Respiratory alkalosis

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Respiratory alkalosis

Renal system

Anatomy and physiology

Renal system anatomy and physiology

Fluid compartments and homeostasis

Hydration

Body fluid compartments

Movement of water between body compartments

Renal clearance, glomerular filtration and renal blood flow

Renal clearance

Glomerular filtration

TF/Px ratio and TF/Pinulin

Measuring renal plasma flow and renal blood flow

Regulation of renal blood flow

Renal tubular reabsorption and secretion

Tubular reabsorption and secretion

Tubular secretion of PAH

Tubular reabsorption of glucose

Urea recycling

Tubular reabsorption and secretion of weak acids and bases

Renal tubular physiology

Proximal convoluted tubule

Loop of Henle

Distal convoluted tubule

Renin-angiotensin-aldosterone system

Renin-angiotensin-aldosterone system

Renal electrolyte regulation

Sodium homeostasis

Potassium homeostasis

Phosphate, calcium and magnesium homeostasis

Renal sodium and water regulation

Osmoregulation

Sodium homeostasis

Antidiuretic hormone

Kidney countercurrent multiplication

Free water clearance

Renal endocrine functions

Vitamin D

Erythropoietin

Acid-base physiology

Physiologic pH and buffers

Buffering and Henderson-Hasselbalch equation

The role of the kidney in acid-base balance

Acid-base map and compensatory mechanisms

Respiratory acidosis

Metabolic acidosis

Plasma anion gap

Respiratory alkalosis

Metabolic alkalosis

Assessments

Respiratory alkalosis

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USMLE® Step 1 questions

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High Yield Notes

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Respiratory alkalosis

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Questions

USMLE® Step 1 style questions USMLE

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A 57-year-old man comes to the emergency department for evaluation of acute-onset shortness of breath and chest pain that began three hours ago. The patient reports poorly-localized chest pain worse with inspiration. He is a business executive and recently returned from an overseas trip. Past medical history includes hypertension and hyperlipidemia. His temperature is 37.3°C (99.1°F), pulse is 91/min, blood pressure is 142/71 mmHg, and respirations are 21/min. Breath sounds are clear to auscultation bilaterally. Examination of the lower extremities reveals swelling and erythema in the right calf. Dorsalis pedis and posterior tibial pulses are 3+ bilaterally. A chest CT is ordered and reveals the following:


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An arterial blood gas is pending. Which of the following findings will most likely be present on laboratory analysis?  

External References

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Hypoxemia

respiratory alkalosis and p. 616

Hysteria

respiratory alkalosis from p. 616

Pulmonary embolism p. 697

respiratory alkalosis p. 616

Respiratory alkalosis p. 616

causes of p. 616

in delirium tremens p. 593

high altitude p. 692

pulmonary embolism p. 697

Salicylates

respiratory alkalosis p. 616

Transcript

Content Reviewers

Rishi Desai, MD, MPH

Evan Debevec-McKenney

Contributors

Antonia Syrnioti, MD

Evan Debevec-McKenney

Jake Ryan

Robyn Hughes, MScBMC

Tanner Marshall, MS

Brittany Norton, MFA

Jung Hee Lee, MScBMC

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.

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 CO2. CO2 binds to water H2O in the blood and forms H2CO3 carbonic acid, which then dissociates into hydrogen H+ and bicarbonate ions HCO3-. So, in order to prevent pH fluctuations, the CO2 concentration, or the partial pressure of CO2, called PCO2, needs to be kept within a fairly narrow range. For this reason, lungs maintain the ventilation rate they need to get rid of CO2 at the same rate that it’s created by the tissues. If PCO2 levels start to fall and pH starts to rise, peripheral chemoreceptors that are located in the walls of the carotid arteries and in the wall of 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 breaths become more shallow, the minute ventilation decreases - that’s the volume of air that moves in and out of the lungs in a minute. The decreased ventilation, means less carbon dioxide CO2 moves out of the body, increasing the PCO2 in the body, which 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 may 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, a low oxygen level, which can happen with diseases like pneumonia or a pulmonary embolism, or even when a person climbs a high mountain like Mount Everest. But, increased ventilation can be an abnormal response that sometimes happens in situations like anxiety and panic attacks, in sepsis, or in overdoses with salicylates.

Summary

Respiratory alkalosis is a type of acid-base imbalance that occurs when there is a decrease in the amount of carbon dioxide (CO2) in the body, leading to an increase in the pH of the blood above 7.45. Respiratory alkalosis can occur due to a variety of causes, including hyperventilation, which is rapid and deep breathing leading to excessive removal of CO2 from the body. Hyperventilation can be seen in conditions like hypoxia, pulmonary embolism, panic attacks, sepsis, or in overdoses with salicylate drugs.

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