Non-invasive haemodynamic effects of two nasal positive pressure ventilation modalities in stable chronic obstructive lung disease patients

Additive effects of non-invasive ventilation to hyperoxia on cerebral oxygenation in COPD patients with exercise-related O2 desaturation

BACKGROUND

It is currently unknown whether potential haemodynamic improvements induced by non-invasive ventilation (NIV) would positively impact upon cerebral oxygenation (COx) in patients with moderate-to-severe chronic obstructive pulmonary disease (COPD).

OBJECTIVE

To investigate the effects of NIV on exercise COx in COPD patients presenting with exercise-related O(2) desaturation.

METHODS

On a double-blind trial, 13 males (FEV1 = 48·8 ± 15·1% predicted) were randomly assigned to NIV (16 cmH(2)O IPS and 5 cmH(2)O PEEP) plus HOx (FiO(2) = 0·4) or sham NIV (7 cmH(2)O IPS and 5 cmH(2)O PEEP to overcome breathing circuit resistance) plus HOx during ramp-incremental exercise performed on different days. Near-infrared spectroscopy and impedance cardiography assessed changes (Δ) in COx and cardiac output (Q(T)), respectively.

RESULTS

There were no significant between-intervention differences in peak work rate, ventilation and reported symptoms (P>0·05). Peripheral oxyhaemoglobin saturation remained above 98% throughout the tests. NIV + HOx was associated with larger increases in Δ COx, Δ Q(T) and Δ stroke volume at maximal and submaximal exercise (P<0·05). Increases in the area under the curve (to an iso-work rate) of Δ COx under NIV + HOx were significantly (P<0·01) correlated with improvements in Δ Q(T) (r = 0·82) and Δ stroke volume (r = 0·87). There was, however, no significant correlation between enhancement in these physiological responses with changes in peak work rate with NIV + HOx (P>0·05).

CONCLUSIONS

NIV added benefit to HOx in improving central haemodynamics and COx in O(2) 'desaturators' with COPD. The clinical relevance of such beneficial effects on exercise tolerance, however, remains to be demonstrated.

Use of Doppler ultrasonography in the assessment of bronchodilator response in acute bronchiolitis

Measurement of the response of acute bronchiolitis (AB) to bronchodilators relies on clinical signs and pulse oximetry. We hypothesized that Doppler ultrasonographic indices of hepatic venous flow may prove to be an objective tool in the assessment of the effect of inhaled salbutamol in infants hospitalized for AB. Previously healthy infants hospitalized for their first episode of AB were prospectively studied. Composite clinical score (CCS, retractions plus wheezing/crackles) and hemoglobin oxygen saturation (SaO(2)) were measured before, and 15-min post-salbutamol nebulization (0.15 mg/kg, minimum 1.5 mg). Peak velocities at the middle hepatic vein (PV-HV) and right renal vein (PV-RV), as well as peripheral-to-middle hepatic vein transit time (TT) of an ultrasound contrast agent were also measured by Doppler ultrasonography pre- and post-nebulization. Nineteen infants were studied. Mean CCS decreased by 0.37 (95% confidence interval [CI]: 0.08-0.66, P = 0.015) and mean SaO(2) increased by 0.68% (95%CI: 0.17-1.19, P = 0.01) post-bronchodilator treatment. Mean TT increased by 9.54 sec (95%CI: 5.95-13.13, P < 0.0001) and PV-HV increased by 16.49 cm/sec (95%CI: 9.07-23.91, P = 0.0002); PV-RV did not change. TT (r = 0.51, P = 0.009), but not PV-HV, correlated negatively with CCS. There was a strong positive correlation between pre- and post-salbutamol TT values (r = 0.92, P < 0.0001). The most likely explanation for these findings is post-salbutamol abolishment of shunting at the pulmonary capillary bed. We conclude that the peripheral-to-middle hepatic vein prolongation of TT measured by Doppler ultrasonography after salbutamol administration in infants with AB can be used as a bedside tool in the objective assessment of clinical response to medication in these patients.

The effect of noninvasive intermittent positive-pressure ventilation during exercise in severe scoliosis

STUDY OBJECTIVES

Noninvasive intermittent positive-pressure ventilation (NIPPV) may improve exercise performance in COPD patients. It is not known whether this also applies to other patient groups such as those with restrictive respiratory diseases.

DESIGN

Randomized controlled trial.

SETTING

Regional center for assisted ventilation.

SUBJECTS

Eight patients with severe congenital scoliosis.

INTERVENTIONS

A submaximal treadmill test was performed with NIPPV applied via a mouthpiece. Each subject performed three walks breathing with three different ventilators and one walk breathing through the mouthpiece alone in random order. In addition, four unencumbered walks breathing normally and without monitoring were performed.

MEASUREMENTS AND RESULTS

The four unencumbered walks did not show a significant learning effect. The mean (SD) distance walked was 204 m (134.9 m). Using the mouthpiece alone, the walking distance fell to 140 m (75.8 m), and with the addition of the ventilators it fell further to 109 m (59.3 m). Grouped-effects analysis of variance showed this to be a significant difference in walking distance according to the type of walk (p = 0.048). There was no difference shown among the three brands of ventilator. At the breakpoint of exercise, significant increases were seen in tidal volume and minute volume (Mv) in the ventilator-assisted walks (p < 0.05) compared to walks performed breathing with the mouthpiece alone.

CONCLUSIONS

Breathing via a mouthpiece impaired exercise performance, and there was no improvement when breathing with a ventilator, despite the observed increase in Mv. NIPPV has no beneficial effect on exercise endurance in patients with severe scoliosis.

Effect of the initiation of noninvasive bi-level positive airway pressure on haemodynamic stability

Noninvasive ventilation using noninvasive bilevel positive airway pressure (Bi-PAP) has been shown to be an effective means of improving oxygenation and respiratory status in patients with obstructive pulmonary disease (COPD) and acute congestive heart failure (CHF). However, it is uncertain what effects this positive airway pressure has on the haemodynamic condition of these patients. This study examines the acute changes in basic circulatory parameters with the initiation of Bi-PAP. Noninvasive measurements of the heart rate, systolic and diastolic arterial pressure, cardiac index, total peripheral resistance, ventricular ejection time, and total diastolic time were determined by impedance cardiography before and after the institution of Bi-PAP (pressures 15/5) in a group of healthy volunteers. In a collateral study, the same measurements were made in COPD patients in whom Bi-PAP was initiated for therapeutic reasons. Changes in the haemodynamic parameters were analysed using a paired t-test (p < 0.05). In the 12 healthy volunteers studied there were no significant differences in any of the haemodynamic parameters measured (average cardiac index: 2.75 +/- 0.78) over a period of 15 minutes after the placement of Bi-PAP. Similar results for most haemodynamic parameters were found in the 7 COPD patients with imminent respiratory failure (average respiratory rate 24.8 +/- 3.2) when Bi-PAP was utilized with the exception of significant but small increases in the cardiac index, stroke volume and oxygen saturation (p<0.05). While Bi-PAP is frequently used in the treatment of patients with acute respiratory failure, little is known about its effect on haemodynamics. This study suggests that the effects of the initiation of Bi-PAP on the general circulation and cardiac output may be of minor relevance.