Question

How would the respiratory mechanism respond to acidosis?  Alkalosis? What of renal mechanism?

Answer 1

Respiratory acidosis is a condition that occurs when the lungs can’t remove enough of the carbon dioxide (CO2) produced by the body. Excess CO2 causes the pH of blood and other bodily fluids to decrease, making them too acidic. Normally, the body is able to balance the ions that control acidity. This balance is measured on a pH scale from 0 to 14. Acidosis occurs when the pH of the blood falls below 7.35 (normal blood pH is between 7.35 and 7.45).

Respiratory acidosis is typically caused by an underlying disease or condition. This is also called respiratory failure or ventilatory failure.

Normally, the lungs take in oxygen and exhale CO2. Oxygen passes from the lungs into the blood. CO2 passes from the blood into the lungs. However, sometimes the lungs can’t remove enough CO2. This may be due to a decrease in respiratory rate or decrease in air movement due to an underlying condition such as:

• asthma
• COPD
• pneumonia
• sleep apnea

Forms of respiratory acidosis

There are two forms of respiratory acidosis: acute and chronic.

Acute respiratory acidosis occurs quickly. It’s a medical emergency. Left untreated, symptoms will get progressively worse. It can become life-threatening.

Chronic respiratory acidosis develops over time. It doesn’t cause symptoms. Instead, the body adapts to the increased acidity. For example, the kidneys produce more bicarbonate to help maintain balance.

Chronic respiratory acidosis may not cause symptoms. Developing another illness may cause chronic respiratory acidosis to worsen and become acute respiratory acidosis.

Symptoms of respiratory acidosis

Initial signs of acute respiratory acidosis include:

• headache
• anxiety
• blurred vision
• restlessness
• confusion

Without treatment, other symptoms may occur. These include:

• sleepiness or fatigue
• lethargy
• delirium or confusion
• shortness of breath
• coma

The chronic form of respiratory acidosis doesn’t typically cause any noticeable symptoms. Signs are subtle and nonspecific and may include:

• memory loss
• sleep disturbances
• personality changes

Common causes of respiratory acidosis

The lungs and the kidneys are the major organs that help regulate your blood’s pH. The lungs remove acid by exhaling CO2, and the kidneys excrete acids through the urine. The kidneys also regulate your blood’s concentration of bicarbonate (a base).

Respiratory acidosis is usually caused by a lung disease or condition that affects normal breathing or impairs the lungs’ ability to remove CO2. Some common causes of the chronic form are:

• asthma
• chronic obstructive pulmonary disease (COPD)
• acute pulmonary edema
• severe obesity (which can interfere with expansion of the lungs)
• neuromuscular disorders (such as multiple sclerosis or muscular dystrophy)
• scoliosis

Some common causes of the acute form are:

• lung disorders (COPD, emphysema, asthma, pneumonia)
• conditions that affect the rate of breathing
• muscle weakness that affects breathing or taking a deep breath
• obstructed airways (due to choking or other causes)
• sedative overdose
• cardiac arrest

Alkalosis

Respiratory alkalosis occurs when the levels of carbon dioxide and oxygen in the blood are not balanced.

Your body needs oxygen to function properly. When you inhale, you introduce oxygen into the lungs. When you exhale, you release carbon dioxide, which is a waste product. Normally, the respiratory system keeps these two gases in balance.

Respiratory alkalosis occurs when you breathe too fast or too deep and carbon dioxide levels drop too low. This causes the pH of the blood to rise and become too alkaline. When the blood becomes too acidic, respiratory acidosis occurs.

Hyperventilation and respiratory alkalosis

Hyperventilation is typically the underlying cause of respiratory alkalosis. Hyperventilation is also known as overbreathing. Someone who is hyperventilating breathes very deeply or rapidly.

Causes of hyperventilation

Panic attacks and anxiety are the most common causes of hyperventilation. However, they’re not the only possible causes. Others include:

• heart attack
• pain
• drug use
• asthma
• fever
• chronic obstructive pulmonary disease
• infection
• pulmonary embolism
• pregnancy

If you’re experiencing hyperventilation (especially for the first time), don’t assume you know the cause. Make an appointment with your doctor.

Symptoms of respiratory alkalosis

Overbreathing is a sign that respiratory alkalosis is likely to develop. However, low carbon dioxide levels in the blood also have a number of physical effects, including:

• dizziness
• bloating
• feeling lightheaded
• numbness or muscle spasms in the hands and feet
• discomfort in the chest area
• confusion
• dry mouth
• tingling in the arms
• heart palpitations
• feeling short of breath

Renal mechanism

Steady state blood CO2 levels remain relatively constant in compensated respiratory acidosis and alkalosis (i.e., CO2 in = CO2 out). Uncompensated respiratory alkalosis is associated with an increased blood pH, and a modestly decreased HCO3 – concentration. Renal compensation for respiratory alkalosisinvolves a decrease in HCO3 – reabsorption. The blood pH may be within the normal range in some mixed acid-base disorders. A mixed acid-base disturbance is indicated when the Pco2 and blood HCO3 – concentration are moving in opposite directions. Mixed acid-base distrubances can be additive, or subtractive. The bicarbonate buffer equation is shifted to the left in metabolic acidosis and respiratory alkalosis. Respiratory alkalosis can be due to either direct or reflex hypoxemic stimulation of the respiratory center, to pulmonary disease, or to excessive mechanical ventilation.