Negative Pressure Technique Research Articles

Evidence for expiratory flow limitation of extrathoracic origin in patients with obstructive sleep apnoea

Background: A study was undertaken to examine the expiratory flow response to a negative pressure (NEP) applied at the airway in patients with no abnormalities of the intrathoracic airway but...

Efecto de la prueba de la caminata de seis minutos sobre la hiperinflación pulmonar en pacientes con enfermedad pulmonar obstructiva crónica avanzada

Exercise tolerance in patients with COPD is highly variable and poorly related to airways obstruction assessed by FEV1. These patients develop dynamic hyperinflation (DH) during an incremental exercise test which can be evaluated through a reduction in inspiratory capacity (IC).To evaluate: a) if the six minute walking test (6 MWD) induce DH reducing IC, b) if the reduction in IC is related to tidal expiratory flow limitation at rest (FL).Thirty eight stable COPD patients (28 FL and ten non FL during resting breathing, determined by the negative pressure technique). Inspiratory capacity was measured before and immediately after the 6 MWD test. Dyspnea, SpO2 and heart rate were measured before and after the test.Inspiratory capacity was lower in FL patients as compared to patients without FL (p < 0.005). Although no differences were found between groups in 6 MWD, dyspnea and HR, a significant reduction in IC after the walking test was observed only in FL patients (p < 0.0001). In addition, SpO2 fell significantly (p < 0.0001) after walking in the same group.Our results demonstrate that a moderate exercise such as the walking test induces DH and hypoxemia in patients with COPD and FL and stresses the importance of assessing DH by measuring IC in these patients.

Comparison of Three Techniques to Inflate the Bronchial Cuff of Left Polyvinylchloride Double-Lumen Tubes

Correct inflation of the cuff of any breathing tube is important; overinflation can damage the mucosa of the tracheobronchial tree and underinflation will cause a leak. Three different techniques to determine cuff seal/leak during inflation of the bronchial cuff of left double-lumen endobronchial tubes (DLT) were each evaluated in 10 patients. DLT size was chosen from a formula based on the patient's height and sex. In the first technique, designated the positive pressure technique of bronchial cuff inflation (PPT), the bronchial side of the DLT is pressurized during connection of the tracheal side to a beaker of water. Air bubbles will appear in the beaker in the absence of bronchial seal. The second technique, designated the CO2 analysis technique of bronchial cuff inflation (CAT), is based on analysis of CO2 content of gas sampled from the tracheal side of the DLT during ventilation of its bronchial side. When the bronchus is sealed, the normal CO2 waveform changes to a flat line. In the third technique, designated the negative pressure technique of bronchial cuff inflation (NPT), suction is applied to the tracheal side of the DLT. The absence of bronchial seal will result in collapse of the reservoir bag within a breathing system connected to the bronchial side of the tube. The bronchial sealing volumes were 1.1 +/- 0.9 mL, 0.9 +/- 0.7 mL, and 0.3 +/- 0.4 mL (mean +/- SD) when measured with the PPT, CAT, and NPT, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

A COMPARISON OF CONTROLLED NEGATIVE PRESSURE AND AEROSOL QUANTITATIVE RESPIRATOR FIT TEST SYSTEMS BY USING FIXED LEAKS

An automated version of a new method for quantitative respirator fit testing by controlled negative pressure was compared with a computerized aerosol fit test system. The controlled negative pressure technique eliminates many of the problems associated with aerosol and pressure decay fit test methods. A series of fixed leaks was used to compare the leak measurement capabilities of the controlled negative pressure system against a standard computerized aerosol fit test system. Negative pressure and aerosol fit factors determined for a series of fixed leaks through hypodermic needles were highly correlated with each other (r = 0.998) and with the cross-sectional areas of the leak needles (r greater than 0.995).

A study of capillary resistance in rheumatoid arthritis with special reference to the effects of long-term low-dosage oral corticosteroid therapy.

SummaryCapillary resistance was measured by a negative pressure technique on 135 female and 135 male healthy subjects, in the area over the insertion of the deltoid muscle. No significant differences were noted between the two sexes, but the capillary resistance fell with increasing age.No differences were observed between decade-matched female rheumatoid patients who had never received corticosteroid therapy and healthy female controls. No significant difference was noted in age and decade-matched female rheumatoid patients receiving long-term low dosage oral corticosteroid therapy and healthy female controls.No correlation was found between the capillary resistance and any of the clinical or laboratory findings in the rheumatoid patients, with the exception of purpura. Patients with very low capillary resistance had purpura, whether or not they were on corticosteroid therapy.

Epidural anesthesia

Although I do not feel that epidural anesthesia is the ideal type, I believe it has numerous advantages particularly in those cases usually considered to be poor operative risks. From this series no definite conclusions can be drawn, but it is certain that epidural anesthesia has not received the attention in this country which it deserves. It should be made part of the armamentarium of every anesthestist and general surgeon. Although there are dangers in its administration, care coupled with the negative pressure technique all but obviates them. The fact that one must wait fifteen to twenty minutes after injection for the anesthesia to become effective makes it probable that epidural anesthesia will not be widely used in busy hospital services. However, the advantages of epidural anesthesia more than compensate for this period of waiting.