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Physiology of the Airways
Published in Anthony J. Hickey, Sandro R.P. da Rocha, Pharmaceutical Inhalation Aerosol Technology, 2019
Anthony J. Hickey, David C. Thompson
Measurement of expiratory flow represents a simple, noninvasive means of estimating airway caliber. However, these measurements are relatively insensitive to changes in peripheral airway caliber. More complicated measures of caliber include airways resistance (RL) and dynamic lung compliance (Cdyn). Airways resistance is thought to measure the caliber of the larger airways, such as the bronchi and bronchioles. Dynamic lung compliance measures the elasticity of the peripheral airways and is given as the change in volume of the lungs for a given change in pressure distending the alveoli. Measurement of these parameters in subjects involves highly specialized equipment (e.g. whole-body plethysmograph and pneumotachygraph) and can be invasive, i.e. requiring the placement of an intraesophageal balloon for intrathoracic pressure measurements. A precise description of the means of estimating these parameters is beyond the scope of the present discussion, but interested readers are directed to reference (Miller et al., 1987).
Respiratory System
Published in Joseph D. Bronzino, Donald R. Peterson, Biomedical Engineering Fundamentals, 2019
Arthur T. Johnson, Christopher G. Lausted, and Joseph D. Bronzino
e simplest PFT is the spirometry maneuver. In this test, the patient inhales to TLC and exhales forcefully to residual volume. e patient exhales into a displacement bell chamber that sits on a water seal. As the bell rises, a pen coupled to the bell chamber inscribes a tracing on a rotating drum. e spirometer oers very little resistance to breathing; therefore, the shape of the spirometry curve (Figure 7.7) is purely a function of the patient’s lung compliance, chest compliance, and airway resistance. At high lung volumes, a rise in intrapleural pressure results in greater expiratory ows. However, at intermediate and low lung volumes, the expiratory ow is independent of eort aer a certain intrapleural pressure is reached.
Drug-induced pulmonary oedema and acute respiratory distress syndrome
Published in Philippe Camus, Edward C Rosenow, Drug-induced and Iatrogenic Respiratory Disease, 2010
Teofilo Lee-Chiong, Richard A Matthay
Hypoxaemia and hypocapnia (or hypercapnia) are common. Leucocytosis and eosinophilia can be present as well. Pulmonary function testing can demonstrate decreased lung compliance. Restrictive or obstructive ventilatory defect, and diminished diffusing capacity, have been described. Chest radiographs may reveal bilateral interstitial and alveolar filling infiltrates.50 Cardiomegaly and pulmonary vascular redistribution are generally absent.
On the design of a compact emergency mechanical ventilator with negative expiratory exit pressure for COVID-19 patients
Published in Journal of Medical Engineering & Technology, 2023
Sheeja Janardhanan, Vidya Chandran, Rajesh Rajan
The lung compliance is an indication of the condition of the lungs and is expressed by the following equation: where C is the compliance of the distressed lung (0.2 l/cm H2O), E is the elastance of the lung, VT is the TV (2.2 l), PP is the plateau pressure (32 cm H2O) and PTot is the total PEEP of the ventilator, calculated as 20 cm H2O from Equation (5). PTot is, however, the sum of internal and external PEEP and is expressed by the following equation: where PI is the intrinsic/auto PEEP of the lungs, usually 5 cm H2O, and PE is the external PEEP of the ventilator, the pressure available at the end of the ETT, calculated as 15 cm H2O from Equation (6); the same negative pressure is retained at the exit of the expiration tube in the present ventilator. Hence, the working pressure of the device is fixed in the range (–15, +15) cm H2O. Lung activities corresponding to piston positions are summarised in Table 1.
Parameters of high-frequency jet ventilation using a mechanical lung model
Published in Journal of Medical Engineering & Technology, 2022
Evgeni Kukuev, Evgeny Belugin, Dafna Willner, Ohad Ronen
Three series of measurement were performed, with only one parameter being altered each time. In the first set, the RR was measured in minutes−1. In the second set of measurements, the inspiratory-expiratory ratio (I:E) was changed, and in the third set, the inspiratory pressure (IP) measured in bar units, was changed. The default I:E ratio was set on 1:1.5. The default airway resistance in the lung model used in this study was 2 cmH2O/L/min. The airway resistance in this lung model is simulated by parabolic restrictors (resistors), which were calibrated in the laboratory to be within prescribed limits. All the measurements were collected under lung compliances of 20, 50 and 80 ml/cmH2O. Lung compliance to a desired setting in the lung model device can be determined. It should be noted that the Monsoon ventilator has a built-in mechanism that alerts in cases of dangerously high pressure, thereby preventing barotrauma. The alarm was set to 20 cmH2O. To increase reliability and accuracy, all measurements were repeated 50 times in each setting, and average data are presented.
Assembly behaviour and thermodynamics of the mixture of cetyltrimethylammonium bromide and bovine serum albumin in aqueous and aqua-ethylene glycol mixed solvents media at several temperatures
Published in Molecular Physics, 2022
Md. Anamul Hoque, Shamim Mahbub, Javed Masood Khan, Md. Tuhinur R. Joy, Mohammed Abdullah Khan, Dileep Kumar, Anis Ahmad, Mohammad Z. Ahmed
Surfactants (amphiphilic substances) exhibit crucial role in fundamental and applied fields such as drug transport systems, drug targeting systems and pharmaceutical formulations, etc. Surfactants are essential in order to prevent the SARS-COV-2. The delivery of surfactants by means of bronchoscopy to acute respiratory distress syndrome patients at a dose of 720 mg in 150 mL normal saline was found to be safe and may reduce the morality [1]. The surface tension reduction property of the surfactant augments oxygenation and lung compliance [2]. In the previous few decades, the interaction of solutes (drug, protein, polymers, etc.) with surfactants has been investigated with rising attention owing to the widespread usages of surfactants in pharmaceutical productions as disintegrating, emulsifying and solubilising agent [3–10]. In such cases surfactants exhibit excellent properties after the development of micelle (aggregate). The micelle formation of surfactants takes place beyond a narrow concentration range of surfactants which is denoted as the critical micelle concentration (CMC) [11–16]. The CMC values of a particular surfactant are known to be changed due to the change of experimental conditions such as temperature, solvent compositions, presence of drugs/polymers/other additives, etc. The interaction of the protein with surfactant can be visualised by the changes of CMC values. Despite having the large application of surfactants, some adverse effect on human health was also observed.