<i>A Comparison of Esophageal and Intrapleural Pressure in Man</i>

Cherniack, Reuben M.; Farhi, Leon E.; Armstrong, Bruce W.; Proctor, Donald F.

doi:10.1152/jappl.1955.8.2.203

Cited by 131 publications

(62 citation statements)

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“…Intrathoracic pressure can be measured from a pressure catheter placed in the mid-lower oesophagus (Poes), whilst intra-abdominal pressure can be assessed from the gastric pressure measured using a catheter placed in the stomach (Pga). Previous studies have confirmed that Poes and Pga are valid measurements by comparing them with directly measured pleural and abdominal pressures [29,30]. Pdi is the arithmetic difference between Pga and Poes, and has become the "gold standard" for assessing diaphragm contractility.…”

Section: Magnetic Stimulation and The Inspiratory Musclesmentioning

confidence: 95%

Magnetic stimulation for the measurement of respiratory and skeletal muscle function

Man¹

2004

European Respiratory Journal

116

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Respiratory and skeletal muscle function is of interest in many areas of pulmonary and critical care medicine. The capacity of the respiratory muscle pump to respond to the load imposed by disease is the basis of an understanding of ventilatory failure. Over the last four decades, considerable progress has been made in quantifying the capacity of the respiratory muscles, in terms of strength, endurance and fatigue. With the development of magnetic stimulation, it has recently become possible to nonvolitionally assess the respiratory muscles in a clinically acceptable way. This is of particular interest in the investigation of patients receiving critical care, those with neuromuscular disease, and in children where volitional efforts are either not possible or likely to be sub-maximal. Furthermore, the adaptation of these techniques to quantify the strength of peripheral muscles, such as the quadriceps, has allowed the effects of muscle training or rehabilitation, uninfluenced by learning effect, to be assessed. This article focuses on the physiological basis of magnetic nerve stimulation, and reviews how the technique has been applied to measure muscle strength and fatigue, with particular emphasis upon the diaphragm. The translation of magnetic stimulation into a clinical tool is described, and how it may be of diagnostic, prognostic and therapeutic value in several areas of pulmonary medicine. In particular, the use of magnetic stimulation in neuromuscular disease, the intensive care setting, chronic obstructive pulmonary disease and paediatrics will be discussed. The nonvolitional assessment of skeletal musclesFor routine muscle strength measurements, the force generated from a maximum voluntary contraction (MVC) is often used. However volitional, effort-dependent manoeuvres for measuring strength are not always suitable for patients as the ability to perform a true MVC relies upon subject motivation and cooperation. This is particularly so in patients on intensive care units (ICU), children, patients with cognitive difficulties, and those patients prevented from performing a true MVC by pain (for example, following surgery). However, even in well-motivated subjects, sub-maximal muscle activation is common in routine clinical practice [1]. As volitional manoeuvres are influenced by a learning effect, the value of MVC is also limited in studies of training or rehabilitation. Consequently, there has been a need for nonvolitional methods to assess muscle strength. Skeletal muscle physiologySkeletal muscle is controlled by electrical impulses conducted by motor neurones that lead to the release of acetylcholine from the motor end plate, thus depolarising the muscle cell membrane. The force generated by muscle contraction is dependent upon a number of factors, including the number of muscle fibres stimulated, muscle length at the time of stimulation and the frequency of stimulation. The force-frequency curve of a muscle is of particular relevance in the understanding of nonvolitional techniques to asse...

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Section: Magnetic Stimulation and The Inspiratory Musclesmentioning

confidence: 95%

Magnetic stimulation for the measurement of respiratory and skeletal muscle function

Man¹

2004

European Respiratory Journal

116

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“…The difference between intraesophageal and intrapleural pressure depends upon the characteristics of the measuring device, its location within the esophagus and the characteristics of the esophageal wall and the adjacent structures (2)(3)(4)(5). Difficulties may ensue in employing intraesophageal pressures as a guide for the determination of absolute lung distention.…”

Section: Methodsmentioning

confidence: 99%

The Mechanics of Breathing in Different Body Positions. I. In Normal Subjects

Attinger¹,

Monroe²,

Segal³

1957

Survey of Anesthesiology

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In preliminary experiments some striking differences in the mechanics of breathing in different body positions were observed. In view of those findings it was thought worthwhile to carry out a more extensive study with the anticipation that the results might shed some light on the factors which influence the compliance and mechanical resistance of the lung.Compliance is defined as the volume change brought about by one centimeter of water pressure (L. per cm. H20). The lower the compliance the stiffer the lung and vice versa. Mechanical resistance measures the amount of pressure necessary to obtain a certain flow rate and is expressed as cm. H20 per L. per sec.In this paper, mechanical resistance includes both the resistance to air flow per se and the resistance to tissue deformation. The latter resistance has been measured to be about 30 to 40 per cent of the total mechanical resistance in normal lungs (1). Because the pressure flow relationships are not linear, the mechanical resistance changes continuously over the respiratory cycle especially in patients with increased resistance. In order to get better comparative values over an entire respiratory cycle, values for mean mechanical resistance are given in this paper. METHODSIntraesophageal pressures were substituted for intrapleural pressures. The method used was essentially the one described by Mead and Whittenberger (2,3), employing an esophageal balloon, 15 cm. in length and inflated with 1 ml. of air. All pressures were measured by mechano-electrical transducers. Flow rates were measured by a pneumotachograph. The volume flow rate was electrically integrated by a condenser-resistor unit. Because the integrator only maintained linearity for 10 seconds, an automatic switch was provided which discharged the condensers at determined time intervals (5 to 8 seconds). A controlled secondary circuit made it possible 1 Research Fellow in Medicine, Tufts University School of Medicine, Boston, Mass.to correct for volume differences caused by the respiratory quotient and temperature and humidity changes between the inspired and expired air. Consequently the base line remained horizontal in a given midposition. The volumes measured are the inspired volumes at 25°C (not saturated) and are reported as such. This would reduce the compliance values about 7 per cent as compared to values corrected for B.T.P.S. All electrical outputs were fed into a Sanborn four channel recording unit.Since considerable variations may occur between individual respiratory cycles caused by heart beats, at least two series of ten cycles each were measured in each position and at each respiratory rate. The mean compliance of the two series was required to check within 0.03 for values above 0.15, within 0.02 for values above 0.1 and within 0.01 for values below 0.1. Resistive pressures were measured by drawing the corrected static intrapleural pressure and obtaining the difference between dynamic and static intrapleural pressure at each gAo of a second for slow respiratory rates and at each %5 ...

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“…Esophageal pressure was used to estimate intrathoracic pressure (5-7) in spite of known differences between esophageal and intrapleural pressures (8), because values for compliance and resistance determined with esophageal pressures approximated those using intrapleural pressure sufficiently in the tidal volume range for evaluation of the physiologic abnormalities under consideration (9). The esophageal pressure was measured by means of an air filled, thin-walled rubber balloon which has been previously described (8).…”

Section: Methodsmentioning

confidence: 99%

“…The esophageal pressure was measured by means of an air filled, thin-walled rubber balloon which has been previously described (8). All measurements were made within the lower third of the esophagus.…”

Section: Methodsmentioning

confidence: 99%

A Comparison of Esophageal and Intrapleural Pressure in Man

Cited by 131 publications

References 0 publications

Magnetic stimulation for the measurement of respiratory and skeletal muscle function

Magnetic stimulation for the measurement of respiratory and skeletal muscle function

The Mechanics of Breathing in Different Body Positions. I. In Normal Subjects

The Physical Properties of the Lung in Chronic Obstructive Pulmonary Emphysema 1

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