Control of breathing in mechanically ventilated patients

Georgopoulos, Dimitris; Roussos, C.

doi:10.1183/09031936.96.09102151

Cited by 39 publications

(28 citation statements)

References 64 publications

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“…The discrepancies are probably related to the fact that in order to compare different groups of patients we expressed the inflation as a percent of predicted TLC. It has been reported [15]that patients with COPD, any time they suffer from bronchoconstriction, show dynamic hyperinflation (auto-PEEP), especially when they need mechanical ventilation, like our patients. Distension of the thoracic clove – resulting from dynamic hyperinflation – may stress inspiratory stretch receptors diminishing their responses to other stimuli.…”

Section: Discussionmentioning

confidence: 99%

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Hering-Breuer Reflex in Normal Adults and in Patients with Chronic Obstructive Pulmonary Disease and Interstitial Fibrosis

et al. 2001

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Background: It has been suggested that the Hering-Breuer reflex (HBR) is unimportant in adults during normal tidal breathing and that it is elicited only if tidal volume is increased above a certain critical threshold. Objective: The aim of this study was (1) to study the occurrence of the HBR in adults with normal pulmonary function and (2) to examine if changes in lung mechanics have any effect on the HBR. Methods: We examined 11 adults with normal pulmonary function, 8 patients with chronic destructive pulmonary disease (COPD) and 3 with interstitial fibrosis (IF). All subjects were lightly sedated with fentanyl, intubated and ventilated with a Servo-900 ventilator. Inspiratory and expiratory flow (and after integration, volume) and mouth pressure were recorded from the endotracheal tube with a pneumotachograph and a pressure transducer. Pressure support ventilation was applied in all patients and functional residual capacity (FRC) was measured with the N₂ washout method. Mean (Te_mean) and maximal expiratory time (Te_max) were determined for each individual for 20 breaths. Following several breaths to establish a stable baseline the airway was occluded at end inspiration by a shutter. A positive HBR was interpreted as longer Te_occ than Te_max (Te_occ/Te_max, %). Occlusion was maintained until negative airway pressure occurred and the occlusion time (Te_occ) was measured. We attempted occlusions after the addition of 5 cm H₂O positive end-expiratory pressure (PEEP) and subsequently with 10, 15 and 20 cm H₂O PEEP. Te_occ was measured of progressively larger lung volumes. To examine the HBR sensitivity in the three groups, we plotted the lung volumes of occlusion against the corresponding Te_occ/Te_max. Results: The ratio Te_occ/Te_max increased from 167.5 ± 82.5 at normal FRC to 474 ± 200.2 s (PEEP₂₀). On the contrary, in patients with COPD, Te_occ/Te_max increased from 125.2 ± 34 to 193.7 ± 74.2 (p < 0.05). Conclusions: The HBR was positive in all subjects. COPD patients were found to be less sensitive to volume changes when compared with normal controls and with IF patients.

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Section: Discussionmentioning

confidence: 99%

“…Another problem is that mechanical ventilation may stimulate various reflexes by changing flow and volume [14]. In order to minimize these effects we used the same type of lung volume change – addition of PEEP – and the same level of consciousness – slightly sedated by fentanyl – for all subjects [15]. …”

Section: Discussionmentioning

confidence: 99%

Hering-Breuer Reflex in Normal Adults and in Patients with Chronic Obstructive Pulmonary Disease and Interstitial Fibrosis

et al. 2001

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“…An esophageal balloon catheter was inserted in 7 of the 9 patients to measure Pes and to monitor patient efforts. The correct positioning of the balloon was made by the occlusion technique [18]. For the remaining 2 patients inspiratory efforts were estimated by additional increases in the flow waveforms, superimposed on the inspiratory curve, as previously described [1].…”

Section: Methodsmentioning

confidence: 99%

Effect of Different Levels of Pressure Support and Proportional Assist Ventilation on Breathing Pattern, Work of Breathing and Gas Exchange in Mechanically Ventilated Hypercapnic COPD Patients with Acute Respiratory Failure

et al. 2003

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Background: Proportional assist ventilation (PAV) has been shown to maintain better patient-ventilator synchrony than pressure support ventilation (PSV); however, its clinical advantage regarding invasive ventilation of COPD patients has not been clarified. Objectives: To compare the effect of PAV and PSV on respiratory parameters of hypercapnic COPD patients with acute respiratory failure (ARF). Methods: Nine intubated hypercapnic COPD patients were placed on the PAV or PSV mode in random sequence. For each mode, four levels (L₁–L₄) of support were applied. At each level, blood gases, flow, tidal volume (V_T), airway pressure (Paw), esophageal pressure (Pes) (n = 7), patient respiratory rate (fp), ventilator rate (fv), missing efforts (ME = fp – fv) were measured. Results: We found increases in ME with increasing levels of PSV but not with PAV. PO₂and V_T increased whereas PCO₂decreased significantly with increasing levels of PSV (p < 0.05). With PAV, PCO₂decreased and V_Tincreased significantly only at L₄ whereas PO₂increased from L₁ to L₄. Runaways were observed at L₃and L₄of PAV. The pressure-time product (PTP) was determined for effective and missing breaths. The mean total PTP per minute (of effective plus missing breaths) was 160 ± 57 cm H₂O/s·min in PSV and 194 ± 60 cm H₂O/s·min in PAV. Conclusion: We conclude that in COPD patients with hypercapnic ARF, with increasing support, PSV causes the appearance of ME whereas PAV develops runaway phenomena, due to the different patient-ventilator interaction; however, these do not limit the improvement of blood gases with the application of both methods.

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“…This suggests that in awake states, during hypocapnia, breathing frequency is relatively insensitive to changes in the partial pressure of carbon dioxide (PCO 2 ). Indeed, it has recently been shown in conscious normal humans ventilated on pressure support or assist volumecontrolled modes, that breathing frequency is unaffected by PCO 2 changes over a wide range of values [10,11]. It follows that, at least during hypocapnia, the reflex response of ttot to varying V'I is not modulated by PCO 2 .…”

Section: Discussionmentioning

confidence: 98%

Effects of pulmonary and intercostal denervation on the response of breathing frequency to varying inspiratory flow

Mitrouska¹,

Bshouty²,

Younes³

et al. 1998

Eur Respir J

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In mechanically ventilated awake and sleeping humans, it has been shown that increasing inspiratory flow rate (V'I) exerted a reflex excitatory effect on respiratory output. Mechanoreceptors located in intercostal muscles or within the lung have been suggested as possible pathways that may mediate the excitatory effect of V'I. To test this, five patients with bilateral lung transplantation (LTP) and eight quadriplegics with spinal cord transection at the level of C6-C7 (QP) were studied. Patients were connected to a volume cycle ventilator in the assist volume-control mode and V'I was randomly changed. V'I pattern was square and all breaths were patient-triggered. V'I values of 30, 60 and 90 L x min(-1) were studied. Each level of V'I was sustained for 15 breaths. Airway pressures, end-tidal partial pressure of carbon dioxide (PCO2), airflows and volumes were measured breath by breath. Thirty seven trials in LTP and sixty in QP, where V'I was randomly changed between 30 and 90 L x min(-1), were analysed. In both groups of patients, minute ventilation increased and total breath duration decreased significantly as V'I increased. These changes were complete in the first breath after V'I transition, without evidence of adaptation of the response. The magnitude of the response did not differ between the two groups of patients and was comparable to that observed previously in conscious normal subjects. We conclude that the excitatory effect of inspiratory flow rate on breathing frequency persists in patients who have pulmonary or intercostal denervation. These results do not favour receptors located within the lung (below the resection lines) or in the intercostal muscles to mediate the response of breathing frequency to flow rate.

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Control of breathing in mechanically ventilated patients

Cited by 39 publications

References 64 publications

Hering-Breuer Reflex in Normal Adults and in Patients with Chronic Obstructive Pulmonary Disease and Interstitial Fibrosis

Hering-Breuer Reflex in Normal Adults and in Patients with Chronic Obstructive Pulmonary Disease and Interstitial Fibrosis

Effect of Different Levels of Pressure Support and Proportional Assist Ventilation on Breathing Pattern, Work of Breathing and Gas Exchange in Mechanically Ventilated Hypercapnic COPD Patients with Acute Respiratory Failure

Effects of pulmonary and intercostal denervation on the response of breathing frequency to varying inspiratory flow

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