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Effect of fixed value positive end expiratory pressure valves on canine thoracic volume and atelectasis
- Allison, A., Huizing, X., Jolliffe, C., Schaafsma, I.
- The journal of small animal practice 2017 v.58 no.11 pp. 645-651
- aeration, anesthesia, body condition, body weight, carbon dioxide, cost effectiveness, dogs, lungs, patients, respiratory rate
- OBJECTIVES: The objective of this study was to investigate whether a fixed 10 cm H₂O positive end‐expiratory pressure valve would increase the aeration of, and reduce atelectasis formation in, the lungs after induction of anaesthesia in dogs undergoing thoracic CT. MATERIALS AND METHODS: 28 dogs were paired based on breed, bodyweight and body condition score and then randomly allocated to either Group Z (0 cm H₂O) or Group P (10 cm H₂O positive end‐expiratory pressure valve) immediately after the induction of anaesthesia. All patients received a standardised anaesthetic protocol, and their lungs were manually hyperventilated before image acquisition. Cardiorespiratory parameters were recorded every 5 minutes. Total lung volume, lung density and degree of atelectasis were determined for each dog from the acquired images. RESULTS: The 10 cm H₂O positive end‐expiratory pressure valve significantly increased lung volume (mL/kg) (Group Z: 52 ±14; Group P: 83 ±17; P<0·001) whilst significantly reducing lung density (Hounsfield units) (Group Z: −775 ±30; Group P: −856 ±22; P<0·001) and the amount of atelectasis (P=0·004). Dogs in Group P had significantly higher end‐tidal carbon dioxide (P<0·05), but there was no difference between the groups for respiratory rate or any cardiovascular variable. CLINICAL SIGNIFICANCE: A fixed‐value positive end‐expiratory pressure valve provides a simple, cost‐effective technique for improving expiratory thoracic CT studies by increasing lung volume and decreasing atelectasis formation.