Respiratory Inspiration

Forced vital capacity (FVC) quantifies the maximum air volume expired following a maximal inspiration and is one of the basic measures of analyzing flow changes such as reduced airway patency observed in asthma. To measure FVC, an individual inhales maximally and then exhales as rapidly and completely as possible. FVC primarily reflects the elastic properties of the respiratory tract. The gas volume forcibly expired within a given time interval, FEV (where t is typically one second, FEVj q)... 

The importance of respiratory heat and water losses is not confined to the respiratory structures. Inspiration of cold, hot, or dry air poses the potential threats of thermal injury or desiccation to the airway epithelium" - T8,69 g challenge to whole-body thermoregulation. 

Airstream neutralization of acid aerosols by NH3 present in the airway-lumen reduces the health risk associated with acid particles by reducing the acid concentration prior to particle deposition.- In addition, the liquid lining of the respiratory tract probably acts as a chemical buffer," further reducing the health hazard posed by inspired acid particles. Principal factors controlling airstream neutralization of acid aerosols, which is considered to be a diffusion-limited process, are particle surface area, and particle... 

In low doses, inhaled NO may have a beneficial therapeutic effect, since NO in the inspired air leads to pulmonary vasodilation. In persistent pulmonary hypertension of the newborn, NO inhalation has already been used with some success. NO inhalation as the treatment for acute respiratory distress syndrome, however, has been disappointing. Only transient improvements of oxygenation were detected and the outcome of placebo-controlled trials did not show any improvement... 

Assume a respiratory rate of 12 min-1. From zero baseline, the curve initially rises slowly owing to the exhalation of dead space gas. Subsequently, it rises steeply during expiration to a normal value and reaches a near horizontal plateau after approximately 3 s. The value just prior to inspiration is the end-tidal C02 (Petco2). Inspiration causes a near vertical decline in the curve to baseline and lasts around 2 s. 

Usually seen when the respiratory rate is slow. The curve starts as normal but the expiratory pause is prolonged owing to the slow rate. Fresh gas within the circuit is able to pass over the sensor causing the Pco2 to fall. During this time, the mechanical pulsations induced by the heart force small quantities of alveolar gas out of the lungs and over the sensor, causing transient spikes. Inspiration in the above example does not occur until point A. 

A sophisticated respiratory host defence system has evolved to clear airborne particles and potential pathogens in inspired air [106, 143], The system comprises mechanical (i.e. air filtration, cough, sneezing and mucociliary clearance), chemical (antioxidants, antiproteases and surfactant lipids) and immunological defence mechanisms and is tightly regulated to minimise inflammatory reactions [92, 143],... 

Detailed descriptions of the convective airflow patterns in cast replicas of the human respiratory tract during steady inspiration were given by Olson et al, Their results show that the effect of the larynx is such that flow patterns typical of smooth bifurcating tubes (secondary motions and high shear rates along the inside wall) do not occur until the lobar bronchi are reached. Turbulent eddies produced by flow separation below the larynx do not decay as rapidly as predicted by theory. Indeed, small eddies were observed as far down as the sublobar bronchi with 200-mt/s flows in the trachea. 

For regions in which the flow is not quasisteady, a transient-flow solution may be possible. For example, Lakin and Lakin and Fox developed a two-dimensional transient-flow solution for an idealized symmetric bifurcation during the period at the end of inspiration and before expiration. Their finding that vortidty decreases at the carina or bifurcation apex suggests that particle- and gas-deposition rates may be increased at these sites in the respiratory tract. It also suggests that reactive-gas deposition rates during normal oscUlatory breathing differ... 

The respiratory tract is exposed to chemicals in the inspired air. The two main factors that determine the tissue responses to chemicals are the functional anatomy of the respiratory tract and the physicochemical nature of the material. ... 

Desflurane does not have a marked bronchodilator effect and in cigarette smokers it is associated with significant bronchoconstriction. In clinical practice, both humidification of inspired gases and opioids are thought to reduce airway irritability but even at moderate concentrations (2 MAC), desflurane is more likely to cause coughing than sevoflurane. In common with other volatile agents, desflurane causes dose-related respiratory depression. Tidal volume is reduced and respiratory rate increases, initially. As inspired concentrations of desflurane increase, the trend is to hypoventilation and hypercardia and apnoea is to be expected at concentrations of 1.5 MAC or greater. 

Enflurane is a potent respiratory depressant and apnoea may occur at inspired... 

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