2315 Intrapulmonary and Intrapleural Pressure

physiology Physiology (; ) is the science, scientific study of function (biology), functions and mechanism (biology), mechanisms in a life, living system. As a branches of science, subdiscipline of biology, physiology focuses on how organisms, organ syst ...

, intrapleural pressure refers to the pressure within the

pleural cavity The pleural cavity, or pleural space (or sometimes intrapleural space), is the potential space between the pleurae of the pleural sac that surrounds each lung. A small amount of serous pleural fluid is maintained in the pleural cavity to enabl ...

. Normally, the pressure within the pleural cavity is slightly less than the

atmospheric pressure Atmospheric pressure, also known as air pressure or barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1,013. ...

, which is known as ''negative pressure''.Khanorkar, p. 205 When the pleural cavity is damaged or ruptured and the intrapleural pressure becomes greater than the atmospheric pressure,

pneumothorax A pneumothorax is collection of air in the pleural space between the lung and the chest wall. Symptoms typically include sudden onset of sharp, one-sided chest pain and dyspnea, shortness of breath. In a minority of cases, a one-way valve is ...

may ensue. Intrapleural pressure is different from intrathoracic pressure. The

thoracic cavity The thoracic cavity (or chest cavity) is the chamber of the body of vertebrates that is protected by the thoracic wall (rib cage and associated skin, muscle, and fascia). The central compartment of the thoracic cavity is the mediastinum. Ther ...

is the space that includes the pleura, lungs, and heart, while the pleural space is only the space between the

parietal pleura The pleurae (: pleura) are the two flattened closed sacs filled with pleural fluid, each ensheathing each lung and lining their surrounding tissues, locally appearing as two opposing layers of serous membrane separating the lungs from the medi ...

and

visceral pleura The pleurae (: pleura) are the two flattened closed sacs filled with pleural fluid, each ensheathing each lung and lining their surrounding tissues, locally appearing as two opposing layers of serous membrane separating the lungs from the media ...

surrounding lungs. Intrapleural pressure depends on the ventilation phase, atmospheric pressure, and the volume of the intrapleural cavity.Blom, p. 7 At rest, there is a negative intrapleural pressure. This provides a

transpulmonary pressure Transpulmonary pressure is the difference between the alveolar pressure and the intrapleural pressure in the pleural cavity. During human ventilation, air flows because of pressure gradients. Ptp = Palv – Pip Where Ptp is transpulmonary press ...

, causing the lungs to expand. If humans didn't maintain a slightly negative pressure even when exhaling, their lungs would collapse on themselves because all the air would rush towards the area of lower pressure. Intra-pleural pressure is sub-atmospheric. This is due to the recoil of the chest and lungs away from each other.

Müller's maneuver Müller's maneuver is a procedure used in medicine to diagnose some types of tinnitus, and other medical problems. Procedure After a forced expiration, an attempt at inspiration is made with closed mouth and nose, whereby the negative pressure i ...

can temporarily but significantly decrease the intrapleural pressure. The relationship between the intra-pulmonary pressure and intra-pleural pressure is that the pressure becomes more negative during inspiration and allows air to get sucked in (

Boyle's law Boyle's law, also referred to as the Boyle–Mariotte law or Mariotte's law (especially in France), is an empirical gas laws, gas law that describes the relationship between pressure and volume of a confined gas. Boyle's law has been stated as: ...

) vs relationship and during expiration, the pressure becomes less negative (Note: still less than atmospheric pressure, also take note of the partial pressure of carbon dioxide) and the air is given out. The only difference between the pressures is that intra-pleural pressure is more negative than intra-pulmonary pressure. Factors affecting are: Physiological effects: # Müller's maneuver (forced inspiration against a closed

glottis The glottis (: glottises or glottides) is the opening between the vocal folds (the rima glottidis). The glottis is crucial in producing sound from the vocal folds. Etymology From Ancient Greek ''γλωττίς'' (glōttís), derived from ''γ ...

results in negative pressure) # # Deep inspiration Pathological effects: #

Emphysema Emphysema is any air-filled enlargement in the body's tissues. Most commonly emphysema refers to the permanent enlargement of air spaces (alveoli) in the lungs, and is also known as pulmonary emphysema. Emphysema is a lower respiratory tract di ...

# # Pneumothorax Condition
A person breathing at rest inhales and exhales approximately half a liter of air during each respiratory cycle, which is called tidal volume. The respiratory rate is directly affected by the concentration of carbon dioxide in the blood. ''Lungs do not collapse after forceful respiration because of the residual volume.''

References

;Books * * Respiratory physiology Pulmonology {{Lung-stub