Combined effects of a nasal dilator and nasal prongs on nasal airflow resistance

STUDY OBJECTIVES: Nasal prongs (NPs), when used to assess nasal flow, can result in dramatic increases in nasal airflow resistance (NR). The aim of this study was to investigate whether the NP-induced increases in NR could be corrected by the simultaneous use of an internal nasal dilator (ND). DESIGN: NR was estimated by posterior rhinomanometry, in the basal state (NRb), and while breathing with NP (NRp), with ND (NRd), and with both ND and NP (NRd + p). PARTICIPANTS: The study was performed in 15 healthy subjects. Measurements and results: NR (mean NRb [+/- SEM], 2.5 +/- 0.4 cm H(2)O/L/s) significantly decreased with ND (NRd = 1.4 +/- 0.2 cm H(2)O/L/s; p < 0.001) and significantly increased with NP (NRp = 3.8 +/- 0.8 cm H(2)O/L/s; p < 0.001). A significant logarithmic relationship was found between NRd and NRb (r(2) = 0.95; p < 0.0001), and a significant exponential relationship was found between NRp and NRb (r(2) = 0.99; p < 0.0001). While breathing with both ND and NP, NRd + p was significantly lower than NRb (1.9 +/- 1.4 cm H(2)O/L/s; p < 0.02). CONCLUSIONS: Our results demonstrate that the ND tends to slightly overcorrect the NP-induced increase in NR and suggest that, in view of the possible effects of NPs on upper airway resistance, the combination of both devices might be used for nasal airflow monitoring during nocturnal polysomnography in patients presenting with highly resistive nares.     

Combined effects of a mechanical nasal dilator and a topical decongestant on nasal airflow resistance.

The goal of this study was to compare the isolated and combined effects of two treatments being used to reduce nasal airflow resistance (NR): an internal nasal mechanical dilator (Nozovent; Prevancure; Sté Pouret, Paris, France) and a topical decongestant, fenoxazoline hydrochloride (Aturgyl; Synthelabo; Le Plessis-Robinson, France). The study was performed in 17 healthy subjects. NR was estimated by active posterior rhinometry at a 0.5 L/s flow under four conditions: in the basal state, with the internal nasal mechanical dilator, after treatment with fenoxazoline hydrochloride, and with both fenoxazoline hydrochloride and the mechanical dilator. The mean NR (+/- SD) decreased from 1.65+/-0.54 cm H2O/L/s in the basal state to 1.02+/-0.27 cm H2O/L/s with the mechanical dilator (p < 0.001), 1.03+/-0.47 cm H2O/L/s with fenoxazoline hydrochloride (p < 0.001), and 0.48+/-0.15 cm H2O/L/s with both the mechanical dilator and fenoxazoline hydrochloride (p < 0.001). The decreases in NR observed after using either the mechanical dilator (deltaNR(N)) or fenoxazoline hydrochloride (deltaNR(A)) were not significantly different. The decrease in NR observed with both (deltaNR(N + A)) was not significantly different from the sum deltaNR(N) + deltaNR(A): 1.16+/-0.53 cm H2O/L/s vs 1.25+/-0.63 cm H2O/L/s, respectively (p > 0.05). deltaNR(N + A) strongly correlated with deltaNR(N) + deltaNR(A): deltaNR(N + A) = 0.80 (deltaNR(N) + deltaNR(A)) + 0.15 (r = 0.96; p < 0.0001). However, the slope of the regression line of deltaNR(N + A) vs deltaNR(N) + deltaNR(A) was significantly lower than unity (p < 0.003). These results demonstrate that, although not totally additive, the effects of using the mechanical dilator and fenoxazoline hydrochloride are cumulative. Further studies that include patients with nasal obstruction would allow us to better evaluate the benefit of a therapy combining both treatments.     

Performance of nasal prongs in sleep studies : spectrum of flow-related events

OBJECTIVES: The use of nasal prongs connected to a pressure transducer is a noninvasive, sensitive method to detect respiratory events, and can be easily implemented in routine sleep studies. Moreover, its good time response allows the detection of several flow-related phenomena of high interest, in addition to apnea and hypopnea. The aims of the study were to examine the quality and performance of the nasal prong flow signal, and to describe other flow-related events during full-night polysomnography studies. METHODS: Twenty-seven subjects were studied (16 male subjects; mean +/- SD age, 49 +/- 14 years; mean body mass index, 27 +/- 4 kg/m(2)): 15 subjects recruited from the general population and 12 consecutive patients with suspected sleep apnea/hypopnea syndrome (SAHS). RESULTS: A blind analysis of the respiratory events detected both by nasal prongs and thermistor was done. The quality of the nasal prong signal recordings was considered optimal for scoring purposes in 78% of cases, and no recording was considered uninterpretable. The nasal prong signal detected additional flow-related events not observed by the thermistor: (1) short and long (> 2 min) periods of inspiratory flow limitation morphology without decrease in the amplitude of the signal; (2) periods of mouth expiration; and (3) snoring. The apnea/hypopnea index was significantly higher with the nasal prong scoring (18 vs 11 [p < 0.05] in the general population and 37 vs 27 [p < 0.001] in the group with suspected SAHS). CONCLUSIONS: The incorporation of nasal prongs in routine full-night studies is an attainable technical option that provides adequate recordings in most cases. Additionally, relevant information not scored by thermistors is obtained on flow-related respiratory events, thus increasing diagnostic accuracy.     

Evaluation of nasal impedance using the forced oscillation technique in infants

By applying oscillations to the respiratory system through a rigid face mask, the infant-adapted Lándsér forced oscillation technique measures impedance of the total respiratory system including the nose, at frequencies from 4 to 52 Hz. The present study was aimed at evaluating nasal impedance in infants from consecutive forced oscillation measurements through both nostrils and each nostril separately, using a simple electrical model. In 30 asthmatic infants with varying degrees of nasal obstruction, aged 1-16 months, calculated nasal resistance (Rn) at 24 Hz ranged from 1 to 16 cm H2O.L-1.s. The ratio of Rn to total respiratory system resistance varied between 1 and 48% (mean: 16%). In seven non-asthmatic infants, aged 0-12 months, Rn was between 1 and 11 cm H2O.L-1.s. Nasal patency (evaluated clinically) was correlated with the calculated Rn (P less than 0.05). Rn showed almost no frequency dependence between 24 and 48 Hz as demonstrated by a mean slope of -0.09 +/- 0.08 cm H2O.s2/L for the asthmatic and of -0.08 +/- 0.07 for the non-asthmatic infants. In seven of the asthmatic infants the differences between two Rn determinations at a 45 min interval ranged from -1.7 to 3.8 cm H2O.L-1.s-1 at 24 Hz and from -3.6 to 1.0 at 48 Hz. Changes in Rn did not correlate with changes in total respiratory system resistance (P greater than 0.05). In conclusion, nasal impedance can be approximated from three consecutive measurements through both nostrils and through each nostril separately.     

Reducing ventilatory response to carbon dioxide by breathing cold air

To study the effect of cooling of nasal receptors on breathing we had 10 normal male volunteers rebreathe through their noses 8% CO2 in oxygen at "warm" (23 to 30 degrees C) and at "cold" (-4 to 10 degrees C) temperatures. In order to further examine the effect of nasal receptors on the control of breathing, 11 subjects had their nasal response to CO2 measured at the warm temperature before and after topical nasal anesthesia. To exclude an increase in nasal resistance as the cause of the reduced response to CO2, 10 subjects had their nasal resistance measured before and after nasal rebreathing of cold 8% CO2 in oxygen. To also exclude increased bronchial resistance, forced expiratory volume in one second (FEV1) was measured in 12 subjects before and after nasal breathing of cold oxygen for 3 min. The mean ventilatory response to CO2 was reduced from 3.0 +/- 1.6 L/min/mmHg to 2.5 +/- 1.1 L/min/mmHg (p less than 0.05) by the cold air. Topical nasal anesthesia increased the response to CO2 at the warm temperature from 2.4 +/- 0.7 to 2.7 +/- 0.9 L/min/mmHg. The effect of nasal breathing of 8% CO2 in oxygen at the cold temperature was to reduce nasal inspiratory resistance at 1 L/s from 4.3 +/- 3.0 cm H2O L/s to 2.6 +/- 1.0 cm H2O L/s (p less than 0.05). Expiratory resistance at 1 L/s fell from 3.7 +/- 1.5 cm H2O L/s to 2.4 +/- 0.7 cm H2O L/s (p less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)     

A physiologic comparison of nasal and oral positive airway pressure

STUDY OBJECTIVES: The effectiveness of nasal continuous positive airway pressure (CPAP) in treating obstructive sleep apnea (OSA) is based on raising the intramural pressure above a critical collapsing pressure of the oropharyngeal airway. It is currently unclear whether CPAP delivered orally is also capable of raising pressure in the oropharynx above the critical collapse pressure. DESIGN: We tested a novel oral CPAP device to determine whether the pressure-flow relationships are similar to nasal CPAP and whether the device alters these relationships. Patients were selected based on having moderately severe apnea and were randomized to nasal CPAP, nasal CPAP with oral device, or oral CPAP. SETTING: Johns Hopkins University, The Johns Hopkins Asthma and Allergy Center, Baltimore, MD. PATIENTS: Five men and two women with OSA were studied. INTERVENTIONS: Individual pressure-flow curves were constructed during the application of nasal or oral CPAP. RESULTS: We found the following: (1) a similar effective pressure eliminated inspiratory flow limitation for the nasal or oral CPAP; (2) as pressure in the nose or mouth was lowered below the effective pressure, a linear pressure-flow curve was obtained and a critical closing pressure was described; (3) similar mean (+/- SD) critical pressures of -0.3 +/- 5.3, 1.7 +/- 4.0, and 0.5 +/- 2.8 cm H(2)O, respectively, occurred for nasal CPAP, nasal CPAP with the oral device in place, and oral CPAP conditions (p > 0.1); and (4) the comparable mean values for upstream resistance were 27.8 +/- 19, 19.1 +/- 8.3, and 26.5 +/- 26.7 cm H(2)O/L/s, respectively, for the above three conditions (p > 0.1). CONCLUSIONS: We concluded that comparable upper airway pressure-flow relationships were obtained during oral and nasal breathing. Moreover, effective treatment pressure is obtained when constant pressure is applied through either the nasal or oral route.     

A reservoir nasal cannula improves protection given by oxygen during muscular exercise in COPD

We verified the utility of an oxygen economizer (Pendant Oxymizer) in assuring greater protection than nasal prongs against worsening of oxyhemoglobin resting desaturation (delta SaO2) induced by muscular exercise in 16 patients (ten with chronic obstructive pulmonary disease [COPD] and six with restrictive pulmonary disease). This worsening was quantified as desaturation surface accumulated within five minutes of exercise and was expressed in arbitrary units (au). Each patient carried out the same exercise three times, in a randomized fashion (breathing air or breathing supplemental oxygen [3 L/min] delivered by either nasal prongs or by oxygen economizer). In patients with obstructive disease, delta SaO2 was reduced from 38 +/- 12.0 au when they were breathing air to 18.1 +/- 11.7 au when breathing oxygen by nasal prongs (p less than 0.001) and to 10.1 +/- 9.5 au when breathing oxygen by economizer (p less than 0.001). In patients with restrictive disease, delta SaO2 was reduced from 35.6 +/- 9.9 au when breathing air to 14.9 +/- 10.2 au breathing oxygen by nasal prongs (p less than 0.01) and to 13.7 +/- 10.3 au breathing oxygen by economizer (p less than 0.01). The difference between breathing by economizer and nasal prongs was significant (paired t-test; p less than 0.01) only in patients with COPD. One explanation could lie in the different values of the respiratory rate, which was significantly greater in patients with restrictive disease (20.7 +/- 1.2 breaths per minute at rest and 25.8 +/- 1.5 with exercise) than in patients with obstructive disease (15.3 +/- 1.2 breaths per minute at rest and 20.8 +/- 1.4 with exercise).     

Measurement of exhaled nitric oxide concentration using nasal continuous negative pressure

Contamination of nasal nitric oxide (NO) is a major obstacle when one needs to sample exhaled NO originating only from the lungs. To eliminate nasal NO, we used the nasal continuous negative pressure (nasal CNP) technique which, we verified, caused closure of the vellum. Exhaled gas was sampled from six healthy volunteers into fraction 1 (initially exhaled 200 mL) and fraction 2 (remainder of the gas) under three conditions; while subjects were wearing a noseclip, using nasal CNP at -5, -10 and -20 cm H2O, and under endotracheal intubation. Exhaled NO concentration ([NO]) obtained with nasal CNP was significantly lower, regardless of the pressure applied, than that measured with a noseclip, and was similar to and closely correlated to that obtained under intubation (F1, r = 0.90; F2, r = 0.88; P < 0.05). Real-time recorded [NO] obtained with nasal CNP of -5 cm H2O was again lower than that measured with a noseclip at any expiratory flow rate examined, indicating nasal NO contamination was eliminated irrespective of the flow rate. In conclusion, because a nasal CNP of -5 cm H2O was easily tolerated without any discomfort, this technique is a simple, easy and effective technique to eliminate nasal NO which should be widely applicable for the measurement of exhaled [NO].     

Effect of HFNC flow rate,cannula size,and nares diameter on generated airway pressures: An in vitro study

Increased use of non‐invasive forms of respiratory support such as CPAP and HFNC in premature infants has generated a need for further investigation of the pulmonary effects of such therapies. In a series of in vitro tests, we measured delivered proximal airway pressures from a HFNC system while varying both the cannula flow and the ratio of nasal prong to simulated nares diameters. Neonatal and infant sized nasal prongs (3.0 and 3.7 mm O.D.) were inserted into seven sizes of simulated nares (range: 3–7 mm I.D. from anatomical measurements in 1–3 kg infants) for nasal prong‐to‐nares ratios ranging from 0.43 to 1.06. The nares were connected to an active test lung set at: TV 10 ml, 60 breaths/min, Ti 0.35 sec, compliance 1.6 ml/cm H₂O and airway resistance 70 cm H₂O/(L/sec), simulating a 1–3 kg infant with moderately affected lungs. A Fisher & Paykel Healthcare HFNC system with integrated pressure relief valve was set to flow rates of 1–6 L/min while cannula and airway pressures and cannula and mouth leak flows were measured during simulated mouth open, partially closed and fully closed conditions. Airway pressure progressively increased with both increasing HFNC flow rate and nasal prong‐to‐nares ratio. At 6 L/min HFNC flow with mouth open, airway pressures remained <1.7 cm H₂O for all ratios; and <10 cm H₂O with mouth closed for ratios <0.9. For ratios >0.9 and 50% mouth leak, airway pressures rapidly increased to 18 cm H₂O at 2 L/min HFNC flow followed by a pressure relief valve limited increase to 24 cm H₂O at 6 L/min. Safe and effective use of HFNC requires careful selection of an appropriate nasal prong‐to‐nares ratio even with an integrated pressure relief valve. Pediatr Pulmonol. 2013; 48:506–514. © 2012 Wiley Periodicals, Inc.     

Influence of respiratory behavior on ventilation,respiratory work and intrinsic PEEP during noninvasive nasal pressure support ventilation in normal subjects

BACKGROUND: In clinical practice, patients have different inspiratory behaviors during noninvasive pressure support ventilation (PSV): some breathe quietly, others actively help PSV by an additional effort, and others even resist the inspiratory pressure of PSV. OBJECTIVE: What is the influence of patient collaboration (inspiratory behavior) on the efficiency of PSV? METHODS: We ventilated 10 normal subjects with nasal PSV (inspiratory/expiratory: 10/0 and 15/5 cm H(2)O) and measured their flow and volume with a pneumotachograph and their esophageal and gastric pressures during three different respiratory voluntary behaviors: relaxed inspiration, active inspiratory work and resisted inspiration. RESULTS: When compared with relaxed inspiration with 10/0 cm H(2)O PSV: (1) an active inspiratory effort increased tidal volume (from 789 +/- 356 to 1,046 +/- 586 ml; p = 0.006), minute ventilation (from 10.40 +/- 4.45 to 15.77 +/- 7.69 liters/min; p < 0.001), transdiaphragmatic work per cycle (from 0.55 +/- 0.33 to 1.72 +/- 1.40 J/cycle; p = 0.002) and inspiratory work per cycle (from 0.14 +/- 0.20 to 1.26 +/- 1.01 J/cycle; p = 0.003); intrinsic positive end-expiratory pressure (PEEP(i)) increased from 1.23 +/- 1.02 to 3.17 +/- 2.30 cm H(2)O; p = 0.002); (2) a resisted inspiration decreased tidal volume (to 457 +/- 230 ml; p = 0.007), minute ventilation (to 6.93 +/- 3.04 liters/min; p = 0.028) along with a decrease in transdiaphragmatic work but no change in PEEP(i). Data obtained during a bilevel PSV of 15/5 cm H(2)O were similar to those obtained with the 10/0 cm H(2)O settings. CONCLUSIONS: Active inspiratory effort increases ventilation during PSV at the expense of an increased breathing work and PEEP(i). Resisted inspiration inversely decreases inspiratory work and ventilation with no air trapping. These differences between inspiratory behaviors could affect the expected beneficial effects of PSV in acutely ill patients.     

Nicorandil infusion leads to good recovery from ischemia of left ventricular regional work in comparison with nitroglycerin.

Nicorandil is an antianginal drug that exerts both a conventional nitrate effect and an independent ATP-dependent potassium channel-opening effect. The present study examined the effects of nicorandil on left ventricular regional work (RW) during coronary angioplasty in 22 patients with angina pectoris who were scheduled for angioplasty to the left anterior descending artery. The patients were randomly assigned to receive either nitroglycerin (group NG, n=12, 0.5 microg x kg(-1) min(-1)) or nicorandil (group NR, n = 10, 1.5 microg x kg(-1) min(-1)). Inflation was performed for 60 s and the data were collected every 10 s. The RW was derived from the relation between mean wall stress and area strain. The RW of the interventricular septum decreased after balloon inflation and was at its minimum after the 60s inflation (group NR: 1.24 +/- 0.72mJ/cm3, group NG: 0.63 +/- 0.25mJ/cm3). After balloon deflation, the septal RW of both groups increased, and recovered to the baseline condition at about 30s. At 20 s after deflation, the septal RW in group NR (3.58 +/- 1.17 mJ/cm3) was significantly higher than that in group NG (2.25 +/- 0.59mJ/cm3) (p < 0.05). An intravenous infusion of nicorandil led to good recovery of RW from ischemia compared with that obtained with nitroglycerin.     

The effects of helium-hyperoxia on 6-min walking distance in COPD: a randomized, controlled trial

BACKGROUND: We hypothesized that breathing helium-hyperoxia (HeO2) would significantly improve 6-min walking test (6MWT) distance in COPD subjects. METHODS: This was a blinded, randomized crossover study. At visit 1, we assessed pulmonary function, exercise capacity, and 6MWT distance. Visits 2 and 3 consisted of four 6MWTs in which the following different inspired gases were used: room air (RA) by mask; 100% O2 by mask (mask O2); 100% O2 by nasal prongs (nasal O2); and 70% He/30% O2 by mask (HeO2). Walking distance, shortness of breath, leg fatigue, O2 saturation, and heart rate (HR) were assessed. RESULTS: Sixteen COPD subjects participated (mean FEV(1)/FVC ratio [+/- SD], 48 +/- 8%; mean FEV1, 55 +/- 13% predicted). Subjects walked farther when breathing HeO2 (564 m) compared to RA (497 m; p < 0.001), mask O2 (520 m; p < 0.001), or nasal O2 (528 m; p < 0.001). Despite the increased distance walked while breathing HeO2, there was no increase in shortness of breath or leg fatigue. There was desaturation when breathing RA (8%; p < 0.001) and nasal O2 (5%; p < 0.001), which was reduced when breathing HeO2 (3%; difference not significant) and mask O(2) (0%; difference not significant). There were no significant differences in HR in the four 6MWTs. CONCLUSIONS: The use of HeO2 increased 6MWT distance in COPD subjects more than either mask O2 or nasal O2 compared to RA. The increased walking distance was not associated with increased shortness of breath or leg fatigue. The results suggest that clinical benefit would be obtained by administering HeO2 during exercise, which may have significant clinical implications for the management of COPD patients.     

Efficacy of mechanical insufflation-exsufflation in medically stable patients with amyotrophic lateral sclerosis

OBJECTIVE: To determine under what circumstances the use of mechanical insufflation-exsufflation (MI-E) can generate clinically effective expiratory flows for airway clearance (> 2.7 L/s) for clinically stable patients with amyotrophic lateral sclerosis (ALS). MATERIALS AND METHOD: Twenty-six consecutive patients with ALS were studied, 15 with severe bulbar dysfunction. Using a pneumotachograph and with the aid of an oronasal mask, we measured FVC, FEV(1), peak cough flow (PCF), maximum insufflation capacity (MIC), PCF generated from a maximum insufflation MIC (PCFMIC), and PCF generated by MI-E (PCFMI-E). MI-E was delivered at +/- 40 cm H(2)O. Maximum inspiratory pressure (PImax) and maximum expiratory pressure (PEmax) at the mouth were also measured. RESULTS: Although both groups had a similar time from ALS symptom onset to diagnosis, statistical differences (p < 0.05) were found between nonbulbar and bulbar patients in lung function and cough capacity parameters: FVC, 2.58 +/- 1.24 L vs 1.62 +/- 0.74 L; FEV(1), 2.26 +/- 1.18 L vs 1.54 +/- 0.69 L; PImax, - 93.45 +/- 47.47 cm H(2)O vs - 3.64 +/- 25.07 cm H(2)O; PEmax, 140.45 +/- 75.98 cm H(2)O vs 69.93 +/- 32.14 cm H(2)O; MIC, 3.02 +/- 1.22 L vs 1.97 +/- 0.75 L; PCF, 5.91 +/- 2.55 L/s vs 3.42 +/- 1.44 L/s; PCFMIC, 6.68 +/- 2.71 L/s vs 4.00 +/- 1.48 L/s; and PCFMI-E, 4.34 +/- 0.82 L/s vs 3.35 +/- 0.77 L/s. Four patients with bulbar dysfunction and MIC > 1 L had PCFMI-E < 2.7 L/s. The receiver operating characteristic (ROC) curve analysis showed PCFMIC of 4 L/s predicting those patients with PCFMIC greater than PCFMI-E. CONCLUSION: MI-E is able to generate clinically effective PCFMI-E (> 2.7 L/s) for stable patients with ALS, except for those with bulbar dysfunction who also have a MIC > 1 L and PCFMIC <2.7 L/s who probably have severe dynamic collapse of the upper airways during the exsufflation cycle. Clinically stable patients with mild respiratory dysfunction and PCFMIC > 4 L/s might not benefit from MI-E except during an acute respiratory illness.     

Comparison of oxygen therapy with nasal continuous positive airway pressure on Cheyne-Stokes respiration during sleep in congestive heart failure

STUDY OBJECTIVES: Both oxygen therapy and nasal continuous positive airway pressure (CPAP) therapy have independently been shown to be effective in the treatment of Cheyne-Stokes respiration (CSR) in patients with congestive heart failure (CHF). The purpose of this study was to compare the short-term effects of oxygen therapy and nasal CPAP therapy on CSR in a group of stable patients with severe CHF. DESIGN: Prospective, randomized, controlled trial. SETTING: University hospital. PATIENTS: Twenty-five stable patients (mean [+/- SD] age, 56 +/- 9) with CHF and a mean left ventricular ejection fraction (LVEF) of 17 +/- 0.8%. INTERVENTIONS AND MEASUREMENTS: All patients had a right heart catheterization prior to the study and an echocardiogram performed to measure LVEF. In addition, all patients had an initial sleep study to identify the presence of CSR. Sleep studies included continuous recordings of breathing pattern, pulse oximetry, and EEG. Those patients identified as having CSR were randomized to a night on oxygen therapy (2 L/min by nasal cannula) and another night on nasal CPAP therapy (9 +/- 0.3 cm H(2)O). RESULTS: Fourteen of the 25 patients (56%) studied had CSR (apnea hypopnea index [AHI], 36 +/- 7 events per hour) during their initial sleep study. Nine of the 14 patients with CSR completed the study. When compared with baseline measurements, both oxygen therapy and nasal CPAP therapy significantly decreased the AHI (from 44 +/- 9 to 18 +/- 5 and 15 +/- 8 events per hour, respectively; p < 0.05), with no significant difference between the two modalities. The mean oxygen saturation increased significantly and to a similar extent with oxygen therapy and nasal CPAP therapy (from 93 +/- 0.7% to 96 +/- 0.8% and 95 +/- 0. 7%, respectively; p < 0.05), as did the lowest oxygen saturation during the night (from 80 +/- 2% to 85 +/- 3% and 88 +/- 2%, respectively; p < 0.05). In addition, the mean percent time the oxygen saturation was < 90% also improved with both interventions (from a baseline of 17 +/- 5 to 6 +/- 3% with oxygen therapy and 5 +/- 2% with nasal CPAP therapy; p < 0.05). When compared with baseline measurements, the apnea-hypopnea length, cycle length, circulation time, and heart rate did not significantly change with either oxygen therapy or nasal CPAP therapy. Total sleep time and sleep efficiency decreased only with nasal CPAP therapy (from 324 +/- 20 to 257 +/- 14 min, and from 82 +/- 3 to 72 +/- 2%, respectively; p < 0.05). The arousal index, when compared with baseline, remained unchanged with both oxygen therapy and nasal CPAP therapy. CONCLUSION: CSR occurs frequently in stable patients with severe CHF. In addition, oxygen therapy and nasal CPAP therapy are equally effective in decreasing the AHI in those CHF patients with CSR.     

Oscillatory resistance measured during noninvasive proportional assist ventilation.

Setting proportional assist ventilation (PAV) requires the measurement of patient resistance and elastance. To avoid patient sedation/paralysis or the use of an esophageal balloon, noninvasive PAV is indirectly set by the "runaway" method or in accordance with patient comfort. The aim of this study was to ascertain whether the forced oscillation technique (FOT) applied by the ventilator during noninvasive PAV is useful in assessing patient respiratory resistance. Nasal PAV was applied to 14 patients with severe chronic obstructive pulmonary disease. During PAV a modified ventilator applied a 5-Hz pressure oscillation to noninvasively assess FOT resistance (Rrs). Lung resistance (RL) was measured in seven of the patients by using an esophageal balloon. Moreover, measurements were also performed in five of the patients when PAV was applied through the mouth. Rrs was close to RL both during nasal (Rrs = 8.9 +/- 3.1, RL = 9.0 +/- 2.6; cm H(2)O x s/L; n = 7, p > 0.05) and mouth (Rrs = 5.6 +/- 2.1, RL = 5.8 +/- 1.4; cm H(2)O x s/L; n = 5, p > 0.05) breathing. Rrs was slightly greater than the maximum value of flow assistance applied during the setting of PAV (FAmax): 11.1 +/- 5.4 and 9.5 +/- 2.9 cm H(2)O x s/L, respectively (n = 14, p > 0.05), both variables being significantly correlated (r = 0.72, p < 0.05). FOT applied by the PAV ventilator allowed the assessment of patient resistance. These results suggest that FOT could be useful in setting PAV flow assistance and in automatically and continuously updating this setting in accordance with patient resistance.     

Hemodynamic effects of bilevel nasal positive airway pressure ventilation in patients with heart failure

AIMS: Benefits of nasal continuous positive airway pressure (CPAP) in patients presenting with chronic heart failure (CHF) are controversial. The purpose of this study was to compare the hemodynamic effects of CPAP and bilevel positive airway pressure (BiPAP) in patients with or without CHF. METHODS AND RESULTS: Twenty patients with CHF and 7 with normal left ventricular function underwent cardiac catheterization. Measurements were made before and after three 20-min periods of BiPAP: expiratory positive airway pressure (EPAP) = 8 cm H2O and inspiratory positive airway pressure (IPAP) = 12 cm H2O, EPAP = 10 cm H2O and IPAP = 15 cm H2O, and CPAP = EPAP = IPAP = 10 cm H2O administered in random order. Positive pressure ventilation decreased cardiac output (CO) and stroke volume. No change was observed in either pulmonary or systemic arterial pressure. There was no difference in the hemodynamic effects of the three ventilation settings. Only mean pulmonary wedge pressure (MPWP) and heart rate were lower with CPAP than with BiPAP. CO decreased only in patients with low MPWP (相似文献   

Airway mechanics and ventilation in response to resistive loading during sleep: influence of gender

The male predominance in obstructive sleep apnea (OSA) is currently poorly understood although differences in pharyngeal airway anatomy and physiology have been proposed. As the response to inspiratory resistive loading (IRL) provides important information on both airway collapsibility (mechanics) and ventilatory control, we compared this respiratory response in eight normal women and eight age and body mass index (BMI)-matched men, during stable nonrapid eye movement (NREM) sleep. Upper airway mechanics, ventilation, plus activation of two dilator muscles (genioglossus [GG] and tensor palatini [TP]) were monitored during basal breathing (BL), followed by four sequentially applied loads (5, 10, 15, 25 cm H(2)O/L/s) for three breaths each. Men developed more severe hypopnea in response to identical applied external loads than did women. At a resistance of 25 cm H(2)O/L/s, VT decreased by 26 +/- 1% in women compared with 44 +/- 1% in men (differences between sexes p < 0.05). Pharyngeal resistance (Rpha) in response to IRL increased significantly more in men than women (37.3 +/- 11.2 cm H(2)O/L/s in men at maximal load, compared with an increase of 6.6 +/- 3.9 cm H(2)O/L/s in women, p < 0.05). Men and women had near identical minute ventilation responses to total load (applied extrinsic plus measured intrinsic), implying no differences in central drive or load response. There were no significant increases in GG or TP activation in response to IRL in either sex. We conclude that normal men are more vulnerable to load-induced hypoventilation than women, due to increased upper airway collapse, which could not be explained by differences in dilator muscle activation. This implies a fundamental difference in the upper airway anatomy and/or tissue characteristics between the two sexes.     

Posture and nasal patency

Effects of recumbency on nasal patency were determined in adult subjects by a sensitive computer-assisted posterior rhinometric technique. A modified body plethysmograph was employed to measure air flow and to avoid the disadvantages of facial masking and nasal intubation. In healthy subjects, assumption of recumbency decreases total nasal patency minimally. Lateral recumbency decreases it markedly in the ipsilateral nasal cavity, in which resistance to breathing often exceeds 10 cm H2O (1.0 kPa)/L/s. A concomitant increase in patency, which takes place contralaterally (resistance is frequently reduced to less than 3 cm H2O (0.3 kPa)/L/s), diminishes change in total nasal patency. Ipsilateral decrease and reciprocal contralateral increase in patency are induced also by unilateral pressures to trunk and limbs in dorsally recumbent subjects. This posture minimizes hydrostatic differences between sides. The results indicate that reciprocal nasal vascular responses to lateral recumbent postures are caused by pressure-induced reflexes, and these changes take place independent of hydrostatic differences. Effects of recumbency on the patency of abnormal noses and their relevance to breathing disorders of sleep are discussed.     

Moderate alcohol ingestion increases upper airway resistance in normal subjects

Apnea during sleep has been associated with both increased pharyngeal resistance and nasal obstruction. Alcohol can worsen obstructive sleep apnea, but its influence on pharyngeal resistance and nasal patency has not been evaluated. Accordingly, we determined the effects of alcohol on pharyngeal and nasal resistances in 11 normal awake subjects on 2 separate days. Baseline pharyngeal resistance prior to placebo and alcohol was not significantly different. After placebo, pharyngeal resistance did not change significantly. However, after alcohol, pharyngeal resistance increased from 1.9 +/- 0.5 (SEM) to 3.3 +/- 0.8 cm H2O/L/s at 45 min (p less than 0.05) and returned to near baseline level by 90 min. Baseline nasal resistance varied considerably within subjects on the 2 days, but the mean values for baseline nasal resistance on alcohol and placebo days were not significantly different. Nasal resistance did not change after placebo, but after alcohol, nasal resistance increased from 2.4 +/- 0.9 at baseline to 3.7 +/- 0.8 at 45 min (NS) and to 4.3 +/- 1.2 cm H2O/L/s at 90 min (p less than 0.05). We conclude that a decrease in pharyngeal airway size and an increase in nasal resistance may account for alcohol's ability to worsen obstructive sleep apnea.