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Pulmonary Medicine
Taking a Respiratory History
  1. Are you having any trouble breathing?


  2. Do you have any chest pain with breathing? If so, what is the pain like, when does it occur, and what relieves it?


  3. Do you have a cough? If yes, what does the cough sound like, when does it occur, do you bring up any phlegm (sputum) when you cough, what does the phlegm look like?
    Normal sputum is thin, clear to white in color, and tasteless and odorless. Yellow-green colored sputum may indicate a bacterial infection and rust-colored sputum is characteristic of pneumonia.


  4. Are you ever short of breath?
    If so, does your shortness of breath occur at rest or with activity?
    Ask the patient specific questions about shortness of breath that impacts daily living, such as being able to carry groceries from a _____, or being able to clean floors or do laundry.


  5. Do you have any problems breathing at night?
    If so, do you use pillows to help you get in a position to breathe easier?


  6. What is your Email address?


  7. What is your name?


  8. What is your date of birth?


  9. What is your mailing address?


  10. What is your telephone number?


  11. Where is the patient now?


  12. How old is the patient?


  13. What is the gender of the patient?


  14. What are the sources of medical history?


  15. What best describes the patient?: Child Adolescent girl Adolescent boy Woman Man


  16. In general, how is your physical and mental health? Excellent Good Fair Poor


  17. Do you have any appointments scheduled with doctors or other specialists? Yes No


  18. Have you been in the hospital in the last month? Yes No


  19. Do you have health problems that you need help with right away? Yes No


  20. Do you need extra help to access services, such as a wheelchair ramp, a computer screen reader or large print materials? Yes No


  21. Screening for survival needs

    Do you have enough of these resources from the state?
    Food
    Clothing
    Housing
    Health care
    Transportation
    Security
    Education
    Consumer goods
    Communication Do you need any of these resources to be enhanced?


  22. What are the issues?


  23. Is your complete medical history ready?
    Yes
    No


  24. What is the number on your medical card?
    A medical card number is usually a nine digit number.


  25. What state or entity has issued this medical card?


  26. What is your height?


  27. What is your weight?


  28. Have you ever worked in any of the following occupations or environments?
    Pottery worker
    Cotton mill worker
    Pipe coverer
    Insulation worker
    Farmer
    Sandblaster
    Talc worker
    Beryllium worker
    Carpenter
    Aluminum worker
    Woodworker
    Plastic worker
    Mica worker
    Pulp mill worker
    Painter
    Railroad worker
    Smelter
    Mining
    Silica dust
    Foundry
    Textile manufacturing
    Insulation product manufacturing


  29. Do you exercise regularly, if yes what type of exercise do you do?


  30. Have you ever smoked cigarettes, cigars or pipe?
    Yes
    No
    If yes, how many years have you/did you smoke?
    ____________
    If yes, how many cigarettes a day (average consumption)?
    ____________
    If yes, do you currently smoke?
    ____________
    If you are no longer smoking, when did you quit?
    ____________


  31. Do you drink alcohol?
    Yes
    No
    If yes, Daily: ____________ per day
    Occasionally: ____________ per month
    Rarely: ____________ per year


  32. Are you allergic to any medications?


  33. Do you have any allergies?
    If yes, how does your allergy affect your breathing?


  34. Do you smoke now or have you ever smoked?
    If yes, how many years did you smoke and how many packs of cigarettes did you smoke daily? Question 35 What kind of work do you do/did you do?
    In your work are/were you exposed to substances such as asbestos, chemicals, or cigarette smoke?


  35. Do you have a personal or family history of asthma, tuberculosis, lung cancer, cystic fibrosis, bronchitis, emphysema, or any other lung disease?


  36. Evaluation, Diagnosis, Treatment by Other Doctors
    Questions you need to answer.

    Has any other doctor evaluated, diagnosed, and treated the patient in previous one year?


  37. What is the profile of the doctor who diagnosed and treated this case?


  38. What explanation has the doctor given about cause or causes of this medical condition?


  39. What did the doctor recommend?


  40. How long do the recommendations of doctor need to continue?


  41. When did the doctor last follow up the case?


  42. How did the doctor calculate the percentage of respiratory insufficiency?


  43. I have read and agree to the Terms & Conditions.

    These are basic questions.
    There are many more.

    Once the above listed relevant questions about comprehensive patient assessment are answered and received, you will get another questions list relevant to age, gender, location, problems, or issues, if any.

    This will be followed by specific recommendations.
Topics to Cover
Classification of Pulmonary Disorders
History
Physical Examination
Pulmonary Function Tests
    Standard PFTs
    Spirometry
    Flow-Volume Loops
    Lung Volumes
    DLCO
    Pimax, Pemax
CXR
ABG
Cases
Pulmonary Testing Normal
Pulmonary Testing Abnoirmal
Obstruction Restriction
Asthma Lung Disease
COPD Muscle Disease
--------- Chest Wall
Pediatric respiratory emergencies.
Adult respiratory medical emergencies.
Respiratory Symptoms
Respiratory Disorders

Respiratory Symptoms
What other symptoms might occur with respiratory symptoms?

Respiratory symptoms may accompany other symptoms that vary depending on the underlying disease, disorder or condition. Symptoms that frequently affect the respiratory tract may also involve other body systems.

Pulmonary symptoms that may occur along with respiratory symptoms

Respiratory symptoms may accompany other symptoms affecting the respiratory system including:

•Absence of breathing (apnea)
•Cough that gets more severe over time
•Coughing up blood (hemoptysis)
•Coughing up clear, yellow, light brown, or green mucus
•Difficulty breathing
•Loose, wet cough that produces thick white or yellow phlegm
•Rapid breathing (tachypnea)
•Shortness of breath
•Wheezing (whistling sound made with breathing)

Cardiovascular symptoms that may occur along with respiratory symptoms

Respiratory symptoms may accompany symptoms related to the cardiovascular system including:

•Absence of heart beat (asystole)
•Angina (chest pain due to decreased blood supply to heart muscle)
•Chest pain or pressure
•Irregular heart beats (arrhythmia)
•Low heart rate (bradycardia)
•Rapid heart rate (tachycardia)

Other symptoms that may occur along with respiratory symptoms

•Respiratory symptoms can accompany other symptoms including:
•Anxiety
•Bluish lips, nails or skin
•Enlargement of lymph nodes
•Fever and chills
•Runny nose (nasal congestion)
•Sore throat
•Sweating
•Thickening of tissue beneath the nail beds (clubbing)

Serious symptoms that might indicate a life-threatening condition In some cases, respiratory symptoms can be life threatening. Seek immediate medical care (call 911) if you, or someone you are with, have any of these life-threatening symptoms including:

•Bluish lips, nails or skin
•Confusion or loss of consciousness for even a brief moment
•Difficulty breathing
•High fever (higher than 101 degrees Fahrenheit)
•Rapid breathing (tachypnea) or shortness of breath
•Rapid heart rate (tachycardia)
•Shallow breathing (hypopnea)
•Wheezing (whistling sound made with breathing)

Causes

What causes respiratory symptoms?

Respiratory symptoms are common symptoms of lung and heart disease, emotions, or injury.

Chronic obstructive pulmonary disease (COPD, includes emphysema and chronic bronchitis) and asthma are common causes of respiratory symptoms. Other common causes include infections, such as pneumonia or acute bronchitis. Inflammation also causes respiratory symptoms, commonly seen in pleuritis or chronic bronchitis.

Heart conditions can lead to respiratory symptoms, especially in severe cases, such as congestive cardiac failure. Anxiety and panic attacks are common causes of respiratory symptoms and include rapid breathing that may result in hyperventilation or fainting.

Pulmonary causes of respiratory symptoms

Respiratory symptoms may be caused by respiratory system disorders including:

•Acute bronchitis
•Asthma or allergies
•Bronchiectasis (widening of the airways)
•Bronchiolitis (inflammation of the small airways) or bronchitis
•Chronic obstructive pulmonary disease (COPD, includes emphysema and chronic bronchitis)
•Decreased inspired oxygen levels from high altitude
•Lung cancer or metastatic tumors
•Pulmonary aspiration (inhaling blood, vomited material or other substances into lungs)
•Pulmonary hypertension (high blood pressure in the arteries of the lungs)
•Respiratory infections, such as cold or flu
•Tuberculosis (serious infection affecting the lungs and other organs)

Cardiovascular system causes of respiratory symptoms

Respiratory symptoms can also be caused by cardiovascular system disorders including:

•Cardiomyopathy (weakened or abnormal heart muscle and function)
•Cardiovascular disease (due to atherosclerosis or hardening of the arteries, or other causes)
•Congenital heart disease
•Congestive heart failure (deterioration of the heart’s ability to pump blood)
•Myocardial infarction (heart attack)

Emotional causes of respiratory symptoms

Respiratory symptoms can also be caused by emotional disorders including:

•Anger
•Anxiety
•Fear
•Panic attack

Serious or life-threatening causes of respiratory symptoms

In some cases, respiratory symptoms may be a symptom of a serious or life-threatening condition that should be immediately evaluated in an emergency setting. These include:

•Alcohol or drug overdose
•Anaphylaxis (life-threatening allergic reaction)
•Chest trauma
•Choking on a foreign object in your airway
•Epiglottitis (life-threatening inflammation and swelling of the epiglottis, a tissue flap between the tongue and windpipe)
•Myocardial infarction (heart attack)
•Pneumonia
•Pneumothorax (collapsed lung)
•Pulmonary embolism (blockage of a pulmonary artery due to blood clot)

Questions for diagnosing the cause of respiratory symptoms

To diagnose your condition, your doctor or licensed health care practitioner will ask you several questions related to your respiratory symptoms including:

•When did you first notice your respiratory symptoms?
•When do you feel respiratory symptoms?
•Do you have any other symptoms?
•What medications are you taking?
•Do you have any allergies?

What are the potential complications of respiratory symptoms?
Because respiratory symptoms can be due to serious diseases, failure to seek treatment can result in serious complications and permanent damage. Once the underlying cause is diagnosed, it is important for you to follow the treatment plan that you and your health care professional design specifically for you to reduce the risk of potential complications including:

•Heart failure
•Myocardial infarction (heart attack)
•Organ failure or dysfunction
•Respiratory failure and respiratory arrest
•Spread of cancer
•Spread of infection
•Stroke

What are the signs of respiratory problems? Respiratory symptoms are common symptoms of lung or heart conditions, emotions, or injury. The medical terms for respiratory symptoms include dyspnea (difficulty breathing), tachypnea (rapid breathing), hypopnea (shallow breathing), hyperpnea (deep breathing), and apnea (absence of breathing). Breathing problems may occur in conditions affecting the lungs alone or may be seen in association with more generalized conditions, such as dehydration or infections.

Chronic obstructive pulmonary disease (COPD, includes emphysema and chronic bronchitis) and asthma are common causes of respiratory symptoms. Other common causes include infections, such as pneumonia or acute bronchitis. Inflammation causes respiratory symptoms, as seen in pleuritis or chronic bronchitis. Depending on the cause, respiratory symptoms may originate from one or both lungs and may be accompanied by rapid heart rate (tachycardia), low blood pressure (hypotension), or other cardiovascular signs and symptoms.

Heart conditions can lead to respiratory symptoms, especially in severe cases, such as congestive cardiac failure. Anxiety and panic attacks are common causes of respiratory symptoms and include rapid breathing that may result in hyperventilation and fainting. Airway obstruction causes respiratory symptoms that may include rapid shallow breathing. Lung injury from chest trauma can also lead to respiratory symptoms.

In some cases, respiratory symptoms can be a sign of a serious or life-threatening condition. Seek immediate medical care (call _______) for serious symptoms, such as sweating and severe difficulty breathing, severe sharp chest pain that may be combined with pale or blue lips, fast heart rate, high fever (higher than 101 degrees Fahrenheit), fainting, or change in level of consciousness or lethargy.

Respiratory Disorders
Intensive Care Unit
Diseases of the Airways
Asthma
Chronic Obstructive Pulmonary Disease
Chronic Bronchiectasis & Cystic Fibrosis
Obstruction of Large Airways
Interstitial Lung Disease
Idiopathic Interstitial Pneumonia
Pulmonary Manifestations of Collagen Vascular Diseases
Sarcoidosis
Pulmonary Alveolar Proteinosis
Pulmonary Langerhans'-Cell Histiocytosis, Lymphangioleiomyomatosis, & Bronchiolitis Obliterans with Organizing Pneumonia
Diseases of the Alveolar Space
Acute Respiratory Distress Syndrome
Eosinophilic Pneumonias
Lung Transplantation
Diseases of the Pulmonary Vasculature
Pulmonary Arterial Hypertension
Pulmonary Thromboembolism
Vasculitis & the Diffuse Alveolar Hemorrhage Syndromes
Diseases of the Pleura
Pneumothorax/Hemothorax
Pleural Effusions, Excluding Hemothorax
Empyema
Diseases of the Mediastinum
Diseases of the Mediastinum
Disorders of Ventilatory Control
Acute Ventilatory Failure
Chronic Ventilatory Failure
Mechanical Ventilation: Invasive and Noninvasive
Sleep Apnea & the Upper Airway Resistance Syndrome
Evaluation of Sleepiness & Sleep Disorders Other Than Sleep Apnea: Narcolepsy, Restless Leg Syndrome, & Periodic Limb Movements
Medical Conditions That Often Cause Daytime Sleepiness
Occupational & Environmental Lung Diseases
Pneumoconiosis
Hypersensitivity Pneumonitis
Drug-Induced Lung Disease
Occupational Asthma
Acute Inhalational Injury
Infectious Lung Disease
Bacterial Pneumonia
Viral & Atypical Pneumonia
Fungal Pneumonias
Mycobacterial Diseases of the Lungs
Pulmonary Complications of HIV Disease
Neoplastic Lung Diseases
Bronchogenic Carcinoma & Solitary Pulmonary Nodules
Pleural Malignancies & Benign Neoplasms of the Lung
Evaluation of the Patient with Pulmonary Disease
Pulmonary Anatomy & Physiology
The History & Physical Examination in Pulmonary Medicine
Diagnostic Imaging
Laboratory Evaluation
Procedures in Pulmonary Medicine
Pulmonary Function Tests
What are normal results for lung function tests?
Because everyone’s bodies and lungs are different sizes, normal results differ from person to person. For instance, taller people and males tend to have larger lungs whereas shorter people and females have smaller lungs. A person’s lungs grow until they are in their mid-twenties and then after that, lung function falls slightly every year. There are standards that your health care provider uses that are based on your height, weight, age, and gender. These numbers are called the predicted values. If your numbers match the standard, the percent of the predicted number will be 100%. Your own lung function can be tracked over time to help see if you have had a change.

What are pulmonary function tests?
Pulmonary function tests (PFTs) are noninvasive diagnostic tests that provide measurable feedback about the function of the lungs. By assessing lung volumes, capacities, rates of flow, and gas exchange, PFTs provide information that, when evaluated by your doctor, can help diagnosis certain lung disorders.

A normally-functioning pulmonary system operates on many different levels to ensure adequate balance. One of the primary functions of the pulmonary system is ventilation, the movement of air into and out of the lungs.

Some medical conditions may interfere with ventilation. These conditions may lead to chronic lung disease. Conditions that interfere with normal ventilation are categorized as restrictive or obstructive. An obstructive condition occurs when air has difficulty flowing out of the lungs due to resistance, causing a decreased flow of air. A restrictive condition occurs when the chest muscles are unable to expand adequately, creating a disruption in air flow.

Pulmonary function tests may be indicated to determine the presence, location, cause, and characteristics of the problem, and to guide treatment.

Pulmonary function tests is an inclusive term that refers to several different procedures that measure lung function in different ways. Some of the more common values that may be measured during pulmonary function testing include:

•Tidal volume (VT). This is the amount of air inhaled or exhaled during normal breathing.

•Minute volume (MV). This is the total amount of air exhaled per minute.

•Vital capacity (VC). This is the total volume of air that can be exhaled after maximum inspiration.

•Functional residual capacity (FRC). This is the amount of air remaining in lungs after normal expiration.

•Total lung capacity. This is the total volume of lungs when maximally inflated.

•Forced vital capacity (FVC). This is the amount of air exhaled forcefully and quickly after maximum inspiration.

•Forced expiratory volume (FEV). This is the volume of air expired during the first, second, and third seconds of the FVC test.

•Forced expiratory flow (FEF). This is the average rate of flow during the middle half of the FVC test.

•Peak expiratory flow rate (PEFR). This is the maximum volume during forced expiration.

Some PFTs involve the use of a spirometer.

The spirometer is an instrument that measures the amount of air breathed in and/or out and how quickly the air is inhaled and expelled from the lungs while breathing through a mouthpiece. The measurements are recorded on a device called a spirograph.

Other test results are derived from calculations based on the results of certain spirometry procedures. In addition to measuring the amount and rate of air inhaled and exhaled, these tests can also indicate how well oxygen and carbon dioxide are being exchanged in the alveoli.

Some PFTs, such as thoracic gas volume or other lung volume measurements, may be determined by plethysmography. During plethysmography, a person sits or stands inside an air-tight box that resembles a short, square telephone booth to perform the tests.

The normal values for PFTs vary from person to person. The amount of air inhaled and exhaled in your test results are compared to the expected average in someone of the same age, height, sex, and race. In addition, results are compared to your previous test results, if previous testing has been done. If you have abnormal PFT measurements or if your results are different from previous tests, you may be referred for other diagnostic tests to establish a medical diagnosis.

Anatomy of the respiratory system


The respiratory system is made up of the organs involved in the exchange of gases, and consists of the:

•Nose
•Pharynx
•Larynx
•Trachea
•Bronchi
•Lungs

The upper respiratory tract includes the:

•Nose
•Nasal cavity
•Ethmoidal air cells
•Frontal sinuses
•Maxillary sinus
•Larynx
•Trachea

The lower respiratory tract includes the lungs, bronchi, and alveoli.

What are the functions of the lungs?
The lungs take in oxygen, which cells need to live and carry out their normal functions. The lungs also get rid of carbon dioxide, a waste product of the body's cells.

The lungs are a pair of cone-shaped organs made up of spongy, pinkish-gray tissue. They take up most of the space in the chest, or the thorax (the part of the body between the base of the neck and diaphragm).

The lungs are enveloped in a membrane called the pleura.

The lungs are separated from each other by the mediastinum, an area that contains the following:

•The heart and its large vessels
•Trachea (windpipe)
•Esophagus
•Thymus
•Lymph nodes

The right lung has three sections called lobes. The left lung has two lobes. When you breathe, the air enters the body through the nose or the mouth. It then travels down the throat through the larynx (voice box) and trachea (windpipe) and goes into the lungs through tubes called mainstem bronchi.

One mainstem bronchus leads to the right lung and one to the left lung. In the lungs, the mainstem bronchi divide into smaller bronchi and then into even smaller tubes called bronchioles. Bronchioles end in tiny air sacs called alveoli.

Different measurements that may be found on your report after spirometry include:
•Expiratory reserve volume (ERV)
•Forced vital capacity (FVC)
•Forced expiratory volume (FEV)
•Forced expiratory flow 25% to 75%
•Functional residual capacity (FRC)
•Maximum voluntary ventilation (MVV)
•Residual volume (RV)
•Peak expiratory flow (PEF).
•Slow vital capacity (SVC)
•Total lung capacity (TLC)
Arterial blood gas analysis
    Respiratory acidosis
    Respiratory alkalosis
    Diabetic ketoacidosis
    Lactic acidosis
    Metabolic acidosis
Arterial Blood Gases
The Test

How is it used?
When is it ordered?
What does the test result mean?
Is there anything else I should know?

The 6 Easy Steps to ABG Analysis:
1. Is the pH normal?
2. Is the CO2 normal?
3. Is the HCO3 normal?
4. Match the CO2 or the HCO3 with the pH
5. Does the CO2 or the HCO3 go the opposite direction of the pH?
6. Are the pO2 and the O2 saturation normal?

Step 1: Analyze the pH The first step in analyzing ABGs is to look at the pH. Normal blood pH is 7.4, plus or minus 0.05, forming the range 7.35 to 7.45. If blood pH falls below 7.35 it is acidic. If blood pH rises above 7.45, it is alkalotic. If it falls into the normal range, label what side of 7.4 it falls on. Lower than 7.4 is normal/acidic, higher than 7.4 is normal/alkalotic. Label it.

Step2: Analyze the CO2 The second step is to examine the pCO2. Normal pCO2 levels are 35-­-45mmHg. Below 35 is alkalotic, above 45 is acidic. Label it.

Step 3: Analyze the HCO3 The third step is to look at the HCO3 level. A normal HCO3 level is 22-­-26 mEq/L. If the HCO3 is below 22, the patient is acidotic. If the HCO3 is above 26, the patient is alkalotic. Label it.

Step 4: Match the CO2 or the HCO3 with the pH Next match either the pCO2 or the HCO3 with the pH to determine the acid-­-base disorder. For example, if the pH is acidotic, and the CO2 is acidotic, then the acid-­-base disturbance is being caused by the respiratory system. Therefore, we call it a respiratory acidosis. However, if the pH is alkalotic and the HCO3 is alkalotic, the acid-­- base disturbance is being caused by the metabolic (or renal) system. Therefore, it will be a metabolic alkalosis.

Step 5: Does the CO2 or HCO3 go the opposite direction of the pH? Fifth, does either the CO2 or HCO3 go in the opposite direction of the pH? If so, there is compensation by that system. For example, the pH is acidotic, the CO2 is acidotic, and the HCO3 is alkalotic. The CO2 matches the pH making the primary acid-­-base disorder respiratory acidosis. The HCO3 is opposite of the pH and would be evidence of compensation from the metabolic system.

Step 6: Analyze the pO2 and the O2 saturation. Finally, evaluate the PaO2 and O2 sat. If they are below normal there is evidence of hypoxemia.
Normal Values (At sea level): Range:
pH 7.35-­-7.45
pCO2 35-­-45 mmHg
pO2 80-­-100 mmHg
O2 Saturation 95-­-100%
HCO3-­- 22-­-26 mEq/L
Base Excess + or -­- 2
NOW LET’S PUT THE 6 STEPS INTO ACTION WITH AN EXAMPLE:
pH 7.27 acidotic
CO2 53 acidotic
pO2 50 low
O2 sat. 79% low
HCO3 24 normal
Step 1: The pH is less than 7.35, therefore is acidotic.
Step 2: The CO2 is greater than 45, and is therefore acidotic.
Step 3: The HCO3 is normal.
Step 4: The CO2 matches the pH, because they are both acidotic. Therefore the imbalance is respiratory acidosis. It is acidotic because the pH is acidotic, it is respiratory because the CO2 matches the pH.
Step 5: The HCO3 is normal, therefore there is no compensation. If the HCO3 is alkalotic (opposite direction) then compensation would be present.
Step 6: Lastly, the PaO2 and O2 sat are low indicating hypoxemia.
The full diagnosis for this blood gas is:
Uncompensated respiratory acidosis with hypoxemia.
This patient has an acute respiratory disorder.
HERE’S ANOTHER EXAMPLE:
pH 7.52 alkalotic
CO2 29 alkalotic
pO2 100 normal
O2 sat. 98% normal
HCO3 23 normal
Step 1: The pH is greater than 7.45, therefore is alkalotic.
Step 2: The CO2 is less than 35, and is therefore alkalotic.
Step 3: The HCO3 is normal.
Step 4: The CO2 matches the pH, because they are both alkalotic. Therefore the imbalance is respiratory alkalosis. It is alkalotic because the pH is alkalotic; it is respiratory because the CO2 matches the pH.
Step 5: The HCO3 is normal, therefore there is no compensation. If the HCO3 is acidotic (opposite direction) then compensation would be present. Step 6: Lastly, the PaO2 and O2 sat are normal indicating normal oxygenation.
The full diagnosis for this blood gas is:
Uncompensated respiratory alkalosis. This patient is probably hyperventilating.


HERE IS ANOTHER
EXAMPLE:
pH 7.18 acidotic
CO2 44 normal
pO2 92 normal
O2 sat. 95% normal
HCO3 16 acidotic
Step 1: The pH is less than 7.35, therefore is acidotic. Step 2: The CO2 is normal. Step 3: The HCO3 is less than 22, and is therefore acidotic. Step 4: The HCO3 matches the pH, because they are both acidotic. Therefore the imbalance is metabolic acidosis. It is acidotic because the pH is acidotic, it is metabolic because the HCO3 matches the pH. Step 5: The CO2 is normal, therefore there is no compensation. If the CO2 is alkalotic (opposite direction) then compensation would be present. Step 6: Lastly, the PaO2 and O2 sat are normal indicating normal oxygenation. The full diagnosis for this blood gas is: Uncompensated metabolic acidosis. This patient probably has an acute metabolic disorder such as DKA.


10 LET’S TRY ANOTHER:
pH 7.60 alkalotic
CO2 37 normal
pO2 92 normal
O2 sat. 98% normal
HCO3 35 alkalotic
Step 1: The pH is greater than 7.45, therefore is alkalotic.
Step 2: The CO2 is normal.
Step 3: The HCO3 is greater than 26, and therefore is alkalotic.
Step 4: The HCO3 matches the pH, because they are both alkalotic. Therefore the imbalance is metabolic alkalosis. It is alkalotic because the pH is alkalotic, it is metabolic because the HCO3 matches the pH.
Step 5: The CO2 is normal, therefore there is no compensation. If the CO2 is acidotic (opposite direction) then compensation would be present.
Step 6: Lastly, the PaO2 and O2 sat are normal. The full diagnosis for this blood gas is: Uncompensated metabolic alkalosis. This patient probably is losing stomach acid from vomiting or NG tube drainage.


11 ONE LAST EXAMPLE:
pH 7.30 acidotic
CO2 30 alkalotic
pO2 68 low
O2 sat. 92% low
HCO3 14 acidotic
Step 1: The pH is less than 7.35, therefore is acidotic.
Step 2: The CO2 is less than 35, and is therefore alkalotic.
Step 3: The HCO3 is less than 22, and therefore is acidotic.
Step 4: The HCO3 matches the pH, because they are both acidotic. Therefore the imbalance is a metabolic acidosis. It is acidotic because the pH is acidotic, it is metabolic because the HCO3 matches the pH.
Step 5: The CO2 is alkalotic and goes the opposite direction of the pH, so there is compensation. Because the pH is not in the normal range the compensation is called partial.
Step 6: Lastly, the PaO2 and O2 sat are low indicating hypoxemia. The full diagnosis for this blood gas is: Partially-­-compensated metabolic acidosis with hypoxemia. There are a number of conditions that can cause metabolic acidosis: renal failure, diarrhea, poisonings, diabetic ketoacidosis, and shock, to name a few. This patient is probably in shock, because his metabolic acidosis associated with poor oxygenation.

How is it used?

Blood gas measurements are used to evaluate your oxygenation and acid/base status. They are typically ordered if you have worsening symptoms of an acid/base imbalance, difficulty breathing, or shortness of breath. Blood gases may be ordered along with other tests, such as electrolytes to determine if an electrolyte imbalance is present, glucose to evaluate blood sugar concentrations, and BUN and creatinine tests to evaluate kidney function.

If you are on continuing supplemental oxygen therapy, blood gases may be used to monitor the effectiveness of that treatment.

When is it ordered?

Blood gas tests are ordered when you have symptoms of an oxygen/carbon dioxide or pH imbalance, such as difficulty breathing, shortness of breath, nausea or vomiting.

Blood gas measurements may be ordered when you are known to have a respiratory, metabolic, or kidney disease and are experiencing respiratory distress.

When you are "on oxygen" (ventilation), you may have your blood gases measured at intervals to monitor the effectiveness of treatment.

Blood gases may also be ordered when you have head or neck trauma, injuries that may affect breathing. When you are undergoing prolonged anesthesia – particularly for cardiac bypass surgery or brain surgery – you may have your blood gases monitored during and for a period after the procedure.

Checking the blood gases from the umbilical cord of newborns may uncover respiratory problems as well as determine the baby's acid/base status. Testing is usually only done if a newborn's condition indicates that he or she may be having difficulty breathing.

What does the test result mean?

Abnormal results of any of the blood gas components may mean that:

  • you are not getting enough oxygen
  • you are not getting rid of enough carbon dioxide
  • there is a problem with kidney function

The results of the PO2 component of the tests for blood gases relates to how much oxygen you are able to breathe in and the amount of oxygen in your blood. Low levels may mean you are not getting enough oxygen while results that are within normal range usually mean your oxygen intake is sufficient.

The results of the other components of the tests for blood gases are interrelated and the results must be considered together. Certain combinations of results, if abnormal, may indicate a condition that is causing acidosis or alkalosis:

  • Respiratory acidosis is characterized by a lower pH and an increased PCO2 and is due to respiratory depression – not enough oxygen in and carbon dioxide out. This can be caused by many things, including pneumonia, chronic obstructive pulmonary disease (COPD), and over-sedation from narcotics.
  • Respiratory alkalosis, characterized by a raised pH and a decreased PCO2, is due to over ventilation caused by hyperventilating, pain, emotional distress, or certain lung diseases that interfere with oxygen exchange.
  • Metabolic acidosis is characterized by a lower pH and decreased HCO3-; the blood is too acidic on a metabolic/kidney level. Causes include diabetes, shock, and renal failure.
  • Metabolic alkalosis is characterized by an elevated pH and increased HCO3- and is seen in hypokalemia, chronic vomiting (losing acid from the stomach), and sodium bicarbonate overdose.

Combinations of results that may be seen in certain conditions are summarized below:

pH result Bicarbonate result PCO2 result Condition Common causes
Less than 7.4 Low Low Metabolic acidosis Kidney failure, shock, diabetic ketoacidosis
Greater than 7.4 High High Metabolic alkalosis Chronic vomiting, low blood potassium
Less than 7.4 High High Respiratory acidosis Lung diseases such as pneumonia, COPD
Greater than 7.4 Low Low Respiratory alkalosis Hyperventilation, pain, anxiety

If left untreated, these conditions can create an imbalance that can eventually be life-threatening. Your doctor will provide the necessary medical intervention for you to regain your body's normal balance, but the underlying cause of the imbalance must also be addressed.

Is there anything else I should know?

Arterial blood sample collection is usually more painful than regular venipuncture. You will experience moderate discomfort, and a compress is required for some time to prevent any bleeding from the site.

Sometimes mixed venous blood taken from a central line is used in particular situations, such as in cardiac catheterization labs and by transplant services. Careful interpretation of the results is required. Peripheral venous blood, such as that taken from a vein in the arm, is of no use for oxygen status.

Common Questions

Normal Arterial Blood Gas Values

pH 7.35-7.45
PaCO2 35-45 mm Hg
PaO2  80-95 mm Hg
HCO3  22-26 mEq/L
O2 Saturation 95-99%
BE  +/- 1

Four-Step Guide to ABG Analysis

  1. Is the pH normal, acidotic or alkalotic?
  2. Are the pCO2 or HCO3 abnormal?  Which one appears to influence the pH?
  3. If both the pCO2 and HCO3 are abnormal, the one which deviates most from the norm is most likely causing an abnormal pH. 
  4. Check the pO2.  Is the patient hypoxic?

I used Swearingen's handbook (1990) to base the results of this calculator.  The book makes the distinction between acute and chronic disorders based on symptoms from identical ABGs.  This calculator only differentiates between acute (pH abnormal) and compensated (pH normal).  Compensation can be seen when both the PCO2 and HCO3 rise or fall together to maintain a normal pH.  Part compensation occurs when the PCO2 and HCO3 rise or fall together but the pH remains abnormal.  This indicates a compensatory mechanism attempted to restore a normal pH.  I have not put exact limits into the calculator.  For example, it will perceive respiratory acidosis as any pH < 7.35 and any CO2 > 45 (i.e. a pH of 1 and CO2 of 1000).  These results do not naturally occur.

pH PaCO2 HCO3
Respiratory Acidosis
Acute < 7.35 > 45 Normal
Partly Compensated < 7.35 > 45 > 26
Compensated Normal > 45 > 26

Respiratory Alkalosis
Acute > 7.45 < 35 Normal
Partly Compensated > 7.45 < 35 < 22
Compensated Normal < 35 < 22

Metabolic Acidosis
Acute < 7.35 Normal < 22
Partly Compensated < 7.35 < 35 < 22
Compensated Normal < 35 < 22

Metabolic Alkalosis
Acute > 7.45 Normal > 26
Partly Compensated > 7.45 > 45 > 26
Compensated Normal > 45 > 26

Mixed Disorders

It's possible to have more than one disorder influencing blood gas values.  For example ABG's with an alkalemic pH may exhibit respiratory acidosis and metabolic alkalosis.  These disorders are termed complex acid-base or mixed disorders.

*This table is able to classify most clinical blood gas values but not all.  In cases where blood gas values do not fall into any of the above classifications, an answer "unable to determine" will appear when using the interpreter.  For example a pH of 7.428, pCO2 43.6, and a HCO3 of 29.1 do not match any of the classifications (I found these results in someone's chart).  While the pH and pCO2 are normal, the HCO3 is abnormally high.