Renoprotective effects of continuous positive airway pressure in chronic kidney disease patients with sleep apnea.

Purpose: Chronic kidney disease (CKD) is associated with a high incidence of obstructive sleep apnea (OSA). We assessed the effect of continuous positive airway pressure (CPAP) on renal function in patients with CKD and OSA.

Methods: In this retrospective cohort study, 42 patients with Stage 3-5 CKD and OSA were stratified into two groups: patients who use CPAP more (average >4 h/night on >70 % of nights) and patients who use CPAP less (average ≤4 h/night on ≤70 % of nights).

Continuous positive airway pressure versus continuous negative pressure around the chest for patients with acute exacerbation of chronic obstructive pulmonary disease in the intensive care unit: a pilot study.

Introduction: With chronic obstructive pulmonary disease (COPD) exacerbations, continuous positive airway pressure (CPAP) has been used to overcome the threshold load provided by intrinsic positive end expiratory pressure and decrease the inspiratory work of breathing. In this pilot study, we observed whether a continuous negative pressure (CNP) around the thorax and upper abdomen with a shell and wrap would provide a similar level of relief in dyspnoea.

Methods: In eight patients with COPD in the intensive care unit receiving CPAP, CNP was alternated twice with CPAP (30 minutes each time).

Use of continuous negative pressure around the chest increases exercise performance in chronic obstructive pulmonary disease patients: a pilot study.

Background: Patients with severe chronic obstructive pulmonary disease (COPD) often have intrinsic positive end-expiratory pressure. Continuous positive airway pressure has been shown to decrease the inspiratory work of breathing and increases exercise capacity in these patients.

Objective: To determine whether continuous negative pressure (CNP) around the chest is able to bring the positive end-expiratory pressure closer to atmospheric pressure, thereby reducing the threshold load and increasing exercise capability.

Non-invasive method for the rapid assessment of central venous pressure: description and validation by a single examiner.

Objectives: This study describes a means of assessing the external jugular venous pressure (JVP) as an indicator of normal or elevated central venous pressure (CVP).

Methods: Intensive care unit patients having CVP monitoring were examined. With patients in bed, the external jugular vein (EJV) was occluded at the base of the neck and observed to distend.

Use of negative extrathoracic pressure to improve hemodynamics after cardiac surgery.

Background: Little attention is given to the mode of mechanical ventilation after cardiac surgery. Positive pressure ventilation with positive end-expiratory pressure (PEEP) has been shown to reduce cardiac output. We hypothesized that positive pressure ventilation with continual negative pressure applied to the chest through a cuirass would increase cardiac output in coronary artery bypass graft patients immediately after surgery.

Hemodynamic differences between continual positive and two types of negative pressure ventilation.

In seven anesthetized dogs, ventilated with matching lung volumes, tidal volumes, and respiratory rates, we compared the effects on cardiac output (CO), arterial venous oxygen saturation difference (SaO2 - SVO2), and femoral and inferior vena cava pressure (1) intermittent positive pressure ventilation with positive end-expiratory pressure (CPPV); (2) iron-lung ventilation with negative end-expiratory pressure (ILV-NEEP); (3) grid and wrap ventilation with NEEP applied to the thorax and upper abdomen (G&W-NEEP). The values of CO and SaO2 - SVO2 with ILV-NEEP were similar to those with CPPV. However, with G&W-NEEP as compared with ILV-NEEP, mean CO was greater (2.

Hemodynamic effects of lobar pulmonary artery occlusion in a porcine sepsis model.

We induced severe pulmonary hypertension and acute lung injury in 6 pigs by Pseudomonas aeruginosa infusion. We studied the effect of pulmonary artery catheter inflation of a pulmonary artery catheter balloon in the left lower lobar pulmonary artery was accompanied by a significant (p less than 0.05, paired t test) increase in pulmonary artery pressure, a decrease in left atrial pressure, a decrease in cardiac output, and a decrease in mean arterial pressure.

Hemodynamic effects of continuous negative chest pressure ventilation in heart failure.

We have previously shown improved cardiac output (QT) with external continuous negative-pressure ventilation (CNPV) compared with continuous positive-pressure ventilation (CPPV) in dogs with low pressure pulmonary edema (1). The current study was done to determine if this effect was reversed in high pressure pulmonary edema. Seven supine, anesthetized dogs were fluid-loaded and treated with disopyramide (3.

Tracheal mucus clearance in high-frequency oscillation: effect of peak flow rate bias.

We have reported previously that high-frequency oscillation of the chest wall (HFO/CW) enhances the tracheal mucus clearance rate (TMCR) in dogs. This enhancement of TMCR may be due in part to the expiratory bias in peak flow rate (VE/VI greater than 1) that occurs during HFO/CW. We examined this factor in 8 anaesthetized, spontaneously breathing dogs by comparing TMCR during the following manoeuvers: 1) HFO/CW, applied by means of a thoracic cuff; 2) symmetric high-frequency oscillation via the airway opening (HFO/AO), applied by means of a piston pump driven by sinusoidal signal; 3) HFO/AO with an expiratory bias in peak flow, and 4) HFO/AO with an inspiratory bias in peak flow.

Clapping or percussion causes atelectasis in dogs and influences gas exchange.

We examined the effects of 10 min of lower lateral chest wall percussion with a mechanical percussor or hand clapping in groups of anesthetized, paralyzed, and ventilated supine dogs. Mechanical percussion was applied at 10-16 Hz and caused an esophageal pressure swing (delta Pes) of 10-17 cmH2O. Hand clapping was applied at 4-7 Hz and caused a delta Pes of 6-17 cmH2O.

Effect of negative-pressure ventilation on lung water in permeability pulmonary edema.

We have previously shown (Am. Rev. Respir.

Hemodynamic effects of external continuous negative pressure ventilation compared with those of continuous positive pressure ventilation in dogs with acute lung injury.

Patients with noncardiogenic pulmonary edema requiring ventilatory assistance are usually supported with CPPV using positive end-expiratory pressure (PEEP), but CPPV requires endotracheal intubation and may decrease cardiac output (QT). The purpose of this study was to examine thoracoabdominal continuous negative pressure ventilation (CNPV) using external negative end-expiratory pressure (NEEP). The effects on gas exchange and hemodynamics were compared with those of CPPV with PEEP, with the premise that CNPV might sustain venous return and improve QT.

Position may reduce or stop pneumothorax formation in dogs receiving mechanical ventilation.

We have previously shown that in dogs with normal lungs, dependent placement of the puncture site reduced and/or stopped pneumothorax formation while breathing spontaneously. This experiment is now repeated in an acute injury model in dogs receiving either intermittent positive pressure ventilation (IPPV) or continuous positive pressure ventilation (CPPV). Pneumothorax was induced by percutaneous transthoracic insertion of a 20-gauge needle into the right lung.

Misleading "pulmonary wedge pressure" after pneumonectomy: its importance in postoperative fluid therapy.

Patients who have undergone pneumonectomy are reported to be at increased risk of serious pulmonary edema. Monitoring fluid therapy using the Swan-Ganz balloon-tipped catheter is therefore important in the perioperative management of these patients. Pulmonary artery occlusion pressure (PAOP), determined by inflating a balloon to occlude a branch of the pulmonary artery, is routinely used to measure pulmonary wedge pressure (PWP).

High-frequency chest wall oscillation. Assistance to ventilation in spontaneously breathing subjects.

In five supine normal subjects breathing spontaneously, we studied the effects of high-frequency chest wall oscillation (HFCWO), which was achieved by oscillating the pressure in an air-filled cuff wrapped around the lower thorax. Oscillations of 3.5 and 8 Hz (in randomized order) were applied for 15 minutes each at both maximal (mean of 90 to 102 cm H2O) and half-maximal peak tolerable cuff pressures.

Wedge pressure in large vs. small pulmonary arteries to detect pulmonary venoconstriction.

Pulmonary arterial wedge pressure measures the pressure where blood flow resumes on the venous side. By occlusion of a large artery, the point where blood flow resumes will be in or near the left atrium. However, by occlusion of a small artery, it is possible to shift the point where flow resumes to a more proximal site in the veins and thus measure a pressure within the small veins.

Nitrogen washout during tidal breathing with superimposed high-frequency chest wall oscillation.

In order to assess the efficacy of high-frequency chest wall oscillation (HFCWO) superimposed on tidal ventilation, multiple-breath nitrogen washout curves were obtained in 7 normal seated subjects. To maintain a regular breathing pattern throughout the study, the subjects breathed synchronously with a Harvard ventilator set at a constant tidal volume and frequency for each subject during a trial period. Washout curves were obtained during 3 different maneuvers performed in random order.

Peripheral mucociliary clearance with high-frequency chest wall compression.

We investigated the effects of high-frequency chest wall compression (HFCWC) on peripheral and tracheal mucus clearance in anesthetized spontaneously breathing dogs. HFCWC was achieved by oscillating the pressure in a thoracic cuff with a piston pump. Regional lung retention of a technetium-99m sulfur colloid aerosol was monitored with a gamma camera.

Tracheal mucus clearance in high-frequency oscillation. II: Chest wall versus mouth oscillation.

We compared the tracheal mucus clearance rate (TMCR) in anesthetized dogs during spontaneous breathing (SB), ventilation by high-frequency oscillation at the airway opening (HFO/AO), and ventilation by high-frequency oscillation of the chest wall (HFO/CW). The HFO/AO was carried out by using a piston pump with a high impedance transverse flow at the proximal end of the endotracheal tube; HFO/CW was effected by creating rapid pressure oscillations in an air-filled cuff wrapped around the lower thorax of the animal, causing small tidal volumes at the mouth. The TMCR was measured by observing the rate of displacement of a charcoal marker in the lower trachea; a fiberoptic bronchoscope was used to deposit the marker before each experiment and to relocate it after a 5-min run.

High frequency chest wall compression and carbon dioxide elimination in obstructed dogs.

High frequency chest wall compression (HFCWC) was studied as a method of assisting ventilation in six spontaneously breathing anesthetized dogs. Under a constant level of anesthesia, the dogs became hypercapneic after airflow obstruction was created by metal beads inserted in the airways. HFCWC was achieved by a piston pump rapidly oscillating the pressure in a modified double blood pressure cuff wrapped around the lower thorax.

Hypotension secondary to balloon inflation of a pulmonary artery catheter.

Inflation of a balloon-tipped catheter for measurement of pulmonary artery wedge pressure caused a decrease in systemic arterial blood pressure in a mechanically ventilated patient after pneumonectomy. Obstruction by the balloon of a significant proportion of the cross-sectional area of the pulmonary circulation results in increased right ventricular afterload with subsequent decreased cardiac output and left atrial pressure. This decreased left atrial pressure can be measured accurately by the inflated balloon-tipped catheter but may be falsely low.

Enhanced tracheal mucus clearance with high frequency chest wall compression.

The clearance of mucus in the trachea during high frequency chest wall compression (HFCWC) was studied in nine anesthetized dogs. High frequency chest wall compression was applied by oscillating the pressure in a thoracic cuff such that it produced oscillatory tidal volumes of 25 to 100 cc at frequencies of 3 to 17 Hz. The tracheal mucus clearance rate (TMCR) was determined by direct observation of the rate of displacement of a charcoal particle spot by means of a fiberoptic bronchoscope.