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A subject takes a breath of 100% oxygen and exhales through a one-way valve measuring nitrogen content and volume. A plot of the nitrogen concentration (as a % of total gas) vs. expired volume is obtained by increasing the nitrogen concentration from zero to the percentage of nitrogen in the alveoli. The nitrogen concentration is initially zero ...
In order to listen to the lungs from the back the patient is asked to move their arms forward to prevent the scapulae (shoulder blades) from obstructing the upper lung fields. These fields are intended to correlate with the lung lobes and are thus tested on the anterior (front) and posterior (back) chest walls.
Using the fact that each gram of hemoglobin can carry 1.34 mL of O2, the oxygen content of the blood (either arterial or venous) can be estimated by the following formula: = [] ( /) + PO2 is the partial pressure of oxygen and reflects the amount of oxygen gas dissolved in the blood. The term 0.0032 * P02 in the equation is very small and ...
The helium dilution technique is the way of measuring the functional residual capacity of the lungs (the volume left in the lungs after normal expiration). This technique is a closed-circuit system where a spirometer is filled with a mixture of helium (He) and oxygen. The amount of He in the spirometer is known at the beginning of the test ...
The normal relaxed state of the lung and chest is partially empty. Further exhalation requires muscular work. Inhalation is an active process requiring work. [4] Some of this work is to overcome frictional resistance to flow, and part is used to deform elastic tissues, and is stored as potential energy, which is recovered during the passive process of exhalation, Tidal breathing is breathing ...
The alveolar gas equation is the method for calculating partial pressure of alveolar oxygen (p A O 2). The equation is used in assessing if the lungs are properly transferring oxygen into the blood. The alveolar air equation is not widely used in clinical medicine, probably because of the complicated appearance of its classic forms.
The lung float test, also called the hydrostatic test or docimasia, [1] is a controversial autopsy procedure used in determining whether lungs have undergone respiration. It has historically been employed in cases of suspected infanticide to help determine whether or not an infant was stillborn. In the test, lungs that float in water are ...
TLC: Total lung capacity: the volume in the lungs at maximal inflation, the sum of VC and RV. TV: Tidal volume: that volume of air moved into or out of the lungs in 1 breath (TV indicates a subdivision of the lung; when tidal volume is precisely measured, as in gas exchange calculation, the symbol TV or V T is used.)