Tag Archives: hypocapnia

Closing Capacity and Gas Exchange in Chronic Heart Failure: Dyspnea

A possible explanation for the finding of increased central drive without a decrease in the VT would be the difference in operational length compensation of the diaphragm. Patients with CHF have smaller lungs and longer resting length of their diaphragms, which results in greater force generation for the same output during quiet breathing. This implies greater inspiratory effort with weaker inspiratory muscles, leading to an increased Borg dyspnea score at rest.
Continue reading

Closing Capacity and Gas Exchange in Chronic Heart Failure: CC and Gas Exchange

Closing Capacity and Gas Exchange in Chronic Heart Failure: CC and Gas ExchangeThere also was no significant difference in CC between CHF patients and control subjects, indicating that in our CHF patients there was “no premature airway closure.” In fact, in CHF patients the CC was actually smaller than that in control subjects, although not significantly. This may reflect the fact that pulmonary fibrosis and/or vascular engorgement- may render the peripheral airways more resistant to collapse. In line with the findings of Collins et al, however, in most of our patients (13 of 20) the CC exceeded the FRC (ie, during tidal breathing there was cyclic opening and closing of peripheral airways with a concurrent maldistribution of ventilation and a risk of mechanical injury to the peripheral airways). As a result of this maldistribution of ventilation, Pa02 decreased and P(A-a)O2 increased (Table 4). review

Continue reading

Closing Capacity and Gas Exchange in Chronic Heart Failure: Lung Volumes

In line with the results of most previous re-ports,’’ our patients exhibited a reduction in TLC and FRC but normal FEV1/FVC ratio. In contrast, Yap et al found a significant reduction in TLC but not in FRC. Their patients, however, were studied just after a period of acute decompensation, which may be associated with the presence of FL and dynamic hyperinflation with the patient in the sitting position. Hart et al found no reduction of either TLC or FRC in 10 CHF patients; half of their patients, however, had CHF due to coronary artery disease. In the present study, only 30% of the patients (6 of 20) had a history of coronary artery disease. cfp-for-you.com

Continue reading

Closing Capacity and Gas Exchange in Chronic Heart Failure: Research

Closing Capacity and Gas Exchange in Chronic Heart Failure: ResearchResting ventilation and P01 were higher in CHF patients than in control subjects (Table 4), with the increase of minute ventilation (Ve) resulting from increased respiratory frequency (fR). While the tidal volume (VT)/inspiratory time (Ti) ratio was significantly higher in CHF patients (reflecting the higher P01), Tl/total breathing cycle time (Ttot) ratio was the same in CHF patients and control subjects. The P01/Plmax ratio (percentage) was, on average, more than twice as large in CHF patients as in control subjects, reflecting in part the increased P0.1 and in part the decreased Plmax. As a result of the increased VE, the PaC02 was lower in CHF patients than in control subjects.

Continue reading

Closing Capacity and Gas Exchange in Chronic Heart Failure: Results

Table 1 provides the anthropometric characteristics and baseline respiratory data for control subjects and CHF patients. In the control subjects, all baseline respiratory data were within normal limits; the MRC and Borg scores were zero, while the CHF patients exhibited slightly higher levels of MRC and Borg dyspnea scores.
In CHF patients, the FEV1/FVC ratio was within normal limits, while TLC and its subdivisions were reduced. This is also shown in Figure 1, where, for comparative purposes, volumes are expressed as the percentage of the predicted TLC. There were no significant differences in lung function between nonsmokers and ex-smokers in both CHF patients and control subjects, except for RV (percent predicted), which in control subjects was significantly (p < 0.05) lower in nonsmokers than in ex-smokers (Table 2). further

Continue reading

Closing Capacity and Gas Exchange in Chronic Heart Failure: Statistical Analysis

Closing Capacity and Gas Exchange in Chronic Heart Failure: Statistical AnalysisBreathing pattern and mouth occlusion pressure 100 ms after onset of inspiratory effort (P0.1), maximal inspiratory pressure (Plmax), CV, CC, and alveolar plateau slope (AN2) were measured (VMAX 229; SensorMedics), as previously described. The Pimax was measured at RV according to American Thoracic Society/ERS criteria with predicted values obtained from Black and Hyatt.
The CV and AN2 were measured in triplicate by a single-breath N2 test with the mean taken as the final value. The CV was expressed in liters or as the percentage of VC measured during the single-breath exhalation. By adding RV to CV, the CC (in liters) was obtained and was also expressed as the percentage of total lung capacity (TLC) [ie, CC/TLC ratio]. Predicted CV/VC and CC/TLC ratios were obtained from Buist and Ross. From these predicted ratios, the predicted values of CV and CC (in liters) were computed using predicted values of VC and TLC, respectively. other
Continue reading

Closing Capacity and Gas Exchange in Chronic Heart Failure: Experimental Protocol

Within 1 month prior to entering our study, Weber class was determined by cardiopulmonary exercise testing: Weber class B, 7 patients; Weber class C, 10 patients; and Weber class D, 3 patients. Heart failure was defined as symptomatic left ventricular dysfunction, with a left ejection fraction of < 0.45 documented by bidimensional echocardiography. Patients were excluded if they had primary pulmonary, neurologic, or myopathic disease. The echocardiographic ejection fraction and systolic pulmonary artery pressure (sPAP) were measured within the 2 weeks preceding entry into our study. The mean ejection fraction was 23% (range, 9 to 34%) [Table 1]. Twenty healthy subjects (control subjects) who were matched for sex and age were also studied with the same protocol as for the CHF patients. All control subjects were nonsmokers, but nine patients were ex-smokers (Table 1). The study was approved by the local ethics committee, and informed consent was obtained from each subject. add comment
Continue reading

Closing Capacity and Gas Exchange in Chronic Heart Failure

Closing Capacity and Gas Exchange in Chronic Heart FailureCollins et al reported that the ratio of closing volume (CV) to vital capacity (VC) was increased in patients with chronic heart failure (CHF), and suggested that pulmonary congestion and edema promote peripheral airway closure. This is in line with the study by Hughes and Rosenzweig, who showed that in isolated perfused dog lungs the volume of trapped gas increased with increased lung water and was greater in the more dependent parts of the lung in which interstitial pulmonary edema was most prominent on histologic examination. They postulated that enhanced air trapping was caused by premature peripheral airway closure due to the presence of cuffs of edema fluid in the loose connective tissue around the extraalveolar peripheral airways before there was any significant change in alveolar wall thickness. An increase in the CV/VC ratio, however, can be due to an increase in CV and/or a decrease in VC. read

Continue reading