Breath-holding time

Lawford P, MacKenzie F. Pressurised bronchodilator aerosol technique influence of breath holding, time and relationship of inhaler to the mouth. Br J Dis Chest 1982 76 229-233. 

Sloan, A., S.C. De Cort, and R. Eccles, 1993. Prolongation of breath-hold time following treatment with an 1-menthol lozenge in healthy man. J. Physiol., 473 53. 

Main drawbacks of single-sHce spiral CT are either insufficient volume coverage within one breath-hold time of the patient or missing spatial resolution in the z-axis due to wide collimation. With single-slice spiral CT, the ideal isotropic resolution, i.e., of equal resolution in all three spatial axes, can only be achieved for very limited scan ranges (Kalender 1995). 

Gated imaging without table movement requires a new way of thinking in terms of protocol selection. The smooth transition between prospective triggering and retrospective reconstruction offers the user complete freedom in tailoring the scan to the clinical question. For each patient, the protocol is optimized balancing the required cardiac phases, temporal resolution, and the radiation dose. Patient comfort is also increased due to the very short breath hold times and no distracting table movement. 

With the introduction of MDCT bi-, tri-, or even quadruple-phasic examinations of the liver can be combined into a thoraco-abdominal CT examination, without compromise with regard to spatial or temporal resolution. The acquisition of the liver with a 64-slice scanner for example only requires a few seconds, despite a submillimeter collimation. Even patients with a compromised general state of health are able to tolerate these breath-hold times. However, even on single-slice spiral CT scanners adequate image quality of the liver can be obtained. However, combination with thoracoabdominal examinations is not possible without compromises in temporal and spatial resolution. 

Consequently, any breathing pattern which increases pulmonary residence times, such as breath-holding, increases fine particle deposition throughout the airway. 

Increasing the time between the end of inspiration and the start of exhalation increases the time for sedimentation to occur. Breath-holding is commonly used to optimize pulmonary drag delivery. For maximum effect, breath-holding for a period of 5-10 seconds post-inspiration is recommended. Under idealized conditions a 5 wm particle will settle a few mm during a 5-second breath hold. 

Put your pencil down and close your eyes. Take a deep breath, hold it for a moment, and let it out slowly. Listen to the sound of your breathing as you repeat this two more times. The few seconds this takes is really all the time your brain needs to relax and refocus. This exercise also helps you control your heart rate, so you can keep anxiety at bay. 

Under normal breathing, submicronic particles are exhaled [unless they are of ultrafine sizes (<0.01 Jim), in which case they can deposit sufficiently rapidly by diffusion]. However, breath holding allows more time for small particles to deposit by sedimentation and diffusion [43]. 

For particles that deposit by sedimentation mechanisms (i.e., particles > 0.5 pm and < 3 pm), an increase in inhalation volume and the use of a breath-hold will enhance deposition in the distal lung as a result of increasing the residence time. 

McKenzie CA, Lim D, Ransil BJ et al (2004) Shortening MR image acquisition time for volumetric interpolated breath-hold examination with a recently developed parallel imaging reconstruction technique clinical feasibility. Radiology 230 589-594... 

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