Transpulmonary pressure is the difference between the

alveolar pressure Alveolar pressure (Palv) is the pressure of air inside the lung alveoli. When the glottis The glottis is the opening between the vocal folds (the rima glottidis). The glottis is crucial in producing vowels and voiced consonants. Etymology ...

and the intrapleural pressure in the

pleural cavity The pleural cavity, pleural space, or interpleural 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 enable lubrication b ...

. During human ventilation, air flows because of

pressure gradient In atmospheric science, the pressure gradient (typically of air but more generally of any fluid) is a physical quantity that describes in which direction and at what rate the pressure increases the most rapidly around a particular location. The ...

s. P_tp = P_alv – P_ip. Where P_tp is transpulmonary pressure, P_alv is alveolar pressure, and P_ip is intrapleural pressure.

Physiology

Since atmospheric pressure is relatively constant, pressure in the lungs must be higher or lower than atmospheric pressure for air to flow between the atmosphere and the alveoli. If 'transpulmonary pressure' = 0 (alveolar pressure = intrapleural pressure), such as when the lungs are removed from the chest cavity or air enters the intrapleural space (a

pneumothorax A pneumothorax is an abnormal 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 shortness of breath. In a minority of cases, a one-way valve ...

), the lungs collapse as a result of their inherent elastic recoil. Under physiological conditions the transpulmonary pressure is always positive; intrapleural pressure is always negative and relatively large, while alveolar pressure moves from slightly negative to slightly positive as a person breathes. For a given lung volume, the transpulmonary pressure is equal and opposite to the elastic recoil pressure of the lung. The transpulmonary pressure vs volume curve of inhalation (usually plotted as volume as a function of pressure) is different from that of exhalation, the difference being described as

hysteresis Hysteresis is the dependence of the state of a system on its history. For example, a magnet may have more than one possible magnetic moment in a given magnetic field, depending on how the field changed in the past. Plots of a single component of ...

. Lung volume at any given pressure during inhalation is more than the lung volume at any given pressure during exhalation.

Measurement

Transpulmonary pressure can be measured by placing pressure transducers. The alveolar pressure is estimated by measuring the pressure in the airways while

holding one's breath Apnea, BrE: apnoea, is the temporal cessation of breathing. During apnea, there is no movement of the muscles of inhalation, and the volume of the lungs initially remains unchanged. Depending on how blocked the airways are ( patency), there may ...

. The intrapleural pressure is estimated by measuring the pressure inside a balloon placed in the

esophagus The esophagus (American English) or oesophagus (British English; both ), non-technically known also as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to the ...

.Ronald B. George (2005) ''Chest medicine: essentials of pulmonary and critical care medicine''. . p. 96 . Measurement of transpulmonary pressure assists in spirometry in availing for calculation of

static lung compliance Spirometry (meaning ''the measuring of breath'') is the most common of the pulmonary function tests (PFTs). It measures lung function, specifically the amount (volume) and/or speed (flow) of air that can be inhaled and exhaled. Spirometry is he ...

References

{{reflist Respiratory physiology