Three methods are in current use for measuring the diffusing capacity of the lungs for carbon monoxide (DL). Two of these are steady state methods, and they differ in the methods used to calculate the mean alveolar carbon monoxide tension. Filley, MacIntosh and Wright (1) calculate the alveolar Pco indirectly, assuming the physiological dead space for carbon dioxide to be the same as that for c...

TO THE EDITOR: In the context of a discussion about a patient with chronic obstructive pulmonary disease (COPD), a secondyear medical student recently asked: What is the definition of hyperventilation? My initial response was that, when the CO2 production rate is constant, an individual who is hypocapnic (i.e., has a lower than normal CO2 tension in arterial blood) must have hyperventilated. Th...

RATIONALE During exercise, heart failure patients (HF) show an out-of-proportion ventilation increase, which in patients with COPD is blunted. When HF and COPD coexist, the ventilatory response to exercise is unpredictable. OBJECTIVES We evaluated a human model of respiratory impairment in 10 COPD-free HF patients and in 10 healthy subjects, tested with a progressive workload exercise with di...

STUDY OBJECTIVE Multiple studies have evaluated capnography for the diagnosis of pulmonary embolism; accordingly, we conduct a meta-analysis of these trials. METHODS We performed a systematic search from 1990 to 2011, using MEDLINE, EMBASE, and the Cochrane Library, including studies evaluating capnography as a diagnostic tool alone or in conjunction with other tests. After study quality eval...

Measured by a variety of techniques, the overall ventilation-perfusion relationship of the normal human lung is different in supine and upright positions, and in the upright position, the upper regions of the lung are relatively poorly perfused (1-4). Similarly, pulmonary diffusing capacity (DL) is reduced when normal subjects change from supine to upright positions (5, 6); in the upright posit...

Five asthmatic patients aged 25-30 years were studied during and after 6-8 minutes of steady exercise on both a bicycle ergometer and a treadmill. For each patient the duration of work, oxygen consumption, minute ventilation, and heart rate were similar in each form of exercise. During exercise all patients had an increase in peak expiratory flow rate. The blood lactate level was higher during ...

Spirometry is difficult for some COPD patient to perform. Volumetric capnography could be a second choice test to evaluate the severity of functional disturbances. The aim of this work is to test this hypothesis. A total number of 98 subjects were classified either as normal ex-smokers (N=14) or COPD patients. The latter were staged following GOLD recommendations. Spirometry and volumetric capn...

The determination of the percentage of CO(2) in the alveolar air, by the method of Haldane and Priestley, is sufficiently accurate for clinical purposes when the individual is at rest. It is evident, however, that an error may arise in the determination of the percentage of CO(2) in the alveolar air, due to the time during the forced expiration, short of the extreme limit, at which the sample m...

Some recent studies of competitive athletes have shown exercise-induced hypoxemia to begin in submaximal exercise. We examined the role of ventilatory factors in the submaximal exercise gas exchange disturbance (GED) of healthy men involved in regular work-related exercise but not in competitive activities. From the 38 national mountain rescue workers evaluated (36 +/- 1 yr), 14 were classified...

The problem concerning the nature and the function of the dead space is of basic importance for the full comprehension of the respiratory physiology and pathophysiology. To study the effect of an imposed external dead space on the optimal respiratory control system, we simulated the optimal neuro-muscular drive and respiratory signals, including instantaneous airflow and lung volume profiles, w...