Respiratiory L4.2 Flashcards
Lung Function Report
Detailed assesment of respiratory health
Vital Capacity (VC)
FEV1 (Forced Expiratory Volume in 1 second)
FEV1 / FVC Ratio
Peak Expiratory Flow Rate (PEFR):
Functional Residual Capacity (FRC)
Residual Volume (RV)
Total Lung Capacity (TLC)
RV / TLC Ratio
Transfer Factor (TLCO or DLCO)
What is the most common approach to lung function testing?
Spirometry
Describe single breath spiroentry
Looks more into LUNG VOL + AIR FLOW
What is forced vital capacity?
What is FVC in healthy adult?
What affects FVC?
How do clinicians assess whether an individuals FVC is within normal range
How do we interpet FVC?
What does a reduced FVC indicate?
- Total vol of air person can exhale forcefully after max inhalation
(max inspiration to max forced expiration) - 5L
- Age, height, sex
- reference tables that predict expected values based on these factors above
- FVC > 80% of the predicted value is considered normal.This means that if the person’s FVC is at least 80% of what is expected for their age, height, and sex, their lung function is generally regarded as normal.
- restrictive lung diseases (e.g., pulmonary fibrosis), where lung volumes are reduced.
What limits vital capacity?
- Compliance of lungs (AFFECTS MAX INSPIRATION)
- Force of inspiratory muscles (diapragm, intercostal muscles) (AFFECTS MAX INSPIRATION)
- Increase in airway resistance + when lungs are comrpessed (reduced MAX EXPIRATION)
This leads to
1) reduced max inpspiration (STIFNESS), reduced max expiration (NARROWNESS), therefore reduced vc
1) What does FEV1 measure?
- Which factors affect FEV1?
3) What is a normal FEV1?
1) volume of air that can be forcefully exhaled in the first second after a maximal inhalation.
2) Airflow speed. FEV1 affected by how quickly air can be exhaled. If airflow slows down rapidly during expiration, less air exhaled in first second
Airway narrowing: COPD, asthma, air flows out more slowly. Reduced FEV1, less air exhaled in first second.
3) FEV1 > 80% of the predicted value is considered normal.
1) What does FEV1/FVC ratio measure?
2) Normal values
3) What is the main factor affecting the ratio?
4) What do values less than 0.70 suggest?
5) High FEV1/FVC value suggests…
1) percentage of the forced vital capacity (FVC) that can be exhaled in the first second (FEV1). FEV1 mainly reduced.
2) 0.75 and 0.85 (75-85%), though this varies with age.
3) AGE - lung elasticity reduces with age
4) Obstrucvtive lung disease. Airways narrowed. This limites airflow. e.g. Asthma (reversible) COPD (irrrerberesible).
5) Resttrictive lung disease (pulmonary fibrosis), lung vol reduced, airflow speed normal. Ratio is normal or sometimes higher becasue FEV1/FVC reduced proprtionally. FVC smaller, but FEV1 normal.
Causes of restrictive deficit
State key features of restrictive defiict?
What happens to FEV1/FVC Ratio?
FILLINF PROBLEM
- Stiffness of lungs (due to pulmonary fibrosis)
- Weak inspiratory muscles
- Chest wall problems (kyphocoliosis)
-Less air inspired
- Plateau lower: On spirometry, the FVC (Forced Vital Capacity) is reduced due to the limited amount of air that can be inhaled and exhaled.
-No airway obstruction, patient has no problem with airwats, so airflow remains norma. Restrictive deficits - limit lung fillings - stiff lungs
FEV1/FVC ratio is normal (or higher) – i.e. ≥ 70
What is an obstructive deficit?
NARROWING PROBLEM
-Obstructive lung diseases (asthma, COPD)
-causes narrowed airways
-Increase reisstance to airflow (particularly expiration)
-Therefore, slower rate of air out of lungs
-Therefore, reduced FEV1
-Filling vol is normal. (Normal FVC)
-Reduced FEV1/FVC ratio (<0.70)
Obstructive vs Restrictive Deficit
1) State two types of “flow-volume” curves?
This explains how airflow changes during expiration.
The left curve helps visualize the rate of volume expired (flow) over time.
The right curve focuses on how airflow changes as the volume of air in the lungs decreases during a forced expiration.
What does PEFR repreent?
- Start of forced expiration, lungs fully inflated
- Airwats stretched open, reducing resistance to airflow, allowing air to move out of lung easily (MINIMAL RESISTANCE AT BEGINNING)
- During forced expiration, flow rate continues to increase until it reaches PEFR (peak expiratory flow rate)
- Decline after PEFR reached: After the PEFR is reached, as the lung volume decreases, the airways begin to narrow, increasing resistance and reducing airflow.
Why use flow volume curves?
More sensitive indicator of airway narrowing than normal single
breath spirometry graph
2. Help to differentiate between large and small airway narrowing
What instrument do we primarily use for monitoring astha?
How do we measure residual volume?
Helium dilution
-Helium used because not normally present in air + insoluble in blood. All heloim inhaled stays in lungs + does not pass into blood stream. What helium is breathed in must be breathed out, easy to track.
- Patient inhales known colc of hekium from spirometer at point of functional residual capacity (after normal exhalation)
- Inhaled helium mixes with air already in lungs (functional residual capacity)
- This dilutes helium conc.
- Measure dilution: because, the amount of helium diluted is proportional to air that was already in lungs (residual volume)
- After few breaths, composition of exhaled air measured
- Change in helium conc allows us to calculate vol of air in lungs
How do we measure serial dead space?
Serial dead space - anatomical dead space - vol of air in respiratory system that does not participaye in gas exchange because it remains in conducting airways
Nitrogen washout method.
- Breath of pure oxygen:
patient inhales pure oxygen for one normal breath
This replaces nitrogen that is normally present in airways with oxygen - Exhalation and Nitrogen Measurement:
The subject then breathes out into a device that measures the percentage of nitrogen in the exhaled air. - At the beginning of exhalation, only oxygen is expired, coming from the conducting airways (which do not participate in gas exchange).
- As the subject continues exhaling, a mixture of oxygen and alveolar air (which contains nitrogen) is expired, marking the transition from the airways to the alveoli.
The point where nitrogen first appears in the exhaled air marks the transition from the conducting airways to the alveoli. - The volume of air expired up until the transition point (when nitrogen first appears) represents the serial dead space or anatomical dead space—the air that remains in the conducting airways and does not reach the alveoli for gas exchang
