SUMMARY OF RECOMMENDATIONS
- 1.
In patients with endotracheal tubes, tracheostomy need not be performed to improve cough effectiveness. Level of evidence, expert opinion; net benefit, substantial; grade of recommendation, E/A
- 2.
Individuals with
Cough mechanics can be evaluated by considering the timing of the varied events that constitute cough. The sequence of events that lead to an effective cough has been previously described, and the phases have been classified as inspiratory, compressive, and expiratory (Fig 1).1, 2, 3, 4, 5, 6, 7 The initial phase of cough is characterized by the inhalation of gas. The volume of gas that is inhaled may be as little as 50% of tidal volume or as great as 50% of vital capacity.8, 9 During
1. In patients with endotracheal tubes, tracheostomy need not be performed to improve cough effectiveness. Level of evidence, expert opinion; net benefit, substantial; grade of recommendation, E/A
Following the initial blast of air, there is a more prolonged period characterized by lower expiratory flows. This stage lasts 200 to 500 ms with sustained flows in the range of 3 to 4 L/s.5 During this timeframe, lung volume falls, transpulmonary pressure decreases, and cough expiratory flows fall. As
Several factors may interfere with the capacity of the respiratory system to produce the requisite pressures and gas velocities needed for effective cough. The initial phase of cough is accompanied by inhaling a volume to near total lung capacity. Inhaling to high lung volumes will optimize expiratory pressures, and will enhance expiratory airflow and velocity. At high lung volumes, the expiratory muscles are near their optimal length and respiratory system elastic recoil is increased; both
2. Individuals with neuromuscular weakness and no concomitant airway obstruction may benefit from mechanical aids to improve cough. Level of evidence, low; net benefit, intermediate; grade of recommendation, C
Expiratory muscle weakness also contributes to cough inefficiency by limiting dynamic airway compression, a condition that augments expiratory gas velocity. Dynamic compression is needed to increase gas velocity for a given flow rate and thereby enhance the kinetic energy available to
An effective cough constitutes an important host-defense mechanism. High intrathoracic pressures promote dynamic airway compression and are needed to generate the requisite expiratory flows and airstream velocities. However, only modest increases in intrathoracic pressure are needed to narrow the large intrathoracic airways and increase cough flow velocity. Thus, cough may be effective in individuals with mild-to-moderate degrees of respiratory muscle weakness. Cough ineffectiveness may occur
3. In patients with ineffective cough, the clinician should be aware of and monitor for possible complications, such as pneumonia, atelectasis, and/or respiratory failure. Level of evidence, low; net benefit, substantial; grade of recommendation, B
SUMMARY OF RECOMMENDATIONS In patients with endotracheal tubes, tracheostomy need not be performed to improve cough effectiveness. Level of evidence, expert opinion; net benefit, substantial; grade of recommendation, E/A Individuals with
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