Unusual Inherited Pulmonary Diseases Which Provide Clues to Pulmonary Physiology and Function
Stephen D. Litwin in Genetic Determinants of Pulmonary Disease, 2020
Idiopathic pulmonary fibrosis is the classic example of the syndrome of alveolar-capillary block [64,65-71]. The characteristic abnormality is a restrictive defect with decreases in the total lung capacity, vital capacity, functional residual capacity, but a normal residual volume. Ventilatory ability is usually preserved with near-normal maximum voluntary ventilation, and conventional indices of airway obstruction using FEV1% and Plethysmographie airway resistance almost always give normal values [72]. However, use of newer tests, such as frequency dependency of dynamic compliance and flow volume curves, show that a significant number of patients have evidence of small airway disease [30,73]. There is increase in the elastic recoil with a shift of the volume-pressure curve downwards and to the right [69]. This decrease in compliance means not only an increase in the work of breathing, but also larger changes in lung volume will require inordinate expenditures of energy. Thus, for a given level of ventilation, less work is involved with a higher breathing frequency and a smaller tidal volume.
α1-Antitrypsin deficiency
William L. Nyhan, Georg F. Hoffmann, Aida I. Al-Aqeel, Bruce A. Barshop in Atlas of Inherited Metabolic Diseases, 2020
Pulmonary disease is the most common expression of the PIZZ phenotype [29] (Figure 107.2). As many as 90 percent develop emphysema. It is classically early in onset, occurring at 20–40 years of age in smokers and 55 in nonsmokers [5, 30, 31]. It is referred to as chronic obstructive pulmonary disease or COPD. The earliest symptom is dyspnea on exertion. Cough develops in about half of the patients, and recurrent pulmonary infections are common. On examination, the patient may be thin, but the diameter of the chest is increased. Breath sounds are diminished, and the chest film reveals hyperinflation, especially in the bases. The diaphragms may be flattened. Pulmonary function tests are typical of severe emphysema consistent with a loss of pulmonary elastic recoil. Total lung capacity is impaired, as is residual volume. Air flow is limited, and diffusion capacity and maximum transpulmonary pressure are reduced. Mild hypoxemia at rest may increase with exercise. Hypocarbia and respiratory alkalosis may be associated with mild pulmonary hypertension. Electrocardiograms may show chronic strain on the right heart with right axis deviation and right atrial hypertrophy. There may be a right bundle branch block.
Donor selection and management
Wickii T. Vigneswaran, Edward R. Garrity, John A. Odell in LUNG Transplantation, 2016
It is well known that lung function generally deteriorates with advancing age. The specific age-related functional changes that occur in the respiratory system are the result of three physiologic events: progressive decreases in compliance of the thorax, static elastic recoil of the lung, and strength of the respiratory muscles.15 As reductions in chest wall compliance occur with advancing age, compliance of the respiratory system is 20% less in a 60-year-old than in a 20-year-old.16 With advancing age, notable homogeneous enlargement of the alveolar duct occurs, with the alveolar ducts increasing in diameter and consequently becoming wider and shallower. The elastic fibers of the lung are reduced, thereby resulting in relaxed recoil pressure, which in turn causes distention of the alveolar spaces and increased lung volume.16 As described by Turner and colleagues, in subjects 20 to 60 years of age, static elastic recoil pressure of the lung decreases as a part of normal aging (0.1 to 0.2 cm H2O/yr), and the static pressure-volume curve for the lung is shifted to the left and has a steeper slope.17 Expiratory flow rates show characteristic changes in the flow-volume curves, thus suggesting increased collapsibility of the peripheral airways; however, gas exchange is remarkably well preserved despite the reduced alveolar surface area and increased ventilation-perfusion heterogeneity.18 These normal changes should not by themselves rule out the use of older lungs, but understanding such changes is still critical when assessing lungs.
Emphysema: looking beyond alpha-1 antitrypsin deficiency
Published in Expert Review of Respiratory Medicine, 2019
Rob Janssen, Ianthe Piscaer, Frits M. E. Franssen, Emiel F. M. Wouters
Although decreased FEV1 contributes to reduced exercise capacity in emphysema, non-obstructive emphysematous subjects also have reduced 6-min walking distance in comparison to those with neither COPD nor emphysema [13]. This highlights that factors other than airflow obstruction contribute to exercise limitation in emphysema, of which hyperinflation is regarded as an important one. Elastic recoil is the term used to describe the natural propensity of lungs to rebound after inflation. Destruction of elastic tissue in emphysema is the main pathological mechanism behind decreased recoil pressure [16,17], leading to reduced resilient properties of the lungs. Consequently, there is less inwardly directed pressure to counteract the outward pressure of the chest wall, i.e. air trapping, resulting in higher lung volumes after expiration. Severity of hyperinflation is related to dyspnea sensation by unfavorably affecting respiratory muscle mechanics [18] and cardiac function [19]. Over-inflation associates with elevated intrathoracic pressure resulting in decreased venous return to the heart. Hyperinflation becomes particularly problematic during exertion. Dynamic hyperinflation develops when breathing frequency increases and time is too short to exhale the whole volume of inhaled air [18].
Mechanical adjuncts for cardiocerebral resuscitation
Published in Expert Review of Medical Devices, 2019
Matthias L. Riess, Claudius Balzer
As stated above, the use of the ITD requires high-quality CPR which could be provided by the use of ACC devices [8,54]. When used during manual CPR [11,14,28], negative intrathoracic pressure by ITD is only generated by the intrinsic elastic recoil of the chest and largely depends on the quality of CPR. A rigid, non-compliant chest or fractured ribs, for example, can significantly reduce the elastic recoil. In addition, limited recoil through leaning has detrimental effects on venous return and intracranial pressure [43,55]. By using the piston device LUCAS®3 with a suction cup, the recoil is supported with a lifting force of around −3 lbs [56]. Compared to a manual ACD device such as the ‘ResQPUMP’ with a lifting force around −20 lbs, the active decompression is lower and does not exceed the neutral level, but depth and frequency are maintained without provider fatigue. Furthermore, its use can be continued during transport in an ambulance or helicopter [57], and reversible causes for cardiac arrest could be treated by interventions in the cardiac catheterization laboratory (CCL) [58].
The evolution of coronary stents
Published in Expert Review of Cardiovascular Therapy, 2018
Peter McKavanagh, George Zawadowski, Naveed Ahmed, Michael Kutryk
The initial years of POBA were met with much enthusiasm and interest. Its early adoption coincided with technological advances aimed at refining the procedure, including the development of the first over-the-wire technique, and then the monorail system [8,9]. However, despite initial procedural success, the limitations of POBA soon became obvious. Acute complications, such as abrupt closure and early elastic recoil, and late issues, of negative remodeling and neointimal proliferation, tempered early enthusiasm [10]. Abrupt closure during POBA was caused by vessel injury and endothelial dissection leading to thrombus formation with an incidence of 3–8% [11,12]. Elastic recoil was caused by the rebound of intimal tissues unrelated to coronary dissection and occurred in 5–10% of cases, usually within minutes to hours after the procedure [13]. Both these conditions caused acute ischemia and often resulted in emergency coronary artery bypass graft (CABG) surgery. In the slightly longer term (1–6 months), an inflammatory response to vessel trauma often caused migration and proliferation of vascular smooth muscle cells, resulting in a neointimal proliferation and negative remodeling due to deposition of an extracellular matrix [14].This was associated with restenosis rates of approximately 33% [15]. There was thus a need for further technological advancement to help maintain the patency of the vessel, which led to the development of the coronary stent.
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