For air flow:
F=(P_alveolar -P_atmosphere)/R
When there is no air flow F= 0 and then P_alveolar -P_atmosphere=0, so they equal each other. Hence the Alveolar pressure is equal to that of the atmosphere, between a breathing cycle.
Intrathoracic pressure, intrapleural pressure, and transmural pulmonary vascular pressure exhibit rhythmic variations with respiration. These variations are important for normal breathing mechanics and gas exchange in the lungs.
The best indication of the adequacy of alveolar ventilation is the partial pressure of carbon dioxide (PaCO2) in arterial blood. This measurement reflects how effectively the lungs are removing carbon dioxide from the body, which is a waste product of metabolism. Proper alveolar ventilation ensures that PaCO2 levels remain within the normal range.
The typical cell making up the alveolar wall is the type I pneumocyte. These cells are thin and delicate, allowing for efficient gas exchange between the alveoli and the blood vessels. Type II pneumocytes are also present in the alveolar wall and play a role in producing surfactant to reduce surface tension and prevent alveolar collapse.
A normal intracranial pressure (ICP) reading for the brain is typically between 5-15 mmHg. Values above 20 mmHg are considered elevated and may indicate increased pressure within the skull which can lead to serious complications.
Surfactant is produced by the type II alveolar cells in the lungs. These cells secrete surfactant which helps lower surface tension in the alveoli, preventing collapse and facilitating gas exchange.
NO
Intra-alveolar pressure is also known as the machinal chain.
Intra-alveolar pressure is also known as the machinal chain.
Equal pressure point (EPP) is the point where Intrapleural pressure and Alveolar pressure are equal. This is similar to the Starling resistor concept in the lung. Instead of flow being determined by the difference between alveolar and mouth pressure- flow is determined by the difference between alveolar and Intrapleural pressure difference. In forced expiration, both intrapleural pressure and alveolar pressure will increase. However alveolar pressure will decrease along the length of the airway until a pressure of zero at the mouth, whereas intrapleural pressure will remain the same. Therefore there will be a point where intrapleural pressure will be equal and subsequently greater than alveolar pressure. If the EPP occurs in the larger cartilaginous airways, the airway remains open. However, if the EPP is in the smaller airways, it will collapse. Increasing the force of expiration does not overcome EPP since it will increase both alveolar and intrapleural pressure. Another interesting concept is that EPP moves distally as expiration progresses because as air leaves the alveolar unit, the pressure in the alveolar decreases hence the pressure in the airway decreases as well. EPP is the cause of dynamic airway compression.
Alveolar carbon dioxide partial pressure can be calculated using the alveolar gas equation: PaCO2 = (Pb-PH2O) * FiCO2 - (PaCO2 / R), where PaCO2 is the alveolar partial pressure of carbon dioxide, Pb is barometric pressure, PH2O is water vapor pressure, FiCO2 is inspired fraction of CO2, and R is the respiratory quotient. This equation helps estimate the partial pressure of CO2 in the alveoli.
Intrathoracic pressure, intrapleural pressure, and transmural pulmonary vascular pressure exhibit rhythmic variations with respiration. These variations are important for normal breathing mechanics and gas exchange in the lungs.
During expiration, alveolar pressure increases as the diaphragm and intercostal muscles relax, causing the lungs to contract. This rise in pressure exceeds atmospheric pressure, leading to the expulsion of air from the lungs. Typically, alveolar pressure during expiration can reach around +1 to +2 mmHg above atmospheric pressure, facilitating airflow out of the respiratory system.
The best indication of the adequacy of alveolar ventilation is the partial pressure of carbon dioxide (PaCO2) in arterial blood. This measurement reflects how effectively the lungs are removing carbon dioxide from the body, which is a waste product of metabolism. Proper alveolar ventilation ensures that PaCO2 levels remain within the normal range.
Atmospheric Pressure - 100 000 Pa or 1 Bar
An alveolar rapture refers to a situation where the alveolus raptures as a result of increased trans alveolar pressure with less pressure in the adjacent intestinal space. The rapture is dangerous because the amount of pulmonary congestion or obstruction that prevents the expansion of the lung is immeasurable, thereby leaving no criteria for safe pressures.
In alveolar air its 569.0 mm Hg. In expired air its 566.0 mm Hg. This is per Guyton & Hall's Textbook of Medical Physiology (1996)
During expiration, the alveolar pressure must exceed atmospheric pressure to allow air to flow out of the lungs. This is achieved by the contraction of the diaphragm and intercostal muscles, which reduces the volume of the thoracic cavity and increases the pressure within the alveoli. As a result, air is expelled from the lungs until the pressures equalize again.