Pleural Pressure Targeted Positive Airway Pressure Improves Cardiopulmonary Function in Spontaneously Breathing Patients With Obesity

Airway Closure in Patients With Cardiogenic Pulmonary Edema as a Cause of Driving Pressure Overestimation: The "Uncorking Effect"

Airway closure is an underestimated phenomenon reported in hypoxemic respiratory failure under mechanical ventilation, during cardiac arrest, and in patients who are obese. Because airway and alveolar pressure are not communicating, it leads to an overestimation of driving pressure and an underestimation of respiratory system compliance. Airway closure also favors denitrogenation atelectasis. To date, it has been described mainly in patients with ARDS and those with obesity. We describe three cases of airway closure in patients with hydrostatic pulmonary edema caused by cardiogenic shock, highlighting its resolution in a limited period of time (24 h) as pulmonary edema resolved. The waveforms show a biphasic reopening that we refer to as the "uncorking effect". The detection of airway closure may require setting positive end-expiratory pressure at or above the airway opening pressure to avoid the overestimation of driving pressure.

Anesthesia Machine and New Modes of Ventilation

Mechanical ventilation is ubiquitous in the operating room. This article explores the anesthesia machine as a ventilator, examining its unique features and differences from ventilators designed for long-term use. It will describe standard and nonstandard modes of ventilation. The reader will develop a more nuanced understanding of how to tailor ventilation and oxygenation strategies based on patient and anesthetic scenarios as well as with the assistance of new technologies.

Retrospective Review of Transpulmonary Pressure Guided Positive End-Expiratory Pressure Titration for Mechanical Ventilation in Class II and III Obesity

OBJECTIVES

Acute respiratory distress syndrome is treated by utilizing a lung protective ventilation strategy. Obesity presents with additional physiologic considerations, and optimizing ventilator settings may be limited with traditional means. Transpulmonary pressure (PL) obtained via esophageal manometry may be more beneficial to titrating positive end-expiratory pressure (PEEP) in this population. We sought to determine the feasibility and impact of implementation of a protocol for use of esophageal balloon to set PEEP in obese patients in a community ICU.

DESIGN

Retrospective cohort study of obese (body mass index [BMI] ≥ 35 kg/m2) patients undergoing individualized PEEP titration with esophageal manometry. Data were extracted from electronic health record, and Wilcoxon signed rank test was performed to determine whether there were differences in the ventilatory parameters over time.

SETTING

Intensive care unit in a community based hospital system in Newark, Delaware.

PATIENTS

Twenty-nine mechanically ventilated adult patients with a median BMI of 45.8 kg/m2 with acute respiratory distress syndrome (ARDS).

INTERVENTION

Individualized titration of PEEP via esophageal catheter obtained transpulmonary pressures.

MEASUREMENTS AND MAIN RESULTS

Outcomes measured include PEEP, oxygenation, and driving pressure (DP) before and after esophageal manometry at 4 and 24 hr. Clinical outcomes including adverse events (pneumothorax and pneumomediastinum), increased vasopressor use, rescue therapies (inhaled pulmonary vasodilators, extracorporeal membrane oxygenation, and new prone position), continuous renal replacement therapy, and tracheostomy were also analyzed. Four hours after PEEP titration, median PEEP increased from 12 to 20 cm H2O (p < 0.0001) with a corresponding decrease in median DP from 15 to 13 cm H2O (p = 0.002). Subsequently, oxygenation improved as median Fio2 decreased from 0.8 to 0.6 (p < 0.0001), and median oxygen saturation/Fio2 (S/F) ratio improved from 120 to 165 (p < 0.0001). One patient developed pneumomediastinum. No pneumothoraces were identified. Improvements in oxygenation continued to be seen at 24 hr, compared with the prior 4 hr mark, Fio2 (0.6-0.45; p < 0.004), and S/F ratio (165-211.11; p < 0.001). Seven patients required an increase in vasopressor support after 4 hours. Norepinephrine and epinephrine were increased by 0.05 (± 0.04) µg/kg/min and 0.02 (± 0.01) µg/kg/min on average, respectively.

CONCLUSIONS

PL-guided PEEP titration in obese patients can be used to safely titrate PEEP and decrease DP, resulting in improved oxygenation.