[this graph is for the flow changes of a normal individual at three levels of lung inflation; high, mid, low lung inflation] in a normal person, FEV1/FVC is approximately 0.8, meaning that 80% of the vital capacity can be expired in the first second of forced expiration (see Fig. 5-6A). In a patient with an obstructive lung disease such as asthma, both FVC and FEV1 are decreased, but FEV1 is decreased more than FVC is. Thus, FEV1/FVC is also decreased, which is typical of airway obstruction with increased resistance to expiratory airflow (see Fig. 5-6B). In a patient with a restrictive lung disease such as fibrosis, both FVC and FEV1 are decreased, but FEV1 is decreased less than FVC is (or indeed may increase). Thus, in fibrosis, FEV1/ FVC is same or actually increased 08/11/13: Respiratory Muscles: Dr. Kevin Murphy Los (from booklet): Lecture 4: Respiratory Muscles (Dr. Kevin Murphy (kevin.murphy@imperial.ac.uk) At the end of this lecture you should be able to: Identify the principal muscles associated with inspiration and expiration. Understand the additional non-respiratory actions of these muscles. Understand how contraction of inspiratory muscles causes the chest wall to expand and the lungs to enlarge. Understand how contraction of expiratory muscles causes the chest wall to contract and the lungs to reduce in size. Recognise that these muscles will be differentially activated during different breathing states. Specifically: identify which will be active during quiet breathing, and which will be active when ventilatory demand is increased such as during exercise or during lung disease. In addition to their primary role in maintaining alveolar ventilation, know that respiratory muscles will control air movement during other behaviours including, speech, laughter, coughing, sneezing and vomiting. Notes: Inspiratory muscles:
[this graph is for the flow changes of a normal individual at three levels of lung inflation; high, mid, low lung inflation] in a normal person, FEV1/FVC is approximately 0.8, meaning that 80% of the vital capacity can be expired in the first second of forced expiration (see Fig. 5-6A). In a patient with an obstructive lung disease such as asthma, both FVC and FEV1 are decreased, but FEV1 is decreased more than FVC is. Thus, FEV1/FVC is also decreased, which is typical of airway obstruction with increased resistance to expiratory airflow (see Fig. 5-6B). In a patient with a restrictive lung disease such as fibrosis, both FVC and FEV1 are decreased, but FEV1 is decreased less than FVC is (or indeed may increase). Thus, in fibrosis, FEV1/ FVC is same or actually increased 08/11/13: Respiratory Muscles: Dr. Kevin Murphy Los (from booklet): Lecture 4: Respiratory Muscles (Dr. Kevin Murphy (kevin.murphy@imperial.ac.uk) At the end of this lecture you should be able to: Identify the principal muscles associated with inspiration and expiration. Understand the additional non-respiratory actions of these muscles. Understand how contraction of inspiratory muscles causes the chest wall to expand and the lungs to enlarge. Understand how contraction of expiratory muscles causes the chest wall to contract and the lungs to reduce in size. Recognise that these muscles will be differentially activated during different breathing states. Specifically: identify which will be active during quiet breathing, and which will be active when ventilatory demand is increased such as during exercise or during lung disease. In addition to their primary role in maintaining alveolar ventilation, know that respiratory muscles will control air movement during other behaviours including, speech, laughter, coughing, sneezing and vomiting. Notes: Inspiratory muscles:
Respiratory-notes-BETA.docx