Biomaterial Database

Inspiratory work with and without continuous positive airway pressure in patients with acute respiratory failure. 1985

J A Katz, and J D Marks

To compare the effects of continuous positive airway pressure (CPAP) with those of ambient end-expiratory pressure (T-tube) on lung mechanics and blood gas exchange, transpulmonary pressure (Ptp), tidal volume (VT), respiratory frequency, and arterial oxygen and carbon dioxide tensions were measured in 16 spontaneously breathing patients recovering from acute respiratory failure. These variables were measured during breathing through a T-tube; with 18, 12, and 6 cmH2O CPAP; and again during breathing through a T-tube. During all levels of CPAP, mean effective lung compliance (Ceff) was higher and mean total pulmonary power during inspiration lower than during breathing through a T-tube before CPAP (P less than 0.05). The data obtained at the level of CPAP producing maximum Ceff (optimum CPAP) were grouped and compared with values obtained during breathing through a T-tube. Mean total pulmonary power of inspiratory muscles during breathing through a T-tube before CPAP (0.7 +/- 0.14 kg X m X min-1) decreased during optimum CPAP (0.44 +/- 0.07 kg X m X min-1) and increased during breathing through a T-tube after CPAP (0.63 +/- 0.12 kg X m X min-1). Mean VT was higher (557 +/- 63 ml vs. 474 +/- 47 ml) and frequency lower (17.5 +/- 1.6 breaths/min vs. 22.5 +/- 2.5 breaths/min) during optimum CPAP than during breathing through a T-tube before CPAP, and inspiratory time was significantly longer. Mean minute ventilation was also lower during optimum CPAP (8.7 +/- 0.6 1/min) than during breathing through a T-tube (9.6 +/- 0.8 1/min); Paco2 did not change significantly. Mean alveolar-to-arterial oxygen pressure difference decreased significantly during optimum CPAP. The authors conclude that CPAP, when adjusted to the appropriate levels, improves lung mechanics in patients recovering from acute respiratory failure. Continuous positive airway pressure reduces total pulmonary power during inspiration and at the same time improves oxygen and carbon dioxide exchange. In these respects, it is preferable to breathing through a T-tube without CPAP.

UI	MeSH Term	Description	Entries
D007442	Intubation, Intratracheal	A procedure involving placement of a tube into the trachea through the mouth or nose in order to provide a patient with oxygen and anesthesia.	Intubation, Endotracheal,Endotracheal Intubation,Endotracheal Intubations,Intratracheal Intubation,Intratracheal Intubations,Intubations, Endotracheal,Intubations, Intratracheal
D008170	Lung Compliance	The capability of the LUNGS to distend under pressure as measured by pulmonary volume change per unit pressure change. While not a complete description of the pressure-volume properties of the lung, it is nevertheless useful in practice as a measure of the comparative stiffness of the lung. (From Best & Taylor's Physiological Basis of Medical Practice, 12th ed, p562)	Compliance, Lung,Compliances, Lung,Lung Compliances
D008297	Male		Males
D008875	Middle Aged	An adult aged 45 - 64 years.	Middle Age
D011175	Positive-Pressure Respiration	A method of mechanical ventilation in which pressure is maintained to increase the volume of gas remaining in the lungs at the end of expiration, thus reducing the shunting of blood through the lungs and improving gas exchange.	Positive End-Expiratory Pressure,Positive-Pressure Ventilation,End-Expiratory Pressure, Positive,End-Expiratory Pressures, Positive,Positive End Expiratory Pressure,Positive End-Expiratory Pressures,Positive Pressure Respiration,Positive Pressure Ventilation,Positive-Pressure Respirations,Positive-Pressure Ventilations,Pressure, Positive End-Expiratory,Pressures, Positive End-Expiratory,Respiration, Positive-Pressure,Respirations, Positive-Pressure,Ventilation, Positive-Pressure,Ventilations, Positive-Pressure
D011312	Pressure	A type of stress exerted uniformly in all directions. Its measure is the force exerted per unit area. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)	Pressures
D011659	Pulmonary Gas Exchange	The exchange of OXYGEN and CARBON DIOXIDE between alveolar air and pulmonary capillary blood that occurs across the BLOOD-AIR BARRIER.	Exchange, Pulmonary Gas,Gas Exchange, Pulmonary
D012119	Respiration	The act of breathing with the LUNGS, consisting of INHALATION, or the taking into the lungs of the ambient air, and of EXHALATION, or the expelling of the modified air which contains more CARBON DIOXIDE than the air taken in (Blakiston's Gould Medical Dictionary, 4th ed.). This does not include tissue respiration (	Breathing
D012123	Pulmonary Ventilation	The total volume of gas inspired or expired per unit of time, usually measured in liters per minute.	Respiratory Airflow,Ventilation Tests,Ventilation, Pulmonary,Expiratory Airflow,Airflow, Expiratory,Airflow, Respiratory,Test, Ventilation,Tests, Ventilation,Ventilation Test
D012129	Respiratory Function Tests	Measurement of the various processes involved in the act of respiration: inspiration, expiration, oxygen and carbon dioxide exchange, lung volume and compliance, etc.	Lung Function Tests,Pulmonary Function Tests,Function Test, Pulmonary,Function Tests, Pulmonary,Pulmonary Function Test,Test, Pulmonary Function,Tests, Pulmonary Function,Function Test, Lung,Function Test, Respiratory,Function Tests, Lung,Function Tests, Respiratory,Lung Function Test,Respiratory Function Test,Test, Lung Function,Test, Respiratory Function,Tests, Lung Function,Tests, Respiratory Function