Spirometers

Respiratory alkalosis associated with mechanical ventilation can often be corrected by decreasing the number of mechanical breaths per minute, using a capnograph and spirometer to adjust ventilator settings more precisely, or increasing dead space in the ventilator circuit. 

Respiratory problems are diagnosed using a spirometer. The patient exhales as hard and as fast as possible into the device. The spirometer measures (1) the total volume exhaled, called the forced vital capacity (FVC), with units in liters (2) the forced expired volume measured at 1 second (FEV,), with units in liters per second (3) forced expiratory flow in the middle range of the vital capacity (FEV 25-75%), measured in liters per second and (4) the ratio of the observed FEVj to FVC X 100 (FEVj/FVC%). 

Most lung volumes can be measured with a spirometer except total lung capacity (TLC), functional residual capacity (FRC) and residual volume (RV). The FRC can be measured by helium dilution or body plethysmography. 

Oxygen Consumption This can be measured at rest and during exercise on a constant-load bicycle ergometer or a treadmill at a level producing a specified percentage of predicted maximal oxygen consumption. Expired air is collected and measured with a spirometer to determine total expired volume, and samples are analyzed for oxygen and carbon dioxide. 

Breath Collection using a spirometer adsorption on Tenax traps thermal desorption cap GC/MS No data No data Barkley et al. 1980... 

Breath Collection into canisters using spirometer cryofocussing thermal desorption cap. GC/MS-SIM low- g/m levels 49-80 Thomas et al. 1991... 

Breath samples are usually collected through a spirometer onto a sorbent cartridge (Barkley et al. 1980) or into passivated canisters (Thomas et al. 1991). Analytes are concentrated cryogenically from a portion of the canister contents or after thermal desorption from the sorbent, then analyzed by GC/MS. Recovery... 

All eight sampling sites were operated by local residents. Preweighed filters were placed in filter holders at U.C. Davis and shipped via U.P.S. to each site. The local operator would measure the flow before and after sampling with a spirometer calibrated orifice meter, and then return this information with the exposed filters. Upon arrival at U.C.D., filters were post-weighed and prepared for x-ray analysis. 

If a mixture of nitrous and oxygen is bubbled through a spirometer having a large volume of water, which gas is more likely to be absorbed (dissolve in) the water Explain. 

Physical sensors (i) Thermal measurement (e.g. core body temperature, surface temperature mapping) (ii) mechanical measurement (e.g. non-invasive sphygmomanometer for blood pressure measurements, spirometer for determination of breathing and pulmonary function) (iii) acoustic measurement (e.g. ultrasound imaging, Doppler sonography for determination of blood flow) and (iv) radiation measurement (e.g. X-ray imaging, CT scanning). 

Usual clinical laboratory methods were used for circulation and blood. With a normal spirometer for the determination of the residual capacity, the method of Fenn, Otis, and Rahn 6) was used for respiration. Nitrogen concentration was determined with the Lilly-Anderson nitrogen meter, which was calibrated with correction for discharge current, pressure, and carbon dioxide (1). 

All the static lung volumes and capaeities except FRC and RV can be measured directly through use of a simple spirometer (an apparatus traditionally consisting of a cylindrical bell immersed in water and equipped with outlets that a person can breathe into, or inhale from, to measure expiratory or inspiratory volumes). Functional residual capacity and RV are measured indirectly by using several alveolar gas dilution techniques. 

One dilution technique for measuring FRC involves having a subject breathe from a spirometer a fixed concentration of a gas, such as helium (He), which is not soluble in blood or lung tissue. In such a maneuver, the subject is connected in closed cireuit to a spirometer and begins to breathe in the He from the spirometer at the end of a normal expiration. Both the initial volume of gas in the spirometer (VJ and the concentration of He (C ) added to the spirometer are measured before the start of the test. The... 

The residual volume (RV) is calculated by subtracting the expiratory reserve volume (measured directly with the spirometer) from the FRC. 

The best way to determine the caliber of the intrathoracic airways is to utilize pulmonary tests measured at maximal flow rates such as forced expiratory volume in 1 second (FEVj) and maximal expiratory flow-volume curves. The forced expiratory volume maneuver requires a subject to inspire maximally and then exhale as hard as possible into a spirometer. The typieal... 

Fig. 11. Typical tracing obtained from a spirometer during a forced expiratory volume maneuver.

To measure compliance, the subject is intubated with an esophageal balloon and then told to breathe in or out of a spirometer in 500-ml increments. During breath holding, with the epiglottis open, the alveolar pressure is the same as the pressure at the mouth. Values of volume change and pleural pressure changes measured simultaneously produce a pressure-volume curve similar to that shown in Fig. 13. 

Forced expiratory volume (FEV) is the single most useful test of lung function, but the instrument required is a spirometer, which is expensive, cumbersome, and not suited for home use. 

Exhaled air Collected in spirometer pre-concentrated on Tenax-GC thermally desorbed HRGC/MS 0.3 ppb 95-99 Wallace et al. 1986a, 1986d... 

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