Breath holding

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

In general, slow, deep inhalation followed by a period of breath holding increases the deposition of aerosols in the peripheral parts of the lungs, whereas rapid inhalation increases the deposition in the oropharynx and in the large central airways. Thus, the frequency of respiration (the flow velocity) and the depth of breath (tidal volume) influence the pattern of pulmonary penetration and deposition of inhaled aerosols. Therefore, an aerosol of ideal size will penetrate deeply into the respiratory tract and the lungs only when the aerosols are inhaled in the correct manner (Sackner, 1978 and Sackner et al., 1975). 

The dried and cured leaves of the nightshade plant Nkotiana tabaaim are known as tobacco. Tobacco is mostly smoked, less frequently chewed or taken as dry snuff. Combustion of tobacco generates approx. 4000 chemical compounds in detectable quantities. The xenobiotic burden on the smoker depends on a range of parameters, including tobacco quality, presence of a filter, rate and temperature of combustion, depth of inhalation, and duration of breath holding. 

SAACh 10 sec breath holding. actuation and inhalation in children... 

SA/3A ICS followed by 10 s breath-holding coordinate Inhalation and actuation. May be particularly useful in elderly. Requires more rapid inspiration to activate than is optimal for deposition. 

SAACh/SAACh combined followed by 10 s breath holding. Open mouth technique holding MDI 2 inches away from open mouth, is comparable to closed-mouth technique (closing Ups around MDI mouthpiece) requires lower doses per actuation... 

SAACh LAACh foUowed by 10 s breath holding. Most appear to have similar... 

Sedative and stimulant effects. A doubleblind, placebo-controlled study assessed subjective effects of smoking cannabis with either a long or short breath-holding dura-... 

At induction, high concentrations are irritant and may provoke coughing or breath-holding. 

At high concentrations enflurane is more irritant than halothane. Coughing, breath-holding and laryngospasm are common at induction if the inspired concentration is increased too rapidly. 

In general, adrenoceptor agonists are best delivered by inhalation because this results in the greatest local effect on airway smooth muscle with the least systemic toxicity. Aerosol deposition depends on the particle size, the pattern of breathing, and the geometry of the airways. Even with particles in the optimal size range of 2-5 Pm, 80-90% of the total dose of aerosol is deposited in the mouth or pharynx. Particles under 1-2 Pm remain suspended and may be exhaled. Bronchial deposition of an aerosol is increased by slow inhalation of a nearly full breath and by more than 5 seconds of breath-holding at the end of inspiration. 

An B, Reinhardt RR. Effects of different duration of breath holding after inhalation of insulin using the AERx insulin diabetes management system. Clin Ther 2003 25 2233 14. 

In this equation, the diffusion coefficient D is related to air viscosity r A and particle diameter dp, with k being the Boltzmann constant and T the absolute temperature. It is clear from this description that diffusion is a rather slow deposition mechanism compared with impaction and sedimentation processes because it depends on the thermal velocity of the particles and not on airflow. It is the primary transport mechanism for small particles and is important when the transport distance becomes small, as in the deep lung. Efficiency of this deposition mechanism can be increased significantly by breath-holding because a portion of the ultrafine particles that are not deposited will be exhaled by the patient. 

Deposition by diffusion is the main mechanism for particles smaller than 0.5 pm, and is important in bronchioles, alveoli, and bronchial bifurcations. Aerosol particles are displaced by a random collision of gas molecules this results in particle collision with the airway walls [24]. Deposition by diffusion increases with the decrease in particle size, and breath-holding following inhalation was also found to increase this deposition [25]. 

Carr JC, Ma J, Desphande V et al. (2002) High-resolution breath-hold contrast-enhanced MR angiography of the entire carotid circulation. AJR Am J Roentgenol 178 543-549... 

Arnold, R.W. (1985). Extremes in human breath hold, facial immersion bradycardia. Undersea Biomed. Res. 12 183-190. 

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. 

Both the air-jet and ultrasonic nebulizer previously described produce an aerosol at a constant rate, irrespective of whether the patient is inhaling, exhaling or in breath-hold. This means that up to two-thirds of... 

Palmes, E. D., Goldring, R. M., Wang, C., and Altshuler, B. (1970), Effect of chronic obstructive pulmonary disease on rate of deposition of aerosols in the lung during breath holding, Inhaled Part., 1,123-130. 

No obvious reason for the problem was found and the authors suggested that coughing while breath-holding during cannabis inhalation had caused the problem. 

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. 

Markus HS, Harrison MJG (1992). Estimation of cerebrovascular reactivity using transcranial Doppler, including the use of breath-holding as the vasodilatory stimulus. Stroke 23 668-673... 

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