanisms during respiratory alkalosis?
-Initially, acidic molecules within cells, particularly red blood cells, release hydrogen ions that bind with bicarbonate to form carbonic acid. This helps reduce the blood's bicarbonate concentration slightly, but not enough to significantly lower pH.
How do the kidneys contribute to compensation during chronic respiratory alkalosis?
-After 3-5 days, the kidneys begin to compensate by reducing bicarbonate reabsorption in the proximal convoluted tubule, increasing its excretion in urine. This helps lower the blood's bicarbonate levels and bring pH closer to normal.
What is the difference between acute and chronic respiratory alkalosis?
-Acute respiratory alkalosis occurs shortly after the onset of hyperventilation and lacks significant renal compensation, while chronic respiratory alkalosis develops over days with the kidneys actively lowering bicarbonate levels to correct the pH imbalance.
What happens to pCO2 and bicarbonate levels during respiratory alkalosis?
-In respiratory alkalosis, pCO2 levels drop below the normal range (typically below 35 mmHg), leading to a reduction in plasma bicarbonate concentration. In acute cases, the decrease is minimal, but in chronic cases, the kidneys can significantly lower bicarbonate levels.
Why can improper ventilator settings cause respiratory alkalosis?
-If a ventilator is set to provide too much ventilation, it can cause excessive removal of carbon dioxide from the blood, leading to respiratory alkalosis by raising the blood pH beyond its normal range.
Outlines
🫁 Understanding Respiratory Alkalosis and Its Effects
This paragraph explains respiratory alkalosis, which refers to a disturbance in the body's pH balance due to excess removal of carbon dioxide (CO2) by the respiratory system. Normally, inhalation and exhalation balance oxygen intake and CO2 removal, which is crucial because CO2 forms carbonic acid in the blood. To maintain pH, the concentration of CO2 must remain stable. When CO2 levels drop and pH rises, chemoreceptors in the body notify the brainstem to reduce breathing, thereby restoring balance. However, in respiratory alkalosis, the respiratory system malfunctions, leading to increased ventilation and excessive CO2 loss.
🏔️ Causes and Triggers of Increased Ventilation
This section discusses situations that trigger increased ventilation, which can lead to respiratory alkalosis. Increased ventilation can be a normal response to low oxygen levels (hypoxia) caused by conditions such as pneumonia, pulmonary embolism, or high altitudes. However, it can also be abnormal, occurring in anxiety, panic attacks, sepsis, salicylate overdoses, or brain stem disorders. In some cases, it can result from medical interventions like incorrect ventilator settings. The outcome in all scenarios is excessive CO2 removal, which lowers CO2 concentration in the blood and increases pH.
⚡ The Body's Immediate Response to Respiratory Alkalosis
The body compensates for the increased pH caused by respiratory alkalosis through rapid mechanisms, mainly involving acidic molecules in red blood cells releasing hydrogen ions. These ions combine with bicarbonate to form carbonic acid, which lowers the concentration of free bicarbonate and mildly decreases pH. However, this compensation is limited and typically insufficient to fully restore pH balance. For each 10 mmHg decrease in CO2, plasma bicarbonate only decreases by about two milliequivalents per liter. In acute phases, the pH remains elevated despite these attempts at compensation.
🩺 Kidney Compensation in Chronic Respiratory Alkalosis
In chronic respiratory alkalosis, the kidneys help correct the high pH by reducing bicarbonate reabsorption, increasing its excretion in urine. Over time (about three to five days), this leads to a more significant drop in plasma bicarbonate levels—approximately four to five milliequivalents per liter for every 10 mmHg decrease in CO2. This process helps bring pH closer to its normal range. This paragraph also recaps respiratory alkalosis as a condition caused by excessive CO2 loss, distinguishing between acute and chronic phases based on renal compensation.
Mindmap
Keywords
💡Respiratory Alkalosis
💡Carbon Dioxide (CO2)
💡pH Balance
💡Ventilation Rate
💡Hypoxia
💡Chemoreceptors
💡Bicarbonate (HCO3−)
💡Renal Compensation
💡Minute Ventilation
💡Proximal Convoluted Tubule
Highlights
Respiratory alkalosis refers to a process where the respiratory system fails to maintain proper pH balance, leading to an increase in blood pH.
Normally, carbon dioxide binds to water in the blood to form carbonic acid, which dissociates into hydrogen ions and bicarbonate, regulating pH.
Lungs maintain ventilation rate to balance carbon dioxide production with exhalation, keeping pCO2 levels stable and preventing pH fluctuations.
Peripheral chemoreceptors in the carotid arteries and aortic arch adjust respiratory rate when pCO2 levels change.
In respiratory alkalosis, minute ventilation increases beyond what's needed to balance pH, leading to excessive carbon dioxide exhalation.
Hyperventilation can be triggered by various causes, including hypoxia, anxiety, sepsis, and overdoses of substances like salicylates.
Increased firing of respiratory centers in the brainstem can be either a compensatory response to low oxygen or an abnormal response.
Medical interventions, such as incorrect ventilator settings, can also cause respiratory alkalosis.
As a result of increased ventilation, pCO2 levels drop below 35 mmHg, leading to a rise in blood pH above 7.45.
The body's first response involves acidic molecules from red blood cells releasing hydrogen ions to buffer the alkalosis.
This buffering mechanism is limited, leading to only minor changes in bicarbonate concentration in the acute phase of respiratory alkalosis.
After three to five days, the kidneys compensate by decreasing bicarbonate reabsorption, leading to greater bicarbonate excretion in the urine.
The renal compensation phase is more effective in lowering bicarbonate levels and bringing pH back to normal over time.
In the acute phase, bicarbonate levels decrease by only 2 mEq/L for each 10 mmHg drop in pCO2, which doesn't significantly lower pH.
During the chronic phase, the kidneys can reduce bicarbonate levels by 4-5 mEq/L for every 10 mmHg decrease in pCO2, more effectively restoring pH balance.
Respiratory alkalosis can be divided into acute and chronic phases, depending on whether renal compensation is present.
Transcripts
don't worry
with respiratory alkalosis alkalosis
refers to a process that causes Alkali
accumulation or acid loss
and respiratory refers to the fact that
it's a failure of the respiratory system
carrying out its normal pH balancing job
now normally during an inhalation the
diaphragm and chest wall muscles
contract to pull open the chest and that
sucks in air like a vacuum cleaner
then during an exhalation the muscles
relax allowing the elastin in the lungs
to recoil pulling the lungs back to
their normal size and pushing that air
out
ultimately the lungs need to pull oxygen
into the body and get rid of carbon
dioxide
carbon dioxide binds to water in the
blood and forms carbonic acid which then
dissociates into hydrogen ions in
bicarbonate ions
so in order to prevent pH fluctuations
the carbon dioxide concentration or the
partial pressure of carbon dioxide
called pco2 needs to be kept within a
fairly narrow range
for this reason the lungs maintain the
ventilation rate they need to get rid of
carbon dioxide at the same rate that
it's created by the tissues
if pco2 levels start to fall and pH
levels start to rise peripheral
chemoreceptors that are found in the
walls of the corroded arteries and in
the wall the aortic Arch start to fire
less
and that notifies the respiratory
centers in the brainstem that they need
to decrease the respiratory rate and
depth of breathing
as the respiratory rate decreases and
breasts become more shallow the minute
ventilation decreases which is the
volume of air that moves in and out of
the lungs in a minute
the decreased ventilation means less
carbon dioxide moves out of the body
which increases the pco2 in the body and
lowers the pH
in respiratory alkalosis the normal
mechanism of ventilation gets Disturbed
and the minute ventilation goes higher
than what's needed to balance the pH
for ventilation to increase the
respiratory centers have to start firing
more than usual
this increased firing might be a normal
compensatory response
or an abnormal response to a situation
that doesn't really call for increased
ventilation
increased ventilation is a normal
response to things like hypoxia which is
a low oxygen level that happens with
diseases like pneumonia or a pulmonary
embolism or even when a person climbs a
high mountain like Mount Everest
increase ventilation though can be an
abnormal response that sometimes happens
in situations like anxiety and panic
attacks
as well as in sepsis or in overdoses
with salicylates
rarely brain stem disorders can irritate
the respiratory centers and make them
fire more
sometimes increased minute ventilation
is iatrogenic meaning that it's a result
of a medical intervention
for example a person might be intubated
and on a ventilator if the ventilator
settings aren't correct it can cause a
respiratory alkalosis
in all these situations the result is
that the lungs get rid of too much
carbon dioxide
the carbon dioxide gets depleted from
the blood so the partial pressure of
carbon dioxide Falls usually below 35
millimeters of mercury
this causes an increase in blood pH
often raising it above 7.45
to compensate for this increase the body
is designed several mechanisms first of
all minutes after the onset of
respiratory alkalosis acidic molecules
from within the cells especially red
blood cells like exposed carboxyl groups
from proteins like hemoglobin give off a
whole bunch of hydrogen ions
these hydrogen ions diffuse into the
blood where they grab bicarbonate ions
in order to form carbonic acid which
will eventually break down to carbon
dioxide in water molecules
this leads to a slight decrease in the
plasma bicarbonate concentration which
is the main alkaline molecule in the
blood
the concentration of these intracellular
proteins though is too low compared to
the amount of bicarbonate floating
around in the blood so essentially only
a limited amount of hydrogen ions are
available to bind and neutralize these
bicarbonate molecules
as a result most of the time the
decrease in free bicarbonate ions is too
little to have a substantial effect on
ph since it's only about two Milli
equivalents per liter for each 10
millimeters of mercury decrease in
partial pressure of carbon dioxide
as an example if pco2 has an acute drop
of 20 millimeters of mercury let's say
it moved from 40 to 20 then this
mechanism could only decrease plasma
bicarbonate by four Milli equivalents
per liter from its reference value of 24
to 20. which does not have a big impact
on the pH
therefore the pH remains High during
this acute phase of the disorder
fortunately within about three to five
days kidneys start sensing that pH is
too high and step up to help correct the
imbalance more specifically the major
way they do this is by making the cells
of the proximal convoluted tubule
decrease reabsorption of hco3 minus
so it's being excreted more in the urine
in fact the kidneys are pretty effective
in doing this since they managed to
decrease the concentration of
bicarbonate about four to five Milli
equivalents per liter for each 10
millimeters of mercury decrease in pco2
so just like before if pco2 went down
from 40 to 20 millimeters of mercury
plasma bicarbonate this time would
decrease by 8 ml equivalents per liter
from 24 to 16.
this can lead to a substantial decrease
in the pH bringing it closer to its
normal range again
alright as a quick recap respiratory
alkalosis happens when lungs blow off
more carbon dioxide than needed which
causes blood pH to increase above 7.45
it can be divided into an acute into
chronic phase according to the absence
or presence of renal compensation
respectively which decreases bicarbonate
concentration in the blood
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