Biomedical subjects

Pierre Gratadour

Publications and source records attributed to Pierre Gratadour.

3 recordsLinked to original sources

PubMed2004

Sildenafil inhibits altitude-induced hypoxemia and pulmonary hypertension.

Exposure to high altitude induces pulmonary hypertension that may lead to life-threatening conditions. In a randomized, double-blind, placebo-controlled study, the effects of oral sildenafil on altitude-induced pulmonary hypertension and gas exchange in normal subjects were examined. Twelve subjects (sildenafil [SIL] n = 6; placebo [PLA] n = 6) were exposed for 6 days at 4,350 m. Treatment (3 x 40 mg/day) was started 6 to 8 hours after arrival from sea level to high altitude and maintained for 6 days. Systolic pulmonary artery pressure (echocardiography) increased at high altitude before treatment (+29% versus sea level, p < 0.01), then normalized in SIL (-6% versus sea level, NS) and remained elevated in PLA (+21% versus sea level, p < 0.05). Pulmonary acceleration time decreased by 27% in PLA versus 6% in SIL (p < 0.01). Cardiac output and systemic blood pressures increased at high altitude then decreased similarly in both groups. Pa(O(2)) was higher and alveolar-arterial difference in O(2) lower in SIL than in PLA at rest and exercise (p < 0.05). The altitude-induced decrease in maximal O(2) consumption was smaller in SIL than in PLA (p < 0.05). Sildenafil protects against the development of altitude-induced pulmonary hypertension and improves gas exchange, limiting the altitude-induced hypoxemia and decrease in exercise performance.

3',5'-Cyclic-GMP Phosphodiesterases↗

PubMed2004

Expiratory trigger setting in pressure support ventilation: from mathematical model to bedside.

OBJECTIVE: To evaluate the feasibility of relying on a mathematical model to adjust the optimal level of expiratory trigger, materialized by the ratio of inspiratory flow at the end of inspiratory effort (V'ti) and peak inspiratory flow (V'peak), or V'ti/V'peak, during pressure support, by comparing its predicted values with those measured in intubated patients. DESIGN: Prospective observational study. SETTING: Medical intensive care unit, university hospital. PATIENTS: There were 28 intubated patients undergoing pressure support. INTERVENTIONS: Pressure support as set by the clinician in charge. MEASUREMENTS AND MAIN RESULTS: A significant correlation was found between predicted and measured V'ti/V'peak ratios (r =.70; p <.001; mean +/- sd difference, -0.025 +/- 0.07; 95% confidence interval, -0.161 to 0.111). Overall, delayed cycling occurred in obstructive conditions, the delay increasing as obstructive disease was more severe. CONCLUSIONS: A significant correlation was observed between predicted values of V'ti/V'peak and those values measured in patients undergoing pressure support. These findings should stimulate further research into the possible applications of this mathematical model to optimize expiratory trigger setting. Furthermore, our findings suggest that expiratory trigger should be adjustable and provide a wider range of cutoff levels than that which is currently available.

Feasibility Studies↗

PubMed2002

Patient-ventilator interactions during partial ventilatory support: a preliminary study comparing the effects of adaptive support ventilation with synchronized intermittent mandatory ventilation plus inspiratory pressure support.

OBJECTIVE: To compare the effects of adaptive support ventilation (ASV) and synchronized intermittent mandatory ventilation plus pressure support (SIMV-PS) on patient-ventilator interactions in patients undergoing partial ventilatory support. DESIGN: Prospective, crossover interventional study. SETTING: Medical intensive care unit, university tertiary care center. PATIENTS: Ten patients, intubated and mechanically ventilated for acute respiratory failure of diverse causes, in the early weaning period, ventilated with SIMV-PS and clinically detectable sternocleidomastoid activity suggesting increased inspiratory load and patient-ventilator dyssynchrony. INTERVENTIONS: Measurement of respiratory mechanics, P0.1, sternocleidomastoid electromyographic activity, arterial blood gases, and systemic hemodynamics in three conditions: 1) after 45 mins with SIMV-PS (SIMV-PS 1); 2) after 45 mins with ASV, set to deliver the same minute-ventilation as during SIMV-PS; 3) 45 mins after return to SIMV-PS (SIMV-PS 2), with settings identical to those of the first SIMV-PS period. MAIN RESULTS: The same minute ventilation was observed during ASV (11.4 +/- 3.1 l/min [mean +/- sd]) as during SIMV-PS 1 (11.6 +/- 3.5 L/min) and SIMV-PS 2 (10.8 +/- 3.4 L/min). No parameter was significantly different between SIMV-PS 1 and 2, hence subsequent results refer to ASV vs. SIMV-PS 1. During ASV, tidal volume increased (538 +/- 91 vs. 671 +/- 100 mL, p <.05) and total respiratory rate decreased (22 +/- 7 vs. 17 +/- 3 breaths/min, p <.05) vs. SIMV-PS. However, spontaneous respiratory rate increased in six patients, decreased in four, and remained unchanged in one. P0.1 decreased during ASV in all patients except three in whom no change was noted (1.8 +/- 0.9 vs. 1.1 +/- 1 cm H2O, p <.05). During ASV, sternocleidomastoid electromyogram activity was markedly reduced (electromyogram index, where SIMV-PS 1 = 100, ASV 34 +/- 41, SIMV-PS 2 89 +/- 36, p <.02) as was palpable muscle activity. No changes were noted in arterial blood gases, pH, or mean systemic pressure during the trial. CONCLUSION: In patients undergoing partial ventilatory support, with clinical and electromyographic signs of increased respiratory muscle loading, ASV provided levels of minute ventilation comparable to those of SIMV-PS. However, with ASV, central respiratory drive and sternocleidomastoid activity were markedly reduced, suggesting decreased inspiratory load and improved patient-ventilator interactions. These preliminary results warrant further testing of ASV for partial ventilatory support.

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