Respiratory alkalosis - causes, symptoms, diagnosis, treatment, pathology

Summary

Respiratory 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

00:00

🫁 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.

05:02

🏔️ 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.

Keywords

💡Respiratory Alkalosis

Respiratory alkalosis is a condition where the lungs expel too much carbon dioxide, leading to a higher blood pH level above 7.45. This happens when the normal mechanism of breathing is disturbed, causing excessive ventilation. The video discusses how this can be caused by factors like anxiety, panic attacks, or even medical interventions such as improper ventilator settings.

💡Carbon Dioxide (CO2)

Carbon dioxide is a waste product produced by the body's tissues that needs to be expelled by the lungs. In the blood, CO2 binds with water to form carbonic acid, which dissociates into hydrogen and bicarbonate ions, affecting the blood's pH level. In the video, the failure to maintain the proper levels of CO2 due to over-ventilation is a central cause of respiratory alkalosis.

💡pH Balance

pH balance refers to the regulation of the body's acid-base equilibrium, which is vital for proper cellular function. The video explains how respiratory alkalosis occurs when the pH level rises above the normal range due to the loss of carbon dioxide, leading to a more alkaline environment. The normal pH range for blood is between 7.35 and 7.45.

💡Ventilation Rate

The ventilation rate is the frequency and depth at which the lungs exchange air with the environment. In the video, increased ventilation rate leads to excessive expulsion of carbon dioxide, which is a key driver of respiratory alkalosis. The video describes how different triggers, like hypoxia or panic attacks, can cause this abnormal increase in ventilation.

💡Hypoxia

Hypoxia refers to a condition where there is an insufficient level of oxygen in the body’s tissues. The video uses hypoxia as an example of a normal response that triggers increased ventilation, which can eventually lead to respiratory alkalosis if excessive. This can happen in conditions such as pneumonia or when climbing to high altitudes.

💡Chemoreceptors

Chemoreceptors are sensors located in places like the carotid arteries and the aortic arch that monitor changes in blood chemistry, particularly pH and CO2 levels. In the video, these chemoreceptors detect when CO2 levels fall and trigger adjustments in the respiratory rate to restore balance, but in respiratory alkalosis, this system is disrupted.

💡Bicarbonate (HCO3−)

Bicarbonate is a key molecule in the body's buffering system that helps maintain pH balance by neutralizing acids. In the video, bicarbonate plays a role in the compensatory mechanisms that occur in response to respiratory alkalosis, where the kidneys reduce bicarbonate reabsorption to lower the blood’s pH back toward normal levels.

💡Renal Compensation

Renal compensation is the process by which the kidneys adjust the body's acid-base balance, particularly in response to respiratory disturbances. The video explains that during the chronic phase of respiratory alkalosis, the kidneys compensate by excreting more bicarbonate to help lower blood pH back to normal levels.

💡Minute Ventilation

Minute ventilation is the total volume of air that moves in and out of the lungs per minute. The video highlights how increased minute ventilation, either as a normal or abnormal response, leads to the excessive elimination of CO2, which causes respiratory alkalosis. This concept is essential in understanding how ventilation rates affect blood pH.

💡Proximal Convoluted Tubule

The proximal convoluted tubule is a part of the kidney that is involved in the reabsorption of substances from the urine. In the video, this structure is mentioned in the context of renal compensation, where it decreases the reabsorption of bicarbonate in response to respiratory alkalosis, helping to lower the blood’s pH.

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