ObjectiveTo evaluate the possible changes in tidal volume, minute volume and
respiratory rate caused by the use of a heat and moisture exchanger in
patients receiving pressure support mechanical ventilation and to quantify
the variation in pressure support required to compensate for the effect
caused by the heat and moisture exchanger.MethodsPatients under invasive mechanical ventilation in pressure support mode were
evaluated using heated humidifiers and heat and moisture exchangers. If the
volume found using the heat and moisture exchangers was lower than that
found with the heated humidifier, an increase in pressure support was
initiated during the use of the heat and moisture exchanger until a pressure
support value was obtained that enabled the patient to generate a value
close to the initial tidal volume obtained with the heated humidifier. The
analysis was performed by means of the paired t test, and
incremental values were expressed as percentages of increase required.ResultsA total of 26 patients were evaluated. The use of heat and moisture
exchangers increased the respiratory rate and reduced the tidal and minute
volumes compared with the use of the heated humidifier. Patients required a
38.13% increase in pressure support to maintain previous volumes when using
the heat and moisture exchanger.ConclusionThe heat and moisture exchanger changed the tidal and minute volumes and
respiratory rate parameters. Pressure support was increased to compensate
for these changes.
Background: Mechanical ventilation can injure lung tissue and respiratory muscles. The aim of the present study is to assess the effect of the amount of spontaneous breathing during mechanical ventilation on patient outcomes.Methods: This is an analysis of the database of the 'Medical Information Mart for Intensive Care (MIMIC)'-III, considering intensive care units (ICUs) of the Beth Israel Deaconess Medical Center (BIDMC), Boston, MA. Adult patients who received invasive ventilation for at least 48 hours were included.Patients were categorized according to the amount of spontaneous breathing, i.e., ≥50% ('high spontaneous breathing') and <50% ('low spontaneous breathing') of time during first 48 hours of ventilation. The primary outcome was the number of ventilator-free days.Results: In total, the analysis included 3,380 patients; 70.2% were classified as 'high spontaneous breathing', and 29.8% as 'low spontaneous breathing'. Patients in the 'high spontaneous breathing' group were older, had more comorbidities, and lower severity scores. In adjusted analysis, the amount of spontaneous breathing was not associated with the number of ventilator-free days [20.0 (0.0-24.2) vs. 19.0 (0.0-23.7) in high vs. low; absolute difference, 0.54 (95% CI, -0.10 to 1.19); P=0.101]. However, 'high spontaneous breathing' was associated with shorter duration of ventilation in survivors [6.5 (3.6 to 12.2) vs. 7.6 (4.1 to 13.9); absolute difference, -0.91 (95% CI, −1.80 to −0.02); P=0.046].
Conclusions:In patients surviving and receiving ventilation for at least 48 hours, the amount of spontaneous breathing during this period was not associated with an increased number of ventilator-free days.
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