China 
Africa 
Explore chapters and articles related to this topic
Pulmonary Vascular Mechanobiology
Published in Jiro Nagatomi, Eno Essien Ebong, Mechanobiology Handbook, 2018
Diana M. Tabima Martinez, Naomi C. Chesler
The effects of gravity on blood pressure in the lung can be significant. The hydrostatic pressure gradient that results from upright posture leads to higher local blood pressures at the base of the lung and lower local blood pressures at the apex. As a consequence, at the apex, normal alveolar pressure exceeds pulmonary arterial pressure such that capillaries are collapsed and not perfused. This is typically termed “zone 1” conditions either anatomically or functionally.176 In the mid-lung or zone 2, pulmonary arterial pressure exceeds pulmonary alveolar pressure, but the alveolar pressure is still higher than venous pressure; therefore, perfusion is dependent on airway pressure and not venous pressure. Because the resulting flow is insensitive to the true downstream (venous) pressure, the phenomenon is known as the waterfall effect. Finally, at the base of the lung or in zone 3 conditions, pulmonary arterial pressure is greater than venous pressure which is greater than airway pressures. In this case, flow is dependent on the difference between arterial and venous pressures.
Ventilation Measurement
Published in John G. Webster, Halit Eren, Measurement, Instrumentation, and Sensors Handbook, 2017
Since the system is globally closed (∆VA = −∆VC), the lung volume VA is related to the alveolar pressure PA (which is taken to be the barometric pressure minus the water vapor pressure at 37 °C) and to the differential pressures ∆PC and ∆PA (equal to the chamber pressure fluctuation and to the alveolar pressure fluctuation, respectively) by the formula: VA=kPAΔPCΔPA
Pleural disease induced by drugs
Published in Philippe Camus, Edward C Rosenow, Drug-induced and Iatrogenic Respiratory Disease, 2010
Spontaneous pneumomediastinum most likely results from rupture of alveoli following a sudden increased bronchovascular pressure gradient. It is commonly associated with increased alveolar pressure during mechanical inhalation and exaggerated Valsalva manoeuvres occurring with emesis, coughing and parturition. It may also occur when there is decreased pulmonary interstitial pressure, as can occur with bronchiolitis. The increased bronchoalveolar pressure gradient promotes alveolar gas dissection along the perivascular sheaths into the mediastinum. The mediastinal air follows the path of least resistance, frequently into the neck along the contiguous layers of the cervical fascia, preventing tamponade and resulting in subcutaneous emphysema. If the mediastinal pressure increases to a critical level, a pneumothorax can develop.
Dynamics of cough and particulate behaviour in the human airway
Published in Mathematical and Computer Modelling of Dynamical Systems, 2021
Olusegun J. Ilegbusi, Don Nadun S Kuruppumullage, Bari Hoffman
The specific features of the voluntary cough airflow waveform recorded from a human subject are shown in Figure 1. During the initial (inspiratory) phase of cough, reduced alveolar pressure (relative to atmospheric pressure) results in the inhalation of air. The mean duration of the inspiratory phase varies from 0.4 to 1 sec [6–8]. The compressive phase immediately follows the initial inspiratory phase. Here, after inhaling a volume of air, the glottis closes, allowing air pressure to build up within the lower airways. During a normal compression phase, airflow ceases for approximately 0.2 s [9]. Although a typical cough profile comprises all three phases described above, reflexive cough events do not normally exhibit an inspiratory phase when laryngeal penetrants are present [10].