PBL 3 Flashcards
What general aspects of the lungs do pulmonary functions tests test for?
- How much air volume can be moved in and out of the lungs
- How fast the air in the lungs can be moved in and out
- How stiff are the lungs and chest wall - a question about compliance
- The diffusion characteristics of the membrane through which the gas moves (determined by special tests)
Pulmonary Function Tests are used for the following reasons:
- Screening for the presence of obstructive and restrictive diseases
- Evaluating the patient prior to surgery
- Evaluating the patient’s condition for weaning from a ventilator.
- Documenting the progression of pulmonary disease - restrictive or obstructive
- Documenting the effectiveness of therapeutic intervention
When is a patient’s condition good enough to try weaning from a ventilator?
If the patient on a ventilator can demonstrate a vital capacity (VC) of 10 - 15 ml/Kg of body weight, it is generally thought that there is enough ventilatory reserve to permit (try) weaning and extubation. Be careful to ensure they are not suffering from malnutrition.
What factors affect the “normal” pulmonary function test scores predicted for a particular patient? (4)
- Age: As a person ages, elasticity of the lungs decreases, so we have decreasing lung volumes and capacities as we age.
- Gender : Usually the lung volumes and capacities of males are larger than those of females.
- Body Height & Size: Body size has a tremendous effect on PFT values. A small man will have a smaller PFT result than a man of the same age who is much larger. If a patient becomes too obese, the abdominal mass prevents the diaphragm from descending as far as it could and the PFT results will demonstrate a smaller measured PFT outcome then expected.
- Race: Race affects PFT values. Black people, Hispanics and Native Americans have different PFT results compared to Caucasians. Therefore, a clinician must use a race appropriate table.
- Other factors such as environmental factors and altitude may have an affect on PFT results but the degree of effect on PFT is not clearly understood at this time.
What is FVC? What units is it expressed in? Which type of disease is it particularly useful for diagnosing?
FVC - Forced Vital Capacity - after the patient has taken in the deepest possible breath, this is the volume of air which can be forcibly and maximally exhaled out of the lungs until no more can be expired. FVC is usually expressed in liters. This PFT value is critically important in the diagnosis of obstructive and restrictive diseases
What is FEV1?
FEV1 - Forced Expiratory Volume in One Second - this is the volume of air which can be forcibly exhaled from the lungs in the first second of a forced expiratory manuever. It is expressed as liters. This PFT value is critically important in the diagnosis of obstructive and restrictive diseases.
What does FEV1/FVC - FEV1 Percent (FEV1%) - show?
FEV1/FVC - FEV1 Percent (FEV1%) - This number is the ratio of FEV1 to FVC - it indicates what percentage of the total FVC was expelled from the lungs during the first second of forced exhalation - this number is called FEV1%, %FEV1 or FEV1/FVC ratio. This PFT value is critically important in the diagnosis of obstructive and restrictive diseases.
What is FEV3?
FEV3 - Forced Expiratory Volume in Three Seconds - this is the volume of air which can be forcibly exhaled in three seconds - measured in Liters - this volume usually is fairly close to the FVC since, in the normal individual, most of the air in the lungs can be forcibly exhaled in three seconds.
What does FEV3/FVC show?
FEV3/FVC - FEV3% - This number is the ratio of FEV3 to the FVC - it indicates what percentage of the total FVC was expelled during the first three seconds of forced exhalation. This is called %FEV3 or FEV3%.
What is PEFR? What units is it measured in?
What is it useful for?
PEFR - Peak Expiratory Flow Rate - this is maximum flow rate achieved by the patient during the forced vital capacity maneuver beginning after full inspiration and starting and ending with maximal expiration - it can either be measured in L/sec or L/min - this is a useful measure to see if the treatment is improving obstructive diseases like bronchoconstriction secondary to asthma.
- What are.
- FEF25%
- FEF50%
- FEF25%-75%
- FEF25% - This measurement describes the amount of air that was forcibly expelled in the first 25% of the total forced vital capacity test.
- FEF50% - This measurement describes the amount of air expelled from the lungs during the first half (50%) of the forced vital capacity test. This test is useful when looking for obstructive disease. The amount of air that will have been expired in an obstucted patient is smaller than that measured in a normal patient.
- FEF25%-75% - This measurement describes the amount of air expelled from the lungs during the middle half of the forced vital capacity test. Many physicians like to look at this value because it is an indicator of obstructive disease.
What is MVV, when is it used and what caution should the clinician be aware of?
MVV - Maximal Voluntary Ventilation - this value is determined by having the patient breathe in and out as rapidly and fully as possible for 12 -15 seconds - the total volume of air moved during the test can be expressed as L/sec or L/min - this test parameter reflects the status of the respiratory muscles, compliance of the thorax-lung complex, and airway resistance. Surgeons like this test value because it is a quick and easy way to assess the strength of the patient’s pulmonary musculature prior to surgery. One major cautionary note is that this test is effort dependant.
If flow of air out of the lungs is impeded, what type of defect is the cause?
If volume of the lungs is reduced, what type of defect is the cause?
If flow is impeded, the defect is obstructive
If volume is reduced, the problem is restrictive
What are the 5 Stages?
Pulmonary Function Tests - A Systematic Way To Interpretation
- Step 1. Look at the forced vital capacity (FVC) to see if it is within normal limits.
- Step 2. Look at the forced expiratory volume in one second (FEV1) and determine if it is within normal limits.
- Step 3. If both FVC and FEV1 are normal, then you do not have to go any further - the patient has a normal PFT test.
- Step 4. If FVC and/or FEV1 are low, then the presence of disease is highly likely.
- Step 5. If Step 4 indicates that there is disese then you need to go to the %predicted for FEV1/FVC. If the %predicted for FEV1/FVC is 88%-90% or higher, then the patient has a restrictive lung disease. If the %predicted for FEV1/FVC is 69% or lower, then the patient has an obstructive lung disease
Microbiological sputum samples are usually used to look for infections by which organisms? (4)
- Moraxella catarrhalis,
- Mycobacterium tuberculosis,
- Streptococcus pneumoniae
- Haemophilus influenzae.
- Other pathogens can also be found.
What three kinds of Bloody Sputum (Hemoptysis) are there? What do they show? (3)
- blood-streaked sputum - inflammation of throat, bronchi; lung cancer;
- Pink sputum - sputum evenly mixed with blood, from alveoli, small bronchi;
- massive blood - cavitary tuberculosis of lung, lung abscess, bronchiectasis, infarction, embolism
What does Rusty colored sputum indicate?
Rusty sputum - usually caused by pneumococcal bacteria (in pneumonia)
What 4 types of Purulent sputum are there? (containing pus)
What do they each indicate?
- A yellow-greenish (mucopurulent) color suggests that treatment with antibiotics can reduce symptoms. Green color is caused by Neutrophil Myeloperoxidase.
- A white, milky, or opaque (mucoid) appearance often means that antibiotics will be ineffective in treating symptoms.
- Foamy white - may come from obstruction or even edema.
- Frothy pink - pulmonary edema
What is lung compliance?
How easy it is for the lung to change shape due to the stiffness of the lungs and chest wall
What is a restrictive lung disorder?
Restrictive disorder: one in which the lungs ability to expand is impaired, eg pulmonary fibrosis or kyphoscoliosis
What is an obstructive disorder of the lungs?
Obstructive disorder: one in which there is narrowing of the airways eg asthma, bronchitis
What are the different reasons for performing PFTs?
- Screening for the presence of obstructive and restrictive diseases
- Evaluating the patient prior to surgery
- Evaluating the patient’s condition for weaning from a ventilator. If the patient on a ventilator can demonstrate a vital capacity (VC) of 10 - 15 ml/Kg of body weight, it is generally thought that there is enough ventilatory reserve to permit (try) weaning and extubation.
- Documenting the progression of pulmonary disease - restrictive or obstructive
- Documenting the effectiveness of therapeutic intervention
What is a Spirograph?
What is a Spirogram?
- Spirograph: device attached to the spirometer, measures the movement of gas in and out of the chest.
- Spirogram: sometimes the spirograph is replaced by a printer. The resulting tracing is called a Spirogram
you use a bronchodilator to test the reversibility of airflow of an airway disease. How do you tell if the airway is reversible by pulmonary function test?
- Reversible airway obstruction that is responsive to medication, 2 out of 3:
- FVC: an increase of 10% or more
- FEV1: an increase of 200 ml or 15% of the baseline FEV1
- FEF25%-75% : an increase of 20% or more
Infection of the lower respiratory tract may be considered as a process involving 5 steps, what are they?
- exposure to the pathogen,
- inhalation or aspiration of the organism into the lungs,
- adherence to the respiratory epithelium,
- failure of clearance,
- invasion of tissues and initiation of an inflammatory and immune response
What are the main defences of the lungs against infection? (3)
- The mucociliary escalator.
- Anti microbial peptides present in lung secretions. These include lactoferrin, transferrin, lysozyme, defensins and cathelicidins.
- Immunoglobulin A in lung secretions
As the lungs fight infection, respiratory disease evolves through four classical stages, which represent the gross appearances of the lung during the various stages of the inflammatory response. What are they?
- congestion,
- red hepatisation,
- grey hepatisation and
- resolution
If infection is not cleared, how does it lead to lung damage?
If the infection is not cleared the phase of resolution fails to occur. A persistent, uncontrolled inflammatory response results in tissue damage, which disrupts the epithelium and the mucociliary escalator.
This encourages adherence of bacteria to the mucosa causing further inflammation and progressive lung damage.
- What are the microbiological approach to respiratory infections? (3)
- What are the clinical aspects of a respiratory infection? (2)
- They must be viewed together to manage the patient.
Microbial:
- the identification of the pathogen
- its characteristics
- its susceptibility to antimicrobial therapy.
Clinical:
- the site in the respiratory tract involved,
- the characteristics of the patient
In respiratory infection, which areas can the infection spread to?
- Upper respiratory tract (many are self-limiting)
- Lower respiratory tract infections may be:
- Confined to the bronchi (bronchitis)
- Spread to the lung parenchyma (pneumonia)
- The pleural space (empyema)
- Bloodstream (septicaemia)
The initial clinical approach is to classify pneumonia one of three things:
- Community-acquired
- Hospital-acquired (nosocomial)
- Pneumonia in the immunocompromised patient
What are the pathogens which cause community-acquired pneumonia, including the percentage of illnesses caused by each. (7)
- Streptococcus pneumoniae (G+) 60-70%
- Mycoplasma pneumoniae 10%
- Haemophilus influenza 5-10%
- Viruses (e.g. influenza) 5-10%
- Staphylococcus aureus 3%
- Legionella pneumophila 2-5%
- Others (e.g. Chlamydia pneumoniae) 5%
What are the clinical features of community acquired severe pneumonia associated with an increased risk of death? (7)
- Respiratory rate > 30/min
- Diastolic blood pressure < 60 mmHg
- Age > 60 years
- Underlying disease
- Confusion
- Atrial fibrillation
- Multilobar involvement
What are the laboratory features of community acquired severe pneumonia associated with an increased risk of death?
- Serum urea > 7 mmol/L
- Serum albumin < 35 g/L
- Hypoxaemia: Po2 < 8 kPa (60 mmHg)
- White cell count < 4000 x 10^9/L
- White cell count > 20 000 × 10^9/L
- Bacteraemia
