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Biomedical subjects

M Cosio

Publications and source records attributed to M Cosio.

11 recordsLinked to original sources
PubMed1987

Inspiratory muscle activity as a trigger causing the airways to open in obstructive sleep apnea.

This report discusses mechanisms causing the airways to open during obstructive sleep apnea (OSAS). In 4 male patients with OSAS, 92 nonrapid eye movement (NERM) sleep apnea episodes and 37 rapid eye movement (REM) sleep apnea episodes were analyzed breath by breath during a one-night study. We calculated the pressure time index of the diaphragm (the product of inspiratory time/cycle duration (Tl/Ttot) and mean transdiaphragmatic pressure swing), evaluated the sleep stages via EEG, and performed frequency spectrum analysis of the EMG of the diaphragm. It was found that with each occluded inspiratory effort the tension time index of the diaphragm (TTdi) increased progressively to reach or slightly exceed the fatigue threshold, 0.15 to 0.18 (during NREM sleep the TTdi of the last occluded breath was 0.195 +/- 0.045 and during REM sleep the TTdi of the last occluded breath was 0.153 +/- 0.037); that a close time relationship was observed as well between the onset of arousal and the opening of the airways. Our data suggest that the airways may be triggered to open by a protective reflex originating in the larynx or the inspiratory muscles upon reaching a certain degree of contraction.

Adult↗
PubMed1985

Alteration of airway reactivity by mucus.

In 11 beagles with permanent tracheostomies we investigated whether mucus hypersecretion alters airway reactivity to inhaled aerosols. Mucus was collected from the dogs while awake by resting a cytology brush on the lower tracheal mucosa; the mucus collection rate was used as an index of mucus flux. Mucus linear velocity was determined under light sedation by bronchoscopically observing the rate of particle clearance in the trachea. Mucus depth was then computed from the flux and velocity. On a separate occasion, under pentobarbital anesthesia, methacholine aerosols (1 min duration) were given at 10 min intervals in doubling doses up to at least 2 mg/ml. Pulmonary resistance RL was determined prior to and 2 min after each dose. After a 1 h pause, methacholine was infused at a constant rate of 40 micrograms X kg-1 X min-1 for 10 min. This dose produced a plateau in RL after approximately 3 min; the mean rise in RL was similar to that achieved with the 2 mg/ml aerosol. The infusion response Rinf was defined as the change in RL 4-5 min post infusion; the aerosol response Raer was defined as the change in RL 2 min post 2 mg/ml aerosol. There was no significant correlation between Rinf and Raer, nor between either Rinf or Raer and mucus flux. There was, however, a strong positive association between Rinf/Raer and mucus flux and a similar positive association between Rinf/Raer and mucus depth. These associations indicate that dogs with elevated secretion levels are relatively unresponsive to aerosolized as opposed to infused methacholine. Thus, to the extent that infusion reactivity reflects innate airway reactivity, the reactivity to inhaled aerosol may underestimate the true value when mucus hypersecretion occurs.

Aerosols↗
PubMed1985

Effect of chronic cigarette smoke exposure on pulmonary vasomotion in beagle dogs.

To study the effect of chronic cigarette smoke exposure on the resistive properties of the pulmonary vasculature, left lower lobes from 12 control beagles and 6 beagles who had smoked cigarettes (50 cigarettes/wk for 40 wk) were perfused in situ to measure the vascular pressure-flow relationship and the resistance of the three vascular segments with the arterial and venous occlusion technique. In control subjects the vascular resistance in the arterial, middle, and venous segments was 23, 36, and 41% of the total, respectively. The segmental distribution of vascular resistance was not significantly different in the cigarette smoke-exposed dogs, despite the fact that the absolute values were 30-40% less than that of the control group. The longitudinal distribution of resistance among the three vascular segments and their response to drugs were different in beagles than was previously found in mongrels. In all beagles the veins were considerably more reactive than arteries. Vasoconstriction with serotonin (5-HT) prostaglandin F2 alpha (PGF2 alpha), norepinephrine, histamine, and methacholine (M) infusion occurred predominantly in the veins. The effect of PGF2 alpha and 5-HT was totally different than that previously observed in mongrels in which the constriction was predominantly in the arteries. Chronic cigarette smoking reduced the basal pulmonary vascular resistance and attenuated the venoconstrictor response to 5-HT and M but potentiated the hypoxic pressor response of the microvessels.

Animals↗
PubMed1985

A morphologic grading scheme for membranous and respiratory bronchioles.

We describe a system for grading pathologic changes in the small airways. This system consists of determining a score of 0 to 3 using a set of pictorial reference standards for any or all of the following variables: wall inflammation, fibrosis, muscle hypertrophy, pigment deposition, epithelial goblet and squamous metaplasia, and intralumenal macrophages. Grading of this type is much faster and easier than formal morphometric analysis. This system has produced a good correlation with pulmonary function test abnormalities, indicating obstruction in cigarette smokers and has also been used to detect lesions produced by other inhaled agents such as mineral dusts.

Bronchi↗
PubMed1980

Intraregional basis for sequential filling and emptying of the lung.

We studied the sequential pattern of lung filing by measuring the slope of the alveolar plateau in single breath helium washouts after inhaling a bolus at a lung volume (VI) equivalent to 20. 40, 60 and 80% of vital capacity (VC). In seated subjects, prone dogs, both with the chest intact and wide open, and individual canine lobes, slopes at VI = 20% VC were more positive than those at VI = 80% VC, indicating a "first in - last out' pattern. Furthermore the range of slopes, which reflects the magnitude of sequencing, was comparable in the four situations. We conclude that sequential filing and emptying of the lung has predominantly an intraregional basis. A two compartment optimization analysis using single exponential pressure-volume curves suggests that only a small proportion of the lung needs to behave differently to produce the sequencing observed in individual lobes.

Adult↗
PubMed1978

The relations between structural changes in small airways and pulmonary-function tests.

To examine the relation between small-airways abnormalities and specific lung functions, we performed pulmonary-function tests in 36 patients, of whom two were nonsmokers, one to three days before open-lung biopsy for localized pulmonary lesions. The primary lesion in the small airways was a progressive inflammatory reaction leading to fibrosis with connective-tissue deposition in the airway walls. Increase in disease in small airways correlated with deterioration in lung function. Lesions could be reliably detected (P less than 0.05) by tests for closing capacity, the volume at which air and helium flow ere equal (a test of airway caliber and elastic recoil), and the slope of phase III of the single-breath washout curve (which tests evenness of ventilation). These tests showed abnormalities at a time when the pathologic changes were still potentially reversible and when other tests were not appreciably changed.

Adult↗
PubMed1977

Influence of pericardial fluid on cardiogenic gas mixing in the lung.

Respirat. Environ. Exercise Physiol. 42(1): 5-12, 1977. -In eight open-chested dogs we measured the end-inspiratory N2 concentration within 12 airways, 2.5-8.3 mm in diameter during constant flow inflations with 0.5 liter of O2 before and after the introduction of saline into the pericardial sac. The critical flow rate necessary to achieve a given end-inspiratory FN2, as well as the maximal amplitude of cardiogenic N2 fluctuations, became smaller in the presence of pericardial fluid (PF). In the presence of only 25-50 ml of saline in the pericardium the effective diffusion coefficient, incorporating cardiogenic gas mixing, decreased by as much as 50-66%, respectively. Studies in two dogs with the chest intact showed that PF caused a qualitatively similar impairment of gas mixing during breath holding. Multiple-breath N2 washouts did not reflect the decreases in gas mixing produced by PF. We believe that PF decreases cardiogenic gas mixing mainly by protecting the lung from the rotational thrust of the heart during myocardial contraction.

Animals↗