The American review of respiratory disease
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Am. Rev. Respir. Dis. · Feb 1990
Randomized Controlled Trial Comparative Study Clinical TrialBreath-stacking increases the depth and duration of chest expansion by incentive spirometry.
Although the objective of incentive spirometry is to achieve and hold high lung volumes, many patients with pain or weakness are unable to sustain the effort needed to perform effective exercises. We questioned whether using a one-way valve to prevent exhalation would allow rest between inspiratory efforts and cause volume to cumulate during successive tidal efforts, improving both the depth and duration of the inspiratory maneuver. We studied 26 cooperative but naive patients recovering from surgery, trauma, or critical illness whose pain or weakness impaired ability to achieve and sustain deep inspiration. ⋯ When compared with IC, "breath stacking" (valved) maneuvers increased inspired volume by an average of 15 to 20% (p less than 0.05). More importantly, there was a severalfold increase in the time over which high lung volume was sustained (p less than 0.001). Our results indicate that one-way valving helps to achieve and sustain deep inspiration, even in uncoached patients.
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Am. Rev. Respir. Dis. · Feb 1990
Comparative StudyLung microvascular transport properties measured by multiple indicator dilution methods in patients with adult respiratory distress syndrome. A comparison between patients reversing respiratory failure and those failing to reverse.
We conducted indicator dilution studies on the lungs of patients in the early phases of adult respiratory distress syndrome (ARDS) to test the hypothesis that capillary permeability was increased in patients with respiratory failure. Indicator dilution studies were performed using 51Cr-erythrocytes, 125I-albumin, 14C-urea, and 3H-water as tracers. The injectate was infused as a bolus into a central venous line. ⋯ Linear regression analysis showed significant correlations for all of the following in the nonreversal group: Ve and all measures of permeability, pulmonary vascular resistance (PVR), and the inverse of permeability-surface area measures and AaDO2 and PVR. Only measures of Ve and PS correlated in the reversal group. These results support the hypothesis that capillary permeability is increased in patients with early ARDS and continuing respiratory failure.(ABSTRACT TRUNCATED AT 250 WORDS)
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Am. Rev. Respir. Dis. · Feb 1990
Comparative StudyVentilatory muscle loads and the frequency-tidal volume pattern during inspiratory pressure-assisted (pressure-supported) ventilation.
Pressure support ventilation (PSV) is a new form of mechanical ventilatory support that assists a patient's spontaneous ventilatory effort with a clinician-selected amount of inspiratory pressure. In order to assess the muscle unloading effect and the ventilatory pattern response to increasing levels of this inspiratory pressure assist, we first utilized a computer respiratory system model with variable alveolar ventilation demands and impedances. From this model, we calculated ventilatory muscle loads (expressed either as the work/min or as the pressure time index) during simulated, unassisted breathing and during simulated breathing with levels of inspiratory pressure assist up to that which resulted in a VT of 800 ml and no work being performed by the muscles (defined as PSVmax for the model conditions being studied). ⋯ Specifically, at low levels of inspiratory pressure assist, the model predicted that the applied pressure would only partially unload the ventilatory muscles. Continued muscle energy expenditure would thus still be required, whereas the ventilatory pattern would change little. Conversely, at higher levels of inspiratory pressure assist, the model predicted that the applied pressure would be sufficient to completely unload the ventilatory muscles.(ABSTRACT TRUNCATED AT 250 WORDS)
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Am. Rev. Respir. Dis. · Feb 1990
Comparative StudyContinuous positive airway pressure reduces work of breathing and dyspnea during weaning from mechanical ventilation in severe chronic obstructive pulmonary disease.
Dynamic hyperinflation and the development of intrinsic positive end-expiratory pressure (PEEPi) are commonly observed in patients with severe chronic obstructive pulmonary disease (COPD) and acute respiratory failure. The presence of intrinsic PEEP acts as an inspiratory threshold load, and contributes significantly to the observed increase in work and oxygen cost of breathing. The present study examined the effects of continuous positive airway pressure (CPAP) (at 5, 10, and 15 cm H2O) and its ability to reduce the mechanical load imposed by PEEPi on breathing pattern, work of breathing, and dyspnea in seven patients with severe COPD during weaning from mechanical ventilation. ⋯ Similar progressive reductions were also obtained in the pressure-time product for the inspiratory muscles and the diaphragm, which amounted to decreases of 42.9 and 42.2%, respectively, at the highest level of CPAP. End-expiratory lung volume remained stable at the lowest level of CPAP, with only modest increases occurring at the higher levels. In addition, all patients reported a reduction in dyspnea during the administration of CPAP.(ABSTRACT TRUNCATED AT 250 WORDS)