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A significant alteration in ventilation that affects elimination of CO 2 can cause a respiratory acid-base disorder. The PaCO 2 is maintained within a range of 35–45 mm Hg in normal states. [citation needed] Alveolar ventilation is under the control of the respiratory center, which is located in the pons and the medulla.
While both ventilation and perfusion increase going from the apex to the base, perfusion increases to a greater degree than ventilation, lowering the V/Q ratio at the base of the lungs. The principal factor involved in the creation of this V/Q gradient between the apex and the base of the lung is gravity (this is why V/Q ratios change in ...
Ventilation rate (V) is the total gas volume that enters and leaves the alveoli in a given amount of time, commonly measured per minute. To calculate the ventilation rate, the tidal volume (inhaled or exhaled gas volume during normal breath) is multiplied by the frequency of breaths per minute, which is represented by the formula:
The rest of the difference is due to the continual uptake of oxygen by the pulmonary capillaries, and the continual diffusion of CO 2 out of the capillaries into the alveoli. The alveolar pO 2 is not routinely measured but is calculated from blood gas measurements by the alveolar gas equation.
The Pa/Pv difference remains unchanged since Pi is applied over both vessels. The ventilation/perfusion ratio (V/Q ratio) is higher in zone #1 (the apex of lung) when a person is standing than it is in zone #3 (the base of lung) because perfusion is nearly absent. However, ventilation and perfusion are highest in base of the lung, resulting in ...
The control of ventilation is the physiological mechanisms involved in the control of breathing, which is the movement of air into and out of the lungs. Ventilation facilitates respiration. Respiration refers to the utilization of oxygen and balancing of carbon dioxide by the body as a whole, or by individual cells in cellular respiration. [1]
A ventilation perfusion scan or lung scintigraphy can be used to diagnose areas of lungs being ventilated but not adequately perfused. This results in a raised Alveolar-arterial (A-a) gradient which is responsive to supplemental oxygen. In conditions with right to left shunts, there are also ventilation perfusion defects with high A-a gradients.
The brainstem respiratory centers decrease alveolar ventilation (hypoventilation) to create a rise in arterial carbon dioxide (CO 2) tension, resulting in a decrease of plasma pH. [1] However, as there is limitation for decreasing respiration, respiratory compensation is less efficient at compensating for metabolic alkalosis than for acidosis.