Respiratory Care

BACKGROUND: The clinical utility of measures of dyspnea has been debated in the health care community. Although breathlessness can be evaluated with various instruments, the most effective dyspnea measurement tool for patients with chronic lung disease or for measuring treatment effectiveness remains uncertain. Understanding the evidence for the validity and reliability of these instruments may provide a basis for appropriate clinical application. OBJECTIVE: Evaluate instruments designed to measure breathlessness, either as single-symptom or multidimensional instruments, based on psychometrics foundations such as validity, reliability, and discriminative and evaluative properties. Classification of each dyspnea measurement instrument will recommend clinical application in terms of exercise, benchmarking patients, activities of daily living, patient outcomes, clinical trials, and responsiveness to treatment. METHODS: Eleven dyspnea mea-surement instruments were selected. Each instrument was assessed as discriminative or evaluative and then analyzed as to its psychometric properties and purpose of design. RESULTS: Descriptive data from all studies were described according to their primary patient application (ie, chronic obstructive pulmonary disease, asthma, or other patient populations). The Borg Scale and the Visual Analogue Scale are applicable to exertion and thus can be applied to any cardiopulmonary patient to determine dyspnea. All other measures were determined appropriate for chronic obstructive pulmonary disease, whereas the Shortness of Breath Questionnaire can be applied to cystic fibrosis and lung transplant patients. The most appropriate utility for all instruments was measuring the effects on activities of daily living and for benchmarking patient progress. Instruments that quantify function and health-related quality of life have great utility for documenting outcomes but may be limited as to documenting treatment responsiveness in terms of clinically important changes. CONCLUSIONS: The dyspnea measurement instruments we studied meet important standards of validity and reliability. Discriminative measures have limited clinical utility and, when used for populations or conditions for which they are not designed or validated, the data collected may not be clinically relevant. Evaluative measures have greater clinical utility and can be applied for outcome purposes. Measures should be applied to the populations and conditions for which they were designed. The relationship between clinical therapies and the measurement of dyspnea as an outcome can develop as respiratory therapists become more comfortable with implementing dyspnea measurement instruments and use the data to improve patient treatment. Dyspnea evaluation should be considered for all clinical practice guidelines and care pathways.

BACKGROUND: Infants receiving mechanical ventilation require narrow-lumen, small-diameter endotracheal tubes. OBJECTIVE: Compare the resistances of endotracheal tubes used in the neonatal intensive care unit. METHODS: Endotracheal tubes of internal diameter 2.5, 3.0, 3.5, and 4.0 mm were tested with a standard neonatal ventilator and a test lung. An endotracheal tube of each diameter was cut to 12 cm and connected to a flow transducer at one end and the test lung at the other. Serial measurements of resistance were made at various flows (6, 8, 10, and 12 L/min) and ventilator rates (30-90 breaths/min) encompassing the ranges of clinical practice. Analysis of variance was performed for each tube size, comparing resistance to flows and ventilator rates. RESULTS: Resistance was significantly higher with the 2.5 mm tube than with the others. There was also a consistent trend, in all the tube sizes, towards higher resistance as flow was increased. CONCLUSIONS: The higher resistance of the 2.5 mm tube may be detrimental to extremely low birthweight infants kept on mechanical support merely "to grow." The higher resistance may increase the work of breathing and thus increase caloric expenditure and impede growth. [Respir Care 2002;47(9):994-997]

We report the case of a 42-year-old woman with Rendu-Osler-Weber syndrome (hereditary hemorrhagic telangiectasia) and a huge pulmonary arteriovenous fistula that involved the entire right middle lobe. She had a history of dyspnea and intermittent atrial flutter for 6 months. A chest radiograph showed a discrete shadowing of the middle part of the right lung. Arteriovenous fistula was suspected based on the echocardiographic finding of immediate bubble detection in the left atrium on introducing echocardiographic contrast medium into the venous system. Atrial shunt was excluded. Angiography revealed a huge pulmonary arteriovenous fistula in the entire middle lobe of the right lung. A trial of interventional embolization was performed, but the size of the fistula made it impossible to achieve complete closure of all segmental fistulas. Furthermore, the patient complained of unusual, severe chest pain after implantation of the first coil, so that the coil had to be removed. Therefore the patient underwent surgical resection of the entire right middle lobe and the upper part of the right lower lobe. Anatomy was clearly delineated and all connecting vessels were suture-closed, but both lungs showed diffuse microscopic superficial pulmonary arteriovenous fistulas, which were too small to be detected by angiography and which were also partly closed. The postoperative course was uneventful: the patient recovered completely, she no longer had shortness of breath, and blood gas analysis showed normal Pao₂. It is not clear whether the patient's improved physical performance will last, because the development of diffuse microscopic arteriovenous fistulas bilaterally in the lungs is not predictable. Therefore close follow-up is necessary and in the case of recurrence (ie, enlargement of the existing small fistulas), early interventional embolization should be performed.

Venoarterial extracorporeal membrane oxygenation (VA ECMO) has become a valuable technique in the critical care of children with congenital heart disease who require mechanical cardiorespiratory support. The use of VA ECMO in cardiac patients has expanded from an extension of intraoperative cardiopulmonary bypass and now includes rescue therapy during cardiopulmonary resuscitation, temporary circulatory support for reversible heart failure, and bridge support preceding heart or heart/lung transplantation. In the majority of clinical applications VA ECMO is used in reaction to impending or ongoing cardiorespiratory failure and not in anticipation of an induced change in clinical status. We describe the anticipatory use of VA ECMO to prepare a patient with complex cyanotic congenital heart disease for a high-risk interventional cardiac catheterization. A 2.5 kg neonate with severe Ebstein's anomaly of the tricuspid valve and recurrent episodes of life-threatening supraventricular tachycardia was electively cannulated for VA ECMO in the cardiac intensive care unit. She underwent successful electrophysiologic mapping and transcatheter radiofrequency ablation of an accessory conduction pathway, resulting in termination of the tachycardia. Following an uncomplicated ECMO course she was decannulated in the cardiac intensive care unit and subsequently discharged home in stable condition. The case illustrates the proactive use of ECMO during a procedure in which severe hemodynamic instability could be predicted. We discuss this concept of ECMO use in the context of accepted indications for ECMO in cardiac patients and encourage an expanded role for its use to prevent cardiorespiratory collapse in planned interventions on compromised patients who are at risk of acute deterioration.

Many technologic and management strategies related to mechanical ventilation have been introduced in recent years. Strategies that avoid intubation and get patients extubated sooner decrease costs related to mechanical ventilation. In general, "people" solutions such as weaning protocols are preferable to "technology" solutions such as new ventilator modes. It must be remembered that mechanical ventilation is supportive—it is not curative—and has the potential to do harm if applied incorrectly. There is an increasing list of examples in which short-term physiologic outcomes such as improvements in blood gas values are not related to patient-important outcomes such as survival. When new mechanical ventilation technology and strategies are introduced, a question we need to ask ourselves is whether these are solutions for problems or whether these are simply solutions in search of problems.