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Effects of Intrathoracic Pressure changes on Diaphragmatic Blood Flow during Mechanical Ventilation
Author(s) -
Horn Andrew Gary,
Baumfalk Dryden R.,
Schulze Kiana Marie,
Colburn Trenton David,
Weber Ramona Elaine,
Kunkel Olivia Nicole,
Bruells Christian S.,
Musch Timothy I.,
Poole David C.,
Behnke Bradley Jon
Publication year - 2020
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2020.34.s1.07112
Subject(s) - medicine , diaphragm (acoustics) , anesthesia , blood flow , mechanical ventilation , perfusion , diaphragmatic breathing , positive end expiratory pressure , pneumothorax , lung , hemodynamics , cardiology , surgery , pathology , physics , alternative medicine , acoustics , loudspeaker
Although mechanical ventilation (MV) is a life‐saving intervention, prolonged MV can lead to deleterious effects on diaphragm function, such as ventilator‐induced diaphragmatic dysfunction (VIDD) and vascular incompetence. Specifically, prolonged MV elicits time‐dependent reductions in diaphragm blood flow, induces vascular dysfunction, and limits the hyperemic response to contractions associated with weaning. During MV, positive‐end expiratory pressure (PEEP) is used to maintain small airway patency and mitigate alveolar damage; yet increased intrathoracic pressure with high levels of PEEP may impair diaphragm perfusion. Purpose To test the following hypotheses: 1) Diaphragm blood flow during MV will be less with high vs. low‐peep, and 2) ablation of intrathoracic pressures (via pneumothorax (PTX)) will not alter diaphragm blood flow during MV vs. the low‐peep condition. Methods Female Sprague‐Dawley rats (~5 mo) were randomly divided into low PEEP (LP; 1cmH 2 O, n=7) or high PEEP (HP; 9 cmH 2 O, n=6) groups during mechanical ventilation. Blood flow, via the fluorescent microsphere technique, was determined during spontaneous breathing (SB) and 10 minutes after intubation and the onset of MV with LP or HP. Thereafter, for a third determination of diaphragm blood flow, the LP group underwent a surgical laparotomy (LAP; to determine effects of intrabdominal pressure on perfusion) and the HP group was subjected to a pneumothorax (PTX), with microsphere infusions occurring 10 minutes after the completion of surgery. Following the final fluorescent microsphere infusion, tissues were harvested for blood flow analysis. The diaphragm was sectioned into costal (ventral, medial, and dorsal) and crural portions to determine diaphragmatic blood flow distribution. Results Compared to SB, both LP and HP MV significantly reduced diaphragm medial costal blood flow (LP, 61.9 ± 7.5 vs 43.8 ± 4.9; HP, 46.2 ± 7.7 vs 21.8 ± 3.7 mL/100g/min; P≤0.05). HP MV significantly reduced blood flow to the ventral and medial costal diaphragm compared to LP MV (P≤0.05). In the HP MV+PTX condition, medial and dorsal costal blood flow was significantly increased versus HP MV (P≤0.05). LP MV + LAP did not significantly increase diaphragm blood flow compared to LP MV. Diaphragm perfusion during HP MV+PTX and LP MV were not different (P>0.05). Conclusion This study demonstrates that HP MV reduces diaphragmatic blood flow to a greater extent than LP MV. Following a PTX in the HP MV condition, diaphragmatic blood flow is not different compared to the LP MV condition, suggesting that the reductions in diaphragmatic blood flow with LP MV are independent of intrathoracic pressure changes, and due likely to diaphragm quiescence. Support or Funding Information Supported by: NIH HL137156‐01A1