Resp Care
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Tracheal gas insufflation (TGI) is the continuous or phasic insufflation of fresh gas into the central airways for the purpose of improving the efficiency of alveolar ventilation and/or minimizing the ventilatory pressure requirements. Fresh gas is insufflated near the main carina, usually at flow rates of 2-15 L/min. During expiration, TGI clears the anatomic and apparatus dead space proximal to the catheter tip, thus improving carbon dioxide (CO2) clearance. ⋯ At that point, increasing catheter flow rate decreases PaCO2 much less, probably because of turbulent mixing in the airways distal to the catheter tip. In clinical practice, TGI can be applied either to decrease PaCO2 while maintaining tidal volume constant or to decrease tidal volume while keeping PaCO2 constant. In the former strategy, TGI is used to protect pH, whereas in the latter it is used to minimize the stretch forces acting on the lung parenchyma, to minimize ventilator-associated lung injury.
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Case Reports
Lung collapse during low tidal volume ventilation in acute respiratory distress syndrome.
Current ventilator management for acute respiratory distress syndrome (ARDS) incorporates low tidal volume (V(T)) ventilation in order to limit ventilator-induced lung injury. Low V(T) ventilation in supine patients, without the use of intermittent hyperinflations, may cause small airway closure, progressive atelectasis, and secretion retention. Use of high positive end-expiratory pressure (PEEP) levels with low V(T) ventilation may not counter this effect, because regional differences in intra-abdominal hydrostatic pressure may diminish the volume-stabilizing effects of PEEP. ⋯ Low V(T) ventilation in ARDS may increase the risk of small airway closure and retained secretions. This adverse effect highlights the importance of pulmonary hygiene measures in ARDS during lung-protective ventilation.
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Meta Analysis
2000 Donald F. Egan Scientific Lecture. Are respiratory therapists effective? Assessing the evidence.
In the current cost-attentive health care climate, the effectiveness of various providers in delivering care is being examined closely. To evaluate the effectiveness of respiratory therapists (RTs) in delivering respiratory care in the intensive care unit (ICU), in adult non-ICU inpatient care, and in ambulatory care, this 27th Egan Lecture presents a systematic review of the available literature examining RTs' effectiveness in these settings. Overall, available studies support the effectiveness of RTs in providing care in various roles in all clinical venues, with the strongest evidence based on the results of concordant randomized controlled clinical trials. ⋯ Lower levels of evidence support RTs' roles in performing intubation, placing indwelling arterial lines, performing mini-bronchoalveolar lavage, allocating arterial blood gases, and in various counseling and teaching roles. Notwithstanding the considerable body of available evidence that buttresses RTs' effectiveness in delivering care, additional rigorously designed studies are needed to examine RTs' effectiveness in new roles (eg, geriatric care, pediatric care), in new venues (eg, extended care facilities), and to assure the generalizability of available findings to the broad spectrum of health care facilities (eg, academic and community-based facilities alike). Finally, the respiratory therapy community must continue to cultivate and suppport investigative expertise to assure continued inquiry.
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Weaning of mechanical ventilation in patients optimally includes meeting their needs by making frequent ventilator adjustments. The Siemens Servo 300A mechanical ventilator is designed to allow the ventilator to be interactive with the patient's needs by making breath-by-breath adjustments in both control and support modes. We undertook the following experiment to validate that the Automode algorithm responded appropriately using a pediatric animal model when apnea occurred and if there was any impact on work of breathing. ⋯ The Automode algorithm performed as expected in this animal experiment. We conclude that differences in response time and negative deflection of pressure, as an indication of animal effort, and maximum flow reached were due to continued weakness from the neuro-muscular blocker. However, the ventilator continued to trigger despite decreased effort by the animal.