Inspiratory muscles

Deeper inspirations are achieved by more forceful contraction of the diaphragm and external intercostal muscles. Furthermore, accessory inspiratory muscles, including the scalenus and sternocleidomastoid muscles, contribute to this process. Located mainly in the neck, these muscles raise the sternum and elevate the first two ribs. As a result, the upper portion of the thoracic cavity is enlarged. 

Weiner P, Azgad Y, Weiner M. The effect of corticosteroids on inspiratory muscle performance in humans. Chest 1993 104(6) 1788-91. 

There has been an intensive effort to develop new ways to deliver aerosols. The DPI devices were developed for the following reasons (1) They allow aerosol delivery without propellants, (2) they avoid the high velocity of MDI propellants, which leads to excess deposition in the oropharynx and (3) they do not require the same hand-inspiratory muscle coordination needed for MDIs. Patient performance is still important with DPIs. Inspiratory flow must be properly maintained to achieve optimal performance. Lung deposition falls appreciably using a variety of devices when flow falls very much below the optimal rate of about 60L/min [55,56]. It is important to recognize that the recommended flowrate varies widely for different DPIs and that adherence to proper flow for each device is important. Acceptance of DPIs in the United States is well behind that in Europe. 

Normal expiration is a passive process, and when the inspiratory muscles end their contraction, the elastic recoil of the lung pulls the lung back to its original size and shape. This process makes the alveolar pressure positive relative to the pressure at the mouth, and air flows out of the lung. During inspiration, the respiratory muscles must overcome the elastic properties of the lung (elastic recoil) and the resistance to airflow by the airways. During expiration, the flow of air is determined primarily by the elastic recoil and airway resistance. 

Hiccup, or singultus, is a spasmodic, involuntary contraction of the inspiratory muscles, associated with delayed, abrupt glottic closure, causing a peculiar sound, expressed by different words around the world. They are ... 

The mechanical plant is propelled by the respiratory muscles which serve as a mechanical pump. Normally, Pmus is sustained by the inspiratory muscles (principally the diaphragm and, to a lesser extent, the external intercostal and parasternal muscles). During hyperpnea or with increased expiratory load the expiratory muscles maybe recruited [Marroquin, 1991], as are accessory muscles which may contribute significantly to the generation of Pmus in paraplegics. 

The terms Pmax and Pmax denote the limiting capacities of the inspiratory muscles, and n is an efficiency index. The optimal Pmus(t) output is found by minimization of / subjects to the constraints set by the chemical and mechanical plants. Equation 11.1 and Equation 11.9. Because Pmusif) is generally a continuous time function with sharp phase transitions, this amounts to solving a difficult dynamic nonlinear optimal control problem with piecewise smooth trajectories. An alternative approach adopted by Poon and coworkers [1992] is to model Pmus t) as a biphasic function... 

Brancaleone P, Perez T, Robin S, et al. Clinical impact of inspiratory muscle impairment in sarcoidosis. Sarcoidosis Vase Diffuse Lung Dis 2004 21(3) 219-227. 

The function of the ventilatory pump is critically dependent on three factors the respiratory workload, the respiratory muscle strength, and the ventilatory drive (Fig. 1). Chronic hypercapnic respiratory failure can result from one or more of these abnormalities inadequate ventilatory drive, excessive respiratory load, and inadequate inspiratory muscle... 

During spontaneous breathing the inspiratory muscles must generate sufficient force to overcome the elastic and resistive load of the respiratory system. The pressure developed by the inspiratory muscles per breath (Pi) is increased if the elastic (decreased compliance of the lungs or the chest wall) or resistive (airway obstruction) load is increased. Furthermore, in patients with hyperinflation of the chest wall (see below), a substantial effort must be... 

Begin P, Grassino A. Inspiratory muscle dysfunction and chronic hypercapnia in chronic obstructive pulmonary disease. Am Rev Respir Dis 1991 143 905-912. 

Appendini L, Purro A, Patessio A, et al. Partitioning of inspiratory muscle workload and pressure assistance in ventilator-dependent COPD patients. Am J Respir Crit Care Med 1996 154 1301-1309. 

Jardim J, Farkas G, Prefaut C, et al. The failing inspiratory muscles under normoxic and hypoxic conditions. Am Rev Respir Dis 1981 124 274-279. 

Lisboa C, Moreno R, Fava M, et al. Inspiratory muscle function in patients with severe kyphoscoliosis. Am Rev Respir Dis 1985 132 48-52. 

PPMV modes that permit spontaneous ventilatory activity are termed interactive modes, in that patients can affect various aspects of the mechanical ventilator s functions. These interactions can range from simple triggering of mechanical breaths to more complex processes affecting delivered flow patterns and breath timing. Interactive modes allow for inspiratory muscle activity which, when done at nonfatiguing or physiologic levels, may prevent muscle atrophy and facilitate recovery (31-34). Spontaneous patient ventilatory activity and comfortable interactive modes may improve ventilation and reduce the need for the sedation or neuromuscular blockers that may be required to prevent patients from fighting machine-controlled ventilation (27,35-37). 

Aldrich TK, Karpel JP, Uhrlass RM, et al. Weaning from mechanical ventilation adjunctive use of inspiratory muscle resistive training. Crit Care Med 1989 17(2) 143-147. 

Preusser BA, Winningham ML, Clanton TL. High- vs low-intensity inspiratory muscle interval training in patients with COPD. Chest 1994 106(1) 110-117. 

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