Conventional Approaches

Although heated humidifiers are considered the most efficient humidification devices for mechanical ventilation, endotracheal tube occlusion caused by dry secretions has been reported with heated-wire humidifiers. To evaluate whether inlet chamber temperature, influenced by ambient air and ventilator output temperatures, may affect humidifier performance, Lellouche and coworkers measured hygrometry with three different humidifiers under several conditions, varying ambient air temperatures (high, 28–30°C, and normal, 22–24°C), ventilators with different gas temperatures, and 2-minute ventilation levels. Clinical measurements were performed to confirm bench measurements. Humidifier performance was strongly correlated with inlet chamber temperature in both the bench (p < 0.0001, r² = 0.93) and the clinical study. With unfavorable conditions, absolute humidity of inspired gas was much lower than recommended ( $~$ 20 mg H₂O/L). Performance was improved by specific settings or new compensatory algorithms. Hygrometry could be evaluated from condensation on the wall chamber only when ambient air temperature was normal but not with high air temperature. Increase in inlet chamber temperature induced by high ambient temperature markedly reduced the performance of heated-wire humidifiers, leading to a risk of endotracheal tube occlusion. The authors concluded that such systems should be avoided in these conditions unless automatic compensation algorithms are used.

To determine the level of understanding of mechanical ventilation among internal medicine residents, Cox and coworkers administered a 19-question examination to 259 residents at 31 residency programs. The average score on the test was 74% correct (range, 37 to 100%). Most residents correctly identified tension pneumothorax (86% correct) and clinical findings suggestive of severe hypotension secondary to auto positive end-expiratory pressure (intrinsic PEEP) (93% correct). High rates of incorrect answers were found for the setting of tidal volume in patients with the acute respiratory distress syndrome (ARDS) (48% incorrect), identifying whether a patient was ready for a weaning trial (38% incorrect), and recognizing an indication for noninvasive ventilation (27% incorrect). Higher scores were associated with closed-unit versus open-unit organization (76 versus 71% correct), resident perception of greater versus lesser knowledge (79 versus 71% correct), and graduation from a U.S. versus a foreign medical school (75 versus 69% correct). Only 46% of residents were satisfied with their training in mechanical ventilation. The authors conclude that residents in internal medicine programs may not be gaining knowledge essential for providing care to patients requiring mechanical ventilation. An editorial commentary by Dunn accompanies this article.

In nine patients with neuromuscular disease receiving mechanical ventilation through a cuffless tracheostomy, Prigent and coworkers compared the effect of assist-control ventilation and bilevel positive-pressure ventilation (pressure support and PEEP) on speech production. At rest, breathing pattern was equivalent with the two modes. Speech was accompanied by a 20% increase in inspiratory time during bilevel ventilation but not during assist-control ventilation. The volume released by the ventilator during speech was greater with bilevel ventilation than during assist-control ventilation: 172 versus 26 ml. The maximum duration of speech (as a fraction of a respiratory cycle) was greater with bilevel ventilation than with assist-control ventilation: 74 versus 39%. Speech continued into expiration with bilevel ventilation and three patients were able to speak continuously during several respiratory cycles. Comfort during speech was greater with bilevel ventilation. The authors conclude that the duration of speech during a respiratory cycle was greater during bilevel positive-pressure ventilation (pressure support and PEEP) than during assist-control ventilation. An editorial commentary by Hoit and Banzett accompanies this article.

Citations 1-5 of 5 total displayed.

Influence of Ambient and Ventilator Output Temperatures on Performance of Heated-Wire Humidifiers

François Lellouche, Solenne Taillé, Salvatore M. Maggiore, Siham Qader, Erwan L'Her, Nicolas Deye, and Laurent Brochard
Am. J. Respir. Crit. Care Med. 170: 1073 -1079. First published online as doi:10.1164/rccm.200309-1245OC [Abstract] [Full text]

Je Peux Parler!

Jeannette D. Hoit and Robert B. Banzett
Am. J. Respir. Crit. Care Med. 167: 101-102. [Full text]

Comparative Effects of Two Ventilatory Modes on Speech in Tracheostomized Patients with Neuromuscular Disease

Hélène Prigent, Christiane Samuel, Bruno Louis, Marie-France Abinun, Françoise Zerah-Lancner, Michèle Lejaille, Jean-Claude Raphael, and Frédéric Lofaso
Am. J. Respir. Crit. Care Med. 167: 114 -119. First published online as doi:10.1164/rccm.200201-026OC [Abstract] [Full text]

Education Theory Applied to Critical Care: Dewey versus Tradition: It Really Does Matter

William F. Dunn
Am. J. Respir. Crit. Care Med. 167: 4-5. [Full text]

Effectiveness of Medical Resident Education in Mechanical Ventilation

Christopher E. Cox, Shannon S. Carson, E. Wesley Ely, Joseph A. Govert, Joanne M. Garrett, Roy G. Brower, David G. Morris, Edward Abraham, Vincent Donnabella, Antoinette Spevetz, and Jesse B. Hall
Am. J. Respir. Crit. Care Med. 167: 32 -38. First published online as doi:10.1164/rccm.200206-624OC [Abstract] [Full text]

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