combined lung and chest-wall system is less than that of either structure alone (like a balloon in a balloon) [nb the combined compliance curve changes with diseases] Emphysema (increased lung compliance). Emphysema is associated with loss of elastic fibers in the lungs. Reduced collapsing at a given volume Thus, the combined lung and chest-wall system seeks a new higher FRC, where the two opposing forces can be balanced breathe at higher lung volumes (in recognition of the higher FRC) and will have a barrel-shaped chest. Fibrosis (decreased lung compliance) stiffening of lung tissues Increased collapsing force at a given volume Thus, the combined lung and system seeks a new lower FRC, where the two opposing forces can be balanced breathe at lung volumes Keeping the alveoli open during inspiration: the alveolar pressure is negative during this period so think they would want to collapse Alveoli can be considered as gas bubbles in a liquid so can use the Law of Laplace Law of Laplace states that P = 2T/R for such a bubble to be stable and to stop collapsing, P = pressure at which the bubble is stable (want it to be low), T=tension (ie low allows for lower pressure) and R=radius (ie high allows for lower pressure) Hence smaller alveoli require larger pressures to remain open and should be the first to collapse This problem is avoided by a higher surfactant concentration at smaller alveoli; the surfactant (produced by type II pneumocytes) lowers surface tension to allow alveoli stability at reduced pressures and by using higher surfactant concentrations at smaller alveoli further reductions in surface tension are offered to compensate for their greater propensity to collapse. For a given drop in pressure, as alveoli start to shrink (reducing R, radius) the tension (T, surface tension) falls faster, therefore will quickly reach a new set of R&T values that via the equation match the required P value which was previously too high. Surfactant info: Is dipalmatoylphosphatidyl choline mainly Has the lowest surface tension of any biological substance
[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:
Inspiration Expiration Quiet Augmented Quiet Augmented Resisted (eg in speech after large inhalation) Diaphragm mainly (others to a small degree) Diaphragm No muscles (passive: elastic recoil gives return to FRC) External oblique Diaphragm (to retard flow) Internal oblique Scalene Transversalis External intercostals Rectus abdominis Parasternal muscles Internal intercostals 08/11/13: Lung Development: Dr Matthew Hind Los (from slides): Understand that lung development is a continuous process [continues well after birth]
COPD [Chronic obstructive pulmonary disease (COPD) is the name for a collection of lung diseases including chronic bronchitis, emphysema and chronic obstructive airways disease]: obstructive Bronchiectasis: obstructive [Involved are dilated, inflamed, and easily collapsible, resulting in airway obstruction and impaired clearance of secretions] cystic fibrosis: obstructive [It is characterized by abnormal transport of and across an , leading to thick, viscous secretions] pulmonary fibrosis: Restrictive non-productive pneumonia: restrictive (ie if was producing fluid further up the airways then could have an obstructive component too) Pneumothorax: restrictive Kyphoscoliosis: restrictive (curvature of the spine) Neurological and neuromuscular disorders resulting in difficulties activating respiratory muscles [like motor neurone disease, multiple sclerosis, polio, or myasthenia gravis]: restrictive 19/11/13: Regulation of Breathing & Asleep) Los (from slides): [says we must understand blood gases (and know their normal values) and be able to interpret lung function (ie as well as the below)] Distinguish the primary purpose of the automatic reflex and the behavioural controller Define neuronal groups in the brainstem that make up the automatic reflex controller for breathing, and structures in higher brain areas (suprapontine) that drive behavioural (non-automatic) control of breathing. Explain how they can act independently or interact for control of the respiratory pump. Recall the sources of sensory input to the respiratory control system and the common motor outputs (also see Lecture 11) Explain the ventilatory response to increased arterial PCO2, decreased arterial PO2 Recognise breathlessness (“dyspnoea”) and to consider its role in breathing control (lectures 12,13&15). Recognise the effects on respiratory control of the neurological conditions; ‘locked in’ syndrome and ‘congenital central hypoventilation syndrome’ Explain the effect sleep on breathing and blood gases in healthy people Summarise the changes in chemosensitvity that occur during sleep and define the apnoeic threshold Explain how the changes in chemosensitivity and the apnoeic threshold led to central apnoea
Lung cancer: 4th most common cause of death in Uk 5yr survival = 10% Surgery is the only curative treatment But even then may have metastasised, etc Resection not usually possible [lobectomy/pneumonectomy] Disease likely to have spread significantly through the lung Resection reduce cardiopulmonary reserve Especially cannot resect if is at carina [unless pneumonectomy] Symptoms: Cancer general symptoms: Night sweats Weight loss Fatigue Lung cancer: SOB Haemoptysis Local invasion Persistent / unexplained: chest/shoulder pain, hoarse voice, cough, dyspnoea Distant spread (metastases) Bone, brain, liver, adrenals, skin etc effects paraneoplastic syndrome: is a disease or symptom that is the consequence of the presence of cancer in the body, but is not due to the local presence of cancer cells.[1] These phenomena are mediated by humoral factors (by hormones or cytokines) excreted by tumor cells or by an immune response against the tumor. Clubbing, malaise, weight loss Eg ADH production: causes low sodium – life threatening Eg PTH production: causes high Ca – life threatening The primary metastatic spread is by the lymphatics (not the blood) Metastasis is actually surprisingly uncommon Specific organs seem to be affected: Seed and soil hypothesis The "seed and soil" hypothesis states that specific organs harbor metastases from one type of cancer by stimulating their growth better than other types of cancer. This interaction is dynamic and reciprocal, since cancer cells modify the environment they encounter. to diagnose: X ray