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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: OBJECTIVE, METHODS, RESULTS. Meshes: Animals, Blood Gas Analysis, Disease Models, Animal, Extravascular Lung Water, Heart Failure, Sheep, Sleep Apnea, Central, Ventricular Dysfunction, Left.
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Does increased lung water without hypocapnia cause central sleep apnoea in a lamb model? Context: Central sleep apnoea (CSA) in patients with heart failure is associated with an extremely poor prognosis. It is unclear as to whether pulmonary congestion contributes to CSA. We developed a sheep model of congestive cardiac failure (CCF) to address the question of whether pulmonary congestion without hypocapnia could cause CSA. Fourteen lambs were given CCF by overdrive pacing for 3 weeks. CCF was defined by a pulmonary artery occlusion pressure (PAOP) > or = 15 mmHg. There were 11 controls. Extravascular lung water (EVLW) was measured by the double indicator dilution method. The CCF lambs had a PAOP = 18 +/- 3 mmHg and controls had a PAOP = 10 +/- 2 mmHg (P < 0.01). EVLW was 12.6 +/- 1.8 (CCF) compared to 8.9 +/- 2 mL/kg (controls) (P < 0.01). The respiratory rate was 74 +/- 21 b.p.m. (CCF) compared to 47 +/- 6 b.p.m. (controls) (P < 0.05). Acute volume loading with saline raised PAOP without changing respiration. pH and PaCO(2) were the same in both groups (PaCO(2)-37 mmHg).
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These results support the view that hypocapnia is essential for CSA, and demonstrated that increased EVLW causes tachypnoea but not CSA. Final Decision: no