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The alveolar oxygen partial pressure is lower than the atmospheric O 2 partial pressure for two reasons. Firstly, as the air enters the lungs, it is humidified by the upper airway and thus the partial pressure of water vapour (47 mmHg) reduces the oxygen partial pressure to about 150 mmHg.
Alveolar pressure (PA) at end expiration is equal to atmospheric pressure (0 cm H 2 O differential pressure, at zero flow), plus or minus 2 cm H 2 O (1.5 mmHg) throughout the lung. On the other hand, gravity causes a gradient in blood pressure between the top and bottom of the lung of 20 mmHg in the erect position (roughly half of that in the ...
Triggered by the flow of the air, the pressure of the air in the nose, and the quality of the air, impulses from the nasal mucosa are transmitted by the trigeminal nerve to the respiratory center in the brainstem, and the generated response is transmitted to the bronchi, the intercostal muscles and the diaphragm.
However, it is not practical to take a sample of gas from the alveoli in order to directly measure the partial pressure of oxygen. The alveolar gas equation allows the calculation of the alveolar partial pressure of oxygen from data that is practically measurable. It was first characterized in 1946. [1]
is the partial pressure of oxygen in the systemic veins (where it can actually be measured). Thus, the higher the diffusing capacity , the more gas will be transferred into the lung per unit time for a given gradient in partial pressure (or concentration) of the gas. Since it can be possible to know the alveolar oxygen concentration and the ...
Dead space refers to the volume not taking part in gas exchange. [11] Alveolar dead space and insufficient perfusion result in a V/Q ratio above 0.8 with decreased fresh oxygen in the alveoli. [1] This might have been caused by blood clotting, heart failure, pulmonary emphysema, or damage in alveolar capillaries. [12]
Pulmonary compliance is calculated using the following equation, where ΔV is the change in volume, and ΔP is the change in pleural pressure: = For example, if a patient inhales 500 mL of air from a spirometer with an intrapleural pressure before inspiration of −5 cm H 2 O and −10 cm H 2 O at the end of inspiration.
Cardiac monitoring generally refers to continuous or intermittent monitoring of heart activity to assess a patient's condition relative to their cardiac rhythm.Cardiac monitoring is usually carried out using electrocardiography, which is a noninvasive process that records the heart's electrical activity and displays it in an electrocardiogram. [1]